San Onofre reactor leaked radiation after being misused, report says

The San Onofre nuclear power plant was closed after a small radiation leak.
(Allen J. Schaben / Los Angeles Times)

Owners of the failed San Onofre nuclear power plant operated the reactor outside the allowable limits for pressure and temperature, causing the radiation leak that shut down the facility for good, a new report has found.

Citing documents recently obtained from the U.S. Nuclear Regulatory Commission, former Southern California Edison engineer Vinod Arora issued a report Tuesday laying blame for the breakdown squarely on Edison.

“Higher primary reactor coolant temperatures and higher steam pressure caused tube-to-tube contact resulting in dangerous and potentially deadly tube ruptures,” he said.

Excessive tube wear inside replacement steam generators forced the San Onofre Nuclear Generating Station to be shut down in 2012.


Edison called the comments by Arora “misinformed” and again faulted Mitsubishi Heavy Industries, the Japanese firm that built the replacement steam generators that failed decades ahead of schedule.

“As far back as September of 2013, the Nuclear Regulatory Commission (NRC) identified flaws in how Mitsubishi Heavy Industries (MHI) used its computer codes to design the failed steam generators at SONGS,” Edison said in an email. “The NRC further issued a ‘Notice of Non-Conformance’ against MHI for its flawed computer modeling in the failed design.

“In particular, the NRC reports indicated that MHI’s use of its computer codes in the design of the steam generators inaccurately predicted thermal hydraulic conditions in the steam generators, leading to tube vibration and wear, and a steam generator tube leak.”

Arora cited records he obtained under the U.S. Freedom of Information Act that he said show Edison improperly deployed Unit 3 steam generators just before the radiation leak.

For more than a year, Arora has sought daily control-room operations logs but Edison has declined to provide the records.

“If those logs have not been destroyed, they will show immediately whether or not Edison risked the lives of 8.5 million Southern Californians by redlining the Unit 3 generators,” he said.

The California Public Utilities Commission ordered customers to pay $3.3 billion of the $4.7-billion cost of the premature closure, although that decision is being reviewed as a result of improper communications between regulators and utility executives.

Arora said the records obtained from federal regulators show that Edison — not its customers — should be responsible for the costs of the shuttered plant.



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