Remembering San Onofre Unit 1… 30 Years On

The San Onofre site has been home to three nuclear reactors in its history. The iconic domes of Units 2 and 3 grabbed the spotlight as soon as they went operational in 1983 and 1984, respectively.

But a pioneer for nuclear energy on the Southern California coast, and the U.S., was Unit 1, a 395-megawatt plant built by Bechtel Corporation with a design by Westinghouse Electric Corporation.

Unit 1 was permanently retired in 1992 after the California Public Utilities Commission determined that the costs of necessary upgrades to the plant could not be justified.

At Home on Camp P

Just why it was sited where it was is itself an interesting tale. Southern California Edison produced a history book of Unit 1, first published in 1993, a year after its retirement from service (nearly all of this blog post is curated from that book). As the story goes, SCE’s president at the time, Jack Horton, was targeting the Camp Pendleton location because it fell between SCE’s and San Diego Gas & Electric’s service territories (SDG&E had a 20% stake in the facility), and it avoided the booming residential growth taking place all across Southern California.

But Camp Pendleton said no. So did the Department of Navy. President Eisenhower deferred to the military commanders.

Then John F. Kennedy became president and Kennedy was a strong supporter of nuclear energy. During a plane trip from San Diego to San Francisco with former Atomic Energy Commission chairman John McCone (then head of the CIA), it was said McCone got Kennedy’s attention as they passed over San Onofre and mentioned its potential as a nuclear plant site. Kennedy would later approve the plan. But it wasn’t sealed until an act of Congress secured a lease for 90 acres of Camp Pendleton land.

Unit 1 Construction 1
Preparing the site for the Unit 1 reactor.

It's a Go!

The Unit 1 project drew national media attention when it was officially announced in 1963. Even then, nuclear energy was recognized as a “smog-free” form of electricity generation. The reactor would be a larger version of the ones already operating at Shippingport, PA and Yankee Rowe in Massachusetts, at a cost of $87 million ($820 million in 2022 dollars).

On May 14, 1964, ground was broken on a bluff overlooking the Pacific. Amazingly, a year and day later, construction on the “beach ball,” the spherical containment structure, was completed.

Over one seven-year span in the mid-1970s, Unit 1 generated enough clean electricity to avoid the purchase of 30-million barrels of imported fuel oil.

The “beach ball” would eventually disappear inside another containment structure that was required by the Nuclear Regulatory Commission, an extra layer of protection, as residential growth encroached nearer the site.

Unit 1 Construction 3
The "beach ball" begins to stake shape.

The RPV's Journey

The reactor pressure vessel for Unit 1 was fabricated in Chattanooga, TN by Combustion Engineering. Getting the 350-ton piece of equipment to San Onofre took some doing. First a barge trip to New Orleans. Then a freighter through the Panama Canal to the Port of Long Beach. From there, another barge trip to the south end of Camp Pendleton where it was transferred to trailers and hauled up old Highway 101 to the construction site.

In 2020, that same reactor pressure vessel made its final journey, this time to a disposal facility in Utah. And it was no less arduous a trip, as the RPV now weighed twice its original weight.

The video below tells the tale.

Challenges Faced

The operation of Unit 1 did not come without its challenges. But each time one was faced, the team rose to the occasion and the plant continued to operate. A cable tray fire took the plant offline soon after it started commercial operation in 1968. But the subsequent investigation and analysis led to “revised regulations for cable runs in nuclear power plants” including “separation of control, instrumentation and power cables; separate paths for backup wiring; and expanded redundancy requirements.” All would help the nuclear energy industry with safety and reliability going forward.

Throughout the 1980s the plant was off-line a significant amount of time for upgrades as new regulations and requirements were implemented, some stemming from the Three Mile Island event in 1979.

The End of an Era

Unit 1 officially shut down on Nov. 30, 1992. During its 25-year run after first criticality in 1967, it safely generated 53 billion kilowatt-hours of carbon-free electricity for Southern California, and ended its operating life with a 377-day continuous run. All a credit to the men and women who operated and maintained the facility.

Over the next decade, the decommissioning of Unit 1 would take place, dismantling the containment structures and the other systems and equipment associated with the operation of the plant.

Today, the former Unit 1 site is home to the dry fuel storage facility which holds all the spent fuel from Unit 1, as well as Units 2 and 3. Eventually, once there is a national repository and the fuel is relocated, this facility will disappear from the landscape as well. But the memories of safe, clean electricity generation for Southern California will live on.

As Sherry Folsom, a Health Physics engineer, remembered, “The people who worked so hard at Unit One produced more than 50 billion kilowatt-hours of electricity. That power ran factories that made our goods and employed our neighbors; it warmed and lighted our homes; operated traffic lights; and powered life-saving hospital machines. Unit One’s energy replaced more than 82 million barrels of fuel oil and avoided emissions of 55,000 tons of air pollutants, a major contribution to the well-being of all Southern Californians. This is a proud record, achieved by serious people who have done important work.”

(Facts, details and excerpts from Nuclear Pioneer by William A. Myers, first published by SCE in 1993.)

San Onofre Unit 1 artist concept
An artist's concept of Unit 1.