Memorandum concerning the study entitled 'Risk of old Swiss reactors'

This comprehensive memorandum issued by the Swiss Nuclear Safety inspectorate ENSI comments on a risk assessment study of the Swiss nuclear reactors without explicitly naming the authors of the study. The study questions four important measures to be taken to ensure long-term safe operation and concludes that long-term operation is basically problematic. The four measures include aging management, monitoring of embrittlement of the reactor pressure vessel, retrofitting and probabilistic safety analyses. The study is said to list a number of discrepancies with respect to the current state of the art. These include six cases of false facts, four discrepancies concerning rules and two cases of a meaninglessly defined state of the art. Topics commented on include aging processes and their detection, also those concerning the reactor pressure vessel. Aging resulting from improved technical developments is looked at as are retrofitting and probabilistic safety analyses. Verifiability aspects including non-destructive testing are discussed. Opinions on the emergency cooling and after-cooling systems as well as the reactor containment are discussed. Other topics scrutinized include earthquakes, floods, aircraft crashes and cooling systems. Points concerning particular deficits at the older nuclear power stations in Switzerland are listed and comparisons made with the situation in Germany are commented on.