There are two main strategies for decommissioning: immediate dismantling or deferred dismantling after safe enclosure. The German Atomic Energy Act (AtG) originally considered both strategies as equivalent. However, the Act on the Reorganisation of Responsibility in Nuclear Waste Management amended Section 7, paragraph 3 of the Atomic Energy Act: safe enclosure may now be chosen solely on a case-by-case basis for reasons of radiation protection.

The common feature of the two strategies is that between permanent shutdown and the start of decommissioning, there is the post-operational phase, which may last several years. During this period, the fuel assemblies may be removed, or the operational media and waste disposed of, insofar as this is covered by the operating licence for the nuclear power plant. During the post-operational phase, at the latest, the operator of the facility applies for the decommissioning licence. Decommissioning and dismantling activities may commence only when this licence has been granted. 

Each of the two strategies has advantages and disadvantages. An international comparison shows that most nuclear facilities are dismantled immediately. In Germany, too, the Nuclear Waste Management Commission recommends immediate dismantling as the norm; very few facilities are in safe enclosure. 

Process

Immediate dismantlingSafe enclosure and deferred dismantling

 Advantages
    • Availability of personnel who are familiar with the operating history

    • Mitigation of economic effects for the region and workers

    • Security of funding

    • Possibility of earlier reuse of site

    • Reduced measurement effort for radiological assessment
      • Radioactivity decreases with time (decay) 

      • Lower radiation exposure for workers as a result of decay

      • Dismantling work may be performed with simpler techniques (technical advantages)

       

       


      Disadvantages
      • Higher residual radioactivity

      • Higher radiation exposure may make dismantling work technically more difficult

       

      • Measurement effort for radiological assessment increases with time

      • Loss of knowledge about the facility

      • Non-availability of new qualified staff for dismantling after safe enclosure

      • Difficulties securing funding for dismantling over an extended period

      Immediate dismantling

      In the case of immediate dismantling, work on removing the facility starts straight away. Immediately after the post-operational phase, all systems, plant components and installations are dismantled in a stepwise approach. 

      Safe enclosure

      With the alternative strategy, the facility is dismantled after a period of safe enclosure.

      Photo: Tim Reckmann, Luftbild Kraftwerk Westfalen, zugeschnitten und bearbeitet von GRS, CC BY-SA 3.0

      Three phases can be identified:

      1. measures in the facility for the purpose of establishing the safe enclosure,
      2. maintaining the facility in safe enclosure (usually for several decades, e.g. 30 years),
      3. dismantling of the facility.