Decommissioning nuclear facilities

Published: December 30, 2009, 6:20 am

Topics:

Nuclear Energy (main)

This EOE article is adapted from an information paper published by the World Nuclear Association (WNA). WNA information papers are frequently updated, so for greater detail or more up to date numbers, please see the latest version on WNA website (link at end of article).

Introduction

All power plants – coal (Decommissioning nuclear facilities) , gas and nuclear – have a finite life beyond which they are not economically feasible to operate. 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 is necessary to decommission and demolish the facility so that the site can be 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, the International Atomic Energy Agency (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: 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 the radiation hazard during the eventual dismantling. Expected improvements in mechanical techniques should also lead to a reduction in the hazards and costs of decommissioning operations.

In the case of nuclear reactors, about 99% of the radioactivity is associated with the fuel removed following permanent shutdown. Apart from any surface contamination of the 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, cobalt-60, nickel-63, and carbon-14. The first two are highly radioactive, emitting gamma rays. However, their half life is such that after 50 years after closedown, their radioactivity is significantly diminished and the risk to workers largely gone.

Decommissioning Experience

Over the past 35 years, considerable experience has been gained in decommissioning various types of nuclear facilities. Through September 2001, almost 100 commercial power reactors, as well as over 250 research reactors and a number of fuel cycle facilities, had been retired from operation.

France
To decommission its retired gas-cooled reactors at the Chinon, Bugey, and St Laurent nuclear power stations, Electricite 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.

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

The French Atomic Energy Commission (CEA) 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 defense 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 which will be spent on treatment of the wastes stored at the site.

United Kingdom
Decommissioning has begun at ten UK reactors. For instance, the Berkeley nuclear power station (2 x 138 MWe, Magnox reactors) closed for economic reasons in 1989 after 27 years of operation and defuelling was completed in 1992. The plant is currently being prepared for an extended period of Care and Maintenance, scheduled to start around 2006.

Spain
Spain's Vandellos-1, a 480 MWe gas-graphite reactor, was closed down in 1990 after 18 years of 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 in 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.

Japan
Japan's Tokai-1 reactor, a UK Magnox design, is being decommissioned after 30 years of service, ending in 1998. After 5-10 years storage, the unit will be dismantled and the site released for other uses. Total cost is expected to be about 25 billion Yen.

Germany
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 from 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 recycled most of the metal.

Yankee Rowe nuclear power plant in Connecticut before decommissioning.

Yankee Rowe nuclear power plant in Connecticut after decommissioning.

United States
Experience in the US has varied; 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).

The Rancho Seco nuclear plant (913 MWe, PWR), located in Sacramento, California, was closed in 1989 and will be in Safestor until 2008, when funds will be available for dismantling.

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 the operating licence of Unit 1 expires in 2014 so that both units can be decommissioned together. Safestor was also being used for San Onofre 1, which closed in 1992, until licenses for Units 2 and 3 expire in 2013, but after NRC changes, dismantling was brought forward to 1999 and it became a Decon project.

An example of a US Decon project was the 60 MWe reactor at Shippingport, Pennsylvania that 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 will have to be broken down prior to disposal.

Immediate Decon was also the option chosen for the facility at Fort St Vrain, Colorado, a 330 MWe high-temperature, gas-cooled reactor which 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.

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 the Hanford Site in Washington in 1995, and the reactor vessel was removed and transported to Hanford in 1999. Except for the used fuel storage area, the site was released for unrestricted use in 2005.

Another US Decon project was carried out at Maine Yankee, an 860 MWe plant that closed down in 1996 after 24 years of operation. The containment structure was finally demolished in 2004 and, except for 5 hectares of land used for the dry storage of used fuel, the site was released for unrestricted public use in 2005, on schedule and within budget.

In 2005, the site of the small reactor at Saxton, Pennsylvania, which closed in 1972, was ready to be released for unrestricted use.

Many nuclear submarines have been decommissioned over the last decade. In the US, 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.

Costs 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 the US, many utilities have lowered their cost projections in the light of experience, and estimates now average $325 million per reactor for total decommissioning (1998 $).

Financing methods vary from country to country. Among the most common are:

Prepayment, where money is deposited into 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 the US, 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. As of 2001, $23.7 billion of the total estimated cost of decommissioning all US nuclear power plants had been collected, leaving a liability of about $11.6 billion to be covered over the operating lives of 104 reactors (on the basis of average $320 million per unit).

A survey published by the Organisation for Economic Co-operation and Development (OECD) in 2003 reported decommissioning costs by reactor type (in 2001 US$). For western pressurized water reactors (PWRs), most were $200-500/kWe; for Russian water-cooled, water-moderated energy reactor (VVERs), costs were around $330/kWe; for boiling water reactors (BWRs), $300-550/kWe; and for Canadian-designed pressurized heavy water reactors (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.

Further Reading

• WNA paper onDecommissioning nuclear facilities
• The Decommissioning and Dismantling of Nuclear Facilities in OECD/NEA Member Countries, The Nuclear Energy Agency (NEA) /Organisation for Economic Co-operation and Development (OECD).
• Factsheet: Decommissioning of Nuclear Power Plants, Nuclear Energy Institute 2002
• “Preparing for the End of the Line – Radioactive Residues from Nuclear Decommissioning”, IAEA Bulletin 2000
• World Nuclear Association Decommissioning Website and Database
• Nuclear Energy Institute
• U.S. Nuclear Regulatory Commission

Citation

Hore-Lacy, I., & Association, W. (2009). Decommissioning nuclear facilities. Retrieved from http://editors.eol.org/eoearth/wiki/Decommissioning_nuclear_facilities