[Flamanville EPR Series] The neutron sources mounted in the reactor core

In a video published by Alain Morvan, the project director of the EPR at Flamanville, we witness a significant milestone for the future French reactor: the delivery of the primary source rods intended to initiate the nuclear reaction. These were welded to the primary source assemblies by the teams at Framatome. The control rod clusters have also been inserted into the fuel assemblies.

The fuel will be loaded into the Flamanville EPR in a few weeks. Until then, many steps still need to be completed. One of the major steps occurred at the beginning of February with the arrival and installation of the source assemblies. This involves the insertion of a neutron source into the core to generate a sufficient neutron flux to start the reactor. This allows for a reliable measurement of the flux and its changes through instrumentation, a crucial function for safety.

Alain Morvan, Director of the Flamanville 3 project for EDF, shared on LinkedIn: “Last week, another key activity was completed as part of the preparations for loading. It was the end of the assembly of the primary source assemblies, which check the proper functioning of the neutron flux monitoring chains of the reactor core once it is loaded. The teams eagerly awaited the truck carrying the three 4-meter-long primary source rods packed in a 7-ton capsule. The staff underwent specific training and practice for several days to prepare to handle this significant load. Before welding, a dry run was conducted to perform the extraction kinetics and water installation with a dummy assembly. After the training, Framatome’s meticulous welders welded the rods to the primary source assemblies, a meticulous and delicate action that was perfectly executed! I would like to congratulate and thank the EDF fuel division teams for managing this precise operation and the risk prevention division for ensuring safety throughout the area.”

89 control rod clusters

The post is accompanied by a video showing the arrival of this massive metal container, its handling, and the installation of the source assemblies. Alain Morvan also updates on other significant milestones achieved by the future French reactor. He explains, “89 control rod clusters have been inserted into the fuel assemblies. They play a crucial role in safety when the reactor is in operation, as they stop the nuclear reaction when an automatic shutdown of the plant is necessary, and they regulate the power level of the reactor according to their insertion heights into the core.”

At the end of January, during his New Year’s address to the press, Bernard Doroszczuk reviewed the schedule announced by EDF for the Flamanville EPR, namely loading by the end of March for a divergence before summer. “It’s possible, but it’s very tight; there is no margin, especially if EDF does not provide the last elements we have requested,” he stated, while also mentioning the preparation of documents to transition from the construction teams to the operating teams, the compliance certificates for certain pressure equipment, and the holding of the final public consultation on the reactor’s commissioning.■

By Ludovic Dupin (Sfen)

Image: Extract from the video of the assembly of the source clusters on the Flamanville EPR – ©EDF