(Bloomberg/Michelle Ma) — The Diablo Canyon nuclear plant is in the midst of a relicensing process that, if successful, will keep it running for another 20 years.
California’s last source of round-the-clock, carbon-free nuclear power is undergoing a rigorous review to gauge whether it can operate in a safe and cost-effective manner without taking a major toll on the local environment. While the review is ongoing, keeping the plant running has become vital with tech companies desperately searching for power and the grid feeling the increasing strain.
“My near-term hope is that Diablo will run its full 20-year renewed license,” says Maureen Zawalick, PG&E Corp.’s vice president of business and technical services. “So we are laser-focused on that mission.”
Diablo Canyon began operations in 1985, and in some ways, it’s still stuck in time. In the control room, buttons and dials reign supreme over digital screens.
“Operators don’t like change,” says simulation engineer Brian Sawyer.
The plant also has an exact replica of the control room where reactor operators learn how to handle everything from earthquakes to terrorist attacks. Sawyer presses a button to simulate an earthquake, sending a rumble through the training room via a 30-inch subwoofer under the stairs as lights begin flashing. This type of training is so crucial to keeping the plant functioning that Diablo Canyon’s nuclear operators spend every fifth week — about 20% of their careers — running through these simulations.
That way, they’ll be ready if the Big One comes, Sawyer says. In the event of a large earthquake, the plant can shut down its two reactors in two seconds, he explains. Operators are also on guard against wildfires.
During a visit in early August, smoke from the Gifford Fire had Unit 2 running at a reduced output. Smoke can lower conductivity and cause arcing on power lines, so two of the three lines were de-energized as a precautionary measure, explains PG&E Senior Director Tom Jones.
Diablo Canyon’s reactors are entombed in concrete and sit in separate buildings adjacent to the structure that houses the turbines and generators for both of the plant’s reactors. That cavernous space is the size of two-and-a-half football fields and is accessible only after a lengthy screening process that includes passing through what’s colloquially called a “puffer machine,” which uses blasts of air to collect and analyze microscopic particles. Exiting the plant is just as involved, requiring a radiation scan.
These protocols are intended to keep the site secure and the 1,200 PG&E employees working there safe. They also help protect the 1,100 contractors brought in to refuel the reactors. All of these factors and more are considered in the relicensing process. Diablo Canyon has already passed a US Nuclear Regulatory Commission review, but its two licenses are still under review by state agencies.
Nuclear reactors are staying online or being restarted, such as Three Mile Island, reflecting the industry’s changing fortunes. Utilities are racing to meet growing demand as tech companies agree to pay a premium for nuclear power. That will drive a 63% increase in US nuclear capacity by mid-century, according to Bloomberg Intelligence projections. While the trend buoys the idea that Diablo Canyon will be able to renew all its licenses, PG&E has yet to ink a data center deal. And there remain some important hurdles to renewal.
One is related to the water the plant needs to operate. Nuclear power plants are often built near large bodies of water used for cooling purposes. In Diablo Canyon’s case, the large body of water in question is the Pacific Ocean, and the plant withdraws 2 million gallons a minute or 2.5 billion gallons a day.
The utility has a fraught history with the California Coastal Commission, whose former senior scientist dubbed Diablo Canyon California’s largest marine predator because its intake system traps copious ocean larvae. The commission and the state’s water board are both reviewing materials tied to the plant’s licensing renewal.
While PG&E says it expects to get these approvals in the first quarter of 2026, the Coastal Commission has put out a request for additional information from the utility, and the utility’s application remains incomplete, according to Joshua Smith, the California Coastal Commission’s public information officer.
“The Coastal Commission is dedicated to a thorough review of the coastal resource impacts of PG&E’s project. California prides itself on the protection of its marine environment, and this situation is no exception,” said Smith. “The commission believes a path forward is possible given the ongoing cooperation of the investor-owned utility.”
The cost of running the plant has become a rising source of tension in a state grappling with an electricity affordability crisis. When California legislators voted to keep the plant open in 2022, Governor Gavin Newsom authorized a $1.4 billion loan with the expectation that PG&E would repay it using an expected federal loan or profits from operations from 2029 to 2030. But as much as $588 million of those funds are unlikely to come in, according to nonprofit outlet CalMatters.
Altogether, PG&E forecasts that the plant will cost $1.4 billion to run in 2026. The utility expects to make $935 million selling the plant’s power through California’s electricity market, leaving ratepayers on the hook for the remaining $410 million after incorporating fees.
PG&E maintains that there will be a net benefit for its ratepayers, after taking into account the excess energy it generates for the state to meet customer demand.
While there’s a moratorium on new nuclear power in California, Zawalick points out that the power plant’s original design has space for six units and 140 years of spent fuel.
“I would love to see more nuclear built in the US, including California,” said Zawalick.
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