Analysis of the Impact of a Tunnel Fire Environment on a Spent Nuclear Fuel Transportation Cask

On July 18, 2001, a train carrying hazardous materials derailed and caught fire in the Howard Street railroad tunnel in Baltimore, Maryland. Due to this accident, questions were raised about the performance of spent nuclear fuel transportation casks under severe fire conditions, similar to those experienced in the Baltimore tunnel fire. The U.S. Nuclear Regulatory Commission (NRC) evaluates the performance of spent fuel transportation casks under accident conditions. Title 10 of the Code of Federal Regulations Part 71 section 73(c)(4), (10 CFR 71.73(c)(4)) requires that transportation packages used to ship radioactive material must be designed to resist an engulfing fire of a 30 minute duration and prevent release of radioactive material to the environment. The staff of the NRC, in cooperation with the National Transportation Safety Board, the National Institute of Standards and Technology, Pacific Northwest National Labs and the Center for Nuclear Waste Regulatory Analysis, have undertaken an analysis to determine the thermal conditions present in the Howard Street tunnel fire, as well as analyze the effects that such a fire would have on a spent fuel transportation cask. This paper describes the analytic models used in the assessment and presents a discussion of the results.