A report on the causes of equipment failure at Edison International (EIX)’s San Onofre nuclear-power plant in California has fueled debate over what the utility knew about flaws in the gear and when it learned about them.
The U.S. Nuclear Regulatory Commission yesterday released a redacted version of the report produced by Tokyo-based Mitsubishi Heavy Industries Ltd. (7011), the supplier of steam generators that failed, forcing a shutdown of the plant a year ago. The environmental group Friends of the Earth and two Democratic lawmakers said it showed Rosemead, California-based Edison knew about design issues and failed to correct them.
Edison “would never, and did not, install steam generators that it believed would impact public safety or impair reliability,” Pete Dietrich, senior vice president of Southern California Edison Co., the subsidiary that operates the facility, said in an e-mailed statement.
The company idled two reactors at the San Onofre plant between Los Angeles and San Diego in January 2012, after discovering unusual wear on steam-generator tubes. The event has renewed a debate on U.S. nuclear-reactor safety ahead of next week’s second anniversary of meltdowns at Japan’s Fukushima Dai- Ichi plant. Edison is seeking the NRC’s permission to re-start one of the San Onofre units at limited power. The agency hasn’t issued a decision.
“In releasing this report, we are just sharing the information of the lessons learned from the situation with everyone else in the industry,” Patrick Boyle, a spokesman for Mitsubishi Nuclear Energy Systems, a unit of Mitsubishi Heavy Industries, said in a statement. “We are convinced we know what happened and why, and how the problem can be avoided in the future.”
Southern California Edison said the problems were the fault of Mitsubishi. An NRC inspection team found in July that faulty computer modeling by Mitsubishi led engineers to incorrectly measure the steam dryness, Edison said.
Mitsubishi “repeatedly reassured” the utility of the design’s efficacy, according to the Edison statement.
Friends of the Earth, an environmental group, saw reason to blame Edison in the report, which it termed a “bombshell.”
“Edison clearly knew about design problems with the San Onofre replacement steam generators yet failed to take corrective action,” Damon Moglen, energy and climate director for Washington-based Friends of the Earth, said in an e-mailed statement. “It is inconceivable that the NRC would now give approval to restart these damaged reactors without the thorough, public review of a license amendment proceeding.”
While the NRC has made no decision to re-start the reactors, it is investigating documents provided by Edison for accuracy and thoroughness, agency Chairman Allison Macfarlane said in a Feb. 8 letter to Senator Barbara Boxer of California.
Boxer and Representative Edward Markey of Massachusetts, both Democrats, have said the San Onofre plant should remain shuttered until regulators determine it’s safe and complete an investigation into whether Edison complied with its obligations. The 2,200-megawatt San Onofre plant was closed after inspectors found unusual wear on tubes that carry radioactive water at its Unit 2 and Unit 3 reactors.
An unredacted version of the report shows that Edison and Mitsubishi rejected safety modifications to the steam generators to avoid a license amendment and safety review for the plant, the lawmakers said in a joint statement. Along with the report, Mitsubishi also released a redacted supplemental technical report.
“The documents released today show that Southern California Edison and Mitsubishi cut safety corners to avoid a new NRC licensing process,” Markey said in a statement.
Macfarlane told a House Energy and Commerce Committee panel on Feb. 28 that the agency won’t allow any licensed facilities to operate unless it can assure they can do so safely.
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