Friday, August 3, 2012

Ooi Nuke Plant: 200 Cubic Meters of Jellyfish Caught on the Water Intake Screen

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.


Anonymous said...

Those jellyfish have great commitment. We should follow their example.

Anonymous said...

Lowly earthquake and tsunami should never stop a modern Nuclear Power Plant! Be gone!

Atomfritz said...

This could be funny, but it worries me gravely.

The Ooi operators will try to avoid shutting down the plant at all cost, no matter the risks they take.

They'll try to fight the jellyfish onslaught and not retreat a single step and this could well result in them getting succumbed by some later large surprise attack wave, with consequence of a potential total Ooi cooling failure.

This reminds me of the Battle of Stalingrad, where nobody dared to retreat to avoid the devastating defeat, only because of the "Fuehrer" command.

I worry for Japan... let's hope that Ooi won't become the nuclear industry's Stalingrad...

m a x l i said...

Lowly senior vice minister can never stop modern jellyfish.

Anonymous said...

How is it possible that a reduction of 30% of water intake requires only 1.8% of electricity output? The heat discharged should be a fixed percentage of the output (dictated by the efficiency of the steam turbine) so I would expect 30% reduction of output, unless they started discharging water at higher temperature.
Can anyone provide details on this kind of manouvre? Is Kepco taking undue risks again?

Anonymous said...

Good question.
Does Japan have any regulations? Does it matter?

During the sizzling month of July a number of US plants needed to get a special approval of the NRC to raise the temperature of discharge. There are allowable limits, until you need them to be something else.

Go Team Jellies

Anonymous said...

Rockin' Jellyfish.

Atomfritz said...

@ anon 5:29 and @ Beppe

The water discharge temperature is more important for nuclear plants using rivers as water supply. If the water gets too hot, serious downriver damage to flora and fauna would result, and the culprit would be easy to identify.

This is a special situation in which different, relaxed, rules apply. As Ooi must not be shut down, there appears to be a general rule override situation. Remember, there is a government minister on site, so we can well assume all this is governamentally approved.

Localized overcriticalities in the reactor - normally resulting in protective automatic shutdown - overridden.
Alarms blaring - no problem, just ignore.
Cooling water supply low because of jellyfish - just increase discharge up to 36 degrees C, slightly below the point before masses of dead fish and sea animal begin to cover the sea surface.

Anonymous said...

Thanks Atomfritz for the additional details. Especially interesting your interpretation of the presence of the vice minister role, being there to give permission to take risks (which extent he probably does not understand) rather than ensuring the plant is run safely.
This kind of information and its proper interpretation should be given more visibility.

Anonymous said...

KEPCO is going to do something to prevent further jellyfish "attacks"-- wonder what kind of chemicals and such they will dump in the water to kill the critters..Have they considered the increase in jellyfish might be caused by increased contamination?

Anonymous said...

"200 cubic meters worth of jellyfish forced the plant to reduce the water intake by 30%."

So if we had 800 cubic meter of jellyfish they could close the plant? Go Jelly, Go Jelly!

This could be Hayao Miyazaki's next anime where nature gently overwhelms man's folly. I can see it now, as a science fair project a child genius accidentally figures out how to breed 1000's of cubic meters of jellyfish in an incredibly short time. In the anime the Ooi plant could be near the child's experiment when it gets out of hand and clogs the intake. The kid is scared so he/she keep the jellyfish bloom secret as it keeps happening with what seems intelligence and purpose.....

Anonymous said...

Where can I buy an I "heart" jellyfish t-shirt?

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