Improvement of transportcorrected scattering stability and performance using a Jacobi inscatter algorithm for 2DMOC
Abstract
The MPACT code, being developed collaboratively by the University of Michigan and Oak Ridge National Laboratory, is the primary deterministic neutron transport solver being deployed within the Virtual Environment for Reactor Applications (VERA) as part of the Consortium for Advanced Simulation of Light Water Reactors (CASL). In many applications of the MPACT code, transportcorrected scattering has proven to be an obstacle in terms of stability, and considerable effort has been made to try to resolve the convergence issues that arise from it. Most of the convergence problems seem related to the transportcorrected cross sections, particularly when used in the 2D method of characteristics (MOC) solver, which is the focus of this work. Here in this paper, the stability and performance of the 2D MOC solver in MPACT is evaluated for two iteration schemes: GaussSeidel and Jacobi. With the GaussSeidel approach, as the MOC solver loops over groups, it uses the flux solution from the previous group to construct the inscatter source for the next group. Alternatively, the Jacobi approach uses only the fluxes from the previous outer iteration to determine the inscatter source for each group. Consequently for the Jacobi iteration, the loop over groups can be moved from themore »
 Authors:

 Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
 Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Nuclear Engineering and Radiological Sciences
 Publication Date:
 Research Org.:
 Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Consortium for Advanced Simulation of LWRs (CASL)
 Sponsoring Org.:
 USDOE
 OSTI Identifier:
 1349605
 Alternate Identifier(s):
 OSTI ID: 1397019
 Grant/Contract Number:
 AC0500OR22725; AC0500OR22725
 Resource Type:
 Journal Article: Accepted Manuscript
 Journal Name:
 Annals of Nuclear Energy (Oxford)
 Additional Journal Information:
 Journal Volume: 105; Journal Issue: C; Journal ID: ISSN 03064549
 Publisher:
 Elsevier
 Country of Publication:
 United States
 Language:
 English
 Subject:
 97 MATHEMATICS AND COMPUTING; Transport correction; MOC; Jacobi; GaussSeidel; Stability
Citation Formats
Stimpson, Shane, Collins, Benjamin, and Kochunas, Brendan. Improvement of transportcorrected scattering stability and performance using a Jacobi inscatter algorithm for 2DMOC. United States: N. p., 2017.
Web. doi:10.1016/j.anucene.2017.02.024.
Stimpson, Shane, Collins, Benjamin, & Kochunas, Brendan. Improvement of transportcorrected scattering stability and performance using a Jacobi inscatter algorithm for 2DMOC. United States. doi:10.1016/j.anucene.2017.02.024.
Stimpson, Shane, Collins, Benjamin, and Kochunas, Brendan. Fri .
"Improvement of transportcorrected scattering stability and performance using a Jacobi inscatter algorithm for 2DMOC". United States. doi:10.1016/j.anucene.2017.02.024. https://www.osti.gov/servlets/purl/1349605.
@article{osti_1349605,
title = {Improvement of transportcorrected scattering stability and performance using a Jacobi inscatter algorithm for 2DMOC},
author = {Stimpson, Shane and Collins, Benjamin and Kochunas, Brendan},
abstractNote = {The MPACT code, being developed collaboratively by the University of Michigan and Oak Ridge National Laboratory, is the primary deterministic neutron transport solver being deployed within the Virtual Environment for Reactor Applications (VERA) as part of the Consortium for Advanced Simulation of Light Water Reactors (CASL). In many applications of the MPACT code, transportcorrected scattering has proven to be an obstacle in terms of stability, and considerable effort has been made to try to resolve the convergence issues that arise from it. Most of the convergence problems seem related to the transportcorrected cross sections, particularly when used in the 2D method of characteristics (MOC) solver, which is the focus of this work. Here in this paper, the stability and performance of the 2D MOC solver in MPACT is evaluated for two iteration schemes: GaussSeidel and Jacobi. With the GaussSeidel approach, as the MOC solver loops over groups, it uses the flux solution from the previous group to construct the inscatter source for the next group. Alternatively, the Jacobi approach uses only the fluxes from the previous outer iteration to determine the inscatter source for each group. Consequently for the Jacobi iteration, the loop over groups can be moved from the outermost loop$$as is the case with the GaussSeidel sweeper$$to the innermost loop, allowing for a substantial increase in efficiency by minimizing the overhead of retrieving segment, region, and surface index information from the ray tracing data. Several test problems are assessed: (1) Babcock & Wilcox 1810 Core I, (2) Dimple S01ASq, (3) VERA Progression Problem 5a, and (4) VERA Problem 2a. The Jacobi iteration exhibits better stability than GaussSeidel, allowing for converged solutions to be obtained over a much wider range of iteration control parameters. Additionally, the MOC solve time with the Jacobi approach is roughly 2.02.5× faster per sweep. While the performance and stability of the Jacobi iteration are substantially improved compared to the GaussSeidel iteration, it does yield a roughly 8$$10% increase in the overall memory requirement.},
doi = {10.1016/j.anucene.2017.02.024},
journal = {Annals of Nuclear Energy (Oxford)},
issn = {03064549},
number = C,
volume = 105,
place = {United States},
year = {2017},
month = {3}
}
Web of Science