Nuclear Politics: The Closing of California's Last Nuclear Plant

Persiana Saffari
March 19, 2018

Submitted as coursework for PH241, Stanford University, Winter 2018


Fig. 1: The Diablo Canyon nuclear power plant located seaside in San Luis Obispo County, California. (Source: Wikimedia Commons)

Despite the push for clean, renewable energy due to the growing concern surrounding global warming and energy sustainability, nuclear power has remained a highly political, divisive topic. Since the 1960s, there has been a growing movement against nuclear power, particularly in California, to ward off the growing industry. [1] Those opposed to the proliferation of nuclear plants have had a successful streak within the last decade - with only 99 nuclear reactors in operation in the United States, the canceling of several new reactor plans, and closing of several others. Specifically in California, the lone nuclear power plant that remained was the Diablo Canyon facility in San Luis Obispo (Fig. 1). In an unlikely partnership, Pacific Gas and Electric (PG&E) worked alongside several environmental and labor groups to form an agreement to shut down the Diablo Canyon plant in 2016. [2] Most recently, Michael Picker - President of the California Public Utilities Commission - announced in January 2018 regulators' unanimous approval of the shutdown, stating that by phasing out nuclear power, California charts a new energy future. [2] While heavily sought after, the closure of the Diablo Canyon nuclear plant has brought on a new set of questions and challenges for legislators, PG&E, and environmental coalitions.


The Diablo Canyon nuclear power plant has provided electricity to residents of California since 1985. On an annual basis, Diablo Canyon produced nearly 18,000 gigawatt-hours of power - which was used to power 1.7 million homes. [3] Accordingly, the latest reports from the California Energy Commission detail that a little over 9% of California's power is provided through nuclear energy. [2] The clean power generated by Diablo Canyon generates energy without production of greenhouse gases. Despite the plant producing clean energy, concern and debate were raised after the 2011 earthquake in Japan that resulted in the Fukushima Daiichi nuclear power plant disaster. California regulators and residents near the plant feared that given Diablo Canyon's proximity to three prominent fault lines, it would only be a matter of time before the plant was rocked by an earthquake with a magnitude the reactors could not withstand. [4] It was this most recent fear that energized environmental coalitions to lead the charge against nuclear power in California as well as for regulators and providers to analyze the nuclear power plants that remained in operation at the time.

Initially, PG&E attempted to preserve the San Luis Obispo facility, submitting documents to the federal Nuclear Regulatory Commission indicating that the Diablo Canyon plant could withstand flooding, earthquakes, and tsunamis. [4] Upon further reflection and negotiations with environmental and labor coalitions, PG&E concluded that the maintenance and operation of Diablo Canyon would be uneconomical, given California's shifting power grid to other renewable energy resources, increased efficiency measures, and customer migration from traditional utilities to local suppliers. [2] As a result, while the plant will retire its two reactors after their operating licenses expire (in 2024 and 2025), parties on both sides of the Diablo Canyon closure debate are concerned with how PG&E will fill the energy void to power California's residents.

Nuclear Waste Disposal

While there are concerns keeping the Diablo Canyon plant open based on its proximity to seismic fault lines, there is even greater worry surrounding the appropriate disposal of nuclear waste generated at the Diablo Canyon facility. [1] Improperly stored radioactive waste not only serves as a major potential health hazard, but also as a national security risk. Given the hazard that nuclear waste poses for tens of thousands of years after it has been produced, both energy supplies and activists are eager to follow sensible legislation posed by federal regulators for nuclear waste management. [5,6] As a result, the need for safe, effective waste is critical to the successful decommissioning of Diablo Canyon's reactors.

The spent fuel and used uranium pellets at the Diablo Canyon nuclear plant have a combined weight of over 1.35 million kilograms. [5] Currently, the waste that has been and continues to be generated is stored at the Diablo Canyon facility. There, for each reactor's spent fuel, the waste is secured in racks that will be submerged in concrete-walled, stainless steel-lined pools of borated water. [6,7] These storage pools protect employees of the plant as well as the general public from residual radiation while allowing the fuel to cool via continuous circulation of water. In order to facilitate all the waste generated by the plant while federal regulators deliberate where California's remaining nuclear waste should be stored, PG&E built an interim used fuel repository on Diablo Canyon's site. [2,8] Finally, after five years of cooling in the pools, the waste is transferred into a sealed Helium canister that is encased within a 20-feet tall concrete-filled, steel storage vessel; within the cask, the fuel continues to cool via air vents in the storage cask. [5,7] Given the fault lines surrounding the Diablo Canyon plant, another precautionary measure was taken to ensure these casks seismic stability. Each cask was bolted to a 7.5 foot thick, steel-reinforced concrete pad - allowing the can to withstand many potential hazards. [6] While there is enough space for the waste generated at Diablo Canyon during its current operating license to be stored at the San Luis Obispo facility, ultimately, the final destination of where this nuclear waste is deposited remains in the hands of the federal government.

Pro-environmental groups are committed to holding the federal government accountable for properly allocating this waste outside of California. Of course, the easier and economical decision - from the perspective of PG&E - would be to keep the spent fuel stored in Diablo Canyon, thereby avoiding added cost and risk that arise when transporting nuclear waste. [8] In the eyes of the nuclear power protestors, the risk of a single, catastrophic incident resulting in the release of radioactive particles (such as Pu-239 and Tc-99, which have half-lives ranging to the tens of hundreds of thousands of years) is too significant of a health concern to store the casks near a fault line. [6] As plans to move nuclear waste to Yucca Mountain in Nevada were recently gutted, Californians and PG&E continue to press federal regulators to determine a nuclear waste location assignment. Since the announcement of Diablo Canyon's closure, regulators have expressed sites in Texas and Arizona as being potential nuclear waste disposal locations. [5] The politics involved with such a dramatic production - between the transportation of radioactive waste to the safe deposit in a newly designed repository - is the driving factor for the arduous nature that decommissioning a nuclear plant entails.

Plant Closure and Beyond

To bridge the energy disparity left by the impending closure of the Diablo Canyon nuclear power plant, regulators, utilities, and environmentalists are actively debating what the future of energy production will look like in San Luis Obispo County and throughout California. PG&E and the environmental group "Friends of the Earth" developed a deal in which PG&E pledged to bring the company closer to the Californian mandate that 50% of the state's electricity generation will come from renewable energy sources by 2030. [4] Proponents of the Diablo Canyon nuclear plant and nuclear energy remain concerned that PG&E will need to turn to natural gas to replace the clean energy generated by the plant. [4] On the other side of the debate, despite the triumph many environmentalists felt with the decision to close Diablo Canyon, there remains concern over what kind of energy sources will replace nuclear power in California. Dan Jacobson, who serves as the state director for Environment California, contended that by phasing out nuclear energy, the state cannot replace it with "dirty and dangerous fossil fuels like natural gas" in order to move forward with California's green energy initiative. [3] While these environmentalists and pro-nuclear energy groups held opposing views on the closure of Diablo Canyon, they do share the same goal of wanting safe, clean, and reliable energy in California.

Commissioners and regulators do not foresee issues in meeting the demands for clean energy. Given the fact that the reactors will not close down for another six years, there is enough time to appropriately address the energy disparity and ameliorate it with the appropriate clean energy resources. Commissioner Cliff Rechtschaffen expressed that the closing of Diablo Canyon does not indicate a "retreat from our strong commitment to our GHG (greenhouse gas) reduction goals". [3] While determining what that clean energy future looks like is left up to regulators, utilities, and legislators, Diablo Canyon's fate as the last nuclear power plant to provide California residents energy has been sealed. The unanimous vote by regulators to shut down California's last nuclear plant is a historic move to remove nuclear power from the clean energy equation for the state's future. Now, the challenge becomes how to replenish energy resources through clean, carbon-free means for millions of residents across California.

© Persiana Saffari. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] D. R. Baker, "Nuclear Power's Last Stand in California: Will Diablo Canyon Die?," San Francisco Chronicle, 14 Nov 15.

[2] R. Nikolewski, "Regulators Vote to Shut Down Diablo Canyon, California's Last Nuclear Power Plant," Los Angeles Times, 11 Jan 18.

[3] R. Nikolewski, "Nuclear Power Receives its Death Sentence in California: Regulators Vote to Shut Down Diablo Canyon," San Diego Union Tribune, 11 Jan 18.

[4] I. Penn and S. Masunaga, "PG&E to Close Diablo Canyon, California's Last Nuclear Power Plant," Los Angeles Times, 21 Jun 16.

[5] R. Nikolewski, "Diablo's Decommissioning Challenges," San Diego Union Tribune, 21 Jun 16.

[6] S. Sherman, "Radioactive Waste Dangers," Physics 240, Stanford University, Fall 2015.

[7] "Storage of Water Reactor Spent Fuel in Water Pools," International Atomic Energy Agency, Technical Reports Series No. 218, 1992.

[8] Q. Geng, "California Nuclear Waste," Physics 241, Stanford University, Winter 2017.