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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The date to watch for shutdown is not 2025, but September 2023.


It bears repeating : Nuclear power, yes! Diablo Canyon nuclear power plant, no! Diablo canyon nuclear power plant is old, outmoted technology. There are newly designed nuclear plants that produce substantially less toxic radioactive waste and are safer overall.

There are currently millions of pounds of toxic radioactive waste being stored in vulnerable temporary facilities at Diablo Canyon. Diablo canyon‘s cooling system, based on a below sea level seawater cooling system, is vulnerable to tsunami‘s. Diablo Canyon technology is more than half a century old. There are considerably better nuclear alternatives as well as renewable energy choices for our future.


I agree, though not necessarily the argument I would make. Nonetheless, our costs will skyrocket when the nuclear plant closes – when we should be opening them by the dozens.


as soon as we get all those propellers out at sea we’ll be rolling in electricity!

Jorge Estrada

Just plan on seeing upgraded power lines and more nukes in the future. All of this whoopla is for today’s funding increases so that the companies can pay for tomorrows new plants. This won’t be a political decision.

Adam Trask

These are the very best scientists in their fields. Seeing them advocate for a nuclear power plant which has a myriad of negative issues should illustrate to Americans the grave dangers we face from climate change.


Or they are finally going to follow the actual science. The years of hysteria perpetuating the imminence of the “climate crisis” (formerly global warming) contributed to an abrupt, and rapid transition to solar & wind energy (without much consideration for efficiency & environmental impact). These scientists are facing the harsh reality that these so called green energies are not the answer they thought they would be. Currently there is no perfect solution…all energy sources have their own positives & negatives. If our elected officials truly believed the “climate crisis” is actually a “grave danger” they would never have divested from our own energy producers (petroleum), which are arguably the “cleanest” producers on the globe (surface and downhole production). This move has transitioned us to reliance on importing petroleum from foreign producers that pollute more (and pollution is generated in transit) and importing solar panels made in China (which has very limited environmental regulations & has no problem stripping the globe of REE’s as they destroy the environment…ie, mercury gold extraction.


Aren’t these the same scientific “experts” that demanded the closure of Diablo several years ago?


Valiant try folks, but 5 years too late and millions of $ short, and not addressing one of the KEY elements of Diablo closure – PG&E is no longer prepared or interested in continuing to bear the HUGE financial burden and HUMONGOUS RISK of extending nuclear power operation. They have many other very serious operational challenges without continuing to shoulder the responsibility of keeping Diablo operating beyond 2025. Add to that that the state of California also has very serious regulatory requirements, such as Once Through Cooling, that they would have to remove as barriers to continued Diablo operation. And, there is far too much misinformed and misguided anti-nuclear public opinion and supportive anti-nuclear governmental leaders in California. I applaud the efforts by scientific experts and others around the nation expressing their concern and support for our environment and how valuable Diablo Canyon operations are to helping reduce greenhouse gasses, but that will not fly in the face of monumental financial and legal pressures on PG&E to get out of active nuclear power operation. This might be a VERY different situation if someone else (another company or the state of California) were to take over full operation of Diablo Canyon from PG&E, assuming ALL financial, legal and regulatory responsibility. But, that is pie in the sky thinking given the many years it would take to process such a transfer of responsibility. Now, if we end up having dictator government in our nation with a new fascist President, anything can be ordered, resulting in total collapse of American business and free America. But, if that were to come to pass, forget about ANY positive efforts to battle our changing climate — Bring on more climate damaging COAL and NATURAL GAS! Don’t misunderstand — I am a VERY STRONG supporter of nuclear power and keeping Diablo Canyon operating. I have been so for close to 50 years. But, keep in mind that PG&E has already released many vital Diablo operational personnel and has taken many actions to discontinue long term maintenance programs and discontinued purchasing of materials and equipment to support longer plant operation. We are past the point of no return without MAJOR efforts to reverse course that would take many years to pursue, which would most likely mean that Diablo would still cease operation for months or years before being positioned to restart. And, if not operating, equipment and systems degrade without being operated. This would create a monstrous can of physical and administrative worms. PG&E is no longer staffed to deal with the monumental challenges to changing direction to keep Diablo open. SOOOO – who wants to spend billions $ to purchase Diablo Canyon and take over ALL responsibility from PG&E? Any takers? I think not.


Too little, and way way too late.