| Abstract: | In response to U.S. Nuclear Regulatory Commission (NRC) Unresolved Safety Issue (USI) A-46, “Seismic Qualification of Equipment and Operating Nuclear Power Plants”, the Seismic Qualification Utility Group (SQUG), with the support of the Electric Power Research Institute (EPRI), developed a comprehensive program to verify the seismic adequacy of equipment in operating nuclear power plants. The primary thrust of the program has been the development of procedures, criteria, and data to apply actual experience on the performance of equipment during earthquakes to the verification of seismic ruggedness of similar equipment in nuclear plants. While the use of such experience data continues to play a primary part in the SQUG program for resolution of USI A-46, the overall SQUG program includes a number of other significant elements which, taken together, provide a comprehensive approach for verification of the seismic adequacy of equipment in nuclear plants. These elements of the SQUG program include the assimilation and use of seismic shake table data in a generic way; the development of simplified analytical tools and criteria for evaluation of equipment anchorage, tanks, heat exchangers and cable trays; and the development of procedures for identifying and evaluating electrical relays, which are essential to plant shutdown in response to an earthquake. Procedures and data bases for performing and documenting the various seismic evaluations and plant walkdowns, and a program for training the large number of engineers who will be required to implement the SQUG methodology, have also been developed. This paper describes the main elements of the SQUG program for resolution of USI A-46 and provides a status report on the plans for their implementation in SQUG member plants. |
