Decommissioning Strategy

Gundremmingen Nuclear Power Plant is among the well-known examples of immediate dismantling following an early shutdown caused by a serious operational accident.

After the permanent shutdown of a nuclear facility, the operator must decide how the decommissioning process will be implemented. This decision is referred to as the decommissioning strategy and represents one of the most important decisions of the entire process. The selected strategy affects the duration of decommissioning, overall costs, the amount of radioactive waste generated, future site use options, and the radiation exposure of workers.

Worldwide, two principal decommissioning strategies are most commonly used — immediate dismantling and deferred dismantling. In exceptional cases, so-called entombment or in-situ decommissioning may also be applied.

In the case of immediate dismantling, decontamination and dismantling activities begin shortly after the permanent shutdown of the facility. The advantages of this approach include retention of experienced personnel, availability of operational documentation, and the possibility of relatively rapid release of the site for future use. Disadvantages include higher radiation exposure to workers and larger quantities of radioactive waste, since the activity of some radionuclides has not yet had sufficient time to decay naturally.

Overview of the principal decommissioning strategies for nuclear facilities and their typical timeline from reactor shutdown to the achievement of the final site condition.

Dodewaard Nuclear Power Plant represents an example of a deferred decommissioning strategy. After the end of operation, the facility was placed into a safe condition in which it will remain for several decades before final dismantling begins.

Deferred dismantling, sometimes referred to as safe enclosure or safe store, involves placing the facility into a safe long-term condition after shutdown, while the actual dismantling activities are postponed for several decades. During this period, part of the radionuclides naturally decay, which may simplify future work and reduce radiation doses to workers. The disadvantages include the need for long-term monitoring of the facility, preservation of specialist knowledge, and postponement of subsequent site activities.

A third option is entombment, in which radioactive parts of the facility are permanently or long-term enclosed on-site, for example within concrete structures. This approach is generally not considered a standard decommissioning strategy and is used only in exceptional situations, such as following severe nuclear accidents or where dismantling would present unacceptable risks.

The selection of an appropriate strategy depends on a wide range of factors. Important considerations include the radiological condition of the facility, the availability of technologies, waste management options, and financial resources. Social and political aspects, regulatory requirements, and the views of the public and local communities also play an important role.

The P Reactor at the Savannah River Site represents an example of an entombment strategy. The above-ground parts of the facility were progressively removed, while some underground structures will remain permanently enclosed on-site.

Deferred dismantling, sometimes referred to as safe enclosure or safe store, involves placing the facility into a safe long-term condition after shutdown, while the actual dismantling activities are postponed for several decades. During this period, part of the radionuclides naturally decay, which may simplify future work and reduce radiation doses to workers. The disadvantages include the need for long-term monitoring of the facility, preservation of specialist knowledge, and postponement of subsequent site activities.

A third option is entombment, in which radioactive parts of the facility are permanently or long-term enclosed on-site, for example within concrete structures. This approach is generally not considered a standard decommissioning strategy and is used only in exceptional situations, such as following severe nuclear accidents or where dismantling would present unacceptable risks.

During the decommissioning of the BONUS Reactor Facility, some contaminated and activated components were placed beneath the reactor vessel and subsequently long-term enclosed by concrete filling.

The selection of an appropriate strategy depends on a wide range of factors. Important considerations include the radiological condition of the facility, the availability of technologies, waste management options, and financial resources. Social and political aspects, regulatory requirements, and the views of the public and local communities also play an important role.

In some countries, a specific strategy may be directly defined by legislation or national policy. Elsewhere, the decision is left to the facility operator, who must technically justify the selected approach and obtain approval from the regulatory authorities. At present, immediate dismantling is preferred for most newly decommissioned nuclear power plants, primarily due to the availability of modern decontamination and dismantling technologies.