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General information on decommissioning: strategies and technologies

Decommissioning strategies

Two decommissioning strategies have been and are being applied in Germany:

Direct dismantling:
With this strategy, a nuclear power plant is dismantled directly after it is permanently shut down, i.e. all parts of the facility are removed and the natural state is restored in the form of a so-called greenfield site, or the facility is still used once it is no longer subject to monitoring under nuclear legislation (subsequent industrial use). Experience shows that this process lasts several years; in the case of dismantling a nuclear power plant at least a decade. Once dismantling has been completed, a storage site for radioactive waste or spent fuel elements can be retained until these are transported to a disposal site.

Safe enclosure: With this strategy, a nuclear power plant is put in a secure, low maintenance state after it has been completely shut down. It is then only dismantled after a period of safe enclosure, for example 30 years. The safe enclosure strategy has rarely been used in Germany so far, and at present there are no plans to use it for any plants to be decommissioned.

Dismantling a nuclear power plant

Nuclear power plants are dismantled in several stages, which generally require several decommissioning and dismantling licences under nuclear legislation. Before dismantling begins, the plant is still in almost the same technical state as during operation. During this phase between final shutdown and issuing the first licence for decommissioning, measures are taken in preparation of dismantling, for example drawing up a detailed overview of the plant’s radioactive inventory using measurements and samples, removing fire loads and operational waste and drawing up the application documentation for the first decommissioning licence.

The dismantling of plant components generally starts with the areas with low contamination, then moves on to areas with higher contamination (“from the outside to the inside”). Broadly speaking, the dismantling of a nuclear power plant proceeds as follows: 

  • Stage 1: Dismantling of components of the plant no longer required for remaining operation and removal of the spent fuel elements as soon as possible
  • Stage 2: Dismantling of components with higher radioactivity, e.g. the reactor pressure vessel and the biological shield
  • Stage 3: Decontamination of buildings and removal of the entire facility (buildings and site) from supervision under the scope of application of nuclear and radiation legislation
  • Stage 4: Conventional demolition or re-use of the building.

Technologies for dismantling

When decommissioning, it is important to use mature, reliable technologies that satisfy the requirements of safety, radiation protection and swift project implementation. Technologies are required for various processes: decontamination, dismantling and disassembling, activity measurements and waste conditioning.

The following criteria apply when selecting individual technologies: 

  • radiation protection aspects, with the goal of keeping the radiation exposure of staff to a minimum
  • suitability and effectivity of the process
  • the most comprehensive possible clearance of residual substances and plant parts
  • reducing the volume of radioactive waste and space-related aspects. 

The selection and application of technologies is licensed and supervised by the competent Land authority. Technical experts support the authorities in this process.

Last update: 11.12.2015