Are multi-reactor accidents possible?
Yes. In documents acquired by Greenpeace, Canadian Nuclear Safety Commission (CNSC) staff say such accidents are possible. They describe a multi-accident reactor accident in the following way: “At Pickering B some initiating events could produce multiunit accidents. For instance, a medium or large steam line break event at one unit might produce a harsh environment in the common powerhouse leading to common cause accidents at all units with multiple failures of mitigating systems. Since these types of accidents are major contributors to the plant risk according to PRA [Probabilistic Risk Assessment] results, additional risk from adjacent units may not be negligible. Furthermore, if multiple mitigating systems fails due to the harsh environment, several units may have severe core damage simultaneously. This may create such a challenge to the containment that its failure may not be precluded.
