At the end of March, Emmanuel Macron presented the “water plan” that aims to introduce a more sober consumption of the resource and distribute it efficiently among the different uses. As an annual average during the period 2010-2019, power plants consumed half of the 32.8 billion cubic meters of water withdrawn as part of their cooling. However, much of this withdrawn water is returned, so the net consumption of the nuclear sector actually represents only 12% of the approximately 4 billion cubic meters of fresh water actually consumed each year between 2010 and 2019 in the ‘ Hexagon’.
If the nuclear industry is not, therefore, the largest net consumer of water in France, the various electricity-producing infrastructures could see their water needs affected by the phenomena related to global warming that will multiply and intensify in the coming decades .
Despite its oddity, the summer of 2022 demonstrated that a combination of circumstances—low rainfall and a partially shutdown nuclear fleet—could threaten French electricity production. This encourages EDF to take climate risk into account to adapt the water consumption of its existing and future infrastructures.
Substantial drop in river flow by the end of the century
Founder of Callendar, a start-up specializing in climate risks, Thibault Laconde recalls that the risk already exists, although it must be put into perspective: “We have examples every year of a forced drop in power plant production, but we don’t” . I didn’t really have a problem except in 2003 and last year. The projections until 2050 show a worsening of the problem without becoming greater.”
EDF thus estimates that production losses due to environmental causes only represent an average of barely 0.3% of the annual production of the nuclear park in the 21st century. However, global warming is drying up rivers, raising the question of water supply to riverside reactors in the long term.
These perspectives are obvious when 38 of the 56 French reactors are located on the banks of the river and the vast majority, 30 of them, operate in a closed circuit. In this configuration, 10 liters of water per kWh are withdrawn but only 77% is returned to the natural environment, while open-loop power plants take 170 liters of water per kWh but return all of it according to EDF data.
However, the energy company considers that the circuit changes would constitute large-scale substantial modifications. “This would lead to the revision of the entire operating system of the plant and would imply an interruption in the electricity production of the sites”, explains Cécile Laugier, Director of the Environment of the Nuclear Production Division (DPN).
Regulatory changes for five plants in 2022
EDF has already committed to adapting its existing power plants to short-term climate changes, be it episodes of heat waves or drought events. Since 2003, a very hot plan has been implemented in the park and the performance of the cooling systems has been improved so that they consume less water. In addition, the energy company indicates that the episodes of heat waves and low water levels have not had an impact on the safety of the facilities since the ambient temperature in the buildings remained below the limits that guarantee the safety of the equipment.
The energy company has also taken steps on a daily basis to ensure fair water consumption and preservation of the environment, as returned water must meet a certain regulatory temperature limit to limit harmful effects on surrounding biodiversity. For example, operating teams fine-tune steam production during start-up phases and optimize liquid effluent production.
During the summer of 2022, only five nuclear power plants – Blayais, Bugey, Golfech, Saint-Alban and Tricastin – were subject to temporary changes to their regulatory water discharge limits. These modifications made it possible to conserve 0.2 TWh and had no effect on fish mortality or health status, according to the results of monitoring carried out by EDF.
What long-term solutions?
There are also several options on the table to optimize water management at nuclear power plants in the future. The energy company anticipates investments in additional effluent reservoirs and is interested in an innovation by MIT researchers that would allow the recovery of water vapor from power plants and thus reduce water consumption.
As part of the future EPR2, all nuclear sites will incorporate two different systems to cool the reactor core in an emergency, one with water and one with atmospheric air. For new seaside reactors, a design allowance of one meter will be taken to cover the impacts of climate change on sea level rise by 2100.
Jacques Percebois advocates, for his part, for new construction to be concentrated on the promenade, a place that makes it possible to benefit sustainably from large amounts of water. “It is also possible to improve yields so as not to have too much heat to cool and recover part of that heat for agricultural land,” suggests the director of the Center for Research in Energy Economics and Law.
And the hydroelectric production?
The summer of 2022 was marked by three episodes of heat waves that caused very low flows in rivers and water temperatures that reached all-time highs. As for hydraulic stocks, they have been historically low, 2022 having been the least rainy year since 1960 according to EDF data, but the energy company has managed to replenish reserves to have maximum availability for the ‘winter’. During the year 2023, the fill rate of the water reservoir fell to 49% in February, but is now close to 70%, a higher level than the same period last year.
On the other hand, hydroelectric infrastructures, the source of approximately 11% of French production, could be restricted in their role as a complement or even substitute for the nuclear sector in the winter period. “The conflict in the use of water between agricultural uses and electrical uses could increase”, estimates Jacques Percebois.
The professor from the University of Montpellier also points out that renewable energies such as wind turbines can also fall victim to global warming: “If there is little impact on offshore wind energy apart from storms, strong heat waves and periods of extreme cold they can be accompanied by significant reductions in the wind or changes in its direction for onshore wind power.” According to Thibault Laconde, “the danger is facing an overlapping of electricity production problems between the different levers.”
Source: BFM TV
