Stop the closure of Diablo Canyon Nuclear Power Plant

February 3, 2022

Open letter to Gov. Gavin Newsom from a former U.S. secretary of energy and 75 experts

We are some of the leading scientists, entrepreneurs and academics spanning disciplines including climate science, marine biology, air pollution research, energy, planetary science and land conservation. Many of us have dedicated our lives to studying the problems and solutions to energy security and climate change as well as planetary processes in general. With the accelerating threat that climate change poses to life on Earth, we write today to urge that the state reverse the decision to prematurely shut down the Diablo Canyon Nuclear Power Plant, California’s single largest source of carbon free electricity.

We commend your genuine commitment to reducing emissions and meeting the growing threat of climate change. Your leadership on this vital issue cannot be overstated. Fidelity to the principles you stand for on climate change, along with the state’s mandated emissions goals, however, requires our leaders to acknowledge the hard fact that meeting the state’s clean energy goals is incompatible with closing the Diablo Canyon Power Plant. At the very minimum, it’s imperative that plans to close the plant be delayed.

California has enacted groundbreaking laws and regulations to shift away from fossil fuels and the emissions they cause. Utilities, like Pacific Gas & Electric (PG&E) must get 100% of their electricity from clean sources like wind, solar, geothermal and nuclear power by 2045. Building codes have been enacted that encourage developers to shift away from natural gas in order to heat homes. The Air Resources Board has also been directed to slash statewide emissions 40% below 1990 levels by 2030.

These goals are imperative to meet the threat of climate change, but we will go backwards, not forwards, if the state’s largest producer of carbon free energy, Diablo Canyon, is prematurely shuttered.

Senate Bill 1090, authored by Sen. Bill Monning of San Luis Obispo County, amended the Public Utilities Code to mandate that the California Public Utilities Commission replace Diablo Canyon without increasing emissions. This source of clean, zero-emissions power, avoids 7.2 million metric tons of carbon from being added to the atmosphere every year, and the reactors at Diablo Canyon provide approximately 10% of the state’s entire electricity portfolio.

We are convinced it is impossible to replace the carbon-free electric output of Diablo Canyon at or near the time the plants are scheduled to close.

While California boasts a very high portion of electricity from renewable sources, California will have to boost its total renewable energy production by an enormous 20% in just over two years to replace the clean energy being produced at Diablo Canyon. With hydroelectric generation in California falling 19% this year as a result of historic droughts (and with that resource likely to remain unpredictable due to climate effects) the prospect of meeting that goal is increasingly dim.

The joint proposal that was relied upon in deciding to close the plant cautioned that, “the full solution [for Diablo Canyon replacement] will emerge over the 2024-2045 period.” While the California Public Utility Commission (CPUC) recently adopted a procurement order that is ambitious, it is unlikely to bring on sufficient resources in time to replace the plant. If indeed renewables could develop at the pace proposed in that order, with Diablo Canyon continuing to operate the result would simply be that the State would achieve its long term decarbonization goals that much sooner.

While decarbonizing the grid, the state must maintain system reliability, through integration of intermittent renewable resources and by other means. As you know, the need for more energy–at a time when the state is producing less–came to a head in August of 2020, when a heat wave triggered rolling blackouts across the state. Without Diablo Canyon, this situation would have been far worse.

We are less and less able to predict extreme weather events including heat waves, which dictate that California utilities switch off electricity to avoid sparking wildfires. It’s these conditions that led to a state of emergency, and consequently, the Department of Water Resources is building five new natural gas plants and has removed the cap on emissions.

This dynamic will be severely exacerbated by the closure of Diablo Canyon, as the only functional alternative to immediately replace its output is natural gas.  This will have the same impact as adding more than 1 million gasoline powered cars on our roads and streets per year. If there’s any doubt that closing Diablo Canyon will result in increased use of natural gas, the administration need look no further than the increased emissions following the recent closure of the San Onofre plant.  According to the U.S. Energy Information Administration, “after the retirement of the San Onofre Nuclear Generating Station outside Los Angeles, California, natural gas-fired generation increased to offset lost nuclear generation and, at the time, relatively low hydroelectric generation.”

But even if California could replace Diablo Canyon with renewable energy in the near term, that is not the right goal. Mere replacement is not enough; replacement would merely freeze emissions at their currently dangerous level. The right goal is to reduce carbon emissions as fast as possible, and the right means to do that is to add renewables on top of Diablo Canyon’s carbon free energy, not in place of that energy.

The effects of once-through cooling systems on marine life have been studied extensively, with many known remedies and responses. It is important to note that the state has delayed implementation of OTC rules on other gas-fired power plants and it appears it will continue to do so for years to come. Far better to run Diablo Canyon than those facilities. In any case, it is suggested that new technologies are being evaluated that can allow Diablo Canyon to operate in conformance with state regulations that protect marine life.

Past concerns over the proximity of Diablo Canyon to the Los Osos, Hosgri, San Andreas and Shoreline faults have been addressed fully by the Nuclear Regulatory Commission (NRC). Seismic studies have found the plant design basis can withstand earthquakes of shaking amplitude ten times larger than that which the faults in question are capable of triggering.

Comparisons between Diablo Canyon and Fukushima Daiichi are therefore alarmist and misguided. What caused the Fukushima accident wasn’t the earthquake, but the fact that the plant was built 33 feet above sea level and had its backup diesel generators on the lower level. The generators were inundated when the tsunami hit and they stopped working, causing the meltdown. For comparison, the Onagawa plant in Japan was sixty kilometers closer to the epicenter of the 2011 Tohoku earthquake and experienced a larger tsunami. However, because the plant was built 48 feet above sea level, it survived the earthquake and tsunami largely intact. Notably, Diablo Canyon sits on a bluff 85 feet above sea level and has passed multiple NRC safety inspections. It was recently found to face no significant seismic or tsunami hazards.[10]

Finally, while we have focused here on Diablo Canyon’s capability to support a faster and more reliable zero carbon transition, a recent analysis by researchers at Stanford University and MIT concluded that keeping the plant online could reduce the cost of that transition by $2.6 Billion in the short term and up to $21 Billion over the coming decades.  This is the first analysis to look at the economics of Diablo Canyon in the context of the zero-carbon power sector requirement established by law; previous analyses that supported the 2018 shutdown assumed that cheaper gas generation would be available to help provide system reliability, and that is no longer the case.

It’s for these reasons and more that we strongly urge you to delay the closure of the plant until we have a better plan to fully replace it with other clean energy options. The threat of climate change is too real and too pressing to leap before we look. Considering our climate crisis, closing the plant is not only irresponsible, the consequences could be catastrophic. We are in a rush to decarbonize and hopefully save our planet from the worsening effects of climate change. We categorically believe that shutting down Diablo Canyon in 2025 is at odds with this goal. It will increase greenhouse gas emissions, air pollution and make reaching the goal of 100% clean electricity by 2045 much harder and more expensive.

Thank you for your attention to this important issue.

The presenters of this letter include: Dr. Steven Chu, Former U.S. Secretary of Energy (Obama Administration), Nobel Laureate (Physics), Professor, Physics and Molecular and Cellular Physiology, Stanford University; Richard Rhodes, Science Historian, Pulitzer Prize Laureate; Dr. Bruce Damer, Chief Scientist, BIOTA Institute; Dr. Kerry A. Emanuel, Professor of Atmospheric Science, MIT; Ron Gester, MD, Co-founder & CFO of the Science Council for Global Initiatives; Dr. James Hansen, Director, Climate Science, Awareness and Solutions, Columbia University Earth Institute and 62 additional experts.


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Nuclear energy is horrendous, PERIOD. In fact, it makes oil and gas seem like candy in comparison. Satan himself couldn’t pick a more evil fuel. Nowhere does this letter touch on the insane amount of radioactive toxic waste left sitting on the edge of one of the world’s most stunningly beautiful coastlines. Nobody wants to address the glaringly obvious elephant in our room: Humans simply need to consume LESS energy. Micro-grids, decentralized energy from solar / wind and a radical change in our lifestyles are our only ways forward. People are simply blinded by their innate addiction to consumerism. The terrifying truth is that WW3 has long ago begun – it is the battle to save us from ourselves!