PROBABILISTIC RISK ASSESSMENT OF BOLTED DRY SPENTFUEL STORAGE CASKS: REVISITED

摘要

EPRI performed a Probabilistic Risk Assessment (PRA) of a bolted dry spent fuel storage cask inrnDecember of 2003. The study was performed for a bolted cask at a "generic" pressurized waterrnreactor (PWR) site. A generic site was chosen so that the widest variety of challenges could bernconsidered. The study calculated the annual individual radiological risk and consequencernassociated with a single cask lifecycle where the lifecycle is divided into three phases: loading,rnon-site transfer and on-site storage. The study used standard methods of PRA with the followingrnanalysis tasks: initiating events, data analysis, human reliability analysis, structural analysis,rnthermal-hydraulic analysis, accident sequence analysis and consequence analysis. The results ofrnthe original study show that risk is extremely low with no calculated early fatalities and a firstrnyear risk of latent cancer fatality of 3.5E-11 per year per cask. Subsequent year risk to therngeneral public is even lower; with, again no early fatalities and a cancer risk of 4.2E-12 per caskrnper year.rnIn 2004, EPRI revised the spent fuel cask PRA assessment to remove selected conservativernassumptions associated with various analysis simplifications. The updated study calculates arnfirst year cancer risk of 5.6E-13 per year per cask with no early fatalities. This corresponds to arn98% reduction in the latent cancer radiological risk. The update study calculates a subsequentrnyear risk is 1.7E-13 per year per cask. This corresponds to a decrease of 96% decrease in thernlatent cancer radiological risk.rnThe conclusions of the original study and its subsequent update confirm the extremely lowrnradiological risk to the general public of the dry storage of spent nuclear fuel. In addition, thernextremely low radiological risks associated with the dry storage of nuclear fuel indicates arnpotential for increased risk-informing of regulations associated with the design of spent nuclearrnfuel casks and facilities as well as the handling of spent nuclear fuel.