will France run out of water to cool its nuclear power plants?

With global warming increasing the frequency of droughts, will we one day run out of water to cool nuclear power plants? The risk of water shortage is a matter of concern for the opposition, which raised this point during the debates for the adoption of the law Project relating to the acceleration of procedures relating to the construction of new nuclear installations. The text, already adopted in the Senate and discussed Monday, March 13 in the National Assembly, aims in particular to accelerate the installation of six new EPR 2 reactors.

The fear of a lack of water, however, seems unfounded for the rapporteur of the text, Maud Bregeon, Renaissance deputy for Hauts-de-Seine. “I have heard in recent weeks that the power stations are consuming water. We are short of it, so there is no [faudrait] not make power plants. Contrary to what EELV/LFI says, the water needed to cool nuclear power plants is not consumed, but taken and returned.“, insisted the deputy of Hauts-de-Seine, on March 2 in Economic Affairs Committee. Statements considered to be “untruths” by the national secretary of EEVL Marine Tondelier. “Nearly a third of the water consumed in France is dedicated to nuclear power plants, she replies on Twitter March 7. So, once and for all, let’s say it simply and firmly: at this rate, there will soon not be enough water in our rivers to cool the power stations.”

Are nuclear reactors really at risk of running out of water for their cooling? To determine this, franceinfo relied on the expertise of specialists in the sector.

Nuclear consumes hundreds of millions of tons of water

Cooling a reactor, as Marine Tondelier points out, requires colossal quantities of water. According to figures from the Ministry of Ecological Transition (PDF document), nearly 21.5 billion m3 of water were withdrawn in 2009 for cooling power plants, which are mostly nuclear in France. According to this same source, the energy sector accounts for nearly two-thirds of the volumes of water withdrawn in France, far ahead of abstractions for drinking water (17%). Is this resource returned to nature, as Maud Bregeon asserts? Contacted by franceinfo, EDF ensures that “98.5% of the water withdrawn by the 18 nuclear power plants is returned to the natural environment and close to the place of withdrawal.

However, the volume of water withdrawn but not returned to the aquatic environment – ​​mainly fresh water – remains significant. According to EDF, in 2021, 407.6 million m3 of water were thus consumed by the 13 power stations located on the banks of the river. An archived article from the website of the Ministry of Ecological Transition shows that the cooling of power plants, mostly nuclear, represents almost a third (31%) of the annual water consumption in France, which accredits Marine Tondelier’s thesis. Contacted by franceinfo, the ministry adds that this figure, not updated “for 14 years“, however, needs to be updated because “it does not reflect the reality of consumption”. The version currently online of the article in question specifies that the content is “under review”.

Adapting to heat waves, a necessity

In recent years, the recurrence of heat waves has already forced nuclear power plants to adapt their production. Not because of lack of water, but rather due to the excessively high temperature of their cooling water discharges. “The discharges from the power plants must respect a maximum temperature of the rivers downstream”, explains Eric Gaume, hydrologist at the Ecole des Ponts ParisTech. Reactors return warmer water to nature “until about 10 degrees”, explains Olivier Dubois, Deputy Director of Safety Expertise at the Institute for Radiation Protection and Nuclear Safety (IRSN).

This poses a problem during heat waves. During last summer’s droughtthe plants on the Rhône thus had to request an exemption from the Nuclear Safety Authority (ASN) to continue the discharge of their waste water, the temperature of the river downstream of the plants being higher than environmental standards.

“The power plants must also respect minimum flow constraints of the river”, adds Nicolas Goldberg, partner at Colombus Consulting, a firm providing consulting services to companies in the energy sector. “According to agreements signed with Belgium, the Chooz power plant in the Ardennes must, for example, respect thresholds in relation to the flow of the Meuse, illustrates Olivier Dubois. If the flow drops below 22m3 per second, the plant must shut down one of its reactors. Below 20m3 per second, its two reactors must be shut down.

“If we have to lower the power of the reactors during periods of drought, it is above all to preserve biodiversity, not for safety issues”, recalls, however, Nicolas Goldberg. According EDFthe fall in annual production at the Rhône power stations, despite the summer drought, was however limited to 0.2% in 2022.

A “significant” loss of power

What to expect for the future? According to the foresight report Energy Futures 2050 (PDF document, page 413) published by RTE last June, in 2050, for power stations located on the banks of the river, “global warming will increase the risk of unavailability, i.e. a reduction in production or the shutdown of reactors, by “two or three”. “With the drop in river flows, power plants will have less leeway to comply with environmental guidelines on the temperature of their water discharges”, warns Eric Gaume.

In annual total, the loss of electricity production due to heat waves or drought will however remain “very weak”, believes RTE. On the other hand, according to the study, the risk of unavailability of the electrical power of the reactor fleet could reach 8.5 GW during drought days. That is almost 14% of the power of the current fleet (61.4 GW), a loss qualified as “non-negligible” by RTE. “The issue of water consumption will not be the most important problem resulting from global warming, judge however Nicolas Goldberg. Two of the next three construction sites for the new EPRs will be located by the sea, where there will be no water shortage problem. For these reactors, it is therefore rather against the rise in sea level that we must protect ourselves.

With franceinfo, EDF claims to have already taken a number of measures against the effects of climate change. The electrician declares in particular to have improved the performance of the air-cooled cooling systems, recognizable by the large towers of the reactors through which steam escapes, “so that they consume less water”. Despite a tangible impact of climate change, it therefore appears that, even in the long term, nuclear power plants will still find enough water resources to operate.