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Benchmark of Neutron Thermalization in Graphite Using a Pulsed Slowing-Down-Time Experiment

Journal Article · · Nuclear Science and Engineering

A benchmark has been developed using a pulsed slowing-down-time experiment to isolate the thermalization process in graphite. The experiment was conducted at the Oak Ridge Electron Linear Accelerator facility at Oak Ridge National Laboratory, and it measured the time spectrum of neutrons leaking from a graphite pile during slowing down and thermalization within graphite. Simulations of the benchmark experiment were performed using the MCNP6.1 Monte Carlo code and the ENDF/B-VII.1 and ENDF/B-VIII.0 cross-section databases. The benchmark provides a time spectrum (i.e., time-dependent counts in a detector) that allows for validation of the graphite thermal scattering libraries (TSLs). The impact on the simulations using a suite of graphite TSLs was compared with the experimental results. Given the density of nuclear graphite, the TSL corresponding to graphite with 30% porosity, as implemented in ENDF/B-VIII.0, was found to most accurately represent the measured time spectrum corresponding to the thermal energy range with an average deviation of ±1.7%.

Research Organization:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP)
DOE Contract Number:
AC52-07NA27344
OSTI ID:
1971997
Journal Information:
Nuclear Science and Engineering, Journal Name: Nuclear Science and Engineering; ISSN 0029-5639
Publisher:
Taylor & Francis
Country of Publication:
United States
Language:
English

References (5)

Inelastic Thermal Neutron Scattering Cross Sections for Reactor-grade Graphite journal April 2014
Initial MCNP6 Release Overview journal December 2012
ENDF/B-VII.1 Nuclear Data for Science and Technology: Cross Sections, Covariances, Fission Product Yields and Decay Data journal December 2011
ENDF/B-VIII.0: The 8 th Major Release of the Nuclear Reaction Data Library with CIELO-project Cross Sections, New Standards and Thermal Scattering Data journal February 2018
Thermal neutron scattering law calculations using ab initio molecular dynamics journal January 2017