San Onofre Nuclear Generating Station (SONGS), California, United States of America
San Onofre Nuclear Generating Station (SONGS) is a 2,200MW, twin nuclear reactor power station. It is located approximately 6.5km south-east of San Clemente in Orange County, in the state of California. The plant, operational since 1968, is one of the largest nuclear generating stations in the US and the largest in southern California.
As of July 2012, the plant was out of service. Unit 2 was shutdown in January 2012 for planned maintenance and upgrades, while unit 3 was taken out of service in the same month after a leak was discovered in a steam generator tube. Unit 1 was permanently shutdown in 1992.
The plant is expected to resume operations only after receiving permission from the Nuclear Regulatory Commission, an independent agency of the US Government.
Southern California Edison (SCE), a subsidiary of Edison International, is the licensee and is responsible for the management and operations of the plant. SCE has 78.21% working interest in the project.
San Diego Gas & Electric, a subsidiary of Sempra Energy, and the city of Riverside have an ownership of 20% and 1.79% respectively in the plant.
History of California's SONGS
Consent for the installation of unit 1, a three-loop pressurised water reactor from Westinghouse, for the SONGS project was given in 1963. Construction commenced in 1964 and unit 1 was put into commercial operation in January 1968. It was permanently taken out of service in November 1992.
Decommissioning of unit 1 was started in 1999 and most of its structures and facilities were removed from the site by 2008. The decommissioning required an investment of $460m.
Permit for the installation of units 2 and 3 was granted in October 1973. Construction commenced in 1974 and was accomplished in 1981.
Unit 2 was brought online in August 1983, while unit 3 started generating electricity in April 1984. The units required an investment of $4.5bn.
San Onofre nuclear power plant unit details
Located in San Jose, the 602MW Metcalf Energy Center is now delivering power to northern California.
San Onofre nuclear power plant is built on an 84-acre site leased from the US Marine Corps' Camp Pendleton. The plant's existing units, 2 and 3, are two-loop pressurised water reactors.
Each unit can generate up to 1,100MW of power, enough to meet the needs of 700,000 average homes.
The plant's four steam generators, two each for unit 2 and unit 3, were replaced in 2010 and 2011 respectively. The original steam turbine generators were manufactured by English Electric, a British industrial manufacturer which became defunct in 1968.
All four steam turbines were replaced after the end of their service period by new steam turbines manufactured by Mitsubishi Heavy Industries (MHI). Each of the replaced steam turbines is 19.8m tall, 6.7m in diameter and weighs 640t.
A once-through condenser cooling method is used to cool the steam condensers of each reactor. Cooling water for each unit is sourced from the Pacific Ocean via an intake pipe measuring 1,036m in length and 5.4m in diameter.
Used water is discharged back into the sea through two separate discharge pipelines. The discharge pipe meant for the second reactor terminates 2,591m offshore. The third unit discharge pipe terminates 1,874m offshore.
Nuclear generating station contractors
All three units of the San Onofre nuclear power plant were built by Bechtel, currently the largest engineering, construction and project management company in the US. The company also acted as the architect for the plant.
The nuclear reactor for unit 1 was supplied by Westinghouse, while the reactors for units 2 and 3 were supplied by Combustion Engineering.
Strategic location between LA and San Diego
The nuclear plant is situated in a very strategic location with respect to the power grid. It is situated in between Los Angeles and San Diego, the two largest cities of California by population. While the latter is served by San Diego Gas & Electric, the former is served by SCE.
About 50% of the electrical transmission facilities and equipment are owned and operated by these two major utilities.