Nuclear Energy in California

Nuclear Plants in California

PG&E Photo of Diablo Canyon nuclear power plant

As of mid-2012, California had one operating nuclear power plant: Diablo Canyon (2,160 megawatts), near San Luis Obispo [pictured in a PG&E photo to the right].The plant's nuclear units use ocean water for cooling.

Pacific Gas and Electric Company (PG&E) owns the Diablo Canyon Nuclear Power Plant, which consists of two units. Unit 1 is a 1,073 megawatt (MW) PWR which began commercial operation in May 1985, while Unit 2 is a 1,087 MW PWR which began commercial operation in March 1986. Diablo Canyon's operation license expires in 2024 and PG&E must apply to the US Nuclear Regulatory Commission for a 20 year license extension.

The San Onofre Nuclear Generating Station (SONGS) (2,150 megawatts), about midway between Los Angeles and San Diego, went offline in January 2012 and was ordered by the Nuclear Regulatory Commission to stay offline while tubing wear issues were investigated. Subsequently, plant owners announced in June 2013 that remaining Units 2 and 3 would be permanently retired. Plans for Decommissioning of San Onofre Nuclear Generating Station Units 2 and 3 .

California also has four other commercial nuclear power plants and an experimental plant that are no longer in operation. These include:

  • The Santa Susana Sodium Reactor Experiment (SRE) was a small sodium-cooled experimental reactor built by Atomics International as part of a joint program with the United States Atomic Energy Commission at the Santa Susana Field Laboratory, near Moorpark in Ventura County. It came on line in April 1957, began feeding electricity to the grid on July 12, 1957, and closed February 1964. This reactor used sodium rather than water as a coolant and was coupled to a 6.5 megawatts electric-power generating system. It was considered the country's first civilian nuclear plant and the first "commercial" nuclear power plant to provide electricity to the public by powering the near-by city of Moorpark in 1957. On July 26, 1959, the SRE suffered a partial core meltdown. Thirteen of 43 fuel assemblies were damaged due to lack of heat transfer and radioactive contamination was released. The plant has subsequently been decommissioned and associated structures dismantled. Additional information can be found on the U.S. Dept. of Energy's website and the SRE Wikipedia page.

  • The Vallecitos Nuclear Power Plant near Pleasanton, Calif., was jointly built by PG&E and General Electric Company and operated from 1957 to 1967. This was a small, 30 megawatt power plant. On October 19, 1957, Vallecitos connected to the electrical grid and became the first privately funded plant to supply power in megawatt amounts to the electric utility grid. The plant was shut down in December 1967. The plant is in SAFSTOR and there are no plans for any significant dismantlement in the foreseeable future. All nuclear fuel has been removed from the site.

  • The 63 MW Boiling Water Reactor at the Humboldt Bay Nuclear Power Plant in Eureka was in operation by PG&E from August 1963 to July 1976. It was the seventh licensed nuclear plant in the United States. It was closed because the economics of a required seismic retrofit could not be justified following a moderate earthquake from a previously unknown fault just off the coast. It was permanently shut down July 2, 1976, and retired in 1985. The plant was then placed in SAFSTOR (with spent nuclear fuel rods stored in water pools on site) until anticipated full decommissioning in 2015. See more on SAFSTOR below.

  • The 913 MW Pressurized Water Reactor at the Rancho Seco Nuclear Power Plant, located about 25 miles south of Sacramento, is owned by the Sacramento Municipal Utility District in and was operation from April 1975 to June 7, 1989. It was closed by public referendum.

  • The 436 MW San Onofre Unit 1 Pressurized Water Reactor was in operation from January 1968 to November 30, 1992. It was closed by its owners rather than incur $125 million in required modifications.

The Vallecitos, Santa Susana, and San Onofre Unit 1 have been decommissioned (which involves have a plan for dismantling the reactor and transporting all radioactive materials to a site for disposal.) The U.S. Nuclear Regulatory Commission (NRC) staff in 1996 approved the decommissioning plan for the Rancho Seco Nuclear Power Plant.

The dismantling process will occur in stages, with "final teardown" scheduled to begin in 2008. The nuclear spent fuel produced during 14 years of operation at Rancho Seco was kept cool in a water pool on site and is now in protective dry storage.

The Vallecitos facility, a General Electric nuclear plant, was the first reactor in the country to be decommissioned. The plant is in SAFSTOR and there are no plans for any significant dismantlement in the foreseeable future.

Under SAFSTOR, often considered "delayed DECON," a nuclear facility is maintained and monitored in a condition that allows the radioactivity to decay; afterwards, it is dismantled. Under DECON (immediate dismantlement), soon after the nuclear facility closes, equipment, structures, and portions of the facility containing radioactive contaminants are removed or decontaminated to a level that permits release of the property and termination of the NRC license.

Spent fuel can either be reprocessed to recover usable uranium and plutonium, or it can be managed as a waste for long-term ultimate disposal. Since fuel re-processing is not commercially available in the United States and has not been shown to be commercially viable n this country, spent fuel is typically being held in temporary storage at reactor sites until a permanent long-term waste disposal option becomes available.

Nuclear Power Plants in California
Name of Plant Capacity (MW) In Service Owner
Diablo Canyon
Unit 1
Unit 2
San Onofre
Unit 1
Unit 2
Unit 3
1968 - 1992
Humboldt Bay
Unit 3 * 65 1963 - 1976 PG&E
Rancho Seco
913 1975 - 1989 SMUD
30 1957 - 1967 PG&E/GE
Santa Susana
6.5 1957 - 1964 Atomics International

*Units 1 and 2 are natural gas-fired thermal power plants on the same site.
Southern California Edison installed and operated the electric-power generating system.