A practical system for isolating nuclear power plants from earthquake attack

Abstract The earthquake-generated forces and deformations of the main substructures of a nuclear power plant can be reduced by a factor of about ten times by mounting the power plant building on a recently developed base-isolation system. The very high forces which the ‘resonant appendage’ effect may induce in some critical components (such as fuel elements and control rods) may be reduced by a factor of 40 or more by the isolation system. This system combines recently developed hysteretic dampers with components which support the structure while providing high flexibility for horizontal motion. These dampers utilize the plastic deformation of solid steel beams, while a convenient support system with adequate horizontal flexibility may be provided by laminated rubber bearings of the type frequently used to support bridge decks. The earthquake attack on a nuclear power plant is particularly hazardous since it attacks simultaneously all the plant components, including the control and safety systems. Undetected deterioration of a set of components may further increase the probability of multiple failure during earthquakes. Hence the large reduction in earthquake-induced forces and deformations, which may be achieved with the base-isolation system described, will greatly reduce the likelihood of earthquake-induced accident or damage in those nuclear power plants located in regions of high seismicity.