Developing a brittle fracture acceptance criterion for transport casks for adoption by the International Atomic Energy Agency(IAEA)

With increasing nuclear material transportation demands, new generation casks have included designs which propose the use of structural materials other than austenitic stainless steel. Motivation for using alternate materials include potentials for lower cost, easier fabrication, no welding and less weight (higher payload). Examples of candidate materials for structural components include ferritic steels and ductile cast iron for the containment boundary and borated stainless steel for the basket. The primary technical issue which separates these candidate materials from austenitic stainless steel is that they may, under certain combinations of mechanical and environmental loadings, fail in a brittle fracture mode. There is a clear need to develop a consensus criterion that will encompass a broad range of materials and provide a consistent method for evaluating candidate materials with respect to brittle fracture. Adopting such a criterion through the auspices of the IAEA has distinct advantages. An international consensus would provide assurance to regulators and the public that the most appropriate method is used, and countries developing packages using candidate materials could work with a single criterion without concern that another country is setting precedent using a different criterion. The development of such a criterion has been in progress for two and one-half years. There are two major efforts which are being pursued in parallel. There is the technical effort to write a draft document and the formal effort to facilitate adoption of a criterion by the IAEA. 7 refs., 1 fig