LOS ANGELES (AP) -- 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 (http://bit.ly/U5Cfjs ). "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 scheduled a public meeting on the issue Friday in Southern California.
However, an NRC decision is not expected for months.
Information from: The Orange County Register, http://www.ocregister.com