Failure Probabilities of Ferritic Spent-Fuel Casks Subjected to Real Accident Events

This paper discusses an assessment (McConnell et al. 1988), of the probability of breach of containment, which may result in the release of radioactive material, from ferritic spent-fuel transport casks subjected to severe accidents. A motivation for such an analysis is to evaluate the dual-purpose application for ferritic casks which are presently being used to store spent-fuel and which may have some economic advantage over traditional stainless steel casks (Casper et al.). Regulations require the transport cask applicant to demonstrate that the structural containment of a cask can withstand a sequence of hypothetical accident events including a thirty-foot drop onto an unyielding surface and a forty-inch drop onto a mild steel pin. Existing spent-fuel casks licensed for transport are all of a sandwich destgn employing a thin stainless steel containment boundary and a lead or depleted uranium shield (Johnson and Notz). The margin of safety of these casks, particularly for severe, or extra-regulatory events, may be the basis by which cask designs constructed of alternative materials are ultimately evaluated (Barrett).