Insights gained from in-depth reviews of several industry generated PRAs

During the last several years BNL staff have performed in-depth reviews of the containment failure modes and fission product release analyses of all of the industry PRAs submitted to the Office of Nuclear Reactor Regulation, NRC. This program started with a reevaluation of the risks reported in the Zion and Indian Point Probabilistic Safety Studies (PWRs with large dry containments) and was followed by reviews of the Limerick (BWR with Mark II containment) and Big Rock Point (early BWR design) PRAs. Reviews of the GESSAR-II (BWR with a Mark III containment) and Millstone-3 (PWR with a subatmospheric containment) PRAs are nearing completion. This paper therefore presents the insights gained from extensive reevaluations of the risk associated with a wide range of reactor and containment designs. In particular, the paper shows how changing methodology has influenced our understanding of containment performance under degraded core conditions and how this influences the frequency, timing and magnitude of fission product release to the environment, which in turn impacts potential off-site consequences