Nuclear decommissioning is the process leading to the irreversible complete or partial closure of a nuclear facility, usually a nuclear reactor, with the ultimate aim of termination of the operating licence. The process usually runs according to a decommissioning plan, including the whole or partial dismantling and decontamination of the facility, ideally resulting in restoration of the environment to greenfield status. The decommissioning plan is fulfilled when the approved end state of the facility has been reached.
The process typically takes about 15 to 30 years, or many decades more when an interim safe storage period is applied for radioactive decay. Radioactive waste that remains after the decommissioning is either moved to an on-site storage facility where it is still under control of the owner, or moved to a dry cask storage or disposal facility at another location. The final disposal of nuclear waste from past and future decommissioning is a growing, still unsolved, problem.
Decommissioning is an administrative and technical process. The facility is dismantled to the point that it no longer requires measures for radiation protection. This includes clean-up of radioactive materials. Once a facility is fully decommissioned, no radiological danger should persist. The license will be terminated and the site released from regulatory control. The plant licensee is then no longer responsible for the nuclear safety.
The costs of decommissioning are to be covered by funds that are provided for in a decommissioning plan, which is part of the facility's initial authorization. They may be held in a decommissioning fund, which may be structured as a trust fund.
Worldwide, there are hundreds of thousands of small nuclear devices and facilities, for medical, industrial and research purposes, that will have to be decommissioned at some point.Decommissioning of nuclear facilities, p. 52. IAEA, 9 Sep 2002
Definition Nuclear decommissioning is the administrative and technical process leading to the irreversible closure of a nuclear facility such as a nuclear power plant, a research reactor, an isotope production plant, a particle accelerator, or a uranium mine. This will require action to remove all or some of the regulatory controls from the facility, so that the site can be reused. Decommissioning includes planning, decontamination, dismantling and materials management.Decommissioning of nuclear installations. IAEA (accessed Feb 2023)
Decommissioning is the final step in the lifecycle of a nuclear installation. It involves activities ranging from shutdown and removal of nuclear material to the environmental restoration of the site.Decommissioning of nuclear facilities. European Commission (accessed Feb 2023) The term decommissioning covers all measures carried out after a nuclear installation has been granted a decommissioning licence until nuclear regulatory supervision is no longer necessary. The aim is ideally to restore the natural initial state that existed before the construction of the nuclear power plant, the so-called greenfield status.Decommissioning & dismantling. Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) (accessed Feb 2023)
Decommissioning includes all steps as described in the decommissioning plan, leading to the release of a nuclear facility from regulatory control. The decommissioning plan is fulfilled when the approved end state of the facility has been reached. Disposal facilities for radioactive waste are closed rather than decommissioned. The use of the term decommissioning implies that no further use of the facility (or any part of it) for its existing purpose is foreseen. Though decommissioning typically includes dismantling of the facility, it is not necessarily part of it as far as existing structures are reused after decommissioning and decontamination.IAEA Nuclear Safety and Security Glossary, 2022 (p. 137). 3.7 MB. Via
From the owner's perspective, the ultimate aim of decommissioning is termination of the operating license, once he has shown that the radiation at the site is below the legal limits, which in the US is an annual exposure of 25 millirem in order to release the site to the public for unrestricted use. The site will be dismantled to the point that it no longer requires measures for radiation protection. Once a facility is decommissioned no radioactive danger persists and it can be released from regulatory control.
The complete process usually takes about 20 to 30 years. In the US, the decommissioning must be completed within 60 years of the plant ceasing operations, unless a longer time is necessary to protect public health and safety;Backgrounder on Decommissioning Nuclear Power Plants. U.S.NRC, update 17 Oct 2022 up to 50 years are for radioactive decay and 10 years to dismantle the facility.Overview of Reactor Decommissioning. NRC, 18 Oct 2017 (2.4 MB)
Steps in the decommissioning process The decommissioning process encompasses: Pre-decommissioning development of a decommissioning plan involvement of the public (in democracies) application for a decommissioning license permanent shutdown removal and disposal of nuclear fuel, coolant(s) and/or moderator Decommissioning dismantling and decontamination in the US, a License Termination Plan (LTP) has to be submitted two years prior to (the expected) termination of the plant license.Summary of License Termination Plan Submittals by Three Nuclear Power Plants. EPRI, 28 Oct 2002 restoration of the environment termination of the operating license; turn over responsibilities monitoring of the site (in case of deferred dismantling/Safstor) monitoring and maintenance of the interim storage of spent fuel final disposal of radioactive waste
Decommissioning plan
Under supervision of the IAEA, a member state first develops a decommissioning plan to demonstrate the feasibility of decommissioning and to assure that the associated costs are covered. At the final shutdown, a final decommissioning plan describes in detail how the decommissioning will take place, how the facility will be safely dismantled, ensuring radiation protection of the workers and the public, addressing environmental impacts, managing radioactive and non-radioactive materials, and termination of the regulatory authorization. In the EU, decommissioning operations are overseen by Euratom. Member states are assisted by the European Commission.
The progressive demolition of buildings and removal of radioactive material is potentially occupationally hazardous, expensive, and time-intensive, and presents environmental risks that must be addressed to ensure that radioactive materials are either transported elsewhere for storage or safely stored on site.
Disposal of nuclear waste
Radioactive waste that remains after the decommissioning is either moved to an on-site storage facility where it still is under control of the plant owner, or moved to a dry cask storage or disposal facility at another location.Storage of Spent Nuclear Fuel. U.S.NRC, update 9 Jan 2023."Decommissioned Reactor Sites – After terminating reactor operations and removing structures used in reactor operations, the licensee stores spent fuel on-site pending off-site transport to either a site-specific ISFSI that is authorized to receive the spent fuel, or a permanent geologic repository licensed for disposal." The problem of long-term disposal of nuclear waste is still unsolved. Pending the availability of geologic repository sites for long-term disposal, interim storage is necessary. As the planned Yucca Mountain nuclear waste repository – like similar sites elsewhere in the world – is controversial, on- or off-site storage in the US usually takes place in Independent Spent Fuel Storage Facilities (ISFSIs).Independent spent fuel storage installation (ISFSI). U.S.NRC, update 9 March 2021
In the UK, all eleven Magnox reactors are in decommissioning under responsibility of the NDA. The spent fuel was removed and transferred to the Sellafield site in Cumbria for reprocessing.Radiological hazard on all Magnox nuclear sites across UK set to reduce by 99%. Nuclear Decommissioning Authority, 13 Jan 2017 (archived) Facilities for "temporary" storage of nuclear waste – mainly 'Intermediate Level Waste' (ILW) – are in the UK called Interim Storage Facilities (ISFs).Nuclear Decommissioning: Chapelcross a timeline. Newsnet.scot, 10 Jan 2022
Environmental impact assessment
The decommission of a nuclear reactor can only take place after the appropriate licence has been granted pursuant to the relevant legislation. As part of the licensing procedure, various documents, reports and expert opinions have to be written and delivered to the competent authority, e.g. safety report, technical documents and an environmental impact assessment (EIA). In the European Union these documents are a precondition for granting such a licence is an opinion by the European Commission according to Article 37 of the Euratom Treaty. On the basis of such general data, the Commission must be in a position to assess the exposure of reference groups of the population in the nearest neighbouring states.
Options There are several options for decommissioning:
Immediate dismantling (DECON in the United States; ) Shortly after the permanent shutdown, the dismantling and/or decontamination of the facility begins. Equipment, structures, systems and components that contain radioactive material are removed and/or decontaminated to a level that permits the ending of regulatory control of the facility and its release, either for unrestricted use or with restrictions on its future use. The operating license is terminated.
Deferred dismantling (SAFSTOR in the United States; "care and maintenance" (C&M) in the UK) The final decommissioning is postponed for a longer period, usually 30 to 50 years. Often the non-nuclear part of the facility is dismantled and the fuel removed immediately. The radioactive part is maintained and monitored in a condition that allows the radioactivity to decay. Afterwards, the plant is dismantled and the property decontaminated to levels that permit release for unrestricted or restrict use. In the US, the decommissioning must be completed within 60 years. With deferred dismantling, costs are shifted to the future, but this entails the risk of rising expenditures for decades to come and changing rules.US utility's deferred reactor clean-up shows cost pressure on early closures. Reuters Events, 21 Sep 2016 Moreover, the site cannot be re-used until the decommissioning is finished, while there are no longer revenues from production.
Partial entombment The US has introduced the so-called In Situ Decommissioning (ISD) closures. All aboveground structures are dismantled; all remaining belowground structures are entombed by grouting all spaces. Advantages are lower decommissioning costs and safer execution. Disadvantages are main components remaining undismantled and definitively inaccessible. The site has to be monitored indefinitely.
This method was implemented at the Savannah River Site in South Carolina for the closure of the P and R Reactors. With this method, the cost of decommissioning for each reactor was about $73 million. In comparison, the decommissioning of each reactor using traditional methods would have been an estimated $250 million. This resulted in a 71% decrease in cost.SRS P and R Reactor Disassembly Basin In Situ Decommissioning. ARC-EFCOG Collaboration, 2012 Other examples are the Hallam nuclear reactor and the Experimental Breeder Reactor II.
Complete entombment The facility will not be dismantled. Instead it is entombed and maintained indefinitely, and surveillance is continued until the entombed radioactive waste is decayed to a level permitting termination of the license and unrestricted release of the property. The licensee maintains the license previously issued.ENTOMB U.S.NRC (update 9 March 2021)