• Radioactive inventory — Depending on the amount and characteristics of the radioactive inventory the strategy can change. For example, plants which experienced accidents with radioactive release or incidental spilling on the floors, or contamination of insulation, may require special attention. On the other side plants which have been prematurely shutdown may have a lower total inventory and a long Safe Storage period may not be justified.

• Presence of other operating units on the same site or in the country — This situation may imply the maintenance of a high level of nuclear technology that will be available for a longer time. To have them on the same site means also that the site cannot be released anyway and that work force can be easily re-employed. Therefore, generally, it is convenient to wait some time before dismantling.

• Availability of a national waste repository — Decommissioning and dismantling means essentially to cut in pieces a NPP and to concentrate and package the radioactivity. This is of little advantage if all the radioactive material shall remain on-site. In addition, if a repository does not exist, uncertainties are present on the specification of packaging that will be finally required by the repository, once it will made available.

• Clearance levels and waste disposal costs- Clearance levels are of fundamental importance to decide which strategy and which technologies shall be used. Since clearance levels can vary even by one order of magnitude and more, correspondingly the amount of radioactive wastes to be generated, classified as such, can vary by even more than one order of magnitude. This, in connection with the cost of waste final disposal, can force the decision in favor or against the preliminary decontamination of systems and structures.

• Plant layout — Difficulties in the dismantling process due to very compact layouts may lead to decisions about preliminary decontamination and different cutting strategies

• Safety conditions of structures and systems — Costs of maintaining the safe storage condition for decades shall be low to make the SAFSTOR strategy convenient. This means that structural conditions and corrosion conditions of all components shall be good and capable to withstand the expected conditions for several decades, without any need for major refurbishment.

• Expectations about development of licensing rules and of technologies for decommissioning — Licensing rules and available technologies change usually more quickly than expected. This is the experience of the last years. Extrapolations of the situation in 50 or 100 years are extremely difficult to be made and, more important, extremely uncertain. This means that in the case of the safe storage strategy it is wise to use contingencies in cost calculations and to leave open the introduction to new technologies.

• Connections between conventional and nuclear safety — In a NPP there are also some conventional safety issues and a production of conventional waste (such as asbestos). Complications may arise when the same waste is at the same time radioactive and toxic, such as in the case of contaminated asbestos. The extent of such situation may lead to the use of special techniques of dismantling and waste packaging.

• Status of plant configuration documentation — In the lack of a good documentation about plant design bases, plant modifications and plant conditions, the knowledge of the plant staff might lead to the decision to perform as many as possible activities, while the people are still available.

Worker doses are not included in the previous list, since it is assumed that with proper preparation and the use of proper tools, including remote operations and decontamination activities, the worker dose can always be reduced to acceptable levels. Also environment and public health impact levels have not been included in this list, since they are generally so low that do not present any serious concern. Of course also these elements have to be taken into account in a complete strategy evaluation.

In the second group, the following elements have to be considered:

• Availability of funding — Generally the fund accumulation during plant operation is based on a cost evaluation, which, in turn, is based on a specific strategy. Any change of the strategy would imply the identification of different fund sources.

• Expectations about cost evolutions — Calculated costs are affected by a certain level of uncertainties. Uncertainties grow with the extension of calculation extrapolation, because of the uncertainties in the evolution of technologies and the evolution in the safety rules and in the costs of waste disposal. The need to reduce uncertainties implies a reduction of decommissioning duration

• Expectations in terms of inflation rate — Funds tend to grow, because, with proper investments, they will produce a net interest. Assumptions about this net interest (that usually range from 2% to 5 %) are very sensitive for the definition of the convenience of different strategies

• Assumptions in terms of contingencies — Excessive contingencies intended as provisional funds to cover unexpected situations may tend to increase the needed funds. In general, the amount of contingencies may be reduced, obviously, when the decommissioning time is shortened.