France prepares to start dismantling first UNGG reactor

Chinon A2 is one of six gas-cooled reactors (Uranium Naturel Graphite Gaz¸ or UNGG) at Bugey, Chinon and St Laurent-des-Eaux currently being decommissioned by EDF in France. The six UNGG reactors entered service between 1963 and 1972. With the exception of Chinon A1, which closed in 1973, all operated for more than 20 years. Chinon A2 is the lead site for EDF's immediate dismantling strategy for its UNGG fleet. The company's objective is to dismantle the facilities in the shortest timeframe possible.

With the validation of the contractual strategy for dismantling Chinon A2's heat exchangers, the project "has reached a decisive milestone", Cyclife said. "After more than three and a half years of studies conducted jointly by the teams from EDF's Deconstruction and Waste Projects Department (DP2D) and Cyclife Engineering, this milestone paves the way for the launch of the first operational phase of the dismantling of the world's first UNGG reactor."

Subject to the entry into force of the dismantling decree, this first operation will consist of dismantling in series the equipment present in the four heat exchanger rooms of Chinon A2. The heat exchangers made it possible to transfer the heat from the carbon dioxide, heated in the core of the reactor, to the water of the secondary circuit which then turned into steam.

_{Teams from EDF and Cyclife Engineering visting the heat exchangers of Chinon A2 (Image: Cyclife)}

Cyclife said the dismantling operation will "fully benefit" from the lessons learned during the dismantling of the Chinon A3 reactor heat exchangers.

The start of operations is planned for mid-2028, following the public inquiry into the UNGG reactor dismantling strategy, scheduled for 2027. The project is expected to take six years.

"This is an essential step forward in preparing for an exceptional industrial project, which is set to serve as a benchmark for EDF's entire UNGG programme," said Stéphanie Proust, EDF Chinon A-AMI project manager.

In December 2019, EDF and Veolia established the Graphitech joint venture for the decommissioning of reactors that use graphite technology. Graphitech's first objective was to provide EDF with an optimised scenario for decommissioning the Chinon A2 reactor in 2028 and to offer a testing programme to evaluate the technological solutions needed to complete the project. This programme began in 2022 with a development and qualification phase using full-scale models to prepare the remote-operation tools to be used in decommissioning the Chinon reactor.

Graphitech has produced an outline decommissioning methodology for the five remaining UNGG reactors: where possible, transposition of the Chinon A2 methodology to the other reactors; and where not possible, identification of additional engineering work required.

Graphitech will seek contracts for assisting in the dismantling of gas-cooled reactors in France, Italy, Japan, Lithuania, Spain and the UK.