Reinforcing material access buffers: Onet Technologies positions itself to extend the lifespan of nuclear power plants
Designed to improve the robustness of France's 900 MWe power plants in extreme situations, the project to reinforce the equipment access buffers (TAM), entrusted to Onet Technologies in 2007, has just been successfully completed.
Onet Technologies has just completed a long and complex project. A project spread over 13 years (2007-2020, including two years of studies), it involved reinforcing the equipment access buffers (circular steel doors used to close off the access through which equipment and tools are introduced into the reactor buildings) of all French 900 MWe nuclear power plants, as part of the3rd ten-yearly inspection of the plants. Successfully completed despite the technical difficulties associated with the working conditions, on a structure weighing 26 tonnes, 7m40 in diameter and 20 metres above the ground, this work mobilized teams of 10 to 15 people in each of the 26 900 MWe power plants in the country, who had to be trained and coordinated. A great challenge for the company, which has meanwhile won a second contract of the same type for five more recent nuclear power plants (P'4 1300 MWe), and which intends to make the most of its new expertise on the international stage.
Complex operating conditions
In concrete terms, this project, designed to improve the robustness of France's 900 MWe power plants in extreme situations, such as earthquakes, involved replacing the 88 bolts of all their material access buffers, initially 26 mm in diameter, with stronger treated steel bolts 39 mm in diameter.
" The main difficulty of this project was to drill 88 holes of 45 mm diameter in an extremely thick mass (170 mm), create two chamfers of 70 mm diameter on either side, and then fit bolts weighing 7 kg each," explains Patrick Tchadirdjian, business manager at the Nuclear Services Division (DSN), in charge of this project.
Despite this, operations went perfectly.
"Patrick Tchadirdjian is pleased to report: " The worksites were successfully managed, coordinated and completed, while respecting the timing of the nuclear power plants, according to their respective unit shutdowns.
900CPY Material Access Pads in figures
- Diameter: 7m40
- Ferrule thickness: 39 mm
- Depth: 800 mm
- Weight: 26 tonnes
- Level: 20 metres above ground
- Budget: CPY 83,826.01/slice
CP0 58,704.00/tranche
Onet Technologies, the only company to master this type of work
The reinforcement of material access buffers, key elements of reactor building containment (3rd barrier), is one of the upgrading measures recommended by the ASN (Autorité de Sûreté Nucléaire) to extend the operating life of nuclear power plants.
In France, operators are required, at the end of each ten-yearly inspection - in this case, the3rd (VD3) - to guarantee that their facilities comply with the applicable standards, to improve the level of compliance and to correct any deviations detected.
The contract, signed in October 2007, took two years to complete. For Onet Technologies, it represents a real challenge, as the company is currently the only one to carry out this type of work. The expertise it has thus developed has enabled it to position itself on more recent sites (1300 MWe) with another specific technology.
Its agents were trained in-house, on the basis of modules validated by the customer.
900CPY Material Access Pads in figures
- Diameter: 7m40
- Ferrule thickness: 39 mm
- Depth: 800 mm
- Weight: 26 tonnes
- Level: 20 metres above ground
- Budget: CPY 83,826.01/slice
CP0 58,704.00/tranche
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.