2023-08-17 11:09:56
Electricity production in some nuclear power plants will be reduced in the coming days due to the expected high heat.
In the Rhone Valley, nuclear reactors will be idling in the coming days. EDF plans to reduce production at the Bugey (Ain) and Tricastin (Drôme) power plants due to the high heat expected at the end of the week. A usual measure in the event of a heat wave: this was already the case in mid-July and at the beginning of August, as well as on many occasions in previous years, especially in the south-east of France.
It is water that disrupts the operation of nuclear power plants. Because the latter need large quantities of water to permanently cool their installations, which explains why they were all built by the sea or near a river, canal or estuary. . Power plants take cold water, use it to cool nuclear reactors and spent fuel storage pools, then discharge it hotter.
Preserve the fauna and flora
However, these hot water discharges are subject to a strict temperature limit to preserve the fauna and flora – the unusual rise in water temperature, even by a few degrees, is highly detrimental to aquatic biodiversity. For example, downstream of the Saint-Alban power station (Isère), the temperature of the water in the Rhône must not exceed 28°C in summer, which forced EDF to shut down the two reactors. in the summer of 2018 during very hot weather.
Nuclear power plants operating in “open circuit”, that is to say discharging water directly into the river, are the first concerned in the event of a heat wave (Tricastin, Blayais, Saint-Alban, reactors n°2 and n°3 of Bugey, Fessenheim before its closure). But the other power plants, those which have “air-cooling” towers cooling the water in contact with the air before rejecting it, are not spared from this, as in Golfech (Tarn-et-Garonne) in 2019.
Too little water in the river
Moreover, in addition to environmental considerations, the heat wave is also not without consequences for the safety of power plants. A prolonged drought can lead to a period of “low water”, that is to say at the minimum level, for the river. Its flow rate is then insufficient to be able to pump the water necessary for cooling the installations. The drop in the flow of the Meuse had led to the complete shutdown of the Chooz power station, in the Ardennes, in August 2020.
Inside the plant, very high temperatures during a heat wave can also disrupt the operation of ventilation circuits, safety systems or emergency generators, because they need water or use outside air. The rise in the temperature of the river water also promotes the proliferation of algae and micro-organisms which obstruct the entrance to the water pipes supplying the nuclear power plant.
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