Japan Earthquake: nuclear plants

thehammer2

Quote by Jorge Stolfi

This does not happen. No matter what the difference in density, gases that are mixed will stay mixed, and gases that are initially stratified will gradually diffuse into each other, even if they are kept perfectly still (without macroscopic motion). Indeed there must have been significant convection currents in the service floor of #4, because of the powerful heat+steam source in one corner.

That said, IMHO radiolysis seems a better explanation than H2 leakage from #3. I cannot see how a warm steam+H2 mixture, much lighter than air, would have chosen to travel backwards into the venting pipe of #4, and force its way through a tortuous path with several valves and tubing into a closed building with the AC turned off --- instead of flowing up the venting tower. I suppose that if some of the H2+steam from #3 managed to get into the chimney, it would have created negative pressure at its base, thus sucking back any gas that happened to flow towards #4

Yeah, I retract my earlier stupid. I had a brainfart and completely forgot about the convection and the fact that the hydrogen was likely coming up premixed with the steam.

I was definitely thinking about more discrete releases that I've encountered where the gas is pure enough and in quantities where buoyancy is a factor and it can collect at low or high points.

mscharisma

Quote by jlduh

The new live webcam is ON, you can check it by yourself...

http://www.tepco.co.jp/nu/f1-np/camera/index-j.html

Following this link, I get a completely different picture than on the TBS/JNN live feed. Nice weather with almost blue skies on the first, gray and rainy on the latter (http://www.youtube.com/watch?v=FptmoVcgpqg).

westfield

Quote by Atomfritz

snip

Consider this photo just before explosion.
Do you also see steam leaving through building weak points at wall/ceiling corner of reactor building #1 (left)?
Doesn't this indicate high pressure in the reactor building?
(Or maybe I misinterpret this image ? It could be Daini or some other plant?!? But what is that optical distortion looking like steam? German "Spiegel" posted this photo short before Daiichi explosion #1, with picture description suggesting it was Daiichi 1+2...)

So, could the inevitable outcome have been that eventually an explosive hydrogen-oxygen ratio developed, ready to be ignited by a slight spark or some hot surface?

Lol, I'm no power plant spotter but they looks suspiciously coal fired. There's even a coal loader in the image. Thats the quality of MSM I guess.

htf

Quote by Atomfritz

Please do also consider the fact that much, if not most of the steam will condensate at the walls etc due to the very low dew point.

I think NUCENG made a simple conversion error - it get 2 m^3/sec (see my previous post). So it is not that much. Compare it to a steam train which has about the same power (3MW for a big one is realistic).

Consider this photo just before explosion.
Do you also see steam leaving through building weak points at wall/ceiling corner of reactor building #1 (left)?

Besides it is a different NPP I think the effect is simply related to the bright sun light that is reflected towards the camera by the left building.

jim hardy

Needing a mechanism to pull slight vacuum on unit 4?
when did they begin adding water to U-4's SFP?
could the building have got fairly well filled with steam from pool then cooled off?

remember the grade school science project , bring a can with some water to a boil then remove heat and cap it, watch it collapse as steam condenses.

i see from here they report injecting water to pool on 15th. surely there's a record of when they began that operation.

http://www.jaif.or.jp/english/news_i...300189582P.pdf

Jorge Stolfi

Quote by jim hardy

Needing a mechanism to pull slight vacuum on unit 4?
when did they begin adding water to U-4's SFP?

Good question. I believe that between the venting of #3 and the explosion of #4 the latter was completely without power, so it is not clear how they would have managed to pump water into the pool. AFAIK they would have had to rig the pipes inside the building to make it possible to pump water from outside. But the floors are all connected through the elevator shaft and the stairwells, so if they entered the building then any negative pressure inside would have immediately equalized through the entrance door. Or not?

Did they even worry about the #4 SFP before the building exploded?

elektrownik

Quote by Jorge Stolfi

Did they even worry about the #4 SFP before the building exploded?

No, there was no something like SFP problemm, they were fighting to cool down cores... It was funy, there was nothing about SFPs but after unit 4 explosion they were confused that there is such problem...

~kujala~

Just wanted you to know... This ex-skf site sometimes has interesting news but it also is perhaps too sensational. For instance it had a couple of days ago a piece of news about TEPCO roadmap:

http://ex-skf.blogspot.com/2011/05/k...abilizing.html

Somebody posted in the comments a link to a presentation already posted here:

http://dels.nas.edu/resources/static...esentation.pdf

The writer of the blog (arevamirpal::laprimavera) later makes a comment concerning the above presentation:

arevamirpal::laprimavera said...
Sekimura's slide No.18 is a blatant lie. EDG didn't work even before the tsunami, and off-site power went down because of earthquake only.

This of course is not true. AFAIK there is not a single source saying diesel generators didn't work before tsunami, I don't know where the idea has come from?

http://www.world-nuclear-news.org/RS...n_1103111.html

A more serious situation emerged at Tepco's nearby Fukushima Daiichi power plant, after the sudden stoppage of emergency diesel generators. These had started as expected upon automatic reactor shutdown, but stopped after one hour leaving units 1, 2 and 3 with no power for important cooling functions.

ascot317

Quote by Atomfritz

(Or maybe I misinterpret this image ? It could be Daini or some other plant?!? But what is that optical distortion looking like steam? German "Spiegel" posted this photo short before Daiichi explosion #1, with picture description suggesting it was Daiichi 1+2...)

So, could the inevitable outcome have been that eventually an explosive hydrogen-oxygen ratio developed, ready to be ignited by a slight spark or some hot surface?

This Reuters Photo is showing the Haramati Thermal Power Plant (Coal) by Tepco. It was originally distributed by Reuters as "Fukushima Daiichi shortly before the explosion" or similar. I had written Reuters an email about it, but they apparently care little for journalistic accuracy.

You can find the plant by searching for its Japanese name "原町火力発電所" on google maps/earth.

zapperzero

Explosion near reactor #4 during debris removal. TEPCO "assume" it was a buried gas tank. A what, now?

http://online.wsj.com/article/BT-CO-...31-701810.html

tsutsuji

Quote by ~kujala~

I don't know where the idea has come from?

I don't know either. Perhaps the best way is to ask him.

By the way, page 18 of the Sekimura Presentation is hardly different from page 51 of http://www.tepco.co.jp/en/nu/fukushi...10525_01-e.pdf .

zapperzero

Oil tanks at #5 and #6 may be leaking. Not good when you rely on diesels for emergency power.

http://news.xinhuanet.com/english201...c_13903549.htm

Gary7

From the TV Asahi website

On the afternoon of May 31st at Fukushima Daiichi there was a large explosion heard near reactor #4. The explosion is believed to have been caused by a pressurized tank rupturing.

According to Tepco, at 2:30pm today near the south side of the #4 reactor building, remote-controlled heavy equipment was being used to clear away rubble when a large explosion was heard. It is believed the machinery ruptured a tank that was buried in the rubble. Exactly what type of tank it was is now under investigation, but there was no fire and there were no injuries. There was no change in the surrounding radiation levels.

http://news.tv-asahi.co.jp/ann/news/...210531044.html

Borek

Quote by zapperzero

Oil tanks at #5 and #6 may be leaking. Not good when you rely on diesels for emergency power.

Are the diesels already repaired? If not, oil leaks don't matter much. That is - they add to the mess, but they don't make the system more vulnerable.

jlduh

Quote by Gary7

From the TV Asahi website

On the afternoon of March 31st at Fukushima Daiichi there was a large explosion heard near reactor #4. The explosion is believed to have been caused by a pressurized tank rupturing.

According to Tepco, at 2:30pm today near the south side of the #4 reactor building, remote-controlled heavy equipment was being used to clear away rubble when a large explosion was heard. It is believed the machinery ruptured a tank that was buried in the rubble. Exactly what type of tank it was is now under investigation, but there was no fire and there were no injuries. There was no change in the surrounding radiation levels.

http://news.tv-asahi.co.jp/ann/news/...210531044.html

Reported by NHK as an oxygen cylinder:

http://www3.nhk.or.jp/daily/english/31_36.html

An oxygen cylinder has burst at the Fukushima Daiichi nuclear plant. But the plant operator says the blast caused no damage to the plant's facilities, and no injuries.

TCups

Quote by jim hardy

Needing a mechanism to pull slight vacuum on unit 4?

How about the explosion of Unit 3?

see:
http://www.physicsforums.com/showpos...postcount=3766

zapperzero

Quote by Borek

Are the diesels already repaired?

One EDG (emergency diesel generator, is this the approved initialism? alphabet soup in nuke industry is almost as bad as the army) was spared by the tsunami and this is one of the big reasons why 5 and 6 are not in the situation the rest are in. Afaicr they used that EDG exclusively to power cooling, alternatively, to the reactors and their pools until offsite power became available.

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zapperzero	Explosion near reactor #4 during debris removal. TEPCO "assume" it was a buried gas tank. A what, now? http://online.wsj.com/article/BT-CO-...31-701810.html