Influence of probabilistic considerations on the maintenance procedures inSwiss nuclear power plants

Swiss regulations and requirements for in-service inspections and periodica l testing are outlined. It is shown by the operating history of the plants that Swiss maintenance programs prevent failures resulting in undue scrams and unnecessary actuations of safety-related systems. Swiss current activit ies concerning aging and maintenance are described and the application of r isk-based technology at Beznau is explained. Furthermore, advantages of on- line maintenance at Gosgen and Leibstadt are indicated.