Research needs for improved seismic safety of mechanical equipment in nuclear power plants

Seismic design requirements for a safety systems in a nuclear power plant are very stringent. Application of seismic design criteria becomes extremely difficult to meet when operability of safety-related active components is to be assured. The mechanical equipment has to be qualified for very high seismic loads because of building amplifications even in low seismic zones. So far, the approach has been 'curative' in nature. The amplified seismic input is accepted, and mechanical systems and components are designed to withstand these loads and to be operable. The problem can be approached from a 'preventive' side also. The seismic input to systems and components comes from their supports. Thus, the supports are very crucial and significant in aseismic designs. This paper suggests certain areas for research in this direction. (orig.)