California's Last Nuclear Plant Is Slated to Close by 2025. Why Some Scientists Worry That Could Be Bad News for Carbon Emissions

The massive 2,200-megawatt Diablo Canyon Power Plant, the last-standing nuclear power facility in California, is scheduled to fully shut down operations by 2025, ending the state's reliance on nuclear energy. Some energy experts, though, warn that shuttering the plant — a goal long sought by anti-nuclear advocates — could ultimately lead to a spike in the state’s greenhouse gas emissions.

According to a recent report from researchers at Stanford Energy, shuttering the San Luis Obispo County facility, which opened in 1985 in the face of fierce opposition, would likely make the state more dependent on natural gas for its electricity production. Natural gas is composed mostly of methane, a climate-warming gas more potent than carbon dioxide when released into the atmosphere.

The report's findings spurred the Washington Post's editorial board to declare that shutting the plant down would be the "the definition of climate incoherence."

The report's authors recommend delaying the closure of Diablo Canyon by 10 years, to 2035. Doing so, they predict, would yield a 10% reduction over 2017 levels in carbon emissions generated by California's power sector, while saving some $2.6 billion in power system costs and bolstering system reliability.

The report goes on to suggest several new uses for the plant should it remain open for another decade, including as the power source for a major desalination complex that could produce fresh water at 80 times the rate of the Carlsbad Desalination Plant. It also suggests the possibility of connecting the nuclear facility to a hydrogen plant to produce clean hydrogen fuel.

But some energy experts say the analysis simply underscores the need for California to double down on its clean-energy production.

"You shut down Diablo Canyon, something is going to replace it. We still have electricity demand. People still will use the same amount of electricity the day Diablo Canyon goes offline," Mark Specht, an energy analyst at the Union of Concerned Scientists, told The California Report.

Using only natural gas to supplant Diablo Canyon's power supply would be the emissions equivalent of adding 300,000 cars to California's roads, according to research by Specht's team.

But, he says, that should send a clear message that "there is no time to waste" in creating new clean-energy infrastructure to replace the nuclear plant's output.

"We are talking about three or four years and then the power plant goes offline, and building new clean resources takes years. Folks have to be working on this right now to make sure we replace the power plant with clean energy," Specht said.

The debate over the plant's closure comes just weeks after world leaders gathered in Glasgow, Scotland, for the United Nations climate summit in an urgent effort to dramatically reduce global carbon emissions.

Keeping the plant open also doesn't jibe with former state Sen. Bill Monning, who used to represent the district where Diablo Canyon is located, and who worked on legislation securing hundreds of millions of dollars in funding to help the area prepare for the economic impacts of its closure.

"When people say it's clean energy, that's right at a certain level, but it doesn't take into account the waste that is left behind the spent fuel rods," Monning told The California Report.

"And so as people kind of weigh in now and say, 'Well, why don't we keep it open? There's a gap between available renewable energy, this is so-called clean energy' — it doesn't take into account that history [of waste]," he said.

Monning says he's confident the nuclear plant won't continue running past 2025, in large part because no one with decision-making power, including its operator — Pacific Gas and Electric — wants it open.

"PG&E was a member of this agreement and has no interest in seeking to renew their licensing," Monning said. "And there's no evidence that anybody else does, either."

This post includes reporting from NPR's Lauren Sommer.