An analysis of containment venting as a severe accident mitigation strategy for the BWR Mark II containment

An evaluation of a BWR/4 reactor with a Mark-II containment identified the effects of containment venting on core damage frequency and containment failure mode. A limited evaluation of the effects on the off-site consequences was also performed. The analysis was founded upon an existing probabilistic risk assessment (PRA) with the addition of a proposed filtered containment venting system, based on the Swedish Filtra system installed at the Barseback Nuclear Power Station in southern Sweden. Three different containment venting strategies were examined for their effects on plant risk: (1) venting using the proposed Filtra system, (2) venting utilizing existing equipment, and (3) no venting. The consequences of containment venting were examined in conjunction with two sets of assumptions about the effects of a harsh reactor building environment, produced by venting via the containment and reactor building HVAC systems, on the equipment located there. The consequences when a harsh reactor building environment is assumed to have either no adverse effect on equipment or to fail all equipment were analyzed