SCE halted the transfer of fuel from wet to dry intermediate storage following an incident in August 2018 when a canister became wedged during the downloading process. The canister was eventually placed safely into storage.
During the past 11 months, SCE and its contractor, Holtec, have “systematically reviewed and strengthened procedures, oversight and training that directly supports a robust fuel transfer programme”, SCE said in a statement.
As part of the review, new technologies such as cameras and load monitoring gauges have been introduced.
In May the US Nuclear Regulatory Commission said the removal of fuel could be resumed.
The August 2018 incident resulted from the canister being misaligned and becoming stuck on a flange while being lowered into an underground storage vault.
The NRC said plant personnel were transferring a multipurpose canister filled with spent nuclear fuel from the spent fuel pool to the facility’s dry cask storage facility. As the canister was being lowered from the transport cask into the underground storage vault, it became stuck on the gusset or inner ring assembly near the top of the vault’s inner liner, known as the “divider shell”.
The plant personnel believed the canister had been fully inserted, because the rigging that supported the canister had gone slack.
However, after a technician registered radiation readings higher than expected for a properly loaded cask, the personnel realised the problem. They corrected the canister's alignment and completed the operation.
There are three PWRs in permanent shutdown at San Onofre. Unit 1 was shut down in 1992 and Units 2 and 3 in 2013.