Nuclear engineering and services
Dismantling the exchangers at Chinon A3: a look back at an unprecedented technical and industrial challenge
The UNGG ("Uranium Naturel Graphite Gaz", i.e. the first nuclear reactor line) consists of six reactors, including Chinon A3, which was shut down in 1990.
The project to dismantle the heat exchangers at the Chinon A3 reactor, an emblematic EDF DP2D site, involved dismantling, conditioning and evacuating all the heat exchanger circuits in two rooms. All structures to be dismantled were suspended. Thanks to the expertise of the Onet Technologies and EDF teams, the project came to a successful conclusion last February, after 10 years of intensive work. Here's a look back at an extraordinary project that marked a turning point in the nuclear industry, and in which Onet Technologies played a key role.
more
10
years of work
the last bottle on the Chinon A3 dismantling site was removed last February, after ten years of work.
The titanic Chinon A3 worksite began in November 2012 with the deconstruction of the exchangers in the south room, which was successfully completed in May 2018, with the end of removal and evacuation of the 96 south cylinders.
The dismantling of the north exchanger room, meanwhile, began in October 2018, and was able to be held despite the challenges associated with the COVID-19 health crisis in 2020. The first phase, which lasted more than 4 years, was devoted to the removal of major components of the primary CO2 and secondary water-steam circuits (headers, sleeves, tanks, piping, etc.). Some of these were suspended from heights of over 30 metres!
In April 2022, Onet Technologies removed the last large component (excluding exchanger cylinders), a 41-tonne water/steam storage tank, with the participation of Mammoet, a company specializing in lifting and transporting heavy objects.
Dismantling of the 96 cylinders began in June 2022, and was completed on February 15, 2023 after eight months of hard work, marking the end of the dismantling of the Chinon A3 exchangers and a major milestone for all stakeholders. To enable the dismantling of all the exchanger cylinders in the Chinon A3 reactor, the work carried out by Onet Technologies (excluding the study and prescription period) was managed by four different EDF project managers.
An impressive logistical feat
The challenge didn't stop there, however, as the first 64 cylinders had to be transported in their entirety - i.e., without having been cut beforehand - to ANDRA's CIRES (Centre Industriel de Regroupement, d'Entreposage et de Stockage), where they joined the cylinders in the South room. The remaining 32 cylinders joined the others last spring. This represents a real logistical feat, since the total tonnage of waste from this site amounts to 5,200 tonnes of VLA (Very Low Activity) waste, equivalent to half the mass of the Eiffel Tower! One bottle alone already weighs 18 tonnes, is 14 metres high and one metre in diameter!
This colossal operation was only made possible thanks to the collaboration and coordination between all the stakeholders involved in the project, mobilizing an average of twenty people on site. Onet Technologies' teams played an essential role in ensuring the safe and efficient disposal of this waste.
A fruitful collaboration between Onet Technologies and EDF
Indeed, beyond its technical and operational successes, this project demonstrated the power of the collaboration between Onet Technologies and EDF DP2D, who worked hand in hand to bring it to a successful conclusion. Philippe Lalbat, head of the Chinon A decommissioning site, praised the expertise and commitment of the Onet Technologies teams involved in this colossal project: " This project has been masterfully managed by the Onet Technologies and EDF teams, who have demonstrated their adaptability in the face of unexpected constraints, and have risen to numerous challenges over the years ".
Hélène Benoist, batch leader for the dismantling of the Chinon A exchangers, emphasizes the use of cutting-edge technologies such as reciprocating saws, orbital saws, hydro-mobile platforms and cable jacks, which, combined with " a good dose of energy from all the teams in charge of the site ", enabled this dismantling operation to be successfully completed.
Expertise and exemplary teamwork are key to the success of this project. "Achieving this milestone is a real collective success [...]. I would of course like to congratulate the Onet Technologies teams who helped us to successfully evacuate the waste," says Bertrand Debaud, head of the Chinon A project.
The Chinon A3 exchanger dismantling project was also a real showcase for EDF DP2D. It attracted the interest of many players, including Jean-Bernard Lévy (EDF CEO), EDF DP2D management, ASN and ANDRA. The site's mastery of safety and radiation protection was amply demonstrated during these visits, underlining the quality of the work carried out by Onet Technologies and its partners.
Towards new nuclear challenges: dismantling UNGG reactors
The six first-generation UNGG reactors, like Chinon A3, were fuelled with natural uranium, used graphite as a moderator, and were gas-cooled. Chinon A3 is a non-integrated reactor, i.e. the heat exchangers are located on either side of the reactor vessel. Since the primary fluid in UNGGs is a gas, the heat transfer surface area between the primary and secondary circuits is much greater than in reactors currently in operation, necessitating a much larger number of heat exchangers. The dismantling of graphite reactors, such as those at Chinon A3, is a complex operation requiring innovative technologies due to their compact structure and large dimensions. It is unprecedented on our industrial scale, as only two other reactors of this type have been dismantled in the world, and they were of a much more modest size!
The success of this project is not only a source of pride for Onet Technologies and EDF, but also a breakthrough for the entire nuclear industry: it has paved the way for new advances in the dismantling of UNGG reactors.
It demonstrates the expertise and know-how of the Onet Technologies and EDF teams, and positions Onet Technologies as a key reference in the future decommissioning of UNGG reactors.
While the teams at Chinon A are now looking to the future, there are still a number of important stages to be completed, including the site withdrawal phase, which should be finalized before the end of the year (around mid-October), and the completion of the radiological characterization program for the premises in preparation for the clean-up/decommissioning file.
With the successful dismantling of the Chinon A3 exchangers, Onet Technologies has demonstrated its ability to brilliantly manage complex and ambitious worksites, and to contribute to large-scale projects, while guaranteeing the safety of its teams and respecting deadlines.
Congratulations to the Chinon A3 exchanger dismantling teams from Onet Technologies on a fine victory that will go down in the annals of the nuclear industry!
Ces contenus peuvent vous intéresser
Nuclear engineering and services
Do you have a need or a question?
Our Onet Technologies experts are at your disposal to answer all your requests for information or quotes.