Choosing Transport Events for Initiating Splitting and Rouletting

Journal Article · Fri Mar 26 00:00:00 EDT 2021 · Journal of Nuclear Engineering

DOI:https://doi.org/10.3390/jne2020010· OSTI ID:1777699

Gonzalez, Evan S. ^[1]; Davidson, Gregory G. ^[2]

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1. Univ. of Michigan, Ann Arbor, MI (United States)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

A study was performed to determine which transport events should be used to initiate a weight window lookup to achieve the best variance reduction performance. A weight window lookup potentially triggers particle splitting (in important regions of phase space) or rouletting (in unimportant regions), thereby optimizing computational effort. Potential initiating transport events include collisions (both pre- and post-collision), geometry surface crossings, traversing a mean-free path, and streaming across a weight window boundary. Permutations of these initiating events were tested on an urban model with background radiation sources and a spent fuel cask with a neutron dose mesh tally. Generally, all methods perform better with finer weight window meshes. Tracking on weight windows performs well for coarse weight window meshes, while a combination of splitting each mean-free path, geometric surface crossing, and before collisions performs well for fine weight window meshes.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: US Nuclear Regulatory Commission; USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1777699
• Journal Information: Journal of Nuclear Engineering, Journal Name: Journal of Nuclear Engineering Journal Issue: 2 Vol. 2; ISSN 2673-4362
• Publisher: MDPI
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
FW-CADIS
Monte Carlo
shift
variance reduction