LONG-TERM CONTAINMENT THERMAL-HYDRAULIC LOADS IN PRESSURIZED-WATER REACTOR CORE-MELT ACCIDENTS

The TPCONT computer code is used to study the thermal-hydraulic behavi or of a pressurized water reactor containment after a core-melt accide nt. A commercial-sized reactor of 1500-MW (electric) power output is e specially designed to withstand transient and long-term loads with pur ely passive means. It is shown that the decay heat can be removed with an optimized cooling system based on natural-convective airflow in th e annular gap with sufficient safety margins of maximum pressure and t emperature to failure values. Three gap designs, which are different i n the treatment of leakage flow, are investigated. In extensive parame ter studies, the thermal-hydraulic evolution in the containment is fou nd to be rather sensitive to various system data. Therefore, precise p redictions of maximum loads need accurate knowledge of the design data of the reactor under consideration and better physical data, especial ly concerning heat transfer and flow data in the cooling duct. Various parameters are identified that may be exploited in a careful and opti mized design to effectively limit the long-term loads to acceptable va lues.