As one of the regulatory agencies with authority to regulate transportation of spent nuclear fuel (SNF) in the United States, the U.S. Nuclear Regulatory Commission (NRC) requires that SNF transportation packages be designed to endure a fully engulfing fire with an average temperature of 800°C (1,475°F) for 30 minutes, as prescribed in 10 CFR §71.73(c). The work described in this paper was performed to determine the types of railway accident conditions that could produce a severe fire with the potential to fully engulf an SNF transportation package. This paper describes the process used to characterize the important features of rail accidents that would potentially lead to an SNF transport package involved in a severe fire. Historical railway accidents involving hazardous material (HAZMAT) and long duration fires in the United States have been analyzed using data from the Federal Railway Association (FRA) and Pipeline and Hazardous Materials Safety Administration (PHMSA). Parameters that were evaluated from this data include, but were not limited to, type of HAZMAT being transported, speed of accident, and number of railcars derailed. The data analysis revealed that in the past 12 years of rail transport, roughly 9 accidents resulted in a severe fire, which corresponds to a frequency of roughly 1 severe accident per 750 million freight train miles. Similarly, the data analysis indicated that severe fire accidents are generally characterized by derailments in which HAZMAT was released from several cars (i.e., five or more cars). Each release involved thousands of gallons of flammable liquid or gas, and in general, these accidents were caused by rail failure.
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