Dismantling a nuclear facility is a complex and time-consuming operation. Every worksite is therefore an opportunity to test new solutions to increase efficiency and speed up execution. Not surprisingly, AREVA’s dismantling of the first French MOX fuel fabrication plant, in operation at the Cadarache site from 1962 to 2003, was just such a case in point, with experimentation of a range of working methods and new technologies. The 8-year long project will likely serve as a point of reference in the years to come.
So exactly what was objective set for this dismantling project at the outset in 2009? The aim was to completely empty the premises of this former nuclear facility of all of the equipment that had been in service during the 40 years of production of the uranium and plutonium-based MOX fuel: metal tanks, radioactive piping and “glove boxes“. These great big aquarium-like enclosures with transparent walls and metallic structures were what made it possible to safely manipulate the radioactive materials and the tools necessary for the manufacture of the MOX fuel.
How do you go about dismantling such a set of installations? To begin with, it is essential to compact the equipment with a series of individual cutting operations. Each process area is thoroughly examined and mapped with a view to reducing the radioactivity levels by purification operations. In this case, the project involved as many as 300 employees working simultaneously to deal with the 462 glove boxes, 30 tanks and 4 km of radioactive pipework! In order to concentrate and optimize the duration of the project, AREVA treated each worksite area as if it was a complete production unit in its own right. Each stage of the project could therefore be individually cadenced and streamlined.
Dismantling the most contaminated areas, referred to as “red zones” (or prohibited areas), was naturally the most delicate part of the whole undertaking. The items of nuclear equipment were first isolated within special work tents. The employees responsible for carrying out the cutting operations then had to “dive” into these airtight enclosures equipped with special suits, like deep-sea diving suits, isolating them from any radioactive particles! Inside the suit, the breathing air remains clean and pure. Once complete, everything has to be gone, and without any unwanted dispersal of radioactive material! For maximum efficiency and safety, each step of the task is consigned in a checklist. After each dive, the intervention teams are closely examined with the aid of detectors, in addition to full radiological follow-up.
By the end of the operation, some 60 process areas had been completely emptied and cleaned up. Which represents approximately 30,000 storage drums filled with the cut up equipment, work suits, protective vinyl, gloves, etc. The contents of each drum were duly recorded and entrusted to the good care of ANDRA*, responsible for their final disposal. The emptied buildings have been handed over to the French Alternative Energies and Atomic Energy Commission [Commissariat à l’Energie Atomique et aux Energies Alternatives – CEA], who will decide on their future. Mission accomplished!
*ANDRA : “French national radioactive waste management agency”