Operator actions under severe accident conditions for boiling water reactors

This paper discusses the role of the operator in preventing and mitigating severe accidents and the implications of the Emergency Procedure Guidelines (EPGs) to Probabilistic Risk Assessment (PRA) for Boiling Water Reactors (BWRs). Some of the design features that prevent severe accidents are summarized. The EPGs are listed and include: reactor pressure vessel control guideline; primary containment control guideline; secondary containment control guideline; and radioactivity release control guideline. The operator response is the same for all inventory-threatening events in BWRs. This two-part response consists of: first, maintaining reactor water level; and, second, establishing a long-term heat sink after the reactor water level is stabilized. The analytical basis for EPG's related to severe accidents is discussed, and operator actions for PRA events are summarized