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) 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 involved two main efforts: (1) accident prevention through intrinsic design characteristics to avoid accident initiation and reliable, engineered safety systems to prevent core damage, and (2) accident mitigation and containment performance. The purpose of this paper is to describe the URD containment performance requirements for severe accidents. For containment performance, a comprehensive set of severe accident containment challenges was defined and a matrix of design features and operating characteristics specified to address the challenges. Also, the URD requires evaluation of containment response to severe accidents. Twenty-three severe accident containment challenges were identified and a preliminary evaluation of the URD indicated that requirements are adequate for addressing each of the challenges. Further, best estimate severe accident evaluations for the ALWR containment indicate that margin exists to ASME Service Level C limits and this containment leakage during severe accidents should be minimal. An updated accident source term was also developed by the ALWR Program to provide an improved design basis for fission product mitigation system design