Decommissioning of shut-down reactors involves pilot operations corresponding to four different technologies, each with clear specificities: a PWR reactor at Chooz A located in a cave, UNGG (natural uranium graphite gas-cooled) reactors at Bugey, Saint-Laurent and Chinon, a heavy water reactor at Brennilis, a sodium-cooled fast neutron reactor at Creys-Malville, and the first-of-a-kind second-generation PWR reactor at Fessenheim.
The decommissioning costs are based on estimates that take account of accumulated industrial experience, unforeseeable and regulatory developments, and the latest available figures. They have been reviewed annually since 2015.
The industrial scenario for dismantling of the UNGG reactors was reviewed in depth in late 2015, leading in particular to a switch from “underwater” to “in-air” dismantling, which involves:
Under this new strategy, dismantling operations for the reactor caissons should be completed between 2063 and 2093, depending on the reactors.
Updating the industrial decommissioning scenario for first-generation power plants, particularly UNGG plants, led to a €590 million increase in the provision at 31 December 2015.
The amendment made in 2015 to the industrial scenario for dismantling of the UNGG reactors was presented to the ASN’s commissioners on 29 March 2016, and examined by the ASN until 2019. It was reviewed by international experts, examined by the IRSN, and was the subject of three hearings before the ASN’s commissioners, before the ASN issued two decisions dated 3 March 2020. These decisions and the discussions prior to their adoption by the ASN showed that there was convergence on most major technical questions: the dismantling technique (“in-air”), the usefulness of setting up an industrial demonstrator to develop the tools required for these complex operations, the timetable for dismantling the Chinon A2 reactor, and the need to gain experience from operations on a first reactor.
Regarding the timetable of operations, in draft decisions issued for public consultation in 2019, the ASN asked for this work to be brought forward compared to EDF’s proposed schedule, so that dismantling operations on the five reactors after Chinon A2 would begin “no later than 31 December 2055”.
In view of this request for a shorter timescale, the nuclear provisions were increased in 2019 by a total €108 million: €77 million for decommissioning provisions for permanently shut-down nuclear power plants and €31 million for provisions for long-term radioactive waste management (for long-lived low-level waste, very low-level and low and medium-level waste).
The ASN’s decisions concerning dismantling of UNGG reactors were published in March 2020 and did not contradict the principles of the draft decisions of 2019. Consequently, the nuclear provisions for decommissioning of UNGG plants were not subjected to any particular re-estimation in 2020, and reflect the best estimate of the industrial and technical scenario.
In 2021, the annual review of the cost estimates for decommissioning of permanently shut-down plants led to a €77 million increase in provisions due to revision of the industrial decommissioning strategy for Chooz A. That strategy was switched to a full continuous decommissioning scenario, dropping the period of cave runoff water surveillance between the end of installation dismantling and the start of final dismantling and decontamination work, as the quality of the water means this is no longer necessary. Also, the cost estimate for decommissioning of the APEC Fuel Storage Workshop at Creys-Malville – a facility operated by EDF with the principal activity of storing fuel from the Superphénix reactor – was updated based on Summary Preliminary Plan studies conducted in 2020-2021, leading to a €61 million increase in provisions.
Finally, in accordance with its powers under Article 594-4 of the Environment Code, in June 2020 the DGEC commissioned an external audit of the estimated cost of dismantling operations for EDF’s permanently shut-down nuclear facilities (UNGG plants and management of its long-lived low-level waste, Superphenix and Brennilis), conducted by a consortium of specialist firms. This audit took place from December 2020 to July 2021, and the audit report was posted on the Ministry for the Ecological Transition website in November 2021. Its conclusions (confirming the ASN’s observations during its inspection of complex project management, the conclusions of which were released in the first quarter of 2021) highlight “an organization with a structural focus on execution of dismantling projects”, an “annual estimation and revision process [that] is robust, and provides good traceability for the assumptions used and the original data”, and “a long-term industrial approach to overcome the small number of technological challenges that remain”. Finally, the report states that apart from a non-significant correction (taken into account in the 2021 provisions), “the provisions are coherent with the basic scenarios of the projects and cover the full scope of expenses for the scope audited”, and of “adequate sizing” through testing the scale of EDF’s expenses and provisions.
In 2022, following the recommendations made by the DGEC-commissioned audit to confirm scheduling risk assessments and the uncertainty levels concerning estimates, an analytical methodology for assessment of scheduling risks and uncertainties (applied to most of the decommissioning projects currently in process) and an additional level of uncertainty for estimates “based on expert assessment” (used in provisions for decommissioning and long-term radioactive waste management) were introduced. This led to an increase of €116 million to decommissioning provisions for permanently shut-down nuclear plants.
The provision for decommissioning of Chooz A was also increased by €37 million to take account of confirmed experience, regarding unforeseen events and delays observed during the dismantling of the reactor vessel (slower segmentation, and unavailability of the bridge crane). As a result of this experience, the vessel dismantling work has been prolonged by 18 months, and a risk of a further 14-month delay on the overall timetable has been identified.
For UNGG plants, the annual review of cost estimates took into consideration delays in obtaining the dismantling decrees (which are now expected in late 2026 rather than late 2025 as previously). This did not have a significant impact on the provisions.
Over a short-term horizon, the provisions take into account expectations that the rises in certain commodity, energy and transport prices will exceed forecast inflation, particularly given the types of purchases relating to decommissioning expenses. This had an impact of €33 million on provisions for decommissioning of permanently shut-down nuclear plants.
