Three Reactors Shut Down, Nuclear Power Generation Plummets
Électricité de France (EDF) confirmed on August 12 that three reactors at the Gravelines Nuclear Power Plant near Dunkirk in northern France were shut down after cooling water pumps were clogged by large swarms of jellyfish. The plant is the largest nuclear facility in Western Europe, housing six reactors, each with a capacity of 900 megawatts (MW), and relies on a canal connected to the North Sea for cooling water.
EDF stated that of the six reactors, three were shut down due to jellyfish clogging the cooling system, while another was reduced to 50% power as a precautionary measure. One reactor was offline for routine maintenance, leaving only one operating at full capacity. According to data published by EDF since 2015, France’s nuclear power generation on August 9 was already 15.6% below normal levels, and the shutdown is expected to further exacerbate the power supply shortfall.
Jellyfish Clogging Emerges as New Operational Challenge for Nuclear Plants
The Gravelines Nuclear Power Plant’s cooling system depends on seawater from the North Sea, but the massive aggregation of jellyfish rendered the cooling water pumps inoperable, forcing EDF to shut down the reactors to prevent overheating. EDF engineers noted that jellyfish clogging cooling systems is not unprecedented, having previously caused shutdowns at nuclear plants in other countries. In 2013, a Swedish nuclear power plant was forced to halt operations for three days due to jellyfish blockages, while in 1999, a Japanese nuclear plant experienced a significant drop in power generation after encountering similar issues.
To address the jellyfish threat, EDF has installed fixed cameras at the Gravelines plant to monitor debris in the water and has collaborated with French fishing organizations and maritime rescue agencies to track jellyfish swarm movements. However, EDF has not announced a specific timeline for restoring full operations or detailed whether more proactive measures, such as installing filtration systems or adjusting cooling water intake methods, will be implemented.
Impact on Power Supply and Future Risk Assessment
The Gravelines Nuclear Power Plant’s six reactors have a combined capacity of 5,400 MW, accounting for approximately 8% of France’s total nuclear capacity. The shutdown has had a significant impact on the country’s power supply. France’s grid operator has not yet disclosed specific response measures, but it is expected that increased thermal power generation or electricity imports may be used to compensate for the shortfall. Given that nuclear power accounts for nearly 70% of France’s electricity supply, the incident could place pressure on power prices and supply stability.
Environmental experts warn that climate change, which is causing rising sea temperatures, may lead to surges in jellyfish populations, thereby increasing the risk of cooling system blockages at nuclear plants. While EDF has established monitoring mechanisms, long-term solutions remain under evaluation, including potential adjustments to cooling system designs or enhancements to ecological early-warning systems. The French government has not yet issued an official statement regarding the incident, and further intervention remains a subject of interest.
The incident highlights the vulnerability of nuclear power plants to biological blockages and underscores the challenge of balancing energy security with ecological changes, an issue that nuclear operators will need to address moving forward.
