Commissioning of a new nuclear facility: the role of an engineering partner

Victor Reichardt, Flamanville 1-2-3 Business Manager for Assystem, explains: it is only once this first milestone has been reached, under validated performance and safety conditions, that the reactor is connected to the electricity grid. Before this stage, the electricity produced from the first divergence is not distributed to the grid, nor integrated into the national energy mix. Once the reactor is connected, the electricity produced is available for consumption on the grid, and the ramp-up process continues, from 25 to 80 and then to 100% nuclear capacity. This sequence, which will last several months, is divided into 4 phases. Each stage in this process is extremely strategic, ensuring the performance, reliability and safety of the newly commissioned facility.

The commissioning of a reactor is synonymous with a skills and responsibilities transfer between the construction teams and the operating teams, all associated with a major change in nuclear safety standards, since activities then come under the responsibility of the operator.

From the very first days of commissioning, the operating teams are naturally responsible for all the activities relating to plant monitoring. The monitoring teams take charge of the reactor and will precisely supervise it from the fuel loading until full power is reached. At the same time, and contrary to what we might think for a new reactor, the maintenance teams are also hard at work from the very first days of commissioning. Their activities, which have already begun in the early stages of commissioning, continue once the reactor is launched, and will continue throughout its lifecycle, whether it is operating or shut down. In fact, it is only 18 months after the start-up of the plant that its first major maintenance outage is scheduled. Known as ‘VC1’ for ‘Visite Complète 1 [first complete visit]’, the purpose of this shutdown is to carry out control and maintenance operations on the facility after a few months of operation, as well as to carry out some dimensional modifications.

The completion of VC1 cannot be improvised at the end of the 18 month-period; on the contrary, it is anticipated from the very first days of operation of the new reactor through the mobilisation of the teams who will oversee the developments and modifications, and who are therefore responsible for preparing them in terms of engineering. 

Preparatory operations for VC1 can be divided into two parts: on the one hand, activities known as ‘unit in operation’, which are conducted while the reactor is in service; on the other hand, anticipation of the modifications that will have to be made during the unit outage, such as finalising the design studies or selecting the companies that will actually be in charge of maintenance.

As Victor Reichardt adds, ‘we must not overlook the activities relating to the final adjustment work performed during this transitional period, when the construction teams historically present on site and the operator's teams are still working side by side’.

The contribution of engineering to the launch and first months of operation of a reactor

The first few months following the commissioning of a new reactor are a busy time for the operator's teams. The support of its industrial partners, and in particular the engineering companies, is key to achieving the various milestones. From the activities immediately performed during the first 6 months up to the connection of the reactor, then those linked to its gradual ramp-up, and finally up to the launch of VC1 at +18 months, the operator relies on its partner engineering teams to support him for site engineering, for the very first operation and maintenance operations, and for preparing the first unit shutdown.

To illustrate the diversity and strategic nature of these missions, we can mention 3 of the major positions entrusted by EDF to Assystem as part of the commissioning of the Flamanville EPR.

1. Site engineering

With the commissioning of Flamanville 3, we are dealing with a new standard of reactor, and its integration into the existing fleet is unprecedented for EDF. While other EPRs have already been built in China and Finland, or are under construction in the UK, Flamanville 3 will be the only one of this kind to be actually operated and maintained in the French fleet.

Now that this one-of-a-kind reactor is in service, we need to be able to conduct a whole range of engineering operations from the Flamanville 3 site; this site engineering activity will have to be coupled with the engineering teams in charge of operation and maintenance over the long term.

As Victor Reichardt explains, there are many site engineering activities. They include the final justifications for the maturity of the design, or adjustments to be made following the first few weeks since commissioning. They also involve providing technical support for the operating teams, to ensure rigorous control of modifications, a link between manufacturers and suppliers, and the performance of on-site inspections and verifications. They also guarantee configuration control by designing repository management and impact mitigation tools. Finally, site engineering relies, for example, on digital 3D modelling tools to effectively manage assembly planning or the high level of co-activity during these phases of transfer to the operator. Assystem contributes to these subjects, in particular through the support of its experts in visualisation and simulation tools, based in Cherbourg.

2. Support to the testing and finishing teams and transfer to the operator

Already working alongside EDF teams during the construction and testing phases for several months, around a hundred of Assystem's employees have been mobilised since the beginning of 2024 to support the operator towards the extremely important milestone of fuel loading. As this loading officially marks the end of construction, some of the Assystem teams are immediately re-mobilised, in particular to support the teams of finishers and testers. Here, the role of Assystem is to prepare and contribute to the various tests performed throughout the start-up of the EPR. These tests, known as commissioning tests, are intended to guarantee that the installation behaves as expected under operating conditions, to ensure that the EPR will operate safely and reliably. Another part of the team analyses the test results and recommends solutions in the event of inconclusive feedback. Finally, the last part of our team supports EDF during the implementation of these solutions and participates in the instruction of the last modifications of the installation which could not be executed before the loading.

With experienced collaborators who have been involved for several years in the construction of the site, Assystem can also provide EDF with teams of testers and finishers who are fully aware of the objectives and challenges of this decisive start-up phase.

3. Preparing and coordinating the VC1

The third major positioning is established in close collaboration with EDF's operating teams in order to prepare, launch and carry out the first maintenance operations essential for the operation of the new reactor. At the same time, however, we need to look ahead to the future maintenance challenges facing the site, and it is with this long-term perspective that Assystem has the privilege of operating with its specialist teams in industrial control and global safety systems working. Their mission on the EPR is to anticipate and prepare for the constraints of maintenance in operational conditions (MCO) for certain systems that will be used on Flamanville 3.

Assystem is proud to be working with the operator to prepare the VC1, for which our engineering teams are working alongside EDF to appraise modifications as part of the IPE (Ingénierie du Parc en Exploitation / Engineering of the Operating Fleet) process. In this context, we can mention, for example, the support provided by Assystem teams in Marseille for the replacement of the reactor vessel cover, in collaboration with EDF and Framatome teams.  

Once the modifications have been approved, they are shared with the operator through ‘équipes communes’ (joint teams), which are responsible for implementing the modifications to the installations designed by the engineering department, as well as for civil engineering maintenance (EPCm).

Finally, as Victor Reichardt concludes, Assystem will also be involved in training EDF teams in the operation of the ‘équipes communes’ as part of the IPE's engineering sequences. This support will strengthen their skills on the project and guarantee Flamanville 3 the best possible conditions for commissioning and future operation in the months to come.