Drought: Nuclear power plants on the test bench of global warming
With the heat wave, nuclear power plants must also adapt. Across France, the thermometer is racing, with temperatures regularly hitting 40°C and the rivers getting lower and lower. Since August 6, five nuclear power plants benefit from environmental exceptions related to water outlet temperatures due to high temperatures until September 11, despite possible negative effects on the environment.
The working principle of a nuclear reactor is to generate electricity from the heat given off by the chain reaction that takes place in its core. vsnuclear plants must therefore be permanently cooled in order to be able to work absolutely safely. This explains their construction by the sea or near rivers or streams. From this they take large amounts of water, which is needed for their cooling circuit and some reactors, depending on the model, and then pipe it into the nearby stream. However, the discharged water is subject to environmental regulations and must not exceed a temperature threshold to protect the aquatic fauna and flora.
Since the heat wave in the summer of 2003, every affected facility has had to comply with the defined discharge standards the Nuclear Safety Authority (ASN). To do this, the power plants reduce their output in order to discharge less water. However, with power generation in Europe and France at historically low levels, the power grid operator, RTE, has called for production to be maintained. Derogations from the discharge standards were granted to five operating reactors: Bugey (Ain), Blayais (Gironde), Saint-Alban (Isère), Tricastin (Drôme) and Golfech (Tarn-et-Garonne). ).
“The derogation therefore makes it possible to refuse a little more hot water than planned”Jacques Percebois, Director of the Center for Research in Energy Economics and Law.
To date, this exemption has only been used once in 2018. It was at Golfech that the discharged water temperature exceeded the norm. It had taken three days.
But with these heatwaves that are multiplying, aren’t we risking moving to a system of permanent exemptions? For the researcherslightly different standards must be accepted in the future“. But the central point, according to him, is to find locations “more suitable” for the new French nuclear program. Of the 56 French reactors, 30 have a system with “cooling towers “which allows the plant to be cooled and the steam to be exhausted through the steam.”The advantage of this system is that it pumps much less water but recycles less, since some of it ends up in the atmosphere.“, explains Jacques Percebois. The other system is a system called “open“, cooling off at the river or at the sea, where “A 900 megawatt plant requires 40 cubic meters of water per second and then diverts 97% of that water, which heats the river‘ the specialist continues. Of the 26 reactors, 14 are by the sea.
“This means that tomorrow, if we want to build new power plants, we will have to give priority to the coast. The problem is that it’s difficult to find locations.”Jacques Percebois, Director of the Center for Research in Energy Economics and Law.
Last February, Emmanuel Macron announced his intention to build six EPR reactors in France, with studies for eight more. RTE has highlighted the global warming issue of the nuclear fleet in its report on the future of the energy system. Of the first six planned EPR reactors, four are proposed by EDF at sea at Penly (Seine-Maritime) near Dieppe and at Gravelines to the north. The last two could spring up in Tricastin or Bugey on the banks of the Rhône. For them, the manager of the electricity network relies on the water chillers of the cooling circuit. Sufficient space must therefore be found at future EPR installation sites.
To the Jacques Percebois,if there are solutions, this does not call the program into question” but “Additional constraints must be considered he analyses. The system should be preferred air conditioning and thus find space because the towers require more space. There are other solutions, we can try to use residual heat, we can think about storing heat in the ground“.