Until 2013, provisions were estimated based on a 1991 study by the French Ministry of Trade and Industry, which set an estimated benchmark cost for decommissioning expressed in €/MW, confirming the assumptions defined in 1979 by the PEON commission. These estimates were supported from 2009 by a detailed study of decommissioning costs conducted by EDF at the representative site of Dampierre. (four 900MW units), and its results were corroborated by an inter comparison with the study carried out by consultants La Guardia, based mainly on the Maine Yankee reactor in the US.
In 2014 the Dampierre study was reviewed by EDF to make sure that the previous calculations were still valid in view of recent developments and experience, both internationally and internally. For this revision, the decommissioning provisions for plants in operation were based on costs resulting from the Dampierre study, in order to incorporate best estimates and experience from inside and outside France. This change of estimate had no significant impact on the level of provisions at 31 December 2014.
Between June 2014 and July 2015, an audit of dismantling costs for EDF’s nuclear fleet currently in operation was conducted by specialised consulting firms, at the request of the French Department for Energy and Climate (Direction Générale de l’Énergie et du Climat or DGEC). On 15 January 2016 the DGEC published a summary of the audit report. It stated that although estimating the cost of decommissioning nuclear reactors is a demanding exercise due to relatively limited past experience, the prospects of changes in techniques, and the distant timing of the expenditure, overall, the audit confirmed EDF’s estimate of decommissioning costs for its nuclear fleet currently in operation. The DGEC also made a number of recommendations to EDF following this audit.
In 2016, EDF revised the decommissioning estimate, in order to incorporate the audit recommendations and past experience gained from dismantling operations for first-generation reactors (particularly Chooz A).
A detailed analytical approach was used to revise this estimate, identifying all costs for the engineering, construction work, operation and waste processing involved in future decommissioning of reactors currently in operation. This led to figures based on detailed timetables for plant decommissioning. The approach adopted made it possible to explore more thoroughly the assessment of costs specific to the initial units of each series, estimated for each series based on transposition coefficients applied to the baseline costs for the initial 900MW unit, and the series and mutualisation effects, as these costs and effects are inherent to the fleet’s size and configuration.
The natures of the principal series and mutualisation effects used to arrive at the estimate are explained below.
Series effects (effects of work for the first-of-a-kind site on the following sites of the same series) are mainly of two types:
Mutualisation effects (effects between units on the same site, whether in operation or being decommissioned) are of several different types:
Due to mutualisation effects, dismantling a pair of reactors on the same site costs less than dismantling two standalone reactors on two different sites. In France, unlike other countries, there are no single reactors but sites with two or four, and in one case six reactors.
Series and mutualisation effects reduce the estimated decommissioning cost by 10% and 6% respectively compared to an estimate that ignores these effects. Series and mutualisation effects vary depending on the series: they are greater when there are more units in a series (series effect) and more units on a site (mutualisation effect), leading to a combined effect (series and mutualisation effect) of over 16% for the 900MW series.
In particular, series and mutualisation effects explain why it is not appropriate simply to compare the average dismantling cost per reactor between the French fleet and other countries’ nuclear fleets.
In contrast, the estimates only marginally reflect changes in productivity and the learning effect. The external audit of the decommissioning cost for the fleet currently in operation, ordered by the DGEC, considered that this approach resulted in a prudent estimation method.
For reasons of prudence, the estimate also includes an assessment of risks and uncertainties as follows:
The above method for assessing risks and uncertainties leads to an overall margin of some 16.5% for the whole fleet (20% for the first 900MW unit).
This approach, adopted in 2016, and its results were presented to the administrative authority and gave rise to further questions and discussions.
The results of this detailed approach led to limited changes overall in the cost estimate and the associated provisions at 31 December 2016, apart from the consequences of the change in the depreciation period for 900MW series plants (excluding Fessenheim) at 1 January 2016, and the effect of changes in discount rates at 31 December 2016, i.e.:
After its revision in 2016, it was decided that the cost estimate would be reviewed annually. Reviews since 2017 have led to non-significant annual adjustments to this estimate.
EDF continues to confirm its analyses through an international inter comparison, taking care to identify and characterise a number of factors that could distort direct comparisons, for example differences in the scope concerned by the cost estimate, or national and regulatory contexts.
In 2020, in addition to reclassification of the amount concerning the Fessenheim plant to the provision for decommissioning of permanently shut-down plants, the following changes were made to the provisions for decommissioning of nuclear plants currently in operation:
