An improved target velocity sampling algorithm for free gas elastic scattering

Journal Article · 03 February 2018 · Annals of Nuclear Energy (Oxford)

DOI: https://doi.org/10.1016/j.anucene.2017.12.044 · OSTI ID:1425283

Romano, Paul K. ^[1]; Walsh, Jonathan A. ^[2]

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1. Argonne National Lab. (ANL), Argonne, IL (United States)
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

We present an improved algorithm for sampling the target velocity when simulating elastic scattering in a Monte Carlo neutron transport code that correctly accounts for the energy dependence of the scattering cross section. The algorithm samples the relative velocity directly, thereby avoiding a potentially inefficient rejection step based on the ratio of cross sections. Here, we have shown that this algorithm requires only one rejection step, whereas other methods of similar accuracy require two rejection steps. The method was verified against stochastic and deterministic reference results for upscattering percentages in ²³⁸U. Simulations of a light water reactor pin cell problem demonstrate that using this algorithm results in a 3% or less penalty in performance when compared with an approximate method that is used in most production Monte Carlo codes

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States); Lawrence Livermore National Laboratory (LLNL), Livermore, CA
• Sponsoring Organization: USDOE; USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21)
• Grant/Contract Number: AC02-06CH11357; AC52-07NA27344
• OSTI ID: 1425283
• Report Number(s): LLNL-JRNL-745886; 138571
• Journal Information: Annals of Nuclear Energy (Oxford), Journal Name: Annals of Nuclear Energy (Oxford) Journal Issue: C Vol. 114; ISSN 0306-4549
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English