Results and insights from the N reactor level II/III PRA for application to advanced reactor designs

A Level II/III probabilistic risk assessment has been performed for N Reactor, a U.S. Department of Energy production reactor. State-of-the-art methodology was employed based on methods developed by Sandia for the U.S. Nuclear Regulatory Commission for the NUREG-1150 study. Latin Hypercube sampling techniques were used to develop uncertainty distributions for the risks associated with postulated core damage events initiated by fire, seismic and internal events as well as the overall combined risk. The results show the risks from N Reactor to be small. This paper discusses systematic, procedural and phenomenological insights and their significance to future reactor designs. A key insight is that active systems can inadvertently interfere with passive systems unless proper design precautions are taken