Role of Time-Limited Aging Analysis in Managing Aging Effects on Used Fuel Dry Storage Systems

There is currently no designated disposal site for used nuclear fuel in the Unites States, which raises the prospect of extended long-term storage and deferred transportation of used fuel at operating and decommissioned nuclear power plant sites. Under U.S. federal regulations contained in Title 10 of the Code of Federal Regulations 72.42, the initial license term for an independent spent fuel storage installation (ISFSI) must not exceed 40 years from the date of issuance. Licenses may be renewed by the U.S. Nuclear Regulatory Commission upon application by the licensee for a period not to exceed 40 years. Applications for ISFSI license renewals must include the following: (a) time-limited aging analyses (TLAAs) that demonstrate that the design basis analyses for structures, systems, and components (SSCs) important to safety will remain valid and the SSCs will continue to perform their intended function(s) for the requested period of extended operation; and (b) a description of the aging management program in place to guide the management of issues associated with aging that could adversely affect SSCs important to safety. This paper focuses on TLAA issues related to the confinement boundary of bolted- and welded-closure storage casks and canisters. Highlights and discussions are largely extracted from the report, “Managing Aging Effects on Dry Cask Storage Systems for Extended Long-Term Storage and Transportation of Used Fuel, Rev. 1,” FCRD-UFD-2013-000294, September, 2013.