The effects of cladding thermo-physical and thermo-chemical properties on the coping time during a PWR unmitigated LB-LOCA

To evaluate quantitatively the effects of individual thermo-physical and thermo-chemical cladding properties on the coping time, an unmitigated large break loss of coolant accident (LB-LOCA) was simulated using Modular Accident Analysis Program (MAAP) code. For this purpose, hypothetical claddings were created to decompose the influence of each property enhancement. The variations in the cladding properties could not affect the main conditions of the reactor coolant system such as pressure, reactor core water level, etc., but led significantly different variations in the cladding temperature. When the coping time was defined as the time elapsed between departure from normal operation and the moment at which cladding melts, the specific heat capacity (enthalpy) and melting temperature of cladding materials were identified as properties extending the coping time most. The improved oxidation resistance could extend moderately the coping time. On the other hand, the cladding thermal conductivity had no effect on the coping time.