After final shut down of a nuclear facility preparatory works for decommissioning can be carried out during the post operational phase. As a rule, these include:

• unloading of fuel elements or nuclear fuel
• utilisation of radioactive substances and disposal of radioactive wastes from the operational phase
• sampling of systems and components
• decontamination of the facility and systems

Fundamental decommissioning strategies

The post operational phase is followed by decommissioning, which requires a decommissioning licence that - as a rule - suspendes the operational licence. In Germany, the following fundamental decommissioning strategies are applied:

1. Direct dismantling: This strategy involves the dismantling of a nuclear facility and the release from nuclear regulatory control.
   
2. Safe enclosure: This strategy involves transforming the nuclear facility into an almost maintenance-free condition followed by the later dismantling and release from nuclear regulatory control.

• Planning and implementation of decommissioning (technical know-how available in the facility can be used)
• Financing (security of funds must be guaranteed for a relatively short period of time)
• Social concerns (maintaining jobs, minimisation of local economic problems)
• Technical progress for decontamination and for (remote-controlled) dismantling. As a consequence, the decay of radionuclides during safe enclosure has lost importance from the radiation point of view.

Objective of decommissioning

The objective of decommissioning is typically the dismantling of the nuclear facility and the subsequent release of the site from nuclear regulatory control. Often in Germany an end state as greenfield is aimed, that is, all facilities and buildings are completely removed and the site is restored to its natural condition. A number of other objectives are also feasible, for example, the industrial use of a released site, partial dismantling of the nuclear facilities and reuse of remaining buildings.