A Review of Radiolysis Concerns for Water Shielding in Fission Surface Power Applications

NASA Technical Reports Server (NTRS)

Schoenfeld, Michael P.

2008-01-01

This paper presents an overview of radiolysis concerns with regard to water shields for fission surface power. A review of the radiolysis process is presented and key parameters and trends are identified. From this understanding of the radiolytic decomposition of water, shield pressurization and corrosion are identified as the primary concerns. Existing experimental and modeling data addressing concerns are summarized. It was found that radiolysis of pure water in a closed volume results in minimal, if any net decomposition, and therefore reduces the potential for shield pressurization and corrosion. With the space program focus m emphasize more on permanent return to the Moon and eventually manned exploration of Mars, there has been a renewed look at fission power to meet the difficult technical & design challenges associated with this effort. This is due to the ability of fission power to provide a power rich environment that is insensitive to solar intensity and related aspects such as duration of night, dusty environments, and distance from the sun, etc. One critical aspect in the utilization of fission power for these applications of manned exploration is shielding. Although not typically considered for space applications, water shields have been identified as one potential option due to benefits in mass savings and reduced development cost and technical risk (Poston, 2006). However, the water shield option requires demonstration of its ability to meet key technical challenges including such things as adequate natural circulation for thermal management and capability for operational periods up to 8 years. Thermal management concerns have begun to be addressed and are not expected to be a problem (Pearson, 2007). One significant concern remaining is the ability to maintain the shield integrity through its operational lifetime. Shield integrity could be compromised through shield pressurization and corrosion resulting from the radiolytic decomposition of water.

LOADING DEVICE

DOEpatents

Ohlinger, L.A.

1958-10-01

A device is presented for loading or charging bodies of fissionable material into a reactor. This device consists of a car, mounted on tracks, into which the fissionable materials may be placed at a remote area, transported to the reactor, and inserted without danger to the operating personnel. The car has mounted on it a heavily shielded magazine for holding a number of the radioactive bodies. The magazine is of a U-shaped configuration and is inclined to the horizontal plane, with a cap covering the elevated open end, and a remotely operated plunger at the lower, closed end. After the fissionable bodies are loaded in the magazine and transported to the reactor, the plunger inserts the body at the lower end of the magazine into the reactor, then is withdrawn, thereby allowing gravity to roll the remaining bodies into position for successive loading in a similar manner.

Improved Fission Neutron Data Base for Active Interrogation of Actinides

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

Pozzi, Sara; Czirr, J. Bart; Haight, Robert

2013-11-06

This project will develop an innovative neutron detection system for active interrogation measurements. Many active interrogation methods to detect fissionable material are based on the detection of neutrons from fission induced by fast neutrons or high-energy gamma rays. The energy spectrum of the fission neutrons provides data to identify the fissionable isotopes and materials such as shielding between the fissionable material and the detector. The proposed path for the project is as follows. First, the team will develop new neutron detection systems and algorithms by Monte Carlo simulations and bench-top experiments. Next, They will characterize and calibrate detection systems bothmore » with monoenergetic and white neutron sources. Finally, high-fidelity measurements of neutron emission from fissions induced by fast neutrons will be performed. Several existing fission chambers containing U-235, Pu-239, U-238, or Th-232 will be used to measure the neutron-induced fission neutron emission spectra. The challenge for making confident measurements is the detection of neutrons in the energy ranges of 0.01 – 1 MeV and above 8 MeV, regions where the basic data on the neutron energy spectrum emitted from fission is least well known. In addition, improvements in the specificity of neutron detectors are required throughout the complete energy range: they must be able to clearly distinguish neutrons from other radiations, in particular gamma rays and cosmic rays. The team believes that all of these challenges can be addressed successfully with emerging technologies under development by this collaboration. In particular, the collaboration will address the area of fission neutron emission spectra for isotopes of interest in the advanced fuel cycle initiative (AFCI).« less

Three-dimensional Monte Carlo calculation of some nuclear parameters

NASA Astrophysics Data System (ADS)

Günay, Mehtap; Şeker, Gökmen

2017-09-01

In this study, a fusion-fission hybrid reactor system was designed by using 9Cr2WVTa Ferritic steel structural material and the molten salt-heavy metal mixtures 99-95% Li20Sn80 + 1-5% RG-Pu, 99-95% Li20Sn80 + 1-5% RG-PuF4, and 99-95% Li20Sn80 + 1-5% RG-PuO2, as fluids. The fluids were used in the liquid first wall, blanket and shield zones of a fusion-fission hybrid reactor system. Beryllium (Be) zone with the width of 3 cm was used for the neutron multiplication between the liquid first wall and blanket. This study analyzes the nuclear parameters such as tritium breeding ratio (TBR), energy multiplication factor (M), heat deposition rate, fission reaction rate in liquid first wall, blanket and shield zones and investigates effects of reactor grade Pu content in the designed system on these nuclear parameters. Three-dimensional analyses were performed by using the Monte Carlo code MCNPX-2.7.0 and nuclear data library ENDF/B-VII.0.

Active interrogation using low-energy nuclear reactions

NASA Astrophysics Data System (ADS)

Antolak, Arlyn; Doyle, Barney; Leung, Ka-Ngo; Morse, Daniel; Provencio, Paula

2005-09-01

High-energy photons and neutrons can be used to interrogate for heavily shielded fissile materials inside sealed cargo containers by detecting their prompt and/or delayed fission signatures. The FIND (Fissmat Inspection for Nuclear Detection) active interrogation system is based on a dual neutron+gamma source that uses low-energy (< 500 keV) proton- or deuteron-induced nuclear reactions to produce high intensities of mono-energetic gamma rays and/or neutrons. The source can be operated in either pulsed (e.g., to detect delayed photofission neutrons and gammas) or continuous (e.g., detecting prompt fission signatures) modes. For the gamma-rays, the source target can be segmented to incorporate different (p,γ) isotopes for producing gamma-rays at selective energies, thereby improving the probability of detection. The design parameters for the FIND system are discussed and preliminary accelerator-based measurements of gamma and neutron yields, background levels, and fission signals for several target materials under consideration are presented.

Structural Materials and Fuels for Space Power Plants

NASA Technical Reports Server (NTRS)

Bowman, Cheryl; Busby, Jeremy; Porter, Douglas

2008-01-01

A fission reactor combined with Stirling convertor power generation is one promising candidate in on-going Fission Surface Power (FSP) studies for future lunar and Martian bases. There are many challenges for designing and qualifying space-rated nuclear power plants. In order to have an affordable and sustainable program, NASA and DOE designers want to build upon the extensive foundation in nuclear fuels and structural materials. This talk will outline the current Fission Surface Power program and outline baseline design options for a lunar power plant with an emphasis on materials challenges. NASA first organized an Affordable Fission Surface Power System Study Team to establish a reference design that could be scrutinized for technical and fiscal feasibility. Previous papers and presentations have discussed this study process in detail. Considerations for the reference design included that no significant nuclear technology, fuels, or material development were required for near term use. The desire was to build upon terrestrial-derived reactor technology including conventional fuels and materials. Here we will present an overview of the reference design, Figure 1, and examine the materials choices. The system definition included analysis and recommendations for power level and life, plant configuration, shielding approach, reactor type, and power conversion type. It is important to note that this is just one concept undergoing refinement. The design team, however, understands that materials selection and improvement must be an integral part of the system development.

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

Active Proton Interrogation for Homeland Security

NASA Astrophysics Data System (ADS)

Greene, Steven; Morris, Christopher; Canavan, Gregory; Chung, Kiwhan; Elson, Jay; Hogan, Gary; Makela, Mark; Mariam, Fesseha; Murray, Matthew; Saunders, Alexander; Spaulding, Randy; Wang, Zhehui; Waters, Laurie; Wysocki, Frederick

2010-02-01

Energetic proton beams may provide an attractive technology for active interrogation of nuclear threats because: they have large fission cross sections, long mean free paths and high penetration, and proton beams can be manipulated with magnetic optics. We have measured time-dependent cross sections for delayed neutrons and gamma rays using 800 MeV protons from the Los Alamos Neutron Science Center and 4 GeV protons from the Brookhaven Alternating Gradient Synchrotron for a set of bare and shielded targets. The results show significant signals from both unshielded and shielded nuclear materials. Results will be presented. )

Scanning of vehicles for nuclear materials

NASA Astrophysics Data System (ADS)

Katz, J. I.

2014-05-01

Might a nuclear-armed terrorist group or state use ordinary commerce to deliver a nuclear weapon by smuggling it in a cargo container or vehicle? This delivery method would be the only one available to a sub-state actor, and it might enable a state to make an unattributed attack. Detection of a weapon or fissile material smuggled in this manner is difficult because of the large volume and mass available for shielding. Here I review methods for screening cargo containers to detect the possible presence of nuclear threats. Because of the large volume of innocent international commerce, and the cost and disruption of secondary screening by opening and inspection, it is essential that the method be rapid and have a low false-positive rate. Shielding can prevent the detection of neutrons emitted spontaneously or by induced fission. The two promising methods are muon tomography and high energy X-radiography. If they do not detect a shielded threat object they can detect the shield itself.

Scanning of vehicles for nuclear materials

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

Katz, J. I.

2014-05-09

Might a nuclear-armed terrorist group or state use ordinary commerce to deliver a nuclear weapon by smuggling it in a cargo container or vehicle? This delivery method would be the only one available to a sub-state actor, and it might enable a state to make an unattributed attack. Detection of a weapon or fissile material smuggled in this manner is difficult because of the large volume and mass available for shielding. Here I review methods for screening cargo containers to detect the possible presence of nuclear threats. Because of the large volume of innocent international commerce, and the cost andmore » disruption of secondary screening by opening and inspection, it is essential that the method be rapid and have a low false-positive rate. Shielding can prevent the detection of neutrons emitted spontaneously or by induced fission. The two promising methods are muon tomography and high energy X-radiography. If they do not detect a shielded threat object they can detect the shield itself.« less

Demonstrating the Viability and Affordability of Nuclear Surface Power Systems

NASA Technical Reports Server (NTRS)

Vandyke, Melissa K.

2006-01-01

A set of tasks have been identified to help demonstrate the viability, performance, and affordability of surface fission systems. Completion of these tasks will move surface fission systems closer to reality by demonstrating affordability and performance potential. Tasks include fabrication and test of a 19-pin section of a Surface Power Unit Demonstrator (SPUD); design, fabrication, and utilization of thermal simulators optimized for surface fission' applications; design, fabrication, and utilization of GPHS module thermal simulators; design, fabrication, and test of a fission surface power system shield; and work related to potential fission surface power fuel/clad systems. Work on the SPUD will feed directly into joint NASA MSFC/NASA GRC fabrication and test of a surface power plant Engineering Development Unit (EDU). The goal of the EDU will be to perform highly realistic thermal, structural, and electrical testing on an integrated fission surface power system. Fission thermal simulator work will help enable high fidelity non-nuclear testing of pumped NaK surface fission power systems. Radioisotope thermal simulator work will help enable design and development of higher power radioisotope systems (power ultimately limited by Pu-238 availability). Shield work is designed to assess the potential of using a water neutron shield on the surface of the moon. Fuels work is geared toward assessing the current potential of using fuels that have already flown in space.

PBF Reactor Building (PER620) basement, inside cubicle 13. Lead bricks ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

PBF Reactor Building (PER-620) basement, inside cubicle 13. Lead bricks shield the fission product detection system (FPDS). The system detected fission products in pressure loop from in-pile tube. shielding was to prevent other radiation in cubicle from interfering. Assembly of bricks in foreground will slide back to enclose and shield equipment in the three chambers. Date: 1982. INEEL negative no. 82-6376 - Idaho National Engineering Laboratory, SPERT-I & Power Burst Facility Area, Scoville, Butte County, ID

Detection of special nuclear material by observation of delayed neutrons with a novel fast neutron composite detector

NASA Astrophysics Data System (ADS)

Mayer, Michael; Nattress, Jason; Barhoumi Meddeb, Amira; Foster, Albert; Trivelpiece, Cory; Rose, Paul; Erickson, Anna; Ounaies, Zoubeida; Jovanovic, Igor

2015-10-01

Detection of shielded special nuclear material is crucial to countering nuclear terrorism and proliferation, but its detection is challenging. By observing the emission of delayed neutrons, which is a unique signature of nuclear fission, the presence of nuclear material can be inferred. We report on the observation of delayed neutrons from natural uranium by using monoenergetic photons and neutrons to induce fission. An interrogating beam of 4.4 MeV and 15.1 MeV gamma-rays and neutrons was produced using the 11B(d,n-γ)12C reaction and used to probe different targets. Neutron detectors with complementary Cherenkov detectors then discriminate material undergoing fission. A Li-doped glass-polymer composite neutron detector was used, which displays excellent n/ γ discrimination even at low energies, to observe delayed neutrons from uranium fission. Delayed neutrons have relatively low energies (~0.5 MeV) compared to prompt neutrons, which makes them difficult to detect using recoil-based detectors. Neutrons were counted and timed after the beam was turned off to observe the characteristic decaying time profile of delayed neutrons. The expected decay of neutron emission rate is in agreement with the common parametrization into six delayed neutron groups.

Detection of thermal-induced prompt fission neutrons of highly-enriched uranium: A position sensitive technique

NASA Astrophysics Data System (ADS)

Tartaglione, A.; Di Lorenzo, F.; Mayer, R. E.

2009-07-01

Cargo interrogation in search for special nuclear materials like highly-enriched uranium or 239Pu is a first priority issue of international borders security. In this work we present a thermal-pulsed neutron-based approach to a technique which combines the time-of-flight method and demonstrates a capability to detect small quantities of highly-enriched uranium shielded with high or low Z materials providing, in addition, a manner to know the approximate position of the searched material.

Selective perturbation of in vivo linear energy transfer using high- Z vaginal applicators for Cf-252 brachytherapy

NASA Astrophysics Data System (ADS)

Rivard, M. J.; Evans, K. E.; Leal, L. C.; Kirk, B. L.

2004-01-01

Californium-252 ( 252Cf) brachytherapy sources emit both neutrons and photons, and have the potential to vastly improve the current standard-of-practice for brachytherapy. While hydrogenous materials readily attenuate the 252Cf fission energy neutrons, high- Z materials are utilized to attenuate the 252Cf gamma-rays. These differences in shielding materials may be exploited when treating with a vaginal applicator to possibly improve patient survival through perturbation of the in vivo linear energy transfer radiation.

Active Interrogation of Depleted Uranium Using a Single Pulse, High-Intensity Photon and Mixed Photon-Neutron Source

NASA Astrophysics Data System (ADS)

Clemett, Ceri D.; Martin, Philip N.; Hill, Cassie; Threadgold, James R.; Maddock, Robert C.; Campbell, Ben; O'Malley, John; Woolf, Richard S.; Phlips, Bernard F.; Hutcheson, Anthony L.; Wulf, Eric A.; Zier, Jacob C.; Jackson, Stuart L.; Commisso, Robert J.; Schumer, Joseph W.

2015-04-01

Active interrogation is a method used to enhance the likelihood of detection of shielded special nuclear material (SNM); an external source of radiation is used to interrogate a target and to stimulate fission within any SNM present. Radiation produced by the fission process can be detected and used to infer the presence of the SNM. The Atomic Weapons Establishment (AWE) and the Naval Research Laboratory (NRL) have carried out a joint experimental study into the use of single pulse, high-intensity sources of bremsstrahlung x-rays and D(γb, n)H photoneutrons in an active interrogation system. The source was operated in both x-ray-only and mixed x-ray/photoneutron modes, and was used to irradiate a depleted uranium (DU) target which was enclosed by up to 150 g·cm - 2 of steel shielding. Resulting radiation signatures were measured by a suite of over 80 detectors and the data used to characterise detectable fission signatures as a function of the areal mass of the shielding. This paper describes the work carried out and discusses data collected with 3He proportional counters, NaI(Tl) scintillators and Eljen EJ-309 liquid scintillators. Results with the x-ray-only source demonstrate detection ( > 3\\sigmab) of the DU target through a minimum of 113 g·cm - 2 of steel, dropping to 85 g·cm- 2 when using a mixed x-ray/photoneutron source. The 3He proportional counters demonstrate detection ( > 3\\sigmab) of the DU target through the maximum 149. 7 g·cm - 2 steel shielding deployed for both photon and mixed x-ray/photoneutron sources.

Venting of fission products and shielding in thermionic nuclear reactor systems

NASA Technical Reports Server (NTRS)

Salmi, E. W.

1972-01-01

Most thermionic reactors are designed to allow the fission gases to escape out of the emitter. A scheme to allow the fission gases to escape is proposed. Because of the low activity of the fission products, this method should pose no radiation hazards.

Accelerator-based method of producing isotopes

DOEpatents

Nolen, Jr., Jerry A.; Gomes, Itacil C.

2015-11-03

The invention provides a method using accelerators to produce radio-isotopes in high quantities. The method comprises: supplying a "core" of low-enrichment fissile material arranged in a spherical array of LEU combined with water moderator. The array is surrounded by substrates which serve as multipliers and moderators as well as neutron shielding substrates. A flux of neutrons enters the low-enrichment fissile material and causes fissions therein for a time sufficient to generate desired quantities of isotopes from the fissile material. The radio-isotopes are extracted from said fissile material by chemical processing or other means.

Additional adjoint Monte Carlo studies of the shielding of concrete structures against initial gamma radiation. Final report

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

Beer, M.; Cohen, M.O.

1975-02-01

The adjoint Monte Carlo method previously developed by MAGI has been applied to the calculation of initial radiation dose due to air secondary gamma rays and fission product gamma rays at detector points within buildings for a wide variety of problems. These provide an in-depth survey of structure shielding effects as well as many new benchmark problems for matching by simplified models. Specifically, elevated ring source results were obtained in the following areas: doses at on-and off-centerline detectors in four concrete blockhouse structures; doses at detector positions along the centerline of a high-rise structure without walls; dose mapping at basementmore » detector positions in the high-rise structure; doses at detector points within a complex concrete structure containing exterior windows and walls and interior partitions; modeling of the complex structure by replacing interior partitions by additional material at exterior walls; effects of elevation angle changes; effects on the dose of changes in fission product ambient spectra; and modeling of mutual shielding due to external structures. In addition, point source results yielding dose extremes about the ring source average were obtained. (auth)« less

FIFRELIN - TRIPOLI-4® coupling for Monte Carlo simulations with a fission model. Application to shielding calculations

NASA Astrophysics Data System (ADS)

Petit, Odile; Jouanne, Cédric; Litaize, Olivier; Serot, Olivier; Chebboubi, Abdelhazize; Pénéliau, Yannick

2017-09-01

TRIPOLI-4® Monte Carlo transport code and FIFRELIN fission model have been coupled by means of external files so that neutron transport can take into account fission distributions (multiplicities and spectra) that are not averaged, as is the case when using evaluated nuclear data libraries. Spectral effects on responses in shielding configurations with fission sampling are then expected. In the present paper, the principle of this coupling is detailed and a comparison between TRIPOLI-4® fission distributions at the emission of fission neutrons is presented when using JEFF-3.1.1 evaluated data or FIFRELIN data generated either through a n/g-uncoupled mode or through a n/g-coupled mode. Finally, an application to a modified version of the ASPIS benchmark is performed and the impact of using FIFRELIN data on neutron transport is analyzed. Differences noticed on average reaction rates on the surfaces closest to the fission source are mainly due to the average prompt fission spectrum. Moreover, when working with the same average spectrum, a complementary analysis based on non-average reaction rates still shows significant differences that point out the real impact of using a fission model in neutron transport simulations.

Uncovering Special Nuclear Materials by Low-energy Nuclear Reaction Imaging.

PubMed

Rose, P B; Erickson, A S; Mayer, M; Nattress, J; Jovanovic, I

2016-04-18

Weapons-grade uranium and plutonium could be used as nuclear explosives with extreme destructive potential. The problem of their detection, especially in standard cargo containers during transit, has been described as "searching for a needle in a haystack" because of the inherently low rate of spontaneous emission of characteristic penetrating radiation and the ease of its shielding. Currently, the only practical approach for uncovering well-shielded special nuclear materials is by use of active interrogation using an external radiation source. However, the similarity of these materials to shielding and the required radiation doses that may exceed regulatory limits prevent this method from being widely used in practice. We introduce a low-dose active detection technique, referred to as low-energy nuclear reaction imaging, which exploits the physics of interactions of multi-MeV monoenergetic photons and neutrons to simultaneously measure the material's areal density and effective atomic number, while confirming the presence of fissionable materials by observing the beta-delayed neutron emission. For the first time, we demonstrate identification and imaging of uranium with this novel technique using a simple yet robust source, setting the stage for its wide adoption in security applications.

Neutron-multiplicity experiments for enhanced fission modelling

NASA Astrophysics Data System (ADS)

Al-Adili, Ali; Tarrío, Diego; Hambsch, Franz-Josef; Göök, Alf; Jansson, Kaj; Solders, Andreas; Rakapoulos, Vasileios; Gustavsson, Cecilia; Lantz, Mattias; Mattera, Andrea; Oberstedt, Stephan; Prokofiev, Alexander V.; Sundén, Erik A.; Vidali, Marzio; Österlund, Michael; Pomp, Stephan

2017-09-01

The nuclear de-excitation process of fission fragments (FF) provides fundamental information for the understanding of nuclear fission and nuclear structure in neutron-rich isotopes. The variation of the prompt-neutron multiplicity, ν(A), as a function of the incident neutron energy (En) is one of many open questions. It leads to significantly different treatments in various fission models and implies that experimental data are analyzed based on contradicting assumptions. One critical question is whether the additional excitation energy (Eexc) is manifested through an increase of ν(A) for all fragments or for the heavy ones only. A systematic investigation of ν(A) as a function of En has been initiated. Correlations between prompt-fission neutrons and fission fragments are obtained by using liquid scintillators in conjunction with a Frisch-grid ionization chamber. The proof-of-principle has been achieved on the reaction 235U(nth,f) at the Van De Graff (VdG) accelerator of the JRC-Geel using a fully digital data acquisition system. Neutrons from 252Cf(sf) were measured separately to quantify the neutron-scattering component due to surrounding shielding material and to determine the intrinsic detector efficiency. Prelimenary results on ν(A) and spectrum in correlation with FF properties are presented.

Active detection of shielded SNM with 60-keV neutrons

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

Hagmann, C; Dietrich, D; Hall, J

2008-07-08

Fissile materials, e.g. {sup 235}U and {sup 239}Pu, can be detected non-invasively by active neutron interrogation. A unique characteristic of fissile material exposed to neutrons is the prompt emission of high-energy (fast) fission neutrons. One promising mode of operation subjects the object to a beam of medium-energy (epithermal) neutrons, generated by a proton beam impinging on a Li target. The emergence of fast secondary neutrons then clearly indicates the presence of fissile material. Our interrogation system comprises a low-dose 60-keV neutron generator (5 x 10{sup 6}/s), and a 1 m{sup 2} array of scintillators for fast neutron detection. Preliminary experimentalmore » results demonstrate the detectability of small quantities (370 g) of HEU shielded by steel (200 g/cm{sup 2}) or plywood (30 g/cm{sup 2}), with a typical measurement time of 1 min.« less

Nuclear fuel element

DOEpatents

Armijo, Joseph S.; Coffin, Jr., Louis F.

1983-01-01

A nuclear fuel element for use in the core of a nuclear reactor is disclosed and has a composite cladding having a substrate and a metal barrier metallurgically bonded on the inside surface of the substrate so that the metal barrier forms a shield between the substrate and the nuclear fuel material held within the cladding. The metal barrier forms about 1 to about 30 percent of the thickness of the cladding and is comprised of a low neutron absorption metal of substantially pure zirconium. The metal barrier serves as a preferential reaction site for gaseous impurities and fission products and protects the substrate from contact and reaction with such impurities and fission products. The substrate of the composite cladding is selected from conventional cladding materials and preferably is a zirconium alloy. Methods of manufacturing the composite cladding are also disclosed.

Uncovering Special Nuclear Materials by Low-energy Nuclear Reaction Imaging

NASA Astrophysics Data System (ADS)

Rose, P. B.; Erickson, A. S.; Mayer, M.; Nattress, J.; Jovanovic, I.

2016-04-01

Weapons-grade uranium and plutonium could be used as nuclear explosives with extreme destructive potential. The problem of their detection, especially in standard cargo containers during transit, has been described as “searching for a needle in a haystack” because of the inherently low rate of spontaneous emission of characteristic penetrating radiation and the ease of its shielding. Currently, the only practical approach for uncovering well-shielded special nuclear materials is by use of active interrogation using an external radiation source. However, the similarity of these materials to shielding and the required radiation doses that may exceed regulatory limits prevent this method from being widely used in practice. We introduce a low-dose active detection technique, referred to as low-energy nuclear reaction imaging, which exploits the physics of interactions of multi-MeV monoenergetic photons and neutrons to simultaneously measure the material’s areal density and effective atomic number, while confirming the presence of fissionable materials by observing the beta-delayed neutron emission. For the first time, we demonstrate identification and imaging of uranium with this novel technique using a simple yet robust source, setting the stage for its wide adoption in security applications.

Uncovering Special Nuclear Materials by Low-energy Nuclear Reaction Imaging

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

Rose, Jr., P. B.; Erickson, A. S.; Mayer, Michael F.

Weapons-grade uranium and plutonium could be used as nuclear explosives with extreme destructive potential. The problem of their detection, especially in standard cargo containers during transit, has been described as “searching for a needle in a haystack” because of the inherently low rate of spontaneous emission of characteristic penetrating radiation and the ease of its shielding. Currently, the only practical approach for uncovering well-shielded special nuclear materials is by use of active interrogation using an external radiation source. However, the similarity of these materials to shielding and the required radiation doses that may exceed regulatory limits prevent this method frommore » being widely used in practice. We introduce a low-dose active detection technique, referred to as low-energy nuclear reaction imaging, which exploits the physics of interactions of multi-MeV monoenergetic photons and neutrons to simultaneously measure the material’s areal density and effective atomic number, while confirming the presence of fissionable materials by observing the beta-delayed neutron emission. For the first time, we demonstrate identification and imaging of uranium with this novel technique using a simple yet robust source, setting the stage for its wide adoption in security applications.« less

Uncovering Special Nuclear Materials by Low-energy Nuclear Reaction Imaging

DOE PAGES

Rose, P. B.; Erickson, A. S.; Mayer, M.; ...

2016-04-18

Weapons-grade uranium and plutonium could be used as nuclear explosives with extreme destructive potential. The problem of their detection, especially in standard cargo containers during transit, has been described as “searching for a needle in a haystack” because of the inherently low rate of spontaneous emission of characteristic penetrating radiation and the ease of its shielding. Currently, the only practical approach for uncovering well-shielded special nuclear materials is by use of active interrogation using an external radiation source. However, the similarity of these materials to shielding and the required radiation doses that may exceed regulatory limits prevent this method frommore » being widely used in practice. We introduce a low-dose active detection technique, referred to as low-energy nuclear reaction imaging, which exploits the physics of interactions of multi-MeV monoenergetic photons and neutrons to simultaneously measure the material’s areal density and effective atomic number, while confirming the presence of fissionable materials by observing the beta-delayed neutron emission. For the first time, we demonstrate identification and imaging of uranium with this novel technique using a simple yet robust source, setting the stage for its wide adoption in security applications.« less

Uncovering Special Nuclear Materials by Low-energy Nuclear Reaction Imaging

PubMed Central

Rose, P. B.; Erickson, A. S.; Mayer, M.; Nattress, J.; Jovanovic, I.

2016-01-01

Weapons-grade uranium and plutonium could be used as nuclear explosives with extreme destructive potential. The problem of their detection, especially in standard cargo containers during transit, has been described as “searching for a needle in a haystack” because of the inherently low rate of spontaneous emission of characteristic penetrating radiation and the ease of its shielding. Currently, the only practical approach for uncovering well-shielded special nuclear materials is by use of active interrogation using an external radiation source. However, the similarity of these materials to shielding and the required radiation doses that may exceed regulatory limits prevent this method from being widely used in practice. We introduce a low-dose active detection technique, referred to as low-energy nuclear reaction imaging, which exploits the physics of interactions of multi-MeV monoenergetic photons and neutrons to simultaneously measure the material’s areal density and effective atomic number, while confirming the presence of fissionable materials by observing the beta-delayed neutron emission. For the first time, we demonstrate identification and imaging of uranium with this novel technique using a simple yet robust source, setting the stage for its wide adoption in security applications. PMID:27087555

Transport calculation of neutrons leaked to the surroundings of the facilities by the JCO criticality accident in Tokai-mura.

PubMed

Imanaka, T

2001-09-01

A transport calculation of the neutrons leaked to the environment by the JCO criticality accident was carried out based on three-dimensional geometrical models of the buildings within the JCO territory. Our work started from an initial step to simulate the leakage process of neutrons from the precipitation tank, and proceeded to a step to calculate the neutron propagation throughout the JCO facilities. The total fission number during the accident in the precipitation tank was evaluated to be 2.5 x 10(18) by comparing the calculated neutron-induced activities per 235U fission with the measured values in a stainless-steel net sample taken 2 m from the precipitation tank. Shield effects by various structures within the JCO facilities were evaluated by comparing the present results with a previous calculation using two-dimensional models which suppose a point source of the fission spectrum in the air above the ground without any shield structures. The shield effect by the precipitation tank, itself, was obtained to be a factor of 3. The shield factor by the conversion building varied between 1.1 and 2, depending on the direction from the building. The shield effect by the surrounding buildings within the JCO territory was between I and 5, also depending on the direction.

Advanced shield development for a fission surface power system for the lunar surface

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

A. E. Craft; I. J. Silver; C. M. Clark

A nuclear reactor power system such as the affordable fission surface power system enables a potential outpostonthemoon.Aradiation shieldmustbe included in the reactor system to reduce the otherwise excessive dose to the astronauts and other vital system components. The radiation shield is typically the most massive component of a space reactor system, and thus must be optimized to reduce mass asmuchas possible while still providing the required protection.Various shield options for an on-lander reactor system are examined for outpost distances of 400m and 1 kmfromthe reactor. Also investigated is the resulting mass savings from the use of a high performance cermetmore » fuel. A thermal analysis is performed to determine the thermal behaviours of radiation shields using borated water. For an outpost located 1000m from the core, a tetramethylammonium borohydride shield is the lightest (5148.4 kg), followed by a trilayer shield (boron carbide–tungsten–borated water; 5832.3 kg), and finally a borated water shield (6020.7 kg). In all of the final design cases, the temperature of the borated water remains below 400 K.« less

POWER REACTOR

DOEpatents

Zinn, W.H.

1958-07-01

A fast nuclear reactor system ls described for producing power and radioactive isotopes. The reactor core is of the heterogeneous, fluid sealed type comprised of vertically arranged elongated tubular fuel elements having vertical coolant passages. The active portion is surrounded by a neutron reflector and a shield. The system includes pumps and heat exchangers for the primary and secondary coolant circuits. The core, primary coolant pump and primary heat exchanger are disposed within an irapenforate tank which is filled with the primary coolant, in this case a liquid metal such as Na or NaK, to completely submerge these elements. The tank is completely surrounded by a thick walled concrete shield. This reactor system utilizes enriched uranium or plutonium as the fissionable material, uranium or thorium as a diluent and thorium or uranium containing less than 0 7% of the U/sup 235/ isotope as a fertile material.

Device for Detection of Explosives, Nuclear and Other Hazardous Materials in Luggage and Cargo Containers

NASA Astrophysics Data System (ADS)

Kuznetsov, Andrey; Evsenin, Alexey; Gorshkov, Igor; Osetrov, Oleg; Vakhtin, Dmitry

2009-12-01

Device for detection of explosives, radioactive and heavily shielded nuclear materials in luggage and cargo containers based on Nanosecond Neutron Analysis/Associated Particles Technique (NNA/APT) is under construction. Detection module consists of a small neutron generator with built-in position-sensitive detector of associated alpha-particles, and several scintillator-based gamma-ray detectors. Explosives and other hazardous chemicals are detected by analyzing secondary high-energy gamma-rays from reactions of fast neutrons with materials inside a container. The same gamma-ray detectors are used to detect unshielded radioactive and nuclear materials. An array of several neutron detectors is used to detect fast neutrons from induced fission of nuclear materials. Coincidence and timing analysis allows one to discriminate between fission neutrons and scattered probing neutrons. Mathematical modeling by MCNP5 and MCNP-PoliMi codes was used to estimate the sensitivity of the device and its optimal configuration. Comparison of the features of three gamma detector types—based on BGO, NaI and LaBr3 crystals is presented.

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.

Reliability of Monte Carlo simulations in modeling neutron yields from a shielded fission source

NASA Astrophysics Data System (ADS)

McArthur, Matthew S.; Rees, Lawrence B.; Czirr, J. Bart

2016-08-01

Using the combination of a neutron-sensitive 6Li glass scintillator detector with a neutron-insensitive 7Li glass scintillator detector, we are able to make an accurate measurement of the capture rate of fission neutrons on 6Li. We used this detector with a 252Cf neutron source to measure the effects of both non-borated polyethylene and 5% borated polyethylene shielding on detection rates over a range of shielding thicknesses. Both of these measurements were compared with MCNP calculations to determine how well the calculations reproduced the measurements. When the source is highly shielded, the number of interactions experienced by each neutron prior to arriving at the detector is large, so it is important to compare Monte Carlo modeling with actual experimental measurements. MCNP reproduces the data fairly well, but it does generally underestimate detector efficiency both with and without polyethylene shielding. For non-borated polyethylene it underestimates the measured value by an average of 8%. This increases to an average of 11% for borated polyethylene.

Efficiency of Moderated Neutron Lithium Glass Detectors Using Monte Carlo Techniques

NASA Astrophysics Data System (ADS)

James, Brian

2011-10-01

Due to national security concerns over the smuggling of special nuclear materials and the small supply of He-3 for use in neutron detectors, there is a great need for a new kind of neutron detector. Using Monte Carlo techniques I have been studying the use of lithium glass in varying configurations for neutron detectors. My research has included the effects of using a detector with two thin sheets of lithium at varying distances apart. I have also researched the effects of varying amounts of shielding a californium source with varying amounts of water. This is important since shielding would likely be used to make nuclear material more difficult to detect. The addition of one sheet of lithium-6 glass on the front surface of the detector significantly improves the efficiency for the detection of neutrons from a moderated fission source.

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

Selvi, Marco

For all experiments dealing with the rare event searches (neutrino, dark matter, neutrino-less double-beta decay), the reduction of the radioactive background is one of the most important and difficult tasks. There are basically two types of background, electron recoils and nuclear recoils. The electron recoil background is mostly from the gamma rays through the radioactive decay. The nuclear recoil background is from neutrons from spontaneous fission, (α, n) reactions and muoninduced interactions (spallations, photo-nuclear and hadronic interaction). The external gammas and neutrons from the muons and laboratory environment, can be reduced by operating the detector at deep underground laboratories andmore » by placing active or passive shield materials around the detector. The radioactivity of the detector materials also contributes to the background; in order to reduce it a careful screening campaign is mandatory to select highly radio-pure materials. In this review I present the status of current Monte Carlo simulations aimed to estimate and reproduce the background induced by gamma and neutron radioactivity of the materials and the shield of rare event search experiment. For the electromagnetic background a good level of agreement between the data and the MC simulation has been reached by the XENON100 and EDELWEISS experiments, using the GEANT4 toolkit. For the neutron background, a comparison between the yield of neutrons from spontaneous fission and (α, n) obtained with two dedicated softwares, SOURCES-4A and the one developed by Mei-Zhang-Hime, show a good overall agreement, with total yields within a factor 2 difference. The energy spectra from SOURCES-4A are in general smoother, while those from MZH presents sharp peaks. The neutron propagation through various materials has been studied with two MC codes, GEANT4 and MCNPX, showing a reasonably good agreement, inside 50% discrepancy.« less

Review of Monte Carlo simulations for backgrounds from radioactivity

NASA Astrophysics Data System (ADS)

Selvi, Marco

2013-08-01

For all experiments dealing with the rare event searches (neutrino, dark matter, neutrino-less double-beta decay), the reduction of the radioactive background is one of the most important and difficult tasks. There are basically two types of background, electron recoils and nuclear recoils. The electron recoil background is mostly from the gamma rays through the radioactive decay. The nuclear recoil background is from neutrons from spontaneous fission, (α, n) reactions and muoninduced interactions (spallations, photo-nuclear and hadronic interaction). The external gammas and neutrons from the muons and laboratory environment, can be reduced by operating the detector at deep underground laboratories and by placing active or passive shield materials around the detector. The radioactivity of the detector materials also contributes to the background; in order to reduce it a careful screening campaign is mandatory to select highly radio-pure materials. In this review I present the status of current Monte Carlo simulations aimed to estimate and reproduce the background induced by gamma and neutron radioactivity of the materials and the shield of rare event search experiment. For the electromagnetic background a good level of agreement between the data and the MC simulation has been reached by the XENON100 and EDELWEISS experiments, using the GEANT4 toolkit. For the neutron background, a comparison between the yield of neutrons from spontaneous fission and (α, n) obtained with two dedicated softwares, SOURCES-4A and the one developed by Mei-Zhang-Hime, show a good overall agreement, with total yields within a factor 2 difference. The energy spectra from SOURCES-4A are in general smoother, while those from MZH presents sharp peaks. The neutron propagation through various materials has been studied with two MC codes, GEANT4 and MCNPX, showing a reasonably good agreement, inside 50% discrepancy.

Isomer Energy Source for Space Propulsion Systems

DTIC Science & Technology

2004-03-01

1,590 Engine F/W (no shield) 3.4 5.0 20.0 A similar core design replacing the fission fuel with the isomer 178Hfm2 is the starting point for this...particles interact and collide with other atoms in the fuel material, reactor core , or coolant, their energy can be transferred to thermal energy...thrust (44). The program produced several reactors that made it all the way through the testing stages of development . The reactors used uranium-235

LOADING MACHINE FOR REACTORS

DOEpatents

Simon, S.L.

1959-07-01

An apparatus is described for loading or charging slugs of fissionable material into a nuclear reactor. The apparatus of the invention is a "muzzle loading" type comprising a delivery tube or muzzle designed to be brought into alignment with any one of a plurality of fuel channels. The delivery tube is located within the pressure shell and it is also disposed within shielding barriers while the fuel cantridges or slugs are forced through the delivery tube by an externally driven flexible ram.

Nuclear fuel element

DOEpatents

Armijo, Joseph S.; Coffin, Jr., Louis F.

1980-04-29

A nuclear fuel element for use in the core of a nuclear reactor is disclosed and has an improved composite cladding comprised of a moderate purity metal barrier of zirconium metallurgically bonded on the inside surface of a zirconium alloy tube. The metal barrier forms a shield between the alloy tube and a core of nuclear fuel material enclosed in the composite cladding. There is a gap between the cladding and the core. The metal barrier forms about 1 to about 30 percent of the thickness of the composite cladding and has low neutron absorption characteristics. The metal barrier serves as a preferential reaction site for gaseous impurities and fission products and protects the alloy tube from contact and reaction with such impurities and fission products. Methods of manufacturing the composite cladding are also disclosed.

A Practical Approach to Starting Fission Surface Power Development

NASA Technical Reports Server (NTRS)

Mason, Lee S.

2006-01-01

The Prometheus Power and Propulsion Program has been reformulated to address NASA needs relative to lunar and Mars exploration. Emphasis has switched from the Jupiter Icy Moons Orbiter (JIMO) flight system development to more generalized technology development addressing Fission Surface Power (FSP) and Nuclear Thermal Propulsion (NTP). Current NASA budget priorities and the deferred mission need date for nuclear systems prohibit a fully funded reactor Flight Development Program. However, a modestly funded Advanced Technology Program can and should be conducted to reduce the risk and cost of future flight systems. A potential roadmap for FSP technology development leading to possible flight applications could include three elements: 1) Conceptual Design Studies, 2) Advanced Component Technology, and 3) Non-Nuclear System Testing. The Conceptual Design Studies would expand on recent NASA and DOE analyses while increasing the depth of study in areas of greatest uncertainty such as reactor integration and human-rated shielding. The Advanced Component Technology element would address the major technology risks through development and testing of reactor fuels, structural materials, primary loop components, shielding, power conversion, heat rejection, and power management and distribution (PMAD). The Non-Nuclear System Testing would provide a modular, technology testbed to investigate and resolve system integration issues.

Reference reactor module for NASA's lunar surface fission power system

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

Poston, David I; Kapernick, Richard J; Dixon, David D

Surface fission power systems on the Moon and Mars may provide the first US application of fission reactor technology in space since 1965. The Affordable Fission Surface Power System (AFSPS) study was completed by NASA/DOE to determine the cost of a modest performance, low-technical risk surface power system. The AFSPS concept is now being further developed within the Fission Surface Power (FSP) Project, which is a near-term technology program to demonstrate system-level TRL-6 by 2013. This paper describes the reference FSP reactor module concept, which is designed to provide a net power of 40 kWe for 8 years on themore » lunar surface; note, the system has been designed with technologies that are fully compatible with a Martian surface application. The reactor concept uses stainless-steel based. UO{sub 2}-fueled, pumped-NaK fission reactor coupled to free-piston Stirling converters. The reactor shielding approach utilizes both in-situ and launched shielding to keep the dose to astronauts much lower than the natural background radiation on the lunar surface. The ultimate goal of this work is to provide a 'workhorse' power system that NASA can utilize in near-term and future Lunar and Martian mission architectures, with the eventual capability to evolve to very high power, low mass systems, for either surface, deep space, and/or orbital missions.« less

Fission Surface Power for the Exploration and Colonization of Mars

NASA Technical Reports Server (NTRS)

Houts, Mike; Porter, Ron; Gaddis, Steve; Van Dyke, Melissa; Martin, Jim; Godfroy, Tom; Bragg-Sitton, Shannon; Garber, Anne; Pearson, Boise

2006-01-01

The colonization of Mars will require abundant energy. One potential energy source is nuclear fission. Terrestrial fission systems are highly developed and have the demonstrated ability to safely produce tremendous amounts of energy. In space, fission systems not only have the potential to safely generate tremendous amounts of energy, but could also potentially be used on missions where alternatives are not practical. Programmatic risks such as cost and schedule are potential concerns with fission surface power (FSP) systems. To be mission enabling, FSP systems must be affordable and programmatic risk must be kept acceptably low to avoid jeopardizing exploration efforts that may rely on FSP. Initial FSP systems on Mars could be "workhorse" units sized to enable the establishment of a Mars base and the early growth of a colony. These systems could be nearly identical to FSP systems used on the moon. The systems could be designed to be safe, reliable, and have low development and recurring costs. Systems could also be designed to fit on relatively small landers. One potential option for an early Mars FSP system would be a 100 kWt class, NaK cooled system analogous to space reactors developed and flown under the U.S. "SNAP" program or those developed and flown by the former Soviet Union ("BUK" reactor). The systems could use highly developed fuel and materials. Water and Martian soil could be used to provide shielding. A modern, high-efficiency power conversion subsystem could be used to reduce required reactor thermal power. This, in turn, would reduce fuel burnup and radiation damage .effects by reducing "nuclear" fuels and materials development costs. A realistic, non-nuclear heated and fully integrated technology demonstration unit (TDU) could be used to reduce cost and programmatic uncertainties prior to initiating a flight program.

Advanced applications of cosmic-ray muon radiography

NASA Astrophysics Data System (ADS)

Perry, John

The passage of cosmic-ray muons through matter is dominated by the Coulomb interaction with electrons and atomic nuclei. The muon's interaction with electrons leads to continuous energy loss and stopping through the process of ionization. The muon's interaction with nuclei leads to angular diffusion. If a muon stops in matter, other processes unfold, as discussed in more detail below. These interactions provide the basis for advanced applications of cosmic-ray muon radiography discussed here, specifically: 1) imaging a nuclear reactor with near horizontal muons, and 2) identifying materials through the analysis of radiation lengths weighted by density and secondary signals that are induced by cosmic-ray muon trajectories. We have imaged a nuclear reactor, type AGN-201m, at the University of New Mexico, using data measured with a particle tracker built from a set of sealed drift tubes, the Mini Muon Tracker (MMT). Geant4 simulations were compared to the data for verification and validation. In both the data and simulation, we can identify regions of interest in the reactor including the core, moderator, and shield. This study reinforces our claims for using muon tomography to image reactors following an accident. Warhead and special nuclear materials (SNM) imaging is an important thrust for treaty verification and national security purposes. The differentiation of SNM from other materials, such as iron and aluminum, is useful for these applications. Several techniques were developed for material identification using cosmic-ray muons. These techniques include: 1) identifying the radiation length weighted by density of an object and 2) measuring the signals that can indicate the presence of fission and chain reactions. By combining the radiographic images created by tracking muons through a target plane with the additional fission neutron and gamma signature, we are able to locate regions that are fissionable from a single side. The following materials were imaged with this technique: aluminum, concrete, steel, lead, and uranium. Provided that there is sufficient mass, U-235 could be differentiated from U-238 through muon induced fission.

Reference Reactor Module for the Affordable Fission Surface Power System

NASA Astrophysics Data System (ADS)

Poston, David I.; Kapernick, Richard J.; Dixon, David D.; Amiri, Benjamin W.; Marcille, Thomas F.

2008-01-01

Surface fission power systems on the Moon and Mars may provide the first US application of fission reactor technology in space since 1965. The requirements of many surface power applications allow the consideration of systems with much less development risk than most other space reactor applications, because of modest power (10s of kWe) and no driving need for minimal mass (allowing temperatures <1000 K). The Affordable Fission Surface Power System (AFSPS) study was completed by NASA/DOE to determine the cost of a modest performance, low-technical risk surface power system. This paper describes the reference AFSPS reactor module concept, which is designed to provide a net power of 40 kWe for 8 years on the lunar surface; note, the system has been designed with technologies that are fully compatible with a Martian surface application. The reactor concept uses stainless-steel based, UO2-fueled, liquid metal-cooled fission reactor coupled to free-piston Stirling converters. The reactor shielding approach utilizes both in-situ and launched shielding to keep the dose to astronauts much lower than the natural background radiation on the lunar surface. One of the important ``affordability'' attributes is that the concept has been designed to minimize both the technical and programmatic safety risk.

Quantitative Fissile Assay In Used Fuel Using LSDS System

NASA Astrophysics Data System (ADS)

Lee, YongDeok; Jeon, Ju Young; Park, Chang-Je

2017-09-01

A quantitative assay of isotopic fissile materials (U235, Pu239, Pu241) was done at Korea Atomic Energy Research Institute (KAERI), using lead slowing down spectrometer (LSDS). The optimum design of LSDS was performed based on economics, easy maintenance and assay effectiveness. LSDS system consists of spectrometer, neutron source, detection and control. LSDS system induces fissile fission and fast neutrons are collected at fission chamber. The detected signal has a direct relation to the mass of existing fissile isotopes. Many current commercial assay technologies have a limitation in direct application on isotopic fissile assay of spent fuel, except chemical analysis. In the designed system, the fissile assay model was setup and the correction factor for self-shield was obtained. The isotopic fissile content assay was performed by changing the content of Pu239. Based on the fuel rod, the isotopic content was consistent with 2% uncertainty for Pu239. By applying the covering (neutron absorber), the effective shielding was obtained and the activation was calculated on the target. From the assay evaluation, LSDS technique is very powerful and direct to analyze the isotopic fissile content. LSDS is applicable for nuclear fuel cycle and spent fuel management for safety and economics. Additionally, an accurate fissile content will contribute to the international transparency and credibility on spent fuel.

Measurement of Fission Product Yields from Fast-Neutron Fission

NASA Astrophysics Data System (ADS)

Arnold, C. W.; Bond, E. M.; Bredeweg, T. A.; Fowler, M. M.; Moody, W. A.; Rusev, G.; Vieira, D. J.; Wilhelmy, J. B.; Becker, J. A.; Henderson, R.; Kenneally, J.; Macri, R.; McNabb, D.; Ryan, C.; Sheets, S.; Stoyer, M. A.; Tonchev, A. P.; Bhatia, C.; Bhike, M.; Fallin, B.; Gooden, M. E.; Howell, C. R.; Kelley, J. H.; Tornow, W.

2014-09-01

One of the aims of the Stockpile Stewardship Program is a reduction of the uncertainties on fission data used for analyzing nuclear test data [1,2]. Fission products such as 147Nd are convenient for determining fission yields because of their relatively high yield per fission (about 2%) and long half-life (10.98 days). A scientific program for measuring fission product yields from 235U,238U and 239Pu targets as a function of bombarding neutron energy (0.1 to 15 MeV) is currently underway using monoenergetic neutron beams produced at the 10 MV Tandem Accelerator at TUNL. Dual-fission chambers are used to determine the rate of fission in targets during activation. Activated targets are counted in highly shielded HPGe detectors over a period of several weeks to identify decaying fission products. To date, data have been collected at neutron bombarding energies 4.6, 9.0, 14.5 and 14.8 MeV. Experimental methods and data reduction techniques are discussed, and some preliminary results are presented.

Rattling nucleons: New developments in active interrogation of special nuclear material

NASA Astrophysics Data System (ADS)

Runkle, Robert C.; Chichester, David L.; Thompson, Scott J.

2012-01-01

Active interrogation is a vigorous area of research and development due to its promise of offering detection and characterization capabilities of special nuclear material in environments where passive detection fails. The primary value added by active methods is the capability to penetrate shielding—special nuclear material itself, incidental materials, or intentional shielding—and advocates hope that active interrogation will provide a solution to the problem of detecting shielded uranium, which is at present the greatest obstacle to interdiction efforts. The technique also provides a unique benefit for quantifying nuclear material in high background-radiation environments, an area important for nuclear material safeguards and material accountancy. Progress has been made in the field of active interrogation on several fronts, most notably in the arenas of source development, systems integration, and the integration and exploitation of multiple fission and non-fission signatures. But penetration of interrogating radiation often comes at a cost, not only in terms of finance and dose but also in terms of induced backgrounds, system complexity, and extended measurement times (including set up and acquisition). These costs make the calculus for deciding to implement active interrogation more subtle than may be apparent. The purpose of this review is thus to examine existing interrogation methods, compare and contrast their attributes and limitations, and identify missions where active interrogation may hold the most promise.

Extensibility of the fission surface power (FSP) system from the moon to Mars

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

Poston, David Irvin

2011-01-28

Fission reactors have great near-term potential to power human and robotic missions/outposts on the surface of the Moon and Mars (and potentially other planets, moons, and asteroids). The ability to provide a power-rich environment that is independent of solar intensity, nights, dust storms, etc., is of significant (perhaps enabling) importance to the further expansion of humans into our solar system. NASA's Reference Fission Surface Power (FSP) System is a 40 kWe system that has been primarily designed for lunar applications. This paper examines the extensibility of the FSP design and technology for potential missions on Mars. Possible impacts include themore » effects of changes in heat sink, gravity, day-night cycles, mission transit time, communication delay, and the chemistry of the regolith and atmosphere. One of the biggest impacts might be differences in the potential utilization of in-situ materials for shielding. Another major factor is that different missions will likely require different performance requirements, e.g. power, lifetime and mass. This paper concludes that the environmental differences between potential mission locations will not require significant changes in design and technologies, unless performance requirements for a specific mission are substantially different than those adopted for the FSP The primary basis for this conclusion is that the FSP has been designed with robust materials and design margins.« less

Benefits of Time Correlation Measurements for Passive Screening

NASA Astrophysics Data System (ADS)

Murer, David; Blackie, Douglas; Peerani, Paolo

2014-02-01

The “FLASH Portals Project” is a collaboration between Arktis Radiation Detectors Ltd (CH), the Atomic Weapons Establishment (UK), and the Joint Research Centre (European Commission), supported by the Technical Support Working Group (TSWG). The program's goal was to develop and demonstrate a technology to detect shielded special nuclear materials (SNM) more efficiently and less ambiguously by exploiting time correlation. This study presents experimental results of a two-sided portal monitor equipped with in total 16 4He fast neutron detectors as well as four polyvinyltoluene (PVT) plastic scintillators. All detectors have been synchronized to nanosecond precision, thereby allowing the resolution of time correlations from timescales of tens of microseconds (such as (n, γ) reactions) down to prompt fission correlations directly. Our results demonstrate that such correlations can be detected in a typical radiation portal monitor (RPM) geometry and within operationally acceptable time scales, and that exploiting these signatures significantly improves the performance of the RPM compared to neutron counting. Furthermore, the results show that some time structure remains even in the presence of heavy shielding, thus significantly improving the sensitivity of the detection system to shielded SNM.

Conventional and Non-Conventional Nuclear Material Signatures

NASA Astrophysics Data System (ADS)

Gozani, Tsahi

2009-03-01

The detection and interdiction of concealed special nuclear material (SNM) in all modes of transport is one of the most critical security issues facing the United States and the rest of the world. In principle, detection of nuclear materials is relatively easy because of their unique properties: all of them are radioactive and all emit some characteristic gamma rays. A few emit neutrons as well. These signatures are the basis for passive non-intrusive detection of nuclear materials. The low energy of the radiations necessitates additional means of detection and validation. These are provided by high-energy x-ray radiography and by active inspection based on inducing nuclear reactions in the nuclear materials. Positive confirmation that a nuclear material is present or absent can be provided by interrogation of the inspected object with penetrating probing radiation, such as neutrons and photons. The radiation induces specific reactions in the nuclear material yielding, in turn, penetrating signatures which can be detected outside the inspected object. The "conventional" signatures are first and foremost fission signatures: prompt and delayed neutrons and gamma rays. Their intensity (number per fission) and the fact that they have broad energy (non-discrete, though unique) distributions and certain temporal behaviors are key to their use. The "non- conventional" signatures are not related to the fission process but to the unique nuclear structure of each element or isotope in nature. This can be accessed through the excitation of isotopic nuclear levels (discrete and continuum) by neutron inelastic scattering or gamma resonance fluorescence. Finally there is an atomic signature, namely the high atomic number (Z>74), which obviously includes all the nuclear materials and their possible shielding. The presence of such high-Z elements can be inferred by techniques using high-energy x rays. The conventional signatures have been addressed in another article. Non-conventional signatures and some of their current or potential uses will be discussed here.

Shielding Analysis of a Small Compact Space Nuclear Reactor

DTIC Science & Technology

1987-08-01

RESPONSE) =4, MAXWELLIAN FISSION SPECTRUM (ILNTEGRAL RESPONSE) =5, LOS ALAMOS FISSION SPECTRUM, 1982 (INTEGRAL RESPONSE) =6, VITAMIN C NEUTRON SPECTRUM...Appendices Appendix A: Calculations of Effective Radii.. A-1 Appendix B: Atom Density Calculations for FEMPlD and FEMP2D ................ B-I Appendix C ...FEMPID and FEM22D Data........... C -i Appendix D: Energy Group Definition .......... D-I Appendix E: Transport Equation, Legendr4 Polynomial

Measurements of fission product yield in the neutron-induced fission of 238U with average energies of 9.35 MeV and 12.52 MeV

NASA Astrophysics Data System (ADS)

Mukerji, Sadhana; Krishnani, Pritam Das; Shivashankar, Byrapura Siddaramaiah; Mulik, Vikas Kaluram; Suryanarayana, Saraswatula Venkat; Naik, Haladhara; Goswami, Ashok

2014-07-01

The yields of various fission products in the neutron-induced fission of 238U with the flux-weightedaveraged neutron energies of 9.35 MeV and 12.52 MeV were determined by using an off-line gammaray spectroscopic technique. The neutrons were generated using the 7Li(p, n) reaction at Bhabha Atomic Research Centre-Tata Institute of Fundamental Research Pelletron facility, Mumbai. The gamma- ray activities of the fission products were counted in a highly-shielded HPGe detector over a period of several weeks to identify the decaying fission products. At both the neutron energies, the fission-yield values are reported for twelve fission product. The results obtained from the present work have been compared with the similar data for mono-energetic neutrons of comparable energy from the literature and are found to be in good agreement. The peak-to-valley (P/V) ratios were calculated from the fission-yield data and were found to decreases for neutron energy from 9.35 to 12.52 MeV, which indicates the role of excitation energy. The effect of the nuclear structure on the fission product-yield is discussed.

Search for electron and gamma-ray decay of the ^238fPu fission

NASA Astrophysics Data System (ADS)

Beausang, C. W.; Gurdal, G.; Ressler, J.; Barton, C. J.; Caprio, M. A.; Casten, R. F.; Cooper, J. R.; Hecht, A. A.; Hutter, C.; Zamfir, N. V.; Hauschild, K.; Korten, W.; Mergel, E.

2002-04-01

The reaction ^9Be + ^232Th arrow ^241Pu, at beam energies of 50 and 55 MeV, was used in an attempt to populate states in the second minimum (fission isomer) of ^238Pu via the 3n evaporation channel. Prompt gamma-rays, detected using YRAST Ball and conversion electrons, detected using ICE Ball, were collected in coincidence with delayed fission events measured using elements of the Yale SCARY array of solar cell detectors. The solar cell detectors were shielded so as not to view the large prompt fission flux from the target. Instead the detectors were located so that they could detect delayed fission events, originating from the 6 ns fission isomer state in ^238Pu, which occur downstream from the target position. Data analysis is in progress and results to date will be presented. This work is partly supported by the U.S. DOE under grant numbers DE-FG02-91ER-40609, DE-FG02-88ER-40417.

Detection Of Special Nuclear Materials Tagged Neutrons

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

Deyglun, Clement; Perot, Bertrand; Carasco, Cedric

In order to detect Special Nuclear Materials (SNM) in unattended luggage or cargo containers in the field of homeland security, fissions are induced by 14 MeV neutrons produced by an associated particle DT neutron generator, and prompt fission particles correlated with tagged neutron are detected by plastic scintillators. SMN produce high multiplicity events due to induced fissions, whereas nonnuclear materials produce low multiplicity events due to cross-talk, (n,2n) or (n,n'γ) reactions. The data acquisition electronics is made of compact FPGA boards. The coincidence window is triggered by the alpha particle detection, allowing to tag the emission date and direction ofmore » the 14 MeV interrogating neutron. The first part of the paper presents experiment vs. calculation comparisons to validate MCNP-PoliMi simulations and the post-processing tools developed with the data analysis framework ROOT. Measurements have been performed using different targets (iron, lead, graphite), first with small plastic scintillators (10 x 10 x 10 cm{sup 3}) and then with large detectors (10 x 10 x 100 cm{sup 3}) to demonstrate that nuclear materials can be differentiated from nonnuclear dense materials (iron, lead) in iron and wood matrixes. A special attention is paid on SNM detection in abandoned luggage. In the second part of the paper, the performances of a cargo container inspection system are studied by numerical simulation, following previous work reported in. Detectors dimensions and shielding against the neutron generator background are optimized for container inspection. Events not correlated to an alpha particle (uncorrelated background), counting statistics, time and energy resolutions of the data acquisition system are all taken into account in a realistic numerical model. The impact of the container matrix (iron, ceramic, wood) has been investigated by studying the system capability to detect a few kilograms of SNM in different positions in the cargo container, within 10 min acquisitions. (authors)« less

Fission Product Appearance Rate Coefficients in Design Basis Source Term Determinations - Past and Present

NASA Astrophysics Data System (ADS)

Perez, Pedro B.; Hamawi, John N.

2017-09-01

Nuclear power plant radiation protection design features are based on radionuclide source terms derived from conservative assumptions that envelope expected operating experience. Two parameters that significantly affect the radionuclide concentrations in the source term are failed fuel fraction and effective fission product appearance rate coefficients. Failed fuel fraction may be a regulatory based assumption such as in the U.S. Appearance rate coefficients are not specified in regulatory requirements, but have been referenced to experimental data that is over 50 years old. No doubt the source terms are conservative as demonstrated by operating experience that has included failed fuel, but it may be too conservative leading to over-designed shielding for normal operations as an example. Design basis source term methodologies for normal operations had not advanced until EPRI published in 2015 an updated ANSI/ANS 18.1 source term basis document. Our paper revisits the fission product appearance rate coefficients as applied in the derivation source terms following the original U.S. NRC NUREG-0017 methodology. New coefficients have been calculated based on recent EPRI results which demonstrate the conservatism in nuclear power plant shielding design.

Investigation of Active Interrogation Techniques to Detect Special Nuclear Material in Maritime Environments

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

Miller, Thomas Martin; Patton, Bruce W

The detection and interdiction of special nuclear material (SNM) is still a high-priority focus area for many organizations around the world. One method that is commonly considered a leading candidate in the detection of SNM is active interrogation (AI). AI is different from its close relative, passive interrogation, in that an active source is used to enhance or create a detectable signal (usually fission) from SNM, particularly in shielded scenarios or scenarios where the SNM has a low activity. The use of AI thus makes the detection of SNM easier or, in some scenarios, even enables previously impossible detection. Inmore » this work the signal from prompt neutrons and photons as well as delayed neutrons and photons will be combined, as is typically done in AI. In previous work AI has been evaluated experimentally and computationally. However, for the purposes of this work, past scenarios are considered lightly shielded and tightly coupled spatially. At most, the previous work interrogated the contents of one standard cargo container (2.44 x 2.60 x 6.10 m) and the source and detector were both within a few meters of the object being interrogated. A few examples of this type of previous work can be found in references 1 and 2. Obviously, more heavily shielded AI scenarios will require larger source intensities, larger detector surface areas (larger detectors or more detectors), greater detector efficiencies, longer count times, or some combination of these.« less

Energy Dependence of Fission Product Yields from 235U, 238U and 239Pu for Incident Neutron Energies Between 0.5 and 14.8 MeV

NASA Astrophysics Data System (ADS)

Gooden, M. E.; Arnold, C. W.; Becker, J. A.; Bhatia, C.; Bhike, M.; Bond, E. M.; Bredeweg, T. A.; Fallin, B.; Fowler, M. M.; Howell, C. R.; Kelley, J. H.; Krishichayan; Macri, R.; Rusev, G.; Ryan, C.; Sheets, S. A.; Stoyer, M. A.; Tonchev, A. P.; Tornow, W.; Vieira, D. J.; Wilhelmy, J. B.

2016-01-01

Fission Product Yields (FPY) have historically been one of the most observable features of the fission process. They are known to have strong variations that are dependent on the fissioning species, the excitation energy, and the angular momentum of the compound system. However, consistent and systematic studies of the variation of these FPY with energy have proved challenging. This is caused primarily by the nature of the experiments that have traditionally relied on radiochemical procedures to isolate specific fission products. Although radiochemical procedures exist that can isolate all products, each element presents specific challenges and introduces varying degrees of systematic errors that can make inter-comparison of FPY uncertain. Although of high importance in fields such as nuclear forensics and Stockpile Stewardship, accurate information about the energy dependence of neutron induced FPY are sparse, due primarily to the lack of suitable monoenergetic neutron sources. There is a clear need for improved data, and to address this issue, a collaboration was formed between Los Alamos National Laboratory (LANL), Lawrence Livermore National Laboratory (LLNL) and the Triangle Universities Nuclear Laboratory (TUNL) to measure the energy dependence of FPY for 235U, 238U and 239Pu. The measurements have been performed at TUNL, using a 10 MV Tandem Van de Graaff accelerator to produce monoenergetic neutrons at energies between 0.6 MeV to 14.8 MeV through a variety of reactions. The measurements have utilized a dual-fission chamber, with thin (10-100 μg/cm2) reference foils of similar material to a thick (100-400 mg) activation target held in the center between the chambers. This method allows for the accurate determination of the number of fissions that occurred in the thick target without requiring knowledge of the fission cross section or neutron fluence on target. Following activation, the thick target was removed from the dual-fission chamber and gamma-ray counted using shielded HPGe detectors for a period of 1-2 months to determine the yield of various fission products. To the extent possible all irradiation and counting procedures were kept the same to minimize sources of systematic errors. FPY have been determined at incident neutron energies of 0.6, 1.4, 2.4, 3.5, 4.6, 5.5, 8.9 and 14.8 MeV.

Energy dependence of fission product yields from 235U, 238U, and 239Pu with monoenergetic neutrons between thermal and 14.8 MeV

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

Gooden, Matthew; Arnold, Charles; Bhike, Megha

Under a joint collaboration between TUNL-LANL-LLNL, a set of absolute fission product yield measurements has been performed. The energy dependence of a number of cumulative fission product yields (FPY) have been measured using quasi-monoenergetic neutron beams for three actinide targets, 235U, 238U and 239Pu, between 0.5 and 14.8 MeV. The FPYs were measured by a combination of fission counting using specially designed dual-fission chambers and γ-ray counting. Each dual-fission chamber is a back-to-back ionization chamber encasing an activation target in the center with thin deposits of the same target isotope in each chamber. This method allows for the direct measurementmore » of the total number of fissions in the activation target with no reference to the fission cross-section, thus reducing uncertainties. γ-ray counting of the activation target was performed on well-shielded HPGe detectors over a period of two months post irradiation to properly identify fission products. Reported are absolute cumulative fission product yields for incident neutron energies of 0.5, 1.37, 2.4, 3.6, 4.6, 5.5, 7.5, 8.9 and 14.8 MeV. Preliminary results from thermal irradiations at the MIT research reactor will also be presented and compared to present data and evaluations.« less

Energy Dependence of Fission Product Yields from 235U, 238U and 239Pu for Incident Neutron Energies Between 0.5 and 14.8 MeV

NASA Astrophysics Data System (ADS)

Gooden, Matthew; Bredeweg, Todd; Fowler, Malcolm; Vieira, David; Wilhelmy, Jerry; Tonchev, Anton; Stoyer, Mark; Bhike, Megha; Finch, Sean; Krishichayan, Fnu; Tornow, Werner

2017-09-01

The energy dependence of a number of cumulative fission product yields (FPY) have been measured using quasi- monoenergetic neutron beams for three actinide targets, 235U, 238U and 239Pu, between 0.5 and 14.8 MeV. The FPYs were measured by a combi- nation of fission counting using specially designed dual-fission chambers and -ray counting. Each dual-fission chamber is a back-to-back ioniza- tion chamber encasing an activation target in the center with thin de- posits of the same target isotope in each chamber. This method allows for the direct measurement of the total number of fissions in the activa- tion target with no reference to the fission cross-section, thus reducing uncertainties. γ-ray counting of the activation target was performed on well-shielded HPGe detectors over a period of 2 months post irradiation to properly identify fission products. Reported are absolute cumulative fission product yields for incident neutron energies of 0.5, 1.37, 2.4, 3.6, 4.6 and 14.8 MeV. New data in the second chance fission region of 5.5 - 9 MeV are included. Work performed for the U.S. Department of Energy by Los Alamos National Security, LLC under Contract DE-AC52-06NA25396.

Energy dependence of fission product yields from 235U, 238U, and 239Pu with monoenergetic neutrons between thermal and 14.8 MeV

DOE PAGES

Gooden, Matthew; Arnold, Charles; Bhike, Megha; ...

2017-09-13

Under a joint collaboration between TUNL-LANL-LLNL, a set of absolute fission product yield measurements has been performed. The energy dependence of a number of cumulative fission product yields (FPY) have been measured using quasi-monoenergetic neutron beams for three actinide targets, 235U, 238U and 239Pu, between 0.5 and 14.8 MeV. The FPYs were measured by a combination of fission counting using specially designed dual-fission chambers and γ-ray counting. Each dual-fission chamber is a back-to-back ionization chamber encasing an activation target in the center with thin deposits of the same target isotope in each chamber. This method allows for the direct measurementmore » of the total number of fissions in the activation target with no reference to the fission cross-section, thus reducing uncertainties. γ-ray counting of the activation target was performed on well-shielded HPGe detectors over a period of two months post irradiation to properly identify fission products. Reported are absolute cumulative fission product yields for incident neutron energies of 0.5, 1.37, 2.4, 3.6, 4.6, 5.5, 7.5, 8.9 and 14.8 MeV. Preliminary results from thermal irradiations at the MIT research reactor will also be presented and compared to present data and evaluations.« less

A Stainless-Steel, Uranium-Dioxide, Potassium-Heatpipe-Cooled Surface Reactor

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

Amiri, Benjamin W.; Nuclear and Radiological Engineering Department, University of Florida, Gainesville, FL 32611; Sims, Bryan T.

2006-01-20

One of the primary goals in designing a fission power system is to ensure that the system can be developed at a low cost and on an acceptable schedule without compromising reliability. The Heatpipe Power System (HPS) is one possible approach for producing near-term, low-cost, space fission power. The Heatpipe Operated Moon Exploration Reactor (HOMER-25) is a HPS designed to produce 25-kWe on the lunar surface for 5 full-power years. The HOMER-25 core is made up of 93% enriched UO2 fuel pins and stainless-steel (SS)/potassium (K) heatpipes in a SS monolith. The heatpipes transport heat generated in the core throughmore » the water shield to a potassium boiler, which drives six Stirling engines. The operating heatpipe temperature is 880 K and the peak fast fluence is 1.6e21 n/cm2, which is well within an established database for the selected materials. The HOMER-25 is designed to be buried in 1.5 m of lunar regolith during operation. By using technology and materials which do not require extensive technology development programs, the HOMER-25 could be developed at a relatively low cost. This paper describes the attributes, specifications, and performance of the HOMER-25 reactor system.« less

Replacing a 252Cf source with a neutron generator in a shuffler - a conceptual design performed with MCNPX

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

Schear, Melissa A; Tobin, Stephen J

2009-01-01

The {sup 252}Cf shuffler has been widely used in nuclear safeguards and radioactive waste management to assay fissile isotopes, such as {sup 235}U or {sup 239}Pu, present in a variety of samples, ranging from small cans of uranium waste to metal samples weighing several kilograms. Like other non-destructive assay instruments, the shuffler uses an interrogating neutron source to induce fissions in the sample. Although shufflers with {sup 252}Cf sources have been reliably used for several decades, replacing this isotopic source with a neutron generator presents some distinct advantages. Neutron generators can be run in a continuous or pulsed mode, andmore » may be turned off, eliminating the need for shielding and a shuffling mechanism in the shuffler. There is also essentially no dose to personnel during installation, and no reliance on the availability of {sup 252}Cf. Despite these advantages, the more energetic neutrons emitted from the neutron generator (141 MeV for D-T generators) present some challenges for certain material types. For example when the enrichment of a uranium sample is unknown, the fission of {sup 238}U is generally undesirable. Since measuring uranium is one of the main uses of a shuffler, reducing the delayed neutron contribution from {sup 238}U is desirable. Hence, the shuffler hardware must be modified to accommodate a moderator configuration near the source to tailor the interrogating spectrum in a manner which promotes sub-threshold fissions (below 1 MeV) but avoids the over-moderation of the interrogating neutrons so as to avoid self-shielding. In this study, where there are many material and geometry combinations, the Monte Carlo N-Particle eXtended (MCNPX) transport code was used to model, design, and optimize the moderator configuration within the shuffler geometry. The code is then used to evaluate and compare the assay performances of both the modified shuffler and the current {sup 252}Cf shuffler designs for different test samples. The matrix effect and the non-uniformity of the interrogating flux are investigated and quantified in each case. The modified geometry proposed by this study can serve s a guide in retrofitting shufflers that are already in use.« less

Monte Carlo analysis of TRX lattices with ENDF/B version 3 data

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

Hardy, J. Jr.

1975-03-01

Four TRX water-moderated lattices of slightly enriched uranium rods have been reanalyzed with consistent ENDF/B Version 3 data by means of the full-range Monte Carlo program RECAP. The following measured lattice parameters were studied: ratio of epithermal-to-thermal $sup 238$U capture, ratio of epithermal- to-thermal $sup 235$U fissions, ration of $sup 238$U captures to $sup 235$U fissions, ratio of $sup 238$U fissions to $sup 235$U fissions, and multiplication factor. In addition to the base calculations, some studies were done to find sensitivity of the TRX lattice parameters to selected variations of cross section data. Finally, additional experimental evidence is afforded bymore » effective $sup 238$U capture integrals for isolated rods. Shielded capture integrals were calculated for $sup 238$U metal and oxide rods. These are compared with other measurements. (auth)« less

FISPACT-II: An Advanced Simulation System for Activation, Transmutation and Material Modelling

NASA Astrophysics Data System (ADS)

Sublet, J.-Ch.; Eastwood, J. W.; Morgan, J. G.; Gilbert, M. R.; Fleming, M.; Arter, W.

2017-01-01

Fispact-II is a code system and library database for modelling activation-transmutation processes, depletion-burn-up, time dependent inventory and radiation damage source terms caused by nuclear reactions and decays. The Fispact-II code, written in object-style Fortran, follows the evolution of material irradiated by neutrons, alphas, gammas, protons, or deuterons, and provides a wide range of derived radiological output quantities to satisfy most needs for nuclear applications. It can be used with any ENDF-compliant group library data for nuclear reactions, particle-induced and spontaneous fission yields, and radioactive decay (including but not limited to TENDL-2015, ENDF/B-VII.1, JEFF-3.2, JENDL-4.0u, CENDL-3.1 processed into fine-group-structure files, GEFY-5.2 and UKDD-16), as well as resolved and unresolved resonance range probability tables for self-shielding corrections and updated radiological hazard indices. The code has many novel features including: extension of the energy range up to 1 GeV; additional neutron physics including self-shielding effects, temperature dependence, thin and thick target yields; pathway analysis; and sensitivity and uncertainty quantification and propagation using full covariance data. The latest ENDF libraries such as TENDL encompass thousands of target isotopes. Nuclear data libraries for Fispact-II are prepared from these using processing codes PREPRO, NJOY and CALENDF. These data include resonance parameters, cross sections with covariances, probability tables in the resonance ranges, PKA spectra, kerma, dpa, gas and radionuclide production and energy-dependent fission yields, supplemented with all 27 decay types. All such data for the five most important incident particles are provided in evaluated data tables. The Fispact-II simulation software is described in detail in this paper, together with the nuclear data libraries. The Fispact-II system also includes several utility programs for code-use optimisation, visualisation and production of secondary radiological quantities. Included in the paper are summaries of results from the suite of verification and validation reports available with the code.

Energy Dependence of Fission Product Yields from 235U, 238U and 239Pu for Incident Neutron Energies Between 0.5 and 14.8 MeV

NASA Astrophysics Data System (ADS)

Gooden, M.; Arnold, C.; Bredeweg, T.; Vieira, D.; Wilhelmy, J.; Tonchev, A.; Stoyer, M.; Bhike, M.; Krishichayan, F.; Tornow, W.; Fowler, M.

2015-10-01

Under a joint collaboration between TUNL-LANL-LLNL, a set of absolute fission product yield measurements has been performed. The energy dependence of a number of cumulative fission product yields (FPY) have been measured using quasi-monoenergetic neutron beams for three actinide targets, 235U, 238U and 239Pu, between 0.5 and 14.8 MeV. The FPYs were measured by a combination of fission counting using specially designed dual-fission chambers and ?-ray counting. Each dual-fission chamber is a back-to-back ionization chamber encasing an activation target in the center with thin deposits of the same target isotope in each chamber. This method allows for the direct measurement of the total number of fissions in the activation target with no reference to the fission cross-section, thus reducing uncertainties. ?-ray counting of the activation target was performed on well-shielded HPGe detectors over a period of 2 months post irradiation to properly identify fission products. Reported are absolute cumulative fission product yields for incident neutron energies of 0.5, 1.37, 2.4, 3.6, 4.6, 5.5, 7.5, 8.9 and 14.8 MeV. These results are compared to previous measurements and theoretical estimates. This work was performed under the auspices of the USDoE by Los Alamos National Security, LLC under Contract DE-AC52-06NA25396.

PRESSURIZED WATER REACTOR PROGRAM TECHNICAL PROGRESS REPORT FOR THE PERIOD MAY 5, 1955 TO JUNE 16, 1955

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

None

The current PWR plant and core parameters are listed. Resign requirements are briefly summarized for a radiation monitoring system, a fuel handling water system, a coolant purification system, an electrical power distribution system, and component shielding. Results of studies on thermal bowing and stressing of UO/sub 2/ are reported. A graph is presented of reactor power vs. reactor flow for various hot channel conditions. Development of U-- Mo and U-Nb alloys has been stopped because of the recent selection of UO/sub 2/ fuel material for the PWR core and blanket. The fabrication characteristics of UO/sub 2/ powders are being studied.more » Seamless Zircaloy-2 tubing has been tested to determine elastic limits, bursting pressures, and corrosion resistance. Fabrication techniques and tests for corrosion and defects in Zircaloy-clad U-Mo and UO/sub 2/ fuel rods are described. The preparation of UO/sub 2/ by various methods is being studied to determine which method produces a material most suitable for PWR fuel elements. The stability of UO/sub 2/ compacts in high temperature water and steam is being determined. Surface area and density measurements have been performed on samples of UO/sub 2/ powder prepared by various methods. Revelopment work on U-- Mo and U--Nb alloys has included studies of the effect on corrosion behavior of additions to the test water, additions to the alloys, homogenization of the alloys, annealing times, cladding, and fabrication techniques. Data are presented on relaxation in spring materials after exposure to a corrosive environment. Results are reported from loop and autoclave tests on fission product and crud deposition. Results of irradiation and corrosion testing of clad and unclad U--Mo and U-Nh alloys are described. The UO/sub 2/ irradiation program has included studies of dimensional changes, release of fission gases, and activity in the water surrounding the samples. A review of the methods of calculating reactor physics parameters has been completed, and the established procedures have been applied to determination of PWR reference design parameters. Critical experiments and primary loop shielding analyses are described. (D.E.B.)« less

Uranium carbide fission target R&D for RIA - an update

NASA Astrophysics Data System (ADS)

Greene, J. P.; Levand, A.; Nolen, J.; Burtseva, T.

2004-12-01

For the Rare Isotope Accelerator (RIA) facility, ISOL targets employing refractory compounds of uranium are being developed to produce radioactive ions for post-acceleration. The availability of refractory uranium compounds in forms that have good thermal conductivity, relatively high density, and adequate release properties for short-lived isotopes remains an important issue. Investigations using commercially obtained uranium carbide material and prepared into targets involving various binder materials have been carried out at ANL. Thin sample pellets have been produced for measurements of thermal conductivity using a new method based on electron bombardment with the thermal radiation observed using a two-color optical pyrometer and performed on samples as a function of grain size, pressing pressure and sintering temperature. Manufacture of uranium carbide powder has now been achieved at ANL. Simulations have been carried out on the thermal behavior of the secondary target assembly incorporating various heat shield configurations.

Energy dependence of fission product yields from 235U, 238U and 239Pu for incident neutron energies between 0.5 and 14.8 MeV

DOE PAGES

Gooden, M. E.; Arnold, C. W.; Becker, J. A.; ...

2016-01-06

In this study, Fission Product Yields (FPY) have historically been one of the most observable features of the fission process. They are known to have strong variations that are dependent on the fissioning species, the excitation energy, and the angular momentum of the compound system. However, consistent and systematic studies of the variation of these FPY with energy have proved challenging. This is caused primarily by the nature of the experiments that have traditionally relied on radiochemical procedures to isolate specific fission products. Although radiochemical procedures exist that can isolate all products, each element presents specific challenges and introduces varyingmore » degrees of systematic errors that can make inter-comparison of FPY uncertain. Although of high importance in fields such as nuclear forensics and Stockpile Stewardship, accurate information about the energy dependence of neutron induced FPY are sparse, due primarily to the lack of suitable monoenergetic neutron sources. There is a clear need for improved data, and to address this issue, a collaboration was formed between Los Alamos National Laboratory (LANL), Lawrence Livermore National Laboratory (LLNL) and the Triangle Universities Nuclear Laboratory (TUNL) to measure the energy dependence of FPY for 235U, 238U and 239Pu. The measurements have been performed at TUNL, using a 10 MV Tandem Van de Graaff accelerator to produce monoenergetic neutrons at energies between 0.6 MeV to 14.8 MeV through a variety of reactions. The measurements have utilized a dual-fission chamber, with thin (10-100 μg/cm2) reference foils of similar material to a thick (100-400 mg) activation target held in the center between the chambers. This method allows for the accurate determination of the number of fissions that occurred in the thick target without requiring knowledge of the fission cross section or neutron fluence on target. Following activation, the thick target was removed from the dual-fission chamber and gamma-ray counted using shielded HPGe detectors for a period of 1-2 months to determine the yield of various fission products. To the extent possible all irradiation and counting procedures were kept the same to minimize sources of systematic errors. FPY have been determined at incident neutron energies of 0.6, 1.4, 2.4, 3.5, 4.6, 5.5, 8.9 and 14.8 MeV.« less

Energy Dependence of Fission Product Yields from {sup 235}U, {sup 238}U and {sup 239}Pu for Incident Neutron Energies Between 0.5 and 14.8 MeV

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

Gooden, M.E., E-mail: m_gooden@lanl.gov; Arnold, C.W.; Becker, J.A.

2016-01-15

Fission Product Yields (FPY) have historically been one of the most observable features of the fission process. They are known to have strong variations that are dependent on the fissioning species, the excitation energy, and the angular momentum of the compound system. However, consistent and systematic studies of the variation of these FPY with energy have proved challenging. This is caused primarily by the nature of the experiments that have traditionally relied on radiochemical procedures to isolate specific fission products. Although radiochemical procedures exist that can isolate all products, each element presents specific challenges and introduces varying degrees of systematicmore » errors that can make inter-comparison of FPY uncertain. Although of high importance in fields such as nuclear forensics and Stockpile Stewardship, accurate information about the energy dependence of neutron induced FPY are sparse, due primarily to the lack of suitable monoenergetic neutron sources. There is a clear need for improved data, and to address this issue, a collaboration was formed between Los Alamos National Laboratory (LANL), Lawrence Livermore National Laboratory (LLNL) and the Triangle Universities Nuclear Laboratory (TUNL) to measure the energy dependence of FPY for {sup 235}U, {sup 238}U and {sup 239}Pu. The measurements have been performed at TUNL, using a 10 MV Tandem Van de Graaff accelerator to produce monoenergetic neutrons at energies between 0.6 MeV to 14.8 MeV through a variety of reactions. The measurements have utilized a dual-fission chamber, with thin (10-100 μg/cm2) reference foils of similar material to a thick (100-400 mg) activation target held in the center between the chambers. This method allows for the accurate determination of the number of fissions that occurred in the thick target without requiring knowledge of the fission cross section or neutron fluence on target. Following activation, the thick target was removed from the dual-fission chamber and gamma-ray counted using shielded HPGe detectors for a period of 1-2 months to determine the yield of various fission products. To the extent possible all irradiation and counting procedures were kept the same to minimize sources of systematic errors. FPY have been determined at incident neutron energies of 0.6, 1.4, 2.4, 3.5, 4.6, 5.5, 8.9 and 14.8 MeV.« less

Correlated Production and Analog Transport of Fission Neutrons and Photons using Fission Models FREYA, FIFRELIN and the Monte Carlo Code TRIPOLI-4® .

NASA Astrophysics Data System (ADS)

Verbeke, Jérôme M.; Petit, Odile; Chebboubi, Abdelhazize; Litaize, Olivier

2018-01-01

Fission modeling in general-purpose Monte Carlo transport codes often relies on average nuclear data provided by international evaluation libraries. As such, only average fission multiplicities are available and correlations between fission neutrons and photons are missing. Whereas uncorrelated fission physics is usually sufficient for standard reactor core and radiation shielding calculations, correlated fission secondaries are required for specialized nuclear instrumentation and detector modeling. For coincidence counting detector optimization for instance, precise simulation of fission neutrons and photons that remain correlated in time from birth to detection is essential. New developments were recently integrated into the Monte Carlo transport code TRIPOLI-4 to model fission physics more precisely, the purpose being to access event-by-event fission events from two different fission models: FREYA and FIFRELIN. TRIPOLI-4 simulations can now be performed, either by connecting via an API to the LLNL fission library including FREYA, or by reading external fission event data files produced by FIFRELIN beforehand. These new capabilities enable us to easily compare results from Monte Carlo transport calculations using the two fission models in a nuclear instrumentation application. In the first part of this paper, broad underlying principles of the two fission models are recalled. We then present experimental measurements of neutron angular correlations for 252Cf(sf) and 240Pu(sf). The correlations were measured for several neutron kinetic energy thresholds. In the latter part of the paper, simulation results are compared to experimental data. Spontaneous fissions in 252Cf and 240Pu are modeled by FREYA or FIFRELIN. Emitted neutrons and photons are subsequently transported to an array of scintillators by TRIPOLI-4 in analog mode to preserve their correlations. Angular correlations between fission neutrons obtained independently from these TRIPOLI-4 simulations, using either FREYA or FIFRELIN, are compared to experimental results. For 240Pu(sf), the measured correlations were used to tune the model parameters.

A 1055 ft/sec impact test of a two foot diameter model nuclear reactor containment system without fracture

NASA Technical Reports Server (NTRS)

Puthoff, R. L.

1972-01-01

A study to determine the feasibility of containing the fission products of a mobile reactor in the event of an impact is presented. The model simulated the reactor core, energy absorbing gamma shielding, neutron shielding and the containment vessel. It was impacted against an 18,000 pound reinforced concrete block at 1055 ft/sec. The model was significantly deformed and the concrete block demolished. No leaks were detected nor were any cracks observed in the model after impact.

The performance of hafnium and gadolinium self powered neutron detectors in the TREAT reactor

NASA Astrophysics Data System (ADS)

Imel, G. R.; Hart, P. R.

1996-05-01

The use of gadolinium and hafnium self powered neutron detectors in a transient reactor is described in this paper. The detectors were calibrated to the fission rate of U-235 using calibrated fission chambers; the calibration factors were tested in two reactors in steady state and found to be consistent. Calibration of the detectors in transient reactor conditions was done by using uranium wires that were analyzed by radiochemistry techniques to determine total fissions during the transient. This was correlated to the time-integrated current of the detectors during the transient. A temperature correction factor was derived to account for self-shielding effects in the hafnium and gadolinium detectors. The dynamic response of the detectors under transient conditions was studied, and found to be excellent.

Subthreshold neutron interrogator for detection of radioactive materials

DOEpatents

Evans, Michael L.; Menlove, Howard O.; Baker, Michael P.

1980-01-01

A device for detecting fissionable material such as uranium in low concentrations by interrogating with photoneutrons at energy levels below 500 keV, and typically about 26 keV. Induced fast neutrons having energies above 500 keV by the interrogated fissionable material are detected by a liquid scintillator or recoil proportional counter which is sensitive to the induced fast neutrons. Since the induced fast neutrons are proportional to the concentration of fissionable material, detection of induced fast neutrons indicate concentration of the fissionable material.

Remanent Activation in the Mini-SHINE Experiments

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

Micklich, Bradley J.

2015-04-16

Argonne National Laboratory is assisting SHINE Medical Technologies in developing a domestic source of the medical isotope 99Mo through the fission of low-enrichment uranium in a uranyl sulfate solution. In Phase 2 of these experiments, electrons from a linear accelerator create neutrons by interacting in a depleted uranium target, and these neutrons are used to irradiate the solution. The resulting neutron and photon radiation activates the target, the solution vessels, and a shielded cell that surrounds the experimental apparatus. When the experimental campaign is complete, the target must be removed into a shielding cask, and the experimental components must bemore » disassembled. The radiation transport code MCNPX and the transmutation code CINDER were used to calculate the radionuclide inventories of the solution, the target assembly, and the shielded cell, and to determine the dose rates and shielding requirements for selected removal scenarios for the target assembly and the solution vessels.« less

Energy Dependence of Fission Product Yields from 235 U, 238U, and 239Pu for Incident Neutron Energies Between 0.5 and 14.8 MeV

NASA Astrophysics Data System (ADS)

Gooden, Matthew Edgell

A joint collaboration between the Triangle Universities Nuclear Laboratory (TUNL), Los Alamos National Laboratory (LANL) and Lawrence Livermore National Laboratory (LLNL) has performed a set of absolute Fission Product Yield (FPY) measurements. Using monoenergetic neutron at energies between 0.5 and 14.8 MeV, the excitation functions of a number of fission products from 235U, 238U and 239Pu have begun to be mapped out. This work has practical applications for the determination of weapon yields and the rate of burn-up in nuclear reactors, while also providing important insight into the fission process. Combining the use of a dual-fission ionization chamber and gamma-ray spectroscopy, absolute FPYs have been determined for approximately 15 different fission products. The dual-fission chamber is a back-to-back ionization chamber system with a 'thin' actinide foil in each chamber as a monitor or reference foil. The chamber holds a 'thick' target in the center of the system such that the target and reference foils are of the same actinide isotope. This allows for simple mass scaling between the recorded number of fissions in the individual chambers and the number of fissions in the center thick target, eliminating the need for the knowledge of the absolute fission cross section and its uncertainty. The 'thick' target was removed after activation and gamma-rays counted with well shielded High Purity Germanium (HPGe) detectors for a period of 1.5 - 2 months.

Research Technology

NASA Image and Video Library

1999-01-01

In the 1960's U.S. Government laboratories, under Project Orion, investigated a pulsed nuclear fission propulsion system. Small nuclear pulse units would be sequentially discharged from the aft end of the vehicle. A blast shield and shock absorber system would protect the crew and convert the shock loads into a continuous propulsive force.

Radiation shielding materials and containers incorporating same

DOEpatents

Mirsky, Steven M.; Krill, Stephen J.; Murray, Alexander P.

2005-11-01

An improved radiation shielding material and storage systems for radioactive materials incorporating the same. The PYRolytic Uranium Compound ("PYRUC") shielding material is preferably formed by heat and/or pressure treatment of a precursor material comprising microspheres of a uranium compound, such as uranium dioxide or uranium carbide, and a suitable binder. The PYRUC shielding material provides improved radiation shielding, thermal characteristic, cost and ease of use in comparison with other shielding materials. The shielding material can be used to form containment systems, container vessels, shielding structures, and containment storage areas, all of which can be used to house radioactive waste. The preferred shielding system is in the form of a container for storage, transportation, and disposal of radioactive waste. In addition, improved methods for preparing uranium dioxide and uranium carbide microspheres for use in the radiation shielding materials are also provided.

Radiation Shielding Materials and Containers Incorporating Same

DOEpatents

Mirsky, Steven M.; Krill, Stephen J.; and Murray, Alexander P.

2005-11-01

An improved radiation shielding material and storage systems for radioactive materials incorporating the same. The PYRolytic Uranium Compound (''PYRUC'') shielding material is preferably formed by heat and/or pressure treatment of a precursor material comprising microspheres of a uranium compound, such as uranium dioxide or uranium carbide, and a suitable binder. The PYRUC shielding material provides improved radiation shielding, thermal characteristic, cost and ease of use in comparison with other shielding materials. The shielding material can be used to form containment systems, container vessels, shielding structures, and containment storage areas, all of which can be used to house radioactive waste. The preferred shielding system is in the form of a container for storage, transportation, and disposal of radioactive waste. In addition, improved methods for preparing uranium dioxide and uranium carbide microspheres for use in the radiation shielding materials are also provided.

Method to Reduce Long-lived Fission Products by Nuclear Transmutations with Fast Spectrum Reactors.

PubMed

Chiba, Satoshi; Wakabayashi, Toshio; Tachi, Yoshiaki; Takaki, Naoyuki; Terashima, Atsunori; Okumura, Shin; Yoshida, Tadashi

2017-10-24

Transmutation of long-lived fission products (LLFPs: 79 Se, 93 Zr, 99 Tc, 107 Pd, 129 I, and 135 Cs) into short-lived or non-radioactive nuclides by fast neutron spectrum reactors without isotope separation has been proposed as a solution to the problem of radioactive wastes disposal. Despite investigation of many methods, such transmutation remains technologically difficult. To establish an effective and efficient transmutation system, we propose a novel neutron moderator material, yttrium deuteride (YD 2 ), to soften the neutron spectrum leaking from the reactor core. Neutron energy spectra and effective half-lives of LLFPs, transmutation rates, and support ratios were evaluated with the continuous-energy Monte Carlo code MVP-II/MVP-BURN and the JENDL-4.0 cross section library. With the YD 2 moderator in the radial blanket and shield regions, effective half-lives drastically decreased from 106 to 102 years and the support ratios reached 1.0 for all six LLFPs. This successful development and implementation of a transmutation system for LLFPs without isotope separation contributes to a the ability of fast spectrum reactors to reduce radioactive waste by consuming their own LLFPs.

Preliminary Evaluation of Convective Heat Transfer in a Water Shield for a Surface Power Reactor

NASA Technical Reports Server (NTRS)

Pearson J. Boise; Reid, Robert S.

2007-01-01

As part of the Vision for Space Exploration, the end of the next decade will bring man back to the surface of the moon. A crucial issue for the establishment of human presence on the moon will be the availability of compact power sources. This presence could require greater than 10's of kWt's in follow on years. Nuclear reactors are well suited to meet the needs for power generation on the lunar or Martian surface. Radiation shielding is a key component of any surface power reactor system. Several competing concepts exist for lightweight, safe, robust shielding systems such as a water shield, lithium hydride (LiH), and boron carbide. Water offers several potential advantages, including reduced cost, reduced technical risk, and reduced mass. Water has not typically been considered for space reactor applications because of the need for gravity to fix the location of any vapor that could form radiation streaming paths. The water shield concept relies on the predictions of passive circulation of the shield water by natural convection to adequately cool the shield. This prediction needs to be experimentally evaluated, especially for shields with complex geometries. NASA Marshall Space Flight Center has developed the experience and facilities necessary to do this evaluation in its Early Flight Fission - Test Facility (EFF-TF).

A 640 foot per second impact test of a two foot diameter model nuclear reactor containment system without fracture

NASA Technical Reports Server (NTRS)

Puthoff, R. L.

1971-01-01

An impact test was conducted on an 1142 pound 2 foot diameter sphere model. The purpose of this test was to determine the feasibility of containing the fission products of a mobile reactor in an impact. The model simulated the reactor core, energy absorbing gamma shielding, neutron shielding and the containment vessel. It was impacted against an 18,000 pound reinforced concrete block. The model was significantly deformed and the concrete block demolished. No leaks were detected nor cracks observed in the model after impact.

PBF Reactor Building (PER620) basement. Workers wearing protective gear work ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

PBF Reactor Building (PER-620) basement. Workers wearing protective gear work inside cubicle 13 on the fission product detection system. Man on left is atop shielded box shown in previous photo. Posture of second man illustrates waist-high height of shielding box. His hand rests on the access panel, which has been filled with lead bricks and which has been slid shut to enclose detection instruments within box. Photographer: John Capek. Date: January 24, 1983. INEEL negative no. 83-41-3-5 - Idaho National Engineering Laboratory, SPERT-I & Power Burst Facility Area, Scoville, Butte County, ID

Covariance generation and uncertainty propagation for thermal and fast neutron induced fission yields

NASA Astrophysics Data System (ADS)

Terranova, Nicholas; Serot, Olivier; Archier, Pascal; De Saint Jean, Cyrille; Sumini, Marco

2017-09-01

Fission product yields (FY) are fundamental nuclear data for several applications, including decay heat, shielding, dosimetry, burn-up calculations. To be safe and sustainable, modern and future nuclear systems require accurate knowledge on reactor parameters, with reduced margins of uncertainty. Present nuclear data libraries for FY do not provide consistent and complete uncertainty information which are limited, in many cases, to only variances. In the present work we propose a methodology to evaluate covariance matrices for thermal and fast neutron induced fission yields. The semi-empirical models adopted to evaluate the JEFF-3.1.1 FY library have been used in the Generalized Least Square Method available in CONRAD (COde for Nuclear Reaction Analysis and Data assimilation) to generate covariance matrices for several fissioning systems such as the thermal fission of U235, Pu239 and Pu241 and the fast fission of U238, Pu239 and Pu240. The impact of such covariances on nuclear applications has been estimated using deterministic and Monte Carlo uncertainty propagation techniques. We studied the effects on decay heat and reactivity loss uncertainty estimation for simplified test case geometries, such as PWR and SFR pin-cells. The impact on existing nuclear reactors, such as the Jules Horowitz Reactor under construction at CEA-Cadarache, has also been considered.

NEUTRONIC REACTOR

DOEpatents

Wigner, E.P.

1957-09-17

A reactor of the type having coolant liquid circulated through clad fuel elements geometrically arranged in a solid moderator, such as graphite, is described. The core is enclosed in a pressure vessel and suitable shielding, wherein means is provided for circulating vapor through the core to superheat the same. This is accomplished by drawing off the liquid which has been heated in the core due to the fission of the fuel, passing it to a nozzle within a chamber where it flashes into a vapor, and then passing the vapor through separate tubes extending through the moderator to pick up more heat developed in the core due to the fission of the fuel, thereby producing superheated vapor.

Detecting special nuclear materials in containers using high-energy gamma rays emitted by fission products

DOEpatents

Norman, Eric B.; Prussin, Stanley G.

2007-10-02

A method and a system for detecting the presence of special nuclear materials in a container. The system and its method include irradiating the container with an energetic beam, so as to induce a fission in the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

Experimental Evaluation of a Water Shield for a Surface Power Reactor

NASA Technical Reports Server (NTRS)

Pearson, J. Boise; Reid, Robert S.

2006-01-01

As part of the Vision for Space Exploration the end of the next decade will bring man back to the surface of the moon. One of the most critical issues for the establishment of human presence on the moon will be the availability of compact power sources. The establishment of man on the moon will require power from greater than 10's of kWt's in follow on years. Nuclear reactors are extremely we11 suited to meet the needs for power generation on the lunar or Martian surface. reactor system. Several competing concepts exist for lightweight, safe, robust shielding systems such as a water shield, lithium hydride (LiH), Boron Carbide, and others. Water offers several potential advantages, including reduced cost, reduced technical risk, and reduced mass. Water has not typically been considered for space reactor applications because of the need for gravity to remove the potential for radiation streaming paths. The water shield concept relies on predictions of passive circulation of the shield water by natural convection to adequately cool the shield. This prediction needs to be experimentally evaluated, especially for shields with complex geometries. MSFC has developed the experience and fac necessary to do this evaluation in the Early Flight Fission - Test Facility (EFF-TF).

Post Irradiation Evaluation of Thermal Control Coatings and Solid Lubricants to Support Fission Surface Power Systems

NASA Astrophysics Data System (ADS)

Bowman, Cheryl L.; Jaworske, Donald A.; Stanford, Malcolm K.; Persinger, Justin A.; Khorsandi, Behrooz; Blue, Thomas E.

2007-01-01

The development of a nuclear power system for space missions, such as the Jupiter Icy Moons Orbiter or a lunar outpost, requires substantially more compact reactor design than conventional terrestrial systems. In order to minimize shielding requirements and hence system weight, the radiation tolerance of component materials within the power conversion and heat rejection systems must be defined. Two classes of coatings, thermal control paints and solid lubricants, were identified as material systems for which limited radiation hardness information was available. Screening studies were designed to explore candidate coatings under a predominately fast neutron spectrum. The Ohio State Research Reactor Facility staff performed irradiation in a well characterized, mixed energy spectrum and performed post irradiation analysis of representative coatings for thermal control and solid lubricant applications. Thermal control paints were evaluated for 1 MeV equivalent fluences from 1013 to 1015 n/cm2. No optical degradation was noted although some adhesive degradation was found at higher fluence levels. Solid lubricant coatings were evaluated for 1 MeV equivalent fluences from 1015 to 1016 n/cm2 with coating adhesion and flexibility used for post irradiation evaluation screening. The exposures studied did not lead to obvious property degradation indicating the coatings would have survived the radiation environment for the previously proposed Jupiter mission. The results are also applicable to space power development programs such as fission surface power for future lunar and Mars missions.

Post Irradiation Evaluation of Thermal Control Coatings and Solid Lubricants to Support Fission Surface Power Systems

NASA Technical Reports Server (NTRS)

Bowman, Cheryl L.; Jaworske, Donald A.; Stanford, Malcolm K.; Persinger, Justin A.; Khorsandi, Behrooz; Blue, Thomas E.

2007-01-01

The development of a nuclear power system for space missions, such as the Jupiter Icy Moons Orbiter or a lunar outpost, requires substantially more compact reactor design than conventional terrestrial systems. In order to minimize shielding requirements and hence system weight, the radiation tolerance of component materials within the power conversion and heat rejection systems must be defined. Two classes of coatings, thermal control paints and solid lubricants, were identified as material systems for which limited radiation hardness information was available. Screening studies were designed to explore candidate coatings under a predominately fast neutron spectrum. The Ohio State Research Reactor Facility staff performed irradiation in a well characterized, mixed energy spectrum and performed post irradiation analysis of representative coatings for thermal control and solid lubricant applications. Thermal control paints were evaluated for 1 MeV equivalent fluences from 10(exp 13) to 10(exp 15) n per square centimeters. No optical degradation was noted although some adhesive degradation was found at higher fluence levels. Solid lubricant coatings were evaluated for 1 MeV equivalent fluences from 10(exp 15) to 10(exp 16) n per square centimeters with coating adhesion and flexibility used for post irradiation evaluation screening. The exposures studied did not lead to obvious property degradation indicating the coatings would have survived the radiation environment for the previously proposed Jupiter mission. The results are also applicable to space power development programs such as fission surface power for future lunar and Mars missions.

NEUTRONIC REACTOR COUNTER METHOD AND SYSTEM

DOEpatents

Graham, C.B.; Spiewak, I.

1960-05-31

An improved method is given for controlling the rate of fission in circulating-fuel neutronic reactors in which the fuel is a homogeneous liquid containing fissionable material and a neutron moderator. A change in the rate of flssion is effected by preferentially retaining apart from the circulating fuel a variable amount of either fissionable material or moderator, thereby varying the concentration of fissionable material in the fuel. In the case of an aqueous fuel solution a portion of the water may be continuously vaporized from the circulating solution and the amount of condensate, or condensate plus make-up water, returned to the solution is varied to control the fission rate.

DN/DG Screening of Environmental Swipe Samples: FY2016 Report

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

Glasgow, David C.; Croft, Stephen; Venkataraman, Ramkumar

The Delayed Neutron Delayed Gamma (DNDG) technique provides a new analytical capability to the International Atomic Energy Agency (IAEA) for detecting undeclared nuclear activities. IAEA’s Long Term R&D (LTRD) plan has a stated high urgency need to develop elemental and isotopic signatures of nuclear fuel cycle activities and processes (LTRD 2.2). The new DNDG capability is used to co-detect both uranium and plutonium as an extension of a DN only method that is already being utilized by the IAEA for the analysis of swipes to inform on undeclared nuclear activities. Analytical method involving irradiation of swipe samples potentially containing tracemore » quantities of fissile material in a thermal neutron field, followed by the counting of delayed neutrons, is a well-known technique in the field of safeguards and nonproliferation. It is used for detecting the presence of microscopic amounts of fissile material, (typically a linear combination of 233U, 235U, 239Pu, and 241Pu)and quantifying it in terms of the equivalent mass of 235U. The delayed neutron (DN) technique is very sensitive and is been routinely employed at the High Flux Isotope Reactor (HFIR) facility at Oak Ridge National Laboratory (ORNL). Both uranium and plutonium are of high safeguards value. However, the DN technique is not well suited for distinguishing between U and Pu isotopes since the decay curves overlap closely. The delayed gamma (DG) technique will help detect the presence of 239Pu in a mixture of U and Pu. Thus the DNDG approach combines the best of both worlds; the sensitivity of DN counting and the isotopic specificity of DG counting. The present work seeks to build on the delayed neutron and delayed gamma methods that have been developed at ORNL. It is recognized that the distribution profile of heavy fission products remains fairly invariant for the fissile nuclides whereas the distribution of light fission products varies from one isotope to another. That is, the ratio of the yield of a light fission fragment to a heavy fission fragments is isotope specific. Measurement of the ratio of the net full energy peak (FEP) from low/high mass fission products is an elegant way to characterize the fraction of fissile materials present in a mixture. By empirically calibrating the ratio of the net FEP as a function of known concentration of the binary mixture, one can determine the fraction of fissile isotopes in an unknown sample. In the work done in fiscal year (FY) 2016, samples of single fissile material isotopes as well as binary mixtures were irradiated in a well thermalized irradiation field in the HFIR. Delayed neutron counting was performed using the neutron counter at the HFIR Neutron Activation Analysis (NAA) laboratory. Delayed gamma counting was performed using a shielded high purity germanium (HPGe) detector. Delayed neutron decay curve results highlighted the difficulty of distinguishing between U and Pu isotopes, and the need for including the delayed gamma component. Based on delayed gamma spectrometry, twelve ratios of low mass/high fission product gamma ray FEP have been identified as valid candidates. Linearity of the ratios, as a function of 239Pu fraction in 235U+ 239Pu mixtures, was confirmed for the low mass/high mass candidates that were selected. The DNDG method we are spearheading allows not only the presence of total fissile content to be detected, but whether the material is predominantly U or predominantly Pu, or a mixture. This provides additional SG relevant information.« less

Detecting special nuclear materials in suspect containers using high-energy gamma rays emitted by fission products

DOEpatents

Norman, Eric B [Oakland, CA; Prussin, Stanley G [Kensington, CA

2009-05-05

A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

Detecting special nuclear materials in suspect containers using high-energy gamma rays emitted by fission products

DOEpatents

Norman, Eric B [Oakland, CA; Prussin, Stanley G [Kensington, CA

2009-01-27

A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

Detecting special nuclear materials in suspect containers using high-energy gamma rays emitted by fission products

DOEpatents

Norman, Eric B [Oakland, CA; Prussin, Stanley G [Kensington, CA

2009-01-06

A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

Method for studying a sample of material using a heavy ion induced mass spectrometer source

DOEpatents

Fries, D.P.; Browning, J.F.

1999-02-16

A heavy ion generator is used with a plasma desorption mass spectrometer to provide an appropriate neutron flux in the direction of a fissionable material in order to desorb and ionize large molecules from the material for mass analysis. The heavy ion generator comprises a fissionable material having a high n,f reaction cross section. The heavy ion generator also comprises a pulsed neutron generator that is used to bombard the fissionable material with pulses of neutrons, thereby causing heavy ions to be emitted from the fissionable material. These heavy ions impinge on a material, thereby causing ions to desorb off that material. The ions desorbed off the material pass through a time-of-flight mass analyzer, wherein ions can be measured with masses greater than 25,000 amu. 3 figs.

Method for studying a sample of material using a heavy ion induced mass spectrometer source

DOEpatents

Fries, David P.; Browning, James F.

1999-01-01

A heavy ion generator is used with a plasma desorption mass spectrometer to provide an appropriate neutron flux in the direction of a fissionable material in order to desorb and ionize large molecules from the material for mass analysis. The heavy ion generator comprises a fissionable material having a high n,f reaction cross section. The heavy ion generator also comprises a pulsed neutron generator that is used to bombard the fissionable material with pulses of neutrons, thereby causing heavy ions to be emitted from the fissionable material. These heavy ions impinge on a material, thereby causing ions to desorb off that material. The ions desorbed off the material pass through a time-of-flight mass analyzer, wherein ions can be measured with masses greater than 25,000 amu.

System for studying a sample of material using a heavy ion induced mass spectrometer source

DOEpatents

Fries, David P.; Browning, James F.

1998-01-01

A heavy ion generator is used with a plasma desorption mass spectrometer to provide an appropriate neutron flux in the direction of a fissionable material in order to desorb and ionize large molecules from the material for mass analysis. The heavy ion generator comprises a fissionable material having a high n,f reaction cross section. The heavy ion generator also comprises a pulsed neutron generator that is used to bombard the fissionable material with pulses of neutrons, thereby causing heavy ions to be emitted from the fissionable material. These heavy ions impinge on a material, thereby causing ions to desorb off that material. The ions desorbed off the material pass through a time-of-flight mass analyzer, wherein ions can be measured with masses greater than 25,000 amu.

System for studying a sample of material using a heavy ion induced mass spectrometer source

DOEpatents

Fries, D.P.; Browning, J.F.

1998-07-21

A heavy ion generator is used with a plasma desorption mass spectrometer to provide an appropriate neutron flux in the direction of a fissionable material in order to desorb and ionize large molecules from the material for mass analysis. The heavy ion generator comprises a fissionable material having a high (n,f) reaction cross section. The heavy ion generator also comprises a pulsed neutron generator that is used to bombard the fissionable material with pulses of neutrons, thereby causing heavy ions to be emitted from the fissionable material. These heavy ions impinge on a material, thereby causing ions to desorb off that material. The ions desorbed off the material pass through a time-of-flight mass analyzer, wherein ions can be measured with masses greater than 25,000 amu. 3 figs.

Developing an in-situ Detector of Neutron-Induced Fission for Actinide Sputtering Characterization

NASA Astrophysics Data System (ADS)

Fellers, Deion

2016-09-01

The physical mechanism describing the transfer of large amounts of energy due to fission in a material is not well understood and represents one of the modern challenges facing nuclear scientists, with applications including nuclear energy and national defense. Fission fragments cause damage to the material from sputtering of matter as they pass through or near the material's surface. We have developed a new technique at the Los Alamos Neutron Science Center for characterizing the ejecta by using ultracold neutrons (neutrons with kinetic energy less than 300 neV) to induce fission at finely controlled depths in an actinide. This program will ultimately provide a detailed description of the properties of the sputtered particles as a function of the depth of the fission in the material. A key component of this project is accurately quantifying the number of neutron induced fissions in the sample. This poster depicts the development of an in-situ detector of neutron-induced fission for the AShES (Actinide Sputtering from ultracold neutron Exposure at the Surface) experiment.

Remote fabrication and irradiation test of recycled nuclear fuel prepared by the oxidation and reduction of spent oxide fuel

NASA Astrophysics Data System (ADS)

Jin Ryu, Ho; Chan Song, Kee; Il Park, Geun; Won Lee, Jung; Seung Yang, Myung

2005-02-01

A direct dry recycling process was developed in order to reuse spent pressurized light water reactor (LWR) nuclear fuel in CANDU reactors without the separation of sensitive nuclear materials such as plutonium. The benefits of the dry recycling process are the saving of uranium resources and the reduction of spent fuel accumulation as well as a higher proliferation resistance. In the process of direct dry recycling, fuel pellets separated from spent LWR fuel rods are oxidized from UO2 to U3O8 at 500 °C in an air atmosphere and reduced into UO2 at 700 °C in a hydrogen atmosphere, which is called OREOX (oxidation and reduction of oxide fuel). The pellets are pulverized during the oxidation and reduction processes due to the phase transformation between cubic UO2 and orthorhombic U3O8. Using the oxide powder prepared from the OREOX process, the compaction and sintering processes are performed in a remote manner in a shielded hot cell due to the high radioactivity of the spent fuel. Most of the fission gas and volatile fission products are removed during the OREOX and sintering processes. The mini-elements fabricated by the direct dry recycling process are irradiated in the HANARO research reactor for the performance evaluation of the recycled fuel pellets. Post-irradiation examination of the irradiated fuel showed that microstructural evolution and fission gas release behavior of the dry-recycled fuel were similar to high burnup UO2 fuel.

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

Koning, A.J.; Bersillon, O.; Forrest, R. A.

The status of the Joint Evaluated Fission and Fusion file (JEFF) is described. The next version of the library, JEFF-3.1, comprises a significant update of actinide evaluations, evaluations emerging from European nuclear data projects, the activation library JEFF-3/A, the decay data and fission yield library, and fusion-related data files from the EFF project. The revisions were motivated by the availability of new measurements, modelling capabilities, or trends from integral experiments. Various pre-release validation efforts are underway, mainly for criticality and shielding of thermal and fast systems. This JEFF-3.1 library is expected to provide improved performances with respect to previous releasesmore » for a variety of scientific and industrial applications.« less

FUEL ELEMENT

DOEpatents

Fortescue, P.; Zumwalt, L.R.

1961-11-28

A fuel element was developed for a gas cooled nuclear reactor. The element is constructed in the form of a compacted fuel slug including carbides of fissionable material in some cases with a breeder material carbide and a moderator which slug is disposed in a canning jacket of relatively impermeable moderator material. Such canned fuel slugs are disposed in an elongated shell of moderator having greater gas permeability than the canning material wherefore application of reduced pressure to the space therebetween causes gas diffusing through the exterior shell to sweep fission products from the system. Integral fission product traps and/or exterior traps as well as a fission product monitoring system may be employed therewith. (AEC)

Nuclear reactor fuel element

DOEpatents

Johnson, Carl E.; Crouthamel, Carl E.

1980-01-01

A nuclear reactor fuel element is described which has an outer cladding, a central core of fissionable or mixed fissionable and fertile fuel material and a layer of oxygen gettering material on the inner surface of the cladding. The gettering material reacts with oxygen released by the fissionable material during irradiation of the core thereby preventing the oxygen from reacting with and corroding the cladding. Also described is an improved method for coating the inner surface of the cladding with a layer of gettering material.

High-Fidelity Modelng and Simulation for a High Flux Isotope Reactor Low-Enriched Uranium Core Design

DOE PAGES

Betzler, Benjamin R.; Chandler, David; Davidson, Eva E.; ...

2017-05-08

A high-fidelity model of the High Flux Isotope Reactor (HFIR) with a low-enriched uranium (LEU) fuel design and a representative experiment loading has been developed to serve as a new reference model for LEU conversion studies. With the exception of the fuel elements, this HFIR LEU model is completely consistent with the current highly enriched uranium HFIR model. Results obtained with the new LEU model provide a baseline for analysis of alternate LEU fuel designs and further optimization studies. The newly developed HFIR LEU model has an explicit representation of the HFIR-specific involute fuel plate geometry, including the within-plate fuelmore » meat contouring, and a detailed geometry model of the fuel element side plates. Such high-fidelity models are necessary to accurately account for the self-shielding from 238U and the depletion of absorber materials present in the side plates. In addition, a method was developed to account for fuel swelling in the high-density LEU fuel plates during the depletion simulation. In conclusion, calculated time-dependent metrics for the HFIR LEU model include fission rate and cumulative fission density distributions, flux and reaction rates for relevant experiment locations, point kinetics data, and reactivity coefficients.« less

High-Fidelity Modelng and Simulation for a High Flux Isotope Reactor Low-Enriched Uranium Core Design

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

Betzler, Benjamin R.; Chandler, David; Davidson, Eva E.

A high-fidelity model of the High Flux Isotope Reactor (HFIR) with a low-enriched uranium (LEU) fuel design and a representative experiment loading has been developed to serve as a new reference model for LEU conversion studies. With the exception of the fuel elements, this HFIR LEU model is completely consistent with the current highly enriched uranium HFIR model. Results obtained with the new LEU model provide a baseline for analysis of alternate LEU fuel designs and further optimization studies. The newly developed HFIR LEU model has an explicit representation of the HFIR-specific involute fuel plate geometry, including the within-plate fuelmore » meat contouring, and a detailed geometry model of the fuel element side plates. Such high-fidelity models are necessary to accurately account for the self-shielding from 238U and the depletion of absorber materials present in the side plates. In addition, a method was developed to account for fuel swelling in the high-density LEU fuel plates during the depletion simulation. In conclusion, calculated time-dependent metrics for the HFIR LEU model include fission rate and cumulative fission density distributions, flux and reaction rates for relevant experiment locations, point kinetics data, and reactivity coefficients.« less

Spectroscopic neutron detection using composite scintillators

NASA Astrophysics Data System (ADS)

Jovanovic, I.; Foster, A.; Kukharev, V.; Mayer, M.; Meddeb, A.; Nattress, J.; Ounaies, Z.; Trivelpiece, C.

2016-09-01

Shielded special nuclear material (SNM), especially highly enriched uranium, is exceptionally difficult to detect without the use of active interrogation (AI). We are investigating the potential use of low-dose active interrogation to realize simultaneous high-contrast imaging and photofission of SNM using energetic gamma-rays produced by low-energy nuclear reactions, such as 11B(d,nγ)12C and 12C(p,p‧)12C. Neutrons produced via fission are one reliable signature of the presence of SNM and are usually identified by their unique timing characteristics, such as the delayed neutron die-away. Fast neutron spectroscopy may provide additional useful discriminating characteristics for SNM detection. Spectroscopic measurements can be conducted by recoil-based or thermalization and capture-gated detectors; the latter may offer unique advantages since they facilitate low-statistics and event-by-event neutron energy measurements without spectrum unfolding. We describe the results of the development and characterization of a new type of capture-gated spectroscopic neutron detector based on a composite of scintillating polyvinyltoluene and lithium-doped scintillating glass in the form of millimeter-thick rods. The detector achieves >108 neutron-gamma discrimination resulting from its geometric properties and material selection. The design facilitates simultaneous pulse shape and pulse height discrimination, despite the fact that no materials intrinsically capable of pulse shape discrimination have been used to construct the detector. Accurate single-event measurements of neutron energy may be possible even when the energy is relatively low, such as with delayed fission neutrons. Simulation and preliminary measurements using the new composite detector are described, including those conducted using radioisotope sources and the low-dose active interrogation system based on low-energy nuclear reactions.

Performance study of galactic cosmic ray shield materials

NASA Technical Reports Server (NTRS)

Kim, Myung-Hee Y.; Wilson, John W.; Thibeault, Sheila A.; Nealy, John E.; Badavi, Francis F.; Kiefer, Richard L.

1994-01-01

The space program is faced with two difficult radiation protection issues for future long-term operations. First, retrofit of shield material or conservatism in shield design is prohibitively expensive and often impossible. Second, shielding from the cosmic heavy ions is faced with limited knowledge on the physical properties and biological responses of these radiations. The current status of space shielding technology and its impact on radiation health is discussed herein in terms of conventional protection practice and a test biological response model. The impact of biological response on the selection of optimum materials for cosmic ray shielding is presented in terms of the transmission characteristics of the shield material. Although the systematics of nuclear cross sections are able to demonstrate the relation of exposure risk to shield-material composition, the current uncertainty in-nuclear cross sections will not allow an accurate evaluation of risk reduction. This paper presents a theoretical study of risk-related factors and a pilot experiment to study the effectiveness of choice of shield materials to reduce the risk in space operations.

Singlet exciton fission photovoltaics.

PubMed

Lee, Jiye; Jadhav, Priya; Reusswig, Philip D; Yost, Shane R; Thompson, Nicholas J; Congreve, Daniel N; Hontz, Eric; Van Voorhis, Troy; Baldo, Marc A

2013-06-18

Singlet exciton fission, a process that generates two excitons from a single photon, is perhaps the most efficient of the various multiexciton-generation processes studied to date, offering the potential to increase the efficiency of solar devices. But its unique characteristic, splitting a photogenerated singlet exciton into two dark triplet states, means that the empty absorption region between the singlet and triplet excitons must be filled by adding another material that captures low-energy photons. This has required the development of specialized device architectures. In this Account, we review work to develop devices that harness the theoretical benefits of singlet exciton fission. First, we discuss singlet fission in the archetypal material, pentacene. Pentacene-based photovoltaic devices typically show high external and internal quantum efficiencies. They have enabled researchers to characterize fission, including yield and the impact of competing loss processes, within functional devices. We review in situ probes of singlet fission that modulate the photocurrent using a magnetic field. We also summarize studies of the dissociation of triplet excitons into charge at the pentacene-buckyball (C60) donor-acceptor interface. Multiple independent measurements confirm that pentacene triplet excitons can dissociate at the C60 interface despite their relatively low energy. Because triplet excitons produced by singlet fission each have no more than half the energy of the original photoexcitation, they limit the potential open circuit voltage within a solar cell. Thus, if singlet fission is to increase the overall efficiency of a solar cell and not just double the photocurrent at the cost of halving the voltage, it is necessary to also harvest photons in the absorption gap between the singlet and triplet energies of the singlet fission material. We review two device architectures that attempt this using long-wavelength materials: a three-layer structure that uses long- and short-wavelength donors and an acceptor and a simpler, two-layer combination of a singlet-fission donor and a long-wavelength acceptor. An example of the trilayer structure is singlet fission in tetracene with copper phthalocyanine inserted at the C60 interface. The bilayer approach includes pentacene photovoltaic cells with an acceptor of infrared-absorbing lead sulfide or lead selenide nanocrystals. Lead selenide nanocrystals appear to be the most promising acceptors, exhibiting efficient triplet exciton dissociation and high power conversion efficiency. Finally, we review architectures that use singlet fission materials to sensitize other absorbers, thereby effectively converting conventional donor materials to singlet fission dyes. In these devices, photoexcitation occurs in a particular molecule and then energy is transferred to a singlet fission dye where the fission occurs. For example, rubrene inserted between a donor and an acceptor decouples the ability to perform singlet fission from other major photovoltaic properties such as light absorption.

Energy dependence of fission product yields from 235U, 238U, and 239Pu with monoenergetic neutrons between thermal and 14.8 MeV

NASA Astrophysics Data System (ADS)

Gooden, Matthew; Arnold, Charles; Bhike, Megha; Bredeweg, Todd; Fowler, Malcolm; Krishichayan; Tonchev, Anton; Tornow, Werner; Stoyer, Mark; Vieira, David; Wilhelmy, Jerry

2017-09-01

Under a joint collaboration between TUNL-LANL-LLNL, a set of absolute fission product yield measurements has been performed. The energy dependence of a number of cumulative fission product yields (FPY) have been measured using quasi-monoenergetic neutron beams for three actinide targets, 235U, 238U and 239Pu, between 0.5 and 14.8 MeV. The FPYs were measured by a combination of fission counting using specially designed dual-fission chambers and γ-ray counting. Each dual-fission chamber is a back-to-back ionization chamber encasing an activation target in the center with thin deposits of the same target isotope in each chamber. This method allows for the direct measurement of the total number of fissions in the activation target with no reference to the fission cross-section, thus reducing uncertainties. γ-ray counting of the activation target was performed on well-shielded HPGe detectors over a period of two months post irradiation to properly identify fission products. Reported are absolute cumulative fission product yields for incident neutron energies of 0.5, 1.37, 2.4, 3.6, 4.6, 5.5, 7.5, 8.9 and 14.8 MeV. Preliminary results from thermal irradiations at the MIT research reactor will also be presented and compared to present data and evaluations. This work was performed under the auspices of the U.S. Department of Energy by Los Alamos National Security, LLC under contract DE-AC52-06NA25396, Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344 and by Duke University and Triangle Universities Nuclear Laboratory through NNSA Stewardship Science Academic Alliance grant No. DE-FG52-09NA29465, DE-FG52-09NA29448 and Office of Nuclear Physics Grant No. DE-FG02-97ER41033.

Determination of shielding requirements for mammography.

PubMed

Okunade, Akintunde Akangbe; Ademoroti, Olalekan Albert

2004-05-01

Shielding requirements for mammography when considerations are to be given to attenuation by compression paddle, breast tissue, grid and image receptor (intervening materials) has been investigated. By matching of the attenuation and hardening properties, comparisons are made between shielding afforded by breast tissue materials (water, Lucite and 50%-50% adipose-glandular tissue) and some materials considered for shielding diagnostic x-ray beams, namely lead, steel and gypsum wallboard. Results show that significant differences exist between the thickness required to produce equal attenuation and that required to produce equal hardening of a given incident beam. While attenuation equivalent thickness produces equal exposure, it does not produce equal hardening. For shielding purposes, equivalence in exposure reduction without equivalence in penetrating power of an emerging beam does not amount to equivalence in shielding affordable by two different materials. Presented are models and results of sample calculations of additional shielding requirements apart from that provided by intervening materials. The shielding requirements for the integrated beam emerging from intervening materials are different from those for the integrated beam emerging from materials (lead/steel/gypsum wallboard) with attenuation equivalent thicknesses of these intervening materials.

NEUTRON PHYSICS DIVISION ANNUAL PROGRESS REPORT. Period Ending September 1, 1962

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

None

1963-01-11

A total of 74 subsections are included in the report. The information in 4 subsections was previously abstracted in NSA. Separate abstracts were prepared for 38 of the subsections. Those sections for which no abstracts were prepared contain information on prompt neutron lifetime, Rover critical experiments, Pu/sup 239/ fission, neutron decay, the O5R code, alpha scattering, 8 and P wavelengths, proton scattering, deuteron scattering, local optical potentials, N. S. Savamah radiation leakage, reactor shielding, cross section data analysis, gamma transport, gamma energy deposition, gaussian integration, data interpolation, neutron scattering, neutron energy deposition, space vehicles, computer analyses, shielding, positron sources, andmore » secondary particles. (J.R.D.)« less

FUEL ELEMENT CONSTRUCTION

DOEpatents

Zumwalt, L.R.

1961-08-01

Fuel elements having a solid core of fissionable material encased in a cladding material are described. A conversion material is provided within the cladding to react with the fission products to form stable, relatively non- volatile compounds thereby minimizing the migration of the fission products into the coolant. The conversion material is preferably a metallic fluoride, such as lead difluoride, and may be in the form of a coating on the fuel core or interior of the cladding, or dispersed within the fuel core. (AEC)

A transferable model for singlet-fission kinetics.

PubMed

Yost, Shane R; Lee, Jiye; Wilson, Mark W B; Wu, Tony; McMahon, David P; Parkhurst, Rebecca R; Thompson, Nicholas J; Congreve, Daniel N; Rao, Akshay; Johnson, Kerr; Sfeir, Matthew Y; Bawendi, Moungi G; Swager, Timothy M; Friend, Richard H; Baldo, Marc A; Van Voorhis, Troy

2014-06-01

Exciton fission is a process that occurs in certain organic materials whereby one singlet exciton splits into two independent triplets. In photovoltaic devices these two triplet excitons can each generate an electron, producing quantum yields per photon of >100% and potentially enabling single-junction power efficiencies above 40%. Here, we measure fission dynamics using ultrafast photoinduced absorption and present a first-principles expression that successfully reproduces the fission rate in materials with vastly different structures. Fission is non-adiabatic and Marcus-like in weakly interacting systems, becoming adiabatic and coupling-independent at larger interaction strengths. In neat films, we demonstrate fission yields near unity even when monomers are separated by >5 Å. For efficient solar cells, however, we show that fission must outcompete charge generation from the singlet exciton. This work lays the foundation for tailoring molecular properties like solubility and energy level alignment while maintaining the high fission yield required for photovoltaic applications.

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

Sublet, J.-Ch., E-mail: jean-christophe.sublet@ukaea.uk; Eastwood, J.W.; Morgan, J.G.

Fispact-II is a code system and library database for modelling activation-transmutation processes, depletion-burn-up, time dependent inventory and radiation damage source terms caused by nuclear reactions and decays. The Fispact-II code, written in object-style Fortran, follows the evolution of material irradiated by neutrons, alphas, gammas, protons, or deuterons, and provides a wide range of derived radiological output quantities to satisfy most needs for nuclear applications. It can be used with any ENDF-compliant group library data for nuclear reactions, particle-induced and spontaneous fission yields, and radioactive decay (including but not limited to TENDL-2015, ENDF/B-VII.1, JEFF-3.2, JENDL-4.0u, CENDL-3.1 processed into fine-group-structure files, GEFY-5.2more » and UKDD-16), as well as resolved and unresolved resonance range probability tables for self-shielding corrections and updated radiological hazard indices. The code has many novel features including: extension of the energy range up to 1 GeV; additional neutron physics including self-shielding effects, temperature dependence, thin and thick target yields; pathway analysis; and sensitivity and uncertainty quantification and propagation using full covariance data. The latest ENDF libraries such as TENDL encompass thousands of target isotopes. Nuclear data libraries for Fispact-II are prepared from these using processing codes PREPRO, NJOY and CALENDF. These data include resonance parameters, cross sections with covariances, probability tables in the resonance ranges, PKA spectra, kerma, dpa, gas and radionuclide production and energy-dependent fission yields, supplemented with all 27 decay types. All such data for the five most important incident particles are provided in evaluated data tables. The Fispact-II simulation software is described in detail in this paper, together with the nuclear data libraries. The Fispact-II system also includes several utility programs for code-use optimisation, visualisation and production of secondary radiological quantities. Included in the paper are summaries of results from the suite of verification and validation reports available with the code.« less

Radiation fields from neutron generators shielded with different materials

NASA Astrophysics Data System (ADS)

Chichester, D. L.; Blackburn, B. W.

2007-08-01

As a general guide for assessing radiological conditions around a DT neutron generator numerical modeling has been performed to assess neutron and photon dose profiles for a variety of shield materials ranging from 1 to 100 cm thick. In agreement with accepted radiation safety practices high-Z materials such as bismuth and lead have been found to be ineffective biological shield materials, owing in part to the existence of (n,2n) reaction channels available with 14.1 MeV DT neutrons, while low-Z materials serve as effective shields for these sources. Composite materials such as a mixture of polyethylene and bismuth, or regular concrete, are ideal shield materials for neutron generator radiation because of their ability to attenuate internally generated photon radiation resulting from neutron scattering and capture within the shields themselves.

A novel method of utilization of hot dip galvanizing slag using the heat waste from itself for protection from radiation.

PubMed

Dong, Mengge; Xue, Xiangxin; Kumar, Ashok; Yang, He; Sayyed, M I; Liu, Shan; Bu, Erjun

2018-02-15

A novel, unconventional, low cost, eco-friendly and effective shielding materials have been made utilizing the hot dip galvanizing slag using the heat waste from itself, thereby saving the natural resources and preventing the environmental pollution. SEM-EDS of shielding materials indicates that the other elements are distributed in Zn element. The mass attenuation properties of shielding materials were measured using a narrow beam geometrical setup at 0.662MeV, 1.17MeV and 1.33MeV. The half value thickness layer, effective atomic number, and electron density were used to analyze the shielding performance of the materials. The EBFs and EABFs for the prepared shielding materials were also studied with incident photon energy for penetration depths upto 40mfp. The shielding effectiveness has been compared with lead, iron, zinc, some standard shielding concretes, different glasses and some alloys. The shielding effectiveness of the prepared samples is almost found comparable to iron, zinc, selected alloys and glasses while better than some standard shielding concretes. In addition, it is also found that the bending strength of all shielding materials is more than 110MPa. Copyright © 2017 Elsevier B.V. All rights reserved.

Measuring Fission Chain Dynamics Through Inter-event Timing of Correlated Particles

NASA Astrophysics Data System (ADS)

Monterial, Mateusz

Neutrons born from fission may go on to induce subsequent fissions in self-propagating series of reactions resulting in a fission chain. Fissile materials comprise all isotopes capable of sustaining nuclear fission chain reactions, and are therefore a necessary prerequisite for the construction of a nuclear weapon. As a result the accountancy and characterization of fissile material is of great importance for national security and the international community. The rate at which neutrons "multiply" in a fissile material is a function of the composition, total mass, density, and shape of the object. These are key characteristics sought out in areas of nuclear non-proliferation, safeguards, treaty verification and emergency response. This thesis demonstrates a novel technique of measuring the underlying fission chain dynamics in fissile material through temporal correlation of neutrons and gamma rays emitted from fission. Fissile material exhibits key detectable signatures through the emission of correlated neutrons and gamma rays from fission. The Non-Destructive Assay (NDA) community has developed mature techniques of assaying fissile material that detect these signatures, such as neutron counting by thermal capture based detectors, and gamma-ray spectroscopy. An alternative use of fast organic scintillators provides three additional capabilities: (1) discrimination between neutrons and gamma-ray pulses (2) sub-nanosecond scale timing between correlated events (3) measurement of deposited neutron energy in the detector. This thesis leverages these capabilities into to measure a new signature, which is demonstrated to be sensitive to both fissile neutron multiplication and presence of neutronically coupled reflectors. In addition, a new 3D imaging method of sources of correlated gamma rays and neutrons is presented, which can improve estimation of total source volume and localization.

Summary of the Effort to Use Active-induced Time Correlation Techniques to Measure the Enrichment of HEU

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

McConchie, Seth M.; Crye, Jason Michael; Pena, Kirsten

2015-09-30

This document summarizes the effort to use active-induced time correlation techniques to measure the enrichment of bulk quantities of enriched uranium. In summary, these techniques use an external source to initiate fission chains, and the time distribution of the detected fission chain neutrons is sensitive to the fissile material enrichment. The number of neutrons emitted from a chain is driven by the multiplication of the item, and the enrichment is closely coupled to the multiplication of the item. As the enrichment increases (decreases), the multiplication increases (decreases) if the geometry is held constant. The time distribution of fission chain neutronsmore » is a complex function of the enrichment and material configuration. The enrichment contributes to the probability of a subsequent fission in a chain via the likelihood of fissioning on an even-numbered isotope versus an odd-numbered isotope. The material configuration contributes to the same probability via solid angle effects for neutrons inducing subsequent fissions and the presence of any moderating material. To simplify the ability to accurately measure the enrichment, an associated particle imaging (API) D-T neutron generator and an array of plastic scintillators are used to simultaneously image the item and detect the fission chain neutrons. The image is used to significantly limit the space of enrichment and material configuration and enable the enrichment to be determined unambiguously.« less

Controlling Weapons-Grade Fissile Material

ERIC Educational Resources Information Center

Rotblat, J.

1977-01-01

Discusses the problems of controlling weapons-grade fissionable material. Projections of the growth of fission nuclear reactors indicates sufficient materials will be available to construct 300,000 atomic bombs each containing 10 kilograms of plutonium by 1990. (SL)

Double-layer neutron shield design as neutron shielding application

NASA Astrophysics Data System (ADS)

Sariyer, Demet; Küçer, Rahmi

2018-02-01

The shield design in particle accelerators and other high energy facilities are mainly connected to the high-energy neutrons. The deep penetration of neutrons through massive shield has become a very serious problem. For shielding to be efficient, most of these neutrons should be confined to the shielding volume. If the interior space will become limited, the sufficient thickness of multilayer shield must be used. Concrete and iron are widely used as a multilayer shield material. Two layers shield material was selected to guarantee radiation safety outside of the shield against neutrons generated in the interaction of the different proton energies. One of them was one meter of concrete, the other was iron-contained material (FeB, Fe2B and stainless-steel) to be determined shield thicknesses. FLUKA Monte Carlo code was used for shield design geometry and required neutron dose distributions. The resulting two layered shields are shown better performance than single used concrete, thus the shield design could leave more space in the interior shielded areas.

Survey of Materials for Fusion Fission Hybrid Reactors Vol 1 Rev. 0

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

Farmer, Joseph Collin

2007-07-03

Materials for fusion-fission hybrid reactors fall into several broad categories, including fuels, blanket and coolant materials, cladding, structural materials, shielding, and in the specific case of inertial-confinement fusion systems, laser and optical materials. This report surveys materials in all categories of materials except for those required for lasers and optics. Preferred collants include two molten salt mixtures known as FLIBE (Li2BeF4) and FLINABE (LiNaBeF4). In the case of homogenous liquid fuels, UF4 can be dissolved in these molten salt mixtures. The transmutation of lithium in this coolant produces very corrosive hydrofluoric acid species (HF and TF), which can rapidly degrademore » structural materials. Broad ranges of high-melting radiation-tolerant structural material have been proposed for fusion-fission reactor structures. These include a wide variety of steels and refractory alloys. Ferritic steels with oxide-dispersion strengthening and graphite have been given particular attention. Refractory metals are found in Groups IVB and VB of the periodic table, and include Nb, Ta, Cr, Mo, and W, as serve as the basis of refractory alloys. Stable high-melting composites and amorphous metals may also be useful. Since amorphous metals have no lattice structure, neutron bombardment cannot dislodge atoms from lattice sites, and the materials would be immune from this specific mode of degradation. The free energy of formation of fluorides of the alloying elements found in steels and refractory alloys can be used to determine the relative stability of these materials in molten salts. The reduction of lithium transmutation products (H + and T +) drives the electrochemical corrosion process, and liberates aggressive fluoride ions that pair with ions formed from dissolved structural materials. Corrosion can be suppressed through the use of metallic Be and Li, though the molten salt becomes laden with colloidal suspensions of Be and Li corrosion products in the process. Alternatively, imposed currents and other high-temperature cathodic protection systems are envisioned for protection of the structural materials. This novel concept could prove to be enabling technology for such high-temperature molten-salt reactors. The use of UF 4 as a liquid-phase homogenous fuel is also complicated by redox control. For example, the oxidation of tetravalent uranium to hexavalent uranium could result in the formation of volatile UF 6. This too could be controlled through electrochemically manipulated oxidation and reduction reactions. In situ studies of pertinent electrochemical reactions in the molten salts are proposed, and are relevant to both the corrosive attack of structural materials, as well as the volatilization of fuel. Some consideration is given to the potential advantages of gravity fed falling-film blankets. Such systems may be easier to control than vortex systems, but would require that cylindrical reaction vessels be oriented with the centerline normal to the gravitational field.« less

Potential Polymeric Sphere Construction Materials for a Spacecraft Electrostatic Shield

NASA Technical Reports Server (NTRS)

Smith, Joseph G., Jr.; Smith, Trent; Williams, Martha; Youngquist, Robert; Mendell, Wendell

2006-01-01

An electrostatic shielding concept for spacecraft radiation protection under NASA s Exploration Systems Research and Technology Program was evaluated for its effectiveness and feasibility. The proposed shield design is reminiscent of a classic quadrupole with positively and negatively charged spheres surrounding the spacecraft. The project addressed materials, shield configuration, power supply, and compared its effectiveness to that of a passive shield. The report herein concerns the identification of commercially available materials that could be used in sphere fabrication. It was found that several materials were needed to potentially construct the spheres for an electrostatic shield operating at 300 MV.

New applications and developments in the neutron shielding

NASA Astrophysics Data System (ADS)

Uğur, Fatma Aysun

2017-09-01

Shielding neutrons involve three steps that are slowing neutrons, absorption of neutrons, and impregnation of gamma rays. Neutrons slow down with thermal energy by hydrogen, water, paraffin, plastic. Hydrogenated materials are also very effective for the absorption of neutrons. Gamma rays are produced by neutron (radiation) retention on the neutron shield, inelastic scattering, and degradation of activation products. If a source emits gamma rays at various energies, high-energy gamma rays sometimes specify shielding requirements. Multipurpose Materials for Neutron Shields; Concrete, especially with barium mixed in, can slow and absorb the neutrons, and shield the gamma rays. Plastic with boron is also a good multipurpose shielding material. In this study; new applications and developments in the area of neutron shielding will be discussed in terms of different materials.

RER SPECTRA OBTAINED WITH A MULTICRYSTAL SPECTROMETER

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

Austin, W.E.; Champion, W.R.

1959-11-01

Relative gamma spectra were obtained twenty feet from the Hadiation Effects Reactor. The measurements were made using a multicry-stal spectrometer. This design incorporates pair and anticompton spectrometers in combination. Two reactor configurations were used; with shield tanks empty- and water filled. The spectra were obtained before the fuel elements were run at high power. Consequently very little of the fission product spectrum is tntermined. (J.R.D.)

Galactic and Solar Cosmic Ray Shielding in Deep Space

NASA Technical Reports Server (NTRS)

Wilson, John W.; Cucinotta, Francis A.; Tai, H.; Simonsen, Lisa C.; Shinn, Judy L.; Thibeault, Shelia; Kim, M. Y.

1997-01-01

An analysis of the radiation hazards in support of NASA deep space exploration activities is presented. The emphasis is on materials required for radiation protection shielding. Aluminum has been found to be a poor shield material when dose equivalent is used with exposure limits for low Earth orbit (LEO) as a guide for shield requirements. Because the radiation issues are cost related-the parasitic shield mass has high launch costs, the use of aluminum as a basic construction material is clearly not cost-effective and alternate materials need to be developed. In this context, polyethylene is examined as a potentially useful material and demonstrates important advantages as an alternative to aluminum construction. Although polyethylene is useful as a shield material, it may not meet other design criteria (strength, stability, thermal); other polymer materials must be examined.

Ultra-Low Background Measurements Of Decayed Aerosol Filters

NASA Astrophysics Data System (ADS)

Miley, H.

2009-04-01

To experimentally evaluate the opportunity to apply ultra-low background measurement methods to samples collected, for instance, by the Comprehensive Test Ban Treaty International Monitoring System (IMS), aerosol samples collected on filter media were measured using HPGe spectrometers of varying low-background technology approaches. In this way, realistic estimates of the impact of low-background methodology can be assessed on the Minimum Detectable Activities obtained in systems such as the IMS. The current measurement requirement of stations in the IMS is 30 microBq per cubic meter of air for 140Ba, or about 106 fissions per daily sample. Importantly, this is for a fresh aerosol filter. Decay varying form 3 days to one week reduce the intrinsic background from radon daughters in the sample. Computational estimates of the improvement factor for these decayed filters for underground-based HPGe in clean shielding materials are orders of magnitude less, even when the decay of the isotopes of interest is included.

Flexible neutron shielding composite material of EPDM rubber with boron trioxide: Mechanical, thermal investigations and neutron shielding tests

NASA Astrophysics Data System (ADS)

Özdemir, T.; Güngör, A.; Reyhancan, İ. A.

2017-02-01

In this study, EPDM and boron trioxide composite was produced and mechanical, thermal and neutron shielding tests were performed. EPDM rubber (Ethylene Propylene Diene Monomer) having a considerably high hydrogen content is an effective neutron shielding material. On the other hand, the materials containing boron components have effective thermal neutron absorption crossection. The composite of EPDM and boron trioxide would be an effective solution for both respects of flexibility and effectiveness for developing a neutron shielding material. Flexible nature of EPDM would be a great asset for the shielding purpose in case of intervention action to a radiation accident. The theoretical calculations and experimental neutron absorption tests have shown that the results were in parallel and an effective neutron shielding has been achieved with the use of the developed composite material.

Stiff, Thermally Stable and Highly Anisotropic Wood-Derived Carbon Composite Monoliths for Electromagnetic Interference Shielding.

PubMed

Yuan, Ye; Sun, Xianxian; Yang, Minglong; Xu, Fan; Lin, Zaishan; Zhao, Xu; Ding, Yujie; Li, Jianjun; Yin, Weilong; Peng, Qingyu; He, Xiaodong; Li, Yibin

2017-06-28

Electromagnetic interference (EMI) shielding materials for electronic devices in aviation and aerospace not only need lightweight and high shielding effectiveness, but also should withstand harsh environments. Traditional EMI shielding materials often show heavy weight, poor thermal stability, short lifetime, poor tolerance to chemicals, and are hard-to-manufacture. Searching for high-efficiency EMI shielding materials overcoming the above weaknesses is still a great challenge. Herein, inspired by the unique structure of natural wood, lightweight and highly anisotropic wood-derived carbon composite EMI shielding materials have been prepared which possess not only high EMI shielding performance and mechanical stable characteristics, but also possess thermally stable properties, outperforming those metals, conductive polymers, and their composites. The newly developed low-cost materials are promising for specific applications in aerospace electronic devices, especially regarding extreme temperatures.

Comparative evaluation of solar, fission, fusion, and fossil energy resources. Part 2: Power from nuclear fission

NASA Technical Reports Server (NTRS)

Clement, J. D.

1973-01-01

Different types of nuclear fission reactors and fissionable materials are compared. Special emphasis is placed upon the environmental impact of such reactors. Graphs and charts comparing reactor facilities in the U. S. are presented.

Summary of Internship Experience for 2010 DHS/ORISE summer program

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

Pusateri, Elise; Descalle, Marie-Anne

2010-08-13

The U.S. Department of Homeland Security has deemed as a threat to national security the possibility of fissionable materials being concealed in intermodal cargo containers. Detecting these materials is critical to preventing nuclear proliferation and terrorism. Thus, several high-energy photon-based imaging applications are being developed to detect materials with Z>72 in such containers. In an initial study, an array made of plastic scintillator material was considered for a detector in combination with a bremsstrahlung sources. While plastic is a practical and cheap material to use, it has relatively poor energy resolution. When studying the full spectrum of available materials, Bimore » 4Ge 3O 12 (BGO) 2 was considered and was eventually chosen as the scintillation material for its high mass density which permits high spatial resolution with reasonable detection efficiency. The final geometry of the detector chosen by UC Berkeley and Lawrence Livermore National Laboratory was an 8-by-8 array of 0.5-cm-by- 0.5-cm-by-5-cm Bi 4Ge 3O 12 (BGO) crystals, with pixels shielded by 1-mm of lead. The purpose of my research was to model the detector response using MCNP, a Monte Carlo3 code to demonstrate its expected sensitivity and ability to generate images, under conditions that could be tested experimentally and to determine the lowest energy threshold applicable.« less

The Pulsed Fission-Fusion (PUFF) Concept for Deep Space Exploration and Terrestrial Power Generation

NASA Technical Reports Server (NTRS)

Adams, Robert; Cassibry, Jason; Schillo, Kevin

2017-01-01

This team is exploring a modified Z-pinch geometry as a propulsion system, imploding a liner of liquid lithium onto a pellet containing both fission and fusion fuel. The plasma resulting from the fission and fusion burn expands against a magnetic nozzle, for propulsion, or a magnetic confinement system, for terrestrial power generation. There is considerable synergy in the concept; the lithium acts as a temporary virtual cathode, and adds reaction mass for propulsion. Further, the lithium acts as a radiation shield against generated neutrons and gamma rays. Finally, the density profile of the column can be tailored using the lithium sheath. Recent theoretical and experimental developments (e.g. tailored density profile in the fuel injection, shear stabilization, and magnetic shear stabilization) have had great success in mitigating instabilities that have plagued previous fusion efforts. This paper will review the work in evaluating the pellet sizes and z-pinch conditions for optimal PuFF propulsion. Trades of pellet size and composition with z-pinch power levels and conditions for the tamper and lithium implosion are evaluated. Current models, both theoretical and computational, show that a z-pinch can ignite a small (1 cm radius) fission-fusion target with significant yield. Comparison is made between pure fission and boosted fission targets. Performance is shown for crewed spacecraft for high speed Mars round trip missions and near interstellar robotic missions. The PuFF concept also offers a solution for terrestrial power production. PuFF can, with recycling of the effluent, achieve near 100% burnup of fission fuel, providing a very attractive power source with minimal waste. The small size of PuFF relative to today's plants enables a more distributed power network and less exposure to natural or man-made disruptions.

Nuclear Rocket Facility Decommissioning Project: Controlled Explosive Demolition of Neutron-Activated Shield Wall

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

Michael R. Kruzic

2008-06-01

Located in Area 25 of the Nevada Test Site (NTS), the Test Cell A (TCA) Facility (Figure 1) was used in the early to mid-1960s for testing of nuclear rocket engines, as part of the Nuclear Rocket Development Program, to further space travel. Nuclear rocket testing resulted in the activation of materials around the reactors and the release of fission products and fuel particles. The TCA facility, known as Corrective Action Unit 115, was decontaminated and decommissioned (D&D) from December 2004 to July 2005 using the Streamlined Approach for Environmental Restoration (SAFER) process, under the Federal Facility Agreement and Consentmore » Order. The SAFER process allows environmental remediation and facility closure activities (i.e., decommissioning) to occur simultaneously, provided technical decisions are made by an experienced decision maker within the site conceptual site model. Facility closure involved a seven-step decommissioning strategy. First, preliminary investigation activities were performed, including review of process knowledge documentation, targeted facility radiological and hazardous material surveys, concrete core drilling and analysis, shield wall radiological characterization, and discrete sampling, which proved to be very useful and cost-effective in subsequent decommissioning planning and execution and worker safety. Second, site setup and mobilization of equipment and personnel were completed. Third, early removal of hazardous materials, including asbestos, lead, cadmium, and oil, was performed ensuring worker safety during more invasive demolition activities. Process piping was to be verified void of contents. Electrical systems were de-energized and other systems were rendered free of residual energy. Fourth, areas of high radiological contamination were decontaminated using multiple methods. Contamination levels varied across the facility. Fixed beta/gamma contamination levels ranged up to 2 million disintegrations per minute (dpm)/100 centimeters squared (cm2) beta/gamma. Removable beta/gamma contamination levels seldom exceeded 1,000 dpm/100 cm2, but, in railroad trenches on the reactor pad containing soil on the concrete pad in front of the shield wall, the beta dose rates ranged up to 120 milli-roentgens per hour from radioactivity entrained in the soil. General area dose rates were less than 100 micro-roentgens per hour. Prior to demolition of the reactor shield wall, removable and fixed contaminated surfaces were decontaminated to the best extent possible, using traditional decontamination methods. Fifth, large sections of the remaining structures were demolished by mechanical and open-air controlled explosive demolition (CED). Mechanical demolition methods included the use of conventional demolition equipment for removal of three main buildings, an exhaust stack, and a mobile shed. The 5-foot (ft), 5-inch (in.) thick, neutron-activated reinforced concrete shield was demolished by CED, which had never been performed at the NTS.« less

Shields-1, A SmallSat Radiation Shielding Technology Demonstration

NASA Technical Reports Server (NTRS)

Thomsen, D. Laurence, III; Kim, Wousik; Cutler, James W.

2015-01-01

The NASA Langley Research Center Shields CubeSat initiative is to develop a configurable platform that would allow lower cost access to Space for materials durability experiments, and to foster a pathway for both emerging and commercial-off-the-shelf (COTS) radiation shielding technologies to gain spaceflight heritage in a relevant environment. The Shields-1 will be Langleys' first CubeSat platform to carry out this mission. Radiation shielding tests on Shields-1 are planned for the expected severe radiation environment in a geotransfer orbit (GTO), where advertised commercial rideshare opportunities and CubeSat missions exist, such as Exploration Mission 1 (EM-1). To meet this objective, atomic number (Z) graded radiation shields (Zshields) have been developed. The Z-shield properties have been estimated, using the Space Environment Information System (SPENVIS) radiation shielding computational modeling, to have 30% increased shielding effectiveness of electrons, at half the thickness of a corresponding single layer of aluminum. The Shields-1 research payload will be made with the Z-graded radiation shields of varying thicknesses to create dose-depth curves to be compared with baseline materials. Additionally, Shields-1 demonstrates an engineered Z-grade radiation shielding vault protecting the systems' electronic boards. The radiation shielding materials' performances will be characterized using total ionizing dose sensors. Completion of these experiments is expected to raise the technology readiness levels (TRLs) of the tested atomic number (Z) graded materials. The most significant contribution of the Z-shields for the SmallSat community will be that it enables cost effective shielding for small satellite systems, with significant volume constraints, while increasing the operational lifetime of ionizing radiation sensitive components. These results are anticipated to increase the development of CubeSat hardware design for increased mission lifetimes, and enable out of low earth orbit (LEO) missions by using these tested material concepts as shielding for sensitive components and new spaceflight hardware

METHOD OF TESTING THERMAL NEUTRON FISSIONABLE MATERIAL FOR PURITY

DOEpatents

Fermi, E.; Anderson, H.L.

1961-01-24

A process is given for determining the neutronic purity of fissionable material by the so-called shotgun test. The effect of a standard neutron absorber of known characteristics and amounts on a neutronic field also of known characteristics is measured and compared with the effect which the impurities derived from a known quantity of fissionable material has on the same neutronic field. The two readings are then made the basis of calculation from which the amount of impurities can be computed.

Methods and apparatuses for the development of microstructured nuclear fuels

DOEpatents

Jarvinen, Gordon D [Los Alamos, NM; Carroll, David W [Los Alamos, NM; Devlin, David J [Santa Fe, NM

2009-04-21

Microstructured nuclear fuel adapted for nuclear power system use includes fissile material structures of micrometer-scale dimension dispersed in a matrix material. In one method of production, fissile material particles are processed in a chemical vapor deposition (CVD) fluidized-bed reactor including a gas inlet for providing controlled gas flow into a particle coating chamber, a lower bed hot zone region to contain powder, and an upper bed region to enable powder expansion. At least one pneumatic or electric vibrator is operationally coupled to the particle coating chamber for causing vibration of the particle coater to promote uniform powder coating within the particle coater during fuel processing. An exhaust associated with the particle coating chamber and can provide a port for placement and removal of particles and powder. During use of the fuel in a nuclear power reactor, fission products escape from the fissile material structures and come to rest in the matrix material. After a period of use in a nuclear power reactor and subsequent cooling, separation of the fissile material from the matrix containing the embedded fission products will provide an efficient partitioning of the bulk of the fissile material from the fission products. The fissile material can be reused by incorporating it into new microstructured fuel. The fission products and matrix material can be incorporated into a waste form for disposal or processed to separate valuable components from the fission products mixture.

Performance of solar shields. [Skylab 1 micrometeoroid shield difficulties

NASA Technical Reports Server (NTRS)

Schwinghamer, R. J.

1974-01-01

The loss of the micrometeoroid shield from the Orbital Workshop section of Skylab 1 about 63 seconds after lift-off, was the catalyst for a prodigious effort to develop a substitute for the passive portion of the thermal control system. An intensive effort is described in which numerous potential thermal shield materials were assessed, and during which period ten specific shield designs were developed and carried through various stages of development and test. Thermal shield materials data are discussed, including optical, strength, fatigue, outgassing, tackiness, ultraviolet radiation, and material memory properties. Specifically addressed are thermal shield materials selection criteria and the design, development, and test requirements associated with the successful development of Skylab thermal shields, and specifically the two thermal shields subsequently deployed over the exposed gold foil skin of the Orbital Workshop. Also considered are the general performance and thermal improvements provided by both the parasol design deployed by the Skylab 1 crew, and the sail design deployed by the Skylab 2 crew.

EXPERIMENTAL LIQUID METAL FUEL REACTOR

DOEpatents

Happell, J.J.; Thomas, G.R.; Denise, R.P.; Bunts, J.L. Jr.

1962-01-23

A liquid metal fuel nuclear fission reactor is designed in which the fissionable material is dissolved or suspended in a liquid metal moderator and coolant. The liquid suspension flows into a chamber in which a critical amount of fissionable material is obtained. The fluid leaves the chamber and the heat of fission is extracted for power or other utilization. The improvement is in the support arrangement for a segrnented graphite core to permit dif ferential thermal expansion, effective sealing between main and blanket liquid metal flows, and avoidance of excessive stress development in the graphite segments. (AEC)

JACKETED FUEL ELEMENTS FOR GRAPHITE MODERATED REACTORS

DOEpatents

Szilard, L.; Wigner, E.P.; Creutz, E.C.

1959-05-12

Fuel elements for a heterogeneous, fluid cooled, graphite moderated reactor are described. The fuel elements are comprised of a body of natural uranium hermetically sealed in a jacket of corrosion resistant material. The jacket, which may be aluminum or some other material which is non-fissionable and of a type having a low neutron capture cross-section, acts as a barrier between the fissioning isotope and the coolant or moderator or both. The jacket minimizes the tendency of the moderator and coolant to become radioactive and/or contaminated by fission fragments from the fissioning isotope.

Flexible barrier materials for protection against electromagnetic fields and their characterization

NASA Astrophysics Data System (ADS)

Jaroszewski, Maciej

2015-10-01

Composite materials for electromagnetic shielding can be manufactured as textiles using conductive yarns and textiles with conductivity obtained by various finishing processes on textile surfaces. The EM shielding effectiveness of fabrics are improved by lowering its conductivity using different methods and materials. An alternative is the usage of new light shielding materials in the form of metallized nonwoven fabrics or textiles. Their advantages are: a general availability on the market, a low price, good mechanical properties (strength, elasticity) and resistance to the environmental conditions. The composite anisotropic materials with a sandwich structure constituting of materials with different spatial orientations of fibers allow one to achieve relatively high and constant values of the shielding effectiveness which, together with the materials' mechanical properties, leads to a wide range of applicability in various disciplines of modern technology. This article is devoted to innovative flexible materials shielding electromagnetic field. The results of the PEM shielding effectiveness obtained for the polypropylene (PP) nonwoven fabrics metallized by pulsed magnetron sputtering are presented.

FUEL-BREEDER FUEL ELEMENT FOR NUCLEAR REACTOR

DOEpatents

Abbott, W.E.; Balent, R.

1958-09-16

A fuel element design to facilitate breeding reactor fuel is described. The fuel element is comprised of a coatainer, a central core of fertile material in the container, a first bonding material surrounding the core, a sheet of fissionable material immediately surrounding the first bonding material, and a second bonding material surrounding the fissionable material and being in coniact with said container.

Gas-cooled reactor programs. High-temperature gas-cooled reactor technology development program. Annual progress report, December 31, 1983

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

Kasten, P.R.; Rittenhouse, P.L.; Bartine, D.E.

1984-06-01

ORNL continues to make significant contributions to the national program. In the HTR fuels area, we are providing detailed statistical information on the fission product retention performance of irradiated fuel. Our studies are also providing basic data on the mechanical, physical, and chemical behavior of HTR materials, including metals, ceramics, graphite, and concrete. The ORNL has an important role in the development of improved HTR graphites and in the specification of criteria that need to be met by commercial products. We are also developing improved reactor physics design methods. Our work in component development and testing centers in the Componentmore » Flow Test Loop (CFTL), which is being used to evaluate the performance of the HTR core support structure. Other work includes experimental evaluation of the shielding effectiveness of the lower portions of an HTR core. This evaluation is being performed at the ORNL Tower Shielding Facility. Researchers at ORNL are developing welding techniques for attaching steam generator tubing to the tubesheets and are testing ceramic pads on which the core posts rest. They are also performing extensive testing of aggregate materials obtained from potential HTR site areas for possible use in prestressed concrete reactor vessels. During the past year we continued to serve as a peer reviewer of small modular reactor designs being developed by GA and GE with balance-of-plant layouts being developed by Bechtel Group, Inc. We have also evaluated the national need for developing HTRs with emphasis on the longer term applications of the HTRs to fossil conversion processes.« less

Using Ferromagnetic Material to Extend and Shield the Magnetic Field of a Coil

DTIC Science & Technology

2017-06-14

ARL-MR-0954 ● Jun 2017 US Army Research Laboratory Using Ferromagnetic Material to Extend and Shield the Magnetic Field of a...to Extend and Shield the Magnetic Field of a Coil by W Casey Uhlig Weapons and Materials Research Directorate, ARL...Using Ferromagnetic Material to Extend and Shield the Magnetic Field of a Coil 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER

A shielded measurement system for irradiated nuclear fuel measurements

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

Mosby, W.R.; Aumeier, S.E.; Klann, R.T.

1999-07-01

The US Department of Energy (DOE) is driving a transition toward dry storage of irradiated nuclear fuel (INF), toward characterization of INF for final disposition, and toward resumption of measurement-based material control and accountability (MC and A) efforts for INF. For these reasons, the ability to efficiently acquire radiological measurements of INF in a dry environment is important. The DOE has recently developed a guidance document proposing MC and A requirements for INF. The intent of this document is to encourage the direct measurement of INF on inventory within DOE. The guidance document reinforces and clarifies existing material safeguards requirementsmore » as they pertain to INF. Validation of nuclear material contents of non-self-protecting INF must be accomplished by direct measurement, application of validated burnup codes using qualified initial fissile content, burnup data, and age or by other valid means. The fuel units must remain intact with readable identification numbers. INF may be subject to periodic inventories with visual item accountability checks. Quantitative measurements may provide greater assurance of the integrity of INF inventories at a lower cost and with less personnel exposure than visual item accountability checks. Currently, several different approaches are used to measure the radiological attributes of INF. Although these systems are useful for a wide variety of applications, there is currently no relatively inexpensive measurement system that is readily deployable for INF measurements for materials located in dry storage. The authors present the conceptual design of a shielded measurement system (SMS) that could be used for this purpose. The SMS consists of a shielded enclosure designed to house a collection of measurement systems to allow measurements on spent fuel outside of a hot cell. The phase 1 SMS will contain {sup 3}He detectors and ionization chambers to allow for gross neutron and gamma-ray measurements. The phase 2 SMS will be developed by adding additional measurement capabilities to the phase 1 SMS. Planned additions include medium-resolution gamma-ray detectors (CdZnTe or high-pressure Xe), additional {sup 3}He tubes to allow coincidence measurements, and a {sup 252}Cf neutron source and motion control system to allow active neutron interrogation measurements. The phase 2 SMS will be capable of performing more direct measurements of INF properties such as burnup, cooling time, spontaneous fission isotope contents, and total fissile contents.« less

New shielding material development for compact accelerator-driven neutron source

NASA Astrophysics Data System (ADS)

Hu, Guang; Hu, Huasi; Wang, Sheng; Han, Hetong; Otake, Y.; Pan, Ziheng; Taketani, A.; Ota, H.; Hashiguchi, Takao; Yan, Mingfei

2017-04-01

The Compact Accelerator-driven Neutron Source (CANS), especially the transportable neutron source is longing for high effectiveness shielding material. For this reason, new shielding material is researched in this investigation. The component of shielding material is designed and many samples are manufactured. Then the attenuation detection experiments were carried out. In the detections, the dead time of the detector appeases when the proton beam is too strong. To grasp the linear range and nonlinear range of the detector, two currents of proton are employed in Pb attenuation detections. The transmission ratio of new shielding material, polyethylene (PE), PE + Pb, BPE + Pb is detected under suitable current of proton. Since the results of experimental neutrons and γ-rays appear as together, the MCNP and PHITS simulations are applied to assisting the analysis. The new shielding material could reduce of the weight and volume compared with BPE + Pb and PE + Pb.

Microwave thawing apparatus and method

DOEpatents

Fathi, Zakaryae; Lauf, Robert J.; McMillan, April D.

2004-06-01

An apparatus for thawing a frozen material includes: a microwave energy source; a microwave applicator which defines a cavity for applying microwave energy from the microwave source to a material to be thawed; and a shielded region which is shielded from the microwave source, the shielded region in fluid communication with the cavity so that thawed material may flow from the cavity into the shielded region.

A Method to Estimate the Atomic Number and Mass Thickness of Intervening Materials in Uranium and Plutonium Gamma-Ray Spectroscopy Measurements

NASA Astrophysics Data System (ADS)

Streicher, Michael; Brown, Steven; Zhu, Yuefeng; Goodman, David; He, Zhong

2016-10-01

To accurately characterize shielded special nuclear materials (SNM) using passive gamma-ray spectroscopy measurement techniques, the effective atomic number and the thickness of shielding materials must be measured. Intervening materials between the source and detector may affect the estimated source isotopics (uranium enrichment and plutonium grade) for techniques which rely on raw count rates or photopeak ratios of gamma-ray lines separated in energy. Furthermore, knowledge of the surrounding materials can provide insight regarding the configuration of a device containing SNM. The described method was developed using spectra recorded using high energy resolution CdZnTe detectors, but can be expanded to any gamma-ray spectrometers with energy resolution of better than 1% FWHM at 662 keV. The effective atomic number, Z, and mass thickness of the intervening shielding material are identified by comparing the relative attenuation of different gamma-ray lines and estimating the proportion of Compton scattering interactions to photoelectric absorptions within the shield. While characteristic Kα x-rays can be used to identify shielding materials made of high Z elements, this method can be applied to all shielding materials. This algorithm has adequately estimated the effective atomic number for shields made of iron, aluminum, and polyethylene surrounding uranium samples using experimental data. The mass thicknesses of shielding materials have been estimated with a standard error of less than 1.3 g/cm2 for iron shields up to 2.5 cm thick. The effective atomic number was accurately estimated to 26 ± 5 for all iron thicknesses.

Evaluation of an alternative shielding materials for F-127 transport package

NASA Astrophysics Data System (ADS)

Gual, Maritza R.; Mesquita, Amir Z.; Pereira, Cláubia

2018-03-01

Lead is used as radiation shielding material for the Nordion's F-127 source shipping container is used for transport and storage of the GammaBeam -127's cobalt-60 source of the Nuclear Technology Development Center (CDTN) located in Belo Horizonte, Brazil. As an alternative, Th, Tl and WC have been evaluated as radiation shielding material. The goal is to check their behavior regarding shielding and dosing. Monte Carlo MCNPX code is used for the simulations. In the MCNPX calculation was used one cylinder as exclusion surface instead one sphere. Validation of MCNPX gamma doses calculations was carried out through comparison with experimental measurements. The results show that tungsten carbide WC is better shielding material for γ-ray than lead shielding.

A proposed performance index for galactic cosmic ray shielding materials

NASA Technical Reports Server (NTRS)

Wilson, John W.; Wood, J. S.; Shinn, Judy L.; Cucinotta, Francis A.; Nealy, John E.

1993-01-01

In past studies, the reductions in absorbed dose and dose equivalent due to choice of material composition have been used to indicate shield effectiveness against exposure to galactic cosmic rays. However, these quantities are highly inaccurate in assessing shield effectiveness for protection against the biological effects of long-term exposure to the galactic heavy ions. A new quantity for shield performance is defined that correlates well with cell killing and cell transformation behind various shield thicknesses and materials. In addition, a relative performance index is identified that is inversely related to biological injury for different materials at a fixed shield mass and is directly related to the ratio of the fourth- and the second-order linear energy transfer (LET) moments.

Monte carlo simulation of innovative neutron and photon shielding material composing of high density concrete, waste rubber, lead and boron carbide

NASA Astrophysics Data System (ADS)

Aim-O, P.; Wongsawaeng, D.; Phruksarojanakun, P.; Tancharakorn, S.

2017-06-01

High-density concrete exhibits high strength and can perform an important role of gamma ray attenuation. In order to upgrade this material’s radiation-shielding performance, hydrogen-rich material can be incorporated. Waste rubber from vehicles has high hydrogen content which is the prominent characteristic to attenuate neutron. The objective of this work was to evaluate the radiation-shielding properties of this composite material against neutron and photon radiations. Monte Carlo transport simulation was conducted to simulate radiation through the composite material. Am-241/Be was utilized for neutron source and Co-60 for photon source. Parameters of the study included volume percentages of waste rubber, lead and boron carbide and thickness of the shielding material. These designs were also fabricated and the radiation shielding properties were experimentally evaluated. The best neutron and gamma ray shielding material was determined to be high-density concrete mixed with 5 vol% crumb rubber and 5 vol% lead powder. This shielding material increased the neutron attenuation by 64% and photon attenuation by 68% compared to ordinary concrete. Also, increasing the waste rubber content to greater than 5% resulted in a decrease in the radiation attenuation. This innovative composite radiation shielding material not only benefits nuclear science and engineering applications, but also helps solve the environmental issue of waste rubber.

CANNED SLUG

DOEpatents

Burton, M.

1959-02-17

Fuel elements of the type comprised of a core of fissionable material enclosed in a jacket of nonfissionable, corrosion resistant material are presented. In this invention the fissionable core is shorter than the jacket member, to provide a void chamber in one end of the assembled element. The fissionable material is separated from the chamber by an inwardly extending portion of the jacket member containing a gas permeable wafer centrally disposed therein. The outer end of the chamber is closed bv the end of the jacket which has a rupture disk centrally disposed therein. Gases formed by the irradiation of the fissionable material pass through the porous wafer into the chanmber thereby causing a gradual increase in the pressure in the chamber. The rupture disk is designed to fail at a lower pressure than that which would rupture the jacket. Upon rupture of the disk, the gases in the chamber escape into the coolant channel and coolant enters the chamber but is prevented from coming into contact with the fissionable material by the action of the gases under pressure passing outwardly through the wafer. The ruptured fuel element may be readily detected by monitoring the reactor coolant system.

Measuring space radiation shielding effectiveness

NASA Astrophysics Data System (ADS)

Bahadori, Amir; Semones, Edward; Ewert, Michael; Broyan, James; Walker, Steven

2017-09-01

Passive radiation shielding is one strategy to mitigate the problem of space radiation exposure. While space vehicles are constructed largely of aluminum, polyethylene has been demonstrated to have superior shielding characteristics for both galactic cosmic rays and solar particle events due to the high hydrogen content. A method to calculate the shielding effectiveness of a material relative to reference material from Bragg peak measurements performed using energetic heavy charged particles is described. Using accelerated alpha particles at the National Aeronautics and Space Administration Space Radiation Laboratory at Brookhaven National Laboratory, the method is applied to sample tiles from the Heat Melt Compactor, which were created by melting material from a simulated astronaut waste stream, consisting of materials such as trash and unconsumed food. The shielding effectiveness calculated from measurements of the Heat Melt Compactor sample tiles is about 10% less than the shielding effectiveness of polyethylene. Shielding material produced from the astronaut waste stream in the form of Heat Melt Compactor tiles is therefore found to be an attractive solution for protection against space radiation.

Advanced Multifunctional MMOD Shield: Radiation Shielding Assessment

NASA Technical Reports Server (NTRS)

Rojdev, Kristina; Christiansen, Eric

2013-01-01

As NASA is looking to explore further into deep space, multifunctional materials are a necessity for decreasing complexity and mass. One area where multifunctional materials could be extremely beneficial is in the micrometeoroid orbital debris (MMOD) shield. A typical MMOD shield on the International Space Station (ISS) is a stuffed whipple shield consisting of multiple layers. One of those layers is the thermal blanket, or multi-layer insulation (MLI). Increasing the MMOD effectiveness of MLI blankets, while still preserving their thermal capabilities, could allow for a less massive MMOD shield. Thus, a study was conducted to evaluate a concept MLI blanket for an MMOD shield. In conjunction, this MLI blanket and the subsequent MMOD shield was also evaluated for its radiation shielding effectiveness towards protecting crew. The overall MMOD shielding system using the concept MLI blanket proved to only have a marginal increase in the radiation mitigating properties. Therefore, subsequent analysis was performed on various conceptual MMOD shields to determine the combination of materials that may prove superior for radiation mitigating purposes. The following paper outlines the evaluations performed and discusses the results and conclusions of this evaluation for radiation shielding effectiveness.

Nuclear fuel elements and method of making same

DOEpatents

Schweitzer, Donald G.

1992-01-01

A nuclear fuel element for a high temperature gas nuclear reactor that has an average operating temperature in excess of 2000.degree. C., and a method of making such a fuel element. The fuel element is characterized by having fissionable fuel material localized and stabilized within pores of a carbon or graphite member by melting the fissionable material to cause it to chemically react with the carbon walls of the pores. The fissionable fuel material is further stabilized and localized within the pores of the graphite member by providing one or more coatings of pyrolytic carbon or diamond surrounding the porous graphite member so that each layer defines a successive barrier against migration of the fissionable fuel from the pores, and so that the outermost layer of pyrolytic carbon or diamond forms a barrier between the fissionable material and the moderating gases used in an associated high temperature gas reactor. The method of the invention provides for making such new elements either as generally spherically elements, or as flexible filaments, or as other relatively small-sized fuel elements that are particularly suited for use in high temperature gas reactors.

Solar Probe thermal shield design and testing

NASA Technical Reports Server (NTRS)

Millard, Jerry M.; Miyake, Robert N.; Rainen, Richard A.

1992-01-01

This paper discusses the major thermal shield subsystem development activities in support of the Solar Probe study being conducted at JPL. The Solar Probe spacecraft will travel to within 4 solar radii of the sun's center to perform fundamental experiments in space physics. Exposure to 2900 earth suns at perihelion requires the spacecraft to be protected within the shadow envelope of a protective shield. In addition, the mass loss rate off of the shield at elevated temperature must comply with plasma instrument requirements and has become the driver of the shield design. This paper will focus on the analytical design work to size the shield and control the shield mass loss rate for the various spacecraft options under study, the application of carbon-carbon materials for shield components, development and preparation of carbon-carbon samples for materials testing, and a materials testing program for carbon-carbon and tungsten alloys to investigate thermal/optical properties, mass loss (carbon-carbon only), material integrity, and high velocity impact behavior.

Preliminary results utilizing high-energy fission product γ-rays to detect fissionable material in cargo

NASA Astrophysics Data System (ADS)

Slaughter, D. R.; Accatino, M. R.; Bernstein, A.; Church, J. A.; Descalle, M. A.; Gosnell, T. B.; Hall, J. M.; Loshak, A.; Manatt, D. R.; Mauger, G. J.; Moore, T. L.; Norman, E. B.; Pohl, B. A.; Pruet, J. A.; Petersen, D. C.; Walling, R. S.; Weirup, D. L.; Prussin, S. G.; McDowell, M.

2005-12-01

A concept for detecting the presence of special nuclear material (235U or 239Pu) concealed in intermodal cargo containers is described. It is based on interrogation with a pulsed beam of 7 MeV neutrons that produce fission events and their β-delayed neutron emission or β-delayed high-energy γ radiation between beam pulses provide the detection signature. Fission product β-delayed γ-rays above 3 MeV are nearly 10 times more abundant than β-delayed neutrons and are distinct from natural radioactivity and from nearly all of the induced activity in a normal cargo. Detector backgrounds and potential interferences with the fission signature radiation have been identified and quantified.

Radiation protection using Martian surface materials in human exploration of Mars

NASA Technical Reports Server (NTRS)

Kim, M. H.; Thibeault, S. A.; Wilson, J. W.; Heilbronn, L.; Kiefer, R. L.; Weakley, J. A.; Dueber, J. L.; Fogarty, T.; Wilkins, R.

2001-01-01

To develop materials for shielding astronauts from the hazards of GCR, natural Martian surface materials are considered for their potential as radiation shielding for manned Mars missions. The modified radiation fluences behind various kinds of Martian rocks and regolith are determined by solving the Boltzmann equation using NASA Langley's HZETRN code along with the 1977 Solar Minimum galactic cosmic ray environmental model. To develop structural shielding composite materials for Martian surface habitats, theoretical predictions of the shielding properties of Martian regolith/polyimide composites has been computed to assess their shielding effectiveness. Adding high-performance polymer binders to Martian regolith to enhance structural properties also enhances the shielding properties of these composites because of the added hydrogenous constituents. Heavy ion beam testing of regolith simulant/polyimide composites is planned to validate this prediction. Characterization and proton beam tests are performed to measure structural properties and to compare the shielding effects on microelectronic devices, respectively.

A thermal shield concept for the Solar Probe mission

NASA Technical Reports Server (NTRS)

Miyake, Robert N.; Millard, Jerry M.; Randolph, James E.

1991-01-01

The Solar Probe spacecraft will travel to within 4 solar radii of the sun's center while performing a variety of fundamental experiments in space physics. Exposure to 2900 earth suns (400 W/sq cm) at perihelion imposes severe thermal and material demands on a solar shield system designed to protect the payload that will reside within the shield's shadow envelope or umbra. The design of the shield subsystem is a thermal/materials challenge requiring new technology development. While currently in the preproject study phase, anticipating a 1995 project start, shield preliminary design efforts are currently underway. This paper documents the current status of the mission concept, the materials issues, the configuration concept for the shield subsystem, the current configuration studies performed to date, and the required material testing to provide a database to support a design effort required to develop the shield subsystem.

Issues in Space Radiation Protection: Galactic Cosmic Rays

NASA Technical Reports Server (NTRS)

Wilson, J. W.; Kim, M.; Schimmerling, W.; Badavi, F. F.; Thibeault, S. A.; Cucinotta, F. A.; Shinn, J. L.; Kiefer, R.

1995-01-01

With shielding from cosmic heavy ions, one is faced with limited knowledge about the physical properties and biological responses of these radiations. Herein, the current status of space shielding technology and its impact on radiation health is discussed in terms of conventional protection practice and a test biological response model. The impact of biological response on optimum materials selection for cosmic ray shielding is presented in terms of the transmission characteristics of the shield material. Although liquid hydrogen gas is an optimum shield material, evaluation of the effectiveness of polymeric structural materials must await improvement in our knowledge of both the biological response and the nuclear processes.

Planetary surface reactor shielding using indigenous materials

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

Houts, Michael G.; Poston, David I.; Trellue, Holly R.

The exploration and development of Mars will require abundant surface power. Nuclear reactors are a low-cost, low-mass means of providing that power. A significant fraction of the nuclear power system mass is radiation shielding necessary for protecting humans and/or equipment from radiation emitted by the reactor. For planetary surface missions, it may be desirable to provide some or all of the required shielding from indigenous materials. This paper examines shielding options that utilize either purely indigenous materials or a combination of indigenous and nonindigenous materials.

Research of glass fibre used in the electromagnetic wave shielding and absorption composite material

NASA Astrophysics Data System (ADS)

Xu, M.; Jia, F.; Bao, H. Q.; Cui, K.; Zhang, F.

2016-07-01

Electromagnetic shielding and absorption composite material plays an important role in the defence and economic field. Comparing with other filler, Glass fibre and its processed product—metal-coated glass fibre can greatly reduce the material's weight and costs, while it still remains the high strength and the electromagnetic shielding effectiveness. In this paper, the electromagnetic absorption mechanism and the reflection mechanism have been investigated as a whole, and the shielding effectiveness of the double-layer glass fibre composite material is mainly focused. The relationship between the shielding effectiveness and the filled glass fibre as well as its metal-coated product's parameters has also been studied. From the subsequent coaxial flange and anechoic chamber analysis, it can be confirmed that the peak electromagnetic shielding effectiveness of this double-layer material can reach -78dB while the bandwidth is from 2GHz to 18GHz.

Fissile interrogation using gamma rays from oxygen

DOEpatents

Smith, Donald; Micklich, Bradley J.; Fessler, Andreas

2004-04-20

The subject apparatus provides a means to identify the presence of fissionable material or other nuclear material contained within an item to be tested. The system employs a portable accelerator to accelerate and direct protons to a fluorine-compound target. The interaction of the protons with the fluorine-compound target produces gamma rays which are directed at the item to be tested. If the item to be tested contains either a fissionable material or other nuclear material the interaction of the gamma rays with the material contained within the test item with result in the production of neutrons. A system of neutron detectors is positioned to intercept any neutrons generated by the test item. The results from the neutron detectors are analyzed to determine the presence of a fissionable material or other nuclear material.

Neutron Imaging at LANSCE—From Cold to Ultrafast

DOE PAGES

Nelson, Ronald Owen; Vogel, Sven C.; Hunter, James F.; ...

2018-02-23

In recent years, neutron radiography and tomography have been applied at different beam lines at Los Alamos Neutron Science Center (LANSCE), covering a very wide neutron energy range. The field of energy-resolved neutron imaging with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as quantitative density measurements, was pioneered at the Target 1 (Lujan center), Flight Path 5 beam line and continues to be refined. Applications include: imaging of metallic and ceramic nuclear fuels, fission gas measurements, tomography of fossils and studies of dopants in scintillators. The technique provides the ability to characterize materials opaque to thermal neutronsmore » and to utilize neutron resonance analysis codes to quantify isotopes to within 0.1 atom %. The latter also allows measuring fuel enrichment levels or the pressure of fission gas remotely. More recently, the cold neutron spectrum at the ASTERIX beam line, also located at Target 1, was used to demonstrate phase contrast imaging with pulsed neutrons. This extends the capabilities for imaging of thin and transparent materials at LANSCE. In contrast, high-energy neutron imaging at LANSCE, using unmoderated fast spallation neutrons from Target 4 [Weapons Neutron Research (WNR) facility] has been developed for applications in imaging of dense, thick objects. Using fast (ns), time-of-flight imaging, enables testing and developing imaging at specific, selected MeV neutron energies. The 4FP-60R beam line has been reconfigured with increased shielding and new, larger collimation dedicated to fast neutron imaging. The exploration of ways in which pulsed neutron beams and the time-of-flight method can provide additional benefits is continuing. We will describe the facilities and instruments, present application examples and recent results of all these efforts at LANSCE.« less

Neutron Imaging at LANSCE—From Cold to Ultrafast

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

Nelson, Ronald Owen; Vogel, Sven C.; Hunter, James F.

In recent years, neutron radiography and tomography have been applied at different beam lines at Los Alamos Neutron Science Center (LANSCE), covering a very wide neutron energy range. The field of energy-resolved neutron imaging with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as quantitative density measurements, was pioneered at the Target 1 (Lujan center), Flight Path 5 beam line and continues to be refined. Applications include: imaging of metallic and ceramic nuclear fuels, fission gas measurements, tomography of fossils and studies of dopants in scintillators. The technique provides the ability to characterize materials opaque to thermal neutronsmore » and to utilize neutron resonance analysis codes to quantify isotopes to within 0.1 atom %. The latter also allows measuring fuel enrichment levels or the pressure of fission gas remotely. More recently, the cold neutron spectrum at the ASTERIX beam line, also located at Target 1, was used to demonstrate phase contrast imaging with pulsed neutrons. This extends the capabilities for imaging of thin and transparent materials at LANSCE. In contrast, high-energy neutron imaging at LANSCE, using unmoderated fast spallation neutrons from Target 4 [Weapons Neutron Research (WNR) facility] has been developed for applications in imaging of dense, thick objects. Using fast (ns), time-of-flight imaging, enables testing and developing imaging at specific, selected MeV neutron energies. The 4FP-60R beam line has been reconfigured with increased shielding and new, larger collimation dedicated to fast neutron imaging. The exploration of ways in which pulsed neutron beams and the time-of-flight method can provide additional benefits is continuing. We will describe the facilities and instruments, present application examples and recent results of all these efforts at LANSCE.« less

Technical Basis for Expedited Processing of Radiation Dose Assessments for NTPR Hiroshima and Nagasaki Participants

DTIC Science & Technology

2015-11-01

submitted by the Department of Veterans Affairs (VA) for atmospheric nuclear weapons testing veterans with qualifying participant exposure scenarios...the east. Fallout3 was assumed to consist of weapon -specific 3 Measurements verify that weapon debris including fission products were in the Hiroshima...assumed to be outdoors, with no shielding by buildings or other structures. • To model the suspension of in situ neutron -induced soil activation products

Publicly Released Prompt Radiation Spectra Suitable for Nuclear Detonation Simulations

DTIC Science & Technology

2017-03-01

emission. During the Hiroshima and Nagasaki bombings , the prompt radiation contributed from 40%-70% of the free-in-air dose depending on distance from...intermediate- and low-yield thermonuclear weapons for initial radiation shielding calculations No Gritzner, et al. 1976 ( EM -1, Low, Henre...DNA 4267F ( EM -1 Fission) Neutron Gritzner, et al. 1976 1.00 x 1023 Glasstone (Thermonuclear) Neutron Glasstone & Dolan 1977 1.445 x 1023 ORNL-TM

Omni-directional selective shielding material based on amorphous glass coated microwires.

PubMed

Ababei, G; Chiriac, H; David, V; Dafinescu, V; Nica, I

2012-01-01

The shielding effectiveness of the omni-directional selective shielding material based on CoFe-glass coated amorphous wires in 0.8 GHz-3 GHz microwave frequency range is investigated. The measurements were done in a controlled medium using a TEM cell and in the free space using horn antennas, respectively. Experimental results indicate that the composite shielding material can be developed with desired shielding effectiveness and selective absorption of the microwave frequency range by controlling the number of the layers and the length of microwires.

Processing and validation of JEFF-3.1.1 and ENDF/B-VII.0 group-wise cross section libraries for shielding calculations

NASA Astrophysics Data System (ADS)

Pescarini, M.; Sinitsa, V.; Orsi, R.; Frisoni, M.

2013-03-01

This paper presents a synthesis of the ENEA-Bologna Nuclear Data Group programme dedicated to generate and validate group-wise cross section libraries for shielding and radiation damage deterministic calculations in nuclear fission reactors, following the data processing methodology recommended in the ANSI/ANS-6.1.2-1999 (R2009) American Standard. The VITJEFF311.BOLIB and VITENDF70.BOLIB finegroup coupled n-γ (199 n + 42 γ - VITAMIN-B6 structure) multi-purpose cross section libraries, based on the Bondarenko method for neutron resonance self-shielding and respectively on JEFF-3.1.1 and ENDF/B-VII.0 evaluated nuclear data, were produced in AMPX format using the NJOY-99.259 and the ENEA-Bologna 2007 Revision of the SCAMPI nuclear data processing systems. Two derived broad-group coupled n-γ (47 n + 20 γ - BUGLE-96 structure) working cross section libraries in FIDO-ANISN format for LWR shielding and pressure vessel dosimetry calculations, named BUGJEFF311.BOLIB and BUGENDF70.BOLIB, were generated by the revised version of SCAMPI, through problem-dependent cross section collapsing and self-shielding from the cited fine-group libraries. The validation results on the criticality safety benchmark experiments for the fine-group libraries and the preliminary validation results for the broad-group working libraries on the PCA-Replica and VENUS-3 engineering neutron shielding benchmark experiments are reported in synthesis.

X-Ray Computed Tomography Inspection of the Stardust Heat Shield

NASA Technical Reports Server (NTRS)

McNamara, Karen M.; Schneberk, Daniel J.; Empey, Daniel M.; Koshti, Ajay; Pugel, D. Elizabeth; Cozmuta, Ioana; Stackpoole, Mairead; Ruffino, Norman P.; Pompa, Eddie C.; Oliveras, Ovidio;

NUCLEAR REACTOR AND THERMIONIC FUEL ELEMENT THEREFOR

DOEpatents

Rasor, N.S.; Hirsch, R.L.

1963-12-01

The patent relates to the direct conversion of fission heat to electricity by use of thermionic plasma diodes having fissionable material cathodes, said diodes arranged to form a critical mass in a nuclear reactor. The patent describes a fuel element comprising a plurality of diodes each having a fissionable material cathode, an anode around said cathode, and an ionizable gas therebetween. Provision is made for flowing the gas and current serially through the diodes. (AEC)

Aqueous cutting fluid for machining fissionable materials

DOEpatents

Duerksen, Walter K.; Googin, John M.; Napier, Jr., Bradley

1984-01-01

The present invention is directed to a cutting fluid for machining fissionable material. The cutting fluid is formed of glycol, water and boron compound in an adequate concentration for effective neutron attenuation so as to inhibit criticality incidents during machining.

Method and apparatus for measuring reactivity of fissile material

DOEpatents

Lee, David M.; Lindquist, Lloyd O.

1985-01-01

Given are a method and apparatus for measuring nondestructively and non-invasively (i.e., using no internal probing) the burnup, reactivity, or fissile content of any material which emits neutrons and which has fissionable components. No external neutron-emitting interrogation source or fissile material is used and no scanning is required, although if a profile is desired scanning can be used. As in active assays, here both reactivity and content of fissionable material can be measured. The assay is accomplished by altering the return flux of neutrons into the fuel assembly. The return flux is altered by changing the reflecting material. The existing passive neutron emissions in the material being assayed are used as the source of interrogating neutrons. Two measurements of either emitted neutron or emitted gamma-ray count rates are made and are then correlated to either reactivity, burnup, or fissionable content of the material being assayed, thus providing a measurement of either reactivity, burnup, or fissionable content of the material being assayed. Spent fuel which has been freshly discharged from a reactor can be assayed using this method and apparatus. Precisions of 1000 MWd/tU appear to be feasible.

Passive Superconducting Shielding: Experimental Results and Computer Models

NASA Technical Reports Server (NTRS)

Warner, B. A.; Kamiya, K.

2003-01-01

Passive superconducting shielding for magnetic refrigerators has advantages over active shielding and passive ferromagnetic shielding in that it is lightweight and easy to construct. However, it is not as easy to model and does not fail gracefully. Failure of a passive superconducting shield may lead to persistent flux and persistent currents. Unfortunately, modeling software for superconducting materials is not as easily available as is software for simple coils or for ferromagnetic materials. This paper will discuss ways of using available software to model passive superconducting shielding.

Applications of Digitized 3-D Position-Sensitive CdZnTe Spectrometers for National Security and Nuclear Nonproliferation

NASA Astrophysics Data System (ADS)

Streicher, Michael W.

A nuclear weapon detonation remains one of the gravest threats to the global community. Although the likelihood of a nuclear event remains small, the economic and political ramifications of an event are vast. The surest way to reduce the probability of an incident is to account for the special nuclear materials (SNM) which can be used to produce a nuclear weapon. Materials which can be used to manufacture a radiological dispersion device ("dirty bomb") must also be monitored. Rapidly-deployable, commercially-available, room-temperature imaging gamma-ray spectrometers are improving the ability of authorities to intelligently and quickly respond to threats. New electronics which digitally-sample the radiation-induced signals in CdZnTe detectors have expanded the capabilities of these sensors. This thesis explores national security applications where digital readout of CdZnTe detectors significantly enhances capabilities. Radioactive sources can be detected more quickly using digitally-sampled CdZnTe detector due to the improved energy resolution. The excellent energy resolution also improves the accuracy of measurements of uranium enrichment and allows users to measure plutonium grade. Small differences in the recorded gamma-ray energy spectrum can be used to estimate the effective atomic number and mass thickness of materials shielding SNM sources. Improved position resolution of gamma-ray interactions through digital readout allows high resolution gamma-ray images of SNM revealing information about the source configuration. CdZnTe sensors can detect the presence of neutrons, indirectly, through measurement of gamma rays released during capture of thermal neutrons by Cd-113 or inelastic scattering with any constituent nuclei. Fast neutrons, such as those released following fission, can be directly detected through elastic scattering interactions in the detector. Neutrons are a strong indicator of fissile material, and the background neutron rate is much lower than the gamma-ray background rate. Neutrons can more easily penetrate shielding materials as well which can greatly aid in the detection of shielded SNM. Digital CdZnTe readout enables the sensors to maintain excellent energy resolution at high count rates. Pulse pile-up and preamplifier decay can be monitored and corrected for on an event-by-event basis limiting energy resolution degradation in dose rates higher than 100 mR/hr. Finally, new iterations of the digital electronics have enhanced gamma-ray detection capabilities at high photon energies. Currently, gamma rays with energy up to 4.4 MeV have been detected. High-energy photon detection is critical for many proposed active interrogation systems.

Parametric study for use of stainless steel as a material for thermal shield in PIP2IT transferline at Fermilab

NASA Astrophysics Data System (ADS)

Rane, Tejas; Chakravarty, Anindya; Klebaner, Arkadiy

2017-12-01

Transferline thermal shields are cooled by dedicated cooling lines welded/brazed to the shield at a single point along the circumference. Copper/Aluminium is widely used to fabricate thermal shields because of their higher thermal diffusivity. This causes uniformity of temperature along the surface of the shield thus reducing thermal stresses within allowable values. However, factors such as raw material price, the cost of fabrication depending on standard sizes of pipes/tubes, often drives up the final price of thermal shields. To reduce the cost by making use of easily available stock of standard pipe/tube, it is decided to use stainless steel as a material for thermal shields in the PIP2IT transferline. The present paper discusses the design approach, various factors affecting the conservative selection of thermal shield design.

Planetary surface reactor shielding using indigenous materials

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

Houts, Michael G.; Poston, David I.; Trellue, Holly R.

The exploration and development of Mars will require abundant surface power. Nuclear reactors are a low-cost, low-mass means of providing that power. A significant fraction of the nuclear power system mass is radiation shielding necessary for protecting humans and/or equipment from radiation emitted by the reactor. For planetary surface missions, it may be desirable to provide some or all of the required shielding from indigenous materials. This paper examines shielding options that utilize either purely indigenous materials or a combination of indigenous and nonindigenous materials. {copyright} {ital 1999 American Institute of Physics.}

SOC-DS computer code provides tool for design evaluation of homogeneous two-material nuclear shield

NASA Technical Reports Server (NTRS)

Disney, R. K.; Ricks, L. O.

1967-01-01

SOC-DS Code /Shield Optimization Code-Direc Search/, selects a nuclear shield material of optimum volume, weight, or cost to meet the requirments of a given radiation dose rate or energy transmission constraint. It is applicable to evaluating neutron and gamma ray shields for all nuclear reactors.

Solar probe shield developmental testing

NASA Technical Reports Server (NTRS)

Miyake, Robert N.

1991-01-01

The objectives of the Solar Probe mission and the current status of the Solar Probe thermal shield subsystem development are described. In particular, the discussion includes a brief description of the mission concepts, spacecraft configuration and shield concept, material selection criteria, and the required material testing to provide a database to support the development of the shield system.

Absorption and Reflection Contributions to the High Performance of Electromagnetic Waves Shielding Materials Fabricated by Compositing Leather Matrix with Metal Nanoparticles.

PubMed

Liu, Chang; Wang, Xiaoling; Huang, Xin; Liao, Xuepin; Shi, Bi

2018-04-25

Leather matrix (LM), a natural dielectric material, features a hierarchically suprafibrillar structure and abundant dipoles, which provides the possibility to dissipate electromagnetic waves (EW) energy via dipole relaxation combined with multiple diffuse reflections. Conventionally, metal-based materials are used as EW shielding materials due to that their high conductivity can reflect EW effectively. Herein, a lightweight and high-performance EW shielding composite with both absorption and reflection ability to EW was developed by coating metal nanoparticles (MNPs) onto LM. The as-prepared metal/LM membrane with only 4.58 wt % of coated MNPs showed excellent EW shielding effectiveness of ∼76.0 dB and specific shielding effectiveness of ∼200.0 dB cm 3 g -1 in the frequency range of 0.01-3.0 GHz, implying that more than 99.98% of EW was shielded. Further investigations indicated that the high shielding performances of the metal/LM membrane were attributed to the cooperative shielding mechanism between LM and the coating of MNPs.

Graphite/Ultra-High Modulus Polyethylene Hybrid Fiber Composites with Epoxy and Polyethylene Matrices for Cosmic Radiation Shielding

NASA Technical Reports Server (NTRS)

2003-01-01

One of the most significant technical challenges in long-duration space missions is that of protecting the crew from harmful radiation. Protection against such radiation on a manned Mars mission will be of vital importance both during transit and while on the surface of the planet. The development of multifunctional materials that serve as integral structural members of the space vehicle and provide the necessary radiation shielding for the crew would be both mission enabling and cost effective. Additionally, combining shielding and structure could reduce total vehicle mass. Hybrid laminated composite materials having both ultramodulus polyethylene (PE) and graphite fibers in epoxy and PE matrices could meet such mission requirements. PE fibers have excellent physical properties, including the highest specific strength of any known fiber. Moreover, the high hydrogen (H) content of polyethylene makes the material an excellent shielding material for cosmic radiation. When such materials are incorporated into an epoxy or PE matrix a very effective shielding material is expected. Boron (B) may be added to the matrix resin or used as a coating to further increase the shielding effectiveness due to B s ability to slow thermal neutrons. These materials may also serve as micrometeorites shields due to PE s high impact energy absorption properties. It should be noted that such materials can be fabricated by existing equipment and methods. It is the objective of this work therefore to: (a) perform preliminary analysis of the radiation transport within these materials; (b) fabricate panels for mechanical property testing before and after radiation exposure. Preliminary determination on the effectiveness of the combinations of material components on both shielding and structural efficiency will be made.

An approach to achieve progress in spacecraft shielding

NASA Astrophysics Data System (ADS)

Thoma, K.; Schäfer, F.; Hiermaier, S.; Schneider, E.

2004-01-01

Progress in shield design against space debris can be achieved only when a combined approach based on several tools is used. This approach depends on the combined application of advanced numerical methods, specific material models and experimental determination of input parameters for these models. Examples of experimental methods for material characterization are given, covering the range from quasi static to very high strain rates for materials like Nextel and carbon fiber-reinforced materials. Mesh free numerical methods have extraordinary capabilities in the simulation of extreme material behaviour including complete failure with phase changes, combined with shock wave phenomena and the interaction with structural components. In this paper the benefits from combining numerical methods, material modelling and detailed experimental studies for shield design are demonstrated. The following examples are given: (1) Development of a material model for Nextel and Kevlar-Epoxy to enable numerical simulation of hypervelocity impacts on complex heavy protection shields for the International Space Station. (2) The influence of projectile shape on protection performance of Whipple Shields and how experimental problems in accelerating such shapes can be overcome by systematic numerical simulation. (3) The benefits of using metallic foams in "sandwich bumper shields" for spacecraft and how to approach systematic characterization of such materials.

Effect of metal shielding on a wireless power transfer system

NASA Astrophysics Data System (ADS)

Li, Jiacheng; Huang, Xueliang; Chen, Chen; Tan, Linlin; Wang, Wei; Guo, Jinpeng

2017-05-01

In this paper, the effect of non-ferromagnetic metal shielding (NFMS) material on the resonator of wireless power transfer (WPT) is studied by modeling, simulation and experimental analysis. And, the effect of NFMS material on the power transfer efficiency (PTE) of WPT systems is investigated by circuit model. Meanwhile, the effect of ferromagnetic metal shielding material on the PTE of WPT systems is analyzed through simulation. A double layer metal shield structure is designed. Experimental results demonstrate that by applying the novel double layer metal shielding method, the system PTE increases significantly while the electromagnetic field of WPT systems declines dramatically.

Au Foil Activation Measurement and Simulation of the Concrete Neutron Shielding Ability for the Proposed New SANRAD Facility

NASA Astrophysics Data System (ADS)

Radebe, M. J.; Korochinsky, S.; Strydom, W. J.; De Beer, F. C.

The purpose of this study was to measure the effective neutron shielding characteristics of the new shielding material designed and manufactured to be used for the construction of the new SANRAD facility at Necsa, South Africa, through Au foil activation as well as MCNP simulations. The shielding capability of the high density shielding material was investigated in the worst case region (the neutron beam axis) of the experimental chamber for two operational modes. The everyday operational mode includes the 15 cm thick poly crystalline Bismuth filter at room temperature (assumed) to filter gamma-rays and some neutron spectrum energies. The second mode, dynamic imaging, will be conducted without the Bi-filter. The objective was achieved through a foil activation measurement at the current SANRAD facility and MCNP calculations. Several Au foilswere imbedded at different thicknesses(two at each position) of shielding material up to 80 cm thick to track the attenuation of the neutron beam over distance within the shielding material. The neutron flux and subsequently the associated dose rates were calculated from the activation levels of the Au foils. The concrete shielding material was found to provide adequate shielding for all energies of neutrons emerging from beam port no-2 of the SAFARI-1 research reactorwithin a thickness of 40 cm of concrete.

Space Nuclear Power and Propulsion: Materials Challenges for the 21st Century

NASA Technical Reports Server (NTRS)

Houts, Mike

2008-01-01

The current focus of NASA s space fission effort is Fission Surface Power (FSP). FSP systems could be used to provide power anytime, anywhere on the surface of the Moon or Mars. FSP systems could be used at locations away from the lunar poles or in permanently shaded regions, with no performance penalty. A potential reference 40 kWe option has been devised that is cost-competitive with alternatives while providing more power for less mass. The potential reference system is readily extensible for use on Mars. At Mars the system could be capable of operating through global dust storms and providing year-round power at any Martian latitude. To ensure affordability, the potential near-term, 40 kWe reference concept is designed to use only well established materials and fuels. However, if various materials challenges could be overcome, extremely high performance fission systems could be devised. These include high power, low mass fission surface power systems; in-space systems with high specific power; and high performance nuclear thermal propulsion systems. This tutorial will provide a brief overview of space fission systems and will focus on materials challenges that, if overcome, could help enable advanced exploration and utilization of the solar system.

Thermal Protection System (Heat Shield) Development - Advanced Development Project

NASA Technical Reports Server (NTRS)

Kowal, T. John

2010-01-01

The Orion Thermal Protection System (TPS) ADP was a 3 1/2 year effort to develop ablative TPS materials for the Orion crew capsule. The ADP was motivated by the lack of available ablative TPS's. The TPS ADP pursued a competitive phased development strategy with succeeding rounds of development, testing and down selections. The Project raised the technology readiness level (TRL) of 8 different TPS materials from 5 different commercial vendors, eventual down selecting to a single material system for the Orion heat shield. In addition to providing a heat shield material and design for Orion on time and on budget, the Project accomplished the following: 1) Re-invigorated TPS industry & re-established a NASA competency to respond to future TPS needs; 2) Identified a potentially catastrophic problem with the planned MSL heat shield, and provided a viable, high TRL alternate heat shield design option; and 3) Transferred mature heat shield material and design options to the commercial space industry, including TPS technology information for the SpaceX Dragon capsule.

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

Greenwood, L. R.; Cantaloub, M. G.; Burnett, J. L.

PNNL has developed two low-background gamma-ray spectrometers in a new shallow underground laboratory, thereby significantly improving its ability to detect low levels of gamma-ray emitting fission or activation products in airborne particulate in samples from the IMS (International Monitoring System). Furthermore, the combination of cosmic veto panels, dry nitrogen gas to reduce radon and low background shielding results in a reduction of the background count rate by about a factor of 100 compared to detectors operating above ground at our laboratory.

Timing of uplift peripheral to the Red Sea, Saudi Arabia

USGS Publications Warehouse

Naeser, C.W.; Zimmermann, R.A.; Bohannon, R.G.; Schmidt, D.L.; ,

1990-01-01

A Prominent escarpment is found along the western margin of the Arabian Shield. Elevations along this escarpment are up to 3200 m above the Red Sea. Between the Red Sea and the crest of the escarpment is a relatively featureless coastal plane that is ??? 50 km across. The coastal plane abruptly gives way to the steep mountainous terrain, the elevation of which increases abruptly towards the high crest. The elevation slowly decreases to the east of the high crest. Forty-four apatite fission-track ages have been determined on rocks from the Proterozoic Arabian Shield in southwestern Saudi Arabia. These ages range from 13.8 to 568 Ma. In general, the youngest ages are found at low elevations along the base of the escarpment near the eastern edge of the coastal plane. The oldest ages are from along and to the east of the crest. The fission-track data from Saudi Arabia show that there was a period of minor uplift and cooling during the Cretaceous. This was followed by a relatively stable period which lasted until the Mid to Upper Miocene. The latest uplift and erosion began slightly younger than 13.8 Ma. This latest episode resulted in a minimum uplift of 3 km and is related to the Red Sea Rift. Samples totally annealed prior to this latest episode of uplift and cooling have not yet reached the surface.

Evaluation of Shielding Performance for Newly Developed Composite Materials

NASA Astrophysics Data System (ADS)

Evans, Beren Richard

This work details an investigation into the contributing factors behind the success of newly developed composite neutron shield materials. Monte Carlo simulation methods were utilized to assess the neutron shielding capabilities and secondary radiation production characteristics of aluminum boron carbide, tungsten boron carbide, bismuth borosilicate glass, and Metathene within various neutron energy spectra. Shielding performance and secondary radiation data suggested that tungsten boron carbide was the most effective composite material. An analysis of the macroscopic cross-section contributions from constituent materials and interaction mechanisms was then performed in an attempt to determine the reasons for tungsten boron carbide's success over the other investigated materials. This analysis determined that there was a positive correlation between a non-elastic interaction contribution towards a material's total cross-section and shielding performance within the thermal and epi-thermal energy regimes. This finding was assumed to be a result of the boron-10 absorption reaction. The analysis also determined that within the faster energy regions, materials featuring higher non-elastic interaction contributions were comparable to those exhibiting primarily elastic scattering via low Z elements. This allowed for the conclusion that composite shield success within higher energy neutron spectra does not necessitate the use elastic scattering via low Z elements. These findings suggest that the inclusion of materials featuring high thermal absorption properties is more critical to composite neutron shield performance than the presence of constituent materials more inclined to maximize elastic scattering energy loss.

METHOD OF MANUFACTURE OF METAL ENCASED CORE MATERIAL

DOEpatents

Peters, E.J.

1963-06-01

A method of making reactor fuel elements in which the fissionable material is encased and sealed in steel or aluminum cladding having an enclosed channel from the fissionable material to the surface of the cladding at one end is described. Heat and pressure sufficient to bond the assembled fuel element are applied in a nonoxidizing atmosphere. (AEC)

Fission meter

DOEpatents

Rowland, Mark S [Alamo, CA; Snyderman, Neal J [Berkeley, CA

2012-04-10

A neutron detector system for discriminating fissile material from non-fissile material wherein a digital data acquisition unit collects data at high rate, and in real-time processes large volumes of data directly into information that a first responder can use to discriminate materials. The system comprises counting neutrons from the unknown source and detecting excess grouped neutrons to identify fission in the unknown source.

Detection of shielded nuclear material in a cargo container

NASA Astrophysics Data System (ADS)

Jones, James L.; Norman, Daren R.; Haskell, Kevin J.; Sterbentz, James W.; Yoon, Woo Y.; Watson, Scott M.; Johnson, James T.; Zabriskie, John M.; Bennett, Brion D.; Watson, Richard W.; Moss, Cavin E.; Frank Harmon, J.

2006-06-01

The Idaho National Laboratory, along with Los Alamos National Laboratory and the Idaho State University's Idaho Accelerator Center, are developing electron accelerator-based, photonuclear inspection technologies for the detection of shielded nuclear material within air-, rail-, and especially, maritime-cargo transportation containers. This paper describes a developing prototypical cargo container inspection system utilizing the Pulsed Photonuclear Assessment (PPA) technology, incorporates interchangeable, well-defined, contraband shielding structures (i.e., "calibration" pallets) providing realistic detection data for induced radiation signatures from smuggled nuclear material, and provides various shielded nuclear material detection results. Using a 4.8-kg quantity of depleted uranium, neutron and gamma-ray detection responses are presented for well-defined shielded and unshielded configurations evaluated in a selected cargo container inspection configuration.

Magnetic Shielding Design for Coupler of Wireless Electric Vehicle Charging Using Finite Element Analysis

NASA Astrophysics Data System (ADS)

Zhao, W. N.; Yang, X. J.; Yao, C.; Ma, D. G.; Tang, H. J.

2017-10-01

Inductive power transfer (IPT) is a practical and preferable method for wireless electric vehicle (EV) charging which proved to be safe, convenient and reliable. Due to the air gap between the magnetic coupler, the magnetic field coupling decreases and the magnetic leakage increases significantly compared to traditional transformer, and this may lead to the magnetic flux density around the coupler more than the safety limit for human. So magnetic shielding should be adding to the winding made from litz wire to enhance the magnetic field coupling effect in the working area and reduce magnetic field strength in non-working area. Magnetic shielding can be achieved by adding high-permeability material or high-conductivity material. For high-permeability material its magnetic reluctance is much lower than the surrounding air medium so most of the magnetic line goes through the high-permeability material rather than surrounding air. For high-conductivity material the eddy current in the material can produce reverse magnetic field to achieve magnetic shielding. This paper studies the effect of the two types of shielding material on coupler for wireless EV charging and designs combination shielding made from high-permeability material and high-conductivity material. The investigation of the paper is done with the help of finite element analysis.

Preliminary Design of a Galactic Cosmic Ray Shielding Materials Testbed for the International Space Station

NASA Technical Reports Server (NTRS)

Gaier, James R.; Berkebile, Stephen; Sechkar, Edward A.; Panko, Scott R.

2012-01-01

The preliminary design of a testbed to evaluate the effectiveness of galactic cosmic ray (GCR) shielding materials, the MISSE Radiation Shielding Testbed (MRSMAT) is presented. The intent is to mount the testbed on the Materials International Space Station Experiment-X (MISSE-X) which is to be mounted on the International Space Station (ISS) in 2016. A key feature is the ability to simultaneously test nine samples, including standards, which are 5.25 cm thick. This thickness will enable most samples to have an areal density greater than 5 g/sq cm. It features a novel and compact GCR telescope which will be able to distinguish which cosmic rays have penetrated which shielding material, and will be able to evaluate the dose transmitted through the shield. The testbed could play a pivotal role in the development and qualification of new cosmic ray shielding technologies.

Boron cage compound materials and composites for shielding and absorbing neutrons

DOEpatents

Bowen, III, Daniel E; Eastwood, Eric A

2014-03-04

Boron cage compound-containing materials for shielding and absorbing neutrons. The materials include BCC-containing composites and compounds. BCC-containing compounds comprise a host polymer and a BCC attached thereto. BCC-containing composites comprise a mixture of a polymer matrix and a BCC filler. The BCC-containing materials can be used to form numerous articles of manufacture for shielding and absorbing neutrons.

Methods to Collect, Compile, and Analyze Observed Short-lived Fission Product Gamma Data

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

Finn, Erin C.; Metz, Lori A.; Payne, Rosara F.

2011-09-29

A unique set of fission product gamma spectra was collected at short times (4 minutes to 1 week) on various fissionable materials. Gamma spectra were collected from the neutron-induced fission of uranium, neptunium, and plutonium isotopes at thermal, epithermal, fission spectrum, and 14-MeV neutron energies. This report describes the experimental methods used to produce and collect the gamma data, defines the experimental parameters for each method, and demonstrates the consistency of the measurements.

Kilopower: Small and Affordable Fission Power Systems for Space

NASA Technical Reports Server (NTRS)

Mason, Lee; Palac, Don; Gibson, Marc

2017-01-01

The Nuclear Systems Kilopower Project was initiated by NASA's Space Technology Mission Directorate Game Changing Development Program in fiscal year 2015 to demonstrate subsystem-level technology readiness of small space fission power in a relevant environment (Technology Readiness Level 5) for space science and human exploration power needs. The Nuclear Systems Kilopower Project centerpiece is the Kilopower Reactor Using Stirling Technology (KRUSTY) test, which consists of the development and testing of a fission ground technology demonstrator of a 1 kWe-class fission power system. The technologies to be developed and validated by KRUSTY are extensible to space fission power systems from 1 to 10 kWe, which can enable higher power future potential deep space science missions, as well as modular surface fission power systems for exploration. The Kilopower Project is cofounded by NASA and the Department of Energy National Nuclear Security Administration (NNSA).KRUSTY include the reactor core, heat pipes to transfer the heat from the core to the power conversion system, and the power conversion system. Los Alamos National Laboratory leads the design of the reactor, and the Y-12 National Security Complex is fabricating it. NASA Glenn Research Center (GRC) has designed, built, and demonstrated the balance of plant heat transfer and power conversion portions of the KRUSTY experiment. NASA MSFC developed an electrical reactor simulator for non-nuclear testing, and the design of the reflector and shielding for nuclear testing. In 2016, an electrically heated non-fissionable Depleted Uranium (DU) core was tested at GRC in a configuration identical to the planned nuclear test. Once the reactor core has been fabricated and shipped to the Device Assembly Facility at the NNSAs Nevada National Security Site, the KRUSTY nuclear experiment will be assembled and tested. Completion of the KRUSTY experiment will validate the readiness of 1 to 10 kWe space fission technology for NASAs future requirements for sunlight-independent space power. An early opportunity for demonstration of In-Situ Resource Utilization (ISRU) capability on the surface of Mars is currently being considered for 2026 launch. Since a space fission system is the leading option for power generation for the first Mars human outpost, a smaller version of a planetary surface fission power system could be built to power the ISRU demonstration and ensure its end-to-end validity. Planning is underway to start the hardware development of this subscale flight demonstrator in 2018.

Issues In Space Radiation Protection: Galactic Cosmic Rays

NASA Technical Reports Server (NTRS)

Wilson, J. W.; Kim, M.; Schimmerling, W.; Badavi, F. F.; Thibeault, S. A.; Cucinotta, F. A.; Shinn, J. L.; Kiefer, R.

1995-01-01

When shielding from cosmic heavy ions, one is faced with limited knowledge about the physical properties and biological responses of these radiations. Herein, the current health is discussed in terms of conventional protection practice and a test biological response model. The impact of biological response on optimum materials selection for cosmic ray shielding is presented in terms of the transmission characteristics of the shield material. Although liquid hydrogen is an optimum shield material, evaluation of the effectiveness of polymeric structural materials must await improvement in our knowledge of both the biological response and the nuclear processes.

Fission-suppressed fusion breeder on the thorium cycle and nonproliferation

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

Moir, R. W.

2012-06-19

Fusion reactors could be designed to breed fissile material while suppressing fissioning thereby enhancing safety. The produced fuel could be used to startup and makeup fuel for fission reactors. Each fusion reaction can produce typically 0.6 fissile atoms and release about 1.6 times the 14 MeV neutron's energy in the blanket in the fission-suppressed design. This production rate is 2660 kg/1000 MW of fusion power for a year. The revenues would be doubled from such a plant by selling fuel at a price of 60/g and electricity at $0.05/kWh for Q=P{sub fusion}/P{sub input}=4. Fusion reactors could be designed to destroymore » fission wastes by transmutation and fissioning but this is not a natural use of fusion whereas it is a designed use of fission reactors. Fusion could supply makeup fuel to fission reactors that were dedicated to fissioning wastes with some of their neutrons. The design for safety and heat removal and other items is already accomplished with fission reactors. Whereas fusion reactors have geometry that compromises safety with a complex and thin wall separating the fusion zone from the blanket zone where wastes could be destroyed. Nonproliferation can be enhanced by mixing {sup 233}U with {sup 238}U. Also nonproliferation is enhanced in typical fission-suppressed designs by generating up to 0.05 {sup 232}U atoms for each {sup 233}U atom produced from thorium, about twice the IAEA standards of 'reduced protection' or 'self protection.' With 2.4%{sup 232}U, high explosive material is predicted to degrade owing to ionizing radiation after a little over 1/2 year and the heat rate is 77 W just after separation and climbs to over 600 W ten years later. The fissile material can be used to fuel most any fission reactor but is especially appropriate for molten salt reactors (MSR) also called liquid fluoride thorium reactors (LFTR) because of the molten fuel does not need hands on fabrication and handling.« less

Passive magnetic shielding in MRI-Linac systems.

PubMed

Whelan, Brendan; Kolling, Stefan; Oborn, Brad M; Keall, Paul

2018-03-26

Passive magnetic shielding refers to the use of ferromagnetic materials to redirect magnetic field lines away from vulnerable regions. An application of particular interest to the medical physics community is shielding in MRI systems, especially integrated MRI-linear accelerator (MRI-Linac) systems. In these systems, the goal is not only to minimize the magnetic field in some volume, but also to minimize the impact of the shield on the magnetic fields within the imaging volume of the MRI scanner. In this work, finite element modelling was used to assess the shielding of a side coupled 6 MV linac and resultant heterogeneity induced within the 30 cm diameter of spherical volume (DSV) of a novel 1 Tesla split bore MRI magnet. A number of different shield parameters were investigated; distance between shield and magnet, shield shape, shield thickness, shield length, openings in the shield, number of concentric layers, spacing between each layer, and shield material. Both the in-line and perpendicular MRI-Linac configurations were studied. By modifying the shield shape around the linac from the starting design of an open ended cylinder, the shielding effect was boosted by approximately 70% whilst the impact on the magnet was simultaneously reduced by approximately 10%. Openings in the shield for the RF port and beam exit were substantial sources of field leakage; however it was demonstrated that shielding could be added around these openings to compensate for this leakage. Layering multiple concentric shield shells was highly effective in the perpendicular configuration, but less so for the in-line configuration. Cautious use of high permeability materials such as Mu-metal can greatly increase the shielding performance in some scenarios. In the perpendicular configuration, magnetic shielding was more effective and the impact on the magnet lower compared with the in-line configuration.

Passive magnetic shielding in MRI-Linac systems

NASA Astrophysics Data System (ADS)

Whelan, Brendan; Kolling, Stefan; Oborn, Brad M.; Keall, Paul

2018-04-01

Passive magnetic shielding refers to the use of ferromagnetic materials to redirect magnetic field lines away from vulnerable regions. An application of particular interest to the medical physics community is shielding in MRI systems, especially integrated MRI-linear accelerator (MRI-Linac) systems. In these systems, the goal is not only to minimize the magnetic field in some volume, but also to minimize the impact of the shield on the magnetic fields within the imaging volume of the MRI scanner. In this work, finite element modelling was used to assess the shielding of a side coupled 6 MV linac and resultant heterogeneity induced within the 30 cm diameter of spherical volume (DSV) of a novel 1 Tesla split bore MRI magnet. A number of different shield parameters were investigated; distance between shield and magnet, shield shape, shield thickness, shield length, openings in the shield, number of concentric layers, spacing between each layer, and shield material. Both the in-line and perpendicular MRI-Linac configurations were studied. By modifying the shield shape around the linac from the starting design of an open ended cylinder, the shielding effect was boosted by approximately 70% whilst the impact on the magnet was simultaneously reduced by approximately 10%. Openings in the shield for the RF port and beam exit were substantial sources of field leakage; however it was demonstrated that shielding could be added around these openings to compensate for this leakage. Layering multiple concentric shield shells was highly effective in the perpendicular configuration, but less so for the in-line configuration. Cautious use of high permeability materials such as Mu-metal can greatly increase the shielding performance in some scenarios. In the perpendicular configuration, magnetic shielding was more effective and the impact on the magnet lower compared with the in-line configuration.

Determination and Fabrication of New Shield Super Alloys Materials for Nuclear Reactor Safety by Experiments and Cern-Fluka Monte Carlo Simulation Code, Geant4 and WinXCom

NASA Astrophysics Data System (ADS)

Aygun, Bünyamin; Korkut, Turgay; Karabulut, Abdulhalik

2016-05-01

Despite the possibility of depletion of fossil fuels increasing energy needs the use of radiation tends to increase. Recently the security-focused debate about planned nuclear power plants still continues. The objective of this thesis is to prevent the radiation spread from nuclear reactors into the environment. In order to do this, we produced higher performanced of new shielding materials which are high radiation holders in reactors operation. Some additives used in new shielding materials; some of iron (Fe), rhenium (Re), nickel (Ni), chromium (Cr), boron (B), copper (Cu), tungsten (W), tantalum (Ta), boron carbide (B4C). The results of this experiments indicated that these materials are good shields against gamma and neutrons. The powder metallurgy technique was used to produce new shielding materials. CERN - FLUKA Geant4 Monte Carlo simulation code and WinXCom were used for determination of the percentages of high temperature resistant and high-level fast neutron and gamma shielding materials participated components. Super alloys was produced and then the experimental fast neutron dose equivalent measurements and gamma radiation absorpsion of the new shielding materials were carried out. The produced products to be used safely reactors not only in nuclear medicine, in the treatment room, for the storage of nuclear waste, nuclear research laboratories, against cosmic radiation in space vehicles and has the qualities.

Effect of particle size and percentages of Boron carbide on the thermal neutron radiation shielding properties of HDPE/B4C composite: Experimental and simulation studies

NASA Astrophysics Data System (ADS)

Soltani, Zahra; Beigzadeh, Amirmohammad; Ziaie, Farhood; Asadi, Eskandar

2016-10-01

In this paper the effects of particle size and weight percentage of the reinforcement phase on the absorption ability of thermal neutron by HDPE/B4C composites were investigated by means of Monte-Carlo simulation method using MCNP code and experimental studies. The composite samples were prepared using the HDPE filled with different weight percentages of Boron carbide powder in the form of micro and nano particles. Micro and nano composite were prepared under the similar mixing and moulding processes. The samples were subjected to thermal neutron radiation. Neutron shielding efficiency in terms of the neutron transmission fractions of the composite samples were investigated and compared with simulation results. According to the simulation results, the particle size of the radiation shielding material has an important role on the shielding efficiency. By decreasing the particle size of shielding material in each weight percentages of the reinforcement phase, better radiation shielding properties were obtained. It seems that, decreasing the particle size and homogeneous distribution of nano forms of B4C particles, cause to increase the collision probability between the incident thermal neutron and the shielding material which consequently improve the radiation shielding properties. So, this result, propose the feasibility of nano composite as shielding material to have a high performance shielding characteristic, low weight and low thick shielding along with economical benefit.

Accelerator-based tests of radiation shielding properties of materials used in human space infrastructures.

PubMed

Lobascio, C; Briccarello, M; Destefanis, R; Faraud, M; Gialanella, G; Grossi, G; Guarnieri, V; Manti, L; Pugliese, M; Rusek, A; Scampoli, P; Durante, M

2008-03-01

Shielding is the only practical countermeasure for the exposure to cosmic radiation during space travel. It is well known that light, hydrogenated materials, such as water and polyethylene, provide the best shielding against space radiation. Kevlar and Nextel are two materials of great interest for spacecraft shielding because of their known ability to protect human space infrastructures from meteoroids and debris. We measured the response to simulated heavy-ion cosmic radiation of these shielding materials and compared it to polyethylene, Lucite (PMMA), and aluminum. As proxy to galactic nuclei we used 1 GeV n iron or titanium ions. Both physics and biology tests were performed. The results show that Kevlar, which is rich in carbon atoms (about 50% in number), is an excellent space radiation shielding material. Physics tests show that its effectiveness is close (80-90%) to that of polyethylene, and biology data suggest that it can reduce the chromosomal damage more efficiently than PMMA. Nextel is less efficient as a radiation shield, and the expected reduction on dose is roughly half that provided by the same mass of polyethylene. Both Kevlar and Nextel are more effective than aluminum in the attenuation of heavy-ion dose.

Integration and Utilization of Nuclear Systems on the Moon and Mars

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

Houts, Michael G.; Schmidt, George R.; Bragg-Sitton, Shannon

2006-01-20

Over the past five decades numerous studies have identified nuclear energy as an enhancing or enabling technology for planetary surface exploration missions. This includes both radioisotope and fission sources for providing both heat and electricity. Nuclear energy sources were used to provide electricity on Apollo missions 12, 14, 15, 16, and 17, and on the Mars Viking landers. Very small nuclear energy sources were used to provide heat on the Mars Pathfinder, Spirit, and Opportunity rovers. Research has been performed at NASA MSFC to help assess potential issues associated with surface nuclear energy sources, and to generate data that couldmore » be useful to a future program. Research areas include System Integration, use of Regolith as Radiation Shielding, Waste Heat Rejection, Surface Environmental Effects on the Integrated System, Thermal Simulators, Surface System Integration / Interface / Interaction Testing, End-to-End Breadboard Development, Advanced Materials Development, Surface Energy Source Coolants, and Planetary Surface System Thermal Management and Control. This paper provides a status update on several of these research areas.« less

Radiation shielding properties of barite coated fabric by computer programme

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

Akarslan, F.; Molla, T.; Üncü, I. S.

2015-03-30

With the development of technology radiation started to be used in variety of different fields. As the radiation is hazardous for human health, it is important to keep radiation dose as low as possible. This is done mainly using shielding materials. Barite is one of the important materials in this purpose. As the barite is not used directly it can be used in some other materials such as fabric. For this purposes barite has been coated on fabric in order to improve radiation shielding properties of fabric. Determination of radiation shielding properties of coated fabric has been done by usingmore » computer program written C# language. With this program the images obtained from digital Rontgen films is used to determine radiation shielding properties in terms of image processing numerical values. Those values define radiation shielding and in this way the coated barite effect on radiation shielding properties of fabric has been obtained.« less

Space ultra-vacuum facility and method of operation

NASA Technical Reports Server (NTRS)

Naumann, Robert J. (Inventor)

1986-01-01

A wake shield facility providing an ultrahigh vacuum level for space processing is described. The facility is in the shape of a truncated, hollow hemispherical section, one side of the shield convex and the other concave. The shield surface is preferably made of material that has low out-gassing characteristics such as stainless steel. A material sample supporting fixture in the form of a carousel is disposed on the convex side of the shield at its apex. Movable arms, also on the convex side, are connected by the shield in proximity to the carousel, the arms supporting processing fixtures, and providing for movement of the fixtures to predetermined locations required for producing interations with material samples. For MBE processes a vapor jet projects a stream of vaporized material onto a sample surface. The fixtures are oriented to face the surface of the sample being processed when in their extended position, and when not in use they are retractable to a storage position. The concave side of the shield has a support structure including metal struts connected to the shield, extending radially inward. The struts are joined to an end plate disposed parallel to the outer edge of the shield. This system eliminates outgassing contamination.

Nuclear reactor shield including magnesium oxide

DOEpatents

Rouse, Carl A.; Simnad, Massoud T.

1981-01-01

An improvement in nuclear reactor shielding of a type used in reactor applications involving significant amounts of fast neutron flux, the reactor shielding including means providing structural support, neutron moderator material, neutron absorber material and other components as described below, wherein at least a portion of the neutron moderator material is magnesium in the form of magnesium oxide either alone or in combination with other moderator materials such as graphite and iron.

Detection of special nuclear materials with the associate particle technique

NASA Astrophysics Data System (ADS)

Carasco, Cédric; Deyglun, Clément; Pérot, Bertrand; Eléon, Cyrille; Normand, Stéphane; Sannié, Guillaume; Boudergui, Karim; Corre, Gwenolé; Konzdrasovs, Vladimir; Pras, Philippe

2013-04-01

In the frame of the French trans-governmental R&D program against chemical, biological, radiological, nuclear and explosives (CBRN-E) threats, CEA is studying the detection of Special Nuclear Materials (SNM) by neutron interrogation with fast neutrons produced by an associated particle sealed tube neutron generator. The deuterium-tritium fusion reaction produces an alpha particle and a 14 MeV neutron almost back to back, allowing tagging neutron emission both in time and direction with an alpha particle position-sensitive sensor embedded in the generator. Fission prompt neutrons and gamma rays induced by tagged neutrons which are tagged by an alpha particle are detected in coincidence with plastic scintillators. This paper presents numerical simulations performed with the MCNP-PoliMi Monte Carlo computer code and with post processing software developed with the ROOT data analysis package. False coincidences due to neutron and photon scattering between adjacent detectors (cross talk) are filtered out to increase the selectivity between nuclear and benign materials. Accidental coincidences, which are not correlated to an alpha particle, are also taken into account in the numerical model, as well as counting statistics, and the time-energy resolution of the data acquisition system. Such realistic calculations show that relevant quantities of SNM (few kg) can be distinguished from cargo and shielding materials in 10 min acquisitions. First laboratory tests of the system under development in CEA laboratories are also presented.

Beta-manganese dioxide nanorods for sufficient high-temperature electromagnetic interference shielding in X-band

NASA Astrophysics Data System (ADS)

Song, Wei-Li; Cao, Mao-Sheng; Hou, Zhi-Ling; Lu, Ming-Ming; Wang, Chan-Yuan; Yuan, Jie; Fan, Li-Zhen

2014-09-01

As the development of electronic and communication technology, electromagnetic interference (EMI) shielding and attenuation is an effective strategy to ensure the operation of the electronic devices. Among the materials for high-performance shielding in aerospace industry and related high-temperature working environment, the thermally stable metal oxide semiconductors with narrow band gap are promising candidates. In this work, beta-manganese dioxide ( β-MnO2) nanorods were synthesized by a hydrothermal method. The bulk materials of the β-MnO2 were fabricated to evaluate the EMI shielding performance in the temperature range of 20-500 °C between 8.2 and 12.4 GHz (X-band). To understand the mechanisms of high-temperature EMI shielding, the contribution of reflection and absorption to EMI shielding was discussed based on temperature-dependent electrical properties and complex permittivity. Highly sufficient shielding effectiveness greater than 20 dB was observed over all the investigated range, suggesting β-MnO2 nanorods as promising candidates for high-temperature EMI shielding. The results have also established a platform to develop high-temperature EMI shielding materials based on nanoscale semiconductors.

Photofission product yields of 238U and 239Pu with 22-MeV bremsstrahlung

NASA Astrophysics Data System (ADS)

Wen, Xianfei; Yang, Haori

2016-06-01

In homeland security and nuclear safeguards applications, non-destructive techniques to identify and quantify special nuclear materials are in great demand. Although nuclear materials naturally emit characteristic radiation (e.g. neutrons, γ-rays), their intensity and energy are normally low. Furthermore, such radiation could be intentionally shielded with ease or buried in high-level background. Active interrogation techniques based on photofission have been identified as effective assay approaches to address this issue. In designing such assay systems, nuclear data, like photofission product yields, plays a crucial role. Although fission yields for neutron-induced reactions have been well studied and readily available in various nuclear databases, data on photofission product yields is rather scarce. This poses a great challenge to the application of photofission techniques. In this work, short-lived high-energy delayed γ-rays from photofission of 238U were measured in between linac pulses. In addition, a list-mode system was developed to measure relatively long-lived delayed γ-rays from photofission of 238U and 239Pu after the irradiation. Time and energy information of each γ-ray event were simultaneously recorded by this system. Cumulative photofission product yields were then determined using the measured delayed γ-ray spectra.

METHOD OF OPERATING A NEUTRONIC REACTOR

DOEpatents

Turkevich, A.

1963-01-22

This patent relates to one step in a method of operating a neutronic reactor consisting of a slurry of fissionable material in heavy water. Deuterium gas is passed through the slurry to sweep gaseous fission products therefrom and the deuterium is then separated from the gaseous fission products. (AEC)

Linac based photofission inspection system employing novel detection concepts

NASA Astrophysics Data System (ADS)

Stevenson, John; Gozani, Tsahi; Elsalim, Mashal; Condron, Cathie; Brown, Craig

2011-10-01

Rapiscan Systems is developing a LINAC based cargo inspection system for detection of special nuclear material (SNM) in cargo containers. The system, called Photofission Based Alarm Resolution (PBAR) is being developed under a DHD/DNDO Advanced Technology Demonstration (ATD) program. The PBAR system is based on the Rapiscan Eagle P9000 X-ray system, which is a portal system with a commercial 9 MeV LINAC X-ray source. For the purposes of the DNDO ATD program, a conveyor system was installed in the portal to allow scanning and precise positioning of 20 ft ISO cargo containers. The system uses a two step inspection process. In the first step, the basic scan, the container is quickly and completely inspected using two independent radiography arrays: the conventional primary array with high spatial resolution and a lower resolution spectroscopic array employing the novel Z-Spec method. The primary array uses cadmium tungstate (CdWO 4) detectors with conventional current mode readouts using photodiodes. The Z-Spec array uses small plastic scintillators capable of performing very fast (up to 10 8 cps) gamma-ray spectroscopy. The two radiography arrays are used to locate high-Z objects in the image such as lead, tungsten, uranium, which could be potential shielding materials as well as SNM itself. In the current system, the Z-Spec works by measuring the energy spectrum of transmitted X-rays. For high-Z materials the higher end of the energy spectrum is more attenuated than for low-Z materials and thus has a lower mean energy and a narrower width than low- and medium-Z materials. The second step in the inspection process is the direct scan or alarm clearing scan. In this step, areas of the container image, which were identified as high Z, are re-inspected. This is done by precisely repositioning the container to the location of the high-Z object and performing a stationary irradiation of the area with X-ray beam. Since there are a large number of photons in the 9 MV Bremsstrahlung spectrum above the photofission "threshold" of about 6 MeV, the X-ray beam induces numerous fissions if nuclear material is present. The PBAR system looks for the two most prolific fission signatures to confirm the presence of special nuclear materials (SNM). These are prompt neutrons and delayed gamma rays. The PBAR system uses arrays of two types of fast and highly efficient gamma ray detectors: plastic and fluorocarbon scintillators. The latter serves as a detector of fission prompt neutrons using the novel threshold activation detector (TAD) concept as well as a very efficient delayed gamma ray detector. The major advantage of TAD for detecting the prompt neutrons is its insensitivity to the intense source related backgrounds. The current status of the system and experimental results will be shown and discussed.

Sustainably Sourced, Thermally Resistant, Radiation Hard Biopolymer

NASA Technical Reports Server (NTRS)

Pugel, Diane

2011-01-01

This material represents a breakthrough in the production, manufacturing, and application of thermal protection system (TPS) materials and radiation shielding, as this represents the first effort to develop a non-metallic, non-ceramic, biomaterial-based, sustainable TPS with the capability to also act as radiation shielding. Until now, the standing philosophy for radiation shielding involved carrying the shielding at liftoff or utilizing onboard water sources. This shielding material could be grown onboard and applied as needed prior to different radiation landscapes (commonly seen during missions involving gravitational assists). The material is a bioplastic material. Bioplastics are any combination of a biopolymer and a plasticizer. In this case, the biopolymer is a starch-based material and a commonly accessible plasticizer. Starch molecules are composed of two major polymers: amylase and amylopectin. The biopolymer phenolic compounds are common to the ablative thermal protection system family of materials. With similar constituents come similar chemical ablation processes, with the potential to have comparable, if not better, ablation characteristics. It can also be used as a flame-resistant barrier for commercial applications in buildings, homes, cars, and heater firewall material. The biopolymer is observed to undergo chemical transformations (oxidative and structural degradation) at radiation doses that are 1,000 times the maximum dose of an unmanned mission (10-25 Mrad), indicating that it would be a viable candidate for robust radiation shielding. As a comparison, the total integrated radiation dose for a three-year manned mission to Mars is 0.1 krad, far below the radiation limit at which starch molecules degrade. For electron radiation, the biopolymer starches show minimal deterioration when exposed to energies greater than 180 keV. This flame-resistant, thermal-insulating material is non-hazardous and may be sustainably sourced. It poses no hazardous waste threats during its lifecycle. The material composition is radiation-tolerant up to megarad doses, indicating its use as a radiation shielding material. It is lightweight, non-metallic, and able to be mechanically densified, permitting a tunable gradient of thermal and radiation protection as needed. The dual-use (thermal and radiation shielding), sustainable nature of this material makes it suitable for both industrial applications as a sustainable/green building material, and for space applications as thermal protection material and radiation shield.

ENGINEERING TEST REACTOR

DOEpatents

De Boisblanc, D.R.; Thomas, M.E.; Jones, R.M.; Hanson, G.H.

1958-10-21

Heterogeneous reactors of the type which is both cooled and moderated by the same fluid, preferably water, and employs highly enriched fuel are reported. In this design, an inner pressure vessel is located within a main outer pressure vessel. The reactor core and its surrounding reflector are disposed in the inner pressure vessel which in turn is surrounded by a thermal shield, Coolant fluid enters the main pressure vessel, fiows downward into the inner vessel where it passes through the core containing tbe fissionable fuel assemblies and control rods, through the reflector, thence out through the bottom of the inner vessel and up past the thermal shield to the discharge port in the main vessel. The fuel assemblles are arranged in the core in the form of a cross having an opening extending therethrough to serve as a high fast flux test facility.

A Comparison of Fission Power System Options for Lunar and Mars Surface Applications

NASA Technical Reports Server (NTRS)

Mason, Lee S.

2006-01-01

This paper presents a comparison of reactor and power conversion design options for 50 kWe class lunar and Mars surface power applications with scaling from 25 to 200 kWe. Design concepts and integration approaches are provided for three reactor-converter combinations: gas-cooled Brayton, liquid-metal Stirling, and liquid-metal thermoelectric. The study examines the mass and performance of low temperature, stainless steel based reactors and higher temperature refractory reactors. The preferred system implementation approach uses crew-assisted assembly and in-situ radiation shielding via installation of the reactor in an excavated hole. As an alternative, self-deployable system concepts that use earth-delivered, on-board radiation shielding are evaluated. The analyses indicate that among the 50 kWe stainless steel reactor options, the liquid-metal Stirling system provides the lowest mass at about 5300 kg followed by the gas-cooled Brayton at 5700 kg and the liquid-metal thermoelectric at 8400 kg. The use of a higher temperature, refractory reactor favors the gas-cooled Brayton option with a system mass of about 4200 kg as compared to the Stirling and thermoelectric options at 4700 and 5600 kg, respectively. The self-deployed concepts with on-board shielding result in a factor of two system mass increase as compared to the in-situ shielded concepts.

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.

Designing Spacecraft and Mission Operations Plans to Meet Flight Crew Radiation Dose Requirements: Why is this an "Epic Challenge" for Long-Term Manned Interplanetary Flight

NASA Technical Reports Server (NTRS)

Koontz, Steven

2012-01-01

Outline of presentation: (1) Radiation Shielding Concepts and Performance - Galactic Cosmic Rays (GCRs) (1a) Some general considerations (1b) Galactic Cosmic Rays (2)GCR Shielding I: What material should I use and how much do I need? (2a) GCR shielding materials design and verification (2b) Spacecraft materials point dose cosmic ray shielding performance - hydrogen content and atomic number (2c) Accelerator point dose materials testing (2d) Material ranking and selection guidelines (2e) Development directions and return on investment (point dose metric) (2f) Secondary particle showers in the human body (2f-1) limited return of investment for low-Z, high-hydrogen content materials (3) GCR shielding II: How much will it cost? (3a) Spacecraft design and verification for mission radiation dose to the crew (3b) Habitat volume, shielding areal density, total weight, and launch cost for two habitat volumes (3c) It's All about the Money - Historical NASA budgets and budget limits (4) So, what can I do about all this? (4a) Program Design Architecture Trade Space (4b) The Vehicle Design Trade Space (4c) Some Near Term Recommendations

Cosmic Ray Interactions in Shielding Materials

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

Aguayo Navarrete, Estanislao; Kouzes, Richard T.; Ankney, Austin S.

2011-09-08

This document provides a detailed study of materials used to shield against the hadronic particles from cosmic ray showers at Earth’s surface. This work was motivated by the need for a shield that minimizes activation of the enriched germanium during transport for the MAJORANA collaboration. The materials suitable for cosmic-ray shield design are materials such as lead and iron that will stop the primary protons, and materials like polyethylene, borated polyethylene, concrete and water that will stop the induced neutrons. The interaction of the different cosmic-ray components at ground level (protons, neutrons, muons) with their wide energy range (from kilo-electronmore » volts to giga-electron volts) is a complex calculation. Monte Carlo calculations have proven to be a suitable tool for the simulation of nucleon transport, including hadron interactions and radioactive isotope production. The industry standard Monte Carlo simulation tool, Geant4, was used for this study. The result of this study is the assertion that activation at Earth’s surface is a result of the neutronic and protonic components of the cosmic-ray shower. The best material to shield against these cosmic-ray components is iron, which has the best combination of primary shielding and minimal secondary neutron production.« less

Absolute nuclear material assay

DOEpatents

Prasad, Manoj K [Pleasanton, CA; Snyderman, Neal J [Berkeley, CA; Rowland, Mark S [Alamo, CA

2012-05-15

A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

Absolute nuclear material assay

DOEpatents

Prasad, Manoj K [Pleasanton, CA; Snyderman, Neal J [Berkeley, CA; Rowland, Mark S [Alamo, CA

2010-07-13

A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

Method and apparatus for measuring reactivity of fissile material

DOEpatents

Lee, D.M.; Lindquist, L.O.

1982-09-07

Given are a method and apparatus for measuring nondestructively and noninvasively (i.e., using no internal probing) the burnup, reactivity, or fissile content of any material which emits neutrons and which has fissionable components. The assay is accomplished by altering the return flux of neutrons into the fuel assembly by means of changing the reflecting material. The existing passive neutron emissions in the material being assayed are used as the source of interrogating neutrons. Two measurements of either emitted neutron or emitted gamma-ray count rates are made and are then correlated to either reactivity, burnup, or fissionable content of the material being assayed, thus providing a measurement of either reactivity, burnup, or fissionable content of the material being assayed. Spent fuel which has been freshly discharged from a reactor can be assayed using this method and apparatus. Precisions of 1000 MWd/tU appear to be feasible.

Novel calibration for LA-ICP-MS-based fission-track thermochronology

NASA Astrophysics Data System (ADS)

Soares, C. J.; Guedes, S.; Hadler, J. C.; Mertz-Kraus, R.; Zack, T.; Iunes, P. J.

2014-01-01

We present a novel age-equation calibration for fission-track age determinations by laser ablation inductively coupled plasma mass spectrometry. This new calibration incorporates the efficiency factor of an internal surface, [ ηq]is, which is obtained by measuring the projected fission-track length, allowing the determination of FT ages directly using the recommended spontaneous fission decay constant. Also, the uranium concentrations in apatite samples are determined using a Durango (Dur-2, 7.44 μg/g U) crystal and a Mud Tank (MT-7, 6.88 μg/g U) crystal as uranium reference materials. The use of matrix-matched reference materials allows a reduction in the uncertainty of the uranium measurements to those related to counting statistics, which are ca. 1 % taking into account that no extra source of uncertainty has to be considered. The equations as well as the matrix-matched reference materials are evaluated using well-dated samples from Durango, Fish Canyon Tuff, and Limberg as unknown samples. The results compare well with their respective published ages determined through other dating methods. Additionally, the results agree with traditional fission-track ages using both the zeta approach and the absolute approach, suggesting that the calibration presented in this work can be robustly applied in geological context. Furthermore, considering that fission-track ages can be determined without an age standard sample, the fission-track thermochronology approach presented here is assumed to be a valuable dating tool.

Low-background gamma-ray spectrometry for the international monitoring system

DOE PAGES

Greenwood, L. R.; Cantaloub, M. G.; Burnett, J. L.; ...

2016-12-28

PNNL has developed two low-background gamma-ray spectrometers in a new shallow underground laboratory, thereby significantly improving its ability to detect low levels of gamma-ray emitting fission or activation products in airborne particulate in samples from the IMS (International Monitoring System). Furthermore, the combination of cosmic veto panels, dry nitrogen gas to reduce radon and low background shielding results in a reduction of the background count rate by about a factor of 100 compared to detectors operating above ground at our laboratory.

Measurements on radiation shielding efficacy of Polyethylene and Kevlar in the ISS (Columbus)

PubMed Central

Di Fino, L.; Larosa, M.; Zaconte, V.; Casolino, M.; Picozza, P.; Narici, L.

2014-01-01

The study and optimization of material effectiveness as radiation shield is a mandatory step toward human space exploration. Passive radiation shielding is one of the most important element in the entire radiation countermeasures package. Crewmembers will never experience direct exposure to space radiation; they will be either inside some shelter (the spacecraft, a ‘base’) or in an EVA (Extra Vehicular Activity) suit. Understanding the radiation shielding features of materials is therefore an important step toward an optimization of shelters and suits construction in the quest for an integrated solution for radiation countermeasures. Materials are usually tested for their radiation shielding effectiveness first with Monte Carlo simulations, then on ground, using particle accelerators and a number of specific ions known to be abundant in space, and finally in space. Highly hydrogenated materials perform best as radiation shields. Polyethylene is right now seen as the material that merges a high level of hydrogenation, an easiness of handling and machining as well as an affordable cost, and it is often referred as a sort of ‘standard’ to which compare other materials' effectiveness. Kevlar has recently shown very interesting radiation shielding properties, and it is also known to have important characteristics toward debris shielding, and can be used, for example, in space suits. We have measured in the ISS the effectiveness of polyethylene and kevlar using three detectors of the ALTEA system [ 1– 3] from 8 June 2012 to 13 November 2012, in Express Rack 3 in Columbus. These active detectors are able to provide the radiation quality parameters in any orbital region; being identical, they are also suitable to be used in parallel (one for the unshielded baseline, two measuring radiation with two different amounts of the same material: 5 and 10 g/cm2). A strong similarity of the shielding behavior between polyethylene and kevlar is documented. We measured shielding providing as much as ∼40% reduction for high Z ions. In Fig. 1, the integrated behavior (3 ≤LET ≤ 350 keV/µm) is shown (ratios with the baseline measurements with no shield) both for polyethylene and kevlar, in flux, dose and dose equivalent. The measured reductions in dose for the 10 g/cm2 shields for high LET (>50 keV/µm, not shown in the figure) are in agreement with what found in accelerator measurements (Fe, 1 GeV) [4]. The thinner shielding (5 g/cm2) in our measurements performs ∼2% better (in unit areal density). Fig. 1.Integrated behavior (3 ≤ LET ≤ 350 keV/μm) of Flux, Dose and Equivalent Dose. The ratios with the baseline measurements with no shield are shown, both for Kevlar and Polyethylene as measured with the two different material thicknesses.

New Materials for EMI Shielding

NASA Technical Reports Server (NTRS)

Gaier, James R.

1999-01-01

Graphite fibers intercalated with bromine or similar mixed halogen compounds have substantially lower resistivity than their pristine counterparts, and thus should exhibit higher shielding effectiveness against electromagnetic interference. The mechanical and thermal properties are nearly unaffected, and the shielding of high energy x-rays and gamma rays is substantially increased. Characterization of the resistivity of the composite materials is subtle, but it is clear that the composite resistivity is substantially lowered. Shielding effectiveness calculations utilizing a simple rule of mixtures model yields results that are consistent with available data on these materials.

Galileo Probe forebody thermal protection

NASA Technical Reports Server (NTRS)

Green, M. J.; Davy, W. C.

1981-01-01

Material response solutions for the forebody heat shield on the candidate 310-kg Galileo Probe are presented. A charring material ablation analysis predicts thermochemical surface recession, insulation thickness, and total required heat shield mass. Benchmark shock layer solutions provide the imposed entry heating environments on the ablating surface. Heat shield sizing results are given for a nominal entry into modeled nominal and cool-heavy Jovian atmospheres, and for two heat-shield property models. The nominally designed heat shield requires a mass of at least 126 kg and would require an additional 13 kg to survive entry into the less probable cool-heavy atmosphere. The material-property model with a 30% surface reflectance reduces these mass requirements by as much as 16%.

Actinide Sputtering Induced by Fission with Ultra-cold Neutrons

NASA Astrophysics Data System (ADS)

Venuti, Michael; Shi, Tan; Fellers, Deion; Morris, Christopher; 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 energy of UCN, 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, especially for samples with a surface oxide layer, this work has the potential to separate the various damage mechanisms proposed in previous works. During the irradiation with UCN, fission events are monitored by coincidence counting between prompt gamma rays using NaI detectors. Alpha spectroscopy of the ejected actinide material is performed in a custom-built ionization chamber to determine the amount of sputtered material. Actinide samples with various sample properties and surface conditions are irradiated and analyzed. In this presentation, we will discuss our experimental setup and present the preliminary results.

Mitigating the Effects of the Space Radiation Environment: A Novel Approach of Using Graded-Z Materials

NASA Technical Reports Server (NTRS)

Atwell, William; Rojdev, Kristina; Aghara, Sukesh; Sriprisan, Sirikul

2013-01-01

In this paper we present a novel space radiation shielding approach using various material lay-ups, called "Graded-Z" shielding, which could optimize cost, weight, and safety while mitigating the radiation exposures from the trapped radiation and solar proton environments, as well as the galactic cosmic radiation (GCR) environment, to humans and electronics. In addition, a validation and verification (V&V) was performed using two different high energy particle transport/dose codes (MCNPX & HZETRN). Inherently, we know that materials having high-hydrogen content are very good space radiation shielding materials. Graded-Z material lay-ups are very good trapped electron mitigators for medium earth orbit (MEO) and geostationary earth orbit (GEO). In addition, secondary particles, namely neutrons, are produced as the primary particles penetrate a spacecraft, which can have deleterious effects to both humans and electronics. The use of "dopants," such as beryllium, boron, and lithium, impregnated in other shielding materials provides a means of absorbing the secondary neutrons. Several examples of optimized Graded-Z shielding layups that include the use of composite materials are presented and discussed in detail. This parametric shielding study is an extension of some earlier pioneering work we (William Atwell and Kristina Rojdev) performed in 20041 and 20092.

Space radiation shielding studies for astronaut and electronic component risk assessment

NASA Astrophysics Data System (ADS)

Fuchs, Jordan; Gersey, Brad; Wilkins, Richard

The space radiation environment is comprised of a complex and variable mix of high energy charged particles, gamma rays and other exotic species. Elements of this radiation field may also interact with intervening matter (such as a spaceship wall) and create secondary radiation particles such as neutrons. Some of the components of the space radiation environment are highly penetrating and can cause adverse effects in humans and electronic components aboard spacecraft. Developing and testing materials capable of providing effective shielding against the space radiation environment presents special challenges to researchers. Researchers at the Cen-ter for Radiation Engineering and Science for Space Exploration (CRESSE) at Prairie View AM University (PVAMU) perform accelerator based experiments testing the effectiveness of various materials for use as space radiation shields. These experiments take place at the NASA Space Radiation Laboratory at Brookhaven National Laboratory, the proton synchrotron at Loma Linda University Medical Center, and the Los Alamos Neutron Science Center at Los Alamos National Laboratory where charged particles and neutrons are produced at energies similar to those found in the space radiation environment. The work presented in this paper constitutes the beginning phase of an undergraduate research project created to contribute to this ongoing space radiation shielding project. Specifically, this student project entails devel-oping and maintaining a database of information concerning the historical data from shielding experiments along with a systematic categorization and storage system for the actual shielding materials. The shielding materials referred to here range in composition from standard materi-als such as high density polyethylene and aluminum to exotic multifunctional materials such as spectra-fiber infused composites. The categorization process for each material includes deter-mination of the density thickness of individual samples and a clear labeling and filing method that allows immediate cross referencing with other material samples during the experimental design process. Density thickness measurements will be performed using a precision scale that will allow for the fabrication of sets of standard density thicknesses of selected materials for ready use in shielding experiments. The historical data from previous shielding experiments consists primarily of measurements of absorbed dose, dose equivalent and dose distributions from a Tissue Equivalent Proportional Counter (TEPC) as measured downstream of various thicknesses of the materials while being irradiated in one of the aforementioned particle beams. This data has been digitally stored and linked to the composition of each material and may be easily accessed for shielding effectiveness inter-comparisons. This work was designed to facili-tate and increase the efficiency of ongoing space radiation shielding research performed at the CRESSE as well as serve as a way to educate new generations of space radiation researchers.

Nuclear reactor fuel element with vanadium getter on cladding

DOEpatents

Johnson, Carl E.; Carroll, Kenneth G.

1977-01-01

A nuclear reactor fuel element is described which has an outer cladding, a central core of fissionable or mixed fissionable and fertile fuel material and a layer of vanadium as an oxygen getter on the inner surface of the cladding. The vanadium reacts with oxygen released by the fissionable material during irradiation of the core to prevent the oxygen from reacting with and corroding the cladding. Also described is a method for coating the inner surface of small diameter tubes of cladding with a layer of vanadium.

A thrust-sheet propulsion concept using fissionable elements

NASA Technical Reports Server (NTRS)

Moeckel, W. E.

1976-01-01

A space propulsion concept is proposed and analyzed which consists of a thin sheet coated on one side with fissionable material, so that nuclear power is converted directly into propulsive power. Thrust is available both from ejected fission fragments and from thermal radiation. Optimum thicknesses are determined for the active and substrate layers. This concept is shown to have potential mission capability (in terms of velocity increments) superior to that of all other advanced propulsion concepts for which performance estimates are available. A suitable spontaneously fissioning material such as Cf254 could provide an extremely high-performance first stage beyond earth orbit. In contrast with some other advanced nuclear propulsion concepts, there is no minimum size below which this concept is infeasible.

A thrust-sheet propulsion concept using fissionable elements

NASA Technical Reports Server (NTRS)

Moeckel, W. E.

1976-01-01

A space propulsion concept is proposed and analyzed which consists of a thin sheet coated on one side with fissionable material, so that nuclear power is converted directly into propulsive power. Thrust is available both from ejected fission fragments and from thermal radiation. Optimum thicknesses are determined for the active and substrate layers. This concept is shown to have potential mission capability (in terms of velocity increments) superior to that of all other advanced propulsion concepts for which performance estimates are available. A suitable spontaneously fissioning material such as Cf-254 could provide an extremely high-performance first stage beyond earth orbit. In contrast with some other advanced nuclear propulsion concepts, there is no minimum size below which this concept is infeasible.

Detection of Shielded Nuclear Material in a Cargo Container

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

J. L. Jones; D. R. Norman; K. J. Haskell

The Idaho National Laboratory, along with Los Alamos National Laboratory and the Idaho State University’s Idaho Accelerator Center, are developing electron accelerator-based, photonuclear inspection technologies for the detection of shielded nuclear material within air-, rail-, and especially, maritime-cargo transportation containers. This paper describes a developing prototypical cargo container inspection system utilizing the Pulsed Photonuclear Assessment (PPA) technology, incorporates interchangeable, well-defined, contraband shielding structures (i.e., "calibration" pallets) providing realistic detection data for induced radiation signatures from smuggled nuclear material, and provides various shielded nuclear material detection results. Using a 4.8-kg quantity of depleted uranium, neutron and gamma-ray detection responses are presentedmore » for well-defined shielded and unshielded configurations evaluated in a selected cargo container inspection configuration. © 2001 Elsevier Science. All rights reserved« less

Space Radiation and the Challenges Towards Effective Shielding Solutions

NASA Technical Reports Server (NTRS)

Barghouty, Abdulnasser

2014-01-01

The hazards of space radiation and their effective mitigation strategies continue to pose special science and technology challenges to NASA. It is widely accepted now that shielding space vehicles and structures will have to rely on new and innovative materials since aluminum, like all high Z materials, are poor shields against the particulate and highly ionizing nature of space radiation. Shielding solutions, motivated and constrained by power and mass limitations, couple this realization with "multifunctionality," both in design concept as well as in material function and composition. Materials endowed with effective shielding properties as well as with some degree of multi-functionality may be the kernel of the so-called "radiation-smart" structures and designs. This talk will present some of the challenges and potential mitigation ideas towards the realization of such structures and designs.

Dose profile modeling of Idaho National Laboratory's active neutron interrogation laboratory.

PubMed

Chichester, D L; Seabury, E H; Zabriskie, J M; Wharton, J; Caffrey, A J

2009-06-01

A new laboratory has been commissioned at Idaho National Laboratory for performing active neutron interrogation research and development. The facility is designed to provide radiation shielding for deuterium-tritium (DT) fusion (14.1 MeV) neutron generators (2 x 10(8) n/s), deuterium-deuterium (DD) fusion (2.5 MeV) neutron generators (1 x 10(7) n/s), and (252)Cf spontaneous fission neutron sources (6.96 x 10(7) n/s, 30 microg). Shielding at the laboratory is comprised of modular concrete shield blocks 0.76 m thick with tongue-in-groove features to prevent radiation streaming, arranged into one small and one large test vault. The larger vault is designed to allow operation of the DT generator and has walls 3.8m tall, an entrance maze, and a fully integrated electrical interlock system; the smaller test vault is designed for (252)Cf and DD neutron sources and has walls 1.9 m tall and a simple entrance maze. Both analytical calculations and numerical simulations were used in the design process for the building to assess the performance of the shielding walls and to ensure external dose rates are within required facility limits. Dose rate contour plots have been generated for the facility to visualize the effectiveness of the shield walls and entrance mazes and to illustrate the spatial profile of the radiation dose field above the facility and the effects of skyshine around the vaults.

DOSE PROFILE MODELING OF IDAHO NATIONAL LABORATORY’S ACTIVE NEUTRON INTERROGATION TEST FACILITY

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

D. L. Chichester; E. H. Seabury; J. M. Zabriskie

2009-06-01

A new research and development laboratory has been commissioned at Idaho National Laboratory for performing active neutron interrogation research and development. The facility is designed to provide radiation shielding for DT fusion (14.1 MeV) neutron generators (2 x 108 neutrons per second), DD fusion (2.5 MeV) neutron generators (up to 2 x 106 neutrons per second), and 252Cf spontaneous fission neutron sources (6.7 x 107 neutrons per second, 30 micrograms). Shielding at the laboratory is comprised of modular concrete shield blocks 0.76 m thick with tongue-in-groove features to prevent radiation streaming, arranged into one small and one large test vault.more » The larger vault is designed to allow operation of the DT generator and has walls 3.8 m tall, an entrance maze, and a fully integrated electrical interlock system; the smaller test vault is designed for 252Cf and DD neutron sources and has walls 1.9 m tall and a simple entrance maze. Both analytical calculations and numerical simulations were used in the design process for the building to assess the performance of the shielding walls and to ensure external dose rates are within required facility limits. Dose rate contour plots have been generated for the facility to visualize the effectiveness of the shield wall and entrance maze and to illustrate the spatial profile of the radiation dose field above the facility and the effects of skyshine around the vaults.« less

Low-cost electromagnetic shielding using drywall composites: results of RFI (radio-frequency interference) testing of a shielding effectiveness. Final technical report

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

Williams, P.F.; Heyen, K.K.; McCormack, R.G.

1987-10-01

Because of developments in electronics technology, the need for electromagnetic shielding has increased. To reduce the cost of this shielding, new materials are needed. The U.S. Army Corps of Engineers, Fort Worth District (FWD), and the U.S. Army Construction Engineering Research Laboratory (USA-CERL) have developed composite materials that use standard, construction-grade, aluminum foil-backed gypsum board in combination with either a metal mesh or lead foil. Special seams for these composites were designed by U.S. Gypsum Company. USA-CERL evaluated the adequacy of each material and seam design by using radio-frequency antennas and receivers to measure its shielding effectiveness when mounted inmore » the wall of a shielded room. These evaluations showed that the composite panels met the specified requirement of 60 decibels (dB) of shielding. The composites were also shown to be adequate for most communications security applications. However, the addition of a seam decreased shielding by as much as 10 dB.« less

Absolute nuclear material assay using count distribution (LAMBDA) space

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

Prasad, Mano K.; Snyderman, Neal J.; Rowland, Mark S.

A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

Absolute nuclear material assay using count distribution (LAMBDA) space

DOEpatents

Prasad, Manoj K [Pleasanton, CA; Snyderman, Neal J [Berkeley, CA; Rowland, Mark S [Alamo, CA

2012-06-05

A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

Exploratory Environmental Tests of Several Heat Shields

NASA Technical Reports Server (NTRS)

Goodman, George P.; Betts, John, Jr.

1961-01-01

Exploratory tests have been conducted with several conceptual radiative heat shields of composite construction. Measured transient temperature distributions were obtained for a graphite heat shield without insulation and with three types of insulating materials, and for a metal multipost heat shield, at surface temperatures of approximately 2,000 F and 1,450 F, respectively, by use of a radiant-heat facility. The graphite configurations suffered loss of surface material under repeated irradiation. Temperature distribution calculated for the metal heat shield by a numerical procedure was in good agreement with measured data. Environmental survival tests of the graphite heat shield without insulation, an insulated multipost heat shield, and a stainless-steel-tile heat shield were made at temperatures of 2,000 F and dynamic pressures of approximately 6,000 lb/sq ft, provided by an ethylene-heated jet operating at a Mach number of 2.0 and sea-level conditions. The graphite heat shield survived the simulated aerodynamic heating and pressure loading. A problem area exists in the design and materials for heat-resistant fasteners between the graphite shield and the base structure. The insulated multipost heat shield was found to be superior to the stainless-steel-tile heat shield in retarding heat flow. Over-lapped face-plate joints and surface smoothness of the insulated multi- post heat shield were not adversely affected by the test environment. The graphite heat shield without insulation survived tests made in the acoustic environment of a large air jet. This acoustic environment is random in frequency and has an overall noise level of 160 decibels.

Performances of Kevlar and Polyethylene as radiation shielding on-board the International Space Station in high latitude radiation environment.

PubMed

Narici, Livio; Casolino, Marco; Di Fino, Luca; Larosa, Marianna; Picozza, Piergiorgio; Rizzo, Alessandro; Zaconte, Veronica

2017-05-10

Passive radiation shielding is a mandatory element in the design of an integrated solution to mitigate the effects of radiation during long deep space voyages for human exploration. Understanding and exploiting the characteristics of materials suitable for radiation shielding in space flights is, therefore, of primary importance. We present here the results of the first space-test on Kevlar and Polyethylene radiation shielding capabilities including direct measurements of the background baseline (no shield). Measurements are performed on-board of the International Space Station (Columbus modulus) during the ALTEA-shield ESA sponsored program. For the first time the shielding capability of such materials has been tested in a radiation environment similar to the deep-space one, thanks to the feature of the ALTEA system, which allows to select only high latitude orbital tracts of the International Space Station. Polyethylene is widely used for radiation shielding in space and therefore it is an excellent benchmark material to be used in comparative investigations. In this work we show that Kevlar has radiation shielding performances comparable to the Polyethylene ones, reaching a dose rate reduction of 32 ± 2% and a dose equivalent rate reduction of 55 ± 4% (for a shield of 10 g/cm 2 ).

29 CFR 1915.57 - Uses of fissionable material in ship repairing and shipbuilding.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 29 Labor 7 2012-07-01 2012-07-01 false Uses of fissionable material in ship repairing and shipbuilding. 1915.57 Section 1915.57 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND... and shipbuilding. The provisions of this section apply to ship repairing and shipbuilding only. (a) In...

29 CFR 1915.57 - Uses of fissionable material in ship repairing and shipbuilding.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 29 Labor 7 2011-07-01 2011-07-01 false Uses of fissionable material in ship repairing and shipbuilding. 1915.57 Section 1915.57 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND... and shipbuilding. The provisions of this section apply to ship repairing and shipbuilding only. (a) In...

29 CFR 1915.57 - Uses of fissionable material in ship repairing and shipbuilding.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 29 Labor 7 2014-07-01 2014-07-01 false Uses of fissionable material in ship repairing and shipbuilding. 1915.57 Section 1915.57 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND... and shipbuilding. The provisions of this section apply to ship repairing and shipbuilding only. (a) In...

29 CFR 1915.57 - Uses of fissionable material in ship repairing and shipbuilding.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 29 Labor 7 2013-07-01 2013-07-01 false Uses of fissionable material in ship repairing and shipbuilding. 1915.57 Section 1915.57 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND... and shipbuilding. The provisions of this section apply to ship repairing and shipbuilding only. (a) In...

43 CFR 3746.1 - Mining locations for fissionable source materials.

Code of Federal Regulations, 2012 CFR

2012-10-01

... provisions of the Act of August 12, 1953 (67 Stat. 539), and particularly sec. 3 thereof, any mining claim... deposit which is a fissionable source material and which, except for the possible contrary construction of... affected by such possible contrary construction, be valid and effective, in all respects to the same extent...

43 CFR 3746.1 - Mining locations for fissionable source materials.

Code of Federal Regulations, 2013 CFR

2013-10-01

... provisions of the Act of August 12, 1953 (67 Stat. 539), and particularly sec. 3 thereof, any mining claim... deposit which is a fissionable source material and which, except for the possible contrary construction of... affected by such possible contrary construction, be valid and effective, in all respects to the same extent...

Shielded Heavy-Ion Environment Linear Detector (SHIELD): an experiment for the Radiation and Technology Demonstration (RTD) Mission.

PubMed

Shavers, M R; Cucinotta, F A; Miller, J; Zeitlin, C; Heilbronn, L; Wilson, J W; Singleterry, R C

2001-01-01

Radiological assessment of the many cosmic ion species of widely distributed energies requires the use of theoretical transport models to accurately describe diverse physical processes related to nuclear reactions in spacecraft structures, planetary atmospheres and surfaces, and tissues. Heavy-ion transport models that were designed to characterize shielded radiation fields have been validated through comparison with data from thick-target irradiation experiments at particle accelerators. With the RTD Mission comes a unique opportunity to validate existing radiation transport models and guide the development of tools for shield design. For the first time, transport properties will be measured in free-space to characterize the shielding effectiveness of materials that are likely to be aboard interplanetary space missions. Target materials composed of aluminum, advanced composite spacecraft structure and other shielding materials, helium (a propellant) and tissue equivalent matrices will be evaluated. Large solid state detectors will provide kinetic energy and charge identification for incident heavy-ions and for secondary ions created in the target material. Transport calculations using the HZETRN model suggest that 8 g cm -2 thick targets would be adequate to evaluate the shielding effectiveness during solar minimum activity conditions for a period of 30 days or more.

Radiation Shielding of Lunar Regolith/Polyethylene Composites and Lunar Regolith/Water Mixtures

NASA Technical Reports Server (NTRS)

Johnson, Quincy F.; Gersey, Brad; Wilkins, Richard; Zhou, Jianren

2011-01-01

Space radiation is a complex mixed field of ionizing radiation that can pose hazardous risks to sophisticated electronics and humans. Mission planning for lunar exploration and long duration habitat construction will face tremendous challenges of shielding against various types of space radiation in an attempt to minimize the detrimental effects it may have on materials, electronics, and humans. In late 2009, the Lunar Crater Observation and Sensing Satellite (LCROSS) discovered that water content in lunar regolith found in certain areas on the moon can be up to 5.6 +/-2.8 weight percent (wt%) [A. Colaprete, et. al., Science, Vol. 330, 463 (2010). ]. In this work, shielding studies were performed utilizing ultra high molecular weight polyethylene (UHMWPE) and aluminum, both being standard space shielding materials, simulated lunar regolith/ polyethylene composites, and simulated lunar regolith mixed with UHMWPE particles and water. Based on the LCROSS findings, radiation shielding experiments were conducted to test for shielding efficiency of regolith/UHMWPE/water mixtures with various percentages of water to compare relative shielding characteristics of these materials. One set of radiation studies were performed using the proton synchrotron at the Loma Linda Medical University where high energy protons similar to those found on the surface of the moon can be generated. A similar experimental protocol was also used at a high energy spalation neutron source at Los Alamos Neutron Science Center (LANSCE). These experiments studied the shielding efficiency against secondary neutrons, another major component of space radiation field. In both the proton and neutron studies, shielding efficiency was determined by utilizing a tissue equivalent proportional counter (TEPC) behind various thicknesses of shielding composite panels or mixture materials. Preliminary results from these studies indicated that adding 2 wt% water to regolith particles could increase shielding of the regolith materials by about 6%. The findings may be utilized to extend the possibilities of potential candidate materials for lunar habitat structures, will potentially impact the design criteria of future human bases on the moon, and provide some guidelines for future space mission planning with respect to radiation exposure and risks posed on astronauts.

MEANS FOR CONTROLLING REACTIONS

DOEpatents

Nordheim, L.W.; Wigner, E.P.

1961-06-27

The patented means is described for controlling a nuclear reactor which comprises a tank containing a dispersion of a thermally fissionable material in a liquid moderator and a material convertible to a thermally fissionable material in a container disposed about the tank. The control means comprises a control rod chamber, containing only a liquid moderator, disposed within the container and adjacent to the tank and a control rod designed to be inserted into the chamber.

Study on γ-ray exposure buildup factors and fast neutron-shielding properties of some building materials

NASA Astrophysics Data System (ADS)

Singh, Vishwanath P.; Badiger, N. M.; El-Khayatt, A. M.

2014-06-01

We have computed γ-ray exposure buildup factors (EBF) of some building materials; glass, marble, flyash, cement, limestone, brick, plaster of paris (POP) and gypsum for energy 0.015-15 MeV up to 40 mfp (mfp, mean free path) penetration depth. Also, the macroscopic effective removal cross-sections (ΣR) for fast neutron were calculated. We discussed the dependency of EBF values on photon energy, penetration depth and chemical elements. The half-value layer and kinetic energy per unit mass relative to air of building materials were calculated for assessment of shielding effectiveness. Shielding thicknesses for glass, marble, flyash, cement, limestone and gypsum plaster (or Plaster of Paris, POP) were found comparable with ordinary concrete. Among the studied materials limestone and POP showed superior shielding properties for γ-ray and neutron, respectively. Radiation safety inside houses, schools and primary health centers for sheltering and annual dose can be assessed by the determination of shielding parameters of common building materials.

Design Guidelines for Shielding Effectiveness, Current Carrying Capability, and the Enhancement of Conductivity of Composite Materials

NASA Technical Reports Server (NTRS)

Evans, R. W.

1997-01-01

These guidelines address the electrical properties of composite materials which may have an effect on electromagnetic compatibility (EMC). The main topics of the guidelines include the electrical shielding, fault current return, and lightning protection capabilities of graphite reinforced polymers, since they are somewhat conductive but may require enhancement to be adequate for EMC purposes. Shielding effectiveness depends heavily upon the conductivity of the material. Graphite epoxy can provide useful shielding against RF signals, but it is approximately 1,000 times more resistive than good conductive metals. The reduced shielding effectiveness is significant but is still useful in many cases. The primary concern is with gaps and seams in the material just as it is with metal. Current carrying capability of graphite epoxy is adequate for dissipation static charges, but fault currents through graphite epoxy may cause fire at the shorting contact and at joints. The effect of lightning on selected graphite epoxy material and mating surfaces is described, and protection methods are reviewed.

Effective radiation reduction in Space Station and missions beyond the magnetosphere

NASA Technical Reports Server (NTRS)

Jordan, Thomas M.; Stassinopoulos, E. G.

1989-01-01

This paper investigates the efficiency of low- and high-atomic number materials used as protective shields against biologically effective radiation in doses equivalent to those expected in low-earth-orbit and interplanetary manned missions. Results are presented on calculations for single-material shields from polyethylene, water, Be, Al, Fe, and Ta and multilayer shelds made from the combinations of any two or any three of these materials, for both LEO and interplanetary conditions. It is shown that, whereas for protons and Galactic cosmic rays the ordering of shield materials has a negligible effect, for electrons and secondary bremsstrahlung, both the order and the composition are important parameters. It was found that low-atomic-number materials are most effective shields against protons and galactic cosmic rays, and are most effective in decreasing bremsstrahlung production, while high-atomic-number shields are the best attenuators of both primary electrons (if the dose is dominated by primary electrons) and secondary bremsstrahlung (if this is produced).

Aperture Shield Materials Characterized and Selected for Solar Dynamic Space Power System

NASA Technical Reports Server (NTRS)

1995-01-01

The aperture shield in a solar dynamic space power system is necessary to prevent thermal damage to the heat receiver should the concentrated solar radiation be accidentally or intentionally focused outside of the heat receiver aperture opening and onto the aperture shield itself. Characterization of the optical and thermal properties of candidate aperture shield materials was needed to support the joint U.S./Russian solar dynamic space power effort for Mir. The specific objective of testing performed at the NASA Lewis Research Center was to identify a high-temperature material with a low specular reflectance, a low solar absorptance, and a high spectral emittance so that during an off-pointing event, the amount of solar energy reflecting off the aperture shield would be small, the ratio of solar absorptance to spectral emittance would provide the lowest possible equilibrium temperature, and the integrity of the aperture shield would remain intact.

Comparison of graphite, aluminum, and TransHab shielding material characteristics in a high-energy neutron field

NASA Technical Reports Server (NTRS)

Badhwar, G. D.; Huff, H.; Wilkins, R.; Thibeault, Sheila

2002-01-01

Space radiation transport models clearly show that low atomic weight materials provide a better shielding protection for interplanetary human missions than high atomic weight materials. These model studies have concentrated on shielding properties against charged particles. A light-weight, inflatable habitat module called TransHab was built and shown to provide adequate protection against micrometeoroid impacts and good shielding properties against charged particle radiation in the International Space Station orbits. An experiment using a tissue equivalent proportional counter, to study the changes in dose and lineal energy spectra with graphite, aluminum, and a TransHab build-up as shielding, was carried out at the Los Alamos Nuclear Science Center neutron facility. It is a continuation of a previous study using regolith and doped polyethylene materials. This paper describes the results and their comparison with the previous study. Published by Elsevier Science Ltd.

Innovative Research Program: Supershields for Gamma-Ray Astronomy

NASA Technical Reports Server (NTRS)

Hailey, Charles J.

2000-01-01

The supershield project evaluated the importance of novel shield configurations for suppressing neutron induced background in new classes of gamma-ray detectors such as CZT. The basic concept was to use a two-part shield. The outer shield material heavily moderates the incoming neutron spectrum. This moderated neutron beam is then more easily absorbed by the inner material, which is an efficient neutron absorber. This approach is, in principle, more efficient than that in previous attempts to make neutron shields. These previous attempts involved biatomic, monlithic shields (eg. LiH) in which the shield consisted of a single material but with two types of atoms - one for moderating and one for absorbing. The problem with this type of monolithic shield is that moderating neutrons, without the efficient absorption of them, leads to the leakage into the detector of neutrons with a low energy component (approx. 10-100 KeV). These energy neutrons are particularly problematic for many types of detectors. The project was roughly divided into phases. In the first phase we attempted to carefully define the neutron source function incident on any space instrument. This is essential since the design of any shield depends on the shape of the incident neutron spectrum. We found that approximations commonly used in gamma-ray astronomy for photon background is inadequate. In addition, we found that secondary neutrons produced in any passive shield, and dominated by inelastic neutron scattering, are far more important than background due to neutron activation. The second phase of our work involved design of supershield geometries (one and three dimensional) in order to compare different shield configurations and materials for their effectiveness as neutron shields. Moreover we wanted to compare these supershields with previous neutron shields to confirm the performance differences between the supershield (two material) and monolithic (one material) designs and to understand the physics origins of these differences more clearly. The third phase of the supershield program involved the benchmarking of the supershield designs through direct experimental verification. This required fabricating various supershields and exposing them to beams of neutrons to directly characterize their performance. With explicit verification that our modeling procedures can be used with confidence, we are now in a position to design shields for realistic space geometries. Using the supershield modeling capacity developed as part of this program we are attempting to evaluate their utility for a specific proposed mission--the Energetic X-ray Imaging Survey Telescope (EXIST). It is anticipated that this experiment, which is limited by internal background at high energies, might benefit from a neutron shield.

Multilayered Electromagnetic Interference Shielding Structures for Suppressing Magnetic Field Coupling

NASA Astrophysics Data System (ADS)

Watanabe, Atom O.; Raj, Pulugurtha Markondeya; Wong, Denny; Mullapudi, Ravi; Tummala, Rao

2018-05-01

Control of electromagnetic interference (EMI) represents a major challenge for emerging consumer electronics, the Internet of Things, automotive electronics, and wireless communication systems. This paper discusses innovative EMI shielding materials and structures that offer higher shielding effectiveness compared with copper. To create high shielding effectiveness in the frequency range of 1 MHz to 100 MHz, multilayered shielding topologies with electrically conductive and nanomagnetic materials were modeled, designed, fabricated, and characterized. In addition, suppression of out-of-plane and in-plane magnetic-field coupling noise with these structures is compared with that of traditional single-layer copper or nickel-iron films. Compared with single-layered copper shields, multilayered structures consisting of copper, nickel-iron, and titanium showed a 3.9 times increase in shielding effectiveness in suppressing out-of-plane or vertically coupled noise and 1.3 times increase in lateral coupling. The superiority of multilayered thin-film shields over conventional shielding enables greater design flexibility, higher shielding effectiveness, and further miniaturization of emerging radiofrequency (RF) and power modules.

New fission-fragment detector for experiments at DANCE

NASA Astrophysics Data System (ADS)

Rusev, G.; Roman, A. R.; Daum, J. K.; Springs, R. K.; Bond, E. M.; Jandel, M.; Baramsai, B.; Bredeweg, T. A.; Couture, A.; Favalli, A.; Ianakiev, K. D.; Iliev, M. L.; Mosby, S.; Ullmann, J. L.; Walker, C. L.

2015-10-01

A fission-fragment detector based on thin scintillating films has been built to serve as a veto/trigger detector in neutron-induced fission measurements at DANCE. The fissile material is surrounded by scintillating films providing a 4 π detection of the fission fragments. The scintillation events caused by the fission fragment interactions in the films are registered with silicon photomultipliers. Design of the detector and test measurements are described. Work supported by the U.S. Department of Energy through the LANL/LDRD Program and the U.S. Department of Energy, Office of Science, Nuclear Physics under the Early Career Award No. LANL20135009.

Optimization of radiation shielding material aiming at compactness, lightweight, and low activation for a vehicle-mounted accelerator-driven D-T neutron source.

PubMed

Cai, Yao; Hu, Huasi; Lu, Shuangying; Jia, Qinggang

2018-05-01

To minimize the size and weight of a vehicle-mounted accelerator-driven D-T neutron source and protect workers from unnecessary irradiation after the equipment shutdown, a method to optimize radiation shielding material aiming at compactness, lightweight, and low activation for the fast neutrons was developed. The method employed genetic algorithm, combining MCNP and ORIGEN codes. A series of composite shielding material samples were obtained by the method step by step. The volume and weight needed to build a shield (assumed as a coaxial tapered cylinder) were adopted to compare the performance of the materials visually and conveniently. The results showed that the optimized materials have excellent performance in comparison with the conventional materials. The "MCNP6-ACT" method and the "rigorous two steps" (R2S) method were used to verify the activation grade of the shield irradiated by D-T neutrons. The types of radionuclide, the energy spectrum of corresponding decay gamma source, and the variation in decay gamma dose rate were also computed. Copyright © 2018 Elsevier Ltd. All rights reserved.

Production and testing of the ENEA-Bologna VITJEFF32.BOLIB (JEFF-3.2) multi-group (199 n + 42 γ) cross section library in AMPX format for nuclear fission applications

NASA Astrophysics Data System (ADS)

Pescarini, Massimo; Orsi, Roberto; Frisoni, Manuela

2017-09-01

The ENEA-Bologna Nuclear Data Group produced the VITJEFF32.BOLIB multi-group coupled neutron/photon (199 n + 42 γ) cross section library in AMPX format, based on the OECD-NEA Data Bank JEFF-3.2 evaluated nuclear data library. VITJEFF32.BOLIB was conceived for nuclear fission applications as European counterpart of the ORNL VITAMIN-B7 similar library (ENDF/B-VII.0 data). VITJEFF32.BOLIB has the same neutron and photon energy group structure as the former ORNL VITAMIN-B6 reference library (ENDF/B-VI.3 data) and was produced using similar data processing methodologies, based on the LANL NJOY-2012.53 nuclear data processing system for the generation of the nuclide cross section data files in GENDF format. Then the ENEA-Bologna 2007 Revision of the ORNL SCAMPI nuclear data processing system was used for the conversion into the AMPX format. VITJEFF32.BOLIB contains processed cross section data files for 190 nuclides, obtained through the Bondarenko (f-factor) method for the treatment of neutron resonance self-shielding and temperature effects. Collapsed working libraries of self-shielded cross sections in FIDO-ANISN format, used by the deterministic transport codes of the ORNL DOORS system, can be generated from VITJEFF32.BOLIB through the cited SCAMPI version. This paper describes the methodology and specifications of the data processing performed and presents some results of the VITJEFF32.BOLIB validation.

Spacecraft Shielding: An Experimental Comparison Between Open Cell Aluminium Foam Core Sandwich Panel Structures and Whipple Shielding.

NASA Astrophysics Data System (ADS)

Pasini, D. L. S.; Price, M. C.; Burchell, M. J.; Cole, M. J.

2013-09-01

Spacecraft shielding is generally provided by metallic plates in a Whipple shield type configuration [1] where possible. However, mission restrictions such as spacecraft payload mass, can prevent the inclusion of a dedicated protective structure for prevention against impact damage from micrometeoroids. Due to this, often the spacecraft's primary structure will act as the de facto shield. This is commonly an aluminium honeycomb backed with either glass fibre reinforced plastic (GFRP) or aluminium faceplates [2]. Such materials are strong, lightweight and relatively cheap due to their abundance used within the aerospace industry. However, these materials do not offer the best protection (per unit weight) against hypervelocity impact damage. A new material for shielding (porous aluminium foam [3]) is suggested for low risk space missions. Previous studies by NASA [4] have been performed to test this new material against hypervelocity impacts using spherical aluminium projectiles. This showed its potential for protection for satellites in Earth orbit, against metallic space debris. Here we demonstrate the material's protective capabilities against micrometeoroids, using soda-lime glass spheres as projectiles to accurately gauge its potential with relation to silicatious materials, such as micrometeoroids and natural solar system debris. This is useful for spacecraft missions beyond Earth orbit where solar system materials are the dominant threat (via hypervelocity impacts) to the spacecraft, rather than manmade debris.

Optimization of Crew Shielding Requirement in Reactor-Powered Lunar Surface Missions

NASA Technical Reports Server (NTRS)

Barghouty, Abdulnasser F.

2007-01-01

On the surface of the moon -and not only during heightened solar activities- the radiation environment As such that crew protection will be required for missions lasting in excess of six months. This study focuses on estimating the optimized crew shielding requirement for lunar surface missions with a nuclear option. Simple, transport-simulation based dose-depth relations of the three (galactic, solar, and fission) radiation sources am employed in a 1-dimensional optimization scheme. The scheme is developed to estimate the total required mass of lunar-regolith separating reactor from crew. The scheme was applied to both solar maximum and minimum conditions. It is shown that savings of up to 30% in regolith mass can be realized. It is argued, however, that inherent variation and uncertainty -mainly in lunar regolith attenuation properties in addition to the radiation quality factor- can easily defeat this and similar optimization schemes.

Optimization of Crew Shielding Requirement in Reactor-Powered Lunar Surface Missions

NASA Technical Reports Server (NTRS)

Barghouty, A. F.

2007-01-01

On the surface of the moon and not only during heightened solar activities the radiation environment is such that crew protection will be required for missions lasting in excess of six months. This study focuses on estimating the optimized crew shielding requirement for lunar surface missions with a nuclear option. Simple, transport-simulation based dose-depth relations of the three radiation sources (galactic, solar, and fission) are employed in a one-dimensional optimization scheme. The scheme is developed to estimate the total required mass of lunar regolith separating reactor from crew. The scheme was applied to both solar maximum and minimum conditions. It is shown that savings of up to 30% in regolith mass can be realized. It is argued, however, that inherent variation and uncertainty mainly in lunar regolith attenuation properties in addition to the radiation quality factor can easily defeat this and similar optimization schemes.

Gamma neutron assay method and apparatus

DOEpatents

Cole, J.D.; Aryaeinejad, R.; Greenwood, R.C.

1995-01-03

The gamma neutron assay technique is an alternative method to standard safeguards techniques for the identification and assaying of special nuclear materials in a field or laboratory environment, as a tool for dismantlement and destruction of nuclear weapons, and to determine the isotopic ratios for a blend-down program on uranium. It is capable of determining the isotopic ratios of fissionable material from the spontaneous or induced fission of a sample to within approximately 0.5%. This is based upon the prompt coincidence relationships that occur in the fission process and the proton conservation and quasi-conservation of nuclear mass (A) that exists between the two fission fragments. The system is used in both passive (without an external neutron source) and active (with an external neutron source) mode. The apparatus consists of an array of neutron and gamma-ray detectors electronically connected to determine coincident events. The method can also be used to assay radioactive waste which contains fissile material, even in the presence of a high background radiation field. 7 figures.

Gamma neutron assay method and apparatus

DOEpatents

Cole, Jerald D.; Aryaeinejad, Rahmat; Greenwood, Reginald C.

1995-01-01

The gamma neutron assay technique is an alternative method to standard safeguards techniques for the identification and assaying of special nuclear materials in a field or laboratory environment, as a tool for dismantlement and destruction of nuclear weapons, and to determine the isotopic ratios for a blend-down program on uranium. It is capable of determining the isotopic ratios of fissionable material from the spontaneous or induced fission of a sample to within approximately 0.5%. This is based upon the prompt coincidence relationships that occur in the fission process and the proton conservation and quasi-conservation of nuclear mass (A) that exists between the two fission fragments. The system is used in both passive (without an external neutron source and active (with an external neutron source) mode. The apparatus consists of an array of neutron and gamma-ray detectors electronically connected to determine coincident events. The method can also be used to assay radioactive waste which contains fissile material, even in the presence of a high background radiation field.

Emilio Segrè and Spontaneous Fission

Science.gov Websites

fissioned instead. The discovery of fission led in turn to the discovery of the chain reaction that, if material apart before it had a chance to undergo an efficient chain reaction. The possibility of chain reaction. If a similar rate was found in plutonium, it might rule out the use of that element as

Fission meter and neutron detection using poisson distribution comparison

DOEpatents

Rowland, Mark S; Snyderman, Neal J

2014-11-18

A neutron detector system and method for discriminating fissile material from non-fissile material wherein a digital data acquisition unit collects data at high rate, and in real-time processes large volumes of data directly into information that a first responder can use to discriminate materials. The system comprises counting neutrons from the unknown source and detecting excess grouped neutrons to identify fission in the unknown source. Comparison of the observed neutron count distribution with a Poisson distribution is performed to distinguish fissile material from non-fissile material.

Singlet exciton fission in polycrystalline pentacene: from photophysics toward devices.

PubMed

Wilson, Mark W B; Rao, Akshay; Ehrler, Bruno; Friend, Richard H

2013-06-18

Singlet exciton fission is the process in conjugated organic molecules bywhich a photogenerated singlet exciton couples to a nearby chromophore in the ground state, creating a pair of triplet excitons. Researchers first reported this phenomenon in the 1960s, an event that sparked further studies in the following decade. These investigations used fluorescence spectroscopy to establish that exciton fission occurred in single crystals of several acenes. However, research interest has been recently rekindled by the possibility that singlet fission could be used as a carrier multiplication technique to enhance the efficiency of photovoltaic cells. The most successful architecture to-date involves sensitizing a red-absorbing photoactive layer with a blue-absorbing material that undergoes fission, thereby generating additional photocurrent from higher-energy photons. The quest for improved solar cells has spurred a drive to better understand the fission process, which has received timely aid from modern techniques for time-resolved spectroscopy, quantum chemistry, and small-molecule device fabrication. However, the consensus interpretation of the initial studies using ultrafast transient absorption spectroscopy was that exciton fission was suppressed in polycrystalline thin films of pentacene, a material that would be otherwise expected to be an ideal model system, as well as a viable candidate for fission-sensitized photovoltaic devices. In this Account, we review the results of our recent transient absorption and device-based studies of polycrystalline pentacene. We address the controversy surrounding the assignment of spectroscopic features in transient absorption data, and illustrate how a consistent interpretation is possible. This work underpins our conclusion that singlet fission in pentacene is extraordinarily rapid (∼80 fs) and is thus the dominant decay channel for the photoexcited singlet exciton. Further, we discuss our demonstration that triplet excitons generated via singlet fission in pentacene can be dissociated at an interface with a suitable electron acceptor, such as fullerenes and infrared-absorbing inorganic semiconducting quantum dots. We highlight our recent reports of a pentacene/PbSe hybrid solar cell with a power conversion efficiency of 4.7% and of a pentacene/PbSe/amorphous silicon photovoltaic device. Although substantive challenges remain, both to better our understanding of the mechanism of singlet exciton fission and to optimize device performance, this realization of a solar cell where photocurrent is simultaneously contributed from a blue-absorbing fission-capable material and an infrared-absorbing conventional cell is an important step towards a dual-bandgap, single-junction, fission-enhanced photovoltaic device, which could one day surpass the Shockley-Queisser limit.

Cross Section Sensitivity and Propagated Errors in HZE Exposures

NASA Technical Reports Server (NTRS)

Heinbockel, John H.; Wilson, John W.; Blatnig, Steve R.; Qualls, Garry D.; Badavi, Francis F.; Cucinotta, Francis A.

2005-01-01

It has long been recognized that galactic cosmic rays are of such high energy that they tend to pass through available shielding materials resulting in exposure of astronauts and equipment within space vehicles and habitats. Any protection provided by shielding materials result not so much from stopping such particles but by changing their physical character in interaction with shielding material nuclei forming, hopefully, less dangerous species. Clearly, the fidelity of the nuclear cross-sections is essential to correct specification of shield design and sensitivity to cross-section error is important in guiding experimental validation of cross-section models and database. We examine the Boltzmann transport equation which is used to calculate dose equivalent during solar minimum, with units (cSv/yr), associated with various depths of shielding materials. The dose equivalent is a weighted sum of contributions from neutrons, protons, light ions, medium ions and heavy ions. We investigate the sensitivity of dose equivalent calculations due to errors in nuclear fragmentation cross-sections. We do this error analysis for all possible projectile-fragment combinations (14,365 such combinations) to estimate the sensitivity of the shielding calculations to errors in the nuclear fragmentation cross-sections. Numerical differentiation with respect to the cross-sections will be evaluated in a broad class of materials including polyethylene, aluminum and copper. We will identify the most important cross-sections for further experimental study and evaluate their impact on propagated errors in shielding estimates.

Radiation production and absorption in human spacecraft shielding systems under high charge and energy Galactic Cosmic Rays: Material medium, shielding depth, and byproduct aspects

NASA Astrophysics Data System (ADS)

Barthel, Joseph; Sarigul-Klijn, Nesrin

2018-03-01

Deep space missions such as the planned 2025 mission to asteroids require spacecraft shields to protect electronics and humans from adverse effects caused by the space radiation environment, primarily Galactic Cosmic Rays. This paper first reviews the theory on how these rays of charged particles interact with matter, and then presents a simulation for a 500 day Mars flyby mission using a deterministic based computer code. High density polyethylene and aluminum shielding materials at a solar minimum are considered. Plots of effective dose with varying shield depth, charged particle flux, and dose in silicon and human tissue behind shielding are presented.

S/sub n/ analysis of the TRX metal lattices with ENDF/B version III data

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

Wheeler, F.J.; Pearlstein, S.

1975-03-01

Two critical assemblies, designated as thermal-reactor benchmarks TRX-1 and TRX-2 for ENDF/B data testing, were analyzed using the one-dimensional S/sub n/-theory code SCAMP. The two assemblies were simple lattices of aluminum-clad, uranium-metal fuel rods in triangular arrays with D$sub 2$O as moderator and reflector. The fuel was low-enriched (1.3 percent $sup 235$U), 0.387-inch in diameter and had an active height of 48 inches. The volume ratio of water to uranium was 2.35 for the TRX-1 lattice and 4.02 for TRX-2. Full-core S/sub n/ calculations based on Version III data were performed for these assemblies and the results obtained were comparedmore » with the measured values of the multiplication factors, the ratio of epithermal-to-thermal neutron capture in $sup 238$U, the ratio of epithermal-to-thermal fission in $sup 235$U, the ratio of $sup 238$U fission to $sup 235$U fission, and the ratio of capture in $sup 238$U to fission in $sup 235$U. Reaction rates were obtained from a central region of the full- core problems. Multigroup cross sections for the reactor calculation were obtained from S/sub n/ cell calculations with resonance self-shielding calculated using the RABBLE treatment. The results of the analyses are generally consistent with results obtained by other investigators. (auth)« less

Retro Rocket Motor Self-Penetrating Scheme for Heat Shield Exhaust Ports

NASA Technical Reports Server (NTRS)

Marrese-Reading, Colleen; St.Vaughn, Josh; Zell, Peter; Hamm, Ken; Corliss, Jim; Gayle, Steve; Pain, Rob; Rooney, Dan; Ramos, Amadi; Lewis, Doug;

Robust singlet fission in pentacene thin films with tuned charge transfer interactions.

PubMed

Broch, K; Dieterle, J; Branchi, F; Hestand, N J; Olivier, Y; Tamura, H; Cruz, C; Nichols, V M; Hinderhofer, A; Beljonne, D; Spano, F C; Cerullo, G; Bardeen, C J; Schreiber, F

2018-03-05

Singlet fission, the spin-allowed photophysical process converting an excited singlet state into two triplet states, has attracted significant attention for device applications. Research so far has focused mainly on the understanding of singlet fission in pure materials, yet blends offer the promise of a controlled tuning of intermolecular interactions, impacting singlet fission efficiencies. Here we report a study of singlet fission in mixtures of pentacene with weakly interacting spacer molecules. Comparison of experimentally determined stationary optical properties and theoretical calculations indicates a reduction of charge-transfer interactions between pentacene molecules with increasing spacer molecule fraction. Theory predicts that the reduced interactions slow down singlet fission in these blends, but surprisingly we find that singlet fission occurs on a timescale comparable to that in pure crystalline pentacene. We explain the observed robustness of singlet fission in such mixed films by a mechanism of exciton diffusion to hot spots with closer intermolecular spacings.

Improved Spacecraft Materials for Radiation Protection

NASA Technical Reports Server (NTRS)

Wilson, John W.; Cucinotta, Francis A.; Tripathi, Ram K.; Clowdsley, M. S.; Shinn, J. L.; Singleterry, Robert C., Jr.; Thibeault, Sheila Ann; Kim, M.-H. Y.; Heinbockel, John H.; Badhwar, Gautam D.

2001-01-01

Methods by which radiation shielding is optimized need to be developed and materials of improved shielding characteristics identified and validated. The galactic cosmic rays (GCR) are very penetrating and the energy absorbed by the astronaut behind the shield is nearly independent of shield composition and even the shield thickness. However, the mix of particles in the transmitted beam changes rapidly with shield material composition and thickness. This results in part from the breakup of the high-energy heavy ions of the GCR which make contributions to biological effects out of proportion to their deposited energy. So the mixture of particles in the radiation field changes with shielding and the control of risk contributions from dominant particle types is critical to reducing the hazard to the astronaut. The risk of biological injury for a given particle type depends on the type of biological effect and is specific to cell or tissue type. Thus, one is faced with choosing materials which may protect a given tissue against a given effect but leave unchanged or even increase the risk of other effects in the same tissue or increase the risks to other adjacent tissues of a different type in the same individual. The optimization of shield composition will then be tied to a specific tissue and risk to that tissue. Such peculiarities arise from the complicated mixture of particles, the nature of their biological response, and the details of their interaction with material constituents. Aside from the understanding of the biological response to specific components, one also needs an accurate understanding of the radiation emerging from the shield material. This latter subject has been a principal element of this project. In the past ten years our understanding of space radiation interactions with materials has changed radically, with a large impact on shield design. For example, the NCRP estimated that only 2 g/sq cm. of aluminum would be required to meet the annual 500 mSv limit for the exposure of the blood forming organs (this limit is strictly for LEO but can be used as a guideline for the Mars mission analysis). The current estimates require aluminum shield thicknesses above 50 g/sq cm., which is impractical. In such a heavily shielded vehicle, the neutrons produced throughout the vehicle also contribute significantly to the exposure and this demands greater care in describing the angular dependence of secondary particle production processes. As such the continued testing of databases and transport procedures in laboratory and spaceflight experiments has continued. This has been the focus of much of the last year's activity and has resulted in improved neutron prediction capability. These new methods have also improved our understanding of the surface environment of Mars. The Mars 2003 NRA HEDS related surface science requirements were driven by the need to validate predictions on the upward flux of neutrons produced in the Martian regolith and bedrock made by the codes developed under this project. The codes used in the surface environment definition are also being used to look at in situ resources for the development of construction material for Martian surface facilities. For example, synthesis of polyimides and polyethylene as binders of regolith for developing basic structural elements has been studied and targets built for accelerator beam testing of radiation shielding properties. Preliminary mechanical tests have also been promising. Improved spacecraft materials have been identified (using the criteria reported by this project at the last conference) as potentially important for future shielding materials. These are liquid hydrogen, hydrogenated nanofibers, liquid methane, LiH, Polyethylene, Polysulfone, and Polyetherimide (in order of decreasing shield performance). Some of the materials are multifunctional and are required for other onboard systems. We are currently preparing software for trade studies with these materials relative to the Mars Reference Mission as required in the project's final year.

Fabrication of Lightweight Radiation Shielding Composite Materials by Field Assisted Sintering Technique (FAST)

NASA Technical Reports Server (NTRS)

Prasad, Narasimha; Trivedi, Sudhir; Chen, Henry; Kutcher, Susan; Zhang, Dajie; Singh, Jogender

2017-01-01

Advances in radiation shielding technologies are needed to protect humans and electronic components from all threats of space radiation over long durations. In this paper, we report on the use of the innovative and novel fabrication technology known as Field Assisted Sintering Technology (FAST) to fabricate lightweight material with enhanced radiation shielding strength to safeguard humans and electronics suitable for next generation space exploration missions. The base materials we investigated were aluminum (Al), the current standard material for space hardware, and Ultra-High Molecular Weight Polyethylene (UHMWPE), which has high hydrogen content and resistance to nuclear reaction from neutrons, making it a good shielding material for both gamma radiation and particles. UHMWPE also has high resistance to corrosive chemicals, extremely low moisture sensitivity, very low coefficient of friction, and high resistance to abrasion. We reinforced the base materials by adding high density (ie, high atomic weight) metallic material into the composite. These filler materials included: boron carbide (B4C), tungsten (W), tungsten carbide (WC) and gadolinium (Gd).

Thermal, Radiation and Impact Protective Shields (TRIPS) for Robotic and Human Space Exploration Missions

NASA Technical Reports Server (NTRS)

Loomis, M. P.; Arnold, J. L.

2005-01-01

New concepts for protective shields for NASA s Crew Exploration Vehicles (CEVs) and planetary probes offer improved mission safety and affordability. Hazards include radiation from cosmic rays and solar particle events, hypervelocity impacts from orbital debris/ micrometeorites, and the extreme heating environment experienced during entry into planetary atmospheres. The traditional approach for the design of protection systems for these hazards has been to create single-function shields, i.e. ablative and blanket-based heat shields for thermal protection systems (TPS), polymer or other low-molecular-weight materials for radiation shields, and multilayer, Whipple-type shields for protection from hypervelocity impacts. This paper introduces an approach for the development of a single, multifunctional protective shield, employing nanotechnology- based materials, to serve simultaneously as a TPS, an impact shield and as the first line of defense against radiation. The approach is first to choose low molecular weight ablative TPS materials, (existing and planned for development) and add functionalized carbon nanotubes. Together they provide both thermal and radiation (TR) shielding. Next, impact protection (IP) is furnished through a tough skin, consisting of hard, ceramic outer layers (to fracture the impactor) and sublayers of tough, nanostructured fabrics to contain the debris cloud from the impactor before it can penetrate the spacecraft s interior.

FLUORINATION OF OXIDIC NUCLEAR FUEL

DOEpatents

Mecham, W.J.; Gabor, J.D.

1963-07-23

A process of volatilizing fissionable material away from fission products, present together in neutron-bombarded uranium oxide, by reaction with an oxygen-fluorine mixture at 350 to 500 deg C is described. (AEC)

Curved Waveguide Based Nuclear Fission for Small, Lightweight Reactors

NASA Technical Reports Server (NTRS)

Coker, Robert; Putnam, Gabriel

2012-01-01

The focus of the presented work is on the creation of a system of grazing incidence, supermirror waveguides for the capture and reuse of fission sourced neutrons. Within research reactors, neutron guides are a well known tool for directing neutrons from the confined and hazardous central core to a more accessible testing or measurement location. Typical neutron guides have rectangular, hollow cross sections, which are crafted as thin, mirrored waveguides plated with metal (commonly nickel). Under glancing angles with incoming neutrons, these waveguides can achieve nearly lossless transport of neutrons to distant instruments. Furthermore, recent developments have created supermirror surfaces which can accommodate neutron grazing angles up to four times as steep as nickel. A completed system will form an enclosing ring or spherical resonator system to a coupled neutron source for the purpose of capturing and reusing free neutrons to sustain and/or accelerate fission. While grazing incidence mirrors are a known method of directing and safely using neutrons, no method has been disclosed for capture and reuse of neutrons or sustainment of fission using a circular waveguide structure. The presented work is in the process of fabricating a functional, highly curved, neutron supermirror using known methods of Ni-Ti layering capable of achieving incident reflection angles up to four times steeper than nickel alone. Parallel work is analytically investigating future geometries, mirror compositions, and sources for enabling sustained fission with applicability to the propulsion and energy goals of NASA and other agencies. Should research into this concept prove feasible, it would lead to development of a high energy density, low mass power source potentially capable of sustaining fission with a fraction of the standard critical mass for a given material and a broadening of feasible materials due to reduced rates of release, absorption, and non-fission for neutrons. This advance could be applied to direct propulsion through guided fission products or as a secondary energy source for high impulse electric propulsion. It would help meet national needs for highly efficient energy sources with limited dependence on fossil fuels or conflict materials, and it would improve the use of low grade fissile materials which would help reduce national stockpiles and waste.

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

Deyglun, C.; Simony, B.; Perot, B.

The quantification of radioactive material is essential in the fields of safeguards, criticality control of nuclear processes, dismantling of nuclear facilities and components, or radioactive waste characterization. The Nuclear Measurement Laboratory (LMN) of CEA is involved in the development of time-correlated neutron detection techniques using plastic scintillators. Usually, 3He proportional counters are used for passive neutron coincidence counting owing to their high thermal neutron capture efficiency and gamma insensitivity. However, the global {sup 3}He shortage in the past few years has made these detectors extremely expensive. In addition, contrary to {sup 3}He counters for which a few tens of microsecondsmore » are needed to thermalize fast neutrons, in view to maximize the {sup 3}He(n,p){sup 3}H capture cross section, plastic scintillators are based on elastic scattering and therefore the light signal is formed within a few nanoseconds, correlated pulses being detected within a few dozen- or hundred nanoseconds. This time span reflects fission particles time of flight, which allows reducing accordingly the duration of the coincidence gate and thus the rate of random coincidences, which may totally blind fission coincidences when using {sup 3}He counters in case of a high (α,n) reaction rate. However, plastic scintillators are very sensitive to gamma rays, requiring the use of a thick metallic shield to reduce the corresponding background. Cross talk between detectors is also a major issue, which consists on the detection of one particle by several detectors due to elastic or inelastic scattering, leading to true but undesired coincidences. Data analysis algorithms are tested to minimize cross-talk in simultaneously activated detectors. The distinction between useful fission coincidences and the correlated background due to cross-talk, (α,n) and induced (n,2n) or (n,n'γ) reactions, is achieved by measuring 3-fold coincidences. The performances of a passive neutron coincidence counting system for radioactive waste drums using plastic scintillators have been studied using the Monte Carlo radiation transport code MCNPX-PoliMi v2.0 coupled to data processing algorithms developed with ROOT data analysis software. In addition to the correlated background, accidental coincidences are taken into account in the simulation by randomly merging pulses from different calculations with fission and (α,n) sources. (authors)« less

High purity silica reflective heat shield development

NASA Technical Reports Server (NTRS)

Nachtscheim, P. R.; Blome, J. C.

1976-01-01

A hyperpure vitreous silica material is being developed for use as a reflective and ablative heat shield for planetary entry. Various purity grades and forms of raw materials were evaluated along with various processing methods. Slip casting of high purity grain was selected as the best processing method, resulting in a highly reflective material in the wavelength bands of interest (the visible and ultraviolet regions). The selected material was characterized with respect to optical, mechanical and physical properties using a limited number of specimens. The process has been scaled up to produce a one-half scale heat shield (18 in. dia.) (45.72 cm) for a Jupiter entry vehicle. This work is now being extended to improve the structural safety factor of the heat shield by making hyperpure silica material tougher through the addition of silica fibers.

Evaluation of Multi-Functional Materials for Deep Space Radiation Shielding

NASA Technical Reports Server (NTRS)

Rojdev, Kristina; Atwell, William; Wilkins, Richard; Gersey, Brad; Badavi, Francis F.

2009-01-01

Small scale trade study of materials for radiation shielding: a) High-hydrogen polymers; b) Z-graded materials; c) Fiber-reinforced polymer composites. Discussed multi-functionality of fiber-reinforced polymer composites. Preliminary results of ground testing data.

A high-performance magnetic shield with large length-to-diameter ratio.

PubMed

Dickerson, Susannah; Hogan, Jason M; Johnson, David M S; Kovachy, Tim; Sugarbaker, Alex; Chiow, Sheng-wey; Kasevich, Mark A

2012-06-01

We have demonstrated a 100-fold improvement in the magnetic field uniformity on the axis of a large aspect ratio, cylindrical, mumetal magnetic shield by reducing discontinuities in the material of the shield through the welding and re-annealing of a segmented shield. The three-layer shield reduces Earth's magnetic field along an 8 m region to 420 μG (rms) in the axial direction, and 460 and 730 μG (rms) in the two transverse directions. Each cylindrical shield is a continuous welded tube which has been annealed after manufacture and degaussed in the apparatus. We present both experiments and finite element analysis that show the importance of uniform shield material for large aspect ratio shields, favoring a welded design over a segmented design. In addition, we present finite element results demonstrating the smoothing of spatial variations in the applied magnetic field by cylindrical magnetic shields. Such homogenization is a potentially useful feature for precision atom interferometric measurements.

Radiation Shielding Optimization on Mars

NASA Technical Reports Server (NTRS)

Slaba, Tony C.; Mertens, Chris J.; Blattnig, Steve R.

2013-01-01

Future space missions to Mars will require radiation shielding to be optimized for deep space transit and an extended stay on the surface. In deep space, increased shielding levels and material optimization will reduce the exposure from most solar particle events (SPE) but are less effective at shielding against galactic cosmic rays (GCR). On the surface, the shielding provided by the Martian atmosphere greatly reduces the exposure from most SPE, and long-term GCR exposure is a primary concern. Previous work has shown that in deep space, additional shielding of common materials such as aluminum or polyethylene does not significantly reduce the GCR exposure. In this work, it is shown that on the Martian surface, almost any amount of aluminum shielding increases exposure levels for humans. The increased exposure levels are attributed to neutron production in the shield and Martian regolith as well as the electromagnetic cascade induced in the Martian atmosphere. This result is significant for optimization of vehicle and shield designs intended for the surface of Mars.

Tests of shielding effectiveness of Kevlar and Nextel onboard the International Space Station and the Foton-M3 capsule.

PubMed

Pugliese, M; Bengin, V; Casolino, M; Roca, V; Zanini, A; Durante, M

2010-08-01

Radiation assessment and protection in space is the first step in planning future missions to the Moon and Mars, where mission and number of space travelers will increase and the protection of the geomagnetic shielding against the cosmic radiation will be absent. In this framework, the shielding effectiveness of two flexible materials, Kevlar and Nextel, were tested, which are largely used in the construction of spacecrafts. Accelerator-based tests clearly demonstrated that Kevlar is an excellent shield for heavy ions, close to polyethylene, whereas Nextel shows poor shielding characteristics. Measurements on flight performed onboard of the International Space Station and of the Foton-M3 capsule have been carried out with special attention to the neutron component; shielded and unshielded detectors (thermoluminescence dosemeters, bubble detectors) were exposed to a real radiation environment to test the shielding properties of the materials under study. The results indicate no significant effects of shielding, suggesting that thin shields in low-Earth Orbit have little effect on absorbed dose.

Noise Modeling From Conductive Shields Using Kirchhoff Equations.

PubMed

Sandin, Henrik J; Volegov, Petr L; Espy, Michelle A; Matlashov, Andrei N; Savukov, Igor M; Schultz, Larry J

2010-10-09

Progress in the development of high-sensitivity magnetic-field measurements has stimulated interest in understanding the magnetic noise of conductive materials, especially of magnetic shields based on high-permeability materials and/or high-conductivity materials. For example, SQUIDs and atomic magnetometers have been used in many experiments with mu-metal shields, and additionally SQUID systems frequently have radio frequency shielding based on thin conductive materials. Typical existing approaches to modeling noise only work with simple shield and sensor geometries while common experimental setups today consist of multiple sensor systems with complex shield geometries. With complex sensor arrays used in, for example, MEG and Ultra Low Field MRI studies, knowledge of the noise correlation between sensors is as important as knowledge of the noise itself. This is crucial for incorporating efficient noise cancelation schemes for the system. We developed an approach that allows us to calculate the Johnson noise for arbitrary shaped shields and multiple sensor systems. The approach is efficient enough to be able to run on a single PC system and return results on a minute scale. With a multiple sensor system our approach calculates not only the noise for each sensor but also the noise correlation matrix between sensors. Here we will show how the algorithm can be implemented.

Experimental study of some shielding parameters for composite shields

NASA Astrophysics Data System (ADS)

Mkhaiber, Ahmed F.; Dheyaa, Abdulraheem

2018-05-01

In this study radiation protection shields have been prepared consist of composite materials have epoxy as a basis material and different reinforcing materials C Ni PbO and Bi with various reinforcing ratios 10 20 30 40 50 % and dimensions 1 × 10 × 10 cm. For examination the suitability of using this shields to protect from gamma ray some shielding parameters were calculated like: Linear attenuation coefficient μ, effective atomic number Zeffe, heaviness and half value thickness X1/2 for energy rang 1218 – 1480 KeV. These parameters have been measured by using sodium iodide system NaITI with deferent radiation sources 152Eu 60Co and 137Cs. The results show that these parameters are effected by the reinforcing ratio and gamma ray energy, it is found that the linear attenuation coefficient and atomic effective number increases with reinforcing ratio increases and decreased with energy increasing especially with high concentrations 40 50 % and at low energies Eγ < 0662 MeV with certain energy while the values of X1/2 decrease with reinforcing ratio increases. Heaviness was calculated too for all shields, with respect to lead from its values we found that this shields lighter than lead, which make it preferable to traditional material such as lead and concrete.

Ultra high molecular weight polyethylene (UHMWPE) fiber epoxy composite hybridized with Gadolinium and Boron nanoparticles for radiation shielding

NASA Astrophysics Data System (ADS)

Mani, Venkat; Prasad, Narasimha S.; Kelkar, Ajit

2016-09-01

Deep space radiations pose a major threat to the astronauts and their spacecraft during long duration space exploration missions. The two sources of radiation that are of concern are the galactic cosmic radiation (GCR) and the short lived secondary neutron radiations that are generated as a result of fragmentation that occurs when GCR strikes target nuclei in a spacecraft. Energy loss, during the interaction of GCR and the shielding material, increases with the charge to mass ratio of the shielding material. Hydrogen with no neutron in its nucleus has the highest charge to mass ratio and is the element which is the most effective shield against GCR. Some of the polymers because of their higher hydrogen content also serve as radiation shield materials. Ultra High Molecular Weight Polyethylene (UHMWPE) fibers, apart from possessing radiation shielding properties by the virtue of the high hydrogen content, are known for extraordinary properties. An effective radiation shielding material is the one that will offer protection from GCR and impede the secondary neutron radiations resulting from the fragmentation process. Neutrons, which result from fragmentation, do not respond to the Coulombic interaction that shield against GCR. To prevent the deleterious effects of secondary neutrons, targets such as Gadolinium are required. In this paper, the radiation shielding studies that were carried out on the fabricated sandwich panels by vacuum-assisted resin transfer molding (VARTM) process are presented. VARTM is a manufacturing process used for making large composite structures by infusing resin into base materials formed with woven fabric or fiber using vacuum pressure. Using the VARTM process, the hybridization of Epoxy/UHMWPE composites with Gadolinium nanoparticles, Boron, and Boron carbide nanoparticles in the form of sandwich panels were successfully carried out. The preliminary results from neutron radiation tests show that greater than 99% shielding performance was achieved with these sandwich panels. Moreover, the mechanical testing and thermo-physical analysis performed show that core materials can preserve their thermo-physical and mechanical integrity after radiation.

Synthesis of Actinide Materials for the Study of Basic Actinide Science and Rapid Separation of Fission Products

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

Dorhout, Jacquelyn Marie

This dissertation covers several distinct projects relating to the fields of nuclear forensics and basic actinide science. Post-detonation nuclear forensics, in particular, the study of fission products resulting from a nuclear device to determine device attributes and information, often depends on the comparison of fission products to a library of known ratios. The expansion of this library is imperative as technology advances. Rapid separation of fission products from a target material, without the need to dissolve the target, is an important technique to develop to improve the library and provide a means to develop samples and standards for testing separations.more » Several materials were studied as a proof-of-concept that fission products can be extracted from a solid target, including microparticulate (< 10 μm diameter) dUO 2, porous metal organic frameworks (MOFs) synthesized from depleted uranium (dU), and other organicbased frameworks containing dU. The targets were irradiated with fast neutrons from one of two different neutron sources, contacted with dilute acids to facilitate the separation of fission products, and analyzed via gamma spectroscopy for separation yields. The results indicate that smaller particle sizes of dUO 2 in contact with the secondary matrix KBr yield higher separation yields than particles without a secondary matrix. It was also discovered that using 0.1 M HNO 3 as a contact acid leads to the dissolution of the target material. Lower concentrations of acid were used for future experiments. In the case of the MOFs, a larger pore size in the framework leads to higher separation yields when contacted with 0.01 M HNO 3. Different types of frameworks also yield different results.« less

10 CFR Appendix F to Part 50 - Policy Relating to the Siting of Fuel Reprocessing Plants and Related Waste Management Facilities

Code of Federal Regulations, 2010 CFR

2010-01-01

... transferred to a Federal repository no later than 10 years following separation of fission products from the.... Disposal of high-level radioactive fission product waste material will not be permitted on any land other... of the policy stated above with respect to high-level radioactive fission product wastes generated...

10 CFR Appendix F to Part 50 - Policy Relating to the Siting of Fuel Reprocessing Plants and Related Waste Management Facilities

Code of Federal Regulations, 2011 CFR

2011-01-01

... transferred to a Federal repository no later than 10 years following separation of fission products from the.... Disposal of high-level radioactive fission product waste material will not be permitted on any land other... of the policy stated above with respect to high-level radioactive fission product wastes generated...

Gamma-ray mirror technology for NDA of spent fuel

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

Descalle, M. A.; Ruz-Armendariz, J.; Decker, T.

Direct measurements of gamma rays emitted by fissile material have been proposed as an alternative to measurements of the gamma rays from fission products. From a safeguards applications perspective, direct detection of uranium (U) and plutonium (Pu) K-shell fluorescence emission lines and specific lines from some of their isotopes could lead to improved shipper-receiver difference or input accountability at the start of Pu reprocessing. However, these measurements are difficult to implement when the spent fuel is in the line-of-sight of the detector, as the detector is exposed to high rates dominated by fission product emissions. To overcome the combination ofmore » high rates and high background, grazing incidence multilayer mirrors have been proposed as a solution to selectively reflect U and Pu hard X-ray and soft gamma rays in the 90 to 420 keV energy into a high-purity germanium (HPGe) detector shielded from the direct line-of-sight of spent fuel. Several groups demonstrated that K-shell fluorescence lines of U and Pu in spent fuel could be detected with Ge detectors. In the field of hard X-ray optics the performance of reflective multilayer coated reflective optics was demonstrated up to 645 keV at the European Synchrotron Radiation Facility. Initial measurements conducted at Oak Ridge National Laboratory with sealed sources and scoping experiments conducted at the ORNL Irradiated Fuels Examination Laboratory (IFEL) with spent nuclear fuel further demonstrated the pass-band properties of multilayer mirrors for reflecting specific emission lines into 1D and 2D HPGe detectors, respectively.« less

Feasibility study of 235U and 239Pu characterization in radioactive waste drums using neutron-induced fission delayed gamma rays

NASA Astrophysics Data System (ADS)

Nicol, T.; Pérot, B.; Carasco, C.; Brackx, E.; Mariani, A.; Passard, C.; Mauerhofer, E.; Collot, J.

2016-10-01

This paper reports a feasibility study of 235U and 239Pu characterization in 225 L bituminized waste drums or 200 L concrete waste drums, by detecting delayed fission gamma rays between the pulses of a deuterium-tritium neutron generator. The delayed gamma yields were first measured with bare samples of 235U and 239Pu in REGAIN, a facility dedicated to the assay of 118 L waste drums by Prompt Gamma Neutron Activation Analysis (PGNAA) at CEA Cadarache, France. Detectability in the waste drums is then assessed using the MCNPX model of MEDINA (Multi Element Detection based on Instrumental Neutron Activation), another PGNAA cell dedicated to 200 L drums at FZJ, Germany. For the bituminized waste drum, performances are severely hampered by the high gamma background due to 137Cs, which requires the use of collimator and shield to avoid electronics saturation, these elements being very penalizing for the detection of the weak delayed gamma signal. However, for lower activity concrete drums, detection limits range from 10 to 290 g of 235U or 239Pu, depending on the delayed gamma rays of interest. These detection limits have been determined by using MCNPX to calculate the delayed gamma useful signal, and by measuring the experimental gamma background in MEDINA with a 200 L concrete drum mock-up. The performances could be significantly improved by using a higher interrogating neutron emission and an optimized experimental setup, which would allow characterizing nuclear materials in a wide range of low and medium activity waste packages.

Comparison of fresh fuel experimental measurements to MCNPX calculations using self-interrogation neutron resonance densitometry

NASA Astrophysics Data System (ADS)

LaFleur, Adrienne M.; Charlton, William S.; Menlove, Howard O.; Swinhoe, Martyn T.

2012-07-01

A new non-destructive assay technique called Self-Interrogation Neutron Resonance Densitometry (SINRD) is currently being developed at Los Alamos National Laboratory (LANL) to improve existing nuclear safeguards measurements for Light Water Reactor (LWR) fuel assemblies. SINRD consists of four 235U fission chambers (FCs): bare FC, boron carbide shielded FC, Gd covered FC, and Cd covered FC. Ratios of different FCs are used to determine the amount of resonance absorption from 235U in the fuel assembly. The sensitivity of this technique is based on using the same fissile materials in the FCs as are present in the fuel because the effect of resonance absorption lines in the transmitted flux is amplified by the corresponding (n,f) reaction peaks in the fission chamber. In this work, experimental measurements were performed in air with SINRD using a reference Pressurized Water Reactor (PWR) 15×15 low enriched uranium (LEU) fresh fuel assembly at LANL. The purpose of this experiment was to assess the following capabilities of SINRD: (1) ability to measure the effective 235U enrichment of the PWR fresh LEU fuel assembly and (2) sensitivity and penetrability to the removal of fuel pins from an assembly. These measurements were compared to Monte Carlo N-Particle eXtended transport code (MCNPX) simulations to verify the accuracy of the MCNPX model of SINRD. The reproducibility of experimental measurements via MCNPX simulations is essential to validating the results and conclusions obtained from the simulations of SINRD for LWR spent fuel assemblies.

Measurements of Short-Lived Fission Isomers

NASA Astrophysics Data System (ADS)

Finch, Sean; Bhike, Megha; Howell, Calvin; Krishichayan, Fnu; Tornow, Werner

2016-09-01

Fission yields of the short lived isomers 134mTe (T1 / 2 = 162 ns) and 136mXe (T1 / 2 = 2 . 95 μs) were measured for 235U and 238U. The isomers were detected by the γ rays associated with the decay of the isomeric states using high-purity germanium detectors. Fission was induced using both monoenergetic γ rays and neutrons. At TUNL's High-Intensity Gamma-ray Source (HI γS), γ rays of 9 and 11 MeV were produced . Monoenergetic 8 MeV neutrons were produced at TUNL's tandem accelerator laboratory. Both beams were pulsed to allow for precise time-gated spectroscopy of both prompt and delayed γ rays following fission. This technique offers a non-destructive probe of special nuclear materials that is sensitive to the isotopic identity of the fissile material.

Delayed Gamma-ray Spectroscopy for Safeguards Applications

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

Mozin, Vladimir

The delayed gamma-ray assay technique utilizes an external neutron source (D-D, D-T, or electron accelerator-driven), and high-resolution gamma-ray spectrometers to perform characterization of SNM materials behind shielding and in complex configurations such as a nuclear fuel assembly. High-energy delayed gamma-rays (2.5 MeV and above) observed following the active interrogation, provide a signature for identification of specific fissionable isotopes in a mixed sample, and determine their relative content. Potential safeguards applications of this method are: 1) characterization of fresh and spent nuclear fuel assemblies in wet or dry storage; 2) analysis of uranium enrichment in shielded or non-characterized containers or inmore » the presence of a strong radioactive background and plutonium contamination; 3) characterization of bulk and waste and product streams at SNM processing plants. Extended applications can include warhead confirmation and warhead dismantlement confirmation in the arms control area, as well as SNM diagnostics for the emergency response needs. In FY16 and prior years, the project has demonstrated the delayed gamma-ray measurement technique as a robust SNM assay concept. A series of empirical and modeling studies were conducted to characterize its response sensitivity, develop analysis methodologies, and analyze applications. Extensive experimental tests involving weapons-grade Pu, HEU and depleted uranium samples were completed at the Idaho Accelerator Center and LLNL Dome facilities for various interrogation time regimes and effects of the neutron source parameters. A dedicated delayed gamma-ray response modeling technique was developed and its elements were benchmarked in representative experimental studies, including highresolution gamma-ray measurements of spent fuel at the CLAB facility in Sweden. The objective of the R&D effort in FY17 is to experimentally demonstrate the feasibility of the delayed gamma-ray interrogation of shielded SNM samples with portable neutron sources suitable for field applications.« less

Concepts and strategies for lunar base radiation protection - Prefabricated versus in-situ materials

NASA Technical Reports Server (NTRS)

Simonsen, Lisa C.; Nealy, John E.; Townsend, Lawrence W.

1992-01-01

The most recently accepted environment data are used as inputs for the Langley nucleon and heavy-ion transport codes, BRYNTRN and HZETRN, to examine the shield effectiveness of lunar regolith in comparison with commercially-used shield materials in nuclear facilities. Several of the fabricated materials categorized as neutron absorbers exhibit favorable characteristics for space radiation protection. In particular, polyethylene with additive boron is analyzed with regard to response to the predicted lunar galactic cosmic ray and solar proton flare environment during the course of a complete solar cycle. Although this effort is not intended to be a definitive trade study for specific shielding recommendations, attention is given to several factors that warrant consideration in such trade studies. For example, the transporting of bulk shield material to the lunar site as opposed to regolith-moving and processing equipment is assessed on the basis of recent scenario studies. The transporting of shield material from Earth may also be a viable alternative to the use of regolith from standpoints of cost-effectiveness, EVA time required, and risk factor.

Effect of Discontinuities and Penetrations on the Shielding Efficacy of High Temperature Superconducting Magnetic Shields

NASA Astrophysics Data System (ADS)

Hatwar, R.; Kvitkovic, J.; Herman, C.; Pamidi, S.

2015-12-01

High Temperature Superconducting (HTS) materials have been demonstrated to be suitable for applications in shielding of both DC and AC magnetic fields. Magnetic shielding is required for protecting sensitive instrumentation from external magnetic fields and for preventing the stray magnetic fields produced by high power density equipment from affecting neighbouring devices. HTS shields have high current densities at relatively high operating temperatures (40-77 K) and can be easily fabricated using commercial HTS conductor. High current densities in HTS materials allow design and fabrication of magnetic shields that are lighter and can be incorporated into the body and skin of high power density devices. HTS shields are particularly attractive for HTS devices because a single cryogenic system can be used for cooling the device and the associated shield. Typical power devices need penetrations for power and signal cabling and the penetrations create discontinuities in HTS shields. Hence it is important to assess the effect of the necessary discontinuities on the efficacy of the shields and the design modifications necessary to accommodate the penetrations.

Nuclear energy waste-space transportation and removal

NASA Technical Reports Server (NTRS)

Burns, R. E.

1975-01-01

A method for utilizing the decay heat of actinide wastes to power an electric thrust vehicle is proposed. The vehicle, launched by shuttle to earth orbit and to earth escape by a tug, obtains electrical power from the actinide waste heat by thermionic converters. The heavy gamma ray and neutron shielding which is necessary as a safety feature is removed in orbit and returned to earth for reuse. The problems associated with safety are dealt with in depth. A method for eliminating fission wastes via chemical propulsion is briefly discussed.

BUGJEFF311.BOLIB (JEFF-3.1.1) and BUGENDF70.BOLIB (ENDF/B-VII.0) - Generation Methodology and Preliminary Testing of two ENEA-Bologna Group Cross Section Libraries for LWR Shielding and Pressure Vessel Dosimetry

NASA Astrophysics Data System (ADS)

Pescarini, Massimo; Sinitsa, Valentin; Orsi, Roberto; Frisoni, Manuela

2016-02-01

Two broad-group coupled neutron/photon working cross section libraries in FIDO-ANISN format, dedicated to LWR shielding and pressure vessel dosimetry applications, were generated following the methodology recommended by the US ANSI/ANS-6.1.2-1999 (R2009) standard. These libraries, named BUGJEFF311.BOLIB and BUGENDF70.BOLIB, are respectively based on JEFF-3.1.1 and ENDF/B-VII.0 nuclear data and adopt the same broad-group energy structure (47 n + 20 γ) of the ORNL BUGLE-96 similar library. They were respectively obtained from the ENEA-Bologna VITJEFF311.BOLIB and VITENDF70.BOLIB libraries in AMPX format for nuclear fission applications through problem-dependent cross section collapsing with the ENEA-Bologna 2007 revision of the ORNL SCAMPI nuclear data processing system. Both previous libraries are based on the Bondarenko self-shielding factor method and have the same AMPX format and fine-group energy structure (199 n + 42 γ) as the ORNL VITAMIN-B6 similar library from which BUGLE-96 was obtained at ORNL. A synthesis of a preliminary validation of the cited BUGLE-type libraries, performed through 3D fixed source transport calculations with the ORNL TORT-3.2 SN code, is included. The calculations were dedicated to the PCA-Replica 12/13 and VENUS-3 engineering neutron shielding benchmark experiments, specifically conceived to test the accuracy of nuclear data and transport codes in LWR shielding and radiation damage analyses.

Optimal shielding design for minimum materials cost or mass

DOE PAGES

Woolley, Robert D.

2015-12-02

The mathematical underpinnings of cost optimal radiation shielding designs based on an extension of optimal control theory are presented, a heuristic algorithm to iteratively solve the resulting optimal design equations is suggested, and computational results for a simple test case are discussed. A typical radiation shielding design problem can have infinitely many solutions, all satisfying the problem's specified set of radiation attenuation requirements. Each such design has its own total materials cost. For a design to be optimal, no admissible change in its deployment of shielding materials can result in a lower cost. This applies in particular to very smallmore » changes, which can be restated using the calculus of variations as the Euler-Lagrange equations. Furthermore, the associated Hamiltonian function and application of Pontryagin's theorem lead to conditions for a shield to be optimal.« less

Nuclear reactor fuel element having improved heat transfer

DOEpatents

Garnier, J.E.; Begej, S.; Williford, R.E.; Christensen, J.A.

1982-03-03

A nuclear reactor fuel element having improved heat transfer between fuel material and cladding is described. The element consists of an outer cladding tube divided into an upper fuel section containing a central core of fissionable or mixed fissionable and fertile fuel material, slightly smaller in diameter than the inner surface of the cladding tube and a small lower accumulator section, the cladding tube being which is filled with a low molecular weight gas to transfer heat from fuel material to cladding during irradiation. A plurality of essentially vertical grooves in the fuel section extend downward and communicate with the accumulator section. The radial depth of the grooves is sufficient to provide a thermal gradient between the hot fuel surface and the relatively cooler cladding surface to allow thermal segregation to take place between the low molecular weight heat transfer gas and high molecular weight fission product gases produced by the fuel material during irradiation.

Multi-Detector Analysis System for Spent Nuclear Fuel Characterization

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

Reber, Edward Lawrence; Aryaeinejad, Rahmat; Cole, Jerald Donald

1999-09-01

The Spent Nuclear Fuel (SNF) Non-Destructive Analysis (NDA) program at INEEL is developing a system to characterize SNF for fissile mass, radiation source term, and fissile isotopic content. The system is based on the integration of the Fission Assay Tomography System (FATS) and the Gamma-Neutron Analysis Technique (GNAT) developed under programs supported by the DOE Office of Non-proliferation and National Security. Both FATS and GNAT were developed as separate systems to provide information on the location of special nuclear material in weapons configuration (FATS role), and to measure isotopic ratios of fissile material to determine if the material was frommore » a weapon (GNAT role). FATS is capable of not only determining the presence and location of fissile material but also the quantity of fissile material present to within 50%. GNAT determines the ratios of the fissile and fissionable material by coincidence methods that allow the two prompt (immediately) produced fission fragments to be identified. Therefore, from the combination of FATS and GNAT, MDAS is able to measure the fissile material, radiation source term, and fissile isotopics content.« less

Modeling the Production of Beta-Delayed Gamma Rays for the Detection of Special Nuclear Materials

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

Hall, J M; Pruet, J A; Brown, D A

2005-02-14

The objective of this LDRD project was to develop one or more models for the production of {beta}-delayed {gamma} rays following neutron-induced fission of a special nuclear material (SNM) and to define a standardized formatting scheme which will allow them to be incorporated into some of the modern, general-purpose Monte Carlo transport codes currently being used to simulate inspection techniques proposed for detecting fissionable material hidden in sea-going cargo containers. In this report, we will describe a Monte Carlo model for {beta}-delayed {gamma}-ray emission following the fission of SNM that can accommodate arbitrary time-dependent fission rates and photon collection histories.more » The model involves direct sampling of the independent fission yield distributions of the system, the branching ratios for decay of individual fission products and spectral distributions representing photon emission from each fission product and for each decay mode. While computationally intensive, it will be shown that this model can provide reasonably detailed estimates of the spectra that would be recorded by an arbitrary spectrometer and may prove quite useful in assessing the quality of evaluated data libraries and identifying gaps in the libraries. The accuracy of the model will be illustrated by comparing calculated and experimental spectra from the decay of short-lived fission products following the reactions {sup 235}U(n{sub th}, f) and {sup 239}Pu(n{sub th}, f). For general-purpose transport calculations, where a detailed consideration of the large number of individual {gamma}-ray transitions in a spectrum may not be necessary, it will be shown that a simple parameterization of the {gamma}-ray source function can be defined which provides high-quality average spectral distributions that should suffice for calculations describing photons being transported through thick attenuating media. Finally, a proposal for ENDF-compatible formats that describe each of the models and allow for their straightforward use in Monte Carlo codes will be presented.« less

Dynamic Test Method Based on Strong Electromagnetic Pulse for Electromagnetic Shielding Materials with Field-Induced Insulator-Conductor Phase Transition

NASA Astrophysics Data System (ADS)

Wang, Yun; Zhao, Min; Wang, Qingguo

2018-01-01

In order to measure the pulse shielding performance of materials with the characteristic of field-induced insulator-conductor phase transition when materials are used for electromagnetic shielding, a dynamic test method was proposed based on a coaxial fixture. Experiment system was built by square pulse source, coaxial cable, coaxial fixture, attenuator, and oscilloscope and insulating components. S11 parameter of the test system was obtained, which suggested that the working frequency ranges from 300 KHz to 7.36 GHz. Insulating performance is good enough to avoid discharge between conductors when material samples is exposed in the strong electromagnetic pulse field up to 831 kV/m. This method is suitable for materials with annular shape, certain thickness and the characteristic of field-induced insulator-conductor phase transition to get their shielding performances of strong electromagnetic pulse.

Investigation of ionizing radiation shielding effectiveness of decorative building materials used in Bangladeshi dwellings

NASA Astrophysics Data System (ADS)

Yesmin, Sabina; Sonker Barua, Bijoy; Uddin Khandaker, Mayeen; Tareque Chowdhury, Mohammed; Kamal, Masud; Rashid, M. A.; Miah, M. M. H.; Bradley, D. A.

2017-11-01

Following the rapid growing per capita income, a major portion of Bangladeshi dwellers is upgrading their non-brick houses by rod-cement-concrete materials and simultaneously curious to decorate the houses using luxurious marble stones. Present study was undertaken to investigate the gamma-ray attenuation co-efficient of decorative marble materials leading to their suitability as shielding of ionizing radiation. A number of commercial grades decorative marble stones were collected from home and abroad following their large-scale uses. A well-shielded HPGe γ-ray spectrometer combined with associated electronics was used to evaluate the mass attenuation coefficients of the studied materials for high energy photons. Some allied parameters such as half-value layer and radiation protection efficacy of the investigated marbles were calculated. The results showed that among the studied samples, the marble 'Carrara' imported from Italy is suitable to be used as radiation shielding material.

The research Of Multilayer Thermal Insulation With Mechanical Properties Based On Model Analysis Test

NASA Astrophysics Data System (ADS)

Lianhua, Yin

The heat shield of aircraft is made of the major thrusts structure with multilayer thermal insulation part. For protecting against thermo-radiation from larger thrusting force engine,the heat shield is installed around this engine nearby.The multilayer thermal insulation part with multilayer radiation/reflection structure is made of reflection layer and interval layer.At vacuum condition,these materials is higher heat insulation capability than other material,is applied for lots of pats on aircraft extensively.But because of these material is made of metal and nonmetal,it is impossible to receive it's mechanical properties of materials from mechanical tests.These paper describes a new measure of mechanical properties of materials in the heat shield based on model analysis test.At the requirement for the first order lateral frequency,these measure provide for the FEM analysis foundation on the optimization structure of the heat shield.

Neutron detector using sol-gel absorber

DOEpatents

Hiller, John M.; Wallace, Steven A.; Dai, Sheng

1999-01-01

An neutron detector composed of fissionable material having ions of lithium, uranium, thorium, plutonium, or neptunium, contained within a glass film fabricated using a sol-gel method combined with a particle detector is disclosed. When the glass film is bombarded with neutrons, the fissionable material emits fission particles and electrons. Prompt emitting activated elements yielding a high energy electron contained within a sol-gel glass film in combination with a particle detector is also disclosed. The emissions resulting from neutron bombardment can then be detected using standard UV and particle detection methods well known in the art, such as microchannel plates, channeltrons, and silicon avalanche photodiodes.

Ground-Based Testing of TiB2 and Al2O3/TiB2 Response to Space Environment

NASA Technical Reports Server (NTRS)

Jefferies, Sharon A.; Logan, Kathryn V.

2007-01-01

Two materials, titanium diboride and an alumina/titanium diboride composite, exhibit characteristics favorable for use in multiple space applications. These characteristics include low mass (4.52 gm/cc), high strain rate impact resistance, high temperature use (3000oC M.P.), thermal and electrical conductivity, thermal shock resistance, and high visible-range reflectivity. Additionally, the presence of boron in these materials gives them the potential to shield against neutron radiation as well as charged radiation. These materials are flying on MISSE 6 to assess material changes resulting from exposure to the space environment. This study provides a preliminary, ground-based examination of these materials' interactions with individual components of the space environment, in particular atomic oxygen (AO) and neutron radiation, in order to better predict and understand post-flight results. Individual specimens are exposed to ground state AO and surface oxidation is measured. Equivalent exposures of up to 13 months show no rapid oxidation, however evidence indicates some surface oxidation occurring. Other samples are placed near a polyethylene moderated, one Ci Am/Be neutron source to determine their shielding capability. Comparisons between exposed and shielded indium foil, which is activated by transmitted neutrons, measure each material's ability to shield neutrons. Preliminary results indicate a significant shielding benefit provided by both materials.

Input comparison of radiogenic neutron estimates for ultra-low background experiments

NASA Astrophysics Data System (ADS)

Cooley, J.; Palladino, K. J.; Qiu, H.; Selvi, M.; Scorza, S.; Zhang, C.

2018-04-01

Ultra-low-background experiments address some of the most important open questions in particle physics, cosmology and astrophysics: the nature of dark matter, whether the neutrino is its own antiparticle, and does the proton decay. These rare event searches require well-understood and minimized backgrounds. Simulations are used to understand backgrounds caused by naturally occurring radioactivity in the rock and in every piece of shielding and detector material used in these experiments. Most important are processes like spontaneous fission and (α,n) reactions in material close to the detectors that can produce neutrons. A comparison study of the (α,n) reactions between two dedicated software packages is detailed. The cross section libraries, neutron yields, and spectra from the Mei-Zhang-Hime and the SOURCES-4A codes are presented. The resultant yields and spectra are used as inputs to direct dark matter detector toy models in GEANT4, to study the impact of their differences on background estimates and fits. Although differences in neutron yield calculations up to 50% were seen, there was no systematic difference between the Mei-Hime-Zhang and SOURCES-4A results. Neutron propagation simulations smooth differences in spectral shape and yield, and both tools were found to meet the broad requirements of the low-background community.

Meeting Radiation Protection Requirements and Reducing Spacecraft Mass - A Multifunctional Materials Approach

NASA Technical Reports Server (NTRS)

Atwell, William; Koontz, Steve; Reddell, Brandon; Rojdev, Kristina; Franklin, Jennifer

2010-01-01

Both crew and radio-sensitive systems, especially electronics must be protected from the effects of the space radiation environment. One method of mitigating this radiation exposure is to use passive-shielding materials. In previous vehicle designs such as the International Space Station (ISS), materials such as aluminum and polyethylene have been used as parasitic shielding to protect crew and electronics from exposure, but these designs add mass and decrease the amount of usable volume inside the vehicle. Thus, it is of interest to understand whether structural materials can also be designed to provide the radiation shielding capability needed for crew and electronics, while still providing weight savings and increased useable volume when compared against previous vehicle shielding designs. In this paper, we present calculations and analysis using the HZETRN (deterministic) and FLUKA (Monte Carlo) codes to investigate the radiation mitigation properties of these structural shielding materials, which includes graded-Z and composite materials. This work is also a follow-on to an earlier paper, that compared computational results for three radiation transport codes, HZETRN, HETC, and FLUKA, using the Feb. 1956 solar particle event (SPE) spectrum. In the following analysis, we consider the October 1989 Ground Level Enhanced (GLE) SPE as the input source term based on the Band function fitting method. Using HZETRN and FLUKA, parametric absorbed doses at the center of a hemispherical structure on the lunar surface are calculated for various thicknesses of graded-Z layups and an all-aluminum structure. HZETRN and FLUKA calculations are compared and are in reasonable (18% to 27%) agreement. Both codes are in agreement with respect to the predicted shielding material performance trends. The results from both HZETRN and FLUKA are analyzed and the radiation protection properties and potential weight savings of various materials and materials lay-ups are compared.

FUEL ELEMENT FOR NUCLEAR REACTORS

DOEpatents

Bassett, C.H.

1961-05-01

A nuclear reactor fuel element comprising high density ceramic fissionable material enclosed in a tubular cladding of corrosion-resistant material is described. The fissionable material is in the form of segments of a tube which have cooperating tapered interfaces which produce outward radial displacement when the segments are urged axially together. A resilient means is provided within the tubular housing to constantly urge the fuel segments axially. This design maintains the fuel material in tight contacting engagement against the inner surface of the outer cladding tube to eliminate any gap therebetween which may be caused by differential thermal expansion between the fuel material and the material of the tube.

Unit mechanisms of fission gas release: Current understanding and future needs

DOE PAGES

Tonks, Michael; Andersson, David; Devanathan, Ram; ...

2018-03-01

Gaseous fission product transport and release has a large impact on fuel performance, degrading fuel and gap properties. While gaseous fission product behavior has been investigated with bulk reactor experiments and simplified analytical models, recent improvements in experimental and modeling approaches at the atomistic and mesoscales are beginning to reveal new understanding of the unit mechanisms that define fission product behavior. Here, existing research on the basic mechanisms of fission gas release during normal reactor operation are summarized and critical areas where work is needed are identified. Here, this basic understanding of the fission gas behavior mechanisms has the potentialmore » to revolutionize our ability to predict fission product behavior and to design fuels with improved performance. In addition, this work can serve as a model on how a coupled experimental and modeling approach can be applied to understand the unit mechanisms behind other critical behaviors in reactor materials.« less

Unit mechanisms of fission gas release: Current understanding and future needs

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

Tonks, Michael; Andersson, David; Devanathan, Ram

Gaseous fission product transport and release has a large impact on fuel performance, degrading fuel and gap properties. While gaseous fission product behavior has been investigated with bulk reactor experiments and simplified analytical models, recent improvements in experimental and modeling approaches at the atomistic and mesoscales are beginning to reveal new understanding of the unit mechanisms that define fission product behavior. Here, existing research on the basic mechanisms of fission gas release during normal reactor operation are summarized and critical areas where work is needed are identified. Here, this basic understanding of the fission gas behavior mechanisms has the potentialmore » to revolutionize our ability to predict fission product behavior and to design fuels with improved performance. In addition, this work can serve as a model on how a coupled experimental and modeling approach can be applied to understand the unit mechanisms behind other critical behaviors in reactor materials.« less

Unit mechanisms of fission gas release: Current understanding and future needs

NASA Astrophysics Data System (ADS)

Tonks, Michael; Andersson, David; Devanathan, Ram; Dubourg, Roland; El-Azab, Anter; Freyss, Michel; Iglesias, Fernando; Kulacsy, Katalin; Pastore, Giovanni; Phillpot, Simon R.; Welland, Michael

2018-06-01

Gaseous fission product transport and release has a large impact on fuel performance, degrading fuel and gap properties. While gaseous fission product behavior has been investigated with bulk reactor experiments and simplified analytical models, recent improvements in experimental and modeling approaches at the atomistic and mesoscales are beginning to reveal new understanding of the unit mechanisms that define fission product behavior. Here, existing research on the basic mechanisms of fission gas release during normal reactor operation are summarized and critical areas where work is needed are identified. This basic understanding of the fission gas behavior mechanisms has the potential to revolutionize our ability to predict fission product behavior and to design fuels with improved performance. In addition, this work can serve as a model on how a coupled experimental and modeling approach can be applied to understand the unit mechanisms behind other critical behaviors in reactor materials.

10 CFR 170.31 - Schedule of fees for materials licenses and other regulatory services, including inspections, and...

Code of Federal Regulations, 2014 CFR

2014-01-01

... for irradiation of materials in which the source is not removed from its shield (self-shielded units... curies of byproduct material in sealed sources for irradiation of materials in which the source is exposed for irradiation purposes. This category also includes underwater irradiators for irradiation of...

Effect of vacuum processing on outgassing within an orbiting molecular shield

NASA Technical Reports Server (NTRS)

Outlaw, R. A.

1982-01-01

The limiting hydrogen number density in an orbiting molecular shield is highly dependent on the outgassing rates from the materials of construction for the shield, experimental apparatus, and other hardware contained within the shield. Ordinary degassing temperatures used for ultrahigh vacuum studies (less than 450 C) are not sufficient to process metals so that the contribution to the number density within the shield due to outgassing is less than the theoretically attainable level (approximately 200 per cu. cm). Pure aluminum and type 347 stainless steel were studied as candidate shield materials. Measurements of their hydrogen concentration and diffusion coefficients were made, and the effects of high temperature vacuum processing (greater than 600 C) on their resulting outgassing rates was determined. The densities in a molecular shield due to the outgassing from either metal were substantially less ( 0.003) than the density due to the ambient atomic hydrogen flux at an orbital altitude of 500 km.

Portable convertible blast effects shield

DOEpatents

Pastrnak, John W.; Hollaway, Rocky; Henning, Carl D.; Deteresa, Steve; Grundler, Walter; Hagler,; Lisle B.; Kokko, Edwin; Switzer, Vernon A

2010-10-26

A rapidly deployable portable convertible blast effects shield/ballistic shield includes a set two or more telescoping cylindrical rings operably connected to each other to convert between a telescopically-collapsed configuration for storage and transport, and a telescopically-extended upright configuration forming an expanded inner volume. In a first embodiment, the upright configuration provides blast effects shielding, such as against blast pressures, shrapnel, and/or fire balls. And in a second embodiment, the upright configuration provides ballistic shielding, such as against incoming weapons fire, shrapnel, etc. Each ring has a high-strength material construction, such as a composite fiber and matrix material, capable of substantially inhibiting blast effects and impinging projectiles from passing through the shield. And the set of rings are releasably securable to each other in the telescopically-extended upright configuration, such as by click locks.

Portable convertible blast effects shield

DOEpatents

Pastrnak, John W [Livermore, CA; Hollaway, Rocky [Modesto, CA; Henning, Carl D [Livermore, CA; Deteresa, Steve [Livermore, CA; Grundler, Walter [Hayward, CA; Hagler, Lisle B [Berkeley, CA; Kokko, Edwin [Dublin, CA; Switzer, Vernon A [Livermore, CA

2007-05-22

A rapidly deployable portable convertible blast effects shield/ballistic shield includes a set two or more telescoping cylindrical rings operably connected to each other to convert between a telescopically-collapsed configuration for storage and transport, and a telescopically-extended upright configuration forming an expanded inner volume. In a first embodiment, the upright configuration provides blast effects shielding, such as against blast pressures, shrapnel, and/or fire balls. And in a second embodiment, the upright configuration provides ballistic shielding, such as against incoming weapons fire, shrapnel, etc. Each ring has a high-strength material construction, such as a composite fiber and matrix material, capable of substantially inhibiting blast effects and impinging projectiles from passing through the shield. And the set of rings are releasably securable to each other in the telescopically-extended upright configuration, such as by click locks.

Radiation Specifications for Fission Power Conversion Component Materials

NASA Technical Reports Server (NTRS)

Bowman, Cheryl L.; Shin, E. Eugene; Mireles, Omar R.; Radel, Ross F.; Qualls, A. Louis

2011-01-01

NASA has been supporting design studies and technology development that could provide power to an outpost on the moon, Mars, or an asteroid. One power-generation system that is independent of sunlight or power-storage limitations is a fission-based power plant. There is a wealth of terrestrial system heritage that can be transferred to the design and fabrication of a fission power system for space missions, but there are certain design aspects that require qualification. The radiation tolerance of the power conversion system requires scrutiny because the compact nature of a space power plant restricts the dose reduction methodologies compared to those used in terrestrial systems. An integrated research program has been conducted to establish the radiation tolerance of power conversion system-component materials. The radiation limit specifications proposed for a Fission Power System power convertor is 10 Mrad ionizing dose and 5 x 10(exp 14) neutron per square centimeter fluence for a convertor operating at 150 C. Specific component materials and their radiation tolerances are discussed. This assessment is for the power convertor hardware; electronic components are not covered here.

Instrumentation concepts and requirements for a space vacuum research facility. [molecular shield for spaceborne experiments

NASA Technical Reports Server (NTRS)

Norton, H. N.

1979-01-01

An earth-orbiting molecular shield that offers a unique opportunity for conducting physics, chemistry, and material processing experiments under a combination of environmental conditions that are not available in terrestrial laboratories is equipped with apparatus for forming a molecular beam from the freestream. Experiments are carried out using a moderate energy, high flux density, high purity atomic oxygen beam in the very low density environment within the molecular shield. As a minimum, the following instruments are required for the molecular shield: (1) a mass spectrometer; (2) a multifunction material analysis instrumentation system; and (3) optical spectrometry equipment. The design is given of a furlable molecular shield that allows deployment and retrieval of the system (including instrumentation and experiments) to be performed without contamination. Interfaces between the molecular shield system and the associated spacecraft are given. An in-flight deployment sequence is discussed that minimizes the spacecraft-induced contamination in the vicinity of the shield. Design approaches toward a precursor molecular shield system are shown.

A direct method for fabricating tongue-shielding stent.

PubMed

Wang, R R; Olmsted, L W

1995-08-01

During oral cancer radiotherapy, a tongue-shielding radiation stent guides the patient's upper and lower jaws to a repeatable position, attenuates radiation doses, and protects the tongue and structures adjacent to the irradiated field. Conventionally, a tongue-shielding radiation stent is made of heat-cured polymethyl methacrylate resin in which a low-melting Pb-Bi-Sn alloy is embedded as a shielding layer. Its use involves multiple and lengthy clinical and laboratory procedures. An improved polyvinyl siloxane-metal composite shielding system for radioprotection has recently been developed. This two-component, base and catalyst, putty material offers a shielding effect similar to that of the conventional shielding alloys. Its major advantages are that it is simple to use, requires only one clinical appointment, and affords efficient collaboration between dental and medical teams during cancer treatment. This article describes a simplified direct method of fabricating a tongue-shielding stent with the use of a new polyvinylsiloxane-metal composite in conjunction with impression putty material.

NEUTRONIC REACTOR SYSTEM

DOEpatents

Goett, J.J.

1961-01-24

A system is described which includes a neutronic reactor containing a dispersion of fissionable material in a liquid moderator as fuel and a conveyor to which a portion of the dispersion may be passed and wherein the self heat of the slurry evaporates the moderator. Means are provided for condensing the liquid moderator and returning it to the reactor and for conveying the dried fissionable material away from the reactor.

ELECTRIC DISCHARGE APPARATUS

DOEpatents

Ryan, T.M.

1962-04-01

A steel or aluminum small diameter (1/4 in.) tube-type neutron detector containing an inert atmosphere and having a coating of fissionable material on its inner circumference is described. A conducting wire, positioned along the axis of the tube by spaced insulators, is connected to a power source. The coating of fissionable material is brushed onto a nickel foil which is inserted into the tube and supported between the insulators. (AEC)

Lightweight reduced graphene oxide-Fe3O4 nanoparticle composite in the quest for an excellent electromagnetic interference shielding material.

PubMed

Singh, Ashwani Kumar; Kumar, Ajit; Haldar, Krishna Kamal; Gupta, Vinay; Singh, Kedar

2018-06-15

This work reports a detailed study of reduced graphene oxide (rGO)-Fe 3 O 4 nanoparticle composite as an excellent electromagnetic (EM) interference shielding material in GHz range. A rGO-Fe 3 O 4 nanoparticle composite was synthesized using a facile, one step, and modified solvothermal method with the reaction of FeCl 3 , ethylenediamine and graphite oxide powder in the presence of ethylene glycol. Various structural, microstructural and optical characterization tools were used to determine its synthesis and various properties. Dielectric, magnetic and EM shielding parameters were also evaluated to estimate its performance as a shielding material for EM waves. X-ray diffraction patterns have provided information about the structural and crystallographic properties of the as-synthesized material. Scanning electron microscopy micrographs revealed the information regarding the exfoliation of graphite into rGO. Well-dispersed Fe 3 O 4 nanoparticles over the surface of the graphene can easily be seen by employing transmission electron microscopy. For comparison, rGO nanosheets and Fe 3 O 4 nanoparticles have also been synthesized and characterized in a similar fashion. A plot of the dielectric and magnetic characterizations provides some useful information related to various losses and the relaxation process. Shielding effectiveness due to reflection (SE R ), shielding effectiveness due to absorption (SE A ), and total shielding effectiveness (SE T ) were also plotted against frequency over a broad range (8-12 GHz). A significant change in all parameters (SE A value from 5 dB to 35 dB for Fe 3 O 4 nanoparticles to rGO-Fe 3 O 4 nanoparticle composite) was found. An actual shielding effectiveness (SE T ) up to 55 dB was found in the rGO-Fe 3 O 4 nanoparticle composite. These graphs give glimpses of how significantly this material shows shielding effectiveness over a broad range of frequency.

Lightweight reduced graphene oxide-Fe3O4 nanoparticle composite in the quest for an excellent electromagnetic interference shielding material

NASA Astrophysics Data System (ADS)

Singh, Ashwani Kumar; Kumar, Ajit; Kamal Haldar, Krishna; Gupta, Vinay; Singh, Kedar

2018-06-01

This work reports a detailed study of reduced graphene oxide (rGO)-Fe3O4 nanoparticle composite as an excellent electromagnetic (EM) interference shielding material in GHz range. A rGO-Fe3O4 nanoparticle composite was synthesized using a facile, one step, and modified solvothermal method with the reaction of FeCl3, ethylenediamine and graphite oxide powder in the presence of ethylene glycol. Various structural, microstructural and optical characterization tools were used to determine its synthesis and various properties. Dielectric, magnetic and EM shielding parameters were also evaluated to estimate its performance as a shielding material for EM waves. X-ray diffraction patterns have provided information about the structural and crystallographic properties of the as-synthesized material. Scanning electron microscopy micrographs revealed the information regarding the exfoliation of graphite into rGO. Well-dispersed Fe3O4 nanoparticles over the surface of the graphene can easily be seen by employing transmission electron microscopy. For comparison, rGO nanosheets and Fe3O4 nanoparticles have also been synthesized and characterized in a similar fashion. A plot of the dielectric and magnetic characterizations provides some useful information related to various losses and the relaxation process. Shielding effectiveness due to reflection (SER), shielding effectiveness due to absorption (SEA), and total shielding effectiveness (SET) were also plotted against frequency over a broad range (8–12 GHz). A significant change in all parameters (SEA value from 5 dB to 35 dB for Fe3O4 nanoparticles to rGO-Fe3O4 nanoparticle composite) was found. An actual shielding effectiveness (SET) up to 55 dB was found in the rGO-Fe3O4 nanoparticle composite. These graphs give glimpses of how significantly this material shows shielding effectiveness over a broad range of frequency.

Measuring Fission Fragment Mass Distributions as a Function of Incident Neutron Energy Using the fissionTPC

NASA Astrophysics Data System (ADS)

Gearhart, Joshua; Niffte Collaboration

2017-09-01

Fission fragment mass distributions are important observables for developing next generation dynamical models of fission. Many previous measurements have utilized ionization chambers to measure fission fragment energies and emission angles which are then used for mass calculations. The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) collaboration has built a time projection chamber (fissionTPC) that is capable of measuring additional quantities such as the ionization profiles of detected particles, allowing for the association of an individual fragment's ionization profile with its mass. The fragment masses are measured using the previously established 2E method. The fissionTPC takes its data using a continuous incident neutron energy spectrum provided by the Los Alamos Neutron Science CEnter (LANSCE). Mass distribution measurements across a continuous range of neutron energies put stronger constraints on fission models than similar measurements conducted at a handful of discrete neutron energies. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Numbers DE-NA0003180 and DE-NA0002921.

Considerations Concerning the Development and Testing of In-situ Materials for Martian Exploration

NASA Technical Reports Server (NTRS)

Kim, M.-H. Y.; Heilbronn, L.; Thibeault, S. A.; Simonsen, L. C.; Wilson, J. W.; Chang, K.; Kiefer, R. L.; Maahs, H. G.

2000-01-01

Natural Martian surface materials are evaluated for their potential use as radiation shields for manned Mars missions. The modified radiation fluences behind various kinds of Martian rocks and regolith are determined by solving the Boltzmann equation using NASA Langley s HZETRN code along with the 1977 Solar Minimum galactic cosmic ray environmental model. To make structural shielding composite materials from constituents of the Mars atmosphere and from Martian regolith for Martian surface habitats, schemes for synthesizing polyimide from the Mars atmosphere and for processing Martian regolith/polyimide composites are proposed. Theoretical predictions of the shielding properties of these composites are computed to assess their shielding effectiveness. Adding high-performance polymer binders to Martian regolith to enhance structural properties enhances the shielding properties of these composites because of the added hydrogenous constituents. Laboratory testing of regolith simulant/polyimide composites is planned to validate this prediction.

On thermal stress failure of the SNAP-19A RTG heat shield

NASA Technical Reports Server (NTRS)

Pitts, W. C.; Anderson, L. A.

1974-01-01

Results of a study on thermal stress problems in an amorphous graphite heat shield that is part of the launch-abort protect system for the SNAP-19A radio-isotope thermoelectric generators (RTG) that will be used on the Viking Mars Lander are presended. The first result is from a thermal stress analysis of a full-scale RTG heat source that failed to survive a suborbital entry flight test, possibly due to thermal stress failure. It was calculated that the maximum stress in the heat shield was only 50 percent of the ultimate strength of the material. To provide information on the stress failure criterion used for this calculation, some heat shield specimens were fractured under abort entry conditions in a plasma arc facility. It was found that in regions free of stress concentrations the POCO graphite heat shield material did fracture when the local stress reached the ultimate uniaxial stress of the material.

Identifying and quantifying short-lived fission products from thermal fission of HEU using portable HPGe detectors

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

Pierson, Bruce D.; Finn, Erin C.; Friese, Judah I.

2013-03-01

Due to the emerging potential for trafficking of special nuclear material, research programs are investigating current capabilities of commercially available portable gamma ray detection systems. Presented in this paper are the results of three different portable high-purity germanium (HPGe) detectors used to identify short-lived fission products generated from thermal neutron interrogation of small samples of highly enriched uranium. Samples were irradiated at the Washington State University (WSU) Nuclear Radiation Center’s 1MW TRIGA reactor. The three portable, HPGe detectors used were the ORTEC MicroDetective, the ORTEC Detective, and the Canberra Falcon. Canberra’s GENIE-2000 software was used to analyze the spectral datamore » collected from each detector. Ultimately, these three portable detectors were able to identify a large range of fission products showing potential for material discrimination.« less

A fast-neutron detection detector based on fission material and large sensitive 4H silicon carbide Schottky diode detector

NASA Astrophysics Data System (ADS)

Liu, Linyue; Liu, Jinliang; Zhang, Jianfu; Chen, Liang; Zhang, Xianpeng; Zhang, Zhongbing; Ruan, Jinlu; Jin, Peng; Bai, Song; Ouyang, Xiaoping

2017-12-01

Silicon carbide radiation detectors are attractive in the measurement of the total numbers of pulsed fast neutrons emitted from nuclear fusion and fission devices because of high neutron-gamma discrimination and good radiation resistance. A fast-neutron detection system was developed based on a large-area 4H-SiC Schottky diode detector and a 235U fission target. Excellent pulse-height spectra of fission fragments induced by mono-energy deuterium-tritium (D-T) fusion neutrons and continuous energy fission neutrons were obtained. The detector is proven to be a good candidate for pulsed fast neutron detection in a complex radiation field.

Effectiveness of metal matrix and ceramic matrix composites as orbital debris shield materials

NASA Technical Reports Server (NTRS)

Mcgill, Preston B.; Mount, Angela R.

1992-01-01

The effectiveness of two metal matrix composites and one ceramic matrix material in defeating hypervelocity impacts at about 3.8 km/s are evaluated to determine the potential of these composites as spacecraft shield materials. The metal matrix composites investigated consist of SiC particles (70 percent by volume) in an aluminum matrix and Al2O3 particles (50 percent by volume) in an Al matrix. The ceramic composite consists of ZrB2 platelets in a ZrC matrix. Both the metal matrix and ceramic matrix composites are found to perform as well or better than 6061-T6 aluminum, which is presently used in the Whipple type bumper shield of Space Station Freedom. Test results indicate that the composites tested may have applications as micrometeoroid/orbital debris shield materials.

Experiences with a New Shielding Material

NASA Astrophysics Data System (ADS)

Bücherl, T.; Calzada, E.; Liu, S. Q.; Stöwer, W.; Kortmann, F.; Größlhuber, H.; von Gostomski, Ch. Lierse

Recent modifications of the NECTAR facility included the set-up of a new beam dump. One of its main components is based on a reusable shielding material developed at TUM. The provided base material was characterized and its advantages and limitations were investigated by simulation studies and by measurements.

Aluminum-titanium hydride-boron carbide composite provides lightweight neutron shield material

NASA Technical Reports Server (NTRS)

Poindexter, A. M.

1967-01-01

Inexpensive lightweight neutron shield material has high strength and ductility and withstands high internal heat generation rates without excessive thermal stress. This composite material combines structural and thermal properties of aluminum, neutron moderating properties of titanium hydride, and neutron absorbing characteristics of boron carbide.

Studies of ionizing radiation shielding effectiveness of silica-based commercial glasses used in Bangladeshi dwellings

NASA Astrophysics Data System (ADS)

Yasmin, Sabina; Barua, Bijoy Sonker; Khandaker, Mayeen Uddin; Chowdhury, Faruque-Uz-Zaman; Rashid, Md. Abdur; Bradley, David A.; Olatunji, Michael Adekunle; Kamal, Masud

2018-06-01

Following the rapid growing economy, the Bangladeshi dwellers are replacing their traditional (mud-, bamboo-, and wood-based) houses to modern multistoried buildings, where different types of glasses are being used as decorative as well as structural materials due to their various advantageous properties. In this study, we inquire the protective and dosimetric capability of commercial glasses for ionizing radiation. Four branded glass samples (PHP-Bangladesh, Osmania-Bangladesh, Nasir-Bangladesh, and Rider-China) of same thickness and color but different elemental weight fractions were analyzed for shielding and dosimetric properties. The chemical composition of the studied material was evaluated by EDX technique. A well-shielded HPGe γ-ray spectrometer combined with associated electronics was used to evaluate the attenuation coefficients of the studied materials for 59 keV, 661 keV, 1173 keV and 1332 keV photon energies. A number of shielding parameters- half value layer (HVL), radiation protection efficiency (RPE) and effective atomic number (Zeff) were also evaluated. The data were compared with the available literature (where applicable) to understand its shielding capability relative to the standard materials such as lead. Among the studied brands, Rider (China) shows relatively better indices to be used as ionizing radiation shielding material. The obtained, Zeff of the studied glass samples showed comparable values to the TLD-200 dosimeter, thus considered suitable for environmental radiation monitoring purposes.

Transparent thin shield for radio frequency transmit coils.

PubMed

Rivera, Debra S; Schulz, Jessica; Siegert, Thomas; Zuber, Verena; Turner, Robert

2015-02-01

To identify a shielding material compatible with optical head-motion tracking for prospective motion correction and which minimizes radio frequency (RF) radiation losses at 7 T without sacrificing line-of-sight to an imaging target. We evaluated a polyamide mesh coated with silver. The thickness of the coating was approximated from the composition ratio provided by the material vendor and validated by an estimate derived from electrical conductivity and light transmission measurements. The performance of the shield is compared to a split-copper shield in the context of a four-channel transmit-only loop array. The mesh contains less than a skin-depth of silver coating (300 MHz) and attenuates light by 15 %. Elements of the array vary less in the presence of the mesh shield as compared to the split-copper shield indicating that the array behaves more symmetrically with the mesh shield. No degradation of transmit efficiency was observed for the mesh as compared to the split-copper shield. We present a shield compatible with future integration of camera-based motion-tracking systems. Based on transmit performance and eddy-current evaluations the mesh shield is appropriate for use at 7 T.

NPR Reactor shield calculations

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

Peterson, E.G.

1961-09-27

At the request of IPD Personnel, calculations on neutron and gamma attenuation were made for the NPR shield. The calculations were made using a new shielding computer code developed for the IBM 7090. The calculations show the thermal neutron flux, total neutron dose rate, and gamma dose rate distribution through the entire shield assembly. The calculations show that the side and top primary shield design is adequate to reduce the radiation level below design tolerances. The radiation leakage through the front shield was higher than the design tolerances. Two alternate biological shield materials were studied for use on the frontmore » face. These two materials were iron serpentine concrete mixtures with densities of 245 lb/ft{sup 3} and 265 lb/ft{sup 3} (designated by I-S-245-P and I-S-265-P, respectively). Both of these concretes reduced the radiation below design tolerances. It is recommended that the present front face biological shield be changed from I-S-220-P to I-S-245-P. With this change the NPR shield is adequate according to these calculations. The calculations reported here do not include leakage through penetration in the shield.« less

Potential Use of In Situ Material Composites such as Regolith/Polyethylene for Shielding Space Radiation

NASA Technical Reports Server (NTRS)

Theriot, Corey A.; Gersey, Buddy; Bacon, Eugene; Johnson, Quincy; Zhang, Ye; Norman, Jullian; Foley, Ijette; Wilkins, Rick; Zhou, Jianren; Wu, Honglu

2010-01-01

NASA has an extensive program for studying materials and methods for the shielding of astronauts to reduce the effects of space radiation when on the surfaces of the Moon and Mars, especially in the use of in situ materials native to the destination reducing the expense of materials transport. The most studied material from the Moon is Lunar regolith and has been shown to be as efficient as aluminum for shielding purposes (1). The addition of hydrogenous materials such as polyethylene should increase shielding effectiveness and provide mechanical properties necessary of structural materials (2). The neutron radiation shielding effectiveness of polyethylene/regolith stimulant (JSC-1A) composites were studied using confluent human fibroblast cell cultures exposed to a beam of high-energy spallation neutrons at the 30deg-left beam line (ICE house) at the Los Alamos Neutron Science Center. At this angle, the radiation spectrum mimics the energy spectrum of secondary neutrons generated in the upper atmosphere and encountered when aboard spacecraft and high-altitude aircraft. Cell samples were exposed in series either directly to the neutron beam, within a habitat created using regolith composite blocks, or behind 25 g/sq cm of loose regolith bulk material. In another experiment, cells were also exposed in series directly to the neutron beam in T-25 flasks completely filled with either media or water up to a depth of 20 cm to test shielding effectiveness versus depth and investigate the possible influence of secondary particle generation. All samples were sent directly back to JSC for sub-culturing and micronucleus analysis. This presentation is of work performed in collaboration with the NASA sponsored Center for Radiation Engineering and Science for Space Exploration (CRESSE) at Prairie View A&M.

FROM THE HISTORY OF PHYSICS: The nuclear shield in the 'thirty-year war' of physicists against ignorant criticism of modern physical theories

NASA Astrophysics Data System (ADS)

Vizgin, Vladimir P.

1999-12-01

This article deals with the almost 'thirty-year war' led by physicists against the authorities' incompetent philosophical and ideological interference with science. The 'war' is shown to have been related to the history of Soviet nuclear weapons. Theoretical milestones of 20th century physics, to wit, theory of relativity and quantum mechanics, suffered endless 'attacks on philosophical grounds'. The theories were proclaimed idealistic as well as unduly abstract and out of touch with practice; their authors and followers were labelled 'physical idealists', and later, in the 1940s and 1950s, even 'cosmopolitans without kith or kin'. Meanwhile, quantum and relativistic theories, as is widely known, had become the basis of nuclear physics and of the means of studying the atomic nucleus (charged particle accelerators, for instance). The two theories thus served, to a great extent, as a basis for both peaceful and military uses of nuclear energy, made possible by the discovery of uranium nuclear fission under the action of neutrons. In the first part, the article recounts how prominent physicists led the way to resisting philosophical and ideological pressure and standing up for relativity, quantum theories and nuclear physics, thus enabling the launch of the atomic project. The second part contains extensive material proving the point that physicists effectively used the 'nuclear shield' in the 1940s and 1950s against the 'philosophical-cosmopolitan' pressure, indeed saving physics from a tragic fate as that of biology at the Academy of Agricultural Sciences (VASKhNIL) session in 1948.

The properties of neutron shielding and flame retardant of EVA polymer after modified by EB accelerator

NASA Astrophysics Data System (ADS)

Wang, Guo-hui; He, Man-li; Jiang, Dan-feng; He, Fan; Chang, Shu-quan; Dai, Yao-dong

2017-11-01

According to the requirements for neutron shielding and flame retardant properties of some nuclear devices, a new kind of polymer composite materials based on ethylene and vinyl acetate (EVA) polymer have been studied. EVA is the copolymer of ethylene and vinyl acetate, It can be used as materials for applications due to its flexibility, good processability, and low cost. Insulating EVA can be used for cable sheath, automotive sound damping and many other appication. Boron nitride (BN), zinc borate (ZB), magnesium hydroxide (MH) and EVA consisted the compounds with the properties of neutron shielding and flame retardant. With increasing of the contents of BN and ZB, the neutron shielding performance of materials increased up to 33.08%. With the increasing contents of MH and ZB as flame retardant, oxygen index of material have been improved. The elongation at break and tensile strength of material decreased with the increasing of filler powders. Sheet E was chosen and modified by electron beam accelerator in different doses. After modification by electron beam irradiation the sheets showed varying degrees of transformation in the OI, neutron shielding rate and mechanical properties.

Electromagnetic shielding of thermal protection system for hypersonic vehicles

NASA Astrophysics Data System (ADS)

Albano, M.; Micheli, D.; Gradoni, G.; Morles, R. B.; Marchetti, M.; Moglie, F.; Mariani Primiani, V.

2013-06-01

The numerical simulation and the measurement of electromagnetic shielding at microwave frequencies of thermal protection system for hypersonic vehicles is presented using nested reverberation chamber. An example of a possible thermal protection system for a re-entry vehicle is presented. This system based on carbon material is electromagnetically characterized. The characterization takes into account not only the materials but also the final assembly configuration of the thermal protection system. The frequency range is 2-8 GHz. The results of measurements and simulations show that the microwave shielding effectiveness of carbon materials is above 60 dB for a single tile and that the tile inter-distance is able to downgrade the shielding effectiveness on the average to about 40 dB.

Post-Flight Evaluation of PICA and PICA-X - Comparisons of the Stardust SRC and Space-X Dragon 1 Forebody Heatshield Materials

NASA Technical Reports Server (NTRS)

Stackpoole, M.; Kao, D.; Qu, V.; Gonzales, G.

2013-01-01

Phenolic Impregnated Carbon Ablator (PICA) was developed at NASA Ames Research Center. As a thermal protection material, PICA has the advantages of being able to withstand high heat fluxes with a relatively low density. This ablative material was used as the forebody heat shield material for the Stardust sample return capsule, which re-entered the Earths atmosphere in 2006. Based on PICA, SpaceX developed a variant, PICA-X, and used it as the heat shield material for its Dragon spacecraft, which successfully orbited the Earth and re-entered the atmosphere during the COTS Demo Flight 1 in 2010. Post-flight analysis was previously performed on the Stardust PICA heat shield material. Similarly, a near-stagnation core was obtained from the post-flight Dragon 1 heat shield, which was retrieved from the Pacific Ocean. Materials testing and analyses were performed on the core to evaluate its ablation performance and post-flight properties. Comparisons between PICA and PICA-X are made where applicable. Stardust and Dragon offer rare opportunities to evaluate materials post-flight - this data is beneficial in understanding material performance and also improves modeling capabilities.

7 CFR 1755.406 - Shield or armor ground resistance measurements.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 11 2010-01-01 2010-01-01 false Shield or armor ground resistance measurements. 1755... MATERIALS, AND STANDARD CONTRACT FORMS § 1755.406 Shield or armor ground resistance measurements. (a) Shield or armor ground resistance measurements shall be made on completed lengths of copper cable and wire...

7 CFR 1755.406 - Shield or armor ground resistance measurements.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 11 2011-01-01 2011-01-01 false Shield or armor ground resistance measurements. 1755... MATERIALS, AND STANDARD CONTRACT FORMS § 1755.406 Shield or armor ground resistance measurements. (a) Shield or armor ground resistance measurements shall be made on completed lengths of copper cable and wire...

Reduction of metal artifact in three-dimensional computed tomography (3D CT) with dental impression materials.

PubMed

Park, W S; Kim, K D; Shin, H K; Lee, S H

2007-01-01

Metal Artifact still remains one of the main drawbacks in craniofacial Three-Dimensional Computed Tomography (3D CT). In this study, we tried to test the efficacy of additional silicone dental impression materials as a "tooth shield" for the reduction of metal artifact caused by metal restorations and orthodontic appliances. 6 phantoms with 4 teeth were prepared for this in vitro study. Orthodontic bracket, bands and amalgam restorations were placed in each tooth to reproduce various intraoral conditions. Standardized silicone shields were fabricated and placed around the teeth. CT image acquisition was performed with and without silicone shields. Maximum value, mean, and standard deviation of Hounsfield Units (HU) were compared with the presence of silicone shields. In every situation, metal artifacts were reduced in quality and quantity when silicone shields are used. Amalgam restoration made most serious metal artifact. Silicone shields made by dental impression material might be effective way to reduce the metal artifact caused by dental restoration and orthodontic appliances. This will help more excellent 3D image from 3D CT in craniofacial area.

Shield Optimization in Simple Geometry for the Gateway Concept

NASA Technical Reports Server (NTRS)

Tripathi, R. K.; Simonsen, L. C.; Nealy, J. E.; Troutman, P. A.; Wilson, J. W.

2002-01-01

The great cost of added radiation shielding is a potential limiting factor in many deep space missions. For this enabling technology, we are developing tools for optimized shield design over multi-segmented missions involving multiple work and living areas in the transport and duty phase of various space missions. The total shield mass over all pieces of equipment and habitats is optimized subject to career dose and dose rate constraints. Preliminary studies of deep space missions indicate that for long duration space missions, improved shield materials will be required. The details of this new method and its impact on space missions and other technologies will be discussed. This study will provide a vital tool for evaluating Gateway designs in their usage context. Providing protection against the hazards of space radiation is one of the challenges to the Gateway infrastructure designs. We will use the mission optimization software to scope the impact of Gateway operations on human exposures and the effectiveness of alternate shielding materials on Gateway infrastructure designs. This study will provide a guide to the effectiveness of multifunctional materials in preparation to more detailed geometry studies in progress.

Analysis of Muon Induced Neutrons in Detecting High Z Nuclear Materials

DTIC Science & Technology

2015-03-01

mass distributions, delayed fission probabilities, and prompt to delayed fission ratios [16]. 10 2.3 Muon Catalyzed Fusion Fusion occurs when two light ...proton number; A is the atomic mass; ⇢ is the material density; = v/c where v is the velocity of the particle and c is the speed of light ; is the...8217) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 81 % Combine all neutron events time stamps into one vector %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% timeindex of

Radiation protection effectiveness of a proposed magnetic shielding concept for manned Mars missions

NASA Technical Reports Server (NTRS)

Townsend, Lawrence W.; Wilson, John W.; Shinn, J. L.; Nealy, John E.; Simonsen, Lisa C.

1990-01-01

The effectiveness of a proposed concept for shielding a manned Mars vehicle using a confined magnetic field configuration is evaluated by computing estimated crew radiation exposures resulting from galactic cosmic rays and a large solar flare event. In the study the incident radiation spectra are transported through the spacecraft structure/magnetic shield using the deterministic space radiation transport computer codes developed at Langley Research Center. The calculated exposures unequivocally demonstrate that magnetic shielding could provide an effective barrier against solar flare protons but is virtually transparent to the more energetic galactic cosmic rays. It is then demonstrated that through proper selection of materials and shield configuration, adequate and reliable bulk material shielding can be provided for the same total mass as needed to generate and support the more risky magnetic field configuration.

A Basic LEGO Reactor Design for the Provision of Lunar Surface Power

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

John Darrell Bess

2008-06-01

A final design has been established for a basic Lunar Evolutionary Growth-Optimized (LEGO) Reactor using current and near-term technologies. The LEGO Reactor is a modular, fast-fission, heatpipe-cooled, clustered-reactor system for lunar-surface power generation. The reactor is divided into subcritical units that can be safely launched with lunar shipments from Earth, and then emplaced directly into holes drilled into the lunar regolith to form a critical reactor assembly. The regolith would not just provide radiation shielding, but serve as neutron-reflector material as well. The reactor subunits are to be manufactured using proven and tested materials for use in radiation environments, suchmore » as uranium-dioxide fuel, stainless-steel cladding and structural support, and liquid-sodium heatpipes. The LEGO Reactor system promotes reliability, safety, and ease of manufacture and testing at the cost of an increase in launch mass per overall rated power level and a reduction in neutron economy when compared to a single-reactor system. A single unshielded LEGO Reactor subunit has an estimated mass of approximately 448 kg and provides approximately 5 kWe. The overall envelope for a single subunit with fully extended radiator panels has a height of 8.77 m and a diameter of 0.50 m. Six subunits could provide sufficient power generation throughout the initial stages of establishing a lunar outpost. Portions of the reactor may be neutronically decoupled to allow for reduced power production during unmanned periods of base operations. During later stages of lunar-base development, additional subunits may be emplaced and coupled into the existing LEGO Reactor network, subject to lunar base power demand. Improvements in reactor control methods, fuel form and matrix, shielding, as well as power conversion and heat rejection techniques can help generate an even more competitive LEGO Reactor design. Further modifications in the design could provide power generative opportunities for use on other extraterrestrial surfaces.« less

300 million years of basin evolution - the thermotectonic history of the Ukrainian Donbas Foldbelt

NASA Astrophysics Data System (ADS)

Spiegel, C.; Danisik, M.; Sachsenhofer, R.; Frisch, W.; Privalov, V.

2009-04-01

The Ukrainian-Russian Pripyat-Dniepr-Donets Basin is a large intracratonic rift structure formed during the Late Devonian. It is situated at the southern margin of the Precambrian East European Craton, adjacent to the Hercynian Tethyan belt in the Black Sea area and the Alpine Caucasus orogen. With a sediment thickness of more than 20 km, it is one of the deepest sedimentary basins on earth. The eastern part of the Pripyat-Dniepr-Donets Basin - called Donbas foldbelt - is strongly folded and inverted. Proposed models of basin evolution are often controversial and numerous issues are still a matter of speculation, particularly the erosion history and the timing of basin inversion. Basin inversion may have taken place during the Permian related to the Uralian orogeny, or in response to Alpine tectonics during the Late Cretaceous to Early Tertiary. We investigated the low-temperature thermal history of the Donbas Foldbelt and the adjacent Ukrainian shield by a combination of zircon fission track, apatite fission track and apatite (U-Th)/He thermochronology. Although apatite fission track ages of all sedimentary samples were reset shortly after deposition during the Carboniferous, we took advantage of the fact that samples contained kinetically variable apatites, which are sensitive to different temperatures. By using statistic-based component analysis incorporating physical properties of individual grains we identified several distinct age population, ranging from late Permian (~265 Ma) to the Late Cretaceous (70 Ma). We could thus constrain the thermal history of the Donbas Foldbelt and the adjacent basement during a ~300 Myr long time period. The Precambrian crystalline basement of the Ukrainian shield was affected by a Permo-Triassic thermal event associated with magmatic activity, which also strongly heated the sediments of the Donbas Foldbelt. The basement rocks cooled to near-surface conditions during the Early to Middle Triassic and since then was thermally stable. The basin margins started to cool during the Permo-Triassic whereas the central parts were residing or slowly cooling through the apatite partial annealing zone during the Jurassic and most of the Cretaceous and eventually cooled to near-surface conditions around the Cretaceous-Paleogene boundary. Our data show that Permian erosion was lower and Mesozoic erosion larger than generally assumed. Inversion and pop-up of the Donbas Foldbelt occurred in the Cretaceous and not in the Permian as previously thought. This is indicated by overall Cretaceous apatite fission track ages in the central parts of the basin.

A fission gas release correlation for uranium nitride fuel pins

NASA Technical Reports Server (NTRS)

Weinstein, M. B.; Davison, H. W.

1973-01-01

A model was developed to predict fission gas releases from UN fuel pins clad with various materials. The model was correlated with total release data obtained by different experimentors, over a range of fuel temperatures primarily between 1250 and 1660 K, and fuel burnups up to 4.6 percent. In the model, fission gas is transported by diffusion mechanisms to the grain boundaries where the volume grows and eventually interconnects with the outside surface of the fuel. The within grain diffusion coefficients are found from fission gas release rate data obtained using a sweep gas facility.

Fission-fragment detector for DANCE based on thin scintillating films

NASA Astrophysics Data System (ADS)

Rusev, G.; Roman, A. R.; Daum, J. K.; Springs, R. K.; Bond, E. M.; Jandel, M.; Baramsai, B.; Bredeweg, T. A.; Couture, A.; Favalli, A.; Ianakiev, K. D.; Iliev, M. L.; Mosby, S.; Ullmann, J. L.; Walker, C. L.

2015-12-01

A fission-fragment detector based on thin scintillating films has been built to serve as a trigger/veto detector in neutron-induced fission measurements at DANCE. The fissile material is surrounded by scintillating films providing 4 π detection of the fission fragments. The scintillation photons were registered with silicon photomultipliers. A measurement of the 235U (n , f) reaction with this detector at DANCE revealed a correct time-of-flight spectrum and provided an estimate for the efficiency of the prototype detector of 11.6(7)%. Design and test measurements with the detector are described.

Optimization Shield Materials Trade Study for Lunar/Gateway Mission

NASA Technical Reports Server (NTRS)

Tripathi, R. K.; Wilson, J. W.; Cucinotta, F. A.; Anderson, B. M.; Simonsen, L. C.

2002-01-01

The great cost of added radiation shielding is a potential limiting factor in many deep space missions. For this enabling technology, we are developing tools for optimized shield design over multi-segmented missions involving multiple work and living areas in the transport and duty phase of various space missions. The total shield mass over all pieces of equipment and habitats is optimized subject to career dose and dose rate constraints. Preliminary studies of deep space missions indicate that for long duration space missions, improved shield materials will be required. The details of this new method and its impact on space missions and other technologies will be discussed. This study will provide a vital tool for evaluating Gateway designs in their usage context. Providing protection against the hazards of space radiation is one of the challenges to the Gateway infrastructure designs. We will use the mission optimization software to scope the impact of Gateway operations on human exposures and the effectiveness of alternate shielding materials on Gateway infrastructure designs. It is being proposed to use Moon and the Lagrange points as the hub for deep space missions. This study will provide a guide to the effectiveness of multifunctional materials in preparation to more detailed geometry studies in progress.

Reusable shielding material for neutron- and gamma-radiation

NASA Astrophysics Data System (ADS)

Calzada, Elbio; Grünauer, Florian; Schillinger, Burkhard; Türck, Harald

2011-09-01

At neutron research facilities all around the world radiation shieldings are applied to reduce the background of neutron and gamma radiation as far as possible in order to perform high quality measurements and to fulfill the radiation protection requirements. The current approach with cement-based compounds has a number of shortcomings: "Heavy concrete" contains a high amount of elements, which are not desired to obtain a high attenuation of neutron and/or gamma radiation (e.g. calcium, carbon, oxygen, silicon and aluminum). A shielding material with a high density of desired nuclei such as iron, hydrogen and boron was developed for the redesign of the neutron radiography facility ANTARES at beam tube 4 (located at a cold neutron source) of FRM-II. The composition of the material was optimized by help of the Monte Carlo code MCNP5. With this shielding material a considerable higher attenuation of background radiation can be obtained compared to usual heavy concretes.

Nuclear Fuel Reprocessing: U.S. Policy Development

DTIC Science & Technology

2006-11-29

to the chemical separation of fissionable uranium and plutonium from irradiated nuclear fuel. The World War II-era Manhattan Project developed...created the Atomic Energy Commission (AEC) and transferred production and control of fissionable materials from the Manhattan Project . As the exclusive

Depletion optimization of lumped burnable poisons in pressurized water reactors

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

Kodah, Z.H.

1982-01-01

Techniques were developed to construct a set of basic poison depletion curves which deplete in a monotonical manner. These curves were combined to match a required optimized depletion profile by utilizing either linear or non-linear programming methods. Three computer codes, LEOPARD, XSDRN, and EXTERMINATOR-2 were used in the analyses. A depletion routine was developed and incorporated into the XSDRN code to allow the depletion of fuel, fission products, and burnable poisons. The Three Mile Island Unit-1 reactor core was used in this work as a typical PWR core. Two fundamental burnable poison rod designs were studied. They are a solidmore » cylindrical poison rod and an annular cylindrical poison rod with water filling the central region.These two designs have either a uniform mixture of burnable poisons or lumped spheroids of burnable poisons in the poison region. Boron and gadolinium are the two burnable poisons which were investigated in this project. Thermal self-shielding factor calculations for solid and annular poison rods were conducted. Also expressions for overall thermal self-shielding factors for one or more than one size group of poison spheroids inside solid and annular poison rods were derived and studied. Poison spheroids deplete at a slower rate than the poison mixture because each spheroid exhibits some self-shielding effects of its own. The larger the spheroid, the higher the self-shielding effects due to the increase in poison concentration.« less

Experimental demonstration of radiation effects on the performance of a stirling-alternator convertor and candidate materials evaluation

NASA Astrophysics Data System (ADS)

Mireles, Omar R.

Free-piston Stirling power convertors are under consideration by NASA for service in the Advanced Stirling Radioisotope Generator (ASRG) and Fission Surface Power (FSP) systems to enable aggressive exploration missions by providing a reliable and constant power supply. The ASRG must withstand environmental radiation conditions, while the FSP system must tolerate a mixed neutron and gamma-ray environment resulting from self-irradiation. Stirling-alternators utilize rare earth magnets and a variety of organic materials whose radiation limits dominate service life estimates and shielding requirements. The project objective was to demonstrate the performance of the alternator, identify materials that exhibit excessive radiation sensitivity, identify radiation tolerant substitutes, establish empirical dose limits, and demonstrate the feasibility of cost effective nuclear and radiation tests by selection of the appropriate personnel and test facilities as a function of hardware maturity. The Stirling Alternator Radiation Test Article (SARTA) was constructed from linear alternator components of a Stirling convertor and underwent significant pre-exposure characterization. The SARTA was operated at the Sandia National Laboratories Gamma Irradiation Facility to a dose of over 40 Mrad. Operating performance was within nominal variation, although modestly decreasing trends occurred in later runs as well as the detection of an electrical fault after the final exposure. Post-irradiation disassembly and internal inspection revealed minimal degradation of the majority of the organic components. Radiation testing of organic material coupons was conducted since the majority of the literature was inconsistent. These inconsistencies can be attributed to testing at environmental conditions vastly different than those Stirling-alternator organics will experience during operation. Samples were irradiated at the Texas A&M TRIGA reactor to above expected FSP neutron fluence. A thorough materials evaluation followed and results indicate that the majority of material properties experienced minimal statistically significant change.

Effect of molybdenum on gamma ray shielding and structural properties of PbO-B2O3 glasses

NASA Astrophysics Data System (ADS)

Dogra, Mridula; Singh, K. J.; Kaur, Kulwinder

2018-04-01

The present study is aimed at developing new shielding materials for gamma ray shielding applications. Transparent glasses of the composition xMoO3-0.7PbO-(0.3-x)B2O3 where x= 0.03 to 0. 06 (mole fraction) have been prepared by using melt-quenchingtechnique. Gamma ray shielding properties have been evaluated in terms of mass attenuation coefficient and half value layer parameter at photon energies 662 and 1173 keV. These shielding parameters are also compared with standard shielding material`concretes'. It has been found that prepared glass system shows better shielding properties than barite and ordinary concretes proving the possibility of its usage as an alternate to conventional concrete for gamma ray shielding applications. The density, molar volume, X-Ray Diffraction, Fourier Transform InfraRed and Raman studies have been performed to study the structural properties of the glass system. It has been analyzed from FTIR and Raman studies that bridging oxygens increase with the decrease of MoO3 content in the glass composition.

First-Principles Quantum Dynamics of Singlet Fission: Coherent versus Thermally Activated Mechanisms Governed by Molecular π Stacking

NASA Astrophysics Data System (ADS)

Tamura, Hiroyuki; Huix-Rotllant, Miquel; Burghardt, Irene; Olivier, Yoann; Beljonne, David

2015-09-01

Singlet excitons in π -stacked molecular crystals can split into two triplet excitons in a process called singlet fission that opens a route to carrier multiplication in photovoltaics. To resolve controversies about the mechanism of singlet fission, we have developed a first principles nonadiabatic quantum dynamical model that reveals the critical role of molecular stacking symmetry and provides a unified picture of coherent versus thermally activated singlet fission mechanisms in different acenes. The slip-stacked equilibrium packing structure of pentacene derivatives is found to enhance ultrafast singlet fission mediated by a coherent superexchange mechanism via higher-lying charge transfer states. By contrast, the electronic couplings for singlet fission strictly vanish at the C2 h symmetric equilibrium π stacking of rubrene. In this case, singlet fission is driven by excitations of symmetry-breaking intermolecular vibrations, rationalizing the experimentally observed temperature dependence. Design rules for optimal singlet fission materials therefore need to account for the interplay of molecular π -stacking symmetry and phonon-induced coherent or thermally activated mechanisms.

Endothermic singlet fission is hindered by excimer formation

NASA Astrophysics Data System (ADS)

Dover, Cameron B.; Gallaher, Joseph K.; Frazer, Laszlo; Tapping, Patrick C.; Petty, Anthony J.; Crossley, Maxwell J.; Anthony, John E.; Kee, Tak W.; Schmidt, Timothy W.

2018-03-01

Singlet fission is a process whereby two triplet excitons can be produced from one photon, potentially increasing the efficiency of photovoltaic devices. Endothermic singlet fission is desired for a maximum energy-conversion efficiency, and such systems have been considered to form an excimer-like state with multiexcitonic character prior to the appearance of triplets. However, the role of the excimer as an intermediate has, until now, been unclear. Here we show, using 5,12-bis((triisopropylsilyl)ethynyl)tetracene in solution as a prototypical example, that, rather than acting as an intermediate, the excimer serves to trap excited states to the detriment of singlet-fission yield. We clearly demonstrate that singlet fission and its conjugate process, triplet-triplet annihilation, occur at a longer intermolecular distance than an excimer intermediate would impute. These results establish that an endothermic singlet-fission material must be designed to avoid excimer formation, thus allowing singlet fission to reach its full potential in enhancing photovoltaic energy conversion.

Endothermic singlet fission is hindered by excimer formation.

PubMed

Dover, Cameron B; Gallaher, Joseph K; Frazer, Laszlo; Tapping, Patrick C; Petty, Anthony J; Crossley, Maxwell J; Anthony, John E; Kee, Tak W; Schmidt, Timothy W

2018-03-01

Singlet fission is a process whereby two triplet excitons can be produced from one photon, potentially increasing the efficiency of photovoltaic devices. Endothermic singlet fission is desired for a maximum energy-conversion efficiency, and such systems have been considered to form an excimer-like state with multiexcitonic character prior to the appearance of triplets. However, the role of the excimer as an intermediate has, until now, been unclear. Here we show, using 5,12-bis((triisopropylsilyl)ethynyl)tetracene in solution as a prototypical example, that, rather than acting as an intermediate, the excimer serves to trap excited states to the detriment of singlet-fission yield. We clearly demonstrate that singlet fission and its conjugate process, triplet-triplet annihilation, occur at a longer intermolecular distance than an excimer intermediate would impute. These results establish that an endothermic singlet-fission material must be designed to avoid excimer formation, thus allowing singlet fission to reach its full potential in enhancing photovoltaic energy conversion.

Dependences of microstructure on electromagnetic interference shielding properties of nano-layered Ti3AlC2 ceramics.

PubMed

Tan, Yongqiang; Luo, Heng; Zhou, Xiaosong; Peng, Shuming; Zhang, Haibin

2018-05-21

The microstructure dependent electromagnetic interference (EMI) shielding properties of nano-layered Ti 3 AlC 2 ceramics were presented in this study by comparing the shielding properties of various Ti 3 AlC 2 ceramics with distinct microstructures. Results indicate that Ti 3 AlC 2 ceramics with dense microstructure and coarse grains are more favourable for superior EMI shielding efficiency. High EMI shielding effectiveness over 40 dB at the whole Ku-band frequency range was achieved in Ti 3 AlC 2 ceramics by microstructure optimization, and the high shielding effectiveness were well maintained up to 600 °C. A further investigation reveals that only the absorption loss displays variations upon modifying microstructure by allowing more extensive multiple reflections in coarse layered grains. Moreover, the absorption loss of Ti 3 AlC 2 was found to be much higher than those of highly conductive TiC ceramics without layered structure. These results demonstrate that nano-layered MAX phase ceramics are promising candidates of high-temperature structural EMI shielding materials and provide insightful suggestions for achieving high EMI shielding efficiency in other ceramic-based shielding materials.

Rigid open-cell polyurethane foam for cryogenic insulation

NASA Technical Reports Server (NTRS)

Faddoul, J. R.; Lindquist, C. R.; Niendorf, L. R.; Nies, G. E.; Perkins, P. J., Jr.

1971-01-01

Lightweight polyurethane foam assembled in panels is effective spacer material for construction of self-evacuating multilayer insulation panels for cryogenic liquid tanks. Spacer material separates radiation shields with barrier that minimizes conductive and convective heat transfer between shields.

Coincident measurements of prompt fission γ rays and fission fragments at DANCE

NASA Astrophysics Data System (ADS)

Walker, C. L.; Baramsai, B.; Jandel, M.; Rusev, G.; Couture, A.; Mosby, S.; Ullmann, J.; Kawano, T.; Stetcu, I.; Talou, P.

2015-10-01

Modern statistical approaches to modeling fission involve the calculation of not only average quantities but also fully correlated distributions of all fission products. Applications such as those involving the detection of special nuclear materials also rely on fully correlated data of fission products. Experimental measurements of correlated data are thus critical to the validation of theory and the development of important applications. The goal of this experiment was to measure properties of prompt fission gamma-ray emission as a function of fission fragments' total kinetic energy in the spontaneous fission of 252Cf. The measurement was carried out at the Detector for Advanced Neutron Capture Experiments (DANCE), a 4 π γ-ray calorimeter. A prototype design consisting of two silicon detectors was installed in the center of DANCE, allowing simultaneous measurement of fission fragments and γ rays. Effort has been taken to simulate fragment kinetic energy losses as well as γ-ray attenuation in DANCE using such tools as GEANT4 and SRIM. Theoretical predictions generated by the code CGMF were also incorporated as input for these simulations. Results from the experiment and simulations will be presented, along with plans for future measurements.

Evaluation Of Shielding Efficacy Of A Ferrite Containing Ceramic Material

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

Verst, C.

2015-10-12

The shielding evaluation of the ferrite based Mitsuishi ceramic material has produced for several radiation sources and possible shielding sizes comparative dose attenuation measurements and simulated projections. High resolution gamma spectroscopy provided uncollided and scattered photon spectra at three energies, confirming theoretical estimates of the ceramic’s mass attenuation coefficient, μ/ρ. High level irradiation experiments were performed using Co-60, Cs-137, and Cf-252 sources to measure penetrating dose rates through steel, lead, concrete, and the provided ceramic slabs. The results were used to validate the radiation transport code MCNP6 which was then used to generate dose rate attenuation curves as a functionmore » of shielding material, thickness, and mass for photons and neutrons ranging in energy from 200 keV to 2 MeV.« less

Investigation of the Feasibility of Utilizing Gamma Emission Computed Tomography in Evaluating Fission Product Migration in Irradiated TRISO Fuel Experiments

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

Jason M. Harp; Paul A. Demkowicz

2014-10-01

In the High Temperature Gas-Cooled Reactor (HTGR) the TRISO particle fuel serves as the primary fission product containment. However the large number of TRISO particles present in proposed HTGRs dictates that there will be a small fraction (~10 -4 to 10 -5) of as manufactured and in-pile particle failures that will lead to some fission product release. The matrix material surrounding the TRISO particles in fuel compacts and the structural graphite holding the TRISO particles in place can also serve as sinks for containing any released fission products. However data on the migration of solid fission products through these materialsmore » is lacking. One of the primary goals of the AGR-3/4 experiment is to study fission product migration from failed TRISO particles in prototypic HTGR components such as structural graphite and compact matrix material. In this work, the potential for a Gamma Emission Computed Tomography (GECT) technique to non-destructively examine the fission product distribution in AGR-3/4 components and other irradiation experiments is explored. Specifically, the feasibility of using the Idaho National Laboratory (INL) Hot Fuels Examination Facility (HFEF) Precision Gamma Scanner (PGS) system for this GECT application is considered. To test the feasibility, the response of the PGS system to idealized fission product distributions has been simulated using Monte Carlo radiation transport simulations. Previous work that applied similar techniques during the AGR-1 experiment will also be discussed as well as planned uses for the GECT technique during the post irradiation examination of the AGR-2 experiment. The GECT technique has also been applied to other irradiated nuclear fuel systems that were currently available in the HFEF hot cell including oxide fuel pins, metallic fuel pins, and monolithic plate fuel.« less

Rotating shielded crane system

DOEpatents

Commander, John C.

1988-01-01

A rotating, radiation shielded crane system for use in a high radiation test cell, comprises a radiation shielding wall, a cylindrical ceiling made of radiation shielding material and a rotatable crane disposed above the ceiling. The ceiling rests on an annular ledge intergrally attached to the inner surface of the shielding wall. Removable plugs in the ceiling provide access for the crane from the top of the ceiling into the test cell. A seal is provided at the interface between the inner surface of the shielding wall and the ceiling.

Experimental Testing of Corpuscular Radiation Detectors. Volume 1. Revision 1

DTIC Science & Technology

1989-09-07

several layers of Sflexible Permag metglass); (c) 1/4" lead shield, against X-rays; (d) Cadmium/boron/lead shield against 14 MeV neutrons. I * I In...balance. Tn Figure 2.3 (d) the shielding of the torsion balance has been complemented with a PERMAG metglass magnetic shield. This is how the sensor looks...dB. The torsion balance was shielded by several layers of PERMAG U high-mu flexible Metglass material. in these two integrations, no lead shield was

SU-F-E-13: Design and Fabrication of Gynacological Brachytherapy Shielding & Non Shielding Applicators Using Indigenously Developed 3D Printing Machine

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

Shanmugam, S

Purpose: In this innovative work we have developed Gynecological Brachytherapy shielding & Non Shielding Applicators and compared with the commercially available applicators by using the indigenously developed 3D Printing machine. Methods: We have successfully indigenously developed the 3D printing machine. Which contain the 3 dimensional motion platform, Heater unit, base plate, ect… To fabricate the Gynecological Brachytherapy shielding & non shielding applicators the 3D design were developed in the computer as virtual design. This virtual design is made in a CAD computer file using a 3D modeling program. Separate programme for the shielding & non shielding applicators. We have alsomore » provided the extra catheter insert provision in the applicator for the multiple catheter. The DICOM file of the applicator were then converted to stereo Lithography file for the 3D printer. The shielding & Non Shielding Applicators were printed on a indigenously developed 3D printer material. The same dimensions were used to develop the applicators in the acrylic material also for the comparative study. A CT scan was performed to establish an infill-density calibration curve as well as characterize the quality of the print such as uniformity and the infill pattern. To commission the process, basic CT and dose properties of the printing materials were measured in photon beams and compared against water and soft tissue. Applicator were then scanned to confirm the placement of multiple catheter position. Finally dose distributions with rescanned CTs were compared with those computer-generated applicators. Results: The doses measured from the ion Chamber and X-Omat film test were within 2%. The shielded applicator reduce the rectal dose comparatively with the non shielded applicator. Conclusion: As of submission 3 unique cylinders have been designed, printed, and tested dosimetrically. A standardizable workflow for commissioning custom 3D printed applicators was codified and will be reported.« less

Cryopump

DOEpatents

McFarlin, David J.

1980-01-01

A cryopump having a cryopanel adapted for being cooled by a first refrigerant and shielded from radiation incident thereon by shields adapted for being cooled with a second refrigerant is disclosed. The cryopanel and the radiation shield are fabricated with a first material having high thermal conductivity, such as aluminum, while means for distributing refrigerant from refrigerant dewars to the cryopanel and shields are made of a second material, such as stainless steel. The stainless steel and aluminum sections are connected by an aluminum-steel transition connector adapted for providing vacuum tight connections at cryogenic temperatures. Both the cryopanel and chevrons comprising the shields are fabricated and extruded aluminum with coolant passages formed therein. Thermal distortions during operation are compensated by the use of stainless steel bellows within refrigerant distribution lines. Additionally the refrigerant distribution lines are utilized to suspend the cryopanel and shields within an evacuated environment of the cryopump.

Portable convertible blast effects shield

DOEpatents

Pastrnak, John W [Livermore, CA; Hollaway, Rocky [Modesto, CA; Henning, Carl D [Livermore, CA; Deteresa, Steve [Livermore, CA; Grundler, Walter [Hayward, CA; Hagler, Lisle B [Berkeley, CA; Kokko, Edwin [Dublin, CA; Switzer, Vernon A [Livermore, CA

2011-03-15

A rapidly deployable portable convertible blast effects shield/ballistic shield includes a set two or more frusto-conically-tapered telescoping rings operably connected to each other to convert between a telescopically-collapsed configuration for storage and transport, and a telescopically-extended upright configuration forming an expanded inner volume. In a first embodiment, the upright configuration provides blast effects shielding, such as against blast pressures, shrapnel, and/or fire balls. And in a second embodiment, the upright configuration provides ballistic shielding, such as against incoming weapons fire, shrapnel, etc. Each ring has a high-strength material construction, such as a composite fiber and matrix material, capable of substantially inhibiting blast effects and impinging projectiles from passing through the shield. And the set of rings are releasably securable to each other in the telescopically-extended upright configuration by the friction fit of adjacent pairs of frusto-conically-tapered rings to each other.

DETECTION OF COATING FAILURES IN A NEUTRONIC REACTOR

DOEpatents

Snell, A.H.; Allison, S.K.

1958-02-11

This patent relates to water-cooled reactor systems and discloses a means to detect leaks in the jackets of jacketed fuel elements comprising a neutron detector located in the cooling water discharge pipe,the pipe being provided with an enlarged portion for housing the detector so that the latter is completely surrounded by the water in its passage through the pipe, said enlarged portion and detector being shielded from the reactor for the purpose of detecting only those delayed neutrons emitted in the cooling water and due to the latter picking up fission fragments from the defective fuel elements.

Thermos reactors

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

Labrousse, M.; Lerouge, B.; Dupuy, G.

1978-04-01

THERMOS is a water reactor designed to provide hot water up to 120/sup 0/C for district heating or for desalination applications. It is a 100-MW reactor based on proven technology: oxide fuel plate elements, integrated primary circuit, and reactor vessel located in the bottom of a pool. As in swimming pool reactors, the pool is used for biological shielding, emergency core cooling, and fission product filtering (in case of an accident). Before economics, safety is the main characteristic of the concept: no fuel failure admitted, core under water in any accidental configuration, inspection of every ''nuclear'' component, and double-wall containment.

Investigation of Radiation Protection Methodologies for Radiation Therapy Shielding Using Monte Carlo Simulation and Measurement

NASA Astrophysics Data System (ADS)

Tanny, Sean

The advent of high-energy linear accelerators for dedicated medical use in the 1950's by Henry Kaplan and the Stanford University physics department began a revolution in radiation oncology. Today, linear accelerators are the standard of care for modern radiation therapy and can generate high-energy beams that can produce tens of Gy per minute at isocenter. This creates a need for a large amount of shielding material to properly protect members of the public and hospital staff. Standardized vault designs and guidance on shielding properties of various materials are provided by the National Council on Radiation Protection (NCRP) Report 151. However, physicists are seeking ways to minimize the footprint and volume of shielding material needed which leads to the use of non-standard vault configurations and less-studied materials, such as high-density concrete. The University of Toledo Dana Cancer Center has utilized both of these methods to minimize the cost and spatial footprint of the requisite radiation shielding. To ensure a safe work environment, computer simulations were performed to verify the attenuation properties and shielding workloads produced by a variety of situations where standard recommendations and guidance documents were insufficient. This project studies two areas of concern that are not addressed by NCRP 151, the radiation shielding workload for the vault door with a non-standard design, and the attenuation properties of high-density concrete for both photon and neutron radiation. Simulations have been performed using a Monte-Carlo code produced by the Los Alamos National Lab (LANL), Monte Carlo Neutrons, Photons 5 (MCNP5). Measurements have been performed using a shielding test port designed into the maze of the Varian Edge treatment vault.

Comparison Of 252Cf Time Correlated Induced Fisssion With AmLi Induced Fission On Fresh MTR Research Reactor Fuel

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

Joshi, Jay Prakash

The effective application of international safeguards to research reactors requires verification of spent fuel as well as fresh fuel. To accomplish this goal various nondestructive and destructive assay techniques have been developed in the US and around the world. The Advanced Experimental Fuel Counter (AEFC) is a nondestructive assay (NDA) system developed at Los Alamos National Laboratory (LANL) combining both neutron and gamma measurement capabilities. Since spent fuel assemblies are stored in water, the system was designed to be watertight to facilitate underwater measurements by inspectors. The AEFC is comprised of six 3He detectors as well as a shielded andmore » collimated ion chamber. The 3He detectors are used for active and passive neutron coincidence counting while the ion chamber is used for gross gamma counting. Active coincidence measurement data is used to measure residual fissile mass, whereas the passive coincidence measurement data along with passive gamma measurement can provide information about burnup, cooling time, and initial enrichment. In the past, most of the active interrogation systems along with the AEFC used an AmLi neutron interrogation source. Owing to the difficulty in obtaining an AmLi source, a 252Cf spontaneous fission (SF) source was used during a 2014 field trail in Uzbekistan as an alternative. In this study, experiments were performed to calibrate the AEFC instrument and compare use of the 252Cf spontaneous fission source and the AmLi (α,n) neutron emission source. The 252Cf source spontaneously emits bursts of time-correlated prompt fission neutrons that thermalize in the water and induce fission in the fuel assembly. The induced fission (IF) neutrons are also time correlated resulting in more correlated neutron detections inside the 3He detector, which helps reduce the statistical errors in doubles when using the 252Cf interrogation source instead of the AmLi source. In this work, two MTR fuel assemblies varying both in size and number of fuel plates were measured using 252Cf and AmLi active interrogation sources. This paper analyzes time correlated induced fission (TCIF) from fresh MTR fuel assemblies due to 252Cf and AmLi active interrogation sources.« less

Detection of special nuclear material from delayed neutron emission induced by a dual-particle monoenergetic source

DOE PAGES

Mayer, Michael F.; Nattress, J.; Jovanovic, I.

2016-06-27

Detection of unique signatures of special nuclear materials is critical for their interdiction in a variety of nuclear security and nonproliferation scenarios. We report on the observation of delayed neutrons from fission of uranium induced in dual-particle active interrogation based on the 11B(d,n γ) 12C nuclear reaction. Majority of the fissions are attributed to fast fission induced by the incident quasi-monoenergetic neutrons. A Li-doped glass–polymer composite scintillation neutron detector, which displays excellent neutron/γ discrimination at low energies, was used in the measurements, along with a recoil-based liquid scintillation detector. Time- dependent buildup and decay of delayed neutron emission from 238Umore » were measured between the interrogating beam pulses and after the interrogating beam was turned off, respectively. Characteristic buildup and decay time profiles were compared to the common parametrization into six delayed neutron groups, finding a good agreement between the measurement and nuclear data. Furthermore, this method is promising for detecting fissile and fissionable materials in cargo scanning applications and can be readily integrated with transmission radiography using low-energy nuclear reaction sources.« less

Thermocouple shield

DOEpatents

Ripley, Edward B [Knoxville, TN

2009-11-24

A thermocouple shield for use in radio frequency fields. In some embodiments the shield includes an electrically conductive tube that houses a standard thermocouple having a thermocouple junction. The electrically conductive tube protects the thermocouple from damage by an RF (including microwave) field and mitigates erroneous temperature readings due to the microwave or RF field. The thermocouple may be surrounded by a ceramic sheath to further protect the thermocouple. The ceramic sheath is generally formed from a material that is transparent to the wavelength of the microwave or RF energy. The microwave transparency property precludes heating of the ceramic sheath due to microwave coupling, which could affect the accuracy of temperature measurements. The ceramic sheath material is typically an electrically insulating material. The electrically insulative properties of the ceramic sheath help avert electrical arcing, which could damage the thermocouple junction. The electrically conductive tube is generally disposed around the thermocouple junction and disposed around at least a portion of the ceramic sheath. The concepts of the thermocouple shield may be incorporated into an integrated shielded thermocouple assembly.

On the feasibility to perform integral transmission experiments in the GELINA target hall at IRMM

NASA Astrophysics Data System (ADS)

Leconte, Pierre; Jean, Cyrille De Saint; Geslot, Benoit; Plompen, Arjan; Belloni, Francesca; Nyman, Markus

2017-09-01

Shielding experiments are relevant to validate elastic and inelastic scattering cross sections in the fast energy range. In this paper, we are focusing on the possibility to use the pulsed white neutron time-of-flight facility GELINA to perform this kind of measurement. Several issues need to be addressed: neutron source intensity, room return effect, distance of the materials to be irradiated from the source, and the sensitivity of various reaction rate distributions through the material to different input cross sections. MCNP6 and TRIPOLI4 calculations of the outgoing neutron spectrum are compared, based on electron/positron/gamma/neutron simulations. A first guess of an integral transmission experiment through a 238U slab is considered. It shows that a 10 cm thickness of uranium is sufficient to reach a high sensitivity to the 238U inelastic scattering cross section in the [2-5 MeV] energy range, with small contributions from elastic and fission cross sections. This experiment would contribute to reduce the uncertainty on this nuclear data, which has a significant impact on the power distribution in large commercial reactors. Other materials that would be relevant for the ASTRID 4th generation prototype reactor are also tested, showing that a sufficient sensitivity to nuclear data would be obtained by using a 50 to 100cm thick slab of side 60x60cm. This study concludes on the feasibility and interest of such experiments in the target hall of the GELINA facility.

Apparatus for characterizing conductivity of materials by measuring the effect of induced shielding currents therein

DOEpatents

Doss, James D.

1991-01-01

Apparatus and method for noncontact, radio-frequency shielding current characterization of materials. Self- or mutual inductance changes in one or more inductive elements, respectively, occur when materials capable of supporting shielding currents are placed in proximity thereto, or undergo change in resistivity while in place. Such changes can be observed by incorporating the inductor(s) in a resonant circuit and determining the frequency of oscillation or by measuring the voltage induced on a coupled inductive element. The present invention is useful for determining the critical temperature and superconducting transition width for superconducting samples.

Intercalated graphite fiber composites as EMI shields in aerospace structures

NASA Technical Reports Server (NTRS)

Gaier, James R.

1990-01-01

The requirements for electromagnetic interference (EMI) shielding in aerospace structures are complicated over that of ground structures by their weight limitations. As a result, the best EMI shielding materials must blend low density, high strength, and high elastic modulus with high shielding ability. In addition, fabrication considerations including penetrations and joints play a major role. The EMI shielding properties are calculated for shields formed from pristine and intercalated graphite fiber/epoxy composites and compared to preliminary experimental results and to shields made from aluminum. Calculations indicate that EMI shields could be fabricated from intercalated graphite composites which would have less than 12 percent of the mass of conventional aluminum shields, based on mechanical properties and shielding properties alone.

LIFE Materials: Thermomechanical Effects Volume 5 - Part I

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

Caro, M; DeMange, P; Marian, J

2009-05-07

Improved fuel performance is a key issue in the current Laser Inertial-Confinement Fusion-Fission Energy (LIFE) engine design. LIFE is a fusion-fission engine composed of a {approx}40-tons fuel blanket surrounding a pulsed fusion neutron source. Fusion neutrons get multiplied and moderated in a Beryllium blanket before penetrating the subcritical fission blanket. The fuel in the blanket is composed of millions of fuel pebbles, and can in principle be burned to over 99% FIMA without refueling or reprocessing. This report contains the following chapters: Chapter A: LIFE Requirements for Materials -- LIFE Fuel; Chapter B: Summary of Existing Knowledge; Chapter C: Identificationmore » of Gaps in Knowledge & Vulnerabilities; and Chapter D: Strategy and Future Work.« less

FUEL ELEMENT FOR NUCLEAR REACTORS

DOEpatents

Bassett, C.H.

1961-11-21

A fuel element is designed which is particularly adapted for reactors of high power density used to generate steam for the production of electricity. The fuel element consists of inner and outer concentric tubes forming an annular chamber within which is contained fissionable fuel pellet segments, wedge members interposed between the fuel segments, and a spring which, acting with wedge members, urges said fuel pellets radially into contact against the inner surface of the outer tube. The wedge members may be a fertile material convertible into fissionable fuel material by absorbing neutrons emitted from the fissionable fuel pellet segments. The costly grinding of cylindrical fuel pellets to close tolerances for snug engagement is reduced because the need to finish the exact size is eliminated. (AEC)

Self shielding in cylindrical fissile sources in the APNea system

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

Hensley, D.

1997-02-01

In order for a source of fissile material to be useful as a calibration instrument, it is necessary to know not only how much fissile material is in the source but also what the effective fissile content is. Because uranium and plutonium absorb thermal neutrons so Efficiently, material in the center of a sample is shielded from the external thermal flux by the surface layers of the material. Differential dieaway measurements in the APNea System of five different sets of cylindrical fissile sources show the various self shielding effects that are routinely encountered. A method for calculating the self shieldingmore » effect is presented and its predictions are compared with the experimental results.« less

Vapor shielding models and the energy absorbed by divertor targets during transient events

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

Skovorodin, D. I., E-mail: dskovorodin@gmail.com; Arakcheev, A. S.; Pshenov, A. A.

2016-02-15

The erosion of divertor targets caused by high heat fluxes during transients is a serious threat to ITER operation, as it is going to be the main factor determining the divertor lifetime. Under the influence of extreme heat fluxes, the surface temperature of plasma facing components can reach some certain threshold, leading to an onset of intense material evaporation. The latter results in formation of cold dense vapor and secondary plasma cloud. This layer effectively absorbs the energy of the incident plasma flow, turning it into its own kinetic and internal energy and radiating it. This so called vapor shieldingmore » is a phenomenon that may help mitigating the erosion during transient events. In particular, the vapor shielding results in saturation of energy (per unit surface area) accumulated by the target during single pulse of heat load at some level E{sub max}. Matching this value is one of the possible tests to verify complicated numerical codes, developed to calculate the erosion rate during abnormal events in tokamaks. The paper presents three very different models of vapor shielding, demonstrating that E{sub max} depends strongly on the heat pulse duration, thermodynamic properties, and evaporation energy of the irradiated target material. While its dependence on the other shielding details such as radiation capabilities of material and dynamics of the vapor cloud is logarithmically weak. The reason for this is a strong (exponential) dependence of the target material evaporation rate, and therefore the “strength” of vapor shield on the target surface temperature. As a result, the influence of the vapor shielding phenomena details, such as radiation transport in the vapor cloud and evaporated material dynamics, on the E{sub max} is virtually completely masked by the strong dependence of the evaporation rate on the target surface temperature. However, the very same details define the amount of evaporated particles, needed to provide an effective shielding to the target, and, therefore, strongly influence resulting erosion rate. Thus, E{sub max} cannot be used for validation of shielding models and codes, aimed at the target material erosion calculations.« less

Optimization of Martian regolith and ultra-high molecular weight polyethylene composites for radiation shielding and habitat structures

NASA Astrophysics Data System (ADS)

Wilkins, Richard; Gersey, Brad; Baburaj, Abhijit; Barnett, Milan; Zhou, Xianren

2012-07-01

In preparation for long duration missions to the moon, Mars or, even near earth asteroids, one challenge, amongst many others, that the space program faces is shielding against space radiation. It is difficult to effectively shield all sources of space radiation because of the broad range of types and high energies found in space, so the most important goal is to minimize the damaging effects that may occur to humans and electronics during long duration space flight. For a long duration planetary habitat, a shielding option is to use in situ resources such as the native regolith. A possible way to utilize regolith on a planet is to combine it with a binder to form a structural material that also exhibits desirable shielding properties. In our studies, we explore Martian regolith and ultra-high molecular weight polyethylene (UHMWPE) composites. We selected UHMWPE as the binder in our composites due to its high hydrogen content; a desirable characteristic for shielding materials in a space environment. Our initial work has focused on the process of developing the right ratio of simulated Martian regolith and UHMWPE to yield the best results in material endurance and strength, while retaining good shielding characteristics. Another factor in our optimization process is to determine the composite ratio that minimizes the amount of ex situ UHMWPE while retaining desirable structural and shielding properties. This consideration seeks to minimize mission weight and costs. Mechanical properties such as tensile strength of the Martian regolith/UHMWPE composite as a function of its grain size, processing parameters, and different temperature variations used are discussed. The radiation shielding effectiveness of loose mixtures of Martian regolith/ UHMWPE is evaluated using a 200 MeV proton beam and a tissue equivalent proportional counter. Preliminary results show that composites with an 80/20 ratio percent weight of regolith to UHMWPE can be fabricated with potentially useful structural strength. I n addition, Martian regolith, while not as efficient as polyethylene at reducing proton energy as a function of shield thickness, compares well with polyethylene at shielding the 200 MeV protons. These preliminary results indicate that native Martian regolith has promising properties as a habitat material for future human missions. Future work studying the shielding effectiveness and radiation tolerance will also be discussed.

NEUTRONIC REACTOR DESIGN TO REDUCE NEUTRON LOSS

DOEpatents

Mills, F.T.

1961-05-01

A nuclear reactor construction is described in which an unmoderated layer of the fissionable material is inserted between the moderated portion of the reactor core and the core container steel wall which is surrounded by successive layers of pure fertile material and fertile material having moderator. The unmoderated layer of the fissionable material will insure that a greater portion of fast neutrons will pass through the steel wall than would thermal neutrons. As the steel has a smaller capture cross-section for the fast neutrons, then greater numbers of the neutrons will pass into the blanket thereby increasing the over-all efficiency of the reactor.

Neutronic Reactor Design to Reduce Neutron Loss

DOEpatents

Miles, F. T.

1961-05-01

A nuclear reactor construction is described in which an unmoderated layer of the fissionable material is inserted between the moderated portion of the reactor core and the core container steel wall. The wall is surrounded by successive layers of pure fertile material and moderator containing fertile material. The unmoderated layer of the fissionable material will insure that a greater portion of fast neutrons will pass through the steel wall than would thermal neutrons. Since the steel has a smaller capture cross section for the fast neutrons, greater nunnbers of neutrons will pass into the blanket, thereby increasing the over-all efficiency of the reactor. (AEC)

Two neutron correlations in photo-fission

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

Dale, D. S.; Kosinov, O.; Forest, T.

2016-01-01

A large body of experimental work has established the strong kinematical correlation between fission fragments and fission neutrons. Here, we report on the progress of investigations of the potential for strong two neutron correlations arising from the nearly back-to-back nature of the two fission fragments that emit these neutrons in the photo-fission process. In initial measurements, a pulsed electron linear accelerator was used to generate bremsstrahlung photons that impinged upon an actinide target, and the energy and opening angle distributions of coincident neutrons were measured using a large acceptance neutron detector array. A planned comprehensive set of measurements of twomore » neutron correlations in the photo-fission of actinides is expected to shed light on several fundamental aspects of the fission process including the multiplicity distributions associated with the light and heavy fission fragments, the nuclear temperatures of the fission fragments, and the mass distribution of the fission fragments as a function of energy released. In addition to these measurements providing important nuclear data, the unique kinematics of fission and the resulting two neutron correlations have the potential to be the basis for a new tool to detect fissionable materials. A key technical challenge of this program arises from the need to perform coincidence measurements with a low duty factor, pulsed electron accelerator. This has motivated the construction of a large acceptance neutron detector array, and the development of data analysis techniques to directly measure uncorrelated two neutron backgrounds.« less

800-MeV proton irradiation of thorium and depleted uranium targets

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

Russell, G.J.; Brun, T.O.; Pitcher, E.J.

As part of the Los Alamos Fertile-to-Fissile-Conversion (FERFICON) program in the late 1980`s, thick targets of the fertile materials thorium and depleted uranium were bombarded by 800-MeV protons to produce the fissile materials {sup 233}U and {sup 239}Pu, respectively. The amount of {sup 233}U made was determined by measuring the {sup 233}Pa activity, and the yield of {sup 239}Pu was deduced by measuring the activity of {sup 239}Np. For the thorium target, 4 spallation products and 34 fission products were also measured. For the depleted uranium target, 3 spallation products and 16 fission products were also measured. The number ofmore » fissions in each target was deduced from fission product mass-yield curves. In actuality, axial distributions of the products were measured, and the distributions were then integrated over the target volume to obtain the total number of products for each reaction.« less

ICP-MS analysis of fission product diffusion in graphite for High-Temperature Gas-Cooled Reactors

NASA Astrophysics Data System (ADS)

Carter, Lukas M.

Release of radioactive fission products from nuclear fuel during normal reactor operation or in accident scenarios is a fundamental safety concern. Of paramount importance are the understanding and elucidation of mechanisms of chemical interaction, nuclear interaction, and transport phenomena involving fission products. Worldwide efforts to reduce fossil fuel dependence coupled with an increasing overall energy demand have generated renewed enthusiasm toward nuclear power technologies, and as such, these mechanisms continue to be the subjects of vigorous research. High-Temperature Gas-Cooled Reactors (HTGRs or VHTRs) remain one of the most promising candidates for the next generation of nuclear power reactors. An extant knowledge gap specific to HTGR technology derives from an incomplete understanding of fission product transport in major core materials under HTGR operational conditions. Our specific interest in the current work is diffusion in reactor graphite. Development of methods for analysis of diffusion of multiple fission products is key to providing accurate models for fission product release from HTGR core components and the reactor as a whole. In the present work, a specialized diffusion cell has been developed and constructed to facilitate real-time diffusion measurements via ICP-MS. The cell utilizes a helium gas-jet system which transports diffusing fission products to the mass spectrometer using carbon nanoparticles. The setup was designed to replicate conditions present in a functioning HTGR, and can be configured for real-time release or permeation measurements of single or multiple fission products from graphite or other core materials. In the present work, we have analyzed release rates of cesium in graphite grades IG-110, NBG-18, and a commercial grade of graphite, as well as release of iodine in IG-110. Additionally we have investigated infusion of graphite samples with Cs, I, Sr, Ag, and other surrogate fission products for use in release or profile measurements of diffusion coefficients.

Simbol-X Mirror Module Thermal Shields: II-Small Angle X-Ray Scattering Measurements

NASA Astrophysics Data System (ADS)

Barbera, M.; Ayers, T.; Collura, A.; Nasillo, G.; Pareschi, G.; Tagliaferri, G.

2009-05-01

The formation flight configuration of the Simbol-X mission implies that the X-ray mirror module will be open to Space on both ends. In order to reduce the power required to maintain the thermal stability and, therefore, the high angular resolution of the shell optics, a thin foil thermal shield will cover the mirror module. Different options are presently being studied for the foil material of these shields. We report results of an experimental investigation conducted to verify that the scattering of X-rays, by interaction with the thin foil material of the thermal shield, will not significantly affect the performances of the telescope.

[Dosimetric evaluation of eye lense shieldings in computed tomography examination--measurements and Monte Carlo simulations].

PubMed

Wulff, Jorg; Keil, Boris; Auvanis, Diyala; Heverhagen, Johannes T; Klose, Klaus Jochen; Zink, Klemens

2008-01-01

The present study aims at the investigation of eye lens shielding of different composition for the use in computed tomography examinations. Measurements with thermo-luminescent dosimeters and a simple cylindrical waterfilled phantom were performed as well as Monte Carlo simulations with an equivalent geometry. Besides conventional shielding made of Bismuth coated latex, a new shielding with a mixture of metallic components was analyzed. This new material leads to an increased dose reduction compared to the Bismuth shielding. Measured and Monte Carlo simulated dose reductions are in good agreement and amount to 34% for the Bismuth shielding and 46% for the new material. For simulations the EGSnrc code system was used and a new application CTDOSPP was developed for the simulation of the computed tomography examination. The investigations show that a satisfying agreement between simulation and measurement with the chosen geometries of this study could only be achieved, when transport of secondary electrons was accounted for in the simulation. The amount of scattered radiation due to the protector by fluorescent photons was analyzed and is larger for the new material due to the smaller atomic number of the metallic components.

Correlated Uncertainties in Radiation Shielding Effectiveness

NASA Technical Reports Server (NTRS)

Werneth, Charles M.; Maung, Khin Maung; Blattnig, Steve R.; Clowdsley, Martha S.; Townsend, Lawrence W.

2013-01-01

The space radiation environment is composed of energetic particles which can deliver harmful doses of radiation that may lead to acute radiation sickness, cancer, and even death for insufficiently shielded crew members. Spacecraft shielding must provide structural integrity and minimize the risk associated with radiation exposure. The risk of radiation exposure induced death (REID) is a measure of the risk of dying from cancer induced by radiation exposure. Uncertainties in the risk projection model, quality factor, and spectral fluence are folded into the calculation of the REID by sampling from probability distribution functions. Consequently, determining optimal shielding materials that reduce the REID in a statistically significant manner has been found to be difficult. In this work, the difference of the REID distributions for different materials is used to study the effect of composition on shielding effectiveness. It is shown that the use of correlated uncertainties allows for the determination of statistically significant differences between materials despite the large uncertainties in the quality factor. This is in contrast to previous methods where uncertainties have been generally treated as uncorrelated. It is concluded that the use of correlated quality factor uncertainties greatly reduces the uncertainty in the assessment of shielding effectiveness for the mitigation of radiation exposure.

Radiation shielding materials characterization in the MoMa-Count program and further evolutions

NASA Astrophysics Data System (ADS)

Lobascio, Cesare

In the frame of the space research programme MoMa (From Molecules to Man) -Count (Coun-termeasures), funded by the Italian Space Agency, multi-functional protections for human space exploration have been investigated, paying particular attention to flexible materials, selected also for their excellent structural, thermal and ballistic performances. Flexible materials such as Kevlar R are qualified for space application, but have poorly known space radiation prop-erties, with consequent uncertainties about their shielding efficiency against the radiation en-vironment. The necessary evaluation of their shielding efficiency has been chiefly based on dedicated ground experiments in accelerators, supplemented by Monte Carlo simulations of the particle transport in the materials or multi-layers. In addition, flight experiments have been performed in Low Earth Orbit (LEO), onboard the International Space Station (ISS) and the re-entry capsule Foton, to measure the shielding behaviour in the actual operating environment of space, via dedicated detectors and dosimeters. This paper aims at presenting the results and lessons learned accrued within the MoMa-Count program, as well as the future actions planned for improving radiation shielding in long duration human exploration missions.

Evaluation of Prototype Head Shield for Hazardous Material Tank Car

DOT National Transportation Integrated Search

1976-12-01

The structural integrity of a prototype tank car head shield for hazardous material railroad tank cars was evaluated under conditions of freight car coupling at moderate to high speeds. This is one of the most severe environments encountered in norma...

Criticality Safety Basics for INL FMHs and CSOs

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

V. L. Putman

2012-04-01

Nuclear power is a valuable and efficient energy alternative in our energy-intensive society. However, material that can generate nuclear power has properties that require this material be handled with caution. If improperly handled, a criticality accident could result, which could severely harm workers. This document is a modular self-study guide about Criticality Safety Principles. This guide's purpose it to help you work safely in areas where fissionable nuclear materials may be present, avoiding the severe radiological and programmatic impacts of a criticality accident. It is designed to stress the fundamental physical concepts behind criticality controls and the importance of criticalitymore » safety when handling fissionable materials outside nuclear reactors. This study guide was developed for fissionable-material-handler and criticality-safety-officer candidates to use with related web-based course 00INL189, BEA Criticality Safety Principles, and to help prepare for the course exams. These individuals must understand basic information presented here. This guide may also be useful to other Idaho National Laboratory personnel who must know criticality safety basics to perform their assignments safely or to design critically safe equipment or operations. This guide also includes additional information that will not be included in 00INL189 tests. The additional information is in appendices and paragraphs with headings that begin with 'Did you know,' or with, 'Been there Done that'. Fissionable-material-handler and criticality-safety-officer candidates may review additional information at their own discretion. This guide is revised as needed to reflect program changes, user requests, and better information. Issued in 2006, Revision 0 established the basic text and integrated various programs from former contractors. Revision 1 incorporates operation and program changes implemented since 2006. It also incorporates suggestions, clarifications, and additional information from readers and from personnel who took course 00INL189. Revision 1 also completely reorganized the training to better emphasize physical concepts behind the criticality controls that fissionable material handlers and criticality safety officers must understand. The reorganization is based on and consistent with changes made to course 00INL189 due to a review of course exam results and to discussions with personnel who conduct area-specific training.« less

Parametric study for use of stainless steel as a material for thermal shield in PIP2IT transferline at FNAL

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

Rane, Tejas

Proton Improvement Plant – II (PIP-II) has been planned at Fermilab for providing high-intensity proton beams to the laboratory’s experiments. Fermilab has undertaken the PIP-II Injector Test (PIP2IT) for integrated systems testing of critical components comprising the PIP-II front end. PIP2IT includes two cryomodules, to be tested using a pre-existing Supercritical helium refrigerator and distribution box. The PIP2IT transferline connects the Distribution box to the cryomodules of PI2IT. It contains 5 process lines as follows - supercritical 5K He supply and return lines, thermal shield supply(40K) and return(80K) lines and a sub-atmospheric 2K return line. Such cryogenic transferlines are generallymore » provided with cylindrical thermal shields at 80K, enclosing multiple process lines. The thermal shields are cooled by dedicated cooling lines welded/brazed to the shield at a single point along the circumference. Higher thermal diffusivity provides faster cooling and uniformity o f temperature along the shield surface. Hence, Copper/Aluminium is widely used to fabricate thermal shields. However, raw material price, the cost of fabrication depending on standard sizes of pipes/tubes, often drives up the final price of thermal shields. To reduce the cost by making use of easily available stock of standard pipe/tube, it is decided to use stainless steel as a material in thermal shields for the PIP2IT transferline. To this effect, a parametric study has been undertaken to evaluate the suitability of replacing Copper/Aluminium with stainless steel in thermal shields. The low thermal conductivity of steel results in bowing of the shield due to differential temperature distribution along the circumferential direction. The resulting suitable design has limiting parameters in terms of maximum allowable length of a shield section and the maximum allowable heat transfer coefficient for cooling flow. Starting with the design specific to PIP2IT transferline, an at tempt is made to have non-dimensionalised parameters for sim! ilar thermal shields.« less

Experimental Shielding Evaluation of the Radiation Protection Provided by Residential Structures

NASA Astrophysics Data System (ADS)

Dickson, Elijah D.

The human health and environmental effects following a postulated accidental release of radioactive material to the environment has been a public and regulatory concern since the early development of nuclear technology and researched extensively to better understand the potential risks for accident mitigation and emergency planning purposes. The objective of this investigation is to research and develop the technical basis for contemporary building shielding factors for the U.S. housing stock. Building shielding factors quantify the protection a certain building-type provides from ionizing radiation. Much of the current data used to determine the quality of shielding around nuclear facilities and urban environments is based on simplistic point-kernel calculations for 1950's era suburbia and is no longer applicable to the densely populated urban environments seen today. To analyze a building's radiation shielding properties, the ideal approach would be to subject a variety of building-types to various radioactive materials and measure the radiation levels in and around the building. While this is not entirely practicable, this research uniquely analyzes the shielding effectiveness of a variety of likely U.S. residential buildings from a realistic source term in a laboratory setting. Results produced in the investigation provide a comparison between theory and experiment behind building shielding factor methodology by applying laboratory measurements to detailed computational models. These models are used to develop a series of validated building shielding factors for generic residential housing units using the computational code MCNP5. For these building shielding factors to be useful in radiologic consequence assessments and emergency response planning, two types of shielding factors have been developed for; (1) the shielding effectiveness of each structure within a semi-infinite cloud of radioactive material, and (2) the shielding effectiveness of each structure from contaminant deposition on the roof and surrounding surfaces. For example, results from this investigation estimate the building shielding factors from a semi-infinite plume between comparable two-story models with a basement constructed with either brick-and-mortar or vinyl siding composing the exterior wall weather and a typical single-wide manufactured home with vinyl siding to be 0.36, 0.65, and 0.82 respectively.

49 CFR 173.314 - Compressed gases in tank cars and multi-unit tank cars.

Code of Federal Regulations, 2012 CFR

2012-10-01

... shield as prescribed in § 179.16(c)(1). (d) Alternative tank car tanks for materials poisonous by... the alternative tank car jacket and head shield. When the jacket and head shield are made from any...., the thickness to be added to the jacket and head shield must be increased by a factor of 1.157...

A&M. Special shielding materials. Stockpile of magnetite, used for making ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

A&M. Special shielding materials. Stockpile of magnetite, used for making high-density concrete, and loading conveyor near TAN-607 construction site. Date: September 25, 1953. INEEL negative no. 8710 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

Extraterrestrial Regolith Derived Atmospheric Entry Heat Shields

NASA Technical Reports Server (NTRS)

Hogue, Michael D.; Mueller, Robert P.; Sibille, Laurent; Hintze, Paul E.; Rasky, Daniel J.

2016-01-01

High-mass planetary surface access is one of NASAs technical challenges involving entry, descent and landing (EDL). During the entry and descent phase, frictional interaction with the planetary atmosphere causes a heat build-up to occur on the spacecraft, which will rapidly destroy it if a heat shield is not used. However, the heat shield incurs a mass penalty because it must be launched from Earth with the spacecraft, thus consuming a lot of precious propellant. This NASA Innovative Advanced Concept (NIAC) project investigated an approach to provide heat shield protection to spacecraft after launch and prior to each EDL thus potentially realizing significant launch mass savings. Heat shields fabricated in situ can provide a thermal-protection system for spacecraft that routinely enter a planetary atmosphere. By fabricating the heat shield with space resources from materials available on moons and asteroids, it is possible to avoid launching the heat-shield mass from Earth. Regolith has extremely good insulating properties and the silicates it contains can be used in the fabrication and molding of thermal-protection materials. In this paper, we will describe three types of in situ fabrication methods for heat shields and the testing performed to determine feasibility of this approach.

Prototype of a Muon Tomography Station with GEM detectors for Detection of Shielded Nuclear Contraband

NASA Astrophysics Data System (ADS)

Staib, Michael; Bhopatkar, Vallary; Bittner, William; Hohlmann, Marcus; Locke, Judson; Twigger, Jessie; Gnanvo, Kondo

2012-03-01

Muon tomography for homeland security aims at detecting well-shielded nuclear contraband in cargo and imaging it in 3D. The technique exploits multiple scattering of atmospheric cosmic ray muons, which is stronger in dense, high-Z materials, e.g. enriched uranium, than in low-Z and medium-Z shielding materials. We have constructed and are operating a compact Muon Tomography Station (MTS) that tracks muons with eight 30 cm x 30 cm Triple Gas Electron Multiplier (GEM) detectors placed on the sides of a cubic-foot imaging volume. A point-of-closest-approach algorithm applied to reconstructed incident and exiting tracks is used to create a tomographic reconstruction of the material within the active volume. We discuss the performance of this MTS prototype including characterization and commissioning of the GEM detectors and the data acquisition systems. We also present experimental tomographic images of small high-Z objects including depleted uranium with and without shielding and discuss the performance of material discrimination using this method.

Experimental results on MgB2 used as ADR magnetic shields, and comparison to NbTi

NASA Astrophysics Data System (ADS)

Prouvé, T.; Duval, J. M.; Luchier, N.; D'escrivan, S.

2014-11-01

Adiabatic Demagnetization Refrigerator (ADR) is an efficient way to obtain sub-Kelvin temperatures in space environments. The SAFARI instrument for the Japanese spaceborne SPICA mission features detectors which will be cooled down to 50 mK. This cooling will be done by a hybrid cooler comprising a 300 mK sorption stage and a 50 mK ADR stage. For this cooler and ADR in general, the main contribution to the overall mass is in the magnetic system and particularly in the magnetic shielding required to keep the stray field within acceptable values. In order to reduce this mass, superconducting materials can be used as active magnetic shields thanks to un-attenuated eddy currents generated while ramping the magnet current. In this way they could reduce the need of heavy ferromagnetic material shields and increase the shielding efficiency to reach very low parasitic values. In the framework of SAFARI we have built a numerical model of a superconductor magnetic shield. The good results regarding the weight gain lead us to an experimental confirmation. In this paper we present an experimental study on MgB2 and NbTi superconducting materials. 2 pairs of rings of typical diameter of 80 mm have been tested using a superconducting magnet matching closely the dimensions of the SAFARI ADR cooler. The magnetic shielding measurements have been compared to a numerical model.

Unit mechanisms of fission gas release: Current understanding and future needs

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

Tonks, Michael; Andersson, David; Devanathan, Ram

Gaseous fission product transport and release has a large impact on fuel performance, degrading fuel properties and, once the gas is released into the gap between the fuel and cladding, lowering gap thermal conductivity and increasing gap pressure. While gaseous fission product behavior has been investigated with bulk reactor experiments and simplified analytical models, recent improvements in experimental and modeling approaches at the atomistic and mesoscales are being applied to provide unprecedented understanding of the unit mechanisms that define the fission product behavior. In this article, existing research on the basic mechanisms behind the various stages of fission gas releasemore » during normal reactor operation are summarized and critical areas where experimental and simulation work is needed are identified. This basic understanding of the fission gas behavior mechanisms has the potential to revolutionize our ability to predict fission product behavior during reactor operation and to design fuels that have improved fission product retention. In addition, this work can serve as a model on how a coupled experimental and modeling approach can be applied to understand the unit mechanisms behind other critical behaviors in reactor materials.« less

Reliability Methods for Shield Design Process

NASA Technical Reports Server (NTRS)

Tripathi, R. K.; Wilson, J. W.

2002-01-01

Providing protection against the hazards of space radiation is a major challenge to the exploration and development of space. The great cost of added radiation shielding is a potential limiting factor in deep space operations. In this enabling technology, we have developed methods for optimized shield design over multi-segmented missions involving multiple work and living areas in the transport and duty phase of space missions. The total shield mass over all pieces of equipment and habitats is optimized subject to career dose and dose rate constraints. An important component of this technology is the estimation of two most commonly identified uncertainties in radiation shield design, the shielding properties of materials used and the understanding of the biological response of the astronaut to the radiation leaking through the materials into the living space. The largest uncertainty, of course, is in the biological response to especially high charge and energy (HZE) ions of the galactic cosmic rays. These uncertainties are blended with the optimization design procedure to formulate reliability-based methods for shield design processes. The details of the methods will be discussed.

Electromagnetic interference shielding effectiveness of polypropylene/conducting fiber composites

NASA Astrophysics Data System (ADS)

Lee, Pyoung-Chan; Kim, Bo-Ram; Jeoung, Sun Kyoung; Kim, Yeung Keun

2016-03-01

Electromagnetic released from the automotive electronic parts is harmful to human body. Electromagnetic interference (EMT) shielding refers to the reflection and/or adsorption of electromagnetic radiation by a material, which thereby acts as a shield against the penetration of the radiation through the shield. Polypropylene (PP)/conductive micro fiber composites containing various fiber contents and fiber length were injection-molded. The effect of fiber content and length on electrical properties of the composites was studied by electrical resistivity and EMT shielding measurements. The through-plane electrical conductivity and dielectric permittivity were obtained by measuring dielectric properties. The EMT shielding effectiveness (SE) was investigated by using S-parameter in the range of 100 ~ 1500 MHz. Reflection, absorption and multiple-reflection are the EMT attenuation mechanisms. From the measurement of S-Parameters, the absorption coefficient, reflection coefficient, and the shielding efficiency of the materials were calculated. The EMT SE of PP/conducing fiber composites is 40 dB over a wide frequency range up to 1.5 GHz, which is higher than that of PP/talc composite used automotive parts, viz. 0 dB.

Magnetic radiation shielding - An idea whose time has returned?

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A.

1991-01-01

One solution to the problem of shielding crew from particulate radiation in space is to use active electromagnetic shielding. Practical types of shield include the magnetic shield, in which a strong magnetic field diverts charged particles from the crew region, and the magnetic/electrostatic plasma shield, in which an electrostatic field shields the crew from positively charged particles, while a magnetic field confines electrons from the space plasma to provide charge neutrality. Advances in technology include high-strength composite materials, high-temperature superconductors, numerical computational solutions to particle transport in electromagnetic fields, and a technology base for construction and operation of large superconducting magnets. These advances make electromagnetic shielding a practical alternative for near-term future missions.

Cytogenetic effects of high-energy iron ions: dependence on shielding thickness and material.

PubMed

Durante, M; George, K; Gialanella, G; Grossi, G; La Tessa, C; Manti, L; Miller, J; Pugliese, M; Scampoli, P; Cucinotta, F A

2005-10-01

We report results for chromosomal aberrations in human peripheral blood lymphocytes after they were exposed to high-energy iron ions with or without shielding at the HIMAC, AGS and NSRL accelerators. Isolated lymphocytes were exposed to iron ions with energies between 200 and 5000 MeV/nucleon in the 0.1-1-Gy dose range. Shielding materials consisted of polyethylene, lucite (PMMA), carbon, aluminum and lead, with mass thickness ranging from 2 to 30 g/cm2. After exposure, lymphocytes were stimulated to grow in vitro, and chromosomes were prematurely condensed using a phosphatase inhibitor (calyculin A). Aberrations were scored using FISH painting. The yield of total interchromosomal exchanges (including dicentrics, translocations and complex rearrangements) increased linearly with dose or fluence in the range studied. Shielding decreased the effectiveness per unit dose of iron ions. The highest RBE value was measured with the 1 GeV/nucleon iron-ion beam at NSRL. However, the RBE for the induction of aberrations apparently is not well correlated with the mean LET. When shielding thickness was increased, the frequency of aberrations per particle incident on the shield increased for the 500 MeV/nucleon ions and decreased for the 1 GeV/nucleon ions. Maximum variation at equal mass thickness was obtained with light materials (polyethylene, carbon or PMMA). Variations in the yield of chromosomal aberrations per iron particle incident on the shield follow variations in the dose per incident particle behind the shield but can be modified by the different RBE of the mixed radiation field produced by nuclear fragmentation. The results suggest that shielding design models should be benchmarked using both physics and biological data.

Apparatus for characterizing conductivity of materials by measuring the effect of induced shielding currents therein

DOEpatents

Doss, J.D.

1991-05-14

Apparatus and method for noncontact, radio-frequency shielding current characterization of materials is disclosed. Self- or mutual inductance changes in one or more inductive elements, respectively, occur when materials capable of supporting shielding currents are placed in proximity thereto, or undergo change in resistivity while in place. Such changes can be observed by incorporating the inductor(s) in a resonant circuit and determining the frequency of oscillation or by measuring the voltage induced on a coupled inductive element. The present invention is useful for determining the critical temperature and superconducting transition width for superconducting samples. 10 figures.

A CHEMICAL METHOD OF TREATING FISSIONABLE MATERIAL

DOEpatents

Olson, C.M.

1959-09-01

One step of a process for separating plutonium from uranium and fission products is presented. A nitric acid solution containing these constituents is treated with formic acid to reduce simultaneously the plutonium to a valence state of not greater than +4 and destroy and eliminate the excess nitric acid.

Fission fragment yields from heavy-ion-induced reactions measured with a fragment separator

NASA Astrophysics Data System (ADS)

Tarasov, O. B.; Delaune, O.; Farget, F.; Morrissey, D. J.; Amthor, A. M.; Bastin, B.; Bazin, D.; Blank, B.; Cacéres, L.; Chbihi, A.; Fernández-Dominguez, B.; Grévy, S.; Kamalou, O.; Lukyanov, S. M.; Mittig, W.; Pereira, J.; Perrot, L.; Saint-Laurent, M.-G.; Savajols, H.; Sherrill, B. M.; Stodel, C.; Thomas, J. C.; Villari, A. C.

2018-04-01

The systematic study of fission fragment yields under different initial conditions has provided valuable experimental data for benchmarking models of fission product yields. Nuclear reactions using inverse kinematics coupled to the use of a high-resolution spectrometer with good fragment identification are shown here to be a powerful tool to measure the inclusive isotopic yields of fission fragments. In-flight fusion-fission was used in this work to produce secondary beams of neutron-rich isotopes in the collisions of a 238U beam at 24 MeV/u with 9Be and 12C targets at GANIL using the LISE3 fragment separator. Unique identification of the A, Z, and atomic charge state, q, of fission products was attained with the Δ E- TKE-B ρ- ToF measurement technique. Mass, and atomic number distributions are reported for the two reactions. The results show the importance of different reaction mechanisms in the two cases. The optimal target material for higher yields of neutron-rich high- Z isotopes produced in fusion-fission reactions as a function of projectile energy is discussed.

Monte Carlo parametric studies of neutron interrogation with the Associated Particle Technique for cargo container inspections

NASA Astrophysics Data System (ADS)

Deyglun, Clément; Carasco, Cédric; Pérot, Bertrand

2014-06-01

The detection of Special Nuclear Materials (SNM) by neutron interrogation is extensively studied by Monte Carlo simulation at the Nuclear Measurement Laboratory of CEA Cadarache (French Alternative Energies and Atomic Energy Commission). The active inspection system is based on the Associated Particle Technique (APT). Fissions induced by tagged neutrons (i.e. correlated to an alpha particle in the DT neutron generator) in SNM produce high multiplicity coincidences which are detected with fast plastic scintillators. At least three particles are detected in a short time window following the alpha detection, whereas nonnuclear materials mainly produce single events, or pairs due to (n,2n) and (n,n'γ) reactions. To study the performances of an industrial cargo container inspection system, Monte Carlo simulations are performed with the MCNP-PoliMi transport code, which records for each neutron history the relevant information: reaction types, position and time of interactions, energy deposits, secondary particles, etc. The output files are post-processed with a specific tool developed with ROOT data analysis software. Particles not correlated with an alpha particle (random background), counting statistics, and time-energy resolutions of the data acquisition system are taken into account in the numerical model. Various matrix compositions, suspicious items, SNM shielding and positions inside the container, are simulated to assess the performances and limitations of an industrial system.

METHOD AND APPARATUS FOR IMPROVING PERFORMANCE OF A FAST REACTOR

DOEpatents

Koch, L.J.

1959-01-20

A specific arrangement of the fertile material and fissionable material in the active portion of a fast reactor to achieve improvement in performance and to effectively lower the operating temperatures in the center of the reactor is described. According to this invention a group of fuel elements containing fissionable material are assembled to form a hollow fuel core. Elements containing a fertile material, such as depleted uranium, are inserted into the interior of the fuel core to form a central blanket. Additional elemenis of fertile material are arranged about the fuel core to form outer blankets which in tunn are surrounded by a reflector. This arrangement of fuel core and blankets results in substantial flattening of the flux pattern.

PRODUCTION OF PURIFIED URANIUM

DOEpatents

Burris, L. Jr.; Knighton, J.B.; Feder, H.M.

1960-01-26

A pyrometallurgical method for processing nuclear reactor fuel elements containing uranium and fission products and for reducing uranium compound; to metallic uranium is reported. If the material proccssed is essentially metallic uranium, it is dissolved in zinc, the sulution is cooled to crystallize UZn/sub 9/ , and the UZn/sub 9/ is distilled to obtain uranium free of fission products. If the material processed is a uranium compound, the sollvent is an alloy of zinc and magnesium and the remaining steps are the same.

Galactic cosmic ray abundances and spectra behind defined shielding.

PubMed

Heinrich, W; Benton, E V; Wiegel, B; Zens, R; Rusch, G

1994-10-01

LET spectra have been measured for lunar missions and for several near Earth orbits ranging from 28 degrees to 83 degrees inclination. In some of the experiments the flux of GCR was determined separately from contributions caused by interactions in the detector material. Results of these experiments are compared to model calculations. The general agreement justifies the use of the model to calculate GCR fluxes. The magnitude of variations caused by solar modulation, geomagnetic shielding, and shielding by matter determined from calculated LET spectra is generally in agreement with experimental data. However, more detailed investigations show that there are some weak points in modeling solar modulation and shielding by material. These points are discussed in more detail.

NEUTRONIC REACTOR SHIELDING

DOEpatents

Borst, L.B.

1961-07-11

A special hydrogenous concrete shielding for reactors is described. In addition to Portland cement and water, the concrete essentially comprises 30 to 60% by weight barytes aggregate for enhanced attenuation of fast neutrons. The biological shields of AEC's Oak Ridge Graphite Reactor and Materials Testing Reactor are particular embodiments.

Hobel stripper for shielded and unshielded flat conductor cable

NASA Technical Reports Server (NTRS)

Angele, W.

1971-01-01

Stripping tool exposes an area of shield for grounding purposes without removing an area of insulation between terminated shield and exposed conductors. Tool does not require heated blade and is capable of removing small portions of material at a time, to any depth.

Shielding Development for Nuclear Thermal Propulsion

NASA Technical Reports Server (NTRS)

Caffrey, Jarvis A.; Gomez, Carlos F.; Scharber, Luke L.

2015-01-01

Radiation shielding analysis and development for the Nuclear Cryogenic Propulsion Stage (NCPS) effort is currently in progress and preliminary results have enabled consideration for critical interfaces in the reactor and propulsion stage systems. Early analyses have highlighted a number of engineering constraints, challenges, and possible mitigating solutions. Performance constraints include permissible crew dose rates (shared with expected cosmic ray dose), radiation heating flux into cryogenic propellant, and material radiation damage in critical components. Design strategies in staging can serve to reduce radiation scatter and enhance the effectiveness of inherent shielding within the spacecraft while minimizing the required mass of shielding in the reactor system. Within the reactor system, shield design is further constrained by the need for active cooling with minimal radiation streaming through flow channels. Material selection and thermal design must maximize the reliability of the shield to survive the extreme environment through a long duration mission with multiple engine restarts. A discussion of these challenges and relevant design strategies are provided for the mitigation of radiation in nuclear thermal propulsion.

Shield fields: Concentrations of small volcanic edifices on Venus

NASA Technical Reports Server (NTRS)

Aubele, J. C.; Crumpler, L. S.

1992-01-01

Pre-Magellan analysis of the Venera 15/16 data indicated the existence of abundant small volcanic edifices, each less than or equal to 20 km diameter, interpreted to be predominantly shield volcanoes and occurring throughout the plains terrain, most common in equidimensional clusters. With the analysis of Magellan data, these clusters of greater than average concentration of small volcanic edifices have been called 'shield fields'. Although individual small shields can and do occur almost everywhere on the plains terrain of Venus, they most commonly occur in fields that are well-defined, predominantly equant, clusters of edifices. Major questions include why the edifices are concentrated in this way, how they relate to the source of the eruptive material, and what the possible relationship of shield fields to plains terrain is. There are three possible models for the origin of fields and small shields: (1) a field represents an 'island' of higher topography subsequently surrounded by later plains material; and (2) a field represents the area of magma reservoir.

Structural materials issues for the next generation fission reactors

NASA Astrophysics Data System (ADS)

Chant, I.; Murty, K. L.

2010-09-01

Generation-IV reactor design concepts envisioned thus far cater to a common goal of providing safer, longer lasting, proliferation-resistant, and economically viable nuclear power plants. The foremost consideration in the successful development and deployment of Gen-W reactor systems is the performance and reliability issues involving structural materials for both in-core and out-of-core applications. The structural materials need to endure much higher temperatures, higher neutron doses, and extremely corrosive environments, which are beyond the experience of the current nuclear power plants. Materials under active consideration for use in different reactor components include various ferritic/martensitic steels, austenitic stainless steels, nickel-base superalloys, ceramics, composites, etc. This article addresses the material requirements for these advanced fission reactor types, specifically addressing structural materials issues depending on the specific application areas.

A preliminary study to metaheuristic approach in multilayer radiation shielding optimization

NASA Astrophysics Data System (ADS)

Arif Sazali, Muhammad; Rashid, Nahrul Khair Alang Md; Hamzah, Khaidzir

2018-01-01

Metaheuristics are high-level algorithmic concepts that can be used to develop heuristic optimization algorithms. One of their applications is to find optimal or near optimal solutions to combinatorial optimization problems (COPs) such as scheduling, vehicle routing, and timetabling. Combinatorial optimization deals with finding optimal combinations or permutations in a given set of problem components when exhaustive search is not feasible. A radiation shield made of several layers of different materials can be regarded as a COP. The time taken to optimize the shield may be too high when several parameters are involved such as the number of materials, the thickness of layers, and the arrangement of materials. Metaheuristics can be applied to reduce the optimization time, trading guaranteed optimal solutions for near-optimal solutions in comparably short amount of time. The application of metaheuristics for radiation shield optimization is lacking. In this paper, we present a review on the suitability of using metaheuristics in multilayer shielding design, specifically the genetic algorithm and ant colony optimization algorithm (ACO). We would also like to propose an optimization model based on the ACO method.

Tokamak DEMO-FNS: Concept of magnet system and vacuum chamber

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

Azizov, E. A., E-mail: Azizov-EA@nrcki.ru; Ananyev, S. S.; Belyakov, V. A.

The level of knowledge accumulated to date in the physics and technologies of controlled thermonuclear fusion (CTF) makes it possible to begin designing fusion—fission hybrid systems that would involve a fusion neutron source (FNS) and which would admit employment for the production of fissile materials and for the transmutation of spent nuclear fuel. Modern Russian strategies for CTF development plan the construction to 2023 of tokamak-based demonstration hybrid FNS for implementing steady-state plasma burning, testing hybrid blankets, and evolving nuclear technologies. Work on designing the DEMO-FNS facility is still in its infancy. The Efremov Institute began designing its magnet systemmore » and vacuum chamber, while the Kurchatov Institute developed plasma-physics design aspects and determined basic parameters of the facility. The major radius of the plasma in the DEMO-FNS facility is R = 2.75 m, while its minor radius is a = 1 m; the plasma elongation is k{sub 95} = 2. The fusion power is P{sub FUS} = 40 MW. The toroidal magnetic field on the plasma-filament axis is B{sub t0} = 5 T. The plasma current is I{sub p} = 5 MA. The application of superconductors in the magnet system permits drastically reducing the power consumed by its magnets but requires arranging a thick radiation shield between the plasma and magnet system. The central solenoid, toroidal-field coils, and poloidal-field coils are manufactured from, respectively, Nb{sub 3}Sn, NbTi and Nb{sub 3}Sn, and NbTi. The vacuum chamber is a double-wall vessel. The space between the walls manufactured from 316L austenitic steel is filled with an iron—water radiation shield (70% of stainless steel and 30% of water).« less

A Radiation Shielding Code for Spacecraft and Its Validation

NASA Technical Reports Server (NTRS)

Shinn, J. L.; Cucinotta, F. A.; Singleterry, R. C.; Wilson, J. W.; Badavi, F. F.; Badhwar, G. D.; Miller, J.; Zeitlin, C.; Heilbronn, L.; Tripathi, R. K.

2000-01-01

The HZETRN code, which uses a deterministic approach pioneered at NASA Langley Research Center, has been developed over the past decade to evaluate the local radiation fields within sensitive materials (electronic devices and human tissue) on spacecraft in the space environment. The code describes the interactions of shield materials with the incident galactic cosmic rays, trapped protons, or energetic protons from solar particle events in free space and low Earth orbit. The content of incident radiations is modified by atomic and nuclear reactions with the spacecraft and radiation shield materials. High-energy heavy ions are fragmented into less massive reaction products, and reaction products are produced by direct knockout of shield constituents or from de-excitation products. An overview of the computational procedures and database which describe these interactions is given. Validation of the code with recent Monte Carlo benchmarks, and laboratory and flight measurement is also included.

HZE reactions and data-base development

NASA Technical Reports Server (NTRS)

Townsend, Lawrence W.; Cucinotta, Francis A.; Wilson, John W.

1993-01-01

The primary cosmic rays are dispersed over a large range of linear energy transfer (LET) values and their distribution over LET is a determinant of biological response. This LET distribution is modified by radiation shielding thickness and shield material composition. The current uncertainties in nuclear cross sections will not allow the composition of the shield material to be distinguished in order to minimize biological risk. An overview of the development of quantum mechanical models of heavy ion reactions will be given and computational results compared with experiments. A second approach is the development of phenomenological models from semi-classical considerations. These models provide the current data base in high charge and energy (HZE) shielding studies. They will be compared with available experimental data. The background material for this lecture will be available as a review document of over 30 years of research at Langley but will include new results obtained over the last year.

Effective shielding to measure beam current from an ion source

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

Bayle, H., E-mail: bayle@bergoz.com; Delferrière, O.; Gobin, R.

To avoid saturation, beam current transformers must be shielded from solenoid, quad, and RFQ high stray fields. Good understanding of field distribution, shielding materials, and techniques is required. Space availability imposes compact shields along the beam pipe. This paper describes compact effective concatenated magnetic shields for IFMIF-EVEDA LIPAc LEBT and MEBT and for FAIR Proton Linac injector. They protect the ACCT Current Transformers beyond 37 mT radial external fields. Measurements made at Saclay on the SILHI source are presented.

Apparatus and method for the simultaneous detection of neutrons and ionizing electromagnetic radiation

DOEpatents

Bell, Zane W.

2000-01-01

A sensor for simultaneously detecting neutrons and ionizing electromagnetic radiation comprising: a sensor for the detection of gamma radiation, the sensor defining a sensing head; the sensor further defining an output end in communication with the sensing head; and an exterior neutron-sensitive material configured to form around the sensing head; wherein the neutron-sensitive material, subsequent to the capture of the neutron, fissions into an alpha-particle and a .sup.7 Li ion that is in a first excited state in a majority of the fissions, the first excited state decaying via the emission of a single gamma ray at 478 keV which can in turn be detected by the sensing head; and wherein the sensing head can also detect the ionizing electromagnetic radiation from an incident radiation field without significant interference from the neutron-sensitive material. A method for simultaneously detecting neutrons and ionizing electromagnetic radiation comprising the steps of: providing a gamma ray sensitive detector comprising a sensing head and an output end; conforming an exterior neutron-sensitive material configured to form around the sensing head of the detector; capturing neutrons by the sensing head causing the neutron-sensitive material to fission into an alpha-particle and a .sup.7 Li ion that is in a first excited state in a majority of the fissions, the state decaying via the emission of a single gamma ray at 478 keV; sensing gamma rays entering the detector through the neutron-sensitive material; and producing an output through a readout device coupled to the output end; wherein the detector provides an output which is proportional to the energy of the absorbed ionizing electromagnetic radiation.

Initial Back-to-Back Fission Chamber Testing in ATRC

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

Benjamin Chase; Troy Unruh; Joy Rempe

2014-06-01

Development and testing of in-pile, real-time neutron sensors for use in Materials Test Reactor experiments is an ongoing project at Idaho National Laboratory. The Advanced Test Reactor National Scientific User Facility has sponsored a series of projects to evaluate neutron detector options in the Advanced Test Reactor Critical Facility (ATRC). Special hardware was designed and fabricated to enable testing of the detectors in the ATRC. Initial testing of Self-Powered Neutron Detectors and miniature fission chambers produced promising results. Follow-on testing required more experiment hardware to be developed. The follow-on testing used a Back-to-Back fission chamber with the intent to providemore » calibration data, and a means of measuring spectral indices. As indicated within this document, this is the first time in decades that BTB fission chambers have been used in INL facilities. Results from these fission chamber measurements provide a baseline reference for future measurements with Back-to-Back fission chambers.« less

High wettability of liquid caesium iodine with solid uranium dioxide.

PubMed

Kurosaki, Ken; Suzuki, Masanori; Uno, Masayoshi; Ishii, Hiroto; Kumagai, Masaya; Anada, Keito; Murakami, Yukihiro; Ohishi, Yuji; Muta, Hiroaki; Tanaka, Toshihiro; Yamanaka, Shinsuke

2017-09-13

In March 2011, the Fukushima Daiichi Nuclear Power Plant accident caused nuclear fuel to melt and the release of high-volatility fission products into the environment. Caesium and iodine caused environmental contamination and public exposure. Certain fission-product behaviours remain unclear. We found experimentally that liquid CsI disperses extremely favourably toward solid UO 2 , exhibiting a contact angle approaching zero. We further observed the presence of CsI several tens of micrometres below the surface of the solid UO 2 sample, which would be caused by the infiltration of pores network by liquid CsI. Thus, volatile fission products released from molten nuclear fuels with complex internal composition and external structure migrate or evaporate to varying extents, depending on the nature of the solid-liquid interface and the fuel material surface, which becomes the pathway for the released fission products. Introducing the concept of the wettability of liquid chemical species of fission products in contact with solid fuels enabled developing accurate behavioural assessments of volatile fission products released by nuclear fuel.

Method and device for fabricating dispersion fuel comprising fission product collection spaces

DOEpatents

Shaber, Eric L; Fielding, Randall S

2015-05-05

A method of fabricating a nuclear fuel comprising a fissile material, one or more hollow microballoons, a phenolic resin, and metal matrix. The fissile material, phenolic resin and the one or more hollow microballoons are combined. The combined fissile material, phenolic resin and the hollow microballoons are heated sufficiently to form at least some fissile material carbides creating a nuclear fuel particle. The resulting nuclear fuel particle comprises one or more fission product collection spaces. In a preferred embodiment, the fissile material, phenolic resin and the one or more hollow microballoons are combined by forming the fissile material into microspheres. The fissile material microspheres are then overcoated with the phenolic resin and microballoon. In another preferred embodiment, the fissile material, phenolic resin and the one or more hollow microballoons are combined by overcoating the microballoon with the fissile material, and phenolic resin.

Lightweight blast shield

DOEpatents

Mixon, Larry C.; Snyder, George W.; Hill, Scott D.; Johnson, Gregory L.; Wlodarski, J. Frank; von Spakovsky, Alexis P.; Emerson, John D.; Cole, James M.; Tipton, John P.

1991-01-01

A tandem warhead missile arrangement that has a composite material housing structure with a first warhead mounted at one end and a second warhead mounted near another end of the composite structure with a dome shaped composite material blast shield mounted between the warheads to protect the second warhead from the blast of the first warhead.

Novel shielding materials for space and air travel.

PubMed

Vana, N; Hajek, M; Berger, T; Fugger, M; Hofmann, P

2006-01-01

The reduction of dose onboard spacecraft and aircraft by appropriate shielding measures plays an essential role in the future development of space exploration and air travel. The design of novel shielding strategies and materials may involve hydrogenous composites, as it is well known that liquid hydrogen is most effective in attenuating charged particle radiation. As precursor for a later flight experiment, the shielding properties of newly developed hydrogen-rich polymers and rare earth-doped high-density rubber were tested in various ground-based neutron and heavy ion fields and compared with aluminium and polyethylene as reference materials. Absorbed dose, average linear energy transfer and gamma-equivalent neutron absorbed dose were determined by means of LiF:Mg,Ti thermoluminescence dosemeters and CR-39 plastic nuclear track detectors. First results for samples of equal aerial density indicate that selected hydrogen-rich plastics and rare-earth-doped rubber may be more effective in attenuating cosmic rays by up to 10% compared with conventional aluminium shielding. The appropriate adaptation of shielding thicknesses may thus allow reducing the biologically relevant dose. Owing to the lower density of the plastic composites, mass savings shall result in a significant reduction of launch costs. The experiment was flown as part of the European Space Agency's Biopan-5 mission in May 2005.

SCALE Code System

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

Jessee, Matthew Anderson

The SCALE Code System is a widely-used modeling and simulation suite for nuclear safety analysis and design that is developed, maintained, tested, and managed by the Reactor and Nuclear Systems Division (RNSD) of Oak Ridge National Laboratory (ORNL). SCALE provides a comprehensive, verified and validated, user-friendly tool set for criticality safety, reactor and lattice physics, radiation shielding, spent fuel and radioactive source term characterization, and sensitivity and uncertainty analysis. Since 1980, regulators, licensees, and research institutions around the world have used SCALE for safety analysis and design. SCALE provides an integrated framework with dozens of computational modules including three deterministicmore » and three Monte Carlo radiation transport solvers that are selected based on the desired solution strategy. SCALE includes current nuclear data libraries and problem-dependent processing tools for continuous-energy (CE) and multigroup (MG) neutronics and coupled neutron-gamma calculations, as well as activation, depletion, and decay calculations. SCALE includes unique capabilities for automated variance reduction for shielding calculations, as well as sensitivity and uncertainty analysis. SCALE’s graphical user interfaces assist with accurate system modeling, visualization of nuclear data, and convenient access to desired results.SCALE 6.2 provides many new capabilities and significant improvements of existing features.New capabilities include:• ENDF/B-VII.1 nuclear data libraries CE and MG with enhanced group structures,• Neutron covariance data based on ENDF/B-VII.1 and supplemented with ORNL data,• Covariance data for fission product yields and decay constants,• Stochastic uncertainty and correlation quantification for any SCALE sequence with Sampler,• Parallel calculations with KENO,• Problem-dependent temperature corrections for CE calculations,• CE shielding and criticality accident alarm system analysis with MAVRIC,• CE depletion with TRITON (T5-DEPL/T6-DEPL),• CE sensitivity/uncertainty analysis with TSUNAMI-3D,• Simplified and efficient LWR lattice physics with Polaris,• Large scale detailed spent fuel characterization with ORIGAMI and ORIGAMI Automator,• Advanced fission source convergence acceleration capabilities with Sourcerer,• Nuclear data library generation with AMPX, and• Integrated user interface with Fulcrum.Enhanced capabilities include:• Accurate and efficient CE Monte Carlo methods for eigenvalue and fixed source calculations,• Improved MG resonance self-shielding methodologies and data,• Resonance self-shielding with modernized and efficient XSProc integrated into most sequences,• Accelerated calculations with TRITON/NEWT (generally 4x faster than SCALE 6.1),• Spent fuel characterization with 1470 new reactor-specific libraries for ORIGEN,• Modernization of ORIGEN (Chebyshev Rational Approximation Method [CRAM] solver, API for high-performance depletion, new keyword input format)• Extension of the maximum mixture number to values well beyond the previous limit of 2147 to ~2 billion,• Nuclear data formats enabling the use of more than 999 energy groups,• Updated standard composition library to provide more accurate use of natural abundances, andvi• Numerous other enhancements for improved usability and stability.« less

Process for making RF shielded cable connector assemblies and the products formed thereby

NASA Technical Reports Server (NTRS)

Fisher, A.; Clatterbuck, C. H. (Inventor)

1973-01-01

A process for making RF shielded cable connector assemblies and the resulting structures is described. The process basically consists of potting wires of a shielded cable between the cable shield and a connector housing to fill in, support, regidize, and insulate the individual wires contained in the cable. The formed potting is coated with an electrically conductive material so as to form an entirely encompassing adhering conductive path between the cable shield and the metallic connector housing. A protective jacket is thereby formed over the conductive coating between the cable shield and the connector housing.

Vacuum Ultraviolet Radiation and Atomic Oxygen Durability Evaluation of HST Bi-Stem Thermal Shield Materials

NASA Technical Reports Server (NTRS)

Dever, Joyce; deGroh, Kim K.

2002-01-01

Bellows-type thermal shields were used on the bi-stems of replacement solar arrays installed on the Hubble Space Telescope (HST) during the first HST servicing mission (SMI) in December 1993. These thermal shields helped reduce the problem of thermal gradient- induced jitter observed with the original HST solar arrays during orbital thermal cycling and have been in use on HST for eight years. This paper describes ground testing of the candidate solar array bi-stem thermal shield materials including backside aluminized Teflon(R)FEP (fluorinated ethylene propylene) with and without atomic oxygen (AO) and ultraviolet radiation protective surface coatings for durability to AO and combined AO and vacuum ultraviolet (VOV) radiation. NASA Glenn Research Center (GRC) conducted VUV and AO exposures of samples of candidate thermal shield materials at HST operational temperatures and pre- and post-exposure analyses as part of an overall program coordinated by NASA Goddard Space Flight Center (GSFC) to determine the on-orbit durability of these materials. Coating adhesion problems were observed for samples having the AO- and combined AO/UV-protective coatings. Coating lamination occurred with rapid thermal cycling testing which simulated orbital thermal cycling. This lack of adhesion caused production of coating flakes from the material that would have posed a serious risk to HST optics if the coated materials were used for the bi-stem thermal shields. No serious degradation was observed for the uncoated aluminized Teflon(R) as evaluated by optical microscopy, although atomic force microscopy (AFM) microhardness testing revealed that an embrittled surface layer formed on the uncoated Teflon(R) surface due to vacuum ultraviolet radiation exposure. This embrittled layer was not completely removed by AO erosion, No cracks or particle flakes were produced for the embrittled uncoated material upon exposure to VUV and AO at operational temperatures to an equivalent exposure of approximately five years in the HST environment. Uncoated aluminized FEP Teflon(R) was determined to be the most appropriate thermal shield material and was used on the bi-stems of replacement solar arrays installed on HST during SMI in December 1993. The SMI -installed solar arrays air scheduled to be replaced during MST's fourth servicing mission (SM3B) in early 2002.

Spectral tailoring device

DOEpatents

Brager, H.R.; Schenter, R.E.; Carter, L.L.; Karnesky, R.A.

1987-08-05

A spectral tailoring device for altering the neutron energy spectra and flux of neutrons in a fast reactor thereby selectively to enhance or inhibit the transmutation rate of a target metrical to form a product isotope. Neutron moderators, neutron filters, neutron absorbers and neutron reflectors may be used as spectral tailoring devices. Depending on the intended use for the device, a member from each of these four classes of materials could be used singularly, or in combination, to provide a preferred neutron energy spectra and flux of the neutrons in the region of the target material. In one embodiment of the invention, an assembly is provided for enhancing the production of isotopes, such as cobalt 60 and gadolinium 153. In another embodiment of the invention, a spectral tailoring device is disposed adjacent a target material which comprises long lived or volatile fission products and the device is used to shift the neutron energy spectra and flux of neutrons in the region of the fission products to preferentially transmute them to produce a less volatile fission product inventory. 6 figs.

Carbon Nanotube-Multilayered Graphene Edge Plane Core-Shell Hybrid Foams for Ultrahigh-Performance Electromagnetic-Interference Shielding.

PubMed

Song, Qiang; Ye, Fang; Yin, Xiaowei; Li, Wei; Li, Hejun; Liu, Yongsheng; Li, Kezhi; Xie, Keyu; Li, Xuanhua; Fu, Qiangang; Cheng, Laifei; Zhang, Litong; Wei, Bingqing

2017-08-01

Materials with an ultralow density and ultrahigh electromagnetic-interference (EMI)-shielding performance are highly desirable in fields of aerospace, portable electronics, and so on. Theoretical work predicts that 3D carbon nanotube (CNT)/graphene hybrids are one of the most promising lightweight EMI shielding materials, owing to their unique nanostructures and extraordinary electronic properties. Herein, for the first time, a lightweight, flexible, and conductive CNT-multilayered graphene edge plane (MLGEP) core-shell hybrid foam is fabricated using chemical vapor deposition. MLGEPs are seamlessly grown on the CNTs, and the hybrid foam exhibits excellent EMI shielding effectiveness which exceeds 38.4 or 47.5 dB in X-band at 1.6 mm, while the density is merely 0.0058 or 0.0089 g cm -3 , respectively, which far surpasses the best values of reported carbon-based composite materials. The grafted MLGEPs on CNTs can obviously enhance the penetration losses of microwaves in foams, leading to a greatly improved EMI shielding performance. In addition, the CNT-MLGEP hybrids also exhibit a great potential as nano-reinforcements for fabricating high-strength polymer-based composites. The results provide an alternative approach to fully explore the potentials of CNT and graphene, for developing advanced multifunctional materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of Multifunctional Radiation Shielding Materials for Long Duration Human Exploration Beyond the Low Earth Orbit

NASA Technical Reports Server (NTRS)

Sen, S.; Bhattacharya, M.; Schofield, E.; Carranza, S.; O'Dell, S.

2007-01-01

One of the major challenges for long duration human exploration beyond the low Earth orbit and sustained human presence on planetary surfaces would be development of materials that would help minimize the radiation exposure to crew and equipment from the interplanetary radiation environment, This radiation environment consists primarily of a continuous flux of galactic cosmic rays (GCR) and transient but intense fluxes of solar energetic particles (SEP). The potential for biological damage by the relatively low percentage of high-energy heavy-ions in the GCR spectrum far outweigh that due to lighter particles because of their ionizing-power and the quality of the resulting biological damage. Although the SEP spectrum does not contain heavy ions and their energy range is much lower than that for GCRs, they however pose serious risks to astronaut health particularly in the event of a bad solar storm The primary purpose of this paper is to discuss our recent efforts in development and evaluation of materials for minimizing the hazards from the interplanetary radiation environment. Traditionally, addition of shielding materials to spacecrafts has invariably resulted in paying a penalty in terms of additional weight. It would therefore be of great benefit if materials could be developed not only with superior shielding effectiveness but also sufficient structural integrity. Such a multifunctional material could then be considered as an integral part of spacecraft structures. Any proposed radiation shielding material for use in outer space should be composed of nuclei that maximize the likelihood of projectile fragmentation while producing the minimum number of target fragments. A modeling based approach will be presented to show that composite materials using hydrogen-rich epoxy matrices reinforced with polyethylene fibers and/or fabrics could effectively meet this requirement. This paper will discuss the fabrication of such a material for a crewed vehicle. Ln addition, the capability of synthesizing radiation shielding materials for habitat structures primarily from Lunar or Martian in-situ resources will also be presented. Such an approach would significantly _reduce the cost associated with transportation of such materials and structures from earth. Results from radiation exposure measurements will be presented demonstrating the shielding effectiveness of the developed materials. Mechanical testing data will be discussed to illustrate that the specific mechanical properties of the developed composites are comparable to structural aluminum based alloys currently used for the space shuttle and space station.

Design of cemented tungsten carbide and boride-containing shields for a fusion power plant

NASA Astrophysics Data System (ADS)

Windsor, C. G.; Marshall, J. M.; Morgan, J. G.; Fair, J.; Smith, G. D. W.; Rajczyk-Wryk, A.; Tarragó, J. M.

2018-07-01

Results are reported on cemented tungsten carbide (cWC) and boride-containing composite materials for the task of shielding the centre column of a superconducting tokamak power plant. The shield is based on five concentric annular shells consisting of cWC and water layers of which the innermost cWC shield can be replaced with boride composites. Sample materials have been fabricated changing the parameters of porosity P, binder alloy fraction f binder and boron weight fraction f boron. For the fabricated materials, and other hypothetical samples with chosen parameters, Monte Carlo studies are made of: (i) the power deposition into the superconducting core, (ii) the fast neutron and gamma fluxes and (iii) the attenuation coefficients through the shield for the deposited power and neutron and gamma fluxes. It is shown that conventional Co-based cWC binder alloy can be replaced with a Fe–Cr alloy (92 wt.% Fe, 8 wt.% Cr), which has lower activation than cobalt with minor changes in shield performance. Boride-based composite materials have been prepared and shown to give a significant reduction in power deposition and flux, when placed close to the superconducting core. A typical shield of cemented tungsten carbide with 10 wt.% of Fe–8Cr binder and 0.1% porosity has a power reduction half-length of 0.06 m. It is shown that the power deposition increases by 4.3% for every 1% additional porosity, and 1.7% for every 1 wt.% additional binder. Power deposition decreased by 26% for an initial 1 wt.% boron addition, but further increases in f boron showed only a marginal decrease. The dependences of power deposited in the core, the maximum neutron and gamma fluxes on the core surface, and the half attenuation distances through the shield have been fitted to within a fractional percentage error by analytic functions of the porosity, metallic binder alloy and boron weight fractions.

Measurements and FLUKA Simulations of Bismuth, Aluminium and Indium Activation at the upgraded CERN Shielding Benchmark Facility (CSBF)

NASA Astrophysics Data System (ADS)

Iliopoulou, E.; Bamidis, P.; Brugger, M.; Froeschl, R.; Infantino, A.; Kajimoto, T.; Nakao, N.; Roesler, S.; Sanami, T.; Siountas, A.; Yashima, H.

2018-06-01

The CERN High energy AcceleRator Mixed field (CHARM) facility is situated in the CERN Proton Synchrotron (PS) East Experimental Area. The facility receives a pulsed proton beam from the CERN PS with a beam momentum of 24 GeV/c with 5·1011 protons per pulse with a pulse length of 350 ms and with a maximum average beam intensity of 6.7·1010 protons per second. The extracted proton beam impacts on a cylindrical copper target. The shielding of the CHARM facility includes the CERN Shielding Benchmark Facility (CSBF) situated laterally above the target that allows deep shielding penetration benchmark studies of various shielding materials. This facility has been significantly upgraded during the extended technical stop at the beginning of 2016. It consists now of 40 cm of cast iron shielding, a 200 cm long removable sample holder concrete block with 3 inserts for activation samples, a material test location that is used for the measurement of the attenuation length for different shielding materials as well as for sample activation at different thicknesses of the shielding materials. Activation samples of bismuth, aluminium and indium were placed in the CSBF in September 2016 to characterize the upgraded version of the CSBF. Monte Carlo simulations with the FLUKA code have been performed to estimate the specific production yields of bismuth isotopes (206 Bi, 205 Bi, 204 Bi, 203 Bi, 202 Bi, 201 Bi) from 209 Bi, 24 Na from 27 Al and 115 m I from 115 I for these samples. The production yields estimated by FLUKA Monte Carlo simulations are compared to the production yields obtained from γ-spectroscopy measurements of the samples taking the beam intensity profile into account. The agreement between FLUKA predictions and γ-spectroscopy measurements for the production yields is at a level of a factor of 2.

Combined Photoneutron And X Ray Interrogation Of Containers For Nuclear Materials

NASA Astrophysics Data System (ADS)

Gozani, Tsahi; Shaw, Timothy; King, Michael J.; Stevenson, John; Elsalim, Mashal; Brown, Craig; Condron, Cathie

2011-06-01

Effective cargo inspection systems for nuclear material detection require good penetration by the interrogating radiation, generation of a sufficient number of fissions, and strong and penetrating detection signatures. Inspection systems need also to be sensitive over a wide range of cargo types and densities encountered in daily commerce. Thus they need to be effective with highly hydrogenous cargo, where neutron attenuation is a major limitation, as well as with dense metallic cargo, where x-ray penetration is low. A system that interrogates cargo with both neutrons and x-rays can, in principle, achieve high performance over the widest range of cargos. Moreover, utilizing strong prompt-neutron (˜3 per fission) and delayed-gamma ray (˜7 per fission) signatures further strengthens the detection sensitivity across all cargo types. The complementary nature of x-rays and neutrons, used as both probing radiation and detection signatures, alleviates the need to employ exceedingly strong sources, which would otherwise be required to achieve adequate performance across all cargo types, if only one type of radiation probe were employed. A system based on the above principles, employing a commercially-available 9 MV linac was developed and designed. Neutrons are produced simultaneously with x-rays by the photonuclear interaction of the x-ray beam with a suitable converter. A total neutron yield on the order of 1011 n/s is achieved with an average electron beam current of 100 μA. If fissionable material is present, fissions are produced both by the high-energy x-ray beam and by the photoneutrons. Photofission and neutron fission dominate in hydrogenous and metallic cargos, respectively. Neutron-capture gamma rays provide information on the cargo composition. The prompt neutrons resulting from fission are detected by two independent detector systems: by very efficient Differential Die Away Analysis (DDAA) detectors, and by direct detection of neutrons with energies higher than 3 MeV using a recently developed fluorine-based threshold activation detector (TAD). The delayed gamma-ray signals are measured with high efficiency with the same TAD and with additional lower-cost plastic scintillators.

Radiation Exposure Effects and Shielding Analysis of Carbon Nanotube Materials

NASA Technical Reports Server (NTRS)

Wilkins, Richard; Armendariz, Lupita (Technical Monitor)

2002-01-01

Carbon nanotube materials promise to be the basis for a variety of emerging technologies with aerospace applications. Potential applications to human space flight include spacecraft shielding, hydrogen storage, structures and fixtures and nano-electronics. Appropriate risk analysis on the properties of nanotube materials is essential for future mission safety. Along with other environmental hazards, materials used in space flight encounter a hostile radiation environment for all mission profiles, from low earth orbit to interplanetary space.

Effect on de-greasing solvents on conductive separable connector shields and semiconductive cable shields

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

Perry, D.D.; Bolcar, J.P.

1990-04-01

A study has been conducted to determine the effects of commercial degreasing solvents on the conductivity of an EPDM separable connector shield and two types of cable shields based on EPR and XLPE, respectively. Solvents tested included a chlorinated solvent based on 1,1,1-trichloroethane and several so-called citrus solvents consisting of the natural terpene, limonene, or blends of limonene with other hydrocarbons. All the solvents significantly degraded the conductivity of the EPR and EPDM materials, but had little effect on the XLPE cable shield. The solvents differed, however, in the extent of their effects, the rate of recovery of conductivity aftermore » removal of the solvent, and the degree to which the original conductivity of the material was restored. The consequences of these results in terms of appropriate field use of these types of solvents by utility personnel are discussed.« less

Personnel Dose Assessment during Active Interrogation

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

Miller, Thomas Martin; Akkurt, Hatice; Patton, Bruce W

A leading candidate in the detection of special nuclear material (SNM) is active interrogation (AI). Unlike passive interrogation, AI uses a source to enhance or create a detectable signal from SNM (usually fission), particularly in shielded scenarios or scenarios where the SNM has a low activity. The use of AI thus makes the detection of SNM easier or, in some scenarios, even enables previously impossible detection. During the development of AI sources, significant effort is put into determining the source strength required to detect SNM in specific scenarios. Usually during this process, but not always, an evaluation of personnel dosemore » is also completed. In this instance personnel dose could involve any of the following: (1) personnel performing the AI; (2) unknown stowaways who are inside the object being interrogated; or (3) in clandestine interrogations, personnel who are known to be inside the object being interrogated but are unaware of the interrogation. In most instances, dose to anyone found smuggling SNM will be a secondary issue. However, for the organizations performing the AI, legal if not moral considerations should make dose to the personnel performing the AI, unknown stowaways, or innocent bystanders in clandestine interrogations a serious concern.« less

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

None, None

This report is concerned with the nature and scope of the technical services to be rendered and the general plan proposed for operation of Building 3525, High Radiation Level Examination Laboratory (HRLEL). The role of postirradiation examination in implementing the over- all task of irradiation testing for various programs under way at the Oak Ridge National Laboratory (ORNL) and the importance of this effort to the United Stat es reactor development program are stressed . The shielded-cell complex with provisions for remote decontamination, hot-equipment storage, and maintenance is described, as well as other supporting activities which are incorporated into themore » facility. The proposed technical functions include general observation, mensuration, nondestructive testing, burnup and induced-activity measurements, fission-gas sampling and analysis, corrosion evaluation and related measurements, disassembly and cutup, metallographic examination, mechanical-property determinations , and x -ray diffraction analyses. Equipment design and operational features to improve detection and measurement of selected properties in radioactive material s are described, also. The current status on design, procurement, construction, and preoperational testing of in- cell equipment in the mockup is presented along with a forecast of future needs. The mode of operation, manpower requirements, and management of the facility are discussed.« less

Radiation Transport Properties of Polyethylene-Fiber Composites

NASA Technical Reports Server (NTRS)

Kaul, Raj K.; Barghouty, A. F.; Dahche, H. M.

2003-01-01

Composite materials that can both serve as effective shielding materials against cosmic-ray and energetic solar particles in deep space as well as structural materials for habitat and spacecraft remain a critical and mission enabling piece in mission planning and exploration. Polyethylene is known to have excellent shielding properties due to its low density coupled with high hydrogen content. Polyethylene fiber reinforced composites promise to combine this shielding effectiveness with the required mechanical properties of structural materials. Samples of Polyethylene-fiber reinforced epoxy matrix composite 1-5 cm thick were prepared at NASA's Marshall Space Flight Center and tested against 500 MeV/nucleon Fe beam at the HIMAC facility of NIRS in Chiba, Japan. This paper presents measured and calculated results for the radiation transport properties of these samples.

Space radiation transport properties of polyethylene-based composites.

PubMed

Kaul, R K; Barghouty, A F; Dahche, H M

2004-11-01

Composite materials that can serve as both effective shielding materials against cosmic-ray and energetic solar particles in deep space, as well as structural materials for habitat and spacecraft, remain a critical and mission enabling component in mission planning and exploration. Polyethylene is known to have excellent shielding properties due to its low density, coupled with high hydrogen content. Polyethylene-fiber reinforced composites promise to combine this shielding effectiveness with the required mechanical properties of structural materials. Samples of polyethylene-fiber reinforced epoxy matrix composite 1-5 cm thick were prepared at the NASA Marshall Space Flight Center and tested against a 500 MeV/nucleon Fe beam at the HIMAC facility of NIRS in Chiba, Japan. This paper presents measured and calculated results for the radiation transport properties of these samples.

Ground-based simulations of cosmic ray heavy ion interactions in spacecraft and planetary habitat shielding materials

NASA Technical Reports Server (NTRS)

Miller, J.; Zeitlin, C.; Heilbronn, L.; Borak, T.; Carter, T.; Frankel, K. A.; Fukumura, A.; Murakami, T.; Rademacher, S. E.; Schimmerling, W.;

Space radiation transport properties of polyethylene-based composites

NASA Technical Reports Server (NTRS)

Kaul, R. K.; Barghouty, A. F.; Dahche, H. M.

2004-01-01

Composite materials that can serve as both effective shielding materials against cosmic-ray and energetic solar particles in deep space, as well as structural materials for habitat and spacecraft, remain a critical and mission enabling component in mission planning and exploration. Polyethylene is known to have excellent shielding properties due to its low density, coupled with high hydrogen content. Polyethylene-fiber reinforced composites promise to combine this shielding effectiveness with the required mechanical properties of structural materials. Samples of polyethylene-fiber reinforced epoxy matrix composite 1-5 cm thick were prepared at the NASA Marshall Space Flight Center and tested against a 500 MeV/nucleon Fe beam at the HIMAC facility of NIRS in Chiba, Japan. This paper presents measured and calculated results for the radiation transport properties of these samples.

Research Activities in Fission Chamber Modeling in Support of the Nuclear Energy Industry

NASA Astrophysics Data System (ADS)

Jammes, C.; Filliatre, P.; Geslot, B.; Oriol, L.; Berhouet, F.; Villard, J.-F.; Vermeeren, L.

2010-12-01

Fission chambers are widely used in the nuclear industry. As an example, they play a major role in the control of any fission reactor and are thus regarded as a key component for ensuring their safety. They are also employed in the material testing reactors for monitoring irradiations. We have recently started a research program, the objective of which is to improve the performance of those neutron detectors in terms of lifetime, calibration, and online diagnosis. In this paper, we present several studies carried out in order to model the signal delivered by a fission chamber. First, the simulation of the deposit evolution allowed us to select the most appropriate fissile material for a given spectrum and fluence. Second, we studied the impact of the bias voltage and filling gas characteristics on the charge collection time. Finally, the simulation of a pulse signal prior to amplification showed how it is important to have a satisfactory knowledge of the energy for creating ion pairs to accurately assess the signal in current or Campbelling mode.

Determine Important Nuclear Fragmentation Processes for Space Radiation Protection in Human Space Explorations

NASA Technical Reports Server (NTRS)

Lin, Zi-wei

2004-01-01

Space radiation from cosmic ray particles is one of the main challenges for long-term human space explorations such as a permanent moon base or a trip to Mars. Material shielding may provide significant radiation protection to astronauts, and models have been developed in order to evaluate the effectiveness of different shielding materials and to predict radiation environment inside the spacecraft. In this study we determine the nuclear fragmentation cross sections which will most effect the radiation risk behind typical radiation shielding materials. These cross sections thus need more theoretical studies and accurate experimental measurements in order for us to more precisely predict the radiation risk in human space explorations.

Determine Important Nuclear Fragmentation Processes for Space Radiation Protection in Human Space Explorations

NASA Technical Reports Server (NTRS)

Lin, Zi-Wei

2004-01-01

Space radiation from cosmic ray particles is one of the main challenges for long-term human space explorations such as a permanent moon base or a trip to Mars. Material shielding may provide significant radiation protection to astronauts, and models have been developed in order to evaluate the effectiveness of different shielding materials and to predict radiation environment inside the spacecraft. In this study we determine the nuclear fragmentation cross sections which will most affect the radiation risk behind typical radiation shielding materials. These cross sections thus need more theoretical studies and accurate experimental measurements in order for us to more precisely predict the radiation risk in human space exploration.

Determine Important Nuclear Fragmentation Processes for Space Radiation Protection in Human Space Explorations

NASA Technical Reports Server (NTRS)

Lin, Zi-Wei

2004-01-01

Space radiation from cosmic ray particles is one of the main challenges for long-term human space explorations such as a permanent moon base or a trip to Mars. Material shielding may provide significant radiation protection to astronauts, and models have been developed in order to evaluate the effectiveness of different shielding materials and to predict radiation environment inside the spacecraft. In this study we determine the nuclear fragmentation cross sections which will most affect the radiation risk behind typical radiation shielding materials. These cross sections thus need more theoretical studies and accurate experimental measurements in order for us to more precisely predict the radiation risk in human space explorations.

Method for correcting for isotope burn-in effects in fission neutron dosimeters

DOEpatents

Gold, Raymond; McElroy, William N.

1988-01-01

A method is described for correcting for effect of isotope burn-in in fission neutron dosimeters. Two quantities are measured in order to quantify the "burn-in" contribution, namely P.sub.Z',A', the amount of (Z', A') isotope that is burned-in, and F.sub.Z', A', the fissions per unit volume produced in the (Z', A') isotope. To measure P.sub.Z', A', two solid state track recorder fission deposits are prepared from the very same material that comprises the fission neutron dosimeter, and the mass and mass density are measured. One of these deposits is exposed along with the fission neutron dosimeter, whereas the second deposit is subsequently used for observation of background. P.sub.Z', A' is then determined by conducting a second irradiation, wherein both the irradiated and unirradiated fission deposits are used in solid state track recorder dosimeters for observation of the absolute number of fissions per unit volume. The difference between the latter determines P.sub.Z', A' since the thermal neutron cross section is known. F.sub.Z', A' is obtained by using a fission neutron dosimeter for this specific isotope, which is exposed along with the original threshold fission neutron dosimeter to experience the same neutron flux-time history at the same location. In order to determine the fissions per unit volume produced in the isotope (Z', A') as it ingrows during the irradiation, B.sub.Z', A', from these observations, the neutron field must generally be either time independent or a separable function of time t and neutron energy E.

Glove box shield

DOEpatents

Brackenbush, L.W.; Hoenes, G.R.

A shield for a glove box housing radioactive material is comprised of spaced apart clamping members which maintain three overlapping flaps in place therebetween. There is a central flap and two side flaps, the side flaps overlapping at the interior edges thereof and the central flap extending past the intersection of the side flaps in order to insure that the shield is always closed when the user wthdraws his hand from the glove box. Lead loaded neoprene rubber is the preferred material for the three flaps, the extent of lead loading depending upon the radiation levels within the glove box.

Novel Concepts for Radiation Shielding Materials

NASA Technical Reports Server (NTRS)

Oliva-Buisson, Yvette J.

2014-01-01

It is critical that safety factors be maximized with respect to long duration, extraterrestrial space flight. Any significant improvement in radiation protection will be critical in ensuring the safety of crew and hardware on such missions. The project goal is to study novel concepts for radiation shielding materials that can be used for long-duration space missions. As part of this project we will investigate the use of thin films for the evaluation of a containment system that can retain liquid hydrogen and provide the necessary hydrogen density for effective shielding.

Brazing of refractory, superalloy, and composite materials for Space Shuttle applications.

NASA Technical Reports Server (NTRS)

Beuyukian, C. S.

1972-01-01

Research work concerning the metallic portion of the shuttle-orbiter heat shield (expected to experience temperatures up to 2500 F) is described. The five metals being evaluated are TD-Ni-Cr, Cb-C129Y, Cb752, Hayes 188, and Inconel 625. Brazing techniques whereby pairs of these materials are joined into thin-membered assemblies for heat shield applications are described. Results obtained with the vacuum-furnace brazing process are examined. In addition, the use of brazed aluminum-boron metal-matrix-contoured composite structures for heat shield applications is evaluated.

Fissile solution measurement apparatus

DOEpatents

Crane, T.W.; Collinsworth, P.R.

1984-06-11

An apparatus for determining the content of a fissile material within a solution by detecting delayed fission neutrons emitted by the fissile material after it is temporarily irradiated by a neutron source. The apparatus comprises a container holding the solution and having a portion defining a neutron source cavity centrally disposed within the container. The neutron source cavity temporarily receives the neutron source. The container has portions defining a plurality of neutron detector ports that form an annular pattern and surround the neutron source cavity. A plurality of neutron detectors count delayed fission neutrons emitted by the fissile material. Each neutron detector is located in a separate one of the neutron detector ports.

Active-Interrogation Measurements of Fast Neutrons from Induced Fission in Low-Enriched Uranium

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

J. L. Dolan; M. J. Marcath; M. Flaska

2014-02-01

A detection system was designed with MCNPX-PoliMi to measure induced-fission neutrons from U-235 and U-238 using active interrogation. Measurements were then performed with this system at the Joint Research Centre (JRC) in Ispra, Italy on low-enriched uranium samples. Liquid scintillators measured induced fission neutron to characterize the samples in terms of their uranium mass and enrichment. Results are presented to investigate and support the use of organic liquid scintillators with active interrogation techniques to characterize uranium containing materials.

Comparison of Martian Meteorites and Martian Regolith as Shield Materials for Galactic Cosmic Rays

NASA Technical Reports Server (NTRS)

Kim, Myung-Hee Y.; Thibeault, Sheila A.; Simonsen, Lisa C.; Wilson, John W.

1998-01-01

Theoretical calculations of radiation attenuation due to energetic galactic cosmic rays behind Martian rock and Martian regolith material have been made to compare their utilization as shields for advanced manned missions to Mars because the detailed chemical signature of Mars is distinctly different from Earth. The modified radiation fields behind the Martian rocks and the soil model were generated by solving the Boltzmann equation using a HZETRN system with the 1977 Solar Minimum environmental model. For the comparison of the attenuation characteristics, dose and dose equivalent are calculated for the five different subgroups of Martian rocks and the Martian regolith. The results indicate that changes in composition of subgroups of Martian rocks have negligible effects on the overall shielding properties because of the similarity of their constituents. The differences for dose and dose equivalent of these materials relative to those of Martian regolith are within 0.5 and 1 percent, respectively. Therefore, the analysis of Martian habitat construction options using in situ materials according to the Martian regolith model composition is reasonably accurate. Adding an epoxy to Martian regolith, which changes the major constituents of the material, enhances shielding properties because of the added hydrogenous constituents.

THORIUM OXALATE-URANYL ACETATE COUPLED PROCEDURE FOR THE SEPARATION OF RADIOACTIVE MATERIALS

DOEpatents

Gofman, J.W.

1959-08-11

The recovery of fission products from neutronirradiated uranium is described. The neutron-irradiated uranium is dissolved in acid and thorium oxalate is precipitated in ihe solution formed, whereby the fission products are carried on the thorium oxalate. The separated thorium oxalate precipitate is then dissolved in an aqueous oxalate solution and the solution formed is acidified, limiting ihe excess acidity to a maximum of 2 N, whereby thorium oxalate precipitates and carries lanthanum-rareearth- and alkaline-earth-metal fission products while the zirconium-fission-product remains in solution. This precipitate, too, is dissolved in an aqaeous oxalate solution at elevated temperature, and lanthanum-rare-earth ions are added to the solution whereby lanthanum-rare-earth oxalate forms and the lanthanum-rare-earth-type and alkalineearth-metal-type fission products are carried on the oxalate. The precipitate is separated from the solution.

Charge Transfer-Mediated Singlet Fission

NASA Astrophysics Data System (ADS)

Monahan, N.; Zhu, X.-Y.

2015-04-01

Singlet fission, the splitting of a singlet exciton into two triplet excitons in molecular materials, is interesting not only as a model many-electron problem, but also as a process with potential applications in solar energy conversion. Here we discuss limitations of the conventional four-electron and molecular dimer model in describing singlet fission in crystalline organic semiconductors, such as pentacene and tetracene. We emphasize the need to consider electronic delocalization, which is responsible for the decisive role played by the Mott-Wannier exciton, also called the charge transfer (CT) exciton, in mediating singlet fission. At the strong electronic coupling limit, the initial excitation creates a quantum superposition of singlet, CT, and triplet-pair states, and we present experimental evidence for this interpretation. We also discuss the most recent attempts at translating this mechanistic understanding into design principles for CT state-mediated intramolecular singlet fission in oligomers and polymers.

Predictions for Radiation Shielding Materials

NASA Technical Reports Server (NTRS)

Kiefer, Richard L.

2002-01-01

Radiation from galactic cosmic rays (GCR) and solar particle events (SPE) is a serious hazard to humans and electronic instruments during space travel, particularly on prolonged missions outside the Earth s magnetic fields. Galactic cosmic radiation (GCR) is composed of approx. 98% nucleons and approx. 2% electrons and positrons. Although cosmic ray heavy ions are 1-2% of the fluence, these energetic heavy nuclei (HZE) contribute 50% of the long-term dose. These unusually high specific ionizations pose a significant health hazard acting as carcinogens and also causing microelectronics damage inside spacecraft and high-flying aircraft. These HZE ions are of concern for radiation protection and radiation shielding technology, because gross rearrangements and mutations and deletions in DNA are expected. Calculations have shown that HZE particles have a strong preference for interaction with light nuclei. The best shield for this radiation would be liquid hydrogen, which is totally impractical. For this reason, hydrogen-containing polymers make the most effective practical shields. Shielding is required during missions in Earth orbit and possibly for frequent flying at high altitude because of the broad GCR spectrum and during a passage into deep space and LunarMars habitation because of the protracted exposure encountered on a long space mission. An additional hazard comes from solar particle events (SPEs) which are mostly energetic protons that can produce heavy ion secondaries as well as neutrons in materials. These events occur at unpredictable times and can deliver a potentially lethal dose within several hours to an unshielded human. Radiation protection for humans requires safety in short-term missions and maintaining career exposure limits within acceptable levels on future long-term exploration missions. The selection of shield materials can alter the protection of humans by an order of magnitude. If improperly selected, shielding materials can actually increase radiation damage due to penetration properties and nuclear fragmentation. Protecting space-borne microelectronics from single event upsets (SEUs) by transmitted radiation will benefit system reliability and system design cost by using optimal shield materials. Long-term missions on the surface of the Moon or Mars will require the construction of habitats to protect humans during their stay. One approach to the construction is to make structural materials from lunar or Martian regolith using a polymeric material as a binder. The hydrogen-containing polymers are considerably more effective for radiation protection than the regolith, but the combination minimizes the amount of polymer to be transported. We have made composites of simulated lunar regolith with two different polymers, LaRC-SI, a high-performance polyimide thermoset, and polyethylene, a thermoplastic.

Rapid Analysis of Mass Distribution of Radiation Shielding

NASA Technical Reports Server (NTRS)

Zapp, Edward

2007-01-01

Radiation Shielding Evaluation Toolset (RADSET) is a computer program that rapidly calculates the spatial distribution of mass of an arbitrary structure for use in ray-tracing analysis of the radiation-shielding properties of the structure. RADSET was written to be used in conjunction with unmodified commercial computer-aided design (CAD) software that provides access to data on the structure and generates selected three-dimensional-appearing views of the structure. RADSET obtains raw geometric, material, and mass data on the structure from the CAD software. From these data, RADSET calculates the distribution(s) of the masses of specific materials about any user-specified point(s). The results of these mass-distribution calculations are imported back into the CAD computing environment, wherein the radiation-shielding calculations are performed.

Fabrication of single/multi-walled hybrid buckypaper composites and their enhancement of electromagnetic interference shielding performance

NASA Astrophysics Data System (ADS)

Lu, Shaowei; Shao, Junyan; Ma, Keming; Wang, Xiaoqiang; Zhang, Lu; Meng, Qingshi

2016-11-01

Multi-walled carbon nanotubes and single-walled carbon nanotubes show great potential for the application as an electromagnetic interference shielding material. In this paper, the electromagnetic interference shielding the effectiveness of a composite surface coated single/multi-walled carbon nanotube hybrid buckypaper was measured, which showed an average shielding effectiveness of ~55 dB with a buckypaper thickness of 50 µm, and bukypaper density of 0.76 g cm-3, it is much higher than other carbon nanotube/resin materials when sample thickness is on the similar order. The structural, specific surface area and conductivity of the buckypapers were examined by field-emission scanning electron microscopy, specific surface area analyzer and four probes resistance tester, respectively.

Extending FEAST-METAL for analysis of low content minor actinide bearing and zirconium rich metallic fuels for sodium fast reactors

NASA Astrophysics Data System (ADS)

Karahan, Aydın

2011-07-01

Computational models in FEAST-METAL fuel behaviour code have been upgraded to simulate minor actinide bearing zirconium rich metallic fuels for use in sodium fast reactors. Increasing the zirconium content to 20-40 wt.% causes significant changes in fuel slug microstructure affecting thermal, mechanical, chemical, and fission gas behaviour. Inclusion of zirconium rich phase reduces the fission gas swelling rate significantly in early irradiation. Above the threshold fission gas swelling, formation of micro-cracks, and open pores increase material compliancy enhance diffusivity, leading to rapid fuel gas swelling, interconnected porosity development and release of the fission gases and helium. Production and release of helium was modelled empirically as a function of americium content and fission gas production, consistent with previous Idaho National Laboratory studies. Predicted fuel constituent redistribution is much smaller compared to typical U-Pu-10Zr fuel operated at EBR-II. Material properties such as fuel thermal conductivity, modulus of elasticity, and thermal expansion coefficient have been approximated using the available database. Creep rate and fission gas diffusivity of high zirconium fuel is lowered by an order of magnitude with respect to the reference low zirconium fuel based on limited database and in order to match experimental observations. The new code is benchmarked against the AFC-1F fuel assembly post irradiation examination results. Satisfactory match was obtained for fission gas release and swelling behaviour. Finally, the study considers a comparison of fuel behaviour between high zirconium content minor actinide bearing fuel and typical U-15Pu-6Zr fuel pins with 75% smear density. The new fuel has much higher fissile content, allowing for operating at lower neutron flux level compared to fuel with lower fissile density. This feature allows the designer to reach a much higher burnup before reaching the cladding dose limit. On the other hand, in order to accommodate solid fission product swelling and to control fuel clad mechanical interaction of the stiffer fuel, the fuel smear density is reduced to 70%. In addition, plenum height is increased to accommodate for fission gases.

The Local Tissue Environment During the September 29, 1989 Solar Particle Event

NASA Technical Reports Server (NTRS)

Kim, M.-H. Y.; Wilson, J. W.; Cucinotta, F. A.; Simonsen, L. C.; Atwell, W.; Badavi, F. F.; Miller, J.

2004-01-01

The solar particle event (SPE) of September 29, 1989, produced an iron-rich spectrum with energies approaching 1 GeV/amu with an energy power index of 2.5. These high charge and energy (HZE) ions of the iron-rich SPEs challenge conventional methods of SPE shield design and assessment of astronaut risks. Shield and risk assessments are evaluated using the HZETRN code with computerized anatomical man (CAM) model for astronaut s body tissues. Since the HZE spectra decline rapidly with energy and HZE attenuation in materials is limited by their penetration power, details of the mass distributions about the sensitive tissues (shielding materials and the astronaut's body) are important determining factors of the exposure levels. Typical space suit and lightly shielded structures allow significant contributions from HZE components to some critical body tissues and have important implications on the models for risk assessment. Only a heavily shielded equipment room of a space vehicle or habitat provides sufficient shielding for the early response at sensitive organs from this event. The February 23, 1956 event of similar spectral characteristics and ten times this event may have important medical consequences without a well-shielded region.

Electromagnetic interference shielding effectiveness of polypropylene/conducting fiber composites

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

Lee, Pyoung-Chan, E-mail: pclee@katech.re.kr; Kim, Bo-Ram; Jeoung, Sun Kyoung

Electromagnetic released from the automotive electronic parts is harmful to human body. Electromagnetic interference (EMT) shielding refers to the reflection and/or adsorption of electromagnetic radiation by a material, which thereby acts as a shield against the penetration of the radiation through the shield. Polypropylene (PP)/conductive micro fiber composites containing various fiber contents and fiber length were injection-molded. The effect of fiber content and length on electrical properties of the composites was studied by electrical resistivity and EMT shielding measurements. The through-plane electrical conductivity and dielectric permittivity were obtained by measuring dielectric properties. The EMT shielding effectiveness (SE) was investigated bymore » using S-parameter in the range of 100 ~ 1500 MHz. Reflection, absorption and multiple-reflection are the EMT attenuation mechanisms. From the measurement of S-Parameters, the absorption coefficient, reflection coefficient, and the shielding efficiency of the materials were calculated. The EMT SE of PP/conducing fiber composites is 40 dB over a wide frequency range up to 1.5 GHz, which is higher than that of PP/talc composite used automotive parts, viz. 0 dB.« less

Cloud immersion building shielding factors for US residential structures.

PubMed

Dickson, E D; Hamby, D M

2014-12-01

This paper presents validated building shielding factors designed for contemporary US housing-stock under an idealized, yet realistic, exposure scenario within a semi-infinite cloud of radioactive material. The building shielding factors are intended for use in emergency planning and level three probabilistic risk assessments for a variety of postulated radiological events in which a realistic assessment is necessary to better understand the potential risks for accident mitigation and emergency response planning. Factors are calculated from detailed computational housing-units models using the general-purpose Monte Carlo N-Particle computational code, MCNP5, and are benchmarked from a series of narrow- and broad-beam measurements analyzing the shielding effectiveness of ten common general-purpose construction materials and ten shielding models representing the primary weather barriers (walls and roofs) of likely US housing-stock. Each model was designed to scale based on common residential construction practices and include, to the extent practical, all structurally significant components important for shielding against ionizing radiation. Calculations were performed for floor-specific locations as well as for computing a weighted-average representative building shielding factor for single- and multi-story detached homes, both with and without basement, as well for single-wide manufactured housing-units.

Evaluation of lunar regolith geopolymer binder as a radioactive shielding material for space exploration applications

NASA Astrophysics Data System (ADS)

Montes, Carlos; Broussard, Kaylin; Gongre, Matthew; Simicevic, Neven; Mejia, Johanna; Tham, Jessica; Allouche, Erez; Davis, Gabrielle

2015-09-01

Future manned missions to the moon will require the ability to build structures using the moon's natural resources. The geopolymer binder described in this paper (Lunamer) is a construction material that consists of up to 98% lunar regolith, drastically reducing the amount of material that must be carried from Earth in the event of lunar construction. This material could be used to fabricate structural panels and interlocking blocks that have radiation shielding and thermal insulation characteristics. These panels and blocks could be used to construct living quarters and storage facilities on the lunar surface, or as shielding panels to be installed on crafts launched from the moon surface to deep-space destinations. Lunamer specimens were manufactured in the laboratory and compressive strength results of up to 16 MPa when cast with conventional methods and 37 MPa when cast using uniaxial pressing were obtained. Simulation results have shown that the mechanical and chemical properties of Lunamer allow for adequate radiation shielding for a crew inside the lunar living quarters without additional requirements.

Composite solid-state scintillators for neutron detection

DOEpatents

Dai, Sheng; Im, Hee-Jung; Pawel, Michelle D.

2006-09-12

Applicant's present invention is a composite scintillator for neutron detection comprising a matrix material fabricated from an inorganic sol-gel precursor solution homogeneously doped with a liquid scintillating material and a neutron absorbing material. The neutron absorbing material yields at least one of an electron, a proton, a triton, an alpha particle or a fission fragment when the neutron absorbing material absorbs a neutron. The composite scintillator further comprises a liquid scintillating material in a self-assembled micelle formation homogeneously doped in the matrix material through the formation of surfactant-silica composites. The scintillating material is provided to scintillate when traversed by at least one of an electron, a proton, a triton, an alpha particle or a fission fragment. The scintillating material is configured such that the matrix material surrounds the micelle formation of the scintillating material. The composite scintillator is fabricated and applied as a thin film on substrate surfaces, a coating on optical fibers or as a glass material.

Analysis of plasmas generated by fission fragments. [nuclear pumped lasers and helium plasma

NASA Technical Reports Server (NTRS)

Deese, J. E.; Hassan, H. A.

1977-01-01

A kinetic model is developed for a plasma generated by fission fragments and the results are employed to study helium plasma generated in a tube coated with fissionable material. Because both the heavy particles and electrons play important roles in creating the plasma, their effects are considered simultaneously. The calculations are carried out for a range of neutron fluxes and pressures. In general, the predictions of the theory are in good agreement with available intensity measurements. Moreover, the theory predicts the experimentally measured inversions. However, the calculated gain coefficients are such that lasing is not expected to take place in a helium plasma generated by fission fragments. The effects of an externally applied electric field are also considered.

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

Berkelbach, Timothy C., E-mail: tcb2112@columbia.edu; Reichman, David R., E-mail: drr2103@columbia.edu; Hybertsen, Mark S., E-mail: mhyberts@bnl.gov

We extend our previous work on singlet exciton fission in isolated dimers to the case of crystalline materials, focusing on pentacene as a canonical and concrete example. We discuss the proper interpretation of the character of low-lying excited states of relevance to singlet fission. In particular, we consider a variety of metrics for measuring charge-transfer character, conclusively demonstrating significant charge-transfer character in the low-lying excited states. The impact of this electronic structure on the subsequent singlet fission dynamics is assessed by performing real-time master-equation calculations involving hundreds of quantum states. We make direct comparisons with experimental absorption spectra and singletmore » fission rates, finding good quantitative agreement in both cases, and we discuss the mechanistic distinctions that exist between small isolated aggregates and bulk systems.« less

Final Progress Report

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

Josef Michl

2011-10-31

In this project we have established guidelines for the design on organic chromophores suitable for producing high triplet yields via singlet fission. We have proven their utility by identifying a chromophore of a structural class that had never been examined for singlet fission before, 1,3-diphenylisobenzofuran, and demonstrating in two independent ways that a thin layer of this material produces a triplet yield of 200% within experimental error. We have also designed a second chromophore of a very different type, again of a structural class that had not been examined for singlet fission before, and found that in a thin layermore » it produces a 70% triplet yield. Finally, we have enhanced the theoretical understanding of the quantum mechanical nature of the singlet fission process.« less

RADIATION SHIELDING COMPOSITION

DOEpatents

Dunegan, H.L.

1963-01-29

A light weight radiation shielding composition is described whose mechanical and radiological properties can be varied within wide limits. The composition of this shielding material consists of four basic ingredients: powder of either Pb or W, a plastic resin, a resin plasticizer, and a polymerization catalyst to promote an interaction of the plasticizer with the plastic resin. Air may be mixed into the above ingredients in order to control the density of the final composition. For equivalent gamma attenuation, the shielding composition weighs one-third to one-half as much as conventional Pb shielding. (AEC)

Orion Heat Shield Move

NASA Image and Video Library

2017-10-23

Technicians move the Orion heat shield for Exploration Mission-1 toward the thermal chamber in the Neil Armstrong Operations and Checkout Building high bay at NASA's Kennedy Space Center in Florida. Protective pads are being attached to the heat shield surface. The heat shield will undergo a thermal cycle test to verify acceptable workmanship and material quality. The test also serves to verify the heat shield's thermal protection systems have been manufactured and assembled correctly. The Orion spacecraft will launch atop NASA's Space Launch System rocket on its first uncrewed integrated flight.

Investigation of Mechanical and Electromagnetic Interference Shielding Properties of Nickel-CFRP Textile Composites

NASA Astrophysics Data System (ADS)

Tugirumubano, Alexandre; Vijay, Santhiyagu Joseph; Go, Sun Ho; Kwac, Lee Ku; Kim, Hong Gun

2018-05-01

The most common materials used for electromagnetic interference shielding are metals and their alloys. However, those materials are heavy and highly reflective. In order to eliminate or reduce the intensity of wave radiation in their working environment, lightweight materials that have interference shielding properties are needed. In this paper, nickel wire mesh yarns (warps) were woven into carbon fibers-reinforced plastic yarns (wefts) to produce metal-carbon textile composite materials. The plain weave and 2/2 twill weave techniques were used, and the woven fabrics were laminated to manufacture experimental test samples. The nickel, which has high magnetic permeability and good electric conductivity, and carbon fibers, which have good electrical, thermal and mechanical properties, were used together to achieve the desired properties. The shielding effectiveness of each sample was investigated using a network analyzer connected with coaxial transmission line test in accordance with ASTM 4935-99 standard, with the frequencies ranging from 500 MHz to 1.5 GHz. Here, the plain weave structure showed higher shielding effectiveness than twill weave. The absorption losses for both materials were relatively greater than reflection losses. In reference to the orientation of wire mesh yarns about the loading axis, the tensile strengths in the transversal direction were 19.04 and 16.34% higher than the tensile strengths in longitudinal direction for plain weave and twill weave, respectively. The fractography analysis with SEM showed a ductile fracture of wire mesh and brittle fracture of epoxy matrix and carbon fibers.

Investigation of Mechanical and Electromagnetic Interference Shielding Properties of Nickel-CFRP Textile Composites

NASA Astrophysics Data System (ADS)

Tugirumubano, Alexandre; Vijay, Santhiyagu Joseph; Go, Sun Ho; Kwac, Lee Ku; Kim, Hong Gun

2018-04-01

The most common materials used for electromagnetic interference shielding are metals and their alloys. However, those materials are heavy and highly reflective. In order to eliminate or reduce the intensity of wave radiation in their working environment, lightweight materials that have interference shielding properties are needed. In this paper, nickel wire mesh yarns (warps) were woven into carbon fibers-reinforced plastic yarns (wefts) to produce metal-carbon textile composite materials. The plain weave and 2/2 twill weave techniques were used, and the woven fabrics were laminated to manufacture experimental test samples. The nickel, which has high magnetic permeability and good electric conductivity, and carbon fibers, which have good electrical, thermal and mechanical properties, were used together to achieve the desired properties. The shielding effectiveness of each sample was investigated using a network analyzer connected with coaxial transmission line test in accordance with ASTM 4935-99 standard, with the frequencies ranging from 500 MHz to 1.5 GHz. Here, the plain weave structure showed higher shielding effectiveness than twill weave. The absorption losses for both materials were relatively greater than reflection losses. In reference to the orientation of wire mesh yarns about the loading axis, the tensile strengths in the transversal direction were 19.04 and 16.34% higher than the tensile strengths in longitudinal direction for plain weave and twill weave, respectively. The fractography analysis with SEM showed a ductile fracture of wire mesh and brittle fracture of epoxy matrix and carbon fibers.

Photonic Bandgap (PBG) Shielding Technology

NASA Technical Reports Server (NTRS)

Bastin, Gary L.

2007-01-01

Photonic Bandgap (PBG) shielding technology is a new approach to designing electromagnetic shielding materials for mitigating Electromagnetic Interference (EM!) with small, light-weight shielding materials. It focuses on ground planes of printed wiring boards (PWBs), rather than on components. Modem PSG materials also are emerging based on planar materials, in place of earlier, bulkier, 3-dimensional PBG structures. Planar PBG designs especially show great promise in mitigating and suppressing EMI and crosstalk for aerospace designs, such as needed for NASA's Constellation Program, for returning humans to the moon and for use by our first human visitors traveling to and from Mars. Photonic Bandgap (PBG) materials are also known as artificial dielectrics, meta-materials, and photonic crystals. General PBG materials are fundamentally periodic slow-wave structures in I, 2, or 3 dimensions. By adjusting the choice of structure periodicities in terms of size and recurring structure spacings, multiple scatterings of surface waves can be created that act as a forbidden energy gap (i.e., a range of frequencies) over which nominally-conductive metallic conductors cease to be a conductor and become dielectrics. Equivalently, PBG materials can be regarded as giving rise to forbidden energy gaps in metals without chemical doping, analogous to electron bandgap properties that previously gave rise to the modem semiconductor industry 60 years ago. Electromagnetic waves cannot propagate over bandgap regions that are created with PBG materials, that is, over frequencies for which a bandgap is artificially created through introducing periodic defects

Application peculiarities of magnetic materials for protection from magnetic fields

NASA Astrophysics Data System (ADS)

Wai, P.; Dmitrenko, V.; Grabchikov, S.; Vlasik, K.; Novikov, A.; Petrenko, D.; Trukhanov, V.; Ulin, S.; Uteshev, Z.; Chernysheva, V.; Shustov, A.

2016-02-01

In different materials for magnetic shields, the maximum permeability is achieved for different values of the magnetic field. This determines the choice of material. So for protection from magnetic fields strength of 10 - 150 A/m it is advisable to apply the amorphous ribbon 84KXCP. For stronger fields (more than 400 A/m) it is recommended to use MFS based on Ni20Fe80. Use of these materials allows creating an effective shield working in a wide range of magnetic field strengths.

Spectral analysis of shielded gamma ray sources using precalculated library data

NASA Astrophysics Data System (ADS)

Holmes, Thomas Wesley; Gardner, Robin P.

2015-11-01

In this work, an approach has been developed for determining the intensity of a shielded source by first determining the thicknesses of three different shielding materials from a passively collected gamma-ray spectrum by making comparisons with predetermined shielded spectra. These evaluations are dependent on the accuracy and validity of the predetermined library spectra which were created by changing the thicknesses of the three chosen materials lead, aluminum and wood that are used to simulate any actual shielding. Each of the spectra produced was generated using MCNP5 with a sufficiently large number of histories to ensure a low relative error at each channel. The materials were held in the same respective order from source to detector, where each material consisted of three individual thicknesses and a null condition. This then produced two separate data sets of 27 total shielding material situations and subsequent predetermined libraries that were created for each radionuclide source used. The technique used to calculate the thicknesses of the materials implements a Levenberg-Marquardt nonlinear search that employs a tri-linear interpolation with the respective predetermined libraries within each channel for the supplied input unknown spectrum. Given that the nonlinear parameters require an initial guess for the calculations, the approach demonstrates first that when the correct values are input, the correct thicknesses are found. It then demonstrates that when multiple trials of random values are input for each of the nonlinear parameters, the average of the calculated solutions that successfully converges also produced the correct thicknesses. Under situations with sufficient information known about the detection situation at hand, the method was shown to behave in a manner that produces reasonable results and can serve as a good preliminary solution. This technique has the capability to be used in a variety of full spectrum inverse analysis problems including homeland security issues.

Thermally and chemically responsive nanoporous materials for efficient capture of fission product gases.

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

Stroeve, Pieter; Faller, Roland

The objective of this project was to develop robust, high-efficiency materials for capture of fission product gases such as He, Xe and Kr in scenarios relevant for both reactor fuels and reprocessing operations. The relevant environments are extremely harsh, encompassing temperatures up to 1500 °C, high levels of radiation, as well as potential exposures to highly-reactive chemicals such as nitric acid and organic solvents such as kerosene. The requirement for nanostructured capture materials is driven in part by the very short (few micron) diffusion distances for product gases in nuclear fuel. We achieved synthesis, characterization and detailed modeling of themore » materials. Although not all materials reviewed in this report will be feasible for the ultimate goal of integration in nuclear fuel, nevertheless each material studied has particular properties which will enable an optimized material to be efficiently developed and characterized.« less