[Flamanville EPR Series] Progressing Towards Reactor Divergence

Since the authorization to load fuel into the Flamanville EPR, EDF’s on-site teams, along with major industrial players in the sector, are making rapid progress. With the reactor divergence just a few weeks away, Alain Morvan provides an update on the ongoing tests.

The commissioning of the Flamanville EPR is rapidly advancing. With the fuel now loaded into the reactor core and as we await the first nuclear fission reaction, known as divergence, numerous tests are actively being conducted and have been successfully completed. A post on X highlights that both the operation of the 89 reactor control clusters and the neutron flux measurement system tests within the EPR’s core have been approved.

In a post on LinkedIn, Alain Morvan, the Flamanville project director, describes the ongoing operations in more detail. He writes: “The upper internals of the vessel, which house the control rod mechanisms and core instrumentation, consisting of very thin 12mm tubes, have been inserted into the vessel. The reactor building’s pool was drained to install the 5.7-meter diameter vessel cover. Activities to ensure its tightness took place, such as the passivation of the vessel’s joint surface. By the end of May, the 52 bolts of the cover were tightened using the stud tensioning and loosening machine (MSDG), a meticulous operation that mobilized about twenty people from Framatome! The ‘cable bridge’ was then installed to connect the core control system (control-command) and the instrumentation inserted into the core. Checks were carried out to ensure the tightness of the mechanical connections. Additionally, the preservation of the steam generators was also initiated to configure them for operation.

Testing Equipment Individually

Then, the water level in the primary circuit was lowered to the ‘¾ loop’ level. At that point, the second phase of startup tests began with the vacuuming of the primary circuit followed by filling the control rods, the vessel, and the pressurizer. Initial specific tests on the EPR took place on the ‘aeroballs’ (neutron flux measurement tool), to test their ability to map the core and measure the future neutron flux. The four primary motor pumps were started for the first time since the load at 24 bars, to vent the primary circuit and thus expel the last air bubbles.

The tests of the control rod mechanisms are starting! The 89 control rods will be extracted one by one from the core to verify their operation. Then, the pressure and temperature will continue to rise until reaching the hot shutdown plateau at 303 degrees and 155 bars. The hot pre-critical tests will be conducted at this level.”

The divergence is now expected to occur in July. In the meantime, you can find Alain Morvan’s webinar on the reactor fuel loading, broadcast at the beginning of June 2024.■

By Sfen
Image: Cuve de l’EPR de Flamanville – @EDF