Implications of the Baltimore Rail Tunnel Fire for Full-scale Testing of Shipping Casks

The U.S. Nuclear Regulatory Commission (NRC) does not currently require full-scale physical testing of shipping casks as part of its certification process. Stakeholders have long urged NRC to require full-scale testing as part of certification. NRC is currently preparing a full-scale casktesting proposal as part of the Package Performance Study (PPS) that grew out of the NRC reexamination of the Modal Study. The State of Nevada and Clark County remain committed to the position that demonstration testing would not be an acceptable substitute for a combination of full-scale testing, scale-model tests, and computer simulation of each new cask design prior to certification. Based on previous analyses of cask testing issues, and on preliminary findings regarding the July 2001Baltimore rail tunnel fire, the authors recommend that NRC prioritize extra-regulatory thermal testing of a large rail cask and the GA-4 truck cask under the PPS. The specific fire conditions and other aspects of the full-scale extra-regulatory tests recommended for the PPS are yet to be determined. NRC, in consultation with stakeholders, must consider past real-world accidents and computer simulations to establish temperature failure thresholds for cask containment and fuel cladding. The cost of extra-regulatory thermal testing is yet to be determined. The minimum cost for regulatory thermal testing of a legal-weight truck cask would likely be $3.3-3.8 million. INTRODUCTION The U.S. Nuclear Regulatory Commission (NRC) does not currently require full-scale physical testing as part of its certification process for spent fuel shipping casks. None of the shipping casks currently used in the United States has been tested full-scale. (1) None of the current cask designs likely to be used for shipments to Yucca Mountain has been tested full-scale. (2) Cask designers are allowed to demonstrate compliance with the NRC performance standards through a combination of scale-model testing and computer simulations. (3) The State of Nevada, Clark County, other potentially affected state and local governments, Indian tribes, and public interest organizations have long urged NRC to require full-scale testing. (4,5,6) Nevada has specifically proposed full-scale testing, prior to certification, to assure compliance with the sequential impact, puncture, fire, and immersion tests proscribed in the NRC regulations. Nevada has also proposed testing of a sample production model cask. Alternately, Nevada has suggested that the U. S. Department of Energy (DOE) require full-scale testing as part of the cask procurement process for the proposed Yucca Mountain repository transportation system. (7) NRC is currently proposing demonstration testing of one or more "representative" shipping casks. The proposed testing program is an outgrowth of the Package Performance Study (PPS) being conducted for NRC by Sandia National Laboratories (SNL). NRC commissioned the PPS to update previous studies of spent fuel shipping cask response to severe highway and railway accident conditions. (8)