Nuclear decommissioning is the process whereby a nuclear facility is dismantled to the point that it no longer requires measures for radiation protection. The presence of radioactive material necessitates processes that are potentially occupationally hazardous, expensive, time-intensive, and present environmental risks that must be addressed to ensure radioactive materials are either transported elsewhere for storage or stored on-site in a safe manner. The challenge in nuclear decommissioning is not just technical, but also economical and social.
Decommissioning is an administrative and technical process. It includes clean-up of radioactive materials and progressive demolition of the facility. Once a facility is fully decommissioned, no radiological danger should persist. The costs of decommissioning are generally spread over the lifetime of a facility and saved in a decommissioning fund. After a facility has been completely decommissioned, it is released from regulatory control and the plant licensee is no longer responsible for its nuclear safety. Decommissioning may proceed all the way to "greenfield" status.
Video Nuclear decommissioning
Definition
Nuclear decommissioning is the administrative and technical process whereby a nuclear facility such as a nuclear power plant (NPP), a research reactor, an isotope production plant, a particle accelerator, or uranium mine is dismantled to the point that it no longer requires measures for radiation protection. The progressive demolition of buildings and removal of radioactive material is potentially occupationally hazardous, expensive, time-intensive, and presents environmental risks that must be addressed to ensure radioactive materials are either transported elsewhere for storage or stored on-site in a safe manner. Decommissioning may proceed all the way to "greenfield status". Once a facility is decommissioned no radioactive danger persists and it can be released from regulatory control.
Maps Nuclear decommissioning
Options
The International Atomic Energy Agency defines three options for decommissioning:
- Immediate Dismantling (Early Site Release/Decon in the United States) allows for the facility to be removed from regulatory control relatively soon after shutdown. Final dismantling or decontamination activities begin within a few months or years, and depending on the facility, it could take five years or more. After being removed from regulatory control, the site becomes available for unrestricted use.
- Safe Enclosure (or Safestor(e) Safstor) postpones the final decommissioning for a longer period, usually 40 to 60 years. The nuclear facility is placed into a safe storage configuration during this time.
- Entombment/Entomb involves placing the facility in a condition that allows the remaining radioactive material to remain on-site indefinitely. The size of the area where the radioactive material is located is generally minimized and the facility is encased in a long-lived material such as concrete, with the aim of preventing a release of radioactive material.
Legal aspects
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 study (EIS).
In the European Union these documents are the basis for the environmental impact assessment (EIA) according to Council Directive 85/337/EEC. A precondition for granting such a licence is an opinion by the European Commission according to Article 37 of the Euratom Treaty. Article 37 obliges every Member State of the European Union to communicate certain data relating to the release of radioactive substances to the Commission. This information must reveal whether and if so what radiological impacts decommissioning - planned disposal and accidental release - will have on the environment, i.e. water, soil or airspace, of the EU Member States. On the basis of these general data, the Commission must be in a position to assess the exposure of reference groups of the population in the nearest neighbouring states.
Cost
In the United States, the NRC recommends that the costs of decommissioning should be spread over the lifetime of a facility and saved in a decommissioning fund. Repository delay seems to be effective in reducing NPP decommissioning costs.
In France, decommissioning of Brennilis Nuclear Power Plant, a fairly small 70 MW power plant, already cost EUR480 million (20x the estimate costs) and is still pending after 20 years. Despite the huge investments in securing the dismantlement, radioactive elements such as plutonium, caesium-137 and cobalt-60 leaked out into the surrounding lake.
In the UK, decommissioning of the Windscale Advanced gas cooled reactor (WAGR), a 32 MW prototype power plant, cost EUR117 million. A 2013 estimate by the United Kingdom's Nuclear Decommissioning Authority predicted costs of at least £100 billion to decommission the 19 existing United Kingdom nuclear sites.
In Germany, decommissioning of Niederaichbach nuclear power plant, a 100 MW power plant, amounted to more than EUR143 million.
New methods for decommissioning have been developed in order to minimize the usual high decommissioning costs. One of these methods is in situ decommissioning (ISD), meaning that the reactor is entombed instead of dismantled. This method was implemented at the U.S. Department of Energy Savannah River Site in South Carolina for the closures of the P and R Reactors. With this tactic, the cost of decommissioning both reactors was $73 million. In comparison, the decommissioning of each reactor using traditional methods would have been an estimated $250 million. This results in a 71% decrease in cost by using ISD.
In 2004, in a meeting in Vienna, the International Atomic Energy Agency estimated the total cost for the decommissioning of all nuclear facilities. Decommissioning of all nuclear power reactors in the world would require US$187 billion; US$71 billion for fuel cycle facilities; less than US$7 billion for all research reactors; and US$640 billion for dismantling all military reactors for the production of weapons-grade plutonium, research fuel facilities, nuclear reprocessing chemical separation facilities, etc. The total cost to decommission the nuclear fission industry in the World (from 2001 to 2050) was estimated at around US$1 trillion.
Decommissioning funds
In Europe there is considerable concern over the funds necessary to finance final decommissioning. In many countries either the funds do not appear sufficient to cover decommissioning and in other countries decommissioning funds are used for other activities, putting decommissioning at risk, and distorting competition with parties who do not have such funds available.
In 2016 the European Commission assessed that European Union's nuclear decommissioning liabilities were seriously underfunded by about 118 billion euros, with only 150 billion euros of earmarked assets to cover 268 billion euros of expected decommissioning costs covering both dismantling of nuclear plants and storage of radioactive parts and waste. France had the largest shortfall with only 23 billion euros of earmarked assets to cover 74 billion euros of expected costs.
Similar concerns exist in the United States, where the U.S. Nuclear Regulatory Commission has located apparent decommissioning funding assurance shortfalls and requested 18 power plants to address that issue. The decommissioning cost of Small modular reactors is expected to be twice as much respect to Large Reactors.
International collaboration
Organizations that promote the international sharing of information, knowledge, and experiences related to nuclear decommissioning include the International Atomic Energy Agency, the Organization for Economic Co-operation and Development's Nuclear Energy Agency and the European Atomic Energy Community. In addition, an online system called the Deactivation and Decommissioning Knowledge Management Information Tool was developed under the United States Department of Energy and made available to the international community to support the exchange of ideas and information. The goals of international collaboration in nuclear decommissioning are to reduce decommissioning costs and improve worker safety.
Experience
A wide range of nuclear facilities have been decommissioned so far. The number of decommissioned nuclear reactors out of the List of nuclear reactors is small. As of 2016, 150 nuclear reactors were shut-off, in several early and intermediate stages (cold shut-down, defueling, SAFSTOR, internal demolition), but only 17 have been taken to fully "greenfield status". Some of these sites still host spent nuclear fuel in the form of dry casks embedded in concrete filled steel drums.
Several nuclear engineering and building demolition companies specialize in nuclear decommissioning, which has become a profitable business. More recently, construction and demolition companies in the UK have also begun to develop nuclear decommissioning services. Due to the radioactivity in the reactor structure (specially with high neutron-flux), decommissioning takes place in stages. Plans for decommissioning reactors have a time frame of decades. The long time frame makes reliable cost estimates difficult and cost overruns are common even for "quick" projects.
As of 2017, most nuclear plants operating in the United States were designed for a life of about 30-40 years and are licensed to operate for 40 years by the US Nuclear Regulatory Commission. The average age of these reactors is 32 years. Many plants are coming to the end of their licensing period and if their licenses are not renewed, they must go through a decontamination and decommissioning process.
Ships, mobile reactors, military reactors
Many warships and a few civil ships have used nuclear reactors for propulsion. Former Soviet and American warships have been taken out of service and their power plants removed or scuttled. Dismantling of Russian submarines and ships and American submarines and ships is ongoing. Marine power plants are generally smaller than land-based electrical generating stations.
The biggest American military nuclear facility for the production of weapons-grade plutonium was Hanford site (in the State of Washington), now defueled, but in a slow and problematic process of decontamination, decommissioning, and demolition. There is "the canyon" a giant structure for the chemical extraction of plutonium with the PUREX process. There are also many big containers and underground tanks with a solution of water, hydrocarbons and uranium-plutonium-neptunium-cesium-strontium (all highly radioactive). With all reactors now defueled, some were put in SAFSTOR (with their cooling towers demolished). Several reactors have been declared National Historic Landmarks.
See also
- Lists of nuclear disasters and radioactive incidents
- Nuclear Decommissioning Authority
- Ship-Submarine recycling program
- Nuclear entombment
- Marcoule (French nuclear site)
- D&D KM-IT (Deactivation and Decommissioning Knowledge Management Information Tool)
References
External links
- NUCLEAR ENERGY AGENCY of the Organisation for Economic Co-operation & Development: Cost of Decommissioning Nuclear Energy Plants (2016)
- UNITED STATES NUCLEAR REGULATORY COMMISSION: Backgrounder on Decommissioning Nuclear Power Plants
- Business Insider - UK: Getting Rid Of Old Nuclear Reactors Worldwide Is Going To Cost Way More Than People Think
- Germany's economy minister Sigmar Gabriel says state won't pay for nuclear decommissioning (May 18, 2014)
- Nuclear Decommissioning Report (www.ndreport.com) is the multi-media platform for the nuclear decommissioning industry.
- decommissioning.info is a portal with information on nuclear decommissioning
- US Nuclear Regulatory Commission
- European website on decommissioning of nuclear installations
- Decommissioning Fund Methodologies for Nuclear Installations in the EU, rapport by the German Wuppertal Institute, commissioned by the European Commission. May 2007.
- Master 'Nuclear Energy' - Decommissioning and Waste management
Source of the article : Wikipedia
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