Risk of transporting plutonium dioxide and liquid plutonium nitrate by truck and rail

This paper presents an analysis method developed to assess the risk in the transportation of radioactive materials and demonstrates its application by summarizing the results of risk assessments of the shipment of plutonium dioxide powder and liquid plutonium nitrate by truck and rail in the United States. In the risk assessment, postulated release modes (series of events that could result in a release of radioactive material) are identified using the fault tree analysis method. Two categories of events that could contribute to a release during transportation are considered: accidents and substandard packaging conditions. The likelihood of basic events in these categories are determined from general accident experience, radioactive material shipping experience, engineering analysis, etc. Using the laws of combining probabilities, the likelihood of radioactive material release is then evaluated. Since accidents vary greatly in severity, the releases from these postulated events also vary in magnitude from the no release condition up through release of the entire package contents. The bases for the release quantities assigned to the postulated accidents sequences are discussed. The consequences of these postulated releases are evaluated based on the amount of plutonium estimated to be released to the environs, the probable weather conditions at the time of the accident, and population density downwind from the accident scene. The likelihood and consequence of postulated releases are coupled and expressed as a risk spectra. (author)