ALWR UTILITY REQUIREMENTS DOCUMENT CONTAINMENT PERFORMANCE REQUIREMENTS

U.S. utilities, with substantial support from international utilities, are leading the industry-wide Advanced Light Water Reactor (ALWR) Pro gram. This program is establishing a technical foundation for the next generation of LWRs through development of a comprehensive set of desi gn requirements for the ALWR in the form of a Utility Requirements Doc ument (URD). The approach in the URD for severe accidents involves two main efforts: (1) accident prevention through intrinsic design charac teristics, backed up by reliable safety systems to prevent core damage , and (2) incorporation of design features to ensure severe accident m itigation and containment for the full spectrum of postulated accident s, including core melt accidents. For containment performance, twenty- three severe accident containment challenges are identified, a matrix of design features and operating characteristics is specified to addre ss the challenges, and a preliminary evaluation of the URD indicates t hat requirements are adequate for addressing each of the challenges. F urther, the URD requires evaluation of the containment response to sev ere accidents. The key conclusions from this effort are: that severe a ccident challenges are being systematically and explicitly addressed i n the design of ALWRs; that margin exists between the loads predicted to result from severe accidents and the Service Level C limits; and th at, for a realistic new design basis source term that is expected to b ound that from any credible severe accident sequence, the site boundar y dose is less than 0.5 rem given the predicted intact containment per formance.