I've written about 137 alarms at Ooi Nuclear Power Plant Reactor 4 and the jellyfish protesting the restart (again) in my previous post. Yomiuri Shinbun tells us the scale of the jellyfish attack this time.
200 cubit meters worth of jellyfish forced the plant to reduce the water intake by 30%.
Good job, jellyfish.
From Yomiuri Shinbun (8/3/2012):
KEPCO disclosed on August 2 that the output was lowered for Reactors 3 and 4 at Ooi Nuclear Power Plant in Ooi-cho, Fukui Prefecture for 17 hours at the end of July, because of the swarm of jellyfish near the water intake that reduced the amount of cooling water collected.
Output reduction in Reactor 3 was 1.8% maximum, and 1.3% maximum in Reactor 4. It is the second time since July 8 after the restart process started that the output was reduced because of jellyfish.
According to KEPCO, the number of jellyfish started to increase in the afternoon of July 30, when [both reactors] were in full operation. Reactor 3 started to reduce output at 3:30PM, Reactor 4 at 4PM. Jellyfish started to decrease in numbers by the early morning of July 31, and the output was restored to full at 8:30AM.
Jellyfish attached themselves to the water intake screen which was installed to remove floating debris, and the water intake capacity dropped by more than 30 percent, according to KEPCO. The volume of jellyfish removed is about 200 cubic meters. KEPCO is considering measures to deal with jellyfish.
Easy. Let Senior Vice Minister Makino to scold jellyfish: "Lowly Jerryfish should never stop a modern Nuclear Power Plant! Be gone!"
Otherwise, I think the best countermeasures against jellyfish is to stop the reactors so that no warm water is being released into the ocean from the plant.