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1

Advanced High Temperature Reactor Neutronic Core Design  

SciTech Connect

The AHTR is a 3400 MW(t) FHR class reactor design concept intended to serve as a central generating station type power plant. While significant technology development and demonstration remains, the basic design concept appears sound and tolerant of much of the remaining performance uncertainty. No fundamental impediments have been identified that would prevent widespread deployment of the concept. This paper focuses on the preliminary neutronic design studies performed at ORNL during the fiscal year 2011. After a brief presentation of the AHTR design concept, the paper summarizes several neutronic studies performed at ORNL during 2011. An optimization study for the AHTR core is first presented. The temperature and void coefficients of reactivity are then analyzed for a few configurations of interest. A discussion of the limiting factors due to the fast neutron fluence follows. The neutronic studies conclude with a discussion of the control and shutdown options. The studies presented confirm that sound neutronic alternatives exist for the design of the AHTR to maintain full passive safety features and reasonable operation conditions.

Ilas, Dan [ORNL] [ORNL; Holcomb, David Eugene [ORNL] [ORNL; Varma, Venugopal Koikal [ORNL] [ORNL

2012-01-01

2

McCARD for Neutronics Design and Analysis of Research Reactor Cores  

NASA Astrophysics Data System (ADS)

McCARD is a Monte Carlo (MC) neutron-photon transport simulation code developed exclusively for the neutronics design and analysis of nuclear reactor cores. McCARD is equipped with the hierarchical modeling and scripting functions, the CAD-based geometry processing module, the adjoint-weighted kinetics parameter and source multiplication factor estimation modules as well as the burnup analysis capability for the neutronics design and analysis of both research and power reactor cores. This paper highlights applicability of McCARD for the research reactor core neutronics analysis, as demonstrated for Kyoto University Critical Assembly, HANARO, and YALINA.

Shim, Hyung Jin; Park, Ho Jin; Kwon, Soonwoo; Seo, Geon Ho; Hyo Kim, Chang

2014-06-01

3

Core design study on CANDU-SCWR with 3D neutronics\\/thermal-hydraulics coupling  

Microsoft Academic Search

Using separated heavy water as moderator and supercritical water (SCW) as coolant introduces challenge for CANDU-SCWR to get a negative coolant void reactivity (CVR), due to which the moderator thickness of the fuel channel is optimized in this paper. When SCW flows through the core, there is a rapid variation in SCW density, which is directly related to the neutron

Ping Yang; Liangzhi Cao; Hongchun Wu; Changhui Wang

4

A Monte Carlo model system for core analysis and epithermal neutron beam design at the Washington State University Radiation Center  

SciTech Connect

The Monte Carlo Model System (MCMS) for the Washington State University (WSU) Radiation Center provides a means through which core criticality and power distributions can be calculated, as well as providing a method for neutron and photon transport necessary for BNCT epithermal neutron beam design. The computational code used in this Model System is MCNP4A. The geometric capability of this Monte Carlo code allows the WSU system to be modeled very accurately. A working knowledge of the MCNP4A neutron transport code increases the flexibility of the Model System and is recommended, however, the eigenvalue/power density problems can be run with little direct knowledge of MCNP4A. Neutron and photon particle transport require more experience with the MCNP4A code. The Model System consists of two coupled subsystems; the Core Analysis and Source Plane Generator Model (CASP), and the BeamPort Shell Particle Transport Model (BSPT). The CASP Model incorporates the S({alpha}, {beta}) thermal treatment, and is run as a criticality problem yielding, the system eigenvalue (k{sub eff}), the core power distribution, and an implicit surface source for subsequent particle transport in the BSPT Model. The BSPT Model uses the source plane generated by a CASP run to transport particles through the thermal column beamport. The user can create filter arrangements in the beamport and then calculate characteristics necessary for assessing the BNCT potential of the given filter want. Examples of the characteristics to be calculated are: neutron fluxes, neutron currents, fast neutron KERMAs and gamma KERMAs. The MCMS is a useful tool for the WSU system. Those unfamiliar with the MCNP4A code can use the MCMS transparently for core analysis, while more experienced users will find the particle transport capabilities very powerful for BNCT filter design.

Burns, T.D. Jr.

1996-05-01

5

Core Vessel Insert Handling Robot for the Spallation Neutron Source  

SciTech Connect

The Spallation Neutron Source provides the world's most intense pulsed neutron beams for scientific research and industrial development. Its eighteen neutron beam lines will eventually support up to twenty-four simultaneous experiments. Each beam line consists of various optical components which guide the neutrons to a particular instrument. The optical components nearest the neutron moderators are the core vessel inserts. Located approximately 9 m below the high bay floor, these inserts are bolted to the core vessel chamber and are part of the vacuum boundary. They are in a highly radioactive environment and must periodically be replaced. During initial SNS construction, four of the beam lines received Core Vessel Insert plugs rather than functional inserts. Remote replacement of the first Core Vessel Insert plug was recently completed using several pieces of custom-designed tooling, including a highly complicated Core Vessel Insert Robot. The design of this tool are discussed.

Graves, Van B [ORNL; Dayton, Michael J [ORNL

2011-01-01

6

Modeling and design of a new core-moderator assembly and neutron beam ports for the Penn State Breazeale Nuclear Reactor (PSBR)  

NASA Astrophysics Data System (ADS)

This study is for modeling and designing a new reactor core-moderator assembly and new neutron beam ports that aimed to expand utilization of a new beam hall of the Penn State Breazeale Reactor (PSBR). The PSBR is a part of the Radiation Science and Engineering Facility (RSEC) and is a TRIGA MARK III type research reactor with a movable core placed in a large pool and is capable to produce 1MW output. This reactor is a pool-type reactor with pulsing capability up to 2000 MW for 10-20 msec. There are seven beam ports currently installed to the reactor. The PSBR's existing core design limits the experimental capability of the facility, as only two of the seven available neutron beam ports are usable. The finalized design features an optimized result in light of the data obtained from neutronic and thermal-hydraulics analyses as well as geometrical constraints. A new core-moderator assembly was introduced to overcome the limitations of the existing PSBR design, specifically maximizing number of available neutron beam ports and mitigating the hydrogen gamma contamination of the neutron beam channeled in the beam ports. A crescent-shaped moderator is favored in the new PSBR design since it enables simultaneous use of five new neutron beam ports in the facility. Furthermore, the crescent shape sanctions a coupling of the core and moderator, which reduces the hydrogen gamma contamination significantly in the new beam ports. A coupled MURE and MCNP5 code optimization analysis was performed to calculate the optimum design parameters for the new PSBR. Thermal-hydraulics analysis of the new design was achieved using ANSYS Fluent CFD code. In the current form, the PSBR is cooled by natural convection of the pool water. The driving force for the natural circulation of the fluid is the heat generation within the fuel rods. The convective heat data was generated at the reactor's different operating powers by using TRIGSIMS, the fuel management code of the PSBR core. In the CFD modeling, the amount of heat generated by the fuel is assumed to be transferred totally into the coolant. Therefore, the surface heat flux is applied to the fuel cladding outer surface by considering the depleted fuel composition of each individual fuel rod under a reference core loading condition defined as; 53H at 1MW full power. In order to model the entire PSBR reactor, fine mesh discretization was achieved with 22 millions structured and unstructured computational meshes. The conductive heat transfer inside the fuel rods was ignored in order to decrease the computational mesh requirement. Since the PSBR core operates in the subcooled nucleate boiling region, the CFD simulation of new PSBR design was completed utilizing an Eulerian-Eulerian multiphase flow formulation and RPI wall boiling model. The simulation results showed that the new moderator tank geometry results in secondary flow entering into the core due to decrease in the cross-flow area. Notably, the radial flow improves the local heat transfer conditions by providing radial-mixing in the core. Bubble nucleation occurs on the heated fuel rods but bubbles are collapsing in the subcooled fluid. Furthermore, the bulk fluid properties are not affected by the bubble formation. Yet, subcooled boiling enhances the heat transfer on the fuel rods. Five neutron beam ports are designed for the new reactor. The geometrical configuration, filter and collimator system designs of each neutron beam ports are selected based on the requirements of the experimental facilities. A cold neutron beam port which utilizes cold neutrons from three curved guide tubes is considered. Therefore, there will be seven neutron beams available in the new facility. The neutronic analyses of the new beam port designs were achieved by using MCNP5 code and Burned Coupled Simulation Tool for the PSBR. The MCNP simulation results showed that thermal neutron flux was increased by a factor of minimum 1.23 times and maximum 2.68 times in the new beam port compared to the existing BP4 design. Besides total gamma dose was decreased by a factor

Ucar, Dundar

7

Automated Core Design  

SciTech Connect

Multistate searching methods are a subfield of distributed artificial intelligence that aims to provide both principles for construction of complex systems involving multiple states and mechanisms for coordination of independent agents' actions. This paper proposes a multistate searching algorithm with reinforcement learning for the automatic core design of a boiling water reactor. The characteristics of this algorithm are that the coupling structure and the coupling operation suitable for the assigned problem are assumed and an optimal solution is obtained by mutual interference in multistate transitions using multiagents. Calculations in an actual plant confirmed that the proposed algorithm increased the convergence ability of the optimization process.

Kobayashi, Yoko; Aiyoshi, Eitaro

2005-07-15

8

FAST FOSSIL ROTATION OF NEUTRON STAR CORES  

SciTech Connect

It is argued that the superfluid core of a neutron star super-rotates relative to the crust, because stratification prevents the core from responding to the electromagnetic braking torque, until the relevant dissipative (viscous or Eddington-Sweet) timescale, which can exceed {approx}10{sup 3} yr and is much longer than the Ekman timescale, has elapsed. Hence, in some young pulsars, the rotation of the core today is a fossil record of its rotation at birth, provided that magnetic crust-core coupling is inhibited, e.g., by buoyancy, field-line topology, or the presence of uncondensed neutral components in the superfluid. Persistent core super-rotation alters our picture of neutron stars in several ways, allowing for magnetic field generation by ongoing dynamo action and enhanced gravitational wave emission from hydrodynamic instabilities.

Melatos, A., E-mail: amelatos@unimelb.edu.au [School of Physics, University of Melbourne, Parkville, VIC 3010 (Australia)

2012-12-10

9

Neutronic analysis of three-element core configurations for the Advanced Neutron Source Reactor  

SciTech Connect

Calculations of several important neutronic parameters have been performed for ten different three-element configurations considered for the Advanced Neutron Source (ANS) Reactor. Six of these configurations (labeled ST, SB, MT, MB, LT, and LB) are there result of the permutations of the same three elements. Two configurations (ST- MOD and SB-MOD) have the same element configuration as their base core design (ST and SB) but have slightly different element dimensions, and two configurations (ST-OL1 and ST-OL2) have two overlapping elements to increase the neutron fluxes in the reflector. For each configuration, in addition to the conceptual two-element design, fuel-cycle calculations were performed with calculations required to obtain unperturbed fluxes. The element power densities, peak thermal neutron flux as a function of position throughout the cycle, fast flux, fast-to-thermal flux ratios, irradiation and production region fluxes, and control rod worth curves were determined. The effective multiplication factor for each fuel element criticality. A comparison shows that the ST core configurations have the best overall performance, and the fully overlapping core configuration ST-OL2 has the best performance by a large margin. Therefore, on the basis of the neutronics results, the fully overlapping configuration is recommended for further consideration in using a three-element ANS reactor core. Other considerations such as thermal-hydraulics, safety, and engineering that are not directly related to the core neutronic performance must be weighed before a final design is chosen.

Gehin, J.C.

1995-08-01

10

Air core pulse transformer design  

Microsoft Academic Search

Cylindrical-air-core pulse transformers capable of passing high-voltage\\/high-energy pulse waveforms with high efficiency and low distortion require a much more delicate design balance of physical dimensions and electrical parameters than iron or ferrite core units. Special computer codes were written to evaluate their performance. The analysis includes calculation of the self and mutual inductances as determined by the dimensions and insulation

J. P. O'Loughlin; J. D. Sidler; Gerry J. Rohwein

1988-01-01

11

SmAHTR-CTC Neutronic Design  

SciTech Connect

Building on prior experience for the 2010 initial SmAHTR neutronic design and on 2012 neutronic design for the advanced high temperature reactor (AHTR), this paper presents the main results of the neutronic design effort for the newly re-purposed SmAHTR-CTC reactor concept. The results are obtained based on full-core simulations performed with SCALE6.1. The dimensionality of the SmAHTR design space is reduced by using constraints originating in material fabricability, fuel licensing, molten salt chemistry, thermal-hydraulic and mechanical considerations. The new design represents in many regards a substantial improvement from the neutronic performance standpoint over the 2010 SmAHTR concept. Among other results, it is shown that fuel cycle length of over 2 years or discharged fuel burnup of 40GWd/MTHM are possible with a low, 8% fuel enrichment in a once-through fuel cycle, while 8-year once-through fuel cycle lengths are possible at higher fuel enrichments.

Ilas, Dan [ORNL; Holcomb, David Eugene [ORNL; Gehin, Jess C [ORNL

2014-01-01

12

Fuel, Core Design and Subchannel Analysis of a Superfast Reactor  

Microsoft Academic Search

A compact supercritical water-cooled fast reactor (superfast reactor) core with a power of 700MWe is designed by using a three-dimensional neutronics thermal-hydraulic coupled method. The core consists of 126 seed assemblies and 73 blanket assemblies. In the seed assemblies, 251 fuel rods, consisting of MOX pellets, stainless steel (SUS304) cladding, and fission gas plenum are arranged into a tight triangle

Liangzhi CAO; Yoshiaki OKA; Yuki ISHIWATARI; Zhi SHANG

2008-01-01

13

Conceptual study of advanced PWR core design.  

National Technical Information Service (NTIS)

The purpose of this project is for developing and verifying the core design concepts with enhanced safety and economy, and associated methodologies for core analyses. From the study of the sate-of-art of foreign advanced reactor cores, we developed core c...

H. K. Joo, K. K. Kim, M. H. Chang, Y. I. Kim, Y. J. Kim

1997-01-01

14

Effective delayed neutron fraction and prompt neutron lifetime of Tehran research reactor mixed-core  

PubMed Central

In this work, kinetic parameters of Tehran research reactor (TRR) mixed cores have been calculated. The mixed core configurations are made by replacement of the low enriched uranium control fuel elements with highly enriched uranium control fuel elements in the reference core. The MTR_PC package, a nuclear reactor analysis tool, is used to perform the analysis. Simulations were carried out to compute effective delayed neutron fraction and prompt neutron lifetime. Calculation of kinetic parameters is necessary for reactivity and power excursion transient analysis. The results of this research show that effective delayed neutron fraction decreases and prompt neutron lifetime increases with the fuels burn-up. Also, by increasing the number of highly enriched uranium control fuel elements in the reference core, the prompt neutron lifetime increases, but effective delayed neutron fraction does not show any considerable change. PMID:24976672

Lashkari, A.; Khalafi, H.; Kazeminejad, H.

2013-01-01

15

Optimization of IEC grid design for maximum neutron production  

SciTech Connect

Two different, complementary approaches were taken to determine the effects of an Inertial Electrostatic Confinement (IEC) grid`s design on the neutron production rate of the device. A semi-empirical formula developed from experimental data predicts the neutron yield of an IEC device, given the chamber size, grid radius and transparency, and operating voltage and current. Results from the IXL computer program support some of the scalings found in the semi-empirical formula. A second formula was also developed that predicts the neutron yield of an IEC device using grid design parameters and the ion core radius. The SIMION computer program was used to calculate the ion core radius. These formulas are useful tools for designing grids that will maximize the neutron yield for IEC devices. 7 refs., 9 figs.

Miley, G.H.; DeMora, J.; Stubbers, R.; Tzonev, I.V. [Univ. of Illinois, Urbana, IL (United States); Anderl, R.A. [Lockheed Martin Idaho Technologies Company, Idaho Falls, ID (United States); Nadler, J.H. [Department of Energy, Idaho Falls, ID (United States); Nebel, R. [Los Alamos National Lab., NM (United States)

1996-12-31

16

The advanced neutron source three-element-core fuel grading  

SciTech Connect

The proposed Advanced Neutron Source (ANS) pre-conceptual design consists of a two-element 330 MW{sub f} nuclear reactor fueled with highly-enriched uranium and is cooled, moderated, and reflected with heavy water. Recently, the ANS design has been changed to a three-element configuration in order to permit a reduction of the enrichment, if required, while maintaining or improving the thermal-hydraulic margins. The core consists of three annular fuel elements composed of involute-shaped fuel plates. Each fuel plate has a thickness of 1.27 mm and consists of a fuel meat region Of U{sub 3}Si{sub 2}-Al (50% enriched in one case that was proposed) and an aluminum filler region between aluminum cladding. The individual plates are separated by a 1.27 mm coolant channel. The three element core has a fuel loading of 31 kg of {sup 235}U which is sufficient for a 17-day fuel cycle. The goal in obtaining a new fuel grading is to maximize important temperature margins. The limits imposed axe: (1) Limit the temperature drop over the cladding oxide layer to less than 119{degrees}C to avoid oxide spallation. (2) Limit the fuel centerline temperature to less than 400{degrees}C to avoid fuel damage. (3) Limit the cladding wall temperature to less than the coolant. incipient-boiling temperature to avoid coolant boiling. Other thermal hydraulic conditions, such as critical heat flux, are also considered.

Gehin, J.C.

1995-12-31

17

Design of a Neutron Source for Calibration  

NASA Astrophysics Data System (ADS)

The neutron spectra produced by an isotopic neutron source located at the center of moderating media were calculated using Monte Carlo method in the aim to design a neutron source for calibration purposes. To improve the evaluation of the dosimetric quantities, is recomended to calibrate the radiation protection devices with calibrated neutron sources whose neutron spectra being similar to those met in practice. Here, a 239Pu-Be neutron source was inserted in H2O, D2O and polyethylene cylindrical moderators in order to produce neutron spectra that resembles spectra found in workplaces.

Carrillo-Nuñez, Aureliano; Vega-Carrillo, Héctor René

2002-08-01

18

One pass core design of a super fast reactor  

SciTech Connect

One pass core design for Supercritical-pressure light water-cooled fast reactor (Super FR) is proposed. The whole core is cooled with upward flow in one through flow pattern like PWR. Compared with the previous two pass core design; this new flow pattern can significantly simplify the core concept. Upper core structure, coolant flow scheme as well as refueling procedure are as simple as in PWR. In one pass core design, supercritical-pressure water is at approximately 25.0 MPa and enters the core at 280 C. degrees and is heated up in one through flow pattern upwardly to the average outlet temperature of 500 C. degrees. Great density change in vertical direction can cause significant axial power offset during the cycle. Meanwhile, Pu accumulated in the UO{sub 2} fuel blanket assemblies also introduces great power increase during cycle, which requires large amount of flow for heat removal and makes the outlet temperature of blanket low at the beginning of equilibrium cycle (BOEC). To deal with these issues, some MOX fuel is applied in the bottom region of the blanket assembly. This can help to mitigate the power change in blanket due to Pu accumulation and to increase the outlet temperature of the blanket during cycle. Neutron transport and thermohydraulics coupled calculation shows that this design can satisfy the requirement in the Super FR principle for both 500 C. degrees outlet temperature and negative coolant void reactivity. (authors)

Liu, Qingjie; Oka, Yoshiaki [Cooperative Major in Nuclear Energy, Waseda University, Tokyo 169-8555 (Japan)

2013-07-01

19

Core restraint design for inherent safety  

SciTech Connect

A simple analytical model is developed of core radial expansion for a fast reactor using a limited-free-bow core restraint design. Essentially elementary beam theory is used to calculate the elastic bow of a driver assembly at the core periphery subject to temperature dependent boundary conditions at the nozzle support, ACLP and TLP and subject to thermal and inelastic bowing deformations. The model is used to show the relative importance of grid plate temperature, core temperature rise, and restraint ring temperature in the inherent response of a limited-free-bow core restraint system to thermal transients. It is also used to explore this inherent core expansion. Limited verification of the model using detailed 3-D core restraint calculations is presented.

Moran, T.J.

1988-01-01

20

Advanced neutron source three-element-core fuel grading  

SciTech Connect

The proposed advanced neutron source (ANS) neutron research facility`s purpose is to provide unprecedented experimental capabilities in the areas of neutron scattering, materials research, and isotope production. The primary goals of the ANS project are to obtain neutron flux levels that are 5 to 10 times larger than any current existing facility and to provide isotope irradiation facilities that are at least as good as the High-Flux Isotope Reactor at Oak Ridge National Laboratory. The design changes in the ANS are described.

Gehin, J.C. [Oak Ridge National Lab., TN (United States)

1995-12-31

21

Designing Professional Development around the Common Core  

E-print Network

Designing Professional Development around the Common Core Standards for Mathematical Practice Preparation of Teachers: The Impact of the Common Core State Standards Initiative January 7, 2012 #12;The Standards for Mathematical Practice #12;The Standards for Mathematical Practice "varieties of expertise

Belding, Juliana

22

Magnetohydrodynamics of superfluid and superconducting neutron star cores  

E-print Network

Mature neutron stars are cold enough to contain a number of superfluid and superconducting components. These systems are distinguished by the presence of additional dynamical degrees of freedom associated with superfluidity. In order to consider models with mixtures of condensates we need to develop a multifluid description that accounts for the presence of rotational neutron vortices and magnetic proton fluxtubes. We also need to model the forces that impede the motion of vortices and fluxtubes, and understand how these forces act on the condensates. This paper concerns the development of such a model for the outer core of a neutron star, where superfluid neutrons co-exist with a type II proton superconductor and an electron gas. We discuss the hydrodynamics of this system, focusing on the role of the entrainment effect, the magnetic field, the vortex/fluxtube tension and the dissipative mutual friction forces. Out final results can be directly applied to a number of interesting astrophysical scenarios, e.g....

Glampedakis, K; Samuelsson, L

2010-01-01

23

Standard and Enhanced Cooling of Neutron Stars with Superfluid Cores  

E-print Network

Calculations are performed of the cooling of neutron stars with standard and enhanced neutrino energy losses in the presence of neutron and proton superfluidities in the stellar cores. The effects of superfluidity on the heat capacity and the neutrino luminosity produced by the direct and modified Urca processes and by the neutrino bremsstrahlung emission in nucleon-nucleon collisions are taken into account. The constraints are analyzed on the critical temperatures $\\tn$ and $\\tp$ of the transition of neutrons and protons to the superfluid state, which can be obtained from a comparison of observational data on thermal radiation from neutron stars with theoretical cooling curves for the standard and enhanced neutrino energy losses. Possible ranges of $\\tn$ and $\\tp$ for the pulsar Geminga are discussed.

K. P. Levenfish; D. G. Yakovlev

1996-08-07

24

AHTR Mechanical, Structural, And Neutronic Preconceptual Design  

SciTech Connect

This report provides an overview of the mechanical, structural, and neutronic aspects of the Advanced High Temperature Reactor (AHTR) design concept. The AHTR is a design concept for a large output Fluoride salt cooled High-temperature Reactor (FHR) that is being developed to enable evaluation of the technology hurdles remaining to be overcome prior to FHRs becoming a commercial reactor class. This report documents the incremental AHTR design maturation performed over the past year and is focused on advancing the design concept to a level of a functional, self-consistent system. The AHTR employs plate type coated particle fuel assemblies with rapid, off-line refueling. Neutronic analysis of the core has confirmed the viability of a 6-month 2-batch cycle with 9 weight-percent enriched uranium fuel. Refueling is intended to be performed automatically under visual guidance using dedicated robotic manipulators. The present design intent is for used fuel to be stored inside of containment for at least 6 months and then transferred to local dry wells for intermediate term, on-site storage. The mechanical and structural concept development effort has included an emphasis on transportation and constructability to minimize construction costs and schedule. The design intent is that all components be factory fabricated into rail transportable modules that are assembled into subsystems at an on-site workshop prior to being lifted into position using a heavy-lift crane in an open-top style construction. While detailed accident identification and response sequence analysis has yet to be performed, the design concept incorporates multiple levels of radioactive material containment including fully passive responses to all identified design basis or non-very-low frequency beyond design basis accidents. Key building design elements include: 1) below grade siting to minimize vulnerability to aircraft impact, 2) multiple natural circulation decay heat rejection chimneys, 3) seismic base isolation, and 4) decay heat powered back-up electricity generation. The report provides a preconceptual design of the manipulators, the fuel transfer system, and the salt transfer loops. The mechanical handling of the fuel and how it is accomplished without instrumentation inside the salt is described within the report. All drives for the manipulators reside outside the reactor top flange. The design has also taken into account the transportability of major components and how they will be assembled on site

Varma, Venugopal Koikal [ORNL; Holcomb, David Eugene [ORNL; Peretz, Fred J [ORNL; Bradley, Eric Craig [ORNL; Ilas, Dan [ORNL; Qualls, A L [ORNL; Zaharia, Nathaniel M [ORNL

2012-10-01

25

AHTR Mechanical, Structural, and Neutronic Preconceptual Design  

SciTech Connect

This report provides an overview of the mechanical, structural, and neutronic aspects of the Advanced High Temperature Reactor (AHTR) design concept. The AHTR is a design concept for a large output Fluoride salt cooled High-temperature Reactor (FHR) that is being developed to enable evaluation of the technology hurdles remaining to be overcome prior to FHRs becoming an option for commercial reactor deployment. This report documents the incremental AHTR design maturation performed over the past year and is focused on advancing the design concept to a level of a functional, self-consistent system. The reactor concept development remains at a preconceptual level of maturity. While the overall appearance of an AHTR design is anticipated to be similar to the current concept, optimized dimensions will differ from those presented here. The AHTR employs plate type coated particle fuel assemblies with rapid, off-line refueling. Neutronic analysis of the core has confirmed the viability of a 6-month two-batch cycle with 9 wt. % enriched uranium fuel. Refueling is intended to be performed automatically under visual guidance using dedicated robotic manipulators. The report includes a preconceptual design of the manipulators, the fuel transfer system, and the used fuel storage system. The present design intent is for used fuel to be stored inside of containment for at least six months and then transferred to local dry wells for intermediate term, on-site storage. The mechanical and structural concept development effort has included an emphasis on transportation and constructability to minimize construction costs and schedule. The design intent is that all components be factory fabricated into rail transportable modules that are assembled into subsystems at an on-site workshop prior to being lifted into position using a heavy-lift crane in an open-top style construction. While detailed accident identification and response sequence analysis has yet to be performed, the design concept incorporates fully passive responses to all identified design basis or non-very-low frequency beyond design basis accidents as well as multiple levels of radioactive material containment. Key building design elements include (1) below grade siting to minimize vulnerability to aircraft impact, (2) multiple natural circulation decay heat rejection chimneys, (3) seismic base isolation, and (4) decay heat powered back-up electricity generation.

Varma, V.K.; Holcomb, D.E.; Peretz, F.J.; Bradley, E.C.; Ilas, D.; Qualls, A.L.; Zaharia, N.M.

2012-09-15

26

Sensitivity of detecting in-core vibrations and boiling in pressurized water reactors using ex-core neutron detectors  

Microsoft Academic Search

Neutron transport and diffusion theory space- and energy-dependent reactor kinetics calculations were performed in the frequency domain to determine the sensitivity of an ex-core neutron detector to in-core vibrations and coolant boiling in a PWR. Results of these calculations indicate that the ex-core detectors are sensitive to neutron sources, to vibrations, and to boiling occurring over large regions of the

F. J. Sweeney; J. P. A. Renier

1984-01-01

27

Radiation of Neutron Stars Produced by Superfluid Core  

NASA Astrophysics Data System (ADS)

We find a new mechanism of neutron star radiation wherein radiation is produced by the stellar interior. The main finding is that the neutron star interior is transparent for collisionless electron sound, the same way as it is transparent for neutrinos. In the presence of the magnetic field the electron sound is coupled with electromagnetic radiation; such collective excitation is known as a fast magnetosonic wave. At high densities such waves reduce to the zero sound in electron liquid, while near the stellar surface they are similar to electromagnetic waves in a medium. We find that zero sound is generated by superfluid vortices in the stellar core. Thermally excited helical vortex waves produce fast magnetosonic waves in the stellar crust that propagate toward the surface and transform into outgoing electromagnetic radiation. The magnetosonic waves are partially absorbed in a thin layer below the surface. The absorption is highly anisotropic; it is smaller for waves that in the absorbing layer propagate closer to the magnetic field direction. As a result, the vortex radiation is pulsed with the period of star rotation. The vortex radiation has the spectral index ?~-0.45 and can explain nonthermal radiation of middle-aged pulsars observed in the infrared, optical, and hard X-ray bands. The radiation is produced in the star interior, rather than in the magnetosphere, which allows direct determination of the core temperature. Comparing the theory with available spectra observations, we find that the core temperature of the Vela pulsar is T~8×108 K, while the core temperature of PSR B0656+14 and Geminga exceeds 2×108 K. This is the first measurement of the temperature of a neutron star core. The temperature estimate rules out equations of state incorporating Bose condensations of pions or kaons and quark matter in these objects. The estimate also allows us to determine the critical temperature of triplet neutron superfluidity in the Vela core, Tc=(7.5+/-1.5)×109 K, which agrees well with the value of critical temperature in a core of a canonical neutron star calculated based on recent data for behavior of strong interactions at high energies. We also find that in the middle-aged neutron stars the vortex radiation, rather than thermal conductivity, is the main mechanism of heat transfer from the stellar core to the surface. The core radiation opens a possibility to study composition of neutron star crust by detection of absorption lines corresponding to the low-energy excitations of crust nuclei. Bottom layers of the crust may contain exotic nuclei with the mass number up to 600, and the core radiation creates a perspective to study their properties. In principle, zero sound can also be emitted by other mechanisms, rather than vortices. In this case the spectrum of stellar radiation would contain features corresponding to such processes. As a result, zero sound opens a perspective of direct spectroscopic study of superdense matter in the neutron star interior.

Svidzinsky, Anatoly A.

2003-06-01

28

Nucleation of Quark Matter in Neutron Star Cores  

NASA Astrophysics Data System (ADS)

We consider the general conditions of quark droplet formation in high-density neutron matter. The growth of the quark bubble (assumed to contain a sufficiently large number of particles) can be described by means of a Fokker-Planck equation. The dynamics of the nucleation essentially depends on the physical properties of the medium in which it takes place. The conditions for quark bubble formation are analyzed within the framework of both dissipative and nondissipative (with zero bulk and shear viscosity coefficients) approaches. The conversion time of the neutron star to a quark star is obtained as a function of the equation of state of the neutron matter and of the microscopic parameters of the quark nuclei. As an application of the formalism obtained, we analyze the first-order phase transition from neutron matter to quark matter in rapidly rotating neutron star cores, triggered by the gravitational energy released during the spinning down of the neutron star. The endothermic conversion process, via gravitational energy absorption, could take place in a very short time interval, of the order of a few tens of seconds, in a class of dense compact objects with very high magnetic fields, called magnetars.

Harko, T.; Cheng, K. S.; Tang, P. S.

2004-06-01

29

High-burnup core design using minor actinide-containing metal fuel  

SciTech Connect

A neutronic design study of metal fuel fast reactor (FR) cores is conducted on the basis of an innovative fuel design concept to achieve an extremely high burnup and realize an efficient fuel cycle system. Since it is expected that the burnup reactivity swing will become extremely large in an unprecedented high burnup core, minor actinides (MAs) from light water reactors (LWRs) are added to fresh fuel to improve the core internal conversion. Core neutronic analysis revealed that high burnups of about 200 MWd/kg for a small-scale core and about 300 MWd/kg for a large-scale core can be attained while suppressing the burnup reactivity swing to almost the same level as that of conventional cores with normal burnup. An actinide burnup analysis has shown that the MA consumption ratio is improved to about 60% and that the accumulated MAs originating from LWRs can be efficiently consumed by the high-burnup metal fuel FR. (authors)

Ohta, Hirokazu; Ogata, Takanari [Central Research Institute of Electric Power Industry, 2-11-1, Iwado Kita. Komae-shi, Tokyo 201-8511 (Japan); Obara, T. [Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8550 (Japan)

2013-07-01

30

Viewing the Bilayer Hydrocarbon Core Using Neutron Diffraction  

Microsoft Academic Search

Membrane proteins fold, assemble and function within their native fluid lipid environment. Structural studies of fluid lipid\\u000a bilayers are thus critically important for understanding processes in membranes. Here, we propose a simple approach to visualize\\u000a the hydrocarbon core using neutron diffraction and deuterated lipids that are commercially available. This method should have\\u000a broad utility in structural studies of the bilayer

Xue Han; Kalina Hristova

2009-01-01

31

Identifying the Core in Art and Design.  

ERIC Educational Resources Information Center

Presents a model for systematizing the relationships between core content and educational objectives in British art and design classes. The model shows how the expressive, perceptual, analytic and cultural domains of art and design education are interrelated. Available from Carfax Publishing Company, P.O. Box 25, Abingdon, Oxfordshire OX14 1RW…

Allison, Brian

1982-01-01

32

Inertial modes of neutron stars with the superfluid core  

E-print Network

We investigate the modal properties of inertial modes of rotating neutron stars with the core filled with neutron and proton superfluids, taking account of entrainment effects between the superfluids. In this paper, the entrainment effects are modeled by introducing a parameter $\\eta$ so that no entrainment state is realized at $\\eta=0$. We find that inertial modes of rotating neutron stars with the superfluid core are split into two families, which we call ordinary fluid inertial modes ($i^o$-mode) and superfluid inertial modes ($i^s$-mode). The two superfluids in the core counter-move for the $i^s$-modes. For the $i^o$-modes, $\\kappa_0=\\lim_{\\Omega\\to 0}\\omega/\\Omega$ is only weakly dependent on the entrainment parameter $\\eta$, where $\\Omega$ and $\\omega$ are the angular frequency of rotation and the oscillation frequency observed in the corotating frame of the star, respectively. For the $i^s$-modes, on the other hand, $|\\kappa_0|$ almost linearly increases as $\\eta$ increases. Avoided crossings as functions of $\\eta$ are therefore quite common between $i^o$- and $i^s$-modes. We find that some of the $i^s$-modes that are unstable against the gravitational radiation reaction at $\\eta=0$ become stable when $\\eta$ is larger than $\\eta_{crit}$, the value of which depends on the mode. Since the radiation driven instability associated with the current multipole radiation is quite weak for the inertial modes and the mutual friction damping in the superfluid core is strong, the instability caused by the inertial modes will be easily suppressed unless the entrainment parameter $\\eta$ is extremely small and the mutual friction damping is sufficiently weak.

Shijun Yoshida; Umin Lee

2003-02-16

33

Neutron capture therapy beam design at Harwell.  

PubMed

At Harwell, we have progressed from designing, building, and using small-diameter beams of epithermal neutrons for radiobiology studies to designing a radiotherapy facility for the 25-MW research reactor DIDO. The program is well into the survey phase, where the main emphasis is on tailoring the neutron spectrum. The incorporation of titanium and vanadium in an aluminium spectrum shaper in the D2O reflector has been shown to yield a significant reduction in the mean energy of neutrons incident on the patient by suppression of streaming through the cross-section window in aluminium at 25 keV. PMID:2176459

Constantine, G

1990-01-01

34

Design of composite hollow-core panels  

SciTech Connect

A design method is proposed to describe the static behavior of hollow-core panels under flexure. These panels are made of diagonal stiffeners placed between two faces with a composite material (carbon-epoxy). The hollow-core panels and the design method were both developed by the ENPC for the making of structural components having a high stiffness/weight ratio. An analytical model based on a periodic media homogenization method was developed to obtain the constitutive law of the equivalent homogeneous panel. The accuracy of this model was assessed by comparing the calculated deflections with those of another 3D finite element model. An optimization method, based on the Euler equations, was further developed to provide the minimum weight for a given deflection. The faces and the stiffeners thicknesses were set as variables for the optimization process. With the partnership of the SNCF (the French railroads company), this method was applied to the design of the intermediate floor of the two-levels cabins for the TGV trains (high speed trains). The deflection of the aluminum honeycomb core sandwich floor already used by the SNCF was computed and, afterwards, the optimization method was used to find a hollow-core floor having the same deflection but a minimum weight. The results of the optimization clearly indicate that it is possible to reduce the aluminum TGV floor weight to one third.

Philippe, M.H.; Naciri, T.; Ehrlacher, A. [CERAM-ENPC, Noisy-le-Grand (France)

1996-11-01

35

Stellar encounters involving neutron stars in globular cluster cores  

NASA Technical Reports Server (NTRS)

Encounters between a 1.4 solar mass neutron star and a 0.8 solar mass red giant (RG) and between a 1.4 solar mass neutron star (NS) and an 0.8 solar mass main-sequence (MS) star have been successfully simulated. In the case of encounters involving an RG, bound systems are produced when the separation at periastron passage R(MIN) is less than about 2.5 R(RG). At least 70 percent of these bound systems are composed of the RG core and NS forming a binary engulfed in a common envelope of what remains of the former RG envelope. Once the envelope is ejected, a tight white dwarf-NS binary remains. For MS stars, encounters with NSs will produce bound systems when R(MIN) is less than about 3.5 R(MS). Some 50 percent of these systems will be single objects with the NS engulfed in a thick disk of gas almost as massive as the original MS star. The ultimate fate of such systems is unclear.

Davies, M. B.; Benz, W.; Hills, J. G.

1992-01-01

36

Measurement of the vortex core in sub-100 nm Fe dots using polarized neutron scattering  

E-print Network

OFFPRINT Measurement of the vortex core in sub-100 nm Fe dots using polarized neutron scattering neutron scattering Igor V. Roshchin1,2 , Chang-Peng Li2(a) , Harry Suhl2 , Xavier Batlle3 , S. Roy2(b diffraction and scattering Abstract ­ We use polarized neutron scattering to obtain quantitative information

Roshchin, Igor V.

37

Energy Efficient Engine core design and performance report  

NASA Technical Reports Server (NTRS)

The Energy Efficient Engine (E3) is a NASA program to develop fuel saving technology for future large transport aircraft engines. Testing of the General Electric E3 core showed that the core component performance and core system performance necessary to meet the program goals can be achieved. The E3 core design and test results are described.

Stearns, E. Marshall

1982-01-01

38

Interaction of the control system with core nuclear design for fast spectrum space power reactors  

NASA Astrophysics Data System (ADS)

The reactor control system and operating strategy are essential factors in assessing reactor reliability and safety. The control system and its mode of operation also exert major influences on mechanical design of core components and all aspects of nuclear design. This is especially true of reactors for space power applications because of the imposed requirements regarding compactness, minimum mass, and long term operational reliability without external intervention or maintenance. Generic features of the interaction between nuclear design and reactor control system design for fast spectrum space power reactors are outlined. Several basic control concepts were analyzed. These included ex-core control drums, in-core control rods, burnable poisons, dispersed poisons in the core, and movable fuel segments or regions. Cross sections for calculations were generated with MC sup 2 -2, and neutronics calculations were performed with the VIM Monte Carlo code, ONEDANT, and DIF3D.

Lell, R. M.; Hanan, N. A.

39

BEAM-LOSS DRIVEN DESIGN OPTIMIZATION FOR THE SPALLATION NEUTRON SOURCE (SNS) RING.  

SciTech Connect

This paper summarizes three-stage design optimization for the Spallation Neutron Source (SNS) ring: linear machine design (lattice, aperture, injection, magnet field errors and misalignment), beam core manipulation (painting, space charge, instabilities, RF requirements), and beam halo consideration (collimation, envelope variation, e-p issues etc.).

WEI,J.; BEEBE-WANG,J.; BLASKIEWICZ,M.; CAMERON,P.; DANBY,G.; GARDNER,C.J.; JACKSON,J.; LEE,Y.Y.; LUDEWIG,H.; MALITSKY,N.; RAPARIA,D.; TSOUPAS,N.; WENG,W.T.; ZHANG,S.Y.

1999-03-29

40

Advanced Neutron Source: Plant Design Requirements  

SciTech Connect

The Advanced Neutron Source will be a new world-class facility for research using hot, thermal, cold, and ultra-cold neutrons. The heart of the facility will be a 330-MW (fission), heavy-water cooled and heavy-water moderated reactor. The reactor will be housed in a central reactor building, with supporting equipment located in an adjoining reactor support building. An array of cold neutron guides will fan out into a large guide hall, housing about 30 neutron research stations. Appropriate office, laboratory, and shop facilities will be included to provide a complete facility for users. The ANS is scheduled to begin operation at the Oak Ridge National Laboratory early in the next decade. This PDR document defines the plant-level requirements for the design, construction, and operation of ANS. It also defines and provides input to the individual System Design Description (SDD) documents. Together, this PDR document and the set of SDD documents will define and control the baseline configuration of ANS.

Not Available

1990-07-01

41

Turbo decoder core design for system development  

NASA Astrophysics Data System (ADS)

Due to their near Shannon-capacity performance, turbo codes have received a considerable amount of attention since their introduction. They are particularly attractive for cellular communication systems and have been included in the specifications for both the WCDMA(UMTS) and cdma2000 third-generation cellular standards. The log-MAP decoding algorithm and some technologies used to reduce the complexity have discussed in the past days. But we can see that if we apply the Turbo code to wireless communications,the decoding process rate is the bottleneck. The software implement is not realistic in today"s DSP process rate. So the hardware design is supposed to realize the decoding. The purpose of this paper is to present a full ASIC design way of Turbo decoding. Many technologies are added to the basic Log-MAP algorithm to simple the design and improve the performance. With the log-MAP algorithm, the Jacobi logarithm is computed exactly using max*()=ln(exp(x)+exp(y))=max()+fc(|y-x|),The correction function fc(|y-x|) is important because there will be 0.5dB SNR loss without it. The linear approximation can be used and the linear parameters was selected carefully to suit hardware realize in our design. In order to save the power consumption and also to assure the performance, the quantization is important in ASIC design, we adopt a compromise scheme to save the power and also there is good BER behaves. Many noisy frames can be corrected with a few iterations while some of the more noisy frames need to experience a full number of iterations (NOI). Thus, if the decoder could stop the iteration as soon as the frame becomes correct, the average NOI would be reduced. There are many ways to stop the iteration such as CRC, compare and so on, we adopt a significantly less computation and much less storage stop criteria. For long frames the memory for storing the entire frame of the forward probability ? or the backward probability ? can be very large. Available products all use sliding-window version of the turbo decoder to reduce the memory requirements. This is also true in our design. In addition of this, a new method is adopted to expand the sliding window length but without increasing the storing requirement. This method also improves the performance evidently. The technologies adoped in the paper are suited hardware design for wireless application. For example, this decoding core can be embedded into our 32-bit digital signal processor (MD-32) to realize 3G basestation receiver.

Chen, Xiaoyi; Yao, Qingdong; Liu, Peng

2003-04-01

42

Learn from the Core--Design from the Core  

ERIC Educational Resources Information Center

The current objective, object-oriented approach to design is questioned along with design education viewed as a job-oriented endeavor. Instead relational knowledge and experience in a holistic sense, both tacit and explicit, are valued along with an appreciation of the unique character of the student. A new paradigm for design education is…

Ockerse, Thomas

2012-01-01

43

Core refueling subsystem design description. Revision 1  

SciTech Connect

The Core Refueling Subsystem of the Fuel Handling and Storage System provides the mechanisms and tools necessary for the removal and replacement of the hexagonal elements which comprise the reactor core. The Core Refueling Subsystem is not "safety-related." The Core Refueling Subsystem equipment is used to prepare the plant for element removal and replacement, install the machines which handle the elements, maintain control of air inleakage and radiation release, transport the elements between the core and storage, and control the automatic and manual operations of the machines. Much of the element handling is performed inside the vessel, and the entire exchange of elements between storage and core is performed with the elements in a helium atmosphere. The core refueling operations are conducted with the reactor module shutdown and the primary coolant pressure slightly subatmospheric. The subsystem is capable of accomplishing the refueling in a reliable manner commensurate with the plant availability requirements.

Anderson, J.K.; Harvey, E.C.

1987-07-01

44

SPECTRUM MEASUREMENTS IN THE ZENITH PLUTONIUM CORE 7 USING A NEUTRON CHOPPER  

Microsoft Academic Search

As part of the experimental programme on the first plutonium loading of ZENITH (Core 7) a series of measurements was carried out with the neutron chopper on a beam emerging from the core centre. The general experimental programme on the two ZENITH plutonium cores has been covered elsewhere. Core 7 had a carbon\\/Pu239 atomic ratio of 2666 and a steel\\/Pu239

F. R. Barclay; I. R. Cameron; H. H. W. Pitcher; C. R. Symons

1964-01-01

45

The long-term rotation dynamics of neutron stars with differentially rotating unmagnetized core  

NASA Astrophysics Data System (ADS)

We consider the pulsar long-term rotation dynamics taking into account the non-rigidity of neutron star rotation. We restrict our attention to the models with two essential assumptions: (1) crust-core interaction occurs via the viscosity (magnetic coupling is not important); (2) neutron star shape is symmetrical over the magnetic axis. The neutron star core is described by linearized quasi-stationary Newtonian hydrodynamical equations in one-fluid and two-fluid (neutron superfluidity) approximations. It is shown that in this case the pulsar inclination angle evolves to 0° or 90° very quickly. Since such fast evolution seems to contradict the observation data, either neutron stars are triaxial or the magnetic field plays the leading role in crust-core coupling.

Barsukov, D. P.; Goglichidze, O. A.; Tsygan, A. I.

2014-10-01

46

REVIEWS OF TOPICAL PROBLEMS: Cooling of neutron stars and superfluidity in their cores  

NASA Astrophysics Data System (ADS)

We study the heat capacity and neutrino emission reactions (direct and modified Urca processes, nucleon-nucleon bremsstrahlung, Cooper pairing of nucleons) in the supranuclear density matter of neutron star cores with superfluid neutrons and protons. Various superfluidity types are analysed (singlet-state pairing and two types of triplet-state pairing, without and with gap nodes at the nucleon Fermi surface). The results are used for cooling simulations of isolated neutron stars. Both the standard cooling and the cooling enhanced by the direct Urca process are strongly affected by nucleon superfluidity. Comparison of the cooling theory of isolated neutron stars with observations of their thermal radiation may give stringent constraints on the critical temperatures of the neutron and proton superfluidities in the neutron star cores.

Yakovlev, Dmitrii G.; Levenfish, Kseniya P.; Shibanov, Yurii A.

1999-08-01

47

Sensitivity of ex-core neutron detectors to vibrations of PWR fuel assemblies  

Microsoft Academic Search

The response of an ex-core neutron detector to fuel assembly vibrations in an 1150-MWe Westinghouse pressurized-water reactor (PWR) was determined by performing space-dependent reactor-kinetics calculations. The effect on the detector response of reducing the soluble-boron concentration in the coolant and fuel burnup over the first fuel cycle was also determined. The results of the calculations indicate that the ex-core neutron

F. J. Sweeney; J. P. Renier

1983-01-01

48

Development and preliminary verification of the 3D core neutronic code: COCO  

SciTech Connect

As the recent blooming economic growth and following environmental concerns (China)) is proactively pushing forward nuclear power development and encouraging the tapping of clean energy. Under this situation, CGNPC, as one of the largest energy enterprises in China, is planning to develop its own nuclear related technology in order to support more and more nuclear plants either under construction or being operation. This paper introduces the recent progress in software development for CGNPC. The focus is placed on the physical models and preliminary verification results during the recent development of the 3D Core Neutronic Code: COCO. In the COCO code, the non-linear Green's function method is employed to calculate the neutron flux. In order to use the discontinuity factor, the Neumann (second kind) boundary condition is utilized in the Green's function nodal method. Additionally, the COCO code also includes the necessary physical models, e.g. single-channel thermal-hydraulic module, burnup module, pin power reconstruction module and cross-section interpolation module. The preliminary verification result shows that the COCO code is sufficient for reactor core design and analysis for pressurized water reactor (PWR). (authors)

Lu, H.; Mo, K.; Li, W.; Bai, N.; Li, J. [Reactor Design and Fuel Management Research Center, China Nuclear Power Technology Research Inst., 47F/A Jiangsu Bldg., Yitian Road, Futian District, Shenzhen (China)

2012-07-01

49

Nucleosynthesis by rapid neutron capture in the neutrino-energized wind from supernova cores  

Microsoft Academic Search

As a neutron star forms from the collapse of the iron core of a massive star, escaping neutrinos from the interior interact with material on the surface. This heated matter is then ejected as a baryon wind. As this slightly neutron-rich nucleon gas cools it experiences an alpha-rich freezeout to build A â¼100 seed nuclei which subsequently capture neutrons to

G. J. Mathews; J. R. Wilson; S. E. Woosley; R. D. Hoffman; B. S. Meyer

1993-01-01

50

Core bit design reduces mud invasion, improves ROP  

SciTech Connect

A recently developed core bit reduces fluid invasion in the cut core by minimizing the exposure to the drilling fluid and by increasing the rate of penetration (ROP). A high ROP during coring is one of the major factors in reducing mud filtrate invasion in cores. This new low-invasion polycrystalline diamond compact (PDC) core bit was designed to achieve a higher ROP than conventional PDC core bits without detriment to the cutting structure. The paper describes the bit and its operation, results of lab tests, fluid dynamics, and results of field tests.

Clydesdale, G. (Security DBS, Aberdeen (United Kingdom)); Leseultre, A.; Lamine, E. (Security DBS, Brussels (Belgium))

1994-08-08

51

MPACT Fast Neutron Multiplicity System Design Concepts  

SciTech Connect

This report documents work performed by Idaho National Laboratory and the University of Michigan in fiscal year (FY) 2012 to examine design parameters related to the use of fast-neutron multiplicity counting for assaying plutonium for materials protection, accountancy, and control purposes. This project seeks to develop a new type of neutron-measurement-based plutonium assay instrument suited for assaying advanced fuel cycle materials. Some current-concept advanced fuels contain high concentrations of plutonium; some of these concept fuels also contain other fissionable actinides besides plutonium. Because of these attributes the neutron emission rates of these new fuels may be much higher, and more difficult to interpret, than measurements made of plutonium-only materials. Fast neutron multiplicity analysis is one approach for assaying these advanced nuclear fuels. Studies have been performed to assess the conceptual performance capabilities of a fast-neutron multiplicity counter for assaying plutonium. Comparisons have been made to evaluate the potential improvements and benefits of fast-neutron multiplicity analyses versus traditional thermal-neutron counting systems. Fast-neutron instrumentation, using for example an array of liquid scintillators such as EJ-309, have the potential to either a) significantly reduce assay measurement times versus traditional approaches, for comparable measurement precision values, b) significantly improve assay precision values, for measurement durations comparable to current-generation technology, or c) moderating improve both measurement precision and measurement durations versus current-generation technology. Using the MCNPX-PoliMi Monte Carlo simulation code, studies have been performed to assess the doubles-detection efficiency for a variety of counter layouts of cylindrical liquid scintillator detector cells over one, two, and three rows. Ignoring other considerations, the best detector design is the one with the most detecting volume. However, operational limitations guide a) the maximum acceptable size of each detector cell (due to PSD performance and maximum-acceptable per-channel data throughput rates, limited by pulse pile-up and the processing rate of the electronics components of the system) and b) the affordability of a system due to the number of total channels of data to be collected and processed. As a first estimate, it appears that a system comprised of two rows of detectors 5" Ø ? 3" would yield a working prototype system with excellent performance capabilities for assaying Pu-containing items and capable of handling high signal rates likely when measuring items with Pu and other actinides. However, it is still likely that gamma-ray shielding will be needed to reduce the total signal rate in the detectors. As a first step prior to working with these larger-sized detectors, it may be practical to perform scoping studies using small detectors, such as already-on-hand 3" Ø ? 3" detectors.

D. L. Chichester; S. A. Pozzi; J. L. Dolan; M. T. Kinlaw; A. C. Kaplan; M. Flaska; A. Enqvist; J. T. Johnsom; S. M. Watson

2012-10-01

52

The Spallation Neutron Source accelerator system design  

NASA Astrophysics Data System (ADS)

The Spallation Neutron Source (SNS) was designed and constructed by a collaboration of six U.S. Department of Energy national laboratories. The SNS accelerator system consists of a 1 GeV linear accelerator and an accumulator ring providing 1.4 MW of proton beam power in microsecond-long beam pulses to a liquid mercury target for neutron production. The accelerator complex consists of a front-end negative hydrogen-ion injector system, an 87 MeV drift tube linear accelerator, a 186 MeV side-coupled linear accelerator, a 1 GeV superconducting linear accelerator, a 248-m circumference accumulator ring and associated beam transport lines. The accelerator complex is supported by ~100 high-power RF power systems, a 2 K cryogenic plant, ~400 DC and pulsed power supply systems, ~400 beam diagnostic devices and a distributed control system handling ~100,000 I/O signals. The beam dynamics design of the SNS accelerator is presented, as is the engineering design of the major accelerator subsystems.

Henderson, S.; Abraham, W.; Aleksandrov, A.; Allen, C.; Alonso, J.; Anderson, D.; Arenius, D.; Arthur, T.; Assadi, S.; Ayers, J.; Bach, P.; Badea, V.; Battle, R.; Beebe-Wang, J.; Bergmann, B.; Bernardin, J.; Bhatia, T.; Billen, J.; Birke, T.; Bjorklund, E.; Blaskiewicz, M.; Blind, B.; Blokland, W.; Bookwalter, V.; Borovina, D.; Bowling, S.; Bradley, J.; Brantley, C.; Brennan, J.; Brodowski, J.; Brown, S.; Brown, R.; Bruce, D.; Bultman, N.; Cameron, P.; Campisi, I.; Casagrande, F.; Catalan-Lasheras, N.; Champion, M.; Champion, M.; Chen, Z.; Cheng, D.; Cho, Y.; Christensen, K.; Chu, C.; Cleaves, J.; Connolly, R.; Cote, T.; Cousineau, S.; Crandall, K.; Creel, J.; Crofford, M.; Cull, P.; Cutler, R.; Dabney, R.; Dalesio, L.; Daly, E.; Damm, R.; Danilov, V.; Davino, D.; Davis, K.; Dawson, C.; Day, L.; Deibele, C.; Delayen, J.; DeLong, J.; Demello, A.; DeVan, W.; Digennaro, R.; Dixon, K.; Dodson, G.; Doleans, M.; Doolittle, L.; Doss, J.; Drury, M.; Elliot, T.; Ellis, S.; Error, J.; Fazekas, J.; Fedotov, A.; Feng, P.; Fischer, J.; Fox, W.; Fuja, R.; Funk, W.; Galambos, J.; Ganni, V.; Garnett, R.; Geng, X.; Gentzlinger, R.; Giannella, M.; Gibson, P.; Gillis, R.; Gioia, J.; Gordon, J.; Gough, R.; Greer, J.; Gregory, W.; Gribble, R.; Grice, W.; Gurd, D.; Gurd, P.; Guthrie, A.; Hahn, H.; Hardek, T.; Hardekopf, R.; Harrison, J.; Hatfield, D.; He, P.; Hechler, M.; Heistermann, F.; Helus, S.; Hiatt, T.; Hicks, S.; Hill, J.; Hill, J.; Hoff, L.; Hoff, M.; Hogan, J.; Holding, M.; Holik, P.; Holmes, J.; Holtkamp, N.; Hovater, C.; Howell, M.; Hseuh, H.; Huhn, A.; Hunter, T.; Ilg, T.; Jackson, J.; Jain, A.; Jason, A.; Jeon, D.; Johnson, G.; Jones, A.; Joseph, S.; Justice, A.; Kang, Y.; Kasemir, K.; Keller, R.; Kersevan, R.; Kerstiens, D.; Kesselman, M.; Kim, S.; Kneisel, P.; Kravchuk, L.; Kuneli, T.; Kurennoy, S.; Kustom, R.; Kwon, S.; Ladd, P.; Lambiase, R.; Lee, Y. Y.; Leitner, M.; Leung, K.-N.; Lewis, S.; Liaw, C.; Lionberger, C.; Lo, C. C.; Long, C.; Ludewig, H.; Ludvig, J.; Luft, P.; Lynch, M.; Ma, H.; MacGill, R.; Macha, K.; Madre, B.; Mahler, G.; Mahoney, K.; Maines, J.; Mammosser, J.; Mann, T.; Marneris, I.; Marroquin, P.; Martineau, R.; Matsumoto, K.; McCarthy, M.; McChesney, C.; McGahern, W.; McGehee, P.; Meng, W.; Merz, B.; Meyer, R.; Meyer, R.; Miller, B.; Mitchell, R.; Mize, J.; Monroy, M.; Munro, J.; Murdoch, G.; Musson, J.; Nath, S.; Nelson, R.; Nelson, R.; O'Hara, J.; Olsen, D.; Oren, W.; Oshatz, D.; Owens, T.; Pai, C.; Papaphilippou, I.; Patterson, N.; Patterson, J.; Pearson, C.; Pelaia, T.; Pieck, M.; Piller, C.; Plawski, T.; Plum, M.; Pogge, J.; Power, J.; Powers, T.; Preble, J.; Prokop, M.; Pruyn, J.; Purcell, D.; Rank, J.; Raparia, D.; Ratti, A.; Reass, W.; Reece, K.; Rees, D.; Regan, A.; Regis, M.; Reijonen, J.; Rej, D.; Richards, D.; Richied, D.; Rode, C.; Rodriguez, W.; Rodriguez, M.; Rohlev, A.; Rose, C.; Roseberry, T.; Rowton, L.; Roybal, W.; Rust, K.; Salazer, G.; Sandberg, J.; Saunders, J.; Schenkel, T.; Schneider, W.; Schrage, D.; Schubert, J.; Severino, F.; Shafer, R.; Shea, T.; Shishlo, A.; Shoaee, H.; Sibley, C.; Sims, J.; Smee, S.; Smith, J.; Smith, K.; Spitz, R.; Staples, J.; Stein, P.; Stettler, M.; Stirbet, M.; Stockli, M.; Stone, W.; Stout, D.; Stovall, J.; Strelo, W.; Strong, H.; Sundelin, R.; Syversrud, D.; Szajbler, M.; Takeda, H.; Tallerico, P.; Tang, J.; Tanke, E.; Tepikian, S.; Thomae, R.; Thompson, D.; Thomson, D.; Thuot, M.; Treml, C.; Tsoupas, N.; Tuozzolo, J.; Tuzel, W.; Vassioutchenko, A.; Virostek, S.; Wallig, J.; Wanderer, P.; Wang, Y.; Wang, J. G.; Wangler, T.; Warren, D.; Wei, J.; Weiss, D.; Welton, R.; Weng, J.; Weng, W.-T.; Wezensky, M.; White, M.; Whitlatch, T.; Williams, D.; Williams, E.; Wilson, K.; Wiseman, M.; Wood, R.; Wright, P.; Wu, A.; Ybarrolaza, N.; Young, K.; Young, L.; Yourd, R.; Zachoszcz, A.; Zaltsman, A.; Zhang, S.; Zhang, W.; Zhang, Y.; Zhukov, A.

2014-11-01

53

Neutronic Design and Measured Performance of the Low Energy Neutron Source (LENS) Target Moderator Reflector Assembly  

E-print Network

The Low Energy Neutron Source (LENS) is an accelerator-based pulsed cold neutron facility under construction at the Indiana University Cyclotron Facility (IUCF). The idea behind LENS is to produce pulsed cold neutron beams starting with ~MeV neutrons from (p,n) reactions in Be which are moderated to meV energies and extracted from a small solid angle for use in neutron instruments which can operate efficiently with relatively broad (~1 msec) neutron pulse widths. Although the combination of the features and operating parameters of this source is unique at present, the neutronic design possesses several features similar to those envisioned for future neutron facilities such as long-pulsed spallation sources (LPSS) and very cold neutron (VCN) sources. We describe the underlying ideas and design details of the target/moderator/reflector system (TMR) and compare measurements of its brightness, energy spectrum, and emission time distribution under different moderator configurations with MCNP simulations. Brightnes...

Lavelle, C M; Bogdanov, A; Derenchuk, V P; Kaiser, H; Leuschner, M B; Lone, M A; Lozowski, W; Nann, H; Von Przewoski, B; Remmes, N; Rinckel, T; Shin, Y; Snow, W M; Sokol, P E

2008-01-01

54

Physical design of target station and neutron instruments for China Spallation Neutron Source  

NASA Astrophysics Data System (ADS)

The China Spallation Neutron Source (CSNS) is the first accelerator-based multidiscipline user facility to produce pulsed neutrons by tungsten target under collision of a pulsed proton beam with a beam power of 100 kW at a repetition rate of 25 Hz. In this paper, we focus on the physical design of CSNS target station and neutron instruments. Under optimized design, the flat tungsten target and the compact target-moderator-reflector coupling enhance effective cold and thermal neutron output from moderators. Three wing-type moderators supply four different characteristics of neutrons to 19 beamlines primarily for neutron scattering applications. Layout of neutron instruments are conceptually planned for total 20 beamlines, the configuration and specification have been determined for three day-one neutron instruments. All designs are optimized for the Phase I of 100 kW with a upgradable capacity to 500 kW.

Wang, FangWei; Liang, TianJiao; Yin, Wen; Yu, QuanZhi; He, LunHua; Tao, JuZhou; Zhu, Tao; Jia, XueJun; Zhang, ShaoYing

2013-12-01

55

An intrinsically safe facility for forefront research and training on nuclear technologies — Core design  

NASA Astrophysics Data System (ADS)

The core of a subcritical, low-power research reactor in a lead matrix has been designed using the MCNPX code. The main parameters, like geometry, material composition in the fuel assembly and reflector size, have been optimized for a k eff ˜ 0.95 and a thermal power around 200 Kw. A 70 Mev, 1 mA proton beam incident on a beryllium target has been assumed as neutron source and the corresponding thermal power distribution and neutron fluxes in the reactor have been simulated.

Viberti, C. M.; Ricco, G.

2014-04-01

56

Advanced BWR core component designs and the implications for SFD analysis  

SciTech Connect

Prior to the DF-4 boiling water reactor (BWR) severe fuel damage (SFD) experiment conducted at the Sandia National Laboratories in 1986, no experimental data base existed for guidance in modeling core component behavior under postulated severe accident conditions in commercial BWRs. This paper will present the lessons learned from the DF-4 experiment (and subsequent German CORA BWR SFD tests) and the impact on core models in the current generation of SFD codes. The DF-4 and CORA BWR test assemblies were modeled on the core component designs circa 1985; that is, the 8 x 8 fuel assembly with two water rods and a cruciform control blade constructed of B{sub 4}C-filled tubelets. Within the past ten years, the state-of-the-art with respect to BWR core component development has out-distanced the current SFD experimental data base and SFD code capabilities. For example, modern BWR control blade design includes hafnium at the tips and top of each control blade wing for longer blade operating lifetimes; also water rods have been replaced by larger water channels for better neutronics economy; and fuel assemblies now contain partial-length fuel rods, again for better neutronics economy. This paper will also discuss the implications of these advanced fuel assembly and core component designs on severe accident progression and on the current SFD code capabilities.

Ott, L.J.

1997-02-01

57

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

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

58

Neutronic Design and Measured Performance of the Low Energy Neutron Source (LENS) Target Moderator Reflector Assembly  

E-print Network

The Low Energy Neutron Source (LENS) is an accelerator-based pulsed cold neutron facility under construction at the Indiana University Cyclotron Facility (IUCF). The idea behind LENS is to produce pulsed cold neutron beams starting with ~MeV neutrons from (p,n) reactions in Be which are moderated to meV energies and extracted from a small solid angle for use in neutron instruments which can operate efficiently with relatively broad (~1 msec) neutron pulse widths. Although the combination of the features and operating parameters of this source is unique at present, the neutronic design possesses several features similar to those envisioned for future neutron facilities such as long-pulsed spallation sources (LPSS) and very cold neutron (VCN) sources. We describe the underlying ideas and design details of the target/moderator/reflector system (TMR) and compare measurements of its brightness, energy spectrum, and emission time distribution under different moderator configurations with MCNP simulations. Brightness measurements using an ambient temperature water moderator agree with MCNP simulations within the 20% accuracy of the measurement. The measured neutron emission time distribution from a solid methane moderator is in agreement with simulation and the cold neutron flux is sufficient for neutron scattering studies of materials. We describe some possible modifications to the existing design which would increase the cold neutron brightness with negligible effect on the emission time distribution.

C. M. Lavelle; D. V. Baxter; A. Bogdanov; V. P. Derenchuk; H. Kaiser; M. B. Leuschner; M. A. Lone; W. Lozowski; H. Nann; B. v. Przewoski; N. Remmes; T. Rinckel; Y. Shin; W. M. Snow; P. E. Sokol

2008-03-28

59

Advanced microstructured semiconductor neutron detectors: design, fabrication, and performance.  

E-print Network

??The microstructured semiconductor neutron detector (MSND) was investigated and previous designs were improved and optimized. In the present work, fabrication techniques have been refined and… (more)

Bellinger, Steven Lawrence

2012-01-01

60

Advanced Neutron Source radiological design criteria  

SciTech Connect

The operation of the proposed Advanced Neutron Source (ANS) facility will present a variety of radiological protection problems. Because it is desired to design and operate the ANS according to the applicable licensing standards of the Nuclear Regulatory Commission (NRC), it must be demonstrated that the ANS radiological design basis is consistent not only with state and Department of Energy (DOE) and other usual federal regulations, but also, so far as is practicable, with NRC regulations and with recommendations of such organizations as the Institute of Nuclear Power Operations (INPO) and the Electric Power Research Institute (EPRI). Also, the ANS radiological design basis is in general to be consistent with the recommendations of authoritative professional and scientific organizations, specifically the National Council on Radiation Protection and Measurements (NCRP) and the International Commission on Radiological Protection (ICRP). As regards radiological protection, the principal goals of DOE regulations and guidance are to keep occupational doses ALARA [as low as (is) reasonably achievable], given the current state of technology, costs, and operations requirements; to control and monitor contained and released radioactivity during normal operation to keep public doses and releases to the environment ALARA; and to limit doses to workers and the public during accident conditions. Meeting these general design objectives requires that principles of dose reduction and of radioactivity control by employed in the design, operation, modification, and decommissioning of the ANS. The purpose of this document is to provide basic radiological criteria for incorporating these principles into the design of the ANS. Operations, modification, and decommissioning will be covered only as they are affected by design.

Westbrook, J.L.

1995-08-01

61

ARCADIA{sup R} - A New Generation of Coupled Neutronics / Core Thermal- Hydraulics Code System at AREVA NP  

SciTech Connect

Anticipating future needs of our customers and willing to concentrate synergies and competences existing in the company for the benefit of our customers, AREVA NP decided in 2002 to develop the next generation of coupled neutronics/ core thermal-hydraulic (TH) code systems for fuel assembly and core design calculations for both, PWR and BWR applications. The global CONVERGENCE project was born: after a feasibility study of one year (2002) and a conceptual phase of another year (2003), development was started at the beginning of 2004. The present paper introduces the CONVERGENCE project, presents the main feature of the new code system ARCADIA{sup R} and concludes on customer benefits. ARCADIA{sup R} is designed to meet AREVA NP market and customers' requirements worldwide. Besides state-of-the-art physical modeling, numerical performance and industrial functionality, the ARCADIA{sup R} system is featuring state-of-the-art software engineering. The new code system will bring a series of benefits for our customers: e.g. improved accuracy for heterogeneous cores (MOX/ UOX, Gd...), better description of nuclide chains, and access to local neutronics/ thermal-hydraulics and possibly thermal-mechanical information (3D pin by pin full core modeling). ARCADIA is a registered trademark of AREVA NP. (authors)

Curca-Tivig, Florin; Merk, Stephan; Pautz, Andreas; Thareau, Sebastien [AREVA NP, an AREVA and Siemens Company, Freyeslebenstrasse 1, 91058 Erlangen (Germany)

2007-07-01

62

Spallation neutron source target station design, development, and commissioning  

NASA Astrophysics Data System (ADS)

The spallation neutron source target station is designed to safely, reliably, and efficiently convert a 1 GeV beam of protons to a high flux of about 1 meV neutrons that are available at 24 neutron scattering instrument beam lines. Research and development findings, design requirements, design description, initial checkout testing, and results from early operation with beam are discussed for each of the primary target subsystems, including the mercury target, neutron moderators and reflector, surrounding vessels and shielding, utilities, remote handling equipment, and instrumentation and controls. Future plans for the mercury target development program are also briefly discussed.

Haines, J. R.; McManamy, T. J.; Gabriel, T. A.; Battle, R. E.; Chipley, K. K.; Crabtree, J. A.; Jacobs, L. L.; Lousteau, D. C.; Rennich, M. J.; Riemer, B. W.

2014-11-01

63

Thermal conductivity due to phonons in the core of superfluid neutron stars  

NASA Astrophysics Data System (ADS)

We compute the contribution of phonons to the thermal conductivity in the core of superfluid neutron stars. We use effective field theory techniques to extract the phonon scattering rates, written as a function of the equation of state of the system. We also calculate the phonon dispersion law beyond linear order, which depends on the gap of superfluid neutron matter. With all these ingredients, we solve the Boltzmann equation numerically using a variational approach. We find that the thermal conductivity ? is dominated by combined small- and large-angle binary collisions. As in the color-flavor-locked superfluid, we find that our result can be well approximated by ? ?1 /?6 at low temperature, where ? is the neutron gap, the constant of proportionality depending on the density. We further comment on the possible relevance of electron and superfluid phonon collisions in obtaining the total contribution to the thermal conductivity in the core of superfluid neutron stars.

Manuel, Cristina; Sarkar, Sreemoyee; Tolos, Laura

2014-11-01

64

Neutronic evaluation of GCFR core diluents and reflectors  

E-print Network

Materials are evaluated for use as in-core diluents and as peripheral reflectors for Gas-Cooled Fast Reactor (GFR) service, using coupled Monte Carlo (MCNP) and isotopics (ORIGEN) codes. The principal performance indices ...

Yu, Kun, 1974-

2003-01-01

65

Low-Enriched Fuel Design Concept for the Prismatic Very High Temperature Reactor Core  

SciTech Connect

A new non-TRISO fuel and clad design concept is proposed for the prismatic, heliumcooled Very High Temperature Reactor core. The new concept could substantially reduce the current 10-20 wt% TRISO uranium enrichments down to 4-6 wt% for both initial and reload cores. The proposed fuel form would be a high-temperature, high-density uranium ceramic, for example UO2, configured into very small diameter cylindrical rods. The small diameter fuel rods significantly increase core reactivity through improved neutron moderation and fuel lumping. Although a high-temperature clad system for the concept remains to be developed, recent success in tube fabrication and preliminary irradiation testing of silicon carbide (SiC) cladding for light water reactor applications offers good potential for this application, and for future development of other carbide clad designs. A high-temperature ceramic fuel, together with a high-temperature clad material, could also lead to higher thermal safety margins during both normal and transient reactor conditions relative to TRISO fuel. The calculated neutronic results show that the lowenrichment, small diameter fuel rods and low thermal neutron absorbing clad retain the strong negative Doppler fuel temperature coefficient of reactivity that ensures inherent safe operation of the VHTR, and depletion studies demonstrate that an 18-month power cycle can be achieved with the lower enrichment fuel.

Sterbentz, James W

2007-05-01

66

Neutron collimator design of neutron radiography based on the BNCT facility  

NASA Astrophysics Data System (ADS)

For the research of CCD neutron radiography, a neutron collimator was designed based on the exit of thermal neutron of the Boron Neutron Capture Therapy (BNCT) reactor. Based on the Geant4 simulations, the preliminary choice of the size of the collimator was determined. The materials were selected according to the literature data. Then, a collimator was constructed and tested on site. The results of experiment and simulation show that the thermal neutron flux at the end of the neutron collimator is greater than 1.0×106 n/cm2/s, the maximum collimation ratio (L/D) is 58, the Cd-ratio(Mn) is 160 and the diameter of collimator end is 10 cm. This neutron collimator is considered to be applicable for neutron radiography.

Yang, Xiao-Peng; Yu, Bo-Xiang; Li, Yi-Guo; Peng, Dan; Lu, Jin; Zhang, Gao-Long; Zhao, Hang; Zhang, Ai-Wu; Li, Chun-Yang; Liu, Wan-Jin; Hu, Tao; Lü, Jun-Guang

2014-02-01

67

Fuel and Core Design Experiences in Cofrentes NPP  

SciTech Connect

The electricity market deregulation in Spain is increasing the need for innovations in nuclear power generation, which can be achieved in the fuel area by improving fuel and core designs and by introducing vendors competition. Iberdrola has developed the GIRALDA methodology for design and licensing of Cofrentes reloads, and has introduced mixed cores with fuel from different vendors. The application of GIRALDA is giving satisfactory results, and is showing its capability to adequately reproduce the core behaviour. The nuclear design team is acquiring an invaluable experience and a deep knowledge of the core, very useful to support cycle operation. Continuous improvements are expected for the future in design strategies as well as in the application of new technologies to redesign the methodology processes. (authors)

Garcia-Delgado, L.; Lopez-Carbonell, M.T.; Gomez-Bernal, I. [Iberdrola Generacion, Nuclear Fuel Department, Hermosilla 3, 28001 Madrid (Spain)

2002-07-01

68

Core and Refueling Design Studies for the Advanced High Temperature Reactor  

SciTech Connect

The Advanced High Temperature Reactor (AHTR) is a design concept for a central generating station type [3400 MW(t)] fluoride-salt-cooled high-temperature reactor (FHR). The overall goal of the AHTR development program is to demonstrate the technical feasibility of FHRs as low-cost, large-size power producers while maintaining full passive safety. This report presents the current status of ongoing design studies of the core, in-vessel structures, and refueling options for the AHTR. The AHTR design remains at the notional level of maturity as important material, structural, neutronic, and hydraulic issues remain to be addressed. The present design space exploration, however, indicates that reasonable options exist for the AHTR core, primary heat transport path, and fuel cycle provided that materials and systems technologies develop as anticipated. An illustration of the current AHTR core, reactor vessel, and nearby structures is shown in Fig. ES1. The AHTR core design concept is based upon 252 hexagonal, plate fuel assemblies configured to form a roughly cylindrical core. The core has a fueled height of 5.5 m with 25 cm of reflector above and below the core. The fuel assembly hexagons are {approx}45 cm across the flats. Each fuel assembly contains 18 plates that are 23.9 cm wide and 2.55 cm thick. The reactor vessel has an exterior diameter of 10.48 m and a height of 17.7 m. A row of replaceable graphite reflector prismatic blocks surrounds the core radially. A more complete reactor configuration description is provided in Section 2 of this report. The AHTR core design space exploration was performed under a set of constraints. Only low enrichment (<20%) uranium fuel was considered. The coated particle fuel and matrix materials were derived from those being developed and demonstrated under the Department of Energy Office of Nuclear Energy (DOE-NE) advanced gas reactor program. The coated particle volumetric packing fraction was restricted to at most 40%. The pressure drop across the core was restricted to no more than 1.5 atm during normal operation to minimize the upward force on the core. Also, the flow velocity in the core was restricted to 3 m/s to minimize erosion of the fuel plates. Section 3.1.1 of this report discusses the design restrictions in more detail.

Holcomb, David Eugene [ORNL] [ORNL; Ilas, Dan [ORNL] [ORNL; Varma, Venugopal Koikal [ORNL] [ORNL; Cisneros, Anselmo T [ORNL] [ORNL; Kelly, Ryan P [ORNL] [ORNL; Gehin, Jess C [ORNL] [ORNL

2011-09-01

69

The Design and Verification of a Sorter Core  

Microsoft Academic Search

The design and verification of a high speed sorter core is presented. We present several techniques and tools used to verify the functionality of the sorter. The sorter is a periodic sorter based on recursive butterfly networks. Having a design language that is well-suited to describing these networks has helped us to explore the design space far more effectively than

Koen Claessen; Mary Sheeran; Satnam Singh

2001-01-01

70

Design an Interactive Visualization System for Core Drilling Expeditions  

E-print Network

-playing and social probes to try to step into users' shoes. While these practices might be useful in designingDesign an Interactive Visualization System for Core Drilling Expeditions Using Immersive Empathic Method Overview In this paper, we propose an immersive empathic design method and used it to create

Johnson, Andrew

71

Thermionic in-core heat pipe design and performance  

NASA Astrophysics Data System (ADS)

The heat pipe cooled thermionic reactor (HPTI) relies on in-core sodium heat pipes to provide a redundant means of cooling the 72 thermionic fuel elements (TFEs) and 36 driver fuel pins which comprise the 40 kWe core assembly. In-core heat pipe cooling was selected for the reactor design to meet the requirements for a system design with the potential to achieve a high survivability level against natural and man-made threats and one that possesses no-mission ending single point failures. A detailed study was performed to determine the potential in-core heat pipe geometries which could be developed for an HPTI concept. Requirements and performance estimates were developed for two in-core heat pipe geometries. Both nominal and faulted operating conditions were evaluated using a two-dimensional thermal model of the core to assess TFE and driver fuel pin temperature profiles. A bow tie in-core heat pipe geometry was selected as the optimum design using a HPTI honeycomb core structure.

Determan, W. R.; Hagelston, G.

1992-01-01

72

Observational evidence for superfluidity, and pinning, in the core of neutron stars  

E-print Network

The observed large rates of spinning down after glitches in some radio pulsars has been previously explained in terms of a long-term spin-up behaviour of a superfluid part of the crust of neutron stars. We argue that the suggested mechanism is not viable; being inconsistent with the basic requirements for a superfluid spin-up, in addition to its quantitative disagreement with the data. One may therefore conclude, for the first time, that the presence and the pinned nature of neutron superfluid in the core of neutron stars is evidenced by the existing observational data.

M. Jahan-Miri

1998-08-11

73

Reactor physics analyses of the advanced neutron source three-element core  

SciTech Connect

A reactor physics analysis was performed for the Advanced Neutron Source reactor with a three-element core configuration. The analysis was performed with a two-dimensional r-z 20-energy-group finite-difference diffusion theory model of the 17-d fuel cycle. The model included equivalent r-z geometry representations of the central control rods, the irradiation and production targets, and reflector components. Calculated quantities include fuel cycle parameters, fuel element power distributions, unperturbed neutron fluxes in the reflector and target regions, reactivity perturbations, and neutron kinetics parameters.

Gehin, J.C.

1995-08-01

74

The Design of Core C++ (Notes)  

E-print Network

the real C++ in certain w* *ays in order to streamline the design as well as to disambiguate the semantics T * is a data type for any type T . One might wonder if functions can return arbitrary typed results

Reddy, Uday S.

75

Neutron single-particle strength outside the N=50 core  

NASA Astrophysics Data System (ADS)

The single-neutron properties of N = 51 nuclei have been studied with the (d,p) and (?,3He) reactions, at beam energies of 15 and 50 MeV respectively, on 88Sr, 90Zr, and 92Mo targets. The light reaction products were momentum analyzed using a conventional magnetic spectrometer. Additionally, the 2H(86Kr,p) reaction was measured at a beam energy of 10 MeV/u, where outgoing light ions were analyzed using a helical-orbit spectrometer. Absolute cross sections and angular distributions corresponding to the population of different final states in the heavy product were obtained for each reaction. Spectroscopic factors were extracted and centroids of the single-particle strength were deduced. The observations appear consistent with calculations based on an evolution of single-particle structure driven by the nucleon-nucleon forces acting between valence protons and neutrons.

Sharp, D. K.; Kay, B. P.; Thomas, J. S.; Freeman, S. J.; Schiffer, J. P.; Back, B. B.; Bedoor, S.; Bloxham, T.; Clark, J. A.; Deibel, C. M.; Hoffman, C. R.; Howard, A. M.; Lighthall, J. C.; Marley, S. T.; Mitchell, A. J.; Otsuka, T.; Parker, P. D.; Rehm, K. E.; Shetty, D. V.; Wuosmaa, A. H.

2013-01-01

76

CORE ANALYSIS, DESIGN AND OPTIMIZATION OF A DEEP-BURN PEBBLE BED REACTOR  

SciTech Connect

Achieving a high burnup in the Deep-Burn pebble bed reactor design, while remaining within the limits for fuel temperature, power peaking and temperature reactivity feedback, is challenging. The high content of Pu and Minor Actinides in the Deep-Burn fuel significantly impacts the thermal neutron energy spectrum. This can result in power and temperature peaking in the pebble bed core in locally thermalized regions near the graphite reflectors. Furthermore, the interplay of the Pu resonances of the neutron absorption cross sections at low-lying energies can lead to a positive temperature reactivity coefficient for the graphite moderator at certain operating conditions. To investigate the aforementioned effects a code system using existing codes has been developed for neutronic, thermal-hydraulic and fuel depletion analysis of Deep-Burn pebble bed reactors. A core analysis of a Deep-Burn Pebble Bed Modular Reactor (400 MWth) design has been performed for two Deep-Burn fuel types and possible improvements of the design with regard to power peaking and temperature reactivity feedback are identified.

B. Boer; A. M. Ougouag

2010-05-01

77

Neutron collimator design of neutron radiography based on the BNCT facility  

E-print Network

For the research of CCD neutron radiography, a neutron collimator was designed based on the exit of thermal neutron of the Boron Neutron Capture Therapy (BNCT) reactor. Based on the Geant4 simulations, the preliminary choice of the size of the collimator was determined. The materials were selected according to the literature data. Then, a collimator was constructed and tested on site. The results of experiment and simulation show that the thermal neutron flux at the end of theneutron collimator is greater than 10^6 n/cm^2/s, the maximum collimation ratio (L/D) is 58, the Cd-ratio(Mn) is 160 and the diameter of collimator end is 10 cm. This neutron collimator is considered to be applicable for neutron radiography.

XP. Yang; BX. Yu; YG. Li; D. Peng; J. Lu; GL. Zhang; H. Zhao; AW. Zhang; CY. Li; WJ. Liu; T. Hu; JG. Lv

2013-05-03

78

Conceptual design of an RFQ accelerator-based neutron source for boron neutron-capture therapy  

SciTech Connect

We present a conceptual design of a low-energy neutron generator for treatment of brain tumors by boron neutron capture theory (BNCT). The concept is based on a 2.5-MeV proton beam from a radio-frequency quadrupole (RFQ) linac, and the neutrons are produced by the /sup 7/Li(p,n)/sup 7/Be reaction. A liquid lithium target and modulator assembly are designed to provide a high flux of epithermal neutrons. The patient is administered a tumor-specific /sup 10/Be-enriched compound and is irradiated by the neutrons to create a highly localized dose from the reaction /sup 10/B(n,..cap alpha..)/sup 7/Li. An RFQ accelerator-based neutron source for BNCT is compact, which makes it practical to site the facility within a hospital. 11 refs., 5 figs., 1 tab.

Wangler, T.P.; Stovall, J.E.; Bhatia, T.S.; Wang, C.K.; Blue, T.E.; Gahbauer, R.A.

1989-01-01

79

Neutron Energy Flux Spectrum Measurements for Leu Core of PARR-1.  

National Technical Information Service (NTIS)

The Pakistan Research Reactor-1 has been converted and upgraded from highly enriched uranium (HEU) to low enriched uranium (LEU) fuel from 5 to 9MW. An experimental programme was undertaken to measure the neutron energy spectra in the core and at the irra...

M. Iqbal, S. K. Ayazudin, S. Pervez

1995-01-01

80

Evaluation for 4S core nuclear design method through integration of benchmark data  

SciTech Connect

The 4S is a sodium-cooled small fast reactor which is reflector-controlled for operation through core lifetime about 30 years. The nuclear design method has been selected to treat neutron leakage with high accuracy. It consists of a continuous-energy Monte Carlo code, discrete ordinate transport codes and JENDL-3.3. These two types of neutronic analysis codes are used for the design in a complementary manner. The accuracy of the codes has been evaluated by analysis of benchmark critical experiments and the experimental reactor data. The measured data used for the evaluation is critical experimental data of the FCA XXIII as a physics mockup assembly of the 4S core, FCA XVI, FCA XIX, ZPR, and data of experimental reactor JOYO MK-1. Evaluated characteristics are criticality, reflector reactivity worth, power distribution, absorber reactivity worth, and sodium void worth. A multi-component bias method was applied, especially to improve the accuracy of sodium void reactivity worth. As the result, it has been confirmed that the 4S core nuclear design method provides good accuracy, and typical bias factors and their uncertainties are determined. (authors)

Nagata, A.; Tsuboi, Y. [Advanced System Design and Engineering Dept., Isogo Nuclear Engineering Center, Toshiba Corporation, 8, Shinsugita-Cho, Isogo-ku, Yokohama, 235-8523 (Japan); Moriki, Y. [Power and Industrial Systems Research and Development Center, Toshiba Corporation, 8, Shinsugita-Cho, Isogo-ku, Yokohama, 235-8523 (Japan); Kawashima, M. [Nuclear Technology Application Dept., Toshiba Nuclear Engineering Services Corporation, 8, Shinsugita-Cho, Isogo-ku, Yokohama, 235-8523 (Japan)

2012-07-01

81

Pulsed neutron source cold moderators --- concepts, design and engineering  

SciTech Connect

Moderator design for pulsed neutron sources is becoming more and more an interface area between source designers and instrument designers. Although there exists a high degree of flexibility, there are also physical and technical limitations. This paper aims at pointing out these limitations and examining ways to extend the current state of moderator technology in order to make the next generation neutron sources even more versatile and flexible tools for science in accordance with the users' requirements. (auth)

Bauer, Guenter S.

1997-01-01

82

From the crust to the core of neutron stars on a microscopic basis  

NASA Astrophysics Data System (ADS)

Within a microscopic approach the structure of Neutron Stars is usually studied by modelling the homogeneous nuclear matter of the core by a suitable Equation of State, based on a many-body theory, and the crust by a functional based on a more phenomenological approach. We present the first calculation of Neutron Star overall structure by adopting for the core an Equation of State derived from the Brueckner-Hartree-Fock theory and for the crust, including the pasta phase, an Energy Density Functional based on the same Equation of State, and which is able to describe accurately the binding energy of nuclei throughout the mass table. Comparison with other approaches is discussed. The relevance of the crust Equation of State for the Neutron Star radius is particularly emphasised.

Baldo, M.; Burgio, G. F.; Centelles, M.; Sharma, B. K.; Viñas, X.

2014-09-01

83

Core restraint and seismic analysis of a large heterogeneous free-flowering core design. Final report  

SciTech Connect

The core restraint and seismic performance of a large heterogeneous core was analyzed. A free-flowering core restraint system was selected for this study, as opposed to the limited-free bow system of the FFTF and CRBRP. The key features of the core restraint system, such as stiff reflector assemblies and load pad properties, were specified in this study. Other features - such as the fuel-assembly description, flux and temperature distributions, and clearances between the assembly nozzle and grid plate - were obtained from the other parts of a large, heterogeneous Core Study 11 and 12. Core restraint analysis was performed with NUBOW-3D over the first two cycles of operation. The SCRAP code was used to analyze the time-history seismic response of the core with the effects of fluid, impact, and bowed assemblies modeled in the code. The core restraint system design was assessed in terms of the predicted forces, impacts, displacements, and reactivity effects for different cycle times and power/flow ratios.

Madell, J.T.; Moran, T.J.; Ash, J.E.; Fulford, P.J.

1980-11-01

84

Interweaving Game Design into Core CS Curriculum Yolanda Rankin  

E-print Network

][2][3][7]. It is not sufficient to simply write code that creates a game if students have failed to grasp design conceptsInterweaving Game Design into Core CS Curriculum Yolanda Rankin Northwestern University 2133.a.gooch@gmail.com Abstract Computer Science departments across the country have embraced computer gaming classes as part

Gooch, Bruce

85

Preliminary fracture analysis of the core pressure boundary tube for the Advanced Neutron Source Research Reactor  

SciTech Connect

The outer core pressure boundary tube (CPBT) of the Advanced neutron Source (ANS) reactor being designed at Oak Ridge National Laboratory is currently specified as being composed of 6061-T6 aluminum. ASME Boiler and Pressure Vessel Code fracture analysis rules for nuclear components are based on the use of ferritic steels; the expressions, tables, charts and equations were all developed from tests and analyses conducted for ferritic steels. Because of the nature of the Code, design with thin aluminum requires analytical approaches that do not directly follow the Code. The intent of this report is to present a methodology comparable to the ASME Code for ensuring the prevention of nonductile fracture of the CPBT in the ANS reactor. 6061-T6 aluminum is known to be a relatively brittle material; the linear elastic fracture mechanics (LEFM) approach is utilized to determine allowable flaw sizes for the CPBT. A J-analysis following the procedure developed by the Electric Power Research Institute was conducted as a check; the results matched those for the LEFM analysis for the cases analyzed. Since 6061-T6 is known to embrittle when irradiated, the reduction in K{sub Q} due to irradiation is considered in the analysis. In anticipation of probable requirements regarding maximum allowable flaw size, a survey of nondestructive inspection capabilities is also presented. A discussion of probabilistic fracture mechanics approaches, principally Monte Carlo techniques, is included in this report as an introduction to what quantifying the probability of nonductile failure of the CPBT may entail.

Schulz, K.C. [Univ. of Turabo, Gurabo, Puerto (Puerto Rico). College of Engineering; Yahr, G.T. [Oak Ridge National Lab., TN (United States)

1995-08-01

86

Neutronic calculations for the conversion to LEU of a research reactor core  

SciTech Connect

For a five-year transitional period the Greek Research Reactor (GRR-1) was operating with a mixed core, containing both Low Enrichment (LEU) and High Enrichment (HEU) Uranium MTR- type fuel assemblies. The neutronic study of the GRR-1 conversion to LEU has been performed using a code system comprising the core-analysis code CITATION-LDI2 and the cell-calculation modules XSDRNPM and NITAWL-II of the SCALE code. A conceptual LEU core configuration was defined and analyzed with respect to the three dimensional multi-group neutron fluxes, the power distribution, the control-rod worth and the compliance with pre-defined Operation Limiting Conditions. Perturbation calculations and reactivity feedback computations were also carried out to provide input to a subsequent thermal-hydraulic study. (author)

Varvayanni, M.; Catsaros, N.; Stakakis, E. [National Center for Scientific Research 'DEMOKRITOS', 153 10 Aghia Paraskevi (Greece); Grigoriadis, D. [National Center for Scientific Research 'DEMOKRITOS', 153 10 Aghia Paraskevi (Greece); Department of Mechanical and Manufacturing Engineering, University of Cyprus, P.O. Box 20537, Nicosia 1678 (Cyprus)

2008-07-15

87

Simulation of Fast Neutronics in an Accelerator-Driven Sub-Critical Core  

NASA Astrophysics Data System (ADS)

Accelerator-driven subcritical fission in a molten salt core (ADSMS) is being developed as a technology for green nuclear power. ADSMS burns its fertile fuel to completion, it cannot melt down, and it destroys long-lived minor actinides. The ADSMS core consists of a vessel filled with a molten salt eutectic of UCl3 and NaCl. The fast neutronics of ADSMS makes possible two unique benefits: isobreeding, a steady-state equilibrium in which ^238U is bred to ^239Pu and the ^239Pu fissions, and destruction of minor actinides, in which fission of the intermediary nuclides dominates of breeding. Results of simulations of the fast neutronics in the ADSMS core will be presented.

Gwyn Rosaire, C.; Sattarov, Akhdiyor; McIntyre, Peter; Tsvetkov, Pavel

2011-10-01

88

Current advances in precious metal core-shell catalyst design  

NASA Astrophysics Data System (ADS)

Precious metal nanoparticles are commonly used as the main active components of various catalysts. Given their high cost, limited quantity, and easy loss of catalytic activity under severe conditions, precious metals should be used in catalysts at low volumes and be protected from damaging environments. Accordingly, reducing the amount of precious metals without compromising their catalytic performance is difficult, particularly under challenging conditions. As multifunctional materials, core-shell nanoparticles are highly important owing to their wide range of applications in chemistry, physics, biology, and environmental areas. Compared with their single-component counterparts and other composites, core-shell nanoparticles offer a new active interface and a potential synergistic effect between the core and shell, making these materials highly attractive in catalytic application. On one hand, when a precious metal is used as the shell material, the catalytic activity can be greatly improved because of the increased surface area and the closed interfacial interaction between the core and the shell. On the other hand, when a precious metal is applied as the core material, the catalytic stability can be remarkably improved because of the protection conferred by the shell material. Therefore, a reasonable design of the core-shell catalyst for target applications must be developed. We summarize the latest advances in the fabrications, properties, and applications of core-shell nanoparticles in this paper. The current research trends of these core-shell catalysts are also highlighted.

Wang, Xiaohong; He, Beibei; Hu, Zhiyu; Zeng, Zhigang; Han, Sheng

2014-08-01

89

Design of low-energy neutron beams for boron neutron capture synovectomy  

NASA Astrophysics Data System (ADS)

A novel application of the 10B(n, (alpha) )7Li nuclear reaction for the treatment of rheumatoid arthritis is under development. this application, called Boron Neutron Capture Synovectomy (BNCS), is briefly described here and the differences between BNCS and Boron Neutron Capture Therapy (BNCT) are discussed in detail. These differences lead to substantially altered demands on neutron beam design for each therapy application. In this paper the considerations for neutron beam design for the treatment of arthritic joints via BNCS are discussed, and comparisons with the design requirements for BNCT are made. This is followed by a description of potential moderator/reflector assemblies that are calculated to produce intense, high- quality neutron beams based on the 7Li(p,n) accelerator- based reactions. Total therapy time and therapeutic ratios are given as a function of both moderator length and boron concentration. Finally, a means of carrying out multi- directional irradiations of arthritic joints is proposed.

Yanch, Jacquelyn C.; Shefer, Ruth E.; Binello, E.

1997-02-01

90

Cooling of Neutron Stars with Color Superconducting Quark Cores  

E-print Network

We show that within a recently developed nonlocal chiral quark model the critical density for a phase transition to color superconducting quark matter under neutron star conditions can be low enough for these phases to occur in compact star configurations with masses below 1.3 M_sun. We study the cooling of these objects in isolation for different values of the gravitational mass and argue that, if the quark matter phase would allow unpaired quarks, the corresponding hybrid stars would cool too fast. The comparison with observational data puts tight constraints on possible color superconducting quark matter phases. Possible candidates with diquark gaps of the order of 10 keV - 1 MeV such as the "2SC+X" and the color spin locking (CSL) phase are presented.

David Blaschke; Dmitri N. Voskresensky; Hovik Grigorian

2005-10-27

91

Design of dual-core optical fibers with NEMS functionality.  

PubMed

An optical fiber with nano-electromechanical functionality is presented. The fiber exhibits a suspended dual-core structure that allows for control of the optical properties via nanometer-range mechanical movements. We investigate electrostatic actuation achieved by applying a voltage to specially designed electrodes integrated in the cladding. Numerical and analytical calculations are preformed to optimize the fiber and electrode design. Based on this geometry an all-fiber optical switch is investigated; we find that optical switching of light between the two cores can be achieved in a 10 cm fiber with an operating voltage of 35 V. PMID:24515066

Podoliak, Nina; Lian, Zhenggang; Loh, Wei H; Horak, Peter

2014-01-13

92

How useful is neutron diffusion theory for nuclear rocket engine design  

SciTech Connect

Correct modeling of neutron leakage and geometry effects is important in the design of a nuclear rocket engine because of the need for small reactor cores in space applications. In principle, there are generalized procedures that can account for these effects in a reliable manner (e.g., a three-dimensional, continuous-energy Monte Carlo calculation with all core components explicitly modeled). However, these generalized procedures are not usually suitable for parametric design studies because of the long computational times required, and the feasibility of using faster running, more approrimate neutronic modeling approaches needs to be investigated. Faster running neutronic models are also needed for simulator development to assess the engine performance during startup and power level changes. This paper investigates the potential of the few-group diffusion approach for nuclear rocket engine core design and optimization by comparing the k[sub eff] and power distributions obtained by the MCNP code against those obtained from the LEOPARD and 2DB codes for the particle bed reactor (PBR) concept described. The PBRs have been identified as one of the two near-term options for nuclear thermal propulsion by the joint National Aeronautics and Space Administration (NASA)/US Department of Energy/US Department of Defense program that was recently set up at the NASA Lewis Research Center to develop a flight-rated nuclear rocket engine by the 2020s.

Hilsmeier, T.A.; Aithal, S.M.; Aldemir, T. (Ohio State Univ., Columbus (United States))

1992-01-01

93

Core-collapse Supernova Equations of State Based on Neutron Star Observations  

NASA Astrophysics Data System (ADS)

Many of the currently available equations of state for core-collapse supernova simulations give large neutron star radii and do not provide large enough neutron star masses, both of which are inconsistent with some recent neutron star observations. In addition, one of the critical uncertainties in the nucleon-nucleon interaction, the nuclear symmetry energy, is not fully explored by the currently available equations of state. In this article, we construct two new equations of state which match recent neutron star observations and provide more flexibility in studying the dependence on nuclear matter properties. The equations of state are also provided in tabular form, covering a wide range in density, temperature, and asymmetry, suitable for astrophysical simulations. These new equations of state are implemented into our spherically symmetric core-collapse supernova model, which is based on general relativistic radiation hydrodynamics with three-flavor Boltzmann neutrino transport. The results are compared with commonly used equations of state in supernova simulations of 11.2 and 40 M ? progenitors. We consider only equations of state which are fitted to nuclear binding energies and other experimental and observational constraints. We find that central densities at bounce are weakly correlated with L and that there is a moderate influence of the symmetry energy on the evolution of the electron fraction. The new models also obey the previously observed correlation between the time to black hole formation and the maximum mass of an s = 4 neutron star.

Steiner, A. W.; Hempel, M.; Fischer, T.

2013-09-01

94

CORE-COLLAPSE SUPERNOVA EQUATIONS OF STATE BASED ON NEUTRON STAR OBSERVATIONS  

SciTech Connect

Many of the currently available equations of state for core-collapse supernova simulations give large neutron star radii and do not provide large enough neutron star masses, both of which are inconsistent with some recent neutron star observations. In addition, one of the critical uncertainties in the nucleon-nucleon interaction, the nuclear symmetry energy, is not fully explored by the currently available equations of state. In this article, we construct two new equations of state which match recent neutron star observations and provide more flexibility in studying the dependence on nuclear matter properties. The equations of state are also provided in tabular form, covering a wide range in density, temperature, and asymmetry, suitable for astrophysical simulations. These new equations of state are implemented into our spherically symmetric core-collapse supernova model, which is based on general relativistic radiation hydrodynamics with three-flavor Boltzmann neutrino transport. The results are compared with commonly used equations of state in supernova simulations of 11.2 and 40 M{sub Sun} progenitors. We consider only equations of state which are fitted to nuclear binding energies and other experimental and observational constraints. We find that central densities at bounce are weakly correlated with L and that there is a moderate influence of the symmetry energy on the evolution of the electron fraction. The new models also obey the previously observed correlation between the time to black hole formation and the maximum mass of an s = 4 neutron star.

Steiner, A. W. [Institute for Nuclear Theory, University of Washington, Seattle, WA 98195 (United States); Hempel, M. [Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland); Fischer, T. [Institute for Theoretical Physics, University of Wroclaw, pl. Maxa Borna 9, 50-204, Wroclaw (Poland)

2013-09-01

95

Massive neutron stars with a hyperonic core: A case study with the IUFSU relativistic effective interaction  

NASA Astrophysics Data System (ADS)

The recent discoveries of massive neutron stars, such as PSR J0348+0432 and PSR J1614-2230, have raised questions about the existence of exotic matter such as hyperons in the neutron star core. The validity of many established equations of states (EoSs) like GM1 and FSUGold are also questioned. We investigate the existence of hyperonic matter in the central regions of massive neutron stars by using relativistic mean field (RMF) theory with the recently proposed Indiana University Florida State University (IUFSU) model. The IUFSU model is extended by including hyperons to study the neutron star in ? equilibrium. The effect of different hyperonic potentials, namely ? and ? potentials, on the EoS and hence the maximum mass of neutron stars has been studied. We have also considered the effect of stellar rotation since the observed massive stars are pulsars. It has been found that a maximum mass of 1.93M?, which is within the 3? limit of the observed mass of PSR J0348+0432, can be obtained for rotating stars, with certain choices of the hyperonic potentials. The said star contains a fair amount of hyperons near the core.

Bhowmick, Bipasha; Bhattacharya, Madhubrata; Bhattacharyya, Abhijit; Gangopadhyay, G.

2014-06-01

96

Massive neutron stars with hyperonic core : a case study with the IUFSU model  

E-print Network

The recent discoveries of massive neutron stars, such as PSR J$0348+0432$ and PSR J$1614-2230$, have raised questions about the existence of exotic matter such as hyperons in the neutron star core. The validity of many established equations of states (EoS's) like the GM1 and FSUGold are also questioned. We investigate the existence of hyperonic matter in the central regions of massive neutron stars using Relativistic Mean Field (RMF) theory with the recently proposed IUFSU model. The IUFSU model is extended by including hyperons to study the neutron star in $\\beta$ equilibrium. The effect of different hyperonic potentials, namely $\\Sigma$ and $\\Xi$ potentials, on the EoS and hence the maximum mass of neutron stars has been studied. We have also considered the effect of stellar rotation since the observed massive stars are pulsars. It has been found that a maximum mass of $1.93M_{\\odot}$, which is within the 3$\\sigma$ limit of the observed mass of PSR J$0348+0432$, can be obtained for rotating stars, with certain choices of the hyperonic potentials. The said star contains a fair amount of hyperons near the core.

Bipasha Bhowmick; Madhubrata Bhattacharya; Abhijit Bhattacharyya; G. Gangopadhyay

2014-03-03

97

Crust-core coupling and r-mode damping in neutron stars: a toy model  

E-print Network

R-modes in neutron stars with crusts are damped by viscous friction at the crust-core boundary. The magnitude of this damping, evaluated by Bildsten and Ushomirsky (BU) under the assumption of a perfectly rigid crust, sets the maximum spin frequency for a neutron star spun up by accretion in a Low-Mass X-ray binary (LMXB). In this paper we explore the mechanical coupling between the core r-modes and the elastic crust, using a toy model of a constant density neutron star with a constant shear modulus crust. We find that, at spin frequencies in excess of ~50 Hz, the r-modes strongly penetrate the crust. This reduces the relative motion (slippage) between the crust and the core compared to the rigid crust limit. We therefore revise down, by as much as a factor of 10^2-10^3, the damping rate computed by BU, significantly reducing the maximal possible spin frequency of neutron star with a solid crust. The dependence of the crust-core slippage on the spin frequency is complicated, and is very sensitive to the physical thickness of the crust. If the crust is sufficiently thick, the curve of the critical spin frequency for the onset of the r-mode instability becomes multi-valued for some temperatures; this is related to the avoided crossings between the r-mode and the higher-order torsional modes in the crust. The critical frequencies are comparable to the observed spins of neutron stars in LMXBs and millisecond pulsars.

Yuri Levin; Greg Ushomirsky

2000-06-01

98

The new Cold Neutron Chopper Spectrometer at the Spallation Neutron Source - Design and Performance  

E-print Network

The design and performance of the new Cold Neutron Chopper Spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct geometry inelastic time-of-flight spectrometer, designed to cover essentially the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM2, AMATERAS at J-PARC, PHAROS at LANSCE and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments.

Ehlers, G; Niedziela, J L; Iverson, E B

2011-01-01

99

The new cold neutron chopper spectrometer at the Spallation Neutron Source: design and performance.  

PubMed

The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments. PMID:21895276

Ehlers, G; Podlesnyak, A A; Niedziela, J L; Iverson, E B; Sokol, P E

2011-08-01

100

The new Cold Neutron Chopper Spectrometer at the Spallation Neutron Source -- Design and Performance  

SciTech Connect

The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments.

Ehlers, Georg [ORNL; Podlesnyak, Andrey A [ORNL; Niedziela, Jennifer L [ORNL; Iverson, Erik B [ORNL; Sokol, Paul E [ORNL

2011-01-01

101

The new cold neutron chopper spectrometer at the Spallation Neutron Source: Design and performance  

SciTech Connect

The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments.

Ehlers, G.; Podlesnyak, A. A.; Niedziela, J. L.; Iverson, E. B. [Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Sokol, P. E. [Department of Physics, Indiana University, Bloomington, Indiana 47405 (United States)

2011-08-15

102

Design and demonstration of a quasi-monoenergetic neutron source  

NASA Astrophysics Data System (ADS)

The design of a neutron source capable of producing 24 and 70 keV neutron beams with narrow energy spread is presented. The source exploits near-threshold kinematics of the 7Li (p,n)7Be reaction while taking advantage of the interference ‘notches’ found in the scattering cross-sections of iron. The design was implemented and characterized at the Center for Accelerator Mass Spectrometry at Lawrence Livermore National Laboratory. Alternative filters such as vanadium and manganese are also explored and the possibility of studying the response of different materials to low-energy nuclear recoils using the resultant neutron beams is discussed.

Joshi, T. H.; Sangiorgio, S.; Mozin, V.; Norman, E. B.; Sorensen, P.; Foxe, M.; Bench, G.; Bernstein, A.

2014-08-01

103

Design and demonstration of a quasi-monoenergetic neutron source  

E-print Network

The design of a neutron source capable of producing 24 and 70 keV neutron beams with narrow energy spread is presented. The source exploits near-threshold kinematics of the $^{7}$Li(p,n)$^{7}$Be reaction while taking advantage of the interference `notches' found in the scattering cross-sections of iron. The design was implemented and characterized at the Center for Accelerator Mass Spectrometry at Lawrence Livermore National Laboratory. Alternative filters such as vanadium and manganese are also explored and the possibility of studying the response of different materials to low-energy nuclear recoils using the resultant neutron beams is discussed.

Joshi, T H; Mozin, V; Norman, E B; Sorensen, P; Foxe, M; Bench, G; Bernstein, A

2014-01-01

104

Design and demonstration of a quasi-monoenergetic neutron source  

E-print Network

The design of a neutron source capable of producing 24 and 70 keV neutron beams with narrow energy spread is presented. The source exploits near-threshold kinematics of the $^{7}$Li(p,n)$^{7}$Be reaction while taking advantage of the interference `notches' found in the scattering cross-sections of iron. The design was implemented and characterized at the Center for Accelerator Mass Spectrometry at Lawrence Livermore National Laboratory. Alternative filters such as vanadium and manganese are also explored and the possibility of studying the response of different materials to low-energy nuclear recoils using the resultant neutron beams is discussed.

T. H. Joshi; S. Sangiorgio; V. Mozin; E. B. Norman; P. Sorensen; M. Foxe; G. Bench; A. Bernstein

2014-03-05

105

Analysis and Design of ITER 1 MV Core Snubber  

NASA Astrophysics Data System (ADS)

The core snubber, as a passive protection device, can suppress arc current and absorb stored energy in stray capacitance during the electrical breakdown in accelerating electrodes of ITER NBI. In order to design the core snubber of ITER, the control parameters of the arc peak current have been firstly analyzed by the Fink-Baker-Owren (FBO) method, which are used for designing the DIIID 100 kV snubber. The B-H curve can be derived from the measured voltage and current waveforms, and the hysteresis loss of the core snubber can be derived using the revised parallelogram method. The core snubber can be a simplified representation as an equivalent parallel resistance and inductance, which has been neglected by the FBO method. A simulation code including the parallel equivalent resistance and inductance has been set up. The simulation and experiments result in dramatically large arc shorting currents due to the parallel inductance effect. The case shows that the core snubber utilizing the FBO method gives more compact design.

Wang, Haitian; Li, Ge

2012-11-01

106

Influence Of Low Boron Core Design On PWR Transient Behavior  

SciTech Connect

In conventional pressurized water reactor (PWR) designs, the concentration of boron in primary coolant is limited by the requirement of having a negative moderator density coefficient. As high boron concentrations have significant impact on reactivity feedback properties, design changes to reduce boron concentration in the reactor coolant are of general interest in view of improving PWR inherent safety. In the framework of an investigation into the feasibility of low boron design, a PWR core configuration based on fuel with higher gadolinium (Gd) content has been developed which permits to reduce the natural boron concentration at begin of cycle (BOC) by approx. 50% compared to current German PWR technology. For the assessment of the potential safety advantages, a Loss-of-Feedwater Anticipated Transient Without Scram (ATWS LOFW) has been simulated with the system code ATHLET for two PWR core designs: a low boron design and a standard core design. The most significant difference in the transient performance of both designs is the total primary fluid mass released through the pressurizer (PRZ) valves. It is reduced by a factor of four for the low boron reactor, indicating its improved density reactivity feedback. (authors)

Aleksandrov Papukchiev, Angel; Yubo Liu [Technical University Munich, Arcisstrasse 21, 80333 Muenchen (Germany); Schaefer, Anselm [ISaR Institute for Safety and Reliability, Walther-Meissner-Str. 2 85748 Garching (Germany)

2006-07-01

107

Observer Design for a Core Circadian Rhythm Network  

PubMed Central

The paper investigates the observer design for a core circadian rhythm network in Drosophila and Neurospora. Based on the constructed highly nonlinear differential equation model and the recently proposed graphical approach, we design a rather simple observer for the circadian rhythm oscillator, which can well track the state of the original system for various input signals. Numerical simulations show the effectiveness of the designed observer. Potential applications of the related investigations include the real-world control and experimental design of the related biological networks. PMID:25121122

Zhang, Yuhuan

2014-01-01

108

Calculation of Design Parameters for an Equilibrium LEU Core in the NBSR  

SciTech Connect

A plan is being developed for the conversion of the NIST research reactor (NBSR) from high-enriched uranium (HEU) fuel to low-enriched uranium (LEU) fuel. Previously, the design of the LEU fuel had been determined in order to provide the users of the NBSR with the same cycle length as exists for the current HEU fueled reactor. The fuel composition at different points within an equilibrium fuel cycle had also been determined. In the present study, neutronics parameters have been calculated for these times in the fuel cycle for both the existing HEU and the proposed LEU equilibrium cores. The results showed differences between the HEU and LEU cores that would not lead to any significant changes in the safety analysis for the converted core. In general the changes were reasonable except that the figure-of-merit for neutrons that can be used by experimentalists shows there will be a 10% reduction in performance. The calculations included kinetics parameters, reactivity coefficients, reactivity worths of control elements and abnormal configurations, and power distributions.

Hanson, A.L.; Diamond, D.

2011-09-30

109

Stability of the $?$-equilibrated dense matter and core-crust transition in neutron stars  

E-print Network

The stability of the $\\beta$-equilibrated dense nuclear matter is analyzed with respect to the thermodynamic stability conditions. Based on the density dependent M3Y effective nucleon-nucleon interaction, the effects of the nuclear incompressibility on the proton fraction in neutron stars and the location of the inner edge of their crusts and core-crust transition density and pressure are investigated. The high-density behavior of symmetric and asymmetric nuclear matter satisfies the constraints from the observed flow data of heavy-ion collisions. The neutron star properties studied using $\\beta$-equilibrated neutron star matter obtained from this effective interaction for a pure hadronic model agree with the recent observations of the massive compact stars. The density, pressure and proton fraction at the inner edge separating the liquid core from the solid crust of neutron stars are determined to be $\\rho_t=$ 0.0938 fm$^{-3}$, P$_t=$ 0.5006 MeV fm$^{-3}$ and x$_{p(t)}=$ 0.0308, respectively.

Debasis Atta; D. N. Basu

2014-06-20

110

Phase transitions in rotating neutron stars cores: back bending, stability, corequakes, and pulsar timing  

NASA Astrophysics Data System (ADS)

Aims.We analyze potentially observable phenomena during spin evolution of isolated pulsars, such as back bending and corequakes resulting from instabilities, which could result from phase transitions in neutron star cores. Methods: We study these aspects of spin evolution of isolated compact stars by means of analytical models of equations of state, for both constant-pressure phase transitions and the transitions through the mixed-phase region. We use high-precision 2-D multi-domain spectral code LORENE for the calculation of the evolutionary sequences of rotating neutron stars. This allows us to search the parameter space for possible instability regions, and possible changes in the stability character of rotating stars with phase transitions in their cores. Results: We determine the conditions on the density jump in constant-pressure phase transitions which leads to the back bending phenomena or to the existence of the unstable segments in the evolutionary sequences of spinning down isolated normal neutron stars. We formulate the conjectures concerning the existence of two disjoint families of non-rotating and rotating stationary configurations of neutron stars. To clarify the effect of rotation on the stability of neutron star we present the particular case of EOSs leading to marginal instability of static and rotating configurations: marginal instability point in non-rotating configurations continues to exist in all evolutionary spin-down tracks. We discuss the fate of rotating stars entering the region of instability calculating the change in radius, energy release, and spin-up associated with the corequake in rotating neutron star, triggered by the instability. The energy release is found to be very weakly dependent on the angular momentum of collapsing star.

Zdunik, J. L.; Bejger, M.; Haensel, P.; Gourgoulhon, E.

2006-05-01

111

Advanced Core Design And Fuel Management For Pebble-Bed Reactors  

SciTech Connect

A method for designing and optimizing recirculating pebble-bed reactor cores is presented. At the heart of the method is a new reactor physics computer code, PEBBED, which accurately and efficiently computes the neutronic and material properties of the asymptotic (equilibrium) fuel cycle. This core state is shown to be unique for a given core geometry, power level, discharge burnup, and fuel circulation policy. Fuel circulation in the pebble-bed can be described in terms of a few well?defined parameters and expressed as a recirculation matrix. The implementation of a few heat?transfer relations suitable for high-temperature gas-cooled reactors allows for the rapid estimation of thermal properties critical for safe operation. Thus, modeling and design optimization of a given pebble-bed core can be performed quickly and efficiently via the manipulation of a limited number key parameters. Automation of the optimization process is achieved by manipulation of these parameters using a genetic algorithm. The end result is an economical, passively safe, proliferation-resistant nuclear power plant.

Hans D. Gougar; Abderrafi M. Ougouag; William K. Terry

2004-10-01

112

Physics design of a cold neutron source for KIPT neutron source facility.  

SciTech Connect

Argonne National Laboratory (ANL) of USA and Kharkov Institute of Physics and Technology (KIPT) of Ukraine have been collaborating on the conceptual design development of a neutron source facility. It is based on the use of an electron accelerator driven subcritical (ADS) facility with low enriched uranium fuel, using the existing electron accelerators at KIPT of Ukraine [1]. The neutron source of the subcritical assembly is generated from the interaction of 100-KW electron beam, which has a uniform spatial distribution and the electron energy in the range of 100 to 200 MeV, with a natural uranium target [2]. The main functions of the facility are the production of medical isotopes and the support of the Ukraine nuclear power industry. Neutron beam experiments and material studies are also included. Over the past two-three decades, structures with characteristic lengths of 100 {angstrom} and correspondingly smaller vibrational energies have become increasingly important for both science and technology [3]. The characteristic dimensions of the microstructures can be well matched by neutrons with longer vibrational wavelength and lower energy. In the accelerator-driven subcritical facility, most of the neutrons are generated from fission reactions with energy in the MeV range. They are slowed down to the meV energy range through scattering reactions in the moderator and reflector materials. However, the fraction of neutrons with energies less than 5 meV in a normal moderator spectrum is very low because of up-scattering caused by the thermal motion of moderator or reflector molecules. In order to obtain neutrons with energy less than 5 meV, cryogenically cooled moderators 'cold neutron sources' should be used to slow down the neutrons. These cold moderators shift the neutron energy spectrum down because the thermal motion of moderator molecules as well as the up-scattering is very small, which provides large gains in intensity of low energy neutrons, E < 5 meV. The accelerator driven subcritical facility is designed with a provision to add a cryogenically cooled moderator system. This cold neutron source could provide the neutrons beams with lower energy, which could be utilized in scattering experiment and material structures analysis. This study describes the performed physics analyses to define and characterize the cold neutron source of the KIPT neutron source facility. The cold neutron source is designed to optimize the cold neutron brightness to the experimental instruments outside the radial heavy concrete shield of the facility. Liquid hydrogen or solid methane with 20 K temperature is used as a cold moderator. Monte Carlo computer code MCNPX [4], with ENDF/B-VI nuclear data libraries, is utilized to calculate the cold neutron source performance and estimate the nuclear heat load to the cold moderator. The surface source generation capability of MCNPX code has been used to provide the possibility of analyzing different design configurations and perform design optimization analyses with reasonable computer resources. Several design configurations were analyzed and their performance were characterized and optimized.

Zhong, Z.; Gohar, Y.; Kellogg, R.; Nuclear Engineering Division

2009-02-17

113

China Spallation Neutron Source: Design, R&D, and outlook  

NASA Astrophysics Data System (ADS)

The China Spallation Neutron Source (CSNS) is an accelerator based multidiscipline user facility planned to be constructed in Dongguan, Guangdong, China. The CSNS complex consists of an negative hydrogen linear accelerator, a rapid cycling proton synchrotron accelerating the beam to 1.6 GeV energy, a solid tungsten target station, and instruments for spallation neutron applications. The facility operates at 25 Hz repetition rate with an initial design beam power of 120 kW and is upgradeable to 500 kW. The primary challenge is to build a robust and reliable user's facility with upgrade potential at a fraction of "world standard" cost. We report the status, design, R&D, and upgrade outlook including applications using spallation neutron, muon, fast neutron, and proton, as well as related programs including medical therapy and accelerator-driven sub-critical reactor (ADS) programs for nuclear waste transmutation.

Wei, Jie; Chen, Hesheng; Chen, Yanwei; Chen, Yuanbo; Chi, Yunlong; Deng, Changdong; Dong, Haiyi; Dong, Lan; Fang, Shouxian; Feng, Ji; Fu, Shinian; He, Lunhua; He, Wei; Heng, Yuekun; Huang, Kaixi; Jia, Xuejun; Kang, Wen; Kong, Xiangcheng; Li, Jian; Liang, Tianjiao; Lin, Guoping; Liu, Zhenan; Ouyang, Huafu; Qin, Qing; Qu, Huamin; Shi, Caitu; Sun, Hong; Tang, Jingyu; Tao, Juzhou; Wang, Chunhong; Wang, Fangwei; Wang, Dingsheng; Wang, Qingbin; Wang, Sheng; Wei, Tao; Xi, Jiwei; Xu, Taoguang; Xu, Zhongxiong; Yin, Wen; Yin, Xuejun; Zhang, Jing; Zhang, Zong; Zhang, Zonghua; Zhou, Min; Zhu, Tao

2009-02-01

114

Castilla-La Mancha neutron monitor: situation and design  

NASA Astrophysics Data System (ADS)

This work shows the present status of the Castilla-La Mancha Neutron Monitor (CaLMa). Thanks to the founds recently agree for the Castilla-La Mancha Comunity governement. The new neutron monitor station will be building and placed in the Alcalá University campus in Guadalajara. Being operative in a provisional site at the end of 2010. The station is based on 18NM64 of LND 25373 3He detectors integrated into the Neutron Monitor Data Base (NMDB). Details about geomagnetic conditions, design and schedule are presented.

Medina, Jose; José Blanco, Juan; García, Oscar

2010-05-01

115

Design of composite flywheel rotors with soft cores  

NASA Astrophysics Data System (ADS)

A flywheel is an inertial energy storage system in which the energy or momentum is stored in a rotating mass. Over the last twenty years, high-performance flywheels have been developed with significant improvements, showing potential as energy storage systems in a wide range of applications. Despite the great advances in fundamental knowledge and technology, the current successful rotors depend mainly on the recent developments of high-stiffness and high-strength carbon composites. These composites are expensive and the cost of flywheels made of them is high. The ultimate goal of the study presented here is the development of a cost-effective composite rotor made of a hybrid material. In this study, two-dimensional and three-dimensional analysis tools were developed and utilized in the design of the composite rim, and extensive spin tests were performed to validate the designed rotors and give a sound basis for large-scale rotor design. Hybrid rims made of several different composite materials can effectively reduce the radial stress in the composite rim, which is critical in the design of composite rims. Since the hybrid composite rims we studied employ low-cost glass fiber for the inside of the rim, and the result is large radial growth of the hybrid rim, conventional metallic hubs cannot be used in this design. A soft core developed in this study was successfully able to accommodate the large radial growth of the rim. High bonding strength at the shaft-to-core interface was achieved by the soft core being molded directly onto the steel shaft, and a tapered geometry was used to avoid stress concentrations at the shaft-to-core interface. Extensive spin tests were utilized for reverse engineering of the design of composite rotors, and there was good correlation between tests and analysis. A large-scale composite rotor for ground transportation is presented with the performance levels predicted for it.

Kim, Taehan

116

Neutronics Assessment of Molten Salt Breeding Blanket Design  

E-print Network

Be zone thickness (5 cm) is required in the DC design with Flibe compared to the SC with Flinabe (7 cm1 Neutronics Assessment of Molten Salt Breeding Blanket Design Options Mohamed Sawan Fusion reactor configuration and power loadings used Water cooled steel VV and shield 1D calculations with IB

117

Massive neutron stars with hyperonic core : a case study with the IUFSU model  

E-print Network

Recent discovery of massive neutron stars, such as PSR J$0348+0432$ and PSR J$1614-2230$, has raised questions on the existence of exotic matter such as hyperons in the neutron star core. Also the validity of many established equation of state (EoS) like the GM1 and FSUGold are questioned. We investigate the existence of hyperonic matter in the central regions of massive neutron stars using Relativistic Mean Field (RMF) theory with recently proposed parameter set IUFSU. The IUFSU parameter set is extended by including hyperons to study the neutron star in $\\beta$ equilibrium. The effect of different hyperon potentials, namely $\\Sigma$ and $\\Xi$ potentials, on the EoS and hence the maximum mass of neutron stars has been studied. We have also considered the rotating star configurations since the observed massive stars are pulsars. It has been found that a maximum mass of $1.93M_{\\odot}$, which is within the 3$\\sigma$ limit of the observed mass of PSR J$0348+0432$, can be obtained for rotating stars, with certai...

Bhowmick, Bipasha; Bhattacharyya, Abhijit; Gangopadhyay, G

2014-01-01

118

Weapons-Grade Plutonium-Thorium PWR Assembly Design and Core Safety Analysis  

SciTech Connect

A light water reactor (LWR) fuel assembly design consisting of a blend of weapons-grade plutonium and natural thorium oxides was examined. The design meets current thermal-hydraulic and safety criteria. Such an assembly would have enough reactivity to achieve three cycles of operation. The pin power distribution indicates a fairly level distribution across the assembly, avoiding hot spots near guide tubes, corners, and other sections where excessive power would create significant loss to thermal-hydraulic margins.This work examined a number of physics and core safety analysis parameters that impact the operation and safety of power reactors. Such parameters as moderator coefficients of reactivity, Doppler coefficients, soluble boron worth, control rod worth, prompt neutron lifetime, and delayed-neutron fractions were considered. These in turn were used to examine reactor behavior during a number of operational conditions, transients, and accidents. Such conditions as shutdown from power with one rod stuck out, steam-line break accident, feedwater line break, loss of coolant flow, locked rotor accidents, control rod ejection accidents, and anticipated transients without scram (ATWSs) were examined.The analysis of selected reactor transients demonstrated that it is feasible to license and safely operate a reactor fueled with plutonium-thorium blended fuel. In most cases analyzed, the thorium mixture had less-severe consequences than those for a core comprising low-enriched uranium fuel. In the analyzed cases where the consequences were more severe, they were still within acceptable limits. The ATWS accident condition requires more analysis.

Dziadosz, David; Ake, Timothy N.; Saglam, Mehmet; Sapyta, Joe J. [Framatome ANP, Inc. (France)

2004-07-15

119

Optimization from core to experiment - using Monte Carlo computer codes for the conversion of high flux neutron sources  

SciTech Connect

The performance of a neutron source is not only dependent on the maximum flux, but is a function of available beam time per year, number and efficiency of neutron guides and instruments and available flux at the experiment. The conversion of research reactors, especially for high flux systems, which are used in neutron research often involves the re-optimization of the whole system to increase the performance and minimize losses. The first and inevitable step of the optimization procedure are simulation calculations of the reactor core. But striving to optimize the performance of the complete system it would be well-advised to expand the calculation beyond the moderator tank to address the experimental devices as well . Today, this is possible with a variety of Monte Carlo codes which track the propagation of neutrons through the neutron guides to the instrument and thus virtually simulate a complete experiment . So far, we have used MATHEMATICA as a tool for our simulation routines addressing the reactor core optimization. Now, we implemented MATHEMATICA also as a linkage routine between MCNPX and the neutron ray-tracing code MCSTAS. This code system is capable of assessing and quantifying changes in performance of a high flux research reactor from core to experiment. It could be useful in overall conversion strategies by making the various trade-offs between neutron flux, neutron quality costs of conversion measures and neutron usage at experiments more transparent. (author)

Englert, M

2008-07-15

120

Accelerator shield design of KIPT neutron source facility  

SciTech Connect

Argonne National Laboratory (ANL) of the United States and Kharkov Institute of Physics and Technology (KIPT) of Ukraine have been collaborating on the design development of a neutron source facility at KIPT utilizing an electron-accelerator-driven subcritical assembly. Electron beam power is 100 kW, using 100 MeV electrons. The facility is designed to perform basic and applied nuclear research, produce medical isotopes, and train young nuclear specialists. The biological shield of the accelerator building is designed to reduce the biological dose to less than 0.5-mrem/hr during operation. The main source of the biological dose is the photons and the neutrons generated by interactions of leaked electrons from the electron gun and accelerator sections with the surrounding concrete and accelerator materials. The Monte Carlo code MCNPX serves as the calculation tool for the shield design, due to its capability to transport electrons, photons, and neutrons coupled problems. The direct photon dose can be tallied by MCNPX calculation, starting with the leaked electrons. However, it is difficult to accurately tally the neutron dose directly from the leaked electrons. The neutron yield per electron from the interactions with the surrounding components is less than 0.01 neutron per electron. This causes difficulties for Monte Carlo analyses and consumes tremendous computation time for tallying with acceptable statistics the neutron dose outside the shield boundary. To avoid these difficulties, the SOURCE and TALLYX user subroutines of MCNPX were developed for the study. The generated neutrons are banked, together with all related parameters, for a subsequent MCNPX calculation to obtain the neutron and secondary photon doses. The weight windows variance reduction technique is utilized for both neutron and photon dose calculations. Two shielding materials, i.e., heavy concrete and ordinary concrete, were considered for the shield design. The main goal is to maintain the total dose outside the shield boundary at less than 0.5-mrem/hr. The shield configuration and parameters of the accelerator building have been determined and are presented in this paper. (authors)

Zhong, Z.; Gohar, Y. [Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439 (United States)

2013-07-01

121

Conceptual design of a neutron camera for MAST Upgradea)  

NASA Astrophysics Data System (ADS)

This paper presents two different conceptual designs of neutron cameras for Mega Ampere Spherical Tokamak (MAST) Upgrade. The first one consists of two horizontal cameras, one equatorial and one vertically down-shifted by 65 cm. The second design, viewing the plasma in a poloidal section, also consists of two cameras, one radial and the other one with a diagonal view. Design parameters for the different cameras were selected on the basis of neutron transport calculations and on a set of target measurement requirements taking into account the predicted neutron emissivities in the different MAST Upgrade operating scenarios. Based on a comparison of the cameras' profile resolving power, the horizontal cameras are suggested as the best option.

Weiszflog, M.; Sangaroon, S.; Cecconello, M.; Conroy, S.; Ericsson, G.; Klimek, I.; Keeling, D.; Martin, R.; Turnyanskiy, M.

2014-11-01

122

Study of the neutron beam line shield design for JSNS.  

PubMed

The JSNS, a spallation neutron source of J-PARC (JAERI-KEK Joint Project of the High Intensity Proton Accelerator) has 23 neutron beam lines. In the present study, a database was formulated for an optimum shielding design using the MCNP-X code. The calculations involved two steps. In the first step, the neutron distributions were created in the typical neutron beam line with a model that included the spallation neutron source target. The neutron currents evaluated flowed from the duct into the duct wall which was the boundary source for the bulk shield surrounding the beam line. In the second step, bulk-shield calculations were performed for the various shielding materials (iron, concrete, heavy concrete and so on) used and their composites up to thicknesses of 3 m. The results were compared with each other. Composite material shields of iron and such hydrogeneous materials as polyethylene or concrete were more effective. A typical design was prepared for a beam line within 25 m distance from a moderator, as a sample. PMID:16381789

Kawai, M; Saito, K; Sanami, T; Nakao, N; Maekawa, F

2005-01-01

123

Beamed Core Antimatter Propulsion: Engine Design and Optimization  

E-print Network

A conceptual design for beamed core antimatter propulsion is reported, where electrically charged annihilation products directly generate thrust after being deflected and collimated by a magnetic nozzle. Simulations were carried out using the Geant4 (Geometry and tracking) software toolkit released by the CERN accelerator laboratory for Monte Carlo simulation of the interaction of particles with matter and fields. Geant permits a more sophisticated and comprehensive design and optimization of antimatter engines than the software environment for simulations reported by prior researchers. The main finding is that effective exhaust speeds Ve ~ 0.69c (where c is the speed of light) are feasible for charged pions in beamed core propulsion, a major improvement over the Ve ~ 0.33c estimate based on prior simulations. The improvement resulted from optimization of the geometry and the field configuration of the magnetic nozzle. Moreover, this improved performance is realized using a magnetic field on the order of 10 T at the location of its highest magnitude. Such a field could be produced with today's technology, whereas prior nozzle designs anticipated and required major advances in this area. The paper also briefly reviews prospects for production of the fuel needed for a beamed core engine.

Ronan Keane; Wei-Ming Zhang

2012-01-26

124

Core compressor exit stage study. 1: Aerodynamic and mechanical design  

NASA Technical Reports Server (NTRS)

The effect of aspect ratio on the performance of core compressor exit stages was demonstrated using two three stage, highly loaded, core compressors. Aspect ratio was identified as having a strong influence on compressors endwall loss. Both compressors simulated the last three stages of an advanced eight stage core compressor and were designed with the same 0.915 hub/tip ratio, 4.30 kg/sec (9.47 1bm/sec) inlet corrected flow, and 167 m/sec (547 ft/sec) corrected mean wheel speed. The first compressor had an aspect ratio of 0.81 and an overall pressure ratio of 1.357 at a design adiabatic efficiency of 88.3% with an average diffusion factor or 0.529. The aspect ratio of the second compressor was 1.22 with an overall pressure ratio of 1.324 at a design adiabatic efficiency of 88.7% with an average diffusion factor of 0.491.

Burdsall, E. A.; Canal, E., Jr.; Lyons, K. A.

1979-01-01

125

The Interplay between Proto--Neutron Star Convection and Neutrino Transport in Core-Collapse Supernovae  

NASA Astrophysics Data System (ADS)

We couple two-dimensional hydrodynamics to realistic one-dimensional multigroup flux-limited diffusion neutrino transport to investigate proto-neutron star convection in core-collapse supernovae, and more specifically, the interplay between its development and neutrino transport. Our initial conditions, time-dependent boundary conditions, and neutrino distributions for computing neutrino heating, cooling, and deleptonization rates are obtained from one-dimensional simulations that implement multigroup flux-limited diffusion and one-dimensional hydrodynamics. The development and evolution of proto-neutron star convection are investigated for both 15 and 25 M? models, representative of the two classes of stars with compact and extended iron cores, respectively. For both models, in the absence of neutrino transport, the angle-averaged radial and angular convection velocities in the initial Ledoux unstable region below the shock after bounce achieve their peak values in ~20 ms, after which they decrease as the convection in this region dissipates. The dissipation occurs as the gradients are smoothed out by convection. This initial proto-neutron star convection episode seeds additional convectively unstable regions farther out beneath the shock. The additional proto-neutron star convection is driven by successive negative entropy gradients that develop as the shock, in propagating out after core bounce, is successively strengthened and weakened by the oscillating inner core. The convection beneath the shock distorts its sphericity, but on the average the shock radius is not boosted significantly relative to its radius in our corresponding one-dimensional models. In the presence of neutrino transport, proto-neutron star convection velocities are too small relative to bulk inflow velocities to result in any significant convective transport of entropy and leptons. This is evident in our two-dimensional entropy snapshots, which in this case appear spherically symmetric. The peak angle-averaged radial and angular convection velocities are orders of magnitude smaller than they are in the corresponding ``hydrodynamics-only'' models. A simple analytical model supports our numerical results, indicating that the inclusion of neutrino transport reduces the entropy-driven (lepton-driven) convection growth rates and asymptotic velocities by a factor ~3 (50) at the neutrinosphere and a factor ~250 (1000) at ? = 1012 g cm-3, for both our 15 and 25 M? models. Moreover, when transport is included, the initial postbounce entropy gradient is smoothed out by neutrino diffusion, whereas the initial lepton gradient is maintained by electron capture and neutrino escape near the neutrinosphere. Despite the maintenance of the lepton gradient, proto-neutron star convection does not develop over the 100 ms duration typical of all our simulations, except in the instance where ``low-test'' intial conditions are used, which are generated by core-collapse and bounce simulations that neglect neutrino-electron scattering and ion-ion screening corrections to neutrino-nucleus elastic scattering. Models favoring the development of proto-neutron star convection either by starting with more favorable, albeit artificial (low-test), initial conditions or by including transport corrections that were ignored in our ``fiducial'' models were considered. Our conclusions nonetheless remained the same. Evidence of proto-neutron star convection in our two-dimensional entropy snapshots was minimal, and, as in our fiducial models, the angle-averaged convective velocities when neutrino transport was included remained orders of magnitude smaller than their counterparts in the corresponding hydrodynamics-only models.

Mezzacappa, A.; Calder, A. C.; Bruenn, S. W.; Blondin, J. M.; Guidry, M. W.; Strayer, M. R.; Umar, A. S.

1998-01-01

126

Effects of core excess reactivity and coolant average temperature on maximum operable time of NIRR-1 miniature neutron source reactor  

Microsoft Academic Search

We appraised in this study the effects of core excess reactivity and average coolant temperature on the operable time of the Nigeria Research Reactor-1 (NIRR-1), which is a miniature neutron source reactor (MNSR). The duration of the reactor operating time and fluence depletion under different operation mode as well as change in core excess reactivity with temperature coefficient was investigated

Y. A. Ahmed; I. B. Mansir; I. Yusuf; G. I. Balogun; S. A. Jonah

2011-01-01

127

Preliminary design study of advanced multistage axial flow core compressors  

NASA Technical Reports Server (NTRS)

A preliminary design study was conducted to identify an advanced core compressor for use in new high-bypass-ratio turbofan engines to be introduced into commercial service in the 1980's. An evaluation of anticipated compressor and related component 1985 state-of-the-art technology was conducted. A parametric screening study covering a large number of compressor designs was conducted to determine the influence of the major compressor design features on efficiency, weight, cost, blade life, aircraft direct operating cost, and fuel usage. The trends observed in the parametric screening study were used to develop three high-efficiency, high-economic-payoff compressor designs. These three compressors were studied in greater detail to better evaluate their aerodynamic and mechanical feasibility.

Wisler, D. C.; Koch, C. C.; Smith, L. H., Jr.

1977-01-01

128

Ultracold neutron source at the PULSTAR reactor: Engineering design and cryogenic testing  

NASA Astrophysics Data System (ADS)

Construction is completed and commissioning is in progress for an ultracold neutron (UCN) source at the PULSTAR reactor on the campus of North Carolina State University. The source utilizes two stages of neutron moderation, one in heavy water at room temperature and the other in solid methane at ~40 K, followed by a converter stage, solid deuterium at 5 K, that allows a single down scattering of cold neutrons to provide UCN. The UCN source rolls into the thermal column enclosure of the PULSTAR reactor, where neutrons will be delivered from a bare face of the reactor core by streaming through a graphite-lined assembly. The source infrastructure, i.e., graphite-lined assembly, heavy-water system, gas handling system, and helium liquefier cooling system, has been tested and all systems operate as predicted. The research program being considered for the PULSTAR UCN source includes the physics of UCN production, fundamental particle physics, and material surface studies of nanolayers containing hydrogen. In the present paper we report details of the engineering and cryogenic design of the facility as well as results of critical commissioning tests without neutrons.

Korobkina, E.; Medlin, G.; Wehring, B.; Hawari, A. I.; Huffman, P. R.; Young, A. R.; Beaumont, B.; Palmquist, G.

2014-12-01

129

From hypernuclei to the Inner Core of Neutron Stars: A Quantum Monte Carlo Study  

NASA Astrophysics Data System (ADS)

Auxiliary Field Diffusion Monte Carlo (AFDMC) calculations have been employed to revise the interaction beween A-hyperons and nucleons in hypernuclei. The scheme used to describe the interaction, inspired by the phenomenological Argonne-Urbana forces, is the ?N + ?NN potential firstly introduced by Bodmer, Usmani et al. Within this framework, we performed calculations on light and medium mass hypernuclei in order to assess the extent of the repulsive contribution of the three-body part. By tuning this contribution in order to reproduce the ? separation energy in 5?He and 17?O, experimental findings are reproduced over a wide range of masses. Calculations have then been extended to ?-neutron matter in order to derive an analogous of the symmetry energy to be used in determining the equation of state of matter in the typical conditions found in the inner core of neutron stars.

Lonardoni, D.; Pederiva, F.; Gandolfi, S.

2014-08-01

130

Core polarization for the electric quadrupole moment of neutron-rich aluminum isotopes  

SciTech Connect

The core polarization effects for the electric quadrupole moments of the neutron-rich {sup 31}Al, {sup 33}Al, and {sup 35}Al isotopes in the vicinity of the island of inversion are investigated by means of the microscopic particle-vibration coupling model in which the Skyrme Hartee-Fock-Bogoliubov and quasiparticle random-phase approximations are used to calculate the single-quasiparticle wave functions and the excitation modes. It is found that the polarization charge for the proton 1d{sub 5/2} hole state in {sup 33}Al is quite sensitive to coupling to the neutrons in the pf-shell associated with the pairing correlations and that the polarization charge in {sup 35}Al becomes larger due to the stronger collectivity of the low-lying quadrupole vibrational mode in the neighboring {sup 36}Si nucleus.

Yoshida, Kenichi [RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198 (Japan)

2009-05-15

131

Electron-muon heat conduction in neutron star cores via the exchange of transverse plasmons  

E-print Network

We calculate the thermal conductivity of electrons and muons kappa_{e-mu} produced owing to electromagnetic interactions of charged particles in neutron star cores and show that these interactions are dominated by the exchange of transverse plasmons (via the Landau damping of these plasmons in nonsuperconducting matter and via a specific plasma screening in the presence of proton superconductivity). For normal protons, the Landau damping strongly reduces kappa_{e-mu} and makes it temperature independent. Proton superconductivity suppresses the reduction and restores the Fermi-liquid behavior kappa_{e-mu} ~ 1/T. Comparing with the thermal conductivity of neutrons kappa_n, we obtain kappa_{e-mu}> kappa_n for T>2 GK in normal matter and for any T in superconducting matter with proton critical temperatures T_c>3e9 K. The results are described by simple analytic formulae.

P. S. Shternin; D. G. Yakovlev

2007-05-14

132

Neutronic Analysis of an Advanced Fuel Design Concept for the High Flux Isotope Reactor  

SciTech Connect

This study presents the neutronic analysis of an advanced fuel design concept for the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR) that could significantly extend the current fuel cycle length under the existing design and safety criteria. A key advantage of the fuel design herein proposed is that it would not require structural changes to the present HFIR core, in other words, maintaining the same rated power and fuel geometry (i.e., fuel plate thickness and coolant channel dimensions). Of particular practical importance, as well, is the fact that the proposed change could be justified within the bounds of the existing nuclear safety basis. The simulations herein reported employed transport theory-based and exposure-dependent eigenvalue characterization to help improve the prediction of key fuel cycle parameters. These parameters were estimated by coupling a benchmarked three-dimensional MCNP5 model of the HFIR core to the depletion code ORIGEN via the MONTEBURNS interface. The design of an advanced HFIR core with an improved fuel loading is an idea that evolved from early studies by R. D. Cheverton, formerly of ORNL. This study contrasts a modified and increased core loading of 12 kg of 235U against the current core loading of 9.4 kg. The simulations performed predict a cycle length of 39 days for the proposed fuel design, which represents a 50% increase in the cycle length in response to a 25% increase in fissile loading, with an average fuel burnup increase of {approx}23%. The results suggest that the excess reactivity can be controlled with the present design and arrangement of control elements throughout the core's life. Also, the new power distribution is comparable or even improved relative to the current power distribution, displaying lower peak to average fission rate densities across the inner fuel element's centerline and bottom cells. In fact, the fission rate density in the outer fuel element also decreased at these key locations for the proposed design. Overall, it is estimated that the advanced core design could increase the availability of the HFIR facility by {approx}50% and generate {approx}33% more neutrons annually, which is expected to yield sizeable savings during the remaining life of HFIR, currently expected to operate through 2014. This study emphasizes the neutronics evaluation of a new fuel design. Although a number of other performance parameters of the proposed design check favorably against the current design, and most of the core design features remain identical to the reference, it is acknowledged that additional evaluations would be required to fully justify the thermal-hydraulic and thermal-mechanical performance of a new fuel design, including checks for cladding corrosion performance as well as for industrial and economic feasibility.

Xoubi, Ned [ORNL; Primm, Trent [ORNL; Maldonado, G. Ivan [University of Tennessee, Knoxville (UTK)

2009-01-01

133

Maximum mass of neutron stars and strange neutron-star cores  

NASA Astrophysics Data System (ADS)

Context. The recent measurement of mass of PSR J1614-2230 rules out most existing models of the equation of state (EOS) of dense matter with high-density softening due to hyperonization that were based on the recent hyperon-nucleon and hyperon-hyperon interactions, which leads to a "hyperon puzzle". Aims: We study a specific solution of this hyperon puzzle that consists of replacing a too soft hyperon core by a sufficiently stiff quark core. In terms of the quark structure of the matter, one replaces a strangeness-carrying baryon phase of confined quark triplets, some of them involving s quarks, by a quark plasma of deconfined u, d, and s quarks. Methods: We constructed an analytic approximation that fits modern EOSs of the two flavor (2SC) and the color-flavor-locked (CFL) color-superconducting phases of quark matter very well. Then, we used it to generate a continuum of EOSs of quark matter. This allowed us to simulate continua of sequences of first-order phase transitions at prescribed pressures, from hadronic matter to the 2SC and then to the CFL state of color-superconducting quark matter. Results: We obtain constraints in the parameter space of the EOS of superconducting quark cores, EOS.Q, resulting from Mmax > 2 M?. These constraints depend on the assumed EOS of baryon phase, EOS.B. We also derive constraints that would result from significantly higher measured masses. For 2.4 M? the required stiffness of the CFL quark core is close to the causality limit while the density jump at the phase transition is very small. Conclusions: The condition Mmax > 2 M? puts strong constraints on the EOSs of the 2SC and CFL phases of quark matter. Density jumps at the phase transitions have to be sufficiently small and sound speeds in quark matter sufficiently large. The condition of thermodynamic stability of the quark phase results in a maximum mass of hybrid stars similar to that of purely baryon stars. This is due to the phase transition of quark matter back to the baryon phase (reconfinement) that we find for both EOS.B. Therefore, to obtain Mmax > 2 M? for hybrid stars, both sufficiently strong additional hyperon repulsion at high-density baryon matter and a sufficiently stiff EOS of quark matter would be needed. However, we think that the high-density instability, which results in the reconfinement of quark matter, indicates actually the inadequacy of the point-particle model of baryons in dense matter at ? ? 5 ÷ 8?0. We expect that reconfinement can be removed by a sufficient stiffening of the baryon phase, resulting from the repulsive finite size contribution for baryons to the EOS.

Zdunik, J. L.; Haensel, P.

2013-03-01

134

Coupled 3D-neutronics / thermal-hydraulics analysis of an unprotected loss-of-flow accident for a 3600 MWth SFR core  

SciTech Connect

The core behaviour of a large (3600 MWth) sodium-cooled fast reactor (SFR) is investigated in this paper with the use of a coupled TRACE/PARCS model. The SFR neutron spectrum is characterized by several performance advantages, but also leads to one dominating neutronics drawback - a positive sodium void reactivity. This implies a positive reactivity effect when sodium coolant is removed from the core. In order to evaluate such feedback in terms of the dynamics, a representative unprotected loss-of-flow (ULOF) transient, i.e. flow run-down without SCRAM in which sodium boiling occurs, is analyzed. Although analysis of a single transient cannot allow general conclusions to be drawn, it does allow better understanding of the underlying physics and can lead to proposals for improving the core response during such an accident. The starting point of this study is the reference core design considered in the framework of the Collaborative Project on the European Sodium Fast Reactor (CP-ESFR). To reduce the void effect, the core has been modified by introducing an upper sodium plenum (along with a boron layer) and by reducing the core height-to-diameter ratio. For the ULOF considered, a sharp increase in core power results in melting of the fuel in the case of the reference core. In the modified core, a large dryout leads to melting of the clad. It seems that, for the hypothetical event considered, fuel failure cannot be avoided with just improvement of the neutronics design; therefore, thermal-hydraulics optimization has been considered. An innovative assembly design is proposed to prevent sodium vapour blocking the fuel channel. This results in preventing a downward propagation of the sodium boiling to the core center, thus limiting it to the upper region. Such a void map introduces a negative coolant density reactivity feedback, which dominates the total reactivity change. As a result, the power level and the fuel temperature are effectively reduced, and a large dryout is prevented. As a next step, the classical sodium plenum is replaced by a fission gas plenum (with lower sodium fraction), thus improving flow stability. Stable boiling at a steady power level is achieved in this final configuration. (authors)

Sun, K. [Paul Scherrer Institut PSI, 5232 Villigen PSI (Switzerland); Ecole Polytechnique Federale de Lausanne EPFL, 1015 Lausanne (Switzerland); Chenu, A. [Ecole Polytechnique Federale de Lausanne EPFL, 1015 Lausanne (Switzerland); Mikityuk, K.; Krepel, J. [Paul Scherrer Institut PSI, 5232 Villigen PSI (Switzerland); Chawla, R. [Paul Scherrer Institut PSI, 5232 Villigen PSI (Switzerland); Ecole Polytechnique Federale de Lausanne EPFL, 1015 Lausanne (Switzerland)

2012-07-01

135

A shielding design for an accelerator-based neutron source for boron neutron capture therapy.  

PubMed

Research in boron neutron capture therapy (BNCT) at The Ohio State University Nuclear Engineering Department has been primarily focused on delivering a high quality neutron field for use in BNCT using an accelerator-based neutron source (ABNS). An ABNS for BNCT is composed of a proton accelerator, a high-energy beam transport system, a (7)Li target, a target heat removal system (HRS), a moderator assembly, and a treatment room. The intent of this paper is to demonstrate the advantages of a shielded moderator assembly design, in terms of material requirements necessary to adequately protect radiation personnel located outside a treatment room for BNCT, over an unshielded moderator assembly design. PMID:15308187

Hawk, A E; Blue, T E; Woollard, J E

2004-11-01

136

[Shielding design and detection of neutrons from medical and industrial electron accelerators--simple method of design calculation for neutron shielding].  

PubMed

The neutron leakage from medical and industrial electron accelerators has become an important problem and its detection and shielding is being performed in their facilities. This study provides a new simple method of design calculation for neutron shielding of those electron accelerator facilities by dividing into the following five categories; neutron dose distribution in the accelerator room, neutron attenuation through the wall and the door in the accelerator room, neutron and secondary photon dose distributions in the maze, neutron and secondary photon attenuation through the door at the end of the maze, neutron leakage outside the facility-skyshine. PMID:3704202

Nakamura, T; Uwamino, Y

1986-02-01

137

High Flux Isotope Reactor cold neutron source reference design concept  

SciTech Connect

In February 1995, Oak Ridge National Laboratory`s (ORNL`s) deputy director formed a group to examine the need for upgrades to the High Flux Isotope Reactor (HFIR) system in light of the cancellation of the Advanced neutron Source Project. One of the major findings of this study was that there was an immediate need for the installation of a cold neutron source facility in the HFIR complex. In May 1995, a team was formed to examine the feasibility of retrofitting a liquid hydrogen (LH{sub 2}) cold source facility into an existing HFIR beam tube. The results of this feasibility study indicated that the most practical location for such a cold source was the HB-4 beam tube. This location provides a potential flux environment higher than the Institut Laue-Langevin (ILL) vertical cold source and maximizes the space available for a future cold neutron guide hall expansion. It was determined that this cold neutron beam would be comparable, in cold neutron brightness, to the best facilities in the world, and a decision was made to complete a preconceptual design study with the intention of proceeding with an activity to install a working LH{sub 2} cold source in the HFIR HB-4 beam tube. During the development of the reference design the liquid hydrogen concept was changed to a supercritical hydrogen system for a number of reasons. This report documents the reference supercritical hydrogen design and its performance. The cold source project has been divided into four phases: (1) preconceptual, (2) conceptual design and testing, (3) detailed design and procurement, and (4) installation and operation. This report marks the conclusion of the conceptual design phase and establishes the baseline reference concept.

Selby, D.L.; Lucas, A.T.; Hyman, C.R. [and others

1998-05-01

138

Neutronic assessment of stringer fuel assembly design for liquid-salt-cooledvery high temperature reactor (LS-VHTR).  

SciTech Connect

Neutronic studies of 18-pin and 36-pin stringer fuel assemblies have been performed to ascertain that core design requirements for the Liquid-Salt Cooled Very High Temperature Reactor (LS-VHTR) can be met. Parametric studies were performed to determine core characteristics required to achieve a target core cycle length of 18 months and fuel discharge burnup greater than 100 GWd/t under the constraint that the uranium enrichment be less than 20% in order to support non-proliferation goals. The studies were done using the WIMS9 lattice code and the linear reactivity model to estimate the core reactivity balance, fuel composition, and discharge burnup. The results show that the design goals can be met using a 1-batch fuel management scheme, uranium enrichment of 15% and a fuel packing fraction of 30% or greater for the 36-pin stringer fuel assembly design.

Szakaly, F. J.; Kim, T. K.; Taiwo, T. A.

2006-09-15

139

The neutronic design and performance of the Indiana University Cyclotron Facility (IUCF) Low Energy Neutron Source (LENS)  

Microsoft Academic Search

Neutron scattering research is performed primarily at large-scale facilities. However, history has shown that smaller scale neutron scattering facilities can play a useful role in education and innovation while performing valuable materials research. This dissertation details the design and experimental validation of the LENS TMR as an example for a small scale accelerator driven neutron source. LENS achieves competitive long

Christopher M. Lavelle

2007-01-01

140

Preliminary scoping safety analyses of the limiting design basis protected accidents for the Fast Flux Test Facility tritium production core  

SciTech Connect

The SAS4A/SASSYS-l computer code is used to perform a series of analyses for the limiting protected design basis transient events given a representative tritium and medical isotope production core design proposed for the Fast Flux Test Facility. The FFTF tritium and isotope production mission will require a different core loading which features higher enrichment fuel, tritium targets, and medical isotope production assemblies. Changes in several key core parameters, such as the Doppler coefficient and delayed neutron fraction will affect the transient response of the reactor. Both reactivity insertion and reduction of heat removal events were analyzed. The analysis methods and modeling assumptions are described. Results of the analyses and comparison against fuel pin performance criteria are presented to provide quantification that the plant protection system is adequate to maintain the necessary safety margins and assure cladding integrity.

Heard, F.J.

1997-11-19

141

An integrated design of an accelerator-based neutron source for boron neutron capture therapy  

NASA Astrophysics Data System (ADS)

An Accelerator Based Neutron Source (ABNS) for Boron Neutron Capture Therapy (BNCT) was first proposed at The Ohio State University (OSU). Since the conception of the ABNS for BNCT, OSU has designed and optimized a moderator assembly based on in-air and in-phantom parameters. Additionally, the fabrication of the moderator assembly has commenced along with detailed analyses of the target and its heat removal system. In this dissertation, an integrated design of the ABNS is presented. This integrated design includes the high energy beam transport system (HEBT), the target and heat removal system (HRS), and the moderator assembly. In the integration process, a neutronic model of the HRS was developed and incorporated into the moderator assembly model. Additionally, a preliminary design of a HEBT system was developed that is compatible with both the HRS and the facility shielding. This dissertation also includes the completion of the fabrication of the moderator assembly and its experimental verification. The completion of the moderator assembly fabrication included the refabrication of the moderator and delimiter and the fabrication of the 6Li covering on the front of the moderator assembly. The experimental verification included neutron spectrum calculations and measurements in the irradiation port, and 3He detector response calculations and measurements in-phantom downstream of the moderator assembly.

Dobelbower, Michael Christian

1997-07-01

142

Coupled full core neutron transport/CFD simulations of pressurized water reactors  

SciTech Connect

Recently as part of the CASL project, a capability to perform 3D whole-core coupled neutron transport and computational fluid dynamics (CFD) calculations was demonstrated. This work uses the 2D/1D transport code DeCART and the commercial CFD code STAR-CCM+. It builds on previous CASL work demonstrating coupling for smaller spatial domains. The coupling methodology is described along with the problem simulated and results are presented for fresh hot full power conditions. An additional comparison is made to an equivalent model that uses lower order T/H feedback to assess the importance and cost of high fidelity feedback to the neutronics problem. A simulation of a quarter core Combustion Engineering (CE) PWR core was performed with the coupled codes using a Fixed Point Gauss-Seidel iteration technique. The total approximate calculation requirements are nearly 10,000 CPU hours and 1 TB of memory. The problem took 6 coupled iterations to converge. The CFD coupled model and low order T/H feedback model compared well for global solution parameters, with a difference in the critical boron concentration and average outlet temperature of 14 ppm B and 0.94 deg. C, respectively. Differences in the power distribution were more significant with maximum relative differences in the core-wide pin peaking factor (Fq) of 5.37% and average relative differences in flat flux region power of 11.54%. Future work will focus on analyzing problems more relevant to CASL using models with less approximations. (authors)

Kochunas, B.; Stimpson, S.; Collins, B.; Downar, T. [Dept. of Nuclear Engineering and Radiological Sciences, Univ. of Michigan, 2200 Bonisteel Blvd, Ann Arbor, MI 48104 (United States); Brewster, R.; Baglietto, E. [CD-adapco, 60 Broadhollow Road, Melville, NY 11747 (United States); Yan, J. [Westinghouse Electric Company LLC, Columbia, SC (United States)

2012-07-01

143

Physics design for the Brookhaven Medical Research Reactor epithermal neutron source.  

PubMed

A collaborative effort by researchers at the Idaho National Engineering Laboratory and the Brookhaven National Laboratory has resulted in the design and implementation of an epithermal-neutron source at the Brookhaven Medical Research Reactor (BMRR). Large aluminum containers, filled with aluminum oxide tiles and aluminum spacers, were tailored to pre-existing compartments on the animal side of the reactor facility. A layer of cadmium was used to minimize the thermal-neutron component. Additional bismuth was added to the pre-existing bismuth shield to minimize the gamma component of the beam. Lead was also added to reduce gamma streaming around the bismuth. The physics design methods are outlined in this paper. Information available to date shows close agreement between calculated and measured beam parameters. The neutron spectrum is predominantly in the intermediate energy range (0.5 eV - 10 keV). The peak flux intensity is 6.4E + 12 n/(m2.s.MW) at the center of the beam on the outer surface of the final gamma shield. The corresponding neutron current is 3.8E + 12 n/(m2.s.MW). Presently, the core operates at a maximum of 3 MW. The fast-neutron KERMA is 3.6E-15 cGy/(n/m2) and the gamma KERMA is 5.0E-16 cGY/(n/m2) for the unperturbed beam. The neutron intensity falls off rapidly with distance from the outer shield and the thermal flux realized in phantom or tissue is strongly dependent on the beam-delimiter and target geometry. PMID:2268249

Wheeler, F J; Parsons, D K; Nigg, D W; Wessol, D E; Miller, L G; Fairchild, R G

1990-01-01

144

Neutronic design studies for an unattended, low power reactor  

NASA Astrophysics Data System (ADS)

The Los Alamos National Laboratory is involved in the design and demonstrations of a small, long-lived nuclear heat and electric power source for potential applications at remote sites where alternate fossil energy systems would not be cost effective. This paper describes the neutronic design analysis that was performed to arrive at two conceptual designs, one using thermoelectric conversion, the other using an organic Rankine cycle. To meet the design objectives and constraints a number of scoping and optimization studies were carried out. The results of calculations of control worths, temperature coefficients of reactivity and fuel depletion effects are reported.

Palmer, R. G.; Durkee, J. W., Jr.

145

Seismic responses of a pool-type fast reactor with different core support designs  

SciTech Connect

In designing the core support system for a pool-type fast reactor, there are many issues which must be considered in order to achieve an optimum and balanced design. These issues include safety, reliability, as well as costs. Several design options are possible to support the reactor core. Different core support options yield different frequency ranges and responses. Seismic responses of a large pool-type fast reactor incorporated with different core support designs have been investigated. 4 refs., 3 figs.

Wu, Ting-shu; Seidensticker, R.W. (Argonne National Lab., IL (USA))

1989-01-01

146

IP CORE DESIGN OF MICROCONTROLLER SYSTEM USING VERILOG FOR ROBOT BASED AGRICULTURAL IMPLEMENTS  

Microsoft Academic Search

This paper presents an RTL compliant Verilog IP Core design of a Microcontroller System modeled on the popular 8051 of Intel. This requirement primarily stems from the on-going project to design a Robot based Agricultural Implement. The proposed system consists of a core processor which emulates the existing 8051 Microcontroller. The designed core has 4K internal ROM, 128 bytes of

S. Ramachandran C. S. Mala

2012-01-01

147

IP CORE DESIGN OF MICROCONTROLLER SYSTEM USING VERILOG FOR ROBOT BASED AGRICULTURAL IMPLEMENTS  

Microsoft Academic Search

This paper presents an RTL compliant Verilog IP Core design of a Microcontroller System modeled on the popular 8051 of Intel. This requirement primarily stems from the on-going project to design a Robot based Agricultural Implement. The proposed system consists of a core processor which emulates the existing 8051 Microcontroller. The designed core has 4K internal ROM, 128 bytes of

C. S. Mala; S. Ramachandran

148

5 MW pulsed spallation neutron source, Preconceptual design study  

SciTech Connect

This report describes a self-consistent base line design for a 5 MW Pulsed Spallation Neutron Source (PSNS). It is intended to establish feasibility of design and as a basis for further expanded and detailed studies. It may also serve as a basis for establishing project cost (30% accuracy) in order to intercompare competing designs for a PSNS not only on the basis of technical feasibility and technical merit but also on the basis of projected total cost. The accelerator design considered here is based on the objective of a pulsed neutron source obtained by means of a pulsed proton beam with average beam power of 5 MW, in {approx} 1 {mu}sec pulses, operating at a repetition rate of 60 Hz. Two target stations are incorporated in the basic facility: one for operation at 10 Hz for long-wavelength instruments, and one operating at 50 Hz for instruments utilizing thermal neutrons. The design approach for the proton accelerator is to use a low energy linear accelerator (at 0.6 GeV), operating at 60 Hz, in tandem with two fast cycling booster synchrotrons (at 3.6 GeV), operating at 30 Hz. It is assumed here that considerations of cost and overall system reliability may favor the present design approach over the alternative approach pursued elsewhere, whereby use is made of a high energy linear accelerator in conjunction with a dc accumulation ring. With the knowledge that this alternative design is under active development, it was deliberately decided to favor here the low energy linac-fast cycling booster approach. Clearly, the present design, as developed here, must be carried to the full conceptual design stage in order to facilitate a meaningful technology and cost comparison with alternative designs.

Not Available

1994-06-01

149

The determination of neutron energy spectrum in reactor core C1 of reactor VR-1 Sparrow  

SciTech Connect

This contribution overviews neutron spectrum measurement, which was done on training reactor VR-1 Sparrow with a new nuclear fuel. Former nuclear fuel IRT-3M was changed for current nuclear fuel IRT-4M with lower enrichment of 235U (enrichment was reduced from former 36% to 20%) in terms of Reduced Enrichment for Research and Test Reactors (RERTR) Program. Neutron spectrum measurement was obtained by irradiation of activation foils at the end of pipe of rabit system and consecutive deconvolution of obtained saturated activities. Deconvolution was performed by computer iterative code SAND-II with 620 groups' structure. All gamma measurements were performed on Canberra HPGe. Activation foils were chosen according physical and nuclear parameters from the set of certificated foils. The Resulting differential flux at the end of pipe of rabit system agreed well with typical spectrum of light water reactor. Measurement of neutron spectrum has brought better knowledge about new reactor core C1 and improved methodology of activation measurement. (author)

Vins, M. [Department of Nuclear Reactors, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, V Holesovickach 2, 180 00 Prague 8 (Czech Republic)], E-mail: vinsmiro@seznam.cz

2008-07-15

150

Core restraint and seismic analysis of a large heterogeneous free-flowering core design. Final report  

Microsoft Academic Search

The core restraint and seismic performance of a large heterogeneous core was analyzed. A free-flowering core restraint system was selected for this study, as opposed to the limited-free bow system of the FFTF and CRBRP. The key features of the core restraint system, such as stiff reflector assemblies and load pad properties, were specified in this study. Other features -

J. T. Madell; T. J. Moran; J. E. Ash; P. J. Fulford

1980-01-01

151

Designing accelerator-based epithermal neutron beams for boron neutron capture therapy.  

PubMed

The 7Li(p,n)7Be reaction has been investigated as an accelerator-driven neutron source for proton energies between 2.1 and 2.6 MeV. Epithermal neutron beams shaped by three moderator materials, Al/AlF3, 7LiF, and D2O, have been analyzed and their usefulness for boron neutron capture therapy (BNCT) treatments evaluated. Radiation transport through the moderator assembly has been simulated with the Monte Carlo N-particle code (MCNP). Fluence and dose distributions in a head phantom were calculated using BNCT treatment planning software. Depth-dose distributions and treatment times were studied as a function of proton beam energy and moderator thickness. It was found that an accelerator-based neutron source with Al/AlF3 or 7LiF as moderator material can produce depth-dose distributions superior to those calculated for a previously published neutron beam design for the Brookhaven Medical Research Reactor, achieving up to approximately 50% higher doses near the midline of the brain. For a single beam treatment, a proton beam current of 20 mA, and a 7LiF moderator, the treatment time was estimated to be about 40 min. The tumor dose deposited at a depth of 8 cm was calculated to be about 21 Gy-Eq. PMID:9775379

Bleuel, D L; Donahue, R J; Ludewigt, B A; Vujic, J

1998-09-01

152

Pre-conceptual design and preliminary neutronic analysis of the proposed National Spallation Neutron Source (NSNS)  

SciTech Connect

The Department of Energy (DOE) has initiated a pre-conceptual design study for the National Spallation Neutron Source (NSNS) and given preliminary approval for the proposed facility to be built at Oak Ridge National Laboratory (ORNL). The pre-conceptual design of the NSNS initially consists of an accelerator system capable of delivering a 1 to 2 GeV proton beam with 1 MW of beam power in an approximate 0.5 {micro}s pulse at a 60 Hz frequency onto a single target station. The NSNS will be upgradable to a significantly higher power level with two target stations (a 60 Hz station and a 10 Hz station). There are many possible layouts and designs for the NSNS target stations. This paper gives a brief overview of the proposed NSNS with respect to the target station, as well as the general philosophy adopted for the neutronic design of the NSNS target stations. A reference design is presented, and some preliminary neutronic results for the NSNS are briefly discussed.

Johnson, J.O.; Barnes, J.M.; Charlton, L.A. [Oak Ridge National Lab., TN (United States). Computational Physics and Engineering Div.

1997-03-01

153

Advanced Neutron Source: Plant Design Requirements. Revision 4  

SciTech Connect

The Advanced Neutron Source will be a new world-class facility for research using hot, thermal, cold, and ultra-cold neutrons. The heart of the facility will be a 330-MW (fission), heavy-water cooled and heavy-water moderated reactor. The reactor will be housed in a central reactor building, with supporting equipment located in an adjoining reactor support building. An array of cold neutron guides will fan out into a large guide hall, housing about 30 neutron research stations. Appropriate office, laboratory, and shop facilities will be included to provide a complete facility for users. The ANS is scheduled to begin operation at the Oak Ridge National Laboratory early in the next decade. This PDR document defines the plant-level requirements for the design, construction, and operation of ANS. It also defines and provides input to the individual System Design Description (SDD) documents. Together, this PDR document and the set of SDD documents will define and control the baseline configuration of ANS.

Not Available

1990-07-01

154

Transitions between turbulent and laminar superfluid vorticity states in the outer core of a neutron star  

E-print Network

We investigate the global transition from a turbulent state of superfluid vorticity to a laminar state, and vice versa, in the outer core of a neutron star. By solving numerically the hydrodynamic Hall-Vinen-Bekarevich-Khalatnikov equations for a rotating superfluid in a differentially rotating spherical shell, we find that the meridional counterflow driven by Ekman pumping exceeds the Donnelly-Glaberson threshold throughout most of the outer core, exciting unstable Kelvin waves which disrupt the rectilinear vortex array, creating a vortex tangle. In the turbulent state, the torque exerted on the crust oscillates, and the crust-core coupling is weaker than in the laminar state. This leads to a new scenario for the rotational glitches observed in radio pulsars: a vortex tangle is sustained in the differentially rotating outer core by the meridional counterflow, a sudden spin-up event brings the crust and core into corotation, the vortex tangle relaxes back to a rectilinear vortex array, then the crust spins down electromagnetically until enough meridional counterflow builds up to reform a vortex tangle. The turbulent-laminar transition can occur uniformly or in patches; the associated time-scales are estimated from vortex filament theory. We calculate numerically the global structure of the flow with and without an inviscid superfluid component, for Hall-Vinen and Gorter-Mellink forms of the mutual friction. We also calculate the post-glitch evolution of the angular velocity of the crust and its time derivative, and compare the results with radio pulse timing data, predicting a correlation between glitch activity and Reynolds number.

C. Peralta; A. Melatos; M. Giacobello; A. Ooi

2006-07-08

155

Documented Safety Analysis Addendum for the Neutron Radiography Reactor Facility Core Conversion  

SciTech Connect

The Neutron Radiography Reactor Facility (NRAD) is a Training, Research, Isotope Production, General Atomics (TRIGA) reactor which was installed in the Idaho National Laboratory (INL) Hot Fuels Examination Facility (HFEF) at the Materials and Fuels Complex (MFC) in the mid 1970s. The facility provides researchers the capability to examine both irradiated and non-irradiated materials in support of reactor fuel and components programs through non-destructive neutron radiography examination. The facility has been used in the past as one facet of a suite of reactor fuels and component examination facilities available to researchers at the INL and throughout the DOE complex. The facility has also served various commercial research activities in addition to the DOE research and development support. The reactor was initially constructed using Fuel Lifetime Improvement Program (FLIP)- type highly enriched uranium (HEU) fuel obtained from the dismantled Puerto Rico Nuclear Center (PRNC) reactor. In accordance with international non-proliferation agreements, the NRAD core will be converted to a low enriched uranium (LEU) fuel and will continue to utilize the PRNC control rods, control rod drives, startup source, and instrument console as was previously used with the HEU core. The existing NRAD Safety Analysis Report (SAR) was created and maintained in the preferred format of the day, combining sections of both DOE-STD-3009 and Nuclear Regulatory Commission Regulatory Guide 1.70. An addendum was developed to cover the refueling and reactor operation with the LEU core. This addendum follows the existing SAR format combining required formats from both the DOE and NRC. This paper discusses the project to successfully write a compliant and approved addendum to the existing safety basis documents.

Boyd D. Christensen

2009-05-01

156

Neutron transport analysis for nuclear reactor design  

DOEpatents

Replacing regular mesh-dependent ray tracing modules in a collision/transfer probability (CTP) code with a ray tracing module based upon combinatorial geometry of a modified geometrical module (GMC) provides a general geometry transfer theory code in two dimensions (2D) for analyzing nuclear reactor design and control. The primary modification of the GMC module involves generation of a fixed inner frame and a rotating outer frame, where the inner frame contains all reactor regions of interest, e.g., part of a reactor assembly, an assembly, or several assemblies, and the outer frame, with a set of parallel equidistant rays (lines) attached to it, rotates around the inner frame. The modified GMC module allows for determining for each parallel ray (line), the intersections with zone boundaries, the path length between the intersections, the total number of zones on a track, the zone and medium numbers, and the intersections with the outer surface, which parameters may be used in the CTP code to calculate collision/transfer probability and cross-section values.

Vujic, Jasmina L. (Lisle, IL)

1993-01-01

157

Neutron transport analysis for nuclear reactor design  

DOEpatents

Replacing regular mesh-dependent ray tracing modules in a collision/transfer probability (CTP) code with a ray tracing module based upon combinatorial geometry of a modified geometrical module (GMC) provides a general geometry transfer theory code in two dimensions (2D) for analyzing nuclear reactor design and control. The primary modification of the GMC module involves generation of a fixed inner frame and a rotating outer frame, where the inner frame contains all reactor regions of interest, e.g., part of a reactor assembly, an assembly, or several assemblies, and the outer frame, with a set of parallel equidistant rays (lines) attached to it, rotates around the inner frame. The modified GMC module allows for determining for each parallel ray (line), the intersections with zone boundaries, the path length between the intersections, the total number of zones on a track, the zone and medium numbers, and the intersections with the outer surface, which parameters may be used in the CTP code to calculate collision/transfer probability and cross-section values. 28 figures.

Vujic, J.L.

1993-11-30

158

Shielding Design of the Spallation Neutron Source (SNS)  

SciTech Connect

The shielding design is important for the construction of an intense high-energy accelerator facility like the proposed Spallation Neutron Source (SNS) due to its impact on conventional facility design, maintenance operations, and since the cost for the radiation shielding shares a considerable part of the total facility costs. A calculational strategy utilizing coupled high energy Monte Carlo calculations and multi-dimensional discrete ordinates calculations, along with semi-empirical calculations, was implemented to perform the conceptual design shielding assessment of the proposed SNS. Biological shields have been designed and assessed for the proton beam transport system and associated beam dumps, the target station, and the target service cell and general remote maintenance cell. Shielding requirements have been assessed with respect to weight, space, and dose-rate constraints for operating, shutdown, and accident conditions. A discussion of the proposed facility design, conceptual design shielding requirements, calculational strategy, source terms, preliminary results and conclusions, and recommendations for additional analyses are presented.

Johnson, J.O.

1998-09-17

159

78 FR 32988 - Core Principles and Other Requirements for Designated Contract Markets; Correction  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION 17 CFR Part 38 RIN 3038-AD09 Core Principles and Other Requirements for Designated...Register release of the final rule regarding Core Principles and Other Requirements for Designated...Register release of the final rule regarding Core Principles and Other Requirements for...

2013-06-03

160

ORR core re-configuration measurements to increase the fast neutron flux in the Magnetic Fusion Energy (MFE) experiments  

NASA Astrophysics Data System (ADS)

The relative increases obtainable in the fast neutron flux in the Magnetic Fusion Energy (MFE) experiment positions were studied by reconfiguring the current ORR core. The percentage increase possible in the current displacement per atom (dpa) rate was examined. The principle methods to increase the fast flux, consisted of reducing the current core size (number of fuel elements), to increase the core average power density and arrangement of the fuel elements in the reduced-size core to tilt the core power distribution towards the MFE positions were investigated. It is concluded that fast fluxes in the E-3 core position can be increased by approximately 15 to 20% over current values and in E-5 by approximately 45 to 55%.

Hobbs, R. W.; Stinnett, R. M.; Sims, T. M.

1985-06-01

161

Negative curvature hollow core fibers: design, fabrication, and applications  

NASA Astrophysics Data System (ADS)

In this paper we consider a new type of hollow core microstructured optical fibers (HC MOFs) so called negative curvature hollow core fibers (NCHCFs). NCHCFs are known as hollow core fibers which allow to transmit a light under extremely high material loss of the cladding material. Such unique property of NCHCFs is due to the fact that their guiding mechanism is different from the guiding mechanisms in hollow core photonic crystal fibers (HC PCFs) and hollow core Bragg fibers (HC BFs). The two main factors which determine the guiding properties of NCHCFs are the `negative curvature' (in a more general case, an alternating curvature) of the core - cladding boundary and the density of electromagnetic states of the cladding. It will be shown that the `negative curvature' of the core - cladding boundary determines the type of interference which can lead to strong light localization in the air core. The interference which leads to air core mode formation in HC PCFs or HC BFs can be considered in terms of a linear momentum transfer by the photonic crystal cladding to the air core modes. In the case of NCHCFs the air core mode formation can be considered in terms of an azimuthal momentum transfer by the core - cladding boundary with an alternating curvature to the air core modes. The fabrication process of NCHCFs and several potential applications of NCHCFs in medicine, sensing and high power delivery are discussed.

Pryamikov, Andrey D.

2014-03-01

162

Core design of long life-cycle fast reactors operating without reactivity margin  

SciTech Connect

In this paper we consider a possibility of designing a fast reactor core that operates without reactivity margin for a long time. This study is based on the physical principle of fast reactor operating in a self-adjustable neutron-nuclear regime (SANNR-1) introduced by L.P. Feoktistov (1988-1993) and improved by V. Ya. Gol'din SANNR-2 (1995). The mathematical modeling of active zones of fast reactors in SANNR modes is held by authors since 1992. The numerical simulation is based on solving the neutron transport equation coupled with quasi-diffusion equations. The calculations have been performed using standard 26 energy groups. We use a hierarchy of spatial models of 1D, 1.5D, 2D, and 3D geometries. The spatial models of higher dimensionality are used for verification of results. The calculations showed that operation of the reactor in this mode increases its efficiency, safety and simplifies management. It is possible to achieve continuous work of the reactor in SANNR-2 during 7-10 years without fuel overloads by means of further optimization of the mode. Small reactivity margin is used only for the reactor start up. After first 10-15 days the reactor in SANNR-2 operates without reactivity margin. (authors)

Aristova, E. N.; Baydin, D. F.; Gol'din, V. Y.; Pestryakova, G. A.; Stoynov, M. I. [Keldysh Inst. of Applied Mathematics RAS, Miusskaya sq., bld.4, 125047, Moscow (Russian Federation)

2012-07-01

163

Modeling & analysis of core debris recriticality during hypothetical severe accidents in the Advanced Neutron Source Reactor  

SciTech Connect

This paper discusses salient aspects of severe-accident-related recriticality modeling and analysis in the Advanced Neutron Source (ANS) reactor. The development of an analytical capability using the KEN05A-SCALE system is described including evaluation of suitable nuclear cross-section sets to account for the effects of system geometry, mixture temperature, material dispersion and other thermal-hydraulic conditions. Benchmarking and validation efforts conducted with KEN05-SCALE and other neutronic codes against critical experiment data are described. Potential deviations and biases resulting from use of the 16-group Hansen-Roach library are shown. A comprehensive test matrix of calculations to evaluate the threat of a criticality event in the ANS is described. Strong dependencies on geometry, material constituents, and thermal-hydraulic conditions are described. The introduction of designed mitigative features are described.

Kim, S.H.; Georgevich, V.; Simpson, D.B.; Slater, C.O.; Taleyarkhan, R.P.

1992-10-01

164

Tokamak Fusion Core Experiment: design studies based on superconducting and hybrid toroidal field coils. Design overview  

SciTech Connect

This document is a design overview that describes the scoping studies and preconceptual design effort performed in FY 1983 on the Tokamak Fusion Core Experiment (TFCX) class of device. These studies focussed on devices with all-superconducting toroidal field (TF) coils and on devices with superconducting TF coils supplemented with copper TF coil inserts located in the bore of the TF coils in the shield region. Each class of device is designed to satisfy the mission of ignition and long pulse equilibrium burn. Typical design parameters are: major radius = 3.75 m, minor radius = 1.0 m, field on axis = 4.5 T, plasma current = 7.0 MA. These designs relay on lower hybrid (LHRH) current rampup and heating to ignition using ion cyclotron range of frequency (ICRF). A pumped limiter has been assumed for impurity control. The present document is a design overview; a more detailed design description is contained in a companion document.

Flanagan, C.A. (ed.)

1984-10-01

165

Neutron transport with the method of characteristics for 3-D full core boiling water reactor applications  

NASA Astrophysics Data System (ADS)

The Numerical Nuclear Reactor (NNR) is a code suite that is being developed to provide high-fidelity multi-physics capability for the analysis of light water nuclear reactors. The focus of the work here is to extend the capability of the NNR by incorporation of the neutronics module, DeCART, for Boiling Water Reactor (BWR) applications. The DeCART code has been coupled to the NNR fluid mechanics and heat transfer module STAR-CD for light water reactor applications. The coupling has been accomplished via an interface program, which is responsible for mapping the STAR-CD and DeCART meshes, managing communication, and monitoring convergence. DeCART obtains the solution of the 3-D Boltzmann transport equation by performing a series of 2-D modular ray tracing-based method of characteristics problems that are coupled within the framework of 3-D coarse-mesh finite difference. The relatively complex geometry and increased axial heterogeneity found in BWRs are beyond the modeling capability of the original version of DeCART. In this work, DeCART is extended in three primary areas. First, the geometric capability is generalized by extending the modular ray tracing scheme and permitting an unstructured mesh in the global finite difference kernel. Second, numerical instabilities, which arose as a result of the severe axial heterogeneity found in BWR cores, have been resolved. Third, an advanced nodal method has been implemented to improve the accuracy of the axial flux distribution. In this semi-analytic nodal method, the analytic solution to the transverse-integrated neutron diffusion equation is obtained, where the nonhomogeneous neutron source was first approximated by a quartic polynomial. The successful completion of these three tasks has allowed the application of the coupled DeCART/STAR-CD code to practical BWR problems.

Thomas, Justin W.

166

Media digital signal processor core design for multimedia application  

NASA Astrophysics Data System (ADS)

An embedded single media processor named MediaDSP3200 core fabricated in a six-layer metal 0.18um CMOS process which implemented the RISC instruction set, DSP data processing instruction set and single-instruction-multiple-data (SIMD) multimedia-enhanced instruction set is described. MediaDSP3200 fuses RISC architecture and DSP computation capability thoroughly, which achieves RISC fundamental, DSP extended and single instruction multiple data (SIMD) instruction set with various addressing modes in a unified pipeline stage architecture. These characteristics enhance system digital signal processing performance greatly. The test processor can achieve 32x32-bit multiply-accumulate (MAC) of 320 MOPS, with 16x16-bit MAC of 1280MOPS. The test processor dissipates 600mW at 1.8v, 320MHz. Also, the implementation was primarily standard cell logic design style. MediaDSP3200 targets diverse embedded application systems, which need both powerful processing/control capability and low-cost budget, e.g. set-top-boxes, video conferencing, DTV, etc. MediaDSP3200 instruction set architecture, addressing mode, pipeline design, SIMD feature, split-ALU and MAC are described in this paper. Finally, the performance benchmark based on H.264 and MPEG decoder algorithm are given in this paper.

Liu, Peng; Yu, Guo-jun; Cai, Wei-guang; Yao, Qing-dong

2006-02-01

167

Passive neutron design study for 200-L waste drums  

SciTech Connect

We have developed a passive neutron counter for the measurement of plutonium in 200-L drums of scrap and waste. The counter incorporates high efficiency for the multiplicity counting in addition to the traditional coincidence counting. The {sup 252}Cf add-a-source feature is used to provide an accurate assay over a wide range of waste matrix materials. The room background neutron rate is reduced by using 30 cm of external polyethylene shielding and the cosmic-ray background is reduced by statistical filtering techniques. Monte Carlo Code calculations were used to determine the optimum detector design, including the gas pressure, size, number, and placement of the {sup 3}He tubes in the moderator. Various moderators, including polyethylene, plastics, teflon, and graphite, were evaluated to obtain the maximum efficiency and minimum detectable mass of plutonium.

Menlove, H.O.; Beddingfield, D.B.; Pickrell, M.M. [and others

1997-09-01

168

Multileaf shielding design against neutrons produced by medical linear accelerators.  

PubMed

This work aims at presenting a study using Monte Carlo simulation of a Multileaf Shielding (MLS) System designed to be used for the protection of patients who undergo radiotherapy treatment, against undesired exposure to neutrons produced in the components of the medical linear accelerator heads. The choice of radiotherapy equipment as the subject of study fell on the Varian Clinac 2,100/2,300 with MLC-120 operating at 18 MeV. The general purpose Monte Carlo N-Particle radiation transport code, MCNP5, was used in the computer simulation in order to determine the ambient dose equivalent, H (10), on several points on the patient's plane, with the equipment operation with and without the MLS. The results of the simulations showed a significant neutron dose reduction after the inclusion of the proposed shielding. PMID:17569690

Rebello, W F; Silva, A X; Facure, A

2008-01-01

169

Design and fabrication of embedded two elliptical cores hollow fiber  

NASA Astrophysics Data System (ADS)

We propose a novel embedded two elliptical cores fiber with a hollow air hole, and demonstrate the fabrication of the embedded two elliptical cores hollow fiber (EECHF). By using a suspended core-in-tube technique, the fibers are drawn from the preform utilizing a fiber drawing system with a pressure controller. The fiber have a 60?m diameter hollow air hole centrally, a 125?m diameter cladding, two 7.2?m /3.0?m (major axis/minor axis) elliptical cores, and a 3?m thickness silica cladding between core layer and air hole. The EECHF has a great potential for PMFs, high sensitivity in-fiber interferometers, poling fiber and Bio-sensor based on evanescent wave field. The fabrication technology is simple and versatile, and can be easily utilized to fabricate multi-core fiber with any desired aspect ratio elliptical core.

Tian, Fengjun; Yuan, Libo; Dai, Qian; Liu, Zhihai

2011-11-01

170

Quadrupole transition strength in the ^{74}ni nucleus and core polarization effects in the neutron-rich ni isotopes.  

PubMed

The reduced transition probability B(E2;0^{+}?2^{+}) has been measured for the neutron-rich nucleus ^{74}Ni in an intermediate energy Coulomb excitation experiment performed at the National Superconducting Cyclotron Laboratory at Michigan State University. The obtained B(E2;0^{+}?2^{+})=642_{-226}^{+216}??e^{2}?fm^{4} value defines a trend which is unexpectedly small if referred to ^{70}Ni and to a previous indirect determination of the transition strength in ^{74}Ni. This indicates a reduced polarization of the Z=28 core by the valence neutrons. Calculations in the pfgd model space reproduce well the experimental result indicating that the B(E2) strength predominantly corresponds to neutron excitations. The ratio of the neutron and proton multipole matrix elements supports such an interpretation. PMID:25396363

Marchi, T; de Angelis, G; Valiente-Dobón, J J; Bader, V M; Baugher, T; Bazin, D; Berryman, J; Bonaccorso, A; Clark, R; Coraggio, L; Crawford, H L; Doncel, M; Farnea, E; Gade, A; Gadea, A; Gargano, A; Glasmacher, T; Gottardo, A; Gramegna, F; Itaco, N; John, P R; Kumar, R; Lenzi, S M; Lunardi, S; McDaniel, S; Michelagnoli, C; Mengoni, D; Modamio, V; Napoli, D R; Quintana, B; Ratkiewicz, A; Recchia, F; Sahin, E; Stroberg, R; Weisshaar, D; Wimmer, K; Winkler, R

2014-10-31

171

Quadrupole Transition Strength in the 7Ni4 Nucleus and Core Polarization Effects in the Neutron-Rich Ni Isotopes  

NASA Astrophysics Data System (ADS)

The reduced transition probability B (E 2 ;0+?2+) has been measured for the neutron-rich nucleus 7Ni4 in an intermediate energy Coulomb excitation experiment performed at the National Superconducting Cyclotron Laboratory at Michigan State University. The obtained B (E 2 ;0+?2+)=64 2-226+216 e2 fm4 value defines a trend which is unexpectedly small if referred to 7Ni0 and to a previous indirect determination of the transition strength in 7Ni4 . This indicates a reduced polarization of the Z =28 core by the valence neutrons. Calculations in the p f g d model space reproduce well the experimental result indicating that the B (E 2 ) strength predominantly corresponds to neutron excitations. The ratio of the neutron and proton multipole matrix elements supports such an interpretation.

Marchi, T.; de Angelis, G.; Valiente-Dobón, J. J.; Bader, V. M.; Baugher, T.; Bazin, D.; Berryman, J.; Bonaccorso, A.; Clark, R.; Coraggio, L.; Crawford, H. L.; Doncel, M.; Farnea, E.; Gade, A.; Gadea, A.; Gargano, A.; Glasmacher, T.; Gottardo, A.; Gramegna, F.; Itaco, N.; John, P. R.; Kumar, R.; Lenzi, S. M.; Lunardi, S.; McDaniel, S.; Michelagnoli, C.; Mengoni, D.; Modamio, V.; Napoli, D. R.; Quintana, B.; Ratkiewicz, A.; Recchia, F.; Sahin, E.; Stroberg, R.; Weisshaar, D.; Wimmer, K.; Winkler, R.

2014-10-01

172

Determination of neutron flux density distribution in the core with LEU fuel IRT-4M at the training reactor VR-1  

SciTech Connect

The objective of this work was to determine the neutron flux density distribution in various places of the training reactor VR-1 Sparrow. This experiment was performed on the new core design C1, composed of the new low-enriched uranium fuel cells IRT-4M (19.7 %). This fuel replaced the old high-enriched uranium fuel IRT-3M (36 %) within the framework of the RERTR Program in September 2005. The measurement used the neutron activation analysis method with gold wires. The principle of this method consists in neutron capture in a nucleus of the material forming the activation detector. This capture can change the nucleus in a radioisotope, whose activity can be measured. The absorption cross-section values were evaluated by MCNP computer code. The gold wires were irradiated in seven different positions in the core C1. All irradiations were performed at reactor power level 1E8 (1 kW{sub therm}). The activity of segments of irradiated wires was measured by special automatic device called 'Drat' (Wire in English). (author)

Huml, O. [Department of Nuclear Reactors, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Prague V Holesovickach 2, 180 00, Prague 8 (Czech Republic)

2008-07-15

173

Neutronics Assessment of Molten Salt Breeding Blanket Design Options  

SciTech Connect

Neutronics assessment has been performed for molten salt breeding blanket design options that can be utilized in fusion power plants. The concepts evaluated are a self-cooled Flinabe blanket with Be multiplier and dual-coolant blankets with He-cooled FW and structure. Three different molten salts were considered including the high melting point Flibe, a low melting point Flibe, and Flinabe. The same TBR can be achieved with a thinner self-cooled blanket compared to the dual-coolant blanket. A thicker Be zone is required in designs with Flinabe. The overall TBR will be {approx}1.07 based on 3-D calculations without breeding in the divertor region. Using Be yields higher blanket energy multiplication than obtainable with Pb. A modest amount of tritium is produced in the Be ({approx}3 kg) over the blanket lifetime of {approx}3 FPY. Using He gas in the dual-coolant blanket results in about a factor of 2 lower blanket shielding effectiveness. We show that it is possible to ensure that the shield is a lifetime component, the vacuum vessel is reweldable, and the magnets are adequately shielded. We conclude that molten salt blankets can be designed for fusion power plants with neutronics requirements such as adequate tritium breeding and shielding being satisfied.

Sawan, M.E. [University of Wisconsin-Madison (United States); Malang, S. [Fusion Nuclear Technology Consulting (United States); Wong, C.P.C. [General Atomics (United States); Youssef, M.Z. [University of California-Los Angeles (United States)

2005-04-15

174

Facing Challenges for Monte Carlo Analysis of Full PWR Cores : Towards Optimal Detail Level for Coupled Neutronics and Proper Diffusion Data for Nodal Kinetics  

NASA Astrophysics Data System (ADS)

Safety analysis of innovative reactor designs requires three dimensional modeling to ensure a sufficiently realistic description, starting from steady state. Actual Monte Carlo (MC) neutron transport codes are suitable candidates to simulate large complex geometries, with eventual innovative fuel. But if local values such as power densities over small regions are needed, reliable results get more difficult to obtain within an acceptable computation time. In this scope, NEA has proposed a performance test of full PWR core calculations based on Monte Carlo neutron transport, which we have used to define an optimal detail level for convergence of steady state coupled neutronics. Coupling between MCNP for neutronics and the subchannel code COBRA for thermal-hydraulics has been performed using the C++ tool MURE, developed for about ten years at LPSC and IPNO. In parallel with this study and within the same MURE framework, a simplified code of nodal kinetics based on two-group and few-point diffusion equations has been developed and validated on a typical CANDU LOCA. Methods for the computation of necessary diffusion data have been defined and applied to NU (Nat. U) and Th fuel CANDU after assembly evolutions by MURE. Simplicity of CANDU LOCA model has made possible a comparison of these two fuel behaviours during such a transient.

Nuttin, A.; Capellan, N.; David, S.; Doligez, X.; El Mhari, C.; Méplan, O.

2014-06-01

175

Design and Applications of a {sup 252}Cf Cold Neutron Source  

SciTech Connect

The goal was to design a source of cold neutrons from such sources as {sup 252}Cf, {sup 241}Am-Be, {sup 244}Cm-Be, or {sup 124}Sb-Be and to find the limitations when such a source is applied to neutron activation analysis. Here, cold neutrons are neutrons with a kinetic energy < 0.01 eV. The initial kinetic energy of most of the neutrons produced from the decay of the {sup 252}Cf nucleus lies in the range from 0.5 to 10 MeV, so moderation is necessary to produce a significant quantity of cold neutrons from these initial neutrons. The same is true for the other three neutron sources. The general design that was selected for the cold neutron source has two moderation regions, and the geometry was restricted to cylindrical symmetry with the sample region along the cylindrical axis. The moderation regions may have different temperatures and may contain different moderating materials. The design tasks are then to find the optimum geometry, moderating materials, and moderating temperatures. A cold neutron flux in the sample region of 2.7 x 10 {sup -3} cold neutrons per source neutron is obtainable in a {sup 252}Cf cold neutron source that has polyethylene as the cold and thermal moderator or with trimethylbenzene as the cold moderator and polyethylene as the thermal moderator. The neutron fluxes obtained are probably within 10{percent} of the fluxes that would be obtained in an actual cold neutron source that is based on the model used. This flux of cold neutrons is adequate for sensitive prompt and delayed neutron activation analysis measurements. The results show that a useful flux of cold neutrons can be obtained from small amounts of {sup 252}Cf, {sup 241}Am, {sup 244}Cm, or {sup 124}Sb.

Elijah Johnson; Larry Robinson; Li Zhao

2000-11-12

176

Design of the Mechanical Parts for the Neutron Guide System at HANARO  

SciTech Connect

The research reactor HANARO (High-flux Advanced Neutron Application ReactOr) in Korea will be equipped with a neutron guide system, in order to transport cold neutrons from the neutron source to the neutron scattering instruments in the neutron guide hall near the reactor building. The neutron guide system of HANARO consists of the in-pile plug assembly with in-pile guides, the primary shutter with in-shutter guides, the neutron guides in the guide shielding room with dedicated secondary shutters, and the neutron guides connected to the instruments in the neutron guide hall. Functions of the in-pile plug assembly are to shield the reactor environment from nuclear radiation and to support the neutron guides and maintain them precisely oriented. The primary shutter is a mechanical structure to be installed just after the in-pile plug assembly, which stops neutron flux on demand. This paper describes the design of the in-pile assembly and the primary shutter for the neutron guide system at HANARO. The design of the guide shielding assembly for the primary shutter and the neutron guides is also presented.

Shin, J. W.; Cho, Y. G.; Cho, S. J.; Ryu, J. S. [Korea Atomic Energy Research Institute, 1045 Daedeok-daero, Yuseong-gu, Daejeon 305-353 (Korea, Republic of)

2008-03-17

177

Design study of a medical proton linac for neutron therapy  

SciTech Connect

This paper describes a design study which establishes the physical parameters of the low energy beam transport, radiofrequency quadrupole, and linac, using computer programs available at Fermilab. Beam dynamics studies verify that the desired beam parameters can be achieved. The machine described here meets the aforementioned requirements and can be built using existing technology. Also discussed are other technically feasible options which could be attractive to clinicians, though they would complicate the design of the machine and increase construction costs. One of these options would allow the machine to deliver 2.3 MeV protons to produce epithermal neutrons for treating brain tumors. A second option would provide 15 MeV protons for isotope production. 21 refs., 33 figs.

Machida, S.; Raparia, D.

1988-08-26

178

UWindsor Nios II: A soft-core processor for design space exploration  

Microsoft Academic Search

Field-programmable gate arrays (FPGAs) are increasingly being used for implementing embedded systems. Soft-core processors for FPGAs are also becoming popular due to reduced design costs and better flexibility. Commercial soft-core processors such as Altera Nios II and Xilinx Microblaze have been widely deployed. While some research has been done exploring the design space of soft-core CPUs, much work remains to

Omar A. Al Rayahi; Mohammed A. S. Khalid

2009-01-01

179

Equation of state of neutron star cores and spin down of isolated pulsars  

NASA Astrophysics Data System (ADS)

We study possible impact of a softening of the equation of state by a phase transition, or appearance of hyperons, on the spin evolution of isolated pulsars. Numerical simulations are performed using exact 2-D simulations in general relativity. The equation of state of dense matter at supranuclear densities is poorly known. Therefore, the accent is put on the general correlations between evolution and equation of state, and mathematical strictness. General conjectures referring to the structure of the one-parameter families of stationary configurations are formulated. The interplay of the back bending phenomenon and stability with respect to axisymmetric perturbations is described. Changes of pulsar parameters in a corequake following instability are discussed, for a broad choice of phase transitions predicted by different theories of dense matter. The energy release in a corequake, at a given initial pressure, is shown to be independent of the angular momentum of collapsing configuration. This result holds for various types of phases transition, with and without metastability. We critically review observations of pulsars that could be relevant for the detection of the signatures of the phase transition in neutron star cores.

Haensel, P.; Zdunik, J. L.

2007-04-01

180

A new paradigm for local-global coupling in whole-core neutron transport.  

SciTech Connect

A new paradigm that increases the efficiency of whole-core neutron transport calculations without lattice homogenization is introduced. Quasi-reflected interface conditions are formulated to partially decouple periodic lattice effects from global flux gradients. The starting point is the finite subelement form of the variational nodal code VARIANT that eliminates fuel-coolant homogenization through the use of heterogeneous nodes. The interface spherical harmonics expansions that couple pin-cell-sized nodes are divided into low-order and high-order terms, and reflected interface conditions are applied to the high-order terms. Combined with an integral transport method within the node, the new approach dramatically reduces both the formation time and the dimensions of the nodal response matrices and leads to sharply reduced memory requirements and computational time. The method is applied to the two-dimensional C5G7 problem, an Organisation for Economic Co-operation and Development/Nuclear Energy Agency pressurized water reactor benchmark containing mixed oxide (MOX) and UO{sub 2} fuel assemblies, as well as to a three-dimensional MOX fuel assembly. Results indicate the new approach results in very little loss of accuracy relative to the corresponding full spherical harmonics expansions while reducing computational times by well over an order of magnitude.

Lewis, E.; Smith, M.; Palmiotti, G,; Nuclear Engineering Division; Northwestern Univ.; INL

2009-01-01

181

Conditions for designing single-mode air-core waveguides in three-dimensional photonic crystals  

E-print Network

in the band diagram.13 Almost any line defect structure in a 3D complete band gap PC behaves as a waveguideConditions for designing single-mode air-core waveguides in three-dimensional photonic crystals that allows the design of single-mode air-core waveguides in three-dimensional photonic crystals

Fan, Shanhui

182

DESIGN AND OPERATION OF A WIRELINE RETRIEVABLE MOTOR DRIVEN CORE BARREL  

E-print Network

DESIGN AND OPERATION OF A WIRELINE RETRIEVABLE MOTOR DRIVEN CORE BARREL OCEAN DRILLING PROGRAM) Ocean Research Institute of the University of Tokyo (Japan) National Science Foundation (United States of a Motor-Driven Core Barrel 9 1.0 Introduction 9 1.1 Conceptual Design 9 Chapter 2: NCB1: Development, Land

183

Flavor Evolution of the Neutronization Neutrino Burst From an O-Ne-Mg Core-Collapse Supernova  

SciTech Connect

We present results of 3-neutrino flavor evolution simulations for the neutronization burst from an O-Ne-Mg core-collapse supernova. We find that nonlinear neutrino self-coupling engineers a single spectral feature of stepwise conversion in the inverted neutrino mass hierarchy case and in the normal mass hierarchy case, a superposition of two such features corresponding to the vacuum neutrino mass-squared differences associated with solar and atmospheric neutrino oscillations. These neutrino spectral features offer a unique potential probe of the conditions in the supernova environment and may allow us to distinguish between O-Ne-Mg and Fe core-collapse supernovae.

Duan Huaiyu [Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195 (United States); Fuller, George M. [Department of Physics, University of California, San Diego, La Jolla, California 92093 (United States); Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195 (United States); Carlson, J. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Qian Yongzhong [School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

2008-01-18

184

Flavor Evolution of the Neutronization Neutrino Burst from an O-Ne-Mg Core-Collapse Supernova  

E-print Network

We present results of 3-neutrino flavor evolution simulations for the neutronization burst from an O-Ne-Mg core-collapse supernova. We find that nonlinear neutrino self-coupling engineers a single spectral feature of stepwise conversion in the inverted neutrino mass hierarchy case and in the normal mass hierarchy case, a superposition of two such features corresponding to the vacuum neutrino mass-squared differences associated with solar and atmospheric neutrino oscillations. These neutrino spectral features offer a unique potential probe of the conditions in the supernova environment and may allow us to distinguish between O-Ne-Mg and Fe core-collapse supernovae.

Huaiyu Duan; George M. Fuller; J. Carlson; Yong-Zhong Qian

2007-10-05

185

CTSI Quantitative Methods Pilot Program The Design, Biostatistics and Epidemiology (DBE) Core, the Pilot Core, and the Novel  

E-print Network

1 CTSI Quantitative Methods Pilot Program The Design, Biostatistics and Epidemiology (DBE) Core, a quantitative methods researcher is an investigator with a background in statistics, biostatistics, epidemiology the career development of junior investigators in the fields of statistics, biostatistics, and epidemiology

Sibille, Etienne

186

Error Assessment of Homogenized Cross Sections Generation for Whole Core Neutronic Calculation  

NASA Astrophysics Data System (ADS)

The objective of the work here was to assess the errors introduced by using 2D, few group homogenized cross sections to perform neutronic analysis of BWR problems with significant axial heterogeneities. The 3D method of characteristics code DeCART is used to generate 2-group assembly homogenized cross sections first using a conventional 2D lattice model and then using a full 3D solution of the assembly. A single BWR fuel assembly model based on an advanced BWR lattice design is used with a typical void distribution applied to the fuel channel coolant. This model is validated against an MCNP model. A comparison of the cross sections is performed for the assembly homogenized planar cross sections from the DeCART 3D and DeCART 2D solutions.

Hursin, Mathieu; Kochunas, Brendan; Downar, Thomas J.

2007-10-01

187

Error Assessment of Homogenized Cross Sections Generation for Whole Core Neutronic Calculation  

SciTech Connect

The objective of the work here was to assess the errors introduced by using 2D, few group homogenized cross sections to perform neutronic analysis of BWR problems with significant axial heterogeneities. The 3D method of characteristics code DeCART is used to generate 2-group assembly homogenized cross sections first using a conventional 2D lattice model and then using a full 3D solution of the assembly. A single BWR fuel assembly model based on an advanced BWR lattice design is used with a typical void distribution applied to the fuel channel coolant. This model is validated against an MCNP model. A comparison of the cross sections is performed for the assembly homogenized planar cross sections from the DeCART 3D and DeCART 2D solutions.

Hursin, Mathieu; Kochunas, Brendan; Downar, Thomas J. [University of California at Berkeley, 3115 Etcheverry Hall, Berkeley CA (United States)

2007-10-26

188

A NEW EQUATION OF STATE FOR NEUTRON STAR MATTER WITH NUCLEI IN THE CRUST AND HYPERONS IN THE CORE  

SciTech Connect

The equation of state for neutron stars in a wide-density range at zero temperature is constructed. The chiral quark-meson coupling model within relativistic Hartree-Fock approximation is adopted for uniform nuclear matter. The coupling constants are determined so as to reproduce the experimental data of atomic nuclei and hypernuclei. In the crust region, nuclei are taken into account within the Thomas-Fermi calculation. All octet baryons are considered in the core region, while only ?{sup –} appears in neutron stars. The resultant maximum mass of neutron stars is 1.95 M{sub ?}, which is consistent with the constraint from the recently observed massive pulsar, PSR J1614-2230.

Miyatsu, Tsuyoshi [Department of Physics, Soongsil University, Seoul 156-743 (Korea, Republic of); Yamamuro, Sachiko; Nakazato, Ken'ichiro, E-mail: tmiyatsu@ssu.ac.kr [Department of Physics, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan)

2013-11-01

189

Neutronic model for modal multichannel analysis of out-of-phase instability in boiling water reactor cores  

Microsoft Academic Search

A neutronic model for linear multichannel analysis of out-of-phase (regional) instability in a BWR core is derived. In this model, the zero-power transfer function of a spatial-harmonic mode, the nodal component of the harmonic amplitude and the node-wise feedback coefficients for the mode appear. Applying the modal expansion technique to a transient flux, we can formulate the above transfer function,

Kengo Hashimoto; Akitoshi Hotta; Toshikazu Takeda

1997-01-01

190

CORE SIM: A multi-purpose neutronic tool for research and education Christophe Demazire  

E-print Network

calculations Dynamic calculations Neutron noise Model development Benchmarking a b s t r a c t This paper deals with the development, validation, and demonstration of an innovative neutronic tool. The novelty of the tool resides neutron source can be studied, and static and dynamic cases in the frequency domain (i.e. for stationary

Demazière, Christophe

191

Spallation neutron source cryomodule heat loads and thermal design  

SciTech Connect

When complete, the Spallation Neutron Source (SNS) will provide a 1 GeV, 2 MW beam for experiments. One portion of the machine's linac consists of over 80 Superconducting Radio Frequency (SRF) 805 MHz cavities housed in a minimum of 23 cryomodules operating at a saturation temperature of 2.1 K. Minimization of the total heat load is critical to machine performance and for efficient operation of the system. The total heat load of the cryomodules consists of the fixed static load and the dynamic load, which is proportional to the cavity performance. The helium refrigerator supports mainly the cryomodule loads and to a lesser extent the distribution system loads. The estimated heat loads and calculated thermal performance are discussed along with two unique features of this design: the helium heat exchanger housed in the cryomodule return end can and the helium gas cooled fundamental power coupler.

E. F. Daly; V. Ganni; C. H. Rode; W. J. Schneider; K. M. Wilson; M. A. Wiseman

2002-05-10

192

Spallation neutron source cryomodule heat loads and thermal design  

NASA Astrophysics Data System (ADS)

When complete, the Spallation Neutron Source (SNS) will provide a 1 GeV, 2 MW beam for experiments. One portion of the machine's linac consists of over 80 Superconducting Radio Frequency (SRF) 805 MHz cavities housed in a minimum of 23 cryomodules operating at a saturation temperature of 2.1 K. Minimization of the total heat load is critical to machine performance and for efficient operation of the system. The total heat load of the cryomodules consists of the fixed static load and the dynamic load, which is proportional to the cavity performance. The helium refrigerator supports mainly the cryomodule loads and to a lesser extent the distribution system loads. The estimated heat loads and calculated thermal performance are discussed along with two unique features of this design: the helium heat exchanger housed in the cryomodule return end can and the helium gas cooled fundamental power coupler.

Daly, E. F.; Ganni, V.; Rode, C. H.; Schneider, W. J.; Wilson, K. M.; Wiseman, M. A.

2002-05-01

193

Innovative and Advanced Coupled Neutron Transport and Thermal Hydraulic Method (Tool) for the Design, Analysis and Optimization of VHTR/NGNP Prismatic Reactors  

SciTech Connect

This project will develop a 3D, advanced coarse mesh transport method (COMET-Hex) for steady- state and transient analyses in advanced very high-temperature reactors (VHTRs). The project will lead to a coupled neutronics and thermal hydraulic (T/H) core simulation tool with fuel depletion capability. The computational tool will be developed in hexagonal geometry, based solely on transport theory without (spatial) homogenization in complicated 3D geometries. In addition to the hexagonal geometry extension, collaborators will concurrently develop three additional capabilities to increase the code’s versatility as an advanced and robust core simulator for VHTRs. First, the project team will develop and implement a depletion method within the core simulator. Second, the team will develop an elementary (proof-of-concept) 1D time-dependent transport method for efficient transient analyses. The third capability will be a thermal hydraulic method coupled to the neutronics transport module for VHTRs. Current advancements in reactor core design are pushing VHTRs toward greater core and fuel heterogeneity to pursue higher burn-ups, efficiently transmute used fuel, maximize energy production, and improve plant economics and safety. As a result, an accurate and efficient neutron transport, with capabilities to treat heterogeneous burnable poison effects, is highly desirable for predicting VHTR neutronics performance. This research project’s primary objective is to advance the state of the art for reactor analysis.

Rahnema, Farzad; Garimeela, Srinivas; Ougouag, Abderrafi; Zhang, Dingkang

2013-11-29

194

Results of a Neutronic Simulation of HTR-Proteus Core 4.2 using PEBBED and other INL Reactor Physics Tools: FY-09 Report  

SciTech Connect

The Idaho National Laboratory’s deterministic neutronics analysis codes and methods were applied to the computation of the core multiplication factor of the HTR-Proteus pebble bed reactor critical facility. A combination of unit cell calculations (COMBINE-PEBDAN), 1-D discrete ordinates transport (SCAMP), and nodal diffusion calculations (PEBBED) were employed to yield keff and flux profiles. Preliminary results indicate that these tools, as currently configured and used, do not yield satisfactory estimates of keff. If control rods are not modeled, these methods can deliver much better agreement with experimental core eigenvalues which suggests that development efforts should focus on modeling control rod and other absorber regions. Under some assumptions and in 1D subcore analyses, diffusion theory agrees well with transport. This suggests that developments in specific areas can produce a viable core simulation approach. Some corrections have been identified and can be further developed, specifically: treatment of the upper void region, treatment of inter-pebble streaming, and explicit (multiscale) transport modeling of TRISO fuel particles as a first step in cross section generation. Until corrections are made that yield better agreement with experiment, conclusions from core design and burnup analyses should be regarded as qualitative and not benchmark quality.

Hans D. Gougar

2009-08-01

195

Design of 6Mev linear accelerator based pulsed thermal neutron source: FLUKA simulation and experiment.  

PubMed

The 6MeV LINAC based pulsed thermal neutron source has been designed for bulk materials analysis. The design was optimized by varying different parameters of the target and materials for each region using FLUKA code. The optimized design of thermal neutron source gives flux of 3×10(6)ncm(-2)s(-1) with more than 80% of thermal neutrons and neutron to gamma ratio was 1×10(4)ncm(-2)mR(-1). The results of prototype experiment and simulation are found to be in good agreement with each other. PMID:21908197

Patil, B J; Chavan, S T; Pethe, S N; Krishnan, R; Bhoraskar, V N; Dhole, S D

2012-01-01

196

Core design calculations for MEU fuel in FSV  

Microsoft Academic Search

Results of a study on the feasibility of converting the Fort St. Vrain reactor core from the present 6-year, High Enriched Uranium (HEU) fuel cycle using uranium enriched to 93% U-235 and thorium to a 6-year, Medium Enriched Uranium (MEU) fuel cycle using uranium enriched to 20% U-235 and thorium, are described. The study shows that a transition from the

M. E. Fehrenbach; A. M. Baxter

1979-01-01

197

Modified Anchor Shaped Post Core Design for Primary Anterior Teeth  

PubMed Central

Restoring severely damaged primary anterior teeth is challenging to pedodontist. Many materials are tried as a post core but each one of them has its own drawbacks. This a case report describing a technique to restore severely damaged primary anterior teeth with a modified anchor shaped post. This technique is not only simple and inexpensive but also produces better retention. PMID:25379294

Rajesh, R.; Baroudi, Kusai; Reddy, K. Bala Kasi; Praveen, B. H.; Kumar, V. Sumanth; Amit, S.

2014-01-01

198

Teaching to the Common Core by Design, Not Accident  

ERIC Educational Resources Information Center

The Bill & Melinda Gates Foundation has created tools and supports intended to help teachers adapt to the Common Core State Standards in English language arts and mathematics. The tools seek to find the right balance between encouraging teachers' creativity and giving them enough guidance to ensure quality. They are the product of two years of…

Phillips, Vicki; Wong, Carina

2012-01-01

199

Design of an Aluminum Proton Beam Window for the Spallation Neutron Source  

SciTech Connect

An aluminum proton beam window design is being considered at the Spallation Neutron Source primarily to increase the lifetime of the window, with secondary advantages of higher beam transport efficiency and lower activation. The window separates the core vessel, the location of the mercury target, from the vacuum of the accelerator, while withstanding the pass through of a proton beam of up to 2 MW with 1.0 GeV proton energy. The current aluminum alloy being investigated for the window material is 6061-T651 due to its combination of high strength, high thermal conductivity, and good resistance to aqueous corrosion, as well as demonstrated dependability in previous high-radiation environments. The window design will feature a thin plate with closely spaced cross drilled cooling holes. An analytical approach was used to optimize the dimensions of the window before finite element analysis was used to simulate temperature profiles and stress fields resulting from thermal and static pressure loading. The resulting maximum temperature of 60 C and Von Mises stress of 71 MPa are very low compared to allowables for Al 6061-T651. A significant challenge in designing an aluminum proton beam window for SNS is integrating the window with the current 316L SS shield blocks. Explosion bonding was chosen as a joining technique because of the large bonding area required. A test program has commenced to prove explosion bonding can produce a robust vacuum joint. Pending successful explosion bond testing, the aluminum proton beam window design will be proven acceptable for service in the Spallation Neutron Source.

Janney, Jim G [ORNL; McClintock, David A [ORNL

2012-01-01

200

Design of a boiling water reactor equilibrium core using thorium-uranium fuel  

Microsoft Academic Search

In this paper the design of a Boiling Water Reactor (BWR) equilibrium core using thorium is presented; a heterogeneous blanket-seed core arrangement concept was adopted. The design was developed in three steps: in the first step two different assemblies were designed based on the integrated blanket-seed concept, they are the blanket-dummy assembly and the blanket-seed assembly. The integrated blanketseed concept

J. L. Francois; A. Nunez-Carrera; G. Espinosa-Paredes; C. Martin-del-Campo

2004-01-01

201

Design of a boiling water reactor equilibrium core using thorium-uranium fuel  

Microsoft Academic Search

In this paper the design of a Boiling Water Reactor (BWR) equilibrium core using thorium is presented; a heterogeneous blanket-seed core arrangement concept was adopted. The design was developed in three steps: in the first step two different assemblies were designed based on the integrated blanket-seed concept, they are the blanket-dummy assembly and the blanket-seed assembly. The integrated blanket- seed

Juan-Luis François; Alejandro Núñez-Carrera; Gilberto Espinosa-Paredes; Cecilia Martín-del-Campo

202

High accuracy modeling for advanced nuclear reactor core designs using Monte Carlo based coupled calculations  

NASA Astrophysics Data System (ADS)

The main objective of this PhD research is to develop a high accuracy modeling tool using a Monte Carlo based coupled system. The presented research comprises the development of models to include the thermal-hydraulic feedback to the Monte Carlo method and speed-up mechanisms to accelerate the Monte Carlo criticality calculation. Presently, deterministic codes based on the diffusion approximation of the Boltzmann transport equation, coupled with channel-based (or sub-channel based) thermal-hydraulic codes, carry out the three-dimensional (3-D) reactor core calculations of the Light Water Reactors (LWRs). These deterministic codes utilize nuclear homogenized data (normally over large spatial zones, consisting of fuel assembly or parts of fuel assembly, and in the best case, over small spatial zones, consisting of pin cell), which is functionalized in terms of thermal-hydraulic feedback parameters (in the form of off-line pre-generated cross-section libraries). High accuracy modeling is required for advanced nuclear reactor core designs that present increased geometry complexity and material heterogeneity. Such high-fidelity methods take advantage of the recent progress in computation technology and coupled neutron transport solutions with thermal-hydraulic feedback models on pin or even on sub-pin level (in terms of spatial scale). The continuous energy Monte Carlo method is well suited for solving such core environments with the detailed representation of the complicated 3-D problem. The major advantages of the Monte Carlo method over the deterministic methods are the continuous energy treatment and the exact 3-D geometry modeling. However, the Monte Carlo method involves vast computational time. The interest in Monte Carlo methods has increased thanks to the improvements of the capabilities of high performance computers. Coupled Monte-Carlo calculations can serve as reference solutions for verifying high-fidelity coupled deterministic neutron transport methods with detailed and accurate thermal-hydraulic models. The development of such reference high-fidelity coupled multi-physics scheme is described in this dissertation on the basis of MCNP5, NEM, NJOY and COBRA-TF (CTF) computer codes. This work presents results from studies performed and implemented at the Pennsylvania State University (PSU) on both accelerating Monte Carlo criticality calculations by using hybrid nodal diffusion Monte Carlo schemes and thermal-hydraulic feedback modeling in Monte Carlo core calculations. The hybrid MCNP5/CTF/NEM/NJOY coupled code system is proposed and developed in this dissertation work. The hybrid coupled code system contains a special interface developed to update the required MCNP5 input changes to account for dimension and density changes provided by the thermal-hydraulics feedback module. The interface has also been developed to extract the flux and reaction rates calculated by MCNP5 to later transform the data into the power feedback needed by CTF (axial and radial peaking factors). The interface is contained in a master program that controls the flow of the calculations. Both feedback modules (thermal-hydraulic and power subroutines) use a common internal interface to further accelerate the data exchange. One of the most important steps to correctly include the thermal hydraulic feedback into MCNP5 calculations begins with temperature dependent cross section libraries. If the cross sections used for the calculations are not at the correct temperature, the temperature feedback cannot be included into MCNP5 (referred to the effect of temperature on cross sections: Doppler boarding of resolve and unresolved resonances, thermal scattering and elastic scattering). The only method of considering the temperature effects on cross sections is through the generation (or as introduced in this dissertation through a novel interpolation mechanism) of continuous energy temperature-dependent cross section libraries. An automated methodology for generation of continuous energy temperature-dependent cross section libraries has been developed

Espel, Federico Puente

203

Fusion Engineering and Design 42 (1998) 281288 The use of MNCP for neutronics calculations within large  

E-print Network

Fusion Engineering and Design 42 (1998) 281­288 The use of MNCP for neutronics calculations within-3796(98)00215-4 #12;J.E. Eggleston et al. / Fusion Engineering and Design 42 (1998) 281­288282 Discrete ordinates

Abdou, Mohamed

204

Determination of the response function for two personal neutron dosemeter designs based on PADC.  

PubMed

Since 1998 neutron dosimetry based on PADC (poly allyl diglycol carbonate) is done with a so-called original Paul Scherrer Institute (PSI) design at PSI. The original design (i.e. holder) was later changed. Both designs are optimised for use in workplaces around high-energy accelerators, where the neutron energy spectra are dominated by fast neutrons ranging up to some 100 MeV. In addition to the change of the dosemeter design a new evaluation method based on a microscope scanning technique has been introduced and the etching conditions have been optimised. In the present work, the responses obtained with the original and the new dosemeter designs are compared for fields of radionuclide sources and monoenergetic reference fields using the new evaluation method. The response curves in terms of the personal dose equivalent for normally incident neutrons were built as functions of the incident neutron energy. PMID:24179145

Mayer, S; Assenmacher, F; Boschung, M

2014-10-01

205

Iron-core superconducting magnet design and test results for Maglev application  

Microsoft Academic Search

Design and test results are presented for a superconducting electromagnet for levitating and propelling Maglev vehicles at high velocities. A U-shaped iron core carries a superconducting magnet around its back leg and a normal control coil around each leg of the U-core. The open side of the U-core is bridged by an iron rail through a large airgap between the

S. Kalsi; M. Proise; T. Schultheiss; B. Dawkins; K. Herd

1995-01-01

206

Design, status and first operations of the spallation neutron source polyphase resonant converter modulator system  

SciTech Connect

The Spallation Neutron Source (SNS) is a new 1.4 MW average power beam, 1 GeV accelerator being built at Oak Ridge National Laboratory. The accelerator requires 15 converter-modulator stations each providing between 9 and 11 MW pulses with up to a 1 .I MW average power. The converter-modulator can be described as a resonant 20 kHz polyphase boost inverter. Each converter modulator derives its buss voltage from a standard substation cast-core transformer. Each substation is followed by an SCR pre-regulator to accommodate voltage changes from no load to full load, in addition to providing a soft-start function. Energy storage is provided by self-clearing metallized hazy polypropylene traction capacitors. These capacitors do not fail short, but clear any internal anomaly. Three 'H-Bridge' IGBT transistor networks are used to generate the polyphase 20 kHz transformer primary drive waveforms. The 20 kHz drive waveforms are time-gated to generate the desired klystron pulse width. Pulse width modulation of the individual 20 lcHz pulses is utilized to provide regulated output waveforms with DSP based adaptive feedforward and feedback techniques. The boost transformer design utilizes nanocrystalline alloy that provides low core loss at design flux levels and switching frequencies. Capacitors are used on the transformer secondary networks to resonate the leakage inductance. The transformers are wound for a specific leakage inductance, not turns ratio. This design technique generates multiple secondary volts per turn as compared to the primary. With the appropriate tuning conditions, switching losses are minimized. The resonant topology has the added benefit of being deQed in a klystron fault condition, with little energy deposited in the arc. This obviates the need of crowbars or other related networks. A review of these design parameters, operational performance, production status, and OWL installation and performance to date will be presented.

Reass, W. A. (William A.); Apgar, S. E. (Sean E.); Baca, D. M. (David M.); Doss, James D.; Gonzales, J. (Jacqueline); Gribble, R. F. (Robert F.); Hardek, T. W. (Thomas W.); Lynch, M. T. (Michael T.); Rees, D. E. (Daniel E.); Tallerico, P. J. (Paul J.); Trujillo, P. B. (Pete B.); Anderson, D. E. (David E.); Heidenreich, D. A. (Dale A.); Hicks, J. D. (Jim D.); Leontiev, V. N.

2003-01-01

207

Design and construction of a cold neutron source for use in the Cornell University TRIGA reactor  

SciTech Connect

A cold neutron source has been designed and constructed for insertion into the 6''-radial beam port of the Cornell University TRIGA reactor for use with a neutron guide tube system. The main differences between this cold source and other existing sources are the use of heat conduction as the method of cooling and the use of mesitylene (1,3,5-trimethylbenzene; melting point, 228/sup 0/K; boiling point, 437/sup 0/K) as the moderating material. This thesis describes the design and construction details of the cold neutron source, discusses its safety aspects, and presents its cryogenic performance curves and also the results of a test of its neutron moderating ability. To test the neutron moderating ability of the cold neutron source, an out-of-reactor neutron transmission experiment was performed with the moderator chamber first at room temperature and then at about 23/sup 0/K. The results indicate that the neutron energy spectrum is strongly shifted to lower energies when the chamber is cold. The neutrons have an apparent temperature of 98/sup 0/K, if the moderated flux is assumed to be Maxwellian. This, however, is unlikely to be the actual case since the geometry of the chamber, neutron beam, and detector and the complexities of the neutron scattering and absorption processes in mesitylene doubtlessly distort the leakage energy spectrum.

Young, L.J.

1983-01-01

208

Neutron transport benchmark examples with web-based AGENT  

Microsoft Academic Search

The AGENT (Arbitrary GEometry Neutron Transport) an open-architecture reactor modeling tool is deterministic neutron transport code for two- or three-dimensional heterogeneous neutronic design and analysis of the whole reactor cores regardless of geometry types and material configurations. The AGENT neutron transport methodology is applicable to all generations of nuclear power and research reactors. It combines three theories: (1) mathematical theory

Tatjana Jevremovic; Shanjie Xiao; Nader Satvat; Godfree Gert; John Hopkins

2008-01-01

209

Double core evolution. 7: The infall of a neutron star through the envelope of its massive star companion  

NASA Technical Reports Server (NTRS)

Binary systems with properties similar to those of high-mass X-ray binaries are evolved through the common envelope phase. Three-dimensional simulations show that the timescale of the infall phase of the neutron star depends upon the evolutionary state of its massive companion. We find that tidal torques more effectively accelerate common envelope evolution for companions in their late core helium-burning stage and that the infall phase is rapid (approximately several initial orbital periods). For less evolved companions the decay of the orbit is longer; however, once the neutron star is deeply embedded within the companion's envelope the timescale for orbital decay decreases rapidly. As the neutron star encounters the high-density region surrounding the helium core of its massive companion, the rate of energy loss from the orbit increases dramatically leading to either partial or nearly total envelope ejection. The outcome of the common envelope phase depends upon the structure of the evolved companion. In particular, it is found that the entire common envelope can be ejected by the interaction of the neutron star with a red supergiant companion in binaries with orbital periods similar to those of long-period Be X-ray binaries. For orbital periods greater than or approximately equal to 0.8-2 yr (for companions of mass 12-24 solar mass) it is likely that a binary will survive the common envelope phase. For these systems, the structure of the progenitor star is characterized by a steep density gradient above the helium core, and the common envelope phase ends with a spin up of the envelope to within 50%-60% of corotation and with a slow mass outflow. The efficiency of mass ejection is found to be approximately 30%-40%. For less evolved companions, there is insufficient energy in the orbit to unbind the common envelope and only a fraction of it is ejected. Since the timescale for orbital decay is always shorter than the mass-loss timescale from the common envelope, the two cores will likely merge to form a Thorne-Zytkow object. Implications for the origin of Cyg X-3, an X-ray source consisting of a Wolf-Rayet star and a compact companion, and for the fate of the remnant binary consisting of a helium star and a neutron star are briefly discussed.

Terman, James L.; Taam, Ronald E.; Hernquist, Lars

1995-01-01

210

Neutron micro-beam design simulation by Monte Carlo  

NASA Astrophysics Data System (ADS)

Over the last two decades neutron micro-beam has increasingly been developing in view of various applications in molecular activation analysis, micro-radiography in space and aviation and in radiation induced bystander effects in bio-cells. In this paper the structure and simulation of a neutron micro-beam is presented. The collimator for micro-beam is made of a polyethylene cylinder with a small hole along the centerline of the cylinder. The hole is filled with very thin needles in triangular or rectangular arrangement. The neutron source was reactor neutrons or a spontaneous Cf-252 neutron source falling on the top side of the collimator. The outgoing thermal and epithermal neutron fluxes were calculated.

Pazirandeh, Ali; Taheri, Ali

2007-09-01

211

Neutronic design of the APT Target/Blanket  

SciTech Connect

The primary function of the Accelerator Production of Tritium Target/Blanket assembly is the safe and efficient production of tritium. The T/B accepts a 1.7-GeV, 100-mA proton beam and produces neutrons via the spallation process. These neutrons then react with {sup 3}He to produce tritium. Neutronic optimization of the T/B is achieved by efficiently using the proton beam to produce neutrons and then, once produced, assuring that they are captured mostly by {sup 3}He. This optimization must occur within the constraints imposed by engineering considerations such as heat flux limits, structural integrity, fabricability, and safe and reliable operation. The target/blanket achieves these goals with a neutron production rate that is 75% of that achievable with an ideal target, and a neutronic efficiency of 84%, leading to an overall tritium production rate that is 63% of the theoretical maximum.

Pitcher, E.J.; Russell, G.J.; Kidman, R.B.; Ferguson, P.D. [and others

1997-12-01

212

Near-Core and In-Core Neutron Radiation Monitors for Real Time Neutron Flux Monitoring and Reactor Power Level Measurements  

SciTech Connect

MPFDs are a new class of detectors that utilize properties from existing radiation detector designs. A majority of these characteristics come from fission chamber designs. These include radiation hardness, gamma-ray background insensitivity, and large signal output.

Douglas S. McGregor; Marvin L. Adams; Igor Carron; Paul Nelson

2006-06-12

213

76 FR 14825 - Core Principles and Other Requirements for Designated Contact Markets  

Federal Register 2010, 2011, 2012, 2013

...3038-AD09 Core Principles and Other Requirements for Designated Contact Markets AGENCY: Commodity Futures Trading Commission. ACTION...site at http://www.cftc.gov. FOR FURTHER INFORMATION CONTACT: Nancy Markowitz, Assistant Deputy Director,...

2011-03-18

214

Development of optimized core design and analysis methods for high power density BWRs  

E-print Network

Increasing the economic competitiveness of nuclear energy is vital to its future. Improving the economics of BWRs is the main goal of this work, focusing on designing cores with higher power density, to reduce the BWR ...

Shirvan, Koroush

2013-01-01

215

Real-Time Operating System Hardware Extension Core for System-on-Chip Designs.  

E-print Network

??This thesis presents a real-time operating system hardware extension core which supports the integration of hardware accelerators into real-time system-on-chip designs as hardware tasks. The… (more)

Best, Joel

2013-01-01

216

Core Curriculum / 18 credits IS 6420 Database Theory and Design 3  

E-print Network

Core Curriculum / 18 credits IS 6420 Database Theory and Design 3 IS 6410 Information Systems Analytics 3 IS 6571 IT Forensics 3 IS 6570 IT Security 3 ACCTG 6520 IT Risks and Controls 3 The MSIS program

Tipple, Brett

217

Very High Temperature Reactor (VHTR) Deep Burn Core and Fuel Analysis -- Complete Design Selection for the Pebble Bed Reactor  

SciTech Connect

The Deep-Burn (DB) concept focuses on the destruction of transuranic nuclides from used light water reactor fuel. These transuranic nuclides are incorporated into TRISO coated fuel particles and used in gas-cooled reactors with the aim of a fractional fuel burnup of 60 to 70% in fissions per initial metal atom (FIMA). This high performance is expected through the use of multiple recirculation passes of the fuel in pebble form without any physical or chemical changes between passes. In particular, the concept does not call for reprocessing of the fuel between passes. In principle, the DB pebble bed concept employs the same reactor designs as the presently envisioned low-enriched uranium core designs, such as the 400 MWth Pebble Bed Modular Reactor (PBMR-400). Although it has been shown in the previous Fiscal Year (2009) that a PuO2 fueled pebble bed reactor concept is viable, achieving a high fuel burnup, while remaining within safety-imposed prescribed operational limits for fuel temperature, power peaking and temperature reactivity feedback coefficients for the entire temperature range, is challenging. The presence of the isotopes 239-Pu, 240-Pu and 241-Pu that have resonances in the thermal energy range significantly modifies the neutron thermal energy spectrum as compared to a ”standard,” UO2-fueled core. Therefore, the DB pebble bed core exhibits a relatively hard neutron energy spectrum. However, regions within the pebble bed that are near the graphite reflectors experience a locally softer spectrum. This can lead to power and temperature peaking in these regions. Furthermore, a shift of the thermal energy spectrum with increasing temperature can lead to increased absorption in the resonances of the fissile Pu isotopes. This can lead to a positive temperature reactivity coefficient for the graphite moderator under certain operating conditions. The effort of this task in FY 2010 has focused on the optimization of the core to maximize the pebble discharge burnup level, while retaining its inherent safety characteristics. Using generic pebble bed reactor cores, this task will perform physics calculations to evaluate the capabilities of the pebble bed reactor to perform utilization and destruction of LWR used-fuel transuranics. The task will use established benchmarked models, and will introduce modeling advancements appropriate to the nature of the fuel considered (high TRU content and high burn-up).

B. Boer; A. M. Ougouag

2010-09-01

218

Designing a Core Curriculum. Proceedings of an Institute on Core Curriculum Design at Saint Joseph's College, Rensselaer, Indiana, June 3-8, 1979.  

ERIC Educational Resources Information Center

A report of the proceedings of an Institute on Core Curriculum Design, held in June, 1979 at Saint Joseph's College, Rensselaer, Indiana, is presented. Contents include: prefatory matter including the director's preface, the editor's preface, a list of participants, the schedule of the activities of the institute, the keynote address ("On Getting…

Nichols, John P., Ed.; Groppe, John D., Ed.

219

Legal Protection on IP Cores for System-on-Chip Designs  

NASA Astrophysics Data System (ADS)

The current semiconductor industry has shifted from vertical integrated model to horizontal specialization model in term of integrated circuit manufacturing. In this circumstance, IP cores as solutions for System-on-Chip (SoC) have become increasingly important for semiconductor business. This paper examines to what extent IP cores of SoC effectively can be protected by current intellectual property system including integrated circuit layout design law, patent law, design law, copyright law and unfair competition prevention act.

Kinoshita, Takahiko

220

What makes a protein a protein? Hydrophobic core designs that specify stability and structural properties  

Microsoft Academic Search

Here we describe how the systematic redesign of a protein's hydrophobic core alters its structure and stability. We have repacked the hydrophobic core of the four-helix-bundle protein, Rop, with altered packing patterns and various side chain shapes and sizes. Several designs reproduce the structure and native-like properties of the wild- type, while increasing the thermal stability. Other designs, either with

Mary Munson; Suganthi Balasubramanian; Karen G. Fleming; Athena D. Nagi; Ronan O'Brien; Julian M. Sturtevant; Lynne Regan

1996-01-01

221

Design of neutron beams at the Argonne Continuous Wave Linac (ACWL) for boron neutron capture therapy and neutron radiography  

SciTech Connect

Neutron beams are designed for capture therapy based on p-Li and p-Sc reactions using the Argonne Continuous Wave Linac (ACWL). The p-Li beam will provide a 2.5 {times} 10{sup 9} n/cm{sup 2}s epithermal flux with 7 {times} 10{sup 5} {gamma}/cm{sup 2}s contamination. On a human brain phantom, this beam allows an advantage depth (AD) of 10 cm, an advantage depth dose rate (ADDR) of 78 cGy/min and an advantage ratio (AR) of 3.2. The p-Sc beam offers 5.9 {times} 10{sup 7} n/cm{sup 2}s and a dose performance of AD = 8 cm and AR = 3.5, suggesting the potential of near-threshold (p,n) reactions such as the p-Li reaction at E{sub p} = 1.92 MeV. A thermal radiography beam could also be obtained from ACWL.

Zhou, X.L. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Nuclear Engineering; McMichael, G.E. [Argonne National Lab., Idaho Falls, ID (United States). Technology Development Div.

1994-10-01

222

Conceptual design studies of GDT-based neutron source  

Microsoft Academic Search

An analysis shows that the existing nuclear technology data bases are not sufficient to arrive at a DEMO with reasonable confidence in achieving target availability levels. In order to provide these data, a testing facility capable of simulating neutron environment in a fusion reactor is needed. A number of proposals for plasma-type neutron sources have been made recently to meet

A. A. Ivanov; E. P. Kruglyakov; Yu. A. Tsidulko; V. G. Krasnoperovt; V. V. Korshakovt

1995-01-01

223

Inductor Design Methods With Low-Permeability RF Core Materials  

E-print Network

This paper presents a design procedure for inductors based on low-permeability magnetic materials, for use in very high frequency power conversion. The proposed procedure offers an easy and fast way to compare different ...

Han, Yehui

224

Development of 3D full-core ERANOS-2.2/MCNPX-2.7.0 models and neutronic analysis of the BFS-2 zero-power facility  

SciTech Connect

The present paper is addressing the development and validation against experimental data of 3D full-core models of the BFS-2 zero-power fast-reactor using both the deterministic system code ERANOS-2.2 and the stochastic code MCNPX-2.7.0. The model configuration of BFS considered for analysis is the BFS-62-3A benchmark. To extend the - deterministic/stochastic - code-to-code comparison, neutronic parameters, i.e. reactivity, neutron spectrum and reaction rates, were also simulated at the cell level with the Monte Carlo code SERPENT-1.1.7 with two modern data libraries, ENDF-B/VII and JEFF-3.1.1. The BFS-2 critical zero-power facility at the Inst. of Physics and Power Engineering (IPPE) was designed for simulations of the core and shielding of sodium-cooled, fast reactors, for neutron data validation and comparison with experimental results. At the BFS-2 facility, the BFS-62-3A critical benchmark experiment was set-up as a mock-up of the BN-600 reactor, with hybrid MOX fuel and stainless steel reflectors. A UO{sub 2} blanket and a large non-homogeneous stainless-steel reflector surround the core. The lattice is hexagonal of pitch 5.1 cm and metallic dowels are used to keep in central position cylindrical rods made of different types of material (fissile, fertile, blanket, plenum, shielding and absorber). A typical subassembly is formed in piling up various pellets of about 1 cm in height and 4.6 cm in diameter, conferring large heterogeneity in the axial direction. The full-core model development was a complex task due to the large number of subassemblies and the axial subassembly heterogeneity. In ERANOS-2.2, it was necessary to homogenize axially per region the pellets used to form the subassembly. The self-shielded macroscopic cross-sections were calculated using the cell code ECCO in association with JEFF-3.1 and ENDF/B-VI.8 data libraries. The core calculations were performed with broad cross-sections data in 33 neutron energy groups with the solver AVNM in the diffusion approximation, mostly. In MCNPX-2.7.0, a step-by-step approach was used, starting with a model in which the fissile rods were simulated on a homogeneous level, to finally integrate the actual heterogeneous description of the subassemblies. The code-to-code cell analysis performed between ECCO, SERPENT and MCNPX with different modern nuclear data library revealed that the results for the infinite multiplication factor between Monte Carlo and deterministic analysis are in good agreement ({Delta}p < 100 pcm). The differences between the results were observed to be larger for the neutron data libraries, with reactivity differences up to 350 pcm. (authors)

Girardin, G.; Alonso, M. [Ecole Polytechnique Federale de Lausanne EPFL, CH-1015 Lausanne (Switzerland); Mikityuk, K. [Paul Scherrer Institut PSI, CH-5232 Villigen-PSI (Switzerland)

2012-07-01

225

Preliminary Neutronics Design and Analysis of D2O Cooled High Conversion PWRs  

SciTech Connect

This report presents a neutronics analysis of tight-pitch D2O-cooled PWRs loaded with MOX fuel and focuses essentially on the Pu breeding potential of such reactors as well as on an important safety parameter, the void coefficient, which has to be negative. It is well known that fast reactors have a better neutron economy and are better suited than thermal reactors to breed fissile material from neutron capture in fertile material. Such fast reactors (e.g. sodium-cooled reactors) usually rely on technologies that are very different from those of existing water-cooled reactors and are probably more expensive. This report investigates another possibility to obtain a fast neutron reactor while still relying mostly on a PWR technology by: (1) Tightening the lattice pitch to reduce the water-to-fuel volume ratio compared to that of a standard PWR. Water-to-fuel volume ratios of between 0.45 and 1 have been considered in this study while a value of about 2 is typical of standard PWRs, (2) Using D2O instead of H2O as a coolant. Indeed, because of its different neutron physics properties, the use of D2O hardens the neutron spectrum to an extent impossible with H2O when used in a tight-pitch lattice. The neutron spectra thus obtained are not as fast as those in sodium-cooled reactor but they can still be characterized as fast compared to that of standard PWR neutron spectra. In the phase space investigated in this study we did not find any configurations that would have, at the same time, a positive Pu mass balance (more Pu at the end than at the beginning of the irradiation) and a negative void coefficient. At this stage, the use of radial blankets has only been briefly addressed whereas the impact of axial blankets has been well defined. For example, with a D2O-to-fuel volume ratio of 0.45 and a core driver height of about 60 cm, the fissile Pu mass balance between the fresh fuel and the irradiated fuel (50 GWd/t) would be about -7.5% (i.e. there are 7.5% fewer fissile Pu isotopes at the end than at the beginning of the irradiation) and the void coefficient would be negative. The addition of 1 cm of U-238 blanket at the top and bottom of the fuel would bring the fissile Pu mass balance from -7.5% to -6.5% but would also impact the void coefficient in the wrong way. In fact, it turns out that the void coefficient is so sensitive to the presence of axial blanket that it limits its size to only a few cm for driver fuel height of about 50-60 cm. For reference, the fissile Pu mass balance is about -35% in a standard PWR MOX fuel such as those used in France. In order to reduce the fissile Pu deficit and potentially reach a true breeding regime (i.e. a positive Pu mass balance), it would be necessary to make extensive use of radial blankets, both internal and external. Even though this was not addressed in detail here, it is reasonable to believe that at least as much U-238 blanket subassemblies as MOX driver fuel subassemblies would be necessary to breed enough Pu to compensate for the Pu deficit in the driver fuel. Hence, whereas a relatively simple D2O-cooled PWR core design makes it possible to obtain a near-breeder core, it may be necessary to more than double the mass of heavy metal in the core as well as the mass of heavy metal to reprocess per unit of energy produced in order to breed the few percents of Pu missing to reach a true breeding regime. It may be interesting to quantify these aspects further in the future.

Hikaru Hiruta; Gilles Youinou

2012-09-01

226

Design of new ultracold neutron source at PNPI Presenter: Arcady ZAKHAROV  

E-print Network

Design of new ultracold neutron source at PNPI Presenter: Arcady ZAKHAROV Research project leader Neutrons. Physics & Sources. St.-Petersburg-Moscow , June 2011 #12;UCN source position on the reactor #12: Anatoli SEREBROV Petersburg Nuclear Physics Institute 8-th International Workshop. Ultra Cold & Cold

Titov, Anatoly

227

A Workshop on Methods for Neutron Scattering Instrument Design. Introduction and Summary  

SciTech Connect

The future of neutron and x-ray scattering instrument development and international cooperation was the focus of the workshop on ``Methods for Neutron Scattering Instrument Design`` September 23-25 at the E.O. Lawrence Berkeley National Laboratory. These proceedings are a collection of a portion of the invited and contributed presentations.

Hjelm, Rex P.

1996-12-31

228

Modified Y-TZP core design improves all-ceramic crown reliability.  

PubMed

This study tested the hypothesis that all-ceramic core-veneer system crown reliability is improved by modification of the core design. We modeled a tooth preparation by reducing the height of proximal walls by 1.5 mm and the occlusal surface by 2.0 mm. The CAD-based tooth preparation was replicated and positioned in a dental articulator for core and veneer fabrication. Standard (0.5 mm uniform thickness) and modified (2.5 mm height lingual and proximal cervical areas) core designs were produced, followed by the application of veneer porcelain for a total thickness of 1.5 mm. The crowns were cemented to 30-day-aged composite dies and were either single-load-to-failure or step-stress-accelerated fatigue-tested. Use of level probability plots showed significantly higher reliability for the modified core design group. The fatigue fracture modes were veneer chipping not exposing the core for the standard group, and exposing the veneer core interface for the modified group. PMID:21057036

Silva, N R F A; Bonfante, E A; Rafferty, B T; Zavanelli, R A; Rekow, E D; Thompson, V P; Coelho, P G

2011-01-01

229

Modified Y-TZP Core Design Improves All-ceramic Crown Reliability  

PubMed Central

This study tested the hypothesis that all-ceramic core-veneer system crown reliability is improved by modification of the core design. We modeled a tooth preparation by reducing the height of proximal walls by 1.5 mm and the occlusal surface by 2.0 mm. The CAD-based tooth preparation was replicated and positioned in a dental articulator for core and veneer fabrication. Standard (0.5 mm uniform thickness) and modified (2.5 mm height lingual and proximal cervical areas) core designs were produced, followed by the application of veneer porcelain for a total thickness of 1.5 mm. The crowns were cemented to 30-day-aged composite dies and were either single-load-to-failure or step-stress-accelerated fatigue-tested. Use of level probability plots showed significantly higher reliability for the modified core design group. The fatigue fracture modes were veneer chipping not exposing the core for the standard group, and exposing the veneer core interface for the modified group. PMID:21057036

Silva, N.R.F.A.; Bonfante, E.A.; Rafferty, B.T.; Zavanelli, R.A.; Rekow, E.D.; Thompson, V.P.; Coelho, P.G.

2011-01-01

230

The design, fabrication and properties of B4C/Al neutron absorbers  

NASA Astrophysics Data System (ADS)

Neutron absorber is used for the criticality safety during the storage or transportation of spent nuclear fuel. In this work, the metal matrix composite with good mechanical property and thermal neutron absorbing ability was investigated based on B4C/Al neutron radiation shielding material. The composition ratio for B4C/Al composite was firstly designed and the dependence of the neutron transmission on the thickness of the material was calculated. By vacuum hot-pressing technique at a low temperature, the neutron absorbers with high concentration of B4C were fabricated. Furthermore, the corresponding microstructure, physical, mechanical and corrosion properties as well as fracture surface were analyzed, proving that the developed composites can shield the neutron radiation as effectively as cadmium materials.

Zhang, Peng; Li, Yuli; Wang, Wenxian; Gao, Zhanping; Wang, Baodong

2013-06-01

231

Cylindrical Detector and Preamplifier Design for Detecting Neutrons  

E-print Network

Tissue equivalent proportional counters are frequently used to measure dose and dose equivalent in mixed radiation fields that include neutrons; however, detectors simulating sites 1?m in diameter underestimate the quality factor, Q, for low energy...

Xia, Zhenghua

2010-01-14

232

Multiangle simulation of flavor evolution in the neutronization neutrino burst from an O-Ne-Mg core-collapse supernova  

SciTech Connect

We report results of the first 3x3 'multiangle' simulation of the evolution of neutrino flavor in the core-collapse supernova environment. In particular, we follow neutrino flavor transformation in the neutronization neutrino burst of an O-Ne-Mg core-collapse event. Though in a qualitative sense our results are consistent with those obtained in 3x3 single-angle simulations, at least in terms of neutrino mass hierarchy dependence, performing multiangle calculations is found to reduce the adiabaticity of flavor evolution in the normal neutrino mass hierarchy, resulting in lower swap energies. Differences between single-angle and multiangle results are largest for the normal neutrino mass hierarchy. Our simulations also show that current uncertainties in the measured mass-squared and mixing angle parameters translate into uncertainties in neutrino swap energies. Our results show that at low {theta}{sub 13} it may be difficult to resolve the neutrino mass hierarchy using the O-Ne-Mg neutronization neutrino burst.

Cherry, John F.; Fuller, George M.; Carlson, J.; Duan Huaiyu; Qian Yongzhong [Department of Physics, University of California, San Diego, La Jolla, California 92093 (United States); Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

2010-10-15

233

Designing and testing the neutron source deployment system and calibration plan for a dark matter detector  

E-print Network

In this thesis, we designed and tested a calibration and deployment system for the MiniCLEAN dark matter detector. The deployment system uses a computer controlled winch to lower a canister containing a neutron source into ...

Westerdale, Shawn (Shawn S.)

2011-01-01

234

Design/Operations review of core sampling trucks and associated equipment  

SciTech Connect

A systematic review of the design and operations of the core sampling trucks was commissioned by Characterization Equipment Engineering of the Westinghouse Hanford Company in October 1995. The review team reviewed the design documents, specifications, operating procedure, training manuals and safety analysis reports. The review process, findings and corrective actions are summarized in this supporting document.

Shrivastava, H.P.

1996-03-11

235

Neutron capture on Pt isotopes in iron meteorites and the Hf-W chronology of core formation in planetesimals  

NASA Astrophysics Data System (ADS)

The short-lived 182Hf-182W isotope system can provide powerful constraints on the timescales of planetary core formation, but its application to iron meteorites is hampered by neutron capture reactions on W isotopes resulting from exposure to galactic cosmic rays. Here we show that Pt isotopes in magmatic iron meteorites are also affected by capture of (epi)thermal neutrons and that the Pt isotope variations are correlated with variations in 182W/184W. This makes Pt isotopes a sensitive neutron dosimeter for correcting cosmic ray-induced W isotope shifts. The pre-exposure 182W/184W derived from the Pt-W isotope correlations of the IID, IVA and IVB iron meteorites are higher than most previous estimates and are more radiogenic than the initial 182W/184W of Ca-Al-rich inclusions (CAI). The Hf-W model ages for core formation range from +1.6±1.0 million years (Ma; for the IVA irons) to +2.7±1.3 Ma after CAI formation (for the IID irons), indicating that there was a time gap of at least ˜1 Ma between CAI formation and metal segregation in the parent bodies of some iron meteorites. From the Hf-W ages a time limit of <1.5-2 Ma after CAI formation can be inferred for the accretion of the IID, IVA and IVB iron meteorite parent bodies, consistent with earlier conclusions that the accretion of differentiated planetesimals predated that of most chondrite parent bodies.

Kruijer, Thomas S.; Fischer-Gödde, Mario; Kleine, Thorsten; Sprung, Peter; Leya, Ingo; Wieler, Rainer

2013-01-01

236

A review of irradiation effects on LWR core internal materials - Neutron embrittlement  

NASA Astrophysics Data System (ADS)

Austenitic stainless steels (SSs) are used extensively as structural alloys in the internal components of light water reactor (LWR) pressure vessels because of their relatively high strength, ductility, and fracture toughness. However, exposure to neutron irradiation for extended periods not only changes the microstructure and microchemistry of these steels, but also degrades their fracture properties. The existing data on irradiated austenitic SSs are reviewed to determine the effects of key parameters such as material type and condition and irradiation temperature, dose, and dose rate on neutron embrittlement. Differences in the radiation-induced degradation of fracture properties between LWR and fast-reactor irradiations are also discussed. The results are used to (a) define a threshold fluence above which irradiation effects on fracture toughness of the material are significant, (b) evaluate the potential of neutron embrittlement under LWR operating conditions, and (c) assess the potential effects of voids on fracture toughness.

Chopra, O. K.; Rao, A. S.

2011-05-01

237

Electric dipole response of $^6$He: Halo-neutron and core excitations  

E-print Network

Electric dipole ($E1$) response of $^{6}$He is studied with a fully microscopic six-body calculation. The wave functions for the ground and excited states are expressed as a superposition of explicitly correlated Gaussians (CG). Final state interactions of three-body decay channels are explicitly taken into account. The ground state properties and the low-energy $E1$ strength are obtained consistently with observations. Two main peaks as well as several small peaks are found in the $E1$ strength function. The peak at the high-energy region indicates a typical macroscopic picture of the giant dipole resonance, the out-of-phase proton-neutron motion. The transition densities of the lower-lying peaks exhibit in-phase proton-neutron motion in the internal region, out-of-phase motion near the surface region, and spatially extended neutron oscillation, indicating a soft-dipole mode (SDM) and its vibrationally excited mode.

D. Mikami; W. Horiuchi; Y. Suzuki

2014-05-24

238

Dynamical analysis of innovative core designs facing unprotected transients with the MAT5 DYN code  

SciTech Connect

Since 2007, advanced Sodium-cooled Fast Reactors (SFR) are investigated by CEA, AREVA and EDF in the framework of a joint French collaboration. A prototype called ASTRID, sets out to demonstrate progress made in SFR technology, is due to operate in the years 2020's. The modeling of unprotected transients by computer codes is one of the key safety issues in the design approach to such SFR systems. For that purpose, the activity on CATHARE, which is the reference code for the transient analysis of ASTRID, has been strengthened during last years by CEA. In the meantime, EDF has developed a simplified and multi-channel code, named MAT5 DYN, to analyze and validate innovative core designs facing protected and unprotected transients. First, the paper consists in a description of MAT5 DYN: a code based on the existing code MAT4 DYN including major improvements on geometry description and physical modeling. Second, two core designs based on the CFV core design developed at CEA are presented. Then, the dynamic response of those heterogeneous cores is analyzed during unprotected loss of flow (ULOF) transient and unprotected transient of power (UTOP). The results highlight the importance of the low void core effect specific to the CFV design. Such an effect, when combined with a sufficient primary pump halving time and an optimized cooling group scheme, allows to delay (or, possibly, avoid) the sodium boiling onset during ULOF accidents. (authors)

Darmet, G.; Massara, S. [EDF R and D, 1 avenue du general de Gaulle, 92140 Clamart (France)

2012-07-01

239

Cyclic fatigue testing of five endodontic post designs supported by four core materials  

Microsoft Academic Search

Purpose. This pilot study examined the cyclic fatigue of five endodontic post systems (AccessPost, Flexi-Flange, Flexi-Post, ParaPost, and Vlock) with four core materials (Tytin silver amalgam, Ti-Core, Ketac-Silver and G-C Miracle Mix).Material and methods. In vitro cyclic fatigue was performed with a machine designed to simulate masticatory fatigue forces. An instantaneous force of 22.2 N (5 pounds) was applied to

Brett I. Cohen; Mark K. Pagnillo; Ira Newman; Barry Lee Musikant; Allan S. Deutsch

1997-01-01

240

Neutronic sensitivity analysis of the experimental test reactor TIBER II blanket design  

SciTech Connect

In this paper, the TIBER II blanket design is chosen for a neutronic sensitivity analysis using Monte Carlo perturbation theory. A preliminary analysis is carried out with both deterministic and Monte Carlo simulation codes to estimate the sensitivity of the tritium breeding in the blanket to the atomic density ratio of tungsten multiplier and aqueous solution breeder. Derivatives of the neutron collision density in the blanket are then sampled using the collision estimator in the MORSE code. It is found that for small perturbations, the neutron fluxes and tritium breeding rates can be predicted quite accurately, thus saving substantial computing in a preliminary design study.

Koreshi, Z.U.; Kinrot, A.; Lewins, J.D. (Cambridge Univ. (United Kingdom). Dept. of Engineering)

1992-11-01

241

Shielding design studies for a neutron irradiator system based on a 252Cf source.  

PubMed

This study aims to investigate a shielding design against neutrons and gamma rays from a source of 252Cf, using Monte Carlo simulation. The shielding materials studied were borated polyethylene, borated-lead polyethylene and stainless steel. The Monte Carlo code MCNP4B was used to design shielding for 252Cf based neutron irradiator systems. By normalising the dose equivalent rate values presented to the neutron production rate of the source, the resulting calculations are independent of the intensity of the actual 252Cf source. The results show that the total dose equivalent rates were reduced significantly by the shielding system optimisation. PMID:11707031

da Silva, A X; Crispim, V R

2001-01-01

242

Design and pilot evaluation of the RAH-66 Comanche Core AFCS  

NASA Technical Reports Server (NTRS)

This paper addresses the design and pilot evaluation of the Core Automatic Flight Control System (AFCS) for the Reconnaissance/Attack Helicopter (RAH-66) Comanche. During the period from November 1991 through February 1992, the RAH-66 Comanche control laws were evaluated through a structured pilot acceptance test using a motion base simulator. Design requirements, descriptions of the control law design, and handling qualities data collected from ADS-33 maneuvers are presented.

Fogler, Donald L., Jr.; Keller, James F.

1993-01-01

243

Analysis of Stainless Steel Sandwich Panels with a Metal Foam Core for Lightweight Fan Blade Design  

NASA Technical Reports Server (NTRS)

The quest for cheap, low density and high performance materials in the design of aircraft and rotorcraft engine fan and propeller blades poses immense challenges to the materials and structural design engineers. The present study investigates the use of a sandwich foam fan blade mae up of solid face sheets and a metal foam core. The face sheets and the metal foam core material were an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. The resulting structures possesses a high stiffness while being lighter than a similar solid construction. The material properties of 17-4 PH metal foam are reviewed briefly to describe the characteristics of sandwich structure for a fan blade application. A vibration analysis for natural frequencies and a detailed stress analysis on the 17-4 PH sandwich foam blade design for different combinations of kin thickness and core volume are presented with a comparison to a solid titanium blade.

Min, James B.; Ghosn, Louis J.; Lerch, Bradley A.; Raj, Sai V.; Holland, Frederic A., Jr.; Hebsur, Mohan G.

2004-01-01

244

Design of air-gapped magnetic-core inductors for superimposed direct and alternating currents  

NASA Technical Reports Server (NTRS)

Using data on standard magnetic-material properties and standard core sizes for air-gap-type cores, an algorithm designed for a computer solution is developed which optimally determines the air-gap length and locates the quiescent point on the normal magnetization curve so as to yield an inductor design with the minimum number of turns for a given ac voltage and frequency and with a given dc bias current superimposed in the same winding. Magnetic-material data used in the design are the normal magnetization curve and a family of incremental permeability curves. A second procedure, which requires a simpler set of calculations, starts from an assigned quiescent point on the normal magnetization curve and first screens candidate core sizes for suitability, then determines the required turns and air-gap length.

Ohri, A. K.; Wilson, T. G.; Owen, H. A., Jr.

1976-01-01

245

Core Noise: Implications of Emerging N+3 Designs and Acoustic Technology Needs  

NASA Technical Reports Server (NTRS)

This presentation is a summary of the core-noise implications of NASA's primary N+3 aircraft concepts. These concepts are the MIT/P&W D8.5 Double Bubble design, the Boeing/GE SUGAR Volt hybrid gas-turbine/electric engine concept, the NASA N3-X Turboelectric Distributed Propulsion aircraft, and the NASA TBW-XN Truss-Braced Wing concept. The first two are future concepts for the Boeing 737/Airbus A320 US transcontinental mission of 180 passengers and a maximum range of 3000 nm. The last two are future concepts for the Boeing 777 transpacific mission of 350 passengers and a 7500 nm range. Sections of the presentation cover: turbofan design trends on the N+1.5 time frame and the already emerging importance of core noise; the NASA N+3 concepts and associated core-noise challenges; the historical trends for the engine bypass ratio (BPR), overall pressure ratio (OPR), and combustor exit temperature; and brief discussion of a noise research roadmap being developed to address the core-noise challenges identified for the N+3 concepts. The N+3 conceptual aircraft have (i) ultra-high bypass ratios, in the rage of 18 - 30, accomplished by either having a small-size, high-power-density core, an hybrid design which allows for an increased fan size, or by utilizing a turboelectric distributed propulsion design; and (ii) very high OPR in the 50 - 70 range. These trends will elevate the overall importance of turbomachinery core noise. The N+3 conceptual designs specify the need for the development and application of advanced liners and passive and active control strategies to reduce the core noise. Current engineering prediction of core noise uses semi-empirical methods based on older turbofan engines, with (at best) updates for more recent designs. The models have not seen the same level of development and maturity as those for fan and jet noise and are grossly inadequate for the designs considered for the N+3 time frame. An aggressive program for the development of updated noise prediction tools for integrated core assemblies as well as and strategies for noise reduction and control is needed in order to meet the NASA N+3 noise goals. The NASA Fundamental Aeronautics Program has the principal objective of overcoming today's national challenges in air transportation. The SFW Reduced-Perceived-Noise Technical Challenge aims to develop concepts and technologies to dramatically reduce the perceived aircraft noise outside of airport boundaries. This reduction of aircraft noise is critical to enabling the anticipated large increase in future air traffic.

Hultgren, Lennart S.

2011-01-01

246

Protein structures by spallation neutron crystallography.  

PubMed

The Protein Crystallography Station at Los Alamos Neutron Science Center is a high-performance beamline that forms the core of a capability for neutron macromolecular structure and function determination. This capability also includes the Macromolecular Neutron Crystallography (MNC) consortium between Los Alamos (LANL) and Lawrence Berkeley National Laboratories for developing computational tools for neutron protein crystallography, a biological deuteration laboratory, the National Stable Isotope Production Facility, and an MNC drug design consortium between LANL and Case Western Reserve University. PMID:18421142

Langan, Paul; Fisher, Zoë; Kovalevsky, Andrii; Mustyakimov, Marat; Sutcliffe Valone, Amanda; Unkefer, Cliff; Waltman, Mary Jo; Coates, Leighton; Adams, Paul D; Afonine, Pavel V; Bennett, Brad; Dealwis, Chris; Schoenborn, Benno P

2008-05-01

247

Design and Performance of South Ukraine Nuclear Power Plant Mixed Cores  

SciTech Connect

In 2010, 42 Westinghouse fuel assemblies (WFAs) were loaded into the core of South Ukraine Nuclear Power Plant (SUNPP) Unit 3 after four successful cycles with 6 Westinghouse Lead Test Assemblies. The scope of safety substantiating documents required for the regulatory approval of this mixed core was extended considerably, particularly with development and implementation of new methodologies and 3-D kinetic codes. Additional verification for all employed codes was also performed. Despite the inherent hydraulic non-uniformity of a mixed core, it was possible to demonstrate that all design and operating restrictions for three different types of fuel (TVS-M, TVSA and WFA) loaded in the core were conservatively met. This paper provides the main results from the first year of operation of the core loaded with 42 WFAs, the predicted parameters for the transition and equilibrium cycles with WFAs, comparisons of predicted versus measured core parameters, as well as the acceptable margin evaluation results for reactivity accidents using the 3-D kinetic codes. To date WFA design parameters have been confirmed by operation experience.

Abdullayev, A. M.; Baydulin, V.; Zhukov, A. I.; Latorre, Richard

2011-09-24

248

The design and performance of IceCube DeepCore  

NASA Astrophysics Data System (ADS)

The IceCube neutrino observatory in operation at the South Pole, Antarctica, comprises three distinct components: a large buried array for ultrahigh energy neutrino detection, a surface air shower array, and a new buried component called DeepCore. DeepCore was designed to lower the IceCube neutrino energy threshold by over an order of magnitude, to energies as low as about 10 GeV. DeepCore is situated primarily 2100 m below the surface of the icecap at the South Pole, at the bottom center of the existing IceCube array, and began taking physics data in May 2010. Its location takes advantage of the exceptionally clear ice at those depths and allows it to use the surrounding IceCube detector as a highly efficient active veto against the principal background of downward-going muons produced in cosmic-ray air showers. DeepCore has a module density roughly five times higher than that of the standard IceCube array, and uses photomultiplier tubes with a new photocathode featuring a quantum efficiency about 35% higher than standard IceCube PMTs. Taken together, these features of DeepCore will increase IceCube's sensitivity to neutrinos from WIMP dark matter annihilations, atmospheric neutrino oscillations, galactic supernova neutrinos, and point sources of neutrinos in the northern and southern skies. In this paper we describe the design and initial performance of DeepCore.

Abbasi, R.; Abdou, Y.; Abu-Zayyad, T.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Allen, M. M.; Altmann, D.; Andeen, K.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S. W.; Bay, R.; Bazo Alba, J. L.; Beattie, K.; Beatty, J. J.; Bechet, S.; Becker, J. K.; Becker, K.-H.; Benabderrahmane, M. L.; BenZvi, S.; Berdermann, J.; Berghaus, P.; Berley, D.; Bernardini, E.; Bertrand, D.; Besson, D. Z.; Bindig, D.; Bissok, M.; Blaufuss, E.; Blumenthal, J.; Boersma, D. J.; Bohm, C.; Bose, D.; Böser, S.; Botner, O.; Brown, A. M.; Buitink, S.; Caballero-Mora, K. S.; Carson, M.; Chirkin, D.; Christy, B.; Clevermann, F.; Cohen, S.; Colnard, C.; Cowen, D. F.; Cruz Silva, A. H.; D'Agostino, M. V.; Danninger, M.; Daughhetee, J.; Davis, J. C.; De Clercq, C.; Degner, T.; Demirörs, L.; Descamps, F.; Desiati, P.; de Vries-Uiterweerd, G.; DeYoung, T.; Díaz-Vélez, J. C.; Dierckxsens, M.; Dreyer, J.; Dumm, J. P.; Dunkman, M.; Eisch, J.; Ellsworth, R. W.; Engdegård, O.; Euler, S.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Fedynitch, A.; Feintzeig, J.; Feusels, T.; Filimonov, K.; Finley, C.; Fischer-Wasels, T.; Fox, B. D.; Franckowiak, A.; Franke, R.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Gladstone, L.; Glüsenkamp, T.; Goldschmidt, A.; Goodman, J. A.; Góra, D.; Grant, D.; Griesel, T.; Groß, A.; Grullon, S.; Gurtner, M.; Ha, C.; Haj Ismail, A.; Hallgren, A.; Halzen, F.; Han, K.; Hanson, K.; Heinen, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hill, G. C.; Hoffman, K. D.; Hoffmann, B.; Homeier, A.; Hoshina, K.; Huelsnitz, W.; Hülß, J.-P.; Hulth, P. O.; Hultqvist, K.; Hussain, S.; Ishihara, A.; Jacobi, E.; Jacobsen, J.; Japaridze, G. S.; Johansson, H.; Kampert, K.-H.; Kappes, A.; Karg, T.; Karle, A.; Kenny, P.; Kiryluk, J.; Kislat, F.; Klein, S. R.; Köhne, J.-H.; Kohnen, G.; Kolanoski, H.; Köpke, L.; Koskinen, D. J.; Kowalski, M.; Kowarik, T.; Krasberg, M.; Kroll, G.; Kurahashi, N.; Kuwabara, T.; Labare, M.; Laihem, K.; Landsman, H.; Larson, M. J.; Lauer, R.; Lünemann, J.; Madsen, J.; Marotta, A.; Maruyama, R.; Mase, K.; Matis, H. S.; Meagher, K.; Merck, M.; Mészáros, P.; Meures, T.; Miarecki, S.; Middell, E.; Milke, N.; Miller, J.; Montaruli, T.; Morse, R.; Movit, S. M.; Nahnhauer, R.; Nam, J. W.; Naumann, U.; Nygren, D. R.; Odrowski, S.; Olivas, A.; Olivo, M.; O'Murchadha, A.; Panknin, S.; Paul, L.; Pérez de los Heros, C.; Petrovic, J.; Piegsa, A.; Pieloth, D.; Porrata, R.; Posselt, J.; Price, P. B.; Przybylski, G. T.; Rawlins, K.; Redl, P.; Resconi, E.; Rhode, W.; Ribordy, M.; Richman, M.; Rodrigues, J. P.; Rothmaier, F.; Rott, C.; Ruhe, T.; Rutledge, D.; Ruzybayev, B.; Ryckbosch, D.; Sander, H.-G.; Santander, M.; Sarkar, S.; Schatto, K.; Schmidt, T.; Schönwald, A.; Schukraft, A.; Schultes, A.; Schulz, O.; Schunck, M.; Seckel, D.; Semburg, B.; Seo, S. H.; Sestayo, Y.; Seunarine, S.; Silvestri, A.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Strahler, E. A.; Ström, R.; Stüer, M.; Sullivan, G. W.; Swillens, Q.; Taavola, H.; Taboada, I.; Tamburro, A.; Tepe, A.; Ter-Antonyan, S.; Tilav, S.; Toale, P. A.; Toscano, S.; Tosi, D.; van Eijndhoven, N.; Vandenbroucke, J.; Van Overloop, A.; van Santen, J.; Vehring, M.; Voge, M.; Walck, C.; Waldenmaier, T.; Wallraff, M.; Walter, M.; Weaver, Ch.; Wendt, C.; Westerhoff, S.; Whitehorn, N.; Wiebe, K.; Wiebusch, C. H.; Williams, D. R.; Wischnewski, R.; Wissing, H.; Wolf, M.; Wood, T. R.; Woschnagg, K.; Xu, C.; Xu, D. L.; Xu, X. W.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zarzhitsky, P.; Zoll, M.

2012-05-01

249

The Design and Performance of IceCube DeepCore  

NASA Technical Reports Server (NTRS)

The IceCube neutrino observatory in operation at the South Pole, Antarctica, comprises three distinct components: a large buried array for ultrahigh energy neutrino detection, a surface air shower array, and a new buried component called DeepCore. DeepCore was designed to lower the IceCube neutrino energy threshold by over an order of magnitude, to energies as low as about 10 GeV. DeepCore is situated primarily 2100 m below the surface of the icecap at the South Pole, at the bottom center of the existing IceCube array, and began taking pbysics data in May 2010. Its location takes advantage of the exceptionally clear ice at those depths and allows it to use the surrounding IceCube detector as a highly efficient active veto against the principal background of downward-going muons produced in cosmic-ray air showers. DeepCore has a module density roughly five times higher than that of the standard IceCube array, and uses photomultiplier tubes with a new photocathode featuring a quantum efficiency about 35% higher than standard IceCube PMTs. Taken together, these features of DeepCore will increase IceCube's sensitivity to neutrinos from WIMP dark matter annihilations, atmospheric neutrino oscillations, galactic supernova neutrinos, and point sources of neutrinos in the northern and southern skies. In this paper we describe the design and initial performance of DeepCore.

Stamatikos, M.

2012-01-01

250

Analysis of neutron flux noise due to coolant parameter fluctuations in a VVÉR core  

Microsoft Academic Search

The results of investigations of noise appearing in the signals from direct-charge sensors of the in-reactor monitoring system\\u000a of VVÉR reactors as a result of coolant parameter fluctuations are presented. The calculations and experimental data are used\\u000a to analyze the dependence of the amplitude of the neutron flux oscillations (local intensity) at the locations of sensors\\u000a as a function of

Yu. M. Semchenkov; V. A. Mil’to; A. A. Pinegin; B. E. Shumskii

2007-01-01

251

Error Assessment of Homogenized Cross Sections Generation for Whole Core Neutronic Calculation  

Microsoft Academic Search

The objective of the work here was to assess the errors introduced by using 2D, few group homogenized cross sections to perform neutronic analysis of BWR problems with significant axial heterogeneities. The 3D method of characteristics code DeCART is used to generate 2-group assembly homogenized cross sections first using a conventional 2D lattice model and then using a full 3D

Mathieu Hursin; Brendan Kochunas; Thomas J. Downar

2007-01-01

252

Thermal neutron irradiation field design for boron neutron capture therapy of human explanted liver.  

PubMed

The selective uptake of boron by tumors compared to that by healthy tissue makes boron neutron capture therapy (BNCT) an extremely advantageous technique for the treatment of tumors that affect a whole vital organ. An example is represented by colon adenocarcinoma metastases invading the liver, often resulting in a fatal outcome, even if surgical resection of the primary tumor is successful. BNCT can be performed by irradiating the explanted organ in a suitable neutron field. In the thermal column of the Triga Mark II reactor at Pavia University, a facility was created for this purpose and used for the irradiation of explanted human livers. The neutron field distribution inside the organ was studied both experimentally and by means of the Monte Carlo N-particle transport code (MCNP). The liver was modeled as a spherical segment in MCNP and a hepatic-equivalent solution was used as an experimental phantom. In the as-built facility, the ratio between maximum and minimum flux values inside the phantom ((phi(max)/phi(min)) was 3.8; this value can be lowered to 2.3 by rotating the liver during the irradiation. In this study, the authors proposed a new facility configuration to achieve a uniform thermal neutron flux distribution in the liver. They showed that a phi(max)/phi(min) ratio of 1.4 could be obtained without the need for organ rotation. Flux distributions and dose volume histograms were reported for different graphite configurations. PMID:18196797

Bortolussi, S; Altieri, S

2007-12-01

253

Thermo-mechanical and neutron lifetime modeling and design of Be pebbles in the neutron multiplier for the LIFE engine  

SciTech Connect

Concept designs for the laser-initiated fusion/fission engine (LIFE) include a neutron multiplication blanket containing Be pebbles flowing in a molten salt coolant. These pebbles must be designed to withstand the extreme irradiation and temperature conditions in the blanket to enable a safe and cost-effective operation of LIFE. In this work, we develop design criteria for spherical Be pebbles on the basis of their thermomechanical behavior under continued neutron exposure. We consider the effects of high fluence/fast flux on the elastic, thermal and mechanical properties of nuclear-grade Be. Our results suggest a maximum pebble diameter of 30 mm to avoid tensile failure, coated with an anti-corrosive, high-strength metallic shell to avoid failure by pebble contact. Moreover, we find that the operation temperature must always be kept above 450 C to enable creep to relax the stresses induced by swelling, which we estimate to be at least 16 months if uncoated and up to six years when coated. We identify the sources of uncertainty on the properties used and discuss the advantages of new intermetallic beryllides and their use in LIFE's neutron multiplier. To establish Be-pebble lifetimes with improved confidence, reliable experiments to measure irradiation creep must be performed.

DeMange, P; Marian, J; de Caro, M S; Caro, A

2009-03-16

254

High-j single-particle neutron states outside the N=82 core  

E-print Network

The behaviour of the i13/2 and h9/2 single-neutron strength was studied with the (4He,3He) reaction on 138Ba, 140Ce, 142Nd and 144Sm targets at a beam energy of 51 MeV. The separation between the single-neutron states i13/2 and h9/2 was measured in N =83 nuclei with changing proton number. To this end spectroscopic factors for states populated in high-l transfer were extracted from the data. Some mixing of l=5 and 6 strength was observed with states that are formed by coupling the f7/2 state to the 2+ and 3- vibrational states and the mixing matrix elements were found to be remarkably constant. The centroids of the strength indicate a systematic change in the energies of the i13/2 and h9/2 single-neutron states with increasing proton number that is in quantitative agreement with the effects expected from the tensor interaction.

B. P. Kay; S. J. Freeman; J. P. Schiffer; J. A. Clark; C. Deibel; A. Heinz; A. Parikh; C. Wrede

2007-09-04

255

Boiling water neutronic reactor incorporating a process inherent safety design  

DOEpatents

A boiling-water reactor core is positioned within a prestressed concrete reactor vessel of a size which will hold a supply of coolant water sufficient to submerge and cool the reactor core by boiling for a period of at least one week after shutdown. Separate volumes of hot, clean (nonborated) water for cooling during normal operation and cool highly borated water for emergency cooling and reactor shutdown are separated by an insulated wall during normal reactor operation with contact between the two water volumes being maintained at interfaces near the top and bottom ends of the reactor vessel. Means are provided for balancing the pressure of the two water volumes at the lower interface zone during normal operation to prevent entry of the cool borated water into the reactor core region, for detecting the onset of excessive power to coolant flow conditions in the reactor core and for detecting low water levels of reactor coolant. Cool borated water is permitted to flow into the reactor core when low reactor coolant levels or excessive power to coolant flow conditions are encountered.

Forsberg, C.W.

1985-02-19

256

Boiling water neutronic reactor incorporating a process inherent safety design  

DOEpatents

A boiling-water reactor core is positioned within a prestressed concrete reactor vessel of a size which will hold a supply of coolant water sufficient to submerge and cool the reactor core by boiling for a period of at least one week after shutdown. Separate volumes of hot, clean (non-borated) water for cooling during normal operation and cool highly borated water for emergency cooling and reactor shutdown are separated by an insulated wall during normal reactor operation with contact between the two water volumes being maintained at interfaces near the top and bottom ends of the reactor vessel. Means are provided for balancing the pressure of the two volumes at the lower interface zone during normal operation to prevent entry of the cool borated water into the reactor core region, for detecting the onset of excessive power to coolant flow conditions in the reactor core and for detecting low water levels of reactor coolant. Cool borated water is permitted to flow into the reactor core when low reactor coolant levels or excessive power to coolant flow conditions are encountered.

Forsberg, Charles W. (Kingston, TN)

1987-01-01

257

Modeling and analysis of core debris recriticality during hypothetical severe accidents in the Advanced Neutron Source Reactor  

SciTech Connect

This paper discusses salient aspects of severe-accident-related recriticality modeling and analysis in the Advanced Neutron Source (ANS) reactor. The development of an analytical capability using the KENO V.A-SCALE system is described including evaluation of suitable nuclear cross-section sets to account for the effects of system geometry, mixture temperature, material dispersion and other thermal-hydraulic conditions. Benchmarking and validation efforts conducted with KENO V.A-SCALE and other neutronic codes against critical experiment data are described. Potential deviations and biases resulting from use of the 16-group Hansen-Roach library are shown. A comprehensive test matrix of calculations to evaluate the threat of a recriticality event in the ANS is described. Strong dependencies on geometry, material constituents, and thermal-hydraulic conditions are described. The introduction of designed mitigative features is described.

Taleyarkhan, R.P.; Kim, S.H.; Slater, C.O.; Moses, D.L.; Simpson, D.B.; Georgevich, V.

1993-05-01

258

Design and performance of a cryogenic apparatus for magnetically trapping ultracold neutrons  

NASA Astrophysics Data System (ADS)

The cryogenic design and performance of an apparatus used to magnetically confine ultracold neutrons (UCN) is presented. The apparatus is part of an effort to measure the beta-decay lifetime of the free neutron and is comprised of a high-current superconducting magnetic trap that surrounds ?21 l of isotopically pure 4He cooled to approximately 250 mK. A 0.89 nm neutron beam can enter the apparatus from one end of the magnetic trap and a light collection system allows visible light generated within the helium by decays to be transported to detectors at room temperature. Two cryocoolers are incorporated to reduce liquid helium consumption.

Huffman, P. R.; Coakley, K. J.; Doyle, J. M.; Huffer, C. R.; Mumm, H. P.; O'Shaughnessy, C. M.; Schelhammer, K. W.; Seo, P.-N.; Yang, L.

2014-11-01

259

Design and Effects of the Proton Window of the Spallation Neutron Source  

SciTech Connect

Design parameters for the target region of the Spallation Neutron Source were calculated by following histories of 1 GeV protons and their shower of particles with the Monte Carlo code MCNPX. In particular, neutron currents, radiation damages, doses and heat distributions for the target region of the facility along the path of the proton beam are presented from the point of view of the perturbation effects of the proton beam window.

Difilippo, F.C.

2000-10-23

260

The HANARO neutron reflectometer with horizontal sample geometry; engineering designs and performance simulation  

Microsoft Academic Search

A new neutron reflectometer with a horizontal sample geometry was designed and is now under construction at the HANARO, 30 MW research reactor. It was originally built and operated at the H9-A beam port at BNL, and was relocated to HANARO in 2004. We performed simulations of neutron ray-tracing to evaluate the performance of all of the optical components of the

Oh-Sun Kwon; Kwanwoo Shin; Dong-Jin Choi; Kwang Pho Hong; Myung Kook Moon; Sang Jin Cho; Young Hyun Choi; Jeong Soo Lee; Change-Hee Lee

2007-01-01

261

Optimization of the Ballistic Guide Design for the SNS FNPB 8.9 A Neutron Line  

E-print Network

The optimization of the ballistic guide design for the SNS Fundamental Neutron Physics Beamline 8.9 A line is described. With a careful tuning of the shape of the curve for the tapered section and the width of the straight section, this optimization resulted in more than 75% increase in the neutron flux exiting the 33 m long guide over a straight m=3.5 guide with the same length.

Takeyasu M. Ito; Christopher B. Crawford; Geoffrey L. Greene

2006-04-24

262

Conceptual design of a reversed-field pinch fusion neutron source  

SciTech Connect

The conceptual design of an ohmically-heated, reversed-field pinch (RFP) operating with a 5-MWm/sup 2/ steady-state DT fusion neutron wall loading while generating /approximately/100-MW total fusion power is presented. These results are also useful in projecting the development of an economic source of DT neutrons for large-volume (/approximately/10 m/sup 3/) fusion nuclear testing. 6 refs., 4 figs., 5 tabs.

Bathke, C.G.; Krakowski, R.A.; Manzanares, R.G.; Miller, R.L.; Werley, K.A.

1988-01-01

263

Hardware accelerated high performance neutron transport computation based on AGENT methodology  

Microsoft Academic Search

The spatial heterogeneity of the next generation Gen-IV nuclear reactor core designs brings challenges to the neutron transport analysis. The Arbitrary Geometry Neutron Transport (AGENT) AGENT code is a three-dimensional neutron transport analysis code being developed at the Laboratory for Neutronics and Geometry Computation (NEGE) at Purdue University. It can accurately describe the spatial heterogeneity in a hierarchical structure through

Shanjie Xiao

2009-01-01

264

Active Learning: Effects of Core Training Design Elements on Self-Regulatory Processes, Learning, and Adaptability  

Microsoft Academic Search

This research describes a comprehensive examination of the cognitive, motivational, and emotional processes underlying active learning approaches, their effects on learning and transfer, and the core training design elements (exploration, training frame, emotion-control) and individual differences (cognitive ability, trait goal orientation, trait anxiety) that shape these processes. Participants (N = 350) were trained to operate a complex computer-based simulation. Exploratory

Bradford S. Bell; Steve W. J. Kozlowski

2008-01-01

265

Design and Implementation of the National Institute of Environmental Health Sciences Dublin Core Metadata Schema  

Microsoft Academic Search

The National Institute of Environmental Health Sciences (NIEHS) has formed a team to design and implement a Dublin Core-based metadata schema to enhance the public's ability to retrieve pertinent public health information on the organization's Web site. The team decided to use the DC schema because it is a de facto standard and because of its flexibility. With a little

W. Davenport Robertson; Ellen M. Leadem; Jed Dube; Jane Greenberg

2001-01-01

266

Fusion-power-core design of a compact Reversed-Field Pinch Reactor (CRFPR)  

SciTech Connect

A conceptual design of a fusion power core (FPC, i.e., plasma chamber, first wall, blanket, shield, coils) based on a Reversed-Field Pinch (RFP) has been completed. After a brief statement of rationale and description of the reactor configuration, the FPC integration is described in terms of power balance, thermal-hydraulics, and mechanical design. The engineering versatility, promise, and problems of this high-power-density approach to fusion are addressed.

Copenhaver, C.; Battak, M.E.; Cappiello, C.; Chaffee, A.D.; Davidson, J.W.; Hayenson, R.L.; Krakowski, R.A.; Lujan, R.E.; Mynard, R.C.; Schnurr, N.M.

1985-07-01

267

Fusion-power-core design of a compact Reversed-Field Pinch Reactor (CRFPR)  

SciTech Connect

A conceptual design of a fusion power core (FPC, i.e., plasma chamber, first wall, blanket, shield, coils) based on a Reversed-Field Pinch (RFP) has been completed. After a brief statement of rationale and description of the reactor configuration, the FPC integration is described in terms of power balance, thermal-hydraulics, and mechanical design. The engineering versatility, promise, and problems of this high-power-density approach to fusion are addressed.

Copenhaver, C.; Schnurr, N.M.; Krakowski, R.A.; Hagenson, R.L.; Mynard, R.C.; Cappiello, C.; Lujan, R.E.; Davidson, J.W.; Chaffee, A.D.; Battat, M.E.

1985-01-01

268

Designing an extended energy range single-sphere multi-detector neutron spectrometer  

NASA Astrophysics Data System (ADS)

This communication describes the design specifications for a neutron spectrometer consisting of 31 thermal neutron detectors, namely Dysprosium activation foils, embedded in a 25 cm diameter polyethylene sphere which includes a 1 cm thick lead shell insert that degrades the energy of neutrons through (n,xn) reactions, thus allowing to extension of the energy range of the response up to hundreds of MeV neutrons. The new spectrometer, called SP2 (SPherical SPectrometer), relies on the same detection mechanism as that of the Bonner Sphere Spectrometer, but with the advantage of determining the whole neutron spectrum in a single exposure. The Monte Carlo transport code MCNPX was used to design the spectrometer in terms of sphere diameter, number and position of the detectors, position and thickness of the lead shell, as well as to obtain the response matrix for the final configuration. This work focuses on evaluating the spectrometric capabilities of the SP2 design by simulating the exposure of SP2 in neutron fields representing different irradiation conditions (test spectra). The simulated SP2 readings were then unfolded with the FRUIT unfolding code, in the absence of detailed pre-information, and the unfolded spectra were compared with the known test spectra. The results are satisfactory and allowed approving the production of a prototypal spectrometer.

Gómez-Ros, J. M.; Bedogni, R.; Moraleda, M.; Esposito, A.; Pola, A.; Introini, M. V.; Mazzitelli, G.; Quintieri, L.; Buonomo, B.

2012-06-01

269

Design criteria for electronics for resistive charge division in thermal neutron detection  

Microsoft Academic Search

An amplifier has been designed for optimal use of position-sensitive thermal neutron detectors based upon the principle of resistive charge division. The important points in this optimization are: high counting rates and good spatial resolution (low noise). In this paper, we present a short theoretical analysis of the problem that led us to our design. We make an analysis of

Patrick Van Esch; Thomas Gahl; Bruno Guérard

2004-01-01

270

ESS-Bilbao light-ion linear accelerator and neutron source: design and applications  

Microsoft Academic Search

The baseline design for the ESS-Bilbao light-ion linear accelerator and neutron source has been completed and the normal conducting section of the linac is at present under construction. The machine has been designed to be compliant with ESS specifications following the international guidelines of such project as described in Ref. [1]. The new accelerator facility in Bilbao will serve as

E. Abad; I. Arredondo; I. Badillo; D. Belver; F. J. Bermejo; I. Bustinduy; D. Cano; D. Cortazar; D. de Cos; S. Djekic; S. Domingo; P. Echevarria; M. Eguiraun; V. Etxebarria; D. Fernandez; F. J. Fernandez; J. Feuchtwanger; N. Garmendia; G. Harper; H. Hassanzadegan; J. Jugo; F. Legarda; M. Magan; R. Martinez; A. Megia; L. Muguira; G. Mujika; J. L. Muñoz; A. Ortega; J. Ortega; M. Perlado; J. Portilla; I. Rueda; F. Sordo; V. Toyos; A. Vizcaino

2011-01-01

271

The SNL100-02 blade : advanced core material design studies for the Sandia 100-meter blade.  

SciTech Connect

A series of design studies are performed to investigate the effects of advanced core materials and a new core material strategy on blade weight and performance for large blades using the Sandia 100-meter blade designs as a starting point. The initial core material design studies were based on the SNL100-01 100- meter carbon spar design. Advanced core material with improved performance to weight was investigated with the goal to reduce core material content in the design and reduce blade weight. A secondary element of the core study was to evaluate the suitability of core materials from natural, regrowable sources such as balsa and recyclable foam materials. The new core strategy for the SNL100-02 design resulted in a design mass of 59 tons, which is a 20% reduction from the most recent SNL100-01 carbon spar design and over 48% reduction from the initial SNL100-00 all-glass baseline blade. This document provides a description of the final SNL100-02 design, includes a description of the major design modifications, and summarizes the pertinent blade design information. This document is also intended to be a companion document to the distribution of the NuMAD blade model files for SNL100-02 that are made publicly available.

Griffith, Daniel

2013-11-01

272

The magnetic structure of neutron stars and their surface-to-core temperature relation  

E-print Network

We study the relation between the mean effective surface temperature T_s and the internal temperature T_b for magnetic neutron stars, assuming that the magnetic field near the surface has a presumably small-scale structure. The heavy-element (iron) and light-element (accreted) heat-blanketing envelopes are considered, and the results are compared with the case of a dipole magnetic field. We argue that the difference in the T_b(T_s)-relation for different magnetic configurations is always much smaller than a possible difference caused by variations of the chemical composition in the envelope.

A. Y. Potekhin; V. Urpin; G. Chabrier

2005-08-19

273

The behavior of reactor power and flux resulting from changes in core-coolant temperature for a miniature neutron source reactor  

Microsoft Academic Search

In this work, measurements were performed to verify the theoretical predictions of reactor power and flux parameters that result from changes in core inlet temperature (Tin) and the temperature difference between the coolant inlet and outlet (?T) in the Nigeria Research Reactor-1 (NIRR-1), which is a Miniature Neutron Source Reactor (MNSR). The measured data shows that there is a strong

Y. A. Ahmed; G. I. Balogun; S. A. Jonah; I. I. Funtua

2008-01-01

274

Coupled Neutronics Thermal-Hydraulic Solution of a Full-Core PWR Using VERA-CS  

SciTech Connect

The Consortium for Advanced Simulation of Light Water Reactors (CASL) is developing a core simulator called VERA-CS to model operating PWR reactors with high resolution. This paper describes how the development of VERA-CS is being driven by a set of progression benchmark problems that specify the delivery of useful capability in discrete steps. As part of this development, this paper will describe the current capability of VERA-CS to perform a multiphysics simulation of an operating PWR at Hot Full Power (HFP) conditions using a set of existing computer codes coupled together in a novel method. Results for several single-assembly cases are shown that demonstrate coupling for different boron concentrations and power levels. Finally, high-resolution results are shown for a full-core PWR reactor modeled in quarter-symmetry.

Clarno, Kevin T [ORNL; Palmtag, Scott [ORNL; Davidson, Gregory G [ORNL; Salko, Robert K [ORNL; Evans, Thomas M [ORNL; Turner, John A [ORNL; Belcourt, Kenneth [Sandia National Laboratories (SNL); Hooper, Russell [Sandia National Laboratories (SNL); Schmidt, Rodney [Sandia National Laboratories (SNL)

2014-01-01

275

Designing a New Fuel for HFIR-Performance Parameters for LEU Core Configurations  

SciTech Connect

An engineering design study for a fuel that would enable the conversion of the High Flux Isotope Reactor from highly enriched uranium to low enriched uranium fuel is ongoing as part of an effort sponsored by the U.S. Department of Energy's National Nuclear Security Administration through the Global Threat Reduction Initiative. Given the unique fuel and core design and high power density of the reactor and the requirement that the impact of the fuel change on the core performance and operation be minimal, this conversion study presents a complex and challenging task, requiring improvements in the computational models currently used to support the operation of the reactor and development of new models that would take advantage of newly available simulation methods and tools. The computational models used to search for a fuel design that would meet the requirements for the conversion study and the results obtained with these models are presented and discussed. Estimates of relevant reactor performance parameters for the low enriched uranium fuel core are presented and compared to the corresponding data for the currently operating highly enriched uranium fuel core.

Ilas, Germina [ORNL; Primm, Trent [ORNL; Gehin, Jess C [ORNL

2009-01-01

276

Fuel and Core Design for Long Operating Cycle Simplified BWR (LSBWR)  

SciTech Connect

This paper describes an innovative core concept currently being developed for long operating cycle simplified BWR (LSBWR). The LSBWR adopts the long cycle operation (15 years) for the elimination of the fuel pool and the refueling machines and for the capacity usage ratio improvement. To achieve long cycle operation, a combination of enriched gadolinium and 0.7- times sized small bundle with peripheral-positioned gadolinium rod is adopted as a key design concept. A nuclear design for fuel bundle has been determined based on three dimensional nuclear and thermal hydraulic calculation. A core performance has been evaluated based on this bundle design and thermal performance and reactivity characteristics indicated preferable value. (authors)

Noriyuki Yoshida; Kouji Hiraiwa; Mikihide Nakamaru; Hideaki Heki [Toshiba Corporation, Isogo Nuclear Engineering Center, 8, Shinsugita-cho, Isogo-ku, Yokohama 235-8523 (Japan)

2002-07-01

277

Design and performance considerations for perforated semiconductor thermal-neutron detectors  

NASA Astrophysics Data System (ADS)

Perforated silicon structures backfilled with either B10 or LiF6 are presently under construction as high efficiency thermal-neutron detectors. Although many perforated structures are possible, there are three fundamental designs that are studied in the present work, namely (a) cylindrical perforations where holes are filled with neutron reactive material, (b) pillar configurations where semiconductor pillars are surrounded by neutron reactive material, and (c) trench structures where the trenches are filled with neutron reactive material. From results of Monte Carlo simulations, it is found that the trench structure affords the best efficiencies, exceeding 20% using conservative geometries, and over 35% for more aggressive structures. Simulated spectroscopic features and manufacturing constraints are presented and discussed.

Shultis, J. K.; McGregor, D. S.

2009-07-01

278

Preliminary shielding analysis in support of the CSNS target station shutter neutron beam stop design  

NASA Astrophysics Data System (ADS)

The construction of China Spallation Neutron Source (CSNS) has been initiated in Dongguan, Guangdong, China. Thus a detailed radiation transport analysis of the shutter neutron beam stop is of vital importance. The analyses are performed using the coupled Monte Carlo and multi-dimensional discrete ordinates method. The target of calculations is to optimize the neutron beamline shielding design to guarantee personal safety and minimize cost. Successful elimination of the primary ray effects via the two-dimensional uncollided flux and the first collision source methodology is also illustrated. Two-dimensional dose distribution is calculated. The dose at the end of the neutron beam line is less than 2.5 ?Sv/h. The models have ensured that the doses received by the hall staff members are below the standard limit required.

Zhang, Bin; Chen, Yi-Xue; Wang, Wei-Jin; Yang, Shou-Hai; Wu, Jun; Yin, Wen; Liang, Tian-Jiao; Jia, Xue-Jun

2011-08-01

279

Multi-core fiber design and analysis: coupled-mode theory and coupled-power theory.  

PubMed

Coupled-mode and coupled-power theories are described for multi-core fiber design and analysis. First, in order to satisfy the law of power conservation, mode-coupling coefficients are redefined and then, closed-form power-coupling coefficients are derived based on exponential, Gaussian, and triangular autocorrelation functions. Using the coupled-mode and coupled-power theories, impacts of random phase-offsets and correlation lengths on crosstalk in multi-core fibers are investigated for the first time. The simulation results are in good agreement with the measurement results. Furthermore, from the simulation results obtained by both theories, it is confirmed that the reciprocity is satisfied in multi-core fibers. PMID:22274004

Koshiba, Masanori; Saitoh, Kunimasa; Takenaga, Katsuhiro; Matsuo, Shoichiro

2011-12-12

280

Target station design for a 1 MW pulsed spallation neutron source  

SciTech Connect

Target stations are vital components of the 1 MW, next generation spallation neutron source proposed for LANSCE. By and large, target stations design determines the overall performance of the facility. Many traditional concepts will probably have to be rethought, and many new concepts will have to be put forward to meet the 1 MW challenge. This article gives a brief overview of the proposed neutron spallation source from the target station viewpoint, as well as the general philosophy adopted for the design of the LANSCE-II target stations. Some of the saliant concepts and features envisioned for LANSCE-II are briefly described.

Russell, G.J.; Baker, G.D.; Brewton, R.J. [and others

1993-12-31

281

An optimized design of a dual-core photonic crystal fiber coupler  

NASA Astrophysics Data System (ADS)

An optical fiber coupler is a very important component in realizing all-fiber communication system. The appearance of dual-core photonic crystal fibers (PCFs) has enabled a new method of designing fiber coupler. Directional coupler based on the dual-core PCFs was investigated and shows intriguing properties, e.g., broadband coupling, the shorter coupling length, and polarized-mode coupling. However, the coupling bandwidth is the one of the most key properties due to the wavelength dependent of coupling efficiency for optical fiber coupler. In order to obtain the wavelength flattened response coupler with insensitive to deformation of air holes, in this paper an asymmetry dual-core PCF coupler with depressed-doped core is proposed and its coupling characteristics are also investigated by full-vector beam propagation method (BPM) in detail. The result of simulation shows that the coupling coefficient of 50%+/- 0.5% over a wide wavelength from 1.3?m to 1.7?m. Its coupling length is about 394?m, which is much shorter than that of other dual-core PCF couplers reported in literature. The fluctuation of coupling ratio is smaller than 5% with variation of the coupling length of 10%. We also demonstrate it could be more robust caused from the shorter coupling length. Furthermore, the mode field of the coupler is Gaussian-shape which means that additional insertion loss will not be introduced.

Xu, Feng; Tao, Dashi; Shi, Miaomiao; Jiang, Chao; Zhang, Bo; Shi, Xiaolong; Yu, Benli

2009-11-01

282

Design of Ultra Small Angle Neutron Scattering (KIST-USANS) at HANARO Cold Neutron Guide, CG4B  

NASA Astrophysics Data System (ADS)

The ultra small angle neutron scattering instrument can measure the lower limit of scattering vector to near Q ˜ 2.0x10-5 å-1 while the upper limit can reach to an intermediate scattering vector Q ˜ 10-2 å-1 of a typical small angle neutron scattering (SANS) depending on the contrast of sample. USANS is useful when measuring objects that are micron to submicron in size while SANS is useful when measuring objects that are micron to nano in size. When both USANS and SANS were used together, we could measure sizes from micron to nano scale, which is useful when studying the hierarchical structures in the wide scale of Q and total cross-section, d?/d?(Q). Recently, KIST has developed the USANS (so called KIST-USANS) at HANARO cold neutron guide hall of KAERI. We will present the instrument design, performance, future plan, and some examples of measurements that cover approximately 11 orders of magnitude in the d?/d?(Q) and 4 orders in the Q.

Kim, Man-Ho

2013-03-01

283

Force analysis of the Advanced Neutron Source control rod drive latch mechanism  

Microsoft Academic Search

The Advanced Neutron Source reactor (ANS), a proposed Department of Energy research reactor currently undergoing conceptual design, will generate a thermal neutron flux approximating 1020 m-2 -s-1. The compact core necessary to produce this flux provides little space for the shim\\/safety control rods, which are located in the central annulus of the core. Without proper control rod drive design, the

B. Damiano

1990-01-01

284

Design and development of position sensitive detectors for neutron scattering instruments at National Facility for Neutron Beam Research in India  

NASA Astrophysics Data System (ADS)

Various neutron scattering instruments at Dhruva reactor, BARC, are equipped with indigenously developed neutron detectors. Range of detectors includes proportional counters, beam monitors and linear position sensitive detectors (PSD). One of the instruments is recently upgraded with multi-PSD system of high efficiency and high resolution PSDs arranged in stacking geometry. These efforts have resulted in improving the throughput of the instrument and reducing experiment time. Global scarcity of 3He has made essential to explore other options like BF3 gas and 10B coatings. PSDs with coaxial geometry using BF3 gas and 10B coating (90% enriched) are fabricated and characterized successfully. These PSDs are used as the alternative to 3He PSD in equivalent geometry. Though efficiency of PSDs in similar dimensions is lower than that with 3He, these large numbers of PSDs can be arranged in multi-PSD system. The PSD design is optimized for reasonable efficiency. An array of 60 BF3 filled PSDs (1 m long) is under development for the Time of Flight Instrument at Dhruva. Further improvement in efficiency can be obtained with novel designs with complex anode-cathode geometry. Various challenges arise for long term operation of PSDs with BF3 gas, in addition to complexity of data acquisition electronics. Study of gas aging with detector fabrication materials has been carried out. PSDs with 10B coating show advantage of non toxic nature but have low efficiency. Multiple 10B layers intercepting neutron beam are used to increase the efficiency. PSD designed with small anode- cathode spacing and array of multiwire grids placed between double sided 10B coated plates are being fabricated. Assembly is arranged in curvilinear geometry with zero parallax. Overview of these developments is presented.

Desai, Shraddha S.

2014-07-01

285

Design and fabrication of an asymmetric twin-core fiber directional coupler for gain-flattened EDFA  

Microsoft Academic Search

Fiber directional couplers made of highly asymmetric twin-cores (ATC), one of which is doped with erbium, are designed to achieve an inherently gain flattened erbium doped fiber amplifier (EDFA). The refractive index profiles of the fibers as well as the spacing between the two cores were carefully designed to achieve a targeted gain with low gain excursions across the C-band.

B. Nagarajua; M. Udeb; S. Trzesienb; B. Dussardierb; R. K. Varshneya; G. Monnom; W. Blanc; B. P. Pal

2011-01-01

286

Whole-core neutron transport calculations without fuel-coolant homogenization  

SciTech Connect

The variational nodal method implemented in the VARIANT code is generalized to perform full core transport calculations without spatial homogenization of cross sections at either the fuel-pin cell or fuel assembly level. The node size is chosen to correspond to one fuel-pin cell in the radial plane. Each node is divided into triangular finite subelements, with the interior spatial flux distribution represented by piecewise linear trial functions. The step change in the cross sections at the fuel-coolant interface can thus be represented explicitly in global calculations while retaining the fill spherical harmonics capability of VARIANT. The resulting method is applied to a two-dimensional seven-group representation of a LWR containing MOX fuel assemblies. Comparisons are made of the accuracy of various space-angle approximations and of the corresponding CPU times.

Smith, M. A.; Tsoulfanidis, N.; Lewis, E. E.; Palmiotti, G.; Taiwo, T. A.

2000-02-10

287

Shielding design of a treatment room for an accelerator-based neutron source for BNCT  

SciTech Connect

For several years, research has been ongoing in the Ohio State University (OSU) Nuclear Engineering Program toward the development of an accelerator-based irradiation facility (ANIF) neutron source for boron neutron capture therapy (BNCT). The ANIF, which is planned to be built in a hospital, has been conceptually designed and analyzed. After Qu, an OSU researcher, determined that the shielding design of a 6-MV X-ray treatment room was inadequate to protect personnel from an accelerator neutron source operating at 30 mA, we decided to analyze and determine the shielding requirements of a treatment room for an ANIF. We determined the amount of shielding that would be sufficient to protect facility personnel from excessive radiation exposure caused by operation of the accelerator at 30 mA.

Evans, J.F.; Blue, T.E. [Ohio State Univ., Columbus, OH (United States)

1995-12-31

288

Design status of an intense 14 MeV neutron source for cancer therapy  

NASA Astrophysics Data System (ADS)

Design and development of an intense 14 MeV neutron source for cancer therapy is in progress at the Institute of Nuclear Research of Lanzhou University. The neutrons from the T(d,n) 4He reaction are produced by bombarding a rotating titanium tritide target with a 40 mA deuteron beam at 600 keV. The designed neutron yield is 8×10 12 n/s and the maximum dose rate at a 100 cm source-to-skin distance is 25 cGy/min. The HV terminal, accelerating column and HV power supply are enclosed inside a stainless steel pressure vessel containing 6 atm SF 6 gas to provide the electrical insulation.

Yao, Ze-En; Su, Tong-Ling; Cheng, Shang-Wen; Jia, Wen-Bao

2002-09-01

289

An accelerator-based epithermal neutron beam design for BNCT and dosimetric evaluation using a voxel head phantom.  

PubMed

The beam shaping assembly design has been investigated in order to improve the epithermal neutron beam for accelerator-based boron neutron capture therapy in intensity and quality, and dosimetric evaluation for the beams has been performed using both mathematical and voxel head phantoms with MCNP runs. The neutron source was assumed to be produced from a conventional 2.5 MeV proton accelerator with a thick (7)Li target. The results indicate that it is possible to enhance epithermal neutron flux remarkably as well as to embody a good spectrum shaping to epithermal neutrons only with the proper combination of moderator and reflector. It is also found that a larger number of thermal neutrons can reach deeply into the brain and, therefore, can reduce considerably the treatment time for brain tumours. Consequently, the epithermal neutron beams designed in this study can treat more effectively deep-seated brain tumours. PMID:15353726

Lee, Deok-jae; Han, Chi Young; Park, Sung Ho; Kim, Jong Kyung

2004-01-01

290

Energy Efficient Engine integrated core/low spool design and performance report  

NASA Technical Reports Server (NTRS)

The Energy Efficient Engine (E3) is a NASA program to create fuel saving technology for future transport aircraft engines. The E3 technology advancements were demonstrated to operate reliably and achieve goal performance in tests of the Integrated Core/Low Spool vehicle. The first build of this undeveloped technology research engine set a record for low fuel consumption. Its design and detailed test results are herein presented.

Stearns, E. Marshall

1985-01-01

291

Test Planning and Design Space Exploration in a Core-Based Environment  

Microsoft Academic Search

This paper proposes a comprehensive model for testplanning in a core-based environment. The main contributionof this work is the use of several types of TAMs and theconsideration of different optimization factors (area, pinsand test time) during the global TAM and test schedule definition.This expansion of concerns makes possible an efficientyet fine-grained search in the huge design space ofa reuse-based environment.

Erika Cota; Luigi Carro; Marcelo Lubaszewski; Alex Orailoglu

2002-01-01

292

Accurate, scalable and informative design space exploration for large and sophisticated multi-core oriented architectures  

Microsoft Academic Search

Abstract—As microprocessors become more complex, early design space exploration plays an essential role in reducing the time to market and post-silicon surprises. The trend toward multi-\\/many- core processors will result in sophisticated large- scale architecture substrates (e.g. non-uniformly accessed caches interconnected by network-on-chip) that exhibit increasingly complex and heterogeneous behavior. While conventional analytical modeling techniques can be used to efficiently

Chang-Burm Cho; James Poe; Tao Li; Jingling Yuan

2009-01-01

293

New cathode design boron lined proportional counters for neutron area monitoring application  

NASA Astrophysics Data System (ADS)

A new cathode design boron lined proportional counter of 26 mm ID×100 mm sensitive length SS304 cathode has been developed with boron-coated baffles separated by 3 mm spacers inserted in the sensitive volume perpendicular to the axis. The baffles and the spacers were coated with indigenously available 27.7% enriched 10B. The introduction of baffles enhanced the boron coated surface area by a factor of 2.8. Tests in 120 nv thermal neutron flux show that the counter has 0.84 cps/nv thermal neutron sensitivity, which shows enhancement in the sensitivity by a factor of 2.78 due to baffle structure. For comparison standard cylindrical cathode geometry counter coated with 92% enriched 10B on its inner wall with a coating thickness of 0.8 mg/cm2 is developed with same outer dimensions for neutron area monitoring applications. The counter has 1 cps/nv thermal neutron sensitivity. Comparative tests carried out on counters with and without baffle structure show that the baffles enhance the neutron sensitivity and in 2 kR/h gamma background the effect of gamma pile up is similar on both the counters. The variation in cathode internal diameter due to baffle structure gives higher voltage plateau slope (2.8%/10 V) as compared to conventional cylindrical geometry counter (1.2%/10 V). The usability of boron lined counters for neutron area monitoring applications for the cylindrical geometry counter has been studied.

Dighe, Priyamvada M.

2007-06-01

294

Design and verification of the shielding around the new Neutron Standards Laboratory (LPN) at CIEMAT.  

PubMed

The construction of the new Neutron Standards Laboratory at CIEMAT (Laboratorio de Patrones Neutrónicos) has been finalised and is ready to provide service. The facility is an ?8 m×8 m×8 m irradiation vault, following the International Organization for Standardization 8529 recommendations. It relies on several neutron sources: a 5-GBq (5.8× 10(8) s(-1)) (252)Cf source and two (241)Am-Be neutron sources (185 and 11.1 GBq). The irradiation point is located 4 m over the ground level and in the geometrical centre of the room. Each neutron source can be moved remotely from its storage position inside a water pool to the irradiation point. Prior to this, an important task to design the neutron shielding and to choose the most appropriate materials has been developed by the Radiological Security Unit and the Ionizing Radiations Metrology Laboratory. MCNPX was chosen to simulate the irradiation facility. With this information the walls were built with a thickness of 125 cm. Special attention was put on the weak points (main door, air conditioning system, etc.) so that the ambient dose outside the facility was below the regulatory limits. Finally, the Radiation Protection Unit carried out a set of measurements in specific points around the installation with an LB6411 neutron monitor and a Reuter-Stokes high-pressure ion chamber to verify experimentally the results of the simulation. PMID:24478306

Méndez-Villafañe, R; Guerrero, J E; Embid, M; Fernández, R; Grandio, R; Pérez-Cejuela, P; Márquez, J L; Alvarez, F; Ortego, P

2014-10-01

295

Prototypic design of the single-flux-quantum microprocessor, CORE1  

NASA Astrophysics Data System (ADS)

We have designed a prototype of a microprocessor based on single-flux-quantum logic. The microprocessor called CORE1 has seven instructions and represents the simplest implementation of our CORE (complexity-reduced) architecture concept. Both instructions and data are 8-bit-wide, bit-serial, and their bit operations are performed with 16 GHz local clocks. The microprocessor is composed of a controller, a 5-bit program counter, an 8-bit instruction register, two 8-bit registers and a bit-serial ALU. We put together these components and some substitute shift registers for a memory into one microprocessor made up of 1301 cells, 4999 Josephson junctions. Using floor plans, both block-level and cell-level simulation techniques, we completed the timing design of all signal lines between the components. The designed CORE1 chip executes each instruction in six system clocks and we estimated its performance and power consumption at 167 million instructions per second and 1.6 mW, respectively.

Tanaka, M.; Matsuzaki, F.; Kondo, T.; Nakajima, N.; Yamanashi, Y.; Terai, H.; Yorozu, S.; Yoshikawa, N.; Fujimaki, A.; Hayakawa, H.

2003-12-01

296

A CONCEPTUAL DESIGN STUDY OF SUPERCONDUCTING PROTON LINEAR ACCELERATOR FOR NEUTRON SCIENCE PROJECT  

Microsoft Academic Search

The Neutron Science Project (NSP) at Japan Atomic Energy Research Institute (JAERI) calls for an 8MW cw and pulsed proton linac. The current JAERI design proposes a superconducting proton linac for the energy range from 100MeV to 1.5GeV. Here, the present linac structure and the beam simulation are described.

Y. Honda; K. Hasegawa; N. Ouchi; J. Kusano; M. Mizumoto

297

Lunar in-core thermionic nuclear reactor power system conceptual design  

NASA Technical Reports Server (NTRS)

This paper presents a conceptual design of a lunar in-core thermionic reactor power system. The concept consists of a thermionic reactor located in a lunar excavation with surface mounted waste heat radiators. The system was integrated with a proposed lunar base concept representative of recent NASA Space Exploration Initiative studies. The reference mission is a permanently-inhabited lunar base requiring a 550 kWe, 7 year life central power station. Performance parameters and assumptions were based on the Thermionic Fuel Element (TFE) Verification Program. Five design cases were analyzed ranging from conservative to advanced. The cases were selected to provide sensitivity effects on the achievement of TFE program goals.

Mason, Lee S.; Schmitz, Paul C.; Gallup, Donald R.

1991-01-01

298

Design and simulation of a neutron source based on an electron linear accelerator for BNCT of skin melanoma.  

PubMed

The PNS project is devoted to the design and simulation of a Photo-Neutron Source for BNCT using a Varian 2300C/D electron accelerator. This paper describes the production of the high-energy gamma-rays followed by neutron production in (gamma,n) reaction. To optimize the whole setup and maximize the neutron flux, the FLUKA code is employed to simulate the system. The results show the neutron flux creation in the order of 10?(n/cm² s) with a neutron spectrum that is practical for superficial cancers treatment using BNCT. PMID:21334211

Pazirandeh, Ali; Torkamani, Ali; Taheri, Ali

2011-05-01

299

Nuclear safety analyses and core design calculations to convert the Texas A & M University Nuclear Science Center reactor to low enrichment uranium fuel. Final report  

SciTech Connect

This project involved performing the nuclear design and safety analyses needed to modify the license issued by the Nuclear Regulatory Commission to allow operation of the Texas A& M University Nuclear Science Center Reactor (NSCR) with a core containing low enrichment uranium (LEU) fuel. The specific type of LEU fuel to be considered was the TRIGA 20-20 fuel produced by General Atomic. Computer codes for the neutronic analyses were provided by Argonne National Laboratory (ANL) and the assistance of William Woodruff of ANL in helping the NSCR staff to learn the proper use of the codes is gratefully acknowledged. The codes applied in the LEU analyses were WIMSd4/m, DIF3D, NCTRIGA and PARET. These codes allowed full three dimensional, temperature and burnup dependent calculations modelling the NSCR core to be performed for the first time. In addition, temperature coefficients of reactivity and pulsing calculations were carried out in-house, whereas in the past this modelling had been performed at General Atomic. In order to benchmark the newly acquired codes, modelling of the current NSCR core with highly enriched uranium fuel was also carried out. Calculated results were compared to both earlier licensing calculations and experimental data and the new methods were found to achieve excellent agreement with both. Therefore, even if an LEU core is never loaded at the NSCR, this project has resulted in a significant improvement in the nuclear safety analysis capabilities established and maintained at the NSCR.

Parish, T.A.

1995-03-02

300

Design and performance of a pulse transformer based on Fe-based nanocrystalline core.  

PubMed

A dry-type pulse transformer based on Fe-based nanocrystalline core with a load of 0.88 nF, output voltage of more than 65 kV, and winding ratio of 46 is designed and constructed. The dynamic characteristics of Fe-based nanocrystalline core under the impulse with the pulse width of several microseconds were studied. The pulse width and incremental flux density have an important effect on the pulse permeability, so the pulse permeability is measured under a certain pulse width and incremental flux density. The minimal volume of the toroidal pulse transformer core is determined by the coupling coefficient, the capacitors of the resonant charging circuit, incremental flux density, and pulse permeability. The factors of the charging time, ratio, and energy transmission efficiency in the resonant charging circuit based on magnetic core-type pulse transformer are analyzed. Experimental results of the pulse transformer are in good agreement with the theoretical calculation. When the primary capacitor is 3.17 ?F and charge voltage is 1.8 kV, a voltage across the secondary capacitor of 0.88 nF with peak value of 68.5 kV, rise time (10%-90%) of 1.80 ?s is obtained. PMID:21895262

Yi, Liu; Xibo, Feng; Lin, Fuchang

2011-08-01

301

Physics Analyses in the Design of the HFIR Cold Neutron Source  

SciTech Connect

Physics analyses have been performed to characterize the performance of the cold neutron source to be installed in the High Flux Isotope Reactor at the Oak Ridge National Laboratory in the near future. This paper provides a description of the physics models developed, and the resulting analyses that have been performed to support the design of the cold source. These analyses have provided important parametric performance information, such as cold neutron brightness down the beam tube and the various component heat loads, that have been used to develop the reference cold source concept.

Bucholz, J.A.

1999-09-27

302

Design of a neutron converter for fission studies at the IGISOL facility  

NASA Astrophysics Data System (ADS)

The upgraded IGISOL facility with JYFLTRAP, at the accelerator laboratory of the University of Jyväskylä, has been supplied with a new cyclotron which will provide proton or deuteron beams of the order of 100 ?A with up to 30 MeV energy. This makes it an ideal place for measurements of neutron-induced fission fragments from various actinides, in view of proposed future nuclear fuel cycles. In the present paper, some considerations for the design of a neutron converter, based on simulations with the Monte Carlo codes MCNPX and FLUKA, are described.

Lantz, M.; Gorelov, D.; Mattera, A.; Penttilä, H.; Pomp, S.; Rados, D.; Ryzhov, I.; the IGISOL Group

2012-10-01

303

The reversed-field-pinch (RFP) fusion neutron source: A conceptual design  

SciTech Connect

The conceptual design of an ohmically heated, reversed-field pinch (RFP) operating at /approximately/5-MW/m/sup 2/ steady-state DT fusion neutron wall loading and /approximately/124-MW total fusion power is presented. These results are useful in projecting the development of a cost effective, low input power (/approximately/206 MW) source of DT neutrons for large-volume (/approximately/10 m/sup 3/), high-fluence (3.4 MW yr/m/sup 2/) fusion nuclear materials and technology testing. 19 refs., 15 figs., 9 tabs.

Bathke, C.G.; Krakowski, R.A.; Miller, R.L.; Werley, K.A.

1989-01-01

304

Design of bus-on-chip core for micro-satellite avionics  

NASA Astrophysics Data System (ADS)

This paper discusses a layout of bus-on-chip core referring to SoC thinking which is composed of six sections based on a physical chip of FPGA: multi-Processor cache coherence unit, external bus control module, TT&C module, Ethernet Mac interface, EDAC/DMA module, and AMBA bridges. Multi-processor cache coherence unit, as a key part of the bus core, is used to serve the rapid parallel computing by means of the breakthrough of write/read speed of EMS memory and enhances the reliability of OBC with the service of supporting the hot standby of redundancy and the reconfiguration of fault-tolerance. External bus control module is made to support the PnP of external components applying varieties of buses, which is designed by means of soft-core in order to adapt the variation of macro-design and improve the flexibility of external application. TT&C module is the interface of subsystems of telemetry, telecommand and communication, which involves the protocols of HDLC. Ethernet Mac interface based on TCP/IP acts as the access of ISL for formation flying, constellation, etc. EDAC/DMA module mainly manages the data exchange between AMBA bus and RAM, and assigns DMA for the payloads.

Liu, Youjun; You, Zheng; Li, Bin; Zhang, Xiangqi; Meng, Ziyang

2007-11-01

305

Design of the radiation shielding for the time of flight enhanced diagnostics neutron spectrometer at Experimental Advanced Superconducting Tokamaka)  

NASA Astrophysics Data System (ADS)

A radiation shielding has been designed to reduce scattered neutrons and background gamma-rays for the new double-ring Time Of Flight Enhanced Diagnostics (TOFED). The shielding was designed based on simulation with the Monte Carlo code MCNP5. Dedicated model of the EAST tokamak has been developed together with the emission neutron source profile and spectrum; the latter were simulated with the Nubeam and GENESIS codes. Significant reduction of background radiation at the detector can be achieved and this satisfies the requirement of TOFED. The intensities of the scattered and direct neutrons in the line of sight of the TOFED neutron spectrometer at EAST are studied for future data interpretation.

Du, T. F.; Chen, Z. J.; Peng, X. Y.; Yuan, X.; Zhang, X.; Gorini, G.; Nocente, M.; Tardocchi, M.; Hu, Z. M.; Cui, Z. Q.; Xie, X. F.; Ge, L. J.; Hu, L. Q.; Zhong, G. Q.; Lin, S. Y.; Wan, B. N.; Li, X. Q.; Zhang, G. H.; Chen, J. X.; Fan, T. S.

2014-11-01

306

Design of a boiling water reactor equilibrium core using thorium-uranium fuel  

SciTech Connect

In this paper the design of a Boiling Water Reactor (BWR) equilibrium core using thorium is presented; a heterogeneous blanket-seed core arrangement concept was adopted. The design was developed in three steps: in the first step two different assemblies were designed based on the integrated blanket-seed concept, they are the blanket-dummy assembly and the blanket-seed assembly. The integrated blanketseed concept comes from the fact that the blanket and the seed rods are located in the same assembly, and are burned-out in a once-through cycle. In the second step, a core design was developed to achieve an equilibrium cycle of 365 effective full power days in a standard BWR with a reload of 104 fuel assemblies designed with an average 235U enrichment of 7.5 w/o in the seed sub-lattice. The main operating parameters, like power, linear heat generation rate and void distributions were obtained as well as the shutdown margin. It was observed that the analyzed parameters behave like those obtained in a standard BWR. The shutdown margin design criterion was fulfilled by addition of a burnable poison region in the assembly. In the third step an in-house code was developed to evaluate the thorium equilibrium core under transient conditions. A stability analysis was also performed. Regarding the stability analysis, five operational states were analyzed; four of them define the traditional instability region corner of the power-flow map and the fifth one is the operational state for the full power condition. The frequency and the boiling length were calculated for each operational state. The frequency of the analyzed operational states was similar to that reported for BWRs; these are close to the unstable region that occurs due to the density wave oscillation phenomena in some nuclear power plants. Four transient analyses were also performed: manual SCRAM, recirculation pumps trip, main steam isolation valves closure and loss of feed water. The results of these transients are similar to those obtained with the traditional UO2 nuclear fuel.

Francois, J-L.; Nunez-Carrera, A.; Espinosa-Paredes, G.; Martin-del-Campo, C.

2004-10-06

307

Effect of photobleaching on radiation-induced transmission loss of fused-silica-core optical fibres under gamma-ray and 14 MeV neutron irradiation  

Microsoft Academic Search

The effect of photobleaching on radiation-induced transmission loss of fused-silica-core optical fibres was examined under 60Co gamma-ray and 14 MeV neutron irradiation. In the visible wavelength range, the radiation-induced transmission loss could be reduced by photobleaching under both types of irradiation. It is considered that the number of radiation-induced defects such as E' centre and NBOHC that cause optical absorption

K. Toh; T. Shikama; S. Nagata; B. Tsuchiya; M. Yamauchi; T. Nishitani

2006-01-01

308

Photobleaching effect on gamma-ray and 14 MeV fast neutron induced transmission loss of fused silica core optical fiber  

Microsoft Academic Search

A photo-bleaching effect on radiation-induced transmission loss of fused silica core optical fibers was examined under 60Co gamma-ray and 14 MeV fast neutron irradiation. In the visible wavelength range, radiation induced loss could be reduced by the photo-bleaching under the both irradiation. For using optical fibers in visible wavelength range such as a light guide and an image guide, the

K. Toh; T. Shikama; S. Nagata; Bun Tsuchiya; M. Yamauchi; T. Nishitani

2005-01-01

309

Design of the neutron imaging pinhole for use at the national ignition facility  

SciTech Connect

The Neutron Imaging (NI) diagnostic is designed to be used at the National Ignition Facility (NIF). This instrument will be used to image both primary (14MeV neutrons) and down scattered (6-8MeV neutrons). The pinhole body sits 225mm from the target, while the scintillator and recording systems are located 28m from the target. The diagnostic uses port 90, 315 and the recording system is located in a specifically built room located outside of switchyard I. The location of the pinhole and the recording system combine to give a magnification of 104. The recording of both the primary and downscattered image is done by recording the image from both the front and back side of the scintillator.

Fatherley, Valerie E [Los Alamos National Laboratory; Day, Robert D [Los Alamos National Laboratory; Garcia, Felix P [Los Alamos National Laboratory; Grim, Gary P [Los Alamos National Laboratory; Oertel, John A [Los Alamos National Laboratory; Wilde, Carl H [Los Alamos National Laboratory; Wilke, Mark D [Los Alamos National Laboratory

2010-01-01

310

Efficient Design and Analysis of Lightweight Reinforced Core Sandwich and PRSEUS Structures  

NASA Technical Reports Server (NTRS)

Design, analysis, and sizing methods for two novel structural panel concepts have been developed and incorporated into the HyperSizer Structural Sizing Software. Reinforced Core Sandwich (RCS) panels consist of a foam core with reinforcing composite webs connecting composite facesheets. Boeing s Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) panels use a pultruded unidirectional composite rod to provide axial stiffness along with integrated transverse frames and stitching. Both of these structural concepts are ovencured and have shown great promise applications in lightweight structures, but have suffered from the lack of efficient sizing capabilities similar to those that exist for honeycomb sandwich, foam sandwich, hat stiffened, and other, more traditional concepts. Now, with accurate design methods for RCS and PRSEUS panels available in HyperSizer, these concepts can be traded and used in designs as is done with the more traditional structural concepts. The methods developed to enable sizing of RCS and PRSEUS are outlined, as are results showing the validity and utility of the methods. Applications include several large NASA heavy lift launch vehicle structures.

Bednarcyk, Brett A.; Yarrington, Phillip W.; Lucking, Ryan C.; Collier, Craig S.; Ainsworth, James J.; Toubia, Elias A.

2012-01-01

311

Neutron imaging with coded sources: design pitfalls and the implementation of a simultaneous iterative reconstruction technique  

NASA Astrophysics Data System (ADS)

The limitations in neutron flux and resolution (1/D) of current neutron imaging systems can be addressed with a Coded Source Imaging system with magnification (xCSI). More precisely, the multiple sources in an xCSI system can exceed the flux of a single pinhole system for several orders of magnitude, while maintaining a higher 1 / D with the small sources. Moreover, designing for an xCSI system reduces noise from neutron scattering, because the object is placed away from the detector to achieve magnification. However, xCSI systems are adversely affected by correlated noise such as non-uniform illumination of the neutron source, incorrect sampling of the coded radiograph, misalignment of the coded masks, mask transparency, and the imperfection of the system Point Spread Function (PSF). We argue that a model-based reconstruction algorithm can overcome these problems and describe the implementation of a Simultaneous Iterative Reconstruction Technique algorithm for coded sources. Design pitfalls that preclude a satisfactory reconstruction are documented.

Santos-Villalobos, Hector J.; Bingham, Philip R.; Gregor, Jens

2013-02-01

312

A new MCNPX PTRAC coincidence capture file capability: a tool for neutron detector design  

SciTech Connect

The existing Monte Carlo N-Particle (MCNPX) particle tracking (PTRAC) coincidence capture file allows a full list of neutron capture events to be recorded in any simulated detection medium. The originating event history number (e.g. spontaneous fission events), capture time, location and source particle number are tracked and output to file for post-processing. We have developed a new MCNPX PTRAC coincidence capture file capability to aid detector design studies. New features include the ability to track the nuclides that emitted the detected neutrons as well as induced fission chains in mixed samples before detection (both generation number and nuclide that underwent induced fission). Here, the power of this tool is demonstrated using a detector design developed for the non-destructive assay (NDA) of spent nuclear fuel. Individual capture time distributions have been generated for neutrons originating from Curium-244 source spontaneous fission events and induced fission events in fissile nuclides of interest: namely Plutonium-239, Plutonium-241, and Uranium-235. Through this capability, a full picture for the attribution of neutron capture events in the detector can be simulated.

Evans, Louise G [Los Alamos National Laboratory; Schear, Melissa A [Los Alamos National Laboratory; Hendricks, John S [Los Alamos National Laboratory; Swinhoe, Martyn T [Los Alamos National Laboratory; Tobin, Stephen J [Los Alamos National Laboratory; Croft, Stephen [Los Alamos National Laboratory

2011-02-16

313

Design, development and characterization of a novel neutron and x-ray combined computed tomography system  

NASA Astrophysics Data System (ADS)

Visualizing the three dimensional structure of objects (e.g. nuclear fuel, nuclear materials, explosives and bio materials) and phenomena (e.g. particle tracking) can be very important in nondestructive testing applications. Computed tomography systems are indispensable tools for these types of applications because they provide a versatile non-destructive technique for analysis. A novel neutron and X-ray combined computed tomography (NXCT) system has been designed and developed at the Missouri University of Science & Technology. The neutron and X-ray combined computed tomography system holds much promise for non-destructive material detection and analysis where multiple materials having similar atomic number and differing thermal cross section or vice versa may be present within an object, exclusive neutron or X-ray analysis may exhibit shortcomings in distinguishing interfaces. However, fusing neutron image and X-ray image offers the strengths of both and may provide a superior method of analysis. In addition, a feasible design of a sample positioning system which allows the user to remotely and automatically manipulate the objects makes the NXCT system viable for commercial applications. Moreover, characterization of the newly developed digital imaging system is imperative to the performance evaluation, as well as for describing the associated parameters. The performance of a combined neutron/X-ray digital imaging system was evaluated in terms of modulation transfer function (MTF), noise power spectrum (NPS) and detective quantum efficiency (DQE). This dissertation is a complete overview of the design of the NXCT system, operation, algorithms, performance evaluation and results.

Sinha, Vaibhav

314

Analysis of Process Parameters Affecting Spray-Dried Oily Core Nanocapsules Using Factorial Design  

Microsoft Academic Search

The purpose of this work was to optimize the process parameters required for the production of spray-dried oily core nanocapsules\\u000a (NCs) with targeted size and drug yield using a two-level four-factor fractional factorial experimental design (FFED). The\\u000a coded process parameters chosen were inlet temperature (X\\u000a 1), feed flow rate (X\\u000a 2), atomizing air flow (X\\u000a 3), and aspiration rate (X

Tao Zhang; Bi-Botti C. Youan

2010-01-01

315

Fuel performance models for high-temperature gas-cooled reactor core design  

SciTech Connect

Mechanistic fuel performance models are used in high-temperature gas-cooled reactor core design and licensing to predict failure and fission product release. Fuel particles manufactured with defective or missing SiC, IPyC, or fuel dispersion in the buffer fail at a level of less than 5 x 10/sup -4/ fraction. These failed particles primarily release metallic fission products because the OPyC remains intact on 90% of the particles and retains gaseous isotopes. The predicted failure of particles using performance models appears to be conservative relative to operating reactor experience.

Stansfield, O.M.; Simon, W.A.; Baxter, A.M.

1983-09-01

316

Gigawatt, Closed Cycle, Vapor Core-Mhd Space Power System Conceptual Design Study  

NASA Astrophysics Data System (ADS)

A conceptual design study for a closed cycle gigawatt electric space power system has been conducted. The closed cycle static operation reduces power system interaction effects upon the space craft. This system utilizes a very high temperature (5500 K) plasma core reactor and a magnetohydrodynamic (MHD) power conversion subsystem to provide a power density of about 8 kWe/kg (0.13 kg/kWe) for several kilo-seconds. Uranium vapor is the fuel. Candidate working fluids are metal vapors such as lithium or calcium. The system is based on a Rankine cycle to minimize the electromagnetic pumping power requirement. The fission fragment induced nonequilibrium ionization in the plasma in the MHD power duct provides the plasma electric conductivity for gigawatt power generation. Waste heat is rejected utilizing lithium heat pipes at temperatures just below 2000 K, thus minimizing the radiator area requirement. Key technology issues are identified, including the containment of the 5500 K 'sun-liken plasma at 4 to 0 MPa In a reflector moderated, gas/vapor filled cavity core reactor. A promising scheme to protect the refractory metal reactor inner wall is presented, together with a heating load analysis in the wall. This scheme utilizes an ablating film of liquid lithium/calcium that evaporates into the cavity core to become the working fluid of the cycle.

Wetch, Joseph R.; Rhee, Hyop S.; Koester, J. Kent; Goodman, Julius; Maya, Issac

1988-04-01

317

Design progress of cryogenic hydrogen system for China Spallation Neutron Source  

NASA Astrophysics Data System (ADS)

China Spallation Neutron Source (CSNS) is a large proton accelerator research facility with 100 kW beam power. Construction started in October 2011 and is expected to last 6.5 years. The cryogenic hydrogen circulation is cooled by a helium refrigerator with cooling capacity of 2200 W at 20 K and provides supercritical hydrogen to neutron moderating system. Important progresses of CSNS cryogenic system were concluded as follows. Firstly, process design of cryogenic system has been completed including helium refrigerator, hydrogen loop, gas distribution, and safety interlock. Secondly, an accumulator prototype was designed to mitigate pressure fluctuation caused by dynamic heat load from neutron moderation. Performance test of the accumulator has been carried out at room and liquid nitrogen temperature. Results show the accumulator with welding bellows regulates hydrogen pressure well. Parameters of key equipment have been identified. The contract for the helium refrigerator has been signed. Mechanical design of the hydrogen cold box has been completed, and the hydrogen pump, ortho-para hydrogen convertor, helium-hydrogen heat exchanger, hydrogen heater, and cryogenic valves are in procurement. Finally, Hydrogen safety interlock has been finished as well, including the logic of gas distribution, vacuum, hydrogen leakage and ventilation. Generally, design and construction of CSNS cryogenic system is conducted as expected.

Wang, G. P.; Zhang, Y.; Xiao, J.; He, C. C.; Ding, M. Y.; Wang, Y. Q.; Li, N.; He, K.

2014-01-01

318

Common Core State Standards for Mathematics. Appendix A: Designing High School Mathematics Courses Based on the Common Core State Standards  

ERIC Educational Resources Information Center

The Common Core State Standards (CCSS) for Mathematics are organized by grade level in Grades K-8. At the high school level, the standards are organized by conceptual category (number and quantity, algebra, functions, geometry, modeling and probability and statistics), showing the body of knowledge students should learn in each category to be…

Common Core State Standards Initiative, 2011

2011-01-01

319

Design of dual core resonant leaky fiber for inherent gain flattening of S-band EDFA  

NASA Astrophysics Data System (ADS)

We present a novel co-axial dual core resonant leaky fiber (DCRLF) design for inherent gain equalization of S-band erbium doped fiber amplifier (EDFA). Spectral leakage loss variation of the structure has been utilized to suppress the amplified spontaneous emission (ASE) in the C-band and to achieve inherent gain flattening in the S-band of an EDFA. We show 19 dB flat gain with +/- 1.1 dB ripple over 30 nm bandwidth (1490-1520 nm) and 20 dB flat gain with +/- 2.1 dB ripple over 40 nm bandwidth (1485-1525 nm). We have also carried out a detailed tolerance study of the designed Sband EDFA with respect to the outer cladding parameters.

Kamakshi, Koppole; Rastogi, Vipul

2011-05-01

320

Reactor core design and modeling of the MIT research reactor for conversion to LEU  

SciTech Connect

Feasibility design studies for conversion of the MIT Research Reactor (MITR) to LEU are described. Because the reactor fuel has a rhombic cross section, a special input processor was created in order to model the reactor in great detail with the REBUS-PC diffusion theory code, in 3D (triangular-z) geometry. Comparisons are made of fuel assembly power distributions and control blade worth vs. axial position, between REBUS-PC results and Monte Carlo predictions from the MCNP code. Results for the original HEU core at zero burnup are also compared with measurement. These two analysis methods showed remarkable agreement. Ongoing fuel cycle studies are summarized. A status report will be given as to results thus far that affect key design decisions. Future work plans and schedules to achieve completion of the conversion are presented. (author)

Newton, Thomas H. Jr. [Nuclear Reactor Laboratory, Massachusetts Institute of Technology, 138 Albany St., Cambridge, MA 02139 (United States); Olson, Arne P.; Stillman, John A. [RERTR Program, Argonne National Laboratory, Argonne, IL 60439 (United States)

2008-07-15

321

Enhancement of REBUS-3/DIF3D for whole-core neutronic analysis of prismatic very high temperature reactor (VHTR).  

SciTech Connect

Enhancements have been made to the REBUS-3/DIF3D code suite to facilitate its use for the design and analysis of prismatic Very High Temperature Reactors (VHTRs). A new cross section structure, using table-lookup, has been incorporated to account for cross section changes with burnup and fuel and moderator temperatures. For representing these cross section dependencies, three new modules have been developed using FORTRAN 90/95 object-oriented data structures and implemented within the REBUS-3 code system. These modules provide a cross section storage procedure, construct microscopic cross section data for all isotopes, and contain a single block of banded scattering data for efficient data management. Fission products other than I, Xe, Pm, and Sm, can be merged into a single lumped fission product to save storage space, memory, and computing time without sacrificing the REBUS-3 solution accuracy. A simple thermal-hydraulic (thermal-fluid) feedback model has been developed for prismatic VHTR cores and implemented in REBUS-3 for temperature feedback calculations. Axial conduction was neglected in the formulation because of its small magnitude compared to radial (planar) conduction. With the simple model, the average fuel and graphite temperatures are accurately estimated compared to reference STAR-CD results. The feedback module is currently operational for the non-equilibrium fuel cycle analysis option of REBUS-3. Future work should include the extension of this capability to the equilibrium cycle option of the code and additional verification of the feedback module. For the simulation of control rods in VHTR cores, macroscopic cross section deviations (deltas) have been defined to account for the effect of control rod insertion. The REBUS-3 code has been modified to use the appropriately revised cross sections when control rods are inserted in a calculation node. In order to represent asymmetric core blocks (e.g., fuel blocks or reflector blocks containing asymmetric absorber rods), surface-dependent discontinuity factors based on nodal equivalence theory have been introduced into the nodal diffusion theory option of the DIF3D code (DIF3D-nodal) to improve modeling accuracy. Additionally, the discontinuity factors based on the Simplified Equivalence Theory (SET) have been incorporated as an alternative and may be employed for both the DIF3D-nodal and DIF3D-VARIANT (nodal transport) solution options. Two- and three-dimensional core calculations have been performed using the routines developed and modified in this work, along with cross sections generated from single fuel block and one-dimensional or two-dimensional fuel-reflector model. Generally, REBUS-3/DIF3D results for the core multiplication factor and power distribution are found to be in good agreement with reference results (generated with MCNP continuous energy calculations) particularly when discontinuity factors are applied. The DIF3D-VARIANT option was found to provide a more accurate solution in its diffusion approximation than the DIF3D-nodal option. Control rod worths can be estimated with acceptably small errors compared to MCNP results. However, estimation of the core power tilt needs to be improved by introducing the surface-dependent discontinuity factor capability in DIF3D-VARIANT.

Lee, C. H.; Zhong, Z.; Taiwo, T.A.; Yang, W.S.; Khalil, H.S.; Smith, M.A.; Nuclear Engineering Division

2006-10-13

322

Small Launch Vehicle Design Approaches: Clustered Cores Compared with Multi-Stage Inline Concepts  

NASA Technical Reports Server (NTRS)

In an effort to better define small launch vehicle design options two approaches were investigated from the small launch vehicle trade space. The primary focus was to evaluate a clustered common core design against a purpose built inline vehicle. Both designs focused on liquid oxygen (LOX) and rocket propellant grade kerosene (RP-1) stages with the terminal stage later evaluated as a LOX/methane (CH4) stage. A series of performance optimization runs were done in order to minimize gross liftoff weight (GLOW) including alternative thrust levels, delivery altitude for payload, vehicle length to diameter ratio, alternative engine feed systems, re-evaluation of mass growth allowances, passive versus active guidance systems, and rail and tower launch methods. Additionally manufacturability, cost, and operations also play a large role in the benefits and detriments for each design. Presented here is the Advanced Concepts Office's Earth to Orbit Launch Team methodology and high level discussion of the performance trades and trends of both small launch vehicle solutions along with design philosophies that shaped both concepts. Without putting forth a decree stating one approach is better than the other; this discussion is meant to educate the community at large and let the reader determine which architecture is truly the most economical; since each path has such a unique set of limitations and potential payoffs.

Waters, Eric D.; Beers, Benjamin; Esther, Elizabeth; Philips, Alan; Threet, Grady E., Jr.

2013-01-01

323

Shielding analysis and design of the KIPT experimental neutron source facility of Ukraine.  

SciTech Connect

Argonne National Laboratory (ANL) of USA and Kharkov Institute of Physics and Technology (KIPT) of Ukraine have been collaborating on the conceptual design development of an experimental neutron source facility based on the use of an electron accelerator driven subcritical (ADS) facility [1]. The facility uses the existing electron accelerators of KIPT in Ukraine. The neutron source of the sub-critical assembly is generated from the interaction of 100 KW electron beam with a natural uranium target. The electron beam has a uniform spatial distribution and the electron energy in the range of 100 to 200 MeV, [2]. The main functions of the facility are the production of medical isotopes and the support of the Ukraine nuclear power industry. Reactor physics experiments and material performance characterization will also be carried out. The subcritical assembly is driven by neutrons generated by the electron beam interactions with the target material. A fraction of these neutrons has an energy above 50 MeV generated through the photo nuclear interactions. This neutron fraction is very small and it has an insignificant contribution to the subcritical assembly performance. However, these high energy neutrons are difficult to shield and they can be slowed down only through the inelastic scattering with heavy isotopes. Therefore the shielding design of this facility is more challenging relative to fission reactors. To attenuate these high energy neutrons, heavy metals (tungsten, iron, etc.) should be used. To reduce the construction cost, heavy concrete with 4.8 g/cm{sup 3} density is selected as a shielding material. The iron weight fraction in this concrete is about 0.6. The shape and thickness of the heavy concrete shield are defined to reduce the biological dose equivalent outside the shield to an acceptable level during operation. At the same time, special attention was give to reduce the total shield mass to reduce the construction cost. The shield design is configured to maintain the biological dose equivalent during operation {le} 0.5 mrem/h inside the subcritical hall, which is five times less than the allowable dose for working forty hours per week for 50 weeks per year. This study analyzed and designed the thickness and the shape of the radial and top shields of the neutron source based on the biological dose equivalent requirements inside the subcritical hall during operation. The Monte Carlo code MCNPX is selected because of its capabilities for transporting electrons, photons, and neutrons. Mesh based weight windows variance reduction technique is utilized to estimate the biological dose outside the shield with good statistics. A significant effort dedicated to the accurate prediction of the biological dose equivalent outside the shield boundary as a function of the shield thickness without geometrical approximations or material homogenization. The building wall was designed with ordinary concrete to reduce the biological dose equivalent to the public with a safety factor in the range of 5 to 20.

Zhong, Z.; Gohar, M. Y. A.; Naberezhnev, D.; Duo, J.; Nuclear Engineering Division

2008-10-31

324

Design of a backscatter 14-MeV neutron time-of-flight spectrometer for experiments at ITER  

NASA Astrophysics Data System (ADS)

Neutron energy spectrometry diagnostics play an important role in present-day experiments related to fusion energy research. Measurements and thorough analysis of the neutron emission from the fusion plasma give information on a number of basic fusion performance quantities, on the condition of the neutron source and plasma behavior. Here we discuss the backscatter Time-of-Flight (bTOF) spectrometer concept as a possible instrument for performing high resolution measurements of 14 MeV neutrons. The instrument is based on two sets of scintillators, a first scatterer exposed to a collimated neutron beam and a second detector set placed in the backward direction. The scintillators of the first set are enriched in deuterium to achieve neutron backscattering. The energy resolution and efficiency of a bTOF instrument have been determined for various geometrical configurations. A preliminary design of optimal geometry for the two scintillator sets has been obtained by Monte Carlo simulations based on the MCNPX code.

Dzysiuk, N.; Hellesen, C.; Conroy, S.; Ericsson, G.; Hjalmarsson, A.; Skiba, M.

2014-08-01

325

Design and performance of horizontal-type neutron reflectometer SOFIA at J-PARC/MLF  

NASA Astrophysics Data System (ADS)

Neutron reflectometry is a powerful method for investigating the surface and interfacial structures of materials in the spatial range from nanometers to sub-micrometers. At the Japan Proton Accelerator Research Complex (J-PARC), a high-intensity pulsed neutron beam is produced with a proton accelerator at 220kW, which will be upgraded to 1MW in future. Beamline 16 (BL16) at the Materials and Life Science Experimental Facility (MLF) in J-PARC is dedicated to a horizontal-type reflectometer, and in this beamline, neutrons are transported downward at two different angles, 2.2° and 5.7° , relative to the horizontal. In December 2008, we started to accept the neutron beam at BL16 with the old ARISA reflectometer relocated from the KENS facility, KEK, Japan; and we have now replaced it with the brand-new reflectometer SOFIA (SOFt Interface Analyzer). With a high-flux beam and instrumental upgrade, the observable reflectivity of SOFIA reaches around 10-7 within a few hours for specimens on 3" substrates. In this paper, we will present the design and performance of the SOFIA reflectometer, and discuss some preliminary results on the device development for further upgrade.

Yamada, N. L.; Torikai, N.; Mitamura, K.; Sagehashi, H.; Sato, S.; Seto, H.; Sugita, T.; Goko, S.; Furusaka, M.; Oda, T.; Hino, M.; Fujiwara, T.; Takahashi, H.; Takahara, A.

2011-11-01

326

Rotatable multifunctional load frames for neutron diffractometers at FRM II—design, specifications and applications  

NASA Astrophysics Data System (ADS)

Novel tensile rigs have been designed and manufactured at the research reactor Heinz Maier-Leibnitz (FRM II, Garching near Munich). Besides tensile and compressive stress, also torsion can be applied. The unique Eulerian cradle type design (?, ?, and ? axis) allows orienting the stress axis with respect to the scattering vector. Applications of these tensile rigs at our neutron diffractometers enable various investigations of structural changes under mechanical load, e.g. crystallographic texture evolution, stress-induced phase transformations or lattice expansion, and the anisotropy of mechanical response.

Hoelzel, M.; Gan, W. M.; Hofmann, M.; Randau, C.; Seidl, G.; Jüttner, Ph.; Schmahl, W. W.

2013-05-01

327

Optimal design at inner core of the shaped pyramidal truss structure  

SciTech Connect

Sandwich material is a type of composite material with lightweight, high strength, good dynamic properties and high bending stiffness-to-weight ratio. This can be found well such structures in the nature (for example, internal structure of bones, plants, etc.). New trend which prefers eco-friendly products and energy efficiency is emerging in industries recently. Demand for materials with high strength and light weight is also increasing. In line with these trends, researches about manufacturing methods of sandwich material have been actively conducted. In this study, a sandwich structure named as “Shaped Pyramidal Truss Structure” is proposed to improve mechanical strength and to apply a manufacturing process suitable for massive production. The new sandwich structure was designed to enhance compressive strength by changing the cross-sectional shape at the central portion of the core. As the next step, optimization of the shape was required. Optimization technique used here was the SZGA(Successive Zooming Genetic Algorithm), which is one of GA(Genetic Algorithm) methods gradually reducing the area of design variable. The objective function was defined as moment of inertia of the cross-sectional shape of the strut. The control points of cubic Bezier curve, which was assumed to be the shape of the cross section, were used as design variables. By using FEM simulation, it was found that the structure exhibited superior mechanical properties compared to the simple design of the prior art.

Lee, Sung-Uk; Yang, Dong-Yol [Department of Mechanical Engineering, KAIST 291 Daehak-ro (373-1 Guseong-dong), Yuseong-gu, Dae-jeon, 305-701 (Korea, Republic of)

2013-12-16

328

Design, installation and implementation of a Neutron Depth Profiling facility at the Texas A&M Nuclear Science Center  

E-print Network

DESIGN, INSTALLATION AND IMPLEMENTATION OF A NEUTRON DEPTH PROFILING FACILITY AT THE TEXAS A&M NUCLEAR SCIENCE CENTER A Thesis by NAZIR SABBAR KHALIL Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE August 1989 Major Subject: Nuclear Engineering DESIGN, INSTALLATION AND IMPLEMENTATION OF A NEUTRON DEPTH PROFILING FACILITY AT THE TEXAS A(IM NUCLEAR SCIENCE CENTER A Thesis by NAZIR SABBAR KHALIL...

Khalil, Nazir Sabbar

2012-06-07

329

Dynamic analysis of sandwich panels and topological design of cores considering the size effect  

Microsoft Academic Search

A typical sandwich panel is composed of the upper and lower skins separated by a lightweight core, for instance, foams, trusshoneycombs and corrugated cores (1-4). And each kind of cores has various structural forms. For example, the foam cores have polymer and metallic ones with open-cell and close- cell ones; the truss cores have tetrahedral, pyramidal, 3D Kagome and diamond

K. Qiu; W. Zhang; P. Duysinx

330

America's Next Great Ship: Space Launch System Core Stage Transitioning from Design to Manufacturing  

NASA Technical Reports Server (NTRS)

The Space Launch System (SLS) Program is essential to achieving the Nation's and NASA's goal of human exploration and scientific investigation of the solar system. As a multi-element program with emphasis on safety, affordability, and sustainability, SLS is becoming America's next great ship of exploration. The SLS Core Stage includes avionics, main propulsion system, pressure vessels, thrust vector control, and structures. Boeing manufactures and assembles the SLS core stage at the Michoud Assembly Facility (MAF) in New Orleans, LA, a historical production center for Saturn V and Space Shuttle programs. As the transition from design to manufacturing progresses, the importance of a well-executed manufacturing, assembly, and operation (MA&O) plan is crucial to meeting performance objectives. Boeing employs classic techniques such as critical path analysis and facility requirements definition as well as innovative approaches such as Constraint Based Scheduling (CBS) and Cirtical Chain Project Management (CCPM) theory to provide a comprehensive suite of project management tools to manage the health of the baseline plan on both a macro (overall project) and micro level (factory areas). These tools coordinate data from multiple business systems and provide a robust network to support Material & Capacity Requirements Planning (MRP/CRP) and priorities. Coupled with these tools and a highly skilled workforce, Boeing is orchestrating the parallel buildup of five major sub assemblies throughout the factory. Boeing and NASA are transforming MAF to host state of the art processes, equipment and tooling, the most prominent of which is the Vertical Assembly Center (VAC), the largest weld tool in the world. In concert, a global supply chain is delivering a range of structural elements and component parts necessary to enable an on-time delivery of the integrated Core Stage. SLS is on plan to launch humanity into the next phase of space exploration.

Birkenstock, Benjamin; Kauer, Roy

2014-01-01

331

Design and implementation of a multiaxial loading capability during heating on an engineering neutron diffractometer  

NASA Astrophysics Data System (ADS)

A gripping capability was designed, implemented, and tested for in situ neutron diffraction measurements during multiaxial loading and heating on the VULCAN engineering materials diffractometer at the spallation neutron source at Oak Ridge National Laboratory. The proposed capability allowed for the acquisition of neutron spectra during tension, compression, torsion, and/or complex loading paths at elevated temperatures. The design consisted of age-hardened, Inconel® 718 grips with direct attachment to the existing MTS load frame having axial and torsional capacities of 100 kN and 400 N.m, respectively. Internal cooling passages were incorporated into the gripping system for fast cooling rates during high temperature experiments up to ˜1000 K. The specimen mounting couplers combined a threaded and hexed end-connection for ease of sample installation/removal without introducing any unwanted loads. Instrumentation of this capability is documented in this work along with various performance parameters. The gripping system was utilized to investigate deformation in NiTi shape memory alloys under various loading/control modes (e.g., isothermal, isobaric, and cyclic), and preliminary results are presented. The measurements facilitated the quantification of the texture, internal strain, and phase fraction evolution in NiTi shape memory alloys under various loading/control modes.

Benafan, O.; Padula, S. A.; Skorpenske, H. D.; An, K.; Vaidyanathan, R.

2014-10-01

332

Design and implementation of a multiaxial loading capability during heating on an engineering neutron diffractometer.  

PubMed

A gripping capability was designed, implemented, and tested for in situ neutron diffraction measurements during multiaxial loading and heating on the VULCAN engineering materials diffractometer at the spallation neutron source at Oak Ridge National Laboratory. The proposed capability allowed for the acquisition of neutron spectra during tension, compression, torsion, and/or complex loading paths at elevated temperatures. The design consisted of age-hardened, Inconel(®) 718 grips with direct attachment to the existing MTS load frame having axial and torsional capacities of 100 kN and 400 N·m, respectively. Internal cooling passages were incorporated into the gripping system for fast cooling rates during high temperature experiments up to ?1000 K. The specimen mounting couplers combined a threaded and hexed end-connection for ease of sample installation/removal without introducing any unwanted loads. Instrumentation of this capability is documented in this work along with various performance parameters. The gripping system was utilized to investigate deformation in NiTi shape memory alloys under various loading/control modes (e.g., isothermal, isobaric, and cyclic), and preliminary results are presented. The measurements facilitated the quantification of the texture, internal strain, and phase fraction evolution in NiTi shape memory alloys under various loading/control modes. PMID:25362410

Benafan, O; Padula, S A; Skorpenske, H D; An, K; Vaidyanathan, R

2014-10-01

333

Chemical and colloidal stability of carboxylated core-shell magnetite nanoparticles designed for biomedical applications.  

PubMed

Despite the large efforts to prepare super paramagnetic iron oxide nanoparticles (MNPs) for biomedical applications, the number of FDA or EMA approved formulations is few. It is not known commonly that the approved formulations in many instances have already been withdrawn or discontinued by the producers; at present, hardly any approved formulations are produced and marketed. Literature survey reveals that there is a lack for a commonly accepted physicochemical practice in designing and qualifying formulations before they enter in vitro and in vivo biological testing. Such a standard procedure would exclude inadequate formulations from clinical trials thus improving their outcome. Here we present a straightforward route to assess eligibility of carboxylated MNPs for biomedical tests applied for a series of our core-shell products, i.e., citric acid, gallic acid, poly(acrylic acid) and poly(acrylic acid-co-maleic acid) coated MNPs. The discussion is based on physicochemical studies (carboxylate adsorption/desorption, FTIR-ATR, iron dissolution, zeta potential, particle size, coagulation kinetics and magnetization measurements) and involves in vitro and in vivo tests. Our procedure can serve as an example to construct adequate physico-chemical selection strategies for preparation of other types of core-shell nanoparticles as well. PMID:23857054

Szekeres, Márta; Tóth, Ildikó Y; Illés, Erzsébet; Hajdú, Angéla; Zupkó, István; Farkas, Katalin; Oszlánczi, Gábor; Tiszlavicz, László; Tombácz, Etelka

2013-01-01

334

Chemical and Colloidal Stability of Carboxylated Core-Shell Magnetite Nanoparticles Designed for Biomedical Applications  

PubMed Central

Despite the large efforts to prepare super paramagnetic iron oxide nanoparticles (MNPs) for biomedical applications, the number of FDA or EMA approved formulations is few. It is not known commonly that the approved formulations in many instances have already been withdrawn or discontinued by the producers; at present, hardly any approved formulations are produced and marketed. Literature survey reveals that there is a lack for a commonly accepted physicochemical practice in designing and qualifying formulations before they enter in vitro and in vivo biological testing. Such a standard procedure would exclude inadequate formulations from clinical trials thus improving their outcome. Here we present a straightforward route to assess eligibility of carboxylated MNPs for biomedical tests applied for a series of our core-shell products, i.e., citric acid, gallic acid, poly(acrylic acid) and poly(acrylic acid-co-maleic acid) coated MNPs. The discussion is based on physicochemical studies (carboxylate adsorption/desorption, FTIR-ATR, iron dissolution, zeta potential, particle size, coagulation kinetics and magnetization measurements) and involves in vitro and in vivo tests. Our procedure can serve as an example to construct adequate physico-chemical selection strategies for preparation of other types of core-shell nanoparticles as well. PMID:23857054

Szekeres, Marta; Toth, Ildiko Y.; Illes, Erzsebet; Hajdu, Angela; Zupko, Istvan; Farkas, Katalin; Oszlanczi, Gabor; Tiszlavicz, Laszlo; Tombacz, Etelka

2013-01-01

335

Novel design of dual-core microstructured fiber with enhanced longitudinal strain sensitivity  

NASA Astrophysics Data System (ADS)

Constantly refined technology of manufacturing increasingly complex photonic crystal fibers (PCF) leads to new optical fiber sensor concepts. The ways of enhancing the influence of external factors (such as hydrostatic pressure, temperature, acceleration) on the fiber propagating conditions are commonly investigated in literature. On the other hand longitudinal strain analysis, due to the calculation difficulties caused by the three dimensional computation, are somehow neglected. In this paper we show results of such a 3D numerical simulation and report methods of tuning the fiber strain sensitivity by changing the fiber microstructure and core doping level. Furthermore our approach allows to control whether the modes' effective refractive index is increasing or decreasing with strain, with the possibility of achieving zero strain sensitivity with specific fiber geometries. The presented numerical analysis is compared with experimental results of the fabricated fibers characterization. Basing on the aforementioned methodology we propose a novel dual-core fiber design with significantly increased sensitivity to longitudinal strain for optical fiber sensor applications. Furthermore the reported fiber satisfies all conditions necessary for commercial applications like good mode matching with standard single-mode fiber, low confinement loss and ease of manufacturing with the stack-and-draw technique. Such fiber may serve as an integrated Mach-Zehnder interferometer when highly coherent source is used. With the optimization of single mode transmission to 850 nm, we propose a VCSEL source to be used in order to achieve a low-cost, reliable and compact strain sensing transducer.

Szostkiewicz, Lukasz; Tenderenda, T.; Napierala, M.; Szyma?ski, M.; Murawski, M.; Mergo, P.; Lesiak, P.; Marc, P.; Jaroszewicz, L. R.; Nasilowski, T.

2014-05-01

336

Neutron and Synchrotron Radiation Studies for Designer Materials, Sustainable Energy and Healthy Lives  

NASA Astrophysics Data System (ADS)

Probably the most prolific use of large accelerators today is in the creation of bright beams of x-ray photons or neutrons. The number of scientific users of such sources in the US alone is approaching 10,000. I will describe the some of the major applications of synchrotron and neutron radiation and their impact on society. If you have AIDS, need a better IPOD or a more efficient car, or want to clean up a superfund site, you are benefitting from these accelerators. The design of new materials is becoming more and more dependent on structural information from these sources. I will identify the trends in applications which are demanding new sources with greater capabilities.

Gibson, J. Murray

2009-05-01

337

Thoria-based cermet nuclear fuel : neutronics fuel design and fuel cycle analysis.  

SciTech Connect

Cermet nuclear fuel has been demonstrated to have significant potential to enhance fuel performance because of low internal fuel temperatures and low stored energy. The combination of these benefits with the inherent proliferation resistance, high burnup capability, and favorable neutronic properties of the thorium fuel cycle produces intriguing options for advanced nuclear fuel cycles. This paper describes aspects of a Nuclear Energy Research Initiative (NERI) project with two primary goals: (1) Evaluate the feasibility of implementing the thorium fuel cycle in existing or advanced reactors using a zirconium-matrix cermet fuel, and (2) Develop enabling technologies required for the economic application of this new fuel form. This paper will first describes the fuel thermal performance model developed for the analysis of dispersion metal matrix fuels. The model is then applied to the design and analysis of thorium/uranium/zirconium metal-matrix fuel pins for light-water reactors using neutronic simulation methods.

Downar, T.J.; McDeavitt, S.M.; Revankar, S.T.; Solomon, A.A.; Kim, T.K.

2002-01-09

338

Design and fabrication of an asymmetric twin-core fiber directional coupler for gain-flattened EDFA  

E-print Network

of such an inherently gain flattened EDFA by the MCVD fiber preform fabrication process, the design had to be modified from the two assembled preforms. Preliminary characterization of the fabricated fiber shows filteringDesign and fabrication of an asymmetric twin-core fiber directional coupler for gain-flattened EDFA

Paris-Sud XI, Université de

339

Design and fabrication of an asymmetric twin-core fiber directional coupler for gain-flattened EDFA  

NASA Astrophysics Data System (ADS)

Fiber directional couplers made of highly asymmetric twin-cores (ATC), one of which is doped with erbium, are designed to achieve an inherently gain flattened erbium doped fiber amplifier (EDFA). The refractive index profiles of the fibers as well as the spacing between the two cores were carefully designed to achieve a targeted gain with low gain excursions across the C-band. One of the designs yielded a theoretical median gain ~ 38 dB with an excursion within +/-1 dB. In order to suite fabrication of such an inherently gain flattened EDFA by the MCVD fiber preform fabrication process, the design had to be modified and a more modest target of about 20 dB was set with excursion below +/- 1.5 dB for metro-centric applications. It involved preparation of two independent preforms, which required selective polishing of the cladding from one side by a certain amount to meet the required nominal separation between the two cores set at the design stage of the fiber. Several intricate operations were required to implement the fiber drawing step from the two assembled preforms. Preliminary characterization of the fabricated fiber shows filtering of ASE peak through selective wavelength coupling from Er-doped core to un-doped core.

Nagaraju, B.; Ude, M.; Trzésien, S.; Dussardier, B.; Varshney, R. K.; Monnom, G.; Blanc, W.; Pal, B. P.

2011-12-01

340

Fluence-limited burnup as a function of fast reactor core parameters  

E-print Network

The limiting factor in current designs for fast reactors is not only the reactivity, but also the maximum permissible fast-neutron fluence in the cladding, especially for reduced uranium enrichment cores using high-albedo ...

Kersting, Alyssa (Alyssa Rae)

2011-01-01

341

Parameter Design and Optimal Control of an Open Core Flywheel Energy Storage System  

NASA Technical Reports Server (NTRS)

In low earth orbit (LEO) satellite applications spacecraft power is provided by photovoltaic cells and batteries. To overcome battery shortcomings the University of Maryland, working in cooperation with NASA/GSFC and NASA/LeRC, has developed a magnetically suspended flywheel for energy storage applications. The system is referred to as an Open Core Composite Flywheel (OCCF) energy storage system. Successful application of flywheel energy storage requires integration of several technologies, viz. bearings, rotor design, motor/generator, power conditioning, and system control. In this paper we present a parameter design method which has been developed for analyzing the linear SISO model of the magnetic bearing controller for the OCCF. The objective of this continued research is to principally analyze the magnetic bearing system for nonlinear effects in order to increase the region of stability, as determined by high speed and large air gap control. This is achieved by four tasks: (1) physical modeling, design, prototyping, and testing of an improved magnetically suspended flywheel energy storage system, (2) identification of problems that limit performance and their corresponding solutions, (3) development of a design methodology for magnetic bearings, and (4) design of an optimal controller for future high speed applications. Both nonlinear SISO and MIMO models of the magnetic system were built to study limit cycle oscillations and power amplifier saturation phenomenon observed in experiments. The nonlinear models include the inductance of EM coils, the power amplifier saturation, and the physical limitation of the flywheel movement as discussed earlier. The control program EASY5 is used to study the nonlinear SISO and MIMO models. Our results have shown that the characteristics and frequency responses of the magnetic bearing system obtained from modeling are comparable to those obtained experimentally. Although magnetic saturation is shown in the bearings, there are good correlations between the theoretical model and experimental data. Both simulation and experiment confirm large variations of the magnetic bearing characteristics due to air gap growth. Therefore, the gap growth effect should be considered in the magnetic bearing system design. Additionally, the magnetic bearing control system will be compared to other design methods using not only parameter design but H-infinity optimal control and mu synthesis.

Pang, D.; Anand, D. K.; Kirk, J. A.

1996-01-01

342

On the development of computational tools for the design of beam assemblies for boron neutron capture therapy  

NASA Astrophysics Data System (ADS)

This article is the first in a series devoted to the development of efficient and accurate computational tools for the design of beam assemblies for boron neutron capture therapy within the framework of discrete ordinates spectral nodal methods of neutron transport theory. We begin our study with a multi-layer representation of an assembly, and we derive a discrete ordinates matrix operator that replaces without spatial truncation error the entire multi-layer domain in neutron transmission computations. With the matrix operator derived here, we compute without further ado the angular distribution of neutrons leaving the multi-layer assembly, avoiding thus the use of general-purpose discrete ordinates codes founded in the discretization and numerical solution of the neutron transport equation over a number of spatial cells and angular directions throughout the domain. We perform numerical experiments with a four-layer model assembly, and we conclude this article with a discussion and directions for further developments.

de Abreu, Marcos Pimenta

2007-07-01

343

Design and analysis of a refractive index sensor based on dual-core large-mode-area fiber  

NASA Astrophysics Data System (ADS)

We present a novel co-axial dual core large-mode-area (LMA) fiber design for refractive index sensing. In a dual-core fiber there is resonant coupling between the two cores, which is strongly affected by the refractive index (RI) of the outermost region. The transmittance of the fiber, therefore, varies sharply with the refractive index of surrounding medium. This characteristic of the proposed structure has been utilized to design a RI sensor. We have analyzed the structure by using the transfer matrix method. Our numerical results show that the proposed sensor is highly sensitive with the resolution of 2.0 × 10-6 around nex = 1.44376. Effect of design parameters on sensitivity of the proposed sensor has also been investigated.

Kamakshi, Koppole; Rastogi, Vipul; Kumar, Ajeet

2013-08-01

344

Design Study for a Low-Enriched Uranium Core for the High Flux Isotope Reactor, Annual Report for FY 2006  

SciTech Connect

Neutronics and thermal-hydraulics studies show that, for equivalent operating power [85 MW(t)], a low-enriched uranium (LEU) fuel cycle based on uranium-10 wt % molybdenum (U-10Mo) metal foil with radially, “continuously graded” fuel meat thickness results in a 15% reduction in peak thermal flux in the beryllium reflector of the High Flux Isotope Reactor (HFIR) as compared to the current highly enriched uranium (HEU) cycle. The uranium-235 content of the LEU core is almost twice the amount of the HEU core when the length of the fuel cycle is kept the same for both fuels. Because the uranium-238 content of an LEU core is a factor of 4 greater than the uranium-235 content, the LEU HFIR core would weigh 30% more than the HEU core. A minimum U-10Mo foil thickness of 84 ?m is required to compensate for power peaking in the LEU core although this value could be increased significantly without much penalty. The maximum U-10Mo foil thickness is 457?m. Annual plutonium production from fueling the HFIR with LEU is predicted to be 2 kg. For dispersion fuels, the operating power for HFIR would be reduced considerably below 85 MW due to thermal considerations and due to the requirement of a 26-d fuel cycle. If an acceptable fuel can be developed, it is estimated that $140 M would be required to implement the conversion of the HFIR site at Oak Ridge National Laboratory from an HEU fuel cycle to an LEU fuel cycle. To complete the conversion by fiscal year 2014 would require that all fuel development and qualification be completed by the end of fiscal year 2009. Technological development areas that could increase the operating power of HFIR are identified as areas for study in the future.

Primm, R. T. [ORNL] [ORNL; Ellis, R. J. [ORNL] [ORNL; Gehin, J. C. [ORNL] [ORNL; Clarno, K. T. [ORNL] [ORNL; Williams, K. A. [ORNL] [ORNL; Moses, D. L. [ORNL] [ORNL

2006-11-01

345

Design of a new lithium ion battery test cell for in-situ neutron diffraction measurements  

NASA Astrophysics Data System (ADS)

This paper introduces a new cell design for the construction of lithium ion batteries with conventional electrochemical performance whilst allowing in situ neutron diffraction measurement. A cell comprising of a wound cathode, electrolyte and anode stack has been prepared. The conventional hydrogen-containing components of the cell have been replaced by hydrogen-free equivalents. The electrodes are fabricated using a PTFE binder, the electrolyte consists of deuterated solvents which are supported in a quartz glass fibre separator. Typical battery performance is reported using the hydrogen-free components with a specific capacity of 140 mA h g-1 being observed for LiFePO4 at a rate of 0.2 C. Neutron diffraction patterns of full cells were recorded with phase change reactions monitored. When aluminium packaging was used a better signal to noise ratio was obtained. The obtained atomic positions and lattice parameters for all cells investigated were found to be consistent with parameters refined from the diffraction pattern of a powder of the pure electrode material. This paper highlights the pertinent points in designing cells for these measurements and addresses some of the problems.

Roberts, Matthew; Biendicho, Jordi Jacas; Hull, Stephen; Beran, Premysl; Gustafsson, Torbjörn; Svensson, Gunnar; Edström, Kristina

2013-03-01

346

The design and performance of a water cooling system for a prototype coupled cavity linear particle accelerator for the spallation neutron source  

Microsoft Academic Search

The Spallation Neutron Source (SNS) is a facility being designed for scientific and industrial research and development. The SNS will generate and employ neutrons as a research tool in a variety of disciplines including biology, material science, superconductivity, chemistry, etc. The neutrons will be produced by bombarding a heavy metal target with a high-energy beam of protons, generated and accelerated

John D. Bernardin; Curtt Ammerman; Steve Hopkins

2002-01-01

347

Large Core Code Evaluation Working Group Benchmark Problem Four: neutronics and burnup analysis of a large heterogeneous fast reactor. Part 1. Analysis of benchmark results. [LMFBR  

Microsoft Academic Search

The Large Core Code Evaluation Working Group Benchmark Problem Four was specified to provide a stringent test of the current methods which are used in the nuclear design and analyses process. The benchmark specifications provided a base for performing detailed burnup calculations over the first two irradiation cycles for a large heterogeneous fast reactor. Particular emphasis was placed on the

C. L. Cowan; R. Protsik; J. W. Lewellen

1984-01-01

348

Modular Approach to Launch Vehicle Design Based on a Common Core Element  

NASA Technical Reports Server (NTRS)

With a heavy lift launch vehicle as the centerpiece of our nation's next exploration architecture's infrastructure, the Advanced Concepts Office at NASA's Marshall Space Flight Center initiated a study to examine the utilization of elements derived from a heavy lift launch vehicle for other potential launch vehicle applications. The premise of this study is to take a vehicle concept, which has been optimized for Lunar Exploration, and utilize the core stage with other existing or near existing stages and boosters to determine lift capabilities for alternative missions. This approach not only yields a vehicle matrix with a wide array of capabilities, but also produces an evolutionary pathway to a vehicle family based on a minimum development and production cost approach to a launch vehicle system architecture, instead of a purely performance driven approach. The upper stages and solid rocket booster selected for this study were chosen to reflect a cross-section of: modified existing assets in the form of a modified Delta IV upper stage and Castor-type boosters; potential near term launch vehicle component designs including an Ares I upper stage and 5-segment boosters; and longer lead vehicle components such as a Shuttle External Tank diameter upper stage. The results of this approach to a modular launch system are given in this paper.

Creech, Dennis M.; Threet, Grady E., Jr.; Philips, Alan D.; Waters, Eric D.; Baysinger, Mike

2010-01-01

349

Concrete core activation and suspended ceilings: Designing for comfort, energy efficiency, and good acoustics.  

PubMed

The trend to design energy-efficient buildings continues. Both legislation as sustainability assessment methods have increased the popularity of thermally activated concrete slabs. It is a way to use low temperature heating and high temperature cooling which makes it very suited for the use in low energy systems. The efficiency of these systems relate to the surface area, often the ceiling area. Exactly that surface was already the domain for the sound absorbing ceiling. So in new buildings with high energy performance due to concrete core activation, the sound absorption is often banned, resulting in very poor acoustics. The use of open, sound absorbing ceilings will have an influence on the thermal capacity of the concrete slabs, However, little is known about this effect. To investigate the effect of open ceilings to both the cooling capacity as the sound absorption, theoretical/empirical models have been made to estimate the effect on the cooling capacity and the sound absorption. The method is also tested in a field situation. It turns out that optimization is possible, with both cooling capacity as sound absorption around 70% of the maximum. PMID:25235705

Vercammen, Martijn; Peperkamp, Hanneke

2014-04-01

350

Design of a boiling water reactor core based on an integrated blanket–seed thorium–uranium concept  

Microsoft Academic Search

This paper is concerned with the design of a boiling water reactor (BWR) equilibrium core using thorium as a nuclear material in an integrated blanket–seed (BS) assembly. The integrated BS concept comes from the fact that the blanket and the seed rods are located in the same assembly, and are burned out in a once-through cycle. The idea behind the

Alejandro Núñez-Carrera; Juan Luis François; Cecilia Martín-del-Campo; Gilberto Espinosa-Paredes

2005-01-01

351

Common Core Curriculum for Vocational Education. Category G: Evaluation and Research. G-4: Research Design in Vocational Education.  

ERIC Educational Resources Information Center

This module on research design in vocational education is one of a set of five on evaluation and research and is part of a larger series of thirty-four modules constituting a core curriculum for use in the professional preparation of vocational educators in the areas of agricultural, business, home economics, and industrial education. Following…

Moshier, Kenneth

352

Enhancing the Practicum Experience for Pre-Service Chemistry Teachers through Collaborative CoRe Design with Mentor Teachers  

ERIC Educational Resources Information Center

This paper reports findings from an ongoing study exploring how the Content Representation (CoRe) design can be used as a tool to help chemistry student teachers begin acquiring the professional knowledge required to become expert chemistry teachers. Phase 2 of the study, reported in this paper, investigated how collaboration with school-based…

Hume, Anne; Berry, Amanda

2013-01-01

353

Modeling and analysis framework for core damage propagation during flow-blockage-initiated accidents in the Advanced Neutron Source Reactor at Oak Ridge National Laboratory  

SciTech Connect

This paper describes modeling and analysis to evaluate the extent of core damage during flow blockage events in the Advanced Neutron Source (ANS) reactor planned to be built at the Oak Ridge National Laboratory (ORNL). Damage propagation is postulated to occur from thermal conduction between damaged and undamaged plates due to direct thermal contact. Such direct thermal contact may occur because of fuel plate swelling during fission product vapor release or plate buckling. Complex phenomena of damage propagation were modeled using a one-dimensional heat transfer model. A scoping study was conducted to learn what parameters are important for core damage propagation, and to obtain initial estimates of core melt mass for addressing recriticality and steam explosion events. The study included investigating the effects of the plate contact area, the convective heat transfer coefficient, thermal conductivity upon fuel swelling, and the initial temperature of the plate being contacted by the damaged plate. Also, the side support plates were modeled to account for their effects on damage propagation. The results provide useful insights into how various uncertain parameters affect damage propagation.

Kim, S.H.; Taleyarkhan, R.P.; Navarro-Valenti, S.; Georgevich, V.

1995-09-01

354

Lead-Cooled Fast Reactor (LFR) Design: Safety, Neutronics, Thermal Hydraulics, Structural Mechanics, Fuel, Core, and Plant Design  

SciTech Connect

The idea of developing fast spectrum reactors with molten lead (or lead alloy) as a coolant is not a new one. Although initially considered in the West in the 1950s, such technology was not pursued to completion because of anticipated difficulties associated with the corrosive nature of these coolant materials. However, in the Soviet Union, such technology was actively pursued during the same time frame (1950s through the 1980s) for the specialized role of submarine propulsion. More recently, there has been a renewal of interest in the West for such technology, both for critical systems as well as for Accelerator Driven Subcritical (ADS) systems. Meanwhile, interest in the former Soviet Union, primarily Russia, has remained strong and has expanded well beyond the original limited mission of submarine propulsion. This section reviews the past and current status of LFR development.

Smith, C

2010-02-22

355

Design and Performance Improvements of the Prototype Open Core Flywheel Energy Storage System  

NASA Technical Reports Server (NTRS)

A prototype magnetically suspended composite flywheel energy storage (FES) system is operating at the University of Maryland. This system, designed for spacecraft applications, incorporates recent advances in the technologies of composite materials, magnetic suspension, and permanent magnet brushless motor/generator. The current system is referred to as an Open Core Composite Flywheel (OCCF) energy storage system. This paper will present design improvements for enhanced and robust performance. Initially, when the OCCF prototype was spun above its first critical frequency of 4,500 RPM, the rotor movement would exceed the space available in the magnetic suspension gap and touchdown on the backup mechanical bearings would occur. On some occasions it was observed that, after touchdown, the rotor was unable to re-suspend as the speed decreased. Additionally, it was observed that the rotor would exhibit unstable oscillations when the control system was initially turned on. Our analysis suggested that the following problems existed: (1) The linear operating range of the magnetic bearings was limited due to electrical and magnetic saturation; (2) The inductance of the magnetic bearings was affecting the transient response of the system; (3) The flywheel was confined to a small movement because mechanical components could not be held to a tight tolerance; and (4) The location of the touchdown bearing magnifies the motion at the pole faces of the magnetic bearings when the linear range is crucial. In order to correct these problems an improved design of the flywheel energy storage system was undertaken. The magnetic bearings were re-designed to achieve a large linear operating range and to withstand load disturbances of at least 1 g. The external position transducers were replaced by a unique design which were resistant to magnetic field noise and allowed cancellation of the radial growth of the flywheel at high speeds. A central rod was utilized to ensure the concentricity of the magnetic bearings, the motor/generator, and the mechanical touchdown bearings. In addition, the mechanical touchdown bearings were placed at two ends of the magnetic bearing stack to restrict the motion at pole faces. A composite flywheel was made using a multi-ring interference assembled design for a high specific energy density. To achieve a higher speed and better efficiency, a permanent magnet DC brushless motor was specially designed and fabricated. A vacuum enclosure was constructed to eliminate windage losses for testing at high speeds. With the new improvements the OCCF system was tested to 20,000 RPM with a total stored energy of 15.9 WH and an angular momentum of 54.8 N-m-s (40.4 lb-ft-s). Motor current limitation, caused by power loss in the magnetic bearings, was identified as causing the limit in upper operating speed.

Pang, D.; Anand, D. K. (Editor); Kirk, J. A. (Editor)

1996-01-01

356

Evaluating secondary neutron doses of a refined shielded design for a medical cyclotron using the TLD approach  

NASA Astrophysics Data System (ADS)

An increasing number of cyclotrons at medical centers in Taiwan have been installed to generate radiopharmaceutical products. An operating cyclotron generates immense amounts of secondary neutrons from reactions such the 18O(p, n)18F, used in the production of FDG. This intense radiation can be hazardous to public health, particularly to medical personnel. To increase the yield of 18F-FDG from 4200 GBq in 2005 to 48,600 GBq in 2011, Chung Shan Medical University Hospital (CSMUH) has prolonged irradiation time without changing the target or target current to meet requirements regarding the production 18F. The CSMUH has redesigned the CTI Radioisotope Delivery System shield. The lack of data for a possible secondary neutron doses has increased due to newly designed cyclotron rooms. This work aims to evaluate secondary neutron doses at a CTI cyclotron center using a thermoluminescent dosimeter (TLD-600). Two-dimensional neutron doses were mapped and indicated that neutron doses were high as neutrons leaked through self-shielded blocks and through the L-shaped concrete shield in vault rooms. These neutron doses varied markedly among locations close to the H218O target. The Monte Carlo simulation and minimum detectable dose are also discussed and demonstrated the reliability of using the TLD-600 approach. Findings can be adopted by medical centers to identify radioactive hot spots and develop radiation protection.

Lin, Jye-Bin; Tseng, Hsien-Chun; Liu, Wen-Shan; Lin, Ding-Bang; Hsieh, Teng-San; Chen, Chien-Yi

2013-11-01

357

Design of metallic textile core sandwich panels F.W. Zok *, H.J. Rathbun, Z. Wei, A.G. Evans  

E-print Network

Design of metallic textile core sandwich panels F.W. Zok *, H.J. Rathbun, Z. Wei, A.G. Evans-5050, USA Received 3 March 2003 Abstract Metallic sandwich panels with textile cores have been analyzed are made with competing concepts, especially honeycomb and truss core systems. It is demonstrated that all

Zok, Frank

358

Tuning light absorption in core/shell silicon nanowire photovoltaic devices through morphological design.  

PubMed

Subwavelength diameter semiconductor nanowires can support optical resonances with anomalously large absorption cross sections, and thus tailoring these resonances to specific frequencies could enable a number of nanophotonic applications. Here, we report the design and synthesis of core/shell p-type/intrinsic/n-type (p/i/n) Si nanowires (NWs) with different sizes and cross-sectional morphologies as well as measurement and simulation of photocurrent spectra from single-NW devices fabricated from these NW building blocks. Approximately hexagonal cross-section p/i/n coaxial NWs of various diameters (170-380 nm) were controllably synthesized by changing the Au catalyst diameter, which determines core diameter, as well as shell deposition time, which determines shell thickness. Measured polarization-resolved photocurrent spectra exhibit well-defined diameter-dependent peaks. The corresponding external quantum efficiency (EQE) spectra calculated from these data show good quantitative agreement with finite-difference time-domain (FDTD) simulations and allow assignment of the observed peaks to Fabry-Perot, whispering-gallery, and complex high-order resonant absorption modes. This comparison revealed a systematic red-shift of equivalent modes as a function of increasing NW diameter and a progressive increase in the number of resonances. In addition, tuning shell synthetic conditions to enable enhanced growth on select facets yielded NWs with approximately rectangular cross sections; analysis of transmission electron microscopy and scanning electron microscopy images demonstrate that growth of the n-type shell at 860 °C in the presence of phosphine leads to enhanced relative Si growth rates on the four {113} facets. Notably, polarization-resolved photocurrent spectra demonstrate that at longer wavelengths the rectangular cross-section NWs have narrow and significantly larger amplitude peaks with respect to similar size hexagonal NWs. A rectangular NW with a diameter of 260 nm yields a dominant mode centered at 570 nm with near-unity EQE in the transverse-electric polarized spectrum. Quantitative comparisons with FDTD simulations demonstrate that these new peaks arise from cavity modes with high symmetry that conform to the cross-sectional morphology of the rectangular NW, resulting in low optical loss of the mode. The ability to modulate absorption with changes in nanoscale morphology by controlled synthesis represents a promising route for developing new photovoltaic and optoelectronic devices. PMID:22889329

Kim, Sun-Kyung; Day, Robert W; Cahoon, James F; Kempa, Thomas J; Song, Kyung-Deok; Park, Hong-Gyu; Lieber, Charles M

2012-09-12

359

The design, construction and performance of a variable collimator for epithermal neutron capture therapy beams  

NASA Astrophysics Data System (ADS)

A patient collimator for the fission converter based epithermal neutron beam (FCB) at the Massachusetts Institute of Technology Research Reactor (MITR-II) was built for clinical trials of boron neutron capture therapy (BNCT). A design was optimized by Monte Carlo simulations of the entire beam line and incorporates a modular construction for easy modifications in the future. The device was formed in-house by casting a mixture of lead spheres (7.6 mm diameter) in epoxy resin loaded with either 140 mg cm-3 of boron carbide or 210 mg cm-3 of lithium fluoride (95% enriched in 6Li). The cone shaped collimator allows easy field placement anywhere on the patient and is equipped with a laser indicator of central axis, beam's eye view optics and circular apertures of 80, 100, 120 and 160 mm diameter. Beam profiles and the collateral dose in a half-body phantom were measured for the 160 mm field using fission counters, activation foils as well as tissue equivalent (A-150) and graphite walled ionization chambers. Leakage radiation through the collimator contributes less than 10% to the total collateral dose up to 0.15 m beyond the edge of the aperture and becomes relatively more prominent with lateral displacement. The measured whole body dose equivalent of 24 ± 2 mSv per Gy of therapeutic dose is comparable to doses received during conventional therapy and is due principally (60-80%) to thermal neutron capture reactions with boron. These findings, together with the dose distributions for the primary beam, demonstrate the suitability of this patient collimator for BNCT.

Riley, K. J.; Binns, P. J.; Ali, S. J.; Harling, O. K.

2004-05-01

360

Advanced MOX Core Design Study of Sodium-Cooled Reactors in Current Feasibility Study on Commercialized Fast Reactor Cycle Systems in Japan  

SciTech Connect

Sodium-cooled mixed-oxide core design studies are performed with a target burnup of 150 GWd/t and possible measures against the recriticality issues in core disruptive accidents. Four types of core are compared from the viewpoints of core performance and reliability. Results show that all the types of core satisfy the target and that a homogeneous core with an axial blanket partial elimination subassembly is the superior concept, although experimental demonstration is required of molten fuel motion for mitigation of recriticality following fuel melting and loss of fuel pin integrity.

Mizuno, Tomoyasu; Niwa, Hajime [Japan Nuclear Cycle Development Institute (Japan)

2004-05-15

361

Design for low beam loss in accelerators for intense neutron source applications  

SciTech Connect

Control of beam loss in intense ion linacs involves keeping beam spill below parts in 10[sup [minus]5]--10[sup [minus]8]/m by preventing total beam size from extending to the limiting apertures. Starting from good rms design practices, new analysis of the machine architecture is described in terms of the effects of the machine tune with space-charge, free-energy constraint, and halo-producing mechanisms. It is shown that halos are produced by the time- (or position-) varying nature of common linac aspects (such as misalignment, mismatching, acceleration, and construction techniques) through collective core/single-particle interaction dynamics plus resonances.

Jameson, R.A.

1993-01-01

362

Design for low beam loss in accelerators for intense neutron source applications  

SciTech Connect

Control of beam loss in intense ion linacs involves keeping beam spill below parts in 10{sup {minus}5}--10{sup {minus}8}/m by preventing total beam size from extending to the limiting apertures. Starting from good rms design practices, new analysis of the machine architecture is described in terms of the effects of the machine tune with space-charge, free-energy constraint, and halo-producing mechanisms. It is shown that halos are produced by the time- (or position-) varying nature of common linac aspects (such as misalignment, mismatching, acceleration, and construction techniques) through collective core/single-particle interaction dynamics plus resonances.

Jameson, R.A.

1993-06-01

363

Development of a prompt gamma neutron activation analysis facility for 10B concentration measurements at RA-3: design stage.  

PubMed

A PGNAA facility is being developed for (10)B concentration measurements at RA-3 reactor. Its design targets detection limits better than tenths of a microgram and irradiation times on the order of minutes. Computational models were developed, which estimated thermal neutron fluxes in irradiation position to be larger than 10(9) n cm(-2) s(-1). Calculated amounts of photons and fast neutrons make necessary for filter/moderator arrangements. An irradiation device was designed and numerically tested, which is being built and is to be used for performing characterizing measurements. PMID:21420305

Gonçalves-Carralves, Manuel L Sztejnberg; Gadan, Mario A; Bortolussi, Silva; Pinto, Julián; Ojeda, Juan; Langan, Sebastián; Quintana, Jorge; Miller, Marcelo E

2011-12-01

364

SAS3D analysis of unprotected loss-of-flow transients for 1200MW(electric) liquid-metal fast breeder reactor homogeneous and heterogeneous core designs  

Microsoft Academic Search

A safety comparison was made for two 1200-MW(electric) liquid-metal fast breeder reactor cores with homogeneous and heterogeneous fuel arrangements, respectively. The two cores were conceptually designed to be identical except for those parameters affected by different fuel arrangements. The comparison was limited to the issue of initiating phase energetics in the hypothetical core disruptive accident. Both cores were assumed to

T. A. Shih; M. I. Temme

1978-01-01

365

Neutron Stars  

NASA Technical Reports Server (NTRS)

Neutron stars were discovered almost 40 years ago, and yet many of their most fundamental properties remain mysteries. There have been many attempts to measure the mass and radius of a neutron star and thereby constrain the equation of state of the dense nuclear matter at their cores. These have been complicated by unknown parameters such as the source distance and burning fractions. A clean, straightforward way to access the neutron star parameters is with high-resolution spectroscopy. I will present the results of searches for gravitationally red-shifted absorption lines from the neutron star atmosphere using XMM-Newton and Chandra.

Cottam, J.

2007-01-01

366

The influence of various core designs on stress distribution in the veneered zirconia crown: a finite element analysis study  

PubMed Central

PURPOSE The purpose of this study was to evaluate various core designs on stress distribution within zirconia crowns. MATERIALS AND METHODS Three-dimensional finite element models, representing mandibular molars, comprising a prepared tooth, cement layer, zirconia core, and veneer porcelain were designed by computer software. The shoulder (1 mm in width) variations in core were incremental increases of 1 mm, 2 mm and 3 mm in proximal and lingual height, and buccal height respectively. To simulate masticatory force, loads of 280 N were applied from three directions (vertical, at a 45° angle, and horizontal). To simulate maximum bite force, a load of 700 N was applied vertically to the crowns. Maximum principal stress (MPS) was determined for each model, loading condition, and position. RESULTS In the maximum bite force simulation test, the MPSs on all crowns observed around the shoulder region and loading points. The compressive stresses were located in the shoulder region of the veneer-zirconia interface and at the occlusal region. In the test simulating masticatory force, the MPS was concentrated around the loading points, and the compressive stresses were located at the 3 mm height lingual shoulder region, when the load was applied horizontally. MPS increased in the shoulder region as the shoulder height increased. CONCLUSION This study suggested that reinforced shoulder play an essential role in the success of the zirconia restoration, and veneer fracture due to occlusal loading can be prevented by proper core design, such as shoulder. PMID:23755346

Ha, Seung-Ryong; Kim, Sung-Hun; Yoo, Seung-Hyun; Jeong, Se-Chul; Lee, Jai-Bong; Yeo, In-Sung

2013-01-01

367

Design, implementation, and testing of a cryogenic loading capability on an engineering neutron diffractometer.  

PubMed

A novel capability was designed, implemented, and tested for in situ neutron diffraction measurements during loading at cryogenic temperatures on the spectrometer for materials research at temperature and stress at Los Alamos National Laboratory. This capability allowed for the application of dynamic compressive forces of up to 250 kN on standard samples controlled at temperatures between 300 and 90 K. The approach comprised of cooling thermally isolated compression platens that in turn conductively cooled the sample in an aluminum vacuum chamber which was nominally transparent to the incident and diffracted neutrons. The cooling/heat rate and final temperature were controlled by regulating the flow of liquid nitrogen in channels inside the platens that were connected through bellows to the mechanical actuator of the load frame and by heaters placed on the platens. Various performance parameters of this system are reported here. The system was used to investigate deformation in Ni-Ti-Fe shape memory alloys at cryogenic temperatures and preliminary results are presented. PMID:20590248

Woodruff, T R; Krishnan, V B; Clausen, B; Sisneros, T; Livescu, V; Brown, D W; Bourke, M A M; Vaidyanathan, R

2010-06-01

368

Design, implementation, and testing of a cryogenic loading capability on an engineering neutron diffractometer  

SciTech Connect

A novel capability was designed, implemented, and tested for in situ neutron diffraction measurements during loading at cryogenic temperatures on the spectrometer for materials research at temperature and stress at Los Alamos National Laboratory. This capability allowed for the application of dynamic compressive forces of up to 250 kN on standard samples controlled at temperatures between 300 and 90 K. The approach comprised of cooling thermally isolated compression platens that in turn conductively cooled the sample in an aluminum vacuum chamber which was nominally transparent to the incident and diffracted neutrons. The cooling/heat rate and final temperature were controlled by regulating the flow of liquid nitrogen in channels inside the platens that were connected through bellows to the mechanical actuator of the load frame and by heaters placed on the platens. Various performance parameters of this system are reported here. The system was used to investigate deformation in Ni-Ti-Fe shape memory alloys at cryogenic temperatures and preliminary results are presented.

Woodruff, T. R.; Krishnan, V. B.; Vaidyanathan, R. [Department of Mechanical, Materials, and Aerospace Engineering, Advanced Materials Processing and Analysis Center (AMPAC), University of Central Florida, Orlando, Florida 32816 (United States); Clausen, B.; Sisneros, T.; Livescu, V.; Brown, D. W.; Bourke, M. A. M. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2010-06-15

369

Laser Intertial Fusion Energy: Neutronic Design Aspects of a Hybrid Fusion-Fission Nuclear Energy System  

SciTech Connect

This study investigates the neutronics design aspects of a hybrid fusion-fission energy system called the Laser Fusion-Fission Hybrid (LFFH). A LFFH combines current Laser Inertial Confinement fusion technology with that of advanced fission reactor technology to produce a system that eliminates many of the negative aspects of pure fusion or pure fission systems. When examining the LFFH energy mission, a significant portion of the United States and world energy production could be supplied by LFFH plants. The LFFH engine described utilizes a central fusion chamber surrounded by multiple layers of multiplying and moderating media. These layers, or blankets, include coolant plenums, a beryllium (Be) multiplier layer, a fertile fission blanket and a graphite-pebble reflector. Each layer is separated by perforated oxide dispersion strengthened (ODS) ferritic steel walls. The central fusion chamber is surrounded by an ODS ferritic steel first wall. The first wall is coated with 250-500 {micro}m of tungsten to mitigate x-ray damage. The first wall is cooled by Li{sub 17}Pb{sub 83} eutectic, chosen for its neutron multiplication and good heat transfer properties. The {sub 17}Pb{sub 83} flows in a jacket around the first wall to an extraction plenum. The main coolant injection plenum is immediately behind the Li{sub 17}Pb{sub 83}, separated from the Li{sub 17}Pb{sub 83} by a solid ODS wall. This main system coolant is the molten salt flibe (2LiF-BeF{sub 2}), chosen for beneficial neutronics and heat transfer properties. The use of flibe enables both fusion fuel production (tritium) and neutron moderation and multiplication for the fission blanket. A Be pebble (1 cm diameter) multiplier layer surrounds the coolant injection plenum and the coolant flows radially through perforated walls across the bed. Outside the Be layer, a fission fuel layer comprised of depleted uranium contained in Tristructural-isotropic (TRISO) fuel particles having a packing fraction of 20% in 2 cm diameter fuel pebbles. The fission blanket is cooled by the same radial flibe flow that travels through perforated ODS walls to the reflector blanket. This reflector blanket is 75 cm thick comprised of 2 cm diameter graphite pebbles cooled by flibe. The flibe extraction plenum surrounds the reflector bed. Detailed neutronics designs studies are performed to arrive at the described design. The LFFH engine thermal power is controlled using a technique of adjusting the {sup 6}Li/{sup 7}Li enrichment in the primary and secondary coolants. The enrichment adjusts system thermal power in the design by increasing tritium production while reducing fission. To perform the simulations and design of the LFFH engine, a new software program named LFFH Nuclear Control (LNC) was developed in C++ to extend the functionality of existing neutron transport and depletion software programs. Neutron transport calculations are performed with MCNP5. Depletion calculations are performed using Monteburns 2.0, which utilizes ORIGEN 2.0 and MCNP5 to perform a burnup calculation. LNC supports many design parameters and is capable of performing a full 3D system simulation from initial startup to full burnup. It is able to iteratively search for coolant {sup 6}Li enrichments and resulting material compositions that meet user defined performance criteria. LNC is utilized throughout this study for time dependent simulation of the LFFH engine. Two additional methods were developed to improve the computation efficiency of LNC calculations. These methods, termed adaptive time stepping and adaptive mesh refinement were incorporated into a separate stand alone C++ library name the Adaptive Burnup Library (ABL). The ABL allows for other client codes to call and utilize its functionality. Adaptive time stepping is useful for automatically maximizing the size of the depletion time step while maintaining a desired level of accuracy. Adaptive meshing allows for analysis of fixed fuel configurations that would normally require a computationally burdensome number of depletion zones. Alternatively, Adaptive M

Kramer, K

2010-04-08

370

Design of single-mode large-mode area bandgap fibre with microstructured-core  

NASA Astrophysics Data System (ADS)

Tailoring the modal characteristics of all-solid photonic bandgap fibre by the inclusion of low-index rods in the fibre core is investigated. By lowering the core index of the fibre, the high-order modes in the fibre can be shifted to the border of the bandgap, as a result, single-mode operation in large-mode area bandgap fibre can be realized without bending the fibre. In addition, large-mode area and single-mode operation in the all-solid microstructured-core bandgap fibre can be achieved by bending the fibre at a wide bending radius range.

Chen, Ming-Yang; Gong, Tian-Yi; Gao, Yong-Feng; Zhou, Jun

2014-11-01

371

Designing of the 14 MeV neutron moderator for BNCT  

NASA Astrophysics Data System (ADS)

In boron neutron capture therapy (BNCT), the ratio of the fast neutron flux to the neutron flux in the tumor (RFNT) must be less than 3%. If a D-T neutron generator is used in BNCT, the 14 MeV neutron moderator must be optimized to reduce the RFNT. Based on the neutron moderation theory and the simulation results, tungsten, lead and diamond were used to moderate the 14 MeV neutrons. Satisfying RFNT of less than 3%, the maximum neutron flux in the tumor was achieved with a three-layer moderator comprised of a 3 cm thick tungsten layer, a 14 cm thick lead layer and a 21 cm thick diamond layer.

Cheng, Dao-Wen; Lu, Jing-Bin; Yang, Dong; Liu, Yu-Min; Wang, Hui-Dong; Ma, Ke-Yan

2012-09-01

372

Design and Characterization of a Collimated Neutron Beam User Facility at SUNY Geneseo  

NASA Astrophysics Data System (ADS)

The Collimated Neutron Beam (CNB) Facility at SUNY Geneseo provides users an opportunity to perform neutron experiments that require a low neutron background. Neutrons with energies up to 10 MeV are produced by a Plutonium-Beryllium (Pu-Be) source and are collimated to form a well characterized beam. A six foot high, 18 inch thick shielding wall made of water-bricks was built to reduce neutron background in the target area. Neutron and gamma radiation were extensively mapped throughout the facility using a calibrated Bonner sphere, Geiger counter, plastic scintillator and an HPGe detector. Potential uses for the CNB include neutron activation, time-of-flight, attenuation and neutron detector calibration experiments. A detailed description and layout of the facility will be displayed on the poster. Funded in part by a grant from the DOE through the Laboratory for Laser Energetics.

Krieger, Michael; Padalino, Stephen; Russ, Megan; Polsin, Danae; Bienstock, Mollie; Ellison, Drew; Simone, Angela

2012-10-01

373

Modeling and analysis framework for core damage propagation during flow-blockage-initiated accidents in the Advanced Neutron Source reactor at Oak Ridge National Laboratory  

SciTech Connect

This paper describes modeling and analysis to evaluate the extent of core damage during flow blockage events in the Advanced Neutron Source (ANS) reactor planned to be built at ORNL. Damage propagation is postulated to occur from thermal conduction between dmaged and undamaged plates due to direct thermal contact. Such direct thermal contact may occur beause of fuel plate swelling during fission product vapor release or plate buckling. Complex phenomena of damage propagation were modeled using a one-dimensional heat transfer model. A parametric study was done for several uncertain variables. The study included investigating effects of plate contact area, convective heat transfer coefficient, thermal conductivity on fuel swelling, and initial temperature of the plate being contacted by the damaged plate. Also, the side support plates were modeled to account for their effects of damage propagation. Results provide useful insights into how variouss uncertain parameters affect damage propagation.

Kim, S.H.; Taleyarkhan, R.P.; Navarro-Valenti, S.; Georgevich, V.

1995-12-31

374

The Landscape of the Neutrino Mechanism of Core-Collapse Supernovae: Neutron Star and Black Hole Mass Functions, Explosion Energies and Nickel Yields  

E-print Network

If the neutrino luminosity from the protoneutron star formed during a massive star core collapse exceeds a critical threshold, a supernova (SN) results. The normalization of this critical threshold and its dependencies on the parameters of the system remain uncertain. Using spherical quasi-static evolutionary sequences for many hundreds of progenitors over a wide range of metallicities, we study how the explosion threshold maps onto observables - (1) fraction of successful explosions, (2) remnant neutron star (NS) and black hole (BH) mass functions, (3) explosion energies (E_SN), (4) nickel yields (M_Ni) - and their mutual correlations. We show that the neutrino mechanism can in principle explain the observed properties of SNe and the compact objects they produce. Successful explosions are intertwined with failures in a complex but well-defined pattern that is not well described by the progenitor initial mass and is not simply related to compactness. In the context of single-star progenitors, we show that the...

Pejcha, Ondrej

2014-01-01

375

Universal Design for Learning: speech-language pathologists and their teams making the common core curriculum accessible.  

PubMed

The Universal Design for Learning (UDL) framework was named in the supporting documents for the Common Core State Standards (CCSS) as a means of helping all students, especially those with disabilities, to meet and exceed the rigorous expectations. This article will describe the principles of UDL, show how educational teams use the framework to design instruction to teach the CCSS with examples from science and English language arts, and finally explore how the implementation of UDL provides an opportunity for speech-language pathologists to play a critical role in school improvement and instructional design and support. PMID:22538708

Staskowski, Maureen; Hardin, Susan; Klein, Mike; Wozniak, Carrie

2012-05-01

376

Suspended nanowires: fabrication, design and characterization of fibers with nanoscale cores.  

PubMed

We report a new approach for the fabrication of nanowires: the direct drawing of optical fibers with air suspended nanoscale cores. The fibers were made from lead silicate glass using the extrusion technique for preform and jacket tube fabrication. Fibers with core diameters in the range of 420-720 nm and practical outer diameters of 110-200 microm were produced, the smallest core sizes produced to date within optical fibers without tapering. We explored the impact of the core size on the effective mode area and propagation loss of these suspended nanowires relative to circular nanowires reported to date. As for circular nanowires, the propagation loss of these suspended nanowires is dominated by surface roughness induced scattering. PMID:19219168

Ebendorff-Heidepriem, Heike; Warren-Smith, Stephen C; Monro, Tanya M

2009-02-16

377

Design of a horizontal neutron reflectometer for the European Spallation Source  

NASA Astrophysics Data System (ADS)

A design study of a horizontal neutron reflectometer adapted to the general baseline of the long pulse European Spallation Source (ESS) is presented. The instrument layout comprises advanced solutions for the neutron guide, high-resolution pulse shaping and beam bending onto a sample surface being thoroughly adjusted to the properties of the ESS. The length of this instrument is roughly 55 m, enabling ??/? resolutions from 0.5% to 10%. The incident beam is focused in horizontal plane to boost measurements of sample sizes of 1×1 cm2 and smaller with potential beam deflection in both downward and upward directions. The primary range of neutron wavelengths utilized by the instrument is 2-7.1 Å. If the wavelength range needs to be extended, then this is possible by utilizing only every second (third, fourth) pulse by suppressing all other pulses by the chopper system and thus increase the longest usable wavelength to 12.2 (17.3, 22.4) Å. Angles of incidence can be set between 0° and 9° with a total accessible q-range from 4×10-3 Å-1 up to 1 Å-1, while the ??/? resolution can be freely set. The instrument operates in both ?/? (free liquid surfaces) and ?/2? (solid-liquid, air-solid interfaces) geometries. The experimental setup will in particular enable direct studies on ultrathin films (d ?10 Å) and buried monolayers to multilayered structures of up to 3000 Å total thickness. The horizontal reflectometer will further foster investigations of hierarchical systems from nanometer to micrometer length scale (the latter by off-specular scattering), as well as their kinetics and dynamical properties, in particular under load (shear, pressure, external fields). Polarization and polarization analysis as well as the GISANS option are designed as potential modules to be implemented in the generic instrument layout. The instrument is highly flexible and offers a variety of different measurement modes. With respect to its mechanical components the instrument is exclusively based on current technology. Risks of failure for the chosen setup are minimum.

Nekrassov, D.; Trapp, M.; Lieutenant, K.; Moulin, J.-F.; Strobl, M.; Steitz, R.

2014-08-01

378

Biomechanical evaluation of bending strength of spinal pedicle screws, including cylindrical, conical, dual core and double dual core designs using numerical simulations and mechanical tests.  

PubMed

Pedicle screws are used for treating several types of spinal injuries. Although several commercial versions are presently available, they are mostly either fully cylindrical or fully conical. In this study, the bending strengths of seven types of commercial pedicle screws and a newly designed double dual core screw were evaluated by finite element analyses and biomechanical tests. All the screws had an outer diameter of 7 mm, and the biomechanical test consisted of a cantilever bending test in which a vertical point load was applied using a level arm of 45 mm. The boundary and loading conditions of the biomechanical tests were applied to the model used for the finite element analyses. The results showed that only the conical screws with fixed outer diameter and the new double dual core screw could withstand 1,000,000 cycles of a 50-500 N cyclic load. The new screw, however, exhibited lower stiffness than the conical screw, indicating that it could afford patients more flexible movements. Moreover, the new screw produced a level of stability comparable to that of the conical screw, and it was also significantly stronger than the other screws. The finite element analysis further revealed that the point of maximum tensile stress in the screw model was comparable to the point at which fracture occurred during the fatigue test. PMID:25060212

Amaritsakul, Yongyut; Chao, Ching-Kong; Lin, Jinn

2014-09-01

379

Core-shell designed scaffolds of alginate/alpha-tricalcium phosphate for the loading and delivery of biological proteins.  

PubMed

Development of scaffolds to load and deliver therapeutic molecules like growth factors greatly enhances tissue regenerative capacity. Here, we report the core-shell design of fibrous scaffolds made of alginate and ?-tricalcium phosphate (Alg/?-TCP) for in situ protein loading and controllable delivery. Direct deposition of Alg/?-TCP solution through designed coconcentric nozzle in CaCl(2) bath allowed the generation of fibrous scaffolds. Through the process, in situ protein loading was possible and the core and shell composition was controlled. Feasibility of the designed scaffolds in loading and release of biological model protein cytochrome C (cyt C) was investigated. Scaffolding formed in CaCl(2) led to a considerable loss of cyt C in a crosslinking time-dependent manner, and the change in hardening conditions (Alg concentration, CaCl(2) concentration, and Alg/?-TCP ratio) was not as effective in reducing the protein loss. Subsequent release of cyt C from Alg scaffolds displayed a marked initial burst depending on crosslinking conditions, and shortening crosslinking time and decreasing CaCl(2) concentration lowered the initial burst. The ?-TCP addition (up to 75%) resulted in more continual and sustainable release patterns. Composition change (?-TCP content) in core or shell significantly altered the release profiles, suggesting the possible designing core-shell configuration for target release patterns, such as dual-protein delivery. Additionally, the ?-TCP incorporation significantly increased the mechanical stiffness to values much closer to those of hard tissues. Results indicate that coaxial deposited ?-TCP/Alg fibrous scaffolds may be useful for designing proper growth factor delivery systems in hard tissue engineering. PMID:23015482

Perez, Roman A; Kim, Hae-Won

2013-04-01

380

The neutronic and fuel cycle performance of interchangeable 3500 MWth metal and oxide fueled LMRs  

SciTech Connect

This study summarizes the neutronic and fuel cycle analysis performed at Argonne National Laboratory for an oxide and a metal fueled 3500 MWth LMR. The oxide and metal core designs were developed to meet reactor performance specifications that are constrained by requirements for core loading interchangeability and for small burnup reactivity swing. Differences in the computed performance parameters of the oxide and metal cores, arising from basic differences in their neutronic characteristics, were identified and discussed. It is shown that metal and oxide cores designed to the same ground rules exhibit many similar performance characteristics; however, they differ substantially in reactivity coefficients, control strategies, and fuel cycle options. 12 refs., 25 figs.

Fujita, E.K.; Wade, D.C.

1989-03-01

381

Relationship between core size, coolant choice, fuel type, and neutron flux in a fast irradiation test reactor  

SciTech Connect

Currently, the United States has no domestic capability for large volume irradiation testing in a fast-spectrum system to support the development of advanced fuels or materials. The recently-proposed Global Nuclear Energy Partnership includes provisions for a sodium-cooled Advanced Burner Test Reactor which could provide this testing capability. In addition to sodium, lead-bismuth eutectic and helium coolants are being considered for future energy systems. In this paper, sodium, lead-bismuth eutectic, and helium-cooled systems are evaluated to determine the impact on fast flux and fuel enrichment resulting from varying core diameter, fuel volume fraction, fuel type, and coolant. While fast flux is most strongly influenced by core diameter at fixed power, fuel enrichment is a more complicated function of all four parameters. In the end, the combination of high fast flux and low enrichment can best be achieved by a sodium-cooled system. (authors)

Fanning, T. H. [Nuclear Engineering Div., Argonne National Laboratory, Argonne, IL 60439 (United States)

2006-07-01

382

Radiation transport analyses in support of the SNS Target Station Neutron Beam Line Shutters Title I Design  

SciTech Connect

A detailed radiation transport analysis of the Spallation Neutron Source (SNS) shutters is important for the construction of the SNS because of its impact on conventional facility design, normal operation of the facility, and maintenance operations. Thus far the analysis of the SNS shutter travel gaps has been completed. This analysis was performed using coupled Monte Carlo and multi-dimensional discrete ordinates calculations.

Miller, T.M.; Pevey, R.E.; Lillie, R.A.; Johnson, J.O.

2000-12-01

383

Choice of a process design for simultaneous detritiation and upgrading of heavy water for the Advanced Neutron Source  

Microsoft Academic Search

Tritium removal and heavy water upgrading are essential components of the heavy water-moderated reactor that is the heart of the Advanced Neutron Source (ANS) to be built at Oak Ridge National Laboratory. The technologies for these two processes, which are closely related, are reviewed in the context of the ANS requirements. The evolution of the design of the Heavy Water

A. I. Miller; D. A. Spagnolo; J. R. DeVore

1995-01-01

384

High Temperature Reactor (HTR) Deep Burn Core and Fuel Analysis: Design Selection for the Prismatic Block Reactor  

SciTech Connect

The Deep Burn (DB) Project is a U.S. Department of Energy sponsored feasibility study of Transuranic Management using high burnup fuel in the high temperature helium cooled reactor (HTR). The DB Project consists of seven tasks: project management, core and fuel analysis, spent fuel management, fuel cycle integration, TRU fuel modeling, TRU fuel qualification, and HTR fuel recycle. In the Phase II of the Project, we conducted nuclear analysis of TRU destruction/utilization in the HTR prismatic block design (Task 2.1), deep burn fuel/TRISO microanalysis (Task 2.3), and synergy with fast reactors (Task 4.2). The Task 2.1 covers the core physics design, thermo-hydraulic CFD analysis, and the thermofluid and safety analysis (low pressure conduction cooling, LPCC) of the HTR prismatic block design. The Task 2.3 covers the analysis of the structural behavior of TRISO fuel containing TRU at very high burnup level, i.e. exceeding 50% of FIMA. The Task 4.2 includes the self-cleaning HTR based on recycle of HTR-generated TRU in the same HTR. Chapter IV contains the design and analysis results of the 600MWth DB-HTR core physics with the cycle length, the average discharged burnup, heavy metal and plutonium consumptions, radial and axial power distributions, temperature reactivity coefficients. Also, it contains the analysis results of the 450MWth DB-HTR core physics and the analysis of the decay heat of a TRU loaded DB-HTR core. The evaluation of the hot spot fuel temperature of the fuel block in the DB-HTR (Deep-Burn High Temperature Reactor) core under full operating power conditions are described in Chapter V. The investigated designs are the 600MWth and 460MWth DB-HTRs. In Chapter VI, the thermo-fluid and safety of the 600MWth DB-HTRs has been analyzed to investigate a thermal-fluid design performance at the steady state and a passive safety performance during an LPCC event. Chapter VII describes the analysis results of the TRISO fuel microanalysis of the 600MWth and 450MWth DB-HTRs. The TRISO fuel microanalysis covers the gas pressure buildup in a coated fuel particle including helium production, the thermo-mechanical behavior of a CFP, the failure probabilities of CFPs, the temperature distribution in a CPF, and the fission product (FP) transport in a CFP and a graphite. In Chapter VIII, it contains the core design and analysis of sodium cooled fast reactor (SFR) with deep burn HTR reactor. It considers a synergistic combination of the DB-MHR and an SFR burner for a safe and efficient transmutation of the TRUs from LWRs. Chapter IX describes the design and analysis results of the self-cleaning (or self-recycling) HTR core. The analysis is considered zero and 5-year cooling time of the spent LWR fuels.

Francesco Venneri; Chang-Keun Jo; Jae-Man Noh; Yonghee Kim; Claudio Filippone; Jonghwa Chang; Chris Hamilton; Young-Min Kim; Ji-Su Jun; Moon-Sung Cho; Hong-Sik Lim; MIchael A. Pope; Abderrafi M. Ougouag; Vincent Descotes; Brian Boer

2010-09-01

385

The design of an intense accelerator-based epithermal neutron beam prototype for BNCT using near-threshold reactions  

NASA Astrophysics Data System (ADS)

Near-threshold boron neutron capture therapy (BNCT) uses proton energies only tens of rev above the (pan) reaction threshold in lithium in order to reduce the moderation requirements of the neutron source. The goals of this research were to prove the feasibility of this near-threshold concept for BNCT applications, using both calculation and experiment, and design a compact neutron source prototype from these results. This required a multidisciplinary development of methods for calculation of neutron yields, head phantom dosimetry, and accelerator target heat removal. First, a method was developed to accurately calculate thick target neutron yields for both near-threshold and higher energy proton beams, in lithium metal as well as lithium compounds. After these yields were experimentally verified, they were used as neutron sources for Monte Carlo (MCNP) simulations of neutron and photon transport in head phantoms. The theoretical and experimental determination of heat removal from a target backing with multiple fins, as well as numerical calculations of heat deposition profiles based on proton energy loss in target and backing materials, demonstrated that lithium integrity can be maintained for proton beam currents up to 2.5 mA. The final design uses a proton beam energy of 1.95 MeV and has a centerline epithermal neutron flux of 2.2 × 108 n/cm2- sec/mA, an advantage depth of 5.7 cm, an advantage ratio of 4.3, and an advantage depth dose rate of 6.7 RBE- cGy/min/mA, corresponding to an irradiation time of 38 minutes with a 5 mA beam. Moderator, reflector, and shielding weigh substantially less than other accelerator BNCT designs based on higher proton energies, e.g. 2.5 MeV. The near-threshold concept is useful as a portable neutron source for hospital settings, with applications ranging from glioblastomas to melanomas and synovectomy. (Copies available exclusively from MIT Libraries, Rm. 14- 0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

Lee, Charles L.

386

The effects of core geometry on core power for passively safe HTGRs  

SciTech Connect

Decay heat removal under accident conditions is one of the major concerns of nuclear reactor safety. By imposing a limit on the core power density, reactor designers can ensure that the energy generated after shutdown would not pose any problem even when the active cooling agent is lost. On the other hand, it is usually desirable to have a high power density for the competitiveness of the reactor design. Therefore, the design approach must make maximum use of passive means of heat transfer for obtaining the highest achievable core power density without sacrificing passive safety. The strong temperature dependence of radiative heat transfer combined with the high-temperature operability of coated-particle-fueled gas-cooled reactors can provide a valuable opportunity in this regard. To enhance radiative heat transfer within the core, an optimization of the design parameters, such as core geometry, fuel element configuration, and a proper choice of the materials, would be necessary in addition to neutronics considerations.

Kubali, V.C.; Lidsky, L.M. (Massachusetts Institute of Technology, Cambridge (United States))

1993-01-01

387

Optimized design and predicted performance of a deep ocean 50 m piston coring system  

SciTech Connect

Calculational techniques are described which were developed or adapted for the purpose of analyzing the mechanical response of a proposed piston coring system capable of recovering high quality 50 m long cores. The analysis includes the effects of barrel geometry on the mass required to penetrate 50 m of an assumed sediment, the effects of non-vertical entry and pullout on the stresses within the barrel, and the effects of steel cable or parachute piston restraints on the resulting core sample distortion. The results show that a wall thickness of 50 mm in the upper section is necessary to survive an entry of up to 1.5/sup 0/ from vertical or a recovery angle of up to 5/sup 0/. They also show that a mass of 15,400 kg and a pullout force of 330 kN are required. It is shown that active piston control is necessary to eliminate piston motion during penetration.

Karnes, C. H.; Burchett, S. N.; Dzwilewski, P. T.

1980-01-01

388

Design of a compact polarization splitter based on the dual-elliptical-core photonic crystal fiber  

NASA Astrophysics Data System (ADS)

We propose a compact polarization splitter based on dual-elliptical-core photonic crystal fiber. Two elliptical cores are introduced to increase the difference of effective index between x-polarized and y-polarized mode and three elliptical modulation air holes are used to control the power transfer between the two cores. By optimizing the structure parameters, the length of the polarization splitter is distinctly shortened. Numerical results demonstrate that the compact splitter has the length of 775 ?m and up to 50 dB extinction ratio at the central wavelength of 1.55 ?m. The corresponding bandwidth of 32 nm could be achieved from the wavelength of 1.534-1.566 ?m with the extinction ratio over 20 dB

Sheng, Zhufeng; Wang, Jiasheng; Feng, Ruijuan

2014-11-01

389

Design and development of a 3He replacement safeguards neutron counter based on 10B-lined proportional detector technology  

SciTech Connect

This presentation represents an overview of the experimental evaluation of a boron-lined proportional technology performed within an NA-241 sponsored project on testing of boron-lined proportional counters for the purpose of replacement of {sup 3}He technologies. The presented boron-lined technology will be utilized in a design of a full scale safeguards neutron coincidence counter. The design considerations and the Monte Carlo performance predictions for the counter are also presented.

Henzlova, Daniela [Los Alamos National Laboratory; Evans, Louise [Los Alamos National Laboratory; Menlove, Howard O. [Los Alamos National Laboratory; Swinhoe, Martyn T. [Los Alamos National Laboratory; Rael, Carlos D. [Los Alamos National Laboratory; Martinez, Isaac P. [Los Alamos National Laboratory; Marlow, Johnna B. [Los Alamos National Laboratory

2012-07-16

390

Fourth-generation spallation neutron target-moderator-reflector-shield assembly at the Manuel Lujan Jr. neutron scattering center  

NASA Astrophysics Data System (ADS)

This paper describes the basic design of the new Target-Moderator-Reflector-Shield (TMRS) assembly, which was installed at the Los Alamos Neutron Science Center's Manuel Lujan Jr. Neutron Scattering Center (Lujan Center). The current TMRS, known as the Mark-III, is a fourth-generation spallation neutron target in service at the Lujan Center. Our new design makes a number of new improvements over previous iterations on the TMRS. Key among these improvements is the first production implementation of a cold beryllium reflector-filter at the core of the spallation neutron source - this reflector-filter is the first of its type in the world. Although we describe all implemented improvements to the TMRS, we focus on describing the design of the cold beryllium reflector-filter. Also presented are a detailed neutronic analysis of the predicted performance and influence of various external conditions on cold-neutron performance.

Mocko, M.; Muhrer, G.

2013-03-01

391

GNOMER. Solves the Multigroup Neutron Diffusion Equation  

SciTech Connect

GNOMER is a program which solves the multigroup neutron diffusion equation in 1D, 2D and 3D cartesian geometry. The program is designed to calculate the global core power distributions (with thermohydraulic feedbacks), as well as power distribution and homogenized cross sections over a fuel assembly.

Trkiv, A. [Josef Stefan Institute, Ljubljana (Slovenia)

1994-07-29

392

Hardware-Assisted Reliability Enhancement for Embedded Multi-core Virtualization Design  

Microsoft Academic Search

In this paper, we propose a virtualization ar- chitecture for the multi-core embedded system to provide more system reliability and security while maintaining the same performance without introducing additional special hard- ware supports or having to implement complex protection mechanism in the virtualization layer. Virtualization has been widely used in embedded systems, especially in consumer electronics, albeit itself is not

Tsung-Han Lin; Yuki Kinebuchi; Alexandre Courbot; Hiromasa Shimada; Takushi Morita; Hitoshi Mitake; Chen-Yi Lee; Tatsuo Nakajima

2011-01-01

393

A core-theoretic solution for the design of cooperative agreements on transfrontier pollution  

Microsoft Academic Search

For a simple economic model of transfrontier pollution, widely used in theoretical studies of international treaties bearing on joint abatement, we offer in this paper a scheme for sharing national abatement costs through international financial transfers that is inspired by a classical solution concept from the theory of cooperative games—namely, the core of a game. The scheme has the following

Parkash Chander; Henry Tulkens

1995-01-01

394

Designing a VH-mode core/L-mode edge discharge  

NASA Astrophysics Data System (ADS)

An operating mode with a very high confinement core like the VH-mode but a very low power flow to the divertor plates and low edge particle confinement like an L-mode would be beneficial. For a large tokamak like the proposed ITER, the power density at the separatrix is not that far above the scaled H-mode power threshold so not much of the power can be radiated inside the separatrix without causing a return to L-mode. The thicker scrape-off layer of an L-mode increases the radiating volume of the scrape-off layer and helps shield impurities from the core. This is especially important if the first wall is metallic. In this paper an H-mode transport model based on 0741-3335/38/8/055/img6 velocity shear suppression of turbulence will be used to show that it is possible to have a strongly radiating mantle near the separatrix, which keeps the edge in L-mode, while having a VH-mode core with a broad region of suppressed turbulence. The existing results of enhanced L-mode confinement during impurity injection on a number of tokamaks will be surveyed. We will identify the operating conditions which will most likely result in further improvement of the core confinement by control of the heating, fuelling, and torque profiles.

Staebler, G. M.; Hinton, F. L.; Wiley, J. C.

1996-08-01

395

Optimum design of a moderator system based on dose calculation for an accelerator driven Boron Neutron Capture Therapy.  

PubMed

An accelerator based BNCT has been desired because of its therapeutic convenience. However, optimal design of a neutron moderator system is still one of the issues. Therefore, detailed studies on materials consisting of the moderator system are necessary to obtain the optimal condition. In this study, the epithermal neutron flux and the RBE dose have been calculated as the indicators to look for optimal materials for the filter and the moderator. As a result, it was found that a combination of MgF2 moderator with Fe filter gave best performance, and the moderator system gave a dose ratio greater than 3 and an epithermal neutron flux over 1.0×10(9)cm(-2)s(-1). PMID:24440538

Inoue, R; Hiraga, F; Kiyanagi, Y

2014-06-01

396

Fusion-neutron-yield, activation measurements at the Z accelerator: design, analysis, and sensitivity.  

PubMed

We present a general methodology to determine the diagnostic sensitivity that is directly applicable to neutron-activation diagnostics fielded on a wide variety of neutron-producing experiments, which include inertial-confinement fusion (ICF), dense plasma focus, and ion beam-driven concepts. This approach includes a combination of several effects: (1) non-isotropic neutron emission; (2) the 1/r(2) decrease in neutron fluence in the activation material; (3) the spatially distributed neutron scattering, attenuation, and energy losses due to the fielding environment and activation material itself; and (4) temporally varying neutron emission. As an example, we describe the copper-activation diagnostic used to measure secondary deuterium-tritium fusion-neutron yields on ICF experiments conducted on the pulsed-power Z Accelerator at Sandia National Laboratories. Using this methodology along with results from absolute calibrations and Monte Carlo simulations, we find that for the diagnostic configuration on Z, the diagnostic sensitivity is 0.037% ± 17% counts/neutron per cm(2) and is ? 40% less sensitive than it would be in an ideal geometry due to neutron attenuation, scattering, and energy-loss effects. PMID:24784607

Hahn, K D; Cooper, G W; Ruiz, C L; Fehl, D L; Chandler, G A; Knapp, P F; Leeper, R J; Nelson, A J; Smelser, R M; Torres, J A

2014-04-01

397

Fusion-neutron-yield, activation measurements at the Z accelerator: Design, analysis, and sensitivity  

NASA Astrophysics Data System (ADS)

We present a general methodology to determine the diagnostic sensitivity that is directly applicable to neutron-activation diagnostics fielded on a wide variety of neutron-producing experiments, which include inertial-confinement fusion (ICF), dense plasma focus, and ion beam-driven concepts. This approach includes a combination of several effects: (1) non-isotropic neutron emission; (2) the 1/r2 decrease in neutron fluence in the activation material; (3) the spatially distributed neutron scattering, attenuation, and energy losses due to the fielding environment and activation material itself; and (4) temporally varying neutron emission. As an example, we describe the copper-activation diagnostic used to measure secondary deuterium-tritium fusion-neutron yields on ICF experiments conducted on the pulsed-power Z Accelerator at Sandia National Laboratories. Using this methodology along with results from absolute calibrations and Monte Carlo simulations, we find that for the diagnostic configuration on Z, the diagnostic sensitivity is 0.037% ± 17% counts/neutron per cm2 and is ˜ 40% less sensitive than it would be in an ideal geometry due to neutron attenuation, scattering, and energy-loss effects.

Hahn, K. D.; Cooper, G. W.; Ruiz, C. L.; Fehl, D. L.; Chandler, G. A.; Knapp, P. F.; Leeper, R. J.; Nelson, A. J.; Smelser, R. M.; Torres, J. A.

2014-04-01

398

Neutrons for Catalysis Neutrons as  

E-print Network

enzymes: biomimetic catalysts rational catalyst design process development development of non-precious metal catalysts with superior performance #12;Neutrons as microscopic probes in heterogeneous catalysis catalyst structure #12;Selected items from the BES report relevant to the use of neutrons: 2. Design

Pennycook, Steve

399

Optimization algorithms in boiling water reactor lattice design  

E-print Network

Given the highly complex nature of neutronics and reactor physics, efficient methods of optimizing are necessary to effectively design the core reloading pattern and operate a nuclear reactor. The current popular methods ...

Burns, Chad (Chad D.), III

2013-01-01

400

Possible Methods to Estimate Core Location in a Beyond-Design-Basis Accident at a GE BWR with a Mark I Containment Stucture  

SciTech Connect

It is difficult to track to the location of a melted core in a GE BWR with Mark I containment during a beyond-design-basis accident. The Cooper Nuclear Station provided a baseline of normal material distributions and shielding configurations for the GE BWR with Mark I containment. Starting with source terms for a design-basis accident, methods and remote observation points were investigated to allow tracking of a melted core during a beyond-design-basis accident. The design of the GE BWR with Mark-I containment highlights an amazing poverty of expectations regarding a common mode failure of all reactor core cooling systems resulting in a beyond-design-basis accident from the simple loss of electric power. This design is shown in Figure 1. The station blackout accident scenario has been consistently identified as the leading contributor to calculated probabilities for core damage. While NRC-approved models and calculations provide guidance for indirect methods to assess core damage during a beyond-design-basis loss-of-coolant accident (LOCA), there appears to be no established method to track the location of the core directly should the LOCA include a degree of fuel melt. We came to the conclusion that - starting with detailed calculations which estimate the release and movement of gaseous and soluble fission products from the fuel - selected dose readings in specific rooms of the reactor building should allow the location of the core to be verified.

Walston, S; Rowland, M; Campbell, K

2011-07-27

401

Neutronics and Thermal Hydraulics Study for Using a Low-Enriched Uranium Core in the Advanced Test Reactor -- 2008 Final Report  

SciTech Connect

The Advanced Test Reactor (ATR) is a high power density and high neutron flux research reactor operating in the United States. Powered with highly enriched uranium (HEU), the ATR has a maximum thermal power rating of 250 MWth. Because of the large test volumes located in high flux areas, the ATR is an ideal candidate for assessing the feasibility of converting an HEU driven reactor to a low-enriched core. The present work investigates the necessary modifications and evaluates the subsequent operating effects of this conversion. A detailed plate-by-plate MCNP ATR 1/8th core model was developed and validated for a fuel cycle burnup comparison analysis. Using the current HEU U 235 enrichment of 93.0 % as a baseline, an analysis was performed to determine the low-enriched uranium (LEU) density and U-235 enrichment required in the fuel meat to yield an equivalent K-eff versus effective full power days (EFPDs) between the HEU and the LEU cores. The MCNP ATR 1/8th core model was used to optimize the U 235 loading in the LEU core, such that the differences in K-eff and heat flux profiles between the HEU and LEU cores were minimized. The depletion methodology MCWO was used to calculate K-eff versus EFPDs in this paper. The MCWO-calculated results for the LEU demonstrated adequate excess reactivity such that the K-eff versus EFPDs plot is similar to the ATR reference HEU case study. Each HEU fuel element contains 19 fuel plates with a fuel meat thickness of 0.508 mm (20 mil). In this work, the proposed LEU (U-10Mo) core conversion case with nominal fuel meat thickness of 0.330 mm (13 mil) and U-235 enrichment of 19.7 wt% is used to optimize the radial heat flux profile by varying the fuel meat thickness from 0.191 mm (7.0 mil) to 0.330 mm (13.0 mil) at the inner 4 fuel plates (1-4) and outer 4 fuel plates (16-19). A 0.8g of Boron-10, a burnable absorber, was added in the inner and outer plates to reduce the initial excess reactivity, and the peak to average ratio of the inner/outer heat flux more effectively. Because the B-10 (n,a) reaction will produce Helium-4 (He-4), which might degrade the LEU foil type fuel performance, an alternative absorber option is proposed. The proposed LEU case study will have 6.918 g of Cadmium (Cd) mixed with the LEU at the inner 4 fuel plates (1-4) and outer 4 fuel plates (16-19) as a burnable absorber to achieve peak to average ratios similar to those for the ATR reference HEU case study.

G. S. Chang; M. A. Lillo; R. G. Ambrosek

2008-06-01

402

PHISICS multi-group transport neutronic capabilities for RELAP5  

SciTech Connect

PHISICS is a neutronic code system currently under development at INL. Its goal is to provide state of the art simulation capability to reactor designers. This paper reports on the effort of coupling this package to the thermal hydraulic system code RELAP5. This will enable full prismatic core and system modeling and the possibility to model coupled (thermal-hydraulics and neutronics) problems with more options for 3D neutron kinetics, compared to the existing diffusion theory neutron kinetics module in RELAP5 (NESTLE). The paper describes the capabilities of the coupling and illustrates them with a set of sample problems. (authors)

Epiney, A.; Rabiti, C.; Alfonsi, A.; Wang, Y.; Cogliati, J.; Strydom, G. [Idaho National Laboratory (INL), 2525 N. Fremont Ave., Idaho Falls, ID 83402 (United States)

2012-07-01

403

ABWR-II Core Design with Spectral Shift Rods for Operation with All Control Rods Withdrawn  

SciTech Connect

An innovative reactor core concept applying spectral shift rods (SSRs) is proposed to improve the plant economy and the operability of the 1700-MW(electric) Advanced Boiling Water Reactor II (ABWR-II). The SSR is a new type of water rod in which a water level is naturally developed during operation and changed according to the coolant flow rate through the channel. By taking advantage of the large size of the ABWR-II bundle, the enhanced spectral shift operation by eight SSRs allows operation of the ABWR-II with all control rods withdrawn. In addition, the uranium-saving factor of 6 to 7% relative to the reference ABWR-II core with conventional water rods can be expected due to the greater effect of spectral shift. The combination of these advantages means the ABWR-II with SSRs should be an attractive alternative for the next-generation nuclear reactor.

Moriwaki, Masanao [Hitachi, Ltd. (Japan); Aoyama, Motoo [Hitachi, Ltd. (Japan); Anegawa, Takafumi [Tokyo Electric Power Company (Japan); Okada, Hiroyuki [Tokyo Electric Power Company (Japan); Sakurada, Koichi [Toshiba Corporation (Japan); Tanabe, Akira [Global Nuclear Fuel-Japan Company, Ltd. (Japan)

2004-03-15

404

Binary pulsar J0737-3039 - evidence for a new core collapse and neutron star formation mechanism  

NASA Astrophysics Data System (ADS)

The binary pulsar J0737-3039 is the only known system having two observable pulsars, thus offering a unique laboratory to test general relativity and explore pulsar physics. Based on the low eccentricity and the position within the galactic plane, two of us have argued that pulsar B had a non-standard formation scenario with little or no mass ejection and predicted that the system would have a very slow proper motion. Pulsar timing measurements confirmed this prediction. The recent observations of the alignment between the spin of pulsar A and the binary orbit is also in agreement with this scenario. Detailed simulations of the formation process of pulsar B show that its progenitor, just before the collapse, was a massive O-Ne-Mg white dwarf surrounded by a tenuous, 0.1-0.16 M?, envelope. This envelope was ejected when the white dwarf collapsed to form a neutron star. Pulsar B was born as a slow rotator (spin period ˜1 s) and a kick received when the pulsar formed changed its spin direction to the current one. This realization sheds light on the angular momentum evolution of the progenitor star, a process which is strongly affected by interaction with the binary companion. The slow proper motion of the system also implies that the system must have undergone a phase of mass transfer in which star A shed a significant fraction of its mass on to B.

Dall'Osso, Simone; Piran, Tsvi; Shaviv, Nir

2014-02-01

405