Unresolved Safety Issues in the Storage and Transport of Vitrified High-Level Nuclear Waste

Over the next fifteen years, approximately 3000 canisters of vitrified high-level radioactive waste (VHLW) will be shipped by sea to Japan from reprocessing plants in France and the United Kingdom. These VHLW canisters have characteristics and vulnerabilities that have not been fully evaluated with respect to their implications for safety during transport and storage. These include the use of canisters fabricated from high-carbon austenitic stainless steel, which sensitizes during the glass production process and hence experiences a loss of corrosion resistance, and the reduced retention of actinides in the glass in the presence of environmental materials. These properties may significantly enhance the consequences of transport or storage accidents. This paper discusses a number of these issues, and concludes that it is prudent to increase the level of conservatism governing current shipping and storage practices for VHLW, to compensate for the uncertainties associated with the behavior of VHLW under severe accident conditions.