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 confirmed from 2009 by a detailed study of decommissioning costs conducted by EDF at the representative site of Dampierre (four 900MW units), and the results of that study were corroborated by an intercomparison with the study carried out by consultants La Guardia, based mainly on the Maine Yankee reactor in the United States.
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, which called the past estimates into question. For this review, the decommissioning provisions for plants in operation were based on costs resulting from the Dampierre study, in order to incorporate the Company’s 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 decommissioning 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 recommendations resulting from the audit commissioned by the DGEC, 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 provided a more thorough assessment of costs specific to the first-of-their-kind units, 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 at a 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 7% respectively compared to an estimate for a PWR fleet 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 17% 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.
Conversely, the estimates only marginally reflect changes in productivity and the learning effect. The DGEC-ordered external audit of the decommissioning cost for the fleet currently in operation 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 led to an overall margin of some 16.3% for the whole fleet (21% for the reference estimate for the first-of-a-kind 900MW reactor).
Since its in-depth revision in 2016 this cost estimate has been reviewed annually. The reviews have led to non-significant annual adjustments.
EDF also confirms its analyses through an international intercomparison, 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 2021, to take account of the impacts of the longer depreciation period for 1300MW-series plants (see note 26), the sequence of operations for dispatching waste resulting from decommissioning was adapted to reflect the increase in decommissioning waste to be sent for interim storage in certain years.
Additionally, the reference estimate of decommissioning costs for the first 900MW units was updated following preliminary studies conducted in preparation for the decommissioning of Fessenheim, and experience gained at the beginning of the pre-dismantling phase. This update also incorporated optimisation of the industrial scenario for management of decommissioning waste before storage, involving prior processing to reduce the volumes stored. Extrapolation of these elements to the whole PWR fleet had a limited impact on the provisions for decommissioning nuclear plants in operation: they were increased by €149 million via adjustment to balance sheet assets.
The annual review of the estimate did not lead to any significant impact on provisions.
Based on the estimates of the different types of cost, the cost to completion (in 2022 euros) for decommissioning of the two 900MW units of Fessenheim amounts to approximately €1.0 billion, giving an average of €0.45 billion per 900MW unit, compared to an average cost of €0.38 billion per unit for the entire PWR fleet, including the series and mutualisation effects described above.
