MPACT Theory Manual (V.4.3)

Technical Report · Fri Jun 24 00:00:00 EDT 2022

DOI:https://doi.org/10.2172/1887705· OSTI ID:1887705

Larsen, Edward ^[1]; Collins, Benjamin ^[2]; Kochunas, Brendan ^[1]; Graham, Aaron ^[3]; Stimpson, Shane ^[4]

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1. Univ. of Michigan, Ann Arbor, MI (United States)
2. Veracity Nuclear, Lenoir City, TN (United States)
3. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
4. BWX Technologies, Inc., Lynchburg, VA

This manual presents the theory underlying the three-dimensional (3D) whole-core, pin-resolved neutron transport calculation methodologies employed in the MPACT code. MPACT’s primary goal is to provide accurate sub-pin power distributions in a computationally efficient manner. To accomplish this, MPACT offers several different transport method options. The 2D/1D method, in which 3D problems are decomposed into an axial stack of radial “slices,” is currently the most commonly used. In this option, two-dimensional (2D) planar solutions are provided by the method of characteristics (MOC), and axial solutions are provided via one-dimensional (1D) approximate diffusion, or P3 solutions. The radial and axial solutions are coupled by (i) axial and radial transverse leakages, and (ii) a global 3D coarse mesh finite difference (CMFD) solve, which provides both acceleration and stability to the solution iteration scheme. The subsequent chapters of this manual present a range of topics, including MOC, CMFD, axial nodal transport solvers, 2D/1D, self-shielding, depletion, thermal-hydraulics, and transient methods. Development of the underlying theory of the 2D/1D method is presented, diagrams are included to highlight important algorithmic flow, and important concepts are discussed as appropriate. This manual is intended to be self-sufficient, but references to published articles and other materials are included for further reading. MPACT is a relatively new code, with new capabilities and many computational methods that did not exist until recently. This manual is an even newer document, with chapters written by several different code contributors working under time constraints. For these reasons, the manual is not yet complete and finalized. Future versions of this manual will address current deficiencies.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1887705
• Report Number(s): ORNL/SPR-2021/2330
• Country of Publication: United States
• Language: English

Related Subjects

97 MATHEMATICS AND COMPUTING