Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Maxion]

That blog entry is correct. See also http://nucleardata.nuclear.lu.se/nucleardata/toi/nuclide.asp?iZA=520429 for data on Te-129m

The incredible thing is that Tepco do not understand their own measurements. See also http://www.nytimes.com/2011/04/06/world/asia/06tepco.html

Such a company should never have been allowed to operate a nuclear reactor.[/QUOTE

But that does not explain the blue glows above the reactor building.

Wasn't the blue glow only reported by Fox Insider with no reported sources or video material? Also no other media reported on the event that cited anyone else except Fox. I think we can safely say the blue glow didn't happend.

 

[NUCENG]

For those wondering where the oxygen can come from. Water can also be split into hydrogen and oxygen by temperature alone. It occurs above 2500 C and can be catalyzed by metal oxides which lower the temperature required. When the rods in the core are not covered with water, they can reach these temperatures and produce both hydrogen and oxygen even if the zirconium cladding is already burned.

see http://en.wikipedia.org/wiki/Water_splitting

edit added better link

I am on shaky ground talking chemistry, but here is an engineering walk through:

Assume containment is intact when hydrogen begins to be released. The radiological decomposition of water into Hydrogen and Oxygen produces two moles of Hydrogen and one Mole of Oxygen per Mole of Water. If the containment is inerted with nitrogen then oxygen content is too low to support ignition, Adding the hydrogen from Zirconium waterr reaction and twice as much Hydrogen as Oxygen from radiolysis would seem to actually DECREASE the relative partial pressure of Oxygen. Wouldn't that mean there would still be too little oxygen to support a hydrogen burn or detonation.

If so there has to be pre-existing damage with inleakage of air to the containment to allow primary contaiment to be the site of the explosions. TEPCO reports indicated that pressure was above atmosoheric pressure prior to the explosions. Only unit two appeared to depressurize at the time of that explosion. This seems to indicate contaimnents were intact prior to the explosions and there should not have been a combustible or explosive atmosphere . Any Chemists out there?

 

[PietKuip]

Wasn't the blue glow only reported by Fox Insider with no reported sources or video material? Also no other media reported on the event that cited anyone else except Fox. I think we can safely say the blue glow didn't happend.

I would not exclude the possibility. The nights must be really dark in Fukushima prefecture. There are high intensities of ionizing radiation at the plant. So there should be some airglow. Maybe the dark-adapted eye can see it from a distance. Probably too faint for a video camera.

 

[NUCENG]

So the superheated water in the SFP3 littorally exploded!

In order to superheat steam in a fossile plant they take saturated steam from the boiler and rout it in tubes through the firebox. It is under pressure and unabele to expand so it superheats. How can that happen in the Spent Fuel Pool? As the water boils it is able to expand. It is not forced into close contact with a hot fuel bundle.

The alternative for superheating is pressurized water/staem inside some form of pressure vessel or pipe, If a rupture or line break occurs water being released will flash with superheat due to being under a lower pressure. How could that happen in the Spent Fuel Pool? If I remeber correctly the blowout panels on the walls of the Reactor Building are desiged for an internal pressure around 10 inches of water. There just isn't lokely to be significant superheat in the steam.

I remember discussing this with other engineers after the movie "Atomic Twister" In that film throughout the event they were watching spent fuel pool water temperature continuously increasing in temperature after it started to boil. At least they had Sharon Lawrence to smear grease on her shirt and kick the diesel so they could refill the pool.

 

[AntonL]

However, from the TEPCO fax included in NISA release #76 (nominally dated apr/06 05:00), the last measurement of flow rate of unit #1 was taken on apr/03 17:30 and has not been updated since.

I do not know whether that means the rate has been stable since then. In doubt I have just been repeating the same data point at each release.

http://www.meti.go.jp/press/2011/04/20110406002/20110406002-2.pdf

My apologies - I did not notice the note in the report.

 

[heckler73]

Won't adding Nitrogen into a Hydrogen laden environment (under pressure) make Ammonia?
N2(g) + 3 H2(g) = 2 NH3(g)

http://scifun.chem.wisc.edu/chemweek/pdf/ammonia.pdf

Less explosive, but still flammable.

 

[yuriwho]

I am on shaky ground talking chemistry, but here is an engineering walk through:

Assume containment is intact when hydrogen begins to be released. The radiological decomposition of water into Hydrogen and Oxygen produces two moles of Hydrogen and one Mole of Oxygen per Mole of Water. If the containment is inerted with nitrogen then oxygen content is too low to support ignition, Adding the hydrogen from Zirconium waterr reaction and twice as much Hydrogen as Oxygen from radiolysis would seem to actually DECREASE the relative partial pressure of Oxygen. Wouldn't that mean there would still be too little oxygen to support a hydrogen burn or detonation.

If so there has to be pre-existing damage with inleakage of air to the containment to allow primary contaiment to be the site of the explosions. TEPCO reports indicated that pressure was above atmosoheric pressure prior to the explosions. Only unit two appeared to depressurize at the time of that explosion. This seems to indicate contaimnents were intact prior to the explosions and there should not have been a combustible or explosive atmosphere . Any Chemists out there?

I am a chemist.

First, it's thermal production of H2 and O2 not radiological.
2 molecules of water produce one molecule of O2 and 2 molecules of H2
a similar reaction takes 2H2O +Zr -> ZrO2 + 2H2

The purely thermal reaction produces H2 and O2 in equal proportions. This reaction is likely what caused the explosion that blew the torus at Unit 2

 

[NUCENG]

In my travels around YouTube I found a flyover after the sea surge. Units 5&6 not shown up close but if they got saltwater in their equipment it wouldn't take long to ruined a bearing, shaft, wiring connections or a lot of other stuff. Can't find a report on how high the sea reached at the complex. Shouldn't forget about sand either.
http://www.youtube.com/watch?v=LUGAbMVG-qc"

Thanks. If we can find more sources like this it can help distinguish between damage from the tsunami and from the accident that followed.

 

[bytepirate]

I would not exclude the possibility. The nights must be really dark in Fukushima prefecture. There are high intensities of ionizing radiation at the plant. So there should be some airglow. Maybe the dark-adapted eye can see it from a distance. Probably too faint for a video camera.

you can see the cerenkov light on the webcam pics (http://www.tepco.co.jp/nu/f1-np/camera/index-j.html only at night of course). a couple of days ago it was not directly visible, but you could make it visible with photoshop. no idea, if it grew stronger, or if the webcam is adjusted.

someone monitored the spot since march 21st:
http://www.abovetopsecret.com/forum/thread672665/pg433 (3rd post on that page)

 

[AntonL]

I would not exclude the possibility. The nights must be really dark in Fukushima prefecture. There are high intensities of ionizing radiation at the plant. So there should be some airglow. Maybe the dark-adapted eye can see it from a distance. Probably too faint for a video camera.

We do know that the the open air spent fuel pools are glowing blue and the blue light is reflected in the steam rising above, although I would think that Tepco is working 24/7 and there will be lots of temporary illumination around

 

[NUCENG]

I know it's innappropriate but why do I keep hearing the William Tell Overture ? "BOOM!"

The Lone Ranger Theme? or did you mean the 1812 Overture?

 

[|Fred]

animated picture with some annotations
[PLAIN]http://i.min.us/ikyAQe.gif

 

[razzz]

animated picture with some annotations
[PLAIN]http://i.min.us/ikyAQe.gif[/QUOTE]

Why the reddish color of the debris cloud? It only last a few seconds then fads in real time.

 

[razzz]

http://www.youtube.com/watch?v=-W7uGvW8xvY&feature=player_embedded"

 

[Borek]

Assume containment is intact when hydrogen begins to be released. The radiological decomposition of water into Hydrogen and Oxygen produces two moles of Hydrogen and one Mole of Oxygen per Mole of Water. If the containment is inerted with nitrogen then oxygen content is too low to support ignition, Adding the hydrogen from Zirconium waterr reaction and twice as much Hydrogen as Oxygen from radiolysis would seem to actually DECREASE the relative partial pressure of Oxygen. Wouldn't that mean there would still be too little oxygen to support a hydrogen burn or detonation.

Chemical parts of your analysis look OK to me. I guess there is even more to it when it comes to low level of oxygen. Hydrogen/oxygen mixture is not thermodynamically stable, and if you don't separate hydrogen and oxygen fast, they will tend to react back to create water, especially in high temperatures (hydrogen/oxygen mixtures at STP are only kinetically stable). IMHO you can have some small amount of hydrogen & oxygen from water splitting present and much more hydrogen from Zr and water reaction. According to LeChateliers principle amount of free oxygen in the presence of excess hydrogen should be even lower than it could be if there was no hydrogen from Zr/water reaction.

 

[artax]

I hope it's a matter of translation problems and/or exhaustion of the tech workers, and not a matter of incompetence. Finding high levels of very short-lived isotopes (indicative of on-going fission) should have set off some mental alarms in the engineering/technical staff, prompting a lot of double-checking.

With talk of entombment in some circles, this raises a concern in my mind. The process of setting/curing concrete is exothermic. Could entombment result in insufficient cooling of fuels, leading to unanticipated problems? Coming at this from a civil/mechanical mind-set with NO experience in nuclear leaves a lot of questions.

Yes, I think anyone suggesting setting in concrete does not understand the fundamental behaviour of nuclear fuel and the issue of cooling .
Entombment, without some form of gas escape route before colling for years is just silly!

 

[Borek]

Won't adding Nitrogen into a Hydrogen laden environment (under pressure) make Ammonia?
N2(g) + 3 H2(g) = 2 NH3(g)

To get good efficiency you need something like 20 MPa, 400 deg C and a catalyst. Some traces were for sure produced, but not much.

 

[artax]

I know it's innappropriate but why do I keep hearing the William Tell Overture ? "BOOM!"

did you ever play an early computer game called 'BATTLEZONE'?

http://www.youtube.com/watch?v=ghIPGXs3LAo&feature=player_detailpage#t=125s

 

[ian_scotland]

As to panel trajectories from Unit 3...

Sketches I made some time ago but didn't post are attached. These were intended as a reply to a much earlier question about the origin of an almost intact panel leaning against the building just East of the turbine building.

The specific panel in question probably was a Southmost-East facing panel from either the top or second row of panels of Unit 3.

BTW - perspective does make it difficult to judge the source...

.

I see why you would think that this is a wall panel from no.3 reactor building, but that is not a rf conc wall panel you have found - its the flat roof over the entrance to that small building.

I am trying to find a pre-BOOM photo of the site to illustrate this.
Found (not my image annotation, but shows the small flat roof in question)
https://lh5.googleusercontent.com/-...kk/s1600/FukushimaDaiichi-overhead+-+Copy.PNG

 

[NUCENG]

I am a chemist.

First, it's thermal production of H2 and O2 not radiological.
2 molecules of water produce one molecule of O2 and 2 molecules of H2
a similar reaction takes 2H2O +Zr -> ZrO2 + 2H2

The purely thermal reaction produces H2 and O2 in equal proportions. This reaction is likely what caused the explosion that blew the torus at Unit 2

OK I agree with the equation for Zr-H20 reaction, but that yields only ZrO2 which is a solid and H2 gas.

Radiologial or Thermal whatever the source, isn't the equation:
2H2O -> 2H2 + O2

I remember PV = NRT where N is in moles. If you are releasing two molecules of Hydrogen gas for each molecule of oxygen, then the partial pressure of hydrogen increases at twice the rate of Oxygen in a constant volume with both gasses at the same temperature.

The N2 gas and steam would have a constant partial pressure at a given temperature. So as the total pressure rises due to steam Nitrogen, Hydrogen and Oxygen, the partial pressure of Hydrogen would increase from zero before the fuel damage to some new value. and the partial pressure of oxygen would increase from a low inerted pressure to its new value, but at half the rate of the hydrogen. Volumetrically the same relationship is present. Does the containment ever reach an explosive or ignition concentration if the % of oxygen is insufficient for ignition and continues to decrease? What am I missing?

If it does reach an explosive point without air inleakage, it begs the question of why NRC requires BWR MK1 containments to be inerted. Are we sure the Japanese inert their plants? There are tanks on the Fukushima site that look like our liqiud nitrogen storage tanks at US BWRs.

 

[Borek]

I am a chemist.

First, it's thermal production of H2 and O2 not radiological.
2 molecules of water produce one molecule of O2 and 2 molecules of H2
a similar reaction takes 2H2O +Zr -> ZrO2 + 2H2

The purely thermal reaction produces H2 and O2 in equal proportions. This reaction is likely what caused the explosion that blew the torus at Unit 2

Judging from the diagram posted earlier

https://www.physicsforums.com/attachment.php?attachmentid=34079&d=1302058688

you need around 12% oxygen by volume for the explosion. Seems unlikely in the conditions present inside. Thermal decomposition of water needs fast separation of products, otherwise they react back.

 

[artax]

Why the reddish color of the debris cloud? It only last a few seconds then fads in real time.

Some of the videos were seriously contrast enhanced due to the distance shot and telephoto lens so the orange will probably be artificial. Though colour can reveal a lot about the chemistry, I suspect simple confined hydrogen explosion full of particles of concrete/dust.

This image... (or rather the second image with dust plume) though clearly shows how truly vertical that large slab is projected upwards, and that the sideways, (towards us and to the left) is purely an illusion created by the wind taking the lightweight dust to the southeast.
What explosion could project so perfectly vertically... I can only think of the concrete containment vessel again! it's the only thing shaped like the combustion chamber of a rocket. So did it fall back down on the building itself?
Sorry I'm having trouble ggrabbing the image I want from razzzz's post earlier.
watch this vid instead, the tower is directly in line with the buildings diagonal so marks the middle of the building. watch the 'slab' ...

 

[Borek]

The N2 gas and steam would have a constant partial pressure at a given temperature. So as the total pressure rises due to steam Nitrogen, Hydrogen and Oxygen, the partial pressure of Hydrogen would increase from zero before the fuel damage to some new value. and the partial pressure of oxygen would increase from a low inerted pressure to its new value, but at half the rate of the hydrogen. Volumetrically the same relationship is present. Does the containment ever reach an explosive or ignition concentration if the % of oxygen is insufficient for ignition and continues to decrease? What am I missing?

I have the same problem with yuriwho post, I don't see how the mixture can get past lower explosive limit.

 

[AntonL]

500 m**3/day is about 500 tons, about double the daily water used for reactor cooling at the 150 liter/min rate indicated by the NISA. Suggests this leak is drawing on more than just reactor 2.

Does anyone have any idea of how a thin slurry of irradiated reactor fuel could be stored?
Maybe freeze it in place and wait a few years for decay?

I doubt that anyone would want to store a slurry or solution of fission products or fuel.

I would recommend that it be chemically processed in much the same way normal fuel is fabricated. Basically, one simply precipitates the solution. The precipitate is dried, then calcined and finally vitrified, possibly with a glass additive. The solid can then be stored permanently in a geological repository.

One possibility would be to recover the fuel, or fissile and fertile material.

But, In the fukushima case the precipitate would be mostly sea salt. Can salt be vitrified?

 

[AntonL]

OK I agree with the equation for Zr-H20 reaction, but that yields only ZrO2 which is a solid and H2 gas.

Radiologial or Thermal whatever the source, isn't the equation:
2H2O -> 2H2 + O2

I remember PV = NRT where N is in moles. If you are releasing two molecules of Hydrogen gas for each molecule of oxygen, then the partial pressure of hydrogen increases at twice the rate of Oxygen in a constant volume with both gasses at the same temperature.

The N2 gas and steam would have a constant partial pressure at a given temperature. So as the total pressure rises due to steam Nitrogen, Hydrogen and Oxygen, the partial pressure of Hydrogen would increase from zero before the fuel damage to some new value. and the partial pressure of oxygen would increase from a low inerted pressure to its new value, but at half the rate of the hydrogen. Volumetrically the same relationship is present. Does the containment ever reach an explosive or ignition concentration if the % of oxygen is insufficient for ignition and continues to decrease? What am I missing?

If it does reach an explosive point without air inleakage, it begs the question of why NRC requires BWR MK1 containments to be inerted. Are we sure the Japanese inert their plants? There are tanks on the Fukushima site that look like our liqiud nitrogen storage tanks at US BWRs.

I have the same problem with yuriwho post, I don't see how the mixture can get past lower explosive limit.

With all the dissolved oxygen in the water that has been pumped into the reactor a substantial amount could have been accumulated by now as gas

http://docs.engineeringtoolbox.com/documents/841/oxygen_solubility_fresh_sea_water.pdf

http://www.engineeringtoolbox.com/oxygen-solubility-water-d_841.html

 

[MadderDoc]

That's not what I mean. There are large pieces thrown up a long way up but they might be the large sections of the trusses above the SFP that are missing, which I would expect to be much lighter than FHM. It's about the mass really. I find it more plausible that the FHM got blasted sideways in the first explosion towards the north wall, destroying the wall and itself.
Again like I said I might be wrong, no need to get defensive or dismissive.

The FHM and trusses could, I presume, be in the SFP, otherwise the NW corner for either or both is my focus. Attached are a few photos from the MOX loading of the reactor number 3, on 21 August 2010 so we know what we're looking for. More photos from the occasion at:
http://www.gyldengrisgaard.dk/20100821_daiichi03/

 

[NUCENG]

With all the dissolved oxygen in the water that has been pumped into the reactor a substantial amount could have been accumulated by now as gas

http://docs.engineeringtoolbox.com/documents/841/oxygen_solubility_fresh_sea_water.pdf

http://www.engineeringtoolbox.com/oxygen-solubility-water-d_841.html

That may be the answer. I'll look, but I thought they performed containment flood AFTER the explosions? I agree there is free oxygen in containment since flooding now. The explosions may have compromised containment integrity (at least in unit 2 allowing air inleakage.

But with pressure in containment before the explosions where did the oxygen come from to support a belief that a detonation came from the drywell? It is the chicken and the egg question. Did containment failure allow the explosions or did the explosions cause contaiment failure?

Has anybody seen a good detailed timeline based on the plant reports?

 

[Borek]

With all the dissolved oxygen in the water that has been pumped into the reactor a substantial amount could have been accumulated by now as gas

Good point, I forgot about it. Still, I wonder if at the temperatures present and in the presence of ionizing radiation hydrogen would not react with oxygen and create water - without an explosion. It is all in kinetics.

 

[TCups]

Correct me If I'm not understanding this right: flash heating of water lead to fast vaporisation ie: cold watter on a hot pan. What you are suggesting is that the steam pressurized escaping the Primary containment entering the pool full of watter would flash heat the (large amount of) water in the pool ? Just like inserting a really hot metal blade into water?

Now isn't the suppression pool working exactly on the principle of cooling hot steam or gaz with water ?

as far as temperature are concerned we have a max pressure in the drywell of 0.490 MPa (75psi) does this value is consistent with a steam temperature hot enough to flash boil the pool ?

|Fred:

Not cold water. The water in the SFP is absolutely pure and still. The spent fuel is (pre)heating the water in the pool. The water in the pool could have been at the boiling point temperature but not vigorously boiling. Maybe superheated isn't the term, but certainly very, very hot.

In the example I mentioned, heating water in a clean flask, the boiling chip is not a catalyst. It is just a rough surface that is a rough surface to initiate vaporization. Sometimes beer glasses use laser etching on the bottom of the glass to make the CO2 come out of solution.

Not saying that there aren't small rough surfaces on the fuel rod assemblies. But in a very pure, very hot pool of water, already at or very near the boiling point, a hot blast of any sort would 1) raise the surface temperature and 2) agitate the entire pool. In the presence of burning hydrogen + oxygen, a large amount of water could be quickly converted to steam. And although the SFP isn't shaped like a rocket nozzle, it is a deep, vertical structure. Recall also that the initial blast blows the roof off over the SFP.

BTW, one of the earlier posts did confirm that the dozer work was to clear high level waste and another confirms that pieces of radioactive fuel rod have been found large distances from the pool.

Did those come from the core of the reactor or from the SFP? My vote is SFP and the only vertical blast out of the SFP would have to come from steam.

Water at 100C degrees does not boil. Water at 100C begins a phase change. The heat of transition is 880 cal/gr (been a long time -- correct me if I am wrong), or once 1ml water gets to 100C, another 880 cal is needed to turn that 1ml into steam at 100C. That is why live steam has so much more energy than hot water.

The hot fuel in the still pool could have already supplied most or all of the heat of transition without the water actively boiling. After all, Bldg 4 didn't look like a boiling tea kettle emitting steam before the explosion. It is reasonable to believe that a very large amount of thermal energy was stored in the SFP water, and that a hot explosion that raised the temp of and severely agitated that pool tipped the reaction. The rapid phase change from liquid to gas means a massive increase in volume, and a huge vertical steam plume.

 

[artax]

I don't think it is possible to get the sort of steam explosion you are talking about with a large body of water at or near it's boiling point.
I think the sort of meltdown and water table/steam explosion is a bit of a myth (if you're thinking along those lines)
Someone mentioned earlier... the first time I saw hot lava flowing into water I was surprised to see there wasn't any explosion.

The heat of vapourisation for water is just too high, like it's heat capacity, (precisely why it's so good for cooling)
Only microwaves can deliver this sort of threoughout volume and 'to every molecule', energy transfer instantaeneously.

Still got to be hydrogen to me, or a confined biuld up of steam with vessel failure to give such a large blast.

Sorry mate!

There's an interesting article here

http://www.ieer.org/comments/Daiichi-Fukushima-reactors_IEERstatement.pdf

 

[NUCENG]

With all the dissolved oxygen in the water that has been pumped into the reactor a substantial amount could have been accumulated by now as gas

http://docs.engineeringtoolbox.com/documents/841/oxygen_solubility_fresh_sea_water.pdf

http://www.engineeringtoolbox.com/oxygen-solubility-water-d_841.html

Re: AntonL #3051, NUCENG #3053 BOREK #3054


As promised. I looked at the TEPCO sequence of events and JAIF Plant Status reports.

Explosions were reported on 3/12, 3/14, and 3/15, Unit 4 was damaged about the 15th or 16th.

Seawater had been injected into RPVs on Units 1 and 3.

Seawater injection into containment was still being planned/considered on 3/16.

TEPCO is still reporting no coolant leakage into containment on all units. ?

Conclusion: Sea water injection into contaiment followed explosions and therefor oxygen dissolved in seawater could not have been responsible for creating an explosive mixture inside containment. The only remaining possibility would have been containment failures from the earthquake, but since there was a high pressure in containment, it would be tough to get air inleakage. Unless I missed something about the mixture of steam, oxygen, hydrogen, and nitrogen in containment, I just don't see an condition that could lead to an explosion inside containment.

 

[artax]

have a read of this!

http://www.nytimes.com/2011/04/06/world/asia/06nuclear.html?_r=4&hp

(according to a confidential assessment prepared by the Nuclear Regulatory commission...)"The document also suggests that fragments or particles of nuclear fuel from spent fuel pools above the reactors were blown “up to one mile from the units,” and that pieces of highly radioactive material fell between two units and had to be “bulldozed over,” presumably to protect workers at the site. The ejection of nuclear material, which may have occurred during one of the earlier hydrogen explosions, may indicate more extensive damage to the extremely radioactive pools than previously disclosed. "

 

[TCups]

I don't think it is possible to get the sort of steam explosion you are talking about with a large body of water at or near it's boiling point.
I think the sort of meltdown and water table/steam explosion is a bit of a myth (if you're thinking along those lines)
Someone mentioned earlier... the first time I saw hot lava flowing into water I was surprised to see there wasn't any explosion.

The heat of vapourisation for water is just too high, like it's heat capacity, (precisely why it's so good for cooling)
Only microwaves can deliver this sort of threoughout volume and 'to every molecule', energy transfer instantaeneously.

Still got to be hydrogen to me, or a confined biuld up of steam with vessel failure to give such a large blast.

Sorry mate!

There's an interesting article here

http://www.ieer.org/comments/Daiichi-Fukushima-reactors_IEERstatement.pdf

No worries, artax. I may well be wrong. My difficulty is that I can't match up the photographic evidence, which says:

1) vertical blast from unit 3 following a fireball at the SE corner
2) blast damage over the SE corner is over the SFP3
3) crane and roof girders are still intact and apparently on top of the location of the top plug of the primary containment
4) something that looks a lot like a heavy piece of machinery has gone almost straight up and crashed almost straight down back onto Bldg 4, which IF it is a FHM rather than the plug, then the vertical blast must come out of the SFP, not the primary containment
5) the quality and quantity of the blast at Unit 3 look fundamentally different from the blast at Unit 1 (although different construction) and the proposed hydrogen blast at Bldg 4 (same construction)

None of this excludes a blast originating in the primary containment; in fact, in my opinion, a blast did come from the primary containment, except that the blast was

1) not vertical but instead sidewise into the region of the SFP through the transfer chute.
2) associated with a secondary vertical blast coming from the SFP, and
3) possibly associated with a third blast component in the lower floors of Building 3
4) questioned because of a viable mechanism for ignition of gas within the primary containment atmosphere.

So my difficulty is correlating the pictures with a vertical blast, which all agree occurred, as coming from the mouth of the primary containment, which the photos don't seem to support, or as coming from the spent fuel pool, for which my explanation of a superheated steam blast seems to be inadequate.

Something doesn't fit -- either my interpretation of the photographic evidence (very possible) or my explanation of the etiology of a vertical steam explosion from SFP (also very possible) is wrong. So, either way, I am wrong, I suppose.

Better minds than mine are still pondering. But (sigh), I fear it may all be wasted mental gymnastics given the sum of mounting problems and the implications for the "big picture" at Fukushima.

 

[ian_scotland]

watch this vid instead, the tower is directly in line with the buildings diagonal so marks the middle of the building. watch the 'slab' ...

I don't know if this is of any help to people, but I've an image that may correlate the unit 3 vertical explosion debris visible in the video to the whole Fukushima Daiichi plant layout:

https://www.physicsforums.com/attachments/34094

OK, that attachment failed :-(
How do I attach the image?

 

[artax]

I'm like you, just want to know what happened and work out the consequences, it's just frustrating when you know they're not telling us everything.
That vertical component of the blast has me dumbfounded if the plug didn't blow.
I've searched the web for some other group or engineer that's tried to analyse the blast at unit 3, because it was enormous, and filmed from 30km away!
Seriously are you sure the plug is intact?
That large piece that comes back down on the roof, or the sw/ne axis of reactor 3 was so perfectly vertical it must have a mechanism of almost bullet/barrel like accuracy.
I can see there's no tell tale hole in the roof girders, so it does look like an SPF blast, blowing the roof off.
Anyway, hopefully they'll tell us one day!
PS have you seen the slowed down/zoomed in/de-shaked version of the JFK's assassination? Truely Shocking!