SAN CLEMENTE, CA - MARCH 15: The San Onofre Nuclear Generating Station is seen from the beach along San Onofre State Beach on March 15, 2012 south of San Clemente, California. Three steam generator tubes in Unit 3 of the nuclear reaction facility failed pressure stress tests by Southern California Edison (SCE), prompting the U.S. Nuclear Regulatory Commission to begin assembling a team of nuclear energy inspection experts who will try to determine why the level of wear on the tubes is unusually high. The unit has been shut down since the detection of a leak in one of the steam generator tubes on January 31. Unit 2 is also off line, for routine inspections, and Unit 1 has been decommissioned. (Photo by David McNew/Getty Images)
Federal regulators on Friday released parts of a once-confidential report at the center of a dispute between California Sen. Barbara Boxer and the company that runs the troubled San Onofre nuclear power plant.
However, sections of the 64-page report released by the Nuclear Regulatory Commission were redacted, and it wasn't immediately clear if the issues highlighted by Boxer were included.
The Democratic senator said last month that the study suggests operator Southern California Edison took shortcuts that compromised safety at the seaside plant, which was shut down more than a year ago after a tube break released a trace of radiation.
Edison has said the senator is off the mark.
The report was authored by Mitsubishi Heavy Industries - the Japan-based company that built the plant's troubled steam generators.
The problems at the twin-domed plant between Los Angeles and San Diego center on the huge generators, which were installed in a $670 million overhaul in 2009 and 2010.
After the plant was shut down, investigators found unusual damage on hundreds of tubes that carry radioactive water inside the equipment. NRC investigators later blamed the problem on a flawed computer analysis that resulted in design flaws.
Edison has asked the NRC for permission to restart one of the reactors, Unit 2, and run it as reduced power in hopes of slowing or stopping tube damage.
The generators, which resemble massive steel fire hydrants, control heat in the reactors and operate something like a car radiator. At San Onofre, each one stands 65 feet high, weighs 1.3 million pounds, with 9,727 U-shaped tubes inside, each three-quarters of an inch in diameter.
Overall, NRC records show investigators found wear from friction and vibration in 15,000 places, in varying degrees, in 3,401 tubes inside the plant's four generators, two in each reactor.
The plant is owned by SCE, San Diego Gas & Electric and the city of Riverside.