With the heat wave, nuclear power plants, too, must adapt. The thermometer is racing everywhere in France with temperatures that regularly reach 40°C, and the rivers are lower and lower. Since August 6, five nuclear power plants have benefited from environmental exemptions until September 11 concerning water discharge temperatures due to high temperatures, despite possible negative impacts on the environment.
The operating principle of a nuclear reactor is to produce electricity from the heat given off by the chain reaction that takes place in its core. VSuclear installations must therefore be permanently cooled in order to be able to operate in complete safety. This explains their construction by the sea or near rivers or streams. They draw from it large quantities of water necessary for their cooling circuit and some reactors, depending on the model, then discharge it into the nearby stream. However, the water discharged is subject to environmental constraints and must not exceed a temperature threshold in order to protect the aquatic fauna and flora.
Since the heat wave in the summer of 2003, each plant concerned must comply with discharge standards defined by the Nuclear Safety Authority (ASN). To achieve this, the power stations reduce their power in order to discharge less water. But, the production of electricity being historically low in Europe and in France, the operator of the electricity network, RTE, has requested that production be maintained. Exemptions from discharge standards have thus been granted to five reactors in operation: Bugey (Ain), Blayais (Gironde), Saint-Alban (Isère), Tricastin (Drôme) and Golfech (Tarn-et-Garonne). ).
“The derogation therefore makes it possible to reject a little more hot water than what is planned”
Jacques Percebois, Director of the Center for Research in Energy Economics and Law.franceinfo
So far, this derogation had only been used once in 2018. It was in Golfech, where the temperature of the discharged water exceeded the standard. It had lasted three days.
But with these episodes of heat which multiply, do we not risk arriving at a system of permanent derogation? For the researcher,slightly different standards will have to be accepted in the future“. But the central point according to him is to find sites “better suited” for the new French nuclear program. Of the 56 French reactors, 30 have a system with “cooling towers “, which allow the plant to be cooled and the steam to be evacuated by the steam.”This system has the advantage of pumping much less water, but returns less since part of it goes into the atmosphere.“, explains Jacques Percebois. The other system is a system called “open“, cooling by river or by the sea where “a 900 Megawatt plant needs 40 cubic meters of water per second and then discharges 97% of this water, which heats up the river“, continues the specialist. Of the 26 reactors, 14 are by the sea.
“Which means that tomorrow, if we want to build new power plants, we will have to favor the seaside. The problem is that it is difficult to find sites”
Jacques Percebois, Director of the Center for Research in Energy Economics and Law.franceinfo
Last February, Emmanuel Macron announced his intention to build six EPR reactors in France, with studies for eight more. RTE highlighted the problem of global warming on the nuclear fleet in its report on the future of the energy system. Of the first six EPR reactors planned, four are proposed by EDF by the sea, in Penly (Seine-Maritime), near Dieppe, and in Gravelines in the North. The last two could come out of the ground in Tricastin or Bugey, on the banks of the Rhône. For them, the manager of the electricity network relies on the water refrigeration systems of the cooling circuit. Enough space will therefore have to be found on future EPR installation sites.
For Jacques Percebois,there are solutions, this does not call into question the program” but “Additional constraints will have to be taken into account, he analyzes. The system should be preferred air cooler and therefore find space because the towers require more surface. There are other solutions, we can try to use residual heat, we can think about storing heat in the ground“.