NUREG/CR-6672: BACKGROUND, OBJECTIVES, AND ANALYSIS STRUCTURE

Because a large number of spent fuel shipments to an interim or permanent repository may take place in the near future, during the summer of 1996, the U.S. Nuclear Regulatory Commission asked Sandia National Laboratories to reexamine the risks associated with shipping spent fuel by truck and rail. The results of this study were documented in NUREG/CR-6672 [1], “Reexamination of Spent Fuel Shipment Risks.” This paper describes why this study was performed, the study objectives, and the structure of the analyses conducted to develop the route, source term, and other input data required by RADTRAN 5 [2,3], the transportation risk assessment code that was used to estimate the non-accident and accident risks associated with truck and rail shipments of spent nuclear fuel. In particular, the analysis structure shows how the following data were used to estimate severity and release fractions for 21 hypothetical source terms for severe truck or severe rail accidents: (a) Modal Study accident event trees, fire duration distributions, and speed distributions; (b) rod failure fractions, which were estimated by scaling rod strains for a 30 mph impact to higher speeds and comparing the scaled strains to a strain failure criterion; (c) cask leak areas, which were estimated from unyielding surface finite element impact calculations; (d) the yielding surface impact speeds, that produce these leak areas and failure fractions, which were estimated by partitioning the yielding surface impact energy between the impact surface and the cask and increasing the impact speed until the energy into the cask equaled the result of one of the unyielding surface impact calculations; (e) the cask heating times in fires (calculated by 1-D heat transport methods) needed to reach seal failure, rod burst rupture, and average hydrocarbon fuel fire temperatures; and (f) a critical review of radionuclide release data for sections of spent fuel rods. Subsequent papers in this session will describe in greater detail the development of these data, the results of the RADTRAN 5 calculations that were performed to estimate the risks associated with spent fuel shipments, and the conclusions drawn from these results.