INTRODUCTION TO STRUCTURAL FAILURE MODES FOR NUCLEAR-POWER FACILITIES

This introduction provides a background of the evaluation methods for earthquakes larger than design basis. Seismic probabilistic risk asses sment (SPRA) and seismic margin assessment (SMA) methods are introduce d to the reader. The basic parameters used to define seismic capacity for each method are explained. The objectives of both evaluation metho ds and how they can be used to evaluate the adequacy of a seismic desi gn are discussed. General issues related to computing seismic capacity are reviewed relative to SPRA and SMA. Four companion papers presente d in the journal following this introduction discuss the types of info rmation (i.e., dynamic tests, earthquake experience, and analytical da ta) that are used to determine the real capacity of structures and equ ipment in nuclear power plants to resist earthquakes. The motivation f or discussing these three types of information is presented as an intr oduction to these papers that follow in this journal edition. The purp ose of the present paper is to lay the groundwork and provide motivati on for these papers.