FCMI analysis of multiphysics coupling of fuel rods at the end of cycle of Xi’an pulsed reactor

The Xi’an Pulse Reactor (XAPR), being a small-scale experimental reactor, operates within a very complex environment. Consequently, accurate estimation of neutron-thermo-mechanical coupling of the fuel is a crucial step to prevent operation, particularly pulse operation, outside fuel thermo-mechanical safety margin. To obtain precise temperature and stress distributions within the XAPR, a loosely coupled approach based on the finite element method was employed. In the present work, neutron transport equations were calculated using OpenMC, and the Multiphysics Object-Oriented Simulation Environment (MOOSE), an open-source multi-physics coupling platform, was employed for heat transfer and mechanics calculations. The physical modules have also been verified by comparing calculation results against corresponding experimental data, confirming the reliability of the performed calculations. In addition, we conducted 3-dimensional (3-D) calculations of the bending effects of fuel rods due to Pellet-Clad Mechanical Interaction (PCMI) under different operating conditions and discussed the influence of different pulse state initiation time on the bending of the fuel.