California Sen. Barbara Boxer pressed federal regulators Wednesday to open an investigation into equipment problems at the shuttered San Onofre nuclear power plant.
In a letter to the Nuclear Regulatory Commission, the Democrat said information in a previously unreleased report shows operator Southern California Edison and the company that built the plant's ailing steam generators, Mitsubishi Heavy Industries, were aware of design problems before the equipment was installed.
Edison spokeswoman Maureen Brown did not immediately respond to an email and phone message seeking comment.
San Onofre, located along the coast between Los Angeles and San Diego, hasn't produced electricity since January 2012, after a tiny radiation leak led to the discovery of excessive wear on hundreds of generator tubes that carry radioactive water.
Boxer, who chairs the Environment and Public Works Committee, said the unreleased report raises concerns that Edison and Mitsubishi rejected safety modifications and sidestepped a more rigorous safety review.
Her letter came as Edison is pushing a plan to restart one of the hobbled twin reactors then run it at reduced power in an attempt to stop the vibrations that have damaged tubes.
"Safety, not regulatory short cuts, must be the driving factor in the design of nuclear facilities, as well as NRC's determination on whether (San Onofre) can be restarted," Boxer said in a letter co-signed by Rep. Edward Markey, D-Mass.
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Last year, federal officials blamed a botched computer analysis for design flaws that are largely to blame for unprecedented wear in tubes at the plant. They say a Mitsubishi analysis vastly misjudged how water and steam would flow in the reactors.
Gradual wear is common in steam generator tubing, but the rate of erosion at San Onofre stunned officials because the equipment is relatively new. The generators were replaced in a $670 million overhaul and began operating in April 2010 in Unit 2 and February 2011 in Unit 3.
Overall, 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 future of heavily damaged Unit 3 is not clear.
The plant is owned by SCE, San Diego Gas & Electric and the city of Riverside.
