Decommissioning is a costly activity. Therefore it is needed to calculate its cost well in advance and accumulate the funds during plant operation as an assurance for being able to close the existence cycle of the plant. Therefore both aspects of cost calculations and funding will be briefly addressed.

The total cost of decommissioning is dependent on the sequence and timing of the various stages of the program. Deferment of a stage tends to reduce its cost, due to decreasing radioactivity, but this may be offset by increased storage and surveillance costs.

Even allowing for uncertainties in cost estimates and applicable discount rates, decommissioning contributes less than 5% to total electricity generation costs. In USA many utilities have revised their cost projections downwards in the light of experience, and estimates now average 325 million dollars per reactor all-up.

The cost of decommissioning nuclear power plants is based on the following factors:

• The sequence of decommissioning stages chosen;

• The timing of each decommissioning stage;

• The decommissioning activities accomplished in each stage.

In addition, costs depend on such country — and site-specific factors as the type of reactor, waste management and disposal practices and labor rates. The importance of the last item is due to the fact that decommissioning is a labour intensive activity and, therefore, its cost is strongly connected with labour practices, working hours and, of course, labor rates.

Total decommissioning costs include all costs from the start of decommissioning until the site is released for unrestricted use.

The cost estimates are based on previous decommissioning and decontamination experience, on the cost of maintenance, surveillance and component replacements, and on the cost of similar non-nuclear work. Estimates for large NPPs. have been made by several European countries as well as Japan, Canada and the United States.

The results, which include a 25 per cent contingency factor, showed a range of costs for an immediate Stage 3 decommissioning of between 97 and 173 million U. S. dollars (1984). Costs for combining Stages 1 and 3 ranged from 117 to 181 million dollars. Only the United States estimated the costs of combining Stages 2 and 3, from 158 to 186 million dollars. While these figures cannot be absolutely precise, due to differences in the original contingency factors and definitions of decommissioning stages among countries, they nevertheless show what order of magnitude actual decommissioning costs are likely to be for large power plants.

Various methodologies are available for the calculation of decommissioning costs, which present different levels of reliability and precision and are used according to the different objectives of the evaluations. The major reasons that usually lead to the need of a cost evaluation are the following:

• To provide an input for the decommissioning funding during plant operational life

• To compare costs associated with different strategies for the decision making process

• To prepare long term budgeting and cash flow

• To provide a tool for project control

According to the above objectives, the methods include:

• Scaling up or down from similar plant evaluations or experiences according to plant power, or to the total plant activity or to the waste masses, or to other criteria

• Simple calculations based on unit costs for a number of overall parameters like mass of activated metals, mass of contaminated concrete, mass of contaminated metals. This method can be used also for a generic power plant (not site specific)

• Detailed site specific calculations based on a very detailed bottom-up approach, separating each elementary work package

In the last case a detailed database and a computer code treating a large number of information are needed.

For example, one of these computer codes (STILLKO) has been developed in Germany by NIS Company and has been extensively used not only in Germany, but also in many European countries, including Italy. The STILLKO Cost Breakdown Structure (CBS) includes all decommissioning activities that are necessary for the successful completion of the decommissioning project, beginning with the licensing procedure up to the green field status at the end. The CBS is organized into different levels in a hierarchical structure as described in fig. 3.

Allocate Cost categories to building areas

Plant, Controlled Area, BP, BA, ВТ SAT, Support Building for SBP, Storage facilities. Safe Bndosure Area, Conventional Area

Subdive the Cost Categories within the Ares into sections which allow a time and personnel о rented planning

About 209 tasks; conditioning of primary waste, packaging of primary waste, release measurements, ..

Subdivide the Tasks into sections which allow a dear cost calcuilation

Ex; work permission, preparation of working area, restauration and cleaning of working area, ….

Figure 3 — Decommissioning Cost Breakdown Structure (CBS) Organization

On the first level the division of a decommissioning project is effected according to decommissioning phases which are separated according to time and obtained or necessary permits.

On the second level, the decommissioning phases are divided into the following cost categories:

• Project management and project administration

• Planning and licensing

• Plant operation and security

• Plant technical activities for Safe Enclosure

• Preparations for Dismantling

• Dismantling activated and contaminated components

• Decontamination

• Conventional dismantling

• Waste management

• Radiological and conventional worker protection

These cost categories have been created according to functional points of view and represent the volume of the decommissioning activities. The cost categories may occur in every decommissioning phase, with suitable contents of the cost categories regarding the respective phase.

The third level is used to allocate the decommissioning activities to the buildings and areas on site. Using this level in the cost structure it is possible to assign the work directly to the place where it arises but also to determine the sequence of the activities and their schedule in relation to the specific building.

On the fourth level, individual tasks are defined which allow a room by room or system by system planning, regarding to the situation on site. The execution of the tasks may be done parallel in different buildings, building levels or rooms.

On the fifth, the lowest level, the decommissioning tasks are divided into activities. These activities are formed in a way that each of them can be individually calculated.

It is useful to mention that a standardization of cost items has been developed in the framework of OECD and European Union and that it can be a useful reference for the future.

About financing methods, several alternatives can be used depending on the circumstances of each utility and the country in which it operates. In several countries, a fund of some type has been established, or proposed, to assure the availability of financing. This is usually done by an early estimation of the cost of decommissioning at the end of the normal plant lifetime and requiring payments, either annually or on a charge per kilowatt-hour basis, to ensure that this sum is in place. This estimate is updated regularly and the charge adjusted accordingly.

The drawback to this system is that the amount estimated would not be in place if the plant were to be shut down before the end of its normal lifetime. To avoid this, a fund could be established at the start of the plant’s operation which would cover the cost of decommissioning whenever it became necessary. However, this represents a heavy burden for the utility at the moment when construction and start-up costs are already high, and thus, although it may be imposed by law, this solution is clearly not favoured by utilities.

Financing methods vary from country to country. Among the most common are:

• External sinking fund (Nuclear Power Levy): This is built up over the years from a percentage of the electricity rates charged to consumers. Proceeds are placed in a trust fund outside the utility’s control. This is the main US system, where sufficient funds are set aside during the reactor’s operating lifetime to cover the cost of decommissioning.

• Prepayment, where money is deposited in a separate account to cover decommissioning costs even before the plant begins operation. This may be done in a number of ways, but the funds cannot be withdrawn other than for decommissioning purposes.

• Surety fund, letter of credit, or insurance purchased by the utility to guarantee that decommissioning costs will be covered even if the utility defaults.

However, the uncertainties in cost calculations are among the issues in decommissioning that shall be further developed.

In Italy a fund has been established to enable the decommissioning of Italian NPPs and the closure of the nuclear fuel cycle. These special provisions are included in the Financial Statement of the SOGIN Company.