A swarm of jellyfish has appeared off the coast of France, raising a red flag for the operation of nuclear power plants. The problem arose as jellyfish clung to the reactor, disrupting the supply of cooling water.
On the 4th, according to the Financial Times, Électricité de France (EDF) recently halted one of the two 1,300-megawatt (MW) reactors at the Flamanville nuclear power plant located on the northwestern Normandy coast, while halving the output of another reactor. To safely operate the power plant, seawater must be drawn in to cool the reactor, but the influx of jellyfish clogged the pump filters in the cooling system, hindering the supply of cooling water. The 1,300 MW can supply power to approximately 7.22 million households.
This is not the first time the operation of a nuclear power plant has been temporarily suspended in France. Earlier, on the 11th of last month, EDF also announced that it had halted the operation of four reactors at the Gravelines nuclear power plant due to jellyfish clogging the cooling water intake filters.
At that time, three reactors (Units 2, 3, and 4) were automatically shut down, and Unit 6 reportedly stopped operating a few hours later. EDF explained that the Gravelines power plant has a total of six reactors, and the other two were offline for maintenance. The Gravelines power plant resumed operations about 10 days later.
EDF emphasized that the shutdown at the Flamanville nuclear power plant was a precautionary measure. The area affected by the jellyfish is a 'non-nuclear' part of the reactor, meaning there was no impact on the safety of the nuclear power plant itself. An EDF spokesperson noted that they are supplementing the power supply from other nuclear plants and that the plant could return to normal operations within a day.
Experts believe that this phenomenon is closely related to climate change. This summer, the sea temperatures in the English Channel rose abnormally compared to normal levels, leading to a surge in jellyfish populations, which have severely impacted nuclear power plants that utilize seawater for cooling. According to the Copernicus Climate Change Service (C3S), the marine heat waves are intensifying along the French west coast, and the sea surface temperatures in the English Channel are fluctuating above average.
The rise in sea temperature itself poses a significant risk to nuclear power operations. Each nuclear plant is designed with a set sea temperature for safe operation, and when seawater exceeds this temperature, the cooling efficiency within the plant declines and the risk of equipment failure increases. To raise the design sea temperature, operators must reinforce the plant's equipment, which leads to increased expenses.
To prevent a recurrence of similar incidents, EDF is reviewing additional safety measures for the Flamanville and Gravelines nuclear plants. For example, they are considering installing underwater speakers or high-frequency devices nearby to physically deter marine organisms from approaching.