Reflood experiments at elevated pressures using intact and deformed rod bundles to simulate small and medium break loss-of-coolant accidents

Reflood experiments at elevated pressures for small and medium break loss-of-coolant accidents were performed to investigate the influence of fuel deformation on the peak cladding temperature and local quenching behaviors. The typical experimental parameters such as initial water level, power, reflood rate, system pressure, initial wall temperature, and fluid temperature were varied to cover a wide range of flow conditions under a medium and high pressure. The experimental results showed remarkable differences in the peak cladding temperature and local quenching behaviors between the intact and deformed rod bundles due to the flow blockage effect. The present results implied that the fuel rod deformation can enhance the coolability of fuel rods by the flow blockage in the present fully blocked channel. Any bypass in a partially blocked channel may change those results due to a crossflow between intact and deformed rods. The experimental results were then used to validate the system analysis code, Multi-dimensional Analysis of Reactor Safety-KINS Standard (MARS-KS). The MARS-KS code showed good prediction of the present experimental data for most of the flow conditions.