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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Verification of Revised and Upcoming Nuclear Data Sensitivity MCNP Features [Poster]

Nuclear data is ubiquitous across nuclear applications. Improved nuclear data means more accurate simulations. Past focus on k eff caused compensating error and areas of unvalidated nuclear data. Sensitivity can be used to optimize experiments to focus on specific areas. Sensitivity capabilities must be expanded and improved to design multivariate experiments focused on nuclear data needs.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Modeling and evaluating 239 Pu and 235 U PFNS and average prompt-neutron multiplicity [Slides]

The following are currently in VIII.1 LANL and IAEA test files: 239 Pu nu-bar including CGMF modeling and CEA data, 239 Pu PFNS including Chi-Nu & CEA data, 239 Pu(n,f) cross section including fission TPC data. The following are currently being tested: 235 U nu-bar including CGMF modeling and 235 U PFNS including Chi-Nu data. Upcoming tasks include the correction of 235 U Chi-Nu PFNS at higher E inc , benchmarking 235 U PFNS and nu-bar evaluations, and getting 238 U nu-bar.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

EUCLID: Experiments Underpinned by Computational Learning for Improvements in Nuclear Data [Slides]

EUCLID will design validation experiments optimized to resolve compensating errors and adjust nuclear data to experiments. A big part of the success of the EUCLID proposal was due to previous work supported by NCSP (MCNP, nuclear data, and NCERC capabilities). The work performed under EUCLID will similarly benefit the NCSP mission. It will lead to new MCNP capabilities, improved nuclear data and nuclear data capabilities, and new methodology and tools that will have large impact on future NCERC experiments.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Verification of MCNP Critical Benchmark Model of U233-COMP-THERM-004 [Slides]

The verification of U233-COMP-THERM-004 contributed to the LANL centralized repository that’s currently under development. Revisions made to the MCNP model were statistically significant. Magnitude of bias is relatively small in comparison to other uranium benchmark biases and thus will likely have not a significant effect on the USL.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Deterministic and Monte Carlo Nuclear Data Adjustment Methods [Slides]

For the Bayesian Monte Carlo methodology, a need to understand convergence of the posterior moments as a function of the number of parameter realizations is required. In high-dimensional systems, it can be very costly to sample entire parameter space and perform functional evaluation for every realization. Bayesian Monte Carlo allows one to relax the GLLS approximations of model linearity and prior/posterior PDF shape. The Bayesian Stochastic Collocation Method is a deterministic approach to “sample” the parameter space. It allows one to relax the GLLS approximations of model linearity and posterior PDF shape. Higher-order posterior moments (i.e., skewness, kurtosis, etc.) can be studied through polynomial expansion. Tensor product quadrature scales poorly and can use sparse grid quadrature methods.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

IER 501: Pulsed Neutron Die-Away Experiments at LLNL [Slides]

Pulsed neutron die away experiments occur as follows: (1) a pulse of neutrons is injected into a target material via a D-T neutron generator, (2) neutrons thermalize, (3) neutrons spatially equilibrate, and (4) exponential decay is measured in fundamental mode.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

IER-297: TEX-HEU Baseline Assemblies Benchmark and Results [Slides]

The pending resolution of comments was accepted by the ICSBEP TRG in December 2021. Subgroup includes Catherine Percher, Dave Heinrichs, Michael Zerkle (NNL), and Jeffrey Favorite (LANL). The full resolution of comments is anticipated by March 31, 2022. Plans to execute TEX-HEU-Hf variant of experiment design are anticipated for FY22.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Parallel-Plate Avalanche Counter (PPAC) Fabrication for 240 Pu PFNS Measurement [Slides]

A LANL-LLNL joint program has been developed successfully to measure PFNS and established the most precisely determined $\chi$ matrices for 235,238 U and 239 Pu. It has been extended to 240 Pu now and possibly to 233 U in the future. An alternative method was developed to fabricate 240 Pu and a total of 12 targets were made with a total mass of 17.9 mg. The PFNS measurement for 240 Pu will begin in June, 2022 when the new beam cycle starts and the data analysis follows immediately afterward.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

LLNL FY21 NCSP Overview [Slides]

This presentation details the impacts of the COVID-19 pandemic on LLNL in fiscal year 2021, as well as budget information and major accomplishments for the lab in IE, analytical methods, nuclear data, training and education, and IPD.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Accomplishments of Thermal Neutron Scattering Research at North Carolina State University [Slides]

Thermal neutron scattering law (TSL) data evaluations have been completed and contributed to ENDF. New evaluations are underway. FLASSH is developing as a modern platform for thermal neutron data analysis featuring an enhanced user experience and low learning overhead. Advanced TSL techniques in combination with Doppler analysis have been developed, which were incorporated into FLASSH. ML/DL NeTS method development has been initiated. Experimental capabilities for validation have been developed at the PULSTAR reactor.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Thermal Neutron Scattering Law for Beryllium Hydride and Critical Mass Calculations [Slides]

TSLs for H(BeH 2 ) and Be(BeH 2 ) were evaluated in the incoherent approximation using FLASSH. Minimum critical mass estimates were performed using MC21 continuous energy Monte Carlo calculations with the BeH 2 TSLs. Researchers confirmed very low estimated critical mass for BeH 2 -moderated and Be- reflected spheres. These were the lowest critical masses NNL has studied to date. Future work includes relaxation of the incoherent approximation for Be(BeH 2 ). A small increase in critical mass is expected due to increased neutron transmission at sub-Bragg cutoff energies.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Thermal Neutron Scattering Law Evaluations for Zirconium Carbide and Critical Mass Calculations [Slides]

Zirconium Carbide (ZrC) is a refractory material currently being investigated for high temperature reactor applications. ZrC was studied as a base of (U,Zr)C solid solution and UC 2 composite fuels for NERVA-type cores during the Rover program. Testing of the material was performed at Nuclear Furnace 1 (NF-1) located at Los Alamos. Thermal Scattering Law (TSL) evaluations generated with FLASSH are a new contribution to ENDF/B-VIII.1.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Comparative Critical Mass Calculations for NNL and ENDF/B-VIII.0 Zirconium Hydride Thermal Scattering Laws [Slides]

Zirconium Hydride (ZrH x ) is a moderator material for TRIGA reactors and SNAP-10A.The thermal scattering has the behavior of quantum oscillator favorable for moderator feedback. ZrH x occurs as a corrosion product in LWR. Previously new phase specific TSL evaluations were generated and submitted to ENDF/B- VIII.1. These include the effects of crystal structure on elastic scattering of Zr(ZrH x ), permit flexibility in stoichiometry for use in reactor physics calculations and fuel characterization, and expand the TSL material sub-library. ENDF/B-VIII.0 ZrH TSLs do not distinguish between material phase. Current work involves preliminary validation & verification testing on the effect of TSLs on critical mass and associated thermal flux.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Update on NNL TSL Validation Efforts [Slides]

A new sub-thermal neutron transmission capability at RPI LINAC has been used to validate Be (metal). NNL transmission measurements validated NCSU Be and Be+Sd TSLs for ENDF/B-VIII.1 and showed improvements WRT ENDF/B-VII.1 and ENDF/B-VIII.0. Amplitude differences highlighted the importance of sample characterization. Additional measurement is in progress for CY2022. PNDA is being developed as an alternative to critical experiment validation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗