The neutron flux monitors from 20 keV to 1 MeV for BNCT: performance study using accelerator-based neutron sources

NASA Astrophysics Data System (ADS)

Guan, X. C.; Gong, Y.; Murata, I.; Wang, T. S.

2018-05-01

The performance of the neutron flux monitors from 20 keV to 1 MeV developed for boron neutron capture therapy (BNCT) is studied by Monte Carlo simulations using accelerator-based neutron sources (ABNSs). The results show that the performance of the neutron flux monitors is very satisfactory and they can be efficiently used in practical applications to measure the neutron fluxes from 20 keV to 1 MeV of ABNSs for BNCT to high accuracy.

ReactorHealth Physics operations at the NIST center for neutron research.

PubMed

Johnston, Thomas P

2015-02-01

Performing health physics and radiation safety functions under a special nuclear material license and a research and test reactor license at a major government research and development laboratory encompasses many elements not encountered by industrial, general, or broad scope licenses. This article reviews elements of the health physics and radiation safety program at the NIST Center for Neutron Research, including the early history and discovery of the neutron, applications of neutron research, reactor overview, safety and security of radiation sources and radioactive material, and general health physics procedures. These comprise precautions and control of tritium, training program, neutron beam sample processing, laboratory audits, inventory and leak tests, meter calibration, repair and evaluation, radioactive waste management, and emergency response. In addition, the radiation monitoring systems will be reviewed including confinement building monitoring, ventilation filter radiation monitors, secondary coolant monitors, gaseous fission product monitors, gas monitors, ventilation tritium monitor, and the plant effluent monitor systems.

Measurements and usage of cross sections of various (n,xn) threshold reactions

NASA Astrophysics Data System (ADS)

Chudoba, P.; Vrzalová, J.; Svoboda, O.; Krása, A.; Kugler, A.; Majerle, M.; Suchopár, M.; Wagner, V.

2017-03-01

Current trend in nuclear reactor physics is a transition from technologies using thermal neutrons to technologies utilizing fast neutrons. Unfortunately focus was put mainly on the thermal neutrons for a long time and lead to very good knowledge about this low energy region, but very scarce coverage of the high energy region. This means that there is a gap in the knowledge of excitation functions for higher energies. This gap spreads from 20 MeV up to 1 GeV and higher. This is exactly the energy region needed for description of advanced nuclear systems such as accelerator driven systems (ADS). Our group from Nuclear Physics Institute (NPI) of the CAS is a member of an international collaboration Energy & Transmutation of Radioactive Waste (E&T RAW). This collaboration focuses on ADS for many years. In order to measure neutron field within ADS models it is necessary to know excitation functions of reactions used to monitor the neutron field. In many cases there are almost no experimental data for suitable reactions. Worse and quite common case is that there are no data at all. Therefore we are also focusing on measurements of these data in order to fill the databases as well as to allow further improvements of codes for nuclear data calculations.

Neutron beam flux monitors in coaxial and planar geometry for neutron scattering instruments at Dhruva reactor

NASA Astrophysics Data System (ADS)

Desai, Shraddha S.; Devan, Shylaja; Das, Amrita; Patkar, S. M.; Rao, Mala N.

2018-04-01

Neutron scattering instruments at Dhruva reactor are equipped with in house developed neutron beam flux monitors. Measurements of variations in intensity are essential to normalize the scattered neutron spectra against the reactor power fluctuations, energy of monochromatic beam, and various other factors. Two different beam monitor geometries are considered as per the beam size and optics. These detectors are fabricated with tailor-made designs to suit individual beam size and neutron flux. Pencil size beam monitors for integral intensity measurement are fabricated with coaxial geometry and BF3 fill gas for high n-gamma discrimination and count rate capability. Brass cathode design is modified to SS based rugged design, considering beam transmission. Coaxial beam monitor partially intercepts the collimated beam and gives relative magnitude of the flux with time. For certain experiments, size of beam varies due to use of focusing monochromator. Thus a beam monitor with square sensitive region covering entire beam is essential. Multiwire based planar detector for use in transmission mode is designed. Negligible absorption of neutron beam intensity within the detector hardware is ensured. Design of detectors is tailor made for beam geometry. Both these types of beam monitors are fabricated and characterized at G2 beam line and Triple Axis Spectrometer at Dhruva reactor. Performance of detector is suitable for the beam monitoring up to neutron flux ˜ 106 n/cm2/sec. Design aspects and performance details of these beam monitors are mentioned in the paper.

Heliospheric Modulation Strength During The Neutron Monitor Era

NASA Astrophysics Data System (ADS)

Usoskin, I. G.; Alanko, K.; Mursula, K.; Kovaltsov, G. A.

Using a stochastic simulation of a one-dimensional heliosphere we calculate galactic cosmic ray spectra at the Earth's orbit for different values of the heliospheric mod- ulation strength. Convoluting these spectra with the specific yield function of a neu- tron monitor, we obtain the expected neutron monitor count rates for different values of the modulation strength. Finally, inverting this relation, we calculate the modula- tion strength using the actually recorded neutron monitor count rates. We present the reconstructed annual heliospheric modulation strengths for the neutron monitor era (1953­2000) using several neutron monitors from different latitudes, covering a large range of geomagnetic rigidity cutoffs from polar to equatorial regions. The estimated modulation strengths are shown to be in good agreement with the corresponding esti- mates reported earlier for some years.

Application of pixel-cell detector technology for Advanced Neutron Beam Monitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kopp, Daniel M.

2011-01-11

Application of Pixel-Cell Detector Technology for Advanced Neutron Beam Monitors Specifications of currently available neutron beam detectors limit their usefulness at intense neutron beams of large-scale national user facilities used for the advanced study of materials. A large number of neutron-scattering experiments require beam monitors to operate in an intense neutron beam flux of >10E+7 neutrons per second per square centimeter. For instance, a 4 cm x 4 cm intense beam flux of 6.25 x 10E+7 n/s/cm2 at the Spallation Neutron Source will put a flux of 1.00 x 10E+9 n/s at the beam monitor. Currently available beam monitors withmore » a typical efficiency of 1 x 10E-4 will need to be replaced in less than two years of operation due to wire and gas degradation issues. There is also a need at some instruments for beam position information that are beyond the capabilities of currently available He-3 and BF3 neutron beam monitors. ORDELA, Inc.’s research under USDOE SBIR Grant (DE-FG02-07ER84844) studied the feasibility of using pixel-cell technology for developing a new generation of stable, long-life neutron beam monitors. The research effort has led to the development and commercialization of advanced neutron beam detectors that will directly benefit the Spallation Neutron Source and other intense neutron sources such as the High Flux Isotope Reactor. A prototypical Pixel-Cell Neutron Beam Monitor was designed and constructed during this research effort. This prototype beam monitor was exposed to an intense neutron beam at the HFIR SNS HB-2 test beam site. Initial measurements on efficiency, uniformity across the detector, and position resolution yielded excellent results. The development and test results have provided the required data to initiate the fabrication and commercialization of this next generation of neutron-detector systems. ORDELA, Inc. has (1) identified low-cost design and fabrication strategies, (2) developed and built pixel-cell detectors and instrumented a 64-pixel-cell detector to specifications for the Cold-Neutron Chopper Spectrometer and POWGEN instruments, (3) investigated the general characteristics of this technology, (4) studied pixel-cell configurations and arrived at an optimized modular design, and (5) evaluated fabrication costs of mass production for these configurations. The resulting technology will enable a complete line of pixel-cell-based neutron detectors to be commercially under available. ORDELA, Inc has a good track history of application of innovative technology into the marketplace. Our commercialization record reflects this. For additional information, please contact Daniel Kopp at ORDELA, Inc. at +1 (865) 483-8675 or check our website at www.ordela.com.« less

Neutronic analysis of the 1D and 1E banks reflux detection system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blanchard, A.

1999-12-21

Two H Canyon neutron monitoring systems for early detection of postulated abnormal reflux conditions in the Second Uranium Cycle 1E and 1D Mixer-Settle Banks have been designed and built. Monte Carlo neutron transport simulations using the general purpose, general geometry, n-particle MCNP code have been performed to model expected response of the monitoring systems to varying conditions.The confirmatory studies documented herein conclude that the 1E and 1D neutron monitoring systems are able to achieve adequate neutron count rates for various neutron source and detector configurations, thereby eliminating excessive integration count time. Neutron count rate sensitivity studies are also performed. Conversely,more » the transport studies concluded that the neutron count rates are statistically insensitive to nitric acid content in the aqueous region and to the transition region length. These studies conclude that the 1E and 1D neutron monitoring systems are able to predict the postulated reflux conditions for all examined perturbations in the neutron source and detector configurations. In the cases examined, the relative change in the neutron count rates due to postulated transitions from normal {sup 235}U concentration levels to reflux levels remain satisfactory detectable.« less

Improved determination of the neutron lifetime.

PubMed

Yue, A T; Dewey, M S; Gilliam, D M; Greene, G L; Laptev, A B; Nico, J S; Snow, W M; Wietfeldt, F E

2013-11-27

The most precise determination of the neutron lifetime using the beam method was completed in 2005 and reported a result of τ(n)=(886.3±1.2[stat]±3.2[syst]) s. The dominant uncertainties were attributed to the absolute determination of the fluence of the neutron beam (2.7 s). The fluence was measured with a neutron monitor that counted the neutron-induced charged particles from absorption in a thin, well-characterized 6Li deposit. The detection efficiency of the monitor was calculated from the areal density of the deposit, the detector solid angle, and the evaluated nuclear data file, ENDF/B-VI 6Li(n,t)4He thermal neutron cross section. In the current work, we measure the detection efficiency of the same monitor used in the neutron lifetime measurement with a second, totally absorbing neutron detector. This direct approach does not rely on the 6Li(n,t)4He cross section or any other nuclear data. The detection efficiency is consistent with the value used in 2005 but is measured with a precision of 0.057%, which represents a fivefold improvement in the uncertainty. We verify the temporal stability of the neutron monitor through ancillary measurements, allowing us to apply the measured neutron monitor efficiency to the lifetime result from the 2005 experiment. The updated lifetime is τ(n)=(887.7±1.2[stat]±1.9[syst]) s.

Development of real-time thermal neutron monitor using boron-loaded plastic scintillator with optical fiber for boron neutron capture therapy.

PubMed

Ishikawa, M; Ono, K; Sakurai, Y; Unesaki, H; Uritani, A; Bengua, G; Kobayashi, T; Tanaka, K; Kosako, T

2004-11-01

A new thermal neutron monitor for boron neutron capture therapy was developed in this study. We called this monitor equipped boron-loaded plastic scintillator that uses optical fiber for signal transmission as an [scintillator with optical fiber] SOF detector. A water phantom experiment was performed to verify how the SOF detector compared with conventional method of measuring thermal neutron fluence. Measurements with a single SOF detector yielded indistinguishable signals for thermal neutrons and gamma rays. To account for the gamma ray contribution in the signal recorded by the SOF detector, a paired SOF detector system was employed. This was composed of an SOF detector with boron-loaded scintillator and an SOF detector with a boron-free scintillator. The difference between the recorded counts of these paired SOF detectors was used as the measure of the gamma ray contribution in the measured neutron fluence. The paired SOF detectors were ascertained to be effective in measuring thermal neutron flux in the range above 10(6)(n/cm(2)/s). Clinical trials using paired SOF to measure thermal neutron flux during therapy confirmed that paired SOF detectors were effective as a real-time thermal neutron flux monitor.

Improved Determination of the Neutron Lifetime

NASA Astrophysics Data System (ADS)

Yue, A.

2013-10-01

The most precise determination of the neutron lifetime using the beam method reported a result of τn = (886 . 3 +/- 3 . 4) s. The dominant uncertainties were attributed to the absolute determination of the fluence of the neutron beam (2.7 s). The fluence was determined with a monitor that counted the neutron-induced charged particles from absorption in a thin, well-characterized 6Li deposit. The detection efficiency of the monitor was calculated from the areal density of the deposit, the detector solid angle, and the ENDF/B-VI 6Li(n,t)4He thermal neutron cross section. We have used a second, totally-absorbing neutron detector to directly measure the detection efficiency of the monitor on a monochromatic neutron beam of precisely known wavelength. This method does not rely on the 6Li(n,t)4He cross section or any other nuclear data. The monitor detection efficiency was measured to an uncertainty of 0.06%, which represents a five-fold improvement in uncertainty. We have verified the temporal stability of the monitor with ancillary measurements, and the measured neutron monitor efficiency has been used to improve the fluence determination in the past lifetime experiment. An updated neutron lifetime based on the improved fluence determination will be presented. Work done in collaboration with M. Dewey, D. Gilliam, J. Nico, National Institute of Standards and Technology; G. Greene, University of Tennessee / Oak Ridge National Laboratory; A. Laptev, Los Alamos National Laboratory; W. Snow, Indiana University; and F. Wietfeldt, Tulane University.

14 MeV calibration of JET neutron detectors—phase 1: calibration and characterization of the neutron source

NASA Astrophysics Data System (ADS)

Batistoni, P.; Popovichev, S.; Cufar, A.; Ghani, Z.; Giacomelli, L.; Jednorog, S.; Klix, A.; Lilley, S.; Laszynska, E.; Loreti, S.; Packer, L.; Peacock, A.; Pillon, M.; Price, R.; Rebai, M.; Rigamonti, D.; Roberts, N.; Tardocchi, M.; Thomas, D.; Contributors, JET

2018-02-01

In view of the planned DT operations at JET, a calibration of the JET neutron monitors at 14 MeV neutron energy is needed using a 14 MeV neutron generator deployed inside the vacuum vessel by the JET remote handling system. The target accuracy of this calibration is  ±10% as also required by ITER, where a precise neutron yield measurement is important, e.g. for tritium accountancy. To achieve this accuracy, the 14 MeV neutron generator selected as the calibration source has been fully characterised and calibrated prior to the in-vessel calibration of the JET monitors. This paper describes the measurements performed using different types of neutron detectors, spectrometers, calibrated long counters and activation foils which allowed us to obtain the neutron emission rate and the anisotropy of the neutron generator, i.e. the neutron flux and energy spectrum dependence on emission angle, and to derive the absolute emission rate in 4π sr. The use of high resolution diamond spectrometers made it possible to resolve the complex features of the neutron energy spectra resulting from the mixed D/T beam ions reacting with the D/T nuclei present in the neutron generator target. As the neutron generator is not a stable neutron source, several monitoring detectors were attached to it by means of an ad hoc mechanical structure to continuously monitor the neutron emission rate during the in-vessel calibration. These monitoring detectors, two diamond diodes and activation foils, have been calibrated in terms of neutrons/counts within  ±5% total uncertainty. A neutron source routine has been developed, able to produce the neutron spectra resulting from all possible reactions occurring with the D/T ions in the beam impinging on the Ti D/T target. The neutron energy spectra calculated by combining the source routine with a MCNP model of the neutron generator have been validated by the measurements. These numerical tools will be key in analysing the results from the in-vessel calibration and to derive the response of the JET neutron detectors to DT plasma neutrons starting from the response to the generator neutrons, and taking into account all the calibration circumstances.

Development of Neutron Energy Spectral Signatures for Passive Monitoring of Spent Nuclear Fuels in Dry Cask Storage

NASA Astrophysics Data System (ADS)

Harkness, Ira; Zhu, Ting; Liang, Yinong; Rauch, Eric; Enqvist, Andreas; Jordan, Kelly A.

2018-01-01

Demand for spent nuclear fuel dry casks as an interim storage solution has increased globally and the IAEA has expressed a need for robust safeguards and verification technologies for ensuring the continuity of knowledge and the integrity of radioactive materials inside spent fuel casks. Existing research has been focusing on "fingerprinting" casks based on count rate statistics to represent radiation emission signatures. The current research aims to expand to include neutron energy spectral information as part of the fuel characteristics. First, spent fuel composition data are taken from the Next Generation Safeguards Initiative Spent Fuel Libraries, representative for Westinghouse 17ˣ17 PWR assemblies. The ORIGEN-S code then calculates the spontaneous fission and (α,n) emissions for individual fuel rods, followed by detailed MCNP simulations of neutrons transported through the fuel assemblies. A comprehensive database of neutron energy spectral profiles is to be constructed, with different enrichment, burn-up, and cooling time conditions. The end goal is to utilize the computational spent fuel library, predictive algorithm, and a pressurized 4He scintillator to verify the spent fuel assemblies inside a cask. This work identifies neutron spectral signatures that correlate with the cooling time of spent fuel. Both the total and relative contributions from spontaneous fission and (α,n) change noticeably with respect to cooling time, due to the relatively short half-life (18 years) of the major neutron source 244Cm. Identification of this and other neutron spectral signatures allows the characterization of spent nuclear fuels in dry cask storage.

Method for Monitoring of Neutron Fields near High-Energy Accelerators

NASA Astrophysics Data System (ADS)

Beskrovnaia, L. G.; Guseva, S. V.; Timoshenko, G. N.

2018-05-01

The monitoring of neutron radiation from high-energy accelerators cannot fully rely on the standard dosimeters and radiometers manufactured in Russia, since these are sensitive only to neutrons with energies below some 10 MeV. This is because neutrons of higher energies can significantly contribute to the personnel doses both close to the accelerator shield and in the neutron multiscattered field around the shield. In this paper, we propose to measure the ambient neutron dose in energy range 10-2 MeV to 1 GeV with a device consisting of two polyethylene balls with diameters of 3 and 10 in. housing slow-neutron detectors. The larger ball also comprises a lead converter (10'' + Pb). This device can be implemented in zonal radiation monitoring in the near-accelerator area.

Measurement of the Neutron Lifetime with Ultra-cold Neutrons Stored in a Magneto-gravitational Trap

NASA Astrophysics Data System (ADS)

Ezhov, V. F.; Andreev, A. Z.; Ban, G.; Bazarov, B. A.; Geltenbort, P.; Glushkov, A. G.; Knyazkov, V. A.; Kovrizhnykh, N. A.; Krygin, G. B.; Naviliat-Cuncic, O.; Ryabov, V. L.

2018-05-01

We report a measurement of the neutron lifetime using ultra-cold neutrons stored in a magneto-gravitational trap made of permanent magnets. Neutrons surviving in the trap after fixed storage times have been counted and the trap losses have continuously been monitored during storage by detecting neutrons leaking from the trap. The value of the neutron lifetime resulting from this measurement is τ n = (878.3 ± 1.6stat ± 1.0syst) s. A unique feature of this experiment is the monitoring of leaking neutrons providing a robust control of the main systematic loss.

Fast neutron mutants database and web displays at SoyBase

USDA-ARS?s Scientific Manuscript database

SoyBase, the USDA-ARS soybean genetics and genomics database, has been expanded to include data for the fast neutron mutants produced by Bolon, Vance, et al. In addition to the expected text and sequence homology searches and visualization of the indels in the context of the genome sequence viewer, ...

From a single Neutron Monitor to an International Network: the Real-Time Database for High-Resolution Neutron Monitor Measurements (NMDB)

NASA Astrophysics Data System (ADS)

Steigies, C. T.

2016-12-01

Cosmic rays are routinely measured by standardized ground-based Neutron Monitors (NM) around the world. Stations provide measurements as 1-hour averages to the World-Data Center for Cosmic Rays, but most stations can also provide high-resolution measurements at 1-minute cadence. Measurements of one station provide information about the cosmic ray intensity over time at this location. By correcting the measurement for changes in atmospheric pressure, the intensity of the incoming radiation at the top of the atmosphere can be determined. Studying this time series gives information about long-term changes in the heliospheric environment (11 and 22 year solar cycles), as well as information on shorter (Forbush decrease, Fd) and impulsive (Ground Level Enhancement, GLE) events. Since the measurement of a NM is a cumulative measurement a single station can provide only limited information on the spectrum of the incoming radiation. The whole network of Neutron Monitors, however, can act as a large spectrometer. By combining the measurements of many NM stations, the direction and the spectrum of the incoming radiation can be modeled. With this method, high energy solar particle events (that lead to GLEs) and the precursors of Coronal Mass Ejections (CME, manifesting as a Fd) can be detected by the ground-based instruments before the lower energy particles can harm satellites or astronauts. These ALERT systems require the availability of NM data in real-time, which wass one of the goals of the NMDB project. The easy to use NEST interface (nest.nmdb.eu) to NMDB data allows everyone to plot and download data for all participating stations. Since the project started, not only space agencies and ALERT systems make use of the data, but NMDB has attracted several users outside the cosmic ray community. This data is now also used for example as reference value for soil humidity measurements with cosmic rays, or by the DHS for radiation monitors at border crossings, as well as for computer companies testing the susceptibility of their ICs to cosmic rays. These new uses have only become possible since the individual stations have agreed to share their data freely. We encourage all NM stations that are not yet part of NMDB to join the network, and the space and funding agencies to continue to support these important measurements.

Measurements of the (n,2n) Reaction Cross Section of 181Ta from 8 to 15 MeV

NASA Astrophysics Data System (ADS)

Bhatia, C.; Gooden, M. E.; Tornow, W.; Tonchev, A. P.

2014-05-01

The cross section for the reaction 181Ta(n,2n)180Tag was measured from 8 to 15 MeV in small energy steps to resolve inconsistencies in the existing databases. The activation technique was used, and the 93.4 keV γ-ray from the decay of the 180Tag ground state was recorded with a HPGe detector. In addition, the γ-rays from the monitor reactions 27Al(n,α)24Na and 197Au(n,2n)196Au were measured for neutron fluence determination. As a cross check, a calibrated neutron detector was also used. The ENDF/B-VII.1 and TENDL-2011 evaluations are in considerable disagreement with the present data, which in turn agree very well with the majority of the existing data in the 14 MeV energy region.

Search for solar neutrons using NM-64 equipment

NASA Technical Reports Server (NTRS)

Martinic, N. J.; Reguerin, A.; Palenque, E.; Taquichiri, M. A.; Wada, M.; Inoue, A.; Takahashi, K.

1985-01-01

Two years (1980 to 1982) neutron monitor data from the Chacaltaya (geographic coordinates: N16.32 deg W68. 15 deg; cutoff rigidity: 13.1 GV; altitude: 5,300 m a.s.l.) station has been scanned; the sampling time of the 12NM-64 neutron monitor is 5 min. The nucleonic component increases have been correlated with 66 hard X-, gamma rays satellite data from solar origin, as reported by several groups. Typical neutron monitor time profiles of the events are presented. Chree-analysis was performed discriminating the events according to its solar coordinates. Ground data from solar limb locii are more enhanced at the time of the onset than other geometrically visible flares. Chree histograms of neutron monitor output profiles are also presented from geometrically invisible events from the Chacaltaya station.

Acceleration, Transport, Forecasting and Impact of solar energetic particles in the framework of the 'HESPERIA' HORIZON 2020 project

NASA Astrophysics Data System (ADS)

Malandraki, Olga; Klein, Karl-Ludwig; Vainio, Rami; Agueda, Neus; Nunez, Marlon; Heber, Bernd; Buetikofer, Rolf; Sarlanis, Christos; Crosby, Norma

2017-04-01

High-energy solar energetic particles (SEPs) emitted from the Sun are a major space weather hazard motivating the development of predictive capabilities. In this work, the current state of knowledge on the origin and forecasting of SEP events will be reviewed. Subsequently, we will present the EU HORIZON2020 HESPERIA (High Energy Solar Particle Events foRecastIng and Analysis) project, its structure, its main scientific objectives and forecasting operational tools, as well as the added value to SEP research both from the observational as well as the SEP modelling perspective. The project addresses through multi-frequency observations and simulations the chain of processes from particle acceleration in the corona, particle transport in the magnetically complex corona and interplanetary space to the detection near 1 AU. Furthermore, publicly available software to invert neutron monitor observations of relativistic SEPs to physical parameters that can be compared with space-borne measurements at lower energies is provided for the first time by HESPERIA. In order to achieve these goals, HESPERIA is exploiting already available large datasets stored in databases such as the neutron monitor database (NMDB) and SEPServer that were developed under EU FP7 projects from 2008 to 2013. Forecasting results of the two novel SEP operational forecasting tools published via the consortium server of 'HESPERIA' will be presented, as well as some scientific key results on the acceleration, transport and impact on Earth of high-energy particles. Acknowledgement: This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 637324.

Application of an ultraminiature thermal neutron monitor for irradiation field study of accelerator-based neutron capture therapy

PubMed Central

Ishikawa, Masayori; Tanaka, Kenichi; Endo, Satrou; Hoshi, Masaharu

2015-01-01

Abstract Phantom experiments to evaluate thermal neutron flux distribution were performed using the Scintillator with Optical Fiber (SOF) detector, which was developed as a thermal neutron monitor during boron neutron capture therapy (BNCT) irradiation. Compared with the gold wire activation method and Monte Carlo N-particle (MCNP) calculations, it was confirmed that the SOF detector is capable of measuring thermal neutron flux as low as 105 n/cm2/s with sufficient accuracy. The SOF detector will be useful for phantom experiments with BNCT neutron fields from low-current accelerator-based neutron sources. PMID:25589504

Study of an External Neutron Source for an Accelerator-Driven System using the PHITS Code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sugawara, Takanori; Iwasaki, Tomohiko; Chiba, Takashi

A code system for the Accelerator Driven System (ADS) has been under development for analyzing dynamic behaviors of a subcritical core coupled with an accelerator. This code system named DSE (Dynamics calculation code system for a Subcritical system with an External neutron source) consists of an accelerator part and a reactor part. The accelerator part employs a database, which is calculated by using PHITS, for investigating the effect related to the accelerator such as the changes of beam energy, beam diameter, void generation, and target level. This analysis method using the database may introduce some errors into dynamics calculations sincemore » the neutron source data derived from the database has some errors in fitting or interpolating procedures. In this study, the effects of various events are investigated to confirm that the method based on the database is appropriate.« less

Recent Research applications at the Athens Neutron Monitor Station

NASA Astrophysics Data System (ADS)

Mavromichalaki, H.; Gerontidou, M.; Paschalis, P.; Papaioannou, A.; Paouris, E.; Papailiou, M.; Souvatzoglou, G.

2015-08-01

The ground based neutron monitor measurements play a key role in the field of space physics, solar-terrestrial relations, and space weather applications. The Athens cosmic ray group has developed several research applications such as an optimized automated Ground Level Enhancement Alert (GLE Alert Plus) and a web interface, providing data from multiple Neutron Monitor stations (Multi-Station tool). These services are actually available via the Space Weather Portal operated by the European Space Agency (http://swe.ssa.esa.int). In addition, two simulation tools, based on Geant4, have also been implemented. The first one is for the simulation of the cosmic ray showers in the atmosphere (DYASTIMA) and the second one is for the simulation of the 6NM-64 neutron monitor. The contribution of the simulation tools to the calculations of the radiation dose received by air crews and passengers within the Earth's atmosphere and to the neutron monitor study is presented as well. Furthermore, the accurate calculation of the barometric coefficient and the primary data processing by filtering algorithms, such as the well known Median Editor and the developed by the Athens group ANN Algorithm and Edge Editor which contribute to the provision of high quality neutron monitor data are also discussed. Finally, a Space Weather Forecasting Center which provides a three day geomagnetic activity report on a daily basis has been set up and has been operating for the last two years at the Athens Neutron Monitor Station.

The First Ground-Level Enhancement of Solar Cycle 24 on 17 May 2012 and Its Real-Time Detection

NASA Astrophysics Data System (ADS)

Papaioannou, A.; Souvatzoglou, G.; Paschalis, P.; Gerontidou, M.; Mavromichalaki, H.

2014-01-01

Ground-level enhancements (GLEs) are defined as sudden increases in the recorded intensity of cosmic-ray particles, usually by neutron monitors (NMs). In this work we present a time-shifting analysis (TSA) for the first arriving particles that were detected at Earth by NMs. We also present an automated real-time GLE alert that has been developed and is operating via the Neutron Monitor Database (NMDB), which successfully identified the 17 May 2012 event, designated as GLE71. We discuss the time evolution of the real-time GLE alert that was issued for GLE71 and present the event onset-time for NMs that contributed to this GLE alert based on their archived data. A comparison with their real-time time-stamp was made to illustrate the necessity for high-resolution data ( e.g. 1-min time resolution) made available at every minute. The first results on the propagation of relativistic protons that have been recorded by NMs, as inferred by the TSA, imply that they are most probably accelerated by the coronal-mass-ejection-driven shock. Furthermore, the successful usage of NM data and the corresponding achievement of issuing a timely GLE alert are discussed.

Novel methods for aircraft corrosion monitoring

NASA Astrophysics Data System (ADS)

Bossi, Richard H.; Criswell, Thomas L.; Ikegami, Roy; Nelson, James; Normand, Eugene; Rutherford, Paul S.; Shrader, John E.

1995-07-01

Monitoring aging aircraft for hidden corrosion is a significant problem for both military and civilian aircraft. Under a Wright Laboratory sponsored program, Boeing Defense & Space Group is investigating three novel methods for detecting and monitoring hidden corrosion: (1) atmospheric neutron radiography, (2) 14 MeV neutron activation analysis and (3) fiber optic corrosion sensors. Atmospheric neutron radiography utilizes the presence of neutrons in the upper atmosphere as a source for interrogation of the aircraft structure. Passive track-etch neutron detectors, which have been previously placed on the aircraft, are evaluated during maintenance checks to assess the presence of corrosion. Neutrons generated by an accelerator are used via activation analysis to assess the presence of distinctive elements in corrosion products, particularly oxygen. By using fast (14 MeV) neutrons for the activation, portable, high intensity sources can be employed for field testing of aircraft. The third novel method uses fiber optics as part of a smart structure technology for corrosion detection and monitoring. Fiber optic corrosion sensors are placed in the aircraft at locations known to be susceptible to corrosion. Periodic monitoring of the sensors is used to alert maintenance personnel to the presence and degree of corrosion at specific locations on the aircraft. During the atmospheric neutron experimentation, we identified a fourth method referred to as secondary emission radiography (SER). This paper discusses the development of these methods.

Gamma-Ray Signatures Improvement of the EURITRACK Tagged Neutron Inspection System Database

NASA Astrophysics Data System (ADS)

Kanawati, Wassila El; Carasco, Cedric; Perot, Bertrand; Mariani, Alain; Raoux, Anne-Cecile; Valkovic, Vladivoj; Sudac, Davorin; Obhodas, Jasmina; Baricevic, Martina

2010-10-01

The EURopean Illicit TRAfficking Countermeasures Kit (EURITRACK) inspection system uses 14 MeV neutrons produced by the D(T,n α) reaction to detect explosives in cargo containers. Reactions induced by fast neutrons inside the container produce gamma rays, which are detected in coincidence with the associated alpha particle, the detection of which allows the neutron direction to be determined. The neutron path length is obtained from a neutron time-of-flight measurement, thus allowing the origin of the gamma rays inside the container to be determined, while the chemical composition of the target material is correlated with their energy spectrum. Gamma-ray spectra have been collected with the inspection portal equipped with large volume NaI (Tl) detectors, in order to build a database of signatures for various elements (C, O, N, Fe, Pb, Al, Na, Si, Cl, Cu, Zn) with a low energy threshold of 0.6 MeV. The spectra are compared with previous ones, which were acquired with a 1.35 MeV threshold. The new library is currently being tested to unfold the energy spectra of transported goods into elemental contributions. Results are compared with data processed with the old 1.35 MeV threshold database, thus illustrating the improvement for material identification.

Suggestions for improving the efficiency of ground-based neutron monitors for detecting solar neutrons

NASA Technical Reports Server (NTRS)

Iucci, N.; Parisi, M.; Signorini, C.; Storini, M.; Villoresi, G.

1985-01-01

On the occasion of the June 3, 1982 intense gamma-ray solar flare a significant increase in counting rate due to solar neutrons was observed by the neutron monitors of Junsfraujoch and Lomnicky Stit located at middle latitudes and high altitudes. In spite of a larger detector employed and of the smaller solar zenith angle, the amplitude of the same event observed at Rome was much smaller and the statistical fluctuations of the salactic cosmic ray background higher than the ones registered at the two mountain stations, because of the greater atmospheric depth at which the Rome monitor is located. The effeciency for detecting a solar neutron event by a NM-64 monitor as a function of the Sun zenith angle, atmospheric depth and threshold rigidity of the station was studied.

Power monitoring in space nuclear reactors using silicon carbide radiation detectors

NASA Technical Reports Server (NTRS)

Ruddy, Frank H.; Patel, Jagdish U.; Williams, John G.

2005-01-01

Space reactor power monitors based on silicon carbide (SiC) semiconductor neutron detectors are proposed. Detection of fast leakage neutrons using SiC detectors in ex-core locations could be used to determine reactor power: Neutron fluxes, gamma-ray dose rates and ambient temperatures have been calculated as a function of distance from the reactor core, and the feasibility of power monitoring with SiC detectors has been evaluated at several ex-core locations. Arrays of SiC diodes can be configured to provide the required count rates to monitor reactor power from startup to full power Due to their resistance to temperature and the effects of neutron and gamma-ray exposure, SiC detectors can be expected to provide power monitoring information for the fill mission of a space reactor.

Monitoring of the Irradiated Neutron Fluence in the Neutron Transmutation Doping Process of Hanaro

NASA Astrophysics Data System (ADS)

Kim, Myong-Seop; Park, Sang-Jun

2009-08-01

Neutron transmutation doping (NTD) for silicon is a process of the creation of phosphorus impurities in intrinsic or extrinsic silicon by neutron irradiation to obtain silicon semiconductors with extremely uniform dopant distribution. HANARO has two vertical holes for the NTD, and the irradiation for 5 and 6 inch silicon ingots has been going on at one hole. In order to achieve the accurate neutron fluence corresponding to the target resistivity, the real time neutron flux is monitored by self-powered neutron detectors. After irradiation, the total irradiation fluence is confirmed by measuring the absolute activity of activation detectors. In this work, a neutron fluence monitoring method using zirconium foils with the mass of 10 ~ 50 mg was applied to the NTD process of HANARO. We determined the proportional constant of the relationship between the resistivity of the irradiated silicon and the neutron fluence determined by using zirconium foils. The determined constant for the initially n-type silicon was 3.126 × 1019 n·Ω/cm. It was confirmed that the difference between this empirical value and the theoretical one was only 0.5%. Conclusively, the practical methodology to perform the neutron transmutation doping of silicon was established.

Construction of 144, 565 keV and 5.0 MeV monoenergetic neutron calibration fields at JAERI.

PubMed

Tanimura, Y; Yoshizawa, M; Saegusa, J; Fujii, K; Shimizu, S; Yoshida, M; Shibata, Y; Uritani, A; Kudo, K

2004-01-01

Monoenergetic neutron calibration fields of 144, 565 keV and 5.0 MeV have been developed at the Facility of Radiation Standards of JAERI using a 4 MV Pelletron accelerator. The 7Li(p,n)7Be and 2H(d,n)3He reactions are employed for neutron production. The neutron energy was measured by the time-of-flight method with a liquid scintillation detector and calculated with the MCNP-ANT code. A long counter is employed as a neutron monitor because of the flat response. The monitor is set up where the influence of inscattered neutrons from devices and their supporting materials at a calibration point is as small as possible. The calibration coefficients from the monitor counts to the neutron fluence at a calibration point were obtained from the reference fluence measured with the transfer instrument of the primary standard laboratory (AIST), a 24.13 cm phi Bonner sphere counter. The traceability of the fields to AIST was established through the calibration.

Strategy for the absolute neutron emission measurement on ITER.

PubMed

Sasao, M; Bertalot, L; Ishikawa, M; Popovichev, S

2010-10-01

Accuracy of 10% is demanded to the absolute fusion measurement on ITER. To achieve this accuracy, a functional combination of several types of neutron measurement subsystem, cross calibration among them, and in situ calibration are needed. Neutron transport calculation shows the suitable calibration source is a DT/DD neutron generator of source strength higher than 10(10) n/s (neutron/second) for DT and 10(8) n/s for DD. It will take eight weeks at the minimum with this source to calibrate flux monitors, profile monitors, and the activation system.

Calibration of ITER Instant Power Neutron Monitors: Recommended Scenario of Experiments at the Reactor

NASA Astrophysics Data System (ADS)

Borisov, A. A.; Deryabina, N. A.; Markovskij, D. V.

2017-12-01

Instant power is a key parameter of the ITER. Its monitoring with an accuracy of a few percent is an urgent and challenging aspect of neutron diagnostics. In a series of works published in Problems of Atomic Science and Technology, Series: Thermonuclear Fusion under a common title, the step-by-step neutronics analysis was given to substantiate a calibration technique for the DT and DD modes of the ITER. A Gauss quadrature scheme, optimal for processing "expensive" experiments, is used for numerical integration of 235U and 238U detector responses to the point sources of 14-MeV neutrons. This approach allows controlling the integration accuracy in relation to the number of coordinate mesh points and thus minimizing the number of irradiations at the given uncertainty of the full monitor response. In the previous works, responses of the divertor and blanket monitors to the isotropic point sources of DT and DD neutrons in the plasma profile and to the models of real sources were calculated within the ITER model using the MCNP code. The neutronics analyses have allowed formulating the basic principles of calibration that are optimal for having the maximum accuracy at the minimum duration of in situ experiments at the reactor. In this work, scenarios of the preliminary and basic experimental ITER runs are suggested on the basis of those principles. It is proposed to calibrate the monitors only with DT neutrons and use correction factors to the DT mode calibration for the DD mode. It is reasonable to perform full calibration only with 235U chambers and calibrate 238U chambers by responses of the 235U chambers during reactor operation (cross-calibration). The divertor monitor can be calibrated using both direct measurement of responses at the Gauss positions of a point source and simplified techniques based on the concepts of equivalent ring sources and inverse response distributions, which will considerably reduce the amount of measurements. It is shown that the monitor based on the average responses of the horizontal and vertical neutron chambers remains spatially stable as the source moves and can be used in addition to the staff monitor at neutron fluxes in the detectors four orders of magnitude lower than on the first wall, where staff detectors are located. Owing to low background, detectors of neutron chambers do not need calibration in the reactor because it is actually determination of the absolute detector efficiency for 14-MeV neutrons, which is a routine out-of-reactor procedure.

Monitoring Short-term Cosmic-ray Spectral Variations Using Neutron Monitor Time-delay Measurements

NASA Astrophysics Data System (ADS)

Ruffolo, D.; Sáiz, A.; Mangeard, P.-S.; Kamyan, N.; Muangha, P.; Nutaro, T.; Sumran, S.; Chaiwattana, C.; Gasiprong, N.; Channok, C.; Wuttiya, C.; Rujiwarodom, M.; Tooprakai, P.; Asavapibhop, B.; Bieber, J. W.; Clem, J.; Evenson, P.; Munakata, K.

2016-01-01

Neutron monitors (NMs) are ground-based detectors of cosmic-ray showers that are widely used for high-precision monitoring of changes in the Galactic cosmic-ray (GCR) flux due to solar storms and solar wind variations. In the present work, we show that a single neutron monitor station can also monitor short-term changes in the GCR spectrum, avoiding the systematic uncertainties in comparing data from different stations, by means of NM time-delay histograms. Using data for 2007-2014 from the Princess Sirindhorn Neutron Monitor, a station at Doi Inthanon, Thailand, with the world’s highest vertical geomagnetic cutoff rigidity of 16.8 GV, we have developed an analysis of time-delay histograms that removes the chance coincidences that can dominate conventional measures of multiplicity. We infer the “leader fraction” L of neutron counts that do not follow a previous neutron count in the same counter from the same atmospheric secondary, which is inversely related to the actual multiplicity and increases for increasing GCR spectral index. After correction for atmospheric pressure and water vapor, we find that L indicates substantial short-term GCR spectral hardening during some but not all Forbush decreases in GCR flux due to solar storms. Such spectral data from Doi Inthanon provide information about cosmic-ray energies beyond the Earth’s maximum geomagnetic cutoff, extending the reach of the worldwide NM network and opening a new avenue in the study of short-term GCR decreases.

MONITORING SHORT-TERM COSMIC-RAY SPECTRAL VARIATIONS USING NEUTRON MONITOR TIME-DELAY MEASUREMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruffolo, D.; Sáiz, A.; Mangeard, P.-S.

Neutron monitors (NMs) are ground-based detectors of cosmic-ray showers that are widely used for high-precision monitoring of changes in the Galactic cosmic-ray (GCR) flux due to solar storms and solar wind variations. In the present work, we show that a single neutron monitor station can also monitor short-term changes in the GCR spectrum, avoiding the systematic uncertainties in comparing data from different stations, by means of NM time-delay histograms. Using data for 2007–2014 from the Princess Sirindhorn Neutron Monitor, a station at Doi Inthanon, Thailand, with the world’s highest vertical geomagnetic cutoff rigidity of 16.8 GV, we have developed anmore » analysis of time-delay histograms that removes the chance coincidences that can dominate conventional measures of multiplicity. We infer the “leader fraction” L of neutron counts that do not follow a previous neutron count in the same counter from the same atmospheric secondary, which is inversely related to the actual multiplicity and increases for increasing GCR spectral index. After correction for atmospheric pressure and water vapor, we find that L indicates substantial short-term GCR spectral hardening during some but not all Forbush decreases in GCR flux due to solar storms. Such spectral data from Doi Inthanon provide information about cosmic-ray energies beyond the Earth’s maximum geomagnetic cutoff, extending the reach of the worldwide NM network and opening a new avenue in the study of short-term GCR decreases.« less

Absorbed dose rates in tissue from prompt gamma emissions from near-thermal neutron absorption

DOE PAGES

Schwahn, Scott O.

2015-10-01

Prompt gamma emission data from the International Atomic Energy Agency s Prompt Gamma-ray Neutron Activation Analysis database are analyzed to determine the absorbed dose rates in tissue to be expected when natural elements are exposed in a near-thermal neutron environment.

Comparisons of monthly mean cosmic ray counting rates observes from worldwide network of neutron monitors

NASA Technical Reports Server (NTRS)

Ryu, J. Y.; Wada, M.

1985-01-01

In order to examine the stability of neutron monitor observation, each of the monthly average counting rates of a neutron monitors is correlated to those of Kiel neutron monitor. The regression coefficients thus obtained are compared with the coupling coefficients of isotropic intensity radiation. The results of the comparisons for five year periods during 1963 to 1982, and for whole period are given. The variation spectrum with a single power law with an exponent of -0.75 up to 50 GV is not so unsatisfactory one. More than one half of the stations show correlations with the coefficient greater than 0.9. Some stations have shifted the level of mean counting rates by changing the instrumental characteristics which can be adjusted.

Coupling functions for lead and lead-free neutron monitors from the latitudinal measurements performed in 1982 in the research station Academician Kurchatov

NASA Technical Reports Server (NTRS)

Alekanyan, T. M.; Dorman, L. I.; Yanke, V. G.; Korotkov, V. K.

1985-01-01

The latitudinal behavior of intensities and multiplicities was registered by the neutron monitor 2 NM and the lead-free neutron monitor 3 SND (slow-neuron detector) in the equator-Kaliningrad line in the Atlantic Ocean. Coupling coefficients for 3 SND show the sensitivity of this detector to primary particles of cosmic rays of energies on the average lower than for 2 NM. As multiplicities increase, the coupling coefficients shift towards higher energies.

Wireless, in-vessel neutron monitor for initial core-loading of advanced breeder reactors

NASA Technical Reports Server (NTRS)

Delorenzo, J. T.; Kennedy, E. J.; Blalock, T. V.; Rochelle, J. M.; Chiles, M. M.; Valentine, K. H.

1981-01-01

An experimental wireless, in-vessel neutron monitor was developed to measure the reactivity of an advanced breeder reactor as the core is loaded for the first time to preclude an accidental critically incident. The environment is liquid sodium at a temperature of approx. 220 C, with negligible gamma or neutron radiation. With ultrasonic transmission of neutron data, no fundamental limitation was observed after tests at 230 C for 2000 h. The neutron sensitivity was approx. 1 count/s-nv, and the potential data transmission rate was approx. 10,000 counts/s.

Assessment of the neutron cross section database for mercury for the ORNL spallation source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leal, L.C.; Spencer, R.R.; Ingersoll, D.T.

1996-06-01

Neutron source generation based on a high energy particle accelerator has been considered as an alternative to the canceled Advanced Neutron Source project at Oak Ridge National Laboratory. The proposed technique consists of a spallation neutron source in which neutrons are produced via the interaction of high-energy charged particles in a heavy metal target. Preliminary studies indicate that liquid mercury bombarded with GeV protons provides an excellent neutron source. Accordingly, a survey has been made of the available neutron cross-section data. Since it is expected that spectral modifiers, specifically moderators, will also be incorporated into the source design, the surveymore » included thermal energy, resonance region, and high energy data. It was found that data of individual isotopes were almost non-existent and that the only evaluation found for the natural element had regions of missing data or discrepant data. Therefore, it appears that to achieve the desired degree of accuracy in the spallation source design it is necessary to re-evaluate the mercury database including making new measurements. During the presentation the currently available data will be presented and experiments proposed which can lead to design quality cross sections.« less

Vadose Zone Transport Field Study: Status Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gee, Glendon W.; Ward, Anderson L.

2001-11-30

Studies were initiated at the Hanford Site to evaluate the process controlling the transport of fluids in the vadose zone and to develop a reliable database upon which vadose-zone transport models can be calibrated. These models are needed to evaluate contaminant migration through the vadose zone to underlying groundwaters at Hanford. A study site that had previously been extensively characterized using geophysical monitoring techniques was selected in the 200 E Area. Techniques used previously included neutron probe for water content, spectral gamma logging for radionuclide tracers, and gamma scattering for wet bulk density. Building on the characterization efforts of themore » past 20 years, the site was instrumented to facilitate the comparison of nine vadose-zone characterization methods: advanced tensiometers, neutron probe, electrical resistance tomography (ERT), high-resolution resistivity (HRR), electromagnetic induction imaging (EMI), cross-borehole radar (XBR), and cross-borehole seismic (XBS). Soil coring was used to obtain soil samples for analyzing ionic and isotopic tracers.« less

STATUS OF VARIOUS SNS DIAGNOSTIC SYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blokland, Willem; Purcell, J David; Patton, Jeff

2007-01-01

The Spallation Neutron Source (SNS) accelerator systems are ramping up to deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. Enhancements or additions have been made to several instrument systems to support the ramp up in intensity, improve reliability, and/or add functionality. The Beam Current Monitors now support increased rep rates, the Harp system now includes charge density calculations for the target, and a new system has been created to collect data for the beam accounting and present the data over the web and to the operator consoles. The majority of themore » SNS beam instruments are PC-based and their configuration files are now managed through the Oracle relational database. A new version for the wire scanner software was developed to add features to correlate the scan with beam loss, parking in the beam, and measuring the longitudinal beam current. This software is currently being tested. This paper also includes data from the selected instruments.« less

Study of the triton-burnup process in different JET scenarios using neutron monitor based on CVD diamond

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nemtsev, G., E-mail: g.nemtsev@iterrf.ru; Amosov, V.; Meshchaninov, S.

We present the results of analysis of triton burn-up process using the data from diamond detector. Neutron monitor based on CVD diamond was installed in JET torus hall close to the plasma center. We measure the part of 14 MeV neutrons in scenarios where plasma current varies in a range of 1-3 MA. In this experiment diamond neutron monitor was also able to detect strong gamma bursts produced by runaway electrons arising during the disruptions. We can conclude that CVD diamond detector will contribute to the study of fast particles confinement and help predict the disruption events in future tokamaks.

New measurement system for on line in core high-energy neutron flux monitoring in materials testing reactor conditions.

PubMed

Geslot, B; Vermeeren, L; Filliatre, P; Lopez, A Legrand; Barbot, L; Jammes, C; Bréaud, S; Oriol, L; Villard, J-F

2011-03-01

Flux monitoring is of great interest for experimental studies in material testing reactors. Nowadays, only the thermal neutron flux can be monitored on line, e.g., using fission chambers or self-powered neutron detectors. In the framework of the Joint Instrumentation Laboratory between SCK-CEN and CEA, we have developed a fast neutron detector system (FNDS) capable of measuring on line the local high-energy neutron flux in fission reactor core and reflector locations. FNDS is based on fission chambers measurements in Campbelling mode. The system consists of two detectors, one detector being mainly sensitive to fast neutrons and the other one to thermal neutrons. On line data processing uses the CEA depletion code DARWIN in order to disentangle fast and thermal neutrons components, taking into account the isotopic evolution of the fissile deposit. The first results of FNDS experimental test in the BR2 reactor are presented in this paper. Several fission chambers have been irradiated up to a fluence of about 7 × 10(20) n∕cm(2). A good agreement (less than 10% discrepancy) was observed between FNDS fast flux estimation and reference flux measurement.

New measurement system for on line in core high-energy neutron flux monitoring in materials testing reactor conditions

NASA Astrophysics Data System (ADS)

Geslot, B.; Vermeeren, L.; Filliatre, P.; Lopez, A. Legrand; Barbot, L.; Jammes, C.; Bréaud, S.; Oriol, L.; Villard, J.-F.

2011-03-01

Flux monitoring is of great interest for experimental studies in material testing reactors. Nowadays, only the thermal neutron flux can be monitored on line, e.g., using fission chambers or self-powered neutron detectors. In the framework of the Joint Instrumentation Laboratory between SCK-CEN and CEA, we have developed a fast neutron detector system (FNDS) capable of measuring on line the local high-energy neutron flux in fission reactor core and reflector locations. FNDS is based on fission chambers measurements in Campbelling mode. The system consists of two detectors, one detector being mainly sensitive to fast neutrons and the other one to thermal neutrons. On line data processing uses the CEA depletion code DARWIN in order to disentangle fast and thermal neutrons components, taking into account the isotopic evolution of the fissile deposit. The first results of FNDS experimental test in the BR2 reactor are presented in this paper. Several fission chambers have been irradiated up to a fluence of about 7 × 1020 n/cm2. A good agreement (less than 10% discrepancy) was observed between FNDS fast flux estimation and reference flux measurement.

High Conduction Neutron Absorber to Simulate Fast Reactor Environment in an Existing Test Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guillen, Donna; Greenwood, Lawrence R.; Parry, James

2014-06-22

A need was determined for a thermal neutron absorbing material that could be cooled in a gas reactor environment without using large amounts of a coolant that would thermalize the neutron flux. A new neutron absorbing material was developed that provided high conduction so a small amount of water would be sufficient for cooling thereby thermalizing the flux as little as possible. An irradiation experiment was performed to assess the effects of radiation and the performance of a new neutron absorbing material. Neutron fluence monitors were placed inside specially fabricated holders within a set of drop-in capsules and irradiated formore » up to four cycles in the Advanced Test Reactor. Following irradiation, the neutron fluence monitor wires were analyzed by gamma and x-ray spectrometry to determine the activities of the activation products. The adjusted neutron fluences were calculated and grouped into three bins – thermal, epithermal and fast to evaluate the spectral shift created by the new material. Fluence monitors were evaluated after four different irradiation periods to evaluate the effects of burn-up in the absorbing material. Additionally, activities of the three highest activity isotopes present in the specimens are given.« less

High conduction neutron absorber to simulate fast reactor environment in an existing test reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donna Post Guillen; Larry R. Greenwood; James R. Parry

2014-06-22

A new metal matrix composite material has been developed to serve as a thermal neutron absorber for testing fast reactor fuels and materials in an existing pressurized water reactor. The performance of this material was evaluated by placing neutron fluence monitors within shrouded and unshrouded holders and irradiating for up to four cycles. The monitor wires were analyzed by gamma and X-ray spectrometry to determine the activities of the activation products. Adjusted neutron fluences were calculated and grouped into three bins—thermal, epithermal, and fast—to evaluate the spectral shift created by the new material. A comparison of shrouded and unshrouded fluencemore » monitors shows a thermal fluence decrease of ~11 % for the shielded monitors. Radioisotope activity and mass for each of the major activation products is given to provide insight into the evolution of thermal absorption cross-section during irradiation. The thermal neutron absorption capability of the composite material appears to diminish at total neutron fluence levels of ~8 × 1025 n/m2. Calculated values for dpa in excess of 2.0 were obtained for two common structural materials (iron and nickel) of interest for future fast flux experiments.« less

FIELD CALIBRATION OF A TLD ALBEDO DOSEMETER IN THE HIGH-ENERGY NEUTRON FIELD OF CERF.

PubMed

Haninger, T; Kleinau, P; Haninger, S

2017-04-28

The new albedo dosemeter-type AWST-TL-GD 04 has been calibrated in the CERF neutron field (Cern-EU high-energy Reference Field). This type of albedo dosemeter is based on thermoluminescent detectors (TLDs) and used by the individual monitoring service of the Helmholtz Zentrum München (AWST) since 2015 for monitoring persons, who are exposed occupationally against photon and neutron radiation. The motivation for this experiment was to gain a field specific neutron correction factor Nn for workplaces at high-energy particle accelerators. Nn is a dimensionless factor relative to a basic detector calibration with 137Cs and is used to calculate the personal neutron dose in terms of Hp(10) from the neutron albedo signal. The results show that the sensitivity of the albedo dosemeter for this specific neutron field is not significantly lower as for fast neutrons of a radionuclide source like 252Cf. The neutron correction factor varies between 0.73 and 1.16 with a midrange value of 0.94. The albedo dosemeter is therefore appropriate to monitor persons, which are exposed at high-energy particle accelerators. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Optical Sensors for Monitoring Gamma and Neutron Radiation

NASA Technical Reports Server (NTRS)

Boyd, Clark D.

2011-01-01

For safety and efficiency, nuclear reactors must be carefully monitored to provide feedback that enables the fission rate to be held at a constant target level via adjustments in the position of neutron-absorbing rods and moderating coolant flow rates. For automated reactor control, the monitoring system should provide calibrated analog or digital output. The sensors must survive and produce reliable output with minimal drift for at least one to two years, for replacement only during refueling. Small sensor size is preferred to enable more sensors to be placed in the core for more detailed characterization of the local fission rate and fuel consumption, since local deviations from the norm tend to amplify themselves. Currently, reactors are monitored by local power range meters (LPRMs) based on the neutron flux or gamma thermometers based on the gamma flux. LPRMs tend to be bulky, while gamma thermometers are subject to unwanted drift. Both electronic reactor sensors are plagued by electrical noise induced by ionizing radiation near the reactor core. A fiber optic sensor system was developed that is capable of tracking thermal neutron fluence and gamma flux in order to monitor nuclear reactor fission rates. The system provides near-real-time feedback from small- profile probes that are not sensitive to electromagnetic noise. The key novel feature is the practical design of fiber optic radiation sensors. The use of an actinoid element to monitor neutron flux in fiber optic EFPI (extrinsic Fabry-Perot interferometric) sensors is a new use of material. The materials and structure used in the sensor construction can be adjusted to result in a sensor that is sensitive to just thermal, gamma, or neutron stimulus, or any combination of the three. The tested design showed low sensitivity to thermal and gamma stimuli and high sensitivity to neutrons, with a fast response time.

Gadolinium-doped water cerenkov-based neutron and high energy gamma-ray detector and radiation portal monitoring system

DOEpatents

Dazeley, Steven A; Svoboda, Robert C; Bernstein, Adam; Bowden, Nathaniel

2013-02-12

A water Cerenkov-based neutron and high energy gamma ray detector and radiation portal monitoring system using water doped with a Gadolinium (Gd)-based compound as the Cerenkov radiator. An optically opaque enclosure is provided surrounding a detection chamber filled with the Cerenkov radiator, and photomultipliers are optically connected to the detect Cerenkov radiation generated by the Cerenkov radiator from incident high energy gamma rays or gamma rays induced by neutron capture on the Gd of incident neutrons from a fission source. The PMT signals are then used to determine time correlations indicative of neutron multiplicity events characteristic of a fission source.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harker, Y.D.

On August 3-4, 1994, an INEL team made measurements related to a real-time monitoring system for use on the epithermal beam facility at the BMRR. BNL has installed two fission chambers in front of the beam collimator, which are to monitor the beam coming from the reactor. These two monitors are located with one just above the 16-cm dia. front aperture and the other is just below. The fission chambers contain depleted uranium, but because of the small amount of U-235 present, they respond to thermal and near thermal neutrons rather than fast neutrons. This feature combined with their relativelymore » small size (0.6 cm dia x 4 cm long) makes them very good monitors in the BMRR epithermal neutron beam. The INEL team worked with H.B. Lui (BNL) in performing initial tests of these monitors and established the settings to achieve stable operation. The main purpose of the measurement studies was to establish a basis for a monitoring method that tracks the dose the patient is receiving rather than the neutron fluence being delivered down the beam line.« less

Cosmic Rays and Clouds, 1. Formation of Lead Mesoatoms In Neutron Monitor By Soft Negative Muons and Expected Atmospheric Electric Field Effect In The Cosmic Ray Neutron Component

NASA Astrophysics Data System (ADS)

Dorman, L. I.; Dorman, I. V.

We extend our model (Dorman and Dorman, 1995) of cosmic ray atmospheric electric field effect on the case of neutron monitor. We take into account that about 0.07 of neu- tron monitor counting rate caused by negative soft muons captured by lead nucleons and formed mesoatoms with generation of several MeV energy neutrons from lead. In this case the neutron monitor or neutron supermonitor works as analyzer which de- tects muons of only one, negative sign. It is very important because the atmospheric electric field effect have opposite signs for positive and negative muons that main part of this effect in the muon telescope or in ionization chamber is compensated and we can observe only small part of total effect of one sign muons. On the basis of our gen- eral theory of cosmic ray meteorological effects with taking into account of negative soft muon acceleration and deceleration in the Earth atmosphere (in dependence of di- rection and intensity of electric field) we discuss the possibility of existing this effect in cosmic ray neutron component and made some rough estimations. REFERENCES: Dorman L.I. and Dorman I.V., 1995. "Cosmic-ray atmospheric electric field effects". Canadian J. of Physics, Vol. 73, pp. 440-443.

Mini Neutron Monitors at Concordia Research Station, Central Antarctica

NASA Astrophysics Data System (ADS)

Poluianov, Stepan; Usoskin, Ilya; Mishev, Alexander; Moraal, Harm; Kruger, Helena; Casasanta, Giampietro; Traversi, Rita; Udisti, Roberto

2015-12-01

Two mini neutron monitors are installed at Concordia research station (Dome C, Central Antarctica, 75° 06' S, 123° 23' E, 3,233 m.a.s.l.). The site has unique properties ideal for cosmic ray measurements, especially for the detection of solar energetic particles: very low cutoff rigidity < 0.01 GV, high elevation and poleward asymptotic acceptance cones pointing to geographical latitudes > 75° S. The instruments consist of a standard neutron monitor and a "bare" (lead-free) neutron monitor. The instrument operation started in mid-January 2015. The barometric correction coefficients were computed for the period from 1 February to 31 July 2015. Several interesting events, including two notable Forbush decreases on 17 March 2015 and 22 June 2015, and a solar particle event of 29 October 2015 were registered. The data sets are available at cosmicrays.oulu.fi and nmdb.eu.

Determination of the thermal and epithermal neutron sensitivities of an LBO chamber.

PubMed

Endo, Satoru; Sato, Hitoshi; Shimazaki, Takuto; Nakajima, Erika; Kotani, Kei; Suda, Mitsuru; Hamano, Tsuyoshi; Kajimoto, Tsuyoshi; Tanaka, Kenichi; Hoshi, Masaharu

2017-08-01

An LBO (Li 2 B 4 O 7 ) walled ionization chamber was designed to monitor the epithermal neutron fluence in boron neutron capture therapy clinical irradiation. The thermal and epithermal neutron sensitivities of the device were evaluated using accelerator neutrons from the 9 Be(d, n) reaction at a deuteron energy of 4 MeV (4 MeV d-Be neutrons). The response of the chamber in terms of the electric charge induced in the LBO chamber was compared with the thermal and epithermal neutron fluences measured using the gold-foil activation method. The thermal and epithermal neutron sensitivities obtained were expressed in units of pC cm 2 , i.e., from the chamber response divided by neutron fluence (cm -2 ). The measured LBO chamber sensitivities were 2.23 × 10 -7  ± 0.34 × 10 -7 (pC cm 2 ) for thermal neutrons and 2.00 × 10 -5  ± 0.12 × 10 -5 (pC cm 2 ) for epithermal neutrons. This shows that the LBO chamber is sufficiently sensitive to epithermal neutrons to be useful for epithermal neutron monitoring in BNCT irradiation.

Early clinical experience utilizing scintillator with optical fiber (SOF) detector in clinical boron neutron capture therapy: its issues and solutions.

PubMed

Ishikawa, Masayori; Yamamoto, Tetsuya; Matsumura, Akira; Hiratsuka, Junichi; Miyatake, Shin-Ichi; Kato, Itsuro; Sakurai, Yoshinori; Kumada, Hiroaki; Shrestha, Shubhechha J; Ono, Koji

2016-08-09

Real-time measurement of thermal neutrons in the tumor region is essential for proper evaluation of the absorbed dose in boron neutron capture therapy (BNCT) treatment. The gold wire activation method has been routinely used to measure the neutron flux distribution in BNCT irradiation, but a real-time measurement using gold wire is not possible. To overcome this issue, the scintillator with optical fiber (SOF) detector has been developed. The purpose of this study is to demonstrate the feasibility of the SOF detector as a real-time thermal neutron monitor in clinical BNCT treatment and also to report issues in the use of SOF detectors in clinical practice and their solutions. Clinical measurements using the SOF detector were carried out in 16 BNCT clinical trial patients from December 2002 until end of 2006 at the Japanese Atomic Energy Agency (JAEA) and Kyoto University Research Reactor Institute (KURRI). The SOF detector worked effectively as a real-time thermal neutron monitor. The neutron fluence obtained by the gold wire activation method was found to differ from that obtained by the SOF detector. The neutron fluence obtained by the SOF detector was in better agreement with the expected fluence than with gold wire activation. The estimation error for the SOF detector was small in comparison to the gold wire measurement. In addition, real-time monitoring suggested that the neutron flux distribution and intensity at the region of interest (ROI) may vary due to the reactor condition, patient motion and dislocation of the SOF detector. Clinical measurements using the SOF detector to measure thermal neutron flux during BNCT confirmed that SOF detectors are effective as a real-time thermal neutron monitor. To minimize the estimation error due to the displacement of the SOF probe during treatment, a loop-type SOF probe was developed.

Nuclear Forensics and Radiochemistry: Cross Sections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rundberg, Robert S.

The neutron activation of components in a nuclear device can provide useful signatures of weapon design or sophistication. This lecture will cover some of the basics of neutron reaction cross sections. Nuclear reactor cross sections will also be presented to illustrate the complexity of convolving neutron energy spectra with nuclear excitation functions to calculate useful effective reactor cross sections. Deficiencies in the nuclear database will be discussed along with tools available at Los Alamos to provide new neutron cross section data.

Preview of the BATSE Earth Occultation Catalog of Low Energy Gamma Ray Sources

NASA Technical Reports Server (NTRS)

Harmon, B. A.; Wilson, C. A.; Fishman, G. J.; McCollough, M. L.; Robinson, C. R.; Sahi, M.; Paciesas, W. S.; Zhang, S. N.

1999-01-01

The Burst and Transient Source Experiment (BATSE) aboard the Compton Gamma Ray Observatory (CGRO) has been detecting and monitoring point sources in the high energy sky since 1991. Although BATSE is best known for gamma ray bursts, it also monitors the sky for longer-lived sources of radiation. Using the Earth occultation technique to extract flux information, a catalog is being prepared of about 150 sources potential emission in the large area detectors (20-1000 keV). The catalog will contain light curves, representative spectra, and parametric data for black hole and neutron star binaries, active galaxies, and super-nova remnants. In this preview, we present light curves for persistent and transient sources, and also show examples of what type of information can be obtained from the BATSE Earth occultation database. Options for making the data easily accessible as an "on line" WWW document are being explored.

Neutron Deep Penetration Calculations in Light Water with Monte Carlo TRIPOLI-4® Variance Reduction Techniques

NASA Astrophysics Data System (ADS)

Lee, Yi-Kang

2017-09-01

Nuclear decommissioning takes place in several stages due to the radioactivity in the reactor structure materials. A good estimation of the neutron activation products distributed in the reactor structure materials impacts obviously on the decommissioning planning and the low-level radioactive waste management. Continuous energy Monte-Carlo radiation transport code TRIPOLI-4 has been applied on radiation protection and shielding analyses. To enhance the TRIPOLI-4 application in nuclear decommissioning activities, both experimental and computational benchmarks are being performed. To calculate the neutron activation of the shielding and structure materials of nuclear facilities, the knowledge of 3D neutron flux map and energy spectra must be first investigated. To perform this type of neutron deep penetration calculations with the Monte Carlo transport code, variance reduction techniques are necessary in order to reduce the uncertainty of the neutron activation estimation. In this study, variance reduction options of the TRIPOLI-4 code were used on the NAIADE 1 light water shielding benchmark. This benchmark document is available from the OECD/NEA SINBAD shielding benchmark database. From this benchmark database, a simplified NAIADE 1 water shielding model was first proposed in this work in order to make the code validation easier. Determination of the fission neutron transport was performed in light water for penetration up to 50 cm for fast neutrons and up to about 180 cm for thermal neutrons. Measurement and calculation results were benchmarked. Variance reduction options and their performance were discussed and compared.

Study of neutron generation in the compact tokamak TUMAN-3M in support of a tokamak-based fusion neutron source

NASA Astrophysics Data System (ADS)

Kornev, V. A.; Askinazi, L. G.; Belokurov, A. A.; Chernyshev, F. V.; Lebedev, S. V.; Melnik, A. D.; Shabelsky, A. A.; Tukachinsky, A. S.; Zhubr, N. A.

2017-12-01

The paper presents DD neutron flux measurements in neutron beam injection (NBI) experiments aimed at the optimization of target plasma and heating beam parameters to achieve maximum neutron flux in the TUMAN-3M compact tokamak. Two ion sources of different design were used, which allowed the separation of the beam’s energy and power influence on the neutron rate. Using the database of experiments performed with the two ion sources, an empirical scaling was derived describing the neutron rate dependence on the target plasma and heating beam parameters. Numerical modeling of the neutron rate in the NBI experiments performed using the ASTRA transport code showed good agreement with the scaling.

SU-E-T-108: Development of a Novel Clinical Neutron Dose Monitor for Proton Therapy Based On Twin TLD500 Chips in a Small PE Moderator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hentschel, R; Mukherjee, B

2014-06-01

Purpose: In proton therapy, it could be desirable to measure out-of-field fast neutron doses at critical locations near and outside the patient body. Methods: The working principle of a novel clinical neutron dose monitor is verified by MCNPX simulation. The device is based on a small PE moderator of just 5.5cm side length for easy handling covered with a thermal neutron suppression layer. In the simulation, a polystyrene phantom is bombarded with a standard proton beam. The secondary thermal neutron flux produced inside the moderator by the impinging fast neutrons from the treatment volume is estimated by pairs of α-Al2O3:Cmore » (TLD500) chips which are evaluated offline after the treatment either by TL or OSL methods. The first chip is wrapped with 0.5mm natural Gadolinium foil converting the thermal neutrons to gammas via (n,γ) reaction. The second chip is wrapped with a dummy material. The chip centers have a distance of 2cm from each other. Results: The simulation shows that the difference of gamma doses in the TLD500 chips is correlated to the mean fast neutron dose delivered to the moderator material. Different outer shielding materials have been studied. 0.5mm Cadmium shielding is preferred for cost reasons and convenience. Replacement of PE moderator material by other materials like lead or iron at any place is unfavorable. The spatial orientation of the moderator cube is uncritical. Using variance reduction techniques like splitting/Russian roulette, the TLD500 gamma dose simulation give positive differences up to distances of 0.5m from the treatment volume. Conclusion: Applicability and basic layout of a novel clinical neutron dose monitor are demonstrated. The monitor measures PE neutron doses at locations outside the patient body up to distances of 0.5m from the treatment volume. Tissue neutron doses may be calculated using neutron kerma factors.« less

Progress in the development of the neutron flux monitoring system of the French GEN-IV SFR: simulations and experimental validations [ANIMMA--2015-IO-98

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jammes, C.; Filliatre, P.; De Izarra, G.

The neutron flux monitoring system of the French GEN-IV sodium-cooled fast reactor will rely on high temperature fission chambers installed in the reactor vessel and capable of operating over a wide-range neutron flux. The definition of such a system is presented and the technological solutions are justified with the use of simulation and experimental results. (authors)

Spectra of solar proton ground level events using neutron monitor and neutron moderated detector recordings

NASA Technical Reports Server (NTRS)

Stoker, P. H.

1985-01-01

Recordings on relativistic solar flare protons observed at Sanae, Antarctic, show that the percentage increase in counting rates of the neutron moderated detector (4NMD) is larger than the percentage increase in counting rates of the 3NM64 neutron monitor. These relative increases are described by solar proton differential spectra j sub s(P) = AP(beta). The power beta is determined for each event and the hardnesses of the temporal variations of beta, found for the ground level events (GLE) of 7 May, 1978 and 22 November, 1977.

Characteristics of cosmic ray pole-equator anisotropy derived from spherical harmonic analysis of neutron monitor data

NASA Technical Reports Server (NTRS)

Takahashi, H.; Yahagi, N.

1985-01-01

The spherical harmonic analysis of cosmic ray neutron data from the worldwide network neutron monitor stations during the years, 1966 to 1969 was carried out. The second zonal harmonic component obtained from the analysis corresponds to the Pole-Equator anisotropy of the cosmic ray neutron intensity. Such an anisotropy makes a semiannual variation. In addition to this, it is shown that the Pole-Equator anisotropy makes a variation depending on the interplanetary magnetic field (IMF) sector polarities around the passages of the IMF sector boundary. A mechanism to interpret these results is also discussed.

Time dependent 14 MeV neutrons measurement using a polycrystalline chemical vapor deposited diamond detector at the JET tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Angelone, M.; Pillon, M.; Bertalot, L.

A polycrystalline chemical vapor deposited (CVD) diamond detector was installed on a JET tokamak in order to monitor the time dependent 14 MeV neutron emission produced by D-T plasma pulses during the Trace Tritium Experiment (TTE) performed in October 2003. This was the first tentative ever attempted to use a CVD diamond detector as neutron monitor in a tokamak environment. Despite its small active volume, the detector was able to detect the 14 MeV neutron emission (>1.0x10{sup 15} n/shot) with good reliability and stability during the experimental campaign that lasted five weeks. The comparison with standard silicon detectors presently usedmore » at JET as 14 MeV neutron monitors is reported, showing excellent correlation between the measurements. The results prove that CVD diamond detectors can be reliably used in a tokamak environment and therefore confirm the potential of this technology for next step machines like ITER.« less

The Self-Powered Detector Simulation `MATiSSe' Toolbox applied to SPNDs for severe accident monitoring in PWRs

NASA Astrophysics Data System (ADS)

Barbot, Loïc; Villard, Jean-François; Fourrez, Stéphane; Pichon, Laurent; Makil, Hamid

2018-01-01

In the framework of the French National Research Agency program on nuclear safety and radioprotection, the `DIstributed Sensing for COrium Monitoring and Safety' project aims at developing innovative instrumentation for corium monitoring in case of severe accident in a Pressurized Water nuclear Reactor. Among others, a new under-vessel instrumentation based on Self-Powered Neutron Detectors is developed using a numerical simulation toolbox, named `MATiSSe'. The CEA Instrumentation Sensors and Dosimetry Lab developed MATiSSe since 2010 for Self-Powered Neutron Detectors material selection and geometry design, as well as for their respective partial neutron and gamma sensitivity calculations. MATiSSe is based on a comprehensive model of neutron and gamma interactions which take place in Selfpowered neutron detector components using the MCNP6 Monte Carlo code. As member of the project consortium, the THERMOCOAX SAS Company is currently manufacturing some instrumented pole prototypes to be tested in 2017. The full severe accident monitoring equipment, including the standalone low current acquisition system, will be tested during a joined CEA-THERMOCOAX experimental campaign in some realistic irradiation conditions, in the Slovenian TRIGA Mark II research reactor.

TWO NEW SINGLE-EXPOSURE, MULTI-DETECTOR NEUTRON SPECTROMETERS FOR RADIATION PROTECTION APPLICATIONS IN WORKPLACE MONITORING.

PubMed

Gómez-Ros, J M; Bedogni, R; Bortot, D; Domingo, C; Esposito, A; Introini, M V; Lorenzoli, M; Mazzitelli, G; Moraleda, M; Pola, A; Sacco, D

2017-04-01

This communication describes two new instruments, based on multiple active thermal neutron detectors arranged within a single moderator, that permit to unfold the neutron spectrum (from thermal to hundreds of MeV) and to determine the corresponding integral quantities with only one exposure. This makes them especially advantageous for neutron field characterisation and workplace monitoring in neutron-producing facilities. One of the devices has spherical geometry and nearly isotropic response, the other one has cylindrical symmetry and it is only sensitive to neutrons incident along the cylinder axis. In both cases, active detectors have been specifically developed looking for the criteria of miniaturisation, high sensitivity, linear response and good photon rejection. The calculated response matrix has been validated by experimental irradiations in neutron reference fields with a global uncertainty of 3%. The measurements performed in realistic neutron fields permitted to determine the neutron spectra and the integral quantities, in particular H*(10). © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Criteria for personal dosimetry in mixed radiation fields in space. [analyzing trapped protons, tissue disintegration stars, and neutrons

NASA Technical Reports Server (NTRS)

Schaefer, H. J.

1974-01-01

The complexity of direct reading and passive dosimeters for monitoring radiation is studied to strike the right balance of compromise to simplify the monitoring procedure. Trapped protons, tissue disintegration stars, and neutrons are analyzed.

Radial Flux Distribution of Low-Energy Neutrons.

ERIC Educational Resources Information Center

Higinbotham, J.

1979-01-01

Describes an experiment designed to illustrate the basic principle involved in the process of moderation of fast neutrons by water, and the monitoring of the low-energy neutron flux using indium as a probe. (GA)

Amorphous Silicon Based Neutron Detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Liwei

2004-12-12

Various large-scale neutron sources already build or to be constructed, are important for materials research and life science research. For all these neutron sources, neutron detectors are very important aspect. However, there is a lack of a high-performance and low-cost neutron beam monitor that provides time and temporal resolution. The objective of this SBIR Phase I research, collaboratively performed by Midwest Optoelectronics, LLC (MWOE), the University of Toledo (UT) and Oak Ridge National Laboratory (ORNL), is to demonstrate the feasibility for amorphous silicon based neutron beam monitors that are pixilated, reliable, durable, fully packaged, and fabricated with high yield usingmore » low-cost method. During the Phase I effort, work as been focused in the following areas: 1) Deposition of high quality, low-defect-density, low-stress a-Si films using very high frequency plasma enhanced chemical vapor deposition (VHF PECVD) at high deposition rate and with low device shunting; 2) Fabrication of Si/SiO2/metal/p/i/n/metal/n/i/p/metal/SiO2/ device for the detection of alpha particles which are daughter particles of neutrons through appropriate nuclear reactions; and 3) Testing of various devices fabricated for alpha and neutron detection; As the main results: · High quality, low-defect-density, low-stress a-Si films have been successfully deposited using VHF PECVD on various low-cost substrates; · Various single-junction and double junction detector devices have been fabricated; · The detector devices fabricated have been systematically tested and analyzed. · Some of the fabricated devices are found to successfully detect alpha particles. Further research is required to bring this Phase I work beyond the feasibility demonstration toward the final prototype devices. The success of this project will lead to a high-performance, low-cost, X-Y pixilated neutron beam monitor that could be used in all of the neutron facilities worldwide. In addition, the technologies developed here could be used to develop X-ray and neutron monitors that could be used in the future for security checks at the airports and other critical facilities. The project would lead to devices that could significantly enhance the performance of multi-billion dollar neutron source facilities in the US and bring our nation to the forefront of neutron beam sciences and technologies which have enormous impact to materials, life science and military research and applications.« less

Phase space representation of neutron monitor count rate and atmospheric electric field in relation to solar activity in cycles 21 and 22.

PubMed

Silva, H G; Lopes, I

Heliospheric modulation of galactic cosmic rays links solar cycle activity with neutron monitor count rate on earth. A less direct relation holds between neutron monitor count rate and atmospheric electric field because different atmospheric processes, including fluctuations in the ionosphere, are involved. Although a full quantitative model is still lacking, this link is supported by solid statistical evidence. Thus, a connection between the solar cycle activity and atmospheric electric field is expected. To gain a deeper insight into these relations, sunspot area (NOAA, USA), neutron monitor count rate (Climax, Colorado, USA), and atmospheric electric field (Lisbon, Portugal) are presented here in a phase space representation. The period considered covers two solar cycles (21, 22) and extends from 1978 to 1990. Two solar maxima were observed in this dataset, one in 1979 and another in 1989, as well as one solar minimum in 1986. Two main observations of the present study were: (1) similar short-term topological features of the phase space representations of the three variables, (2) a long-term phase space radius synchronization between the solar cycle activity, neutron monitor count rate, and potential gradient (confirmed by absolute correlation values above ~0.8). Finally, the methodology proposed here can be used for obtaining the relations between other atmospheric parameters (e.g., solar radiation) and solar cycle activity.

Neutron Capture Gamma-Ray Libraries for Nuclear Applications

NASA Astrophysics Data System (ADS)

Sleaford, B. W.; Firestone, R. B.; Summers, N.; Escher, J.; Hurst, A.; Krticka, M.; Basunia, S.; Molnar, G.; Belgya, T.; Revay, Z.; Choi, H. D.

2011-06-01

The neutron capture reaction is useful in identifying and analyzing the gamma-ray spectrum from an unknown assembly as it gives unambiguous information on its composition. This can be done passively or actively where an external neutron source is used to probe an unknown assembly. There are known capture gamma-ray data gaps in the ENDF libraries used by transport codes for various nuclear applications. The Evaluated Gamma-ray Activation file (EGAF) is a new thermal neutron capture database of discrete line spectra and cross sections for over 260 isotopes that was developed as part of an IAEA Coordinated Research Project. EGAF is being used to improve the capture gamma production in ENDF libraries. For medium to heavy nuclei the quasi continuum contribution to the gamma cascades is not experimentally resolved. The continuum contains up to 90% of all the decay energy and is modeled here with the statistical nuclear structure code DICEBOX. This code also provides a consistency check of the level scheme nuclear structure evaluation. The calculated continuum is of sufficient accuracy to include in the ENDF libraries. This analysis also determines new total thermal capture cross sections and provides an improved RIPL database. For higher energy neutron capture there is less experimental data available making benchmarking of the modeling codes more difficult. We are investigating the capture spectra from higher energy neutrons experimentally using surrogate reactions and modeling this with Hauser-Feshbach codes. This can then be used to benchmark CASINO, a version of DICEBOX modified for neutron capture at higher energy. This can be used to simulate spectra from neutron capture at incident neutron energies up to 20 MeV to improve the gamma-ray spectrum in neutron data libraries used for transport modeling of unknown assemblies.

The LOFT perspective on neutron star thermonuclear bursts: White paper in support of the mission concept of the large observatory for X-ray timing

DOE Office of Scientific and Technical Information (OSTI.GOV)

in't Zand, J. J.M.; Malone, Christopher M.; Altamirano, D.

2015-01-14

The Large Area Detector (LAD) on the Large Observatory For X-ray Timing ( LOFT ), with a 8.5 m 2 photon- collecting area in the 2–30 keV bandpass at CCD-class spectral resolving power (λ/Δλ = 10 – 100), is designed for optimum performance on bright X-ray sources. Thus, it is well-suited to study thermonuclear X-ray bursts from Galactic neutron stars. These bursts will typically yield 2 x 10 5 photon detections per second in the LAD, which is at least 15 times more than with any other instrument past, current or anticipated. The Wide Field Monitor (WFM) foreseen for LOFTmore » uniquely combines 2–50 keV imaging with large (30%) prompt sky coverage. This will enable the detection of tens of thousands of thermonuclear X-ray bursts during a 3-yr mission, including tens of superbursts. Both numbers are similar or more than the current database gathered in 50 years of X-ray astronomy.« less

On the solar cycle variation in the barometer coefficients of high latitude neutron monitors

NASA Technical Reports Server (NTRS)

Kusunose, M.; Ogita, N.

1985-01-01

Evaluation of barometer coefficients of neutron monitors located at high latitudes has been performed by using the results of the spherical harmonic analysis based on the records from around twenty stations for twelve years from January 1966 to December 1977. The average of data at eight stations, where continuous records are available for twelve years, show that the absolute value of barometer coefficient is in positive correlation with the cosmic ray neutron intensity. The variation rate of the barometer coefficient to the cosmic ray neutron intensity is influenced by the changes in the cutoff rigidity and in the primary spectrum.

Neutron measurements of the OGO-VI Spacecraft

NASA Technical Reports Server (NTRS)

Lockwood, J. A.

1973-01-01

The neutron measurements with the OGO-6 spacecraft are reported. Topics discussed include: the design and calibration of a neutron monitor for measuring the cosmic ray neutron leakages from the earth's atmosphere, determination of latitude dependence of cosmic ray leakage flux, determination of the angular distribution of neutron leakage flux as deduced by measurements of the altitude dependence, and verification of the solar modulation of the cosmic ray source for the neutron leakage.

Fast response neutron emission monitor for fusion reactor using stilbene scintillator and Flash-ADC.

PubMed

Itoga, T; Ishikawa, M; Baba, M; Okuji, T; Oishi, T; Nakhostin, M; Nishitani, T

2007-01-01

The stilbene neutron detector which has been used for neutron emission profile monitoring in JT-60U has been improved, to respond to the requirement to observe the high-frequency phenomena in megahertz region such as toroidicity-induced Alfvén Eigen mode in burning plasma as well as the spatial profile and the energy spectrum. This high-frequency phenomenon is of great interest and one of the key issues in plasma physics in recent years. To achieve a fast response in the stilbene detector, a Flash-ADC is applied and the wave form of the anode signal stored directly, and neutron/gamma discrimination was carried out via software with a new scheme for data acquisition mode to extend the count rate limit to MHz region from 1.3 x 10(5) neutron/s in the past, and confirmed the adequacy of the method.

Neutron-flux profile monitor for use in a fission reactor

DOEpatents

Kopp, M.K.; Valentine, K.H.

1981-09-15

A neutron flux monitor is provided which consists of a plurality of fission counters arranged as spaced-apart point detectors along a delay line. As a fission event occurs in any one of the counters, two delayed current pulses are generated at the output of the delay line. The time separation of the pulses identifies the counter in which the particular fission event occurred. Neutron flux profiles of reactor cores can be more accurately measured as a result.

Neutron flux profile monitor for use in a fission reactor

DOEpatents

Kopp, Manfred K.; Valentine, Kenneth H.

1983-01-01

A neutron flux monitor is provided which consists of a plurality of fission counters arranged as spaced-apart point detectors along a delay line. As a fission event occurs in any one of the counters, two delayed current pulses are generated at the output of the delay line. The time separation of the pulses identifies the counter in which the particular fission event occured. Neutron flux profiles of reactor cores can be more accurately measured as a result.

Development of neutron-monitor detector using liquid organic scintillator coupled with 6Li + ZnS(Ag) Sheet.

PubMed

Sato, Tatsuhiko; Endo, Akira; Yamaguchi, Yasuhiro; Takahashi, Fumiaki

2004-01-01

A phoswitch-type detector has been developed for monitoring neutron doses in high-energy accelerator facilities. The detector is composed of a liquid organic scintillator (BC501A) coupled with ZnS(Ag) sheets doped with 6Li. The dose from neutrons with energies above 1 MeV is evaluated from the light output spectrum of the BC501A by applying the G-function, which relates the spectrum to the neutron dose directly. The dose from lower energy neutrons, on the other hand, is estimated from the number of scintillations emitted from the ZnS(Ag) sheets. Characteristics of the phoswitch-type detector were studied experimentally in some neutron fields. It was found from the experiments that the detector has an excellent property of pulse-shape discrimination between the scintillations of BC501A and the ZnS(Ag) sheets. The experimental results also indicate that the detector is capable of reproducing doses from thermal neutrons as well as neutrons with energies from one to several tens of megaelectronvolts (MeV).

Ion Acceleration in Solar Flares Determined by Solar Neutron Observations

NASA Astrophysics Data System (ADS)

Watanabe, K.; Solar Neutron Observation Group

2013-05-01

Large amounts of particles can be accelerated to relativistic energy in association with solar flares and/or accompanying phenomena (e.g., CME-driven shocks), and they sometimes reach very near the Earth and penetrate the Earth's atmosphere. These particles are observed by ground-based detectors (e.g., neutron monitors) as Ground Level Enhancements (GLEs). Some of the GLEs originate from high energy solar neutrons which are produced in association with solar flares. These neutrons are also observed by ground-based neutron monitors and solar neutron telescopes. Recently, some of the solar neutron detectors have also been operating in space. By observing these solar neutrons, we can obtain information about ion acceleration in solar flares. Such neutrons were observed in association with some X-class flares in solar cycle 23, and sometimes they were observed by two different types of detectors. For example, on 2005 September 7, large solar neutron signals were observed by the neutron monitor at Mt. Chacaltaya in Bolivia and Mexico City, and by the solar neutron telescopes at Chacaltaya and Mt. Sierra Negra in Mexico in association with an X17.0 flare. The neutron signal continued for more than 20 minutes with high statistical significance. Intense gamma-ray emission was also registered by INTEGRAL, and by RHESSI during the decay phase. We analyzed these data using the solar-flare magnetic-loop transport and interaction model of Hua et al. (2002), and found that the model could successfully fit the data with intermediate values of loop magnetic convergence and pitch angle scattering parameters. These results indicate that solar neutrons were produced at the same time as the gamma-ray line emission and that ions were continuously accelerated at the emission site. In this paper, we introduce some of the solar neutron observations in solar cycle 23, and discuss the tendencies of the physical parameters of solar neutron GLEs, and the energy spectrum and population of the accelerated particles produced in these solar flares, etc. We also report recent solar neutron observations by the Space Environment Data Acquisition equipment-Attached Payload (SEDA-AP) which has been installed on the international space station, and introduce the plan for the new solar neutron detector of the SciBar for the Cosmic Ray Telescope (SciCRT) at Mt. Sierra Negra in Mexico.

A scintillator-based approach to monitor secondary neutron production during proton therapy.

PubMed

Clarke, S D; Pryser, E; Wieger, B M; Pozzi, S A; Haelg, R A; Bashkirov, V A; Schulte, R W

2016-11-01

The primary objective of this work is to measure the secondary neutron field produced by an uncollimated proton pencil beam impinging on different tissue-equivalent phantom materials using organic scintillation detectors. Additionally, the Monte Carlo code mcnpx-PoliMi was used to simulate the detector response for comparison to the measured data. Comparison of the measured and simulated data will validate this approach for monitoring secondary neutron dose during proton therapy. Proton beams of 155- and 200-MeV were used to irradiate a variety of phantom materials and secondary particles were detected using organic liquid scintillators. These detectors are sensitive to fast neutrons and gamma rays: pulse shape discrimination was used to classify each detected pulse as either a neutron or a gamma ray. The mcnpx-PoliMi code was used to simulate the secondary neutron field produced during proton irradiation of the same tissue-equivalent phantom materials. An experiment was performed at the Loma Linda University Medical Center proton therapy research beam line and corresponding models were created using the mcnpx-PoliMi code. The authors' analysis showed agreement between the simulations and the measurements. The simulated detector response can be used to validate the simulations of neutron and gamma doses on a particular beam line with or without a phantom. The authors have demonstrated a method of monitoring the neutron component of the secondary radiation field produced by therapeutic protons. The method relies on direct detection of secondary neutrons and gamma rays using organic scintillation detectors. These detectors are sensitive over the full range of biologically relevant neutron energies above 0.5 MeV and allow effective discrimination between neutron and photon dose. Because the detector system is portable, the described system could be used in the future to evaluate secondary neutron and gamma doses on various clinical beam lines for commissioning and prospective data collection in pediatric patients treated with proton therapy.

Results of neutron irradiation of GEM detector for plasma radiation detection

NASA Astrophysics Data System (ADS)

Jednorog, S.; Bienkowska, B.; Chernyshova, M.; Łaszynska, E.; Prokopowicz, R.; Ziołkowski, A.

2015-09-01

The detecting devices dedicated for plasma monitoring will be exposed for massive fluxes of neutron, photons as well as other rays that are components of fusion reactions and their product interactions with plasma itself or surroundings. In result detecting module metallic components will be activated becoming a source of radiation. Moreover, electronics components could change their electronic properties. The prototype GEM detector constructed for monitoring soft X-ray radiation in ITER oriented tokamaks was used for plasma monitoring during experimental campaign on tokamak ASDEX Upgrade. After that it became a source of gamma radiation caused by neutrons. The present work contains description of detector activation in the laboratory conditions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burgett, Eric; Al-Sheikhly, Mohamad; Summers, Christopher

An advanced in-pile multi-parameter reactor monitoring system is being proposed in this funding opportunity. The proposed effort brings cutting edge, high-fidelity optical measurement systems into the reactor environment in an unprecedented fashion, including in-core, in-cladding and in-fuel pellet itself. Unlike instrumented leads, the proposed system provides a unique solution to a multi-parameter monitoring need in core while being minimally intrusive in the reactor core. Detector designs proposed herein can monitor fuel compression and expansion in both the radial and axial dimensions as well as monitor linear power profiles and fission rates during the operation of the reactor. In addition tomore » pressure, stress, strain, compression, neutron flux, neutron spectra, and temperature can be observed inside the fuel bundle and fuel rod using the proposed system. The proposed research aims at developing radiation-hard, harsh-environment multi-parameter systems for insertion into the reactor environment. The proposed research holds the potential to drastically increase the fidelity and precision of in-core instrumentation with little or no impact in the neutron economy in the reactor environment while providing a measurement system capable of operation for entire operating cycles. Significant work has been done over the last few years on the use of nanoparticle-based scintillators. Through the use of metamaterials, the PIs aim to develop planar neutron detectors and large-volume neutron detectors. These detectors will have high efficiencies for neutron detection and will have a high gamma discrimination capability.« less

High Hydrogen Content Graphene Hydride Compounds & High Cross-­ Section Cladding Coatings for Fast Neutron Detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chandrashekhar, MVS

The objective is to develop and implement a superior low-cost, large area (potentially >32in), easily deployable, close proximity, harsh environment innovative neutron sensor needed for next generation fuel cycle monitoring. We will exploit recent breakthroughs at the PI’s lab on the electrochemistry of epitaxial graphene (EG) formed on commercial SiC wafers, a transformative nanomaterial system with superior radiation detection and durability properties to develop a new paradigm in detection for fast neutrons, a by-product of fission reactors. There are currently few effective detection/monitoring schemes, especially solid-state ones at present. This is essential for monitoring and control of future fuel cyclesmore » to make them more efficient and reliable. By exploiting these novel materials, as well as innovative hybrid SiC/EG/Cladding device architectures conceived by the team, will develop low-cost, high performance solutions to fast-neutron detection. Finally, we will also explore 3-terminal device implementations for neutron detectors with built-in electronic gain to further shrink these devices and improve their sensitivity.« less

Monitoring of snowpack dynamics in mountainous terrain by cosmic-ray neutron sensing compared to Terrestrial Laser Scanning observations

NASA Astrophysics Data System (ADS)

Schattan, P.; Baroni, G.; Schrön, M.; Köhli, M.; Oswald, S. E.; Huttenlau, M.; Achleitner, S.

2017-12-01

Monitoring a mountain snowpack in a representative domain of several hectares is challenging due to its high heterogeneity in time and space. Recent studies have suggested cosmic-ray neutron sensing (CRNS) as a promising method for monitoring snow representatively at these scales. Little is known however about the depth of sensitivity, the effects of fractional snow coverage in complex terrain or the influence of snow density profiles. Therefore, a field campaign in the Austrian Alps was conducted from March 2014 to June 2016. The main scope was to evaluate the characteristics of CRNS for monitoring a snowpack in a relatively wet and mountainous environment. During the experiment, the study site experienced a peak snow accumulation in terms of snow water equivalent (SWE) of up to 600 mm in the 2014/2015 winter season. Snow depth (SD) and SWE measurements from an automatic weather station were compared to CRNS neutron counts. Several spatially distributed Terrestrial Laser Scanning (TLS)-based SD and SWE maps were additionally used to cope with the spatial heterogeneity of the site. Furthermore, an URANOS neutron transport model was set up to provide additional insights into the response of CRNS to the presence of a complex snowpack. Therein, spatially distributed SWE scenarios and different snow density assumptions are used for hypothesis testing. The field measurements revealed an unexpectedly high potential of CRNS for monitoring heterogeneous snowpack dynamics beyond shallow snowpacks. A clear, nonlinear relation was found for both SD and SWE with neutron counts. In contrast to previous studies suggesting signal saturation at around 100 mm of SWE, complete signal saturation was observed only for SWE values beyond 500 to 600 mm. In addition, first modelling results highlight the effects of snow density profiles, small-scale changes in SWE, and the complex patterns of fractional snow cover on neutron counts. Understanding the interactions between neutrons and snow cover in complex terrain potentially improves the transferability of the results to other locations.

Impact of Fission Neutron Energies on Reactor Antineutrino Spectra

NASA Astrophysics Data System (ADS)

Hermanek, Keith; Littlejohn, Bryce; Gustafson, Ian

2017-09-01

Recent measurements of the reactor antineutrino spectra (Double Chooz, Reno, and Daya Bay) have shown a discrepancy in the 5-7 MeV region when compared to current theoretical models (Vogel and Huber-Mueller). There are numerous theories pertaining to this antineutrino anomaly, including theories that point to new physics beyond the standard model. In the paper ``Possible Origins and Implications of the Shoulder in Reactor Neutrino Spectra'' by A. Hayes et al., explanations for this anomaly are suggested. One theory is that there are interactions from fast and epithermal incident neutrons which are significant enough to create more events in the 5-7 MeV by a noticeable amount. In our research, we used the Oklo software network created by Dan Dwyer. This generates ab initio antineutrino and beta decay spectra based on standard fission yield databases ENDF, JENDL, JEFF, and the beta decay transition database ENSDF-6. Utilizing these databases as inputs, we show with reasonable assumptions one can prove contributions of fast and epithermal neutrons is less than 3% in the 5-7 MeV region. We also discovered rare isotopes are present in beta decay chains but not well measured and have no corresponding database information, and studied its effect onto the spectrum.

Neutron Monitors as a Tool for Specifying Solar Energetic Particle Effects on Earth and in Near-Earth Space

NASA Astrophysics Data System (ADS)

Bieber, J. W.; Clem, J.; Evenson, P.; Kuwabara, T.; Pyle, R.; Ruffolo, D.; Saiz, A.

2007-12-01

Neutron monitors are ground-based instruments that record the byproducts of collisions between cosmic rays and molecules in Earth's atmosphere. When linked together in real-time coordinated arrays, these instruments can make valuable contributions to the specification of major solar energetic particle events. Neutron monitors can provide the earliest alert of elevated radiation levels in Earth's atmosphere caused by the arrival of relativistic solar particles (Ground Level Enhancement or GLE). Early detection of GLE is of interest to the aviation industry because of the associated radiation hazard for pilots and air crews, especially for those flying polar routes. Network observations can also be used to map, in principle in real time, the distribution of radiation in Earth's atmosphere, taking into account the particle anisotropy which can be very large in early phases of the event. Observations from the large GLE of January 20, 2005 and December 13, 2006 will be used to illustrate these applications of neutron monitors. Supported by NSF grant ATM-0527878, the Thailand Research Fund, and the Mahidol University Postdoctoral Fellowship Program.

Scintillator and solid-state neutron detectors and their applications

NASA Astrophysics Data System (ADS)

Carturan, Sara Maria; Marchi, Tommaso; Fanchini, Erica; De Vita, Raffaella; Finocchiaro, Paolo; Pappalardo, Alfio

2014-10-01

The application range of neutron detectors covers many topics, not only involving experimental research, but spanning tens of industrial, health, transport, cultural heritage fields of interest. Several studies focus on new scintillating materials where the light response, under fast and slow neutrons exposure, is triggered by proton recoil or by the presence of neutron capture materials as 10B, 6Li or 157Gd. Neutron monitors, where the robustness of silicon-based detectors can be fully exploited by coupling with suitable neutron absorber/converter materials, have recently proved their outstanding performances. Discrimination between neutron signals from other radiations, such as - or cosmic rays, is achieved through timing techniques or with pulse shape analysis. Furthermore, the choice of the detection/discrimination techniques depends on the type of application the detector will be used for. An example is Radiation Portal Monitors (RPM) for cargo inspection or luggage control that are required to satisfy specific international standards for and neutron detection efficiencies. This paper is an overview of some of the National Institute of Nuclear Physics (INFN) activities in the field of neutron detection, involving novel technologies. We will describe the most recent advances related to scintillators and silicon-based detectors coupled with thin films of suitable converters for neutron detection and we will discuss applications in the field of nuclear security.

New Organic Scintillators for Neutron Detection

DTIC Science & Technology

2016-03-01

highly enriched uranium and weapons grade plutonium. Neutrons and gamma rays are two signatures of these materials. Gamma ray detection techniques are...New Organic Scintillators for Neutron Detection Distribution Statement A. Approved for public release; distribution is unlimited. March...Title: New Organic Scintillators for Neutron Detection I. Abstract In this project, Radiation Monitoring Devices (RMD) proposes to develop novel

Measuring and monitoring KIPT Neutron Source Facility Reactivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Yan; Gohar, Yousry; Zhong, Zhaopeng

2015-08-01

Argonne National Laboratory (ANL) of USA and Kharkov Institute of Physics and Technology (KIPT) of Ukraine have been collaborating on developing and constructing a neutron source facility at Kharkov, Ukraine. The facility consists of an accelerator-driven subcritical system. The accelerator has a 100 kW electron beam using 100 MeV electrons. The subcritical assembly has k eff less than 0.98. To ensure the safe operation of this neutron source facility, the reactivity of the subcritical core has to be accurately determined and continuously monitored. A technique which combines the area-ratio method and the flux-to-current ratio method is purposed to determine themore » reactivity of the KIPT subcritical assembly at various conditions. In particular, the area-ratio method can determine the absolute reactivity of the subcritical assembly in units of dollars by performing pulsed-neutron experiments. It provides reference reactivities for the flux-to-current ratio method to track and monitor the reactivity deviations from the reference state while the facility is at other operation modes. Monte Carlo simulations are performed to simulate both methods using the numerical model of the KIPT subcritical assembly. It is found that the reactivities obtained from both the area-ratio method and the flux-to-current ratio method are spatially dependent on the neutron detector locations and types. Numerical simulations also suggest optimal neutron detector locations to minimize the spatial effects in the flux-to-current ratio method. The spatial correction factors are calculated using Monte Carlo methods for both measuring methods at the selected neutron detector locations. Monte Carlo simulations are also performed to verify the accuracy of the flux-to-current ratio method in monitoring the reactivity swing during a fuel burnup cycle.« less

Cherenkov neutron detector for fusion reaction and runaway electron diagnostics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheon, MunSeong, E-mail: munseong@nfri.re.kr; Kim, Junghee

2015-08-15

A Cherenkov-type neutron detector was newly developed and neutron measurement experiments were performed at Korea Superconducting Tokamak Advanced Research. It was shown that the Cherenkov neutron detector can monitor the time-resolved neutron flux from deuterium-fueled fusion plasmas. Owing to the high temporal resolution of the detector, fast behaviors of runaway electrons, such as the neutron spikes, could be observed clearly. It is expected that the Cherenkov neutron detector could be utilized to provide useful information on runaway electrons as well as fusion reaction rate in fusion plasmas.

Semiconductor neutron detector

DOEpatents

Ianakiev, Kiril D [Los Alamos, NM; Littlewood, Peter B [Cambridge, GB; Blagoev, Krastan B [Arlington, VA; Swinhoe, Martyn T [Los Alamos, NM; Smith, James L [Los Alamos, NM; Sullivan, Clair J [Los Alamos, NM; Alexandrov, Boian S [Los Alamos, NM; Lashley, Jason Charles [Santa Fe, NM

2011-03-08

A neutron detector has a compound of lithium in a single crystal form as a neutron sensor element. The lithium compound, containing improved charge transport properties, is either lithium niobate or lithium tantalate. The sensor element is in direct contact with a monitor that detects an electric current. A signal proportional to the electric current is produced and is calibrated to indicate the neutrons sensed. The neutron detector is particularly useful for detecting neutrons in a radiation environment. Such radiation environment may, e.g. include gamma radiation and noise.

Triple ionization chamber method for clinical dose monitoring with a Be-covered Li BNCT field.

PubMed

Nguyen, Thanh Tat; Kajimoto, Tsuyoshi; Tanaka, Kenichi; Nguyen, Chien Cong; Endo, Satoru

2016-11-01

Fast neutron, gamma-ray, and boron doses have different relative biological effectiveness (RBE). In boron neutron capture therapy (BNCT), the clinical dose is the total of these dose components multiplied by their RBE. Clinical dose monitoring is necessary for quality assurance of the irradiation profile; therefore, the fast neutron, gamma-ray, and boron doses should be separately monitored. To estimate these doses separately, and to monitor the boron dose without monitoring the thermal neutron fluence, the authors propose a triple ionization chamber method using graphite-walled carbon dioxide gas (C-CO 2 ), tissue-equivalent plastic-walled tissue-equivalent gas (TE-TE), and boron-loaded tissue-equivalent plastic-walled tissue-equivalent gas [TE(B)-TE] chambers. To use this method for dose monitoring for a neutron and gamma-ray field moderated by D 2 O from a Be-covered Li target (Be-covered Li BNCT field), the relative sensitivities of these ionization chambers are required. The relative sensitivities of the TE-TE, C-CO 2 , and TE(B)-TE chambers to fast neutron, gamma-ray, and boron doses are calculated with the particle and heavy-ion transport code system (PHITS). The relative sensitivity of the TE(B)-TE chamber is calculated with the same method as for the TE-TE and C-CO 2 chambers in the paired chamber method. In the Be-covered Li BNCT field, the relative sensitivities of the ionization chambers to fast neutron, gamma-ray, and boron doses are calculated from the kerma ratios, mass attenuation coefficient tissue-to-wall ratios, and W-values. The Be-covered Li BNCT field consists of neutrons and gamma-rays which are emitted from a Be-covered Li target, and this resultant field is simulated by using PHITS with the cross section library of ENDF-VII. The kerma ratios and mass attenuation coefficient tissue-to-wall ratios are determined from the energy spectra of neutrons and gamma-rays in the Be-covered Li BNCT field. The W-value is calculated from recoil charged particle spectra by the collision of neutrons and gamma-rays with the wall and gas materials of the ionization chambers in the gas cavities of TE-TE, C-CO 2 , and TE(B)-TE chambers ( 10 B concentrations of 10, 50, and 100 ppm in the TE-wall). The calculated relative sensitivity of the C-CO 2 chamber to the fast neutron dose in the Be-covered Li BNCT field is 0.029, and those of the TE-TE and TE(B)-TE chambers are both equal to 0.965. The relative sensitivities of the C-CO 2 , TE-TE, and TE(B)-TE chambers to the gamma-ray dose in the Be-covered Li BNCT field are all 1 within the 1% calculation uncertainty. The relative sensitivities of TE(B)-TE to boron dose with concentrations of 10, 50, and 100 ppm 10 B are calculated to be 0.865 times the ratio of the in-tumor to in-chamber wall boron concentration. The fast neutron, gamma-ray, and boron doses of a tumor in-air can be separately monitored by the triple ionization chamber method in the Be-covered Li BNCT field. The results show that these doses can be easily converted to the clinical dose with the depth correction factor in the body and the RBE.

Investigation of the response of a neutron-Hand monitor dedicated to the powder diffractometer at CENM-Maamora

DOE Office of Scientific and Technical Information (OSTI.GOV)

Messous, M.Y.; Belhorma, B.; Labrim, H.

2015-07-01

Neutrons are used for the study of condensed matter. A neutron beam can indeed easily penetrate the solid material and undergo diffraction phenomena. Analysis of the diffused neutrons allows studying the atomic structure of crossed material. Their neutral electric charge makes them nondestructive probe of a great interest. In general, the size of the powder samples is very small and therefore the centering of the beam on these is very crucial. It is in this context we proceed to test a portable neutron monitor for centering and checking beam leak around the shielding to be installed around the diffractometer inmore » TRIGA Mark II of CENM. It's consisting of a scintillation neutron detector NE426 ({sup 6}LiF + ZnS (Ag)) with electronic module and data acquisition system. The effect of radiation from radioactive neutrons source {sup 252}Cf is shown. Sensitivity and differential linearity are also performed. This study indicates several advantages of this detector with very good detection sensitivity and excellent stability during the counting time. (authors)« less

Applicability of self-activation of an NaI scintillator for measurement of photo-neutrons around a high-energy X-ray radiotherapy machine.

PubMed

Wakabayashi, Genichiro; Nohtomi, Akihiro; Yahiro, Eriko; Fujibuchi, Toshioh; Fukunaga, Junichi; Umezu, Yoshiyuki; Nakamura, Yasuhiko; Nakamura, Katsumasa; Hosono, Makoto; Itoh, Tetsuo

2015-01-01

The applicability of the activation of an NaI scintillator for neutron monitoring at a clinical linac was investigated experimentally. Thermal neutron fluence rates are derived by measurement of the I-128 activity generated in an NaI scintillator irradiated by neutrons; β-rays from I-128 are detected efficiently by the NaI scintillator. In order to verify the validity of this method for neutron measurement, we irradiated an NaI scintillator at a research reactor, and the neutron fluence rate was estimated. The method was then applied to neutron measurement at a 10-MV linac (Varian Clinac 21EX), and the neutron fluence rate was estimated at the isocenter and at 30 cm from the isocenter. When the scintillator was irradiated directly by high-energy X-rays, the production of I-126 was observed due to photo-nuclear reactions, in addition to the generation of I-128 and Na-24. From the results obtained by these measurements, it was found that the neutron measurement by activation of an NaI scintillator has a great advantage in estimates of a low neutron fluence rate by use of a quick measurement following a short-time irradiation. Also, the future application of this method to quasi real-time monitoring of neutrons during patient treatments at a radiotherapy facility is discussed, as well as the method of evaluation of the neutron dose.

Magnetic Field Monitoring in the SNS and LANL Neutron EDM Experiments

NASA Astrophysics Data System (ADS)

Aleksandrova, Alina; SNS nEDM Collaboration; LANL nEDM Collaboration

2017-09-01

The SNS neutron EDM experiment requires the ability to precisely control and monitor the magnetic field inside of the fiducial volume. However, it is not always practical (or even possible) to measure the field within the region of interest directly. To remedy this issue, we have designed a field monitoring system that will allow us to reconstruct the field inside of the fiducial volume using noninvasive measurements of the field components at discrete locations external to this volume. A prototype probe array (consisting of 12 single-axis fluxgate magnetometer sensors) was used to monitor the magnetic field within the fiducial volume of an in-house magnetic testing apparatus. In this talk, the design and results of this test will be presented, and the possible implementation of this field monitoring method may have in the room temperature LANL neutron EDM experiment will be discussed. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Award Number DE-SC-0014622.

A method for the monitoring of metal recrystallization based on the in-situ measurement of the elastic energy release using neutron diffraction.

PubMed

Christien, F; Telling, M T F; Knight, K S; Le Gall, R

2015-05-01

A method is proposed for the monitoring of metal recrystallization using neutron diffraction that is based on the measurement of stored energy. Experiments were performed using deformed metal specimens heated in-situ while mounted at the sample position of the High Resolution Powder Diffractometer, HRPD (ISIS Facility), UK. Monitoring the breadth of the resulting Bragg lines during heating not only allows the time-dependence (or temperature-dependence) of the stored energy to be determined but also the recrystallized fraction. The analysis method presented here was developed using pure nickel (Ni270) specimens with different deformation levels from 0.29 to 0.94. In situ temperature ramping as well as isothermal annealing was undertaken. The method developed in this work allows accurate and quantitative monitoring of the recrystallization process. The results from neutron diffraction are satisfactorily compared to data obtained from calorimetry and hardness measurements.

Real-time detection of fast and thermal neutrons in radiotherapy with CMOS sensors.

PubMed

Arbor, Nicolas; Higueret, Stephane; Elazhar, Halima; Combe, Rodolphe; Meyer, Philippe; Dehaynin, Nicolas; Taupin, Florence; Husson, Daniel

2017-03-07

The peripheral dose distribution is a growing concern for the improvement of new external radiation modalities. Secondary particles, especially photo-neutrons produced by the accelerator, irradiate the patient more than tens of centimeters away from the tumor volume. However the out-of-field dose is still not estimated accurately by the treatment planning softwares. This study demonstrates the possibility of using a specially designed CMOS sensor for fast and thermal neutron monitoring in radiotherapy. The 14 microns-thick sensitive layer and the integrated electronic chain of the CMOS are particularly suitable for real-time measurements in γ/n mixed fields. An experimental field size dependency of the fast neutron production rate, supported by Monte Carlo simulations and CR-39 data, has been observed. This dependency points out the potential benefits of a real-time monitoring of fast and thermal neutron during beam intensity modulated radiation therapies.

Non-streaming high-efficiency perforated semiconductor neutron detectors, methods of making same and measuring wand and detector modules utilizing same

DOEpatents

McGregor, Douglas S.; Shultis, John K.; Rice, Blake B.; McNeil, Walter J.; Solomon, Clell J.; Patterson, Eric L.; Bellinger, Steven L.

2010-12-21

Non-streaming high-efficiency perforated semiconductor neutron detectors, method of making same and measuring wands and detector modules utilizing same are disclosed. The detectors have improved mechanical structure, flattened angular detector responses, and reduced leakage current. A plurality of such detectors can be assembled into imaging arrays, and can be used for neutron radiography, remote neutron sensing, cold neutron imaging, SNM monitoring, and various other applications.

Experiments in the EXFOR library for evaluation of thermal neutron constants

NASA Astrophysics Data System (ADS)

Otuka, Naohiko; Capote, Roberto; Semkova, Valentina; Kawai, Takuma; Noguere, Gilles

2017-09-01

E.J. Axton's experimental database adopted in evaluation of thermal neutron constants by himself and also by a recent project to update the IAEA Neutron Standard was checked against the experimental literature and EXFOR library. We discovered that many data are found neither in the EXFOR library nor in the articles quoted by Axton due to various reasons. This paper summarizes the status of the experimental data cited by Axton in the experimental literature as well as in the EXFOR library.

Calculation of self–shielding factor for neutron activation experiments using GEANT4 and MCNP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romero–Barrientos, Jaime, E-mail: jaromero@ing.uchile.cl; Universidad de Chile, DFI, Facultad de Ciencias Físicas Y Matemáticas, Avenida Blanco Encalada 2008, Santiago; Molina, F.

2016-07-07

The neutron self–shielding factor G as a function of the neutron energy was obtained for 14 pure metallic samples in 1000 isolethargic energy bins from 1·10{sup −5}eV to 2·10{sup 7}eV using Monte Carlo simulations in GEANT4 and MCNP6. The comparison of these two Monte Carlo codes shows small differences in the final self–shielding factor mostly due to the different cross section databases that each program uses.

Prompt Neutron Spectrometry for Identification of SNM in Unknown Shielding Configurations: FY16 ONR YIP Final Report

DTIC Science & Technology

2016-05-31

UMKC-YIP-TR-2016 May 2016 Technical Report Prompt Neutron Spectrometry for Identification of SNM in Unknown Shielding...University of Missouri – Kansas City MSND: Micro-structured Neutron Detector HRM: Handheld Radiation Monitor PHS: Pulse Height Spectrum ANI: Active... Neutron Interrogation Distribution Statement A 6 Administrative Information and Acknowledgements Members of the University of Missouri

Determination of effective resonance energy for the 193Ir(n,γ)194Ir reaction by the cadmium ratio method

NASA Astrophysics Data System (ADS)

Budak, Mustafa Guray; Karadag, Mustafa; Yücel, Haluk

2016-04-01

In this work, the effective resonance energy, Ebarr -value for the 193Ir(n,γ)194Ir reaction was measured using cadmium ratio method. A dual monitor (197Au-98Mo), which has convenient resonance properties, was employed for characterization of the irradiation sites. Then analytical grade iridium oxide samples diluted with CaCO3 to lower neutron self-shielding effect stacked in small cylindrical Teflon boxes were irradiated once with a 1 mm thick Cd cylindrical box placed in a thermalized neutron field of an 241Am-Be neutron source then without it. The activities produced in samples during 193Ir(n,γ)194Ir reaction were measured using a p-type HPGe detector γ-ray spectrometer with a 44.8% relative efficiency. The correction factors for thermal, epithermal neutron self-shielding (Gth, Gepi), true coincidence summing (Fcoi) and gamma-ray self-absorption (Fs) effects were determined with appropriate approaches and programs. Thus, the experimental Ebarr -value was determined to be 2.65 ± 0.61 eV for 193Ir target nuclide. The recent data for Q0 and FCd values for Ebarr determination were based on k0-NAA online database. The present experimental Ebarr value was calculated and compared with more recent values for Q0 and FCd for 193Ir. Additionally, the Ebarr -values was theoretically calculated from the up-to-date resonance data obtained from ENDF/B VII library using two different approaches. Since there is no experimentally determined Ebarr -value for the 193Ir isotope, the results are compared with the calculated ones given in the literature.

Cyclotron Lines in Accreting Neutron Star Spectra

NASA Astrophysics Data System (ADS)

Wilms, Jörn; Schönherr, Gabriele; Schmid, Julia; Dauser, Thomas; Kreykenbohm, Ingo

2009-05-01

Cyclotron lines are formed through transitions of electrons between discrete Landau levels in the accretion columns of accreting neutron stars with strong (1012 G) magnetic fields. We summarize recent results on the formation of the spectral continuum of such systems, describe recent advances in the modeling of the lines based on a modification of the commonly used Monte Carlo approach, and discuss new results on the dependence of the measured cyclotron line energy from the luminosity of transient neutron star systems. Finally, we show that Simbol-X will be ideally suited to build and improve the observational database of accreting and strongly magnetized neutron stars.

A new monitor set for the determination of neutron flux parameters in short-time k0-NAA

NASA Astrophysics Data System (ADS)

Kubešová, Marie; Kučera, Jan; Fikrle, Marek

2011-11-01

Multipurpose research reactors such as LVR-15 in Řež require monitoring of the neutron flux parameters (f, α) in each batch of samples analyzed when k0 standardization in NAA is to be used. The above parameters may change quite unpredictably, because experiments in channels adjacent to those used for NAA require an adjustment of the reactor operation parameters and/or active core configuration. For frequent monitoring of the neutron flux parameters the bare multi-monitor method is very convenient. The well-known Au-Zr tri-isotopic monitor set that provides a good tool for determining f and α after long-time irradiation is not optimal in case of short-time irradiation because only a low activity of the 95Zr radionuclide is formed. Therefore, several elements forming radionuclides with suitable half-lives and Q0 and Ēr parameters in a wide range of values were tested, namely 198Au, 56Mn, 88Rb, 128I, 139Ba, and 239U. As a result, an optimal mixture was selected consisting of Au, Mn, and Rb to form a well suited monitor set for irradiation at a thermal neutron fluence rate of 3×1017 m-2 s-1. The procedure of short-time INAA with the new monitor set for k0 standardization was successfully validated using the synthetic reference material SMELS 1 and several matrix reference materials (RMs) representing matrices of sample types frequently analyzed in our laboratory. The results were obtained using the Kayzero for Windows program.

Space Weather Effects on Range Operations

DTIC Science & Technology

2013-02-01

to give a significant albedo neutron flux at LEO spacecraft. The decay of these albedo neutrons into protons is believed to populate the inner...significant fluxes of secondary neutrons . This mechanism is thought to be the dominant SEE hazard for current and near future avionics at most... neutron monitor at Climax. A version of the CREAM detector made regular flights on-board Concorde G-BOAB between November 1988 and December 1992. Results

Characterization of a prototype neutron portal monitor detector

NASA Astrophysics Data System (ADS)

Nakhoul, Nabil

The main objective of this thesis is to provide characterization measurements on a prototype neutron portal monitor (NPM) detector constructed at the University of Massachusetts Lowell. NPM detectors are deployed at all United States border crossings and shipping ports to stop the illicit transfer of weapons-grade plutonium (WGPu) into our country. This large prototype detector with its 0.93 square meter face area is based on thermal neutron capture in 6Li as an alternate technology to the current, very expensive, 3He-based NPM. A neutron detection efficiency of 27.5 % is measured with a 252Cf source which has a spontaneous fission neutron spectrum very similar to that of 240Pu in WGPu. Measurements with an intense 137Cs source establish the extreme insensitivity of the prototype NPM to gamma-ray backgrounds with only one additional count registered for 1.1 million incident gamma rays. This detector also has the ability to locate neutron sources to within an angle of a few degrees. Its sensitivity is further demonstrated by discovering in a few-second measurement the presence of a 2 curie PuBe neutron source even at a distance of 95.5 feet. This thesis also covers in considerable detail the design features that give rise to both a high intrinsic neutron detection efficiency and an extreme gamma-ray insensitivity.

Footprint Characteristics of Cosmic-Ray Neutron Sensors for Soil Moisture Monitoring

NASA Astrophysics Data System (ADS)

Schrön, Martin; Köhli, Markus; Zreda, Marek; Dietrich, Peter; Zacharias, Steffen

2015-04-01

Cosmic-ray neutron sensing is a unique and an increasingly accepted method to monitor the effective soil water content at the field scale. The technology is famous for its low maintenance, non-invasiveness, continuous measurement, and most importantly, for its large footprint. Being more representative than point data and finer resolved than remote-sensing products, cosmic-ray neutron derived soil moisture products provide unrivaled advantage for mesoscale hydrologic and land surface models. The method takes advantage of neutrons induced by cosmic radiation which are extraordinarily sensitive to hydrogen and behave like a hot gas. Information about nearby water sources are quickly mixed in a domain of tens of hectares in air. Since experimental determination of the actual spatial extent is hardly possible, scientists have applied numerical models to address the footprint characteristics. We have revisited previous neutron transport simulations and present a modified conceptual design and refined physical assumptions. Our revised study reveals new insights into probing distance and water sensitivity of detected neutrons under various environmental conditions. These results sharpen the range of interpretation concerning the spatial extent of integral soil moisture products derived from cosmic-ray neutron counts. Our findings will have important impact on calibration strategies, on scales for data assimilation and on the interpolation of soil moisture data derived from mobile cosmic-ray neutron surveys.

Data-based Considerations in Portal Radiation Monitoring of Cargo Vehicles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weier, Dennis R.; O'Brien, Robert F.; Ely, James H.

2004-07-01

Radiation portal monitoring of cargo vehicles often includes a configuration of four-panel monitors that record gamma and neutron counts from vehicles transporting cargo. As vehicles pass the portal monitors, they generate a count profile over time that can be compared to the average panel background counts obtained just prior to the time the vehicle entered the area of the monitors. Pacific Northwest National Laboratory has accumulated considerable data regarding such background radiation and vehicle profiles from portal installations, as well as in experimental settings using known sources and cargos. Several considerations have a bearing on how alarm thresholds are setmore » in order to maintain sensitivity to radioactive sources while also controlling to a manageable level the rate of false or nuisance alarms. False alarms are statistical anomalies while nuisance alarms occur due to the presence of naturally occurring radioactive material (NORM) in cargo, for example, kitty litter. Considerations to be discussed include: • Background radiation suppression due to the shadow shielding from the vehicle. • The impact of the relative placement of the four panels on alarm decision criteria. • Use of plastic scintillators to separate gamma counts into energy windows. • The utility of using ratio criteria for the energy window counts rather than simply using total window counts. • Detection likelihood for these various decision criteria based on computer simulated injections of sources into vehicle profiles.« less

Perforated semiconductor neutron detectors for battery operated portable modules

NASA Astrophysics Data System (ADS)

McGregor, Douglas S.; Bellinger, Steven L.; Bruno, David; McNeil, Walter J.; Patterson, Eric; Shultis, J. Kenneth; Solomon, C. J.; Unruh, Troy

2007-09-01

Perforated semiconductor diode detectors have been under development for several years at Kansas State University for a variety of neutron detection applications. The fundamental device configuration is a pin diode detector fabricated from high-purity float zone refined Si wafers. Perforations are etched into the diode surface with inductively-coupled plasma (ICP) reactive ion etching (RIE) and backfilled with 6LiF neutron reactive material. The perforation shapes and depths can be optimized to yield a flat response to neutrons over a wide variation of angles. The prototype devices delivered over 3.8% thermal neutron detection efficiency while operating on only 15 volts. The highest efficiency devices thus far have delivered over 12% thermal neutron detection efficiency. The miniature devices are 5.6 mm in diameter and require minimal power to operate, ranging from 3.3 volts to 15 volts, depending upon the amplifying electronics. The battery operated devices have been incorporated into compact modules with a digital readout. Further, the new modules have incorporated wireless readout technology and can be monitored remotely. The neutron detection modules can be used for neutron dosimetry and neutron monitoring. When coupled with high-density polyethylene, the detectors can be used to measure fission neutrons from spontaneous fission sources. Monto Carlo analysis indicates that the devices can be used in cargo containers as a passive search tool for spontaneous fission sources, such as 240Pu. Measurements with a 252Cf source are being conducted for verification.

A method for the monitoring of metal recrystallization based on the in-situ measurement of the elastic energy release using neutron diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Christien, F., E-mail: frederic.christien@univ-nantes.fr; Le Gall, R.; Telling, M. T. F.

2015-05-15

A method is proposed for the monitoring of metal recrystallization using neutron diffraction that is based on the measurement of stored energy. Experiments were performed using deformed metal specimens heated in-situ while mounted at the sample position of the High Resolution Powder Diffractometer, HRPD (ISIS Facility), UK. Monitoring the breadth of the resulting Bragg lines during heating not only allows the time-dependence (or temperature-dependence) of the stored energy to be determined but also the recrystallized fraction. The analysis method presented here was developed using pure nickel (Ni270) specimens with different deformation levels from 0.29 to 0.94. In situ temperature rampingmore » as well as isothermal annealing was undertaken. The method developed in this work allows accurate and quantitative monitoring of the recrystallization process. The results from neutron diffraction are satisfactorily compared to data obtained from calorimetry and hardness measurements.« less

NICER observations of highly magnetized neutron stars: Initial results

NASA Astrophysics Data System (ADS)

Enoto, Teruaki; Arzoumanian, Zaven; Gendreau, Keith C.; Nynka, Melania; Kaspi, Victoria; Harding, Alice; Guver, Tolga; Lewandowska, Natalia; Majid, Walid; Ho, Wynn C. G.; NICER Team

2018-01-01

The Neutron star Interior Composition Explorer (NICER) was launched on June 3, 2017, and attached to the International Space Station. The large effective area of NICER in soft X-rays makes it a powerful tool not only for its primary science objective (diagnostics of the nuclear equation state) but also for studying neutron stars of various classes. As one of the NICER science working groups, the Magnetars and Magnetospheres (M&M) team coordinates monitoring and target of opportunity (ToO) observations of magnetized neutron stars, including magnetars, high-B pulsars, X-ray dim isolated neutron stars, and young rotation-powered pulsars. The M&M working group has performed simultaneous X-ray and radio observations of the Crab and Vela pulsars, ToO observations of the active anomalous X-ray pulsar 4U 0142+61, and a monitoring campaign for the transient magnetar SGR 0501+4516. Here we summarize the current status and initial results of the M&M group.

Long-Term Solar and Cosmic Radiation Data Bases

DTIC Science & Technology

1991-01-01

determine the magnitude of the variations in the cosmic ray intensity caused by solar activity. Neutron monitors, with their much lower energy threshold...expression that neutron monitors are sensors on spacecraft EARTH. Here we will consider cosmic ray detectors to measure two components of cosmic ...A comparison with the solar cycle as illustrated by the sunspot number in Fig. 1. shows that the maximum cosmic ray intensity occurs near sunspot

Simple dynamic electromagnetic radiation detector

NASA Technical Reports Server (NTRS)

Been, J. F.

1972-01-01

Detector monitors gamma dose rate at particular position in a radiation facility where a mixed neutron-gamma environment exists, thus determining reactor power level changes. Device also maps gamma intensity profile across a neutron-gamma beam.

Responses of selected neutron monitors to cosmic radiation at aviation altitudes.

PubMed

Yasuda, Hiroshi; Yajima, Kazuaki; Sato, Tatsuhiko; Takada, Masashi; Nakamura, Takashi

2009-06-01

Cosmic radiation exposure of aircraft crew, which is generally evaluated by numerical simulations, should be verified by measurements. From the perspective of radiological protection, the most contributing radiation component at aviation altitude is neutrons. Measurements of cosmic neutrons, however, are difficult in a civilian aircraft because of the limitations of space and electricity; a small, battery-operated dosimeter is required whereas larger-size instruments are generally used to detect neutrons with a broad range of energy. We thus examined the applicability of relatively new transportable neutron monitors for use in an aircraft. They are (1) a conventional rem meter with a polyethylene moderator (NCN1), (2) an extended energy-range rem meter with a tungsten-powder mixed moderator (WENDI-II), and (3) a recoil-proton scintillation rem meter (PRESCILA). These monitors were installed onto the racks of a business jet aircraft that flew two times near Japan. Observed data were compared to model calculations using a PHITS-based Analytical Radiation Model in the Atmosphere (PARMA). Excellent agreement between measured and calculated values was found for the WENDI-II. The NCN1 showed approximately half of predicted values, which were lower than those expected from its response function. The observations made with PRESCILA showed much higher than expected values; which is attributable to the presence of cosmic-ray protons and muons. These results indicate that careful attention must be paid to the dosimetric properties of a detector employed for verification of cosmic neutron dose.

Gamma and fast neutron radiation monitoring inside spent reactor fuel assemblies

NASA Astrophysics Data System (ADS)

Lakosi, L.; Tam Nguyen, C.

2007-09-01

Gamma and neutron signatures of spent reactor fuel were monitored by small-size silicon diode and track etch detectors, respectively, in a nuclear power plant (NPP). These signatures, reflecting gross gamma intensity and the 242,244Cm content, contain information on the burn-up (BU) and cooling time (CT) of the fuel. The small size of the detectors allows close access to inside parts of the assemblies out of reach of other methods. A commercial Si diode was encapsulated in a cylindrical steel case and was used for gross γ monitoring. CR-39 detectors were used for neutron measurements. Irradiation exposures at the NPP were implemented in the central dosimetric channel of spent fuel assemblies (SFAs) stored in borated water. Gross γ and neutron axial profiles were taken up by scanning with the aid of a long steel guide tube, lowered down to the spent fuel pond by crane and fitted to the headpiece of the fuel assemblies. Gamma measurements were performed using a long cable introduced in this tube, with the Si diode at the end. A long steel wire was also led through the guide tube, to which a chain of 15 sample holder capsules was attached, each containing a track detector. Gamma dose rates of 0.1-10 kGy h -1, while neutron fluxes in a range of (0.25-26) 10 4 cm -2 s -1 were recorded. The results are in good correlation with those of a calculation for spent fuel neutron yield.

Cryostat system for investigation on new neutron moderator materials at reactor TRIGA PUSPATI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dris, Zakaria bin, E-mail: zakariadris@gmail.com; Centre for Nuclear Energy, Universiti Tenaga Nasional; Mohamed, Abdul Aziz bin

2016-01-22

A simple continuous flow (SCF) cryostat was designed to investigate the neutron moderation of alumina in high temperature co-ceramic (HTCC) and polymeric materials such as Teflon under TRIGA neutron environment using a reflected neutron beam from a monochromator. Cooling of the cryostat will be carried out using liquid nitrogen. The cryostat will be built with an aluminum holder for moderator within stainless steel cylinder pipe. A copper thermocouple will be used as the temperature sensor to monitor the moderator temperature inside the cryostat holder. Initial measurements of neutron spectrum after neutron passing through the moderating materials have been carried outmore » using a neutron spectrometer.« less

Shape-Independent Model of Monitor Neutron Activation Analysis

NASA Astrophysics Data System (ADS)

Yusuf, Siaka Ojo

The technique of monitor neutron activation analysis has been improved by developing a shape-independent model to solve the problem of the treatment of the epithermal reaction contribution to the reaction rate in reactor neutron activation analysis. It is a form of facility characterization in which differential approximations to neither the neutron flux distribution as a function of energy nor the reaction cross section as a function of energy are necessary. The model predicts a linear relationship when the k-factors (ratios of reaction rates of two nuclides at a given irradiation position) for element x, k _{c} (x), is plotted against the k-factor for the monitor, k_{c} (m). The slope of this line, B(x,c,m) is measured for each element x to provide the calibration of the irradiation facility for monitor activation analysis. In this thesis, scandium was chosen as the comparator and antimony as the epithermal monitor. B(x, Sc, Sb) has been accurately measured for a number of nuclides in three different reactors. The measurement was done by irradiating filter papers containing binary mixture of the elements x and the flux monitor Sc at the various irradiation positions in these three reactors. The experiment was designed in such a way that systematic errors due to mass ratios and efficiency ratios cancel out. Also, rate related errors and backgrounds were kept at negligible values. The results show that B(x,c,m) depends not only on x, c, and m, but also on the type of moderator used for the reactor. We want this new approach to be adopted at all laboratories where routine analysis of multi-element samples are done with the monitor method since the choices of c and m are flexible.

Neutron Data Compilation Centre, European Nuclear Energy Agency, Newsletter No. 13

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

1972-02-15

This edition of the newsletter is intended to inform all users of neutron data about the content of the CCDN Experimental Neutron Data Library as of February 1972. It supercedes the last index issue, no. 11, published in October 1969. Since then, the database has been greatly enlarged thanks to the collaboration of neutron data users in the ENEA area (Western Europe plus Japan) and to the truly worldwide cooperation between the four existing data centers: NNCSC at Brookhaven Lab. in Upton, NY, United States, CCDN in Gif-sur_yvette, France, Centr po Jadernym Dannym in Obninsk, USSR, and the Nuclear Datamore » Section, IAEA, Vienna, Austria.« less

Verification of the databases EXFOR and ENDF

NASA Astrophysics Data System (ADS)

Berton, Gottfried; Damart, Guillaume; Cabellos, Oscar; Beauzamy, Bernard; Soppera, Nicolas; Bossant, Manuel

2017-09-01

The objective of this work is for the verification of large experimental (EXFOR) and evaluated nuclear reaction databases (JEFF, ENDF, JENDL, TENDL…). The work is applied to neutron reactions in EXFOR data, including threshold reactions, isomeric transitions, angular distributions and data in the resonance region of both isotopes and natural elements. Finally, a comparison of the resonance integrals compiled in EXFOR database with those derived from the evaluated libraries is also performed.

14 MeV Neutron Irradiation Effect on Superconducting Magnet Materials for Fusion Device

NASA Astrophysics Data System (ADS)

Nishimura, A.; Hishinuma, Y.; Seo, K.; Tanaka, T.; Muroga, T.; Nishijima, S.; Katagiri, K.; Takeuchi, T.; Shindo, Y.; Ochiai, K.; Nishitani, T.; Okuno, K.

2006-03-01

As a large-scale plasma experimental device is planned and designed, the importance of investigations on irradiation effect of 14 MeV neutron increases and an experimental database is desired to be piled up. Recently, intense streaming of fast neutron from ports are reported and degradation of superconducting magnet performance is anticipated. To investigate the pure neutron effect on superconducting magnet materials, a cryogenic target system was newly developed and installed at Fusion Neutronics Source in Japan Atomic Energy Research Institute. Although production rate of 14 MeV neutron is not large, only 14 MeV neutron can be supplied to irradiation test without gamma ray. Copper wires, superconducting wires, glass fiber reinforced composites are irradiated and the irradiation effects are characterized. At the same time, sensors for measuring temperature and magnetic field are irradiated and their performance was investigated after irradiation. This paper presents outline of the cryogenic target system and some irradiation test results.

DIMA.Tools: An R package for working with the database for inventory, monitoring, and assessment

USDA-ARS?s Scientific Manuscript database

The Database for Inventory, Monitoring, and Assessment (DIMA) is a Microsoft Access database used to collect, store and summarize monitoring data. This database is used by both local and national monitoring efforts within the National Park Service, the Forest Service, the Bureau of Land Management, ...

Neutron activation analysis system

DOEpatents

Taylor, M.C.; Rhodes, J.R.

1973-12-25

A neutron activation analysis system for monitoring a generally fluid media, such as slurries, solutions, and fluidized powders, including two separate conduit loops for circulating fluid samples within the range of radiation sources and detectors is described. Associated with the first loop is a neutron source that emits s high flux of slow and thermal neutrons. The second loop employs a fast neutron source, the flux from which is substantially free of thermal neutrons. Adjacent to both loops are gamma counters for spectrographic determination of the fluid constituents. Other gsmma sources and detectors are arranged across a portion of each loop for deterMining the fluid density. (Official Gazette)

Investigation of the MTC noise estimation with a coupled neutronic/thermal-hydraulic dedicated model - 'Closing the loop'

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demaziere, C.; Larsson, V.

2012-07-01

This paper investigates the reliability of different noise estimators aimed at determining the Moderator Temperature Coefficient (MTC) of reactivity in Pressurized Water Reactors. By monitoring the inherent fluctuations in the neutron flux and moderator temperature, an on-line monitoring of the MTC without perturbing reactor operation is possible. In order to get an accurate estimation of the MTC by noise analysis, the point-kinetic component of the neutron noise and the core-averaged moderator temperature noise have to be used. Because of the scarcity of the in-core instrumentation, the determination of these quantities is difficult, and several possibilities thus exist for estimating themore » MTC by noise analysis. Furthermore, the effect of feedback has to be negligible at the frequency chosen for estimating the MTC in order to get a proper determination of the MTC. By using an integrated neutronic/thermal- hydraulic model specifically developed for estimating the three-dimensional distributions of the fluctuations in neutron flux, moderator properties, and fuel temperature, different approaches for estimating the MTC by noise analysis can be tested individually. It is demonstrated that a reliable MTC estimation can only be provided if the core is equipped with a sufficient number of both neutron detectors and temperature sensors, i.e. if the core contain in-core detectors monitoring both the axial and radial distributions of the fluctuations in neutron flux and moderator temperature. It is further proven that the effect of feedback is negligible for frequencies higher than 0.1 Hz, and thus the MTC noise estimations have to be performed at higher frequencies. (authors)« less

3He and BF 3 neutron detector pressure effect and model comparison

NASA Astrophysics Data System (ADS)

Lintereur, Azaree; Conlin, Kenneth; Ely, James; Erikson, Luke; Kouzes, Richard; Siciliano, Edward; Stromswold, David; Woodring, Mitchell

2011-10-01

Radiation detection systems for homeland security applications must possess the capability of detecting both gamma rays and neutrons. The radiation portal monitor systems that are currently deployed use a plastic scintillator for detecting gamma rays and 3He gas-filled proportional counters for detecting neutrons. Proportional counters filled with 3He are the preferred neutron detectors for use in radiation portal monitor systems because 3He has a large neutron cross-section, is relatively insensitive to gamma-rays, is neither toxic nor corrosive, can withstand extreme environments, and can be operated at a lower voltage than some of the alternative proportional counters. The amount of 3He required for homeland security and science applications has depleted the world supply and there is no longer enough available to fill the demand. Thus, alternative neutron detectors are being explored. Two possible temporary solutions that could be utilized while a more permanent solution is being identified are reducing the 3He pressure in the proportional counters and using boron trifluoride gas-filled proportional counters. Reducing the amount of 3He required in each of the proportional counters would decrease the rate at which 3He is being used; not enough to solve the shortage, but perhaps enough to increase the amount of time available to find a working replacement. Boron trifluoride is not appropriate for all situations as these detectors are less sensitive than 3He, boron trifluoride gas is corrosive, and a much higher voltage is required than what is used with 3He detectors. Measurements of the neutron detection efficiency of 3He and boron trifluoride as a function of tube pressure were made. The experimental results were also used to validate models of the radiation portal monitor systems.

Earthquake effects in thermal neutron variations at the high-altitude station of Northern

NASA Astrophysics Data System (ADS)

Antonova, Valentina; Chubenko, Alexandr; Kryukov, Sergey; Lutsenko, Vadim

2016-04-01

Results of study of thermal neutron variations under various space and geophysical conditions on the basis of measurements on stationary installations with high statistical accuracy are presented. Installations are located close to the fault of the earth's crust at the high-altitude station of cosmic rays (3340 m above sea level, 43.02 N, 76.56 E, 20 km from Almaty) in the mountains of Northern Tien-Shan. Responses of the most effective gelio- and geophysical events (variations of atmospheric pressure, coronal mass ejections, earthquakes) has consistently considered in the variations of the thermal neutron flux and compared with variations of high-energy neutrons (standard monitor 18NM64) of galactic origin during these periods. Coefficients of correlation were calculated between data of thermal neutron detectors and data of the neutron monitor, recording the intensity of high-energy particles. High correlation coefficients and similarity of responses to changes of space and geophysical conditions are obtained, that confirms the conclusion of the genetic connection of thermal neutrons with high-energy neutrons of galactic origin and suggests same sources of disturbances in the absence of seismic activity. Observations and analysis of experimental data during the activation of seismic activity in the vicinity of Almaty showed the frequent breakdown of the correlation between the intensity of thermal and high-energy neutrons and the absence of similarity between variations during these periods. We suppose that the additional thermal neutron flux of the lithospheric origin appears under these conditions. Method of separating of thermal neutron flux variations of the lithospheric origin from neutrons variations generated in the atmosphere by subtracting the normalized data is proposed, taking into account the conclusion that variations caused with the atmospheric and interplanetary origins in thermal neutron detectors are similar to variations of high-energy neutrons, and the probability of detecting by 18NM64 monitor of thermal neutrons is extremely low (less than 0, 01). We used it for analysis variations of thermal neutrons during earthquakes 2006-2015. The catalog of earthquakes in the vicinity of Almaty with intensity ≥ 3b, including 25 events, is composed on the basis of observations of the Kazakhstan National Data center. Experimental data of registration of thermal and high-energy neutrons (≥ 200 MeV) with duration not less than 14 days are prepared for an each event. The main statistical characteristics of experimental data are calculated and the normalization is carried out. The increase of thermal neutrons flux of the lithospheric origin during of seismic processes activation is observed for ~ 60% of events. However, before the earthquake the increase of thermal neutron flux is observed only for ~ 30-35% of events. It is shown that the amplitude of the additional thermal neutron flux from the Earth's crust is equal to 5-7% of the background level. Sometimes it reaches values of 10-12%. We propose to employ method of allocating the thermal neutron flux of the lithospheric origin for short-term prediction of earthquakes in seismoactive regions.

Characterization of a neutron imaging setup at the INES facility

NASA Astrophysics Data System (ADS)

Durisi, E. A.; Visca, L.; Albertin, F.; Brancaccio, R.; Corsi, J.; Dughera, G.; Ferrarese, W.; Giovagnoli, A.; Grassi, N.; Grazzi, F.; Lo Giudice, A.; Mila, G.; Nervo, M.; Pastrone, N.; Prino, F.; Ramello, L.; Re, A.; Romero, A.; Sacchi, R.; Salvemini, F.; Scherillo, A.; Staiano, A.

2013-10-01

The Italian Neutron Experimental Station (INES) located at the ISIS pulsed neutron source (Didcot, United Kingdom) provides a thermal neutron beam mainly used for diffraction analysis. A neutron transmission imaging system was also developed for beam monitoring and for aligning the sample under investigation. Although the time-of-flight neutron diffraction is a consolidated technique, the neutron imaging setup is not yet completely characterized and optimized. In this paper the performance for neutron radiography and tomography at INES of two scintillator screens read out by two different commercial CCD cameras is compared in terms of linearity, signal-to-noise ratio, effective dynamic range and spatial resolution. In addition, the results of neutron radiographies and a tomography of metal alloy test structures are presented to better characterize the INES imaging capabilities of metal artifacts in the cultural heritage field.

A system for monitoring the radiation effects of a proton linear accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skorkin, V. M., E-mail: skorkin@inr.ru; Belyanski, K. L.; Skorkin, A. V.

2016-12-15

The system for real-time monitoring of radioactivity of a high-current proton linear accelerator detects secondary neutron emission from proton beam losses in transport channels and measures the activity of radionuclides in gas and aerosol emissions and the radiation background in the environment affected by a linear accelerator. The data provided by gamma, beta, and neutron detectors are transferred over a computer network to the central server. The system allows one to monitor proton beam losses, the activity of gas and aerosol emissions, and the radiation emission level of a linear accelerator in operation.

Comparison of Fast Neutron Detector Technologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stange, Sy; Mckigney, Edward Allen

2015-02-09

This report documents the work performed for the Department of Homeland Security Domestic Nuclear Detection O ce as the project Fast Neutron Detection Evaluation under contract HSHQDC-14-X-00022. This study was performed as a follow-on to the project Study of Fast Neutron Signatures and Measurement Techniques for SNM Detection - DNDO CFP11-100 STA-01. That work compared various detector technologies in a portal monitor con guration, focusing on a comparison between a number of fast neutron detection techniques and two standard thermal neutron detection technologies. The conclusions of the earlier work are contained in the report Comparison of Fast Neutron Detector Technologies.more » This work is designed to address questions raised about assumptions underlying the models built for the earlier project. To that end, liquid scintillators of two di erent sizes{ one a commercial, o -the-shelf (COTS) model of standard dimensions and the other a large, planer module{were characterized at Los Alamos National Laboratory. The results of those measurements were combined with the results of the earlier models to gain a more complete picture of the performance of liquid scintillator as a portal monitor technology.« less

Expert system for surveillance and diagnosis of breach fuel elements

DOEpatents

Gross, K.C.

1988-01-21

An apparatus and method are disclosed for surveillance and diagnosis of breached fuel elements in a nuclear reactor. A delayed neutron monitoring system provides output signals indicating the delayed neutron activity and age and the equivalent recoil area of a breached fuel element. Sensors are used to provide outputs indicating the status of each component of the delayed neutron monitoring system. Detectors also generate output signals indicating the reactor power level and the primary coolant flow rate of the reactor. The outputs from the detectors and sensors are interfaced with an artificial intelligence-based knowledge system which implements predetermined logic and generates output signals indicating the operability of the reactor. 2 figs.

Expert system for surveillance and diagnosis of breach fuel elements

DOEpatents

Gross, Kenny C.

1989-01-01

An apparatus and method are disclosed for surveillance and diagnosis of breached fuel elements in a nuclear reactor. A delayed neutron monitoring system provides output signals indicating the delayed neutron activity and age and the equivalent recoil areas of a breached fuel element. Sensors are used to provide outputs indicating the status of each component of the delayed neutron monitoring system. Detectors also generate output signals indicating the reactor power level and the primary coolant flow rate of the reactor. The outputs from the detectors and sensors are interfaced with an artificial intelligence-based knowledge system which implements predetermined logic and generates output signals indicating the operability of the reactor.

A multi-detector neutron spectrometer with nearly isotropic response for environmental and workplace monitoring

NASA Astrophysics Data System (ADS)

Gómez-Ros, J. M.; Bedogni, R.; Moraleda, M.; Delgado, A.; Romero, A.; Esposito, A.

2010-01-01

This communication describes an improved design for a neutron spectrometer consisting of 6Li thermoluminescent dosemeters located at selected positions within a single moderating polyethylene sphere. The spatial arrangement of the dosemeters has been designed using the MCNPX Monte Carlo code to calculate the response matrix for 56 log-equidistant energies from 10 -9 to 100 MeV, looking for a configuration that permits to obtain a nearly isotropic response for neutrons in the energy range from thermal to 20 MeV. The feasibility of the proposed spectrometer and the isotropy of its response have been evaluated by simulating exposures to different reference and workplace neutron fields. The FRUIT code has been used for unfolding purposes. The results of the simulations as well as the experimental tests confirm the suitability of the prototype for environmental and workplace monitoring applications.

Seasonal and Lunar Month Periods Observed in Natural Neutron Flux at High Altitude

NASA Astrophysics Data System (ADS)

Stenkin, Yuri; Alekseenko, Victor; Cai, Zeyu; Cao, Zhen; Cattaneo, Claudio; Cui, Shuwang; Giroletti, Elio; Gromushkin, Dmitry; Guo, Cong; Guo, Xuewen; He, Huihai; Liu, Ye; Ma, Xinhua; Shchegolev, Oleg; Vallania, Piero; Vigorito, Carlo; Zhao, Jing

2017-07-01

Air radon concentration measurement is useful for research on geophysical effects, but it is strongly sensitive to site geology and many geophysical and microclimatic processes such as wind, ventilation, air humidity and so on inducing very big fluctuations on the concentration of radon in air. On the contrary, monitoring the radon concentration in soil by measuring the thermal neutron flux reduces environmental effects. In this paper, we report some experimental results on the natural thermal neutron flux as well as on the concentration of air radon and its variations at 4300 m asl. These results were obtained with unshielded thermal neutron scintillation detectors (en-detectors) and radon monitors located inside the ARGO-YBJ experimental hall. The correlation of these variations with the lunar month and 1-year period is undoubtedly confirmed. A method for earthquake prediction provided by a global net of en-detectors is currently under study.

Observation of Neutron Skyshine from an Accelerator Based Neutron Source

NASA Astrophysics Data System (ADS)

Franklyn, C. B.

2011-12-01

A key feature of neutron based interrogation systems is the need for adequate provision of shielding around the facility. Accelerator facilities adapted for fast neutron generation are not necessarily suitably equipped to ensure complete containment of the vast quantity of neutrons generated, typically >1011 nṡs-1. Simulating the neutron leakage from a facility is not a simple exercise since the energy and directional distribution can only be approximated. Although adequate horizontal, planar shielding provision is made for a neutron generator facility, it is sometimes the case that vertical shielding is minimized, due to structural and economic constraints. It is further justified by assuming the atmosphere above a facility functions as an adequate radiation shield. It has become apparent that multiple neutron scattering within the atmosphere can result in a measurable dose of neutrons reaching ground level some distance from a facility, an effect commonly known as skyshine. This paper describes a neutron detection system developed to monitor neutrons detected several hundred metres from a neutron source due to the effect of skyshine.

Neutron detection with noble gas scintillation: a review of recent results

NASA Astrophysics Data System (ADS)

Lavelle, C. M.; Coplan, Michael; Miller, Eric C.; Thompson, Alan K.; Kowler, Alex; Vest, Rob; Yue, Andrew; Koeth, Tim; Al-Sheikhly, Mohammad; Clark, Charles

2015-08-01

Thermal neutron detection is of vital importance to many disciplines, including neutron scattering, workplace monitoring, and homeland protection. We survey recent results from our collaboration which couple low-pressure noble gas scintillation with novel approaches to neutron absorbing materials and geometries to achieve potentially advantageous detector concepts. Noble gas scintillators were used for neutron detection as early as the late 1950's. Modern use of noble gas scintillation includes liquid and solid forms of argon and xenon in the dark matter and neutron physics experiments and commercially available high pressure applications have achieved high resolution gamma ray spectroscopy. Little attention has been paid to the overlap between low pressure noble gas scintillation and thermal neutron detection, for which there are many potential benefits.

Characterization of the Medley setup for measurements of neutron-induced fission cross sections at the GANIL-NFS facility

NASA Astrophysics Data System (ADS)

Tarrío, Diego; Prokofiev, Alexander V.; Gustavsson, Cecilia; Jansson, Kaj; Andersson-Sundén, Erik; Al-Adili, Ali; Pomp, Stephan

2017-09-01

Neutron-induced fission cross sections of 235U and 238U are widely used as standards for monitoring of neutron beams and fields. An absolute measurement of these cross sections at an absolute scale, i.e., versus the H(n,p) scattering cross section, is planned with the white neutron beam under construction at the Neutrons For Science (NFS) facility in GANIL. The experimental setup, based on PPACs and ΔE-ΔE-E telescopes containing Silicon and CsI(Tl) detectors, is described. The expected uncertainties are discussed.

Peculiarities of cosmic ray modulation in the solar minimum 23/24

NASA Astrophysics Data System (ADS)

Alania, M. V.; Modzelewska, R.; Wawrzynczak, A.

2014-06-01

We study changes of the galactic cosmic ray (GCR) intensity for the ending period of the solar cycle 23 and the beginning of the solar cycle 24 using neutron monitors experimental data. We show that an increase of the GCR intensity in 2009 is generally related with decrease of the solar wind velocity U, the strength B of the interplanetary magnetic field (IMF), and the drift in negative (A < 0) polarity epoch. We present that temporal changes of rigidity dependence of the GCR intensity variation, before reaching maximum level in 2009 and after it, do not noticeably differ from each other. The rigidity spectrum of the GCR intensity variations calculated based on neutron monitors data (for rigidities > 10 GV) is hard in the minimum and near-minimum epoch. We do not recognize any nonordinary changes in the physical mechanism of modulation of the GCR intensity in the rigidity range of GCR particles to which neutron monitors respond. We compose 2-D nonstationary model of transport equation to describe variations of the GCR intensity for 1996-2012 including the A > 0 (1996-2001) and the A < 0 (2002-2012) periods; diffusion coefficient of cosmic rays for rigidity 10-15 GV is increased by 30% in 2009 (A < 0) comparing with 1996 (A > 0). We believe that the proposed model is relatively realistic, and obtained results are satisfactorily compatible with neutron monitors data.

Reasons for 2011 Release of the Evaluated Nuclear Data Library (ENDL2011.0)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, D.; Escher, J.; Hoffman, R.

LLNL's Computational Nuclear Physics Group and Nuclear Theory and Modeling Group have collaborated to create the 2011 release of the Evaluated Nuclear Data Library (ENDL2011). ENDL2011 is designed to sup- port LLNL's current and future nuclear data needs. This database is currently the most complete nuclear database for Monte Carlo and deterministic transport of neutrons and charged particles, surpassing ENDL2009.0 [1]. The ENDL2011 release [2] contains 918 transport-ready eval- uations in the neutron sub-library alone. ENDL2011 was assembled with strong support from the ASC program, leveraged with support from NNSA science campaigns and the DOE/Offce of Science US Nuclear Datamore » Pro- gram.« less

Characterization of low power research reactor neutrons for the validation of k(0)-INAA standardization based on k(0)-IAEA software.

PubMed

Baidoo, I K; Nyarko, B J B; Akaho, E H K; Dampare, S B; Sogbadji, R B M; Poku, L O

2013-09-01

Channel Bsite2 of Ghana research reactor-1 has been characterized for k0-INAA application. Cadmium ratio and bare multi-monitor were used to determine flux parameters using 0.1%Au-Al, Fe, and Zr wire as flux monitors. The parameters determined were 18.36±1.91, 0.0479±0.012, 5.12×10(11)±0.42×10(11) ncm(-2)s(-1), 2.74×10(10)±0.14×10(10) ncm(-2)s(-1), 7.73×10(10)±0.16×10(10) ncm(-2)s(-1) and 16.75±1.58, -0.034±0.0028, 4.28×10(11)±1.71×10(11) ncm(-2)s(-1), 2.55×10(10)±0.15×10(10) ncm(-2)s(-1) respectively for thermal-to-epithermal flux ratio, alpha, thermal neutron, epithermal neutron and fast neutron flux using cadmium ratio and multi-monitor method accordingly. The k0-INAA performance assessment based on z-score distributions showed most results within |z|<2. Copyright © 2013 Elsevier Ltd. All rights reserved.

Prompt gamma and neutron detection in BNCT utilizing a CdTe detector.

PubMed

Winkler, Alexander; Koivunoro, Hanna; Reijonen, Vappu; Auterinen, Iiro; Savolainen, Sauli

2015-12-01

In this work, a novel sensor technology based on CdTe detectors was tested for prompt gamma and neutron detection using boronated targets in (epi)thermal neutron beam at FiR1 research reactor in Espoo, Finland. Dedicated neutron filter structures were omitted to enable simultaneous measurement of both gamma and neutron radiation at low reactor power (2.5 kW). Spectra were collected and analyzed in four different setups in order to study the feasibility of the detector to measure 478 keV prompt gamma photons released from the neutron capture reaction of boron-10. The detector proved to have the required sensitivity to detect and separate the signals from both boron neutron and cadmium neutron capture reactions, which makes it a promising candidate for monitoring the spatial and temporal development of in vivo boron distribution in boron neutron capture therapy. Copyright © 2015 Elsevier Ltd. All rights reserved.

Benchmarking of Neutron Flux Parameters at the USGS TRIGA Reactor in Lakewood, Colorado

NASA Astrophysics Data System (ADS)

Alzaabi, Osama E.

The USGS TRIGA Reactor (GSTR) located at the Denver Federal Center in Lakewood Colorado provides opportunities to Colorado School of Mines students to do experimental research in the field of neutron activation analysis. The scope of this thesis is to obtain precise knowledge of neutron flux parameters at the GSTR. The Colorado School of Mines Nuclear Physics group intends to develop several research projects at the GSTR, which requires the precise knowledge of neutron fluxes and energy distributions in several irradiation locations. The fuel burn-up of the new GSTR fuel configuration and the thermal neutron flux of the core were recalculated since the GSTR core configuration had been changed with the addition of two new fuel elements. Therefore, a MCNP software package was used to incorporate the burn up of reactor fuel and to determine the neutron flux at different irradiation locations and at flux monitoring bores. These simulation results were compared with neutron activation analysis results using activated diluted gold wires. A well calibrated and stable germanium detector setup as well as fourteen samplers were designed and built to achieve accuracy in the measurement of the neutron flux. Furthermore, the flux monitoring bores of the GSTR core were used for the first time to measure neutron flux experimentally and to compare to MCNP simulation. In addition, International Atomic Energy Agency (IAEA) standard materials were used along with USGS national standard materials in a previously well calibrated irradiation location to benchmark simulation, germanium detector calibration and sample measurements to international standards.

MONDO: a neutron tracker for particle therapy secondary emission characterisation

NASA Astrophysics Data System (ADS)

Marafini, M.; Gasparini, L.; Mirabelli, R.; Pinci, D.; Patera, V.; Sciubba, A.; Spiriti, E.; Stoppa, D.; Traini, G.; Sarti, A.

2017-04-01

Tumour control is performed in particle therapy using particles and ions, whose high irradiation precision enhances the effectiveness of the treatment, while sparing the healthy tissue surrounding the target volume. Dose range monitoring devices using photons and charged particles produced by the beam interacting with the patient’s body have already been proposed, but no attempt has been made yet to exploit the detection of the abundant neutron component. Since neutrons can release a significant dose far away from the tumour region, precise measurements of their flux, production energy and angle distributions are eagerly sought in order to improve the treatment planning system (TPS) software. It will thus be possible to predict not only the normal tissue toxicity in the target region, but also the risk of late complications in the whole body. The aforementioned issues underline the importance of an experimental effort devoted to the precise characterisation of neutron production, aimed at the measurement of their abundance, emission point and production energy. The technical challenges posed by a neutron detector aimed at high detection efficiency and good backtracking precision are addressed within the MONDO (monitor for neutron dose in hadrontherapy) project, whose main goal is to develop a tracking detector that can target fast and ultrafast neutrons. A full reconstruction of two consecutive elastic scattering interactions undergone by the neutrons inside the detector material will be used to measure their energy and direction. The preliminary results of an MC simulation performed using the FLUKA software are presented here, together with the DSiPM (digital SiPM) readout implementation. New detector readout implementations specifically tailored to the MONDO tracker are also discussed, and the neutron detection efficiency attainable with the proposed neutron tracking strategy are reported.

MONDO: a neutron tracker for particle therapy secondary emission characterisation.

PubMed

Marafini, M; Gasparini, L; Mirabelli, R; Pinci, D; Patera, V; Sciubba, A; Spiriti, E; Stoppa, D; Traini, G; Sarti, A

2017-04-21

Tumour control is performed in particle therapy using particles and ions, whose high irradiation precision enhances the effectiveness of the treatment, while sparing the healthy tissue surrounding the target volume. Dose range monitoring devices using photons and charged particles produced by the beam interacting with the patient's body have already been proposed, but no attempt has been made yet to exploit the detection of the abundant neutron component. Since neutrons can release a significant dose far away from the tumour region, precise measurements of their flux, production energy and angle distributions are eagerly sought in order to improve the treatment planning system (TPS) software. It will thus be possible to predict not only the normal tissue toxicity in the target region, but also the risk of late complications in the whole body. The aforementioned issues underline the importance of an experimental effort devoted to the precise characterisation of neutron production, aimed at the measurement of their abundance, emission point and production energy. The technical challenges posed by a neutron detector aimed at high detection efficiency and good backtracking precision are addressed within the MONDO (monitor for neutron dose in hadrontherapy) project, whose main goal is to develop a tracking detector that can target fast and ultrafast neutrons. A full reconstruction of two consecutive elastic scattering interactions undergone by the neutrons inside the detector material will be used to measure their energy and direction. The preliminary results of an MC simulation performed using the FLUKA software are presented here, together with the DSiPM (digital SiPM) readout implementation. New detector readout implementations specifically tailored to the MONDO tracker are also discussed, and the neutron detection efficiency attainable with the proposed neutron tracking strategy are reported.

Response measurement of single-crystal chemical vapor deposition diamond radiation detector for intense X-rays aiming at neutron bang-time and neutron burn-history measurement on an inertial confinement fusion with fast ignition.

PubMed

Shimaoka, T; Kaneko, J H; Arikawa, Y; Isobe, M; Sato, Y; Tsubota, M; Nagai, T; Kojima, S; Abe, Y; Sakata, S; Fujioka, S; Nakai, M; Shiraga, H; Azechi, H; Chayahara, A; Umezawa, H; Shikata, S

2015-05-01

A neutron bang time and burn history monitor in inertial confinement fusion with fast ignition are necessary for plasma diagnostics. In the FIREX project, however, no detector attained those capabilities because high-intensity X-rays accompanied fast electrons used for plasma heating. To solve this problem, single-crystal CVD diamond was grown and fabricated into a radiation detector. The detector, which had excellent charge transportation property, was tested to obtain a response function for intense X-rays. The applicability for neutron bang time and burn history monitor was verified experimentally. Charge collection efficiency of 99.5% ± 0.8% and 97.1% ± 1.4% for holes and electrons were obtained using 5.486 MeV alpha particles. The drift velocity at electric field which saturates charge collection efficiency was 1.1 ± 0.4 × 10(7) cm/s and 1.0 ± 0.3 × 10(7) cm/s for holes and electrons. Fast response of several ns pulse width for intense X-ray was obtained at the GEKKO XII experiment, which is sufficiently fast for ToF measurements to obtain a neutron signal separately from X-rays. Based on these results, we confirmed that the single-crystal CVD diamond detector obtained neutron signal with good S/N under ion temperature 0.5-1 keV and neutron yield of more than 10(9) neutrons/shot.

Neutron detection with a NaI spectrometer using high-energy photons

NASA Astrophysics Data System (ADS)

Holm, Philip; Peräjärvi, Kari; Sihvonen, Ari-Pekka; Siiskonen, Teemu; Toivonen, Harri

2013-01-01

Neutrons can be indirectly detected by high-energy photons. The performance of a 4″×4″×16″ NaI portal monitor was compared to a 3He-based portal monitor with a comparable cross-section of the active volume. Measurements were performed with bare and shielded 252Cf and AmBe sources. With an optimum converter and moderator structure for the NaI detector, the detection efficiencies and minimum detectable activities of the portal monitors were similar. The NaI portal monitor preserved its detection efficiency much better with shielded sources, making the method very interesting for security applications. For heavily shielded sources, the NaI detector was 2-3 times more sensitive than the 3He-based detector.

Are neutrons precursors of solar flares?

NASA Astrophysics Data System (ADS)

Martirosyan, H.

2001-08-01

The analysis of data of a worldwide network of neutron monitors (NM) shows, that at local noon and during approximately 4 hours after, the NM sometimes register statistically significant excess. Enhancement of count rate is approxi-mately ≈ 1.5÷2%. Depending on the geographical coordinates the time slice is determined, during which the global increase of a registered ux (characteristic time of the order of tens of hours) is observed. These data are correlated with data from space-borne sensors, proving significant increase ( ≈ 5 ÷ 10 times) of the low energy protons and electrons in near-earth space. In both cases the ux enhancement during tenths of hours is proceeding by an impulse phase of the next solar are. The analysis of data allows to put forward a hypothesis that the enhancement of the protons and electrons ux is stipulated by decay of solar neutrons with energies 10 ÷ 30 MeV . These neutrons during tenths of hours before an impulse phase of a are are born in active areas of the Sun, as a product of thermonuclear reactions (D + d → He3 + n, T + d → He4 + n). The part of neutrons are decaying in the interplanetary space, and part of high en-ergy neutrons (En > 20 V ) penetrate through terrestrial atmosphere (with probability ≈ 10-7 and are registered by neutron monitors.

MTR FAST NEUTRON FLUX MEASUREMENTS FOR CYCLE 146

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weber, L D; Hogg, C H

1962-03-20

The fast neutron fluxes in selected positions of the MTR were measured for Cycle 146. The measurements were made at the beginning, throughout, and at the end of the cycle (564 Mwd). Vertical traverses for each position monitors are shown. (auth)

MONDO: A neutron tracker for particle therapy secondary emission fluxes measurements

NASA Astrophysics Data System (ADS)

Marafini, M.; Patera, V.; Pinci, D.; Sarti, A.; Sciubba, A.; Spiriti, E.

2016-07-01

Cancer treatment is performed, in Particle Therapy, using accelerated charged particles whose high irradiation precision and conformity allows the tumor destruction while sparing the surrounding healthy tissues. Dose release monitoring devices using photons and charged particles produced by the beam interaction with the patient body have already been proposed, but no attempt based on the detection of the abundant secondary radiation neutron component has been made yet. The reduced attenuation length of neutrons yields a secondary particle sample that is larger in number when compared to photons and charged particles. Furthermore, neutrons allow for a backtracking of the emission point that is not affected by multiple scattering. Since neutrons can release a significant dose far away from the tumor region, a precise measurement of their flux, production energy and angle distributions is eagerly needed in order to improve the Treatment Planning Systems (TPS) software, so to predict not only the normal tissue toxicity in the target region but also the risk of late complications in the whole body. All the aforementioned issues underline the importance for an experimental effort devoted to the precise characterization of the neutron production gaining experimental access both to the emission point and production energy. The technical challenges posed by a neutron detector aiming for a high detection efficiency and good backtracking precision will be addressed within the MONDO (MOnitor for Neutron Dose in hadrOntherapy) project. The MONDO's main goal is to develop a tracking detector targeting fast and ultrafast secondary neutrons. The tracker is composed by a scintillating fiber matrix (4 × 4 × 8cm3). The full reconstruction of protons, produced in elastic interactions, will be used to measure energy and direction of the impinging neutron. The neutron tracker will measure the neutron production yields, as a function of production angle and energy, using different therapeutic beams at CNAO in Pavia (protons, 12C ions and possibly 4He and 16O ions).

FEMOS - Advanced Neutron Monitor System for Waste Management

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simon, G.G.; Sokcic-Kostic, M.

2006-07-01

FEMOS is a specially developed monitor to detect fissile materials for waste characterisation and it is also suitable to identify the main neutron emitters. The latest measuring prototype is in routine operation at FZK-HDB (Germany) for determining Plutonium content and alpha activity in 2001 and 4001 drums from the reprocessing plant Karlsruhe (WAK). Authorities license the measurement procedure. Routine measurements conducted over a period of about 6 years and the results show that all specified prerequisites are met with the required reliability. (authors)

An efficient 14-MeV neutron detector for use in mixed 2. 5- and 14-MeV neutron beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Croft, S.; Bond, D.S.; Hawkes, N.P.

1993-06-01

A neutron detector capable of measuring the time-dependent yield of 14-MeV neutrons from a D--D plasma producing predominantly 2.5-MeV neutrons has been developed. The detector consists of a thick polythene recoil proton radiator backed by a graphite foil attached to a large area totally depleted ion-implanted diode. Protons scattered in the forward direction by 14-MeV neutrons pass through the graphite foil and are registered in the diode. Recoil protons from 2.5-MeV neutrons, however, are prevented from reaching the diode by the foil. When operated with a 1.5-MeV energy bias, the measured neutron detection efficiency for 15-MeV neutrons is 3.2[times]10[sup [minus]3]more » per neutron. The corresponding figure for 3.1-MeV neutrons is a factor of 540 lower. The neutron detector and its laboratory calibration are described, as is its deployment at the Joint European Torus where it serves as a triton burn-up monitor.« less

Observation of Neutron Skyshine from an Accelerator Based Neutron Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franklyn, C. B.

2011-12-13

A key feature of neutron based interrogation systems is the need for adequate provision of shielding around the facility. Accelerator facilities adapted for fast neutron generation are not necessarily suitably equipped to ensure complete containment of the vast quantity of neutrons generated, typically >10{sup 11} n{center_dot}s{sup -1}. Simulating the neutron leakage from a facility is not a simple exercise since the energy and directional distribution can only be approximated. Although adequate horizontal, planar shielding provision is made for a neutron generator facility, it is sometimes the case that vertical shielding is minimized, due to structural and economic constraints. It ismore » further justified by assuming the atmosphere above a facility functions as an adequate radiation shield. It has become apparent that multiple neutron scattering within the atmosphere can result in a measurable dose of neutrons reaching ground level some distance from a facility, an effect commonly known as skyshine. This paper describes a neutron detection system developed to monitor neutrons detected several hundred metres from a neutron source due to the effect of skyshine.« less

The Emergence of a Lanthanide-rich Kilonova Following the Merger of Two Neutron Stars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanvir, N. R.; Levan, A. J.; González-Fernández, C.

Here, we report the discovery and monitoring of the near-infrared counterpart (AT2017gfo) of a binary neutron-star merger event detected as a gravitational wave source by Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo (GW170817) and as a short gamma-ray burst by Fermi Gamma-ray Burst Monitor (GBM) and Integral SPI-ACS (GRB 170817A). The evolution of the transient light is consistent with predictions for the behavior of a "kilonova/macronova" powered by the radioactive decay of massive neutron-rich nuclides created via r-process nucleosynthesis in the neutron-star ejecta. In particular, evidence for this scenario is found from broad features seen in Hubble Space Telescope infrared spectroscopy, similar to those predicted for lanthanide-dominated ejecta, and the much slower evolution in the near-infraredmore » $${K}_{{\\rm{s}}}$$-band compared to the optical. This indicates that the late-time light is dominated by high-opacity lanthanide-rich ejecta, suggesting nucleosynthesis to the third r-process peak (atomic masses $$A\\approx 195$$). This discovery thus confirms that neutron-star mergers produce kilo-/macronovae and that they are at least a major—if not the dominant—site of rapid neutron capture nucleosynthesis in the universe.« less

The Emergence of a Lanthanide-rich Kilonova Following the Merger of Two Neutron Stars

DOE PAGES

Tanvir, N. R.; Levan, A. J.; González-Fernández, C.; ...

2017-10-16

Here, we report the discovery and monitoring of the near-infrared counterpart (AT2017gfo) of a binary neutron-star merger event detected as a gravitational wave source by Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo (GW170817) and as a short gamma-ray burst by Fermi Gamma-ray Burst Monitor (GBM) and Integral SPI-ACS (GRB 170817A). The evolution of the transient light is consistent with predictions for the behavior of a "kilonova/macronova" powered by the radioactive decay of massive neutron-rich nuclides created via r-process nucleosynthesis in the neutron-star ejecta. In particular, evidence for this scenario is found from broad features seen in Hubble Space Telescope infrared spectroscopy, similar to those predicted for lanthanide-dominated ejecta, and the much slower evolution in the near-infraredmore » $${K}_{{\\rm{s}}}$$-band compared to the optical. This indicates that the late-time light is dominated by high-opacity lanthanide-rich ejecta, suggesting nucleosynthesis to the third r-process peak (atomic masses $$A\\approx 195$$). This discovery thus confirms that neutron-star mergers produce kilo-/macronovae and that they are at least a major—if not the dominant—site of rapid neutron capture nucleosynthesis in the universe.« less

REACTOR MONITORING

DOEpatents

Bugbee, S.J.; Hanson, V.F.; Babcock, D.F.

1959-02-01

A neutron density inonitoring means for reactors is described. According to this invention a tunnel is provided beneath and spaced from the active portion of the reactor and extends beyond the opposite faces of the activc portion. Neutron beam holes are provided between the active portion and the tunnel and open into the tunnel near the middle thereof. A carriage operates back and forth in the tunnel and is adapted to convey a neutron detector, such as an ion chamber, and position it beneath one of the neutron beam holes. This arrangement affords convenient access of neutron density measuring instruments to a location wherein direct measurement of neutron density within the piles can be made and at the same time affords ample protection to operating personnel.

Preliminary measurements of neutrons from the D-D reaction in the COMPASS tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dankowski, J., E-mail: jan.dankowski@ifj.edu.pl; Kurowski, A.; Twarog, D.

Recent results of measured fast neutrons created in the D-D reaction on the COMPASS tokamak during ohmic discharges are presented in this paper. Two different type detectors were used during experiment. He-3 detectors and bubble detectors as a support. The measurements are an introduction for neutron diagnostic on tokamak COMPASS and monitoring neutrons during discharges with Neutral Beam Injection (NBI). The He-3 counters and bubble detectors were located in two positions near tokamak vacuum chamber at a distance less than 40 cm to the centre of plasma. The neutrons flux was observed in ohmic discharges. However, analysis of our resultsmore » does not indicate any clear source of neutrons production during ohmic discharges.« less

Characterization of neutron calibration fields at the TINT's 50 Ci americium-241/beryllium neutron irradiator

NASA Astrophysics Data System (ADS)

Liamsuwan, T.; Channuie, J.; Ratanatongchai, W.

2015-05-01

Reliable measurement of neutron radiation is important for monitoring and protection in workplace where neutrons are present. Although Thailand has been familiar with applications of neutron sources and neutron beams for many decades, there is no calibration facility dedicated to neutron measuring devices available in the country. Recently, Thailand Institute of Nuclear Technology (TINT) has set up a multi-purpose irradiation facility equipped with a 50 Ci americium-241/beryllium neutron irradiator. The facility is planned to be used for research, nuclear analytical techniques and, among other applications, calibration of neutron measuring devices. In this work, the neutron calibration fields were investigated in terms of neutron energy spectra and dose equivalent rates using Monte Carlo simulations, an in-house developed neutron spectrometer and commercial survey meters. The characterized neutron fields can generate neutron dose equivalent rates ranging from 156 μSv/h to 3.5 mSv/h with nearly 100% of dose contributed by neutrons of energies larger than 0.01 MeV. The gamma contamination was less than 4.2-7.5% depending on the irradiation configuration. It is possible to use the described neutron fields for calibration test and routine quality assurance of neutron dose rate meters and passive dosemeters commonly used in radiation protection dosimetry.

Derivation of relativistic SEP properties through neutron monitor data modeling

NASA Astrophysics Data System (ADS)

Plainaki, C.; Laurenza, M.; Mavromichalaki, H.; Storini, M.; Gerontidou, M.; Kanellakopoulos, A.; Andriopoulou, M.; Belov, A.; Eroshenko, E.; Yanke, V.

2015-08-01

The Ground Level Enhancement (GLE) data recorded by the worldwide Neutron Monitor (NM) network are useful resources for space weather modeling during solar extreme events. The derivation of Solar Energetic Particles (SEPs) properties through NM-data modeling is essential for the study of solar-terrestrial physics, providing information that cannot be obtained through the exclusive use of space techniques; an example is the derivation of the higher-energy part of the SEP spectrum. We briefly review how the application of the Neutron Monitor Based Anisotropic GLE Pure Power Law (NMBANGLE PPOLA) model (Plainaki et al. 2010), can provide the characteristics of the relativistic SEP flux, at a selected altitude in the Earth's atmosphere, during a GLE. Technically, the model treats the NM network as an integrated omnidirectional spectrometer and solves the inverse problem of the SEP-GLE coupling. As test cases, we present the results obtained for two different GLEs, namely GLE 60 and GLE 71, occurring at a temporal distance of ∼ 11 years.

Report: EPA Needs to Strengthen Financial Database Security Oversight and Monitor Compliance

EPA Pesticide Factsheets

Report #2007-P-00017, March 29, 2007. Weaknesses in how EPA offices monitor databases for known security vulnerabilities, communicate the status of critical system patches, and monitor the access to database administrator accounts and privileges.

"XANSONS for COD": a new small BOINC project in crystallography

NASA Astrophysics Data System (ADS)

Neverov, Vladislav S.; Khrapov, Nikolay P.

2018-04-01

"XANSONS for COD" (http://xansons4cod.com) is a new BOINC project aimed at creating the open-access database of simulated x-ray and neutron powder diffraction patterns for nanocrystalline phase of materials from the collection of the Crystallography Open Database (COD). The project uses original open-source software XaNSoNS to simulate diffraction patterns on CPU and GPU. This paper describes the scientific problem this project solves, the project's internal structure, its operation principles and organization of the final database.

Smaller, Lower-Power Fast-Neutron Scintillation Detectors

NASA Technical Reports Server (NTRS)

Patel, Jagdish; Blaes, Brent

2008-01-01

Scintillation-based fast-neutron detectors that are smaller and less power-hungry than mainstream scintillation-based fast-neutron detectors are undergoing development. There are numerous applications for such detectors in monitoring fast-neutron fluxes from nuclear reactors, nuclear materials, and natural sources, both on Earth and in outer space. A particularly important terrestrial application for small, low-power, portable fast-neutron detectors lies in the requirement to scan for nuclear materials in cargo and baggage arriving at international transportation facilities. The present development of miniature, low-power scintillation-based fast-neutron detectors exploits recent advances in the fabrication of avalanche photodiodes (APDs). Basically, such a detector includes a plastic scintillator, typically between 300 and 400 m thick with very thin silver mirror coating on all its faces except the one bonded to an APD. All photons generated from scintillation are thus internally reflected and eventually directed to the APD. This design affords not only compactness but also tight optical coupling for utilization of a relatively large proportion of the scintillation light. The combination of this tight coupling and the avalanche-multiplication gain (typically between 750 and 1,000) of the APD is expected to have enough sensitivity to enable monitoring of a fast-neutron flux as small as 1,000 cm(exp -2)s(exp -1). Moreover, pulse-height analysis can be expected to provide information on the kinetic energies of incident neutrons. It has been estimated that a complete, fully developed fast-neutron detector of this type, would be characterized by linear dimensions of the order of 10 cm or less, a mass of no more than about 0.5 kg, and a power demand of no more than a few watts.

Astrophysics

Science.gov Websites

, microquasars, neutron stars, pulsars, black holes astro-ph.IM - Instrumentation and Methods for Astrophysics Astrophysics. Methods for data analysis, statistical methods. Software, database design astro-ph.SR - Solar and

Onsets of Solar Proton Events in Satellite and Ground Level Observations: A Comparison

NASA Astrophysics Data System (ADS)

He, Jing; Rodriguez, Juan V.

2018-03-01

The early detection of solar proton event onsets is essential for protecting humans and electronics in space, as well as passengers and crew at aviation altitudes. Two commonly compared methods for observing solar proton events that are sufficiently large and energetic to be detected on the ground through the creation of secondary radiation—known as ground level enhancements (GLEs)—are (1) a network of ground-based neutron monitors (NMs) and (2) satellite-based particle detectors. Until recently, owing to the different time resolution of the two data sets, it has not been feasible to compare these two types of observations using the same detection algorithm. This paper presents a comparison between the two observational platforms using newly processed >100 MeV 1 min count rates and fluxes from National Oceanic and Atmospheric Administration's Geostationary Operational Environmental Satellite (GOES) 8-12 satellites, and 1 min count rates from the Neutron Monitor Database. We applied the same detection algorithm to each data set (tuned to the different background noise levels of the instrument types). Seventeen SPEs with GLEs were studied: GLEs 55-70 from Solar Cycle 23 and GLE 71 from Solar Cycle 24. The median difference in the event detection times by GOES and NM data is 0 min, indicating no innate benefit in time of either system. The 10th, 25th, 75th, and 90th percentiles of the onset time differences (GOES minus NMs) are -7.2 min, -1.5 min, 2.5 min, and 4.2 min, respectively. This is in contrast to previous studies in which NM detections led GOES by 8 to 52 min without accounting for different alert protocols.

Optimising the neutron environment of Radiation Portal Monitors: A computational study

NASA Astrophysics Data System (ADS)

Gilbert, Mark R.; Ghani, Zamir; McMillan, John E.; Packer, Lee W.

2015-09-01

Efficient and reliable detection of radiological or nuclear threats is a crucial part of national and international efforts to prevent terrorist activities. Radiation Portal Monitors (RPMs), which are deployed worldwide, are intended to interdict smuggled fissile material by detecting emissions of neutrons and gamma rays. However, considering the range and variety of threat sources, vehicular and shielding scenarios, and that only a small signature is present, it is important that the design of the RPMs allows these signatures to be accurately differentiated from the environmental background. Using Monte-Carlo neutron-transport simulations of a model 3He detector system we have conducted a parameter study to identify the optimum combination of detector shielding, moderation, and collimation that maximises the sensitivity of neutron-sensitive RPMs. These structures, which could be simply and cost-effectively added to existing RPMs, can improve the detector response by more than a factor of two relative to an unmodified, bare design. Furthermore, optimisation of the air gap surrounding the helium tubes also improves detector efficiency.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Furuta, H.; Imura, A.; Furuta, Y.

Recently, technique of Gadolinium loaded liquid scintillator (Gd-LS) for reactor neutrino oscillation experiments has attracted attention as a monitor of reactor operation and 'nuclear Gain (GA)' for IAEA safeguards. For the practical use, R and D of the 1 ton class compact detector, which is measurable above ground, is necessary. Especially, it is important to reduce much amount of fast neutron background induced by cosmic muons with data analysis for the measurement above ground. We developed a prototype of the Gd-LS detector with 200 L of the target volume, which has Pulse Shape Discrimination (PSD) ability for the fast neutronmore » reduction with data analysis. Usually, it is well known that it is difficult to keep high fast neutron reduction power of PSD with the large volume size such as the neutrino reactor monitor. We evaluated the PSD ability of our prototype with real fast neutrons induced by the muons in our laboratory above ground, and we could confirm to keep the high fast neutron reduction power with even our large detector size. (authors)« less

Measurements of the thermal neutron cross-section and resonance integral for the 108Pd(n,γ)109Pd reaction

NASA Astrophysics Data System (ADS)

Hien, Nguyen Thi; Kim, Guinyun; Kim, Kwangsoo; Do, Nguyen Van; Khue, Pham Duc; Thanh, Kim Tien; Shin, Sung-Gyun; Cho, Moo-Hyun

2018-06-01

The thermal neutron capture cross-section (σ0) and resonance integral (I0) of the 108Pd(n,γ)109Pd reaction have been measured relative to that of the monitor reaction 197Au(n,γ)198Au. The measurements were carried out using the neutron activation with the cadmium ratio method. Both the samples and monitors were irradiated with and without cadmium cover of 0.5 mm thickness. The induced activities of the reaction products were measured with a well calibrated HPGe γ-ray detector. In order to improve the accuracy of the results, the necessary corrections for the counting losses were made. The thermal neutron capture cross-section and resonance integral of the 108Pd(n,γ)109Pd reaction were determined to be σ0,Pd = 8.68 ± 0.41 barn and I0,Pd = 245.6 ± 24.8 barn, respectively. The obtained results are compared with literature values and discussed.

Response measurement of single-crystal chemical vapor deposition diamond radiation detector for intense X-rays aiming at neutron bang-time and neutron burn-history measurement on an inertial confinement fusion with fast ignition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shimaoka, T., E-mail: t.shimaoka@eng.hokudai.ac.jp; Kaneko, J. H.; Tsubota, M.

A neutron bang time and burn history monitor in inertial confinement fusion with fast ignition are necessary for plasma diagnostics. In the FIREX project, however, no detector attained those capabilities because high-intensity X-rays accompanied fast electrons used for plasma heating. To solve this problem, single-crystal CVD diamond was grown and fabricated into a radiation detector. The detector, which had excellent charge transportation property, was tested to obtain a response function for intense X-rays. The applicability for neutron bang time and burn history monitor was verified experimentally. Charge collection efficiency of 99.5% ± 0.8% and 97.1% ± 1.4% for holes andmore » electrons were obtained using 5.486 MeV alpha particles. The drift velocity at electric field which saturates charge collection efficiency was 1.1 ± 0.4 × 10{sup 7} cm/s and 1.0 ± 0.3 × 10{sup 7} cm/s for holes and electrons. Fast response of several ns pulse width for intense X-ray was obtained at the GEKKO XII experiment, which is sufficiently fast for ToF measurements to obtain a neutron signal separately from X-rays. Based on these results, we confirmed that the single-crystal CVD diamond detector obtained neutron signal with good S/N under ion temperature 0.5–1 keV and neutron yield of more than 10{sup 9} neutrons/shot.« less

Large Cleaner Detectors for the UCN τ Neutron Lifetime Experiment

NASA Astrophysics Data System (ADS)

Gonzalez, Francisco; UCNtau Collaboration

2017-09-01

The UCN τ experiment at Los Alamos National Laboratory measures the neutron β-decay lifetime by storing ultracold neutrons (UCNs) in a magneto-gravitational trap for holding times longer than the neutron's lifetime. Neutrons with energies above the trapping potential can escape the trap, giving rise to a systematic error. To mitigate this effect, a large polyethylene sheet is lowered into the trap to remove the high energy unbound neutrons. High energy UCN upscatter in the polyethylene sheet and leave the trap. Such a ``UCN spectrum cleaner,'' covering half the trap top, was shown to be effective in removing high-energy neutrons in previous run cycles. During this run cycle, the UCN τ collaboration has added two thermal neutron detectors on the spectrum cleaner. The new thermal neutron detectors will monitor high-energy neutrons throughout upcoming run cycles, providing important information on the neutron normalization, spectral cleaning, and heating during storage. These detectors use LiF-ZnS sheets coupled to a wavelength-shifting plastic slab, with silicon photomultipliers attached to the edges. We will present results of the light detection simulation and performance tests of these detectors.

Evaluation of prompt gamma-ray data and nuclear structure of niobium-94 with statistical model calculations

NASA Astrophysics Data System (ADS)

Turkoglu, Danyal

Precise knowledge of prompt gamma-ray intensities following neutron capture is critical for elemental and isotopic analyses, homeland security, modeling nuclear reactors, etc. A recently-developed database of prompt gamma-ray production cross sections and nuclear structure information in the form of a decay scheme, called the Evaluated Gamma-ray Activation File (EGAF), is under revision. Statistical model calculations are useful for checking the consistency of the decay scheme, providing insight on its completeness and accuracy. Furthermore, these statistical model calculations are necessary to estimate the contribution of continuum gamma-rays, which cannot be experimentally resolved due to the high density of excited states in medium- and heavy-mass nuclei. Decay-scheme improvements in EGAF lead to improvements to other databases (Evaluated Nuclear Structure Data File, Reference Input Parameter Library) that are ultimately used in nuclear-reaction models to generate the Evaluated Nuclear Data File (ENDF). Gamma-ray transitions following neutron capture in 93Nb have been studied at the cold-neutron beam facility at the Budapest Research Reactor. Measurements have been performed using a coaxial HPGe detector with Compton suppression. Partial gamma-ray production capture cross sections at a neutron velocity of 2200 m/s have been deduced relative to that of the 255.9-keV transition after cold-neutron capture by 93Nb. With the measurement of a niobium chloride target, this partial cross section was internally standardized to the cross section for the 1951-keV transition after cold-neutron capture by 35Cl. The resulting (0.1377 +/- 0.0018) barn (b) partial cross section produced a calibration factor that was 23% lower than previously measured for the EGAF database. The thermal-neutron cross sections were deduced for the 93Nb(n,gamma ) 94mNb and 93Nb(n,gamma) 94gNb reactions by summing the experimentally-measured partial gamma-ray production cross sections associated with the ground-state transitions below the 396-keV level and combining that summation with the contribution to the ground state from the quasi-continuum above 396 keV, determined with Monte Carlo statistical model calculations using the DICEBOX computer code. These values, sigmam and sigma 0, were (0.83 +/- 0.05) b and (1.16 +/- 0.11) b, respectively, and found to be in agreement with literature values. Comparison of the modeled population and experimental depopulation of individual levels confirmed tentative spin assignments and suggested changes where imbalances existed.

Precision determination of absolute neutron flux

DOE PAGES

Yue, A. T.; Anderson, E. S.; Dewey, M. S.; ...

2018-06-08

A technique for establishing the total neutron rate of a highly-collimated monochromatic cold neutron beam was demonstrated using an alpha–gamma counter. The method involves only the counting of measured rates and is independent of neutron cross sections, decay chain branching ratios, and neutron beam energy. For the measurement, a target of 10B-enriched boron carbide totally absorbed the neutrons in a monochromatic beam, and the rate of absorbed neutrons was determined by counting 478 keV gamma rays from neutron capture on 10B with calibrated high-purity germanium detectors. A second measurement based on Bragg diffraction from a perfect silicon crystal was performedmore » to determine the mean de Broglie wavelength of the beam to a precision of 0.024%. With these measurements, the detection efficiency of a neutron monitor based on neutron absorption on 6Li was determined to an overall uncertainty of 0.058%. We discuss the principle of the alpha–gamma method and present details of how the measurement was performed including the systematic effects. We further describe how this method may be used for applications in neutron dosimetry and metrology, fundamental neutron physics, and neutron cross section measurements.« less

Precision determination of absolute neutron flux

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yue, A. T.; Anderson, E. S.; Dewey, M. S.

A technique for establishing the total neutron rate of a highly-collimated monochromatic cold neutron beam was demonstrated using an alpha–gamma counter. The method involves only the counting of measured rates and is independent of neutron cross sections, decay chain branching ratios, and neutron beam energy. For the measurement, a target of 10B-enriched boron carbide totally absorbed the neutrons in a monochromatic beam, and the rate of absorbed neutrons was determined by counting 478 keV gamma rays from neutron capture on 10B with calibrated high-purity germanium detectors. A second measurement based on Bragg diffraction from a perfect silicon crystal was performedmore » to determine the mean de Broglie wavelength of the beam to a precision of 0.024%. With these measurements, the detection efficiency of a neutron monitor based on neutron absorption on 6Li was determined to an overall uncertainty of 0.058%. We discuss the principle of the alpha–gamma method and present details of how the measurement was performed including the systematic effects. We further describe how this method may be used for applications in neutron dosimetry and metrology, fundamental neutron physics, and neutron cross section measurements.« less

Hadfield holds bubble detectors for the RaDI-N Experiment in the Columbus Module

NASA Image and Video Library

2013-01-25

ISS034-E-034506 (25 Jan. 2013) --- Canadian Space Agency astronaut Chris Hadfield, Expedition 34 flight engineer, holds bubble detectors for the RaDI-N experiment in the International Space Station?s Kibo laboratory. RaDI-N measures neutron radiation levels onboard the space station. RaDI-N uses bubble detectors as neutron monitors which have been designed to only detect neutrons and ignore all other radiation.

APPARATUS FOR MEASURING TOTAL NEUTRON CROSS SECTIONS

DOEpatents

Cranberg, L.

1959-10-13

An apparatus is described for measuring high-resolution total neutron cross sections at high counting rate in the range above 50-kev neutron energy. The pulsed-beam time-of-flight technique is used to identify the neutrons of interest which are produced in the target of an electrostatic accelerator. Energy modulation of the accelerator . makes it possible to make observations at 100 energy points simultaneously. 761O An apparatus is described for monitoring the proton resonance of a liquid which is particulariy useful in the continuous purity analysis of heavy water. A hollow shell with parallel sides defines a meander chamber positioned within a uniform magnetic fieid. The liquid passes through an inlet at the outer edge of the chamber and through a spiral channel to the central region of the chamber where an outlet tube extends into the chamber perpendicular to the magnetic field. The radiofrequency energy for the monitor is coupled to a coil positioned coaxially with the outlet tube at its entrance point within the chamber. The improvement lies in the compact mechanical arrangement of the monitor unit whereby the liquid under analysis is subjected to the same magnetic field in the storage and sensing areas, and the entire unit is shielded from external electrostatic influences.

NEUTRON CHARACTERIZATION OF ENSA-DPT TYPE SPENT FUEL CASK AT TRILLO NUCLEAR POWER PLANT.

PubMed

Méndez-Villafañe, Roberto; Campo-Blanco, Xandra; Embid, Miguel; Yéboles, César A; Morales, Ramón; Novo, Manuel; Sanz, Javier

2018-04-23

The Neutron Standards Laboratory of CIEMAT has conducted the characterization of the independent spent fuel storage installation at the Trillo Nuclear Power Plant. At this facility, the spent fuel assemblies are stored in ENSA-DPT type dual purpose casks. Neutron characterization was performed by dosimetry measurements with a neutron survey meter (LB6411) inside the facility, around an individual cask and between stored casks, and outside the facility. Spectra measurements were also performed with a Bonner sphere system in order to determine the integral quantities and validate the use of the neutron monitor at the different positions. Inside the facility, measured neutron spectra and neutron ambient dose equivalent rate are consistent with the casks spatial distribution and neutron emission rates, and measurements with both instruments are consistent with each other. Outside the facility, measured neutron ambient dose equivalent rates are well below the 0.5 μSv/h limit established by the nuclear regulatory authority.

In-Pile Instrumentation Multi- Parameter System Utilizing Photonic Fibers and Nanovision

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burgett, Eric

2015-10-13

An advanced in-pile multi-parameter reactor monitoring system is being proposed in this funding opportunity. The proposed effort brings cutting edge, high fidelity optical measurement systems into the reactor environment in an unprecedented fashion, including in-core, in-cladding and in-fuel pellet itself. Unlike instrumented leads, the proposed system provides a unique solution to a multi-parameter monitoring need in core while being minimally intrusive in the reactor core. Detector designs proposed herein can monitor fuel compression and expansion in both the radial and axial dimensions as well as monitor linear power profiles and fission rates during the operation of the reactor. In additionmore » to pressure, stress, strain, compression, neutron flux, neutron spectra, and temperature can be observed inside the fuel bundle and fuel rod using the proposed system. The proposed research aims at developing radiation-hard, harsh-environment multi-parameter systems for insertion into the reactor environment. The proposed research holds the potential to drastically increase the fidelity and precision of in-core instrumentation with little or no impact in the neutron economy in the reactor environment while providing a measurement system capable of operation for entire operating cycles.« less

Evaluation of neutron flux parameters in irradiation sites of research reactor using the Westcott-formalism for the k0 neutron activation analysis method

NASA Astrophysics Data System (ADS)

Kasban, H.; Hamid, Ashraf

2015-12-01

Instrumental Neutron Activation Analysis using k0 (k0-INAA) method has been used to determine a number of elements in sediment samples collected from El-Manzala Lake in Egypt. k0-INAA according to Westcott's formalism has been implemented using the complete irradiation kit of the fast pneumatic rabbit and some selected manually loaded irradiation sites for short and long irradiation at Egypt Second Research Reactor (ETRR-2). Zr-Au and Co sets as neutron flux monitors are used to determine the neutron flux parameters (f and α) in each irradiation sites. Two reference materials IAEA Soil-7 samples have been inserted and implemented for data validation and an internal monostandard multi monitor used (k0 based IM-NAA). It was given a good agreement between the experimental analyzed values and that obtained of the certified values. The major and trace elements in the sediment samples have been evaluated with the use of Co as an internal and Au as an external monostandard comparators. The concentrations of the elements (Cr, Mn and Zn) in the sediment samples of the present work are discussed regarding to those obtained from other sites.

MCNP SIMULATION OF THE HP(10) ENERGY RESPONSE OF A BRAZILIAN TLD ALBEDO NEUTRON INDIVIDUAL DOSEMETER, FROM THERMAL TO 20 MeV.

PubMed

Freitas, B M; Martins, M M; Pereira, W W; da Silva, A X; Mauricio, C L P

2016-09-01

The Brazilian Instituto de Radioproteção e Dosimetria (IRD) runs a neutron individual monitoring system with a home-made TLD albedo dosemeter. It has already been characterised and calibrated in some reference fields. However, the complete energy response of this dosemeter is not known, and the calibration factors for all monitored workplace neutron fields are difficult to be obtained experimentally. Therefore, to overcome such difficulties, Monte Carlo simulations have been used. This paper describes the simulation of the HP(10) neutron response of the IRD TLD albedo dosemeter using the MCNPX transport code, for energies from thermal to 20 MeV. The validation of the MCNPX modelling is done comparing the simulated results with the experimental measurements for ISO standard neutron fields of (241)Am-Be, (252)Cf, (241)Am-B and (252)Cf(D2O) and also for (241)Am-Be source moderated with paraffin and silicone. Bare (252)Cf are used for normalisation. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Perspectives in biological physics: the nDDB project for a neutron Dynamics Data Bank for biological macromolecules.

PubMed

Rusevich, Leonid; García Sakai, Victoria; Franzetti, Bruno; Johnson, Mark; Natali, Francesca; Pellegrini, Eric; Peters, Judith; Pieper, Jörg; Weik, Martin; Zaccai, Giuseppe

2013-07-01

Neutron spectroscopy provides experimental data on time-dependent trajectories, which can be directly compared to molecular dynamics simulations. Its importance in helping us to understand biological macromolecules at a molecular level is demonstrated by the results of a literature survey over the last two to three decades. Around 300 articles in refereed journals relate to neutron scattering studies of biological macromolecular dynamics, and the results of the survey are presented here. The scope of the publications ranges from the general physics of protein and solvent dynamics, to the biologically relevant dynamics-function relationships in live cells. As a result of the survey we are currently setting up a neutron Dynamics Data Bank (nDDB) with the aim to make the neutron data on biological systems widely available. This will benefit, in particular, the MD simulation community to validate and improve their force fields. The aim of the database is to expose and give easy access to a body of experimental data to the scientific community. The database will be populated with as much of the existing data as possible. In the future it will give value, as part of a bigger whole, to high throughput data, as well as more detailed studies. A range and volume of experimental data will be of interest in determining how quantitatively MD simulations can reproduce trends across a range of systems and to what extent such trends may depend on sample preparation and data reduction and analysis methods. In this context, we strongly encourage researchers in the field to deposit their data in the nDDB.

Monte Carlo Simulations Comparing the Response of a Novel Hemispherical Tepc to Existing Spherical and Cylindrical Tepcs for Neutron Monitoring and Dosimetry.

PubMed

Broughton, David P; Waker, Anthony J

2017-05-01

Neutron dosimetry in reactor fields is currently mainly conducted with unwieldy flux monitors. Tissue Equivalent Proportional Counters (TEPCs) have been shown to have the potential to improve the accuracy of neutron dosimetry in these fields, and Multi-Element Tissue Equivalent Proportional Counters (METEPCs) could reduce the size of instrumentation required to do so. Complexity of current METEPC designs has inhibited their use beyond research. This work proposes a novel hemispherical counter with a wireless anode ball in place of the traditional anode wire as a possible solution for simplifying manufacturing. The hemispherical METEPC element was analyzed as a single TEPC to first demonstrate the potential of this new design by evaluating its performance relative to the reference spherical TEPC design and a single element from a cylindrical METEPC. Energy deposition simulations were conducted using the Monte Carlo code PHITS for both monoenergetic 2.5 MeV neutrons and the neutron energy spectrum of Cf-D2O moderated. In these neutron fields, the hemispherical counter appears to be a good alternative to the reference spherical geometry, performing slightly better than the cylindrical counter, which tends to underrespond to H*(10) for the lower neutron energies of the Cf-D2O moderated field. These computational results are promising, and if follow-up experimental work demonstrates the hemispherical counter works as anticipated, it will be ready to be incorporated into an METEPC design.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klix, A.; Fischer, U.; Raj, P.

Fusion power reactors will rely on the internal production of the fuel tritium from lithium in the tritium breeding blanket. Test Blanket Modules (TBM) will be installed in ITER with the aim to investigate the nuclear performance of different breeding blanket designs. Currently there is no fully qualified nuclear instrumentation available for the measurement of neutron fluxes and tritium production rates which would be able to withstand the harsh environment conditions in the TBM such as high temperature (>400 deg. C) and, depending on the operation scenario, intense radiation levels. As partner of the European Consortium on Nuclear Data andmore » Measurement Techniques in the framework of several F4E specific grants and contracts, KIT and ENEA have jointly studied the possibility to develop and test detectors suitable to operate in ITER-TBMs. Here we present an overview of ongoing work on three types of neutron flux monitors under development for the TBMs with focus on the KIT activities. A neutron activation system (NAS) with pneumatic sample transport could provide absolute neutron flux measurements in selected positions. A test system for investigating activation materials with short half-lives was constructed at the DT neutron generator laboratory of Technical University of Dresden to investigate the neutronics aspects. Several irradiations have been performed with focus on the simultaneous measurement of the extracted activated probes. An engineering assessment of a TBM NAS in the conceptual design phase has been done which considered issues of design requirements and integration. Last but not least, a mechanical test bench is under construction at KIT which will address issues of driving the activation probes, solutions for loading the system etc. experimentally. Self-powered neutron detectors (SPND) are widely applied in fission reactor monitoring, and the commercially available SPNDs are sensitive to thermal neutrons. We are investigating novel materials for SPND which would be sensitive also to the fast neutron flux expected in the TBMs. To this end simulations were done with the European Activation System EASY and neutron flux spectra which were calculated with MCNP for the HCPB TBM. Preliminary tests with commercial SPND in a fast reactor were performed. As a result of these activities, several materials have been found which may be suitable for the measurement of fast neutron fluxes in the TBM. Test detectors are under preparation for testing with DT neutron generators. Within the I{sub S}MART project, funded by KIC InnoEnergy, KIT is developing an online detector based on silicon carbide electronics for the TBMs. The operation of such detectors at TBM relevant temperatures is expected to incur lower accumulated radiation damage to them than at room temperature due to annealing effects. Detectors of several designs have been already irradiated with DT neutrons. Irradiation tests at elevated temperatures have been done and further tests are currently underway. This paper summarizes the status of the work for these three neutron flux monitor systems. (authors)« less

Calculations to support JET neutron yield calibration: Modelling of neutron emission from a compact DT neutron generator

NASA Astrophysics Data System (ADS)

Čufar, Aljaž; Batistoni, Paola; Conroy, Sean; Ghani, Zamir; Lengar, Igor; Milocco, Alberto; Packer, Lee; Pillon, Mario; Popovichev, Sergey; Snoj, Luka; JET Contributors

2017-03-01

At the Joint European Torus (JET) the ex-vessel fission chambers and in-vessel activation detectors are used as the neutron production rate and neutron yield monitors respectively. In order to ensure that these detectors produce accurate measurements they need to be experimentally calibrated. A new calibration of neutron detectors to 14 MeV neutrons, resulting from deuterium-tritium (DT) plasmas, is planned at JET using a compact accelerator based neutron generator (NG) in which a D/T beam impinges on a solid target containing T/D, producing neutrons by DT fusion reactions. This paper presents the analysis that was performed to model the neutron source characteristics in terms of energy spectrum, angle-energy distribution and the effect of the neutron generator geometry. Different codes capable of simulating the accelerator based DT neutron sources are compared and sensitivities to uncertainties in the generator's internal structure analysed. The analysis was performed to support preparation to the experimental measurements performed to characterize the NG as a calibration source. Further extensive neutronics analyses, performed with this model of the NG, will be needed to support the neutron calibration experiments and take into account various differences between the calibration experiment and experiments using the plasma as a source of neutrons.

Reactor-Produced Medical Radionuclides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mirzadeh, Saed; Mausner, Leonard; Garland, Marc A

2011-01-01

The therapeutic use of radionuclides in nuclear medicine, oncology and cardiology is the most rapidly growing use of medical radionuclides. Since most therapeutic radionuclides are neutron rich and decay by beta emission, they are reactor-produced. This chapter deals mainly with production approaches with neutrons. Neutron interactions with matter, neutron transmission and activation rates, and neutron spectra of nuclear reactors are discussed in some detail. Further, a short discussion of the neutron-energy dependence of cross sections, reaction rates in thermal reactors, cross section measurements and flux monitoring, and general equations governing the reactor production of radionuclides are presented. Finally, the chaptermore » is concluded by providing a number of examples encompassing the various possible reaction routes for production of a number of medical radionuclides in a reactor.« less

Measurement of low to middle energy neutron spectra in aircraft at aviation altitude

NASA Astrophysics Data System (ADS)

Yajima, Kazuaki; Goka, Tateo; Yasuda, Hiroshi; Takada, Masashi; Nakamura, Takashi

Neutron energy spectra ranging from thermal to 10 MeV were measured at aviation altitude (9.1-11 km) with Bonner-Boll-type neutron spectral measurement system named BBND which has been developed for use on board the International Space Station (ISS) by NASDA (currently JAXA). The BBND was set and manipulated in a business jet chartered for observation experiments, and 4 flights were carried out around the Nagoya Airport, which located in the middle of Japan. It is found that the variation of neutron flux on the flight traced the altitude variation. The estimated energy spectra will be incorporated into the determination of whole energy spectra of cosmic neutrons from thermal to hundreds MeV using the prototype neutron monitor based on the phoswich-type detector.

Pulsed neutron detector

DOEpatents

Robertson, deceased, J. Craig; Rowland, Mark S.

1989-03-21

A pulsed neutron detector and system for detecting low intensity fast neutron pulses has a body of beryllium adjacent a body of hydrogenous material the latter of which acts as a beta particle detector, scintillator, and moderator. The fast neutrons (defined as having En>1.5 MeV) react in the beryllium and the hydrogenous material to produce larger numbers of slow neutrons than would be generated in the beryllium itself and which in the beryllium generate hellium-6 which decays and yields beta particles. The beta particles reach the hydrogenous material which scintillates to yield light of intensity related to the number of fast neutrons. A photomultiplier adjacent the hydrogenous material (scintillator) senses the light emission from the scintillator. Utilization means, such as a summing device, sums the pulses from the photo-multiplier for monitoring or other purposes.

Monte Carlo simulation of moderator and reflector in coal analyzer based on a D-T neutron generator.

PubMed

Shan, Qing; Chu, Shengnan; Jia, Wenbao

2015-11-01

Coal is one of the most popular fuels in the world. The use of coal not only produces carbon dioxide, but also contributes to the environmental pollution by heavy metals. In prompt gamma-ray neutron activation analysis (PGNAA)-based coal analyzer, the characteristic gamma rays of C and O are mainly induced by fast neutrons, whereas thermal neutrons can be used to induce the characteristic gamma rays of H, Si, and heavy metals. Therefore, appropriate thermal and fast neutrons are beneficial in improving the measurement accuracy of heavy metals, and ensure that the measurement accuracy of main elements meets the requirements of the industry. Once the required yield of the deuterium-tritium (d-T) neutron generator is determined, appropriate thermal and fast neutrons can be obtained by optimizing the neutron source term. In this article, the Monte Carlo N-Particle (MCNP) Transport Code and Evaluated Nuclear Data File (ENDF) database are used to optimize the neutron source term in PGNAA-based coal analyzer, including the material and shape of the moderator and neutron reflector. The optimized targets include two points: (1) the ratio of the thermal to fast neutron is 1:1 and (2) the total neutron flux from the optimized neutron source in the sample increases at least 100% when compared with the initial one. The simulation results show that, the total neutron flux in the sample increases 102%, 102%, 85%, 72%, and 62% with Pb, Bi, Nb, W, and Be reflectors, respectively. Maximum optimization of the targets is achieved when the moderator is a 3-cm-thick lead layer coupled with a 3-cm-thick high-density polyethylene (HDPE) layer, and the neutron reflector is a 27-cm-thick hemispherical lead layer. Copyright © 2015 Elsevier Ltd. All rights reserved.

Automation system for neutron activation analysis at the reactor IBR-2, Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna, Russia.

PubMed

Pavlov, Sergey S; Dmitriev, Andrey Yu; Frontasyeva, Marina V

The present status of development of software packages and equipment designed for automation of NAA at the reactor IBR-2 of FLNP, JINR, Dubna, RF, is described. The NAA database, construction of sample changers and software for automation of spectra measurement and calculation of concentrations are presented. Automation of QC procedures is integrated in the software developed. Details of the design are shown.

A database application for wilderness character monitoring

Treesearch

Ashley Adams; Peter Landres; Simon Kingston

2012-01-01

The National Park Service (NPS) Wilderness Stewardship Division, in collaboration with the Aldo Leopold Wilderness Research Institute and the NPS Inventory and Monitoring Program, developed a database application to facilitate tracking and trend reporting in wilderness character. The Wilderness Character Monitoring Database allows consistent, scientifically based...

Designing a new type of neutron detector for neutron and gamma-ray discrimination via GEANT4.

PubMed

Shan, Qing; Chu, Shengnan; Ling, Yongsheng; Cai, Pingkun; Jia, Wenbao

2016-04-01

Design of a new type of neutron detector, consisting of a fast neutron converter, plastic scintillator, and Cherenkov detector, to discriminate 14-MeV fast neutrons and gamma rays in a pulsed n-γ mixed field and monitor their neutron fluxes is reported in this study. Both neutrons and gamma rays can produce fluorescence in the scintillator when they are incident on the detector. However, only the secondary charged particles of the gamma rays can produce Cherenkov light in the Cherenkov detector. The neutron and gamma-ray fluxes can be calculated by measuring the fluorescence and Cherenkov light. The GEANT4 Monte Carlo simulation toolkit is used to simulate the whole process occurring in the detector, whose optimum parameters are known. Analysis of the simulation results leads to a calculation method of neutron flux. This method is verified by calculating the neutron fluxes using pulsed n-γ mixed fields with different n/γ ratios, and the results show that the relative errors of all calculations are <5%. Copyright © 2016 Elsevier Ltd. All rights reserved.

Application of thin-film breakdown counters for characterization of neutron field of the VESUVIO instrument at the ISIS spallation source

NASA Astrophysics Data System (ADS)

Smirnov, A. N.; Pietropaolo, A.; Prokofiev, A. V.; Rodionova, E. E.; Frost, C. D.; Ansell, S.; Schooneveld, E. M.; Gorini, G.

2012-09-01

The high-energy neutron field of the VESUVIO instrument at the ISIS facility has been characterized using the technique of thin-film breakdown counters (TFBC). The technique utilizes neutron-induced fission reactions of natU and 209Bi with detection of fission fragments by TFBCs. Experimentally determined count rates of the fragments are ≈50% higher than those calculated using spectral neutron flux simulated with the MCNPX code. This work is a part of the project to develop ChipIr, a new dedicated facility for the accelerated testing of electronic components and systems for neutron-induced single event effects in the new Target Station 2 at ISIS. The TFBC technique has shown to be applicable for on-line monitoring of the neutron flux in the neutron energy range 1-800 MeV at the position of the device under test (DUT).

A Study of Neutron Leakage in Finite Objects

NASA Technical Reports Server (NTRS)

Wilson, John W.; Slaba, Tony C.; Badavi, Francis F.; Reddell, Brandon D.; Bahadori, Amir A.

2015-01-01

A computationally efficient 3DHZETRN code capable of simulating High charge (Z) and Energy (HZE) and light ions (including neutrons) under space-like boundary conditions with enhanced neutron and light ion propagation was recently developed for simple shielded objects. Monte Carlo (MC) benchmarks were used to verify the 3DHZETRN methodology in slab and spherical geometry, and it was shown that 3DHZETRN agrees with MC codes to the degree that various MC codes agree among themselves. One limitation in the verification process is that all of the codes (3DHZETRN and three MC codes) utilize different nuclear models/databases. In the present report, the new algorithm, with well-defined convergence criteria, is used to quantify the neutron leakage from simple geometries to provide means of verifying 3D effects and to provide guidance for further code development.

Method for non-intrusively identifying a contained material utilizing uncollided nuclear transmission measurements

DOEpatents

Morrison, John L.; Stephens, Alan G.; Grover, S. Blaine

2001-11-20

An improved nuclear diagnostic method identifies a contained target material by measuring on-axis, mono-energetic uncollided particle radiation transmitted through a target material for two penetrating radiation beam energies, and applying specially developed algorithms to estimate a ratio of macroscopic neutron cross-sections for the uncollided particle radiation at the two energies, where the penetrating radiation is a neutron beam, or a ratio of linear attenuation coefficients for the uncollided particle radiation at the two energies, where the penetrating radiation is a gamma-ray beam. Alternatively, the measurements are used to derive a minimization formula based on the macroscopic neutron cross-sections for the uncollided particle radiation at the two neutron beam energies, or the linear attenuation coefficients for the uncollided particle radiation at the two gamma-ray beam energies. A candidate target material database, including known macroscopic neutron cross-sections or linear attenuation coefficients for target materials at the selected neutron or gamma-ray beam energies, is used to approximate the estimated ratio or to solve the minimization formula, such that the identity of the contained target material is discovered.

DIMA quick start, database for inventory, monitoring and assessment

USDA-ARS?s Scientific Manuscript database

The Database for Inventory, Monitoring and Assessment (DIMA) is a highly-customized Microsoft Access database for collecting data electronically in the field and for organizing, storing and reporting those data for monitoring and assessment. While DIMA can be used for any number of different monito...

Characterisation of ionisation chambers for a mixed radiation field and investigation of their suitability as radiation monitors for the LHC.

PubMed

Theis, C; Forkel-Wirth, D; Perrin, D; Roesler, S; Vincke, H

2005-01-01

Monitoring of the radiation environment is one of the key tasks in operating a high-energy accelerator such as the Large Hadron Collider (LHC). The radiation fields consist of neutrons, charged hadrons as well as photons and electrons with energy spectra extending from those of thermal neutrons up to several hundreds of GeV. The requirements for measuring the dose equivalent in such a field are different from standard uses and it is thus necessary to investigate the response of monitoring devices thoroughly before the implementation of a monitoring system can be conducted. For the LHC, it is currently foreseen to install argon- and hydrogen-filled high-pressure ionisation chambers as radiation monitors of mixed fields. So far their response to these fields was poorly understood and, therefore, further investigation was necessary to prove that they can serve their function well enough. In this study, ionisation chambers of type IG5 (Centronic Ltd) were characterised by simulating their response functions by means of detailed FLUKA calculations as well as by calibration measurements for photons and neutrons at fixed energies. The latter results were used to obtain a better understanding and validation of the FLUKA simulations. Tests were also conducted at the CERF facility at CERN in order to compare the results with simulations of the response in a mixed radiation field. It is demonstrated that these detectors can be characterised sufficiently enough to serve their function as radiation monitors for the LHC.

Neutron Capture gamma ENDF libraries for modeling and identification of neutron sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sleaford, B

2007-10-29

There are a number of inaccuracies and data omissions with respect to gammas from neutron capture in the ENDF libraries used as field reference information and by modeling codes used in JTOT. As the use of Active Neutron interrogation methods is expanded, these shortfalls become more acute. A new, more accurate and complete evaluated experimental database of gamma rays (over 35,000 lines for 262 isotopes up to U so far) from thermal neutron capture has recently become available from the IAEA. To my knowledge, none of this new data has been installed in ENDF libraries and disseminated. I propose tomore » upgrade libraries of {sup 184,186}W, {sup 56}Fe, {sup 204,206,207}Pb, {sup 104}Pd, and {sup 19}F the 1st year. This will involve collaboration with Richard Firestone at LBL in evaluating the data and installing it in the libraries. I will test them with the transport code MCNP5.« less

Elastic and inelastic scattering of neutrons from 56Fe

NASA Astrophysics Data System (ADS)

Ramirez, Anthony Paul; McEllistrem, M. T.; Liu, S. H.; Mukhopadhyay, S.; Peters, E. E.; Yates, S. W.; Vanhoy, J. R.; Harrison, T. D.; Rice, B. G.; Thompson, B. K.; Hicks, S. F.; Howard, T. J.; Jackson, D. T.; Lenzen, P. D.; Nguyen, T. D.; Pecha, R. L.

2015-10-01

The differential cross sections for elastic and inelastic scattered neutrons from 56Fe have been measured at the University of Kentucky Accelerator Laboratory (www.pa.uky.edu/accelerator) for incident neutron energies between 2.0 and 8.0 MeV and for the angular range 30° to 150°. Time-of-flight techniques and pulse-shape discrimination were employed for enhancing the neutron energy spectra and for reducing background. An overview of the experimental procedures and data analysis for the conversion of neutron yields to differential cross sections will be presented. These include the determination of the energy-dependent detection efficiencies, the normalization of the measured differential cross sections, and the attenuation and multiple scattering corrections. Our results will also be compared to evaluated cross section databases and reaction model calculations using the TALYS code. This work is supported by grants from the U.S. Department of Energy-Nuclear Energy Universities Program: NU-12-KY-UK-0201-05, and the Donald A. Cowan Physics Institute at the University of Dallas.

Radiation Embrittlement Archive Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klasky, Hilda B; Bass, Bennett Richard; Williams, Paul T

2013-01-01

The Radiation Embrittlement Archive Project (REAP), which is being conducted by the Probabilistic Integrity Safety Assessment (PISA) Program at Oak Ridge National Laboratory under funding from the U.S. Nuclear Regulatory Commission s (NRC) Office of Nuclear Regulatory Research, aims to provide an archival source of information about the effect of neutron radiation on the properties of reactor pressure vessel (RPV) steels. Specifically, this project is an effort to create an Internet-accessible RPV steel embrittlement database. The project s website, https://reap.ornl.gov, provides information in two forms: (1) a document archive with surveillance capsule(s) reports and related technical reports, in PDF format,more » for the 104 commercial nuclear power plants (NPPs) in the United States, with similar reports from other countries; and (2) a relational database archive with detailed information extracted from the reports. The REAP project focuses on data collected from surveillance capsule programs for light-water moderated, nuclear power reactor vessels operated in the United States, including data on Charpy V-notch energy testing results, tensile properties, composition, exposure temperatures, neutron flux (rate of irradiation damage), and fluence, (Fast Neutron Fluence a cumulative measure of irradiation for E>1 MeV). Additionally, REAP contains data from surveillance programs conducted in other countries. REAP is presently being extended to focus on embrittlement data analysis, as well. This paper summarizes the current status of the REAP database and highlights opportunities to access the data and to participate in the project.« less

A pulsed neutron generator for in vivo body composition studies

NASA Astrophysics Data System (ADS)

Weinlein, J. H.; O'Neal, M. L.; Bacon, F. M.

1991-05-01

A neutron generator system utilizing two Zetatron neutron tubes has been designed and delivered to the U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University for use in clinical measurements of body carbon by neutron inelastic scattering. Each neutron tube is capable of delivering 10 3-10 4 14-MeV neutrons in a 7-μs pulse at repetition rates of 4 or 8 kHz, and can be operated independently as well as in a master-slave mode. The neutron tubes are gas filled with a mixture of deuterium and tritium; the target of the tube is operated at - 30 to - 60 kV dc and the ion source is operated with a 2.5-kV, 7-μs pulse. The tube gas pressure is monitored and controlled by measuring the total current in the high voltage circuit and feeding it back to the gas-reservoir drive circuit. Neutrons were measured with a plastic scintillator and photomultiplier tube.

Performance study of the neutron-TPC

NASA Astrophysics Data System (ADS)

Huang, Meng; Li, Yulan; Niu, Libo; Deng, Zhi; Cheng, Xiaolei; He, Li; Zhang, Hongyan; Fu, Jianqiang; Yan, Yangyang; Cai, Yiming; Li, Yuanjing

2017-02-01

Fast neutron spectrometers will play an important role in the future of the nuclear industry and nuclear physics experiments, in tasks such as fast neutron reactor monitoring, thermo-nuclear fusion plasma diagnostics, nuclear reaction cross-section measurement, and special nuclear material detection. Recently, a new fast neutron spectrometer based on a GEM (Gas Electron Multiplier amplification)-TPC (Time Projection Chamber), named the neutron-TPC, has been under development at Tsinghua University. It is designed to have a high energy resolution, high detection efficiency, easy access to the medium material, an outstanding n/γ suppression ratio, and a wide range of applications. This paper presents the design, test, and experimental study of the neutron-TPC. Based on the experimental results, the energy resolution (FWHM) of the neutron-TPC can reach 15.7%, 10.3% and 7.0% with detection efficiency higher than 10-5 for 1.2 MeV, 1.81 MeV and 2.5 MeV neutrons respectively. Supported by National Natural Science Foundation of China (11275109)

Neutronic calculation of fast reactors by the EUCLID/V1 integrated code

NASA Astrophysics Data System (ADS)

Koltashev, D. A.; Stakhanova, A. A.

2017-01-01

This article considers neutronic calculation of a fast-neutron lead-cooled reactor BREST-OD-300 by the EUCLID/V1 integrated code. The main goal of development and application of integrated codes is a nuclear power plant safety justification. EUCLID/V1 is integrated code designed for coupled neutronics, thermomechanical and thermohydraulic fast reactor calculations under normal and abnormal operating conditions. EUCLID/V1 code is being developed in the Nuclear Safety Institute of the Russian Academy of Sciences. The integrated code has a modular structure and consists of three main modules: thermohydraulic module HYDRA-IBRAE/LM/V1, thermomechanical module BERKUT and neutronic module DN3D. In addition, the integrated code includes databases with fuel, coolant and structural materials properties. Neutronic module DN3D provides full-scale simulation of neutronic processes in fast reactors. Heat sources distribution, control rods movement, reactivity level changes and other processes can be simulated. Neutron transport equation in multigroup diffusion approximation is solved. This paper contains some calculations implemented as a part of EUCLID/V1 code validation. A fast-neutron lead-cooled reactor BREST-OD-300 transient simulation (fuel assembly floating, decompression of passive feedback system channel) and cross-validation with MCU-FR code results are presented in this paper. The calculations demonstrate EUCLID/V1 code application for BREST-OD-300 simulating and safety justification.

Neutron detection using a water Cherenkov detector with pure water and a single PMT

NASA Astrophysics Data System (ADS)

Sidelnik, Iván; Asorey, Hernán; Blostein, Juan Jerónimo; Gómez Berisso, Mariano

2017-12-01

We present the performance of a novel neutron detector based on a water Cherenkov detector (WCD) employing pure water and a single photomultiplier tube (PMT). The experiments presented in this work were performed using 241AmBe and 252Cf neutron sources in different neutron moderator and shielding configurations. We show that fast neutrons from the 241AmBe and 241Cf sources, as well as thermal neutrons from a neutron moderator, despite having different spectral characteristics, produce essentially the same pulse histogram shape. This characteristic pulse-height histogram shapes are recorded as a clear signature of neutrons with energies lower than ≃ 11 MeV . This is verified in different experimental conditions. Our estimation of the neutron detection efficiency is at the level of (15±5)%, for fast neutrons. Since water is the material employed as active volume, the results of this study are of interest for the construction of low cost and large active volume neutron detectors for various applications. Of special importance are those related with space weather phenomena monitoring as well as those for the detection of fissile special nuclear material, including uranium or plutonium.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nekoogar, F; Dowla, F; Wang, T

Recent advancements in the ultra-wide band Radio Frequency Identification (RFID) technology and solid state pillar type neutron detectors have enabled us to move forward in combining both technologies for advanced neutron monitoring. The LLNL RFID tag is totally passive and will operate indefinitely without the need for batteries. The tag is compact, can be directly mounted on metal, and has high performance in dense and cluttered environments. The LLNL coin-sized pillar solid state neutron detector has achieved a thermal neutron detection efficiency of 20% and neutron/gamma discrimination of 1E5. These performance values are comparable to a fieldable {sup 3}He basedmore » detector. In this paper we will discuss features about the two technologies and some potential applications for the advanced safeguarding of nuclear materials.« less

Fissile material detector

DOEpatents

Ivanov, Alexander I.; Lushchikov, Vladislav I.; Shabalin, Eugeny P.; Maznyy, Nikita G.; Khvastunov, Michael M.; Rowland, Mark

2002-01-01

A detector for fissile materials which provides for integrity monitoring of fissile materials and can be used for nondestructive assay to confirm the presence of a stable content of fissile material in items. The detector has a sample cavity large enough to enable assay of large items of arbitrary configuration, utilizes neutron sources fabricated in spatially extended shapes mounted on the endcaps of the sample cavity, incorporates a thermal neutron filter insert with reflector properties, and the electronics module includes a neutron multiplicity coincidence counter.

Background and Source Term Identification in Active Neutron Interrogation Methods

DTIC Science & Technology

2011-03-24

interactions occurred to observe gamma ray peaks and not unduly increase simulation time. Not knowing the uranium enrichment modeled by Gozani, pure U...neutron interactions can occur. The uranium targets, though, should have increased neutron fluencies as the energy levels become below 2 MeV. This is...Assessment Monitor Site (TEAMS) at Kirtland AFB, NM. Iron (Fe-56), lead (Pb-207), polyethylene (C2H4 –– > C-12 & H-1), and uranium (U-235 and U-238) were

Integrating workplace exposure databases for occupational medicine services and epidemiologic studies at a former nuclear weapons facility.

PubMed

Ruttenber, A J; McCrea, J S; Wade, T D; Schonbeck, M F; LaMontagne, A D; Van Dyke, M V; Martyny, J W

2001-02-01

We outline methods for integrating epidemiologic and industrial hygiene data systems for the purpose of exposure estimation, exposure surveillance, worker notification, and occupational medicine practice. We present examples of these methods from our work at the Rocky Flats Plant--a former nuclear weapons facility that fabricated plutonium triggers for nuclear weapons and is now being decontaminated and decommissioned. The weapons production processes exposed workers to plutonium, gamma photons, neutrons, beryllium, asbestos, and several hazardous chemical agents, including chlorinated hydrocarbons and heavy metals. We developed a job exposure matrix (JEM) for estimating exposures to 10 chemical agents in 20 buildings for 120 different job categories over a production history spanning 34 years. With the JEM, we estimated lifetime chemical exposures for about 12,000 of the 16,000 former production workers. We show how the JEM database is used to estimate cumulative exposures over different time periods for epidemiological studies and to provide notification and determine eligibility for a medical screening program developed for former workers. We designed an industrial hygiene data system for maintaining exposure data for current cleanup workers. We describe how this system can be used for exposure surveillance and linked with the JEM and databases on radiation doses to develop lifetime exposure histories and to determine appropriate medical monitoring tests for current cleanup workers. We also present time-line-based graphical methods for reviewing and correcting exposure estimates and reporting them to individual workers.

Calibration of the radiation monitors from DESY and SPring-8 at the quasi-mono-energetic neutron beams using 100 and 300 MeV 7Li(p,n) reaction at RCNP in Osaka Japan in November 2014

NASA Astrophysics Data System (ADS)

Leuschner, Albrecht; Asano, Yoshihiro; Klett, Alfred

2017-09-01

At the ring cyclotron facility of the Research Center for Nuclear Physics (RCNP) Osaka University, Osaka, Japan a series of measurement campaigns had been continued with quasi mono-energetic neutron beams in November 2014. A 7Li target was bombarded with 100 and 300 MeV protons and the generated neutron beams were directed into a long time-of-flight tunnel at 0 and 25 degrees deflection angle with respect to the proton beam. At a distance of 41 m the cross section of the neutron beam was large enough for the illumination of square meter sized objects like extended range rem-counters. The research institutes SPring-8/RIKEN, Japan, and DESY, Germany, participated in this campaign for the calibration of 4 different types of active ambient dose rate monitors: LB 6411, LB 6411-Pb, LB 6419 and LB 6420. The measurements of their responses are reported and compared with the calculated values.

Mössbauer studies of hemoglobin in erythrocytes exposed to neutron radiation

NASA Astrophysics Data System (ADS)

Niemiec, Katarzyna; Kaczmarska, Magdalena; Buczkowski, Mateusz; Fornal, Maria; Pohorecki, Władysław; Matlak, Krzysztof; Korecki, Józef; Grodzicki, Tomasz; Burda, Kvetoslava

2012-03-01

We studied radiation effects on the stability of various states of hemoglobin (Hb) in red blood cells (RBC) irradiated with a very low dose of neutron rays, 50 μGy. We investigated RBCs isolated from blood of healthy donors. Mössbauer spectroscopy was applied to monitor different forms of Hb. Our results show, for the first time, that oxyhemoglobin (OxyHb) and deoxyhemoglobin (DeoxyHb) are two Hb forms sensitive to such a low neutron radiation. Both Hbs change into a new Hb form (Hbirr). Additionally, OxyHb transfers into HbOH/H2O, which under our experimental conditions is resistant to the action of neutron rays.

Boiling-Water Reactor internals aging degradation study. Phase 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luk, K.H.

1993-09-01

This report documents the results of an aging assessment study for boiling water reactor (BWR) internals. Major stressors for BWR internals are related to unsteady hydrodynamic forces generated by the primary coolant flow in the reactor vessel. Welding and cold-working, dissolved oxygen and impurities in the coolant, applied loads and exposures to fast neutron fluxes are other important stressors. Based on results of a component failure information survey, stress corrosion cracking (SCC) and fatigue are identified as the two major aging-related degradation mechanisms for BWR internals. Significant reported failures include SCC in jet-pump holddown beams, in-core neutron flux monitor drymore » tubes and core spray spargers. Fatigue failures were detected in feedwater spargers. The implementation of a plant Hydrogen Water Chemistry (HWC) program is considered as a promising method for controlling SCC problems in BWR. More operating data are needed to evaluate its effectiveness for internal components. Long-term fast neutron irradiation effects and high-cycle fatigue in a corrosive environment are uncertainty factors in the aging assessment process. BWR internals are examined by visual inspections and the method is access limited. The presence of a large water gap and an absence of ex-core neutron flux monitors may handicap the use of advanced inspection methods, such as neutron noise vibration measurements, for BWR.« less

Measurements of secondary neutrons from cosmic radiation with a Bonner sphere spectrometer at 79 degrees N.

PubMed

Rühm, Werner; Mares, V; Pioch, C; Weitzenegger, E; Vockenroth, R; Paretzke, H G

2009-04-01

Air crew members and airline passengers are continuously exposed to cosmic radiation during their flights. Particles ejected by the sun during so-called solar particle events (SPEs) in periods of high solar activity can contribute to this exposure. In rare cases the dose from a single SPE might even exceed the annual dose limit of 1 mSv above which dose monitoring of air crews is legally required in Germany. Measurements performed by means of neutron monitors have already shown that the relative intensity of secondary neutrons from cosmic radiation is enhanced during an SPE, particularly at regions close to the magnetic poles of the Earth where shielding of the cosmic radiation by the geomagnetic field is low. Here we describe a Bonner sphere spectrometer installed at the Koldewey station at 79 degrees N, i.e. about 1,000 km from the geographic North pole, which is designed to provide first experimental data on the time-dependent energy spectrum of neutrons produced in the atmosphere during an SPE. This will be important to calculate doses from these neutrons to air crew members. The system is described in detail and first results are shown that were obtained during quiet periods of sun activity.

Impact of the Revised 10 CFR 835 on the Neutron Dose Rates at LLNL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Radev, R

2009-01-13

In June 2007, 10 CFR 835 [1] was revised to include new radiation weighting factors for neutrons, updated dosimetric models, and dose terms consistent with the newer ICRP recommendations. A significant aspect of the revised 10 CFR 835 is the adoption of the recommendations outlined in ICRP-60 [2]. The recommended new quantities demand a review of much of the basic data used in protection against exposure to sources of ionizing radiation. The International Commission on Radiation Units and Measurements has defined a number of quantities for use in personnel and area monitoring [3,4,5] including the ambient dose equivalent H*(d) tomore » be used for area monitoring and instrument calibrations. These quantities are used in ICRP-60 and ICRP-74. This report deals only with the changes in the ambient dose equivalent and ambient dose rate equivalent for neutrons as a result of the implementation of the revised 10 CFR 835. In the report, the terms neutron dose and neutron dose rate will be used for convenience for ambient neutron dose and ambient neutron dose rate unless otherwise stated. This report provides a qualitative and quantitative estimate of how much the neutron dose rates at LLNL will change with the implementation of the revised 10 CFR 835. Neutron spectra and dose rates from selected locations at the LLNL were measured with a high resolution spectroscopic neutron dose rate system (ROSPEC) as well as with a standard neutron rem meter (a.k.a., a remball). The spectra obtained at these locations compare well with the spectra from the Radiation Calibration Laboratory's (RCL) bare californium source that is currently used to calibrate neutron dose rate instruments. The measurements obtained from the high resolution neutron spectrometer and dose meter ROSPEC and the NRD dose meter compare within the range of {+-}25%. When the new radiation weighting factors are adopted with the implementation of the revised 10 CFR 835, the measured dose rates will increase by up to 22%. The health physicists should consider this increase for any areas that have dose rates near a posting limit, such as near the 100 mrem/hr for a high radiation area, as this increase in measured dose rate may result in some changes to postings and consequent radiological controls.« less

Automation system for measurement of gamma-ray spectra of induced activity for multi-element high volume neutron activation analysis at the reactor IBR-2 of Frank Laboratory of Neutron Physics at the joint institute for nuclear research

NASA Astrophysics Data System (ADS)

Pavlov, S. S.; Dmitriev, A. Yu.; Chepurchenko, I. A.; Frontasyeva, M. V.

2014-11-01

The automation system for measurement of induced activity of gamma-ray spectra for multi-element high volume neutron activation analysis (NAA) was designed, developed and implemented at the reactor IBR-2 at the Frank Laboratory of Neutron Physics. The system consists of three devices of automatic sample changers for three Canberra HPGe detector-based gamma spectrometry systems. Each sample changer consists of two-axis of linear positioning module M202A by DriveSet company and disk with 45 slots for containers with samples. Control of automatic sample changer is performed by the Xemo S360U controller by Systec company. Positioning accuracy can reach 0.1 mm. Special software performs automatic changing of samples and measurement of gamma spectra at constant interaction with the NAA database.

INTEGRATED MONITORING HARDWARE DEVELOPMENTS AT LOS ALAMOS

DOE Office of Scientific and Technical Information (OSTI.GOV)

R. PARKER; J. HALBIG; ET AL

1999-09-01

The hardware of the integrated monitoring system supports a family of instruments having a common internal architecture and firmware. Instruments can be easily configured from application-specific personality boards combined with common master-processor and high- and low-voltage power supply boards, and basic operating firmware. The instruments are designed to function autonomously to survive power and communication outages and to adapt to changing conditions. The personality boards allow measurement of gross gammas and neutrons, neutron coincidence and multiplicity, and gamma spectra. In addition, the Intelligent Local Node (ILON) provides a moderate-bandwidth network to tie together instruments, sensors, and computers.

High Intensity Tests of the NuMI Beam Monitoring Ionization Chambers

NASA Astrophysics Data System (ADS)

Zwaska, Robert

2002-04-01

The NuMI facility at Fermilab will generate an intense beam of neutrinos directed toward Soudan, MN, 735 km away. Components of the planned beam monitoring system will be exposed to fluences of up to 8 x 10^9 charge particles / cm^2 and 6 x 10^10 neutrons / cm^2 in an 8.6 us beam spill. These fluences will be measured by an array of Helium ionization chambers. We tested a pair of chambers with 8 GeV protons at the Fermilab Booster accelerator, and with high intensity neutron sources at the Texas Experimental Nuclear Facility.

Solar-geophysical data number 479, July 1984. Part 1: (Prompt reports). Data for June 1984, May 1984 and later data

NASA Technical Reports Server (NTRS)

Coffey, H. E. (Editor)

1984-01-01

Solar and geophysical data for May and June 1984 are reported. Topics include: detailed index for 1983/1984; data for June 1984 (solar activity indices, solar flares, solar radio emission, mean solar magnetic field, boulder geomagnetic substorm log); data for May 1984 (solar active regions, sudden ionospheric disturbances, solar radio spectral observations, cosmic ray measurements by neutron monitor, geomagnetic indices, radio propagation indices); and late data (geomagnetic indices March and April 1984 sudden commencements/solar flare effects, cosmic ray measurements by neutron monitor, and solar active regions).

A custom-tailored FAMOS burn-up meter for VVER 440 fuel assemblies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simon, G.G.; Golochtchapov, S.; Glazov, A.G.

1995-12-31

The FAMOS fuel assembly monitoring system had been originally developed for monitoring irradiated fuel assemblies of the Karlsruhe Nuclear Research Center concentrating on neutron detection systems for special applications.The measurements in the past had demonstrated that FAMOS can perform precise measurements to control or measure with accuracy the main physical parameters of spent fuel. The FAMOS 3 system is specialized for burn-up determination of fuel assemblies. Thus it is possible to take into account the burn-up for the purposes of storage and transportation. The Kola NPP VVER 440 requirements necessitated developing an especially adopted FAMOS 3 system. In addition tomore » the passive neutron measurement, a gross gamma detection and a boron concentration monitoring system are implemented. The new system was constructed as well as tested in laboratory experiments. The monitoring system has been delivered to the customer and is ready for use.« less

Novel concept for neutron detection: proportional counter filled with 10B nanoparticle aerosol

NASA Astrophysics Data System (ADS)

Amaro, F. D.; Monteiro, C. M. B.; Dos Santos, J. M. F.; Antognini, A.

2017-02-01

The high neutron detection efficiency, good gamma-ray discrimination and non-toxicity of 3He made of proportional counters filled with this gas the obvious choice for neutron detection, particularly in radiation portal monitors (RPM), used to control the illicit transport of nuclear material, of which neutron detectors are key components. 3He is very rare and during the last decade this gas has become increasingly difficult to acquire. With the exception of BF3, which is toxic, no other gas can be used for neutron detection in proportional counters. We present an alternative where the 3He atoms are replaced by nanoparticles made of another neutron sensitive material, 10B. The particles are dispersed in a gaseous volume, forming an aerosol with neutron sensitive properties. A proportional counter filled with such aerosol was exposed to a thermal neutron beam and the recorded response indicates that the neutrons have interacted with the particles in the aerosol. This original technique, which transforms a standard proportional gas mixture into a neutron sensitive aerosol, is a breakthrough in the field of radiation detection and has the potential to become an alternative to the use of 3He in proportional counters.

Detailed characterisation of the incident neutron beam on the TOSCA spectrometer

NASA Astrophysics Data System (ADS)

Pinna, Roberto S.; Rudić, Svemir; Capstick, Matthew J.; McPhail, David J.; Pooley, Daniel E.; Howells, Gareth D.; Gorini, Giuseppe; Fernandez-Alonso, Felix

2017-10-01

We report a detailed characterisation of the incident neutron beam on the TOSCA spectrometer. A bespoke time-of-flight neutron monitor has been designed, constructed and used to perform extensive spatially resolved measurements of the absolute neutron flux and its underlying time structure at the instrument sample position. The obtained data give a quantitative understanding of the current instrument beyond neutronic simulations and provide a baseline in order to assess the performance of the upgraded instrument. At an average proton current-on-target of 153 μA (ISIS Target Station 1; at the time of measurements) we have found that the wavelength-integrated neutron flux (from 0.28 Å to 4.65 Å) at the position of the TOSCA instrument sample (spatially averaged across the 3 × 3cm2 surface centred around (0,0) position) is approximately 1 . 2 × 106 neutrons cm-2s-1, while the whole beam has a homogeneous distribution across the 3 . 0 × 3 . 5cm2 sample surface. The spectra reproduced the well-known shape of the neutrons moderated by the room temperature water moderator and exhibit a neutron flux of 7 . 3 × 105 neutrons cm-2s-1Å-1 at 1 Å.

Nuclear data activities at the n_TOF facility at CERN

NASA Astrophysics Data System (ADS)

Gunsing, F.; Aberle, O.; Andrzejewski, J.; Audouin, L.; Bécares, V.; Bacak, M.; Balibrea-Correa, J.; Barbagallo, M.; Barros, S.; Bečvář, F.; Beinrucker, C.; Belloni, F.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brugger, M.; Caamaño, M.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Cardella, R.; Casanovas, A.; Castelluccio, D. M.; Cerutti, F.; Chen, Y. H.; Chiaveri, E.; Colonna, N.; Cortés-Giraldo, M. A.; Cortés, G.; Cosentino, L.; Damone, L. A.; Deo, K.; Diakaki, M.; Domingo-Pardo, C.; Dressler, R.; Dupont, E.; Durán, I.; Fernández-Domínguez, B.; Ferrari, A.; Ferreira, P.; Finocchiaro, P.; Frost, R. J. W.; Furman, V.; Ganesan, S.; García, A. R.; Gawlik, A.; Gheorghe, I.; Glodariu, T.; Gonçalves, I. F.; González, E.; Goverdovski, A.; Griesmayer, E.; Guerrero, C.; Göbel, K.; Harada, H.; Heftrich, T.; Heinitz, S.; Hernández-Prieto, A.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Katabuchi, T.; Kavrigin, P.; Ketlerov, V.; Khryachkov, V.; Kimura, A.; Kivel, N.; Kokkoris, M.; Krtička, M.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Lerendegui, J.; Licata, M.; Lo Meo, S.; Lonsdale, S. J.; Losito, R.; Macina, D.; Marganiec, J.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Matteucci, F.; Maugeri, E. A.; Mazzone, A.; Mendoza, E.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Mirea, M.; Montesano, S.; Musumarra, A.; Nolte, R.; Oprea, A.; Palomo-Pinto, F. R.; Paradela, C.; Patronis, N.; Pavlik, A.; Perkowski, J.; Porras, I.; Praena, J.; Quesada, J. M.; Rajeev, K.; Rauscher, T.; Reifarth, R.; Riego-Perez, A.; Robles, M.; Rout, P.; Radeck, D.; Rubbia, C.; Ryan, J. A.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schmidt, S.; Schumann, D.; Sedyshev, P.; Smith, A. G.; Stamatopoulos, A.; Suryanarayana, S. V.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tarrío, D.; Tassan-Got, L.; Tsinganis, A.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Warren, S.; Weigand, M.; Weiss, C.; Wolf, C.; Woods, P. J.; Wright, T.; Žugec, P.

2016-10-01

Nuclear data in general, and neutron-induced reaction cross sections in particular, are important for a wide variety of research fields. They play a key role in the safety and criticality assessment of nuclear technology, not only for existing power reactors but also for radiation dosimetry, medical applications, the transmutation of nuclear waste, accelerator-driven systems, fuel cycle investigations and future reactor systems as in Generation IV. Applications of nuclear data are also related to research fields as the study of nuclear level densities and stellar nucleosynthesis. Simulations and calculations of nuclear technology applications largely rely on evaluated nuclear data libraries. The evaluations in these libraries are based both on experimental data and theoretical models. Experimental nuclear reaction data are compiled on a worldwide basis by the international network of Nuclear Reaction Data Centres (NRDC) in the EXFOR database. The EXFOR database forms an important link between nuclear data measurements and the evaluated data libraries. CERN's neutron time-of-flight facility n_TOF has produced a considerable amount of experimental data since it has become fully operational with the start of the scientific measurement programme in 2001. While for a long period a single measurement station (EAR1) located at 185 m from the neutron production target was available, the construction of a second beam line at 20 m (EAR2) in 2014 has substantially increased the measurement capabilities of the facility. An outline of the experimental nuclear data activities at CERN's neutron time-of-flight facility n_TOF will be presented.

High Fluency Low Flux Embrittlement Models of LWR Reactor Pressure Vessel Embrittlement and a Supporting Database from the UCSB ATR-2 Irradiation Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Odette, G. Robert

Reactor pressure vessel embrittlement may limit the lifetime of light water reactors (LWR). Embrittlement is primarily caused by formation of nano-scale precipitates, which cause hardening and a subsequent increase in the ductile-to-brittle transition temperature of the steel. While the effect of Cu has historically been the largest research focus of RPV embrittlement, there is increasing evidence that Mn, Ni and Si are likely to have a large effect at higher fluence, where Mn-Ni-Si precipitates can form, even in the absence of Cu. Therefore, extending RPV lifetimes will require a thorough understanding of both precipitation and embrittlement at higher fluences thanmore » have ever been observed in a power reactor. To address this issue, test reactors that irradiate materials at higher neutron fluxes than power reactors are used. These experiments at high neutron flux can reach extended life neutron fluences in only months or several years. The drawback of these test irradiations is that they add additional complexity to interpreting the data, as the irradiation flux also plays a role into both precipitate formation and irradiation hardening and embrittlement. This report focuses on developing a database of both microstructure and mechanical property data to better understand the effect of flux. In addition, a previously developed model that enables the comparison of data taken over a range of neutron flux is discussed.« less

Managing NIF safety equipment in a high neutron and gamma radiation environment.

PubMed

Datte, Philip; Eckart, Mark; Jackson, Mark; Khater, Hesham; Manuel, Stacie; Newton, Mark

2013-06-01

The National Ignition Facility (NIF) is a 192 laser beam facility that supports the Inertial Confinement Fusion program. During the ignition experimental campaign, the NIF is expected to perform shots with varying fusion yield producing 14 MeV neutrons up to 20 MJ or 7.1 × 10(18) neutrons per shot and a maximum annual yield of 1,200 MJ. Several infrastructure support systems will be exposed to varying high yield shots over the facility's 30-y life span. In response to this potential exposure, analysis and testing of several facility safety systems have been conducted. A detailed MCNP (Monte Carlo N-Particle Transport Code) model has been developed for the NIF facility, and it includes most of the major structures inside the Target Bay. The model has been used in the simulation of expected neutron and gamma fluences throughout the Target Bay. Radiation susceptible components were identified and tested to fluences greater than 10(13) (n cm(-2)) for 14 MeV neutrons and γ-ray equivalent. The testing includes component irradiation using a 60Co gamma source and accelerator-based irradiation using 4- and 14- MeV neutron sources. The subsystem implementation in the facility is based on the fluence estimates after shielding and survivability guidelines derived from the dose maps and component tests results. This paper reports on the evaluation and implementation of mitigations for several infrastructure safety support systems, including video, oxygen monitoring, pressure monitors, water sensing systems, and access control interfaces found at the NIF.

Progress in the development of the neutron flux monitoring system of the French GEN-IV SFR: simulations and experimental validations [ANIMMA--2015-IO-392

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jammes, C.; Filliatre, P.; Izarra, G. de

France has a long experience of about 50 years in designing, building and operating sodium-cooled fast reactors (SFR) such as RAPSODIE, PHENIX and SUPER PHENIX. Fast reactors feature the double capability of reducing nuclear waste and saving nuclear energy resources by burning actinides. Since this reactor type is one of those selected by the Generation IV International Forum, the French government asked, in the year 2006, CEA, namely the French Alternative Energies and Atomic Energy Commission, to lead the development of an innovative GEN-IV nuclear- fission power demonstrator. The major objective is to improve the safety and availability of anmore » SFR. The neutron flux monitoring (NFM) system of any reactor must, in any situation, permit both reactivity control and power level monitoring from startup to full power. It also has to monitor possible changes in neutron flux distribution within the core region in order to prevent any local melting accident. The neutron detectors will have to be installed inside the reactor vessel because locations outside the vessel will suffer from severe disadvantages; radially the neutron shield that is also contained in the reactor vessel will cause unacceptable losses in neutron flux; below the core the presence of a core-catcher prevents from inserting neutron guides; and above the core the distance is too large to obtain decent neutron signals outside the vessel. Another important point is to limit the number of detectors placed in the vessel in order to alleviate their installation into the vessel. In this paper, we show that the architecture of the NFM system will rely on high-temperature fission chambers (HTFC) featuring wide-range flux monitoring capability. The definition of such a system is presented and the justifications of technological options are brought with the use of simulation and experimental results. Firstly, neutron-transport calculations allow us to propose two in-vessel regions, namely the above-core and under-core structures. We verify that they comply with the main objective, that is the neutron power and flux distribution monitoring. HTFC placed in these two regions can detect an inadvertent control rod withdrawal that is a postulated initiating event for safety demonstration. Secondly, we show that the HTFC reliability is enhanced thanks to a more robust physical design and the fact that it has been justified that the mineral insulation is insensitive to any increase in temperature. Indeed, the HTFC insulation is subject to partial discharges at high temperature when the electric field between their electrodes is greater than about 200 V/mm or so. These discharges give rise to signals similar to the neutron pulses generated by a fission chamber itself, which may bias the HTFC count rate at start-up only. However, as displayed in Figure 1, we have experimentally verified that one can discriminate neutron pulses from partial discharges using online estimation of pulse width. Thirdly, we propose to estimate the count rate of a HTFC using the third order cumulant of its signal that is described by a filtered Poisson process. For such a statistic process, it is known that any cumulant, also called cumulative moment, is proportional to the process intensity that is here the count rate of a fission chamber. One recalls that the so-called Campbelling mode of such a detector is actually based on the signal variance, which is the second-order cumulant as well. The use of this extended Campbelling mode based on the third-order cumulant will permit to ensure the HTFC response linearity over the entire neutron flux range using a signal processing technique that is simple enough to satisfy design constraints on electric devices important for nuclear safety. We also show that this technique, named high order Campbelling method (HOC), is significantly more robust than another technique based on the change in the HTFC filling gas, which consists in adding a few percent of nitrogen. Finally, we also present an experimental campaign devoted to the required calibration process of the so-called HOC method. The Campbelling results show a good agreement with the simple pulse counting estimation at low count rates. It is also shown that the HOC technique provides a linear estimation of the count rates at higher power levels as well.« less

Boron-coated straws as a replacement for 3He-based neutron detectors

NASA Astrophysics Data System (ADS)

Lacy, Jeffrey L.; Athanasiades, Athanasios; Sun, Liang; Martin, Christopher S.; Lyons, Tom D.; Foss, Michael A.; Haygood, Hal B.

2011-10-01

US and international government efforts to equip major seaports with large area neutron detectors, aimed to intercept the smuggling of nuclear materials, have precipitated a critical shortage of 3He gas. It is estimated that the annual demand of 3He for US security applications alone is more than the worldwide supply. This is strongly limiting the prospects of neutron science, safeguards, and other applications that rely heavily on 3He-based detectors. Clearly, alternate neutron detection technologies that can support large sensitive areas, and have low gamma sensitivity and low cost must be developed. We propose a low-cost technology based on long copper tubes (straws), coated on the inside with a thin layer of 10B-enriched boron carbide ( 10B 4C). In addition to the high abundance of boron on Earth and low cost of 10B enrichment, the boron-coated straw (BCS) detector offers distinct advantages over conventional 3He-based detectors, and alternate technologies such as 10BF 3 tubes and 10B-coated rigid tubes. These include better distribution inside moderator assemblies, many-times faster electronic signals, no pressurization, improved gamma-ray rejection, no toxic or flammable gases, and ease of serviceability. We present the performance of BCS detectors dispersed in a solid plastic moderator to address the need for portal monitoring. The design adopts the outer dimensions of currently deployed 3He-based monitors, but takes advantage of the small BCS diameter to achieve a more uniform distribution of neutron converter throughout the moderating material. We show that approximately 63 BCS detectors, each 205 cm long, distributed inside the moderator, can match or exceed the detection efficiency of typical monitors fitted with a 5 cm diameter 3He tube, 187 cm long, pressurized to 3 atm.

Status of the NIST Penning-Trap Neutron Lifetime Measurement

NASA Astrophysics Data System (ADS)

Snow, W. M.; Fei, X.; Chowdhuri, Z.; Dewey, M. S.; Gilliam, D.; Nico, J. S.; Greene, G. L.

1998-10-01

The decay rate of the free neutron is important input for Big-Bang Nucleosynthesis calculations of the primordial ^4He abundance in the universe(T. P. Walker et al, Astrophys. J. 376, 51 (1991).) and for tests of the electroweak model in the charged-current sector(I. S. Towner, Nucl. Phys. A540, 478 (1992).). We will describe an experiment in progress at NIST to measure the neutron decay rate. The technique uses a Penning trap to trap and count protons from in-beam neutron decay(J. Byrne et al., Phys. Rev. Lett. 65, 289 (1990).) and an absolutely calibrated beam monitor to measure the neutron density in the beam(R. D. Scott et al., Nucl. Inst. Meth. A362, 151 (1995).). We will present data taken in the spring and summer of 1998.

Fast neutron-gamma discrimination on neutron emission profile measurement on JT-60U.

PubMed

Ishii, K; Shinohara, K; Ishikawa, M; Baba, M; Isobe, M; Okamoto, A; Kitajima, S; Sasao, M

2010-10-01

A digital signal processing (DSP) system is applied to stilbene scintillation detectors of the multichannel neutron emission profile monitor in JT-60U. Automatic analysis of the neutron-γ pulse shape discrimination is a key issue to diminish the processing time in the DSP system, and it has been applied using the two-dimensional (2D) map. Linear discriminant function is used to determine the dividing line between neutron events and γ-ray events on a 2D map. In order to verify the validity of the dividing line determination, the pulse shape discrimination quality is evaluated. As a result, the γ-ray contamination in most of the beam heating phase was negligible compared with the statistical error with 10 ms time resolution.

Fast neutron-gamma discrimination on neutron emission profile measurement on JT-60U

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishii, K.; Okamoto, A.; Kitajima, S.

2010-10-15

A digital signal processing (DSP) system is applied to stilbene scintillation detectors of the multichannel neutron emission profile monitor in JT-60U. Automatic analysis of the neutron-{gamma} pulse shape discrimination is a key issue to diminish the processing time in the DSP system, and it has been applied using the two-dimensional (2D) map. Linear discriminant function is used to determine the dividing line between neutron events and {gamma}-ray events on a 2D map. In order to verify the validity of the dividing line determination, the pulse shape discrimination quality is evaluated. As a result, the {gamma}-ray contamination in most of themore » beam heating phase was negligible compared with the statistical error with 10 ms time resolution.« less

A Unique Outside Neutron and Gamma Ray Instrumentation Development Test Facility at NASA's Goddard Space Flight Center

NASA Technical Reports Server (NTRS)

Bodnarik, J.; Evans, L.; Floyd, S.; Lim, L.; McClanahan, T.; Namkung, M.; Parsons, A.; Schweitzer, J.; Starr, R.; Trombka, J.

2010-01-01

An outside neutron and gamma ray instrumentation test facility has been constructed at NASA's Goddard Space Flight Center (GSFC) to evaluate conceptual designs of gamma ray and neutron systems that we intend to propose for future planetary lander and rover missions. We will describe this test facility and its current capabilities for operation of planetary in situ instrumentation, utilizing a l4 MeV pulsed neutron generator as the gamma ray excitation source with gamma ray and neutron detectors, in an open field with the ability to remotely monitor and operate experiments from a safe distance at an on-site building. The advantage of a permanent test facility with the ability to operate a neutron generator outside and the flexibility to modify testing configurations is essential for efficient testing of this type of technology. Until now, there have been no outdoor test facilities for realistically testing neutron and gamma ray instruments planned for solar system exploration

Neutron scattering cross section measurements for Fe 56

DOE PAGES

Ramirez, A. P. D.; Vanhoy, J. R.; Hicks, S. F.; ...

2017-06-09

Elastic and inelastic differential cross sections for neutron scattering from 56Fe have been measured for several incident energies from 1.30 to 7.96 MeV at the University of Kentucky Accelerator Laboratory. Scattered neutrons were detected using a C 6D 6 liquid scintillation detector using pulse-shape discrimination and time-of-flight techniques. The deduced cross sections have been compared with previously reported data, predictions from evaluation databases ENDF, JENDL, and JEFF, and theoretical calculations performed using different optical model potentials using the TALYS and EMPIRE nuclear reaction codes. The coupled-channel calculations based on the vibrational and soft-rotor models are found to describe the experimentalmore » (n,n 0) and (n,n 1) cross sections well.« less

Neutron scattering cross section measurements for 56Fe

NASA Astrophysics Data System (ADS)

Ramirez, A. P. D.; Vanhoy, J. R.; Hicks, S. F.; McEllistrem, M. T.; Peters, E. E.; Mukhopadhyay, S.; Harrison, T. D.; Howard, T. J.; Jackson, D. T.; Lenzen, P. D.; Nguyen, T. D.; Pecha, R. L.; Rice, B. G.; Thompson, B. K.; Yates, S. W.

2017-06-01

Elastic and inelastic differential cross sections for neutron scattering from 56Fe have been measured for several incident energies from 1.30 to 7.96 MeV at the University of Kentucky Accelerator Laboratory. Scattered neutrons were detected using a C6D6 liquid scintillation detector using pulse-shape discrimination and time-of-flight techniques. The deduced cross sections have been compared with previously reported data, predictions from evaluation databases ENDF, JENDL, and JEFF, and theoretical calculations performed using different optical model potentials using the talys and empire nuclear reaction codes. The coupled-channel calculations based on the vibrational and soft-rotor models are found to describe the experimental (n ,n0 ) and (n ,n1 ) cross sections well.

Neutron induced fission of 237Np - status, challenges and opportunities

NASA Astrophysics Data System (ADS)

Ruskov, Ivan; Goverdovski, Andrei; Furman, Walter; Kopatch, Yury; Shcherbakov, Oleg; Hambsch, Franz-Josef; Oberstedt, Stephan; Oberstedt, Andreas

2018-03-01

Nowadays, there is an increased interest in a complete study of the neutron-induced fission of 237Np. This is due to the need of accurate and reliable nuclear data for nuclear science and technology. 237Np is generated (and accumulated) in the nuclear reactor core during reactor operation. As one of the most abundant long-lived isotopes in spent fuel ("waste"), the incineration of 237Np becomes an important issue. One scenario for burning of 237Np and other radio-toxic minor actinides suggests they are to be mixed into the fuel of future fast-neutron reactors, employing the so-called transmutation and partitioning technology. For testing present fission models, which are at the basis of new generation nuclear reactor developments, highly accurate and detailed neutron-induced nuclear reaction data is needed. However, the EXFOR nuclear database for 237Np on neutron-induced capture cross-section, σγ, and fission cross-section, σf, as well as on the characteristics of capture and fission resonance parameters (Γγ, Γf, σoΓf, fragments mass-energy yield distributions, multiplicities of neutrons vn and γ-rays vγ), has not been updated for decades.

Lessons Learned From Developing Reactor Pressure Vessel Steel Embrittlement Database

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jy-An John

Materials behaviors caused by neutron irradiation under fission and/or fusion environments can be little understood without practical examination. Easily accessible material information system with large material database using effective computers is necessary for design of nuclear materials and analyses or simulations of the phenomena. The developed Embrittlement Data Base (EDB) at ORNL is this comprehensive collection of data. EDB database contains power reactor pressure vessel surveillance data, the material test reactor data, foreign reactor data (through bilateral agreements authorized by NRC), and the fracture toughness data. The lessons learned from building EDB program and the associated database management activity regardingmore » Material Database Design Methodology, Architecture and the Embedded QA Protocol are described in this report. The development of IAEA International Database on Reactor Pressure Vessel Materials (IDRPVM) and the comparison of EDB database and IAEA IDRPVM database are provided in the report. The recommended database QA protocol and database infrastructure are also stated in the report.« less

Neutron Transport Simulations for NIST Neutron Lifetime Experiment

NASA Astrophysics Data System (ADS)

Li, Fangchen; BL2 Collaboration Collaboration

2016-09-01

Neutrons in stable nuclei can exist forever; a free neutron lasts for about 15 minutes on average before it beta decays to a proton, an electron, and an antineutrino. Precision measurements of the neutron lifetime test the validity of weak interaction theory and provide input into the theory of the evolution of light elements in the early universe. There are two predominant ways of measuring the neutron lifetime: the bottle method and the beam method. The bottle method measures decays of ultracold neutrons that are stored in a bottle. The beam method measures decay protons in a beam of cold neutrons of known flux. An improved beam experiment is being prepared at the National Institute of Science and Technology (Gaithersburg, MD) with the goal of reducing statistical and systematic uncertainties to the level of 1 s. The purpose of my studies was to develop computer simulations of neutron transport to determine the beam collimation and study the neutron distribution's effect on systematic effects for the experiment, such as the solid angle of the neutron flux monitor. The motivation for the experiment and the results of this work will be presented. This work was supported, in part, by a Grant to Gettysburg College from the Howard Hughes Medical Institute through the Precollege and Undergraduate Science Education Program.

Influence of Extraterrestrial Radiation on Radiation Portal Monitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keller, Paul E.; Kouzes, Richard T.

2009-06-01

Cosmic radiation and solar flares can be a major source of background radiation at the Earth’s surface. This paper examines the relationship between extraterrestrial radiation and the detectable background in radiation portal monitors used for homeland security applications. Background radiation data from 13 radiation portal monitor facilities are examined and compared against external sources of data related to extraterrestrial radiation, including measurements at neutron monitors located at 53 cosmic-ray observatories around the Earth, four polar orbiting satellites, three geostationary satellites, ground-based geomagnetic field data from observatories around the Earth, a solar magnetic index, solar radio flux data, and sunspot activitymore » data. Four-years (January 2003 through December 2006) of data are used in this study, which include the latter part of Solar Cycle 23 as solar activity was on the decline. The analysis shows a significant relationship between some extraterrestrial radiation and the background detected in the radiation portal monitors. A demonstrable decline is shown in the average gamma ray and neutron background at the radiation portal monitors as solar activity declined over the period of the study.« less

Enhanced multifunctional paint for detection of radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farmer, Joseph C.; Moses, Edward Ira; Rubenchik, Alexander M.

An enhanced multifunctional paint apparatus, systems, and methods for detecting radiation on a surface include providing scintillation particles; providing an enhance neutron absorptive material; providing a binder; combining the scintillation particles, the enhance neutron absorptive material, and the binder creating a multifunctional paint; applying the multifunctional paint to the surface; and monitoring the surface for detecting radiation.

Synopsis of moisture monitoring by neutron probe in the unsaturated zone at Area G

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vold, E.

1997-12-31

Moisture profiles from neutron probe data provide valuable information in site characterization and to supplement ground water monitoring efforts. The neutron probe precision error (reproducibility) is found to be about 0.2 vol% under in situ field conditions where the slope in moisture content with depth is varying slowly. This error is about 2 times larger near moisture spikes (e.g., at the vapor phase notch), due to the sensitivity of the probe response to vertical position errors on the order of 0.5 inches. Calibrations were performed to correct the downhole probe response to the volumetric moisture content determined on core samples.more » Calibration is sensitive to borehole diameter and casing type, requiring 3 separate calibration relations for the boreholes surveyed here. Power law fits were used for calibration in this study to assure moisture content results greater than zero. Findings in the boreholes reported here confirm the broad features seen previously in moisture profiles at Area G, a near-surface region with large moisture variability, a very dry region at greater depths, and a moisture spike at the vapor phase notch (VPN). This feature is located near the interface between the vitrified and vitrified stratigraphic units and near the base of the mesa. This report describes the in-field calibration methods used for the neutron moisture probe measurements and summarizes preliminary results of the monitoring program in the in-situ monitoring network at Area G. Reported results include three main areas: calibration studies, profiles from each of the vertical boreholes at Area G, and time-dependent variations in a select subset of boreholes. Results are reported here for the vertical borehole network. Results from the horizontal borehole network will be described when available.« less

Measurement of the 115In(n,γ)116 m In reaction cross-section at the neutron energies of 1.12, 2.12, 3.12 and 4.12 MeV

NASA Astrophysics Data System (ADS)

Lawriniang, Bioletty Mary; Badwar, Sylvia; Ghosh, Reetuparna; Jyrwa, Betylda; Vansola, Vibha; Naik, Haladhara; Goswami, Ashok; Naik, Yeshwant; Datrik, Chandra Shekhar; Gupta, Amit Kumar; Singh, Vijay Pal; Pol, Sudir Shibaji; Subramanyam, Nagaraju Balabenkata; Agarwal, Arun; Singh, Pitambar

2015-08-01

The 115In(n,γ)116 m In reaction cross section at neutron energies of 1.12, 2.12, 3.12 and 4.12 MeV was determined by using an activation and off-line γ-ray spectrometric technique. The monoenergetic neutron energies of 1.12 - 4.12 MeV were generated from the 7Li(p,n) reaction by using proton beam with energies of 3 and 4 MeV from the folded tandem ion beam accelerator (FOTIA) at Bhabha Atomic Research Centre (BARC) and with energies of 5 and 6 MeV from the Pelletron facility at Tata Institute of Fundamental Research (TIFR), Mumbai. The 197Au(n,γ)198Au reaction cross-section was used as the neutron flux monitor.The 115In(n,γ)116 m In reaction cross section at neutron energies of 1.12, 2.12, 3.12 and 4.12 MeV was determined by using an activation and off-line γ-ray spectrometric technique. The monoenergetic neutron energies of 1.12 - 4.12 MeV were generated from the 7Li(p,n) reaction by using proton beam with energies of 3 and 4 MeV from the folded tandem ion beam accelerator (FOTIA) at Bhabha Atomic Research Centre (BARC) and with energies of 5 and 6 MeV from the Pelletron facility at Tata Institute of Fundamental Research (TIFR), Mumbai. The 197Au(n,γ)198 Au reaction cross-section was used as the neutron flux monitor. The 115In(n,γ)116 m In reaction cross-sections at neutron energies of 1.12 - 4.12 MeV were compared with the literature data and were found to be in good agreement with one set of data, but not with others. The 115In(n,γ)116 m In cross-section was also calculated theoretically by using the computer code TALYS 1.6 and was found to be slightly lower than the experimental data from the present work and the literature.)198Au reaction cross-section was used as the neutron flux monitor. The 115In(n,γ)116 m In reaction cross-sections at neutron energies of 1.12 - 4.12 MeV were compared with the literature data and were found to be in good agreement with one set of data, but not with others. The 115In(n,γ)116 m In cross-section was also calculated theoretically by using the computer code TALYS 1.6 and was found to be slightly lower than the experimental data from the present work and the literature.

Physical principles of neutron-gamma materials monitoring

NASA Astrophysics Data System (ADS)

Pekarskii, G. Sh.

1986-03-01

The physical principles of secondary radiation methods in nondestructive testing are discussed. Among the techniques considered are: neutron activation analysis (NAA); the induced-radiation method; and quasialbedo recording of secondary gamma-radiation. Emphasis is given to the neutron-gamma method which consists of exposing test material to a neutron flux and recording the secondary gamma-radiation by means of a spectrometer. The limitations of the method in detecting local inhomogeneous defects (filled pores cracks, and inclusions) in metal layers and multicomponents materials are described, and some advantages of the method over NAA are discussed. Formulas are derived for estimating the optimum density of the gamma-ray flux which is received by the detector.

Physical principles of neutron-gamma materials monitoring

NASA Astrophysics Data System (ADS)

Pekarskii, G. Sh.

1985-07-01

The physical principles of secondary radiation methods in nondestructive testing are discussed. Among the techniques considered are: neutron activation analysis (NAA); the induced-radiation method; and quasialbedo recording of secondary gamma-radiation. Emphasis is given to the neutron-gamma method which consists of exposing test material to a neutron flux and recording the secondary gamma-radiation by means of a spectrometer. The limitations of the method in detecting local inhomogeneous defects (filled pores cracks, and inclusions) in metal layers and multicomponents materials are described, and some advantages of the method over NAA are discussed. Formulas are derived for estimating the optimum density of the gamma-ray flux which is received by the detector.

Source-to-incident-flux relation in a Tokamak blanket module

NASA Astrophysics Data System (ADS)

Imel, G. R.

The next-generation Tokamak experiments, including the Tokamak fusion test reactor (TFTR), will utilize small blanket modules to measure performance parameters such as tritium breeding profiles, power deposition profiles, and neutron flux profiles. Specifically, a neutron calorimeter (simply a neutron moderating blanket module) which permits inferring the incident 14 MeV flux based on measured temperature profiles was proposed for TFTR. The problem of how to relate this total scalar flux to the fusion neutron source is addressed. This relation is necessary since the calorimeter is proposed as a total fusion energy monitor. The methods and assumptions presented was valid for the TFTR Lithium Breeding Module (LBM), as well as other modules on larger Tokamak reactors.

Evaluation of radioisotope tracer and activation analysis techniques for contamination monitoring in space environment simulation chambers

NASA Technical Reports Server (NTRS)

Smathers, J. B.; Kuykendall, W. E., Jr.; Wright, R. E., Jr.; Marshall, J. R.

1973-01-01

Radioisotope measurement techniques and neutron activation analysis are evaluated for use in identifying and locating contamination sources in space environment simulation chambers. The alpha range method allows the determination of total contaminant concentration in vapor state and condensate state. A Cf-252 neutron activation analysis system for detecting oils and greases tagged with stable elements is described. While neutron activation analysis of tagged contaminants offers specificity, an on-site system is extremely costly to implement and provides only marginal detection sensitivity under even the most favorable conditions.

Observing quantum vacuum lensing in a neutron star binary system.

PubMed

Dupays, Arnaud; Robilliard, Cécile; Rizzo, Carlo; Bignami, Giovanni F

2005-04-29

In this Letter we study the propagation of light in the neighborhood of magnetized neutron stars. Because of the optical properties of quantum vacuum in the presence of a magnetic field, the light emitted by background astronomical objects is deviated, giving rise to a phenomenon of the same kind as the gravitational one. We give a quantitative estimation of this effect, and we discuss the possibility of its observation. We show that this effect could be detected by monitoring the evolution of the recently discovered double neutron star system J0737-3039.

Application of nuclear analytical techniques using long-life sealed-tube neutron generators.

PubMed

Bach, P; Cluzeau, S; Lambermont, C

1994-01-01

The new range of sealed-tube neutron generators developed by SODERN appears to be appropriate for the industrial environment. The main characteristics are the high emission stability during the very long lifetime of the tube, flexible pulsed mode capability, safety in operation with no radiation in "off" state, and the easy transportation of equipment. Some applications of the neutron generators, called GENIE, are considered: high-sensitivity measurement of transuranic elements in nuclear waste drums, bulk material analysis for process control, and determination of the airborne pollutants for environmental monitoring.

Exclusive data-based modeling of neutron-nuclear reactions below 20 MeV

NASA Astrophysics Data System (ADS)

Savin, Dmitry; Kosov, Mikhail

2017-09-01

We are developing CHIPS-TPT physics library for exclusive simulation of neutron-nuclear reactions below 20 MeV. Exclusive modeling reproduces each separate scattering and thus requires conservation of energy, momentum and quantum numbers in each reaction. Inclusive modeling reproduces only selected values while averaging over the others and imposes no such constraints. Therefore the exclusive modeling allows to simulate additional quantities like secondary particle correlations and gamma-lines broadening and avoid artificial fluctuations. CHIPS-TPT is based on the formerly included in Geant4 CHIPS library, which follows the exclusive approach, and extends it to incident neutrons with the energy below 20 MeV. The NeutronHP model for neutrons below 20 MeV included in Geant4 follows the inclusive approach like the well known MCNP code. Unfortunately, the available data in this energy region is mostly presented in ENDF-6 format and semi-inclusive. Imposing additional constraints on secondary particles complicates modeling but also allows to detect inconsistencies in the input data and to avoid errors that may remain unnoticed in inclusive modeling.

Neutron diffraction as a tool to monitor the establishment of the electro-osmotic flux during realkalisation of carbonated concrete

NASA Astrophysics Data System (ADS)

Castellote, Marta; Llorente, I.; Andrade, Carmen; Turrillas, X.; Alonso, Cruz; Campo, Javier

2006-11-01

Realkalisation is an electrochemical technique for repairing concrete structures damaged by rebar corrosion due to carbonation. The treatment aims at restoring alkalinity of the concrete by application of a continuous current between the rebar, acting as a cathode, and an external auxiliary electrode placed in a carbonate solution and connected to a positive pole of a power supply. Here we report the application of neutron diffraction in the in situ monitoring of a realkalisation treatment, analysing at the same time the development of the electro-osmotic flux and the microstructural variations in the surroundings of the rebar.

Used fuel storage monitoring using novel 4He scintillation fast neutron detectors and neutron energy discrimination analysis

NASA Astrophysics Data System (ADS)

Kelley, Ryan P.

With an increasing quantity of spent nuclear fuel being stored at power plants across the United States, the demand exists for a new method of cask monitoring. Certifying these casks for transportation and long-term storage is a unique dilemma: their sealed nature lends added security, but at the cost of requiring non-invasive measurement techniques to verify their contents. This research will design and develop a new method of passively scanning spent fuel casks using 4He scintillation detectors to make this process more accurate. 4He detectors are a relatively new technological development whose full capabilities have not yet been exploited. These detectors take advantage of the high 4He cross section for elastic scattering at fast neutron energies, particularly the resonance around 1 MeV. If one of these elastic scattering interactions occurs within the detector, the 4He nucleus takes energy from the incident neutron, then de-excites by scintillation. Photomultiplier Tubes (PMTs) at either end of the detector tube convert this emitted light into an electrical signal. The goal of this research is to use the neutron spectroscopy features of 4He scintillation detectors to maintain accountability of spent fuel in storage. This project will support spent fuel safeguards and the detection of fissile material, in order to minimize the risk of nuclear proliferation and terrorism.

Continued Analysis of the NIST Neutron Lifetime Measurement Using Ultracold Neutrons

NASA Astrophysics Data System (ADS)

Huffer, Craig; Huffman, P. R.; Schelhammer, K. W.; Dewey, M. S.; Huber, M. G.; Hughes, P. P.; Mumm, H. P.; Thompson, A. K.; Coakley, K.; Yue, A. T.; O'Shaughnessy, C. M.; Yang, L.

2013-10-01

The neutron lifetime is an important parameter for constraining the Standard Model and providing input for Big Bang Nucleosynthesis. The current disagreement in the most recent generation of lifetime experiments suggests unknown or underestimated systematics and motivates the need for alternative measurement methods as well as additional investigations into potential systematics. Our measurement was performed using magnetically trapped Ultracold Neutrons in a 3.1 T Ioffe type trap configuration. The decay rate of the neutron population is recorded in real time by monitoring visible light resulting from beta decay. Data collected in late 2010 and early 2011 is being analyzed and systematic effects are being investigated. An overview of our current work on the analysis, Monte Carlo simulations, and systematic effects will be provided. This work was supported by the NSF and NIST.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giacomelli, L.; Department of Physics, Università degli Studi di Milano-Bicocca, Milano; Conroy, S.

The Joint European Torus (JET, Culham, UK) is the largest tokamak in the world devoted to nuclear fusion experiments of magnetic confined Deuterium (D)/Deuterium-Tritium (DT) plasmas. Neutrons produced in these plasmas are measured using various types of neutron detectors and spectrometers. Two of these instruments on JET make use of organic liquid scintillator detectors. The neutron emission profile monitor implements 19 liquid scintillation counters to detect the 2.45 MeV neutron emission from D plasmas. A new compact neutron spectrometer is operational at JET since 2010 to measure the neutron energy spectra from both D and DT plasmas. Liquid scintillation detectorsmore » are sensitive to both neutron and gamma radiation but give light responses of different decay time such that pulse shape discrimination techniques can be applied to identify the neutron contribution of interest from the data. The most common technique consists of integrating the radiation pulse shapes within different ranges of their rising and/or trailing edges. In this article, a step forward in this type of analysis is presented. The method applies a tomographic analysis of the 3-dimensional neutron and gamma pulse shape and pulse height distribution data obtained from liquid scintillation detectors such that n/γ discrimination can be improved to lower energies and additional information can be gained on neutron contributions to the gamma events and vice versa.« less

Determining Light Decay Curves in a Plastic Scintillator using Cosmic Ray Muons

NASA Astrophysics Data System (ADS)

Wakwella, Praveen; Mandanas, Sarah; Wilson, John; Visca, Hannah; Padalino, Stephen; Sangster, T. Craig; Regan, Sean P.

2017-10-01

Plastic scintillators are used in ICF research to measure neutron energies via their time of flight (nToF). The energy resolution and sensitivity of an nToF system is directly correlated with the scintillation decay time of the plastic. To decrease the decay time, some scintillators are quenched with oxygen. Consequently, they become less efficient at producing light. As time passes, oxygen defuses out of the scintillator this in turn increases light production and the decay time. Mono-energetic calibration neutrons produced at accelerator facilities can be used to monitor the decreased oxygen content, however this is a time consuming process and requires that the scintillators be removed from the ICF facilities on a regular basis. Here, a possible method for cross calibrating accelerator neutrons with cosmic ray muons is presented. This method characterizes the scintillator with accelerator-generated neutrons and then cross calibrates them with cosmic ray muons. Once the scintillators are redeployed at the ICF facility the oxygen level can be regularly monitored using muons in situ. Funded in part by the United States Department of Energy through a Grant from the Laboratory for Laser Energetics.

CAD-Based Shielding Analysis for ITER Port Diagnostics

NASA Astrophysics Data System (ADS)

Serikov, Arkady; Fischer, Ulrich; Anthoine, David; Bertalot, Luciano; De Bock, Maartin; O'Connor, Richard; Juarez, Rafael; Krasilnikov, Vitaly

2017-09-01

Radiation shielding analysis conducted in support of design development of the contemporary diagnostic systems integrated inside the ITER ports is relied on the use of CAD models. This paper presents the CAD-based MCNP Monte Carlo radiation transport and activation analyses for the Diagnostic Upper and Equatorial Port Plugs (UPP #3 and EPP #8, #17). The creation process of the complicated 3D MCNP models of the diagnostics systems was substantially accelerated by application of the CAD-to-MCNP converter programs MCAM and McCad. High performance computing resources of the Helios supercomputer allowed to speed-up the MCNP parallel transport calculations with the MPI/OpenMP interface. The found shielding solutions could be universal, reducing ports R&D costs. The shield block behind the Tritium and Deposit Monitor (TDM) optical box was added to study its influence on Shut-Down Dose Rate (SDDR) in Port Interspace (PI) of EPP#17. Influence of neutron streaming along the Lost Alpha Monitor (LAM) on the neutron energy spectra calculated in the Tangential Neutron Spectrometer (TNS) of EPP#8. For the UPP#3 with Charge eXchange Recombination Spectroscopy (CXRS-core), an excessive neutron streaming along the CXRS shutter, which should be prevented in further design iteration.

Self powered neutron detectors as in-core detectors for Sodium-cooled Fast Reactors

NASA Astrophysics Data System (ADS)

Verma, V.; Barbot, L.; Filliatre, P.; Hellesen, C.; Jammes, C.; Svärd, S. Jacobsson

2017-07-01

Neutron flux monitoring system forms an integral part of the design of a Generation IV sodium cooled fast reactor. Diverse possibilities of detector system installation must be studied for various locations in the reactor vessel in order to detect any perturbations in the core. Results from a previous paper indicated that it is possible to detect changes in neutron source distribution initiated by an inadvertent withdrawal of outer control rod with in-vessel fission chambers located azimuthally around the core. It is, however, not possible to follow inner control rod withdrawal and precisely know the location of the perturbation in the core. Hence the use of complimentary in-core detectors coupled with the peripheral fission chambers is proposed to enable robust core monitoring across the radial direction. In this paper, we assess the feasibility of using self-powered neutron detectors (SPNDs) as in-core detectors in fast reactors for detecting local changes in the power distribution when the reactor is operated at nominal power. We study the neutron and gamma contributions to the total output current of the detector modelled with Platinum as the emitter material. It is shown that this SPND placed in an SFR-like environment would give a sufficiently measurable prompt neutron induced current of the order of 600 nA/m. The corresponding induced current in the connecting cable is two orders of magnitude lower and can be neglected. This means that the SPND can follow in-core power fluctuations. This validates the operability of an SPND in an SFR-like environment.

On scaling cosmogenic nuclide production rates for altitude and latitude using cosmic-ray measurements

NASA Astrophysics Data System (ADS)

Desilets, Darin; Zreda, Marek

2001-11-01

The wide use of cosmogenic nuclides for dating terrestrial landforms has prompted a renewed interest in characterizing the spatial distribution of terrestrial cosmic rays. Cosmic-ray measurements from neutron monitors, nuclear emulsions and cloud chambers have played an important role in developing new models for scaling cosmic-ray neutron intensities and, indirectly, cosmogenic production rates. Unfortunately, current scaling models overlook or misinterpret many of these data. In this paper, we describe factors that must be considered when using neutron measurements to determine scaling formulations for production rates of cosmogenic nuclides. Over the past 50 years, the overwhelming majority of nucleon flux measurements have been taken with neutron monitors. However, in order to use these data for scaling spallation reactions, the following factors must be considered: (1) sensitivity of instruments to muons and to background, (2) instrumental biases in energy sensitivity, (3) solar activity, and (4) the way of ordering cosmic-ray data in the geomagnetic field. Failure to account for these factors can result in discrepancies of as much as 7% in neutron attenuation lengths measured at the same location. This magnitude of deviation can result in an error on the order of 20% in cosmogenic production rates scaled from 4300 m to sea level. The shapes of latitude curves of nucleon flux also depend on these factors to a measurable extent, thereby causing additional uncertainties in cosmogenic production rates. The corrections proposed herein significantly improve our ability to transfer scaling formulations based on neutron measurements to scaling formulations applicable to spallation reactions, and, therefore, constitute an important advance in cosmogenic dating methodology.

The application of selected radionuclides for monitoring of the D-D reactions produced by dense plasma-focus device.

PubMed

Jednorog, S; Szydlowski, A; Bienkowska, B; Prokopowicz, R

The dense plasma focus (DPF) device-DPF-1000U which is operated at the Institute of Plasma Physics and Laser Microfusion is the largest that type plasma experiment in the world. The plasma that is formed in large plasma experiments is characterized by vast numbers of parameters. All of them need to be monitored. A neutron activation method occupies a high position among others plasma diagnostic methods. The above method is off-line, remote, and an integrated one. The plasma which has enough temperature to bring about nuclear fusion reactions is always a strong source of neutrons that leave the reactions area and take along energy and important information on plasma parameters and properties as well. Silver as activated material is used as an effective way of neutrons measurement, especially when they are emitted in the form of short pulses like as it happens from the plasma produced in Dense Plasma-Focus devices. Other elements such as beryllium and yttrium are newly introduced and currently tested at the Institute of Plasma Physics and Laser Microfusion to use them in suitable activation neutron detectors. Some specially designed massive indium samples have been recently adopted for angular neutrons distribution measurements (vertical and horizontal) and have been used in the recent plasma experiment conducted on the DPF-1000U device. This choice was substantiated by relatively long half-lives of the neutron induced isotopes and the threshold character of the 115 In(n,n') 115m In nuclear reaction.

Intense fusion neutron sources

NASA Astrophysics Data System (ADS)

Kuteev, B. V.; Goncharov, P. R.; Sergeev, V. Yu.; Khripunov, V. I.

2010-04-01

The review describes physical principles underlying efficient production of free neutrons, up-to-date possibilities and prospects of creating fission and fusion neutron sources with intensities of 1015-1021 neutrons/s, and schemes of production and application of neutrons in fusion-fission hybrid systems. The physical processes and parameters of high-temperature plasmas are considered at which optimal conditions for producing the largest number of fusion neutrons in systems with magnetic and inertial plasma confinement are achieved. The proposed plasma methods for neutron production are compared with other methods based on fusion reactions in nonplasma media, fission reactions, spallation, and muon catalysis. At present, intense neutron fluxes are mainly used in nanotechnology, biotechnology, material science, and military and fundamental research. In the near future (10-20 years), it will be possible to apply high-power neutron sources in fusion-fission hybrid systems for producing hydrogen, electric power, and technological heat, as well as for manufacturing synthetic nuclear fuel and closing the nuclear fuel cycle. Neutron sources with intensities approaching 1020 neutrons/s may radically change the structure of power industry and considerably influence the fundamental and applied science and innovation technologies. Along with utilizing the energy produced in fusion reactions, the achievement of such high neutron intensities may stimulate wide application of subcritical fast nuclear reactors controlled by neutron sources. Superpower neutron sources will allow one to solve many problems of neutron diagnostics, monitor nano-and biological objects, and carry out radiation testing and modification of volumetric properties of materials at the industrial level. Such sources will considerably (up to 100 times) improve the accuracy of neutron physics experiments and will provide a better understanding of the structure of matter, including that of the neutron itself.

3D imaging of neutron tracks using confocal microscopy

NASA Astrophysics Data System (ADS)

Gillmore, Gavin; Wertheim, David; Flowers, Alan

2016-04-01

Neutron detection and neutron flux assessment are important aspects in monitoring nuclear energy production. Neutron flux measurements can also provide information on potential biological damage from exposure. In addition to the applications for neutron measurement in nuclear energy, neutron detection has been proposed as a method of enhancing neutrino detectors and cosmic ray flux has also been assessed using ground-level neutron detectors. Solid State Nuclear Track Detectors (or SSNTDs) have been used extensively to examine cosmic rays, long-lived radioactive elements, radon concentrations in buildings and the age of geological samples. Passive SSNTDs consisting of a CR-39 plastic are commonly used to measure radon because they respond to incident charged particles such as alpha particles from radon gas in air. They have a large dynamic range and a linear flux response. We have previously applied confocal microscopy to obtain 3D images of alpha particle tracks in SSNTDs from radon track monitoring (1). As a charged particle traverses through the polymer it creates an ionisation trail along its path. The trail or track is normally enhanced by chemical etching to better expose radiation damage, as the damaged area is more sensitive to the etchant than the bulk material. Particle tracks in CR-39 are usually assessed using 2D optical microscopy. In this study 6 detectors were examined using an Olympus OLS4100 LEXT 3D laser scanning confocal microscope (Olympus Corporation, Japan). The detectors had been etched for 2 hours 50 minutes at 85 °C in 6.25M NaOH. Post etch the plastics had been treated with a 10 minute immersion in a 2% acetic acid stop bath, followed by rinsing in deionised water. The detectors examined had been irradiated with a 2mSv neutron dose from an Am(Be) neutron source (producing roughly 20 tracks per mm2). We were able to successfully acquire 3D images of neutron tracks in the detectors studied. The range of track diameter observed was between 4 and 10 microns. Thus this study suggests that, using confocal microscopy, 3D imaging of neutron tracks in SSNTDs is feasible. (1) Wertheim D, Gillmore G, Brown L, Petford N. A new method of imaging particle tracks in solid state nuclear track detectors. J Microsc. 2010; 237: 1-6.

Updated and revised neutron reaction data for 236,238Np

NASA Astrophysics Data System (ADS)

Chen, Guochang; Wang, Jimin; Cao, Wentian; Tang, Guoyou; Yu, Baosheng

2017-09-01

Nuclear data with high accuracy for minor actinides play an important role in nuclear technology applications, including reactor design and operation, fuel cycle, estimation of the amount of minor actinides in high burn-up reactors and the minor actinides transmutation. Based on a new set of neutron optical model parameter and the reaction cross section systematics of fissile isotopes, a full set of 236,238Np neutron reaction data from 10-5 eV ˜20 MeV are updated and improved through theoretical calculation. Mainly revised quantities include the total, elastic, inelastic, fission, (n, 2n) and (n, γ) reaction cross sections as well as angular distribution etc. The promising results are obtained when the renewal evaluated data of 236,238Np will replace the evaluated data in CENDL-3.1 database.

Investigations of Forbush decreases in the PAMELA experiment

NASA Astrophysics Data System (ADS)

Lagoida, I. A.; Voronov, S. A.; Mikhailov, V. V.

2017-01-01

A phenomenon in cosmic ray physics now called Forbush decrease (FD), or Forbush effect was discovered by S. Forbush in 1937 [1], it is a sudden decrease of galactic cosmic ray (GCR) intensity near the Earth. However, despite of the long term investigations the nature of this phenomenon is still not completely understood. Today this effect is studied mostly by the neutron monitors and muon hodoscopes, which are located on the Earth’s surface. But these monitors can detect only products of GCR interaction with the Earth atmosphere. Satellite detectors allow to obtain more accurate information about the characteristics of FD. Examples of FDs registered by the PAMELA telescope and observed with Oulu neutron monitor are presented. About 10 events with amplitude more than 3% have been registered from 2006 till 2016 with the PAMELA experiment.

Organic liquid scintillation detectors for on-the-fly neutron/gamma alarming and radionuclide identification in a pedestrian radiation portal monitor

NASA Astrophysics Data System (ADS)

Paff, Marc Gerrit; Ruch, Marc L.; Poitrasson-Riviere, Alexis; Sagadevan, Athena; Clarke, Shaun D.; Pozzi, Sara

2015-07-01

We present new experimental results from a radiation portal monitor based on the use of organic liquid scintillators. The system was tested as part of a 3He-free radiation portal monitor testing campaign at the European Commission's Joint Research Centre in Ispra, Italy, in February 2014. The radiation portal monitor was subjected to a wide range of test conditions described in ANSI N42.35, including a variety of gamma-ray sources and a 20,000 n/s 252Cf source. A false alarm test tested whether radiation portal monitors ever alarmed in the presence of only natural background. The University of Michigan Detection for Nuclear Nonproliferation Group's system triggered zero false alarms in 2739 trials. It consistently alarmed on a variety of gamma-ray sources travelling at 1.2 m/s at a 70 cm source to detector distance. The neutron source was detected at speeds up to 3 m/s and in configurations with up to 8 cm of high density polyethylene shielding. The success of on-the-fly radionuclide identification varied with the gamma-ray source measured as well as with which of two radionuclide identification methods was used. Both methods used a least squares comparison between the measured pulse height distributions to library spectra to pick the best match. The methods varied in how the pulse height distributions were modified prior to the least squares comparison. Correct identification rates were as high as 100% for highly enriched uranium, but as low as 50% for 241Am. Both radionuclide identification algorithms produced mixed results, but the concept of using liquid scintillation detectors for gamma-ray and neutron alarming in radiation portal monitor was validated.

Tomographic analysis of neutron and gamma pulse shape distributions from liquid scintillation detectors at Joint European Torus.

PubMed

Giacomelli, L; Conroy, S; Gorini, G; Horton, L; Murari, A; Popovichev, S; Syme, D B

2014-02-01

The Joint European Torus (JET, Culham, UK) is the largest tokamak in the world devoted to nuclear fusion experiments of magnetic confined Deuterium (D)/Deuterium-Tritium (DT) plasmas. Neutrons produced in these plasmas are measured using various types of neutron detectors and spectrometers. Two of these instruments on JET make use of organic liquid scintillator detectors. The neutron emission profile monitor implements 19 liquid scintillation counters to detect the 2.45 MeV neutron emission from D plasmas. A new compact neutron spectrometer is operational at JET since 2010 to measure the neutron energy spectra from both D and DT plasmas. Liquid scintillation detectors are sensitive to both neutron and gamma radiation but give light responses of different decay time such that pulse shape discrimination techniques can be applied to identify the neutron contribution of interest from the data. The most common technique consists of integrating the radiation pulse shapes within different ranges of their rising and/or trailing edges. In this article, a step forward in this type of analysis is presented. The method applies a tomographic analysis of the 3-dimensional neutron and gamma pulse shape and pulse height distribution data obtained from liquid scintillation detectors such that n/γ discrimination can be improved to lower energies and additional information can be gained on neutron contributions to the gamma events and vice versa.

The neutron guide upgrade of the TOSCA spectrometer

NASA Astrophysics Data System (ADS)

Pinna, Roberto S.; Rudić, Svemir; Parker, Stewart F.; Armstrong, Jeff; Zanetti, Matteo; Škoro, Goran; Waller, Simon P.; Zacek, Daniel; Smith, Clive A.; Capstick, Matthew J.; McPhail, David J.; Pooley, Daniel E.; Howells, Gareth D.; Gorini, Giuseppe; Fernandez-Alonso, Felix

2018-07-01

The primary flightpath of the TOSCA indirect geometry neutron spectrometer has been upgraded with a high-m 14.636 m (including 0.418 m of air gaps) neutron guide composed of ten sections in order to boost the neutron flux at the sample position. The upgraded incident neutron beam has been characterised with the help of the time-of-flight neutron monitor; the beam profile and the gain in the neutron flux data are presented. At an average proton current-on-target of 160 μA and proton energy of 800 MeV (ISIS Target Station 1; at the time of the measurements) we have found that the wavelength-integrated neutron flux (from 0.28 Å to 4.65 Å) at the position of the TOSCA instrument sample (spatially averaged across a 3.0 × 3.0 cm2 surface centred around the (0,0) position) is approximately 2.11 × 107 neutrons cm-2 s-1 while the gain in the neutron flux is as much as 46-fold for neutrons with a wavelength of 2.5 Å. The instrument's excellent spectral resolution and low spectral background have been preserved upon the upgrade. The much improved count rate allows faster measurements where useful data of hydrogen rich samples can be recorded within minutes, as well as experiments involving smaller samples that were not possible in the past.

Ionization signals from diamond detectors in fast-neutron fields

NASA Astrophysics Data System (ADS)

Weiss, C.; Frais-Kölbl, H.; Griesmayer, E.; Kavrigin, P.

2016-09-01

In this paper we introduce a novel analysis technique for measurements with single-crystal chemical vapor deposition (sCVD) diamond detectors in fast-neutron fields. This method exploits the unique electronic property of sCVD diamond sensors that the signal shape of the detector current is directly proportional to the initial ionization profile. In fast-neutron fields the diamond sensor acts simultaneously as target and sensor. The interaction of neutrons with the stable isotopes 12 C and 13 C is of interest for fast-neutron diagnostics. The measured signal shapes of detector current pulses are used to identify individual types of interactions in the diamond with the goal to select neutron-induced reactions in the diamond and to suppress neutron-induced background reactions as well as γ-background. The method is verified with experimental data from a measurement in a 14.3 MeV neutron beam at JRC-IRMM, Geel/Belgium, where the 13C(n, α)10Be reaction was successfully extracted from the dominating background of recoil protons and γ-rays and the energy resolution of the 12C(n, α)9Be reaction was substantially improved. The presented analysis technique is especially relevant for diagnostics in harsh radiation environments, like fission and fusion reactors. It allows to extract the neutron spectrum from the background, and is particularly applicable to neutron flux monitoring and neutron spectroscopy.

The neutrons for science facility at SPIRAL-2

NASA Astrophysics Data System (ADS)

Ledoux, X.; Aïche, M.; Avrigeanu, M.; Avrigeanu, V.; Balanzat, E.; Ban-d'Etat, B.; Ban, G.; Bauge, E.; Bélier, G.; Bém, P.; Borcea, C.; Caillaud, T.; Chatillon, A.; Czajkowski, S.; Dessagne, P.; Doré, D.; Fischer, U.; Frégeau, M. O.; Grinyer, J.; Guillous, S.; Gunsing, F.; Gustavsson, C.; Henning, G.; Jacquot, B.; Jansson, K.; Jurado, B.; Kerveno, M.; Klix, A.; Landoas, O.; Lecolley, F. R.; Lecouey, J. L.; Majerle, M.; Marie, N.; Materna, T.; Mrázek, J.; Negoita, F.; Novák, J.; Oberstedt, S.; Oberstedt, A.; Panebianco, S.; Perrot, L.; Plompen, A. J. M.; Pomp, S.; Prokofiev, A. V.; Ramillon, J. M.; Farget, F.; Ridikas, D.; Rossé, B.; Sérot, O.; Simakov, S. P.; Šimečková, E.; Štefánik, M.; Sublet, J. C.; Taïeb, J.; Tarrío, D.; Tassan-Got, L.; Thfoin, I.; Varignon, C.

2017-09-01

Numerous domains, in fundamental research as well as in applications, require the study of reactions induced by neutrons with energies from few MeV up to few tens of MeV. Reliable measurements also are necessary to improve the evaluated databases used by nuclear transport codes. This energy range covers a large number of topics like transmutation of nuclear waste, design of future fission and fusion reactors, nuclear medicine or test and development of new detectors. A new facility called Neutrons For Science (NFS) is being built for this purpose on the GANIL site at Caen (France). NFS is composed of a pulsed neutron beam for time-of-flight facility as well as irradiation stations for cross-section measurements. Neutrons will be produced by the interaction of deuteron and proton beams, delivered by the SPIRAL-2 linear accelerator, with thick or thin converters made of beryllium or lithium. Continuous and quasi-mono-energetic spectra will be available at NFS up to 40 MeV. In this fast energy region, the neutron flux is expected to be up to 2 orders of magnitude higher than at other existing time-of-flight facilities. In addition, irradiation stations for neutron-, proton- and deuteron-induced reactions will allow performing cross-section measurements by the activation technique. After a description of the facility and its characteristics, the experiments to be performed in the short and medium term will be presented.

USE OF A SIMPLE THERMALISED NEUTRON FIELD FOR QUALITY ACCEPTANCE OF WHOLE BODY TLDS.

PubMed

Gilvin, P J; Baker, S T; Eakins, J S; Tanner, R J

2016-09-01

The individual monitoring service of Public Health England (PHE) uses Harshaw™ whole-body and extremity thermoluminescent dosemeters (TLDs) with high-sensitivity lithium fluoride LiF:Mg,Cu,P, together with Harshaw 8800™ automated readers. The neutron-insensitive, (6)Li-depleted variety of TLD material is used by PHE because the service provides separate neutron and photon dosemeters. The neutron dosemeters are not sensitive to photons and vice versa Since insensitivity to neutrons is a supply requirement for TLDs, there is a need to test every new (annual) consignment for this. Because it is thermal neutrons that produce a response in (6)Li TLDs, a thermal field is needed. To this end, PHE has adopted the simple approach of sandwiching the TLDs between two ISO water-filled slab phantoms. In this arrangement, the fast neutrons from an Am-Be source are effectively thermalised. Details of the method are given, together with the results of supporting MCNP calculations and some typical results. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Neutron detection devices with 6LiF converter layers

NASA Astrophysics Data System (ADS)

Finocchiaro, Paolo; Cosentino, Luigi; Meo, Sergio Lo; Nolte, Ralf; Radeck, Desiree

2018-01-01

The demand for new thermal neutron detectors as an alternative to 3He tubes in research, industrial, safety and homeland security applications, is growing. These needs have triggered research and development activities about new generations of thermal neutron detectors, characterized by reasonable efficiency and gamma rejection comparable to 3He tubes. In this paper we show the state of art of a promising lowcost technique, based on commercial solid state silicon detectors coupled with thin neutron converter layers of 6LiF deposited onto carbon fiber substrates. Several configurations were studied with the GEANT4 simulation code, and then calibrated at the PTB Thermal Neutron Calibration Facility. The results show that the measured detection efficiency is well reproduced by the simulations, therefore validating the simulation tool in view of new designs. These neutron detectors have also been tested at neutron beam facilities like ISIS (Rutherford Appleton Laboratory, UK) and n_TOF (CERN) where a few samples are already in operation for beam flux and 2D profile measurements. Forthcoming applications are foreseen for the online monitoring of spent nuclear fuel casks in interim storage sites.

Neutron Radiography, Tomography, and Diffraction of Commercial Lithium-ion Polymer Batteries

NASA Astrophysics Data System (ADS)

Butler, Leslie G.; Lehmann, Eberhard H.; Schillinger, Burkhard

Imaging an intact, commercial battery as it cycles and wears is proved possible with neutron imaging. The wavelength range of imaging neutrons corresponds nicely with crystallographic dimensions of the electrochemically active species and the metal elec- trodes are relatively transparent. The time scale of charge/discharge cycling is well matched to dynamic tomography as performed with a golden ratio based projection angle ordering. The hydrogen content does create scatter which tends to blur internal struc- ture. In this report, three neutron experiments will be described: 3D images of charged and discharged batteries were obtained with monochromatic neutrons at the FRM II reactor. 2D images (PSI) of fresh and worn batteries as a function of charge state may show a new wear pattern. In situ neutron diffraction (SNS) of the intact battery provides more information about the concentrations of electrochemical species within the battery as a function of charge state and wear. The combination of 2D imaging, 3D imaging, and diffraction data show how neutron imaging can contribute to battery development and wear monitoring.

Measurement of Solar Neutrons on 05 March 2012, Using a Fiber-Type Neutron Monitor Onboard the Attached Payload to the ISS

NASA Astrophysics Data System (ADS)

Koga, K.; Muraki, Y.; Masuda, S.; Shibata, S.; Matsumoto, H.; Kawano, H.

2017-08-01

The solar neutron detector Space Environment Data Acquisition Equipment - Attached Payload (SEDA-FIB) onboard the International Space Station (ISS) detected several events from the solar direction associated with three large solar flares observed on 05 (X1.1), 07 (X5.4), and 09 (M6.3) March 2012. In this study, we focus on the interesting event of 05 March, present the temporal profiles of the neutrons, and discuss the physics that may be related to a possible acceleration scenario for ions above the solar surface. We compare our data with images of the flares obtained by the ultraviolet telescope Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO).

Quasi solution of radiation transport equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pogosbekyan, L.R.; Lysov, D.A.

There is uncertainty with experimental data as well as with input data of theoretical calculations. The neutron distribution from the variational principle, which takes into account both theoretical and experimental data, is obtained to increase the accuracy and speed of neutronic calculations. The neutron imbalance in mesh cells and the discrepancy between experimentally measured and calculated functional of the neutron distribution are simultaneously minimized. A fast-working and simple-programming iteration method is developed to minimize the objective functional. The method can be used in the core monitoring and control system for (a) power distribution calculations, (b) in- and ex-core detector calibration,more » (c) macro-cross sections or isotope distribution correction by experimental data, and (d) core and detector diagnostics.« less

Development of monitoring method of spatial neutron distribution in neutrons-gamma rays mixed field using imaging plate for NCT--depression of the field.

PubMed

Tanaka, Kenichi; Endo, Satoru; Hoshi, Masaharu; Takada, Jun

2011-12-01

The degree of depression in the neutron field caused by neutron absorption in the materials of an imaging plate (IP) was investigated using MCNP-4C. Consequently, the IP doped with Gd, which reproduced the distribution of (157)Gd(n,γ)(158)Gd reaction rate in the previous study, depresses the relative distribution by about 50%. The depression for the IP in which Gd is replaced with similar amount of B atoms was estimated to be about 10%. The signal intensity for this IP is estimated to be at a similar level with that for Gd-doped IP. Copyright © 2011 Elsevier Ltd. All rights reserved.

Construction of monoenergetic neutron calibration fields using 45Sc(p, n)45Ti reaction at JAEA.

PubMed

Tanimura, Y; Saegusa, J; Shikaze, Y; Tsutsumi, M; Shimizu, S; Yoshizawa, M

2007-01-01

The 8 and 27 keV monoenergetic neutron calibration fields have been developed by using (45)Sc(p, n)(45)Ti reaction. Protons from a 4-MV Pelletron accelerator are used to bombard a thin scandium target evaporated onto a platinum disc. The proton energies are finely adjusted to the resonance to generate the 8 and 27 keV neutrons by applying a high voltage to the target assemblies. The neutron energies were measured using the time-of-flight method with a lithium glass scintillation detector. The neutron fluences at a calibration point located at 50 cm from the target were evaluated using Bonner spheres. A long counter was placed at 2.2 m from the target and at 60 degrees to the direction of the proton beam in order to monitor the fluence at the calibration point. Fluence and dose equivalent rates at the calibration point are sufficient to calibrate many types of the neutron survey metres.

Capabilities, Calibration, and Impact of the ISS-RAD Fast Neutron Detector

NASA Technical Reports Server (NTRS)

Leitgab, Martin

2015-01-01

In the current NASA crew radiation health risk assessment framework, estimates for the neutron contributions to crew radiation exposure largely rely on simulated data with sizeable uncertainties due to the lack of experimental measurements inside the ISS. Integrated in the ISS-RAD instrument, the ISS-RAD Fast Neutron Detector (FND) will deploy to the ISS on one of the next cargo supply missions. Together with the ISS-RAD Charged Particle Detector, the FND will perform, for the first time, routine and precise direct neutron measurements inside the ISS between 0.5 and 80 MeV. The measurements will close the NASA Medical Operations Requirement to monitor neutrons inside the ISS and impact crew radiation health risk assessments by reducing uncertainties on the neutron contribution to crew exposure, enabling more efficient mission planning. The presentation will focus on the FND detection mechanism, calibration results and expectations about the FND's interaction with the mixed radiation field inside the ISS.

Selected Hydrogeologic Data for the High Plains Aquifer in Southwestern Laramie County, Wyoming, 1931-2006

USGS Publications Warehouse

Hallberg, Laura L.; Mason, Jon P.

2007-01-01

The U.S. Geological Survey, in cooperation with the Wyoming State Engineer's Office, created a hydrogeologic database for southwestern Laramie County, Wyoming. The database contains records from 166 wells and test holes drilled during 1931-2006. Several types of information, including well construction; well or test hole locations; lithologic logs; gamma, neutron, spontaneous-potential, and single-point resistivity logs; water levels; and transmissivities and storativities estimated from aquifer tests, are available in the database. Most wells and test holes in the database have records containing information about construction, location, and lithology; 77 wells and test holes have geophysical logs; 70 wells have tabulated water-level data; and 60 wells have records of aquifer-test results.

Neutron field characterization at the independent spent fuel storage installation of the Trillo nuclear power plant.

PubMed

Campo, Xandra; Méndez, Roberto; Embid, Miguel; Ortego, Alberto; Novo, Manuel; Sanz, Javier

2018-05-01

Neutron fields inside and outside the independent spent fuel storage installation of Trillo Nuclear Power Plant are characterized exhaustively in terms of neutron spectra and ambient dose equivalent, measured by Bonner sphere system and LB6411 monitor. Measurements are consistent with storage casks and building shield characteristics, and also with casks distribution inside the building. Outer values at least five times lower than dose limit for free access area are found. Measurements with LB6411 and spectrometer are consistent with each other. Copyright © 2018 Elsevier Ltd. All rights reserved.

USAF Summer Research Program - 1993 High School Apprenticeship Program Final Reports, Volume 12, Armstrong Laboratory

DTIC Science & Technology

1993-12-01

on Panasonic TLD . Panasonic Industrial Company; Secaucus, New Jersey. 5. Thurlow, Ronald M. "Neutron Dosimetry Using a Panasonic Thermoluminescent...Radiation Dosimetry Branch Brooks Air Force Base San Antonio, Texas 78235 Final Report for: AFOSR Summer Research Program Armstrong Laboratory Sponsored...Associate Radiation Dosimetry Branch Armstrong Laboratory Abstract In an attempt to improve personnel monitoring for neutron emissions, Panasonic has

DOE Office of Scientific and Technical Information (OSTI.GOV)

Corre, G.; Boudergui, K.; Sannie, G.

Homeland security requests the use Radiation Portal Monitor (RPM). They must be able to detect and differentiate gamma and neutron radiation. Gamma detection is required for illicit transportation of radioactive matter detection. Neutron detection is important to control nonproliferation of enriched material. Manufacturers worldwide propose sensors based on {sup 3}He which give the actual state of art in term of neutron detection. The imminent shortage of {sup 3}He forces manufacturers to find viable alternative. From 10 years sensors providers have the challenge to replace previous {sup 3}He detectors that are known to be the most commonly deployed neutron sensor. Asmore » {sup 3}He detectors can only detect neutron, they must be completed with gamma detector. The proposed approach is based on pulse time correlation between adjacent sensors from signal collected by EJ200 plastic scintillators. Results obtained during FP7 Scintilla project test campaigns show the system relevance for replacement of today's {sup 3}He detectors. (authors)« less

Ames collaborative study of cosmic ray neutrons

NASA Technical Reports Server (NTRS)

Hewitt, J. E.; Hughes, L.; Mccaslin, J. B.; Stephens, L. D.; Rindi, A.; Smith, A. R.; Thomas, R. H.; Griffith, R. V.; Welles, C. G.; Baum, J. W.

1976-01-01

The results of a collaborative study to define both the neutron flux and the spectrum more precisely and to develop a dosimetry package that can be flown quickly to altitude for solar flare events are described. Instrumentation and analysis techniques were used which were developed to measure accelerator-produced radiation. The instruments were flown in the Ames Research Center high altitude aircraft. Neutron instrumentation consisted of Bonner spheres with both active and passive detector elements, threshold detectors of both prompt-counter and activation-element types, a liquid scintillation spectrometer based on pulse-shape discrimination, and a moderated BF3 counter neutron monitor. In addition, charged particles were measured with a Reuter-Stokes ionization chamber system and dose equivalent with another instrument. Preliminary results from the first series of flights at 12.5 km (41,000 ft) are presented, including estimates of total neutron flux intensity and spectral shape and of the variation of intensity with altitude and geomagnetic latitude.

A Monte Carlo simulation study for the gamma-ray/neutron dual-particle imager using rotational modulation collimator (RMC).

PubMed

Kim, Hyun Suk; Choi, Hong Yeop; Lee, Gyemin; Ye, Sung-Joon; Smith, Martin B; Kim, Geehyun

2018-03-01

The aim of this work is to develop a gamma-ray/neutron dual-particle imager, based on rotational modulation collimators (RMCs) and pulse shape discrimination (PSD)-capable scintillators, for possible applications for radioactivity monitoring as well as nuclear security and safeguards. A Monte Carlo simulation study was performed to design an RMC system for the dual-particle imaging, and modulation patterns were obtained for gamma-ray and neutron sources in various configurations. We applied an image reconstruction algorithm utilizing the maximum-likelihood expectation-maximization method based on the analytical modeling of source-detector configurations, to the Monte Carlo simulation results. Both gamma-ray and neutron source distributions were reconstructed and evaluated in terms of signal-to-noise ratio, showing the viability of developing an RMC-based gamma-ray/neutron dual-particle imager using PSD-capable scintillators.

GEM detectors development for radiation environment: neutron tests and simulations

NASA Astrophysics Data System (ADS)

Chernyshova, Maryna; Jednoróg, Sławomir; Malinowski, Karol; Czarski, Tomasz; Ziółkowski, Adam; Bieńkowska, Barbara; Prokopowicz, Rafał; Łaszyńska, Ewa; Kowalska-Strzeciwilk, Ewa; Poźniak, Krzysztof T.; Kasprowicz, Grzegorz; Zabołotny, Wojciech; Wojeński, Andrzej; Krawczyk, Rafał D.; Linczuk, Paweł; Potrykus, Paweł; Bajdel, Barcel

2016-09-01

One of the requests from the ongoing ITER-Like Wall Project is to have diagnostics for Soft X-Ray (SXR) monitoring in tokamak. Such diagnostics should be focused on tungsten emission measurements, as an increased attention is currently paid to tungsten due to a fact that it became a main candidate for the plasma facing material in ITER and future fusion reactor. In addition, such diagnostics should be able to withstand harsh radiation environment at tokamak during its operation. The presented work is related to the development of such diagnostics based on Gas Electron Multiplier (GEM) technology. More specifically, an influence of neutron radiation on performance of the GEM detectors is studied both experimentally and through computer simulations. The neutron induced radioactivity (after neutron source exposure) was found to be not pronounced comparing to an impact of other secondary neutron reaction products (during the exposure).

Low-level gamma and neutron monitoring based on use of proportional counter filled with 3He in polythene moderator: study of the responses to gamma and neutrons.

PubMed

Pszona, S; Bantsar, A; Tulik, P; Wincel, K; Zaręba, B

2014-10-01

It has been shown that a proportional counter filled with (3)He placed centrally inside a polythene sphere opens a new possibility for measuring gamma photons and neutrons in the separate pulse-height windows. The responses to gamma and neutrons (in terms of ambient dose equivalent) of the detector assembly consisting of 203-mm polythene sphere with centrally positioned 40-mm diameter (3)He proportional counter have been studied. The response to secondary gammas from capture process in hydrogen has also been studied. The rather preliminary studies indicate that the proposed measuring system has very promising features as an ambient dose equivalent device for mixed gamma-neutron fields. © The Author 2013. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Neutron measurements in near-Earth orbit with COMPTEL

NASA Technical Reports Server (NTRS)

Morris, D. J.; Aarts, H.; Bennett, K.; Lockwood, J. A.; Mcconnell, M. L.; Ryan, J. M.; Schoenfelder, V.; Steinle, H.; Peng, X.

1995-01-01

The fast neutron flux in near-Earth orbit has been measured with the COMPTEL instrument on the Compton Gamma Ray Observatory (CGRO). For this measurement one of COMPTEL's seven liquid scintillator modules was used as an uncollimated neutron detector with threshold of 12.8 MeV. The measurements cover a range of 4.8 to 15.5 GV in vertical cutoff rigidity and 3 deg to 177 deg in spacecraft geocenter zenith angle. One of the measurements occurred near the minimum of the deepest Forbush decrease ever observed by ground-level neutron monitors. After correction for solar modulation, the total flux is well fitted by separable functions in rigidity and zenith angle. With the spacecraft pointed near the nadir the flux is consistent with balloon measurements of the atmospheric neutron albedo. The flux varies by about a factor of 4 between the extremes of rigidity and a factor of 2 between the extremes of zenith angle. The effect of the spacecraft mass in shielding the detector from the atmospheric neutron albedo is much more important than its role as a source of additional secondary neutrons. The neutron spectral hardness varies little with rigidity or zenith angle and lies in the range spanned by earlier atmospheric neutron albedo measurements.

Monitoring the distribution of prompt gamma rays in boron neutron capture therapy using a multiple-scattering Compton camera: A Monte Carlo simulation study

NASA Astrophysics Data System (ADS)

Lee, Taewoong; Lee, Hyounggun; Lee, Wonho

2015-10-01

This study evaluated the use of Compton imaging technology to monitor prompt gamma rays emitted by 10B in boron neutron capture therapy (BNCT) applied to a computerized human phantom. The Monte Carlo method, including particle-tracking techniques, was used for simulation. The distribution of prompt gamma rays emitted by the phantom during irradiation with neutron beams is closely associated with the distribution of the boron in the phantom. Maximum likelihood expectation maximization (MLEM) method was applied to the information obtained from the detected prompt gamma rays to reconstruct the distribution of the tumor including the boron uptake regions (BURs). The reconstructed Compton images of the prompt gamma rays were combined with the cross-sectional images of the human phantom. Quantitative analysis of the intensity curves showed that all combined images matched the predetermined conditions of the simulation. The tumors including the BURs were distinguishable if they were more than 2 cm apart.

Neutron monitor generated data distributions in quantum variational Monte Carlo

NASA Astrophysics Data System (ADS)

Kussainov, A. S.; Pya, N.

2016-08-01

We have assessed the potential applications of the neutron monitor hardware as random number generator for normal and uniform distributions. The data tables from the acquisition channels with no extreme changes in the signal level were chosen as the retrospective model. The stochastic component was extracted by fitting the raw data with splines and then subtracting the fit. Scaling the extracted data to zero mean and variance of one is sufficient to obtain a stable standard normal random variate. Distributions under consideration pass all available normality tests. Inverse transform sampling is suggested to use as a source of the uniform random numbers. Variational Monte Carlo method for quantum harmonic oscillator was used to test the quality of our random numbers. If the data delivery rate is of importance and the conventional one minute resolution neutron count is insufficient, we could always settle for an efficient seed generator to feed into the faster algorithmic random number generator or create a buffer.

Computer-assisted uncertainty assessment of k0-NAA measurement results

NASA Astrophysics Data System (ADS)

Bučar, T.; Smodiš, B.

2008-10-01

In quantifying measurement uncertainty of measurement results obtained by the k0-based neutron activation analysis ( k0-NAA), a number of parameters should be considered and appropriately combined in deriving the final budget. To facilitate this process, a program ERON (ERror propagatiON) was developed, which computes uncertainty propagation factors from the relevant formulae and calculates the combined uncertainty. The program calculates uncertainty of the final result—mass fraction of an element in the measured sample—taking into account the relevant neutron flux parameters such as α and f, including their uncertainties. Nuclear parameters and their uncertainties are taken from the IUPAC database (V.P. Kolotov and F. De Corte, Compilation of k0 and related data for NAA). Furthermore, the program allows for uncertainty calculations of the measured parameters needed in k0-NAA: α (determined with either the Cd-ratio or the Cd-covered multi-monitor method), f (using the Cd-ratio or the bare method), Q0 (using the Cd-ratio or internal comparator method) and k0 (using the Cd-ratio, internal comparator or the Cd subtraction method). The results of calculations can be printed or exported to text or MS Excel format for further analysis. Special care was taken to make the calculation engine portable by having possibility of its incorporation into other applications (e.g., DLL and WWW server). Theoretical basis and the program are described in detail, and typical results obtained under real measurement conditions are presented.

Parallel simulations of Grover's algorithm for closest match search in neutron monitor data

NASA Astrophysics Data System (ADS)

Kussainov, Arman; White, Yelena

We are studying the parallel implementations of Grover's closest match search algorithm for neutron monitor data analysis. This includes data formatting, and matching quantum parameters to a conventional structure of a chosen programming language and selected experimental data type. We have employed several workload distribution models based on acquired data and search parameters. As a result of these simulations, we have an understanding of potential problems that may arise during configuration of real quantum computational devices and the way they could run tasks in parallel. The work was supported by the Science Committee of the Ministry of Science and Education of the Republic of Kazakhstan Grant #2532/GF3.

Cosmic ray sidereal diurnal variation of galactic origin observed by neutron monitors

NASA Technical Reports Server (NTRS)

Ishida, Y.; Nagashima, K.; Mori, S.; Morishita, I.

1985-01-01

Cosmic ray sidereal diurnal variations observed by neutron monitors are analyzed for the period 1961 to 1978, by adding 134 station years data to the previous paper (Nagashima, et al., 1983). Also the dependence of the sidereal variations on Sun's polar magnetic field polarity is examined for two periods; the period of negative polarity in the northern region, 1961 to 1969 and the period of positive polarity, 1970 to 1978. It is obtained that for the former period, the amplitude A=0.0203 + or 0.0020% and the phase phi=6.1 + or - 0.4 h LST and for the latter period, 0.0020% and phi=8.6 + or - 4 h LST, respectively.

Solar-geophysical data number 499, March 1986. Part 1: (Prompt reports). Data for February 1986, January 1986 and late data

NASA Technical Reports Server (NTRS)

Coffey, H. E. (Editor)

1986-01-01

Solar-Geophysical Data Number 499, March 1986, Part 1 (Prompt Reports); Data for February 1986, January 1986 and Late Data, contains the following: Detailed index for 1985 to 1986; Data for February 1986--(IUWDS alert periods (Advance and worldwide), Solar activity indices, Solar flares, Solar radio emission, Vostok inferred interplanetary magnetic field polarity, Stanford mean solar magnetic field); data for January 1986--(Solar active regions, Sudden ionospheric disturbances, Solar radio spectral observations, Cosmic ray measurements by neutron monitor, Geomagnetic indices, Radio propagation indices); Late data-(Solar active regions, Solar radio spectral observations Culgoora, Cosmic ray measurements by neutron monitor, Calcium plage data).

Geophysical Monitoring Methods Evaluation for the FutureGen 2.0 Project

DOE PAGES

Strickland, Chris E.; USA, Richland Washington; Vermeul, Vince R.; ...

2014-12-31

A comprehensive monitoring program will be needed in order to assess the effectiveness of carbon sequestration at the FutureGen 2.0 carbon capture and storage (CCS) field-site. Geophysical monitoring methods are sensitive to subsurface changes that result from injection of CO 2 and will be used for: (1) tracking the spatial extent of the free phase CO 2 plume, (2) monitoring advancement of the pressure front, (3) identifying or mapping areas where induced seismicity occurs, and (4) identifying and mapping regions of increased risk for brine or CO 2 leakage from the reservoir. Site-specific suitability and cost effectiveness were evaluated formore » a number of geophysical monitoring methods including: passive seismic monitoring, reflection seismic imaging, integrated surface deformation, time-lapse gravity, pulsed neutron capture logging, cross-borehole seismic, electrical resistivity tomography, magnetotellurics and controlled source electromagnetics. The results of this evaluation indicate that CO 2 injection monitoring using reflection seismic methods would likely be difficult at the FutureGen 2.0 site. Electrical methods also exhibited low sensitivity to the expected CO 2 saturation changes and would be affected by metallic infrastructure at the field site. Passive seismic, integrated surface deformation, time-lapse gravity, and pulsed neutron capture monitoring were selected for implementation as part of the FutureGen 2.0 storage site monitoring program.« less

Geophysical Monitoring Methods Evaluation for the FutureGen 2.0 Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strickland, Chris E.; USA, Richland Washington; Vermeul, Vince R.

A comprehensive monitoring program will be needed in order to assess the effectiveness of carbon sequestration at the FutureGen 2.0 carbon capture and storage (CCS) field-site. Geophysical monitoring methods are sensitive to subsurface changes that result from injection of CO 2 and will be used for: (1) tracking the spatial extent of the free phase CO 2 plume, (2) monitoring advancement of the pressure front, (3) identifying or mapping areas where induced seismicity occurs, and (4) identifying and mapping regions of increased risk for brine or CO 2 leakage from the reservoir. Site-specific suitability and cost effectiveness were evaluated formore » a number of geophysical monitoring methods including: passive seismic monitoring, reflection seismic imaging, integrated surface deformation, time-lapse gravity, pulsed neutron capture logging, cross-borehole seismic, electrical resistivity tomography, magnetotellurics and controlled source electromagnetics. The results of this evaluation indicate that CO 2 injection monitoring using reflection seismic methods would likely be difficult at the FutureGen 2.0 site. Electrical methods also exhibited low sensitivity to the expected CO 2 saturation changes and would be affected by metallic infrastructure at the field site. Passive seismic, integrated surface deformation, time-lapse gravity, and pulsed neutron capture monitoring were selected for implementation as part of the FutureGen 2.0 storage site monitoring program.« less

Novel Scintillating Materials Based on Phenyl-Polysiloxane for Neutron Detection and Monitoring

NASA Astrophysics Data System (ADS)

Degerlier, M.; Carturan, S.; Gramegna, F.; Marchi, T.; Palma, M. Dalla; Cinausero, M.; Maggioni, G.; Quaranta, A.; Collazuol, G.; Bermudez, J.

Neutron detectors are extensively used at many nuclear research facilities across Europe. Their application range covers many topics in basic and applied nuclear research: in nuclear structure and reaction dynamics (reaction reconstruction and decay studies); in nuclear astrophysics (neutron emission probabilities); in nuclear technology (nuclear data measurements and in-core/off-core monitors); in nuclear medicine (radiation monitors, dosimeters); in materials science (neutron imaging techniques); in homeland security applications (fissile materials investigation and cargo inspection). Liquid scintillators, widely used at present, have however some drawbacks given by toxicity, flammability, volatility and sensitivity to oxygen that limit their duration and quality. Even plastic scintillators are not satisfactory because they have low radiation hardness and low thermal stability. Moreover organic solvents may affect their optical properties due to crazing. In order to overcome these problems, phenyl-polysiloxane based scintillators have been recently developed at Legnaro National Laboratory. This new solution showed very good chemical and thermal stability and high radiation hardness. The results on the different samples performance will be presented, paying special attention to a characterization comparison between synthesized phenyl containing polysiloxane resins where a Pt catalyst has been used and a scintillating material obtained by condensation reaction, where tin based compounds are used as catalysts. Different structural arrangements as a result of different substituents on the main chain have been investigated by High Resolution X-Ray Diffraction, while the effect of improved optical transmittance on the scintillation yield has been elucidated by a combination of excitation/fluorescence measurements and scintillation yield under exposure to alpha and γ-rays.

A portable neutron spectroscope (NSPECT) for detection, imaging and identification of nuclear material

NASA Astrophysics Data System (ADS)

Ryan, James M.; Bancroft, Christopher; Bloser, Peter; Bravar, Ulisse; Fourguette, Dominique; Frost, Colin; Larocque, Liane; McConnell, Mark L.; Legere, Jason; Pavlich, Jane; Ritter, Greg; Wassick, Greg; Wood, Joshua; Woolf, Richard

2010-08-01

We have developed, fabricated and tested a prototype imaging neutron spectrometer designed for real-time neutron source location and identification. Real-time detection and identification is important for locating materials. These materials, specifically uranium and transuranics, emit neutrons via spontaneous or induced fission. Unlike other forms of radiation (e.g. gamma rays), penetrating neutron emission is very uncommon. The instrument detects these neutrons, constructs images of the emission pattern, and reports the neutron spectrum. The device will be useful for security and proliferation deterrence, as well as for nuclear waste characterization and monitoring. The instrument is optimized for imaging and spectroscopy in the 1-20 MeV range. The detection principle is based upon multiple elastic neutron-proton scatters in organic scintillator. Two detector panel layers are utilized. By measuring the recoil proton and scattered neutron locations and energies, the direction and energy spectrum of the incident neutrons can be determined and discrete and extended sources identified. Event reconstruction yields an image of the source and its location. The hardware is low power, low mass, and rugged. Its modular design allows the user to combine multiple units for increased sensitivity. We will report the results of laboratory testing of the instrument, including exposure to a calibrated Cf-252 source. Instrument parameters include energy and angular resolution, gamma rejection, minimum source identification distances and times, and projected effective area for a fully populated instrument.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soldevilla, M.; Salmons, S.; Espinosa, B.

The new application BDDR (Reactor database) has been developed at CEA in order to manage nuclear reactors technological and operating data. This application is a knowledge management tool which meets several internal needs: -) to facilitate scenario studies for any set of reactors, e.g. non-proliferation assessments; -) to make core physics studies easier, whatever the reactor design (PWR-Pressurized Water Reactor-, BWR-Boiling Water Reactor-, MAGNOX- Magnesium Oxide reactor-, CANDU - CANada Deuterium Uranium-, FBR - Fast Breeder Reactor -, etc.); -) to preserve the technological data of all reactors (past and present, power generating or experimental, naval propulsion,...) in a uniquemore » repository. Within the application database are enclosed location data and operating history data as well as a tree-like structure containing numerous technological data. These data address all kinds of reactors features and components. A few neutronics data are also included (neutrons fluxes). The BDDR application is based on open-source technologies and thin client/server architecture. The software architecture has been made flexible enough to allow for any change. (authors)« less

Monitoring system for a liquid-cooled nuclear fission reactor

DOEpatents

DeVolpi, Alexander

1987-01-01

A monitoring system for detecting changes in the liquid levels in various regions of a water-cooled nuclear power reactor, viz., in the downcomer, in the core, in the inlet and outlet plenums, at the head, and elsewhere; and also for detecting changes in the density of the liquid in these regions. A plurality of gamma radiation detectors are used, arranged vertically along the outside of the reactor vessel, and collimator means for each detector limits the gamma-radiation it receives as emitting from only isolated regions of the vessel. Excess neutrons produced by the fission reaction will be captured by the water coolant, by the steel reactor walls, or by the fuel or control structures in the vessel. Neutron capture by steel generates gamma radiation having an energy level of the order of 5-12 MeV, whereas neutron capture by water provides an energy level of approximately 2.2 MeV, and neutron capture by the fission fuel or its cladding provides an energy level of 1 MeV or less. The intensity of neutron capture thus changes significantly at any water-metal interface. Comparative analysis of adjacent gamma detectors senses changes from the normal condition with liquid coolant present to advise of changes in the presence and/or density of the coolant at these specific regions. The gamma detectors can also sense fission-product gas accumulation at the reactor head to advise of a failure of fuel-pin cladding.

Status of the nuclear measurement stations for the process control of spent fuel reprocessing at AREVA NC/La Hague

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eleon, Cyrille; Passard, Christian; Hupont, Nicolas

2015-07-01

Nuclear measurements are used at AREVA NC/La Hague for the monitoring of spent fuel reprocessing. The process control is based on gamma-ray spectroscopy, passive neutron counting and active neutron interrogation, and gamma transmission measurements. The main objectives are criticality and safety, online process monitoring, and the determination of the residual fissile mass and activities in the metallic waste remained after fuel shearing and dissolution (empty hulls, grids, end pieces), which are put in radioactive waste drums before compaction. The whole monitoring system is composed of eight measurement stations which will be described in this paper. The main measurement stations no.more » 1, 3 and 7 are needed for criticality control. Before fuel element shearing for dissolution, station no. 1 allows determining the burn-up of the irradiated fuel by gamma-ray spectroscopy with HP Ge (high purity germanium) detectors. The burn-up is correlated to the {sup 137}Cs and {sup 134}Cs gamma emission rates. The fuel maximal mass which can be loaded in one bucket of the dissolver is estimated from the lowest burn-up fraction of the fuel element. Station no. 3 is dedicated to the control of the correct fuel dissolution, which is performed with a {sup 137}Cs gamma ray measurement with a HP Ge detector. Station no. 7 allows estimating the residual fissile mass in the drums filled with the metallic residues, especially in the hulls, from passive neutron counting (spontaneous fission and alpha-n reactions) and active interrogation (fission prompt neutrons induced by a pulsed neutron generator) with proportional {sup 3}He detectors. The measurement stations have been validated for the reprocessing of Uranium Oxide (UOX) fuels with a burn-up rate up to 60 GWd/t. This paper presents a brief overview of the current status of the nuclear measurement stations. (authors)« less

Project for the development of the linac based NCT facility in University of Tsukuba.

PubMed

Kumada, H; Matsumura, A; Sakurai, H; Sakae, T; Yoshioka, M; Kobayashi, H; Matsumoto, H; Kiyanagi, Y; Shibata, T; Nakashima, H

2014-06-01

A project team headed by University of Tsukuba launched the development of a new accelerator based BNCT facility. In the project, we have adopted Radio-Frequency Quadrupole (RFQ)+Drift Tube Linac (DTL) type linac as proton accelerators. Proton energy generated from the linac was set to 8MeV and average current was 10mA. The linac tube has been constructed by Mitsubishi Heavy Industry Co. For neutron generator device, beryllium is selected as neutron target material; high intensity neutrons are generated by the reaction with beryllium and the 80kW proton beam. Our team chose beryllium as the neutron target material. At present beryllium target system is being designed with Monte-Carlo estimations and heat analysis with ANSYS. The neutron generator consists of moderator, collimator and shielding. It is being designed together with the beryllium target system. We also acquired a building in Tokai village; the building has been renovated for use as BNCT treatment facility. It is noteworthy that the linac tube had been installed in the facility in September 2012. In BNCT procedure, several medical devices are required for BNCT treatment such as treatment planning system, patient positioning device and radiation monitors. Thus these are being developed together with the linac based neutron source. For treatment planning system, we are now developing a new multi-modal Monte-Carlo treatment planning system based on JCDS. The system allows us to perform dose estimation for BNCT as well as particle radiotherapy and X-ray therapy. And the patient positioning device can navigate a patient to irradiation position quickly and properly. Furthermore the device is able to monitor movement of the patient׳s position during irradiation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Modeling of displacement damage in silicon carbide detectors resulting from neutron irradiation

NASA Astrophysics Data System (ADS)

Khorsandi, Behrooz

There is considerable interest in developing a power monitor system for Generation IV reactors (for instance GT-MHR). A new type of semiconductor radiation detector is under development based on silicon carbide (SiC) technology for these reactors. SiC has been selected as the semiconductor material due to its superior thermal-electrical-neutronic properties. Compared to Si, SiC is a radiation hard material; however, like Si, the properties of SiC are changed by irradiation by a large fluence of energetic neutrons, as a consequence of displacement damage, and that irradiation decreases the life-time of detectors. Predictions of displacement damage and the concomitant radiation effects are important for deciding where the SiC detectors should be placed. The purpose of this dissertation is to develop computer simulation methods to estimate the number of various defects created in SiC detectors, because of neutron irradiation, and predict at what positions of a reactor, SiC detectors could monitor the neutron flux with high reliability. The simulation modeling includes several well-known---and commercial---codes (MCNP5, TRIM, MARLOWE and VASP), and two kinetic Monte Carlo codes written by the author (MCASIC and DCRSIC). My dissertation will highlight the displacement damage that may happen in SiC detectors located in available positions in the OSURR, GT-MHR and IRIS. As extra modeling output data, the count rates of SiC for the specified locations are calculated. A conclusion of this thesis is SiC detectors that are placed in the thermal neutron region of a graphite moderator-reflector reactor have a chance to survive at least one reactor refueling cycle, while their count rates are acceptably high.

Simultaneous Forbush decreases and associated geomagnetic storms during the last three solar cycles

NASA Astrophysics Data System (ADS)

Okpala, K. C.

2013-12-01

Forbush decrease (FD) are observed reduction in galactic cosmic ray (GCR) intensity as measured by ground neutron monitors. FD is associated with increased activity of the sun as reflected in the size of the interplanetary coronal mass ejections passing around the Earth and the corotating regions in the Heliosphere. Since the interplanetary anisotropy evolves itself during a geomagnetic storm in addition to the reconfiguration of external magnetospheric currents, it is expected that changes in transmissivity of cosmic rays of glactic origin will occur during Geomagnetic storms. In this study we examine over one hundred and fifty (150) FD events and associated geomagnetic storms over the last three solar cycles from 1970 to 2003. The negative peaks of the FDs and the Dst coincided for most of the events (~70%). There was good correlation (>0.65) between the FDs and Dst. Fresh evidence of the influence of external magnetospheric currents on the count rates of the neutron monitors stations during periods of Forbush decreases (FDs) is provided. This evidence is observed as sudden increases in the count rates during the main phase of simultaneous FD. The magnitude of the sudden rise in the count rates of Neutron monitors and peak dst correlated well (>0.50) both for high latitude and mid latitude stations.

Ground Level Enhancement in the 2014 January 6 Solar Energetic Particle Event

NASA Technical Reports Server (NTRS)

Thakur, N.; Gopalswamy, N.; Xie, H.; Makela, P.; Yashiro, S.; Akiyama, S.; Davila, J. M.

2014-01-01

We present a study of the 2014 January 6 solar energetic particle event which produced a small ground level enhancement (GLE), making it the second GLE of this unusual solar cycle 24. This event was primarily observed by the South Pole neutron monitors (increase of approximately 2.5 percent) while a few other neutron monitors recorded smaller increases. The associated coronal mass ejection (CME) originated behind the western limb and had a speed of 1960 kilometers per second. The height of the CME at the start of the associated metric type II radio burst, which indicates the formation of a strong shock, was measured to be 1.61 solar radii using a direct image from STEREO-A/EUVI. The CME height at the time of the GLE particle release (determined using the South Pole neutron monitor data) was directly measured as 2.96 solar radii based on STEREO-A/COR1 white-light observations. These CME heights are consistent with those obtained for GLE71, the only other GLE of the current cycle, as well as cycle-23 GLEs derived using back-extrapolation. GLE72 is of special interest because it is one of only two GLEs of cycle 24, one of two behind-the-limb GLEs, and one of the two smallest GLEs of cycles 23 and 24.

49 CFR 384.229 - Skills test examiner auditing and monitoring.

Code of Federal Regulations, 2014 CFR

2014-10-01

... overt monitoring must be performed at least once every year; (c) Establish and maintain a database to...; (d) Establish and maintain a database of all third party testers and examiners, which at a minimum... examiner; (e) Establish and maintain a database of all State CDL skills examiners, which at a minimum...

49 CFR 384.229 - Skills test examiner auditing and monitoring.

Code of Federal Regulations, 2013 CFR

2013-10-01

... overt monitoring must be performed at least once every year; (c) Establish and maintain a database to...; (d) Establish and maintain a database of all third party testers and examiners, which at a minimum... examiner; (e) Establish and maintain a database of all State CDL skills examiners, which at a minimum...

Compact telemetry package for remote monitoring of neutron responses in animals

NASA Technical Reports Server (NTRS)

Baker, C. D.

1974-01-01

Battery-powered telemeter includes FM transmitter and is light enough to be mounted on animal's head. Animal has complete freedom of movement while its neuron responses are transmitted to receiver in laboratory. Construction may also be applied to monitor blood pressure, body temperature, and different muscular signals.

Customizable tool for ecological data entry, assessment, monitoring, and interpretation

USDA-ARS?s Scientific Manuscript database

The Database for Inventory, Monitoring and Assessment (DIMA) is a highly customizable tool for data entry, assessment, monitoring, and interpretation. DIMA is a Microsoft Access database that can easily be used without Access knowledge and is available at no cost. Data can be entered for common, nat...

Progress in alternative neutron detection to address the helium-3 shortage

NASA Astrophysics Data System (ADS)

Kouzes, Richard T.; Lintereur, Azaree T.; Siciliano, Edward R.

2015-06-01

One of the main uses for 3He is in gas proportional counters for neutron detection. Such detectors are used at neutron scattering science facilities and in radiation portal monitors deployed for homeland security and non-proliferation applications. Other uses of 3He are for research detectors, commercial instruments, well logging detectors, dilution refrigerators, lung imaging, for targets in nuclear research, and for basic research in condensed matter physics. The supply of 3He comes entirely from the decay of tritium produced for nuclear weapons in the U.S. and Russia. Due to the large increase in use of 3He for science and homeland security (since 2002), the supply could no longer meet the demand. This has led to the development of a number of alternative neutron detection schemes.

Gain stabilization control system of the upgraded magnetic proton recoil neutron spectrometer at JET.

PubMed

Sjöstrand, Henrik; Andersson Sundén, E; Conroy, S; Ericsson, G; Gatu Johnson, M; Giacomelli, L; Gorini, G; Hellesen, C; Hjalmarsson, A; Popovichev, S; Ronchi, E; Tardocchi, M; Weiszflog, M

2009-06-01

Burning plasma experiments such as ITER and DEMO require diagnostics capable of withstanding the harsh environment generated by the intense neutron flux and to maintain stable operating conditions for times longer than present day systems. For these reasons, advanced control and monitoring (CM) systems will be necessary for the reliable operation of diagnostics. This paper describes the CM system of the upgraded magnetic proton recoil neutron spectrometer installed at the Joint European Torus focusing in particular on a technique for the stabilization of the gain of the photomultipliers coupled to the neutron detectors. The results presented here show that this technique provides good results over long time scales. The technique is of general interest for all diagnostics that employ scintillators coupled to photomultiplier tubes.

1983 international intercomparison of nuclear accident dosimetry systems at Oak Ridge National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swaja, R.E.; Greene, R.T.; Sims, C.S.

1985-04-01

An international intercomparison of nuclear accident dosimetry systems was conducted during September 12-16, 1983, at Oak Ridge National Laboratory (ORNL) using the Health Physics Research Reactor operated in the pulse mode to simulate criticality accidents. This study marked the twentieth in a series of annual accident dosimetry intercomparisons conducted at ORNL. Participants from ten organizations attended this intercomparison and measured neutron and gamma doses at area monitoring stations and on phantoms for three different shield conditions. Results of this study indicate that foil activation techniques are the most popular and accurate method of determining accident-level neutron doses at area monitoringmore » stations. For personnel monitoring, foil activation, blood sodium activation, and thermoluminescent (TL) methods are all capable of providing accurate dose estimates in a variety of radiation fields. All participants in this study used TLD's to determine gamma doses with very good results on the average. Chemical dosemeters were also shown to be capable of yielding accurate estimates of total neutron plus gamma doses in a variety of radiation fields. While 83% of all neutron measurements satisfied regulatory standards relative to reference values, only 39% of all gamma results satisfied corresponding guidelines for gamma measurements. These results indicate that continued improvement in accident dosimetry evaluation and measurement techniques is needed.« less

Proton Intensity Spectra during the May 17th, 2012 and January 6th, 2014 Solar Energetic Particle Events - Measurement Capabilities of the Electron Proton Helium Telescope on Board SOHO

NASA Astrophysics Data System (ADS)

Kühl, P.; Banjac, S.; Dresing, N.; Gomez-Herrero, R.; Heber, B.; Klassen, A.; Terasa, C.

2014-12-01

Ground Level Enhancements are solar energetic particle events that show a significant intensity increase at energies that can be measured by ground based instrumentation, i.e. neutron monitors. In the recent history 71 GLEs have been recorded. The last one was the May 17, 2012 event that has not only been measured by more than one neutron monitor but also by sophisticated instrumentation in space like PAMELA and the Electron Proton Helium INstrument (EPHIN) aboard SOHO. The January 6, 2014 solar energetic particle (SEP) event led to an intensity increase of about 3 percent at both South Pole neutron monitors and was considered by Thakur et al. (2014) to be a GLE. Since only one pair of neutron monitors show an unambiguous increase the energy spectra for this event can only be determined by spacecraft like e.g. PAMELA or SOHO/EPHIN. We show that the Electron Proton Helium INstrument at Langragian point L1 is capable to measure the proton energy spectra of solar energetic particle events at energies between 150 MeV and above 700 MeV. A GEANT Monte Carlo simulation has been performed to determine the energy response function of EPHIN for electrons, protons and heavier ions. As a result of this calculation we developed a method using energy loss information of particles measured in the detector stack that allow to derive the proton energy spectra in the range from about 150 MeV to more than 700 MeV. In order to validate our method we compared our results to the one obtained by PAMELA that was published by Bazilevskaya et al. (2013) for the May 2012 event. Furthermore, the January 6, 2014 event spectrum in the given energy range is presented and discussed in comparison to the May 2012 event.

Measurements of 89Y(n,2n)88Y and 89Y(n,3n)87Y, 87mY cross sections for fast neutrons at KIRAMS

NASA Astrophysics Data System (ADS)

In, Eun Jin; Bak, Sang-In; Ham, Cheolmin; Kim, Do Yoon; Myung, Hyunjeong; Shim, Chungbo; Shin, Jae Won; Min, Kyung Joo; Zhou, Yujie; Park, Tae-Sun; Hong, Seung-Woo; Bhoraskar, V. N.

2017-09-01

A proton cyclotron MC-50 in Korea Institute of Radiological & Medical Science (KIRAMS) is used to carry out neutron activation experiments with Y2O3 targets irradiated with neutron beams of a continuous spectrum produced by proton beams on a thick beryllium target. Neutrons are generated by 9Be (p, n) reaction with an incident proton intensity of 20 μA. The neutron spectra generated by proton beams of 30, 35, and 40 MeV are calculated by GEANT4 simulations. Nb powders are used for neutron flux monitoring by measuring the activities of 92mNb through the reaction 93Nb (n, 2n). By using a subtraction method, the average cross section of 89Y(n,2n) and 89Y(n,3n) reactions at the neutron energies of 29.8 ± 1.8 MeV and 34.8 ± 1.8 MeV are extracted and are found to be close to the existing cross sections from the EXFOR data and the evaluated nuclear data libraries such as TENDL-2015 or EAF-2010.

Calibration of neutron detectors on the Joint European Torus.

PubMed

Batistoni, Paola; Popovichev, S; Conroy, S; Lengar, I; Čufar, A; Abhangi, M; Snoj, L; Horton, L

2017-10-01

The present paper describes the findings of the calibration of the neutron yield monitors on the Joint European Torus (JET) performed in 2013 using a 252 Cf source deployed inside the torus by the remote handling system, with particular regard to the calibration of fission chambers which provide the time resolved neutron yield from JET plasmas. The experimental data obtained in toroidal, radial, and vertical scans are presented. These data are first analysed following an analytical approach adopted in the previous neutron calibrations at JET. In this way, a calibration function for the volumetric plasma source is derived which allows us to understand the importance of the different plasma regions and of different spatial profiles of neutron emissivity on fission chamber response. Neutronics analyses have also been performed to calculate the correction factors needed to derive the plasma calibration factors taking into account the different energy spectrum and angular emission distribution of the calibrating (point) 252 Cf source, the discrete positions compared to the plasma volumetric source, and the calibration circumstances. All correction factors are presented and discussed. We discuss also the lessons learnt which are the basis for the on-going 14 MeV neutron calibration at JET and for ITER.

Neutron-gamma flux and dose calculations for feasibility study of DISCOMS instrumentation in case of severe accident in a GEN 3 reactor

NASA Astrophysics Data System (ADS)

Brovchenko, Mariya; Duhamel, Isabelle; Dechenaux, Benjamin

2017-09-01

The present paper presents the study carried out in the frame of the DISCOMS project, which stands for "DIstributed Sensing for COrium Monitoring and Safety". This study concerns the calculation of the neutron and gamma radiations received by the considered instrumentation during the normal reactor operation as well as in case of a severe accident for the EPR reactor, outside the reactor pressure vessel and in the containment basemat. This paper summarizes the methods and hypotheses used for the particle transport simulation outside the vessel during normal reactor operation. The results of the simulations are then presented including the responses for distributed Optical Fiber Sensors (OFS), such as the gamma dose and the fast neutron fluence, and for Self Powered Neutron Detectors (SPNDs), namely the neutron and gamma spectra. Same responses are also evaluated for severe accident situations in order to design the SPNDs being sensitive to the both types of received neutron-gamma radiation. By contrast, fibers, involved as transducers in distributed OFS have to resist to the total radiation gamma dose and neutron fluence received during normal operation and the severe accident.

Absolute efficiency calibration of 6LiF-based solid state thermal neutron detectors

NASA Astrophysics Data System (ADS)

Finocchiaro, Paolo; Cosentino, Luigi; Lo Meo, Sergio; Nolte, Ralf; Radeck, Desiree

2018-03-01

The demand for new thermal neutron detectors as an alternative to 3He tubes in research, industrial, safety and homeland security applications, is growing. These needs have triggered research and development activities about new generations of thermal neutron detectors, characterized by reasonable efficiency and gamma rejection comparable to 3He tubes. In this paper we show the state of the art of a promising low-cost technique, based on commercial solid state silicon detectors coupled with thin neutron converter layers of 6LiF deposited onto carbon fiber substrates. A few configurations were studied with the GEANT4 simulation code, and the intrinsic efficiency of the corresponding detectors was calibrated at the PTB Thermal Neutron Calibration Facility. The results show that the measured intrinsic detection efficiency is well reproduced by the simulations, therefore validating the simulation tool in view of new designs. These neutron detectors have also been tested at neutron beam facilities like ISIS (Rutherford Appleton Laboratory, UK) and n_TOF (CERN) where a few samples are already in operation for beam flux and 2D profile measurements. Forthcoming applications are foreseen for the online monitoring of spent nuclear fuel casks in interim storage sites.

SEE induced in SRAM operating in a superconducting electron linear accelerator environment

NASA Astrophysics Data System (ADS)

Makowski, D.; Mukherjee, Bhaskar; Grecki, M.; Simrock, Stefan

2005-02-01

Strong fields of bremsstrahlung photons and photoneutrons are produced during the operation of high-energy electron linacs. Therefore, a mixed gamma and neutron radiation field dominates the accelerators environment. The gamma radiation induced Total Ionizing Dose (TID) effect manifests the long-term deterioration of the electronic devices operating in accelerator environment. On the other hand, the neutron radiation is responsible for Single Event Effects (SEE) and may cause a temporal loss of functionality of electronic systems. This phenomenon is known as Single Event Upset (SEU). The neutron dose (KERMA) was used to scale the neutron induced SEU in the SRAM chips. Hence, in order to estimate the neutron KERMA conversion factor for Silicon (Si), dedicated calibration experiments using an Americium-Beryllium (241Am/Be) neutron standard source was carried out. Single Event Upset (SEU) influences the short-term operation of SRAM compared to the gamma induced TID effect. We are at present investigating the feasibility of an SRAM based real-time beam-loss monitor for high-energy accelerators utilizing the SEU caused by fast neutrons. This paper highlights the effects of gamma and neutron radiations on Static Random Access Memory (SRAM), placed at selected locations near the Superconducting Linear Accelerator driving the Vacuum UV Free Electron Laser (VUVFEL) of DESY.

Effect of the helically-trapped energetic-ion-driven resistive interchange modes on energetic ion confinement in the Large Helical Device

NASA Astrophysics Data System (ADS)

Ogawa, K.; Isobe, M.; Kawase, H.; Nishitani, T.; Seki, R.; Osakabe, M.; LHD Experiment Group

2018-04-01

The effect of the helically-trapped energetic-ion-driven resistive interchange modes (EICs) on energetic ion confinement is studied in the Large Helical Device deuterium plasmas. Neutron diagnostics such as the neutron flux monitor and the vertical neutron camera (VNC) are used in order to measure neutrons mainly created by beam-plasma reactions. The line-integrated neutron profiles are obtained by VNC in magnetohydrodynamic-quiet plasma with various neutral beam (NB) injection patterns. The profiles are consistent with that expected by the beam ion density calculated using orbit-following simulations. Significant decreases of the total neutron emission rate (S n) and the neutron counting rate of the VNC (C n) in central cords are observed to be synchronized with EIC bursts with perpendicular-NB injection. The drop rates of both S n and C n increase with EIC amplitude and reach around 50%. The line-integrated neutron profiles before and after EIC burst show that in the central cords, C n decrease due to EIC burst whereas there is almost no change in the other cords. The experimental results suggests that the effect of EIC on helically-trapped beam ion is substantial, however the effect of passing beam ion is not significant.

Elemental analysis of granite by instrumental neutron activation analysis (INAA) and X-ray fluorescence analysis (XRF).

PubMed

El-Taher, A

2012-01-01

The instrumental neutron activation analysis technique (INAA) was used for qualitative and quantitative analysis of granite samples collected from four locations in the Aswan area in South Egypt. The samples were prepared together with their standards and simultaneously irradiated in a neutron flux of 7×10(11)n/cm(2)s in the TRIGA Mainz research reactor. Gamma-ray spectra from an hyper-pure germanium detector were analyzed. The present study provides the basic data of elemental concentrations of granite rocks. The following elements have been determined Na, Mg, K, Fe, Mn, Sc, Cr, Ti, Co, Zn, Ga, Rb, Zr, Nb, Sn, Ba, Cs, La, Ce, Nd, Sm, Eu, Yb, Lu, Hf, Ta, Th and U. The X-ray fluorescence (XRF) was used for comparison and to detect elements, which can be detected only by XRF such as F, S, Cl, Co, Cu, Mo, Ni, Pb, Se and V. The data presented here are our contribution to understanding the elemental composition of the granite rocks. Because there are no existing databases for the elemental analysis of granite, our results are a start to establishing a database for the Egyptian granite. It is hoped that the data presented here will be useful to those dealing with geochemistry, granite chemistry and related fields. Copyright © 2011 Elsevier Ltd. All rights reserved.

Recent status of YBJ neutron monitor observation

NASA Astrophysics Data System (ADS)

Miyasaka, H.; Shimoda, S.; Yamada, Y.; Sakamoto, E.; Munakata, K.; Cui, S. W.; He, H. H.; Hu, H. B.; Lan, C. L.; Lu, H.; Luo, G. X.; Shen, P. R.; Tan, Y. H.; Wang, H.; Wu, C. Y.; Zhang, H. M.; Zhang, J. L.; Guo, H. W.; Labaciren; Meng, X. R.; Yuan, A. F.; Zhaxisangzhu; Zhaxiciren; Mu, J.; Yang, X. C.; Le, G. M.; Ye, Z. H.

2001-08-01

The Japan-China international solar neutron observation program at Yangbajing (30.11N 90.53E, 4300m), Tibet has been started in October 1998. 28 NM-64 counters were installed and the single counts and multiplicities from one to eight counts are recorded for every second. Now we have more than 2 and a half-year data for October 1998 to April 2001.Recently we have observed a large Forbush decease related to the solar flare series occurred at April 2001. We also searched for a possible solar neutron signal using our data and the GOSE X-ray data but we could not find any significant signal during this period.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cosentino, L.; Pappalardo, A.; Piscopo, M.

During 2014, the second experimental area (EAR2) was completed at the n-TOF neutron beam facility at CERN (n-TOF indicates neutron beam measurements by means of time of flight technique). The neutrons are produced via spallation, by means of a high-intensity 20 GeV pulsed proton beam impinging on a thick target. The resulting neutron beam covers the energy range from thermal to several GeV. In this paper, we describe two beam diagnostic devices, both exploiting silicon detectors coupled with neutron converter foils containing {sup 6}Li. The first one is based on four silicon pads and allows monitoring of the neutron beammore » flux as a function of the neutron energy. The second one, in beam and based on position sensitive silicon detectors, is intended for the reconstruction of the beam profile, again as a function of the neutron energy. Several electronic setups have been explored in order to overcome the issues related to the gamma flash, namely, a huge pulse present at the start of each neutron bunch which may blind the detectors for some time. The two devices were characterized with radioactive sources and also tested at the n-TOF facility at CERN. The wide energy and intensity range they proved capable of sustaining made them attractive and suitable to be used in both EAR1 and EAR2 n-TOF experimental areas, where they became immediately operational.« less

Ion-Induced Afterpulsing in the Neutron Multiplicity Meter's Photomultiplier Tubes

NASA Astrophysics Data System (ADS)

Nedlik, Christopher; Schnee, Richard; Bunker, Raymond; Chen, Yu; Neutron Multiplicity Meter Collaboration

2013-10-01

The nature of the dark matter in the Universe remains a mystery in modern physics. A leading candidate, Weakly Interacting Massive Particles (WIMPs), may be detectable via scattering from nuclear targets in terrestrial detectors, located underground to prevent fake signals from cosmic-ray showers. The Neutron Multiplicity Meter (NMM) is a detector capable of measuring the muon-induced neutron flux deep underground, a problematic background for WIMP detection. The NMM is a 4.4-tonne Gd-loaded water-Cherenkov detector atop a 20-kilotonne lead target in the Soudan Mine. It measures high-energy neutrons (>50 MeV) by moderating and then detecting (via Gd capture gammas) the secondary neutrons emerging from the lead following a high-energy neutron interaction. The short time scale (~10 μs) for neutron capture in Gd-loaded water enables a custom multiplicity trigger to discriminate against the dominant gamma-ray background. Despite excellent rejection of the gamma-ray-induced background, NMM neutron-candidate events are not entirely background-free. One type of background is from ion-induced afterpulsing (AP) in the four 20'' Hamamatsu R7250 photomultiplier tubes (PMTs) used to monitor the NMM's two water tanks. We show that ion-induced AP in the PMTs can mimic the NMM's low-energy neutron response, potentially biasing a candidate event's measured multiplicity. We present detailed studies of the AP in order to allow identification of AP-induced background events.

Activation cross section and isomeric cross section ratio for the 76Ge(n,2n)75m,gGe process

NASA Astrophysics Data System (ADS)

Luo, Junhua; Jiang, Li; Wang, Xinxing

2018-04-01

We measured neutron-induced reaction cross sections for the 76Ge(n,2n)75m,gGe reactions and their isomeric cross section ratios σm/σg at three neutron energies between 13 and 15MeV by an activation and off-line γ-ray spectrometric technique using the K-400 Neutron Generator at the Chinese Academy of Engineering Physics (CAEP). Ge samples and Nb monitor foils were activated together to determine the reaction cross section and the incident neutron flux. The monoenergetic neutron beams were formed via the 3H( d, n)4He reaction. The pure cross section of the ground state was derived from the absolute cross section of the metastable state and the residual nuclear decay analysis. The cross sections were also calculated using the nuclear model code TALYS-1.8 with different level density options at neutron energies varying from the reaction threshold to 20MeV. Results are discussed and compared with the corresponding literature data.

10-decade wide-range neutron-monitoring system. Final test report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Green, W.K.

The objective of Project Agreement 49 was to design, fabricate, test, and evaluate under actual nuclear reactor operating conditions, one prototype counting-Campbelling wide-range type thermal neutron flux measurement channel. This report describes the basic system designed for PA 49, and describes and presents the results of tests conducted on the system. Individual module descriptions and schematics are contained in the instruction manual which was issued with the system.

Precision Astrometry of the Exoplanet Host Candidate GD 66

DTIC Science & Technology

2012-01-01

companions, including very low mass stars, neutron stars and black holes , for orbital pe- riods p > 4 yr. Remarkably, a period-dependent range of...trend in the pulsation arrival times cannot be due to stellar -mass secondaries, which include low-mass stars, white dwarfs, neutron stars and black ... holes with periods longer than 4 yr. The USNO relative astrometric monitoring of just over a decade rules out stellar -mass, dark companions with periods

Cosmogenic Radionuclides as an Extension of the Neutron Monitor Era into the Past: Potential and Limitations

NASA Astrophysics Data System (ADS)

Beer, J.; McCracken, K. G.; Abreu, J.; Heikkilä, U.; Steinhilber, F.

2013-06-01

The cosmogenic radionuclides, 10Be, 14C and others, provide a record of the paleo-cosmic radiation that extends >10,000 years into the past. They are the only quantitative means at our disposal to study the heliosphere prior to the commencement of routine sunspot observations in the 17th century. The cosmogenic radionuclides are primarily produced by secondary neutrons generated by the galactic cosmic radiation, and can be regarded, in a sense, as providing an extrapolation of the neutron monitor era into the past. However, their characteristics are quite different from the man-made neutron monitor in several important respects: (1) they are sensitive to somewhat lower cosmic ray energies; (2) their temporal resolution is ˜1 to 2 years, being determined by the rapidity with which they are sequestered in ice, biological, or other archives; (3) the statistical precision for annual data is very poor (˜19%); however it is quite adequate (˜5% for 22-year averages) to study the large variations (±40%) that have occurred in the paleo-cosmic ray record in the past between grand solar minima and maxima. The data contains "noise" caused by local meteorological effects, and longer-term climate effects, and the use of principal component analysis to separate these "system" effects from production effects is outlined. The concentrations of 10Be decreased by a factor of two at the commencement of Holocene, the present-day "interglacial", due to a 100% increase in the ice accumulation rates in polar regions. The use of the 10Be flux to study heliospheric properties during the last glacial is discussed briefly.

Annual Report FY2013-- A Kinematically Complete, Interdisciplinary, and Co-Institutional Measurement of the 19F(α,n) Cross-section for Nuclear Safeguards Science

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peters, William A; Smith, Michael Scott; Clement, Ryan

2013-10-01

The goal of this proposal is to enable neutron detection for precision Non-Destructive Assays (NDAs) of actinide-fluoride samples. Neutrons are continuously generated from a UFx matrix in a container or sample as a result of the interaction of alpha particles from uranium-decay α particles with fluorine nuclei in the matrix. Neutrons from 19F(α,n)22Na were once considered a poorly characterized background for assays of UFx samples via 238U spontaneous fission neutron detection [SMI2010B]. However, the yield of decay-α-driven neutrons is critical for 234,235U LEU and HEU assays, as it can used to determine both the total amount of uranium and themore » enrichment [BER2010]. This approach can be extremely valuable in a variety of safeguard applications, such as cylinder monitoring in underground uranium storage facilities, nuclear criticality safety studies, nuclear materials accounting, and other nonproliferation applications. The success of neutron-based assays critically depends on an accurate knowledge of the cross section of the (α,n) reaction that generates the neutrons. The 40% uncertainty in the 19F(α,n)22Na cross section currently limits the precision of such assays, and has been identified as a key factor in preventing accurate enrichment determinations [CRO2003]. The need for higher quality cross section data for (α,n) reactions has been a recurring conclusion in reviews of the nuclear data needs to support safeguards. The overarching goal of this project is to enable neutron detection to be used for precision Non- Destructive Assays (NDAs) of actinide-fluoride samples. This will significantly advance safeguards verification at existing declared facilities, nuclear materials accounting, process control, nuclear criticality safety monitoring, and a variety of other nonproliferation applications. To reach this goal, Idaho National Laboratory (INL), in partnership with Oak Ridge National Laboratory (ORNL), Rutgers University (RU), and the University of Notre Dame (UND), will focus on three specific items: (1) making a precision (better than 10 %) determination of the absolute cross section of the 19F(α,n)22Na reaction as a function of energy; (2) determining the spectrum of neutrons and γ-rays emitted from 19F(α,n)22Na over an energy range pertinent to NDA; and (3) performing simulations with this new cross section to extract the neutron yield (neutrons/gram/second) and resulting neutron- and gamma ray-spectra when α particles interact with fluorine nuclei in actinide samples, to aid in the design and reduce uncertainty of future NDA measurements and simulations.« less

Moisture Monitoring at Area G, Technical Area 54, Los Alamos National Laboratory, 2016 Status Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levitt, Daniel Glenn; Birdsell, Kay Hanson; Jennings, Terry L.

Hydrological characterization and moisture monitoring activities provide data required for evaluating the transport of subsurface contaminants in the unsaturated and saturated zones beneath Area G, and for the Area G Performance Assessment and Composite Analysis. These activities have been ongoing at Area G, Technical Area 54 of the Los Alamos National Laboratory since waste disposal operations began in 1957. This report summarizes the hydrological characterization and moisture monitoring activities conducted at Area G. It includes moisture monitoring data collected from 1986 through 2016 from numerous boreholes and access tubes with neutron moisture meters, as well as data collected by automatedmore » dataloggers for water content measurement sensors installed in a waste disposal pit cover, and buried beneath the floor of a waste disposal pit. This report is an update of a nearly identical report by Levitt et al., (2015) that summarized data collected through early 2015; this report includes additional moisture monitoring data collected at Pit 31 and the Pit 38 extension through December, 2016. It also includes information from the Jennings and French (2009) moisture monitoring report and includes all data from Jennings and French (2009) and the Draft 2010 Addendum moisture monitoring report (Jennings and French, 2010). For the 2015 version of this report, all neutron logging data, including neutron probe calibrations, were investigated for quality and pedigree. Some data were recalculated using more defensible calibration data. Therefore, some water content profiles are different from those in the Jennings and French (2009) report. All of that information is repeated in this report for completeness. Monitoring and characterization data generally indicate that some areas of the Area G vadose zone are consistent with undisturbed conditions, with water contents of less than five percent by volume in the top two layers of the Bandelier tuff at Area G. These data also indicate that other areas of the vadose zone are affected by waste disposal activities that have been ongoing at Area G since 1957, a period of nearly 60 years. In some areas, water content profiles indicate increases in water content to depths of tens of meters, especially in areas covered by asphalt and structures.« less

Study of the response of a lithium yttrium borate scintillator based neutron rem counter by Monte Carlo radiation transport simulations

NASA Astrophysics Data System (ADS)

Sunil, C.; Tyagi, Mohit; Biju, K.; Shanbhag, A. A.; Bandyopadhyay, T.

2015-12-01

The scarcity and the high cost of 3He has spurred the use of various detectors for neutron monitoring. A new lithium yttrium borate scintillator developed in BARC has been studied for its use in a neutron rem counter. The scintillator is made of natural lithium and boron, and the yield of reaction products that will generate a signal in a real time detector has been studied by FLUKA Monte Carlo radiation transport code. A 2 cm lead introduced to enhance the gamma rejection shows no appreciable change in the shape of the fluence response or in the yield of reaction products. The fluence response when normalized at the average energy of an Am-Be neutron source shows promise of being used as rem counter.

Neutron-capture cross-section measurements of Xe136 between 0.4 and 14.8 MeV

NASA Astrophysics Data System (ADS)

Bhike, Megha; Tornow, W.

2014-03-01

Fast-neutron-capture cross-section data on Xe136 have been measured with the activation method between 0.4 and 14.8 MeV. The cross section was found to be of the order of 1 mb at the eleven energies investigated. This result is important to interpret potential neutron-induced backgrounds in the enriched xenon observatory and KamLAND-Zen neutrinoless double-β decay searches that use xenon as both source and detector. A high-pressure sphere filled with Xe136 was irradiated with monoenergetic neutrons produced by the reactions 3H(p ,n)3He, 2H(d ,n)3He, and 3H(d ,n)4He. Indium and gold monitor foils were irradiated simultaneously with the Xe136 to determine the incident neutron flux. The activities of the reaction products were measured with high-resolution γ-ray spectroscopy. The present results are compared to predictions from ENDF/B-VII.1 and TENDL-2012.

Determination of neutron capture cross sections of 232Th at 14.1 MeV and 14.8 MeV using the neutron activation method

NASA Astrophysics Data System (ADS)

Lan, Chang-Lin; Zhang, Yi; Lv, Tao; Xie, Bao-Lin; Peng, Meng; Yao, Ze-En; Chen, Jin-Gen; Kong, Xiang-Zhong

2017-04-01

The 232Th(n, γ)233Th neutron capture reaction cross sections were measured at average neutron energies of 14.1 MeV and 14.8 MeV using the activation method. The neutron flux was determined using the monitor reaction 27Al(n,α)24Na. The induced gamma-ray activities were measured using a low background gamma ray spectrometer equipped with a high resolution HPGe detector. The experimentally determined cross sections were compared with the data in the literature, and the evaluated data of ENDF/B-VII.1, JENDL-4.0u+, and CENDL-3.1. The excitation functions of the 232Th(n,γ)233Th reaction were also calculated theoretically using the TALYS1.6 computer code. Supported by Chinese TMSR Strategic Pioneer Science and Technology Project-The Th-U Fuel Physics Term (XDA02010100) and National Natural Science Foundation of China (11205076, 21327801)

Gamma signatures of the C-BORD Tagged Neutron Inspection System

NASA Astrophysics Data System (ADS)

Sardet, A.; Pérot, B.; Carasco, C.; Sannié, G.; Moretto, S.; Nebbia, G.; Fontana, C.; Pino, F.; Iovene, A.; Tintori, C.

2018-01-01

In the frame of C-BORD project (H2020 program of the EU), a Rapidly relocatable Tagged Neutron Inspection System (RRTNIS) is being developed to non-intrusively detect explosives, chemical threats, and other illicit goods in cargo containers. Material identification is performed through gamma spectroscopy, using twenty NaI detectors and four LaBr3 detectors, to determine the different elements composing the inspected item from their specific gamma signatures induced by fast neutrons. This is performed using an unfolding algorithm to decompose the energy spectrum of a suspect item, selected by X-ray radiography and on which the RRTNIS inspection is focused, on a database of pure element gamma signatures. This paper reports on simulated signatures for the NaI and LaBr3 detectors, constructed using the MCNP6 code. First experimental spectra of a few elements of interest are also presented.

The Application of Lidar to Synthetic Vision System Integrity

NASA Technical Reports Server (NTRS)

Campbell, Jacob L.; UijtdeHaag, Maarten; Vadlamani, Ananth; Young, Steve

2003-01-01

One goal in the development of a Synthetic Vision System (SVS) is to create a system that can be certified by the Federal Aviation Administration (FAA) for use at various flight criticality levels. As part of NASA s Aviation Safety Program, Ohio University and NASA Langley have been involved in the research and development of real-time terrain database integrity monitors for SVS. Integrity monitors based on a consistency check with onboard sensors may be required if the inherent terrain database integrity is not sufficient for a particular operation. Sensors such as the radar altimeter and weather radar, which are available on most commercial aircraft, are currently being investigated for use in a real-time terrain database integrity monitor. This paper introduces the concept of using a Light Detection And Ranging (LiDAR) sensor as part of a real-time terrain database integrity monitor. A LiDAR system consists of a scanning laser ranger, an inertial measurement unit (IMU), and a Global Positioning System (GPS) receiver. Information from these three sensors can be combined to generate synthesized terrain models (profiles), which can then be compared to the stored SVS terrain model. This paper discusses an initial performance evaluation of the LiDAR-based terrain database integrity monitor using LiDAR data collected over Reno, Nevada. The paper will address the consistency checking mechanism and test statistic, sensitivity to position errors, and a comparison of the LiDAR-based integrity monitor to a radar altimeter-based integrity monitor.

High-Accuracy Analysis of Compton Scattering in Chiral EFT: Proton and Neutron Polarisabilities

NASA Astrophysics Data System (ADS)

Griesshammer, Harald W.; Phillips, Daniel R.; McGovern, Judith A.

2013-10-01

Compton scattering from protons and neutrons provides important insight into the structure of the nucleon. A new extraction of the static electric and magnetic dipole polarisabilities αE 1 and βM 1 of the proton and neutron from all published elastic data below 300 MeV in Chiral Effective Field Theory shows that within the statistics-dominated errors, the proton and neutron polarisabilities are identical, i.e. no iso-spin breaking effects of the pion cloud are seen. Particular attention is paid to the precision and accuracy of each data set, and to an estimate of residual theoretical uncertainties. ChiEFT is ideal for that purpose since it provides a model-independent estimate of higher-order corrections and encodes the correct low-energy dynamics of QCD, including, for few-nucleon systems used to extract neutron polarisabilities, consistent nuclear currents, rescattering effects and wave functions. It therefore automatically respects the low-energy theorems for photon-nucleus scattering. The Δ (1232) as active degree of freedom is essential to realise the full power of the world's Compton data.Its parameters are constrained in the resonance region. A brief outlook is provided on what kind of future experiments can improve the database. Supported in part by UK STFC, DOE, NSF, and the Sino-German CRC 110.

Comparison of Image Restoration Methods for Lunar Epithermal Neutron Emission Mapping

NASA Technical Reports Server (NTRS)

McClanahan, T. P.; Ivatury, V.; Milikh, G.; Nandikotkur, G.; Puetter, R. C.; Sagdeev, R. Z.; Usikov, D.; Mitrofanov, I. G.

2009-01-01

Orbital measurements of neutrons by the Lunar Exploring Neutron Detector (LEND) onboard the Lunar Reconnaissance Orbiter are being used to quantify the spatial distribution of near surface hydrogen (H). Inferred H concentration maps have low signal-to-noise (SN) and image restoration (IR) techniques are being studied to enhance results. A single-blind. two-phase study is described in which four teams of researchers independently developed image restoration techniques optimized for LEND data. Synthetic lunar epithermal neutron emission maps were derived from LEND simulations. These data were used as ground truth to determine the relative quantitative performance of the IR methods vs. a default denoising (smoothing) technique. We review and used factors influencing orbital remote sensing of neutrons emitted from the lunar surface to develop a database of synthetic "true" maps for performance evaluation. A prior independent training phase was implemented for each technique to assure methods were optimized before the blind trial. Method performance was determined using several regional root-mean-square error metrics specific to epithermal signals of interest. Results indicate unbiased IR methods realize only small signal gains in most of the tested metrics. This suggests other physically based modeling assumptions are required to produce appreciable signal gains in similar low SN IR applications.

Temporal Evolution of Spectral and Angular Characteristics of SEP Particles during Several GLEs of Solar Cycle 23 Derived from NM Data

NASA Astrophysics Data System (ADS)

Mishev, Alexander; Usoskin, Ilya; Kocharov, Leon

High-energy charged particles of solar origin could represent a severe radiation risk for astronauts and air crew. In addition, they could disrupt technological systems. When a ground-based neutron monitor register abrupt increases in solar energetic particles (SEPs), we observe a special case of solar energetic particle event, a ground-level enhancement (GLE). In order to derive the spectral and angular characteristics of GLE particles a precise computation of solar energetic particle propagation in the Earth's magnetosphere and atmosphere is necessary. It consists of detailed computation of assymptotic cones for neutron monitors (NMs) and application of inverse method using the newly computed neutron monitor yield function. Assymptotic directions are computed using the Planetocosmics code and realistic magnetospheric models, namely IGRF as the internal model and Tsyganenko 89 with the corresponding Kp index as the external one. The inverse problem solution is performed on the basis of non-linear least squares method, namely Levenberg-Marqurdt. In the study presented here, we analyse several major GLEs of the solar cycle 23 as well as the first GLE event of the solar cycle 24, namely GLE69, GLE70 and GLE 71. The SEP spectra and pitch angle distribution are obtained at different momenta since the event's onset. The obtained characteristics are compared with previously reported results. The obtained results are briefly discussed.

The extreme solar cosmic ray particle event on 20 January 2005 and its influence on the radiation dose rate at aircraft altitude.

PubMed

Bütikofer, R; Flückiger, E O; Desorgher, L; Moser, M R

2008-03-01

In January 2005 toward the end of solar activity cycle 23 the Sun was very active. Between 15 and 20 January 2005, the solar active region NOAA AR 10720 produced five powerful solar flares. In association with this major solar activity several pronounced variations in the ground-level cosmic ray intensity were observed. The fifth of these flares (X7.1) produced energetic solar cosmic rays that caused a giant increase in the count rates of the ground-based cosmic ray detectors (neutron monitors). At southern polar neutron monitor stations the increase of the count rate reached several thousand percent. From the recordings of the worldwide network of neutron monitors, we determined the characteristics of the solar particle flux near Earth. In the initial phase of the event, the solar cosmic ray flux near Earth was extremely anisotropic. The energy spectrum of the solar cosmic rays was fairly soft during the main and the decay phase. We investigated also the flux of different secondary particle species in the atmosphere and the radiation dosage at flight altitude. Our analysis shows a maximum increment of the effective dose rate due to solar cosmic rays in the south polar region around 70 degrees S and 130 degrees E at flight altitude of almost three orders of magnitude.

In-Situ Spectrometry of Neutrons

NASA Technical Reports Server (NTRS)

Maurer, Richard H.

1999-01-01

High energy charged particles of extra-galactic, galactic and solar origin collide with spacecraft structures in Earth orbit outside the atmosphere and in interplanetary travel beyond the Earth's magnetosphere. These primaries create a number of secondary particles inside the structures that can produce a significant ionizing radiation environment. This radiation is a threat to long term inhabitants or travelers for space missions and produces an increased risk of cancer and DNA damage. The primary high energy cosmic rays and trapped protons collide with common spacecraft materials such as aluminum and silicon and create secondary particles inside structures that are mostly protons and neutrons. Charged protons are readily detected and instruments are already in existence for this task. Neutrons are electrically neutral and therefore much more difficult to measure and detect. These neutrons are reported to contribute 30-60% of the dose inside space structures and cannot be ignored. Currently there is no compact, portable and real time neutron detector instrumentation available for use inside spacecraft or on planetary surfaces where astronauts will live and work. We propose to design and build a portable, low power and robust neutron spectrometer that will measure the neutron spectrum from 10 KeV to 500 MeV with at least 10% energy resolution in the various energy intervals. This instrument will monitor the existing neutron environment both inside spacecraft structures and on planetary surfaces to determine the safest living areas, warn of high fluxes associated with solar storms and assist the NSBRI Radiation Effects Team in making an accurate assessment of increased cancer risk and DNA damage to astronauts. The instrument uses a highly efficient proportional counter Helium 3 tube at the lowest energy intervals where .equivalent damage factors for tissue are the highest (10 KeV-2 MeV). The Helium 3 tube may be shielded with a cadmium absorber to eliminate the much less damaging, but more prevalent, thermal and epithermal neutrons and to make the structure of the spectrum more accurate in the 20 KeV-2 MeV range; or a pair of tubes, one shielded and one unshielded, can be combined so that the difference in their counts yields the thermal neutron contribution. The spectrometer also uses a 5mm lithium drifted bulk silicon solid state detector in the medium energy range of 2-20 Mev and two standard silicon surface barrier detectors separated by tens of millimeters behind a I cm thick polyethylene moderator in a stack or telescope arrangement for the high energy neutrons (>20 MeV). In the medium and high energy regions equivalent damage factors are lower but hits from one or a small number of neutrons may prove to be important. The silicon detector systems for medium and high energy neutrons will discriminate against charged particles by using a plastic cesium iodide scintillator of an appropriate geometry monitored by a silicon PIN photodiode.

Monitoring SLAC High Performance UNIX Computing Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lettsome, Annette K.; /Bethune-Cookman Coll. /SLAC

2005-12-15

Knowledge of the effectiveness and efficiency of computers is important when working with high performance systems. The monitoring of such systems is advantageous in order to foresee possible misfortunes or system failures. Ganglia is a software system designed for high performance computing systems to retrieve specific monitoring information. An alternative storage facility for Ganglia's collected data is needed since its default storage system, the round-robin database (RRD), struggles with data integrity. The creation of a script-driven MySQL database solves this dilemma. This paper describes the process took in the creation and implementation of the MySQL database for use by Ganglia.more » Comparisons between data storage by both databases are made using gnuplot and Ganglia's real-time graphical user interface.« less

MIMIC II: a massive temporal ICU patient database to support research in intelligent patient monitoring

NASA Technical Reports Server (NTRS)

Saeed, M.; Lieu, C.; Raber, G.; Mark, R. G.

2002-01-01

Development and evaluation of Intensive Care Unit (ICU) decision-support systems would be greatly facilitated by the availability of a large-scale ICU patient database. Following our previous efforts with the MIMIC (Multi-parameter Intelligent Monitoring for Intensive Care) Database, we have leveraged advances in networking and storage technologies to develop a far more massive temporal database, MIMIC II. MIMIC II is an ongoing effort: data is continuously and prospectively archived from all ICU patients in our hospital. MIMIC II now consists of over 800 ICU patient records including over 120 gigabytes of data and is growing. A customized archiving system was used to store continuously up to four waveforms and 30 different parameters from ICU patient monitors. An integrated user-friendly relational database was developed for browsing of patients' clinical information (lab results, fluid balance, medications, nurses' progress notes). Based upon its unprecedented size and scope, MIMIC II will prove to be an important resource for intelligent patient monitoring research, and will support efforts in medical data mining and knowledge-discovery.

Pretest predictions of surface strain and fluid pressures in mercury targets undergoing thermal shock

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taleyarkhan, R.P.; Kim, S.H.; Haines, J.

The authors provide a perspective overview of pretest modeling and analysis work related to thermal shock effects in spallation neutron source targets that were designed for conducting thermal shock experiments at the Los Alamos Neutron Science Center (LANSCE). Data to be derived are to be used for benchmarking computational tools as well as to assess the efficacy of optical gauges for monitoring dynamic fluid pressures and phenomena such as the onset of cavitation.

Absolute configuration of a chiral CHD group via neutron diffraction: confirmation of the absolute stereochemistry of the enzymatic formation of malic acid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bau, R.; Brewer, I.; Chiang, M.Y.

Neutron diffraction has been used to monitor the absolute stereochemistry of an enzymatic reaction. (-)(2S)malic-3-d acid was prepared by the action of fumarase on fumaric acid in D/sub 2/O. After a large number of cations were screened, it was found that (+)(R)..cap alpha..-phenylethylamine forms the large crystals necessary for a neutron diffraction analysis. The subsequent structure determination showed that (+)(R)..cap alpha..-phenylethylammonium (-)(2S)malate-3-d has an absolute configuration of R at the CHD site. This result confirms the absolute stereochemistry of fumarate-to-malate transformation as catalyzed by the enzyme fumarase.

Study on optimization of multiionization-chamber system for BNCT.

PubMed

Fujii, T; Tanaka, H; Maruhashi, A; Ono, K; Sakurai, Y

2011-12-01

In order to monitor stability of doses from the four components such as thermal, epi-thermal, fast neutron and gamma-ray during BNCT irradiation, we are developing a multiionization-chamber system. This system is consisted of four kinds of ionization chamber, which have specific sensitivity for each component, respectively. Since a suitable structure for each chamber depends on the energy spectrum of the irradiation field, the optimization study of the chamber structures for the epi-thermal neutron beam of cyclotron-based epi-thermal neutron source (C-BENS) was performed by using a Monte Carlo simulation code "PHITS" and suitable chamber-structures were determined. Copyright © 2011 Elsevier Ltd. All rights reserved.

Neutron H*(10) estimation and measurements around 18MV linac.

PubMed

Cerón Ramírez, Pablo Víctor; Díaz Góngora, José Antonio Irán; Paredes Gutiérrez, Lydia Concepción; Rivera Montalvo, Teodoro; Vega Carrillo, Héctor René

2016-11-01

Thermoluminescent dosimetry, analytical techniques and Monte Carlo calculations were used to estimate the dose of neutron radiation in a treatment room with a linear electron accelerator of 18MV. Measurements were carried out through neutron ambient dose monitors which include pairs of thermoluminescent dosimeters TLD 600 ( 6 LiF: Mg, Ti) and TLD 700 ( 7 LiF: Mg, Ti), which were placed inside a paraffin spheres. The measurements has allowed to use NCRP 151 equations, these expressions are useful to find relevant dosimetric quantities. In addition, photoneutrons produced by linac head were calculated through MCNPX code taking into account the geometry and composition of the linac head principal parts. Copyright © 2016 Elsevier Ltd. All rights reserved.

Efficient scalable solid-state neutron detector.

PubMed

Moses, Daniel

2015-06-01

We report on scalable solid-state neutron detector system that is specifically designed to yield high thermal neutron detection sensitivity. The basic detector unit in this system is made of a (6)Li foil coupled to two crystalline silicon diodes. The theoretical intrinsic efficiency of a detector-unit is 23.8% and that of detector element comprising a stack of five detector-units is 60%. Based on the measured performance of this detector-unit, the performance of a detector system comprising a planar array of detector elements, scaled to encompass effective area of 0.43 m(2), is estimated to yield the minimum absolute efficiency required of radiological portal monitors used in homeland security.

FAST NEUTRON SPECTROMETER

DOEpatents

Davis, F.J.; Hurst, G.S.; Reinhardt, P.W.

1959-08-18

An improved proton recoil spectrometer for determining the energy spectrum of a fast neutron beam is described. Instead of discriminating against and thereby"throwing away" the many recoil protons other than those traveling parallel to the neutron beam axis as do conventional spectrometers, this device utilizes protons scattered over a very wide solid angle. An ovoidal gas-filled recoil chamber is coated on the inside with a scintillator. The ovoidal shape of the sensitive portion of the wall defining the chamber conforms to the envelope of the range of the proton recoils from the radiator disposed within the chamber. A photomultiplier monitors the output of the scintillator, and a counter counts the pulses caused by protons of energy just sufficient to reach the scintillator.

Response in thermal neutrons intensity on the activation of seismic processes

NASA Astrophysics Data System (ADS)

Antonova, Valentina; Chubenko, Alexandr; Kryukov, Sergey; Lutsenko, Vadim

2017-04-01

Results of study of thermal and high-energy neutrons intensity during the activation of seismic activity are presented. Installations are located close to the fault of the earth's crust at the high-altitude station of cosmic rays (3340 m above sea level, 20 km from Almaty) in the mountains of Northern Tien-Shan. High correlation and similarity of responses to changes of space and geophysical conditions in the absence of seismic activity are obtained between data of thermal neutron detectors and data of the standard neutron monitor, recording the intensity of high-energy particles. These results confirm the genetic connection of thermal neutrons at the Earth's surface with high-energy neutrons of the galactic origin and suggest same sources of disturbances of their flux. However, observations and analysis of experimental data during the activation of seismic activity showed the frequent breakdown of the correlation between the intensity of thermal and high-energy neutrons and the absence of similarity between variations during these periods. We suppose that the cause of this phenomenon is the additional thermal neutron flux of the lithospheric origin, which appears under these conditions. Method of separating of thermal neutron intensity variations of the lithospheric origin from neutrons variations generated in the atmosphere is proposed. We used this method for analysis of variations of thermal neutrons intensity during earthquakes (with intensity ≥ 3b) in the vicinity of Almaty which took place in 2006-2015. The increase of thermal neutrons flux of the lithospheric origin during of seismic processes activation was observed for 60% of events. However, before the earthquake the increase of thermal neutron flux is only observed for 25-30% of events. It is shown that the amplitude of the additional thermal neutron flux from the Earth's crust is equal to 5-7% of the background level.

The Monitoring Erosion of Agricultural Land and spatial database of erosion events

NASA Astrophysics Data System (ADS)

Kapicka, Jiri; Zizala, Daniel

2013-04-01

In 2011 originated in The Czech Republic The Monitoring Erosion of Agricultural Land as joint project of State Land Office (SLO) and Research Institute for Soil and Water Conservation (RISWC). The aim of the project is collecting and record keeping information about erosion events on agricultural land and their evaluation. The main idea is a creation of a spatial database that will be source of data and information for evaluation and modeling erosion process, for proposal of preventive measures and measures to reduce negative impacts of erosion events. A subject of monitoring is the manifestations of water erosion, wind erosion and slope deformation in which cause damaged agriculture land. A website, available on http://me.vumop.cz, is used as a tool for keeping and browsing information about monitored events. SLO employees carry out record keeping. RISWC is specialist institute in the Monitoring Erosion of Agricultural Land that performs keeping the spatial database, running the website, managing the record keeping of events, analysis the cause of origins events and statistical evaluations of keeping events and proposed measures. Records are inserted into the database using the user interface of the website which has map server as a component. Website is based on database technology PostgreSQL with superstructure PostGIS and MapServer UMN. Each record is in the database spatial localized by a drawing and it contains description information about character of event (data, situation description etc.) then there are recorded information about land cover and about grown crops. A part of database is photodocumentation which is taken in field reconnaissance which is performed within two days after notify of event. Another part of database are information about precipitations from accessible precipitation gauges. Website allows to do simple spatial analysis as are area calculation, slope calculation, percentage representation of GAEC etc.. Database structure was designed on the base of needs analysis inputs to mathematical models. Mathematical models are used for detailed analysis of chosen erosion events which include soil analysis. Till the end 2012 has had the database 135 events. The content of database still accrues and gives rise to the extensive source of data that is usable for testing mathematical models.

The behavior of neutron emissions during ICRF minority heating of plasma at EAST

NASA Astrophysics Data System (ADS)

Zhong, Guoqiang; Cao, Hongrui; Hu, Liqun; Zhou, Ruijie; Xiao, Min; Li, Kai; Pu, Neng; Huang, Juan; Liu, Guangzhu; Lin, Shiyao; Lyu, Bo; Liu, Haiqing; Zhang, Xinjun; EAST Team

2016-07-01

Ion cyclotron radio frequency (ICRF) wave heating is a primary method to heat ions in the Experimental Advanced Superconducting Tokamak (EAST). Through neutron diagnostics, effective ion heating was observed in hydrogenminority heating (MH) scenarios. At present, investigation of deuterium-deuterium (DD) fusion neutrons is mostly based on time-resolved flux monitor and spectrometer measurements. When the ICRF was applied, the neutron intensity became one order higher. The H/H  +  D ratio was in the range of 5-10%, corresponding to the hydrogen MH dominated scenario, and a strong high energy tail was not displayed on the neutron spectrum that was measured by a liquid scintillator. Moreover, ion temperature in the plasma center (T i) was inversely calculated by the use of neutron source strength (S n) and the plasma density based on classical fusion reaction equations. This result indicates that T i increases by approximately 30% in L-mode plasma, and by more than 50% in H-mode plasma during ICRF heating, which shows good agreement with x-ray crystal spectrometer (XCS) diagnostics. Finally, the DD neutron source strength scaling law, with regard to plasma current (I P) and ICRF coupling power (P RF) on the typical minority heating condition, was obtained by statistical analysis.

Measurement and Interpretation of DT Neutron Emission from Tftr.

NASA Astrophysics Data System (ADS)

McCauley, John Scott, Jr.

A fast-ion diffusion coefficient of 0.1 +/- 0.1 m^2s ^{-1} has been deduced from the triton burnup neutron emission profile measured by a collimated array of helium-4 spectrometers. The experiment was performed with high-power deuterium discharges produced by Princeton University's Tokamak Fusion Test Reactor (TFTR). The fast ions monitored were the 1.0 MeV tritons produced from the d(d,t)p triton burnup reaction. These tritons "burn up" with deuterons and emit a 14 MeV neutron by the d(t, alpha)n reaction. The measured radial profiles of DT emission were compared with the predictions of a computer transport code. The ratio of the measured-to -calculated DT yield is typically 70%. The measured DT profile width is typically 5 cm larger than predicted by the transport code. The radial 14 MeV neutron profile was measured by a radial array of helium-4 recoil neutron spectrometers installed in the TFTR Multichannel Neutron Collimator (MCNC). The spectrometers are capable of measuring the primary and secondary neutron fluxes from deuterium discharges. The response to 14 MeV neutrons of the array has been measured by cross calibrating with the MCNC ZnS detector array when the emission from TFTR is predominantly DT neutrons. The response was also checked by comparing a model of the recoil spectrum based on nuclear physics data to the observed spectrum from ^{252 }Cf, ^{238}Pu -Be, and DT neutron sources. Extensions of this diagnostic to deuterium-tritium plasma and the implications for fusion research are discussed.

Beam diagnostics at high-intensity storage rings

NASA Astrophysics Data System (ADS)

Plum, Mike

1994-10-01

Beam diagnostics at high-intensity facilities feature their own special set of problems and characteristics, issues peculiar to high-intensity storage rings include beam loss, beam halos, extraction efficiency, beam in the gap, clearing electrodes, and beam-profile measurement. The Los Alamos Proton Storage Ring (PSR) is a nice example of a high-intensity storage ring. I will discuss in some detail three diagnostic systems currently in use at the PSR: the beam-loss-monitor system, the electron-clearing system, and the beam-in-the-gap monitor. Much of our discussion is inspired by the problems we have encountered and the useful things we have learned while commissioning and developing the PSR. Another inspiration is our work on the next-generation neutron-spallation source, also known as the National Center for Neutron Research (NCNR).

Energetic solar particle events

NASA Technical Reports Server (NTRS)

Fenton, K. B.; Fenton, A. G.; Humble, J. E.

1985-01-01

Studies of the arrival directions of energetic solar particles during ground level enhancements (CLE's) observed by neutron monitors have shown that, in general, in the first hour of the event most of the particles arrive with a distribution of pitch angles peaked about the garden hose field direction in the vicinity of Earth. During the first hour some of the particles arrive from the antisolar direction, while in later stages of the event the intensity becomes more nearly isotropic as a result of scattering of particles in interplanetary space. An attempt is made to determine the arrival directions of the particles during the early stages of the GLE of 16 February 1984 using the data currently available from high latitude neutron monitors near sea level where the cut off is essentially atmospheric (approx. LGV).

Neutron multiplicity counting: Confidence intervals for reconstruction parameters

DOE PAGES

Verbeke, Jerome M.

2016-03-09

From nuclear materials accountability to homeland security, the need for improved nuclear material detection, assay, and authentication has grown over the past decades. Starting in the 1940s, neutron multiplicity counting techniques have enabled quantitative evaluation of masses and multiplications of fissile materials. In this paper, we propose a new method to compute uncertainties on these parameters using a model-based sequential Bayesian processor, resulting in credible regions in the fissile material mass and multiplication space. These uncertainties will enable us to evaluate quantitatively proposed improvements to the theoretical fission chain model. Additionally, because the processor can calculate uncertainties in real time,more » it is a useful tool in applications such as portal monitoring: monitoring can stop as soon as a preset confidence of non-threat is reached.« less

A novel digital neutron flux monitor for international thermonuclear experimental reactor

NASA Astrophysics Data System (ADS)

Xiang, ZHOU; Zihao, LIU; Chao, CHEN; Renjie, ZHU; Li, ZHAO; Lingfeng, WEI; Zejie, YIN

2018-04-01

A novel full-digital real-time neutron flux monitor (NFM) has been developed for the International Thermonuclear Experimental Reactor. A measurement range of 109 counts per second is achieved with 3 different sensitive fission chambers. The Counting mode and Campbelling mode have been combined as a means to achieve higher measurement range. The system is based on high speed as well as parallel and pipeline processing of the field programmable gate array and has the ability to upload raw-data of analog-to-digital converter in real-time through the PXIe platform. With the advantages of the measurement range, real time performance and the ability of raw-data uploading, the digital NFM has been tested in HL-2A experiments and reflected good experimental performance.

Nuclear Data Sheets page at the NNDC

Science.gov Websites

Data Sheets is a journal primarily devoted to the publication of evaluated nuclear structure and decay ; neutron, proton, alpha, cluster and cluster emission; fission. Nuclear structure and decay data are basis. The ENSDF database is the source for the nuclear structure and decay articles, which deal with a

Monte Carlo simulations for high-rate fast neutron flux measurements made at the RAON neutron science facility by using MICROMEGAS

NASA Astrophysics Data System (ADS)

Hwang, Dae Hee; Hong, Ser Gi; Kim, Jae Cheon; Kim, Gi Dong; Kim, Yong Kyun

2015-10-01

RAON is a Korean heavy-ion accelerator complex that is planned to be built by 2021. Deuterons (53 MeV) and protons (88 MeV) accelerated by using a low-energy driver linac (SCL1) are delivered to the neutron production target in the Neutron Science Facility (NSF) to produce high-energy neutrons in the interval from 1 to 88 MeV with high fluxes of the order of 1012 n/cm2-sec. The repetition rate of the neutron beam ranges from 1 kHz to 1 MHz, and the maximum beam current is ~12 μA at 1 MHz. The beam width is 1 ~ 2 ns. The high-energy and high-rate fast neutrons are used to estimate accurate neutron-induced cross sections for various nuclides at the NSF. A MICROMEGAS (MICRO Mesh Gaseous Structure), which is a gaseous detector initially developed for tracking in high-rate, high-energy physics experiments, is tentatively being considered as a neutron beam monitor. It can be used to measure both the energy distribution and the flux of the neutron beam. In this study, a MICROMEGAS detector for installation at the NSF was designed and investigated. 6Li, 10B, 235U and 238U targets are being considered as neutron/charged particle converters. For the low-energy region, 6Li(n,α)t and 10B(n,α)7Li are used in the energy range from thermal to 1 MeV. 235U(n,f) and 238U(n,f) reactions are used for high-energy region up to 90 MeV. All calculations are performed by using the GEANT4 toolkit.

In-Pile Qualification of the Fast-Neutron-Detection-System

NASA Astrophysics Data System (ADS)

Fourmentel, D.; Villard, J.-F.; Destouches, C.; Geslot, B.; Vermeeren, L.; Schyns, M.

2018-01-01

In order to improve measurement techniques for neutron flux assessment, a unique system for online measurement of fast neutron flux has been developed and recently qualified in-pile by the French Alternative Energies and Atomic Energy Commission (CEA) in cooperation with the Belgian Nuclear Research Centre (SCK•ECEN). The Fast-Neutron-Detection-System (FNDS) has been designed to monitor accurately high-energy neutrons flux (E > 1 MeV) in typical Material Testing Reactor conditions, where overall neutron flux level can be as high as 1015 n.cm-2.s-1 and is generally dominated by thermal neutrons. Moreover, the neutron flux is coupled with a high gamma flux of typically a few 1015 γ.cm-2.s-1, which can be highly disturbing for the online measurement of neutron fluxes. The patented FNDS system is based on two detectors, including a miniature fission chamber with a special fissile material presenting an energy threshold near 1 MeV, which can be 242Pu for MTR conditions. Fission chambers are operated in Campbelling mode for an efficient gamma rejection. FNDS also includes a specific software that processes measurements to compensate online the fissile material depletion and to adjust the sensitivity of the detectors, in order to produce a precise evaluation of both thermal and fast neutron flux even after long term irradiation. FNDS has been validated through a two-step experimental program. A first set of tests was performed at BR2 reactor operated by SCK•CEN in Belgium. Then a second test was recently completed at ISIS reactor operated by CEA in France. FNDS proved its ability to measure online the fast neutron flux with an overall accuracy better than 5%.

Muon and neutron observations in connection with the corotating interaction regions

NASA Astrophysics Data System (ADS)

da Silva, M. R.; Dal Lago, A.; Echer, E.; de Lucas, A.; Gonzalez, W. D.; Schuch, N. J.; Munakata, K.; Vieira, L. E. A.; Guarnieri, F. L.

Ground cosmic ray observations are used for studying several kinds of interplanetary structures. The cosmic ray data has different responses to each kind of interplanetary structure. This article has as objective to study cosmic ray muon and neutron signatures due to the passage of corotating interaction region (CIR) in the interplanetary medium, and identify the signatures in the cosmic ray data due to these events. The cosmic ray muon data used in this work are recorded by the multidirectional muon detector installed at INPE’s Observatório Espacial do Sul OES/CRSPE/INPE-MCT, in São Martinho da Serra, RS (Brazil) and the neutron data was recorded by the neutron monitor installed in Newark (USA). The CIR events were selected in the period from 2001 to 2004. CIRs clearly affect cosmic ray density in the interplanetary medium in the Earth’s vicinity, where the magnetic field plays an important role.

Neutron Imaging Reveals Internal Plant Hydraulic Dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warren, Jeffrey; Bilheux, Hassina Z; Kang, Misun

2013-01-01

Many terrestrial ecosystem processes are constrained by water availability and transport within the soil. Knowledge of plant water fluxes is thus critical for assessing mechanistic processes linked to biogeochemical cycles, yet resolution of root structure and xylem water transport dynamics has been a particularly daunting task for the ecologist. Through neutron imaging, we demonstrate the ability to non-invasively monitor individual root functionality and water fluxes within Zea mays L. (maize) and Panicum virgatum L. (switchgrass) seedlings growing in a sandy medium. Root structure and growth were readily imaged by neutron radiography and neutron computed tomography. Seedlings were irrigated with watermore » or deuterium oxide and imaged through time as a growth lamp was cycled on to alter leaf demand for water. Sub-millimeter scale resolution reveals timing and magnitudes of root water uptake, redistribution within the roots, and root-shoot hydraulic linkages, relationships not well characterized by other techniques.« less

Fusion neutron irradiation of Ni-Si alloys at high temperature*1

NASA Astrophysics Data System (ADS)

Huang, J. S.; Guinan, M. W.; Hahn, P. A.

1988-07-01

Two Ni-4% Si alloys, with different cold work levels, have been irradiated with 14-MeV fusion neutrons at 623 K, and their Curie temperatures have been monitored during irradiation. The results are compared to those of an identical alloy irradiated by 2-MeV electrons. The results show that increasing dislocation density increases the Curie temperature change rate. At the same damage rate, the Curie temperature change rate for the alloy irradiated by 14-MeV fusion neutrons is only 6-7% of that for an identical alloy irradiated by 2-MeV electrons. It is well known that the migration of radiation induced defects contributes to segregation of silicon atoms at sinks in this alloy, causing the Curie temperature changes. The current results imply that the relative free defect production efficiency decreases from one for the electron irradiated sample to 6-7% for the fusion neutron irradiated sample.

Neutron monitoring and electrode calorimetry experiments in the HIP-1 Hot Ion Plasma

NASA Technical Reports Server (NTRS)

Reinmann, J. J.; Layman, R. W.

1977-01-01

Results are presented for two diagnostic procedures on HIP-1: neutron diagnostics to determine where neutrons originated within the plasma discharge chamber and electrode calorimetry to measure the steady-state power absorbed by the two anodes and cathodes. Results are also reported for a hot-ion plasma formed with a continuous-cathode rod, one that spans the full length of the test section, in place of the two hollow cathodes. The outboard neutron source strength increased relative to that at the midplane when (1) the cathode tips were moved farther outboard, (2) the anode diameters were increased, and (3) one of the anodes was removed. The distribution of neutron sources within the plasma discharge chamber was insensitive to the division of current between the two cathodes. For the continuous cathode, increasing the discharge current increased the midplane neutron source strength relative to the outboard source strength. Each cathode absorbed from 12 to 15 percent of the input power regardless of the division of current between the cathodes. The anodes absorbed from 20 to 40 percent of the input power. The division of power absorption between the anodes varied with plasma operating conditions and electrode placement.

Fusion Power measurement at ITER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bertalot, L.; Barnsley, R.; Krasilnikov, V.

2015-07-01

Nuclear fusion research aims to provide energy for the future in a sustainable way and the ITER project scope is to demonstrate the feasibility of nuclear fusion energy. ITER is a nuclear experimental reactor based on a large scale fusion plasma (tokamak type) device generating Deuterium - Tritium (DT) fusion reactions with emission of 14 MeV neutrons producing up to 700 MW fusion power. The measurement of fusion power, i.e. total neutron emissivity, will play an important role for achieving ITER goals, in particular the fusion gain factor Q related to the reactor performance. Particular attention is given also tomore » the development of the neutron calibration strategy whose main scope is to achieve the required accuracy of 10% for the measurement of fusion power. Neutron Flux Monitors located in diagnostic ports and inside the vacuum vessel will measure ITER total neutron emissivity, expected to range from 1014 n/s in Deuterium - Deuterium (DD) plasmas up to almost 10{sup 21} n/s in DT plasmas. The neutron detection systems as well all other ITER diagnostics have to withstand high nuclear radiation and electromagnetic fields as well ultrahigh vacuum and thermal loads. (authors)« less

Implementation of medical monitor system based on networks

NASA Astrophysics Data System (ADS)

Yu, Hui; Cao, Yuzhen; Zhang, Lixin; Ding, Mingshi

2006-11-01

In this paper, the development trend of medical monitor system is analyzed and portable trend and network function become more and more popular among all kinds of medical monitor devices. The architecture of medical network monitor system solution is provided and design and implementation details of medical monitor terminal, monitor center software, distributed medical database and two kind of medical information terminal are especially discussed. Rabbit3000 system is used in medical monitor terminal to implement security administration of data transfer on network, human-machine interface, power management and DSP interface while DSP chip TMS5402 is used in signal analysis and data compression. Distributed medical database is designed for hospital center according to DICOM information model and HL7 standard. Pocket medical information terminal based on ARM9 embedded platform is also developed to interactive with center database on networks. Two kernels based on WINCE are customized and corresponding terminal software are developed for nurse's routine care and doctor's auxiliary diagnosis. Now invention patent of the monitor terminal is approved and manufacture and clinic test plans are scheduled. Applications for invention patent are also arranged for two medical information terminals.

INEL BNCT Research Program annual report, 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Venhuizen, J.R.

1993-05-01

This report is a summary of the progress and research produced for the Idaho National Engineering Laboratory Boron Neutron Capture Therapy (BNCT) Research Program for calendar year 1992. Contributions from all the principal investigators about their individual projects are included, specifically, chemistry (pituitary tumor targeting compounds, boron drug development including liposomes, lipoproteins, and carboranylalanine derivatives), pharmacology (murine screenings, toxicity testing, inductively coupled plasma-atomic emission spectroscopy (ICP-AES) analysis of biological samples), physics (radiation dosimetry software, neutron beam and filter design, neutron beam measurement dosimetry), and radiation biology (small and large animal models tissue studies and efficacy studies). Information on the potentialmore » toxicity of borocaptate sodium and boronophenylalanine is presented, results of 21 spontaneous-tumor-bearing dogs that have been treated with BNCT at the Brookhaven National Laboratory (BNL) Medical Research Reactor (BMRR) are discussed, and predictions for an epithermal-neutron beam at the Georgia Tech Research Reactor (GTRR) are shown. Cellular-level boron detection and localization by secondary ion mass spectrometry, sputter-initiated resonance ionization spectroscopy, low atomization resonance ionization spectroscopy, and alpha track are presented. Boron detection by ICP-AES is discussed in detail. Several boron carrying drugs exhibiting good tumor uptake are described. Significant progress in the potential of treating pituitary tumors with BNCT is presented. Measurement of the epithermal-neutron flux at BNL and comparison to predictions are shown. Calculations comparing the GTRR and BMRR epithermal-neutron beams are also presented. Individual progress reports described herein are separately abstracted and indexed for the database.« less

Doing Your Science While You're in Orbit

NASA Astrophysics Data System (ADS)

Green, Mark L.; Miller, Stephen D.; Vazhkudai, Sudharshan S.; Trater, James R.

2010-11-01

Large-scale neutron facilities such as the Spallation Neutron Source (SNS) located at Oak Ridge National Laboratory need easy-to-use access to Department of Energy Leadership Computing Facilities and experiment repository data. The Orbiter thick- and thin-client and its supporting Service Oriented Architecture (SOA) based services (available at https://orbiter.sns.gov) consist of standards-based components that are reusable and extensible for accessing high performance computing, data and computational grid infrastructure, and cluster-based resources easily from a user configurable interface. The primary Orbiter system goals consist of (1) developing infrastructure for the creation and automation of virtual instrumentation experiment optimization, (2) developing user interfaces for thin- and thick-client access, (3) provide a prototype incorporating major instrument simulation packages, and (4) facilitate neutron science community access and collaboration. The secure Orbiter SOA authentication and authorization is achieved through the developed Virtual File System (VFS) services, which use Role-Based Access Control (RBAC) for data repository file access, thin-and thick-client functionality and application access, and computational job workflow management. The VFS Relational Database Management System (RDMS) consists of approximately 45 database tables describing 498 user accounts with 495 groups over 432,000 directories with 904,077 repository files. Over 59 million NeXus file metadata records are associated to the 12,800 unique NeXus file field/class names generated from the 52,824 repository NeXus files. Services that enable (a) summary dashboards of data repository status with Quality of Service (QoS) metrics, (b) data repository NeXus file field/class name full text search capabilities within a Google like interface, (c) fully functional RBAC browser for the read-only data repository and shared areas, (d) user/group defined and shared metadata for data repository files, (e) user, group, repository, and web 2.0 based global positioning with additional service capabilities are currently available. The SNS based Orbiter SOA integration progress with the Distributed Data Analysis for Neutron Scattering Experiments (DANSE) software development project is summarized with an emphasis on DANSE Central Services and the Virtual Neutron Facility (VNF). Additionally, the DANSE utilization of the Orbiter SOA authentication, authorization, and data transfer services best practice implementations are presented.

TALYS/TENDL verification and validation processes: Outcomes and recommendations

NASA Astrophysics Data System (ADS)

Fleming, Michael; Sublet, Jean-Christophe; Gilbert, Mark R.; Koning, Arjan; Rochman, Dimitri

2017-09-01

The TALYS-generated Evaluated Nuclear Data Libraries (TENDL) provide truly general-purpose nuclear data files assembled from the outputs of the T6 nuclear model codes system for direct use in both basic physics and engineering applications. The most recent TENDL-2015 version is based on both default and adjusted parameters of the most recent TALYS, TAFIS, TANES, TARES, TEFAL, TASMAN codes wrapped into a Total Monte Carlo loop for uncertainty quantification. TENDL-2015 contains complete neutron-incident evaluations for all target nuclides with Z ≤116 with half-life longer than 1 second (2809 isotopes with 544 isomeric states), up to 200 MeV, with covariances and all reaction daughter products including isomers of half-life greater than 100 milliseconds. With the added High Fidelity Resonance (HFR) approach, all resonances are unique, following statistical rules. The validation of the TENDL-2014/2015 libraries against standard, evaluated, microscopic and integral cross sections has been performed against a newly compiled UKAEA database of thermal, resonance integral, Maxwellian averages, 14 MeV and various accelerator-driven neutron source spectra. This has been assembled using the most up-to-date, internationally-recognised data sources including the Atlas of Resonances, CRC, evaluated EXFOR, activation databases, fusion, fission and MACS. Excellent agreement was found with a small set of errors within the reference databases and TENDL-2014 predictions.

Development of deterministic transport methods for low energy neutrons for shielding in space

NASA Technical Reports Server (NTRS)

Ganapol, Barry

1993-01-01

Transport of low energy neutrons associated with the galactic cosmic ray cascade is analyzed in this dissertation. A benchmark quality analytical algorithm is demonstrated for use with BRYNTRN, a computer program written by the High Energy Physics Division of NASA Langley Research Center, which is used to design and analyze shielding against the radiation created by the cascade. BRYNTRN uses numerical methods to solve the integral transport equations for baryons with the straight-ahead approximation, and numerical and empirical methods to generate the interaction probabilities. The straight-ahead approximation is adequate for charged particles, but not for neutrons. As NASA Langley improves BRYNTRN to include low energy neutrons, a benchmark quality solution is needed for comparison. The neutron transport algorithm demonstrated in this dissertation uses the closed-form Green's function solution to the galactic cosmic ray cascade transport equations to generate a source of neutrons. A basis function expansion for finite heterogeneous and semi-infinite homogeneous slabs with multiple energy groups and isotropic scattering is used to generate neutron fluxes resulting from the cascade. This method, called the FN method, is used to solve the neutral particle linear Boltzmann transport equation. As a demonstration of the algorithm coded in the programs MGSLAB and MGSEMI, neutron and ion fluxes are shown for a beam of fluorine ions at 1000 MeV per nucleon incident on semi-infinite and finite aluminum slabs. Also, to demonstrate that the shielding effectiveness against the radiation from the galactic cosmic ray cascade is not directly proportional to shield thickness, a graph of transmitted total neutron scalar flux versus slab thickness is shown. A simple model based on the nuclear liquid drop assumption is used to generate cross sections for the galactic cosmic ray cascade. The ENDF/B V database is used to generate the total and scattering cross sections for neutrons in aluminum. As an external verification, the results from MGSLAB and MGSEMI were compared to ANISN/PC, a routinely used neutron transport code, showing excellent agreement. In an application to an aluminum shield, the FN method seems to generate reasonable results.

Italian polar data center for capacity building associated with the IHY

NASA Astrophysics Data System (ADS)

Damiani, A.; Bendetti, E.; Storini, M.; Rafanelli, C.

The International Heliophysical Year IHY offers a good opportunity to develop and coordinate studies on the Sun-Earth system by using a large variety of simultaneous data obtained by satellite spacecraft and ground based instruments Among these data we recall the ones coming from solar and interplanetary medium observations auroral neutron monitor geomagnetic field ionospheric meteorological and other atmospheric observatories In this context an Information System for the Italian Research in Antarctica SIRIA has started during 2003 aiming to collect information on the scientific research projects funded by the National Antarctic Research Program PNRA of Italy since its birth 1985 It belongs to the Joint Committee on Antarctic Data Management JCADM of SCAR Scientific Committee on Antarctic Research as the Italian Antarctic Data Center SIRIA being the Italian Polar Database gathers also information on research activities conducted in North Pole regions This Information System can be a relevant resource for capacity building associated with the IHY particularly for people involved in interdisciplinary researches We describe the present status of the Italian Polar Data Center and its potential use

A Case Study in Software Adaptation

DTIC Science & Technology

2002-01-01

1 A Case Study in Software Adaptation Giuseppe Valetto Telecom Italia Lab Via Reiss Romoli 274 10148, Turin, Italy +39 011 2288788...configuration of the service; monitoring of database connectivity from within the service; monitoring of crashes and shutdowns of IM servers; monitoring of...of the IM server all share a relational database and a common runtime state repository, which make up the backend tier, and allow replicas to

Compilation of the ``Atlas of Gamma-rays from the Inelastic Scattering of Reactor Fast Neutrons'' (1978DE41) by A.M. Demidov, L.I. Govor, Yu. K. Cherepantsev, M.R. Ahmed, S. Al-Najjar, M.A. Al-Amili, N. Al-Assafi, and N. Rammo

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurst, Aaron M.; Bernstein, Lee A.; Chong, Su-Ann

A Structured Query Language (SQL) relational database has been developed based on the original (n,n'gamma) work carried out by A.M. Demidov et al., at the Nuclear Research Institute in Baghdad, Iraq [``Atlas of Gamma-Ray Spectra from the Inelastic Scattering of Reactor Fast Neutrons'', Nuclear Research Institute, Baghdad, Iraq (Moscow, Atomizdat 1978)] for 105 independent measurements comprising 76 elemental samples of natural composition and 29 isotopically-enriched samples. The information from this ATLAS includes: gamma-ray energies and intensities; nuclide and level data corresponding to where the gamma-ray originated from; target (sample) experimental-measurement data. Taken together, this information allows for the extraction ofmore » the flux-weighted (n,n'gamma) cross sections for a given transition relative to a defined value. Currently, we are using the fast-neutron flux-weighted partial gamma-ray cross section from ENDF/B-VII.1 for the production of the 847-keV transition from the first excited 2+ state to the 0+ ground state in 56Fe, 468 mb. This value also takes into account contributions to the 847-keV transition following beta(-) decay of 56Mn formed in the 56Fe(n,p) reaction. However, this value can easily be adjusted to accommodate the user preference. The (n,n'gamma) data has been compiled into a series of ASCII comma separated value tables and a suite of Python scripts and C modules are provided to build the database. Upon building, the database can then be interacted with directly via the SQLite engine or accessed via the Jupyter Notebook Python-browser interface. Several examples exploiting these utilities are also provided with the complete software package.« less

Active-Interrogation Measurements of Induced-Fission Neutrons from Low-Enriched Uranium

DOE Office of Scientific and Technical Information (OSTI.GOV)

J. L. Dolan; M. J. Marcath; M. Flaska

2012-07-01

Protection and control of nuclear fuels is paramount for nuclear security and safeguards; therefore, it is important to develop fast and robust controlling mechanisms to ensure the safety of nuclear fuels. Through both passive- and active-interrogation methods we can use fast-neutron detection to perform real-time measurements of fission neutrons for process monitoring. Active interrogation allows us to use different ranges of incident neutron energy to probe for different isotopes of uranium. With fast-neutron detectors, such as organic liquid scintillation detectors, we can detect the induced-fission neutrons and photons and work towards quantifying a sample’s mass and enrichment. Using MCNPX-PoliMi, amore » system was designed to measure induced-fission neutrons from U-235 and U-238. Measurements were then performed in the summer of 2010 at the Joint Research Centre in Ispra, Italy. Fissions were induced with an associated particle D-T generator and an isotopic Am-Li source. The fission neutrons, as well as neutrons from (n, 2n) and (n, 3n) reactions, were measured with five 5” by 5” EJ-309 organic liquid scintillators. The D-T neutron generator was available as part of a measurement campaign in place by Padova University. The measurement and data-acquisition systems were developed at the University of Michigan utilizing a CAEN V1720 digitizer and pulse-shape discrimination algorithms to differentiate neutron and photon detections. Low-enriched uranium samples of varying mass and enrichment were interrogated. Acquired time-of-flight curves and cross-correlation curves are currently analyzed to draw relationships between detected neutrons and sample mass and enrichment. In the full paper, the promise of active-interrogation measurements and fast-neutron detection will be assessed through the example of this proof-of-concept measurement campaign. Additionally, MCNPX-PoliMi simulation results will be compared to the measured data to validate the MCNPX-PoliMi code when used for active-interrogation simulations.« less

Development and Feasibility Testing of a Critical Care EEG Monitoring Database for Standardized Clinical Reporting and Multicenter Collaborative Research.

PubMed

Lee, Jong Woo; LaRoche, Suzette; Choi, Hyunmi; Rodriguez Ruiz, Andres A; Fertig, Evan; Politsky, Jeffrey M; Herman, Susan T; Loddenkemper, Tobias; Sansevere, Arnold J; Korb, Pearce J; Abend, Nicholas S; Goldstein, Joshua L; Sinha, Saurabh R; Dombrowski, Keith E; Ritzl, Eva K; Westover, Michael B; Gavvala, Jay R; Gerard, Elizabeth E; Schmitt, Sarah E; Szaflarski, Jerzy P; Ding, Kan; Haas, Kevin F; Buchsbaum, Richard; Hirsch, Lawrence J; Wusthoff, Courtney J; Hopp, Jennifer L; Hahn, Cecil D

2016-04-01

The rapid expansion of the use of continuous critical care electroencephalogram (cEEG) monitoring and resulting multicenter research studies through the Critical Care EEG Monitoring Research Consortium has created the need for a collaborative data sharing mechanism and repository. The authors describe the development of a research database incorporating the American Clinical Neurophysiology Society standardized terminology for critical care EEG monitoring. The database includes flexible report generation tools that allow for daily clinical use. Key clinical and research variables were incorporated into a Microsoft Access database. To assess its utility for multicenter research data collection, the authors performed a 21-center feasibility study in which each center entered data from 12 consecutive intensive care unit monitoring patients. To assess its utility as a clinical report generating tool, three large volume centers used it to generate daily clinical critical care EEG reports. A total of 280 subjects were enrolled in the multicenter feasibility study. The duration of recording (median, 25.5 hours) varied significantly between the centers. The incidence of seizure (17.6%), periodic/rhythmic discharges (35.7%), and interictal epileptiform discharges (11.8%) was similar to previous studies. The database was used as a clinical reporting tool by 3 centers that entered a total of 3,144 unique patients covering 6,665 recording days. The Critical Care EEG Monitoring Research Consortium database has been successfully developed and implemented with a dual role as a collaborative research platform and a clinical reporting tool. It is now available for public download to be used as a clinical data repository and report generating tool.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramirez, A. P. D.; Vanhoy, J. R.; Hicks, S. F.

Elastic and inelastic differential cross sections for neutron scattering from 56Fe have been measured for several incident energies from 1.30 to 7.96 MeV at the University of Kentucky Accelerator Laboratory. Scattered neutrons were detected using a C 6D 6 liquid scintillation detector using pulse-shape discrimination and time-of-flight techniques. The deduced cross sections have been compared with previously reported data, predictions from evaluation databases ENDF, JENDL, and JEFF, and theoretical calculations performed using different optical model potentials using the TALYS and EMPIRE nuclear reaction codes. The coupled-channel calculations based on the vibrational and soft-rotor models are found to describe the experimentalmore » (n,n 0) and (n,n 1) cross sections well.« less

Database on Performance of Neutron Irradiated FeCrAl Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Field, Kevin G.; Briggs, Samuel A.; Littrell, Ken

The present report summarizes and discusses the database on radiation tolerance for Generation I, Generation II, and commercial FeCrAl alloys. This database has been built upon mechanical testing and microstructural characterization on selected alloys irradiated within the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) up to doses of 13.8 dpa at temperatures ranging from 200°C to 550°C. The structure and performance of these irradiated alloys were characterized using advanced microstructural characterization techniques and mechanical testing. The primary objective of developing this database is to enhance the rapid development of a mechanistic understanding on the radiation tolerancemore » of FeCrAl alloys, thereby enabling informed decisions on the optimization of composition and microstructure of FeCrAl alloys for application as an accident tolerant fuel (ATF) cladding. This report is structured to provide a brief summary of critical results related to the database on radiation tolerance of FeCrAl alloys.« less

Neutron-deuteron analyzing power data at En = 21 MeV and the energy dependence of the three-nucleon analyzing power puzzle

NASA Astrophysics Data System (ADS)

Weisel, G. J.; Tornow, W.; Esterline, J. H.

2015-08-01

We present measurements of n-d analyzing power, {A}y(θ ), at En = 21.0 MeV. The experiment produces neutrons via the 2H(d, n)3He reaction and uses a deuterated liquid-scintillator center detector and six pairs of liquid-scintillator neutron side detectors. Elastic neutron scattering events are identified by using time-of-flight techniques and by setting a gate in the center-detector pulse-height spectrum. Beam polarization is monitored by using a high-pressure helium gas scintillator. The n-d {A}y(θ ) data at 21.0 MeV show a significant discrepancy with the results of rigorous three-body calculations and are consistent with data taken previously by us at 19.0 and 22.5 MeV. We review the overall energy dependence of the three-nucleon analyzing power puzzle in neutron-deuteron elastic scattering, using the best data available. We find that the relative difference between calculations and data is nearly constant at 25% up to En = 22.5 MeV.

Neutron-deuteron analyzing power data at En=22.5 MeV

NASA Astrophysics Data System (ADS)

Weisel, G. J.; Tornow, W.; Crowell, A. S.; Esterline, J. H.; Hale, G. M.; Howell, C. R.; O'Malley, P. D.; Tompkins, J. R.; Witała, H.

2014-05-01

We present measurements of n-d analyzing power, Ay(θ), at En=22.5 MeV. The experiment uses a shielded neutron source which produced polarized neutrons via the 2H(d⃗,n⃗)3He reaction. It also uses a deuterated liquid-scintillator center detector and six pairs of liquid-scintillator neutron side detectors. Elastic neutron scattering events are identified by using time-of-flight techniques and by setting a window in the center detector pulse-height spectrum. The beam polarization is monitored by using a high-pressure helium gas cell and an additional pair of liquid-scintillator side detectors. The n-d Ay(θ) data were corrected for finite-geometry and multiple-scattering effects using a Monte Carlo simulation of the experiment. The 22.5-MeV data demonstrate that the three-nucleon analyzing power puzzle also exists at this energy. They show a significant discrepancy with predictions of high-precision nucleon-nucleon potentials alone or combined with Tucscon-Melbourne or Urbana IX three-nucleon forces, as well as currently available effective-field theory based potentials of next-to-next-to-next-to-leading order.

Neutron dose estimation via LET spectrometry using CR-39 detector for the reaction 9Be (p, n)

PubMed Central

Sahoo, G. S.; Tripathy, S. P.; Paul, S.; Sharma, S. D.; Sharma, S. C.; Joshi, D. S.; Bandyopadhyay, T.

2014-01-01

CR-39 detectors, widely used for neutron dosimetry in accelerator radiation environment, have also been applied in tissue microdosimetry by generating the linear energy transfer (LET) spectrum. In this work, the neutron dose has been estimated via LET spectrometry for 9Be (p, n) reaction which is useful for personnel monitoring around particle accelerators and accelerator based therapy facilities. Neutrons were generated by the interaction of protons of 6 different energies from 4–24 MeV with a thick Be target. The LET spectra were obtained from the major and minor radii of each track and the thickness of removed surface. From the LET spectra, the absorbed dose (DLET) and the dose equivalent (HLET) were estimated using Q-L relationship as given by International Commission on Radiological Protection (ICRP) 60. The track density in CR-39 detector and hence the neutron yield was found to be increasing with the increase in projectile (proton) energy. Similar observations were also obtained for absorbed dose (DLET) and dose equivalents (HLET). PMID:25525310

Development of a digital method for neutron/gamma-ray discrimination based on matched filtering

NASA Astrophysics Data System (ADS)

Korolczuk, S.; Linczuk, M.; Romaniuk, R.; Zychor, I.

2016-09-01

Neutron/gamma-ray discrimination is crucial for measurements with detectors sensitive to both neutron and gamma-ray radiation. Different techniques to discriminate between neutrons and gamma-rays based on pulse shape analysis are widely used in many applications, e.g., homeland security, radiation dosimetry, environmental monitoring, fusion experiments, nuclear spectroscopy. A common requirement is to improve a radiation detection level with a high detection reliability. Modern electronic components, such as high speed analog to digital converters and powerful programmable digital circuits for signal processing, allow us to develop a fully digital measurement system. With this solution it is possible to optimize digital signal processing algorithms without changing any electronic components in an acquisition signal path. We report on results obtained with a digital acquisition system DNG@NCBJ designed at the National Centre for Nuclear Research. A 2'' × 2'' EJ309 liquid scintillator was used to register mixed neutron and gamma-ray radiation from PuBe sources. A dedicated algorithm for pulse shape discrimination, based on real-time filtering, was developed and implemented in hardware.

Lifetime Neutron Fluence Analysis of the Ringhals Unit 1 Boiling Water Reactor

NASA Astrophysics Data System (ADS)

Kulesza, Joel A.; Roudén, Jenny; Green, Eva-Lena

2016-02-01

This paper describes a neutron fluence assessment considering the entire commercial operating history (35 cycles or ˜ 25 effective full power years) of the Ringhals Unit 1 reactor pressure vessel beltline region. In this assessment, neutron (E >1.0 MeV) fluence and iron atom displacement distributions were calculated on the moderator tank and reactor pressure vessel structures. To validate those calculations, five in-vessel surveillance chain dosimetry sets were evaluated as well as material samples taken from the upper core grid and wide range neutron monitor tubes to act as a form of retrospective dosimetry. During the analysis, it was recognized that delays in characterizing the retrospective dosimetry samples reduced the amount of reactions available to be counted and complicated the material composition determination. However, the comparisons between the surveillance chain dosimetry measurements (M) and calculated (C) results show similar and consistent results with the linear average M/C ratio of 1.13 which is in good agreement with the resultant least squares best estimate (BE)/C ratios of 1.10 for both neutron (E >1.0 MeV) flux and iron atom displacement rate.

Quality assurance of temporal variability of natural decay chain and neutron induced background for low-level NORM analysis

DOE PAGES

Yoho, Michael; Porterfield, Donivan R.; Landsberger, Sheldon

2015-09-22

In this study, twenty-one high purity germanium (HPGe) background spectra were collected over 2 years at Los Alamos National Laboratory. A quality assurance methodology was developed to monitor spectral background levels from thermal and fast neutron flux levels and naturally occurring radioactive material decay series radionuclides. 238U decay products above 222Rn demonstrated minimal temporal variability beyond that expected from counting statistics. 238U and 232Th progeny below Rn gas displayed at most twice the expected variability. Further, an analysis of the 139 keV 74Ge(n, γ) and 691 keV 72Ge(n, n') spectral features demonstrated temporal stability for both thermal and fastmore » neutron fluxes.« less

A real-time n/γ digital pulse shape discriminator based on FPGA.

PubMed

Li, Shiping; Xu, Xiufeng; Cao, Hongrui; Yuan, Guoliang; Yang, Qingwei; Yin, Zejie

2013-02-01

A FPGA-based real-time digital pulse shape discriminator has been employed to distinguish between neutrons (n) and gammas (γ) in the Neutron Flux Monitor (NFM) for International Thermonuclear Experimental Reactor (ITER). The discriminator takes advantages of the Field Programmable Gate Array (FPGA) parallel and pipeline process capabilities to carry out the real-time sifting of neutrons in n/γ mixed radiation fields, and uses the rise time and amplitude inspection techniques simultaneously as the discrimination algorithm to observe good n/γ separation. Some experimental results have been presented which show that this discriminator can realize the anticipated goals of NFM perfectly with its excellent discrimination quality and zero dead time. Copyright © 2012 Elsevier Ltd. All rights reserved.

Crystallographic changes in lead zirconate titanate due to neutron irradiation

DOE PAGES

Henriques, Alexandra; Graham, Joseph T.; Landsberger, Sheldon; ...

2014-11-17

Piezoelectric and ferroelectric materials are useful as the active element in non-destructive monitoring devices for high-radiation areas. Here, crystallographic structural refinement (i.e., the Rietveld method) is used to quantify the type and extent of structural changes in PbZr 0 .5Ti 0 .5O 3 after exposure to a 1 MeV equivalent neutron fluence of 1.7 × 10 15 neutrons/cm 2. The results show a measurable decrease in the occupancy of Pb and O due to irradiation, with O vacancies in the tetragonal phase being created preferentially on one of the two O sites. The results demonstrate a method by which themore » effects of radiation on crystallographic structure may be investigated.« less

Phillips-Tikhonov regularization with a priori information for neutron emission tomographic reconstruction on Joint European Torus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bielecki, J.; Scholz, M.; Drozdowicz, K.

A method of tomographic reconstruction of the neutron emissivity in the poloidal cross section of the Joint European Torus (JET, Culham, UK) tokamak was developed. Due to very limited data set (two projection angles, 19 lines of sight only) provided by the neutron emission profile monitor (KN3 neutron camera), the reconstruction is an ill-posed inverse problem. The aim of this work consists in making a contribution to the development of reliable plasma tomography reconstruction methods that could be routinely used at JET tokamak. The proposed method is based on Phillips-Tikhonov regularization and incorporates a priori knowledge of the shape ofmore » normalized neutron emissivity profile. For the purpose of the optimal selection of the regularization parameters, the shape of normalized neutron emissivity profile is approximated by the shape of normalized electron density profile measured by LIDAR or high resolution Thomson scattering JET diagnostics. In contrast with some previously developed methods of ill-posed plasma tomography reconstruction problem, the developed algorithms do not include any post-processing of the obtained solution and the physical constrains on the solution are imposed during the regularization process. The accuracy of the method is at first evaluated by several tests with synthetic data based on various plasma neutron emissivity models (phantoms). Then, the method is applied to the neutron emissivity reconstruction for JET D plasma discharge #85100. It is demonstrated that this method shows good performance and reliability and it can be routinely used for plasma neutron emissivity reconstruction on JET.« less

Continuous monitoring of a mountain snowpack in the Austrian Alps by above-ground neutron sensing

NASA Astrophysics Data System (ADS)

Schattan, Paul; Baroni, Gabriele; Oswald, Sascha E.; Schöber, Johannes; Fey, Christine; Francke, Till; Huttenlau, Matthias; Achleitner, Stefan

2017-04-01

In alpine catchments the knowledge of the spatially and temporally heterogeneous dynamics of snow accumulation and depletion is crucial for modelling and managing water resources. While snow covered area can be retrieved operationally from remote sensing data, continuous measurements of other snow state variables like snow depth (SD) or snow water equivalent (SWE) remain challenging. Existing methods of retrieving both variables in alpine terrain face severe issues like a lack of spatial representativeness, labour-intensity or discontinuity in time. Recently, promising new measurement techniques combining a larger support with low maintenance cost like above-ground gamma-ray scintillators, GPS interferometric reflectometry or above-ground cosmic-ray neutron sensors (CRNS) have been suggested. While CRNS has proven its potential for monitoring soil moisture in a wide range of environments and applications, the empirical knowledge of using CRNS for snowpack monitoring is still very limited and restricted to shallow snowpacks with rather uniform evolution. The characteristics of an above-ground cosmic-ray neutron sensor (CRNS) were therefore evaluated for monitoring a mountain snowpack in the Austrian Alps (Kaunertal, Tyrol) during three winter seasons. The measurement campaign included a number of measurements during the period from 03/2014 to 06/2016: (i) neutron count measurements by CRNS, (ii) continuous point-scale SD and SWE measurements from an automatic weather station and (iii) 17 Terrestrial Laser Scanning (TLS) with simultaneous SD and SWE surveys. The highest accumulation in terms of SWE was found in 04/2014 with 600 mm. Neutron counts were compared to all available snow data. While previous studies suggested a signal saturation at around 100 mm of SWE, no complete signal saturation was found. A strong non-linear relation was found for both SD and SWE with best fits for spatially distributed TLS based snow data. Initially slightly different shapes were found for accumulation and melting season conditions but this could be resolved by accounting for the limited measurement depth. This depth limit is in the range of 200 mm of SWE for dense snowpacks with high liquid water contents and associated snow density values around 450 kg m-3 and above. Furthermore, the results prove that for medium to high snowpack the inter-annual transferability of the results is very high regardless of pre-snowfall soil moisture conditions. These results underline the high potential of CRNS for closing the gap between point-scale measurements, hydrological models and remote sensing in snow hydrology and alpine terrain.

SNM detection with an optimized water Cherenkov neutron detector

NASA Astrophysics Data System (ADS)

Dazeley, S.; Sweany, M.; Bernstein, A.

2012-11-01

Special Nuclear Material (SNM) can either spontaneously fission or be induced to do so: either case results in neutron emission. For this reason, neutron detection performs a crucial role in the functionality of Radiation Portal Monitoring (RPM) devices. Since neutrons are highly penetrating and difficult to shield, they could potentially be detected escaping even a well-shielded cargo container. If the shielding were sophisticated, detecting escaping neutrons would require a highly efficient detector with close to full solid angle coverage. In 2008, we reported the successful detection of neutrons with a 250 liter (l) gadolinium doped water Cherenkov prototype [1]—a technology that could potentially be employed cost effectively with full solid angle coverage. More recently we have built and tested both 1-kl and 3.5-kl versions [2], demonstrating that very large, cost effective, non-flammable and environmentally benign neutron detectors can be operated efficiently without being overwhelmed by background. In this paper, we present a new design for a modular system of water-based neutron detectors that could be deployed as a real RPM. The modules contain a number of optimizations that have not previously been combined within a single system. We present simulations of the new system, based on the performance of our previous detectors. Our simulations indicate that an optimized system such as is presented here could achieve SNM sensitivity competitive with a large 3He-based system. Moreover, the realization of large, cost effective neutron detectors could, for the first time, enable the detection of multiple neutrons per fission from within a large object such as a cargo container. Such a signal would provide a robust indication of the presence of fissioning material, reducing the frequency of false alarms while increasing sensitivity.

SNM Detection with an Optimized Water Cherenkov Neutron Detector

DOE PAGES

Dazeley, S.; Sweany, M.; Bernstein, A.

2012-07-23

Special Nuclear Material (SNM) can either spontaneously fission or be induced to do so: either case results in neutron emission. For this reason, neutron detection performs a crucial role in the functionality of Radiation Portal Monitoring (RPM) devices. Since neutrons are highly penetrating and difficult to shield, they could potentially be detected escaping even a well-shielded cargo container. If the shielding were sophisticated, detecting escaping neutrons would require a highly efficient detector with close to full solid angle coverage. In 2008, we reported the successful detection of neutrons with a 250 liter (l) gadolinium doped water Cherenkov prototype—a technology thatmore » could potentially be employed cost effectively with full solid angle coverage. More recently we have built and tested both 1-kl and 3.5-kl versions, demonstrating that very large, cost effective, non-flammable and environmentally benign neutron detectors can be operated efficiently without being overwhelmed by background. In our paper, we present a new design for a modular system of water-based neutron detectors that could be deployed as a real RPM. The modules contain a number of optimizations that have not previously been combined within a single system. We present simulations of the new system, based on the performance of our previous detectors. These simulations indicate that an optimized system such as is presented here could achieve SNM sensitivity competitive with a large 3He-based system. Moreover, the realization of large, cost effective neutron detectors could, for the first time, enable the detection of multiple neutrons per fission from within a large object such as a cargo container. Such a signal would provide a robust indication of the presence of fissioning material, reducing the frequency of false alarms while increasing sensitivity.« less

Astrophysical quests for neutron capture data of unstable nuclei

NASA Astrophysics Data System (ADS)

Käppeler, F.

2016-11-01

The abundances of the chemical elements heavier than iron can be attributed in about equal parts to the r and to the s process, which are taking place in supernova explosions and during the He and C burning phases of stellar evolution, respectively. So far, quantitative studies on the extremely short-lived neutron-rich nuclei constituting the ( n, γ) network of the r process are out of reach. On the contrary, the situation for the s -process is far advanced, as the reaction path of the s process from 12C to the Pb/Bi region is located within the valley of stability. Accordingly, a comprehensive database of experimental ( n, γ) cross sections has been established. While for many stable isotopes the necessary accuracy is still to be reached, reliable cross sections for the involved unstable isotopes are almost completely missing. Because of the intrinsic γ background of radioactive samples, successful time-of-flight measurements are depending on intense pulsed neutron sources. Such data are fundamental for our understanding of branchings in the s -process reaction path, which carry important model-independent information on neutron flux and temperature in the deep stellar interior.

Cross section measurements for neutron inelastic scattering and the ( n ,   2 n γ ) reaction on Pb 206

DOE PAGES

Negret, A.; Mihailescu, L. C.; Borcea, C.; ...

2015-06-30

We measured excitation functions for γ production associated with the neutron inelastic scattering and the (n, 2n) reactions on 206Pb from threshold up to 18 MeV for about 40 transitions. Two independent measurements were performed using different samples and acquisition systems to check consistency of the results. Moreover, the neutron flux was determined with a 235U fission chamber and a procedure that were validated against a fluence standard. For incident energy higher than the threshold for the first excited level and up to 3.5 MeV, estimates are provided for the total inelastic and level cross sections by combining the presentmore » γ production cross sections with the level and decay data of 206Pb reported in the literature. The uncertainty common to all incident energies is 3.0% allowing overall uncertainties from 3.3% to 30% depending on transition and neutron energy. Finally, the present data agree well with earlier work, but significantly expand the experimental database while comparisons with model calculations using the talys reaction code show good agreement over the full energy range.« less

Evaluation of tritium release properties of advanced tritium breeders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoshino, T.; Ochiai, K.; Edao, Y.

2015-03-15

Demonstration power plant (DEMO) fusion reactors require advanced tritium breeders with high thermal stability. Lithium titanate (Li{sub 2}TiO{sub 3}) advanced tritium breeders with excess Li (Li{sub 2+x}TiO{sub 3+y}) are stable in a reducing atmosphere at high temperatures. Although the tritium release properties of tritium breeders are documented in databases for DEMO blanket design, no in situ examination under fusion neutron (DT neutron) irradiation has been performed. In this study, a preliminary examination of the tritium release properties of advanced tritium breeders was performed, and DT neutron irradiation experiments were performed at the fusion neutronics source (FNS) facility in JAEA. Consideringmore » the tritium release characteristics, the optimum grain size after sintering is <5 μm. From the results of the optimization of granulation conditions, prototype Li{sub 2+x}TiO{sub 3+y} pebbles with optimum grain size (<5 μm) were successfully fabricated. The Li{sub 2+x}TiO{sub 3+y} pebbles exhibited good tritium release properties similar to the Li{sub 2}TiO{sub 3} pebbles. In particular, the released amount of HT gas for easier tritium handling was higher than that of HTO water. (authors)« less

Monte carlo simulations of Yttrium reaction rates in Quinta uranium target

NASA Astrophysics Data System (ADS)

Suchopár, M.; Wagner, V.; Svoboda, O.; Vrzalová, J.; Chudoba, P.; Tichý, P.; Kugler, A.; Adam, J.; Závorka, L.; Baldin, A.; Furman, W.; Kadykov, M.; Khushvaktov, J.; Solnyshkin, A.; Tsoupko-Sitnikov, V.; Tyutyunnikov, S.; Bielewicz, M.; Kilim, S.; Strugalska-Gola, E.; Szuta, M.

2017-03-01

The international collaboration Energy and Transmutation of Radioactive Waste (E&T RAW) performed intensive studies of several simple accelerator-driven system (ADS) setups consisting of lead, uranium and graphite which were irradiated by relativistic proton and deuteron beams in the past years at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. The most recent setup called Quinta, consisting of natural uranium target-blanket and lead shielding, was irradiated by deuteron beams in the energy range between 1 and 8 GeV in three accelerator runs at JINR Nuclotron in 2011 and 2012 with yttrium samples among others inserted inside the setup to measure the neutron flux in various places. Suitable activation detectors serve as one of possible tools for monitoring of proton and deuteron beams and for measurements of neutron field distribution in ADS studies. Yttrium is one of such suitable materials for monitoring of high energy neutrons. Various threshold reactions can be observed in yttrium samples. The yields of isotopes produced in the samples were determined using the activation method. Monte Carlo simulations of the reaction rates leading to production of different isotopes were performed in the MCNPX transport code and compared with the experimental results obtained from the yttrium samples.

International remote monitoring project Argentina Nuclear Power Station Spent Fuel Transfer Remote Monitoring System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, S.; Lucero, R.; Glidewell, D.

1997-08-01

The Autoridad Regulataria Nuclear (ARN) and the United States Department of Energy (DOE) are cooperating on the development of a Remote Monitoring System for nuclear nonproliferation efforts. A Remote Monitoring System for spent fuel transfer will be installed at the Argentina Nuclear Power Station in Embalse, Argentina. The system has been designed by Sandia National Laboratories (SNL), with Los Alamos National Laboratory (LANL) and Oak Ridge National Laboratory (ORNL) providing gamma and neutron sensors. This project will test and evaluate the fundamental design and implementation of the Remote Monitoring System in its application to regional and international safeguards efficiency. Thismore » paper provides a description of the monitoring system and its functions. The Remote Monitoring System consists of gamma and neutron radiation sensors, RF systems, and video systems integrated into a coherent functioning whole. All sensor data communicate over an Echelon LonWorks Network to a single data logger. The Neumann DCM 14 video module is integrated into the Remote Monitoring System. All sensor and image data are stored on a Data Acquisition System (DAS) and archived and reviewed on a Data and Image Review Station (DIRS). Conventional phone lines are used as the telecommunications link to transmit on-site collected data and images to remote locations. The data and images are authenticated before transmission. Data review stations will be installed at ARN in Buenos Aires, Argentina, ABACC in Rio De Janeiro, IAEA Headquarters in Vienna, and Sandia National Laboratories in Albuquerque, New Mexico. 2 refs., 2 figs.« less

Measurement result of the neutron monitor onboard the Space Environment Data Acquisition Equipment - Attached Payload (SEDA-AP)

NASA Astrophysics Data System (ADS)

Koga, K.; Muraki, Y.; Shibata, S.; Yamamoto, T.; Matsumoto, H.; Okudaira, O.; Kawano, H.; Yumoto, K.

2013-12-01

To support future space activities, it is crucial to acquire space environmental data related to the space-radiation degradation of space parts and materials, and spacecraft anomalies. Such data are useful for spacecraft design and manned space activity. SEDA-AP was mounted on 'Kibo' of the ISS (International Space Station) to measure the space environment at a 400-kilometer altitude. Neutrons are very harmful radiation, with electrical neutrality that makes them strongly permeable. SEDA-AP measures the energy of neutrons from thermal to 100 MeV in real time using a Bonner Ball Detector (BBND) and a Scintillation Fiber Detector (FIB). BBND detects neutrons using He-3 counters, which have high sensitivity to thermal neutrons. Neutron energy is derived using the relative response function of polyethylene moderators of 6 different thicknesses. FIB measures the tracks of recoil protons caused by neutrons within a cubic arrayed sensor of 512 scintillation fibers. The charged particles are excluded using an anti-scintillator which surrounds the cube sensor, and the neutron energy is obtained from the track length of a recoil proton. There are three sources of neutrons in space; 1. Albedo Neutrons Produced by reactions of galactic cosmic rays or radiation belt particles with the atmosphere 2. Local Neutrons Produced by the reactions of galactic cosmic rays or radiation belt particles with spacecraft 3. Solar Neutrons Produced by accelerated particles in solar flares An accurate energy spectrum of the solar neutrons includes important information on high-energy particle generation mechanism in a solar flare, because neutrons are unaffected by interplanetary magnetic fields. These data will become useful to forecast solar energetic particles in future. Some candidate events involving solar neutrons were found as a result of analyzing data of the solar flare of M>2 since September 2009. Moreover, it is important to measure albedo neutrons, since protons generated by neutron decays are thought to originate from the radiation belt. This theory is called CRAND (Cosmic Ray Albedo Neutron Decay). Our observation result is consistent with the CRAND theory prediction in the case of low-energy parts. Moreover, the flux and angular distribution of local neutrons were estimated using the nuclear simulation code 'PHITS' to evaluate the influence of local neutrons on the structure of SEDA-AP and 'Kibo'. The results of our analyses on solar and albedo neutrons are reported in this paper.

Operation and reactivity measurements of an accelerator driven subcritical TRIGA reactor

NASA Astrophysics Data System (ADS)

O'Kelly, David Sean

Experiments were performed at the Nuclear Engineering Teaching Laboratory (NETL) in 2005 and 2006 in which a 20 MeV linear electron accelerator operating as a photoneutron source was coupled to the TRIGA (Training, Research, Isotope production, General Atomics) Mark II research reactor at the University of Texas at Austin (UT) to simulate the operation and characteristics of a full-scale accelerator driven subcritical system (ADSS). The experimental program provided a relatively low-cost substitute for the higher power and complexity of internationally proposed systems utilizing proton accelerators and spallation neutron sources for an advanced ADSS that may be used for the burning of high-level radioactive waste. Various instrumentation methods that permitted ADSS neutron flux monitoring in high gamma radiation fields were successfully explored and the data was used to evaluate the Stochastic Pulsed Feynman method for reactivity monitoring.

Detection of lower tropospheric responses to solar energetic particles at midlatitudes.

PubMed

Nicoll, K A; Harrison, R G

2014-06-06

Solar energetic particles (SEPs) occasionally contribute additional atmospheric ionization beyond that arising from the usual galactic cosmic ray background. During an SEP event associated with a solar flare on April 11, 2013, the vertical ionization rate profile obtained using a balloon-borne detector showed enhanced ionization with a 26% increase at 20 km, over Reading, United Kingdom. Fluctuations in atmospheric electrical parameters were also detected at the surface, beneath the balloon's trajectory. As no coincident changes in geomagnetism occurred, the electrical fluctuations are very likely to be associated with increased ionization, as observed by the balloon measurements. The lack of response of surface neutron monitors during this event indicates that energetic particles that are not detected at the surface by neutron monitors can nevertheless enter and influence the atmosphere's weather-generating regions.

Network-Oriented Radiation Monitoring System (NORMS)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rahmat Aryaeinejad; David F. Spencer

2007-10-01

We have developed a multi-functional pocket radiation monitoring system capable of detecting and storing gamma ray and neutron data and then sending the data through a wireless connection to a remote central facility upon request. The device has programmable alarm trigger levels that can be modified for specific applications. The device could be used as a stand-alone device or in conjunction with an array to cover a small or large area. The data is stored with a date/time stamp. The device may be remotely configured. Data can be transferred and viewed on a PDA via direct connection or wirelessly. Functional/benchmore » tests have been completed successfully. The device detects low-level neutron and gamma sources within a shielded container in a radiation field of 10 uR/hr above the ambient background level.« less

Monitoring of services with non-relational databases and map-reduce framework

NASA Astrophysics Data System (ADS)

Babik, M.; Souto, F.

2012-12-01

Service Availability Monitoring (SAM) is a well-established monitoring framework that performs regular measurements of the core site services and reports the corresponding availability and reliability of the Worldwide LHC Computing Grid (WLCG) infrastructure. One of the existing extensions of SAM is Site Wide Area Testing (SWAT), which gathers monitoring information from the worker nodes via instrumented jobs. This generates quite a lot of monitoring data to process, as there are several data points for every job and several million jobs are executed every day. The recent uptake of non-relational databases opens a new paradigm in the large-scale storage and distributed processing of systems with heavy read-write workloads. For SAM this brings new possibilities to improve its model, from performing aggregation of measurements to storing raw data and subsequent re-processing. Both SAM and SWAT are currently tuned to run at top performance, reaching some of the limits in storage and processing power of their existing Oracle relational database. We investigated the usability and performance of non-relational storage together with its distributed data processing capabilities. For this, several popular systems have been compared. In this contribution we describe our investigation of the existing non-relational databases suited for monitoring systems covering Cassandra, HBase and MongoDB. Further, we present our experiences in data modeling and prototyping map-reduce algorithms focusing on the extension of the already existing availability and reliability computations. Finally, possible future directions in this area are discussed, analyzing the current deficiencies of the existing Grid monitoring systems and proposing solutions to leverage the benefits of the non-relational databases to get more scalable and flexible frameworks.

The need for precise and well-documented experimental data on prompt fission neutron spectra from neutron-induced fission of 239Pu

DOE PAGES

Neudecker, Denise; Taddeucci, Terry Nicholas; Haight, Robert Cameron; ...

2016-01-06

The spectrum of neutrons emitted promptly after 239Pu(n,f)—a so-called prompt fission neutron spectrum (PFNS)—is a quantity of high interest, for instance, for reactor physics and global security. However, there are only few experimental data sets available that are suitable for evaluations. In addition, some of those data sets differ by more than their 1-σ uncertainty boundaries. We present the results of MCNP studies indicating that these differences are partly caused by underestimated multiple scattering contributions, over-corrected background, and inconsistent deconvolution methods. A detailed uncertainty quantification for suitable experimental data was undertaken including these effects, and test-evaluations were performed with themore » improved uncertainty information. The test-evaluations illustrate that the inadequately estimated effects and detailed uncertainty quantification have an impact on the evaluated PFNS and associated uncertainties as well as the neutron multiplicity of selected critical assemblies. A summary of data and documentation needs to improve the quality of the experimental database is provided based on the results of simulations and test-evaluations. Furthermore, given the possibly substantial distortion of the PFNS by multiple scattering and background effects, special care should be taken to reduce these effects in future measurements, e.g., by measuring the 239Pu PFNS as a ratio to either the 235U or 252Cf PFNS.« less

APSTNG: neutron interrogation for detection of explosives, drugs, and nuclear and chemical warfare materials

NASA Astrophysics Data System (ADS)

Rhodes, Edgar A.; Peters, Charles W.

1993-02-01

A recently developed neutron diagnostic probe system has the potential to satisfy a significant number of van-mobile and fixed-portal requirements for nondestructive detection, including monitoring of contraband explosives, drugs, and weapon materials, and treaty verification of sealed munitions. The probe is based on a unique associated-particle sealed-tube neutron generator (APSTNG) that interrogates the object of interest with a low-intensity beam of 14- MeV neutrons generated from the deuterium-tritium reaction and that detects the alpha-particle associated with each neutron. Gamma-ray spectra of resulting neutron reactions identify nuclides associated with all major chemicals in explosives, drugs, and chemical warfare agents, as well as many pollutants and fissile and fertile special nuclear material. Flight times determined from detection times of the gamma-rays and alpha-particles yield a separate coarse tomographic image of each identified nuclide. The APSTNG also forms the basis for a compact fast-neutron transmission imaging system that can be used along with or instead of the emission imaging system. Proof-of-concept experiments have been performed under laboratory conditions for simulated nuclear and chemical warfare munitions and for explosives and drugs. The small and relatively inexpensive APSTNG exhibits high reliability and can be quickly replaced. Surveillance systems based on APSTNG technology can avoid the large physical size, high capital and operating expenses, and reliability problems associated with complex accelerators.

An Experiment in Radiation Measurement Using the Depron Instrument

NASA Astrophysics Data System (ADS)

Benghin, Victor V.; Nechaev, Oleg Y.; Zolotarev, Ivan A.; Amelyushkin, Alexander M.; Petrov, Vasiliy L.; Panasyuk, Milhail I.; Yashin, Ivan V.

2018-02-01

Most of the radiation measurements have been made onboard spacecraft flying along orbits with an inclination of up to 51.6 degrees. Due to the prospect of manned missions at orbits with larger inclinations, it is advisable to conduct preliminary detailed dosimetry measurements at a high-inclination orbit; due to its polar orbit, the Lomonosov satellite provides good opportunities for such study. We chose a method of cosmic radiation dosimetry based on semiconductor detectors. This method is widely used onboard spacecraft, including full-time radiation monitoring onboard the International Space Station (ISS). It should be noted that not only did the charged particles contribute significantly in the dose equivalent, but also did the neutrons. Semiconductor detectors have low sensitivity to neutron radiation and are not sufficient for detecting the expected flux of neutrons. We add a thermal neutron counter to the proposed device in order to provide an opportunity for estimation of neutron flux variations along the satellite trajectory. Thus, the design of the instrument DEPRON (Dosimeter of Electrons, PROtons and Neutrons) was determined. DEPRON is intended for registration of the absorbed doses and linear energy transfer spectra for high-energy electrons, protons and nuclei of space radiation, as well as registration of thermal neutrons. The present paper provides a brief description of the DEPRON instrument. Its calibration results and the first mission results of background radiation measurements are also presented.

Development of a neutron measurement system in unified non-destructive assay for the PRIDE facility

NASA Astrophysics Data System (ADS)

Seo, Hee; Park, Se-Hwan; Won, Byung-Hee; Ahn, Seong-Kyu; Shin, Hee-Sung; Na, Sang-Ho; Song, Dae-Yong; Kim, Ho-Dong; Lee, Seung Kyu

2013-12-01

The Korea Atomic Energy Research Institute (KAERI) has made an effort to develop pyroprocessing technology to resolve an on-going problem in Korea, i.e., the management of spent nuclear fuels. To this end, a test-bed facility for pyroprocessing, called PRIDE (PyRoprocessing Integrated inactive DEmonstration facility), is being constructed at KAERI. The main objective of PRIDE is to evaluate the performance of the unit processes, remote operation, maintenance, and proliferation resistance. In addition, integrating all unit processes into a one-step process is also one of the main goals. PRIDE can also provide a good opportunity to test safeguards instrumentations for a pyroprocessing facility such as nuclear material accounting devices, surveillance systems, radiation monitoring systems, and process monitoring systems. In the present study, a non-destructive assay (NDA) system for the testing of nuclear material accountancy of PRIDE was designed by integrating three different NDA techniques, i.e., neutron, gamma-ray, and mass measurements. The developed neutron detection module consists of 56 3He tubes and 16 AMPTEK A111 signal processing circuits. The amplifiers were matched in terms of the gain and showed good uniformity after a gain-matching procedure (%RSD=0.37%). The axial and the radial efficiency distributions within the cavity were then measured using a 252Cf neutron source and were compared with the MCNPX calculation results. The measured efficiency distributions showed excellent agreement with the calculations, which confirmed the accuracy of the MCNPX model of the system.

A Recommender System in the Cyber Defense Domain

DTIC Science & Technology

2014-03-27

monitoring software is a java based program sending updates to the database on the sensor machine. The host monitoring program gathers information about...3.2.2 Database. A MySQL database located on the sensor machine acts as the storage for the sensors on the network. Snort, Nmap, vulnerability scores, and...machine with the IDS and the recommender is labeled “sensor”. The recommender system code is written in java and compiled using java version 1.6.024

Environment/Health/Safety (EHS): Databases

Science.gov Websites

Hazard Documents Database Biosafety Authorization System CATS (Corrective Action Tracking System) (for findings 12/2005 to present) Chemical Management System Electrical Safety Ergonomics Database (for new Learned / Best Practices REMS - Radiation Exposure Monitoring System SJHA Database - Subcontractor Job

Application and Development of Microstructured Solid-State Neutron Detectors

NASA Astrophysics Data System (ADS)

Weltz, Adam D.

Neutron detectors are useful for a number of applications, including the identification of nuclear weapons, radiation dosimetry, and nuclear reactor monitoring, among others. Microstructured solid-state neutron detectors (SSNDs) developed at RPI have the potential to reinvent a variety of neutron detection systems due to their compact size, zero bias requirement, competitive thermal neutron detection efficiency (up to 29%), low gamma sensitivity (below the PNNL recommendation of 10-6 corresponding to a 10 mR/hr gamma exposure), and scalability to large surface areas with a single preamplifier (<20% loss in relative efficiency from 1 to 16 cm2). These microstructured SSNDs have semiconducting substrate etched with a repeated, three-dimensional microstructure of high aspect ratio holes filled with 10B. MCNP simulations optimized the dimensions of each microstructure geometry for each detector application, improving the overall performance. This thesis outlines the development of multiple, novel neutron detection applications using microstructured SSNDs developed at RPI. The Directional and Spectral Neutron Detection System (DSNDS) is a modular and portable system that uses rings of microstructured SSNDs embedded in polyethylene in order to gather real-time information about the directionality and spectrum of an unidentified neutron source. This system can be used to identify the presence of diverted special nuclear material (SNM), determine its position, and gather spectral information in real-time. The compact and scalable zero-bias SSNDs allow for customization and modularity of the detector array, which provides design flexibility and enhanced portability. Additionally, a real-time personal neutron dosimeter is a wearable device that uses a combination of fast and thermal microstructured SSNDs in order to determine an individual's neutron dose rate. This system demonstrates that neutron detection systems utilizing microstructured SSNDs are applicable for personal neutron dosimetry. The development of these systems using the compact, zero-bias microstructured SSNDs lays the groundwork for a new generation of neutron detection tools, outlines the challenges and design considerations associated with the implementation of these devices, and demonstrates the value that these detectors bring to the future of neutron detection systems.

Neutron capture cross-section measurements for 238U between 0.4 and 1.4 MeV

NASA Astrophysics Data System (ADS)

Krishichayan, Fnu; Finch, S. W.; Howell, C. R.; Tonchev, A. P.; Tornow, W.

2017-09-01

Neutron-induced radiative-capture cross-section data of 238U are crucial for fundamental nuclear physics as well as for Stewardship Science, for advanced-fuel-cycle calculations, and for nuclear astrophysics. Based on different techniques, there are a large number of 238U(n, γ) 239U cross-section data available in the literature. However, there is a lack of systematic and consistent measurements in the 0.1 to 3.0 MeV energy range. The goal of the neutron-capture project at TUNL is to provide accurate 238U(n, γ) 239U cross-section data in this energy range. The 238U samples, sandwiched between gold foils of the same size, were irradiated for 8-14 hours with monoenergetic neutrons. To avoid any contribution from thermal neutrons, the 238U and 197Au targets were placed inside of a thin-walled pill-box made of 238U. Finally, the whole pill-box was wrapped in a gold foil as well. After irradiation, the samples were gamma-counted at the TUNL's low-background counting facility using high-efficient HPGe detectors. The 197Au monitor foils were used to calculate the neutron flux. The experimental technique and 238U(n, γ) 239U cross-section results at 6 energies will be discussed during the meeting.

A neutron spectrometer based on temperature variations in superheated drop compositions

NASA Astrophysics Data System (ADS)

Apfel, Robert E.; d'Errico, Francesco

2002-01-01

The response of superheated drop detectors (SDDs) to neutron radiation varies in a self-consistent manner with variations in temperature and pressure, making such compositions suitable for neutron spectrometry. The advantage of this approach is that the response functions of candidate materials versus energy as the temperature or pressure is varied are nested and have distinct thresholds, with no thermal neutron response. These characteristics permit unfolding without the uncertainties associated with other spectrometry techniques, where multiple solutions are possible, thus requiring an initial guess of the spectrum. A spectrometer was developed based on the well-established technology for acoustic sensing of bubble events interfaced with a proportional-integral-derivative temperature controller. The active monitor for neutrons, called REMbrandt™, was used as the platform for controlling temperature on a SDD probe and for data acquisition, thereby automating the process of measuring the neutron energy spectrum. The new instrument, called REM-SPEC™, implements and automates the original BINS approach: it adjusts the temperature of the SDD vial in increasing steps and measures the bubble event rate at each step. By using two distinct SDD materials with overlapping responses, the 0.1-20 MeV range of energies relevant to practical spectrometry is readily covered. Initial experiments with an Am-Be source validate the operational protocols of this device.

Projected Standard on neutron skyshine. [Skyshine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Westfall, R.M.; Williams, D.S.

1987-07-01

Current interest in neutron skyshine arises from the application of dry fuel handling and storage techniques at reactor sites, at the proposed monitored retrievable storage facility and at other facilities being considered as part of the civilian radioactive waste management programs. The chairman of Standards Subcommittee ANS-6, Radiation Protection and Shielding, has requested that a work group be formed to characterize the neutron skyshine problem and, if necessary, prepare a draft Standard. The work group is comprised of representatives of storage cask vendors, architect engineering firms, nuclear utilities, the academic community and staff members of national laboratories and government agencies.more » The purpose of this presentation summary is to describe the activities of the work group and the scope and contents of the projected Standard, ANS-6.6.2, ''Calculation and Measurement of Direct and Scattered Neutron Radiation from Nuclear Power Operations.'' The specific source under consideration by the work group is an array of dry fuel casks located at a reactor site. However, it is recognized that the scope of the standard should be broad enough to encompass other neutron sources. The Standard will define appropriate methodology for properly characterizing the neutron dose due to skyshine. This dose characterization is necessary, for example, in demonstrating compliance with pertinent regulatory criteria.« less

Database usage and performance for the Fermilab Run II experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonham, D.; Box, D.; Gallas, E.

2004-12-01

The Run II experiments at Fermilab, CDF and D0, have extensive database needs covering many areas of their online and offline operations. Delivering data to users and processing farms worldwide has represented major challenges to both experiments. The range of applications employing databases includes, calibration (conditions), trigger information, run configuration, run quality, luminosity, data management, and others. Oracle is the primary database product being used for these applications at Fermilab and some of its advanced features have been employed, such as table partitioning and replication. There is also experience with open source database products such as MySQL for secondary databasesmore » used, for example, in monitoring. Tools employed for monitoring the operation and diagnosing problems are also described.« less

Evaluation of NoSQL databases for DIRAC monitoring and beyond

NASA Astrophysics Data System (ADS)

Mathe, Z.; Casajus Ramo, A.; Stagni, F.; Tomassetti, L.

2015-12-01

Nowadays, many database systems are available but they may not be optimized for storing time series data. Monitoring DIRAC jobs would be better done using a database optimised for storing time series data. So far it was done using a MySQL database, which is not well suited for such an application. Therefore alternatives have been investigated. Choosing an appropriate database for storing huge amounts of time series data is not trivial as one must take into account different aspects such as manageability, scalability and extensibility. We compared the performance of Elasticsearch, OpenTSDB (based on HBase) and InfluxDB NoSQL databases, using the same set of machines and the same data. We also evaluated the effort required for maintaining them. Using the LHCb Workload Management System (WMS), based on DIRAC as a use case we set up a new monitoring system, in parallel with the current MySQL system, and we stored the same data into the databases under test. We evaluated Grafana (for OpenTSDB) and Kibana (for ElasticSearch) metrics and graph editors for creating dashboards, in order to have a clear picture on the usability of each candidate. In this paper we present the results of this study and the performance of the selected technology. We also give an outlook of other potential applications of NoSQL databases within the DIRAC project.

Swift/XRT detects a new accretion outburst of the Galactic center neutron star transient GRS 1741-2853

NASA Astrophysics Data System (ADS)

Degenaar, N.; Wijnands, R.; Reynolds, M. T.; Miller, J. M.; Kennea, J. A.

2017-10-01

Daily Swift/XRT monitoring observations of the Galactic center (Degenaar et al. 2015) have picked up renewed activity of the transient neutron star low-mass X-ray binary and thermonuclear X-ray burster GRS 1741-2853, which is located 10 arcmin NW of Sgr A*. During a 1 ks PC-mode observation performed on 2017 October 11 the source is detected at a net count rate of 0.015 counts/s and it has been steadily brightening since, indicating the onset of a new accretion outburst.

Advanced Neutron Spectrometer

NASA Technical Reports Server (NTRS)

Christl, Mark; Dobson, Chris; Norwood, Joseph; Kayatin, Matthew; Apple, Jeff; Gibson, Brian; Dietz, Kurt; Benson, Carl; Smith, Dennis; Howard, David;

Radiation: Physical Characterization and Environmental Measurements

NASA Technical Reports Server (NTRS)

1997-01-01

In this session, Session WP4, the discussion focuses on the following topics: Production of Neutrons from Interactions of GCR-Like Particles; Solar Particle Event Dose Distributions, Parameterization of Dose-Time Profiles; Assessment of Nuclear Events in the Body Produced by Neutrons and High-Energy Charged Particles; Ground-Based Simulations of Cosmic Ray Heavy Ion Interactions in Spacecraft and Planetary Habitat Shielding Materials; Radiation Measurements in Space Missions; Radiation Measurements in Civil Aircraft; Analysis of the Pre-Flight and Post-Flight Calibration Procedures Performed on the Liulin Space Radiation Dosimeter; and Radiation Environment Monitoring for Astronauts.

Consolidated RXTE Observing Grants on Observation of Neutron Stars and Black Holes in Binaries

NASA Technical Reports Server (NTRS)

Prince, Thomas A.; Vaughan, Brian A.

1998-01-01

This final report is a study of neutron stars and black holes in binaries. The activities focused on observation made with the Rossi X-ray Timing Explorer. The following areas were covered: long term observations of accreting binary pulsars with the All-Sky Monitor (ASM); observations of Centaurus X-3 with the Proportional Counter Array (PCA) and the High-Energy X-ray Timing Experiment (HEXTE); observations of accreting pulsars with the PCA and HEXTE; studies of quasi-periodic oscillations (QPO); and investigations of accreting black-hole candidates.

Data Auditor: Analyzing Data Quality Using Pattern Tableaux

NASA Astrophysics Data System (ADS)

Srivastava, Divesh

Monitoring databases maintain configuration and measurement tables about computer systems, such as networks and computing clusters, and serve important business functions, such as troubleshooting customer problems, analyzing equipment failures, planning system upgrades, etc. These databases are prone to many data quality issues: configuration tables may be incorrect due to data entry errors, while measurement tables may be affected by incorrect, missing, duplicate and delayed polls. We describe Data Auditor, a tool for analyzing data quality and exploring data semantics of monitoring databases. Given a user-supplied constraint, such as a boolean predicate expected to be satisfied by every tuple, a functional dependency, or an inclusion dependency, Data Auditor computes "pattern tableaux", which are concise summaries of subsets of the data that satisfy or fail the constraint. We discuss the architecture of Data Auditor, including the supported types of constraints and the tableau generation mechanism. We also show the utility of our approach on an operational network monitoring database.

Verification of threshold activation detection (TAD) technique in prompt fission neutron detection using scintillators containing 19F

NASA Astrophysics Data System (ADS)

Sibczynski, P.; Kownacki, J.; Moszyński, M.; Iwanowska-Hanke, J.; Syntfeld-Każuch, A.; Gójska, A.; Gierlik, M.; Kaźmierczak, Ł.; Jakubowska, E.; Kędzierski, G.; Kujawiński, Ł.; Wojnarowicz, J.; Carrel, F.; Ledieu, M.; Lainé, F.

2015-09-01

In the present study ⌀ 5''× 3'' and ⌀ 2''× 2'' EJ-313 liquid fluorocarbon as well as ⌀ 2'' × 3'' BaF2 scintillators were exposed to neutrons from a 252Cf neutron source and a Sodern Genie 16GT deuterium-tritium (D+T) neutron generator. The scintillators responses to β- particles with maximum endpoint energy of 10.4 MeV from the n+19F reactions were studied. Response of a ⌀ 5'' × 3'' BC-408 plastic scintillator was also studied as a reference. The β- particles are the products of interaction of fast neutrons with 19F which is a component of the EJ-313 and BaF2 scintillators. The method of fast neutron detection via fluorine activation is already known as Threshold Activation Detection (TAD) and was proposed for photofission prompt neutron detection from fissionable and Special Nuclear Materials (SNM) in the field of Homeland Security and Border Monitoring. Measurements of the number of counts between 6.0 and 10.5 MeV with a 252Cf source showed that the relative neutron detection efficiency ratio, defined as epsilonBaF2 / epsilonEJ-313-5'', is 32.0% ± 2.3% and 44.6% ± 3.4% for front-on and side-on orientation of the BaF2, respectively. Moreover, the ⌀ 5'' EJ-313 and side-on oriented BaF2 were also exposed to neutrons from the D+T neutron generator, and the relative efficiency epsilonBaF2 / epsilonEJ-313-5'' was estimated to be 39.3%. Measurements of prompt photofission neutrons with the BaF2 detector by means of data acquisition after irradiation (out-of-beam) of nuclear material and between the beam pulses (beam-off) techniques were also conducted on the 9 MeV LINAC of the SAPHIR facility.

Activation cross section and isomeric cross-section ratio for the 151Eu(n,2n)150m,gEu process

NASA Astrophysics Data System (ADS)

Luo, Junhua; Li, Suyuan; Jiang, Li

2018-07-01

The cross sections of 151Eu(n,2n)150m,gEu reactions and their isomeric cross section ratios σm/σt have been measured experimentally. Cross sections are measured, relative to a reference 93Nb(n,2n)92mNb reaction cross section, by means of the activation technique at three neutron energies 13.5, 14.1, and 14.8 MeV. Monoenergetic neutron beams were formed via the 3H(d,n)4He reaction and both Eu2O3 samples and Nb monitor foils were activated together to determine the reaction cross section and the incident neutron flux. The activities induced in the reaction products were measured using high-resolution gamma ray spectroscopy. Cross sections were also evaluated theoretically using the numerical nuclear model code, TALYS-1.8 with different level density options at neutron energies varying from the reaction threshold to 20 MeV. Results are discussed and compared with the corresponding literature.

MONDO: A tracker for the characterization of secondary fast and ultrafast neutrons emitted in particle therapy

NASA Astrophysics Data System (ADS)

Mirabelli, R.; Battistoni, G.; Giacometti, V.; Patera, V.; Pinci, D.; Sarti, A.; Sciubba, A.; Traini, G.; Marafini, M.

2018-01-01

In Particle Therapy (PT) accelerated charged particles and light ions are used for treating tumors. One of the main limitation to the precision of PT is the emission of secondary particles due to the beam interaction with the patient: secondary emitted neutrons can release a significant dose far from the tumor. Therefore, a precise characterization of their flux, production energy and angle distribution is eagerly needed in order to improve the Treatment Planning Systems (TPS) codes. The principal aim of the MONDO (MOnitor for Neutron Dose in hadrOntherapy) project is the development of a tracking device optimized for the detection of fast and ultra-fast secondary neutrons emitted in PT. The detector consists of a matrix of scintillating square fibres coupled with a CMOS-based readout. Here, we present the characterization of the detector tracker prototype and CMOS-based digital SPAD (Single Photon Avalanche Diode) array sensor tested with protons at the Beam Test Facility (Frascati, Italy) and at the Proton Therapy Centre (Trento, Italy), respectively.

Implementation of k0-INAA standardisation at ITU TRIGA Mark II research reactor, Turkey based on k0-IAEA software

NASA Astrophysics Data System (ADS)

Esen, Ayse Nur; Haciyakupoglu, Sevilay

2016-02-01

The purpose of this study is to test the applicability of k0-INAA method at the Istanbul Technical University TRIGA Mark II research reactor. The neutron spectrum parameters such as epithermal neutron flux distribution parameter (α), thermal to epithermal neutron flux ratio (f) and thermal neutron flux (φth) were determined at the central irradiation channel of the ITU TRIGA Mark II research reactor using bare triple-monitor method. HPGe detector calibrations and calculations were carried out by k0-IAEA software. The α, f and φth values were calculated to be -0.009, 15.4 and 7.92·1012 cm-2 s-1, respectively. NIST SRM 1633b coal fly ash and intercomparison samples consisting of clay and sandy soil samples were used to evaluate the validity of the method. For selected elements, the statistical evaluation of the analysis results was carried out by z-score test. A good agreement between certified/reported and experimental values was obtained.

Measured 19F(α,n) with VANDLE for Nuclear Safeguards

NASA Astrophysics Data System (ADS)

Peters, William; Clement, R. C. C.; Smith, M. S.; Pain, S.; Febbraro, M.; Pittman, S.; Thomspon, S.; Grinder, M.; Cizewski, J. A.; Reingold, C.; Manning, B.; Burcher, S.; Bardayan, D. W.; Tan, W.-P.; Stech, E.; Smith, M. K.; Avetisyan, R.; Gyurjinyan, A.; Lowe, M.; Ilyushkin, S.; Grzywacz, R.; Madurga, M.; Paulauskas, S. V.; Taylor, S. Z.; Smith, K.

2015-10-01

One of the most promising non-destructive assay (NDA) methods to monitor UF6 canisters consists of measuring gross neutron rates induced by uranium-decay alpha particles reacting with the fluorine and emitting a neutron. This method currently lacks reliable nuclear data on the 19F(α,n) reaction cross section to determine an accurate neutron yield rate for a given sample of UF6. We have measured the cross section and coincident neutron spectrum for the alpha-decay energy range using the VANDLE system. This experiment had two parts: first at Notre Dame with a LaF3 target and and a pulsed alpha-particle beam, and second at ORNL with a windowless He-gas target and a 19F beam. The motivation for this measurement and cross section results will be presented. This work is funded in part by the DOE Office of Science, the National Nuclear Security Administration SSAA and the Office of Defense Nuclear Nonproliferation R&D, and the NSF.

Development of 10B-Based 3He Replacement Neutron Detectors

NASA Astrophysics Data System (ADS)

King, Michael J.; Gozani, Tsahi; Hilliard, Donald B.

2011-12-01

Radiation portal monitors (RPM) are currently deployed at United States border crossings to passively inspect vehicles and persons for any emission of neutrons and/or gamma rays, which may indicate the presence of unshielded nuclear materials. The RPM module contains an organic scintillator with 3He proportional counters to detect gamma rays and thermalized neutrons, respectively. The supply of 3He is rapidly dwindling, requiring alternative detectors to provide the same function and performance. Our alternative approach is one consisting of a thinly-coated 10B flat-panel ionization chamber neutron detector that can be deployed as a direct drop-in replacement for current RPM 3He detectors. The uniqueness of our approach in providing a large-area detector is in the simplicity of construction, scalability of the unit cell detector, ease of adaptability to a variety of applications and low cost. Currently, Rapiscan Laboratories and Helicon Thin Film Systems have designed and developed an operational 100 cm2 multi-layer prototype 10BB-based ionization chamber.

Real-time soft error rate measurements on bulk 40 nm SRAM memories: a five-year dual-site experiment

NASA Astrophysics Data System (ADS)

Autran, J. L.; Munteanu, D.; Moindjie, S.; Saad Saoud, T.; Gasiot, G.; Roche, P.

2016-11-01

This paper reports five years of real-time soft error rate experimentation conducted with the same setup at mountain altitude for three years and then at sea level for two years. More than 7 Gbit of SRAM memories manufactured in CMOS bulk 40 nm technology have been subjected to the natural radiation background. The intensity of the atmospheric neutron flux has been continuously measured on site during these experiments using dedicated neutron monitors. As the result, the neutron and alpha component of the soft error rate (SER) have been very accurately extracted from these measurements, refining the first SER estimations performed in 2012 for this SRAM technology. Data obtained at sea level evidence, for the first time, a possible correlation between the neutron flux changes induced by the daily atmospheric pressure variations and the measured SER. Finally, all of the experimental data are compared with results obtained from accelerated tests and numerical simulation.

Double helix boron-10 powder thermal neutron detector

DOEpatents

Wang, Zhehui; Morris, Christopher L.; Bacon, Jeffrey D.

2015-06-02

A double-helix Boron-10 powder detector having intrinsic thermal neutron detection efficiency comparable to 36'' long, 2-in diameter, 2-bar Helium-3 detectors, and which can be used to replace such detectors for use in portal monitoring, is described. An embodiment of the detector includes a metallic plate coated with Boron-10 powder for generating alpha and Lithium-7 particles responsive to neutrons impinging thereon supported by insulators affixed to at least two opposing edges; a grounded first wire wound in a helical manner around two opposing insulators; and a second wire having a smaller diameter than that of the first wire, wound in a helical manner around the same insulators and spaced apart from the first wire, the second wire being positively biased. A gas, disposed within a gas-tight container enclosing the plate, insulators and wires, and capable of stopping alpha and Lithium-7 particles and generating electrons produces a signal on the second wire which is detected and subsequently related to the number of neutrons impinging on the plate.

Intracellular water - an overlooked drug target? Cisplatin impact in cancer cells probed by neutrons.

PubMed

Marques, M P M; Batista de Carvalho, A L M; Sakai, V Garcia; Hatter, L; Batista de Carvalho, L A E

2017-01-25

The first neutron scattering study on human nucleated cells is reported, addressing the subject of solvent-slaving to a drug by probing intracellular water upon drug exposure. Inelastic and quasi-elastic neutron scattering spectroscopy with isotope labelling was applied for monitoring interfacial water response to the anticancer drug cisplatin, in the low prognosis human metastatic breast cancer cells MDA-MB-231. Optical vibrational data were also obtained for lyophilised cells. Concentration-dependent dynamical changes evidencing a progressive mobility reduction were unveiled between untreated and cisplatin-exposed samples, concurrent with variations in the native organisation of water molecules within the intracellular medium as a consequence of drug action. The results thus obtained yielded a clear picture of the intracellular water response to cisplatin and constitute the first reported experimental proof of a drug impact on the cytomatrix by neutron techniques. This is an innovative way of tackling a drug's pharmacodynamics, searching for alternative targets of drug action.

Calibration of the JET neutron activation system for DT operation

NASA Astrophysics Data System (ADS)

Bertalot, L.; Roquemore, A. L.; Loughlin, M.; Esposito, B.

1999-01-01

The neutron activation system at JET is a pneumatic transfer system capable of positioning activation samples close to the plasma. Its primary purpose is to provide a calibration for the time-dependent neutron yield monitors (fission chambers and solid state detectors). Various activation reactions with different high energy thresholds were used including 56Fe(n,p) 56Mn, 27Al(n,α) 24Na, 93Nb(n,2n) 92mNb, and 28Si(n,p) 28Al reactions. The silicon reaction, with its short half life (2.25 min), provides a prompt determination of the 14 MeV DT yield. The neutron induced γ-ray activity of the Si samples was measured using three sodium iodide scintillators, while two high purity germanium detectors were used for other foils. It was necessary to use a range of sample masses and different counting geometries in order to cover the wide range of neutron yields (1015-1019 neutrons) while avoiding excessive count rates in the detectors. The absolute full energy peak efficiency calibration of the detectors was measured taking into account the source-detector geometry, the self-attenuation of the samples and cross-talk effects. An error analysis of the neutron yield measurement was performed including uncertainties in efficiency calibration, neutron transport calculations, cross sections, and counting statistics. Cross calibrations between the different irradiation ends were carried out in DD and DT (with 1% and 10% tritium content) discharges. The effect of the plasma vertical displacement was also experimentally studied. An agreement within 10% was found between the 14 MeV neutron yields measured from Si, Fe, Al, Nb samples in DT discharges.

Directional Antineutrino Detection

NASA Astrophysics Data System (ADS)

Safdi, B. R.; Suerfu, J.

2014-12-01

We propose the first truly directional antineutrino detector for antineutrinos near the threshold for the inverse beta decay (IBD) of hydrogen, with potential applications including the spatial mapping of geo-neutrinos, searches for stellar antineutrinos, and the monitoring of nuclear reactors. The detector consists of adjacent and separated target and neutron-capture layers. The IBD events, which result in a neutron and a positron, take place in the target layers. These layers are thin enough so that the neutrons escape without scattering elastically. The neutrons are detected in the thicker neutron-capture layers. The location of the IBD event is determined from the energy deposited by the positron as it slows in the medium and from the two gamma rays that come from the positron annihilation. Since the neutron recoils in the direction of the antineutrino's motion, a line may then be drawn between the IBD event location and the neutron-capture location to approximate the antineutrino's velocity. In some events, we may even measure the positron's velocity, which further increases our ability to reconstruct the antineutrino's direction of motion. Our method significantly improves upon previous methods by allowing the neutron to freely travel a long distance before diffusing and being captured. Moreover, our design is a straightforward modification of existing antineutrino detectors; a prototype could easily be built with existing technology. We verify our design through Monte Carlo simulations in Geant4, using commercially-available boron-loaded plastic scintillators for the target and neutron-capture layer materials. We are able to discriminate from background using multiple coincidence signatures within a short, ~microsecond time interval. We conclude that the detector could likely operate above ground with minimal shielding.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kouzes, Richard T.; Lintereur, Azaree T.; Siciliano, Edward R.

One of the main uses for 3He is in gas proportional counters for neutron detection. Such detectors are used at neutron scattering science facilities and in radiation portal monitors deployed for homeland security and non-proliferation applications. Other uses of 3He are for research detectors, commercial instruments, well logging detectors, dilution refrigerators, lung imaging, for targets in nuclear research, and for basic research in condensed matter physics. The supply of 3He comes entirely from the decay of tritium produced for nuclear weapons in the U.S. and Russia. Due to the large increase in use of 3He for science and homeland securitymore » (since 2002), the supply has dwindled, and can no longer meet the demand. This has led to the development of a number of alternative neutron detection schemes.« less

Characterization of Radiation Fields in Biological Shields of Nuclear Power Plants for Assessing Concrete Degradation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Remec, Igor; Rosseel, Thomas M; Field, Kevin G

Life extensions of nuclear power plants to 60 and potentially 80 years of operation have renewed interest in long-term material degradation. One material being considered is concrete with a particular focus on radiation-induced effects. Based on the projected neutron fluence (E > 0.1 MeV) values in the concrete biological shields of the US PWR fleet and the available data on radiation effects on concrete, some decrease in mechanical properties of concrete cannot be ruled out during extended operation beyond 60 years. An expansion of the irradiated concrete database and a reliable determination of relevant neutron fluence energy cutoff value aremore » necessary to assure reliable risk assessment for NPPs extended operation.« less

Performance of an RPM based on Gd-lined plastic scintillator for neutron and gamma detection [ANIMMA--2015-IO-372

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fanchini, Erica

A Radiation Portal Monitor (RPM) was developed by the Istituto Nazionale di Fisica Nucleare (INFN) and Ansaldo Nucleare (ANN) within the FP7 SCINTILLA European project. The system was designed to detect both gamma and neutron radiation with a single technology. It is conceived to monitor vehicle and cargo containers in transits across borders or ports, to find radioactive elements and to avoid illegal trafficking of strategic nuclear materials. The system is based on a {sup 3}He-free neutron detection technology using plastic scintillators coupled to Gadolinium to detect and discriminate gamma from neutron signals. During the 3 years of the SCINTILLAmore » project the construction and test of the first two prototypes drove the definition of the final layout of a full RPM system consisting of two twin pillars as a portal for vehicle and cargo container scan. A custom System Control Software (SCS) manages the electronics of the RPM, the ancillary devices and the data analysis. The combination of the detector layout and of the software functionalities enables both to distinguish neutrons and gammas and to identify the energy range of a detected gamma source. The system was initially characterized via static tests with gamma and neutron sources in the INFN laboratory. These measurements were used to calibrate the detector, evaluate the response of the single pillars as well as of the full system, and optimize the RPM configuration and discrimination algorithm. During this phase, specific tests were performed to study the stability over time of the system, monitoring the measured the neutron and gamma count rates over periods of several weeks. The results allow us to demonstrate the reliability and robustness of the RPM. In a second time the RPM performance was studied via dynamic tests performed during the SCINTILLA test and benchmark campaigns. These measurements took place in the JRC ITRAP+10 facility at Ispra (Varese-Italy). The laboratory is equipped with an experimental set-up for dynamic tests of multiple systems according to international standards. The performed measurements utilized radioactive sources with activities selected according to ANSI and IEC standards to test the detector alarm performances in terms of gamma and neutron response, sensitivity to high gamma fields, sensitivity to moderated neutron sources as well as false alarm rates (FAR). In addition, the RPM was tested in challenging configurations exceeding the requirements set by international standards to determine the real limits of the system. The results obtained during these campaigns demonstrated that the system detection efficiency is not only compliant to international standards for its category, but often exceeds them, demonstrating the validity of the chosen technology and of the implemented layout. The positive performance also showed the effectiveness of the SCS and of its functionalities. To further demonstrate the system capabilities, a test in a real-life environment of the RPM is planned to happen in a near future by installing the detectors in a seaport. In this presentation I will give an overview of the RPM characteristics, of its performances as determined in the test campaign mentioned above and of future plans, to demonstrate how this technology can be an effective choice for the realization of {sup 3}He-free RPM detectors. (authors)« less

Ant-App-DB: a smart solution for monitoring arthropods activities, experimental data management and solar calculations without GPS in behavioral field studies.

PubMed

Ahmed, Zeeshan; Zeeshan, Saman; Fleischmann, Pauline; Rössler, Wolfgang; Dandekar, Thomas

2014-01-01

Field studies on arthropod ecology and behaviour require simple and robust monitoring tools, preferably with direct access to an integrated database. We have developed and here present a database tool allowing smart-phone based monitoring of arthropods. This smart phone application provides an easy solution to collect, manage and process the data in the field which has been a very difficult task for field biologists using traditional methods. To monitor our example species, the desert ant Cataglyphis fortis, we considered behavior, nest search runs, feeding habits and path segmentations including detailed information on solar position and azimuth calculation, ant orientation and time of day. For this we established a user friendly database system integrating the Ant-App-DB with a smart phone and tablet application, combining experimental data manipulation with data management and providing solar position and timing estimations without any GPS or GIS system. Moreover, the new desktop application Dataplus allows efficient data extraction and conversion from smart phone application to personal computers, for further ecological data analysis and sharing. All features, software code and database as well as Dataplus application are made available completely free of charge and sufficiently generic to be easily adapted to other field monitoring studies on arthropods or other migratory organisms. The software applications Ant-App-DB and Dataplus described here are developed using the Android SDK, Java, XML, C# and SQLite Database.

Ant-App-DB: a smart solution for monitoring arthropods activities, experimental data management and solar calculations without GPS in behavioral field studies

PubMed Central

Ahmed, Zeeshan; Zeeshan, Saman; Fleischmann, Pauline; Rössler, Wolfgang; Dandekar, Thomas

2015-01-01

Field studies on arthropod ecology and behaviour require simple and robust monitoring tools, preferably with direct access to an integrated database. We have developed and here present a database tool allowing smart-phone based monitoring of arthropods. This smart phone application provides an easy solution to collect, manage and process the data in the field which has been a very difficult task for field biologists using traditional methods. To monitor our example species, the desert ant Cataglyphis fortis, we considered behavior, nest search runs, feeding habits and path segmentations including detailed information on solar position and azimuth calculation, ant orientation and time of day. For this we established a user friendly database system integrating the Ant-App-DB with a smart phone and tablet application, combining experimental data manipulation with data management and providing solar position and timing estimations without any GPS or GIS system. Moreover, the new desktop application Dataplus allows efficient data extraction and conversion from smart phone application to personal computers, for further ecological data analysis and sharing. All features, software code and database as well as Dataplus application are made available completely free of charge and sufficiently generic to be easily adapted to other field monitoring studies on arthropods or other migratory organisms. The software applications Ant-App-DB and Dataplus described here are developed using the Android SDK, Java, XML, C# and SQLite Database. PMID:25977753

Prescriber Compliance With Liver Monitoring Guidelines for Pazopanib in the Postapproval Setting: Results From a Distributed Research Network.

PubMed

Shantakumar, Sumitra; Nordstrom, Beth L; Hall, Susan A; Djousse, Luc; van Herk-Sukel, Myrthe P P; Fraeman, Kathy H; Gagnon, David R; Chagin, Karen; Nelson, Jeanenne J

2017-04-20

Pazopanib received US Food and Drug Administration approval in 2009 for advanced renal cell carcinoma. During clinical development, liver chemistry abnormalities and adverse hepatic events were observed, leading to a boxed warning for hepatotoxicity and detailed label prescriber guidelines for liver monitoring. As part of postapproval regulatory commitments, a cohort study was conducted to assess prescriber compliance with liver monitoring guidelines. Over a 4-year period, a distributed network approach was used across 3 databases: US Veterans Affairs Healthcare System, a US outpatient oncology community practice database, and the Dutch PHARMO Database Network. Measures of prescriber compliance were designed using the original pazopanib label guidelines for liver monitoring. Results from the VA (n = 288) and oncology databases (n = 283) indicate that prescriber liver chemistry monitoring was less than 100%: 73% to 74% compliance with baseline testing and 37% to 39% compliance with testing every 4 weeks. Compliance was highest near drug initiation and decreased over time. Among patients who should have had weekly testing, the compliance was 56% in both databases. The more serious elevations examined, including combinations of liver enzyme elevations meeting the laboratory definition of Hy's law were infrequent but always led to appropriate discontinuation of pazopanib. Only 4 patients were identified for analysis in the Dutch database; none had recorded baseline testing. In this population-based study, prescriber compliance was reasonable near pazopanib initiation but low during subsequent weeks of treatment. This study provides information from real-world community practice settings and offers feedback to regulators on the effectiveness of label monitoring guidelines.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.

On the optimisation of the use of 3He in radiation portal monitors

NASA Astrophysics Data System (ADS)

Tomanin, Alice; Peerani, Paolo; Janssens-Maenhout, Greet

2013-02-01

Radiation Portal Monitors (RPMs) are used to detect illicit trafficking of nuclear or other radioactive material concealed in vehicles, cargo containers or people at strategic check points, such as borders, seaports and airports. Most of them include neutron detectors for the interception of potential plutonium smuggling. The most common technology used for neutron detection in RPMs is based on 3He proportional counters. The recent severe shortage of this rare and expensive gas has created a problem of capacity for manufacturers to provide enough detectors to satisfy the market demand. In this paper we analyse the design of typical commercial RPMs and try to optimise the detector parameters in order either to maximise the efficiency using the same amount of 3He or minimise the amount of gas needed to reach the same detection performance: by reducing the volume or gas pressure in an optimised design.

Setup and Calibration of SLAC's Peripheral Monitoring Stations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cooper, C.

2004-09-03

The goals of this project were to troubleshoot, repair, calibrate, and establish documentation regarding SLAC's (Stanford Linear Accelerator Center's) PMS (Peripheral Monitoring Station) system. The PMS system consists of seven PMSs that continuously monitor skyshine (neutron and photon) radiation levels in SLAC's environment. Each PMS consists of a boron trifluoride (BF{sub 3}) neutron detector (model RS-P1-0802-104 or NW-G-20-12) and a Geiger Moeller (GM) gamma ray detector (model TGM N107 or LND 719) together with their respective electronics. Electronics for each detector are housed in Nuclear Instrument Modules (NIMs) and are plugged into a NIM bin in the station. All communicationmore » lines from the stations to the Main Control Center (MCC) were tested prior to troubleshooting. To test communication with MCC, a pulse generator (Systron Donner model 100C) was connected to each channel in the PMS and data at MCC was checked for consistency. If MCC displayed no data, the communication cables to MCC or the CAMAC (Computer Automated Measurement and Control) crates were in need of repair. If MCC did display data, then it was known that the communication lines were intact. All electronics from each station were brought into the lab for troubleshooting. Troubleshooting usually consisted of connecting an oscilloscope or scaler (Ortec model 871 or 775) at different points in the circuit of each detector to record simulated pulses produced by a pulse generator; the input and output pulses were compared to establish the location of any problems in the circuit. Once any problems were isolated, repairs were done accordingly. The detectors and electronics were then calibrated in the field using radioactive sources. Calibration is a process that determines the response of the detector. Detector response is defined as the ratio of the number of counts per minute interpreted by the detector to the amount of dose equivalent rate (in mrem per hour, either calculated or measured). Detector response for both detectors is dependent upon the energy of the incident radiation; this trend had to be accounted for in the calibration of the BF{sub 3} detector. Energy dependence did not have to be taken into consideration when calibrating the GM detectors since GM detector response is only dependent on radiation energy below 100 keV; SLAC only produces a spectrum of gamma radiation above 100 keV. For the GM detector, calibration consisted of bringing a {sup 137}Cs source and a NIST-calibrated RADCAL Radiation Monitor Controller (model 9010) out to the field; the absolute dose rate was determined by the RADCAL device while simultaneously irradiating the GM detector to obtain a scaler reading corresponding to counts per minute. Detector response was then calculated. Calibration of the BF{sub 3} detector was done using NIST certified neutron sources of known emission rates and energies. Five neutron sources ({sup 238}PuBe, {sup 238}PuB, {sup 238}PuF4, {sup 238}PuLi and {sup 252}Cf) with different energies were used to account for the energy dependence of the response. The actual neutron dose rate was calculated by date-correcting NIST source data and considering the direct dose rate and scattered dose rate. Once the total dose rate (sum of the direct and scattered dose rates) was known, the response vs. energy curve was plotted. The first station calibrated (PMS6) was calibrated with these five neutron sources; all subsequent stations were calibrated with one neutron source and the energy dependence was assumed to be the same.« less

A compact ion source for intense neutron generation

NASA Astrophysics Data System (ADS)

Perkins, Luke Torrilhon

Today, numerous applications for neutrons, beyond those of the nuclear power industry, are beginning to emerge and become viable. From neutron radiography which, not unlike conventional X-rays, can provide an in-depth image through various materials, to neutron radiotherapy, for the treatment of certain forms of cancer, all these applications promise to improve our quality of life. To meet the growing need for neutrons, greater demands are being made on the neutron 'generator' technology, demands for improved neutron output and reliability at reduced physical sizes and costs. One such example in the field of borehole neutron generators, where, through neutron activation analysis, the elemental composition, concentration and location in the surrounding borehole media can be ascertained. These generators, which commonly rely on the fusion of deuterium (D) and tritium (T) at energies of the order of one hundred thousand Volts, seem to defy their physical limitations to provide neutron outputs approaching a billion per second in packages no greater than two inches in diameter. In an attempt to answer this demand, we, at Lawrence Berkeley National Laboratory (LBNL), have begun developing a new generation of neutron generators making use of recent developments in ion source technology. The specific application which motivates this development is in the environmental monitoring field, where pollutants and their concentrations in the subsurface must be assessed. To achieve the desired direction of low-level concentrations and obtain a better directional sensitivity, a neutron output of 109 to 1010 D-T neutrons per second was targeted for generator package which can fit inside a ~5 cm diameter borehole. To accomplish this performance, a radio-frequency (RF)- driven ion source developed at LBNL was adapted to the requirements of this application. The advantages of this type of ion source are its intrinsic ability to tailor the delivery of RF power to the ion source and therefore control the neutron output (pulse width, repetition rate and magnitude) while operating at low pressures (~5 mTorr). In the experimental testing presented herein, a prototype, 5 cm-diameter, inductively driven ion source has produced unsaturated hydrogen beam current densities in excess of 1 A/cm2 and monatomic species fractions in excess of 90%. This satisfactory performance, with respect to the targeted neutron output, was achieved with a 2 MHz, 60 kW pulse of RF to produce a ~20μs plasma pulse at <100 Hz.

Micro-scale characterization of a CMOS-based neutron detector for in-phantom measurements in radiation therapy

NASA Astrophysics Data System (ADS)

Arbor, Nicolas; Higueret, Stephane; Husson, Daniel

2018-04-01

The CMOS sensor AlphaRad has been designed at the IPHC Strasbourg for real-time monitoring of fast and thermal neutrons over a full energy spectrum. Completely integrated, highly transparent to photons and optimized for low power consumption, this sensor offers very interesting characteristics for the study of internal neutrons in radiation therapy with anthropomorphic phantoms. However, specific effects related to the CMOS metal substructure and to the charge collection process of low energy particles must be carefully estimated before being used for medical applications. We present a detailed characterization of the AlphaRad chip in the MeV energy range using proton and alpha micro-beam experiments performed at the AIFIRA facility (CENBG, Bordeaux). Two-dimensional maps of the charge collection were carried out on a micro-metric scale to be integrated into a Geant4 Monte Carlo simulation of the system. The gamma rejection, as well as the fast and thermal neutrons separation, were studied using both simulation and experimental data. The results highlight the potential of a future system based on CMOS sensor for in-phantom neutron detection in radiation therapies.

Measurement of 235U(n,n'γ) and 235U(n,2nγ) reaction cross sections

NASA Astrophysics Data System (ADS)

Kerveno, M.; Thiry, J. C.; Bacquias, A.; Borcea, C.; Dessagne, P.; Drohé, J. C.; Goriely, S.; Hilaire, S.; Jericha, E.; Karam, H.; Negret, A.; Pavlik, A.; Plompen, A. J. M.; Romain, P.; Rouki, C.; Rudolf, G.; Stanoiu, M.

2013-02-01

The design of generation IV nuclear reactors and the studies of new fuel cycles require knowledge of the cross sections of various nuclear reactions. Our research is focused on (n,xnγ) reactions occurring in these new reactors. The aim is to measure unknown cross sections and to reduce the uncertainty on present data for reactions and isotopes of interest for transmutation or advanced reactors. The present work studies the 235U(n,n'γ) and 235U(n,2nγ) reactions in the fast neutron energy domain (up to 20 MeV). The experiments were performed with the Geel electron linear accelerator GELINA, which delivers a pulsed white neutron beam. The time characteristics enable measuring neutron energies with the time-of-flight (TOF) technique. The neutron induced reactions [in this case inelastic scattering and (n,2n) reactions] are identified by on-line prompt γ spectroscopy with an experimental setup including four high-purity germanium (HPGe) detectors. A fission ionization chamber is used to monitor the incident neutron flux. The experimental setup and analysis methods are presented and the model calculations performed with the TALYS-1.2 code are discussed.

Evaluation of reconstruction errors and identification of artefacts for JET gamma and neutron tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Craciunescu, Teddy, E-mail: teddy.craciunescu@jet.uk; Tiseanu, Ion; Zoita, Vasile

The Joint European Torus (JET) neutron profile monitor ensures 2D coverage of the gamma and neutron emissive region that enables tomographic reconstruction. Due to the availability of only two projection angles and to the coarse sampling, tomographic inversion is a limited data set problem. Several techniques have been developed for tomographic reconstruction of the 2-D gamma and neutron emissivity on JET, but the problem of evaluating the errors associated with the reconstructed emissivity profile is still open. The reconstruction technique based on the maximum likelihood principle, that proved already to be a powerful tool for JET tomography, has been usedmore » to develop a method for the numerical evaluation of the statistical properties of the uncertainties in gamma and neutron emissivity reconstructions. The image covariance calculation takes into account the additional techniques introduced in the reconstruction process for tackling with the limited data set (projection resampling, smoothness regularization depending on magnetic field). The method has been validated by numerically simulations and applied to JET data. Different sources of artefacts that may significantly influence the quality of reconstructions and the accuracy of variance calculation have been identified.« less

Elpasolite Planetary Ice and Composition Spectrometer (EPICS): A Low-Resource Combined Gamma-Ray and Neutron Spectrometer for Planetary Science

NASA Astrophysics Data System (ADS)

Stonehill, L. C.; Coupland, D. D. S.; Dallmann, N. A.; Feldman, W. C.; Mesick, K.; Nowicki, S.; Storms, S.

2017-12-01

The Elpasolite Planetary Ice and Composition Spectrometer (EPICS) is an innovative, low-resource gamma-ray and neutron spectrometer for planetary science missions, enabled by new scintillator and photodetector technologies. Neutrons and gamma rays are produced by cosmic ray interactions with planetary bodies and their subsequent interactions with the near-surface materials produce distinctive energy spectra. Measuring these spectra reveals details of the planetary near-surface composition that are not accessible through any other phenomenology. EPICS will be the first planetary science instrument to fully integrate the neutron and gamma-ray spectrometers. This integration is enabled by the elpasolite family of scintillators that offer gamma-ray spectroscopy energy resolutions as good as 3% FWHM at 662 keV, thermal neutron sensitivity, and the ability to distinguish gamma-ray and neutron signals via pulse shape differences. This new detection technology will significantly reduce size, weight, and power (SWaP) while providing similar neutron performance and improved gamma energy resolution compared to previous scintillator instruments, and the ability to monitor the cosmic-ray source term. EPICS will detect scintillation light with silicon photomultipliers rather than traditional photomultiplier tubes, offering dramatic additional SWaP reduction. EPICS is under development with Los Alamos National Laboratory internal research and development funding. Here we report on the EPICS design, provide an update on the current status of the EPICS development, and discuss the expected sensitivity and performance of EPICS in several potential missions to airless bodies.

Criticality assessment of TRU burial ground culverts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winn, W.G.

1990-09-26

An effort to assess the criticality risks of {sup 239}Pu in TRU Burial Ground Culverts has been underway for several years. The concern arose from discrepancies in two types of monitors that have been used to assay the {sup 239}Pu waste prior to storage in 55-gallon drums that are placed in the culverts. One type is the solid waste monitor (SWM), which is based on gamma-ray measurements; the other is the neutron coincidence monitor, which is based on neutron measurements. The NCC was put into routine service after 1985 and has generally yielded higher 239 Pu assays than the SWM.more » Culverts with pre-1986 waste only had SWM assays of {sup 239}Pu; thus, it was questioned whether their actual {sup 239}Pu loadings could be high enough to pose criticality concerns. Studies to characterize the culvert criticality potential have included appraisal of NCC vs SWM, neutron measurements atop the culverts, gamma-ray measurements atop the culverts, and probabilistic risk analyses. Overall, these studies have implied that the culverts are critically safe; however, their results have not been examined collectively. The present report uses the collective information of the preceding studies to arrive at a more complete assessment of the culvert criticality aspects. A conservative k{sub eff} is estimated for an individual suspicious culvert and a PRA is evaluated for its {open_quotes}worst{close_quotes} drum. These two pieces of information form the basis of the appraisal, but other evidence is also included as support.« less

Relevance of near-Earth magnetic field modeling in deriving SEP properties using ground-based data

NASA Astrophysics Data System (ADS)

Kanellakopoulos, Anastasios; Plainaki, Christina; Mavromichalaki, Helen; Laurenza, Monica; Gerontidou, Maria; Storini, Marisa; Andriopoulou, Maria

2014-05-01

Ground Level Enhancements (GLEs) are short-term increases observed in cosmic ray intensity records of ground-based particle detectors such as neutron monitors (NMs) or muon detectors; they are related to the arrival of solar relativistic particles in the terrestrial environment. Hence, GLE events are related to the most energetic class of solar energetic particle (SEP) events. In this work we investigate how the use of different magnetospheric field models can influence the derivation of the relativistic SEP properties when modeling GLE events. As a case study, we examine the event of 2012 May 17 (also known as GLE71), registered by ground-based NMs. We apply the Tsyganenko 89 and the Tsyganenko 96 models in order to calculate the trajectories of the arriving SEPs in the near-Earth environment. We show that the intersection of the SEP trajectories with the atmospheric layer at ~20 km from the Earth's surface (i.e., where the flux of the generated secondary particles is maximum), forms for each ground-based neutron monitor a specified viewing region that is dependent on the magnetospheric field configuration. Then, we apply the Neutron Monitor Based Anisotropic GLE Pure Power Law (NMBANGLE PPOLA) model (Plainaki et al. 2010, Solar Phys, 264, 239), in order to derive the spectral properties of the related SEP event and the spatial distributions of the SEP fluxes impacting the Earth's atmosphere. We examine the dependence of the results on the used magnetic field models and evaluate their range of validity. Finally we discuss information derived by modeling the SEP spectrum in the frame of particle acceleration scenarios.

Cosmic ray modulation

NASA Astrophysics Data System (ADS)

Agarwal Mishra, Rekha; Mishra, Rajesh Kumar

2016-07-01

Propagation of cosmic rays to and inside the heliosphere, encounter an outward moving solar wind with cyclic magnetic field fluctuation and turbulence, causing convection and diffusion in the heliosphere. Cosmic ray counts from the ground ground-based neutron monitors at different cut of rigidity show intensity changes, which are anti-correlated with sunspot numbers. They also lose energy as they propagate towards the Earth and experience various types of modulations due to different solar activity indices. In this work, we study the first three harmonics of cosmic ray intensity on geo-magnetically quiet days over the period 1965-2014 for Beijing, Moscow and Tokyo neutron monitoring stations located at different cut off rigidity. The amplitude of first harmonic remains high for low cutoff rigidity as compared to high cutoff rigidity on quiet days. The diurnal amplitude significantly decreases during solar activity minimum years. The diurnal time of maximum significantly shifts to an earlier time as compared to the corotational direction having different cutoff rigidities. The time of maximum for first harmonic significantly shifts towards later hours and for second harmonic it shifts towards earlier hours at low cutoff rigidity station as compared to the high cut off rigidity station on quiet days. The amplitude of second/third harmonics shows a good positive correlation with solar wind velocity, while the others (i.e. amplitude and phase) have no significant correlation on quiet days. The amplitude and direction of the anisotropy on quiet days does not show any significant dependence on high-speed solar wind streams for these neutron monitoring stations of different cutoff rigidity threshold. Keywords: cosmic ray, cut off rigidity, quiet days, harmonics, amplitude, phase.

Solar cycles and depositional processes in annual 10Be from two varved lake sediment records

NASA Astrophysics Data System (ADS)

Czymzik, Markus; Muscheler, Raimund; Brauer, Achim; Adolphi, Florian; Ott, Florian; Kienel, Ulrike; Dräger, Nadine; Słowiński, Michał; Aldahan, Ala; Possnert, Göran

2015-10-01

Beryllium 10 concentrations (10Becon) were measured at annual resolution from varved sediment cores of Lakes Tiefer See (TSK) and Czechowskie (JC) for the period 1983-2009 (∼solar cycles 22 and 23). Calibrating the 10Becon time-series against complementing proxy records from the same archive as well as local precipitation and neutron monitor data, reflecting solar forced changes in atmospheric radionuclide production, allowed (i) identifying the main depositional processes and (ii) evaluating the potential for solar activity reconstruction. 10Becon in TSK and JC sediments are significantly correlated to varying neutron monitor counts (TSK: r = 0.5, p = 0.05, n = 16; JC: r = 0.46, p = 0.03, n = 22). However, the further correlations with changes in organic carbon contents in TSK as well as varying organic carbon and detrital matter contents in JC point to catchment specific biases in the 10Becon time-series. In an attempt to correct for these biases multiple regression analysis was applied to extract an atmospheric 10Be production signal (10Beatmosphere). To increase the signal to noise ratio a 10Be composite record (10Becomposite) was calculated from the TSK and JC 10Beatmosphere time-series. 10Becomposite is significantly correlated to variations in the neutron monitor record (r = 0.49, p = 0.01, n = 25) and matches the expected amplitude changes in 10Be production between solar cycle minima and maxima. This calibration study on 10Be from two sites indicates the large potential but also, partly site-specific, limitations of 10Be in varved lake sediments for solar activity reconstruction.

ICRP Publication 107. Nuclear decay data for dosimetric calculations.

PubMed

Eckerman, K; Endo, A

2008-01-01

In this report, the Commission provides an electronic database of the physical data needed in calculations of radionuclide-specific protection and operational quantities. This database supersedes the data of Publication 38 (ICRP, 1983), and will be used in future ICRP publications of dose coefficients for the intake of or exposure to radionuclides in the workplace and the environment.The database contains information on the half-lives, decay chains, and yields and energies of radiations emitted in nuclear transformations of 1252 radionuclides of 97 elements. The CD accompanying the publication provides electronic access to complete tables of the emitted radiations, as well as the beta and neutron spectra. The database has been constructed such that user-developed software can extract the data needed for further calculations of a radionuclide of interest. A Windows-based application is provided to display summary information on a user-specified radionuclide, as well as the general characterisation of the nuclides contained in the database. In addition, the application provides a means by which the user can export the emissions of a specified radionuclide for use in subsequent calculations.

The Need for Precise and Well-documented Experimental Data on Prompt Fission Neutron Spectra from Neutron-induced Fission of {sup 239}Pu

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neudecker, D., E-mail: dneudecker@lanl.gov; Taddeucci, T.N.; Haight, R.C.

2016-01-15

The spectrum of neutrons emitted promptly after {sup 239}Pu(n,f)—a so-called prompt fission neutron spectrum (PFNS)—is a quantity of high interest, for instance, for reactor physics and global security. However, there are only few experimental data sets available that are suitable for evaluations. In addition, some of those data sets differ by more than their 1-σ uncertainty boundaries. We present the results of MCNP studies indicating that these differences are partly caused by underestimated multiple scattering contributions, over-corrected background, and inconsistent deconvolution methods. A detailed uncertainty quantification for suitable experimental data was undertaken including these effects, and test-evaluations were performed withmore » the improved uncertainty information. The test-evaluations illustrate that the inadequately estimated effects and detailed uncertainty quantification have an impact on the evaluated PFNS and associated uncertainties as well as the neutron multiplicity of selected critical assemblies. A summary of data and documentation needs to improve the quality of the experimental database is provided based on the results of simulations and test-evaluations. Given the possibly substantial distortion of the PFNS by multiple scattering and background effects, special care should be taken to reduce these effects in future measurements, e.g., by measuring the {sup 239}Pu PFNS as a ratio to either the {sup 235}U or {sup 252}Cf PFNS.« less

DESIGNING ENVIRONMENTAL MONITORING DATABASES FOR STATISTIC ASSESSMENT

EPA Science Inventory

Databases designed for statistical analyses have characteristics that distinguish them from databases intended for general use. EMAP uses a probabilistic sampling design to collect data to produce statistical assessments of environmental conditions. In addition to supporting the ...

Theory and methods for measuring the effective multiplication constant in ADS

NASA Astrophysics Data System (ADS)

Rugama Saez, Yolanda

2001-10-01

In the thesis an absolute measurements technique for the subcriticality determination is presented. The ADS is a hybrid system where a subcritical system is fed by a proton accelerator. There are different proposals to define an ADS, one is to use plutonium and minor actinides from power plants waste as fuel to be transmuted into non radioactive isotopes (transmuter/burner, ATW). Another proposal is to use a Th232-U233 cycle (Energy Amplifier), being that thorium is an interesting and abundant fertile isotope. The development of accelerator driven systems (ADS) requires the development of methods to monitor and control the subcriticality of this kind of system without interfering with its normal operation mode. With this finality, we have applied noise analysis techniques that allow us to characterise the system when it is operating. The method presented in this thesis is based on the stochastic neutron and photon transport theory that can be implemented by presently available neutron/photon transport codes. In this work, first we analyse the stochastic transport theory which has been applied to define a parameter to determine the subcritical reactivity monitoring measurements. Finally we give the main limitations and recommendations for these subcritical monitoring methodology. As a result of the theoretical methodology, done in the first part of this thesis, a monitoring measurement technique has been developed and verified using two coupled Monte Carlo programs. The first one, LAHET, simulates the spallation collisions and the high energy transport and the other, MCNP-DSP, is used to estimate the counting statistics from a neutron/photon ray counter in a fissile system, as well as the transport for neutron with energies less than 20 MeV. From the coupling of both codes we developed the LAHET/MCNP-DSP code which, has the capability to simulate the total process in the ADS from the proton interaction to the signal detector processing. In these simulations, we compute the cross power spectral densities between pairs of detectors located inside the system which, is defined as the measured parameter. From the comparison of the theoretical predictions with the Monte Carlo simulations, we obtain some practical and simple methods to determine the system multiplication constant. (Abstract shortened by UMI.)

Actinide Sputtering Induced by Fission with Ultra-cold Neutrons

NASA Astrophysics Data System (ADS)

Shi, Tan; Venuti, Michael; Fellers, Deion; Martin, Sean; Morris, Chris; Makela, Mark

2017-09-01

Understanding the effects of actinide sputtering due to nuclear fission is important for a wide range of applications, including nuclear fuel storage, space science, and national defense. A new program at the Los Alamos Neutron Science Center uses ultracold neutrons (UCN) to induce fission in actinides such as uranium and plutonium. By controlling the UCN energy, it is possible to induce fission at the sample surface within a well-defined depth. It is therefore an ideal tool for studying the effects of fission-induced sputtering as a function of interaction depth. Since the mechanism for fission-induced surface damage is not well understood, this work has the potential to deconvolve the various damage mechanisms. During the irradiation with UCN, NaI detectors are used to monitor the fission events and were calibrated by monitoring fission fragments with an organic scintillator. Alpha spectroscopy of the ejected actinide material is performed in an ion chamber to determine the amount of sputtered material. Actinide samples with various sample properties and surface conditions are irradiated and analyzed. In this talk, I will discuss our experimental setup and present the preliminary results from the testing of multiple samples. This work has been supported by Los Alamos National Laboratory and Seaborg Summer Research Fellowship.

PR-EDB: Power Reactor Embrittlement Database - Version 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jy-An John; Subramani, Ranjit

2008-03-01

The aging and degradation of light-water reactor pressure vessels is of particular concern because of their relevance to plant integrity and the magnitude of the expected irradiation embrittlement. The radiation embrittlement of reactor pressure vessel materials depends on many factors, such as neutron fluence, flux, and energy spectrum, irradiation temperature, and preirradiation material history and chemical compositions. These factors must be considered to reliably predict pressure vessel embrittlement and to ensure the safe operation of the reactor. Large amounts of data from surveillance capsules are needed to develop a generally applicable damage prediction model that can be used for industrymore » standards and regulatory guides. Furthermore, the investigations of regulatory issues such as vessel integrity over plant life, vessel failure, and sufficiency of current codes, Standard Review Plans (SRPs), and Guides for license renewal can be greatly expedited by the use of a well-designed computerized database. The Power Reactor Embrittlement Database (PR-EDB) is such a comprehensive collection of data for U.S. designed commercial nuclear reactors. The current version of the PR-EDB lists the test results of 104 heat-affected-zone (HAZ) materials, 115 weld materials, and 141 base materials, including 103 plates, 35 forgings, and 3 correlation monitor materials that were irradiated in 321 capsules from 106 commercial power reactors. The data files are given in dBASE format and can be accessed with any personal computer using the Windows operating system. "User-friendly" utility programs have been written to investigate radiation embrittlement using this database. Utility programs allow the user to retrieve, select and manipulate specific data, display data to the screen or printer, and fit and plot Charpy impact data. The PR-EDB Version 3.0 upgrades Version 2.0. The package was developed based on the Microsoft .NET framework technology and uses Microsoft Access for backend data storage, and Microsoft Excel for plotting graphs. This software package is compatible with Windows (98 or higher) and has been built with a highly versatile user interface. PR-EDB Version 3.0 also contains an "Evaluated Residual File" utility for generating the evaluated processed files used for radiation embrittlement study.« less

TU-F-BRE-07: In Vivo Neutron Detection in Patients Undergoing Stereotactic Ablative Radiotherapy (SABR) for Primary Kidney Cancer Using 6Li and 7Li Enriched TLD Pairs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lonski, P; Kron, T; RMIT University, Melbourne, Victoria

Purpose: Stereotactic ablative radiotherapy (SABR) for primary kidney cancer often involves the use of high-energy photons combined with a large number of monitor units. While important for risk assessment, the additional neutron dose to untargeted healthy tissue is not accounted for in treatment planning. This work aims to detect out-of-field neutrons in vivo for patients undergoing SABR with high-energy (>10 MV) photons and provides preliminary estimates of neutron effective dose. Methods: 3 variations of high-sensitivity LiF:Mg,Cu,P thermoluminescent dosimeter (TLD) material, each with varying {sup 6}Li / {sup 7}Li concentrations, were used in custom-made Perspex holders for in vivo measurements. Themore » variation in cross section for thermal neutrons between Li isotopes was exploited to distinguish neutron from photon signal. Measurements were made out-of-field for 7 patients, each undergoing 3D-conformal SABR treatment for primary kidney cancer on a Varian 21iX linear accelerator. Results: In vivo measurements show increased signal for the {sup 6}Li enriched material for patients treated with 18 MV photons. Measurements on one SABR patient treated using only 6 MV showed no difference between the 3 TLD materials. The out-of-field photon signal decreased exponentially with distance from the treatment field. The neutron signal, taken as the difference between {sup 6}Li enriched and {sup 7}Li enriched TLD response, remains almost constant up to 50 cm from the beam central axis. Estimates of neutron effective dose from preliminary TLD calibration suggest between 10 and 30 mSv per 1000 MU delivered at 18 MV for the 7 patients. Conclusion: TLD was proven to be a useful tool for the purpose of in vivo neutron detection at out-of-field locations. Further work is required to understand the relationship between TL signal and neutron dose. Dose estimates based on preliminary TLD calibration in a neutron beam suggest the additional neutron dose was <30 mSv per 1000 MU at 18 MV.« less

Beyond Californium-A Neutron Generator Alternative for Dosimetry and Instrument Calibration in the U.S.

PubMed

Piper, Roman K; Mozhayev, Andrey V; Murphy, Mark K; Thompson, Alan K

2017-09-01

Evaluations of neutron survey instruments, area monitors, and personal dosimeters rely on reference neutron radiations, which have evolved from the heavy reliance on (α,n) sources to a shared reliance on (α,n) and the spontaneous fission neutrons of californium-252 (Cf). Capable of producing high dose equivalent rates from an almost point source geometry, the characteristics of Cf are generally more favorable when compared to the use of (α,n) and (γ,n) sources or reactor-produced reference neutron radiations. Californium-252 is typically used in two standardized configurations: unmoderated, to yield a fission energy spectrum; or with the capsule placed within a heavy-water moderating sphere to produce a softened spectrum that is generally considered more appropriate for evaluating devices used in nuclear power plant work environments. The U.S. Department of Energy Cf Loan/Lease Program, a longtime origin of affordable Cf sources for research, testing and calibration, was terminated in 2009. Since then, high-activity sources have become increasingly cost-prohibitive for laboratories that formerly benefited from that program. Neutron generators, based on the D-T and D-D fusion reactions, have become economically competitive with Cf and are recognized internationally as important calibration and test standards. Researchers from the National Institute of Standards and Technology and the Pacific Northwest National Laboratory are jointly considering the practicality and technical challenges of implementing neutron generators as calibration standards in the U.S. This article reviews the characteristics of isotope-based neutron sources, possible isotope alternatives to Cf, and the rationale behind the increasing favor of electronically generated neutron options. The evaluation of a D-T system at PNNL has revealed characteristics that must be considered in adapting generators to the task of calibration and testing where accurate determination of a dosimetric quantity is necessary. Finally, concepts are presented for modifying the generated neutron spectra to achieve particular targeted spectra, simulating Cf or workplace environments.

Neutron induced fission cross section measurements of 240Pu and 242Pu

NASA Astrophysics Data System (ADS)

Belloni, F.; Eykens, R.; Heyse, J.; Matei, C.; Moens, A.; Nolte, R.; Plompen, A. J. M.; Richter, S.; Sibbens, G.; Vanleeuw, D.; Wynants, R.

2017-09-01

Accurate neutron induced fission cross section of 240Pu and 242Pu are required in view of making nuclear technology safer and more efficient to meet the upcoming needs for the future generation of nuclear power plants (GEN-IV). The probability for a neutron to induce such reactions figures in the NEA Nuclear Data High Priority Request List [1]. A measurement campaign to determine neutron induced fission cross sections of 240Pu and 242Pu at 2.51 MeV and 14.83 MeV has been carried out at the 3.7 MV Van De Graaff linear accelerator at Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig. Two identical Frisch Grid fission chambers, housing back to back a 238U and a APu target (A = 240 or A = 242), were employed to detect the total fission yield. The targets were molecular plated on 0.25 mm aluminium foils kept at ground potential and the employed gas was P10. The neutron fluence was measured with the proton recoil telescope (T1), which is the German primary standard for neutron fluence measurements. The two measurements were related using a De Pangher long counter and the charge as monitors. The experimental results have an average uncertainty of 3-4% at 2.51 MeV and for 6-8% at 14.81 MeV and have been compared to the data available in literature.

Performance of Large Neutron Detectors Containing Lithium-Gadolinium-Borate Scintillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slaughter, David M.; Stuart, Cory R.; Klaass, R. Fred

2015-07-01

This paper describes the development and testing of a neutron counter, spectrometer, and dosimeter that is compact, efficient, and accurate. A self-contained neutron detection instrument has wide applications in health physics, scientific research, and programs to detect, monitor, and control strategic nuclear materials (SNM). The 1.3 liter detector head for this instrument is a composite detector with an organic scintillator containing uniformly distributed {sup 6}Li{sub 6}{sup nat}Gd{sup 10}B{sub 3}O{sub 9}:Ce (LGB:Ce) microcrystals. The plastic scintillator acts to slow impinging neutrons and emits light proportional to the energy lost by the neutrons as they moderate in the detector body. Moderating neutronsmore » that have slowed sufficiently capture in one of the Lithium-6, Boron-10, or Gadolinium-157 atoms in the LGB:Ce scintillator, which then releases the capture energy in a characteristic cerium emission pulse. The measured captured pulses indicate the presence of neutrons. When a scintillating fluor is present in the plastic, the light pulse resulting from the neutron moderating in the plastic is paired with the LGB:Ce capture pulse to identify the energy of the neutron. About 2% of the impinging neutrons lose all of their energy in a single collision with the detector. There is a linear relationship between the pulse areas of this group of neutrons and energy. The other 98% of neutrons have a wide range of collision histories within the detector body. When these neutrons are 'binned' into energy groups, each group contains a distribution of pulse areas. This data was used to assist in the unfolding of the neutron spectra. The unfolded spectra were then validated with known spectra, at both neutron emitting isotopes and fission/accelerator facilities. Having validated spectra, the dose equivalent and dose rate are determined by applying standard, regulatory damage coefficients to the measured neutron counts for each energy bin of the spectra. Testing at the Los Alamos Neutron Science Center (LANSCE), Edwards Accelerator Laboratory (EAL) at Ohio University and the Radiation Center at University of Massachusetts-Lowell has demonstrated that the instrument can measure neutrons and their spectra over the range between 0.8 MeV and 150 MeV with an uncertainty of only ± 8%. An independent test of the LGB:Ce neutron spectrometer was conducted by a US Defense Threat Reduction Agency (DTRA) team at the Idaho National Laboratory (INL). The results of this evaluation showed that the neutron spectrometer accurately identified bare radioactive isotopes by their spectra. Further, masking and shielding materials alter those spectra in predictable ways that permit an extrapolation from the observed spectra back to the identity of the isotopic spectrum. (authors)« less

Response function of a superheated drop neutron monitor with lead shell in the thermal to 400-MeV energy range.

PubMed

Itoga, Toshiro; Asano, Yoshihiro; Tanimura, Yoshihiko

2011-07-01

Superheated drop detectors are currently used for personal and environmental dosimetry and their characteristics such as response to neutrons and temperature dependency are well known. A new bubble counter based on the superheated drop technology has been developed by Framework Scientific. However, the response of this detector with the lead shell is not clear especially above several tens of MeV. In this study, the response has been measured with quasi-monoenergetic and monoenergetic neutron sources with and without a lead shell. The experimental results were compared with the results of the Monte Carlo calculations using the 'Event Generator Mode' in the PHITS code with the JENDL-HE/2007 data library to clarify the response of this detector with a lead shell in the entire energy range.

P0004-1 quick look

NASA Technical Reports Server (NTRS)

1991-01-01

The P0004-1 'Seeds in Space' experiment consisted of six sealed aluminum canisters which contained tomato seeds and a variety of other seeds for the study of space radiation effects on the seeds. The seeds were contained in cloth bags. Interspersed among the bags of seeds were ten dosimeter packets to monitor the accumulated ionizing radiation exposure of the seeds. In addition to the ten flight dosimeter packets, four ground control packets and one ground movement packet were also included as part of the experiment. The P0004-1 experiment was mounted on the F2 tray, near the trailing edge of the LDEF orbiter. The results indicate that the neutron fluences were higher in the P0004 canisters than in that of P0006. The difference was much greater for thermal neutrons than resonance neutrons. This is consistent with shielding.

In-situ neutron diffraction characterization of temperature dependence deformation in α-uranium

NASA Astrophysics Data System (ADS)

Calhoun, C. A.; Garlea, E.; Sisneros, T. A.; Agnew, S. R.

2018-04-01

In-situ strain neutron diffraction measurements were conducted at temperature on specimens coming from a clock-rolled α-uranium plate, and Elasto-Plastic Self-Consistent (EPSC) modeling was employed to interpret the findings. The modeling revealed that the active slip systems exhibit a thermally activated response, while deformation twinning remains athermal over the temperature ranges explored (25-150 °C). The modeling also allowed assessment of the effects of thermal residual stresses on the mechanical response during compression. These results are consistent with those from a prior study of room-temperature deformation, indicating that the thermal residual stresses strongly influence the internal strain evolution of grain families, as monitored with neutron diffraction, even though accounting for these residual stresses has little effect on the macroscopic flow curve, except in the elasto-plastic transition.

Secondary Neutron Production from Space Radiation Interactions: Advances in Model and Experimental Data Base Development

NASA Technical Reports Server (NTRS)

Heilbronn, Lawrence H.; Townsend, Lawrence W.; Braley, G. Scott; Iwata, Yoshiyuki; Iwase, Hiroshi; Nakamura, Takashi; Ronningen, Reginald M.; Cucinotta, Francis A.

2003-01-01

For humans engaged in long-duration missions in deep space or near-Earth orbit, the risk from exposure to galactic and solar cosmic rays is an important factor in the design of spacecraft, spacesuits, and planetary bases. As cosmic rays are transported through shielding materials and human tissue components, a secondary radiation field is produced. Neutrons are an important component of that secondary field, especially in thickly-shielded environments. Calculations predict that 50% of the dose-equivalent in a lunar or Martian base comes from neutrons, and a recent workshop held at the Johnson Space Center concluded that as much as 30% of the dose in the International Space Station may come from secondary neutrons. Accelerator facilities provide a means for measuring the effectiveness of various materials in their ability to limit neutron production, using beams and energies that are present in cosmic radiation. The nearly limitless range of beams, energies, and target materials that are present in space, however, means that accelerator-based experiments will not provide a complete database of cross sections and thick-target yields that are necessary to plan and design long-duration missions. As such, accurate nuclear models of neutron production are needed, as well as data sets that can be used to compare with, and verify, the predictions from such models. Improvements in a model of secondary neutron production from heavy-ion interactions are presented here, along with the results from recent accelerator-based measurements of neutron-production cross sections. An analytical knockout-ablation model capable of predicting neutron production from high-energy hadron-hadron interactions (both nucleon-nucleus and nucleus-nucleus collisions) has been previously developed. In the knockout stage, the collision between two nuclei result in the emission of one or more nucleons from the projectile and/or target. The resulting projectile and target remnants, referred to as prefragments, then decay by the emission of nucleons, composites, and gamma rays. Recent improvements to the model have incorporated coalescence effects, which effectively tie up single nucleons in the formation of composites during final-state interactions. Comparison of the improved model s predictions with neutron production data near 0 deg in the CA-40+ H reaction at 357 and 565 MeV/nucleon show marked improvement.

Building a structured monitoring and evaluating system of postmarketing drug use in Shanghai.

PubMed

Du, Wenmin; Levine, Mitchell; Wang, Longxing; Zhang, Yaohua; Yi, Chengdong; Wang, Hongmin; Wang, Xiaoyu; Xie, Hongjuan; Xu, Jianglong; Jin, Huilin; Wang, Tongchun; Huang, Gan; Wu, Ye

2007-01-01

In order to understand a drug's full profile in the post-marketing environment, information is needed regarding utilization patterns, beneficial effects, ADRs and economic value. China, the most populated country in the world, has the largest number of people who are taking medications. To begin to appreciate the impact of these medications, a multifunctional evaluation and surveillance system was developed, the Shanghai Drug Monitoring and Evaluative System (SDMES). Set up by the Shanghai Center for Adverse Drug Reaction Monitoring in 2001, the SDMES contains three databases: a population health data base of middle aged and elderly persons; hospital patient medical records; and a spontaneous ADR reporting database. Each person has a unique identification and Medicare number, which permits record-linkage within and between these three databases. After more than three years in development, the population health database has comprehensive data for more than 320,000 residents. The hospital database has two years of inpatient medical records from five major hospitals, and will be increasing to 10 hospitals in 2007. The spontaneous reporting ADR database has collected 20,205 cases since 2001 from approximately 295 sources, including hospitals, pharmaceutical companies, drug wholesalers and pharmacies. The SDMES has the potential to become an important national and international pharmacoepidemiology resource for drug evaluation.

Results and Systematic Studies of the UCN Lifetime Experiment at NIST

NASA Astrophysics Data System (ADS)

Huffer, Craig Reeves

The neutron beta-decay lifetime is important in understanding weak interactions in the framework of the Standard Model, and it is an input to nuclear astrophysics and Big Bang Nucleosynthesis. Current measurements of the neutron beta-decay lifetime disagree, which has motivated additional experiments that are sensitive to different sets of systematic effects. An effort continues at the NIST Center for Neutron Research (NCNR) to improve the statistical and systematic limitations of an experiment to measure the neutron beta-decay lifetime using magnetically trapped UCN. In the experiment, a monoenergetic 0:89 nm cold neutron is incident on a superfluid 4He target within the minimum field region of an Ioffe type magnetic trap. Some of the neutrons are subsequently downscattered by single phonons in the helium to low energies (≈ 200 neV), and those in the appropriate spin state become trapped. The inverse process, upscattering of UCN, is suppressed by the low phonon density in the < 300 mK helium. When the neutron decays, the energetic electron creates EUV scintillation light, which is down-converted and transported out of the cell to PMTs operated at room temperature. With this method, the decay of the UCN population can be monitored in situ. The apparatus, analysis, data, and systematics will be discussed. After accounting for the systematic effects the measured lifetime disagrees with the current PDG mean neutron beta-decay lifetime by about 9 of our standard deviations, which is a strong indication of unaccounted for systematic effects. Additional 3He contamination will be shown to be the most likely candidate for the additional systematic shift, which motivated the commissioning and initial operation of a heat flush purifier for purifying additional 4He. This work ends with a description of the 4He purifier and its performance.

Boron carbide coatings for neutron detection probed by x-rays, ions, and neutrons to determine thin film quality

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nowak, G., E-mail: Gregor.Nowak@hzg.de; Störmer, M.; Horstmann, C.

2015-01-21

Due to the present shortage of {sup 3}He and the associated tremendous increase of its price, the supply of large neutron detection systems with {sup 3}He becomes unaffordable. Alternative neutron detection concepts, therefore, have been invented based on solid {sup 10}B converters. These concepts require development in thin film deposition technique regarding high adhesion, thickness uniformity and chemical purity of the converter coating on large area substrates. We report on the sputter deposition of highly uniform large-area {sup 10}B{sub 4}C coatings of up to 2 μm thickness with a thickness deviation below 4% using the Helmholtz-Zentrum Geesthacht large area sputtering system.more » The {sup 10}B{sub 4}C coatings are x-ray amorphous and highly adhesive to the substrate. Material analysis by means of X-ray-Photoelectron Spectroscopy, Secondary-Ion-Mass-Spectrometry, and Rutherford-Back-Scattering (RBS) revealed low impurities concentration in the coatings. The isotope composition determined by Secondary-Ion-Mass-Spectrometry, RBS, and inelastic nuclear reaction analysis of the converter coatings evidences almost identical {sup 10}B isotope contents in the sputter target and in the deposited coating. Neutron conversion and detection test measurements with variable irradiation geometry of the converter coating demonstrate an average relative quantum efficiency ranging from 65% to 90% for cold neutrons as compared to a black {sup 3}He-monitor. Thus, these converter coatings contribute to the development of {sup 3}He-free prototype detectors based on neutron grazing incidence. Transferring the developed coating process to an industrial scale sputtering system can make alternative {sup 3}He-free converter elements available for large area neutron detection systems.« less

Martian Neutron Energy Spectrometer (MANES)

NASA Technical Reports Server (NTRS)

Maurer, R. H.; Roth, D. R.; Kinnison, J. D.; Goldsten, J. O.; Fainchtein, R.; Badhwar, G.

2000-01-01

High energy charged particles of extragalactic, galactic, and solar origin collide with spacecraft structures and planetary atmospheres. These primaries create a number of secondary particles inside the structures or on the surfaces of planets to produce a significant radiation environment. This radiation is a threat to long term inhabitants and travelers for interplanetary missions and produces an increased risk of carcinogenesis, central nervous system (CNS) and DNA damage. Charged particles are readily detected; but, neutrons, being electrically neutral, are much more difficult to monitor. These secondary neutrons are reported to contribute 30-60% of the dose equivalent in the Shuttle and MIR station. The Martian atmosphere has an areal density of 37 g/sq cm primarily of carbon dioxide molecules. This shallow atmosphere presents fewer mean free paths to the bombarding cosmic rays and solar particles. The secondary neutrons present at the surface of Mars will have undergone fewer generations of collisions and have higher energies than at sea level on Earth. Albedo neutrons produced by collisions with the Martian surface material will also contribute to the radiation environment. The increased threat of radiation damage to humans on Mars occurs when neutrons of higher mean energy traverse the thin, dry Martian atmosphere and encounter water in the astronaut's body. Water, being hydrogeneous, efficiently moderates the high energy neutrons thereby slowing them as they penetrate deeply into the body. Consequently, greater radiation doses can be deposited in or near critical organs such as the liver or spleen than is the case on Earth. A second significant threat is the possibility of a high energy heavy ion or neutron causing a DNA double strand break in a single strike.

Boron carbide coatings for neutron detection probed by x-rays, ions, and neutrons to determine thin film quality

NASA Astrophysics Data System (ADS)

Nowak, G.; Störmer, M.; Becker, H.-W.; Horstmann, C.; Kampmann, R.; Höche, D.; Haese-Seiller, M.; Moulin, J.-F.; Pomm, M.; Randau, C.; Lorenz, U.; Hall-Wilton, R.; Müller, M.; Schreyer, A.

2015-01-01

Due to the present shortage of 3He and the associated tremendous increase of its price, the supply of large neutron detection systems with 3He becomes unaffordable. Alternative neutron detection concepts, therefore, have been invented based on solid 10B converters. These concepts require development in thin film deposition technique regarding high adhesion, thickness uniformity and chemical purity of the converter coating on large area substrates. We report on the sputter deposition of highly uniform large-area 10B4C coatings of up to 2 μm thickness with a thickness deviation below 4% using the Helmholtz-Zentrum Geesthacht large area sputtering system. The 10B4C coatings are x-ray amorphous and highly adhesive to the substrate. Material analysis by means of X-ray-Photoelectron Spectroscopy, Secondary-Ion-Mass-Spectrometry, and Rutherford-Back-Scattering (RBS) revealed low impurities concentration in the coatings. The isotope composition determined by Secondary-Ion-Mass-Spectrometry, RBS, and inelastic nuclear reaction analysis of the converter coatings evidences almost identical 10B isotope contents in the sputter target and in the deposited coating. Neutron conversion and detection test measurements with variable irradiation geometry of the converter coating demonstrate an average relative quantum efficiency ranging from 65% to 90% for cold neutrons as compared to a black 3He-monitor. Thus, these converter coatings contribute to the development of 3He-free prototype detectors based on neutron grazing incidence. Transferring the developed coating process to an industrial scale sputtering system can make alternative 3He-free converter elements available for large area neutron detection systems.

Determination of the Sensitivity of the Antineutrino Probe for Reactor Core Monitoring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cormon, S.; Fallot, M., E-mail: fallot@subatech.in2p3.fr; Bui, V.-M.

This paper presents a feasibility study of the use of the detection of reactor-antineutrinos (ν{sup ¯}{sub e}) for non proliferation purpose. To proceed, we have started to study different reactor designs with our simulation tools. We use a package called MCNP Utility for Reactor Evolution (MURE), initially developed by CNRS/IN2P3 labs to study Generation IV reactors. The MURE package has been coupled to fission product beta decay nuclear databases for studying reactor antineutrino emission. This method is the only one able to predict the antineutrino emission from future reactor cores, which don't use the thermal fission of {sup 235}U, {supmore » 239}Pu and {sup 241}Pu. It is also the only way to include off-equilibrium effects, due to neutron captures and time evolution of the fission product concentrations during a reactor cycle. We will present here the first predictions of antineutrino energy spectra from innovative reactor designs (Generation IV reactors). We will then discuss a summary of our results of non-proliferation scenarios involving the latter reactor designs, taking into account reactor physics constraints.« less

Extension of applicable neutron energy of DARWIN up to 1 GeV.

PubMed

Satoh, D; Sato, T; Endo, A; Matsufuji, N; Takada, M

2007-01-01

The radiation-dose monitor, DARWIN, needs a set of response functions of the liquid organic scintillator to assess a neutron dose. SCINFUL-QMD is a Monte Carlo based computer code to evaluate the response functions. In order to improve the accuracy of the code, a new light-output function based on the experimental data was developed for the production and transport of protons deuterons, tritons, (3)He nuclei and alpha particles, and incorporated into the code. The applicable energy of DARWIN was extended to 1 GeV using the response functions calculated by the modified SCINFUL-QMD code.

Study of the Anatomy of the X-Ray and Neutron Production Scaling Laws in the Plasma Focus (Particle Energy Spectrum and Optimization Criteria).

DTIC Science & Technology

1979-11-01

plasma focus operations have been experimentally analyzed in terms of (A) The fine structure of the axial-current channel during maximum of compression. (B) Correlation coefficient, for neutron yield n (by D2 discharges) and the multiplicity of the electron beam pulses; (C) Different values of the electrode voltage. The current distribution near the axial plasma column during the explosive decay of the column has been monitored and correlated with the electron beam production. Plasma focus discharges by our mode of operation generate high-intensity

Calculation of radiation therapy dose using all particle Monte Carlo transport

DOEpatents

Chandler, William P.; Hartmann-Siantar, Christine L.; Rathkopf, James A.

1999-01-01

The actual radiation dose absorbed in the body is calculated using three-dimensional Monte Carlo transport. Neutrons, protons, deuterons, tritons, helium-3, alpha particles, photons, electrons, and positrons are transported in a completely coupled manner, using this Monte Carlo All-Particle Method (MCAPM). The major elements of the invention include: computer hardware, user description of the patient, description of the radiation source, physical databases, Monte Carlo transport, and output of dose distributions. This facilitated the estimation of dose distributions on a Cartesian grid for neutrons, photons, electrons, positrons, and heavy charged-particles incident on any biological target, with resolutions ranging from microns to centimeters. Calculations can be extended to estimate dose distributions on general-geometry (non-Cartesian) grids for biological and/or non-biological media.

Updated and revised neutron reaction data for 237Np

NASA Astrophysics Data System (ADS)

Chen, Guochang; Wang, Jimin; Cao, Wentian; Tang, Guoyou; Yu, Baosheng

2017-09-01

Nuclear data with high accuracy for minor actinides play an important role in nuclear technology applications, including reactor design and operation, fuel cycle, estimation of the amount of minor actinides in high burn-up reactors and the minor actinides transmutation. Based on the evaluated experimental data, the updated and revised evaluation of a full set of n+237Np nuclear data from 10-5 eV ˜ 20 MeV are carried out and recommended. Mainly revised quantities are neutron multiplicities from fission reaction, inelastic, fission, (n, 2n) and (n, γ) reaction cross sections as well as angular distribution and so on. The promising results are obtained when the renewal evaluated data of 237Np will be used to instead of the evaluated data in CENDL-3.1 database.

Characterization of Radiation Fields in Biological Shields of Nuclear Power Plants for Assessing Concrete Degradationa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Remec, Igor; Rosseel, Thomas M; Field, Kevin G

Life extensions of nuclear power plants to 60 and potentially 80 years of operation have renewed interest in long-term material degradation. One material being considered is concrete, with a particular focus on radiation-induced effects. Based on the projected neutron fluence values (E > 0.1 MeV) in the concrete biological shields of the US pressurized water reactor fleet and the available data on radiation effects on concrete, some decrease in mechanical properties of concrete cannot be ruled out during extended operation beyond 60 years. An expansion of the irradiated concrete database and a reliable determination of relevant neutron fluence energy cutoffmore » value are necessary to ensure reliable risk assessment for extended operation of nuclear power plants.« less

Calculation of radiation therapy dose using all particle Monte Carlo transport

DOEpatents

Chandler, W.P.; Hartmann-Siantar, C.L.; Rathkopf, J.A.

1999-02-09

The actual radiation dose absorbed in the body is calculated using three-dimensional Monte Carlo transport. Neutrons, protons, deuterons, tritons, helium-3, alpha particles, photons, electrons, and positrons are transported in a completely coupled manner, using this Monte Carlo All-Particle Method (MCAPM). The major elements of the invention include: computer hardware, user description of the patient, description of the radiation source, physical databases, Monte Carlo transport, and output of dose distributions. This facilitated the estimation of dose distributions on a Cartesian grid for neutrons, photons, electrons, positrons, and heavy charged-particles incident on any biological target, with resolutions ranging from microns to centimeters. Calculations can be extended to estimate dose distributions on general-geometry (non-Cartesian) grids for biological and/or non-biological media. 57 figs.

Hydroacoustic propagation grids for the CTBT knowledge databaes BBN technical memorandum W1303

DOE Office of Scientific and Technical Information (OSTI.GOV)

J. Angell

1998-05-01

The Hydroacoustic Coverage Assessment Model (HydroCAM) has been used to develop components of the hydroacoustic knowledge database required by operational monitoring systems, particularly the US National Data Center (NDC). The database, which consists of travel time, amplitude correction and travel time standard deviation grids, is planned to support source location, discrimination and estimation functions of the monitoring network. The grids will also be used under the current BBN subcontract to support an analysis of the performance of the International Monitoring System (IMS) and national sensor systems. This report describes the format and contents of the hydroacoustic knowledgebase grids, and themore » procedures and model parameters used to generate these grids. Comparisons between the knowledge grids, measured data and other modeled results are presented to illustrate the strengths and weaknesses of the current approach. A recommended approach for augmenting the knowledge database with a database of expected spectral/waveform characteristics is provided in the final section of the report.« less

Evaluations of Energy Spectra of Neutrons Emitted Promptly in Neutron-induced Fission of 235 U and 239 Pu

DOE PAGES

Neudecker, Denise; Talou, Patrick; Kawano, Toshihiko; ...

2018-02-01

The energy spectra of neutrons emitted promptly in the neutron-induced fission reactions of 235U and 239Pu were re-evaluated for ENDF/B-VIII.0. The evaluations presented here are based on a careful modeling of all relevant physics processes, an extensive analysis of experimental data and a detailed quantification of pertinent uncertainties. Energy spectra of neutrons emitted in up to fourth chance fission are considered and both compound and pre-equilibrium processes are included. Also, important nuclear model parameters, such as the average total kinetic energy of the fission fragments and the multiple chance fission probabilities, and their uncertainties are estimated based on experimental knowledge,more » model information and evaluated data. In addition to experimental information already available for ENDF/B-VII.1, these new evaluations make use of recently published experimental data either of high precision or spanning a broad incident energy range, information on legacy measurements explaining discrepancies and recently measured data of the average total kinetic energy as a function of incident neutron energy. The resulting evaluated data and covariances agree well with the experimental database used for the evaluation. However, the evaluated spectra are softer than the 235U and 239Pu ENDF/B-VII.1, JENDL-4.0 and JEFF-3.2 evaluations for incident neutron energies E inc ≤ 1.5 MeV and E inc ≤ 5 MeV, respectively. For E inc > 5 MeV, the evaluated spectra show structures due to the improved modeling which are not present in ENDF/B-VII.1 and JEFF-3.2 but can be observed in JENDL-4.0 evaluations. Part of these new evaluations were adopted for ENDF/B-VIII.0, while the ENDF/B-VII.1 239Pu PFNS was retained for E inc ≤ 5 MeV awaiting more conclusive experimental evidence.« less

Evaluations of Energy Spectra of Neutrons Emitted Promptly in Neutron-induced Fission of 235U and 239Pu

NASA Astrophysics Data System (ADS)

Neudecker, D.; Talou, P.; Kawano, T.; Kahler, A. C.; White, M. C.; Taddeucci, T. N.; Haight, R. C.; Kiedrowski, B.; O'Donnell, J. M.; Gomez, J. A.; Kelly, K. J.; Devlin, M.; Rising, M. E.

2018-02-01

The energy spectra of neutrons emitted promptly in the neutron-induced fission reactions of 235U and 239Pu were re-evaluated for ENDF/B-VIII.0. These evaluations are based on a careful modeling of all relevant physics processes, an extensive analysis of experimental data and a detailed quantification of pertinent uncertainties. Energy spectra of neutrons emitted in up to fourth chance fission are considered and both compound and pre-equilibrium processes are included. Also, important nuclear model parameters, such as the average total kinetic energy of the fission fragments and the multiple chance fission probabilities, and their uncertainties are estimated based on experimental knowledge, model information and evaluated data. In addition to experimental information already available for ENDF/B-VII.1, these new evaluations make use of recently published experimental data either of high precision or spanning a broad incident energy range, information on legacy measurements explaining discrepancies and recently measured data of the average total kinetic energy as a function of incident neutron energy. The resulting evaluated data and covariances agree well with the experimental database used for the evaluation. However, the evaluated spectra are softer than the 235U and 239Pu ENDF/B-VII.1, JENDL-4.0 and JEFF-3.2 evaluations for incident neutron energies Einc ≤ 1.5 MeV and Einc ≤ 5 MeV, respectively. For Einc > 5 MeV, the evaluated spectra show structures due to the improved modeling which are not present in ENDF/B-VII.1 and JEFF-3.2 but can be observed in JENDL-4.0 evaluations. Part of these new evaluations were adopted for ENDF/B-VIII.0, while the ENDF/B-VII.1 239Pu PFNS was retained for Einc ≤ 5 MeV awaiting more conclusive experimental evidence.

Evaluations of Energy Spectra of Neutrons Emitted Promptly in Neutron-induced Fission of 235 U and 239 Pu

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neudecker, Denise; Talou, Patrick; Kawano, Toshihiko

The energy spectra of neutrons emitted promptly in the neutron-induced fission reactions of 235U and 239Pu were re-evaluated for ENDF/B-VIII.0. The evaluations presented here are based on a careful modeling of all relevant physics processes, an extensive analysis of experimental data and a detailed quantification of pertinent uncertainties. Energy spectra of neutrons emitted in up to fourth chance fission are considered and both compound and pre-equilibrium processes are included. Also, important nuclear model parameters, such as the average total kinetic energy of the fission fragments and the multiple chance fission probabilities, and their uncertainties are estimated based on experimental knowledge,more » model information and evaluated data. In addition to experimental information already available for ENDF/B-VII.1, these new evaluations make use of recently published experimental data either of high precision or spanning a broad incident energy range, information on legacy measurements explaining discrepancies and recently measured data of the average total kinetic energy as a function of incident neutron energy. The resulting evaluated data and covariances agree well with the experimental database used for the evaluation. However, the evaluated spectra are softer than the 235U and 239Pu ENDF/B-VII.1, JENDL-4.0 and JEFF-3.2 evaluations for incident neutron energies E inc ≤ 1.5 MeV and E inc ≤ 5 MeV, respectively. For E inc > 5 MeV, the evaluated spectra show structures due to the improved modeling which are not present in ENDF/B-VII.1 and JEFF-3.2 but can be observed in JENDL-4.0 evaluations. Part of these new evaluations were adopted for ENDF/B-VIII.0, while the ENDF/B-VII.1 239Pu PFNS was retained for E inc ≤ 5 MeV awaiting more conclusive experimental evidence.« less

Study of large Forbush decreases in cosmic-ray intensity observed during solar cycle 23 and 24

NASA Astrophysics Data System (ADS)

Kumar, Anand; Badruddin, B.

2016-07-01

Neutron monitors at different geomagnetic latitude and longitude of Earth measure the cosmic-ray intensity with high precision. Sudden decreases in cosmic-ray intensity within few hours and slow recovery to pre-decrease level within a few days (Forbush decreases) are observed in neutron monitor data. We identify large-amplitude Forbush decreases (FDs), using high counting rate neutron monitor data, that occurred during previous solar cycle 23 (1995-2009) and current solar cycle 24 (2010-2015). We then search for the solar sources and the interplanetary structures responsible for these decreases. We attempt to find the relative importance of various interplanetary plasma and field parameters and the physical mechanism(s) responsible for FDs of varying amplitudes. We analyze a number of interplanetary plasma and field parameters, during both the phases (main and recovery) of FDs. The interplanetary plasma and field data analyzed in this study are the solar-wind velocity, the interplanetary magnetic field, its fluctuations, interplanetary electric field and the time variation of interplanetary electric potential. For monitoring the changes in interplanetary plasma/field conditions during the development of FDs, we also utilize plasma density, temperature and plasma beta, dynamic pressure and Mach number during the passage of interplanetary structures responsible for FDs. In addition to their amplitude, we study the recovery of FDs in detail after determining the time constant during their recovery by exponential fit to the data. As the solar magnetic polarity reversed during the maximum phase of solar cycle 23 (in the year 2000), we study the differences in amplitude, time constant of recovery and plasma/field condition to search for the polarity dependent effects, if any, on the amplitude and recovery of FDs due to implication for the models suggested to explain the Forbush decrease phenomena. The implications of these results are discussed.

X-ray and Neutron Scattering Study of the Formation of Core–Shell-Type Polyoxometalates

DOE PAGES

Yin, Panchao; Wu, Bin; Mamontov, Eugene; ...

2016-02-05

A typical type of core-shell polyoxometalates can be obtained through the Keggin-type polyoxometalate-templated growth of a layer of spherical shell structure of {Mo 72Fe 30}. Small angle X-ray scattering is used to study the structural features and stability of the core-shell structures in aqueous solutions. Time-resolved small angle X-ray scattering is applied to monitor the synthetic reactions and a three-stage formation mechanism is proposed to describe the synthesis of the core-shell polyoxometalates based on the monitoring results. Quasi-elastic and inelastic neutron scattering are used to probe the dynamics of water molecules in the core-shell structures and two different types ofmore » water molecules, the confined and structured water, are observed. These water molecules play an important role in bridging core and shell structures and stabilizing the cluster structures. A typical type of core shell polyoxometalates can be obtained through the Keggin-type polyoxometalate-templated growth of a layer of spherical shell structure of {Mo 72Fe 30}. Small-angle X-ray scattering is used to study the structural features and stability of the core shell structures in aqueous solutions. Time-resolved small-angle X-ray scattering is applied to monitor the synthetic reactions, and a three-stage formation mechanism is proposed to describe the synthesis of the core shell polyoxometalates based on the monitoring results. New protocols have been developed by fitting the X-ray data with custom physical models, which provide more convincing, objective, and completed data interpretation. Quasi-elastic and inelastic neutron scattering are used to probe the dynamics of water molecules in the core shell structures, and two different types of water molecules, the confined and structured water, are observed. These water molecules play an important role in bridging core and shell structures and stabilizing the cluster structures.« less

Database Performance Monitoring for the Photovoltaic Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klise, Katherine A.

The Database Performance Monitoring (DPM) software (copyright in processes) is being developed at Sandia National Laboratories to perform quality control analysis on time series data. The software loads time indexed databases (currently csv format), performs a series of quality control tests defined by the user, and creates reports which include summary statistics, tables, and graphics. DPM can be setup to run on an automated schedule defined by the user. For example, the software can be run once per day to analyze data collected on the previous day. HTML formatted reports can be sent via email or hosted on a website.more » To compare performance of several databases, summary statistics and graphics can be gathered in a dashboard view which links to detailed reporting information for each database. The software can be customized for specific applications.« less

The 14 MeV Neutron Irradiation Facility in MARIA Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prokopowicz, R.; Pytel, K.; Dorosz, M.

2015-07-01

The MARIA reactor with thermal neutron flux density up to 3x10{sup 14} cm{sup -2} s{sup -1} and a number of vertical channels is well suited to material testing by thermal neutron treatment. Beside of that some fast neutron irradiation facilities are operated in MARIA reactor as well. One of them is thermal to 14 MeV neutron converter launched in 2014. It is especially devoted to fusion devices material testing irradiation. The ITER and DEMO research thermonuclear facilities are to be run using the deuterium - tritium fusion reaction. Fast neutrons (of energy approximately 14 MeV) resulting from the reaction aremore » essential to carry away the released thermonuclear energy and to breed tritium. However, constructional materials of which thermonuclear reactors are to be built must be specially selected to survive intense fluxes of fast neutrons. Strong sources of 14 MeV neutrons are needed if research on resistance of candidate materials to such fluxes is to be carried out effectively. Nuclear reactor-based converter capable to convert thermal neutrons into 14 MeV fast neutrons may be used to that purpose. The converter based on two stage nuclear reaction on lithium-6 and deuterium compounds leading to 14 MeV neutron production. The reaction chain is begun by thermal neutron capture by lithium-6 nucleus resulted in triton release. The neutron and triton transport calculations have been therefore carried-out to estimate the thermal to 14 MeV neutron conversion efficiency and optimize converter construction. The usable irradiation space of ca. 60 cm{sup 3} has been obtained. The released energy have been calculated. Heat transport has been asses to ensure proper device cooling. A set of thermocouples has been installed in converter to monitor its temperature distribution on-line. Influence of converter on reactor operation has been studied. Safety analyses of steady states and transients have been done. Performed calculations and analyses allow designing the converter and formulate its operation limits and conditions. During first tested operation of the converter the 14 MeV neutron flux density was estimated to 10{sup 9} cm{sup -2} s{sup -1}, whereas fast fission neutrons inside converter achieved 10{sup 12} cm{sup -2} s{sup -1}, and thermal neutrons were reduced down to 109 cm-2 s-1. Taking into account the feasibility of almost incessant converter operation for a number of months, its arisen as one of the most powerful (in terms of fluence), currently available 14 MeV neutron source. Such a converter currently under operation in the MARIA reactor core will be presented. (authors)« less

Performance of the SciBar cosmic ray telescope (SciCRT) toward the detection of high-energy solar neutrons in solar cycle 24

NASA Astrophysics Data System (ADS)

Sasai, Yoshinori; Nagai, Yuya; Itow, Yoshitaka; Matsubara, Yutaka; Sako, Takashi; Lopez, Diego; Itow, Tsukasa; Munakata, Kazuoki; Kato, Chihiro; Kozai, Masayoshi; Miyazaki, Takahiro; Shibata, Shoichi; Oshima, Akitoshi; Kojima, Hiroshi; Tsuchiya, Harufumi; Watanabe, Kyoko; Koi, Tatsumi; Valdés-Galicia, Jose Francisco; González, Luis Xavier; Ortiz, Ernesto; Musalem, Octavio; Hurtado, Alejandro; Garcia, Rocio; Anzorena, Marcos

2014-12-01

We plan to observe solar neutrons at Mt. Sierra Negra (4,600 m above sea level) in Mexico using the SciBar detector. This project is named the SciBar Cosmic Ray Telescope (SciCRT). The main aims of the SciCRT project are to observe solar neutrons to study the mechanism of ion acceleration on the surface of the sun and to monitor the anisotropy of galactic cosmic-ray muons. The SciBar detector, a fully active tracker, is composed of 14,848 scintillator bars, whose dimension is 300 cm × 2.5 cm × 1.3 cm. The structure of the detector enables us to obtain the particle trajectory and its total deposited energy. This information is useful for the energy reconstruction of primary neutrons and particle identification. The total volume of the detector is 3.0 m × 3.0 m × 1.7 m. Since this volume is much larger than the solar neutron telescope (SNT) in Mexico, the detection efficiency of the SciCRT for neutrons is highly enhanced. We performed the calibration of the SciCRT at Instituto Nacional de Astrofisica, Optica y Electronica (INAOE) located at 2,150 m above sea level in Mexico in 2012. We installed the SciCRT at Mt. Sierra Negra in April 2013 and calibrated this detector in May and August 2013. We started continuous observation in March 2014. In this paper, we report the detector performance as a solar neutron telescope and the current status of the SciCRT.

Neutron Measurements for Radiation Protection in Low Earth Orbit - History and Future

NASA Technical Reports Server (NTRS)

Golightly, M. J.; Se,pmes. E/

2003-01-01

The neutron environment inside spacecraft has been of interest from a scientific and radiation protection perspective since early in the history of manned spaceflight. With 1:.1e exception of a few missions which carried plutonium-fueled radioisotope thermoelectric generators, all of the neutrons inside the spacecraft are secondary radiations resulting from interactions of high-energy charged particles with nuclei in the Earth's atmosphere, spacecraft structural materials, and the astronaut's own bodies. Although of great interest, definitive measurements of the spacecraft neutron field have been difficult due to the wide particle energy range and the limited available volume and power for traditional techniques involving Bonner spheres. A multitude of measurements, however, have been made of the neutron environment inside spacecraft. The majority of measurements were made using passive techniques including metal activation fo ils, fission foils, nuclear photoemulsions, plastic track detectors, and thermoluminescent detectors. Active measurements have utilized proton recoil spectrometers (stilbene), Bonner Spheres eRe proportional counter based), and LiI(Eu)phoswich scintillation detectors. For the International Space Station (ISS), only the plastic track! thermoluminescent detectors are used with any regularity. A monitoring program utilizing a set of active Bonner spheres was carried out in the ISS Lab module from March - December 200l. These measurements provide a very limited look at the crew neutron exposure, both in time coverage and neutron energy coverage. A review of the currently published data from past flights will be made and compared with the more recent results from the ISS. Future measurement efforts using currently available techniques and those in development will be also discussed.

Design and verification of the shielding around the new Neutron Standards Laboratory (LPN) at CIEMAT.

PubMed

Méndez-Villafañe, R; Guerrero, J E; Embid, M; Fernández, R; Grandio, R; Pérez-Cejuela, P; Márquez, J L; Alvarez, F; Ortego, P

2014-10-01

The construction of the new Neutron Standards Laboratory at CIEMAT (Laboratorio de Patrones Neutrónicos) has been finalised and is ready to provide service. The facility is an ∼8 m×8 m×8 m irradiation vault, following the International Organization for Standardization 8529 recommendations. It relies on several neutron sources: a 5-GBq (5.8× 10(8) s(-1)) (252)Cf source and two (241)Am-Be neutron sources (185 and 11.1 GBq). The irradiation point is located 4 m over the ground level and in the geometrical centre of the room. Each neutron source can be moved remotely from its storage position inside a water pool to the irradiation point. Prior to this, an important task to design the neutron shielding and to choose the most appropriate materials has been developed by the Radiological Security Unit and the Ionizing Radiations Metrology Laboratory. MCNPX was chosen to simulate the irradiation facility. With this information the walls were built with a thickness of 125 cm. Special attention was put on the weak points (main door, air conditioning system, etc.) so that the ambient dose outside the facility was below the regulatory limits. Finally, the Radiation Protection Unit carried out a set of measurements in specific points around the installation with an LB6411 neutron monitor and a Reuter-Stokes high-pressure ion chamber to verify experimentally the results of the simulation. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

A NEW SYSTEM TO MONITOR DATA ANALYSES AND RESULTS OF PHYSICS DATA VALIDATION BETWEEN PULSES AT DIII-D

DOE Office of Scientific and Technical Information (OSTI.GOV)

FLANAGAN,A; SCHACHTER,J.M; SCHISSEL,D.P

2003-02-01

A Data Analysis Monitoring (DAM) system has been developed to monitor between pulse physics analysis at the DIII-D National Fusion Facility (http://nssrv1.gat.com:8000/dam). The system allows for rapid detection of discrepancies in diagnostic measurements or the results from physics analysis codes. This enables problems to be detected and possibly fixed between pulses as opposed to after the experimental run has concluded thus increasing the efficiency of experimental time. An example of a consistency check is comparing the experimentally measured neutron rate and the expected neutron emission, RDD0D. A significant difference between these two values could indicate a problem with one ormore » more diagnostics, or the presence of unanticipated phenomena in the plasma. This new system also tracks the progress of MDSplus dispatched data analysis software and the loading of analyzed data into MDSplus. DAM uses a Java Servlet to receive messages, CLIPS to implement expert system logic, and displays its results to multiple web clients via HTML. If an error is detected by DAM, users can view more detailed information so that steps can be taken to eliminate the error for the next pulse.« less

System to monitor data analyses and results of physics data validation between pulses at DIII-D

NASA Astrophysics Data System (ADS)

Flanagan, S.; Schachter, J. M.; Schissel, D. P.

2004-06-01

A data analysis monitoring (DAM) system has been developed to monitor between pulse physics analysis at the DIII-D National Fusion Facility (http://nssrv1.gat.com:8000/dam). The system allows for rapid detection of discrepancies in diagnostic measurements or the results from physics analysis codes. This enables problems to be detected and possibly fixed between pulses as opposed to after the experimental run has concluded, thus increasing the efficiency of experimental time. An example of a consistency check is comparing the experimentally measured neutron rate and the expected neutron emission, RDD0D. A significant difference between these two values could indicate a problem with one or more diagnostics, or the presence of unanticipated phenomena in the plasma. This system also tracks the progress of MDSplus dispatched data analysis software and the loading of analyzed data into MDSplus. DAM uses a Java Servlet to receive messages, C Language Integrated Production System to implement expert system logic, and displays its results to multiple web clients via Hypertext Markup Language. If an error is detected by DAM, users can view more detailed information so that steps can be taken to eliminate the error for the next pulse.

Concept for Inclusion of Analytical and Computational Capability in Optical Plume Anomaly Detection (OPAD) for Measurement of Neutron Flux

NASA Technical Reports Server (NTRS)

Patrick, M. Clinton; Cooper, Anita E.; Powers, W. T.

2004-01-01

Researchers are working on many konts to make possible high speed, automated classification and quantification of constituent materials in numerous environments. NASA's Marshall Space Flight Center has implemented a system for rocket engine flow fields/plumes; the Optical Plume Anomaly Detection (OPAD) system was designed to utilize emission and absorption spectroscopy for monitoring molecular and atomic particulates in gas plasma. An accompanying suite of tools and analytical package designed to utilize information collected by OPAD is known as the Engine Diagnostic Filtering System (EDIFIS). The current combination of these systems identifies atomic and molecular species and quantifies mass loss rates in H2/O2 rocket plumes. Additionally, efforts are being advanced to hardware encode components of the EDIFIS in order to address real-time operational requirements for health monitoring and management. This paper addresses the OPAD with its tool suite, and discusses what is considered a natural progression: a concept for migrating OPAD towards detection of high energy particles, including neutrons and gamma rays. The integration of these tools and capabilities will provide NASA with a systematic approach to monitor space vehicle internal and external environment.

Airborne Detection of Cosmic-Ray Albedo Neutrons for Regional-Scale Surveys of Root-Zone Soil Water on Earth

NASA Astrophysics Data System (ADS)

Schrön, M.; Bannehr, L.; Köhli, M.; Zreda, M. G.; Weimar, J.; Zacharias, S.; Oswald, S. E.; Bumberger, J.; Samaniego, L. E.; Schmidt, U.; Zieger, P.; Dietrich, P.

2017-12-01

While the detection of albedo neutrons from cosmic rays became a standard method in planetary space science, airborne neutron sensing has never been conceived for hydrological research on Earth. We assessed the applicability of atmospheric neutrons to sense root-zone soil moisture averaged over tens of hectares using neutron detectors on an airborne vehicle. Large-scale quantification of near-surface water content is an urgent challenge in hydrology. Information about soil and plant water is crucial to accurately assess the risks for floods and droughts, to adjust regional weather forecasts, and to calibrate and validate the corresponding models. However, there is a lack of data at scales relevant for these applications. Most conventional ground-based geophysical instruments provide root-zone soil moisture only within a few tens of m2, while electromagnetic signals from conventional remote-sensing instruments can only penetrate the first few centimeters below surface, though at larger spatial areas.In the last couple of years, stationary and roving neutron detectors have been used to sense the albedo component of cosmic-ray neutrons, which represents the average water content within 10—15 hectares and 10—50 cm depth. However, the application of these instruments is limited by inaccessible terrain and interfering local effects from roads. To overcome these limitations, we have pioneered first simulations and experiments of such sensors in the field of airborne geophysics. Theoretical investigations have shown that the footprint increases substantially with height above ground, while local effects smooth out throughout the whole area. Campaigns with neutron detectors mounted on a lightweight gyrocopter have been conducted over areas of various landuse types including agricultural fields, urban areas, forests, flood plains, and lakes. The neutron signal showed influence of soil moisture patterns in heights of up to 180 m above ground. We found correlation with ground-truthing data, using mobile cosmic-ray neutron sensors, local soil samples, TDR, and buried wireless soil moisture monitoring networks. The work opens the path towards further systematic assessment of airborne neutron sensing, which could become a valuable addition - or even an alternative - to conventional remote-sensing methods.

In vivo and phantom measurements of the secondary photon and neutron doses for prostate patients undergoing 18 MV IMRT.

PubMed

Reft, Chester S; Runkel-Muller, Renate; Myrianthopoulos, Leon

2006-10-01

For intensity modulated radiation therapy (IMRT) treatments 6 MV photons are typically used, however, for deep seated tumors in the pelvic region, higher photon energies are increasingly being employed. IMRT treatments require more monitor units (MU) to deliver the same dose as conformal treatments, causing increased secondary radiation to tissues outside the treated area from leakage and scatter, as well as a possible increase in the neutron dose from photon interactions in the machine head. Here we provide in vivo patient and phantom measurements of the secondary out-of-field photon radiation and the neutron dose equivalent for 18 MV IMRT treatments. The patients were treated for prostate cancer with 18 MV IMRT at institutions using different therapy machines and treatment planning systems. Phantom exposures at the different facilities were used to compare the secondary photon and neutron dose equivalent between typical IMRT delivered treatment plans with a six field three-dimensional conformal radiotherapy (3DCRT) plan. For the in vivo measurements LiF thermoluminescent detectors (TLDs) and Al2O3 detectors using optically stimulated radiation were used to obtain the photon dose and CR-39 track etch detectors were used to obtain the neutron dose equivalent. For the phantom measurements a Bonner sphere (25.4 cm diameter) containing two types of TLDs (TLD-600 and TLD-700) having different thermal neutron sensitivities were used to obtain the out-of-field neutron dose equivalent. Our results showed that for patients treated with 18 MV IMRT the photon dose equivalent is greater than the neutron dose equivalent measured outside the treatment field and the neutron dose equivalent normalized to the prescription dose varied from 2 to 6 mSv/Gy among the therapy machines. The Bonner sphere results showed that the ratio of neutron equivalent doses for the 18 MV IMRT and 3DCRT prostate treatments scaled as the ratio of delivered MUs. We also observed differences in the measured neutron dose equivalent among the three therapy machines for both the in vivo and phantom exposures.

[Implementation of Oncomelania hupensis monitoring system based on Baidu Map].

PubMed

Zhi-Hua, Chen; Yi-Sheng, Zhu; Zhi-Qiang, Xue; Xue-Bing, Li; Yi-Min, Ding; Li-Jun, Bi; Kai-Min, Gao; You, Zhang

2017-10-25

To construct the Oncomelania hupensis snail monitoring system based on the Baidu Map. The environmental basic information about historical snail environment and existing snail environment, etc. was collected with the monitoring data about different kinds of O. hupensis snails, and then the O. hupensis snail monitoring system was built. Geographic Information System (GIS) and the electronic fence technology and Application Program Interface (API) were applied to set up the electronic fence of the snail surveillance environments, and the electronic fence was connected to the database of the snail surveillance. The O. hupensis snail monitoring system based on the Baidu Map were built up, including three modules of O. hupensis Snail Monitoring Environmental Database, Dynamic Monitoring Platform and Electronic Map. The information about monitoring O. hupensis snails could be obtained through the computer and smartphone simultaneously. The O. hupensis snail monitoring system, which is based on Baidu Map, is a visible platform to follow the process of snailsearching and molluscaciding.

Investigation of fusion reactions in palladium and titanium tritide using galvanostatic, coulometric, and hydrogen permeation techniques

NASA Astrophysics Data System (ADS)

Guilinger, T. R.; Kelly, M. J.; Scully, J. R.; Christensen, T. M.; Ingersoll, D.; Knapp, J. A.; Ewing, R. I.; Casey, W. H.; Tsao, S. S.

1990-09-01

We describe several electrochemical methods used to investigate the possibility of cold fusion phenomena in palladium and titanium tritide cathodes. We performed long-term (up to 77 days) electrolysis experiments with electrochemical cells of the University of Utah type at current densities as high as 1 A/cm2, while monitoring neutron and tritium levels. With some cells, we pulsed the current to determine if neutron bursts would result. In another cell, we used titanium tritide as the cathode to determine if D-T reactions yielding neutrons would occur. In no instance were levels of neutrons or tritium significantly above background except in the titanium tritide cell where isotopic exchange, occcurring between the electrode and the electrolyte, resulted in significant tritium levels. We also combined x-ray photoelectron spectroscopy (XPS) and electrochemical hydrogen permeation experiments to determine the effectiveness of various Pd surface treatment procedures on the resultant electrochemical hydrogen absorption efficiency. Electroanalytical and thermal desorption/gas analysis techniques indicated the maximum loading of H in Pd was to a ratio of H∶Pd=0.8.

Piezoelectric Materials Under Natural and Man-Made Radiation: The Potential for Direct Radiation Detection

NASA Astrophysics Data System (ADS)

Wart, Megan; Simpson, Evan; Flaska, Marek

2018-01-01

Radiation detection systems used for monitoring long term waste storage need to be compact, rugged, and have low or no power requirements. By using piezoelectric materials it may be possible to create a reliable self-powered radiation detection system. To determine the feasibility of this approach, the electrical signal response of the piezoelectric materials to radiation must be characterized. To do so, an experimental geometry has been designed and a neutron source has been chosen as described in this paper, which will be used to irradiate a uranium foil for producing fission fragments. These future experiments will be aimed at finding the threshold of exposure of lead zirconate titanate (PZT) plates needed to produce and electrical signal. Based on the proposed experimental geometry the thermal neutron beam-line at the Breazeale Reactor at The Pennsylvania State University will be used as the neutron source. The uranium foil and neutron source will be able to supply a maximum flux of 1.5e5 fission fragments/second*cm2 to each of the PZT plates.

Radiation tolerance of piezoelectric bulk single-crystal aluminum nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

David A. Parks; Bernhard R. Tittmann

2014-07-01

For practical use in harsh radiation environments, we pose selection criteria for piezoelectric materials for nondestructive evaluation (NDE) and material characterization. Using these criteria, piezoelectric aluminum nitride is shown to be an excellent candidate. The results of tests on an aluminumnitride-based transducer operating in a nuclear reactor are also presented. We demonstrate the tolerance of single-crystal piezoelectric aluminum nitride after fast and thermal neutron fluences of 1.85 × 1018 neutron/cm2 and 5.8 × 1018 neutron/cm2, respectively, and a gamma dose of 26.8 MGy. The radiation hardness of AlN is most evident from the unaltered piezoelectric coefficient d33, which measured 5.5more » pC/N after a fast and thermal neutron exposure in a nuclear reactor core for over 120 MWh, in agreement with the published literature value. The results offer potential for improving reactor safety and furthering the understanding of radiation effects on materials by enabling structural health monitoring and NDE in spite of the high levels of radiation and high temperatures, which are known to destroy typical commercial ultrasonic transducers.« less

The 13C(n,α0)10Be cross section at 14.3 MeV and 17 MeV neutron energy

NASA Astrophysics Data System (ADS)

Kavrigin, P.; Belloni, F.; Frais-Koelbl, H.; Griesmayer, E.; Plompen, A. J. M.; Schillebeeckx, P.; Weiss, C.

2017-09-01

At nuclear fusion reactors, CVD diamond detectors are considered an advantageous solution for neutron flux monitoring. For such applications the knowledge of the cross section of neutron-induced nuclear reactions on natural carbon are of high importance. Especially the (n,α0) reactions, yielding the highest energy reaction products, are of relevance as they can be clearly distinguished in the spectrum. The 13C(n,α0)10Be cross section was measured relative to 12C(n,α0)9Be at the Van de Graaff facility of EC-JRC Geel, Belgium, at 14.3 MeV and 17.0 MeV neutron energies. The measurement was performed with an sCVD (single-crystal Chemical Vapor Deposition) diamond detector, where the detector material acted simultaneously as sample and as sensor. A novel data analysis technique, based on pulse-shape discrimination, allowed an efficient reduction of background events. The results of the measurement are presented and compared to previously published values for this cross-section.

In situ high-pressure measurement of crystal solubility by using neutron diffraction

NASA Astrophysics Data System (ADS)

Chen, Ji; Hu, Qiwei; Fang, Leiming; He, Duanwei; Chen, Xiping; Xie, Lei; Chen, Bo; Li, Xin; Ni, Xiaolin; Fan, Cong; Liang, Akun

2018-05-01

Crystal solubility is one of the most important thermo-physical properties and plays a key role in industrial applications, fundamental science, and geoscientific research. However, high-pressure in situ measurements of crystal solubility remain very challenging. Here, we present a method involving high-pressure neutron diffraction for making high-precision in situ measurements of crystal solubility as a function of pressure over a wide range of pressures. For these experiments, we designed a piston-cylinder cell with a large chamber volume for high-pressure neutron diffraction. The solution pressures are continuously monitored in situ based on the equation of state of the sample crystal. The solubility at a high pressure can be obtained by applying a Rietveld quantitative multiphase analysis. To evaluate the proposed method, we measured the high-pressure solubility of NaCl in water up to 610 MPa. At a low pressure, the results are consistent with the previous results measured ex situ. At a higher pressure, more reliable data could be provided by using an in situ high-pressure neutron diffraction method.

Cross-section measurement for the 67Zn(n, α)64Ni reaction at 6.0 MeV

NASA Astrophysics Data System (ADS)

Zhang, Guohui; Wu, Hao; Zhang, Jiaguo; Liu, Jiaming; Chen, Jinxiang; Gledenov, Yu. M.; Sedysheva, M. V.; Khuukhenkhuu, G.; Szalanski, P. J.

2010-01-01

Up to now, no experimental cross-section data exist for the 67Zn ( n, α) 64Ni reaction in the MeV neutron energy region. In the present work, the cross-section of the 67Zn ( n, α) 64Ni reaction was measured at E n = 6.0 MeV. Experiments were performed at the Van de Graaff accelerator of Peking University, China. Fast neutrons were produced through the D ( d, n) 3He reaction using a deuterium gas target. Absolute neutron flux was determined by a small 238U fission chamber and a BF3 long counter was used as a neutron flux monitor. A twin gridded ionization chamber was employed as the α -particle detector and two back-to-back 67Zn samples were used for α events measurement. Background was measured and subtracted from foreground. The measured cross-section of the 67Zn ( n, α) 64Ni reaction was 7.3 (1±15%) mb at 6.0MeV. The present result was compared with existing evaluations and TALYS code calculations.

Fleet-Wide Prognostic and Health Management Suite: Asset Fault Signature Database

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vivek Agarwal; Nancy J. Lybeck; Randall Bickford

Proactive online monitoring in the nuclear industry is being explored using the Electric Power Research Institute’s Fleet-Wide Prognostic and Health Management (FW-PHM) Suite software. The FW-PHM Suite is a set of web-based diagnostic and prognostic tools and databases that serves as an integrated health monitoring architecture. The FW-PHM Suite has four main modules: (1) Diagnostic Advisor, (2) Asset Fault Signature (AFS) Database, (3) Remaining Useful Life Advisor, and (4) Remaining Useful Life Database. The paper focuses on the AFS Database of the FW-PHM Suite, which is used to catalog asset fault signatures. A fault signature is a structured representation ofmore » the information that an expert would use to first detect and then verify the occurrence of a specific type of fault. The fault signatures developed to assess the health status of generator step-up transformers are described in the paper. The developed fault signatures capture this knowledge and implement it in a standardized approach, thereby streamlining the diagnostic and prognostic process. This will support the automation of proactive online monitoring techniques in nuclear power plants to diagnose incipient faults, perform proactive maintenance, and estimate the remaining useful life of assets.« less

The roles of nearest neighbor methods in imputing missing data in forest inventory and monitoring databases

Treesearch

Bianca N. I. Eskelson; Hailemariam Temesgen; Valerie Lemay; Tara M. Barrett; Nicholas L. Crookston; Andrew T. Hudak

2009-01-01

Almost universally, forest inventory and monitoring databases are incomplete, ranging from missing data for only a few records and a few variables, common for small land areas, to missing data for many observations and many variables, common for large land areas. For a wide variety of applications, nearest neighbor (NN) imputation methods have been developed to fill in...

Advances in Neutron Radiography: Application to Additive Manufacturing Inconel 718

DOE PAGES

Bilheux, Hassina Z; Song, Gian; An, Ke; ...

2016-01-01

Reactor-based neutron radiography is a non-destructive, non-invasive characterization technique that has been extensively used for engineering materials such as inspection of components, evaluation of porosity, and in-operando observations of engineering parts. Neutron radiography has flourished at reactor facilities for more than four decades and is relatively new to accelerator-based neutron sources. Recent advances in neutron source and detector technologies, such as the Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory (ORNL) in Oak Ridge, TN, and the microchannel plate (MCP) detector, respectively, enable new contrast mechanisms using the neutron scattering Bragg features for crystalline information such as averagemore » lattice strain, crystalline plane orientation, and identification of phases in a neutron radiograph. Additive manufacturing (AM) processes or 3D printing have recently become very popular and have a significant potential to revolutionize the manufacturing of materials by enabling new designs with complex geometries that are not feasible using conventional manufacturing processes. However, the technique lacks standards for process optimization and control compared to conventional processes. Residual stresses are a common occurrence in materials that are machined, rolled, heat treated, welded, etc., and have a significant impact on a component s mechanical behavior and durability. They may also arise during the 3D printing process, and defects such as internal cracks can propagate over time as the component relaxes after being removed from its build plate (the base plate utilized to print materials on). Moreover, since access to the AM material is possible only after the component has been fully manufactured, it is difficult to characterize the material for defects a priori to minimize expensive re-runs. Currently, validation of the AM process and materials is mainly through expensive trial-and-error experiments at the component level, whereas in conventional processes the level of confidence in predictive computational modeling is high enough to allow process and materials optimization through computational approaches. Thus, there is a clear need for non-destructive characterization techniques and for the establishment of processing- microstructure databases that can be used for developing and validating predictive modeling tools for AM.« less

The Epimed Monitor ICU Database®: a cloud-based national registry for adult intensive care unit patients in Brazil.

PubMed

Zampieri, Fernando Godinho; Soares, Márcio; Borges, Lunna Perdigão; Salluh, Jorge Ibrain Figueira; Ranzani, Otávio Tavares

2017-01-01

To describe the Epimed Monitor Database®, a Brazilian intensive care unit quality improvement database. We described the Epimed Monitor® Database, including its structure and core data. We presented aggregated informative data from intensive care unit admissions from 2010 to 2016 using descriptive statistics. We also described the expansion and growth of the database along with the geographical distribution of participating units in Brazil. The core data from the database includes demographic, administrative and physiological parameters, as well as specific report forms used to gather detailed data regarding the use of intensive care unit resources, infectious episodes, adverse events and checklists for adherence to best clinical practices. As of the end of 2016, 598 adult intensive care units in 318 hospitals totaling 8,160 intensive care unit beds were participating in the database. Most units were located at private hospitals in the southeastern region of the country. The number of yearly admissions rose during this period and included a predominance of medical admissions. The proportion of admissions due to cardiovascular disease declined, while admissions due to sepsis or infections became more common. Illness severity (Simplified Acute Physiology Score - SAPS 3 - 62 points), patient age (mean = 62 years) and hospital mortality (approximately 17%) remained reasonably stable during this time period. A large private database of critically ill patients is feasible and may provide relevant nationwide epidemiological data for quality improvement and benchmarking purposes among the participating intensive care units. This database is useful not only for administrative reasons but also for the improvement of daily care by facilitating the adoption of best practices and use for clinical research.

Monitoring product safety in the postmarketing environment.

PubMed

Sharrar, Robert G; Dieck, Gretchen S

2013-10-01

The safety profile of a medicinal product may change in the postmarketing environment. Safety issues not identified in clinical development may be seen and need to be evaluated. Methods of evaluating spontaneous adverse experience reports and identifying new safety risks include a review of individual reports, a review of a frequency distribution of a list of the adverse experiences, the development and analysis of a case series, and various ways of examining the database for signals of disproportionality, which may suggest a possible association. Regulatory agencies monitor product safety through a variety of mechanisms including signal detection of the adverse experience safety reports in databases and by requiring and monitoring risk management plans, periodic safety update reports and postauthorization safety studies. The United States Food and Drug Administration is working with public, academic and private entities to develop methods for using large electronic databases to actively monitor product safety. Important identified risks will have to be evaluated through observational studies and registries.