“We’re in the final stretch”: At Flamanville, EDF is nearing the launch of the first nuclear chain reaction in its new-generation EPR reactor, a symbolic step before the first megawatts reach the Norman countryside this summer.
After 17 years of a challenging and costly construction process, marked by numerous setbacks and delays, EDF is putting the finishing touches on the actual start-up of the 57th reactor in the French nuclear fleet, a first in nearly a quarter of a century for the nation of nuclear power.
“We’re in the final stretch of testing before this very important step of divergence,” confirms Grégory Heinfling, operations manager for Flamanville 3, which will become the most powerful reactor in the country (1,600 MW) and will eventually employ 800 people, including 200 subcontractor employees.
EDF is cautious about the timing of the operation, which involves obtaining the first nuclear fission chain reaction in the heart of “Fla3,” but it is reportedly only a matter of “days” or even “weeks.”
At that point, the reactor housed under its 50-meter-diameter dome will not yet produce electricity, but “its heart begins to beat,” explains EDF. “It’s the moment when the reactor comes to life,” illustrates Alain Morvan, director of the Flamanville 3 project, during a visit for a few journalists in the concrete cathedral facing the English Channel.
“The cold tests are finished, and now we’re doing hot tests, raising the reactor to 155 bars and 303 degrees, the nominal temperature, before divergence,” continues the project’s conductor. To launch this operation, EDF will need to obtain the green light from the French nuclear safety watchdog, the ASN.
“The goal of divergence is not simply to press a button, but to bring the entire reactor into physical conditions to achieve the fission reaction,” summarizes François Tronet, a trainer at Flamanville.
The operating teams, who work in three eight-hour shifts, have already prepared for this operation in a simulator, an exact replica of the fully digitized control room – an EPR innovation – with its wall of screens displaying the reactor’s inner workings. “Each shift team has played this scenario at least two or three times,” assures Grégory Heinfling.
The first nuclear reaction is obtained when a neutron splits a uranium atom nucleus, which releases a large amount of energy and other neutrons, which in turn trigger other nuclear reactions.
On D-Day, the operators in the control room will hear a repetition of “toc-toc-toc,” an audio cue to guide them through the process.
To initiate this chain reaction gradually and in a controlled manner, and to allow the release of neutrons, they will have to raise the control rods centimeter by centimeter, a mechanism in the form of rods that allows them to control the reactor’s power.
“Each ‘toc’ we hear represents 1,000 neutrons hitting the detector,” emphasizes François Tronet.
Since May 7th, when the ASN gave the green light to commission this EPR, 12 years after the scheduled date, EDF has already passed several key milestones and conducted numerous tests and verifications.
After loading the 60,000 fuel rods into the vessel, EDF focused on testing the proper functioning of the 89 control rods, which are crucial because they allow the nuclear reaction to be controlled and stopped in an emergency.
The reactor will send its first electrons onto the high-voltage lines by the end of the summer, according to EDF, when it has reached 25% of its power, a condition for connecting it to the grid – this is called “coupling.” It will then be the turn of the imposing Arabelle turbine, 70 meters long and weighing 1,200 tons, to come into action. At the time of “coupling,” this machine, which is currently waiting in the machine room, will rotate at 1,500 revolutions per minute to produce electricity, driven by the steam created by the reactor’s heat.
It will be necessary to wait a little longer to reach full production at 100%, intended to supply 3 million homes, a step that EDF promises by the end of the year.