Nuclear engineering and services
Dismantling of the Saint-Laurent-des-Eaux nuclear power plant: Onet Technologies' expertise contributes to the success of the project
On December 3, 2024, a major milestone in the dismantling of the Saint-Laurent-des-Eaux nuclear power plant was successfully reached: the completion of electromechanical dismantling operations under the caisson of Unit 2.
This project, carried out by Onet Technologies in collaboration with EDF DP2D teams, illustrates the technical and organizational excellence of our teams, who met numerous challenges to bring the operations to a successful conclusion.
Technical challenges mastered by our teams
Dismantling the electromechanical circuits under the A2 reactor vessel represented a major challenge for the teams working on the project.
Among the most complex technical challenges, our teams had to ensure :
- Maintaining the vessel's vacuum: the differential pressure had to remain at 300 Pa*. Each pipe cut (over 720 in all) required rigorous monitoring to guarantee the integrity of the casing.
- Validation of welds on the casing: our welders have passed specific qualifications, known as QMOS, to meet safety requirements. The welding and penetrant testing skills of our teams at Chinon were mobilized as back-up.
- Management of ALPHA and CMR risks (asbestos and lead): the installation of stato-dynamic confinement systems and collective and individual protection devices ensured the safety of workers.
- Working at heights and the ever-present risk of fire: 70% of operations required the use of scaffolding, and heightened vigilance with regard to the risk of fire associated with welding work.
- Optimizing nuclear waste management: as the pace of dismantling exceeded that of waste processing, internal reorganization was necessary to meet contractual milestones.
*In the nuclear context, "Pa" is the abbreviation for Pascal, which is the unit of pressure measurement in the International System (SI).
Specific know-how
In order to meet the technical challenges involved in dismantling the electromechanical components of unit 2 of the Saint-Laurent A plant, our teams had to mobilize specific expertise:
- The installation of double-skin architectural containments with a negative pressure of -20 Pa to prevent any dispersal of contamination,
- The use of a special hydraulic clamp to minimize the impact of cut-outs on the casing seal,
- Autonomy in scaffolding construction, allowing greater flexibility in work organization,
- Rigorous assessment of chemical risks thanks to measurements at the carrier and regular environmental analyses.
Safety, one of Onet Technologies' top priorities on this site
What's more, in addition to the know-how deployed and the technical issues mastered by our teams, an in-depth approach to safety has enabled our employees to effectively anticipate and prevent risks on the Saint-Laurent A site, as we do on all our dismantling sites.
Indeed, since 2021, no lost-time accident has been recorded on this site, testifying to the rigor of our procedures and the commitment of our teams to safety. At Onet Technologies, we focus on learning and rigorously applying industry best practices, as well as developing constant vigilance and a proactive attitude to risk.
This milestone represented a major safety challenge, and Onet Technologies was able to deliver ahead of schedule, while guaranteeing impeccable safety and quality standards. No radiation protection deviations or incidents were identified, and operations were fully traceable. This result is the fruit of a committed team and efficient organization.
The commitment and discipline of our teams have enabled us to achieve an exemplary level of performance in risk prevention.
An exemplary partnership with EDF DP2D to meet the challenges of the SLA dismantling project
To effectively absorb the workload of this industrial challenge, an optimized methodology was implemented, with an adaptation of cutting and a revision of welding schedules. Efficient management mobilized and supported teams to achieve optimum work rates.
From the outset of the project, we worked closely with EDF DP2D, facilitating coordination in the face of technical and logistical challenges, and strengthening the relationship of trust between our teams and those of EDF. Throughout the project, a constant dialogue with EDF DP2D was maintained through the regular organization of Local Monitoring Committees (CLS), guaranteeing the safety of operations and the anticipation of potential risks.
This success is above all a story of partnership and pragmatism. In the field, the teams have shown remarkable adaptability.
Onet Technologies, a key player in nuclear dismantling
This success in Saint-Laurent A once again confirms Onet Technologies' expertise in nuclear decommissioning. Thanks to our proven expertise, we are able to support our customers in the success of their most complex industrial projects. A true team effort, supported by the professionalism of our employees!
And now? With the end of this dismantling phase at SLA, Onet Technologies continues to support EDF DP2D in the liberation of the MEC cell and the dismantling of the pool premises, a stage in an overall project scheduled to run until 2029.
Dismantling UNGG reactors: a major industrial challenge
Uranium Natural Graphite Gas (UNGG) reactors, like those at Saint-Laurent A, present specific challenges due to their particular design.
Unlike pressurized water reactors (PWRs), they use carbon dioxide as a coolant and require a specific approach to the management of sheath rupture detection (DRG) circuits.
Controlling alpha contamination and managing irradiated waste are major challenges requiring specific expertise and technical solutions, which Onet Technologies teams are successfully deploying.
Thanks to our collaborators Romain Williame and Pierre Plantier for their contributions, which have enriched this article.
This content may be of interest to you
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.