By Tom Palmisano, Southern California Edison’s vice president of decommissioning and chief nuclear officer
I write to offer your readers important facts regarding the continued safe storage of used nuclear fuel at San Onofre nuclear plant, and to correct errors on this topic in a letter to the editor published in the April 1 edition of the San Clemente Times.
San Onofre nuclear plant stores one-third of its used nuclear fuel in licensed, regulated dry cask storage canisters. We plan to transfer the remaining two-thirds, currently in steel-lined concrete pools, to dry storage by 2019. Similar storage systems have been safely used for 30 years in the United States, and the Electric Power Research Institute (EPRI) projects it would take a minimum of 80 years before canisters like those at San Onofre might experience a crack.
The April 1 letter incorrectly interpreted a 2015 Sandia National Labs study, which reviewed and compared previously performed experimental “accelerated” corrosion rates, using conditions impossible to achieve in the natural environment of existing dry storage canisters.
The Nuclear Regulatory Commission (NRC) has reviewed the Sandia report, and noted the Sandia work included experimental corrosion studies intended to provide a basis to mitigate stress corrosion cracking on a new standardized canister. The study concluded that stress corrosion cracking may be possible within 150 years, the authors’ proposed regulatory lifetime of the new canister. The report does not conclude that corrosion could occur in very short time intervals in real-world conditions, as asserted in the letter to SC Times.
The dry storage canisters at San Onofre are initially licensed for 20-year periods by the NRC, which inspects the design, manufacture and use of dry casks to ensure adherence to safety and security requirements. The NRC conducts safety reviews prior to re-licensing canisters for 20- to 40-year periods.
Used nuclear fuel must be in canisters before it can be transferred from San Onofre to an off-site location, as proposed by numerous community and elected leaders. As long as fuel remains at San Onofre, Southern California Edison (SCE), majority owner of the plant, will continue to safely store and monitor it in accordance with NRC regulations. In addition, SCE will partner with the EPRI to apply leading-edge cask inspection techniques at San Onofre.
The California Coastal Commission appropriately approved, with conditions, SCE’s Coastal Development Permit to expand dry storage at San Onofre, based on issues within the commission’s jurisdiction.