Effect of extreme forces on structures and equipment of nuclear power plants

An analysis is made of extreme effects on nuclear power plants, i.e., effects of forces of nature, effects caused by extraneous human activity and effects arising inside the nuclear power plant which may cause accidents threatening nuclear safety. These are unplanned events whose occurrence is expected with a probability of less that 10-1/year and higher than 10-6 to 10-7/year. The theory and practice of nuclear power plant project designing devote almost no attention to such events, with the exception of earthquakes. The basic classification is presented of these effects according to valid regulations in the USA, the USSR and the FRG and also under IAEA regulations. A detailed analysis is also made of extreme effects on the structures and equipment of nuclear power plants in Czechoslovak conditions. (Z.M.)