Located on the Channel coast near Dunkirk, Gravelines is the largest nuclear power plant in western Europe, with six 900 megawatt reactors.

Four reactors at France’s Gravelines nuclear power plant, located along the English Channel, were temporarily shut down over the weekend after a swarm of jellyfish threatened to clog critical water intake systems.

Late Sunday, a jellyfish swarm clogged the cooling-water filters at Gravelines, a six-reactor plant on France’s North Sea coast. Four units shut down automatically. It was a bad timing, as two other reactors were already offline for maintenance,