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Title: Uncertainty in Fast Reactor-Relevant Critical Benchmark Simulations due to Unresolved Resonance Structure

Authors:
; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1357345
Report Number(s):
LLNL-CONF-724158
DOE Contract Number:
AC52-07NA27344
Resource Type:
Conference
Resource Relation:
Conference: Presented at: International Conference on Mathematics & Computational Methods Applied to Nuclear Science & Engineering, Jeju, South Korea, Apr 17 - Apr 20, 2017
Country of Publication:
United States
Language:
English
Subject:
22 GENERAL STUDIES OF NUCLEAR REACTORS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 97 MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE

Citation Formats

Walsh, J A, Forget, B, Smith, K S, and Brown, F B. Uncertainty in Fast Reactor-Relevant Critical Benchmark Simulations due to Unresolved Resonance Structure. United States: N. p., 2017. Web.
Walsh, J A, Forget, B, Smith, K S, & Brown, F B. Uncertainty in Fast Reactor-Relevant Critical Benchmark Simulations due to Unresolved Resonance Structure. United States.
Walsh, J A, Forget, B, Smith, K S, and Brown, F B. Tue . "Uncertainty in Fast Reactor-Relevant Critical Benchmark Simulations due to Unresolved Resonance Structure". United States. doi:. https://www.osti.gov/servlets/purl/1357345.
@article{osti_1357345,
title = {Uncertainty in Fast Reactor-Relevant Critical Benchmark Simulations due to Unresolved Resonance Structure},
author = {Walsh, J A and Forget, B and Smith, K S and Brown, F B},
abstractNote = {},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Feb 14 00:00:00 EST 2017},
month = {Tue Feb 14 00:00:00 EST 2017}
}

Conference:
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  • The purpose of this study is to investigate the eigenvalue sensitivity to changes in unresolved resonance treatment by comparing RACER Monte Carlo calculations for several fast and intermediate spectrum critical experiments. Calculations performed using smooth, dilute-average, tabulated cross sections were compared with calculations using the probability table method to produce stochastically generated resonance cross sections in the unresolved resonance region. The use of the probability table method is superior to the dilute-average cross section method for representing the unresolved resonance region because the table method properly accounts for resonance self shielding; thereby, reducing the effectiveness of the cross sections inmore » the region. The unresolved resonance region is typically found in the intermediate and fast energy range. Eleven benchmark critical assemblies that span a range of {sup 235}U enrichments (93.8 to 10.2%) and four highly enriched {sup 239}Pu and {sup 233}U assemblies were analyzed. These benchmarks were chosen to accentuate the reactivity importance of the unresolved resonance range.« less
  • The GCFR Phase I assembly is the initial Gas-Cooled Fast Reactor Benchmark assembly on the ZPR-9 reactor at Argonne National Laboratory. It represents the first full scale mockup of a GCFR ever assembled. It is a clean, simple geometry benchmark reference for the 300 MW(e) GCFR Demonstration Plant designed by General Atomic Company. A description and the evaluated specifications (zero-excess reactivity critical mass and dimensions) of the benchmark assembly are presented. (auth)
  • Evaluators face special problems in the resolved and unresolved resonance regions where cross sections are not given directly in the evaluated files but only in the form of individual or statistical resonance parameters. Combination of resolved parameter sets is difficult if they are derived from data taken with widely differing energy resolution. Systematic uncertainties from calibration or background subtraction get lost if in the usual least-squares parametrization all data points are treated as statistically independent. Evaluations in the unresolved resonance region must cope with, and distinguish between, unobserved genuine cross section fluctuations and uncertainties. Recent evaluation work on Fe andmore » {sup 238}U illustrates (1) how these problems can be addressed and (2) how unobserved total cross section fluctuations can be predicted with level statistical methods (Hauser-Feshbach theory).« less