2024-07-11 06:30:08
The Flamanville EPR reactor loaded its fuel in mid-May and is expected to diverge in July. The ASN continues to closely monitor the various phases of this start-up spread over several months.
The saga of the construction of the EPR in Flamanville seems to be coming to an end. The new nuclear power plant, whose work began in December 2007 and was marred by several deviations and non-conformities, saw the loading of its radioactive fuel begin last May. Several phases will follow that will lead to the operation of the 1,630 MW of the 57th reactor in the French nuclear fleet.
Initially planned for 2012, the EPR should be commissioned by the end of the year. But a nuclear power plant is not started up as easily as a wind farm. Several months of ramp-up and specific tests are planned to verify that approximately 1,500 safety criteria have been met.
The first phase of the start-up involved loading the fuel into the reactor vessel. 241 assemblies containing the uranium – each measuring 5 m high and weighing 800 kg – were placed in the reactor pool from the storage pool. This step, carried out from 8 to 15 May, was checked and validated by the Nuclear Safety Authority (ASN).
Closing of the tank… ephemeral
This first step was made possible thanks to the ASN gives green light May 7. With its decision to commission, the nuclear regulator has confirmed EDF’s ability to carry out the start-up of the EPR, following several checks carried out previously: inspections on the preparation of tests, in particular those on the instrumentation of the reactor core and those prior to loading the fuel, inspections on the preparation of the operating teams, conformity assessments of nuclear pressure equipment, etc.
After the fuel loading, the first phase of the start-up was completed by the installation, in the vessel, of the cluster control mechanisms and the core instrumentation, equipment necessary for controlling the nuclear reaction. The vessel cover (145 tonnes) was then installed and secured by tightening 52 studs. It should nevertheless be remembered that this cover, having suffered manufacturing anomalies, should have been changed this summer, and that the ASN authorized the postponement of this replacement to the first shutdown for reloading of the reactor, i.e. 15 to 18 months following its commissioning.
EDF continued with the second phase of the start-up: cold precritical tests at 55°C. The primary circuit was evacuated, the steam generator hairpin pipes were filled with water from the primary circuit, as well as the vessel and the pressurizer. The start-up of the four primary pumps allowed the primary circuit to be vented, i.e. the removal of residual air in the circuit. The cold tests are supplemented by tests of the core instrumentation required for measuring temperatures, the water level in the vessel and the neutron flux. The 89 control rod clusters are also tested, in particular their drop time in the vessel, a crucial device in the event of an emergency for an automatic shutdown of the reactor.
Reaching the divergence
The third phase of the start-up is that of the hot precritical tests. It was able to start on June 20, with the increase in pressure (155 bar) and temperature (304 °C) of the primary circuit. This hot shutdown stage led to the pressurizer switching to two-phase state, which keeps the water in the primary circuit in a liquid state. The change from a temperature of 110 °C was the subject of a non-objection from the ASN, necessary to continue, because this is the regulatory temperature for declaring the commissioning of the primary and secondary circuits. The increase in temperature also provided the opportunity to carry out tests on the steam generators.
During all these tests, several significant events for safety, three of which at level 1 on the INES scale were declared by EDF to the ASN. At the beginning of June, this led the national energy company to temporarily suspend start-up operations. The implementation of corrective actions shows that EDF is still in the learning phase and that vigilance remains essential.
Subsequently, the neutron flux will be increased by diluting the boron contained in the primary circuit, inducing the divergence of the reactor, i.e. the launch of the nuclear chain reaction. This should occur during July. It will have to be approved by the ASN, as will the continuation of the tests at a power greater than 25% of the nominal power, as well as the increase to 80%.
After the divergence, EDF will be able to couple the turbine to the electricity grid this summer. And finally deliver electrons to the French, almost 20 years following the orientation law of July 13, 2005 which officially gave birth to the project, and for a total cost of 19 billion euros, financial costs included. An increase in delays (+ 12 years) and costs (+ 15.7 billion euros) that would not have been tolerated in any other industry…
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