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.
- — From Wikipedia's article on Nuclear Decommissioning
Some of the expense of decommissioning is due to excessively stringent regulations applied to the nuclear industry but not to other industries producing radioactive waste materials. For example
... scrap steel from gas plants may be recycled if it has less than 500,000 Bq/kg (0.5 MBq/kg) radioactivity (the exemption level). This level however is one thousand times higher than the clearance level for recycled material (both steel and concrete) from the nuclear industry! Anything above 500 Bq/kg may not be cleared from regulatory control for recycling. Current IAEA Basic Safety Standards (BSS) clearance levels specify 1 Bq/g for natural radionuclides in the U-238 series in secular equilibrium with progeny, and the same for those in the Th-232 series. IAEA BSS clearance levels for bulk amounts being recycled are: Fe-55 1 MBq/kg, Co-60m 1 MBq/kg, Ni-63 100 kBq/kg, C-14 1 kBq/kg, Cs-137 0.1 kBq/kg, Ra-226 1 kBq/kg.
Decommissioning experts are increasingly concerned about double standards developing in Europe which allow 30 times the dose rate from non-nuclear recycled materials than from those out of the nuclear industry. In respect to actual dose limits, 0.3 to 1.0 mSv/yr individual dose constraint is applied to oil and gas recyclables, and 0.01 mSv/yr for release of materials with the same kind of radiation from the nuclear industry.
The concern arises because of the very large amounts of NORM needing recycling or disposal from many sources. The largest NORM waste stream is coal ash, with 280 million tonnes arising globally each year, and carrying U-238 and all its non-gaseous decay products, as well as Th-232 and its progeny. This is usually just buried. However, the double standard means that the same radionuclide, at the same concentration, can either be sent to deep disposal or released for use in building materials, depending on where it comes from. The 0.3 mSv/yr dose limit is still only one tenth of most natural background levels, and two orders of magnitude lower than those experienced naturally by many people, who suffer no apparent ill effects.
The main radionuclide in scrap from the oil and gas industry is radium-226, with a half-life of 1600 years as it decays to radon. Those in nuclear industry scrap are cobalt-60 and caesium-137, with much shorter half-lives. Application of a 0.3 mSv/yr dose limit results in a clearance level for Ra-226 of 500 Bq/kg for oil/gas scrap, compared with 10 Bq/kg for nuclear material.
In the UK decommissioning is the responsibility of the Nuclear Decommissioning Authority (Wikipedia):
The Nuclear Decommissioning Authority (NDA) is a non-departmental public body of the British Department of Energy and Climate Change, formed by the Energy Act 2004. It evolved from the Coal and Nuclear Liabilities Unit of the Department of Trade and Industry. It came into existence during late 2004, and took on its main functions on 1 April 2005. Its purpose is to deliver the decommissioning and clean-up of the UK’s civil nuclear legacy in a safe and cost-effective manner, and where possible to accelerate programmes of work that reduce hazard. The NDA does not directly manage the UK's nuclear sites. It oversees the work through contracts with specially designed companies known as site licence companies. The NDA determines the overall strategy and priorities for managing decommissioning. Although the NDA itself only employs 300 staff, its annual budget is £3.2 billion. The vast majority of the NDA budget is spent through contracts with site licence companies, who also sub contract to other companies which provide special services. The NDA aims to do this by introducing innovation and contractor expertise through a series of competitions similar to the model that has been used in the United States.
The UK government's gateway web page carries a link to the NDA's latest report: Nuclear Provision: the cost of cleaning up Britain’s historic nuclear sites Updated 4 July 2019
What is the “Nuclear Provision”?
The Nuclear Provision is the best estimate of how much it will cost to clean up 17 of the UK’s earliest nuclear sites over a programme lasting around 120 years.
The estimate is based on the expected costs of:
- dismantling and demolishing the buildings
- managing and disposing of all waste
- remediation of land
The Nuclear Provision also includes the costs of running more modern plants that are still operational, in particular Sellafield’s reprocessing facilities.
Decommissioning many of these facilities will continue well into the 22nd century. Over this timescale, plans and forecasts will be affected by technology improvements, changes in government policy, economic circumstances and environmental issues.
The figure is updated annually but should be regarded as an informed estimate that depends on assumptions about future developments and lies within a range of possible figures.
See also UK's nuclear clean-up cost estimate dips to $154 billion World Nuclear News; 15 Jul 2016
According to a 2017 post on the Nukes Pretty Please blog:
In UK, all the DECC decommissioning costs (to UK government) are for weapons sites (including submarines) and shut Magnox reactors (which are now all shut). Costs of decommissioning other power reactors: PWR and AGR, is solely the responsibility of the owners. EDF own all remaining power reactors. EDF have a fund growing annually for this mandated by UK government. It's a kind of tax. ~ 5% of their revenue. This is how decommissioning is handled in all Western democracies I know of.
Magnox spent fuel is all being reprocessed to remove plutonium. UK has a PUREX plant called THORP to do this. This extracts plutonium from spent fuel. That plutonium is not quite weapons grade but could provide very useful fuel for fast reactors. Alternatively - if anti-nukes have their way this plutonium will have to be disposed of too so that is cannot be used to make even substandard nuclear weapons. Only Magnox reactors will bear this extra reprocessing cost because Magnox reactors were special. The design was dual purpose. The spent fuel can be used to make nuclear weapons. Magnox are also far more expensive to decommission than PWRs because decommissioning was not considered in advance of their design.
Footnotes and references
- Naturally-Occurring Radioactive Materials (NORM) World Nuclear Association; Updated April 2020