INVESTIGATIONS ON COOLING POSSIBILITIES OF A DEGRADED CORE IN A MBLOCA SCENARIO FOR A GERMAN PWR WITH ATHLET-CD

摘要

The recent accident in Fukushima revealed that there is always a residual risk of failure of emergency cooling systems which can lead to a core melt. It was observed that it may be possible during the course of the accident to re-establish water injection into the primary system at a later time. This paper investigates to which extent a core can be cooled after its degradation has begun, which has been simulated with the system code ATHLET-CD. The calculations are based on a plant model for a generic German PWR. The investigated scenario is a MBLOCA sequence with a 200 cm~2 leakage in the hot leg next to the pressurizer surge line with failure to switch to sump recirculation. Variation calculations are carried out which include late reflooding initiated after varying degrees of core damage at different injection rates. The results show, that a coolable state can be reached if the core degradation was just beginning.