Spent fuel transportation risk assessment: overview

Abstract

The US Nuclear Regulatory Commission (NRC) is responsible for issuing regulations for the packaging of spent fuel (and other large quantities of radioactive material) for transport that provide for public health and safety during transport [Title 10 of the Code of Federal Regulations (10 CFR) Part 71, ‘Packaging and transportation of radioactive waste’, dated 26 January 2004]. In September 1977, the NRC published NUREG 0170, ‘Final environmental statement on the transportation of radioactive material by air and other modes’, which assessed the adequacy of those regulations to provide safety assurance. In that assessment, the measure of safety was the risk of radiation doses to the public under routine and accident transport conditions, and the risk was found to be acceptable. Since that time, there have been two affirmations of this conclusion for spent nuclear fuel (SNF) transportation, each using improved tools and information that supported the earlier studies. This report presents the results of a fourth investigation into the safety of SNF transportation. The risks associated with SNF transportation come from the radiation that the spent fuel gives off, which is attenuated, but not eliminate, by the transportation casks shielding, and the possibility of the release of some quantity of radioactive material during a severe accident. This investigation shows that the risk from the radiation emitted from the casks is a small fraction of naturally occurring background radiation and the risk from accidental release of radioactive material is several orders of magnitude less. Because there have been only minor changes to the radioactive material transportation regulations between NUREG 0170 and this risk assessment, the calculated dose due to the external radiation from the cask under routine transport conditions is similar to what was found in earlier studies. The improved analysis tools and techniques, improved data availability, and a reduction in the number of conservative assumptions has made the estimate of accident risk from the release of radioactive material in this study approximately five orders of magnitude less than what was estimated in NUREG 0170. The results demonstrate that NRC regulations continue to provide adequate protection of public health and safety during the transportation of SNF.

Keywords:

• Spent fuel, Risk assessment, Transportation, Public dose