ROSEMEAD, Calif. — Setting the stage for costly, lengthy litigation, Southern California Edison Thursday blamed a Japanese manufacturer of stream generators for the permanent closure of the San Onofre Nuclear Generating Station in northern San Diego county.
The utility announced in a statement issued at its headquarters in Rosemead that it had sent Mitsubishi Heavy Industries Ltd. and Mitsubishi Nuclear Energy Systems a Formal Notice of Dispute over the steam generators Mitsubishi supplied for use at the nuclear station, known as SONGS.
Mitsubishi had warranted that the generators would operate reliably for 20 years, but SCE had to take SONGS offline in January 2012 when one of the steam generators experienced a leak of radioactive coolant leak after less than a year of operation, according to SCE’s statement.
Moreover, Mitsubishi failed to make repairs even though it was required to do so “with due diligence and dispatch,” according to the SCE Notice of Dispute.
“SCE alleges that Mitsubishi, as designer and manufacturer of the faulty (generators), is responsible for the enormous harm its failures have caused to California ratepayers, SCE, and the other SONGS owners,” the SCE statement said.
Edison owns 78.2 percent of the plant, leaving 20 percent belonging to San Diego Gas & Electric and 1.8 percent to the city of Riverside.
SCE on June 7 announced SONG’ permanent closure. It said that as a result, it would record a charge in the second quarter of between $450 million and $650 million before taxes. The utility estimated in February that the closure had already cost it $400 million.
The plant’s two reactor units, referred to as Unit 2 and Unit 3, had been offline since early 2012. Unit 1 was in operation from 1968 to 1992, when it was shut down over fears it could not withstand a major earthquake.
Unit 2 was taken out of service Jan. 9, 2012, for planned routine maintenance, while Unit 3 was shut down abruptly on Jan. 31, 2012, after a small leak of radioactive steam occurred. No one was hurt, but both reactors were kept offline while the issue was investigated.
Edison executives would later reveal the leak was caused by premature wearing of steam pressure tubes in the reactors. Each reactor has nearly 20,000 tubes and hundreds of those were found to have been worn down prematurely by rubbing against each other due to vibrations and a settling of support equipment.
The tubes carry hot, pressurized radioactive water from the reactors. The tubes then heat non-radioactive water surrounding them, producing steam used to turn turbines to create electricity.
The tubes also provide a critical safety function, forming a barrier between the radioactive and non-radioactive sides of the plant.
Edison has spent months trying to gain permission from the Nuclear Regulatory Commission to restart one unit at 70 percent power for five months as a test run. However, the plan was strongly opposed by the anti-nuclear group Friends of the Earth and Sen. Barbara Boxer, D-Calif., who accused Edison of skirting federal regulations designed to prevent such mishaps.