Originally published November 30, 2012 at 10:19 a.m., updated November 30, 2012 at 3:11 p.m.
Someone may have tampered with an emergency generator at the San Onofre nuclear power plant, but there was no danger because both reactors at the California coastal facility are shut down, operators said.
In late October, coolant was found in the oil system of the backup diesel generator for the Unit 3 reactor, Southern California Edison disclosed Thursday.
Edison notified the Nuclear Regulatory Commission on Tuesday that an internal investigation found evidence of potential tampering as the cause of the "abnormal condition."
"The evidence is not conclusive that it's tampering," Edison spokeswoman Jennifer Manfre told the Orange County Register. "But of course we are doing a very thorough investigation, so that has not been ruled out."
The generator was down for maintenance so it would not have been used in an emergency, Manfre said.
Edison has increased security at the plant, where the reactors have been offline since January. Unit 3 was shut down after a steam tube broke and released trace amounts of radiation.
Technicians later found excessive wear on hundreds of tubes in units 3 and 2, which had been taken offline earlier for maintenance.
The problems center on damage to alloy tubing in four steam generators that were installed during a $670 million overhaul in 2009 and 2010.
A three-month federal probe blamed a botched computer analysis for generator design flaws that ultimately resulted in excessive wear to the tubes.
Last month, Edison asked federal regulators for permission to restart the Unit 2 reactor and run it at reduced power.
The utility and the NRC have a public meeting re review that request Friday evening in Mission Viejo.
Critics of the plant say the meeting is a poor substitute for a more formal hearing into whether Edison should have filed for a license renewal before replacing the steam generators.
Meanwhile 3 Buddhist monks have walked from Dana Point to San Clement Pier to begin a 6 day fast to protest plans to restart the plant.
An NRC decision is not expected for months.