A substantial influx of jellyfish triggered automatic shutdowns of four reactors at the Gravelines nuclear power plant in northern France during the weekend, following blockages in the water intake systems used for reactor cooling.

The reactors—numbered 2, 3, and 4—ceased operations late on Sunday evening, and reactor 6 followed on Monday morning, adding to the two units already offline for scheduled maintenance.

The disruptions occurred when jellyfish accumulated in the filter drums of the plant’s pumping stations, which draw seawater from a canal linked to the North Sea.

Safety systems responded promptly, and the operator confirmed that there was no impact on the facility’s integrity, personnel safety, or the surrounding environment.

Gravelines is among the largest nuclear facilities in Western Europe, comprising six reactors each with a capacity of approximately nine hundred megawatts.

The site supplies a significant share of regional electricity and draws seawater for cooling via a canal connection to the North Sea.

This incident is not unique; similar jellyfish-related disruptions have occurred in the past at power stations in other countries.

In response, research efforts have produced early warning tools to forecast jellyfish blooms that may threaten coastal power infrastructure.

An EDF spokesperson confirmed that one reactor, unit six, restarted early Wednesday morning, with work under way to bring additional units back online over the following days.