Decommissioning a Nuclear Power Plant - Frequently Asked Questions


Q1. What is decommissioning?

A1. Decommissioning refers to the process of removing residual radioactivity at a commercial nuclear plant once it has been permanently retired.

Nuclear power plant decommissioning is regulated by the Nuclear Regulatory Commission (NRC), and involves safely removing a facility from service and reducing residual radioactivity to a level that permits release of the property and termination of the license. The process for SONGS decommissioning involves disposal of radioactive components and materials; cleanup of radioactivity; and progressive dismantling of the plant so the site can be released for other purposes. The owner remains accountable to the NRC until decommissioning has been completed and the agency has terminated the license.

Q2. Why are nuclear power plants decommissioned?

A2. All power plants - coal, gas and nuclear- have a finite life beyond which it is no longer economically feasible to operate. Nuclear power plants are initially licensed for 40 years, with the option to seek 20-year license extensions. The NRC requires a commercial nuclear power plant to be decommissioned within 60 years once a plant has been permanently retired. The San Onofre Units 2 and 3 were granted licenses to operate for 40 years, which were to expire in February 2022 and November 2022, respectively. Southern California Edison (SCE), majority owner of San Onofre, announced the permanent retirement of Units 2 and 3 in June 2013, citing uncertainty about whether the plant could return to operation following a tube leak in a defective steam generators. The decision was in the best interest of customers, investors and the need to plan for the region’s long-term electricity needs.

Q3. How long will decommissioning take?

A3. The NRC requires that nuclear plants be decommissioned within 60 years of permanently ceasing power operations. SCE intends to complete the dismantling and decommissioning of San Onofre Units 2 and 3 in a timely fashion.

Q4. Who pays for decommissioning and how much will it cost?

A4. Decommissioning costs are paid using dedicated decommissioning trusts funded through customer contributions and investments made while the plant was operating. Customers contributed about one-third of the funds, and the remaining two-thirds are earnings from investments in the trust funds that are overseen by a five-member board. Decommissioning San Onofre will cost an estimated $4.4 billion in 2014$. Based on estimated costs and forecast market conditions, the trust funds are fully funded.

Q5. What is the current status of San Onofre decommissioning?

A5. Both reactors at San Onofre have been permanently defueled and retired. Plant equipment that is no longer needed has been de-energized and removed from service. Major dismantlement work could begin in mid-2019, subject to obtaining the required regulatory approvals.

Used Nuclear Fuel Storage

Ql. What will happen to the used nuclear fuel at San Onofre?

AI. SCE will continue to safely store used nuclear fuel on site as the company has for more than 30 years, following industry best practices and subject to ongoing NRC oversight. San Onofre currently uses a combination of spent fuel pools and dry cask storage, both of which are designed to safely protect and cool the fuel. SCE will manage the used nuclear fuel until the Department of Energy fulfills its contractual obligations to open a permanent spent nuclear fuel repository. In addition, SCE the San Onofre Community Engagement Panel (CEP) and a number of community stakeholders have aligned to support proposals to create interim storage facilities in Texas and New Mexico.

Q2. What is dry cask storage?

A2. Dry cask storage involves sealing used nuclear fuel in airtight steel containers, or casks, that are housed within a robust concrete structure called an Independent Spent Fuel Storage Installations (ISFSI). The ISFSI provides both structural strength and shielding and allows passive cooling of the used nuclear fuel. Dry cask storage systems are designed to withstand various natural phenomena such as floods, projectiles from a tornado, seismic events, tsunamis, temperature extremes and lightning strikes. The dry cask storage systems in use at San Onofre are designed and licensed for both storage and transportation.

Q3. Is dry cask storage used at other nuclear power plant sites?

A3. Dry cask storage is being used at operating and decommissioned plants throughout the country. More than 2,700 used nuclear fuel containers are currently in service at these sites today.

Q4. Will the lSFSI remain on the site even after decommissioning is completed?

A4. Yes, there is a possibility that spent fuel will remain on site after radiological decommissioning has been completed.

And as long as used nuclear fuel remains on site at San Onofre, the ISFSI will continue to be licensed and inspected by the NRC, and the used nuclear fuel will be maintained and protected by SCE. The NRC license requires monitoring of used nuclear fuel and robust security measures. In addition, SCE has committed to the California Coastal Commission to continue to evaluate potential coastal hazards and will, by 2035, evaluate potential alternative sites at SONGS for the ISFSI.

Once fuel is removed from the site, SCE can complete the decommissioning by dismantling ISFSI and removing the remaining substructures.

Q5. How much used nuclear fuel is stored at San Onofre?

A5. San Onofre has 2,668 fuel assemblies in spent fuel pools In Units 2 and 3, and about 800 Unit 2 and 3 assemblies in dry cask storage. In addition, there are about 400 Unit 1 used fuel assemblies in dry cask storage. Combined, that’s a total of about 1,600 metric tons of used nuclear fuel. The transfer of used fuel from spent fuel pools into the new Independent Spent Fuel Storage Installation (ISFSI) began in January 2018 and is expected to be completed in the later part of 2019.

Waste Disposal and Shipping

Q1. What type of waste will be removed from the plant?

A1. Generally, there are two broad types of radioactive waste at San Onofre and other commercial nuclear plants: used nuclear fuel which is high-level waste, and low-level waste such as demolition debris. This waste will be disposed of according to strict guidelines.

Additionally, there also will be non-hazardous industrial waste. An estimated 25 million cubic feet of materials, mainly concrete and steel, will be removed from SONGS during decommissioning. The most significant portion of materials, about 75 percent of the total to be removed from San Onofre, will fall into this non-hazardous waste category and not have any radiological contamination.

Q2. How will the waste be removed from the site?

A2. Waste shipments will leave via trucks and freight trains, both of which are subject to stringent requirements and regulations imposed by the Nuclear Regulatory Commission, Federal Railroad Administration and U.S. Department of Transportation.

Emergency Preparedness

Q1. Does San Onofre continue to have emergency preparedness plans in place in case there is a radiological problem?

A1. Yes, San Onofre continues to have a NRC approved emergency plan in place. The NRC approved a revised emergency plan for San Onofre in June 2015 reflecting the reduced risk at a permanently shut down nuclear plant. Most potential accidents related to an operating plant are no longer possible because the fuel has been removed from the reactors. The revised emergency plan, however, does maintain many of the station's prior emergency plan elements including around-the-clock, trained emergency personnel on site to address unanticipated events, radiological and environmental monitoring drills and close coordination with off-site agencies.

Q2. Will San Onofre’s Community Alert Siren System continue to operate?

A2. Although no longer needed for events at San Onofre, SCE has committed to maintaining and testing the Community Alert Siren System through June 30, 2019. Annual siren testing no longer takes place, however, periodic testing is conducted to ensure the system is operational.

License Termination and Site Restoration

Q1. When will the station’s NRC license be terminated?

A1. Termination of San Onofre’s licenses will take place when site building demolition and remediation operations are complete and the remaining grounds have been surveyed to ensure they meet the NRC criteria for residual radioactivity levels. The specific activities and radiological criteria will be defined in the plant’s termination plan, which will be filed with the NRC at least two years prior to license termination.

Q2. Will the site be safe for any type of use?

A2. San Onofre is located on property owned by the U.S. Navy, which will determine any future use of the site. Once buildings are removed and surveys are completed to meet federal requirements, as well as any additional Navy requirements, the site will be cleared for unrestricted use, except for the portion that houses the ISFSI. Unrestricted use means any residual radiation at the site would be below the NRC's limit of 25 millirem per year.

Regulatory Permitting

Q1. What state and federal agencies are involved in the permitting processes for San Onofre decommissioning?

A1. Several agencies have authority over the San Onofre decommissioning project. On the state level, the primary approvals will be issued by the California State Lands Commission (CSLC) and the California Coastal Commission (CCC). On the federal level, in addition to the NRC, the Navy and the U.S. Army Corps of Engineers also will play roles in the environmental review and approval processes.

Q2. What Is the CEQA process and what is required?

A2. The California Environmental Quality Act (CEQA) process begins with an assessment of whether a specific project triggers a CEQA review. If CEQA applies, the lead agency – in this case the CSLC – will typically conduct an initial study of a project’s potential environmental consequences. The results of the study will determine what type of environmental document must be prepared. San Onofre’s decommissioning, according to the CSLC, requires an Environmental Impact Report. The CEQA process, which is currently underway, provides multiple opportunities for public participation.

Q3. What is the NEPA process?

A3. The National Environmental Policy Act (NEPA) is a statute that establishes a process by which federal agencies must study the environmental effects of their actions. The U.S. Navy will conduct a NEPA review as the lead agency to evaluate potential impacts associated with the site’s final end state.

Q4. What is the relationship between the CEQA and NEPA processes?

A4. The CEQA review ensures that state and local environmental protection requirements are met, while NEPA requires federal agencies to comply with national environmental protection regulations. Both reviews are similar in intent but do have some differences in substantive and procedural requirements. Together, CEQA and NEPA aim to protect the environment by involving the public and informing decision-makers about the potential environmental effects of proposed activities. Therefore, while the two statues are similar, they include separate processes that must be completed.


Q1. Will buildings and structures be removed below grade?

A1. The buildings, structures and components on site will be removed to a depth of at least three feet below grade. Anything that remains on site will be verified to be acceptable for unrestricted use in accordance with NRC and landowner (U.S. Navy) requirements.

Q2. What will happen to the water in the reactors and spent fuel pool?

A2. The water used during the decommissioning project in each reactor cavity and the spent fuel pools will be purified using specialized water treatments. Before treated water is discharged to the ocean, it will be sampled to ensure compliance with NRC regulations and a state NPDES permit, which was approved by the San Diego Regional Water Quality Control Board.