San Onofre Nuclear Generating Station

Kevin Rakestraw
May 24, 2017

Submitted as coursework for PH241, Stanford University, Winter 2017


Fig. 1: Aerial photo of the San Onofre Nuclear Generating Station taken in 2012. (Source: Wikimedia Commons)

The San Onofre Nuclear Generating Station (SONGS), seen in Fig. 1, is a three-unit nuclear power plant that was operational from 1968 until its recent closure in 2013. SONGS is located between Los Angeles and San Diego, just south of San Clemente. It was operated by the Southern California Edison company. [1,2]

Unit 1

Unit 1 is a Pressurized Water Reactor with four coolant loops that take the heated water to a steam generator. It began construction on May 1964 and became commercially operational nearly four years later on January 1968. [3] It operated with a design net capacity of 436 MWe. [3] Unit 1 was permanently shut down on November 1992 after nearly twenty-five years of use. [3]

Units 2 and 3

Units 2 and 3 are both Pressurized Water Reactors, with two coolant loops each. Both began construction in March 1974, just short of twenty years after construction began on Unit 1. [3] These reactors took much longer to become operational. Unit 2 and 3 became commercially operational in August 1983 and April 1984 with a 1070 and 1080 MWe design net capacity respectively. [3] Both were permanently shut down on June 7th, 2013 after a gas leak prompted a shutdown in January 2012. [3-5]

Closure of Units 2 and 3

Edison had replaced the steam generators in both units as part of a $670 million upgrade in 2009 and 2010. [4,5] In January 2012, a small leak of radioactive gas prompted shutdown of one of the two units. [4] The other had already been shut down for a routine maintenance. [4] During this time, unexpected wear was found in the metal tubes in each of the steam generators. [4] Edison sought to restart one of the reactors for continued energy production, but in the end it opted to permanently shut down the nuclear plant due to regulatory uncertainty of the proposed restart. [4] The plant is still in the early stages of being decommissioned. Edison has recently picked two companies, AECOM from Los Angeles and EnergySolutions from Salt Lake City, to begin the long and meticulous process of decommissioning the plant, which is expected to take ten years. [5]

© Kevin Rakestraw. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] B. Bonanni, "San Onofre Nuclear Generating Station", Physics 240, Stanford University, Fall 2016.

[2] D. Lloyd, "San Onofre Nuclear Generating Station", Physics 241, Stanford University, Winter 2016.

[3] "Nuclear Power Reactors in the World: 2016 Edition," International Atomic Energy Agency, AIEA-RDS-2/36, May 2016

[4] P. Brennan, "San Onofre Nuclear Plant to Shut Permanently, Edison Says," Orange County Register, 8 Jun 13

[5] R. Nikolewski, "Shutting It Down: San Onofre Decommissioning Contractors Named," San Diego Union-Tribune, 20 Dec 16.