Japan Earthquake: nuclear plants

Rive

Regarding the explosion on U3 top level the actual status of U4 roof might be useful as it shows signs of various, but more or less systematic damages but without the side columns broken under the deck level.

I still think that the main difference was the breaking of west side columns under deck level (what was the result of the difference between the strength of the explosions).

MadderDoc

westfield

The image shows the roof structure is wholly bent half way across. However if you look at the eastern end of the three trusses we have been referring to there is no rotation.

westfield

Thinking the same way. The U3 roof structure collapse and damage to east wall framing may not be caused directly by the explosion at all but indirectly by the structural failure in the NW corner of the RB in turn pulling the roof and east wall down. As you say, Unit 4 is great evidence of how once the wall panels and roof cladding are blown away the remaining structure still remains incredibly strong. To add to that, the "slice" of roof cladding in the north end of U4's roof may hint at how the cross braces in the same area of U3 were severed.

MadderDoc

I wonder how you come to that conclusion. On the eastern stretches, the projection of the three trusses to the floor appear to me to be either parallel to the crane beams or rotated somewhat ccw relative to them. However the crane beams are rotated ccw relative to the building, so something parallel to them would seem to have been too.

MadderDoc

Indeed, they have been arranged such that the most natural thought is they fell rather much in unison.
Yes, but in the macro scale that may also have happened. If you look in drone photos from the south side, the whole eastern wall of unit 3 does appear to curve outward. Then of course there are details like the top pillars, as you mention 4 of which have become fractured, and are leaning.

One of those, the middle one is forced down by the roof truss to which it is still attached, so no wonder it is leaning inwards. The next leaning pillar towards the south, we find devoid of its top, apparently resting against the sunken remains of the roof truss it was originally attached to, under the influence of gravity of concrete fragments dangling from its top, and perhaps also because most concrete matrix was lost from the inwards side of the fracture.

I am not saying this arrangement couldn't have involved a series of events with at one stage an inward tension from the roof beam, however I fail to see why it should be a necessary assumption to make. We are in that exact area where we saw the initial huge flare or fireball shooting out the building, to the east and upwards far above the roof. So wouldn't it be simpler to assume this really caused a whole lot of destruction in this upper corner of the building, to the end of the roof beams as well as to the top section of the pillars where they were attached, i.e. to where they were fixed to each other. And after that, well, gravity is always ready to make the final arrangement out of the pieces.

(Similarly just for completion, with the next pillar towards the south, which is almost vertical and has its roof beam MIA, why should we try to explain that its roof beam first pulled inwards the pillar, after which the roof beam disappeared, when we know about that huge fireball? And then finally there is the south-most pillar which has a big chunk of concrete hanging from its top, making it lean north around its fracture at the level of the crane beams, that one never had a roof beam attached to it.)

MadderDoc

I was surprised that there were so little in the way of attachment. The ~7 m corrugated iron roof coverings appear to have been just clipped on at the ends. and then tied in with some rebar and concrete poured on top of it. But then of course it was never built to resist a volcanic eruption from below :-)

I think I got them from cryptome .. yes here:.
http://cryptome.org/2012-info/daiich...chi-022012.zip
but as you can see they are from February 2012, when the press with cameramen were invited in. I hope, and I'd expect a repeat photo safari at time soon, for a balanced winding down of PR -- not to often but also not too far apart -- 3 months would seem a good technical choice at this stage. Perhaps not much more to be hoped coming from Tepco, now more than one year on, but the existing photo and video collection built over the last year is still a great resource, and the content could still be improved by replacing with versions of higher fidelity to the original material.

MadderDoc

I find it curious that the hypothesis of possible heat damage to structures in the upper SE corner of Unit 3 is commonly met with disbelief. To me it would seem to be rather the default position that such heat damaged structures should exist in the wrecked building. Indeed were nothing immediately obvious it would make sense to me to look more carefully for evidence of it. Weird then, to experience an urge rather to explain away, or be blind to it.



hires version of above

elektrownik

Japan Nuclear Experts: Fears corium not totally covered in water at Reactor No. 1 — May only be 15 inches deep, even lower than No. 2

Yamanote

I expect a similar situation in all three reactors.

If there is a vessel with (given) holes at the bottom, one can only maintain the waterlevel inside by pouring more water into the vessel than escapes through the holes. Obviously this is not possible at Fukuichi, otherwise they would have flooded the PCVs already. Call it reactor design flaw or not, unless the leaks in the PCVs can be sealed, this situation will not change. And we know that the techniques for that are still under development. There is no quick "plan B", so time has to show us...

MadderDoc

One can say a priori, that an explosion within the confines of the building cannot cause the collapse of its roof structure directly. It can cause it only indirectly by removing its supports, or by damaging parts of it such as to make it loose integrity. in any case: to bring the roof structure down, there is only gravity. So no quibble there.

Your suggestion otoh that specifically the damage to the wall framing in the south section of the east wall might have been caused by a gravity pull mediated by the collapsing roof structure appears to be entirely speculative. You make no reference to any supporting evidence for that theory, nor evidence to contradict other possible causes of the damage. And in fact it flies in the face of the evidence.

Here, from a video of the explosion, in the very first frame which indicates something untoward is going on with the building, we see explosive damage being done to the walls in the southern part of the east wall:

In the next frame a huge flame burns out through the southern part of the east wall.

It continues to burn for the next many frames, here still visible after more than half a second into the event:


So why should we think none of that damaged the east wall and the roof beams in this part of the building?

zapperzero

I can see that the hydrogen explosion made a lot of heat, relatively. I do not see how that brief, intense fireball might have had time to heat up the insides of those rather sizeable steel beams.

I'd expect to see no more than light scouring from heating . Blast effects and the structure tearing itself apart afterwards would seem to me to account in a satisfactory manner for most of the damage.

This is not to say that I don't see how that area might have been very hot for a long period of time (days maybe? as dry steam was being emitted?), leading perhaps to further warping.

MadderDoc

Yes. The hydrogen explosionists appear to claim for their theories the combustion of in the order of magnitude 1000 kg hydrogen. My BOE says that's about 150000 MJ heat of combustion.

I am not sure which brief intense fireball you are referring to. I am talking about the fire phenomenon visible above the south east corner of the building for the better part of one second after the building blew up (or should we say 'started to blow up'? :-) Many burnt fingers have been caused by not realising how little heat it takes to heat iron. We are in the neighbourhood of a few hundred MJ/ton/1000K says my BOE.

So, if the hydrogen explosionists could be so kind as to spare some kg of hydrogen for a perhaps insignificant fire phenomenon, which however was undoubtedly present, and with possibly some effective metal heating hydrogen combustion directed to the part of the building in question.

Perhaps. You are not being very specific.

I'd consider that to be just speculative. I don't think it well fits the evidence.

zapperzero

In the beginning there is an actual round fireball poking out of that corner.


Undoubtedly there was some heating. I am "just" saying that the most energy, by far, went into making a pressure wave. Incidentally, its leading edge was very hot also. But the inside of that impressive ball of fire is empty, at very low pressure and relatively cool, the flame front passes over any given thing for only the briefest of moments, because it is supersonic. If you look at the photos more, you will see that there is still some paint, in patches, on even the most corroded, darkened beams. That does not jive with scorching heat.

Me neither. It's just a remote possibility.

MadderDoc

When, in the beginning? Perhaps you can use this as a reference.

The visible fire phenomenon is almost entirely outside the building, so only relevant from what it tells us about what's concurrently happening inside the building, e.g. where does the burning substance originate from, what source feeds it, what route did it take from there to erupt on the outside of the building, what were the conditions for damage along that route while it burned.

MadderDoc

Apparently 'hydrogen explosion' can be used to explain any effect, any degree of damage, and is not supposed to be held to any high evidential standard. Otoh, if there is just a few patches of something looking like paint to be found on a piece of scrap metal, it is concluded that it cannot have been damaged by heat. I wonder if you'd seriously be willing to use that criterium, if you were shown corroded beams with not a speck of paint left, or 'hydrogen explosion' and a bit of handwaving would be used to explain that away too.

jim hardy

i'm way behind you fellows.

I cant rule out the beams having got roasted by hot gas during or afterward. Rust suggests the paint got cooked off.

Still musing on the columns.
The crane rail, so obvious in that photo, ties the columns together for N-S forces. The east ones still standing fairly well retained that alignment.
The west ones did too, from aerial March 20 (2011) shots of them dangling by rebar.
The resolution of those isn't good enough to say whether the rail is still attached to them but it doesn't appear to be laying under the crane ends up on the deck.

If that substantial beam is one continuous rail it'd add some rigidity for E-W forces too, making the columns into a wall-like structure. That could explain why the eastwest (edit) columns toppled together as a unit. I'd say the westeast ones almost did too.

plodding along. if you guys dismiss this as beating the obvious i'm not offended.

visiting kids now and away from my computer else i'd post that 20 march photo..

old jim