The neutron number probability distribution in coupled lumped assemblies

O’Rourke, Patrick F.; Prinja, Anil K.

doi:10.1016/j.anucene.2023.110063

The neutron number probability distribution in coupled lumped assemblies

Journal Article · Wed Aug 02 00:00:00 EDT 2023 · Annals of Nuclear Energy

DOI:https://doi.org/10.1016/j.anucene.2023.110063· OSTI ID:2477787

^[1]; Prinja, Anil K. ^[2]

Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Univ. of New Mexico, Albuquerque, NM (United States)

Here, the validity of the gamma distribution in describing the neutron number probability distribution function for both isolated and coupled multiplying assemblies when constrained to reproduce the true mean and variance is investigated in lumped geometry by numerical comparison with kinetic Monte Carlo simulations. The mean and variance are obtained from numerical solution of moment equations constructed from the relevant forward Master equation with assembly coupling coefficients obtained from a view factor method. Numerical results for a two-group, two coupled assemblies model, with static and dynamic reactivity insertion, show that except for subcritical assemblies, the gamma distribution well-approximates the number distribution. Differences in the fast and thermal neutron population shapes are explained in terms of effective source strengths due to downscatter and coupling.

Research Organization:: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

Sponsoring Organization:: USDOE National Nuclear Security Administration (NNSA)

Grant/Contract Number:: 89233218CNA000001

OSTI ID:: 2477787

Alternate ID(s):: OSTI ID: 1994419

Report Number(s):: LA-UR--23-20518

Journal Information:: Annals of Nuclear Energy, Journal Name: Annals of Nuclear Energy Vol. 193; ISSN 0306-4549

Publisher:: ElsevierCopyright Statement

Country of Publication:: United States

Language:: English

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