Diablo Canyon: The Shutdown of California's Last Nuclear Plant

Maria Gabrielle Coseteng
March 3, 2018

Submitted as coursework for PH241, Stanford University, Winter 2018


Fig. 1:The Diablo Canyon Power plant at Avila Beach in San Luis Obispo County, California. (Source: Wikimedia Commons)

Diablo Canyon Power Plant will permanently stop operation when its license expires in 2025. [1] The 2200 MW nuclear power plant is on the coast of San Luis Obispo County, shown in Fig. 1, and has been generating electricity since 1985. It is the last remaining operational nuclear power plant in California at the time of writing. [2] Operated by Pacific Gas and Electric Company (PG&E), Diablo Canyon supplies 9% of Californias electricity, or around 18 billion kWh per year, equivalent to powering 1.7 million homes. The nuclear plant provides a steady and constant generation 24-hrs a day, so it serves as the states base load electricity source, whereas other renewable sources are more intermittent. However, PG&E has claimed that the plant will no longer be economically viable due to the dropping costs of solar and wind.

From Nuclear to Renewables

The shutdown of Diablo Canyon is just one step in Californias transition towards renewables. This move aligns with Californias SB 350 that requires that 50% of the states electricity is generated from renewable sources by 2030. PG&E and the California Public Utilities Commission are planning to replace the nuclear plant with more solar and wind projects. [3]

However, nuclear advocates are questioning the economics and feasibility of replacing Diablo Canyon with 2.2 GW of renewable generation. Renewables are more intermittent and add uncertainty to the grid. Unlike nuclear, which is able to run constantly, solar and wind generation have diurnal cycles. In order to fully replace the base load that the nuclear plant provides, the state would have to heavily invest in batteries and storage to meet the demands throughout the day. [2]

Impacts on Local Communities

The closure of the plant could have health benefits to local communities. A recent study found that the annual infant mortality data for ZIP coded areas on the coast near Diablo Canyon between 1989 and 2012 was 28% higher than infant mortality rates in areas further inland. There was also a significant correlation between the increase in infant mortality rates and the release of Tritium into the ocean. [4]

Unfortunately, the residents of San Luis Obispo will bear the brunt of the economic impacts. A study by Cal Poly estimated that Diablo Canyon contributes $920 million a year to the Central Valley's economy in wages and taxes. The closure will affect not only employees, but also the budgets school districts and city councils. [3] No studies have been conducted on the job creation from the replacement renewable energy generation.

The Future of Nuclear in the US

Californias implied moratorium on nuclear might be indicative of a national movement away from nuclear energy. 99 nuclear power plants remain in operation in the United States. [1] Will the other states join in shifting away from supporting nuclear industries? Or is abandoning nuclear energy a folly? Only time will tell how the energy mix will meet the needs of society.

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

[2] P. Mayeda and K. Riener, "Economic Benefits of Diablo Canyon Power Plant," Pacific Gas and Electric Company, June 2013.

[3] L. Sommer, "Why Plans to Replace Diablo Canyon With 100 Percent Clean Energy Could Fall Short," KQED Science, 26 Jun 17.

[4] C. Busby, "Is There Evidence of Adverse Health Effects Near US Nuclear Installations? Infant Mortality in Coastal Communities near The Diablo Canyon Nuclear Power Station in California, 1989-2012," J. J. Epidemiol. Prevent. 2, 030 (2016),