Space & Innovation

California's Last Nuke Plant Will Shut Down

Utility announces its intention to shut down remaining two reactors and replace them with renewable energy by 2025.

The turbulent, controversy-wracked history of nuclear power in California may soon end.

Pacific Gas and Electric, in a joint agreement with labor and environmental groups, is proposing a shutdown of the Diablo Canyon nuclear power plant in San Luis Obispo County, the last remaining nuke facility in the state, by 2025.

Over the next nine years, the 2,150 megawatts that the plant generates -- enough to power 1.7 million homes in central and northern California -- gradually will be replaced by renewable energy sources such as solar and wind, or else offset by improvements in energy efficiency.

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The decision is a reversal for PG&E. In 2009, the utility applied for an extension of the 31-year-old facility's license from the U.S. Nuclear Regulatory Commission, which would have allowed it to keep running until at least 2045. The company cited a state law enacted last year, which requires utilities to transition to 50 percent renewable sources by 2030, as a major factor in the decision.

But a renewal would have faced strident opposition from antinuclear activists, who've argued for years that the plant would be vulnerable to a devastating accident in the event of an earthquake. The investigative publication TruthDig has called Diablo Canyon "California's Fukushima in waiting," a reference to the meltdown of three Japanese nuclear reactors after a 2011 earthquake and ensuing tsunami disabled their cooling systems. (PG&E has claimed that the plant's design would protect it against such an event.)

According to a 2015 San Francisco Chronicle article, the plant has had an ill-starred history. Ironically, PG&E picked the location for Diablo Canyon as a fallback after construction of a nuke plant at Bodega Bay, 40 miles northwest of San Francisco. The project had to be halted in 1964, after excavators dug into what turned out to be a portion of the San Andreas Fault. But in 1971, three years after construction of Diablo Canyon had begun, geologists discovered that it was near the offshore Hosgri Fault, which is capable of generating a.7.5 magnitude quake.

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That revelation forced a major redesign of the plant, and the addition of braces, support struts and concrete buttresses to strengthen its walls. But in 1981, PG&E learned that some of the new supports had been installed backward, necessitating fixes that added an estimated $3 billion to the plant's cost, which soared in the course of construction from $600 million to $5.8 billion.

Environmental critics also have found fault with Diablo Canyon's cooling system, which pulls in 2.5 billion gallons of seawater per day and afterward returns the water to the Pacific 18.5 degrees warmer. That kills 1.5 billion fish eggs and larvae each year, according to the Chronicle.

On the plus side, PG&E's website claims that the plant has helped reduce greenhouse gas emissions by 6 to 7 million tons per year, based on the assumption that fossil fuels would have been burned to generate the electricity.

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