Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[zapperzero]

I think you described Unit 1's explosion perfectly, at least the water flashing to steam part. See beginning at 32 seconds http://www.youtube.com/watch?v=OFt1OHU1u9s"

I see part of a shock front there, going up as if from a large cannon barrel or the tailpipe of a bike when it misfires. I also see a lot of debris/dust/smoke going to the sides and nothing going upwards. No steam until very late on.

If you look closely, you can see the roof going up, as a black spot in the middle of the cloud of dust. The shock front must have passed through it, but not whatever else was beneath, creating conditions for that nice disk to be visible.

If I squint just right, I think I also see some orange light, just before the shock front goes up, obscuring everything. Hey, that's no steam explosion! Must've been Osama.

EDIT: I am not implying there was some sort of barrel involved. Just what it looks like. Of course, the shock front is almost hemispherical, perhaps a bit flattened at the top (the lighter debris and dust travels with it, very visibly marking the parts going outwards; upwards, we have just condensation from compression for a while, then nothing).

EVEN LATER EDIT: The nice condensation disk tells us the shock front was supersonic.

 

[Borek]

However true that is there is still no free lunch as regards the heat of transition.
It must be served, or you will not have any vapour no matter how much you tune down the pressure.

I just did some back of the envelope calculations. To cool down water by 1 deg C one have to change 0.186% of that water into gas.

This is just to give some number to make further discussion easier.

 

[artax]

From a bit of reading I would estimate the unit 3 blast to be less than 10 GJ, based on the Flixborough disaster (60GJ) and the Glennan Barracks bombing (4GJ) though this is somewhat a wild guess as some channelling of the blast at unit 3 could have prevented nearby building damage.

 

[AntonL]

Problem is, as I see it, that this amount of vapour is insufficient to explain the size of the mushrooming cloud and the apparent size of its lifting capability.

Look at this video of US soldiers blowing up a jungle cocaine factory,

Pillar and mushroom development after a small scale military explosion
http://topdocumentaryfilms.com/cocaine-submarines/
[PLAIN]http://k.min.us/in6Hxg.JPG

concerning lifting capacity, all held up by air being a couple of degrees warmer
[URL]http://www.abqballoonrides.com/images/2008_NJFOB.jpg[/URL]

 

[MadderDoc]

Having previously not understood the mechanism for instantaneous conversion of water to steam and the possible resulting high energy explosion, I now do see that it's possible. The PRINCIPLE section of this page:- http://en.wikipedia.org/wiki/Boiler_explosion. explains.
However I think that for the explosion of unit three to be due to a steam explosion, it would mean there had been a catastrophic failure of the pressure vessel to produce so much steam instantly.

If instrument readings can be trusted, the PV had already failed on March 13th. At the time of the explosion, the PV was leaking, held a pressure about 4 bar, while the CV held about 5 bar, and the CV probably had within it the major part of the water contained in the combined system. So it could well also have been a catastrophic failure of the containment vessel. While a steam explosion from the CV couldn't likely have left the PV quite untouched, we cannot conclude that such an event would necessarily lead to the PV spewing all its content into the air.

I think this has been ruled out due to the radioactivity and isotopes found.

Yes, I've been told that before, albeit so far with no proper reference to this allegedly conclusive analysis. :-) (I'm sure my scepticism is showing.)

 

[SteveElbows]

That's either due to local weather at night (as discussed before), or because they fill the SFP's at night and this is creating a lot of fog. Or even both.
It would make sense to fill up the SFP's at night in the latter case; makes for a safer working environment during daytime, doesn't it.

The question of putting water in the pools at night has come up several times before. But the official updates give times for pumping & spraying at various pools, and these times indicate that it is extremely rare for any of this stuff to be done during hours of darkness.

 

[artax]

I must say I assumed some channelling of unit 3 explosion, or barrel if you like, due to the large piece that is propelled perfectly vertically, and falls almost where it rose from,... though probably slightly (though imperseptibly) to the right (or Southeast) due to the wind, the cloud however moves with the wind, due to it's low density.
That large piece must have been directly ballanced on the balloons centre if we're simply talking bouyancy! and what is it? the floor above the SFP?

 

[SteveElbows]

If I squint just right, I think I also see some orange light, just before the shock front goes up, obscuring everything. Hey, that's no steam explosion!

When you say orange light, do you mean the fireball to the south of the building that's clearly visible?

 

[zapperzero]

When you say orange light, do you mean the fireball to the south of the building that's clearly visible?

I circled it in the attachment. It's to the south I think, yes.

 

[AntonL]

I just did some back of the envelope calculations. To cool down water by 1 deg C one have to change 0.186% of that water into gas.

This is just to give some number to make further discussion easier.

or to cool the volume of the SFP by 1^oC would release .596 GJ

 

[TCups]

However true that is there is still no free lunch as regards the heat of transition.
It must be served, or you will not have any vapour no matter how much you tune down the pressure.

Understood. I was attempting to say that the total amount of heat required for phase change is a constant, but that it would not be correct to think that all of it must be applied instantly, or that very high temperatures are necessary to supply the heat of transition. Heat energy continues to be stored in water undergoing heating at 100ºC even though the temperature does not appear to change. There can be a huge difference in the total energy stored in two pools of water, each at 100ºC and each under the same pressure, unless I misunderstand the concept of the heat of transition and phase change.

Edit: Reference added - http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/phase.html

I am not sure what you are saying there. The problem I see is one of size of cloud and one of lifting capability. Water in tiny droplets do not take up much space, and do not contribute to lift.

True, but tiny droplets of water require less total thermal energy (although not per unit volume) than a massive pool of water requires in order to undergo the phase change. Is it not possible that atomized water droplets intermixed with burning hydrogen + oxygen might be efficiently heated and turned into additional steam during the hydrogen explosion itself?

OK, so you don't know that flashing of tons of water to steam was involved. However you do know, I believe, that 'something' propelled a diversity of heavy objects 100s of meters into the air. If a huge amount of water vapour rising didn't do it, what did?

In part, perhaps the hydrogen explosion itself, of course, but I strongly suspect a steam explosion based on what I see, even if I don't "know". I suppose that it is sort of like the old joke about the prostitute (do you know it?) . . . I presume that we have already established, by its characteristics that a large component of the explosion of Unit 3 was a steam explosion. So now, we are just haggling over the "price" (and source) of thermal energy required to fuel it. Anton gave some reasonable calculations, I believe.

Edit: Reference added - http://en.wikipedia.org/wiki/Water_vapor#Lifting_gas

Lifting gas
Due to its low molecular weight, water vapor is a lifting gas under STP conditions; however, it is limited by the low amount of water vapor which can exist in the air at a given point in time. High enough temperatures to maintain a theoretical "steam balloon" yield approximately 60% the lift of helium and twice that of hot air.[9]


Potential sources of thermal energy I can see are these:

1) thermal energy stored in the water of SFP3 transferred from decay heat of spent fuel rods in the pool,
2) thermal energy transferred from burning hydrogen in the building above SFP3,
3) thermal energy from the RPV transferred by explosive venting of steam and hot (radioactive) gasses from the drywell or upper "wet well" or both,
4) thermonuclear energy from sudden criticality occurring in the unspent fuel in SFP.

And say, don't I remember a passive emergency cooling system that operates without electric power driven by a steam turbine that circulates through a cooling pool? Was such a mechanism in operation at Unit 3? Would that have been in any way related to heating SFP3 (ie, was initial emergency cooling of the Unit 3 core at the expense of additional heating of SFP3 or is another water reservoir used for this emergency system, if it was used)?

Are there any other substantial sources of thermal energy that I have not considered?

I remember some earlier, detailed discussion about the calculation of energy released with the explosion of Unit 3 and, I believe that the final conclusion was that it could not even be estimated to within an order of magnitude with any reasonable accuracy. (sigh)

Edit by Borek: TCups, I corrected quote tags so that it is obvious what is a quote and what was your answer. If something is wrong, please contact me by PM and I will correct it again.

 

[artax]

this is one of the best shots without TV channel stuff covering bit up! could do with some contrasting though

http://www.youtube.com/watch?v=RxAHoxEvv7Y&feature=related

 

[jlduh]

Concerning SFP's and plugs, did we already have a clear statement about this subject: are the SFPs normally plugged with concrete removable roofs (some kind of anti-missile protection i think?)?At n°1 i don't see the SFP (maybe under the crane?), so is it plugged with these?

What about N°2 (which we don't see)?

N°3 we know that there is none currently, but what about before the explosion?

For N°4, even if it had some in normal use, it was getting fuel reloading so probably no plug anyway, which is consistent with what we see now.

Again, this subject is fuzzy to me. We can imagine that at N°3 for example, if there was some plug the explosion could be explained much differently.

I was really thinking that SFPs should have plugs for safety (missiles) reasons (which is a problem if cooling is stopped as gases are captured by the way!)

Could this explain the big hole above N°3 SFP, and maybe some big chunks of concrete thrown in the air?

 

[zapperzero]

The question of putting water in the pools at night has come up several times before. But the official updates give times for pumping & spraying at various pools, and these times indicate that it is extremely rare for any of this stuff to be done during hours of darkness.

Well, some nights the plant's all lit up and steam's coming out. Other nights it's pitch black.

 

[elektrownik]

No, there is no protection on SFP, they are open.

 

[PietKuip]

REGARDING THE HIGH SPIKE OF MEASURED RADIATION ASSOCIATED WITH UNIT 3'S EXPLOSION

Could there be another plausible explanation? For example:

Could the spike in measured radiation levels be explained by the explosive release of volatile iodine and cesium (or other highly radioactive isotopes) from the explosion and venting of the contents of the drywell of Unit 3, lofted by the associated steam flash? I believe there were smaller spikes in measured radiation during controlled venting. It would seem to make sense that explosive venting would be a much larger spike.

Could some of the contents of SFP3 also have been damaged by an explosion and steam flash and also lofted and scattered, perhaps also contributing to the spike?

The newspaper article says about this bunker:
"The three-story, white bunker had extra-thick walls and two filtration systems designed to keep out radiation."
http://www.bloomberg.com/news/2011-04-25/japan-s-terrifying-day-saw-unprecedented-exposed-fuel-rods.html

An earthquake-proof radiation shelter. Yet the radiation spike was measurable inside.
To me this is rather strong support for Gundersen's theory.

 

[Rive]

Right, exactly. A cumulus cloud needs no barrel, it has direction 'up' due to gravity and it has considerable lifting properties. So why invoke a need for a barrel in the case of the unit 3 cloud?

There was some really big pieces in that cloud, which cannot be explained by just lifting by heat.

Ps.: regarding that radiation spike in the safe bunker: is there even a direct view from the bunker to U3 service floor? To the depths of SFP?

 

[|Fred]

Concerning SFP's and plugs,

The SFP plugs as quoted in the service floor paper are the removable wall making a "channel" from the core to the SPF.

 

[MadderDoc]

Look at this video of US soldiers blowing up a jungle cocaine factory,

Pillar and mushroom development after a small scale military explosion
http://topdocumentaryfilms.com/cocaine-submarines/
[PLAIN]http://k.min.us/in6Hxg.JPG

Yes, pillar and mushroom development is not per se a signature of steam explosions. A good sized fireball (or steamball) and it is set to go.

concerning lifting capacity, all held up by air being a couple of degrees warmer
[PLAIN]http://www.abqballoonrides.com/images/2008_NJFOB.jpg[/QUOTE]

A hot air balloon is usually operated at between 100 and 120^oC and will then produce a lift of about 3 N/m³. The lift of hot water vapour is about double of that, more than 6 N/m³. This is mainly because water has a much lower molar mass than atmospheric air. For comparison one of the best buoyancy gases we have, helium, has a lift of about 10 N/m³. IOW water vapour has over 60 % of the lifting capability of helium.

 

[pdObq]

Could this explain the big hole above N°3 SFP, and maybe some big chunks of concrete thrown in the air?

Apparently they don't use the concrete shield plugs for the SFPs although those seems to exist (see posts a few pages back). (Still waiting for comments on this issue from those with first hand nuclear plant experience... just a reminder, not being impatient )

But what you write could have applied to the dryer-separator pool. Its shield plugs are much heavier than the SFP ones, and they might have put them in place just to have more floor space available. Maybe that could be related to the heavy floor damage in the NW corner of unit 3. Otoh, although we know there is steam venting from the side of the concrete blocks separating the DS pool from the reactor well, those blocks themselves seem undamaged.

EDIT: See post https://www.physicsforums.com/showpost.php?p=3299661&postcount=7054 which came up while writing this. That would make sense, as they are supposedly rather light. But do you know for sure, any documents where that's stated (might be in the whole document, I just looked at the two extracted pages so far)?

 

[pdObq]

A hot air balloon is usually operated at between 100 and 120^oC and will then produce a lift of about 3 N/m³. The lift of hot water vapour is about double of that, more than 6 N/m³. This is mainly because water has a much lower molar mass than atmospheric air. For comparison one of the best buoyancy gases we have, helium, has a lift of about 10 N/m³. IOW water vapour has over 60 % of the lifting capability of helium.

But you don't want to imply that those large concrete chunks thrown upwards in the explosion are floating on some kind of hot gas?

 

[AntonL]

But you don't want to imply that those large concrete chunks thrown upwards in the explosion are floating on some kind of hot gas?

concrete chunks - I would say roof sheets judging by there size

 

[whoswho69]

http://www.fairewinds.com/updates - Arnold Gundersen

 

[pdObq]

The question of putting water in the pools at night has come up several times before. But the official updates give times for pumping & spraying at various pools, and these times indicate that it is extremely rare for any of this stuff to be done during hours of darkness.

I think someone had the very reasonable explanation that since it is colder at night, the steam condenses more readily, so that it appears as white clouds/fog. Someone else compared it to the cooling tower next to where they live, it strongly depends on the weather whether there is visible condensation of the steam.

 

[MadderDoc]

There was some really big pieces in that cloud, which cannot be explained by just lifting by heat.

Perhaps not, but I think no one has suggested it could. However water vapour .. for a rough estimate, 1 ton of water vapour can produce a lift of 10000 N, the force needed to lift a 1 ton heavy object. If vapour from flash boiling of the sfp should be responsible we can put an upper bound to its capabilities, seeing that a 110C superheated sfp can flash boil at most 30 tons of water. My point is exactly, that we appear to have seen in the explosion significantly more than a sum total of 30 ton of those pieces lifted up and away. So if not enough water vapour could have come from the sfp, we might look for another, potentially larger source. And that source could only be the water contained in the reactor PV and CV. If that source is also not enough, well, then I guess I would have to start taking the criticality issue op to more serious consideration.

 

[jlduh]

There was some really big pieces in that cloud, which cannot be explained by just lifting by heat.

I share this view: due to the size of the big chunks thrown away (some fall on the north side, some on the south side, coming both from the big vertical dark cloud which is coming from the center of the buiding, impossible to be precise at a few meters though) i have a hard time imagining that it can be lifted so high by very warm air...

That's why i only see the gun and barrel explanation really possible IMHO.

 

[pdObq]

concrete chunks - I would say roof sheets judging by there size

Well, sure it might be anything (but it looks like it is breaking apart "in flight", and it looks as if it is reasonably heavy), but that is not really my point. I just don't think that stuff is surfing on hot gas, it has been launched by some explosion and is essentially some kind of projectile.

 

[artax]

I'm sorry Anton, but we're simply talking density here, roof sheets would have been carried with the wind much more than that piece that came straight down back on the building. That piece has to be many tons.

 

[jlduh]

1 ton of water vapour can produce a lift of 10000 N, the force needed to lift a 1 ton heavy object.

Well, you have also to consider the height at which this can be lifted, and the speed...

These big chunks that are for sure heavier than 30 tons have been lifted to something like 300m or more...

Even if it's difficult to see exactly which altitude they reached, we have the impression from the ballistic trajectory that they were not so far from the top of the dust cloud . So if dust is lifted by steam (warm air) at a certain height, it is not conceivable that this height minus a certain percentage (let's say 15% less height visually) can be achevied by the same process (warm air lifting) for very heavy objects like the big chunks. If these big chunks go so high, it's because they gained cinetic energy (1/2 mv2) right after the explosion, which implies very high speeds of ejection in the first moments of explosion.

That's the principle of a bullet: to go far you have to go very quickly at the start. The warm air (quick volume expansion) is only efficient in the tube of the gun to create big acceleration, then the bullet uses it's stored cinetic energy to continue its travel.

Light dust can be lifted by steam but it's a different process (thermodynamics and aerodynamics).

Even if you see big heavy chunks AND dust+steam going in the same direction at almost the same height, the physical and mechanical processes and laws involved are of different nature (more precisely all the laws are applied to both of them but in various contributions to the end results, depending on their own physical properties).

I think some are getting mislead by visual (wrong) evidence comparing the two.

 

[pdObq]

Both images are taken from this Caltech presentation: http://www.galcit.caltech.edu/~jeshep/fukushima/ShepherdFukushima30April2011.pdf

According to these images, it's normal under emergency cooling conditions that the Drywell in Units 2 and 3 is filled with hot steam.

Those attached images from that presentation suggest that the RCIC steam turbines and releated equipment is located in the north side more or less below the DS pool. That of course is a very simplified drawing, and they might be actually located in other places of the buiding.
But it points me again to that large damage on the NW corner of unit 3. If there was a direct steam line from the reactor going there, and there was overpressure or earthquake related seal damage, then H2 might have accumulated there (among other places).

Alternatively, if there was sudden overpressure within the reactor the path of least resistance would be through the steam lines into the RCIC turbine...