Preliminary Coupling of the Monte Carlo Code OpenMC and the Multiphysics Object-Oriented Simulation Environment for Analyzing Doppler Feedback in Monte Carlo Simulations

In recent years, the use of Monte Carlo methods for modeling reactors has become feasible due to the increasing availability of massively parallel computer systems. One of the primary challenges yet to be fully resolved, however, is the efficient and accurate inclusion of multiphysics feedback in Monte Carlo simulations. The research in this paper presents a preliminary coupling of the open-source Monte Carlo code OpenMC with the open-source Multiphysics Object-Oriented Simulation Environment (MOOSE). The coupling of OpenMC and MOOSE will be used to investigate efficient and accurate numerical methods needed to include multiphysics feedback in Monte Carlo codes. An investigation into the sensitivity of Doppler feedback to fuel temperature approximations using a two-dimensional 17 x 17 pressurized water reactor (PWR) fuel assembly is presented in this paper. The results show a functioning multiphysics coupling between OpenMC and MOOSE. The coupling utilizes functional expansion tallies to transfer accurately and efficiently pin power distributions tallied in OpenMC to unstructured finite element meshes used in MOOSE. The two-dimensional PWR fuel assembly case also demonstrates that for a simplified model, the pin-by-pin Doppler feedback can be adequately replicated by scaling a representative pin based on pin relative powers.