Decommissioning Nuclear Facilities

(Updated June 2013)

• To date, about 100 mines, 102 commercial power reactors, 46 experimental or prototype reactors, over 250 research reactors and a number of fuel cycle facilities, have been retired from operation. Some of these have been fully dismantled.
• Most parts of a nuclear power plant do not become radioactive, or are contaminated at only very low levels. Most of the metal can be recycled.
• Proven techniques and equipment are available to dismantle nuclear facilities safely and these have now been well demonstrated in several parts of the world.
• Decommissioning costs for nuclear power plants, including disposal of associated wastes, are reducing and contribute only a small fraction of the total cost of electricity generation.

All power plants, coal, gas and nuclear, have a finite life beyond which it is not economically feasible to operate them. Generally speaking, early nuclear plants were designed for a life of about 30 years, though some have proved capable of continuing well beyond this. Newer plants are designed for a 40 to 60 year operating life. At the end of the life of any power plant, it needs to be decommissioned, decontaminated and demolished so that the site is made available for other uses. For nuclear plants, the term decommissioning includes all clean-up of radioactivity and progressive dismantling of the plant.

At the end of 2005, IAEA reported that eight power plants had been completely decommissioned and dismantled, with the sites released for unconditional use. A further 17 had been partly dismantled and safely enclosed, 31 were being dismantled prior to eventual site release and 30 were undergoing minimum dismantling prior to long-term enclosure.

Decommissioning Options

The International Atomic Energy Agency has defined three options for decommissioning, the definitions of which have been internationally adopted:

• Immediate Dismantling (or Early Site Release/'Decon' in the US): This option allows for the facility to be removed from regulatory control relatively soon after shutdown or termination of regulated activities. Usually, the final dismantling or decontamination activities begin within a few months or years, depending on the facility. Following removal from regulatory control, the site is then available for re-use.
• Safe Enclosure (or 'Safestor'): This option postpones the final removal of controls for a longer period, usually in the order of 40 to 60 years. The facility is placed into a safe storage configuration until the eventual dismantling and decontamination activities occur.
• Entombment (or 'Entomb'): This option entails placing the facility into a condition that will allow the remaining on-site radioactive material to remain on-site without the requirement of ever removing it totally. This option usually involves reducing the size of the area where the radioactive material is located and then encasing the facility in a long-lived structure such as concrete, that will last for a period of time to ensure the remaining radioactivity is no longer of concern.

There is no right or wrong approach, each having its benefits and disadvantages. National policy determines which approach is adopted. In the case of immediate dismantling (or early site release), responsibility for the decommissioning is not transferred to future generations. The experience and skills of operating staff can also be utilised during the decommissioning program. Alternatively, Safe Enclosure (or Safestor) allows significant reduction in residual radioactivity, thus reducing radiation hazard during the eventual dismantling. The expected improvements in mechanical techniques should also lead to a reduction in the hazard and also costs.

In the case of nuclear reactors, about 99% of the radioactivity is associated with the fuel which is removed following permanent shutdown. Apart from any surface contamination of plant, the remaining radioactivity comes from "activation products" such as steel components that have long been exposed to neutron irradiation. Their atoms are changed into different isotopes such as iron-55, iron, 59 and zinc-65. Several are highly radioactive, emitting gamma rays. However, their half life is such (2.7 years, 45 days, 5.3 years, 245 days respectively) after 50 years from closedown their radioactivity is much diminished and the risk to workers largely gone.

Decommissioning Experience

Over the past 40 years considerable experience has been gained in decommissioning various types of nuclear facilities. About 85 commercial power reactors, 45 experimental or prototype power reactors, as well as over 250 research reactors and a number of fuel cycle facilities, have been retired from operation. Of these, about 15 had been fully dismantled, about 51 were being dismantled, 48 were in Safestor, 3 were entombed, and for others the decommissioning strategy was not yet specified.

European reactors

To decommission its retired gas-cooled reactors at the Chinon, Bugey and St Laurent nuclear power stations, Electricité de France chose partial dismantling and postponed final dismantling and demolition for 50 years. As other reactors will continue to operate at those sites, monitoring and surveillance do not add to the cost.

A recycling plant for steel from dismantled nuclear facilities is being built at Marcoule, in France. This metal will contain some activation products, but it can be recycled for other nuclear plants.

Decommissioning has begun at 25 UK reactors. One of the first was Berkeley nuclear power station (2 x 138 MWe, Magnox reactors), closed for economic reasons in 1989 after 27 years of operation, where defuelling was completed in 1992. The cooling ponds were then drained, cleaned and filled in and the turbine hall was dismantled and demolished. The reactor buildings are in an extended Safestor period. Ultimately they too will be dismantled, leaving the site to be leveled and landscaped. The same pattern is being followed at other UK reactor sites.

Spain's Vandellos-1, a 480 MWe gas-graphite reactor, was closed down in 1990 after 18 years operation, due to a turbine fire which made the plant uneconomic to repair. In 2003 ENRESA concluded phase 2 of the reactor decommissioning and dismantling project, which allows much of the site to be released. After 30 years Safestor, when activity levels have diminished by 95%, the remainder of the plant will be removed. The cost of the 63-month project was EUR 93 million.

Germany chose immediate dismantling over safe enclosure for the closed Greifswald nuclear power station in the former East Germany, where five reactors had been operating. Similarly, the site of the 100 MWe Niederaichbach nuclear power plant in Bavaria was declared fit for unrestricted agricultural use in mid-1995. Following removal of all nuclear systems, the radiation shield and some activated materials, the remainder of the plant was below accepted limits for radioactivity and the state government approved final demolition and clearance of the site.

The 250 MWe Gundremmingen-A unit was Germany's first commercial nuclear reactor, operating 1966-77. Decommissioning work started in 1983, and moved to the more contaminated parts in 1990, using underwater cutting techniques. This project demonstrated that decommissioning could be undertaken safely and economically without long delays, and recycling most of the metal.

Japan's Tokai-1 reactor, a 160 MWe UK Magnox design, is being decommissioned after 32 years service to 1998.  After 5-10 years storage, the unit will be dismantled and the site released for other uses about 2018.  The total cost will be JPY 93 billion (USD 1.04 billion) - 35 billion for dismantling and 58 billion for waste treatment which will include the graphite moderator (which escalates the cost significantly).

US reactors

Experience in the USA has varied, but at least 14 power reactors are using the Safestor approach, while 10 are using, or have used, Decon. Procedures are set by the Nuclear Regulatory Commission (NRC), and considerable experience has now been gained. A total of 31 power reactors have been closed and decommissioned. NRC requires that the operating license of a closed reactor be terminated and decommissioning activities be completed within 60 years. Site release often excludes the on-site used fuel storage in an ISFSI (independent spent fuel storage installation), which usually remains, to await the Department of Energy taking away the used fuel (over which it has title) to a national repository sometime in the future.

Rancho Seco (single 913 MWe, PWR) was closed in 1989, and in 1995 NRC approved a Safestor plan for it. However, the utility subsequently decided upon incremental dismantling and this was completed in 2009, leaving about 3 ha still under NRC licence for waste storage. About 32 ha has been released for unrestricted use.

At multi-unit nuclear power stations, the choice has been to place the first closed unit into storage until the others end their operating lives, so that all can be decommissioned in sequence. This will optimise the use of staff and the specialised equipment required for cutting and remote operations, and achieve cost benefits.

Thus, after 14 years of comprehensive clean-up activities, including the removal of fuel, debris and water from the 1979 accident, Three Mile Island 2 was placed in Post-Defuelling Monitored Storage (Safestor) until 2014, when the operating licence of Unit 1 was originally expected to expire, so that both units could be decommissioned together.

San Onofre 1, which closed in 1992, was put into Safestor until licences for Units 2 and 3 expired in 2022-23.  However, after NRC changes, dismantling was brought forward to 1999, so it became an active Decon project which was largely completed in 2008. A small amount of work remains to be completed with eventual decommissioning of units 2 & 3 on the site, which were shut down in May 2013. The cost of fully decommissioning them is estimated at $4 billion.

A US Decon project was the 60 MWe Shippingport reactor, which operated commercially from 1957 to 1982. It was used to demonstrate the safe and cost-effective dismantling of a commercial scale nuclear power plant and the early release of the site. Defuelling was completed in two years, and five years later the site was released for use without any restrictions. Because of its size, the pressure vessel could be removed and disposed of intact. For larger units, such components have to be cut up.

Immediate Decon also the option chosen for Fort St Vrain, a 330 MWe high temperature gas-cooled reactor which was closed in 1989. This took place on a fixed-price contract for US$ 195 million (hence costing less than 1 cent/kWh despite only a 16-year operating life) and the project proceeded on schedule to clear the site and relinquish its licence early in 1997 - the first large US power reactor to achieve this. 

Shoreham BWR, on Long Island, generated very little power and never received a full operating licence. It was shut down in 1989 and became a Decon project, completed in 1994. The 59 MWe Pathfinder prototype BWR in South Dakota, shut down in 1967 after a very short life was also a Decon project, completed in 1992.  Haddam Neck 560 MWe PWR in Connecticut, closed in 1996 after 29 years operation, was a further Decon project, completed in 2007.

For Trojan (1180 MWe, PWR) in Oregon the dismantling was undertaken by the utility itself. The plant closed in 1993, steam generators were removed, transported and disposed of at Hanford in 1995, and the reactor vessel (with internals) was removed and transported to Hanford in 1999. Except for the used fuel storage, the site was released for unrestricted use in 2005. The cooling tower was demolished in 2006.

Yankee Rowe (167 MWe, PWR) was shut down in 1991 after 30 years service. It was a Decon project and demolition was completed in 2006. Licence termination was in August 2007, allowing unrestricted public access, except for 2 ha for used fuel storage.

Another US Decon project was Maine Yankee, a 860 MWe PWR plant which closed down in 1996 after 24 years operation. The containment structure was finally demolished in 2004 and except for 5 ha with the dry store for used fuel, the site was released for unrestricted public use in 2005, on budget and on schedule.

Connecticut Yankee (590 MWe PWR) also shut down in 1996 after 28 years operation.  Decommissioning work began in 1998 and demolition was concluded in 2006. The site was released for unrestricted public use in 2007, apart from 2 ha for dry cask used fuel storage.  Residual contamination on the land is below NRC's limit of 0.25 millisievert per year for maximum radiation dose.

In 2005 the site of the small Saxton reactor which closed in 1972 was ready to be released for unrestricted use. It had been placed into Safstor in 1975 and the fuel shipped off site. Demolition began in 1986.

In 2006 the site of 72 MWe Big Rock Point nuclear power plant in Michigan, shut down in 1997 after 35 years operation, was largely returned to greenfield status. In January 2007 most of the land was released for derestricted public use, though 43 hectares still has the dry cask storage facility where used fuel is stored pending transfer to the national repository.

With Exelon's Zion 1 & 2 reactors (2 x 1098 MWe) closed down in 1998 and in Safstor, a slightly different process is envisaged, considerably accelerating the decommissioning.  Exelon has contracted with a specialist company - EnergySolutions, to remove the plant and return the site to greenfield status. To achieve this, the plant's licence and decommissioning funds will be transferred to EnergySolutions, which will then be owner and licensee, and the site will be returned to Exelon about 2018. Used fuel would remain on site until taken to the national repository.

In summary, US plants with Decon completed are: Big Rock Point, Elk River, Fort St Vrain, Haddam Neck, Maine Yankee, Pathfinder, Rancho Seco, Saxton, Shippingport, Shoreham, Trojan and Yankee Rowe. (Also Santa Susana Sodium Reactor Experimental which is not included in Tables.) Decon is in progress at Fermi 1, Humboldt Bay 3.

US plants in Safstor include Dresden 1, Indian Point 1, LaCrosse, Millstone 1, Peach Bottom 1, Zion 1&2, and San Onofre 1, as well as NS Savannah. Three Mile Island 2 is in post-defueling monitored storage.  San Onofre 2 & 3 will also enter Safstor when defuelled.

The only US plants subject to the Entomb option are small experimental ones: Bonus BWR in Puerto Rico, Piqua organic-moderated reactor in Ohio, and Hallam graphite-moderated sodium-cooled reactor in Nebraska.

In addition to the above is the first floating nuclear power plant, installed in a former liberty ship, and utilised at Panama 1967-76. The Sturgis had a 45 MWt/ 10 MWe (net) PWR which provided power to the Canal Zone. After it was defuelled in 1977, some 89 m³ of solid radioactive waste and 363 m³ of liquid waste was removed and the vessel placed in safstor at Fort Belvoir, Virginia until 2027.

Further information on decommissioning in USA is available from the Nuclear Energy Institute.

Graphite

A number of first-generation reactors had graphite blocks as moderator. This is high-quality reactor-grade material produced at about 3000°C which accumulates some radionuclide contamination while in service, particularly carbon-14 at levels which often means that it must be classified as intermediate-level waste. While it oxidizes slightly under neutron bombardment and also at high temperatures (to CO), it does not burn, but sublimes at 3652°C. There is no risk of oxidation under Safestor conditions.

A 2006 report commissioned by EPRI states: " The graphite moderators of retired gas-cooled nuclear reactors present a difficult challenge during demolition activities. As a result, utilities have not dismantled any moderators of CO2 cooled power reactors to date." However, it concludes that adequate information exists to enable the safe dismantling and processing of graphite moderators, and that the three main options for disposal of this graphite are oxidation to the gas phase and release as carbon dioxide (difficult), direct burial, or recycling into new products for the nuclear industry. In each case, opportunities exist for pre-processing to concentrate or remove radionuclides to enhance the safety of the chosen option. The radionuclide inventory of irradiated graphite is unusual in comparison with other nuclear wastes. Cobalt-60 and tritium are the principal isotopes of short-term importance, carbon-14 and chlorine-36 are dominant in the longer term.

Other facilities

The French Atomic Energy Commission is decommissioning the UP1 reprocessing plant at Marcoule. This plant started up in 1958 and treated 18,600 tonnes of metal fuels from gas-cooled reactors (both defence and civil) to 1997. Progressive decontamination and dismantling of the plant and waste treatment will span 40 years and cost some EUR 5.6 billion, nearly half of this for treatment of the wastes stored on the site.

Areva will decommission the Eurodif enrichment plant at Marcoule from the end of 2012. This will involve over 2012-15 the decontamination with ClF3 gas to remove the residual uranium left inside, and extract it as UF₆, then recovery of all produced chloride and fluoride gas before the opening of equipments and circuits. Then over 2016-25 the plant will be dismantled.

Many nuclear submarines have been decommissioned over the last decade. In USA, after defuelling, the reactor compartments are cut out of the vessels and are transported inland to Hanford, where they are buried as low-level waste.

Cost and Finance

In most countries the operator or owner is responsible for the decommissioning costs.

The total cost of decommissioning is dependent on the sequence and timing of the various stages of the program. Deferment of a stage tends to reduce its cost, due to decreasing radioactivity, but this may be offset by increased storage and surveillance costs.

Even allowing for uncertainties in cost estimates and applicable discount rates, decommissioning contributes a small fraction of total electricity generation costs. In USA many utilities have revised their cost projections downwards in the light of experience.

Financing methods vary from country to country. Among the most common are:
Prepayment, where money is deposited in a separate account to cover decommissioning costs even before the plant begins operation. This may be done in a number of ways but the funds cannot be withdrawn other than for decommissioning purposes.
External sinking fund (Nuclear Power Levy): This is built up over the years from a percentage of the electricity rates charged to consumers. Proceeds are placed in a trust fund outside the utility's control. This is the main US system, where sufficient funds are set aside during the reactor's operatinig lifetime to cover the cost of decommissioning.
Surety fund, letter of credit, or insurance purchased by the utility to guarantee that decommissioning costs will be covered even if the utility defaults.

In USA, utilities are collecting 0.1 to 0.2 cents/kWh to fund decommissioning. They must then report regularly to the NRC on the status of their decommissioning funds. About two thirds of the total estimated cost of decommissioning all US nuclear power reactors has already been collected, leaving a liability of about $9 billion to be covered over the remaining operating lives of 104 reactors (on basis of average $320 million per unit).

An OECD survey published in 2003 reported US dollar (2001) costs by reactor type. For western PWRs, most were $200-500/kWe, for VVERs costs were around $330/kWe, for BWRs $300-550/kWe, for CANDU $270-430/kWe. For gas-cooled reactors the costs were much higher due to the greater amount of radioactive materials involved, reaching $2600/kWe for some UK Magnox reactors.

Constraints on recycling

 Recycling materials from decommissioned nuclear facilities is constrained by the level of radioactivity in them. This is also true for materials from elsewhere, such as gas plants, but the levels specified can be very different. 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, where anything above 500 Bq/kg may not be cleared from regulatory control for recycling.

There is increasing 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. Norway and Holland are the only countries with consistent standards. Elsewhere, 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 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, compared with 10 Bq/kg for nuclear material.

In 2011, 16 decommissioned steam generators from Bruce Power in Canada were to be shipped to Sweden for recycling. Although the Canadian Nuclear Safety Commission (CNSC) approved Bruce Power’s plans in 2011 and confirmed steam generator processing is an excellent example of responsible and safe nuclear waste management practices, this caused public controversy at the time, and following the Fukushima nuclear accident plans for this shipment were shelved. These steam generators were each 12m long and 2.5m diameter, with mass 100 t, and contained some 4g of radionuclides with about 340 GBq of activity. Exposure was 0.08 mSv/hr at one metre. They were classified as low-level waste (LLW). Studsvik in Sweden would recycle much of the metal and return about 10% of the overall volume as LLW for disposal in Ontario. The balance would be under 100 Bq/kg, which appeared to be the clearance level.

In 2012 five steam generators from UK plants were shipped to Studsvik in Sweden for recycling. Studsvik has also set up a plant in the UK, at Lillyhall in Cumbria, to recycle materials from nuclear facilities, and this became fully operational in 2013 after processing 2000 t of metal from numerous sites and recycling 96% of it. The balance went to a LLW repository.

International Cooperation

The IAEA, the OECD's Nuclear Energy Agency and the Commission of the European Communities are among a number of organisations through which experience and knowledge about decommissioning is shared among technical communities in various countries.

In 1985, the OECD Nuclear Energy Agency launched an International Co-operative Program for the Exchange of Scientific and Technical Information Concerning Nuclear Installation Decommissioning Projects. This international collaboration, covering 15 reactors and six fuel-cycle facilities, has produced a great deal of technical and financial information.

The important areas where experience is being gained and shared are the assessment of the radioactive inventories, decontamination methods, cutting techniques, remote operation, radioactive waste management and health and safety. The aims are to minimise the radiological hazards to workers and to optimise the dismantling sequence and timing to reduce the total decommissioning cost.

Reasons for shutdown

Most decommissioned reactors were shut down because there was no longer any economic justification for running them. Practically all are relatively early-model designs, and about 45 are experimental or prototype power reactors. Three categories are listed here:
1. Experimental, early commercial types and commercial unit whose continued operation was no longer justified, usually for economic reasons. Most of these started up before 1980 and their short life is not surprising for the first couple of decades of a major new technology. At least 41 of this 101 (* asterisked) ran relatively full-term, for a design life of 25-35 years or so (design lives today are 40-60 years). Total 102.
2. Units which closed following an accident or serious incident (not necessarily to the reactor itself) which meant that repair was not economically justified. Total 11.
3. Units which were closed prematurely by political decision or due to regulatory impediment without clear or significant economic or technical justification. Total 25, 17 of these being early Soviet designs.
In fact the distinctions are not always sharp, eg Chernobyl 2 was closed in 1991 after a turbine fire when it would have been politically impossible to repair and restart it, Rheinsberg was closed in 1990 though it was nearly at the end of its design life - both these are in the 'political decision' category.

Note that the eight German reactors shut down in 2011 and the two San Onofre units shut down in 2013 are not yet listed here.

Reactors closed following an accident or serious incident (11)

Reactors closed prematurely by political decision (25)

Reactors closed having fulfilled their purpose or being no longer economic to run (102+1)  

- prot= prototype, exp= experimental, * = ran approx full-term

The last, Sturgis FNPP, is the "+1" in top total

Main Sources & References:
''Nuclear Decommissioning", IMechE Conference transaction 1995 -7.
OECD/NEA 1992, Decommissioning Policies for Nuclear Facilities.
OECD/NEA 1992, International Co-operation on Decommissioning.
IAEA Bulletin 42/3/2000, "Preparing for the End of the Line - Radioactive Residues from Nuclear Decommissioning"
OECD/NEA 2003, Decommissioning Nuclear Power Plants - policies, strategies and costs.
OECD/NEA 2006, Decommissioning Funding: Ethics, Implementation, Uncertainties.
Nuclear Energy Institute 2002, Decommissioning of Nuclear Power Plants, factsheet.
Doubleday, EC, 2007, A Decommissioning Wrapup, Radwate Solutions March-April 2007.
IAEA PRIS
Graphite Decommissioning: Options for Graphite Treatment, Recycling, or Disposal, including a discussion of Safety-Related Issues, EPRI, Palo Alto, CA, 1013091 (March 2006)