San Onofre Nuclear Generating Station
| Company type | Nuclear power facility (decommissioned) |
|---|---|
| Industry | Energy (Nuclear power generation) |
| Founded | January 1, 1968 in San Clemente, California, United States |
| Defunct | 2013 |
| Fate | Permanently closed and undergoing decommissioning |
| Headquarters | San Clemente , United States |
Area served | Southern California |
| Owner | Southern California Edison (78.2%), San Diego Gas & Electric (20%), City of Riverside Utilities Department (1.8%) |
Number of employees | 2200+ (At operational peak (prior to 2013)) |
The San Onofre Nuclear Generating Station (SONGS) is a nuclear power facility permanently closed and situated south of San Clemente, California along the Pacific coastline within Nuclear Regulatory Commission Region IV. The plant ceased operations in 2013 following the discovery of flaws in replacement steam generators and is currently undergoing decommissioning. The 2.2 GW capacity lost was compensated by the addition of 1.8 GW from newly constructed natural gas power plants and 250 MW from energy storage initiatives.
Primarily owned by Southern California Edison (SCE), which holds a 78.2% share through its parent company Edison International, ownership also includes San Diego Gas & Electric with 20% and the City of Riverside Utilities Department at 1.8%. At its operational peak, SONGS employed more than 2,200 personnel. The facility’s distinctive twin hemispherical containment structures are prominent landmarks positioned between the Pacific Ocean and the Surf Line railroad.
Unit 1 was operational from 1968 until its closure in 1992; Units 2 and 3 entered service in 1983 and 1984, respectively. Life-extension improvements completed between 2009 and 2010 aimed to add two decades to reactor service but resulted in premature degradation of over 3,000 tubes in the newly installed steam generators. This issue led to shutdowns beginning in January 2012 and triggered an investigation by the Nuclear Regulatory Commission. In May 2013, Barbara Boxer, then-chair of the Senate Environment and Public Works Committee, urged a criminal investigation due to safety concerns for the approximately eight million people living within a 50-mile radius.
In June 2013, Southern California Edison declared the permanent retirement of Units 2 and 3, citing ongoing regulatory challenges and appeals that would delay any potential restart by more than a year. The company indicated that full decommissioning would follow standard procedures over several years. Debates continue surrounding Edison’s strategy for on-site dry cask storage of the substantial nuclear waste accumulated during plant operations.
Reactors
Unit 1 was a first-generation Westinghouse pressurized water reactor that operated for a quarter-century before permanently shutting down in 1992; it has since been dismantled and repurposed as a spent fuel storage facility. This unit featured a spherical containment structure made of concrete and steel with walls at least thick, delivering a gross output of 456 MWe (436 MWe net) at full capacity.
Units 2 and 3 consisted of Combustion Engineering two-loop pressurized water reactors, generating gross outputs of 1,127 MWe and net outputs of approximately 1,070 MWe and 1,080 MWe respectively when operating at full load.
Between 2001 and 2011, Edison invested $671 million to replace steam generators in both reactors with redesigned units supplied by the Mitsubishi Group. Due to the reactors’ unique two-loop configuration, these steam generators ranked among the largest in the sector. A known challenge with such large-scale generators was accelerated tube wear, necessitating earlier replacement than their originally intended 40-year lifespan. Installing these replacements required creating temporary access points in the concrete containment structures. Unit 2’s upgrade was finalized in 2009, followed by Unit 3’s in 2011. Edison anticipated that this refurbishment would yield $1 billion in savings for customers over the remaining license period through 2022.
Prior to its closure in 2012, SONGS provided roughly one-fifth of Southern California’s electricity supply.
Site status summary
The San Onofre Nuclear Generating Station (SONGS), managed by Southern California Edison (SCE), is situated roughly 100 kilometers (60 miles) south of Los Angeles, within the boundaries of Marine Corps Base Camp Pendleton. The facility initially comprised three nuclear reactors: Unit 1 operated from 1968 until 1992, while Units 2 and 3 were permanently shut down in June 2013. The decommissioning of Unit 1 is nearly finalized; the turbine building has been dismantled, and segmentation and cutting of the reactor pressure vessel internals have been completed. However, transportation of the reactor pressure vessel faced delays due to its considerable size and mass. Current plans aim to transport it during the decommissioning process of Units 2 and 3, as its radioactivity levels have diminished sufficiently to be categorized as low-level waste.
SONGS-1 was a Westinghouse-designed, three-loop pressurized water reactor constructed by Bechtel, with a thermal capacity of 1347 MW. It commenced commercial operations on January 1, 1968, and was retired on November 30, 1992. Defueling was finalized by March 1993. Following regulatory approval, SCE proposed a decommissioning strategy placing SONGS-1 in SAFSTOR status until the shutdown of Units 2 and 3. After changes in NRC regulations, active decontamination began in 2000, leading to removal of most structures and equipment for disposal. In 2010, the NRC authorized unrestricted use of offshore portions of Unit 1’s cooling pipes beneath the seabed. Fuel from Unit 1 was relocated to the independent spent fuel storage installation (ISFSI), which was expanded in 2015 onto Unit 1’s former footprint to accommodate all spent fuel from Units 2 and 3. By 2020, all nuclear fuel had been transferred to dry cask storage.
The Reactor Pressure Vessel from Unit 1 was moved via rail and road transport to the Energy Solutions disposal site in Clive, Utah. It departed San Onofre on May 24, 2020, arriving at its destination on July 14, 2020.
Safety issues
Throughout its operational life, SONGS encountered various technical difficulties. In 1977, Bechtel mistakenly installed a nuclear reactor vessel in reverse orientation at the plant. In 2008, the facility received citations for problems including malfunctioning emergency generators, incorrectly wired batteries, and falsification of fire safety records. Although the Nuclear Regulatory Commission (NRC) acknowledged some improvements by 2011, it also pointed out persistent challenges related to human performance and insufficiently effective corrective measures.
Reports indicated that employees feared retaliation for reporting safety concerns; however, by 2011 progress had been made without compromising worker or public safety. An ammonia leak in November 2011 led to evacuation of impacted personnel while the reactors continued operating.
A mid-cycle inspection conducted by the NRC covering July 2011 through June 2012 identified three incidents involving human performance errors and revealed a procedural deficiency concerning cybersecurity evaluations of electronic devices—a gap that was subsequently addressed.
In 2012, contamination of coolant fluid was detected within a backup diesel generator’s oil system that could lead to failure upon activation. An internal inquiry suggested possible tampering with equipment by staff members indicative of potential sabotage.
Environmental risk and mitigation
Following the Fukushima disaster in 2011, Southern California Edison affirmed that the facility was engineered to endure an earthquake measuring up to magnitude 7.0 directly beneath the site. Furthermore, a protective seawall standing approximately 25 feet tall shields the plant from tsunami threats originating from an active fault located five miles offshore. The nearest fault line—the Christianitos fault—lies less than one mile away but is classified as inactive; nonetheless, other nearby active faults may pose some level of risk.
According to an NRC assessment published in August 2010, the annual likelihood of an earthquake causing core damage at San Onofre was estimated at one in 58,824.
In June 2012, S. David Freeman, former head of the Southern California Public Power Authority and prominent anti-nuclear advocate, characterized both San Onofre and Diablo Canyon as "disasters waiting to happen," citing aging reactors situated near seismic fault zones with millions residing nearby.
Due to limited available land adjacent to the site, San Onofre utilized seawater cooling instead of large cooling towers; constructing such towers would have required building across Interstate 5.
Currently, more than four thousand tons of spent nuclear fuel remain stored at San Onofre.
Population in Vicinity
The NRC establishes two emergency planning zones surrounding nuclear facilities: a 10-mile plume exposure pathway zone, which addresses airborne radioactive hazards, and a 50-mile ingestion pathway zone, focused on the risk of contaminated food and beverages. At San Onofre, prevailing winds predominantly blow inland from the west for approximately nine months each year.
In 2010, the population residing within a 10-mile radius of San Onofre was recorded at 92,687, marking a 50% rise compared to the previous ten years. Within a 50-mile radius, the number of inhabitants reached 8,460,508, reflecting a 14.9% increase since 2000. Cities located within 20 miles include San Clemente and Laguna Beach in Orange County, as well as Oceanside in San Diego County. The city of San Diego is situated about 45 miles to the south, with Los Angeles approximately 60 miles to the north of the plant.
Anti-Nuclear Demonstrations, 1977–Present
On August 6, 1977, roughly one thousand protesters opposing nuclear energy gathered outside the San Onofre Nuclear Generating Station while Units 2 and 3 were under construction.
On March 11, 2012, more than two hundred activists assembled at the facility to mark the first anniversary of the Fukushima Daiichi nuclear disaster. Among the speakers were Japanese citizens affected by Fukushima and former congressional candidate Raymond Lutz, who advocated for the plant’s permanent closure following its offline status since January 2012. In May of that year, environmental organizations held demonstrations at Southern California Edison’s Irvine headquarters, pressing for the decommissioning of San Onofre.
Feline Incident
On January 31, 1996, an adult cat was discovered near Unit 1 by an animal control officer and was held overnight due to lethargy before being released close to the site.
The following day, four kittens were found between two administrative buildings adjacent to Unit 1. Although located outside the radiologically controlled zone, attempts by workers to rescue them triggered contamination alarms. Health physics experts determined that each kitten exhibited elevated radiation levels (initially around 6000 counts per minute), contaminated with isotopes including cesium-137, cesium-134, and cobalt-60. After thorough washing reduced their radioactivity to acceptable levels, the kittens were deemed healthy.
Subsequent inquiry connected these kittens to the previously found adult cat; trace isotopes were identified on items linked to it. The remains of this adult cat were later discovered on nearby Interstate 5 with matching radioactive contamination. Plant employees adopted the kittens and named them Alpha, Beta, Gamma, and Neutron.
Shutdown Initiation
Unit 2 underwent shutdown in early January 2012 for scheduled refueling and replacement of its reactor vessel head. On January 31, Unit 3 experienced a radioactive leak primarily contained within its containment structure; environmental releases remained below regulatory limits. This incident prompted an immediate shutdown as per protocol. Subsequent investigations uncovered premature degradation affecting over 3,000 tubes in the replacement steam generators installed during 2011 across both units. Plant management pledged not to resume operations until a comprehensive understanding of the tube deterioration causes was achieved. Neither unit ever resumed operation afterward. Although this shutdown did not result in power outages, reliance on natural gas-fired plants increased, contributing to elevated pollution levels and higher utility expenses.
NRC, SCE and public response
In March 2012, the NRC imposed a ban on the plant’s reopening until the root causes of its equipment malfunctions were fully identified and corrected. Irvine Councilman Larry Agran urged for a swift and secure decommissioning process, citing concerns related to nuclear waste storage, potential health risks, and evacuation protocols. Nearby municipalities Laguna Beach and San Clemente passed resolutions calling for enhanced safety measures in nuclear waste containment and demanded greater transparency regarding radiation data. Edison International pledged to engage with the community by addressing their inquiries.
In June 2012, the environmental organization Friends of the Earth filed a petition with the NRC, requesting that any decision to restart be treated as a license amendment subject to a public hearing. They referenced expert evaluations indicating that the degradation of steam generator tubes was due to a Mitsubishi design defect, and that reducing power output would not sufficiently mitigate failure risks. Both SCE and NRC personnel opposed this petition.
By July 2012, an NRC report highlighted ten issues needing further investigation and prohibited resumption of operations until a validated plan to halt additional tube deterioration was established. The shutdown expenses had climbed to $165 million, including $117 million allocated for replacement power. Edison International’s Chairman Ted Craver acknowledged uncertainty regarding Unit 3’s restart without significant repairs.
In August 2012, SCE announced workforce reductions amounting to 730 employees—approximately one-third of its staff—attributing these layoffs to pre-existing plans formulated years earlier; however, critics questioned the company’s openness about the plant’s future direction.
September 2012 brought confirmation from NRC Chair Allison Macfarlane that Unit 3 would remain offline for an extended period and undergo defueling due to severe damage. Additionally, the NRC discontinued monitoring requirements for systems no longer in operation.
In October 2012, SCE submitted its "Unit 2 Return to Service Report," proposing a restart at 70% power capacity accompanied by tube plugging and inspections aimed at preventing vibration-related wear. Analyses suggested that operating at reduced power levels would alleviate excessive wear caused by elevated steam velocity and insufficient tube supports.
By November 2012, the NRC referred Friends of the Earth’s hearing request to the Atomic Safety and Licensing Board. Meanwhile, outage costs had surpassed $300 million, and deliberations regarding Unit 2’s restart were deferred.
December 2012 saw the final shipment of four aged steam generators dispatched to Clive, Utah for disposal.
In February 2013, the NRC requested Mitsubishi Heavy Industries submit a redacted report detailing steam generator problems. This document outlined design modifications such as removal of a support cylinder, changes to tube support plates and anti-vibration bars, along with the addition of roughly 400 tubes.
By December 2013, the NRC cited SONGS for inadequate review of steam generator design—a contributing factor in the shutdown—although no fines were levied; this finding complicated SCE’s legal position. The California Public Utilities Commission considered mandating a multimillion-dollar refund to customers.
Atomic Safety and Licensing Board ruling, May 2013
On May 13, 2013, the Atomic Safety and Licensing Board issued its ruling on Friends of the Earth’s June 2012 hearing request. It concluded that the current NRC procedure effectively constituted a license amendment requiring a public hearing for three principal reasons:
- SCE's plan to operate Unit 2 at only 70% power conflicted with existing license terms, necessitating an amendment;
- Unit 2 could not safely function within full licensed parameters without modifications;
- Restarting operations with compromised steam generator tubes at reduced power prior to reinspection qualified as "tests or experiments," also triggering license amendment requirements.
In May 2013, Senator Barbara Boxer called upon the United States Justice Department to investigate potential misconduct by Edison executives. This followed revelations from a 2004 letter by an Edison official expressing concerns that new steam generators were not genuine "like-for-like" replacements and might cause issues similar to those resulting in the 2012 shutdown. Boxer accused Edison of deliberately misleading regulators and the public to circumvent comprehensive safety evaluations and hearings. Edison denied any wrongdoing but indicated it might permanently close the plant if permission was not granted to restart one reactor at reduced capacity.[1][2]
Plant shutdown, June 2013
On June 7, 2013, Southern California Edison declared the permanent shutdown of Units 2 and 3, halting attempts to restart the facility at a diminished output. The company intended to cut the SONGS workforce from roughly 1,500 employees to approximately 400, with most reductions slated for 2013. Edison also pursued compensation claims against Mitsubishi Heavy Industries, the provider of replacement steam generators; however, the contract capped liability at $138 million and excluded consequential damages. The CEO of Edison International remarked that the plant’s current licenses would expire in 2022, and due to post-Fukushima regulatory changes—including reassessments of seismic risks—license renewal was uncertain, while costly repairs would not be financially justified before expiration.
California Senator Dianne Feinstein endorsed the shutdown, emphasizing safety risks to more than seven million people living within a 50-mile radius of San Onofre. Conversely, Representative Darrell Issa, whose district includes the plant, underscored the elimination of over a thousand specialized jobs and the loss of a vital source of affordable clean energy, committing to support nuclear power initiatives nationwide. Sierra Club Director Kathryn Phillips praised the closure decision and encouraged utilities to boost local renewable energy production such as rooftop solar installations.
In 2015, State Attorney General Kamala Harris initiated an inquiry into the Office of Ratepayer Advocates, San Diego Gas and Electric, and Southern California Edison. Investigators uncovered records suggesting that utility regulator Michael Peevey met with an Edison executive in Poland to negotiate a settlement that resulted in San Diego ratepayers bearing a $3.3 billion cost linked to the plant’s closure. This investigation was discontinued during Harris’s 2016 Senate campaign following Barbara Boxer’s retirement.
Environmental consequences
Between 2011 and 2012, total greenhouse gas emissions from California’s power plants increased by 35%, partly attributed to San Onofre’s premature closure, as reported by the California Air Resources Board and World Nuclear News.
Decommissioning process, 2014–present
The decommissioning of San Onofre is expected to span several decades. In February 2014, SCE announced plans to sell non-radioactive equipment by March 2015. By August 2014, SCE estimated a decommissioning period of about 20 years with expenses totaling $4.4 billion; spent nuclear fuel will remain onsite in dry cask storage indefinitely, while low-level radioactive waste is transported to facilities in Texas and Utah. In December 2016, SCE appointed a joint venture between AECOM and EnergySolutions as the primary contractor overseeing decommissioning activities.
Nuclear waste management
Following the cancellation of the Yucca Mountain repository project in 2008, San Onofre’s nuclear waste must remain stored onsite until Congress designates an alternative disposal site.
Initially, spent fuel is kept in steel-lined concrete pools (wet storage) for cooling purposes before being moved into permanent dry storage within eighty underground steel-lined concrete monoliths engineered by Holtec International. These canisters exceed typical U.S. standards in thickness and are designed to comply with California’s stringent earthquake, fire, and tsunami safety regulations.
Nonetheless, their close proximity to the ocean subjects these canisters to chloride-induced stress corrosion cracking—a condition that currently cannot be inspected or repaired. Holtec is developing inspection techniques while supplying an additional onsite canister as a precautionary measure. The Electric Power Research Institute (EPRI) advocates for proactive corrosion management through environmental monitoring and scheduled visual inspections.
After legal pressure from Citizens Oversight, Southern California Edison agreed in April 2017 to explore offsite storage alternatives for spent nuclear fuel. In July 2020, the California Coastal Commission authorized an inspection and maintenance program permitting ongoing onsite storage at San Onofre.
Financial resolution
In July 2013, Southern California Edison (SCE) commenced a 90-day dispute resolution period with Mitsubishi Heavy Industries (MHI), which proved unsuccessful and resulted in binding arbitration under the International Chamber of Commerce in October 2013. SCE sought $7.57 billion (930 billion yen) in damages, whereas MHI argued that contractual terms capped compensation at $137 million.
By October 2015, the plant’s owners reached a $400 million settlement with insurers due to operational shutdowns: SCE obtained $312.8 million, San Diego Gas & Electric (SDG&E) received $80 million, and Riverside was allocated $7.16 million. The arbitration proceedings against MHI remained ongoing.
In March 2017, the ICC tribunal ruled that MHI must pay $125 million, corresponding to the liability limit stated in the contract, dismissing allegations of fraud and gross negligence. Additionally, the claimants were ordered to cover $58 million in legal expenses owed to MHI.
In popular culture
The San Onofre Nuclear Generating Station served as inspiration for the domed Volcano House located in Newberry Springs, California, constructed in 1968.
SONGS appeared in the 1987 motion picture Made in U.S.A. and was featured in Godfrey Reggio’s 1982 experimental film Koyaanisqatsi, showcasing sunbathers at San Onofre State Beach. Its containment structures influenced the lyrics of the Descendents’ 1986 song "Kids" and were humorously referenced in The Naked Gun (1988).
The facility acted as a filming location for the Californian nuclear reactor depicted in Cloud Atlas (2012) and appeared in a 1967 episode of Batman. It was also shown during surfing scenes in the 2017 series Animal Kingdom and portrayed as a target for extraterrestrial theft of fuel rods in the 2010 television series The Event.
See also
- Anti-nuclear movement in California
- Nuclear power in the United States
- Diablo Canyon Power Plant
- List of largest power stations in the United States
- List of articles associated with nuclear issues in California