Japan Earthquake: nuclear plants

rmattila

Not being familiar with the local culture and phraseology, this is sometimes very difficult to follow: already in May, in their long report to the IAEA, TEPCO told that the IC hd been shut down at 15:03, to be replaced with the HPCI as the decay heat removal method at 15:07 (IIRC, see earlier postings in this thread for reference). Then it was said having been reactivated briefly between 18:18 to 18:25 (at the time there possible already was some hydrogen to hinder its functionality) and depending on the report you choose to follow, steam either was or was not detected. And then its valve was finally opened at 21:30, at the time it would certainly have been useless.

And now they appear to be hesitant to admit that the logical consequence of their earlier testimony - i.e. that the IC is full of water - is true.

tsutsuji

My understanding is that the NHK journalist is trying to figure out what happened at 18:25. See also the quotes of the second report to IAEA I made at http://www.physicsforums.com/showpos...ostcount=11314 . But as everyone seems to agree with the fact that "steam was confirmed" at 21:30, It seems that there was water in the condenser at 21:30. So I don't really understand why the NHK journalist views the 65% water gauge reading of 18 October as a "contradiction".

hbjon

You criticize the only two people (almost) that the establishment has allowed to put a message out there warning people of some of the dangers we may face. I like both of them because they can do it with a calm and controlled demeanor. Myself, when I try to tell people the physics of Fukushima, I seem frantic and hysterical.

Shinjukusam

So we should throw out scientific analysis and proof as long as the spokesman is calm and controlled? No, I don't think so. I listed the reasons that their testimony should be doubted, if you should choose to dismiss me then that's your prerogative.

elektrownik

Important: Tepco fixed one of reactor 2 water level indicators and... reactor 2 water level is down scale which mean that water level is at last 5m below top of fuel rods, so reactor could be dry

gregtomko

It looked to me like he was just trying to point out some facts that were not being addressed. Information is very tightly guarded around the Fukushima nuclear plant, so it looked to me like he was doing the best he could with what little was available. Everybody gets some things wrong some times.

Thats kind of what my feeling was too, but at least an interesting fruitcake :-)

SteveElbows

Gunderson deserves even worse criticism than you see here recently. I don't care how calm he is, he went on about how he knew a thing or two about spent fuel pools, and then proceeded to analyse a video of unit 4 spent fuel pool in a very wrong way. He said the crane had fallen into the pool, and that fuel racks were exposed. He made little or no effort to correct this terrible inaccuracy later. Meanwhile other people who did not have his background or experience were able to look at the same video and reach much better conclusions.

tsutsuji

http://www.asahi.com/national/update...110180453.html (18 October) there was a leak of high level contaminated water (290,000 Bq/cm³ of Cs 137) that was found on 18 October during maintenance at the Kurion system when workers entered the area to change a motor. The cause is investigated. The leaked water has already been pumped back to the concentrated waste treatement facility. With 3 tons, it is the second amount of leaked highly radioactive water after the 6 ton leak that occured in June.

Or in Tepco's words:

http://kyushu.yomiuri.co.jp/news/nat...OYS1T00221.htm The reason of the automatic shutdown of Genkai NPP unit 4 on October 4 was a wrong instruction manual used during maintenance work at a system related with the condenser, Kyushu electric announced on 21 October. The workers removed a cable that supplied electric power to a valve. The degree of vacuum in the condenser declined and that triggered the automatic shutdown.

http://www.kyuden.co.jp/library/pdf/.../111021b-2.pdf Kyushu electric's press release on Genkai unit 4's shutdown. The maintenance was the change of a torque switch at the main turbine gland steam valve. It is a a control cable (not a power cable) that was unplugged, and it resulted in a closure signal being transmitted to the gland steam control valves. It was the first time that this maintenance was done while the plant is running.

Azby

I would make even stronger criticisms of them both. The problem with Gundersen is that he's sometimes been right. But he continues to repeat speculation without substantiating it, even after others have proven him wrong, and I've never seen him retract anything (like the "unit 4 is leaning story"). And he continues to talk about a piece of fuel rod found over 1km away from the plant, but has never shown the evidence for that to my knowledge. As for Busby, the "science" behind his claims and risk estimates has been solidly debunked time and again, even by other anti-nukes and people who are inclined to want to support his positions. It's as bad as UFOlogy. Just because he seems like a nice guy and stands up to authority is no reason to accept his scientific opinion. Wrong is wrong, misleading is misleading, and disinformation is disinformation no matter what the source or motivation.

hbjon

Chris Busby is a fruitcake? Why? Because he says the stuff that was in those building was really really bad stuff, and it can kill ya? Because he uses the "bedtime story" approach at presenting this dreadfull information? Or is his science all wrong? He seems to think he knows what he is talking about. It is hard to get worried listening to him. I find myself going to sleep.

tsutsuji

"Tepco never pushed electrical safety plan at nuke plant":

LabratSR

Unedited Fukushima accident manual released, loss of power sources not envisioned

http://mdn.mainichi.jp/mdnnews/news/...na007000c.html

NUCENG

First question: What are the pressure limits and process requirements for venting? Did they follow their manual?

LabratSR

From the Japan Times article on the manuals.
http://www.japantimes.co.jp/text/nn20111026a1.html

"Instructions in the manuals were all based on the assumption that two backup direct current batteries at reactor 1 would keep working throughout any emergency. In fact, the batteries were knocked out by water when the monster tsunami struck and crippled the Fukushima plant.

The manuals also failed to instruct workers to open by hand critical valves normally powered by electricity to vent steam and thus reduce pressure in the containment vessel. The DC batteries were supposed to supply power to operate those valves.

The containment vessel is the last line of defense to prevent radioactive materials from escaping the reactors. Tepco tried to open the valves to keep the vessel from breaking apart on March 12. Pressure also needed to be reduced to allow coolant water to be injected to prevent a meltdown of the reactor core.

But it took hours for Tepco workers, who apparently had no training in how to open the valves manually, to vent the steam and relieve the pressure, and many experts say the delay may be a key factor that led to the meltdown at unit 1."

Norman

Interesting paper posted on the Xenon and Cesium releases from the disaster.

http://www.atmos-chem-phys-discuss.n...8319-2011.html

The paper states there is some evidence the that Xenon release happened very early correlating with the Earthquake and not the Tsunami damage.

NUCENG

That is possible. Venting would reduce pressure in containment and subsequently allow continued depressurization for the RPV. This would allow low pressure external fire pumps or trucks to make up water to the reactor. If melting was not already underway then delaying venting could be a key factor.

However, as I understand the timeline at unit 1 the Isolation Condenser had been tripped, there was no water makeup to the core, inventory was being lost due to the SRVs venting the vessel to containment, and containment was more than double its pressure rating for a period of hours. Under those conditions the core would have begun melting shortly after fuel was uncovered, increasing temperatures at a rate of about 1 degree per second. Once zirc water reactions start that is an exothermic reaction increasing boiloff and heating. A large part of the delay was to get government permission to vent. IMO, operator training for manual vent operation is a contributing cause but not at the top of the list. Operators did not have the authority to take action when it might have helped. Their emergency manuals may have been woefully inadequate, so naturally the training or lack of training on implementing the manual would be suspect. In short, the core was probably melting before they even tried to vent.

I know I have harped on this before, but even that wasn't the real root cause. Japanese industry and regulators built plants and then stopped looking. They ignored geological findings about earthquakes and tsunamis. They built up a regulatory system that left noone responsible. The repeated scandals of fudged paperwork and testing were warnings. The KK earthquake was a warning. Japanese attitudes that they didn't need to worry about 9/11 terror because Japan was a 'stable society' was a warning.

Was it complacency, or greed, or negligence, or incompetence? I know this is the technical thread, but in this case I am not sure the accident could have been prevented by any technical solutions.

Astronuc

Certainly not after the fact.

The proactive actions of ensuring the protection of EDGs and their fuel supply, and ensuring the protection of the electrical lines from EDGs to the ECCS and safety systems, should have been a priority. Ensuring protection = prevention of flooding and prevention of failure due to seismic loads.