Requalification of an existing underground liquid storage facility for the postulated site specific maximum potential earthquake event

The seismic requalification of existing nuclear facilities basically aims at reviewing the adequacy of these facilities to withstand the seismic hazard with respect to current approach and methodology of a seismic design. The methodology of a seismic design of structures, systems and components (SSC) have been evolved over a number of years and several important safety-related facilities were designed and built according to the standards prevailing at the time of their construction. Therefore, it is desirable to reassess the capability of the SSC of older safety-related facilities and to ensure their integrity under seismic ground motion to meet the present statutory requirements. The present paper deals with the seismic response analysis and re-evaluation of design stresses for an existing underground liquid storage tank to assess the available safety margins for the postulated site specific maximum potential earthquake event i.e. safe shutdown earthquake (SSE)