MPACT is a transient one-step code that primarily relies on the 2D/1D method for whole core transport and has been applied to PWRs (dozens of operational cycles), and BWRs. With this approach, 3D geometries are separated into 2D-radial and pin-homogenized, 1D-axial problems. For the 2D solvers, the method of characteristics is used and for the 1D solvers, P3 transport with a fourth-order Legendre-based spatial flux expansion is used. These 2D and 1D solvers are coupled through axial and radial transverse leakages and accelerated with a 3D-coarse mesh finite difference solver. MPACT uses inline cross section generation based on the subgroup method and uses ORIGEN for depletion.
Applications and Integrations
Nuclear reactor physics steady-state eigenvalue (core follow) and transient simulation (load follow and NRC Chapter 15 licensing events) with cross section feedback and material isotopic depletion
Full integration with the thermal-hydraulics code CTF, fuel temperature codes CTFFuel and BISON, crud chemistry code MAMBA, and ex-core transport code Shift.
Planned capabilities for the future include:
- BWR Support
- Extended transient analysis for series of operational transients
- MPACT Team, “MPACT Theory Manual,” Technical Report, CASL-U-2019-1874-001, Oak Ridge National Laboratory, Nov. (2019).
- MPACT Team, “MPACT User Manual,” Technical Report, CASL-U-1873-001, Oak Ridge National Laboratory, Nov. (2019).
- B. Collins, S. Stimpson, B. Kelley, M. Young, B. Kochunas, A. Graham, E. Larsen, T. Downar, A. Godfrey, “Stability and accuracy of 3D neutron transport simulations using the 2D/1D method in MPACT,” Journal of Computational Physics, 326 (2016), 612-628.
- B. Kochunas, D. Jabaay, T. Downar, B. Collins, S. Stimpson, A. Godfrey, K. Kim, J. Gehin, S. Palmtag, F. Franceschini, “Validation and Application of the 3D Neutron Transport MPACT within CASL VERA-CS, NURETH-16, Intl. Top. Mtg. on Nuclear Reactor Hydraulics, Chicago, Aug 30-Sep 4, 2015.
- B. Kochunas, B. Collins, S. Stimpson, R. Salko, D. Jabaay, A. Graham, Y. Liu, K. Kim, W. Wieselquist, A. Godfrey, K. Clarno, S. Palmtag, T. Downar, J. Gehin, “VERA Core Simulator Methodology for Pressurized Water Reactor Cycle Depletion,” Nuclear Science and Engineering, 185 (2017), 612-628.
3D Rod-by-Rod Power Distribution
2-D Slice of the MPACT Model (left) and MPACT Flux Distribution (right) of the NuScale SMR with Detailed Reflector Model