N Reactor external events probabilistic risk assessment using NUREG-1150 methods

This is the first full-scope Level-III PRA completed for the DOE Category A reactor using the updated NUREG-1150 methods. The comparisons to the quantitative NRC safety objectives and DOE nuclear safety guidelines also set analytical precedent for DOE production reactors. Generally speaking, the risks of operating N Reactor are low because of a combination of factors such as low power density, large confinement volume, effective redundant scram systems and core cooling systems, remote location, etc. This work has been a major effort to evaluate the N Reactor risk using state-of-the-art PRA technology. It is believed that this PRA has resulted in realistic, or slightly conservative, results (as opposed to unduly conservative or nonconservative results). The study concluded that the risk to the public and to nearby DOE workers from the operation of N Reactor is very low. This analysis also found that N Reactor meets all the quantitative NRC safety objectives and DOE nuclear safety guidelines, and is generally as safe as, or safer than most commercial reactors in terms of societal and individual risks. The calculated risk to Hanford onsite workers is comparable to public risk from commercial reactors in the NUREG-1150 study. As a result of these low-riskmore » estimates, only a small effort has been devoted to identifying significant risk reduction alternatives. 22 refs., 2 figs., 10 tabs.« less