Southern California Edison (SCE) said recent problems with a backup emergency diesel generator at one of the idle San Onofre Nuclear Generating Station (SONGS) units could be the result of deliberate “tampering.”
The Edison International (NYSE: EIX) subsidiary acknowledged the issue in a Nov. 29 news release. Both units at the San Diego County nuclear station have been offline since January as a result of tube wear issues in steam generators that were installed only a few years ago.
The possible “tampering” was reported as the Nuclear Regulatory Commission (NRC) is considering whether to allow the unit with less tube wear problems to restart at reduce power.
During routine monitoring in late October, plant staff detected engine coolant in an oil system on a backup emergency diesel generator in Unit 3.
Plant staff notified the NRC site inspector on Oct. 30 in compliance with government reporting requirements. “Since Unit 3 is safely offline, defueled and not scheduled to restart in the near term, the presence of the coolant posed no safety risk. The diesel generator was out of service for routine maintenance activities when the discovery was made,” SCE said.
Then on Nov. 27, SCE, which is the operator and primary owner of the nuclear plant, notified NRC that an internal investigation found evidence of potential tampering as the cause of the abnormal condition. “The evidence did not confirm that actual tampering occurred. The investigation of this potential security issue continues,” the utility said.
The investigation has included rigorous tests, a review of station logs and employee interviews to determine the cause of the presence of the residual engine coolant, SCE said.
Based on the unexpected discovery of the coolant in the diesel oil system and the ongoing investigation, security at the plant has been enhanced, the company said.
“SCE is committed to the safety of the public and its employees and takes this matter very seriously,” said Pete Dietrich, senior vice president and chief nuclear officer of San Onofre.
SCE submitted technical information to the NRC on Oct. 4 in support of a proposed restart of Unit 2, which is also safely offline. The unit will not be restarted until all plans have been approved by the NRC. The Unit 3 restart was not included in that regulatory filing and remains shut down.
Southern California Edison owns more than 78% of the San Onofre plant. Minority owners include Sempra Energy (NYSE: SRE) subsidiary San Diego Gas & Electric (20%) and the City of Riverside (less than 2%).