California could soon shut down its last nuclear power plant, Diablo Canyon.
Diablo Canyon nuclear power plant in San Luis Obispo County, California. Tracey Adams / Wikimedia Commons C.C. 2.0 Generic License
When Gavin Newsom was California’s Lieutenant Governor, and in 2016 already eyeing a run at the state’s top job, he led the campaign to shut down the state’s last operating nuclear power plant. The Diablo Canyon nuclear facility churns out about eight percent of all energy produced in California, according to researchers at Stanford University and Massachusetts Institute of technology, and 15 percent of the carbon-free electricity.
In 2016, Newsom was highly skeptical that the plant, located just off Avila Beach in San Luis Obispo County and near a complex of seismic fault lines, would—or should—survive. As chair of the State Lands Commission, the board that would decide whether to renew PG&E’s licenses to operate the plant’s two reactors, Newsom said “I don’t think that PG&E, in its quiet moments, would disagree that this may not have been the ideal site for a plant,” and added that the power plant would not “survive beyond 2024, 2025.”
Six years later, as the incumbent governor, Newsom did an about-face. In November, 2021, Congress had passed one of Pres. Joe Biden’s signature legislative initiatives, the Infrastructure Investment and Jobs Act—more popularly known as the “Bipartisan Infrastructure Bill.” Contained in that law’s $1.2 trillion in spending were $6 billion for a new plan called the Civil Nuclear Credit Program. The money would go to bail out nuclear power plants in danger of shutting down.
Though PG&E said it would kick in $50 million to cover lost property taxes in San Luis Obispo County, which would result from the shutdown, the company said that it would ultimately cost more to keep the plant running than to close it. In 2018, the California Public Utilities Commission voted unanimously to approve the Diablo Canyon shutdown plan.
In an April 2022 interview with the Los Angeles Times editorial board, Newsom said he wanted some of that $6 billion—to keep Diablo Canyon running after all. The governor said that PG&E would be “remiss” if it failed to file an application for a share of the federal money.
Though Newsom’s spokespeople said that he still wants to see the Diablo Canyon reactors shut down “in the long term,” his support for keeping the plant open past 2025 seemed like a stunning reversal. What happened? Why did Newsom support ending nuclear power in California in the first place, and why did he change his mind?
Nuclear power has generated intense controversy since humans first learned to harness the energy contained in atoms eight decades ago. The Atomic Energy Act of 1946, the first U.S. law regulating how to use this awesome new technology for “peaceful purposes,” warned of “unknown factors” involved in the civilian application of nuclear power. (It was called “atomic” power back then, though the terms mean essentially the same thing).
For all of its futuristic potential as well as destructive power, nothing yet discovered on this planet can generate energy as efficiently as nuclear fuel.
Derived from uranium, a common metal that occurs naturally in the Earth’s crust, nuclear fuel is contained in small, ceramic pellets each one about the size of a Tootsie Roll, the small kind. A single pellet contains as much energy as a ton of coal or 149 gallons of oil.
The pellets are packed into long metal tubes and inserted into the core of a nuclear reactor, the huge machine that, through its own complicated process, causes the fuel to burn. A typical pressurized water reactor (PWR, the most-used type) contains about 51,000 rods holding approximately 18 million pellets.
The burning nuclear fuel heats up water, which generates steam. In turn, the steam powers huge turbines, and that’s where the electricity comes from. How much water does a nuclear power plant use? Diablo Canyon, which operates two PWRs, draws 2.5 billion gallons of water from the Pacific Ocean per day. Some of the water remains clean and is returned to the ocean, but water heated by the reactor and used to generate steam becomes highly radioactive and must remain inside the containment structure.
A PWR pressurizes the water, allowing it to heat up to about 575 degrees Fahrenheit without boiling. The superheated water is then used to power steam generators, where a giant pool of non-radioactive water boils. The steam it creates then turns a set of turbines, creating electricity.
A standard PWR can pump out one gigawatt or 1,000 megawatts. Every hour that the reactor runs at full capacity generates one “gigawatt-hour” of electricity. That’s enough power for 750,000 typical homes.
Most nuclear power plants operate multiple reactors. Of the 55 plants operating in the U.S. as of 2022, 32 operated two reactors while there were three triple-reactor plants running. The three-reactor Palo Verde Generating Station in Maricopa County, Arizona—about 110 miles east of the California state line—is the largest nuclear power plant in the country.
As you may know, nine of the 10 hottest years in recorded history came in the 10-year period ending with 2021, which was the sixth-warmest year ever recorded. All of this heating, and all of the many dangers that come with it, are caused by greenhouse gasses, mainly carbon dioxide, methane, and nitrous oxide. What creates greenhouse gasses? Burning fossil fuels for energy. And what does not create greenhouse gasses? Nuclear power.
According to the Nuclear Energy Institute—a lobbying group—in 2019 alone the amount of electricity provided by nuclear plants would have spewed a staggering 471.3 million metric tons of carbon dioxide into the atmosphere if it were produced by fossil fuels. That’s the amount produced by 100 million automobiles.
To be clear, nuclear power is not “carbon neutral.” Over the entire life cycle of a plant—including construction, decommissioning, uranium mining, and radioactive waste disposal—a nuclear plant produces 117 grams of carbon dioxide for every kilowatt-hour, measured over a plant’s entire life cycle. That’s according to a study by the World Information Service on Energy, an anti-nuclear group based in the Netherlands. Brown coal, according to the same study, produces more than 1,000 grams of CO2 per kilowatt-hour. Natural gas coughs up 442 grams per kilowatt-hour.
A 2021 United Nations study had even better news for the nuclear industry and its supporters. The study assessed total environmental impact of all energy sources—environmental factors such as water consumption, land use (a typical nuclear plant occupies about one square mile), use of material resources, radiation, and “human toxicity,” which includes cancer-causing potential and other poisonous effects.
The study found that of 22 energy-producing technologies, nuclear power scored second-lowest for overall environmental impact throughout its life cycle. Only hydroelectric power scored better.
Nuclear power has other advantages as well, according to its advocates and various studies, including its sheer reliability. Nuclear plants are the workhorse of the U.S. energy industry, operating almost year-round day and night.
According to a study by the U.S. Energy Information Administration (EIA), in 2021 nuclear plants were on line and producing power 93 percent of the time, compared to just 49 percent for coal, 37 percent for hydroelectric plants, 25 percent for photovoltaic solar panels, and just 54 percent for natural gas.
Every energy source comes with its drawbacks. Even with some optimistic studies projecting that the entire world could be powered by renewable resources by the year 2050, there are considerable limitations on those types of energy sources. Renewables suct as solar, wind, hydroelectric, and biomass, are “clean,” and constantly replenished by nature but, as noted above, they aren’t highly efficient, at least not in their present form.
So why not just go all-in on nuclear power? Perhaps the most basic reason is cost. According to the 2022 EIA Energy Outlook study, every kilowatt of power produced by a one-gigawatt reactor costs $5,366 in construction expenses. A wind farm costs $1,980 per kilowatt to build, while a natural gas facility costs a scant $912 per kilowatt.
Why are the costs of building nuclear power plants so high? Safety. After a frightening accident at the Three Mile Island plant near the Pennsylvania state capital of Harrisburg in 1979, regulators cracked down. New, “permanent and sweeping” safety requirements were imposed on the 51 plants being built at the time, ranging from enhanced preparation for accidents to upgrades in design and construction. This rapidly raised the price of building new nuclear facilities—in fact, no new plants broke ground at all until 2013.
Two reactors in South Carolina that began construction that year, however, were halted in 2017 due to delays and rising costs.
That brings us, of course, to the scariest problem with nuclear power plants. Safety.
A 2007 study published in the medical journal Lancet found that among energy technologies, nuclear power has one of the lowest rates of death associated with its use and “one of the smallest levels of direct health effects.” But the effects of a possible nuclear accident could, in theory, be catastrophic. The uranium fuel used in reactors is not nearly as pure as used in nuclear bombs, which means that even in the worst scenario, a nuclear power accident won’t cause a nuclear explosion. But that doesn’t mean an accident cannot be deadly.
The worst-case scenario is a “meltdown,” which occurs when the nuclear chain reaction inside a reactor gets out of control, causing the fuel rods to overheat and melt. The melted fuel can be as hot as 3,600 degrees Fahrenheit, the approximate temperature of the melted fuel rods in the 1986 Chernobyl nuclear disaster in Ukraine, then part of the Soviet Union. That’s almost 10 times as hot as a California wildfire.
The super-heated fuel is also highly radioactive. If it pools at the bottom of a reactor containment structure, burning a hole through the floor, the melted fuel releases its deadly radioactivity into the surrounding environment.
The water used to cool the reactor core is also radioactive, and overheats when a meltdown takes place, potentially causing steam explosions that can blow a hole in the structure, spewing radioactivity into the air.
When that happens, the results are brutal. After the 1986 Chernobyl meltdown, Soviet officials released a death toll of 31 people, but subsequent research by the United Nations, the National Research Center for Radiation Medicine in Ukraine, and the Ukrainian government suggest that the Soviet figure was a gross underestimate.
Fortunately, these doomsday scenarios have not happened in the United States—not even during the Three Mile Island accident in 1979.
At about four in the morning on March 28, 1979, the second of two reactors at the plant located on an island in Pennsylvania’s Susquehanna River experienced a breakdown in its cooling system. The reactor shut down automatically and immediately, but a cooling valve remained open.
Due to poorly operating instruments in the plant’s control room, and a lack of proper emergency training, workers at the plant missed the open valve. Not enough coolant reached the reactor core, overheating it and causing a partial meltdown. Fortunately, the walls of the reactor’s containment structure remained intact, and only a small amount of radiation escaped into the surrounding environment.
Five years later, investigators were able to access the reactor, and found that 45 percent of the core had melted down—but even though 19 tons of melted nuclear fuel had settled in the bottom of the containment unit, it wasn’t enough to cause damage to the structure.
Some radiation escaped from the plant, but multiple investigations by federal and state authorities, as well as independent groups found that radioactivity levels in the plant’s vicinity increased only slightly, and not enough to cause serious health problems for local residents or damage to the environment.
The safety improvements throughout the nuclear industry that resulted from the Three MIle Island accident appear to have proven effective. The U.S. has not seen a nuclear accident of any scale in the decades since. In 2002, an inspection at Davis-Besse Nuclear Power Station in Oak Harbor, Ohio, revealed cracking in nozzles leading to the head of the reactor “vessel,” the structure containing the reactor core. The plant shut down for two years while the cracks were repaired.
While nuclear power is relatively “clean” when it comes to generating greenhouse gasses, it is definitely not clean when it comes to producing waste. Taking out this nuclear garbage is not as simple as dumping it in a landfill. Nuclear waste, especially “high level” waste, is extremely radioactive and must be disposed of in ways that do not allow radioactivity to escape.
High-level waste consists of nuclear fuel pellets that have been “spent,” that is, they have generated all the energy they have in them and are now useless. Once spent, the fuel is far more dangerous than before it is used in a reactor. As long as 10 years after it becomes spent, a used fuel rod gives off a dose of radioactivity 20 times greater than a dose that would be fatal to humans.
And it stays that way, for all effective purposes, forever. While radioactive atoms, or isotopes, eventually decay and become harmless, the process takes years, even centuries. Plutonium-239, which is one of the isotopes found in spent nuclear fuel rods, has a half-life (meaning the time it takes to become 50 percent decayed) of 24,000 years. According to the Centers for Disease Control, it takes seven half-lives for radioactive material to reduce to one percent of its original radiation level.
Uranium-238, the main component of nuclear waste, has a half-life of 4.5 billion years.
Safely storing this massively toxic nuclear waste is one of the toughest problems with nuclear power. The amount of waste produced by nuclear plants fortunately takes up relatively little space. According to a Scientific American report published in 2009, by that point the entire nuclear industry had pumped out about 64,000 metric tons of waste. That amount could, in theory, be stored in a pit seven feet deep and the size of a football field (approximately one acre).
In practice, it doesn’t really work that way, because packing all those radioactive rods that tightly together would set off a nuclear chain reaction. In fact, most nuclear power plants store their waste on their own grounds, because there’s nowhere else to put it.
The fear that Diablo Canyon’s placement created the possibility of an earthquake that could damage the reactors and set off a release of radiation or even a meltdown, was one main reason cited by Newsom for shutting the facility down. But a 2014 study by the plant’s owner, PG&E, declared that the Diablo Canyon plant “and its major components are designed to withstand—and perform their safety functions during and after—a major seismic event.”
On the other hand, a report submitted by Michael Peck, former senior resident inspector for the Nuclear Regulatory Commission at Diablo Canyon, claims that "three of the nearby faults are capable of generating earthquakes stronger than the reactors were designed to withstand."
Why reverse course and keep the plant open? The 2021 Stanford-MIT study provided at least the theoretical answer.
“A 10-year extension in Diablo Canyon’s operations would reduce carbon emissions from California’s power sector by more than 10 percent annually from 2017 levels, reduce reliance on natural gas and save ratepayers a total of $2.6 billion,” the researchers wrote. “Operating the plant until 2045 could save ratepayers up to $21 billion.”
The study also found that, in addition to producing a reliable source of electricity, the plant could also be used to ease the state’s ongoing drought by converting ocean water to fresh water usable by humans. Diablo Canyon could be “a powerful driver of low-cost desalination to serve fresh water to urban, industrial and agricultural users,” the study found.
Even if Diablo Canyon does close, the nuclear waste generated there will remain at the site for any foreseeable future. The plant already has 58 “casks” on site, storing spent fuel rods. In April, 2022, PG&E said it needed more and had picked a contractor to build them.
Whatever happens to the plant will likely depend on whether PG&E can get its hands on the federal funds set aside for keeping nuclear power plants open. The nonprofit Natural Resources Defense Council, one of the environmental groups pushing to close Diablo Canyon, doesn’t believe that will happen.
“The widely supported agreement to retire and replace the plant ... has been affirmed by multiple state and federal regulators,” the group’s senior attorney Ralph Cavanagh told the Associated Press.
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