A fully coupled Monte Carlo/discrete ordinates solution to the neutron transport equation. Final report

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1990

DOI:https://doi.org/10.2172/10136650· OSTI ID:10136650

Baker, Randal Scott ^[1]

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1. Univ. of Arizona, Tucson, AZ (United States)

The neutron transport equation is solved by a hybrid method that iteratively couples regions where deterministic (S_N) and stochastic (Monte Carlo) methods are applied. Unlike previous hybrid methods, the Monte Carlo and S_N regions are fully coupled in the sense that no assumption is made about geometrical separation or decoupling. The hybrid method provides a new means of solving problems involving both optically thick and optically thin regions that neither Monte Carlo nor S_N is well suited for by themselves. The fully coupled Monte Carlo/S_N technique consists of defining spatial and/or energy regions of a problem in which either a Monte Carlo calculation or an S_N calculation is to be performed. The Monte Carlo region may comprise the entire spatial region for selected energy groups, or may consist of a rectangular area that is either completely or partially embedded in an arbitrary S_N region. The Monte Carlo and S_N regions are then connected through the common angular boundary fluxes, which are determined iteratively using the response matrix technique, and volumetric sources. The hybrid method has been implemented in the S_N code TWODANT by adding special-purpose Monte Carlo subroutines to calculate the response matrices and volumetric sources, and linkage subrountines to carry out the interface flux iterations. The common angular boundary fluxes are included in the S_N code as interior boundary sources, leaving the logic for the solution of the transport flux unchanged, while, with minor modifications, the diffusion synthetic accelerator remains effective in accelerating S_N calculations. The special-purpose Monte Carlo routines used are essentially analog, with few variance reduction techniques employed. However, the routines have been successfully vectorized, with approximately a factor of five increase in speed over the non-vectorized version.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Arizona Univ., Tucson, AZ (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 10136650
• Report Number(s): LA-SUB--94-61; ON: DE94009071
• Country of Publication: United States
• Language: English

Related Subjects

663610
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
97 MATHEMATICS AND COMPUTING
990200
BENCHMARKS
CROSS SECTIONS
ITERATIVE METHODS
MATHEMATICS AND COMPUTERS
MONTE CARLO METHOD
NEUTRON PHYSICS
NEUTRON TRANSPORT THEORY
PROGRESS REPORT
RESPONSE MATRIX METHOD