For many of the facilities that are currently being decommissioned, little attention was given to decommissioning in their design (Review of Radioactive Waste Management Policy, 1995). This has resulted in an increase in costs in some cases. In the UK for example, the regulator now requires that consideration be given to decommissioning in the design of a plant. This is in regard to a number of factors, construction techniques, choice of materials, the provision of suitable access and the availability of adequate waste storage facilities.

The costs of decommissioning for different reactor types and different countries were considered in an IAEA review of selected cost drivers for decisions on the continued operation of the older nuclear reactors (IAEA-TECDOC-1084, 1999). This review covered pressurised water reactors (PWR and VVER), BWRs, HWRs, light water cooled, graphite moderated reactors (LWGW or RBMK type) and gas reactors (GCR and AGR).

Two categories of decommissioning costs are considered. The first category (Stage 1 and/or Stage 2 decommissioning followed eventually by Stage 3) is decommissioning with long-term storage. This takes advantage of the natural decay of the radioactive isotopes, which makes dismantling operations at a later time much easier. The second category is the decommissioning approach with immediate dismantling of the plant up to the ‘green­field’ (non-restricted use) or ‘grey-field’ (somewhat restricted use) condition (Stage 3 decommissioning). This structuring of the decommissioning stages is based on the well — established IAEA terminology.

It is noted that decommissioning practices differ substantially from country to country and this affects any comparable cost estimates. For example in some countries, the cost of fuel unloading is included as a standard part of decommissioning costs. In most countries, it is not. There is not necessarily a consistent practice within a particular country. The study in IAEA-TECDOC-1084 (1999) aimed to focus on total costs and made no attempt to consider the relative importance of various cost components.

Section 6.11.1 summarises the estimated costs of decommissioning after storage, for the principal types of reactor in operation at the present time. Data are taken from IAEA-TECDOC-1084 (1999). It should be noted that the costs considered were total costs excluding discounting. It should further be recognised that not all costs in the data were normalised to exactly the same time period.