Frequently Asked Questions
Below are frequently asked questions about the efforts to keep Diablo Canyon Nuclear Power Plant running.
Q.
Is Diablo Canyon safe to operate? What would happen if there were an earthquake nearby?
A.
Diablo Canyon can safely withstand even the strongest and rarest earthquakes possible at the site, according to a thorough, nine-year assessment process conducted by the NRC and peer-reviewed by several California, national and international experts.
Diablo Canyon’s ability to withstand seismic events was underscored in a recent letter to Gov. Gavin Newsom authored by scientific experts, which concluded that Diablo Canyon “does not pose a seismic danger, and thus the seismic issue should be taken off the table when considering increasing DCNPP’s useful life and operation.” Additionally, during the most recent quarter, the NRC determined that the performance of both units at the Diablo Canyon Power Plant was within the highest performance category of the NRC’s safety rating system.
Diablo Canyon is designed for a peak ground acceleration (PGA) of 0.75g – an earthquake considered to be a one in a 100,000-year event at the site. The electrical systems have a small probability of failing in the event of a much larger earthquake, however, these components have been tested on shaker tables, so experts know when and how they could fail and have planned accordingly. Diablo Canyon has been retrofitted with special equipment and procedures known as FLEX, which ensures reliable cooling of the reactor core and spent fuel pool even if all design-basis safety systems have been disabled by a severe accident. Mobile backup equipment from a regional site in Arizona can also be transferred to the site for further protection.
Q.
Is Diablo Canyon safe from tsunamis? What is the risk of a flooding event similar to what was seen at Fukushima?
A.
In response to the Fukushima event, the NRC directed all U.S. nuclear power plants to reassess the potential for seismic and flooding hazards, including those related to tsunamis. The reevaluation determined that Diablo Canyon’s key safety systems are safe from the maximum tsunami waves and rainfall that could affect the site. It’s important to note that Diablo Canyon sits on a cliff 85 feet (8 stories high) above sea level, a very different situation than was present at Fukushima. Additionally, flood protection was strengthened at Diablo Canyon to provide additional safety against rainfall that significantly exceeds any known precipitation event previously recorded at the site.
Q.
Is relicensing Diablo Canyon economically viable? What would be the impact on electric bills?
A.
Yes, relicensing Diablo Canyon is not only economically viable, but will actually save ratepayers money. A recent study conducted by the Brattle Group found that electric costs would be lower with Diablo Canyon continuing to operate. If the plant were kept online until 2045, Californians would save more than $4 billion in energy costs, even assuming the state can meet its ambitious clean technology deployment objectives. If Diablo Canyon goes offline, the state will rely more heavily on gas-powered plants, which have higher capital and maintenance costs than clean energy sources, as well as out of state fossil fuel imports. Economic studies have compared Diablo Canyon to energy portfolios that include carbon-emitting gas fired generation on an unrestricted basis, which is counter to the state’s climate policies.
Q.
Does Diablo Canyon require a subsidy to continue operating?
A.
No, Diablo Canyon can continue operating without any state subsidies and still significantly reduce energy system costs for California ratepayers. A study completed by the Brattle Group showed that even with significant capital investments to allow for extended operations, there would be a $4 billion net present value (NPV) savings for California ratepayers from keeping Diablo Canyon open. Recent actions at the state and federal level, including provisions that would allow Diablo Canyon to qualify for the Department of Energy’s Civil Nuclear Credit Program, would only serve to further reduce systemwide costs if Diablo Canyon were to remain open.
Q.
A.
As the state’s largest source of always-available, carbon-free power, Diablo Canyon is critical to keeping the lights on for homes and businesses. As California continues to face reliability concerns, the state has analyzed how much capacity is needed to maintain reliability in extreme weather scenarios.
The California Energy Commission found that the state must procure more than 20 GW – increasing California’s electrical capacity by 25 percent – over the next five years to remain in alignment with the state’s clean energy goals. Amidst the persistent global supply chain disruption, the state would need to immediately triple the deployment of solar energy and storage while adding massive amounts of new and controversial hydroelectric storage and geothermal energy.
Analysis conducted by the Brattle Group found if this does occur, and California only achieves the 2021 rate of storage installation, the state could face a 3.4 GW shortfall in 2025 when Diablo Canyon goes offline. Extending operations at Diablo Canyon would provide 2.2 GW of clean, reliable power to help fill the gaps and keep the lights on.
The Brattle study demonstrates that in the short- and long-term – even assuming unconstrained renewables build – California must burn substantially higher amounts of natural gas to make up for the reliability that Diablo Canyon provides.
Put another way: to maintain reliability, the choice is not between Diablo and renewables, it is between Diablo and natural gas.
Q.
Why revisit this issue? What has changed since 2018 when the decision was made to shutter Diablo Canyon?
A.
The world has changed since the 2018 decision to shut down Diablo Canyon. The climate crisis has become increasingly urgent with warming temperatures, wildfires and record drought conditions. Since 2018, California has set new emission reduction targets – including the requirement that all the state’s electricity come from emission-free sources by 2045 – and is exploring solutions to meet these targets sooner. But on its current trajectory, California is in danger of missing even its current climate goals. Renewable energy development in the state has not kept pace with growing electricity demand, and even with efforts to accelerate buildout seen in recent years, including the incorporation of new technologies like offshore wind, California will still likely fall short of producing the clean energy needed to supply growing demand by the time Diablo Canyon is scheduled to close. A recent analysis conducted by Next 10 and Beacon Economics found that at the state’s current three-year average rate of greenhouse gas reductions, California will miss its 2030 and 2050 goals by decades; a June 2022 report by Energy Innovation indicates the state must triple its decarbonization rate over recent history to meet its 2030 target. Extending Diablo Canyon would provide a critical runway as state leaders pursue additional clean energy solutions to ensure we meet our climate goals as quickly as possible.
Q.
Does Diablo Canyon have capacity to store more spent fuel if operations are extended?
A.
After 35 years of power generation, Diablo Canyon safely houses approximately 60 dry casks of spent fuel on less than 0.5 acres. There is space to store another 20 years of spent fuel in both the spent fuel pools and the dry cask area onsite. Eventually, these dry casks will be transferred to a permanent disposal site. Diablo Canyon’s spent fuel is classified as high-level radioactive waste. Once removed from the reactors, it is stored for several years in the spent fuel pool located within the plant. As its radioactivity decreases over time, spent fuel is transferred to specialized containers called ‘dry casks.’ Dry cask technology has been rigorously tested and developed over 20 years and safely deployed to 60 nuclear power plants across the nation. Dry casks include specialized radiation shielding which help make it safe for handling and short-term storage.
Q.
Would operating Diablo Canyon curtail or supplant the state’s development of renewable energy?
A.
No. The state must pursue all forms of clean, carbon-free energy as rapidly as possible to address the urgent climate crisis and accelerate progress toward our emission reduction goals. The Brattle Group study, which assumed unconstrained deployment of renewable energy, demonstrates that an all-of-the-above carbon-free strategy that utilizes Diablo Canyon, in addition to renewables and other sources of clean power generation, would significantly reduce California’s power sector emissions by bolstering the grid with reliable, carbon-free energy as the state transitions to larger shares of wind and solar energy.
Q.
Would the continued operation of Diablo Canyon crowd out new offshore wind projects that would be dependent on using the transmission lines out of the nuclear plant site?
A.
Envisioning a decarbonized future power sector, California has exciting and ambitious plans for a major wind energy development off the Central Coast near Diablo Canyon. Keeping Diablo Canyon online will not impede development, even if the development plans to use the Diablo Canyon substation to connect the offshore wind resources. There are three existing high voltage power lines emanating from the Diablo Canyon plant, presently with excess capacity. The California Independent System Operator is now assessing how to accommodate major offshore wind resources and the continued operation of Diablo Canyon. In the short term, the existing lines have the capacity for both Diablo Canyon and approximately 3,000 MW of offshore wind power generation, which is the amount planned for deployment by 2030. In the long term, California proposes substantially more offshore wind energy, up to 20,000 MW by 2045. That level of offshore wind development will require substantial upgrades to the entire bulk transmission system regardless of whether Diablo Canyon stays online.
Q.
A.
Yes. With the proper licensing and regulatory approvals at the state and federal levels, Diablo Canyon can remain operational beyond 2025. The facility’s relicensing process was already underway when the decision was made to close the plant, and that process did not identify the need to undertake any major refurbishment or replacement actions to maintain the functionality of important systems, structures or components during the license renewal period of 2025 to 2045.
Q.
A.
Efforts to extend the life of Diablo Canyon have received support from leaders in the business community, labor organizations, the technology sector and current and former elected officials, including U.S. Energy Secretary Jennifer Granholm, former U.S. Energy Secretaries Steven Chu and Ernest Moniz, U.S. Senator Dianne Feinstein, California Assemblymember Jordan Cunningham and San Luis Obispo County Supervisor Dawn Ortiz-Legg.
Q.
How will Diablo Canyon meet new once-through cooling intake reduction requirements?
A.
Any continued operation of Diablo Canyon must be consistent with other state laws and regulations including limits on once-through cooling. The Stanford-MIT study examined new technology that would be compliant with once-through cooling requirements. Specifically, the potential of mechanical brush-cleaned wedge wire screens as an alternative for intake flow rate reduction, which would be significantly less costly and have less environmental impacts than the assumed approach of constructing an intake gallery below the ocean floor. Similar intake systems have been used elsewhere in the U.S. and are currently being tested at Carlsbad as a potential replacement for their existing intake system.
Q.
What is Carbon Free California? Who is behind the effort to keep Diablo Canyon open?
A.
Carbon Free California brings together leaders from business, labor, environmental and climate advocates, and the technology sector to focus on creating a pathway to a carbon-free future and securing the clean, reliable energy needed to power the world’s fifth-largest economy. Carbon Free California believes the state must pursue all forms of emission free energy to address the climate crisis and achieve our urgent emission reduction goals. Extending the operation of the Diablo Canyon Nuclear Power Plant will bolster the grid with reliable carbon-free energy and enable the state to transition to increasing shares of wind and solar power, while avoiding disruptive and costly rolling blackouts. Carbon Free California is funded by California-based entrepreneurs and receives no funding from utility or nuclear industry interests.