Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[quark42]

Here some quotes about the hydrogen collecting up in the buildings:
.
.
Just my unqualified 2 cents:
First of all, thanks to Nuceng and all the others for their valuable insights!

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.
The increased pressure even speeds up condensation.
This means that the mixture steam-hydrogen inevitably gets richer in hydrogen with time, because hydrogen cannot condensate under earthly temperatures/pressures.
Until explodable conditions have been achieved, Then just a little spark or hot surface could initiate the "kaboom procedure"...

The observation that only RB#2, the only that allowed hydrogen to escape, remained in shape, appears to confirm my hypothesis as far I see.

Compare this to a fridge where you put a pot of boiling water in. The steam will condense at the walls, some leaking out at the door, but not popping it open.
(Finally, due to lack of (pressed out) air the fridge will develop underpressure, making it difficult to open the door. Unlike a reactor...)

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?

I'm not sure where that is, but I'm confident it's not Fukushima 1. As to the distortion, I'd say it's due to hot exhaust from the heli.

 

[Jorge Stolfi]

Consider this photo just before explosion. German "Spiegel" posted this photo short before Daiichi explosion #1, with picture description suggesting it was Daiichi 1+2...)

It is not Daiichi. Check the checkers pattern and other details. The tower is very similar though, so it may be Daini.

 

[thehammer2]

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]

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 ().

 

[westfield]

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]

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_images/pdf/ENGNEWS01_1300189582P.pdf

 

[Jorge Stolfi]

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]

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 http://ex-skf.blogspot.com/" 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/kyodo-news-tepco-believes-stabilizing.html

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

http://dels.nas.edu/resources/static-assets/nrsb/miscellaneous/SekimuraPresentation.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_Massive_earthquake_hits_Japan_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]

(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-20110531-701810.html

 

[tsutsuji]

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/fukushima-np/images/handouts_110525_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/english2010/world/2011-05/31/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/web/html/210531044.html

 

[Borek]

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]

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/web/html/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]

Needing a mechanism to pull slight vacuum on unit 4?

How about the explosion of Unit 3?

see:
https://www.physicsforums.com/showpost.php?p=3247529&postcount=3766

 

[zapperzero]

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.

 

[zapperzero]

Just wanted you to know... This http://ex-skf.blogspot.com/" sometimes has interesting news but it also is perhaps too sensational.

The amount of bad news and utter BS s/he's wading through could make anyone a bit frantic. The source material, though? Pure gold, everything or almost everything confirmed, all open source info...

 

[NUCENG]

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).


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.

Nope, no conversion error. When writing my post I copied the number wrong. Thanks.

 

[elektrownik]

I know that some generators were in inspection/modyfication, so they were offline and doesn't turn on

 

[elektrownik]

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.

one generator (and only one) was working after earthquake (this for unit 5,6), there is power lines and generators drawing in this big report which was posted here some pages back

 

[NUCENG]

OK. Some remarks. If I am correct, the size of R4 building is 35 x 45 m. Assuming that the height of the refuelling floor is close to 15 m, it;'s volume is about 20.000 m^3, about a tenth of what you specify. This space, which I assume is well isolated (apart from the open blowout panels) and is not mechanically ventilated anymore, is heated by a large SPF, which generates about 3 MW of heat. I am not a physicist, but I assume that such a powerfull heat source, dumping an amount of steam in this space which is enough to fill it completely in just 1,5 minutes, will heat it to a temperature close to 100 degrees and will effectively refresh it's (steamy) atmosphere every few minutes.

I used 19260 m^3 in my calculation for refuel floor volume. Did I copy another number wrong? As pointed out by others I miscopied the 2.0 m^3/sec steam rate as 20 m^3/sec.

 

[MiceAndMen]

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

Shouldn't that be May 31st? A simple typo today but in the future someone might search the thread looking for info about this latest explosion and get the wrong idea.

 

[MiceAndMen]

NUCENG, I think this is what he was referring to...

... That 20 m^3/sec will not result in a flow out the openings of 20 m^3/sec. The approximate volume of the refuel floor is about 2E5 m^3. It will be hot and humid and there will be some steam dilution and mixing of hydrogen. However over time the hydrogen concentration has 24 hours from the minimum time I calculated to accumulate to the Lower Explosive Limit in the top of the bulding.

Maybe you meant to write 2E4 cubic meters

 

[Gary7]

Shouldn't that be May 31st? A simple typo today but in the future someone might search the thread looking for info about this latest explosion and get the wrong idea.

Yes - thanks for that. Now fixed.

 

[NUCENG]

NUCENG, I think this is what he was referring to...


Maybe you meant to write 2E4 cubic meters

yep. Looks like I need a new set of hands so I can count zeros.

 

[AntonL]

First step set in getting SFP under control

Cooling system being tested at No. 2 reactor

http://www3.nhk.or.jp/daily/english/31_26.html][/PLAIN] The operator of the troubled Fukushima Daiichi nuclear power plant has installed a circulatory cooling system at one of the plant's crippled reactors.

The Tokyo Electric Power Company started trial operation of the system at the No. 2 reactor building on Tuesday.

The utility has been pumping about 50 tons of water into a used fuel pool in the building every few days.

The pool's temperature is around 70 degrees Celsius, apparently producing steam that is filling the building and resulting in a humidity level of 99.9 percent. The humidity and high radiation levels have been hampering repair work at the site.

The new system is to pump water out of the pool to a heat exchanger and return the water to the pool as coolant.

The firm says it plans to bring the pool's temperature to around 40 degrees Celsius in a month through the system.

TEPCO hopes to reduce the humidity level before installing equipment to remove radioactive substances in the building.

The cooling system is the first to be completed at the plant. The firm hopes to start operating similar systems at the plant's No. 1 and 3 reactors in June, and at the No. 4 reactor in July.
Tuesday, May 31, 2011 19:04 +0900 (JST)

SFP-2 is producing about 400kW compared to the 2 to 3 MW of SFP-4

Furthermore we soon will get to know where the steam is coming from - the fuel pool or the reactor.
Where is the steam produced in the reactor disappearing to?

 

[elektrownik]

But how they can do this without entering building ? And why they can't do this for other units ? Steam is not only from sfp, unit 2 is at atmospheric pressure and also we know that there is water leak from core to turbine building, so drywell/torus must be leaking also.