Final used fuel transfer marks SONGS decommissioning milestone

11 August 2020

The final canister of used fuel from the shut-down San Onofre Nuclear Generating Station (SONGS) has now been transferred into dry storage, marking a milestone for the decommissioning of the California site.

The lid is placed on the designated storage vault of the final MPC at SONGS (Image: Holtec)

The last of 73 multi-purpose canisters (MPC) containing used fuel was transferred to the Holtec HI-STORM UMAX storage system on 7 August. In addition to the 73 MPCs, 50 canisters of used fuel are in a TN-NUHOMS dry storage system. With the transfer of the final MPC most of the plant is now a deconstruction site, Southern California Edison (SCE) said. Dismantlement activities have already begun, and building demolition is expected to start early in 2021.

According to Holtec, SCE selected the subterranean MPC system primarily because of its "demonstrable indestructability under any conceivable threat", including earthquake intensity levels greater than any ever recorded. Enhancements to support the transfer of used fuel from wet to dry storage developed for the SONGS project are now being used across the Holtec fleet, the company said. These include the development of a new training programme, detailed loading procedures with process improvements and the development and implementation of camera systems and load monitoring equipment.

The used fuel will ultimately be transported to an off-site facility when one becomes available, and
SCE Vice President and Chief Nuclear Officer Doug Bauder said the company remains committed to ensuring it is safely stored until then. "We are developing a strategic plan to help us explore opportunities for advancing various alternatives to get the spent fuel off-site, as well as make sure that our fuel is ready for pickup when the opportunity presents itself," he said.

SCE expects to release the strategic plan early next year. This will explore alternatives for relocating San Onofre's used fuel to an off-site facility either for permanent disposal or temporary storage.

Holtec is working to establish the HI-STORE consolidated interim storage facility (CISF) in south-eastern New Mexico, which would use a similar subterranean storage system to that at San Onofre. In addition, the MPCs in use at SONGS are licensed for transport and are ready to be shipped to a CISF when one becomes available, Holtec said. Removal of used fuel from shuttered nuclear power plants allows the full site to be returned to more productive use, it added.

SONGS units 2 and 3 were permanently retired in June 2013 owing to regulatory delay and uncertainty after problems were found in replacement steam generators.

Researched and written by World Nuclear News