The Dangers of Diablo Canyon: Why the Nuclear Plant Built on a Faultline Should Close as Planned

Diablo Canyon nuclear power plant. Photo: US Nuclear Regulatory Commission.

California’s Central Growing Valley is America’s most productive agricultural region providing more than half of the fruits, nuts and vegetables grown in the United States. Sadly, Diablo Canyon’s two nuclear reactors sit on our state’s central coastline and because coastal winds have a tendency to blow inland, there’s the frightening prospect that a megathrust earthquake, “The Big One”, could trigger a nuclear meltdown sending radioactive clouds into the Central Valley which would irradiate and poison much of the Central Valley’s produce.

Furthermore, Diablo’s radioactive plumes could contaminate the drinking water that flows from the Sierra Mountains through the Central Valley and into cities like San Francisco and Los Angeles, which would lead to a mass migration out of California.

Pacific Gas & Electric Company’s nuclear plant, located near Avila Beach in San Luis Obispo County, is surrounded by a confluence of 13 known fault lines on the seismically active “Pacific Ring of Fire” earthquake and tsunami zone.

Originally designed to withstand a magnitude 6.75 earthquake and later reconstructed to endure a magnitude 7.5 quake, Diablo’s tolerances underestimate the true seismic potential of today’s mega-thrust shakers.

Additionally, there are two fault lines, the “Diablo Cove Fault” and the “San Luis Range/“IOF” Thrust”, that run directly under the Diablo Canyon nuclear plant.  The Diablo Cove Fault extends through the foundation, under the power plants’ Unit One turbine generator and reactor containment vessel.

The east-west trending Diablo Cove Fault runs offshore and intersects with the nearby Shoreline Fault, which in turn is connected to the Hosgari Fault Line, a component of the San Andreas Fault System. The power stored within this network of seismically linked faults could create an earthquake sufficient to exceed Diablo Canyon’s safeguards.

On June 28th, 2016, the moment of truth as to Diablo’s vulnerability came to light. PG&E announced that it would not seek to renew the plant’s two operating licenses with the Nuclear Regulatory Commission, which would have permitted the nuclear facility to operate until 2045.

Instead, the company agreed to close the plant on August 26, 2025 if Diablo was allowed to “avoid” a proposed environmental impact assessment known as CEQA. The deal was accepted.

CEQA, or the California Environmental Quality Act, is a statute that requires both state and local agencies to identify “significant environmental impacts” and to avoid or mitigate those impacts if feasible. PG&E knew that Diablo would fail to get a clean bill of health if the CEQA review was allowed to proceed, especially after the catastrophic meltdowns at Japan’s Fukushima Daiichi nuclear power plant on March 11th, 2011.

The casks containing stored radioactive waste, along with the reactors themselves, are at risk of damage due to an earthquake at the Diablo Canyon nuclear power plant. (Photo:US NRC)

Unfortunately, PG&E’s Unit One Reactor has a documented history of being dangerously embrittled since 2003.  Knowing how “seismically vulnerable” the nuclear plant is, there were many calls to inspect and test Diablo’s radioactive containment vessel for embrittlement and cracks as well as investigate the rest of the facility for the mishandling of nuclear waste, “deferred maintenance”, earthquake vulnerability and managerial competence.

Once again, on February 28th, 2019, PG&E asked the Nuclear Regulatory Commission for relief from a “Reactor Vessel Internal Visual Examination” of its Units One and Two reactor containment vessels, which they received. The deeply troubling question is, why was PG&E so afraid of having its nuclear facility inspected for safety and reliance?

PG&E’s Diablo Canyon nuclear plant presents too many risks for the people and the economy of California. It isn’t an asset, it’s a horrendous liability!

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It’s time to embrace our move towards a “truly” renewable energy future both for us, our children, and future generations.

This article was first published on Beyond Nuclear International.

Harvey Sherback is a renewable energy advocate who lives in Berkeley, California.