CHOOZ A: EDF STARTS THE DISMANTLING OF THE REACTOR TANK 26 Apr 2017 energeek
In an increasingly competitive global dismantling market, the French group EDF has the ambition to become one of the leaders in nuclear decommissioning internationally, and intends to rely on its experience in France. The first pressurized water reactor to be dismantled in the French fleet, Chooz A allows to test and validate technical solutions that can be used for other nuclear sites. Launched in 2007 for a period of fifteen years, this dismantling site entered Wednesday, 8 March 2017, in its final phase intended to cut the most sensitive part of the installation: the reactor vessel.
A technological demonstrator of construction and deconstructionNestled in a loop of the Meuse in the heart of the Ardennes, the Chooz power plant is not limited to its two units of 1.450 megawatts (MW) each, but also contains in its basements the "little Chooz" (also called Chooz A ), a prototype of the pressurized water reactor model that makes up the majority of French and world nuclear power plants. Commissioned in 1967 and definitively shut down in 1991, it displayed 305 MW production power and continued, even out of service, to fulfill a technological demonstrator role.
Entered the phase of deconstruction in 2007, it is indeed the scene of a non-standard shipyard whose feedbacks will complete the French know-how in terms of dismantling, and will benefit in the future for all hexagonal park. If the working conditions are particular here because of the underground installation of the reactor, this site allows since the beginning of the works to test the various regulatory and technical stages of the long process of nuclear dismantling.
In particular, this year it crossed a new landmark with the opening of the reactor vessel, twenty years after the unloading of the fuel..
Dismantling of the tank: heart of the installationIn accordance with the schedule originally planned and in compliance with the budget allocated for this type of operation (between 350 and 400 million euros), the yard has therefore entered since March in its final phase consisting in the deconstruction of the reactor vessel, the most delicate operation of the entire project. Centerpiece of the installation, this steel tank weighs more than 220 tons and is immersed underground, at the bottom of a pool eight meters deep and about 1000 cubic meters, a volume equivalent to that of a municipal swimming pool of 25 meters long. It contained (before it was removed in the 1990 years) the nuclear fuel necessary for the operation of the plant, and was therefore logically exposed to ionizing radiation more than any other part of the reactor.
This particularity imposes on the operator a particular attention and a maximum precaution. In order to avoid the exposure of the teams of engineers and technicians in charge, the cutting operations will be carried out in total immersion, water still constituting at the moment the best radiological barrier. Remotely operated robots equipped with circular saws will allow them to perform each maneuver remotely under optimal conditions of safety, security and radiation protection. Already successfully tested on other dismantling sites, particularly in the United States and Spain (the Spanish reactor Zohrita for example is very similar to that of Chooz A), this size intervention should end on the horizon 2022 , and allow decommissioning and gradual rehabilitation of the site. To date, only the lid of 50 tons has been removed using a lifting bridge and will soon be sent to the storage center of the National Radioactive Waste Management Agency in Aube.
A pilot project "representative" of the French nuclear fleet
As for the rest of the plant, the Chooz A dismantling site is coming to an end and is already a reference in the world of the nuclear industry. Since 2007 and the full approval of the Nuclear Safety Authority (ASN), several unpublished operations have been carried out. Cutting plants and waste storage silos have been built inside the site and have facilitated the primary circuit assembly, as well as the extraction and decontamination of the main components such as the four generators. steam or pressurizer.
Today, the majority of equipment has already been evacuated (fuel cooling pool, backup systems, pumps, circuits and auxiliary auxiliaries), demonstrating the technical feasibility of this type of project, and especially the EDF group's capacity to meet the technological challenge of nuclear decommissioning within the prescribed deadlines.