Efficient Multiphysics Coupling for Fast Burst Reactors in Slab Geometry

Abstract

An efficient neutron transport-based multiphysics coupling algorithm is developed to model fast-burst reactor dynamics. It extends the previously developed tightly coupled implicit-explicit (IMEX) multiphysics algorithm based on neutron diffusion and linear mechanics to follow the dynamic time scale of the problem. The diffusion model is not expected to adequately represent the neutronic behavior of the system due its small size. The transport effects are incorporated using the moment-based acceleration concept. This concept enables us to isolate the angular flux from the coupled multiphysics system by using a consistently discretized lower-order system for the scalar flux in the coupling equations, thus helping to mitigate the increased numerical burden associated with a neutron transport model. Solution of a representative slab model demonstrates the difference between diffusion and transport models and also demonstrates second-order convergence in the coupled simulation with the combination of the moment-based acceleration concept and the IMEX algorithm.

Keywords:

• neutron transport
• nonlinear diffusion acceleration
• HOLO
• fast burst reactors
• IMEX
• multiphysics

Additional information

Funding

This work was performed under U.S. government contract DE-AC52–06NA25396 for Los Alamos National Laboratory, which is operated by Los Alamos National Security, LLC, for the U.S. Department of Energy.