Reduced seismic loads for temporary conditions

A new methodology, developed under an EPRI Tailored Collaboration Project, to calculate and apply reduced seismic loads (RLSs) for evaluation of tempo rary conditions (TCs) in nuclear power plants using design-basis (DB) allow ables is described. The methodology, which was submitted to Nuclear Regulat ory Commission (NRC) through the Nuclear Energy Institute (NEI), calculates load reduction factors based on an allowed limit for time-averaged increas e in seismic core damage frequency within the duration of a refueling cycle . For this allowable in the range 5 x 10(-6) to 1 x 10(-5) per reactor year , substantial reduction relative to DB seismic load is possible. The method ology is equally applicable to plants with and without seismic probabilisti c risk analysis model. (C) 1999 Elsevier Science S.A. All rights reserved.