Development and coupling of the 1-D neutronics code PoKiMON with ANSYS CFX for reactor shutdown simulations

Abstract Nowadays, nuclear reactor safety simulations of real nuclear plants are still performed using approximated system codes which rely on one-dimensional lumped-parameters or subchannel methods. Many of these one-dimensional codes are not able to fully simulate intrinsic multi-dimensional effects that occur within a nuclear reactor. On the other hand, Computational Fluid Dynamics (CFD) codes, thanks to the recent advances in computer technology, are now capable of tackling complex multi-dimensional fluid-dynamics problems for a large variety of nuclear and non-nuclear applications. The neutronics code Point Kinetics Multi-Purpose Online Neutronic code (PoKiMON), has been developed in order to provide realistic 1-D neutronics feedbacks to the CFD one. The goal of this work is then to extend the range of applications of coupled neutronics/CFD simulations towards boron ingress shutdown scenarios in light water small modular reactors. The coupled system was also verified considering two fuel assembly-level calculations against the code SUBCHANFLOW, a heat decay calculation against classic decay heat equation and was validated considering the IFA-507 experiment performed at the Halden reactor facility.