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The last nuclear plant in California – and the unexpected quest to save it

The Diablo Canyon nuclear plant, on the edge of the Pacific ocean, was due to close in three years.
The Diablo Canyon nuclear plant, on the edge of the Pacific ocean, was due to close in three years. Photograph: Mark Ralston/AFP/Getty Images
The Diablo Canyon nuclear plant, on the edge of the Pacific ocean, was due to close in three years. Photograph: Mark Ralston/AFP/Getty Images

The Diablo Canyon facility, which provides 9% of the state’s energy, was due to shutter in 2025, but the state’s energy crunch could save it

California’s last nuclear plant was nearing the end of its life.

Tucked against picturesque bluffs along California’s central coast, the aging facility known as Diablo Canyon began operating in 1985. It was designed for a different era, with analog knobs and systems that no longer comply with the state’s environmental standards. The plant has faced controversies over its impact on underwater ecosystems, the production of toxic waste and its proximity to earthquake fault lines – and its planned closure by 2025 seemed an all-but-certain step in California’s ambitious journey toward a greener future.

But with just three years to go, the fate of Diablo Canyon now looks less assured.

California is facing steep energy challenges that are only expected to worsen as the climate crisis intensifies. The plant still provides roughly 9% of the state’s energy – the largest single source of electricity and enough to supply more than 3 million residents. The state is still far from finding a reliable and climate-friendly replacement, and concerns are rising that it will fall back on fossil fuels to fill the gap.

Now, decades-old discussions about whether the plant should continue to play a role in California’s renewable energy transition are being rehashed. A diverse league of advocates – including energy officials, scientists, California’s governor Gavin Newsom, and even the musician Grimes – are pushing for renewed life for Diablo Canyon. Critics, meanwhile, say keeping the plant open would only be a step backward.

Diablo Canyon has come to signify broader questions about the state’s energy future, and whether it’s ready to leave nuclear power behind. It’s an issue also lingering in the thoughts of officials across the US. Half of the country’s clean energy comes from nuclear power plants – but in many areas, it is being phased out.

“It’s a sort of a bellwether – a test – of the political future for nuclear power in California and in the shifting environmental coalitions,” said Alex Trembath, the deputy director of the Breakthrough Institute, an energy and environment thinktank that advocates in favor of nuclear energy. “I think the story of Diablo Canyon is more important than just another plant.”

Protests and money problems

The many plants that once dotted California have closed one by one, and a law passed in 1976 banned new construction of nuclear stations until waste could be permanently disposed of. That’s left Diablo Canyon as the sole provider of nuclear energy.

The Diablo Canyon nuclear power plant in 1987, two years after it became operational.
The Diablo Canyon nuclear power plant in 1987, two years after it became operational. Photograph: George D Lepp/Getty Images

Even before it began operating, Diablo Canyon was a source of scrutiny. For years it was the site of demonstrations as anti-nuclear sentiments grew in the wake of disasters like Chernobyl, Three Mile Island, and later on, Fukushima. There were concerns raised about environmental degradation and questions about storage of the nuclear waste produced by the facility.

But it was not the protests that led to Diablo Canyon’s closure timeline. Instead, it was a matter of money.

California regulators had cracked down on the system used at Diablo Canyon in 2010, a process known as “once-through cooling” for its impact on marine life. Roughly 2.5bn gallons of seawater slosh through the plant’s enormous intake tubes each day, cooling hot steam heated by nuclear reactors. The warmed water flushed back into the sea has had profound effects on ocean ecosystems and animals, including fish, sea lions, turtles, and other creatures are killed by the millions each year by the systems themselves, according to the California water board.

Facing requirements for expensive upgrades and retrofits, estimated at roughly $4.5bn, and an increasingly competitive energy market centered around renewables, the plant’s owner and operator PG&E agreed to a settlement in 2016 with environmental groups and labor organizations not to seek renewal on the licenses for its two reactors, which expire in 2024 and 2025 respectively.

Endorsed by state regulators in 2018, the plan also gave California nearly a decade to ramp up the decarbonization of its grid and replace the lost energy with more affordable renewable sources. Unlike other plants that shut down abruptly due to mechanical errors or financing issues, the end of Diablo Canyon was heralded as an opportunity to phase out nuclear the right way.

Energy challenges amid the climate crisis

But in the years since, the energy landscape has shifted. California, which has pledged to run on 100% renewable electricity by 2045, is not on track to meet its goals. In order to get there, it needs to triple its current capacity and expand renewable sources at a “record-breaking rate”, according to the state’s energy commission.

The climate crisis has also put the grid under immense strain. A historic drought has left the American west with waning water levels, threatening hydropower production, and spiking temperatures have caused surges in energy use, resulting in seasonal threats of rolling blackouts. Wildfires have also threatened disruptions, taking out transmission and distribution lines.

Energy officials warned it will be especially difficult to navigate seasons when climate disasters hit all at once, potentially leaving millions of Californians without power during peak times of need in the coming years.

The grid has grown more efficient and reliable due to renewables coming online and upgrades in systems, but the state’s energy agencies projected a significant shortfall that matches the energy lost when Diablo Canyon ceases to contribute. Meanwhile, energy costs will continue to rise.

“This is a challenge,” said Lucas Davis, an expert on energy economics and professor at the University of California Berkeley. “When a major generation source closes there is less supply so that pushes up wholesale prices,” he said. The timing is bad. With cities mandating the phase-out of natural gas and more consumers switching to electric cars, demand for electricity is also expected to increase, driving up the price further.

“We will need more generation,” Davis said.

The plant, which sits along the central California coast, has faced years of scrutiny.
The plant, which sits along the central California coast, has faced years of scrutiny. Photograph: Mimi Ditchie Photography/Getty Images

There are growing concerns that the state will be forced to fall back on polluting forms of energy, including natural gas, once the Diablo Canyon goes dark. As things stand currently, California would have to increase renewable energy by 20% over the next two years, as hydroelectric power wanes, the chances of which experts said were “increasingly dim”.

If decarbonization is not escalated quickly, California stands to emit an additional 15.5m metric tons of greenhouse gasses with the closure of Diablo Canyon, according to an analysis by the Union of Concerned Scientists published last year.

Trembath, of the Breakthrough Institute, says the fact that Diablo’s closure could create more emissions rather than reduce them provides a powerful test of California’s commitment to clean energy. Keeping the plant would not hinder new sources of renewable energy, he says, rather those new sources could go toward providing more energy for the grid, rather than just plugging the gap left by Diablo.

“If the plant closes it won’t mean that California can’t keep making progress,” he said. “It will just be an indication that no matter how dire or ambitious our rhetoric is about our climate goals – if we close the plant that’s a signal that it’s just rhetoric.”

But Ralph Cavanagh, the energy co-director of the environmental advocacy organization Natural Resources Defense Council’s Climate and clean energy program, who was involved in negotiating the joint settlement in 2016, sees little use in rehashing old debates and instead would like to see the momentum directed into finding new sources. Either way, he said, the plant is going to close.

“This ship has sailed,” Cavanagh said.

A new future for nuclear?

Advocates of a nuclear future, however, have envisioned new opportunities for the plant. They argue that, despite its risks, nuclear’s promise of cleaner energy is essential for helping to stave off the worse effects of climate change while bolstering the grid. Nuclear energy is a zero-emissions energy source, which doesn’t emit carbon the way other energy sources do. It produces minimal waste and –though there are always risks of disaster – officials have certified that the plants and the byproducts they produce are safe.

“The challenges here in California and globally are bigger than ever and the window of opportunity to mitigate climate change is closing fast,” Steven Chu and Ernest Moniz, two former US secretaries of energy wrote in a Los Angeles Times op-ed in support of Diablo Canyon. They cited a 2021 study from researchers at Stanford and Massachusetts Institute of Technology that examined new opportunities for the plant, including adding desalination and hydrogen production, another type of energy that is often made from natural gas.

The study, published last year, helped reignite the debate around Diablo Canyon and how to bring it up-to-date. Researchers analyzed the viability of adding new features to the aging facility and concluded that by providing grid electricity, desalinated water and hydrogen, the overall value produced by the plant would increase, which would help offset the high investment costs required.

A flock of goats feed under the power lines above Diablo Canyon. Advocates have envisioned new features that could make the aging facility more valuable.
A flock of goats feed under the power lines above Diablo Canyon. Advocates have envisioned new features that could make the aging facility more valuable. Photograph: Phil Klein/REUTERS

That also spurred a change in tune from the governor. Newsom helped shape discussions about closing Diablo back in 2016 as Lt Governor and chair of the tate lands commission. But this year, now facing significant energy challenges as head of the state, Newsom became outspoken in favor of prolonging its life. While he said he wants to see it shutter eventually, he told the Los Angeles Times that its current trajectory may be too soon.

Still, the financial piece of the puzzle remains. Diablo Canyon will have to be upgraded if it continues to exist, and it’s unclear whether PG&E will be willing to invest further in the beleaguered plant. One option could be federal funding – the Biden administration has set aside $6bn to keep existing nuclear plants open, though whether Diablo would pursue that option remains to be seen. Meanwhile, the researchers at Stanford and MIT have raised other less-costly options that could mitigate impacts on marine life, but their conclusions have been questioned by critics of the plant, including Cavanagh. He remains adamant that the issue is a non-starter, likening the new momentum to “wishful thinking”.

Noting that he believes in the importance of nuclear power’s contribution to the clean energy transition and reducing carbon emissions, Cavanagh emphasized that there are still three years to go before it is scheduled to fully power down. In that time, he said, the state should prioritize and invest in transitioning to renewables and seek solutions to power problems.

“The danger of Diablo Canyon,” he said, “is that it is a tempting way of somehow assuming that there’s an easy way to avoid responsibility for the next phases of the clean energy transition.”