Year
2014
Abstract
The approved contents for US Nuclear Regulatory Commission licensed spent nuclear fuel transportation casks are typically based on bounding used nuclear fuel (UNF) characteristics. However, the actual contents of the UNF casks when shipped can be expected to be considerably heterogeneous in terms of fuel assembly burnup, initial enrichment, decay time, cladding integrity, etc. The Used Nuclear Fuel Storage, Transportation & Disposal Analysis Resource and Data System (UNF-ST&DARDS) is an integrated data and analysis system that facilitates automated caskspecific analyses based on actual characteristics of the as-loaded UNF. The UNF-ST&DARDS analysis capabilities have recently been expanded to include dose rate analysis of as-loaded transportation packages. Realistic dose rate values based on actual cask contents can be used to support development of packaging operations procedures, evaluation of radiation-related transportation risks, and communication with stakeholders. This paper1 describes the UNFST&DARDS dose rate analysis methodology based on actual UNF cask contents and presents sample dose rate calculation results. The dose rate was calculated in the air regions external to the transportation package for both normal conditions of transport and hypothetical accident conditions and then compared against the 10 CFR 71 dose rate limits. For the cask system evaluated, the limiting dose rate with respect to the 10 CFR 71 requirements is the dose rate at 2 m from the cask radial surface for normal conditions of transport (i.e., 10 mrem/h). The calculated dose rate values corresponding to year 2025 were between 4 and 12 times lower than the regulatory dose rate limit of 10 mrem/h.