San Onofre Plant’s Unit 1 to Shut Nov. 30 : Power: Oldest commercial nuclear generator in state will be decommissioned because of costs.

California’s oldest commercial nuclear generator, San Onofre Unit 1, alongside Interstate 5 between Oceanside and San Clemente, will shut down for good Nov. 30, ending 25 years of service to Southern California, the U.S. Nuclear Regulatory Commission announced Friday.

The end of the workhorse’s career was previously conceded by Southern California Edison, which owns 80% of the plant, and San Diego Gas & Electric Co., which owns 20%.

The plant’s retirement was approved in August by the state Public Utilities Commission after its ratepayers advocacy division argued that the plant was no longer a good deal for customers because it was slipping as a cost-effective generator of electricity.

Besides, the unit faced $125 million or more in improvements by the end of the year.

“In many respects, it’s sad to see a plant shut down,” said Bobby Faulkenberry, deputy regional administrator for the NRC’s Region 5, which includes the Pacific Rim states and Arizona. “As long as they’re producing power, it’s such a loss.”

But he acknowledged the declining efficiency of the plant which, over its lifetime, is considered to have produced about 51% of its maximum potential power. Today, industry standards are closer to 75%.

The landmark, cylinder-shaped nuclear power plant is the oldest of three at the San Onofre Nuclear Generating Station.

The adjoining twin, dome-shaped plants that were constructed in 1983 and 1984 are expected to remain in operation into the 2020s. Each produces more than twice the electricity of Unit 1, which was designed to produce electricity until the year 2004.

The shutdown of Unit 1 will leave 108 other commercial nuclear generators operating in the United States; six more are under construction.

After San Onofre’s Unit 1 is shut down, California will have four nuclear power generators: the other two at San Onofre and the two plants at Diablo Canyon, near San Luis Obispo and operated by Pacific Gas & Electric Co.

Over the past 25 years, 17 nuclear power plants that contributed commercial electricity have been shut down nationwide, ranging from early prototypes to the closure of the troubled Rancho Seco nuclear plant near Sacramento in 1989 after a vote of its ratepayers.

In Oregon, Portland General Electric Co. has decided to close by 1996 its own 15-year-old Trojan Nuclear Power Plant near Portland because of cracks in its steam generator system. But a ballot measure before voters there next month calls for the plant’s immediate closing.

At San Onofre, NRC officials met with nuclear engineers from the two utilities Friday morning to begin discussions of the plant’s shutdown--and its decommissioning as a nuclear power site, a process that could take up to 60 years.

Although Unit 1 has slipped in efficiency in recent years and can no longer keep production pace with newer nuclear generators, it nonetheless has operated for more than 300 consecutive days, a record among the three San Onofre units.

Engineers will begin the shutdown of Unit 1 on Nov. 16 with a so-called “coast-down from full operating power,” said the NRC’s Faulkenberry.

The unit’s normal refueling period would occur in late November, when a third of the 125 or so bundles of fuel rods, with production lives of four to five years, would be replaced with bundles of fuel rods containing fresh pellets of plutonium.

Instead of refueling this time, however, an engineer will simply flip the switch that will force control rods into the nuclear vessel, virtually shutting off the nuclear process instantly.

Then, in January, after some of the residual radioactivity has safely cooled, engineers will lift all the fuel rod bundles through water to storage pools--one inside Unit 1 and another inside Unit 3, where they will remain until a permanent, high-level radioactive waste site is developed.

“The defueling is a very controlled, very safe operation,” Faulkenberry said.

The process of shutting down Unit 1 is essentially the same process used in refueling the plant, except that this time new fuel won’t be brought in, and all the fuel will be taken out, said Harold Ray, senior vice president for nuclear operations at Edison.

“San Onofre Unit 1 is in its 11th fuel cycle, which means it has been refueled 10 times. Every time we do that, we do what we’ll do when we shut it down for the last time,” he said. “The only difference this time is, we won’t refuel it.”

The utilities could have rejiggered the alignment of the remaining fuel rods within the vessel to eke out more performance, but decided it wasn’t worth the cost.

After the shutdown, a comprehensive plan will be submitted for NRC approval on Unit 1’s decomissioning, meaning its interior will be freed of any traces of radioactivity and made safe for public use.

The two utilities say they will make up for the loss of Unit 1’s power by purchasing electricity from other, cheaper sources.

The shutdown agreement with the PUC allows the two utilities to recover from ratepayers the $460 million in costs, plus interest, that they have sunk into Unit 1 and not yet recouped over the years.

During its first 11 years, Unit 1 generally worked at more than 70% efficiency, earning the reputation of a cost-effective and clean power source for Southern California. It provided about 2.5% of Edison’s power needs and 3% of SDG&E;’s.

But, since 1980, the plant was inoperative for extended periods as its owners pumped more than $300 million into retrofitting and other repairs to meet new seismic and safety standards mandated by the NRC.