Risk-Informed Basis for Establishing Non-Fixed Surface Contamination Limits for Spent Fuel Transportation Casks

摘要

The current internationally accepted basis for establishing non-fixed surface contamination limits for spent fuel casks is the same as that for other transportation package types. This study examined the suitability of the currently used exposure model, taking into account exposure pathways and parameters representative of typical light-water-reactor spent fuel cask handling, loading, and transportation activities. Because the currently used model was found to be inappropriate for spent fuel casks, a new exposure model was developed using pathways and parameters specific to spent fuel casks. Results show that individual and collective doses to members of the public are very low and that worker doses dominate the total collective dose from non-fixed surface contamination. Worker doses that vary as a function of allowable surface contamination limits were calculated and were found to be dominated by doses due to decontamination and surface contamination monitoring activities performed after the cask is drained. An approach was developed for evaluating the overall dose implications of higher allowable non-fixed surface contamination limits. This approach was used to examine the reduction in doses to workers performing cask decontamination and monitoring activities necessary to offset increased doses due to other worker and public exposure pathways.