LOS ANGELES (AP) — The idled San Onofre nuclear power plant is facing new scrutiny from Congress as the utility that operates it moves closer to proposing a fix to get the twin reactors back in service.
The chair of the U.S. Senate's environment committee pressed federal regulators Tuesday to disclose details about the design of the plant's troubled steam generators, in which hundreds of tubes that carry radioactive water have been damaged by unexpected vibration and friction.
Meanwhile, operator Southern California Edison said it was working toward meeting federal benchmarks that could open the way for a restart of at least one of the reactors, perhaps in time to meet summer power demand.
The twin reactors, located along the coast between San Diego and Los Angeles, have been shut down for more than three months while investigators try to determine the cause of the unusual tube wear.
On Tuesday, Sen. Barbara Boxer asked Nuclear Regulatory Commission Chairman Gregory Jaczko for documentation on how the federal agency reviewed a series of modifications to the generators, which might be the culprit in the mechanical trouble. Boxer, who chairs the Environment and Public Works Committee, sent a similar letter to SCE parent Edison International.
At issue is whether Edison sidestepped any federal requirements by conducting extensive design changes, a claim leveled by an environmental group that said the alterations are at the heart of the plant's problems.
"Concerns have been raised that design changes in the steam generators contributed to accelerated wear in tubes carrying radioactive water," wrote Boxer, D-Calif. "The determination to restart the San Onofre reactors must ensure the safety of the millions of Californians who live and work near the plant."
A 13-page report issued by Friends of the Earth, a group critical of the nuclear industry, warned that running the plant at reduced power would not resolve problems with badly worn tubing.
Earlier this month Edison announced a tentative plan to restart and run the seaside reactors at lower power, at least for several months, because engineers believe that will ease vibration that could be eroding tubes.
The four generators at San Onofre each have nearly 10,000 alloy tubes that carry radioactive water.
The generators function something like a car radiator, which controls heat in a vehicle's engine. The generator tubes circulate hot, radioactive water from the reactors, which heats a bath of non-radioactive water surrounding them. That makes steam, which is used to turn turbines to make electricity.
The tubes represent a critical safety barrier — if a tube breaks, there is the potential that radioactivity can escape into the atmosphere.
The Friends of the Earth report also expanded an earlier allegation that Edison misled federal regulators about the modifications, a claim disputed by the Nuclear Regulatory Commission and the company.