The fight for water: the Rhône, a changing river at the center of energy issues

He is the “River-King”. Still he too must bow down SourceSource Swiss giant’s PortePorte Its name: Rhône Glacier, north of the canton of Valais. According to a Water Agency report published in March 2023, the drama playing out there is responsible for the increasingly significant decline. pacepace River’s. In 2050, its low flow rate – the lowest average annual level of a river by which floods are measured – will be reduced by an average of 20%. However, the Rhône today feeds one million people, provides water to more than two million and alone produces “A quarter of the country’s electricity production”, There are at least 19 hydroelectric power stations and four nuclear power stations on its coasts. They’re the ones we talk about the most… but is that really fair?

Water is essential for the operation of power plants.

In France, the reactors of our nuclear power plants are pressurized water reactors which provide 70.6% of the country’s electricity production. To function, water taken from an external source (river, river, sea) supplies three independent circuits that respectively produce large quantities ofthermal energythermal energy In the reactor, to convert it into mechanical energy and cool the system. backupbackup Of the reactor. The first two circuits are “closed” circuits: water “goes into the circle” with no way out. Therefore they consume less water.

Open or closed cooling circuit: you have to choose

The cooling circuit is more demanding. This is what we are interested in. These are of two types: open circuit and closed circuit. In open circuit power plants, chilled water taken from an external source cools the backup system, then is completely released into the water source. This is for example the case of the Bugey, Tricastin and Saint-Alban power plants – power plants where an average of 57m³/second is drawn from the Rhône.

“The counterpart is that if electricity production is significant then the induced warming in the environment can be quite significant, Cecil Laugier, EDF’s director of environment and foresight, expressed anger at a press conference given by the company last May on global warming. In practice, for our nuclear power plants, this causes an average of 4° to 5° warming in the environment. ,

Closed circuit plants take very little water (about 2 m³/second). After passing through the cooling circuit, the water is sent to an air-cooling tower where a call systemAirAir Cold reduces its temperature. Some portion of the water falls as drops, while the rest runs out through the chimneyschimneys : This is the famous plume of water vapor, epinal image of power stations. This process has the advantage of rejecting cold water into the source, but it does not allow everything to return: out of 2 m³ of cold water, about 0.7 m³ evaporates, so we recover about 1 m³ of water. . This cooling circuit prevents the external water from overheating.

In short: without water, nuclear power plants cannot operate; And without a guarantee that the water released will not raise the temperature of the source beyond a certain limit, no operation is possible, as the law requires. It therefore appears that the decline in low flow rates of the Rhône does not bode well for the cooling circuits of our power plants, which are supplied with water from the river…

Decline in the flow of the Rhone: what is the future of nuclear power plants and the millions of people who depend on them? (part 2)

Nuclear power plants cannot operate without water. Four of them are located on the banks of the Rhone, the country’s most powerful river, whose source is in danger of disappearing. So the announced decline in flows should encourage power plants to remain vigilant, but the rise in temperatures puts them in particular trouble.

Since 1960, the lower flow rate of the Rhône has decreased by 7 to 13%, depending on the location. One problem that never comes alone, heat also has to be dealt with: “Since 1970, the average water temperature has increased from 2.2 °C in the north to 4.5 °C in the south”, says the water agency. Temperatures too high to ensure sustainability of biodiversity. According to, the situation will get worse due to global warming weather reportweather report-In France this increase could reach +2.3°C by 2055.

So, should we be concerned about the proper functioning of the eight open circuit reactors spread across three of the four power plants bordering the Rhône? Contrary to all expectations, the answer is not clear, says Hervé Bodineau. This deputy to the director of safety expertise at the Institute of Radiation Protection and Nuclear Safety (IRSN) has an easygoing smile and a penchant for the right word. “The flow of the Rhone is typically around 1,000 m³/second, he explains. Which makes it the largest in the entire country. So even if it declined by 20%, there would still be enough energy to power a nuclear power plant and ensure its safety., In the medium term, Rhône “Will generally remain a powerful river with high flow rates”Laurent Roy, director general of the Rhône-Mediterranean-Corsica Water Agency, agrees in a press release.

Rising temperatures: a big issue

If the decline in flows, in the medium term, does not affect the proper functioning of power plants, then the increase in temperatures creates more problems: we should not do this “make food PiscesPisces , , Jokes (half) Hervé Bodineau. The chances of this happening at such temperatures are very less. Breathing, on the other hand, is a different story… because, generally speaking, the warmer the water, the less oxygen it contains, and the lower its solubility – its ability to dissolve in water to form a homogeneous mixture. She goes.

Therefore rising temperatures pose a risk ExpressionExpression At power plants: If the flow rate is too low to properly dilute the hot water, or if the power plant cannot cool the waste water sufficiently, it can legally reduce the power of the reactors or Even that is bound to shut them down. completely. For example, this was the case during a heat wavea heat wave Of 2022.

Faced with the increasing frequency of these extreme events, and to continue producing electricity, we must develop infrastructure, and very rapidly. A challenge that EDF, the public company in charge of power plants, is preparing to take.

Decline in the flow of the Rhône: what is the future of nuclear power plants and the millions of people who depend on them? (third part)

The first threat to nuclear power plants is rising water temperatures. Due to this, power production is at risk and forces EDF to adapt its infrastructure. For this the company launched the Adapt Project. An ambitious programme, but one which must be part of a framework of cooperation between all stakeholders.

Rethinking the infrastructure of nuclear power plants to deal with global warming and its threats: The challenge is an example of bravery. Unsurprisingly, on the Rhone, the first to be concerned are open circuit power plants, with the water agency warning: “Reduced flow rates, combined with water warming, will create increased operational constraints for nuclear power plants with an open cooling circuit to respect regulatory limits governing cold water discharge”,

opposite of this,Closed circuit power plants have a major advantage. At the request of the Nuclear Safety Agency, EDF deepened its research on the topic as part of a ten-year review of past heatwaves, and found that cold water passing through air coolers is re-oxygenated before returning to its environment. it was done. , Not only does it not contribute to disrupting the life of the Rhône, it also contributes to slightly improving its oxygenation.

Adaptation: EDF’s Titanic Project

The public company is therefore planning to build cooling towers in open-circuit power plants, as part of the ADAPT project launched in April 2023 for the adaptation of French nuclear power plants to climate change. A titanic program announced by President Emmanuel Macron and which will solve the problem of extremely high temperatures… Sure, you can say, but Rupees The part of the water that evaporates as it leaves the towers and therefore does not return to the river? jointly with Massachusetts Institute of Technology (MIT), EDF is currently testing a solution at the Budgie Power Station to limit this evaporationevaporation Water in an air cooler, by re-condensing the water vapor so that it no longer evaporates. “So far, the results are very promising! , Hervé Bodineau, deputy director of security expertise at IRSN, is excited.

Usage should also be modified by planning maintenance works in summer – where electricity demand is lower – to be able to meet demand without interruption in winter. Other solutions exist for the most extreme situations: for example, it is possible to operate a nuclear power plant in a desert area (this is especially the case of the Palo Verde power plant in the Arizona desert in the United States), but Hervé Cordier believes ​​that these systems are not current. They “Allow us to adapt to situations that are not what we envisioned in France, that are well beyond what we envisioned in France, even in 2100.”The Group Head of the Engineering and New Nuclear Projects Department explained during an EDF press conference in May 2023.

The future between technology, virtuous consumption and consultation

It remains that even if the proposed solutions are less ambitious, they will remain complex and extremely expensive, and will have to be part of an adapted resource management based on the cooperation of the different actors who use them. “We need the widest possible consultation with all stakeholders, all water users.”, director of EDF Hydro Emmanuel Verger-Chabot concluded during a press conference last May. EDF’s main contacts today remain hydropower producers, especially the Rhône National Council, which in the future will have to deal with a river that is still abundant, but which may undergo significant changes depending on its capacity. season’sseason’s,

From there it is a bit early to say that these measures will be enough to mitigate the consequences of the disappearance of the Rhône Glacier, announced for 2100 by researchers from the Federal Polytechnic Schools of Lausanne and Zurich… and the answer lies in Is future political decisions, at whose mercy will remain EDF and other players dedicated to “King River”.