skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: The Subray Method of Characteristics

Abstract

The MPACT code is being jointly developed by the University of Michigan and Oak Ridge National Laboratory. It uses the 2-D/1-D method to solve neutron transport problems for reactors. The 2-D/1-D method decomposes the problem into a stack of 2-D planes and uses a high-fidelity transport method to resolve all heterogeneity in each plane. These planes are then coupled axially, using a lower-order solver. With this scheme, three-dimensional (3-D) solutions to the transport equation can be obtained at a much lower cost. The 2-D/1-D method assumes that the materials are axially homogeneous for each 2-D plane. Violation of this assumption requires homogenization, which can significantly reduce the accuracy of the calculation. This work proposes the subray method of characteristics (subray MOC) as a solution to this problem. Subray MOC is a subgrid method that allows local heterogeneities to be directly resolved by method of characteristics while treating the rest of the 2-D plane as axially uniform. This improves the accuracy in the neighborhood of the heterogeneity while minimizing the increase in run time. The method was applied to variations of the C5G7 benchmark problems and compared with a previously developed subgrid method called the subplane collision probabilities (SCP) method. Comparisonsmore » were made among results obtained using subray MOC, the SCP method, and no subgrid method. Subray MOC consistently performed best, reducing maximum 3-D power distribution errors from as high as 30% to 2% or less. Moreover, it consistently outperformed the SCP method with run times that were shorter than the reference calculations.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [2]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of Michigan, Ann Arbor, MI (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1511951
DOE Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Nuclear Science and Engineering
Additional Journal Information:
Journal Volume: 193; Journal Issue: 6; Journal ID: ISSN 0029-5639
Publisher:
American Nuclear Society - Taylor & Francis
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; Planar synthesis; 2-D/1-D method; rod cusping; subgrid methods; subray method of characteristics

Citation Formats

Graham, Aaron M., Collins, Benjamin S., and Downar, Thomas J. The Subray Method of Characteristics. United States: N. p., 2019. Web. doi:10.1080/00295639.2018.1550988.
Graham, Aaron M., Collins, Benjamin S., & Downar, Thomas J. The Subray Method of Characteristics. United States. doi:10.1080/00295639.2018.1550988.
Graham, Aaron M., Collins, Benjamin S., and Downar, Thomas J. Fri . "The Subray Method of Characteristics". United States. doi:10.1080/00295639.2018.1550988.
@article{osti_1511951,
title = {The Subray Method of Characteristics},
author = {Graham, Aaron M. and Collins, Benjamin S. and Downar, Thomas J.},
abstractNote = {The MPACT code is being jointly developed by the University of Michigan and Oak Ridge National Laboratory. It uses the 2-D/1-D method to solve neutron transport problems for reactors. The 2-D/1-D method decomposes the problem into a stack of 2-D planes and uses a high-fidelity transport method to resolve all heterogeneity in each plane. These planes are then coupled axially, using a lower-order solver. With this scheme, three-dimensional (3-D) solutions to the transport equation can be obtained at a much lower cost. The 2-D/1-D method assumes that the materials are axially homogeneous for each 2-D plane. Violation of this assumption requires homogenization, which can significantly reduce the accuracy of the calculation. This work proposes the subray method of characteristics (subray MOC) as a solution to this problem. Subray MOC is a subgrid method that allows local heterogeneities to be directly resolved by method of characteristics while treating the rest of the 2-D plane as axially uniform. This improves the accuracy in the neighborhood of the heterogeneity while minimizing the increase in run time. The method was applied to variations of the C5G7 benchmark problems and compared with a previously developed subgrid method called the subplane collision probabilities (SCP) method. Comparisons were made among results obtained using subray MOC, the SCP method, and no subgrid method. Subray MOC consistently performed best, reducing maximum 3-D power distribution errors from as high as 30% to 2% or less. Moreover, it consistently outperformed the SCP method with run times that were shorter than the reference calculations.},
doi = {10.1080/00295639.2018.1550988},
journal = {Nuclear Science and Engineering},
issn = {0029-5639},
number = 6,
volume = 193,
place = {United States},
year = {2019},
month = {1}
}

Works referenced in this record:

Subplane collision probabilities method applied to control rod cusping in 2D/1D
journal, August 2018


Solution of the BEAVRS benchmark using the nTRACER direct whole core calculation code
journal, April 2015


Axial SP N and Radial MOC Coupled Whole Core Transport Calculation
journal, September 2007


Diffusion theory methods for spatial kinetics calculations
journal, January 1996


Stability and accuracy of 3D neutron transport simulations using the 2D/1D method in MPACT
journal, December 2016

  • Collins, Benjamin; Stimpson, Shane; Kelley, Blake W.
  • Journal of Computational Physics, Vol. 326
  • DOI: 10.1016/j.jcp.2016.08.022