INVESTIGATIONS OF SPENT FUEL CASK RESPONSE TO SABOTAGE

Presently, there is no reason to believe that sabotage of radioactive material shipments poses an imminent threat to public health and welfare in the US. The scenarios commonly thought of as “sabotage acts” range from violent protests of a shipping campaign to the capture of a shipment for the purpose of carrying out some terrorist action. The resources required to execute these scenarios vary widely, as does the difficulty in attacking the materials and packagings when shipped by rail, highway, air, or water. Because the threat of sabotage acts cannot be considered absolutely negligible, efforts have continued to provide appropriate safeguards for some classes of radioactive materials in transportation. Of special concern are those materials perceived to have particularly grave consequences if they are not safeguarded from reasonable threats. In particular, Nuclear Regulatory Commission (NRC) regulations require safeguards on spent fuel in transport. A State of Nevada Petition to the NRC seeks to make these requirements even more stringent. The Department of Energy (DOE), in its Draft Environmental Impact Statement (DEIS) for the Yucca Mountain Project, evaluated the potential impact of a particularly severe hypothetical sabotage attack on a spent fuel cask in transit. The consequence analysis in the DEIS examined data obtained in experiments conducted by Sandia National Laboratories in the early 1980s. The projected release fraction obtained for the DEIS was consistent with the results from a more recent experiment performed in France that also used depleted uranium oxide (DUO2) as a surrogate for spent fuel in a nine-assembly storage/transport cask.  While the surrogate spent fuel source term appears to be reasonably well defined for the type of high energy density device (HEDD1 ) used in the experiments to date, the behavior between spent fuel and DUO2 surrogate remains uncertain. This amounts to as much as a factor of 10 in the ratio of the aerosol that would be produced by a HEDD released against real spent fuel to that produced by a DUO2 surrogate (a factor usually termed the SFR). Reducing this uncertainty is the subject of an international cooperative proposal developed among US, German, and French laboratories and agencies to definitively estimate the comparative response of spent fuel and surrogate configurations to HEDD