ALWR utility requirements document containment performance requirements

Abstract

U.S. utilities, with substantial support from international utilities, are leading the industry-wide Advanced Light Water Reactor (ALWR) Program. This program is establishing a technical foundation for the next generation of LWRs through development of a comprehensive set of design requirements for the ALWR in the form of a Utility Requirements Document (URD). The approach in the URD for severe accidents involves two main efforts: (1) accident prevention through intrinsic design characteristics, backed up by reliable safety systems to prevent core damage, and (2) incorporation of design features to ensure severe accident mitigation and containment for the full spectrum of postulated accidents, 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 address the challenges, and a preliminary evaluation of the URD indicates that requirements are adequate for addressing each of the challenges. Further, the URD requires evaluation of the containment response to severe accidents. The key conclusions from this effort are: that severe accident challenges are being systematically and explicitly addressed in the design of ALWRs; that margin exists between the loads predicted to result from severe accidents and the Service Level C limits; and that, for a realistic new design basis source term that is expected to bound that from any credible severe accident sequence, the site boundary dose is less than 0.5 rem given the predicted intact containment performance.