Abstract
Spent nuclear fuel (SNF) is currently stored in dry storage canisters (DSCs) at various reactor sites awaiting final disposal in a future repository site. Many DSCs are made from welded Type 304/304L stainless steel (UNS S30400/S30403) and then placed inside a concrete cask system with passive atmospheric air cooling. The most likely long-term degradation that may result in a breach of the DSC’s containment system is chloride induced stress corrosion cracking (CISCC). A precursor to CISCC is localized corrosion in the form of pit initiation and propagation. This paper describes a model to quantify the time-based occurrence of CISCC on SNF DSCs that includes: weld residual stress, hourly time histories for site weather data, canister aerosol deposition density, SNF decay heat, canister surface temperature, deliquescence of mixed salts, droplet condensation, coalescence, and evaporation, dissolved species concentrations, pit initiation, growth, and repassivation, a criterion for pit-to-crack transition, and strain rate-based SCC crack growth. A supplemental and repeatable (for other designs and applications) experimental study to calibrate the model components is presented. The integrated model incorporates input parameter uncertainties to compute a probabilistic estimate of remaining life.
