MPACT – MPACT is CASL’s whole-core, pin-resolved deterministic transport code designed to perform high-fidelity light water reactor (LWR) analysis. The code consists of several capabilities that provide the functionality necessary for multi-cycle steady-state and transient analysis. The primary methods for MPACT under VERA are 2D (MOC)/1D (P3) method with CMFD acceleration to obtain the neutron transport solution and the subgroup method for in-line resonance self-shielding for cross section feedback.

MPACT is coupled to CTF  for thermal-hydraulic and chemistry feedback for CRUD calculations with MAMBA. MPACT also integrates ORIGEN ( as the depletion solver, and can export solution information to VERAShift  for ex-core analysis MPACT is co-owned and developed by the University of Michigan and Oak Ridge National Laboratory. For inquiries and support related to MPACT contact

MPACT References

  1. MPACT Team, “MPACT Theory Manual,” Technical Report, CASL-U-2019-1874-001, Oak Ridge National Laboratory, Nov. (2019). 
  2. MPACT Team, “MPACT User Manual,” Technical Report, CASL-U-1873-001, Oak Ridge National Laboratory, Nov. (2019). 

MPACT Images


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

2-D Midplane Slice of the MPACT Model (top) and the MPACT Thermal Flux Distribution (bottom) for the Spert III Test Reactor