Jellyfish shut down French nuclear power plant

PARIS – One of the largest nuclear power plants in Europe partially shut down last weekend, overwhelmed by a gooey and spineless foe: jellyfish.

The “massive and unpredictable presence of jellyfish” forced three of the six reactors at the Gravelines Nuclear Power Station in northern France to go offline just before midnight on Aug 10, according to EDF, the company that operates the plant.

A fourth reactor shut down early on Aug 11, the company added.

The jellyfish convened in the filter drums of pumping stations in the non-nuclear part of the facility, EDF said in the statement, adding that “they had no impact on the safety of the facilities, the safety of personnel or the environment”.

The shuttering of the reactors was part of the power plant’s safety and protection systems, EDF said.

The company said workers were trying to restart the reactors safely. EDF did not immediately return a request for comment.

Nuclear plants often require large volumes of seawater to cool their reactors, said Dr Erica Hendy, a professor of biogeochemical cycles at the University of Bristol in England.

The plants’ intake pipes have screens that prevent debris and marine life from being sucked into those cooling systems, she said, but large swarms of jellyfish can block the screens themselves.

Additionally, dead jellyfish can “liquefy into a ‘gel’” and pass through the screens, causing problems deeper in the plant system.

Water that flows from the cooling towers at the plant, located on the edge of the North Sea, is used by a commercial farm to help raise fish because it is warmer than the seawater, according to the American Society of Mechanical Engineers.

Warmer water temperatures have also been associated with larger jellyfish populations.

Jellyfish are 95 per cent water, but in large swarms can cause big problems for nuclear power plants by clogging cooling intake systems.

“The issue of jellyfish and power generation disruption remains a global challenge, as blooms of jellyfish are becoming more frequent and widespread due to factors such as overfishing, climate change and increased coastal development,” according to the Oceanic Invertebrate Research Institute.

Nuclear plants worldwide have been affected by jellyfish swarms.

In 2011 alone, jellyfish caused shutdowns at plants in Israel, Japan and Scotland. In 2013, an invasion of jellyfish paralysed a reactor in Sweden. NYTIMES