ASN specifies the next steps in the decommissioning of the gas cooled reactors (GCR)

In two resolutions, ASN specifies the next steps in the decommissioning of the “first generation” gas cooled reactors (GCR).

The EDF GCR type reactors were shutdown between 1973 and 1994. The fuel, which accounted for virtually the entire risk, has been removed. The installations have only been partially decommissioned.

To date, the Chinon A1 and A2 reactors do not have the required authorisations to continue with decommissioning. The regulations require that ASN stipulate to EDF the deadline for submitting their decommissioning file.

The other GCR reactors (Bugey 1, Chinon A3, Saint-Laurent A1 and A2) have received a decommissioning authorisation based on a scenario set out by EDF in the early 2000s. This scenario consisted in filling the reactor core with water in order to perform the decommissioning operations. EDF aimed to complete decommissioning of these reactors in 2024, 2027 and 2031 respectively.

In 2016, EDF announced that the underwater decommissioning scenario posed major technical difficulties and that it had finally opted for an air decommissioning scenario. This change entailed a significant postponement of the decommissioning operations on the pressure vessels ^[1] of these reactors and EDF felt that the feasibility of these operations needed to be validated by means of an industrial demonstrator, with complete decommissioning carried out on one pressure vessel before decommissioning could begin on the other five.

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ASN duly notes the difficulties encountered in continued decommissioning under water and, in the light of the risks, considers that the change in scenario to air decommissioning is acceptable. ASN also considers that the production of an industrial demonstrator is a pertinent step.

After examination of the evidence presented by the licensee, and then consultation of both the licensee and the public, ASN adopted two resolutions on 3 March 2020 regulating the next steps in the decommissioning of these reactors. The following are notably specified:

• continued decommissioning of the equipment outside the pressure vessels of the Bugey 1, Chinon A3, Saint-Laurent A1 and A2 reactors,
• commissioning and operation of an industrial demonstrator designed to validate the sequence to be followed for reactor pressure vessel decommissioning,
• in-depth work on the management routes for the waste that will be produced by decommissioning,
• compilation of the decommissioning files for the six reactors, which will be transmitted in 2022.

EDF shall demonstrate its ability to manage the deadlines and the interfaces between these projects, so that decommissioning of the GCR reactor pressure vessels can begin.

In the light of the considerable delays accumulated by industry in their decommissioning projects, ASN initiated a decommissioning projects inspection process in 2019. The implementation of these inspections will supplement the examination of the decommissioning files, which shall present detailed data regarding the safety of the installations. These data will be examined by ASN in the light of the risks associated with postponement of the decommissioning of the reactor pressure vessels by several decades.

ASN considers that waiting for the end of decommissioning of a first reactor pressure vessel and analysis of the lessons learned, which would not happen until about 2070, before beginning decommissioning of the other reactor pressure vessels, is not acceptable given the obligation of decommissioning within a time-frame that is as short as possible. ASN however considers that, given the complexity of these operations, which have never before been carried out, it is acceptable for there to be a reasonable time between the beginning of decommissioning of the first and then of the other five pressure vessels. The inspections and examinations mentioned above should, over the coming decade, enable ASN to assess the pertinence of the deadlines that EDF will be proposing for the main steps in the decommissioning of these reactors.

In a letter, ASN informed EDF that it required it to shorten the overall decommissioning schedule for these reactors, given the need to decommission each of the reactors in as short a time as possible. This optimisation shall be taken into account when drawing up the decommissioning or modification files resulting from the ASN resolutions.

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