Jellyfish trouble

Jellyfish problem at nuclear plants

http://www3.nhk.or.jp/daily/english/20120709_34.html

Operators of Japanese nuclear power plants have experienced power reductions at times, caused by a swarm of jellyfish being sucked into water intakes.

Electricity at the plants is generated by steam-driven turbines. The steam is then sent to condensers to be cooled down with pipes in which seawater flows.

An influx of jellyfish to the intakes sometimes disrupts the supply of cooling water, forcing operators to reduce power output to curb heat generation.

Many plants now have filters or equipment to remove sea creatures at the intakes. But these measures do not work perfectly when a massive bloom occurs.

Thermal plants have been affected too. Kansai Electric Power Company says jellyfish problems have forced it to reduce power output in 17 of its generators from April to June, the largest number of affected plants for the utility in the past 5 years.

The Nuclear and Industrial Safety Agency says reports on jellyfish trouble have been made from spring through fall, mainly at plants on the Sea of Japan coast.

But the agency says no reports have been made that jellyfish have completely blocked water intakes. The agency says that safety can be ensured by measures such as monitoring the flow of seawater.