Transient multi-physics coupling analysis of the Xi'an Pulsed Reactor under pulsed condition

Due to the small size of the core, strong neutron leakage, and non-uniform distribution of core power and temperature in the Xi'an Pulsed Reactor (XAPR), there exists a complex coupling between the neutronicsthermalhydraulics behaviors within the reactor core. However, the influence of this coupling phenomenon on the transient behavior of the XAPR remains unclear, necessitating the performance of multi-physics coupling analysis. To this end, an integrated code named Nurus, which couples 3-D neutron diffusion spatial kinetics with thermal-mechanical solvers, has been developed and verified through benchmark problems, utilizing the opensource multi-physics coupling framework MOOSE. The multi-group cross-sections are calculated using the code NECP-X. The transient pulsed condition, featuring a reactivity of 3.45$, in the XAPR has been simulated by Nurus. The results demonstrate that the pulse peak power and FWHM (full width at half maximum) are in good agreement with the experimental data. The maximum radial expansion of the fuel element is approximately 1.3 x 10-4 m, resulting in a short-term contact between the fuel pellet and cladding. The developed code Nurus has been successfully employed in the safety analysis of transient experiments conducted on the XAPR.