Improvement of the 2D/1D Method in MPACT Using the SubPlane Scheme
Abstract
Oak Ridge National Laboratory and the University of Michigan are jointly developing the MPACTcode to be the primary neutron transport code for the Virtual Environment for Reactor Applications (VERA). To solve the transport equation, MPACT uses the 2D/1D method, which decomposes the problem into a stack of 2D planes that are then coupled with a 1D axial calculation. MPACT uses the Method of Characteristics for the 2D transport calculations and P3 for the 1D axial calculations, then accelerates the solution using the 3D Coarse mesh Finite Dierence (CMFD) method. Increasing the number of 2D MOC planes will increase the accuracy of the alculation, but will increase the computational burden of the calculations and can cause slow convergence or instability. To prevent these problems while maintaining accuracy, the subplane scheme has been implemented in MPACT. This method subdivides the MOC planes into subplanes, refining the 1D P3 and 3D CMFD calculations without increasing the number of 2D MOC planes. To test the subplane scheme, three of the VERA Progression Problems were selected: Problem 3, a single assembly problem; Problem 4, a 3x3 assembly problem with control rods and pyrex burnable poisons; and Problem 5, a quarter core problem. These three problemsmore »
 Authors:
 ORNL
 University of Michigan
 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:
 1344278
 DOE Contract Number:
 AC0500OR22725
 Resource Type:
 Conference
 Resource Relation:
 Conference: M&C 2017  International Conference on Mathematics & Computational Methods Applied to Nuclear Science & Engineering, Jeju, South Korea, 20170416, 20170420
 Country of Publication:
 United States
 Language:
 English
Citation Formats
Graham, Aaron M, Collins, Benjamin S, and Downar, Thomas. Improvement of the 2D/1D Method in MPACT Using the SubPlane Scheme. United States: N. p., 2017.
Web.
Graham, Aaron M, Collins, Benjamin S, & Downar, Thomas. Improvement of the 2D/1D Method in MPACT Using the SubPlane Scheme. United States.
Graham, Aaron M, Collins, Benjamin S, and Downar, Thomas. 2017.
"Improvement of the 2D/1D Method in MPACT Using the SubPlane Scheme". United States.
doi:.
@article{osti_1344278,
title = {Improvement of the 2D/1D Method in MPACT Using the SubPlane Scheme},
author = {Graham, Aaron M and Collins, Benjamin S and Downar, Thomas},
abstractNote = {Oak Ridge National Laboratory and the University of Michigan are jointly developing the MPACTcode to be the primary neutron transport code for the Virtual Environment for Reactor Applications (VERA). To solve the transport equation, MPACT uses the 2D/1D method, which decomposes the problem into a stack of 2D planes that are then coupled with a 1D axial calculation. MPACT uses the Method of Characteristics for the 2D transport calculations and P3 for the 1D axial calculations, then accelerates the solution using the 3D Coarse mesh Finite Dierence (CMFD) method. Increasing the number of 2D MOC planes will increase the accuracy of the alculation, but will increase the computational burden of the calculations and can cause slow convergence or instability. To prevent these problems while maintaining accuracy, the subplane scheme has been implemented in MPACT. This method subdivides the MOC planes into subplanes, refining the 1D P3 and 3D CMFD calculations without increasing the number of 2D MOC planes. To test the subplane scheme, three of the VERA Progression Problems were selected: Problem 3, a single assembly problem; Problem 4, a 3x3 assembly problem with control rods and pyrex burnable poisons; and Problem 5, a quarter core problem. These three problems demonstrated that the subplane scheme can accurately produce intraplane axial flux profiles that preserve the accuracy of the fine mesh solution. The eigenvalue dierences are negligibly small, and dierences in 3D power distributions are less than 0.1% for realistic axial meshes. Furthermore, the convergence behavior with the subplane scheme compares favorably with the conventional 2D/1D method, and the computational expense is decreased for all calculations due to the reduction in expensive MOC calculations.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2017,
month = 1
}

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Subplanebased Control Rod Decusping Techniques for the 2D/1D Method in MPACT
The MPACT transport code is being jointly developed by Oak Ridge National Laboratory and the University of Michigan to serve as the primary neutron transport code for the Virtual Environment for Reactor Applications Core Simulator. MPACT uses the 2D/1D method to solve the transport equation by decomposing the reactor model into a stack of 2D planes. A fine mesh flux distribution is calculated in each 2D plane using the Method of Characteristics (MOC), then the planes are coupled axially through a 1D NEMPmore »