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 Southern California Edison disclosed Friday it hopes the move could open the way for the Unit 2 reactor to be back in service by summer, when power demand typically soars in the region.
San Onofre has been shut down since January 2012, after a small radiation leak led to the discovery of unusual damage to hundreds of tubes that carry radioactive water.
Edison has been trying since October to convince the Nuclear Regulatory Commission that it's safe to run Unit 2 at no more than 70 percent power. Company engineers believe the reduced level will limit vibration and friction that can cause excessive wear to tubing.
The tentative proposal amounts to Edison's third attempt to answer a thorny question raised by the NRC: Is the plant that hasn't produced electricity in more than a year capable of running at full power?
In earlier filings, Edison argued that its 70 percent restart target was, in effect, full power. It later submitted another analysis showing the reactor could run at 100 percent power, but the research found the risk of a tube break could reach unacceptable levels after 11 months.
The new proposal could essentially eliminate the debate over the full power threshold.
It calls for capping the plant's power output at 70 percent in the plant's technical operating rules, rather than the now-required 100 percent. It also argues that running the reactor at 70 percent capacity would pose no significant safety risk.
The proposal, known as a license amendment, came as a surprise since Edison has long argued such a revision was unnecessary to restart the plant.
If approved by federal regulators, the move could offer a potentially quicker way to a restart.
"We want to do every responsible thing we can do to get Unit 2 up and running safely before the summer heat hits our region," SCE President Ron Litzinger said in a statement.
Anti-nuclear activists who have opposed the restart accused Edison of trying to circumvent a thorough NRC review of machinery with a history of trouble.
According to Edison documents, members of the public can request a hearing on the amendment, but if NRC staff finds there is no significant hazard, the hearing can be held after the amendment is approved.
"Edison is more focused on making profits than it is in assuring the safety of millions of Southern Californians living near these reactors," Damon Moglen of the advocacy group Friends of the Earth said in a statement.
Daniel Hirsch, a lecturer on nuclear policy at the University of California, Santa Cruz, and a critic of the nuclear power industry, said Edison was trying to delay a substantive review until "long after it has already restarted."
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 "If it is subsequently determined it wasn't safe to do so, it would be way too late," Hirsch said in a statement.
NRC spokesman Victor Dricks said the agency had not received the proposal from Edison.
The problems at San Onofre focus on its steam generators, which were installed in a $670 million overhaul in 2009 and 2010.
Last year, federal regulators blamed heavy tube wear in the generators on a botched computer analysis that they said misjudged how water and steam would flow in the reactors, along with manufacturing problems.
The generators, which resemble massive steel fire hydrants, control heat in the reactors and operate somewhat like a car radiator. At San Onofre, each one stands 65 feet high and weighs 1.3 million pounds, with 9,727 U-shaped tubes inside that are each 0.75 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 future of the heavily damaged Unit 3 reactor, where the radiation leak occurred after a tube break last year, is not clear. Edison has said that because of manufacturing differences, Unit 2's generators did not suffer the extent of deep tube wear witnessed in its sister.
Cracked and corroded generator tubing has vexed the nation's nuclear industry for years.
Decaying generator tubes helped push San Onofre's Unit 1 reactor into retirement in 1992, even though it was designed to run until 2004. The following year, the Trojan nuclear plant, near Portland, Ore., was shuttered because of microscopic cracks in steam generator tubes, cutting years off its expected lifespan.
San Onofre is owned by SCE, San Diego Gas & Electric and the city of Riverside.
[Associated
Press; By MICHAEL R. BLOOD]
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