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Sunday, March 13, 2011

New Japanese Thread

Update: Hydrogen explosion at Daiichi Reactor 3. This is sooooo not good. End update.

NISA released its update 21. In the 20 km evacuation zone, they don't have info at all for Minami Soumashi. That's the one with 70K persons, total evacuation population amounting to 180K persons. Second, readings at Daini are switching around with the wind. Onagawa (60 miles up the coast) declared a legal emergency because it had elevated readings of radiation. But it appears to be coming from Daiichi. Namiemachi's evacuation levels are only reported at about 10% out. Reported levels of radiation outside the plant are still down below 100 microSieverts. A microSievert is one thousandth of a milliSievert (0.001 milliSieverts). A milliSievert is one thousandth of a Sievert. We are not talking big short-term doses of radiation here when they report 70 microSieverts outside the gate. 1 milliSievert is a tenth of a Rem. However the highest reading I have seen quoted inside a Daiichi control room is 1,550 milliSieverts. That is a problem for working in the environment.

Daiichi last TEPCO update: They're looking for water from the municipal authorities for the spent nuclear fuel pool. They need to cool it down. Reactors 1 and 3 are continuing with injections of seawater and boric acid. Both have been vented. They had to manually open the safety relief valve on three to vent it. Reactor 2 is getting just fresh water, and has been vented. The level of water on 2 is below normal but "steady".

Daini last TEPCO update
: Of the four reactors, only reactor has achieved "cold shutdown". Reactors 1 and 4 had earlier alarms indicating that the on each, one of the control rods had not been properly inserted. For 4, they had another signal saying it was correctly inserted. For 1, the alarm ceased on its own and they are sure that the other control rods are inserted. They vented all four on the 12th. They are still trying to restore full cooling function on the other three to head to cold shutdown. They have offsite power on all four, so the gauges and control systems work, which is a big help. They are using the backup water condensate system? recirculates condensed steam? to inject water to continue cooling. They say the have stable water levels on all four. End update.

Update: TEPCO's site continues down. There is a pretty good article at WNN (World Nuclear News) on efforts with reactor 3 at Daiichi. I am going to link again to a prior incident report (from 2009) on reactor 1 at Daiichi because it has exact diagrams. They cannot get the water levels up past a certain point, but they're not sure because gauges may not be working properly. So they are monitoring pressure in the containment vessel and venting as necessary. They did try to inject boron to slow the reaction., NISA Japan is putting out periodic updates. The main link for all these incident reports is here. Reactor number 3 is different; the last incident report on reactor 3 is here, and it contains diagrams specific to the unit. End update.

The death toll is steadily mounting. Probably at least 12,000 casualties eventually.

Daiichi - the latest is that reactor 1 there is being injected with seawater and boric acid. Reactor 3 also ran into trouble, and news reports say that they began to inject that one with seawater. Hopefully they are dumping boric acid or the liquid fuel control rod (the solution with the tiny plastic bubbles suspended that contain neutron-absorbing elements) to that one. It is a MOX reactor. They probably want to get seawater levels above the levels of the control rods before adding the solution or boric acid. Kyodo News.

So that's two reactors that will never come back on line, and an increasing probability that the others there won't either. Japan is going to have a power problem after this is all over. In the short term, Japan has asked Russia for more gas and coal.

There was a new high radiation level inside Daiichi plant reported after venting reactor 3 - 1550 mSv, dropping to 184 about an hour later. Radiation levels have since dropped hard.

There is a place in India called Ransor where natural background levels can peak at over 200 mSv, so the 184 mSv is high, but not at a level that would make the environment unworkable.

This is by no means over. The Japanese are planning rolling power outages for many areas in an attempt to get services over a wider area. Supposedly the middle of Tokyo is exempt.

Comments:
Ace of Spades posted this link: http://ansnuclearcafe.org/ which seems to be a pretty good roundup.
 
184 mSv is the approx. equivalent of the radiation one would be exposed to on 5 transatlantic flights.
 
Third Coast - that's right. That is if it were on a northern loop.

Thanks, Teri.
 
I looked at the diagrams in that control rod over-insertion incident report for Daiichi #3. Probably off-topic, and I'm probably misunderstanding something, but the control rod hydraulic cylinder seems like a weird design to me. Hydraulic pressure is required to insert the control rods. If there's no pressure, it looks like the rods can drop out of the core under their own weight. At any rate, you can't insert the rods if there's no power.

Maybe that's where some of these problems have come from?
 
Oh, so it wasn't just my profound lack of engineering ability?

I couldn't figure out how that thing worked.
 
I could be just misunderstanding, or the diagram isn't exactly representative because apparently they got all the reactors shut down. The damage being done is from residual heat and radiation--this reactor design has to always have the cooling circuit running, even when it's idle.

But yeah, that's the way it looks from the diagram.
 
Neil, I think they are in really bad trouble. I looked through incident reports.

First, these reactors are old. I wouldn't expect those containment vessels to meet original specs.

Second, even on reactor 2 at Daiichi they've been consistently reporting low water levels.

Third, as you say, you always have to keep cooling steadily, so one more severe problem that makes it impossible to work in there and they're probably in cascade. They should boron the whole lot to control risks, concentrate on cooling down the three that were active as of the quake, and then decomission the whole damned thing. It's not safe and it's never going to be safe again.

Last, they obviously have to keep venting. Well, NISA's update 20 shows heightened radiation levels just around Daini, Daiichi and now Onagawa, which is about 60 miles up the coast. There isn't a problem at Onagawa - it appears to be radiation from Daiichi. And the numbers given are microSieverts, and the number at Onagawa dropped after an hour. Still, this means that they have a problem. What the heck are radiation levels inside?

I haven't seen an update on the Daiichi reactor 3 problem, for which they could not get water levels up over a certain point. That's not very reassuring. They thought it might be a valve.

Last, one more hydrogen explosion, and....
 
Oops, we got the extra hydrogen explosion on reactor 3.

Now that's going to be venting into the open air....
 
Ace also has this link, which is a fairly calm and rational explanation of what has happened, and what will and won't happen:

http://theenergycollective.com/barrybrook/53461/fukushima-nuclear-accident-simple-and-accurate-explanation

It's a good read, and it jibs with what I know of reactor operations--which is probably less than MOM, but still, I can do math and do understand the basic principles. The summary is: they had some problems, but the problems aren't as big as people have suggested, and they're not getting worse.
 
Gordon - they are in cascade right now.

Oddly enough, this chain of disaster really started when they brought backup generators to the site after the tsunami swamped the ones already there, and found that they couldn't plug them in. The plugs didn't match. It wasn't the earthquakes (they've had three right around there). It wasn't the tsunami. It was that no one bothered to check for wiring compatibility.

They're in bad trouble now. First, they had to halt pumping seawater in to reactors 1 & 3 yesterday because they ran out of seawater. They started again on 3, which means that 1 probably is getting a bit hot again. Then they lost the freshwater backup pumping system on 2 yesterday. They have now vented 2 and they need to be pumping seawater and boric acid in there. But do they have the capacity? They were using firehoses before. The pit is probably designed to provide seawater for one, but not three, reactors.

Also you now have attrition in workers. Yesterday's count was eleven injuries. Before that it was at least six by my count. I read that they started with a pool of around 90 workers. Because internal radiation levels can get pretty high, they should be rotating them in and out of there.

PS: I would have sworn that I knew very little about nuclear reactors, but now I discover that there are people out there who know even less. I know enough to be deeply frustrated by the inadequacy of the reporting on this topic.
 
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