LOS ANGELES (AP) — The operator a troubled U.S. nuclear power plant on Thursday proposed to restart one of the plant's twin reactors, months after a break in a tube carrying radioactive water.
The San Onofre nuclear power plant is a major source of power in the stretch of Southern California between Los Angeles and San Diego, but it has been shut down since Jan. 31. Investigators later found that a botched computer analysis led to excessive wear on hundreds of tubes inside the plant's steam generators.
About 7.4 million Californians live within 50 miles (80 kilometers) of San Onofre, which can power 1.4 million homes.
Environmental groups and activists have argued the plant is too damaged to be restarted safely.
The restart plan "is a reckless gamble that flies in the face of the utility's claim that it puts safety ahead of profits," the advocacy group Friends of the Earth, which is critical of the nuclear power industry, said in a statement.
Southern California Edison said in a statement it's filed the proposal with the Nuclear Regulatory Commission, which is expected to take months to review. The NRC has said there is no timetable to restart the plant.
"The agency will not permit a restart unless and until we can conclude the reactor can be operated safely," NRC Chairman Allison Macfarlane said. "Our inspections and review will be painstaking, thorough and will not be rushed."
Overall, investigators found wear from friction and vibration in 15,000 places, in varying degrees, in 3,401 tubes inside the four generators. And in about 280 spots — virtually all in the Unit 3 reactor — more than 50 percent of the tube wall was worn away.
The generators control heat in the reactors. If a tube breaks, there is the potential that radioactivity could escape into the atmosphere, and serious leaks can drain cooling water from a reactor.
The steam generators were manufactured by Japan-based Mitsubishi Heavy Industries. The design of the generators also is under congressional scrutiny.
"Safety is our top priority and after conducting more than 170,000 inspections to understand and prevent the problem, and confirming the corrective actions we have taken to solve the problem with the top experts from around the world, we have concluded that Unit 2 at San Onofre can be operated safely," Ron Litzinger, president of SCE, said in a statement.
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, Oregon, was shuttered because of microscopic cracks in steam generator tubes, cutting years off its expected lifespan.