Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Astronuc]

Is it possible at any point to blow a powdered alloy (or perhaps a multi-staged application) onto the damaged cladding that might coat and repair the damage - at least temporarily - then repeat the process?

As far as I know, that would not work, partly because the fuel is supposed to be underwater, there is no way to ensure uniform or appropriate distribution, and there is no satisfactory binder.

They could conceivable dump a bunch of resin powder or beads in the pool. Normally, the coolant or condensate is 'polished' in a filter demineralizer that is a basically a huge filter with a resin coating - much like in principle a 'green sand' filter.

There are two groups of fuel to be concerned about, the fuel in the SFPs and the fuel in the core. If any fuel is damaged, it will be a radiological risk.

Reactor personnel have to deal with failed fuel on occasion (although there has been a program in place for over a decade to drive failure rates to zero). Normally, it's one or a few assemblies with typically 1 failed fuel rod. We maybe looking at 100s or thousands of failed rods, and that's very complicated from a radiological standpoint. If the tie rods are failed, then special tooling will be required to fish the damaged fuel out of the core. In fact, special baskets may be necessary in order to remove damaged fuel.

Hopefully, there are some fuel assemblies in the core which are intact - basically the low power assemblies at the periphery of the core, or the low burnup fuel.

I'd surely like to know the state of the fuel in the SFPs of Units 1-4, particularly unit 4. I suspect 4 has the most damaged fuel, and I'm not sure of the others.

 

[tsutsuji]

Discussing the black smoke at reactor 3 (probably that black smoke which was reported on 23 March), Kenichi Ohmae suspects the reactor pressure vessel is perforated : http://www.nikkeibp.co.jp/article/column/20110404/265766/?ST=business&P=2

 

[Bodge]

There is also a metastable isomer of this isotope, see http://nucleardata.nuclear.lu.se/nucleardata/toi/nuclide.asp?iZA=520429

It has a half-life of 33.6 days, and most of it (63 %) decays to the ground state by emitting a gamma. So the ground state is expected to be in the spectra. In steady state ("equilibrium"), it should be in the data with 63 % of the activity of the metastable isomer.

Its presence does not prove any recent criticality. It does not even point to recent criticality.

Really looks like Gunderson should keep his gob shut.

If CL-38 detection was real then that would be the 'smoking gun'.

 

[michael200]

Cause of Fukushima Unit 4 damage

It is reported that the cause of the unit 4 building damage was a H2 explosion caused by overheating of the discharged fuel in the U4 spent fuel pool. To the best of my knowledge, there is no photgraphic evidence of the explosion. Something that has troubled me since the first pictures of the Unit 4 damage on 16March, was whether there actually was a loss of inventory in the U4 spent fuel pool. Attached is a markup of the first photograph that was released on 16 March showing the U4 buiding damage. One can find the photo on Reuters site. This photo was taken before any water injection/spray in Unit 4. Perhaps, I'm missing something, but it sure looks to me like there was still significant water in the fuel pool on March 16. Anyone have an alternative speculation?

 

[sp2]

http://www.nytimes.com/2011/04/05/world/asia/05japan.html?_r=1&hp

runoff flooding the turbine buildings of 5 and 6? Implies that an entire swath parallel to the ocean is flooded. 5 and 6 are quite far from 1-4

[PLAIN]http://www.visa2tour.com/wp-content/uploads/2011/03/nuclear-power-plant-japan-satellite-images-damage-overal.jpg[/QUOTE]


Don't forget, they did all get hit by a series of very large waves.

(I don't know if water in the basements of 5 and 6 necessarily came all the way over from runoff from 3 and 4.)

 

[TCups]

It is reported that the cause of the unit 4 building damage was a H2 explosion caused by overheating of the discharged fuel in the U4 spent fuel pool. To the best of my knowledge, there is no photgraphic evidence of the explosion. Something that has troubled me since the first pictures of the Unit 4 damage on 16March, was whether there actually was a loss of inventory in the U4 spent fuel pool. Attached is a markup of the first photograph that was released on 16 March showing the U4 buiding damage. One can find the photo on Reuters site. This photo was taken before any water injection/spray in Unit 4. Perhaps, I'm missing something, but it sure looks to me like there was still significant water in the fuel pool on March 16. Anyone have an alternative speculation?

@michael200

Compare your image to this:

http://i306.photobucket.com/albums/nn270/tcups/FHM.jpg

The "reflection" seems dubious. More likely, you are seeing more of the substructure below the operator's platform than a reflection.

 

[michael200]

Your picture is of a different refueling bridge design.

 

[MadderDoc]

Whether the lid is in place or not: The explosion on #3 blasted away the concrete columns on the N, S, and W sides of the building, but left the E columns mostly in place. The metal beams of the roof that were above the crane remained attached to the columns, and presumably so did the crane. Thus it is possible that the ro the crane remained attached to the columns, and presumably so did the crane. Thus it is possible thof and crane were partially lifted by the explosion, pivoting on the W side, and then fell back to their original positions (except for the lack of support on the E side).

However, from looking at

(at time stamps about 10:13:27, and about 10:20:28)
those beams and with them the crane do indeed seem to have fallen flat on the floor -- smack on top of the lid, and with steam gushing out from under it.

 

[TCups]

Your picture is of a different refueling bridge design.

Your reflection is equivocal at best.

 

[TCups]

However, from looking at

(at time stamps about 10:13:27, and about 10:20:28)
those beams and with them the crane do indeed seem to have fallen flat on the floor -- smack on top of the lid, and with steam gushing out from under it.

Look back carefully at the debris on the ground at west side of Bldg 3 and you will see why the crane fell.

 

[NUCENG]

Did I hear that the two fatalities were in the basement of Bldg 4 -- I can't remember for sure? If they were working in the basement of Bldg 4, then were they perhaps trying to do just that when the explosion occurred?

Press Release (Apr 03,2011)
Employees of TEPCO Who Were Missing at Fukushima Daiichi Nuclear Power Station


Due to the Tohoku-Taiheiyou-Oki Earthquake which occurred on March 11th
2011, two TEPCO employees, who had been working at the turbine building
of Unit 4 for site investigation, went missing.
We had put all our strengths to search them, and approximately at 3:25 pm
and at 3:53 pm, today, March 30th, 2011, those employees were found at
the basement of the turbine building and we confirmed their death
yesterday.
We would like to offer our deep regret that our workers died while
working at the plant and heartfelt condolences to the bereaved families.

[Deceased Employees of TEPCO]

Kazuhiko Kokubo (Age: 24) Operation Management Department One, Fukushima
Daiichi Nuclear Power Station
Yoshiki Terashima (Age: 21) Operation Management Department One,
Fukushima Daiichi Nuclear Power Station

 

[WhoWee]

[Deceased Employees of TEPCO]

Kazuhiko Kokubo (Age: 24) Operation Management Department One, Fukushima
Daiichi Nuclear Power Station
Yoshiki Terashima (Age: 21) Operation Management Department One,
Fukushima Daiichi Nuclear Power Station

I'm quite surprised by the ages (24 and 21) of the deceased workers.

 

[TedNugget]

Pure speculation:

Ages 24 and 21 sound like workers who were sent to do something even though there was a Tsunami Alert.
Their listing in the press release just includes their names and division, no titles but could operation Management mean they were in a higher pay grade?
If not, that would mean (a) supervisor(s) still living with guilt.

That they were in Turbine 4, which one would assume everyone on site knew reactor 4 was down, could indicate the caution they had relating to the spent fuel pool. (With the Turbine buildings holding condensers and providing cooling for both the reactor and SFP).
The workers were found in a basement - auxiliary control room as I recall.

 

[AntonL]

I have managed to identify the shared pool No. 7 for very old fuel
one of the thermal images had it labelled in Japanese

It is west of reactor No. 4

 

[MadderDoc]

..Perhaps, I'm missing something, but it sure looks to me like there was still significant water in the fuel pool on March 16. Anyone have an alternative speculation?

I'll think about that. Looking down in the unit 4 sfp with the more recent crane camera there just appears me to be 'something dark' down there -- judging from the railings seen on the far side of the pool, that surface is several meters below floor level --, and it does not look like water. (Alas, seeing steam obviously does continually escape from the pit, there must be some water down there, still

 

[Jorge Stolfi]

it is my understanding that gauges are and have been working in the control room (analog power?) as they had to go every now and then to check the value with torch light.. and now they have regular cellar light

Well, the temperature and pressure data were available since shortly after the accident (at least for some units), well before they brought electricity to the control room. And, AFAIK, the control room panel is still dead.

 

[M. Bachmeier]

Really looks like Gunderson should keep his gob shut.

If CL-38 detection was real then that would be the 'smoking gun'.

When CL-38 was first (reported) found it had a lot of people concerned, but it also had them scratching their heads because other isotopes were missing re: Astronuc and a student of radio chemistry.

The point here is simple. Gunderson should have been checking for reasons to dismiss his hypothesis (good science). And A Google search would have led him here, where questions about the reliability of the reported measures were raised at least two or three days before he made his public proclamations. Astronuc's responses to my and others questions have been frank (if a little scary at times), but showed no indications of bias.

I'd take Astronuc's opinion of event over Gunderson any day.

 

[|Fred]

However, from looking at

nice video
the slab does have a strair like edge
[PLAIN]http://k.min.us/ik5km0.jpg
and the is a similarity with the structure that we see there but is it ?
[PLAIN]http://k.min.us/imQyfs.jpg

 

[M. Bachmeier]

It is reported that the cause of the unit 4 building damage was a H2 explosion caused by overheating of the discharged fuel in the U4 spent fuel pool. To the best of my knowledge, there is no photgraphic evidence of the explosion. Something that has troubled me since the first pictures of the Unit 4 damage on 16March, was whether there actually was a loss of inventory in the U4 spent fuel pool. Attached is a markup of the first photograph that was released on 16 March showing the U4 buiding damage. One can find the photo on Reuters site. This photo was taken before any water injection/spray in Unit 4. Perhaps, I'm missing something, but it sure looks to me like there was still significant water in the fuel pool on March 16. Anyone have an alternative speculation?

One explanation that was and is being looked at is some kind of enhanced explosion. Take your pick from damaged fuel to other gas released due to earthquake damage.

 

[|Fred]

judging from the railings seen on the far side of the pool,

not railing but the other crane

 

[Jorge Stolfi]

However, from looking at {video} those beams and with them the crane do indeed seem to have fallen flat on the floor -- smack on top of the lid, and with steam gushing out from under it.

Agreed for the crane; but one of the roof beams is still attached to its East column in the Aero Service images:

 

[Bob S]

Jorge Stolfi-

Thank you for reporting the CAM radiation measurements in centi-Sieverts.

http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/cams-un1.txt

http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/cams-un2.txt

http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/cams-un3.txt

You are about the only person I know who realizes that 1 centi-Sievert = 1 rem. Makes conversion from rems to Sieverts simple.

Bob S

 

[Jorge Stolfi]

Thank you for reporting the CAM radiation measurements in centi-Sieverts. You are about the only person I know who realizes that 1 centi-Sievert = 1 rem.

I wish I deserved the compliment... but the truth is that I chose cSv/h because I wished the numbers to fit in a five digit field. And I can't recall now why that seemed a good idea at the time.

 

[TCups]

BLAST DAMAGE AT UNIT 3

However, from looking at

(at time stamps about 10:13:27, and about 10:20:28)
those beams and with them the crane do indeed seem to have fallen flat on the floor -- smack on top of the lid, and with steam gushing out from under it.

@ MadderDoc, Fred, et. al.:

Re: New video. Attached is a screenshot from the viedo with and without annotations of what I think I see. As ever, I say the blast came out of the primary containment, through failed seals on the transfer ("cattle") chute gate. But then, it is all too easy to see what you expect to see and want to see. Comments?

http://i306.photobucket.com/albums/nn270/tcups/Screenshot2011-04-04annotated.png

http://i306.photobucket.com/albums/nn270/tcups/Screenshot2011-04-04at50940PM.png

 

[Maxion]

@ MadderDoc, Fred, et. al.:

Re: New video. Attached is a screenshot from the viedo with and without annotations of what I think I see. As ever, I say the blast came out of the primary containment, through failed seals on the transfer ("cattle") chute gate. But then, it is all to easy to see what you expect to see and want to see. Comments?

http://i306.photobucket.com/albums/nn270/tcups/Screenshot2011-04-04annotated.png

http://i306.photobucket.com/albums/nn270/tcups/Screenshot2011-04-04at50940PM.png

You did call this quite a while ago. Nice job there!

 

[shogun338]

Look at the huge steel doors that are where they move the spent fuel rods out in dry casks I believe in lower right of post #2836 . They look like they where almost blown off there hinges in outward direction . The explosion must have traveled into the lower sections of Unit #3 also .

 

[TCups]

Look at the huge steel doors that are where they move the spent fuel rods out in dry casks I believe in lower right of post #2836 . They look like they where almost blown off there hinges in outward direction . The explosion must have traveled into the lower sections of Unit #3 also .

Hmmm . . . yes maybe so. You are referring to the steel doors at ground level on the tunnel-like structure, correct? If so, though, the one on Bldg 4 looks even worse. The whole tunnel is exploded outward.

 

[Jorge Stolfi]

I have updated again my plots of the reactor variables:
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/Main.html"

Up to METI/NISA release 73 (apr/04 15:00).
Also included some data for unit #1 from a plot shown in earlier post on this thread.

Also fixed the "cur" link, sorry --- it was indeed out of date.

 

[jensjakob]

BLAST DAMAGE AT UNIT 3



@ MadderDoc, Fred, et. al.:

Re: New video. Attached is a screenshot from the viedo with and without annotations of what I think I see. As ever, I say the blast came out of the primary containment, through failed seals on the transfer ("cattle") chute gate. But then, it is all to easy to see what you expect to see and want to see. Comments?

http://i306.photobucket.com/albums/nn270/tcups/Screenshot2011-04-04annotated.png


http://i306.photobucket.com/albums/nn270/tcups/Screenshot2011-04-04at50940PM.png

BINGO! You are quite good.

Respect and kudos for your stamina

 

[shogun338]

Hmmm . . . yes maybe so. You are referring to the steel doors at ground level on the tunnel-like structure, correct? If so, though, the one on Bldg 4 looks even worse. The whole tunnel is exploded outward.

Yes .

 

[M. Bachmeier]

I have updated again my plots of the reactor variables:
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/Main.html"

Up to METI/NISA release 73 (apr/04 15:00).
Also included some data for unit #1 from a plot shown in earlier post on this thread.

Also fixed the "cur" link, sorry --- it was indeed out of date.

'Jorge' (sorry-you are not Joe) what is going on with core pressure in number 1? It doesn't deem to correlate with temperature readings?

 

[elektrownik]

and this: http://www.houseoffoust.com/fukushima/heat.html ?

 

[Borek]

I wonder how much sense makes comparison of the IR images if we don't know what was the air temperature and wind. Quite likely differences are in some part effect of the external conditions (that is, IR pictures should be different when wind changes, even if the localization of heat sources and amount of heat produced is constant).

 

[Cire]

'Jorge' (sorry-you are not Joe) what is going on with core pressure in number 1? It doesn't deem to correlate with temperature readings?

The temperature sensors are cooked. I don't believe they're returning real values any longer. There likely is an offset in the output now.

I suspect the temperature is being reported higher then it really is.

 

[M. Bachmeier]

The temperature sensors are cooked. I don't believe they're returning real values any longer. There likely is an offset in the output now.

I suspect the temperature is being reported higher then it really is.

Do you mean temperature is higher than is being reported? Do you have some supporting reference, link etc.?

 

[TCups]

and this: http://www.houseoffoust.com/fukushima/heat.html ?

Are you familiar with the digital imaging terms "window width" and "window level"? If so, go back on every image and look carefully at the color bar on the left to determine where the "center" temperature is, the total spread of high and low temperatures displayed, and the absolute values assigned to each color. Some things that look "hotter" just because they are more toward the red end of the spectrum in one image are not necessarily hotter than something green in the next image, when you check the scale.

I confess I haven't gone frame by frame through your analysis and questions, but at a glance, I can tell you that you have to be very careful comparing one image to the other. The time lapsed during the acquisition of the image and the color scale ascribed to the image vary significantly, I believe.

 

[M. Bachmeier]

Are you familiar with the digital imaging terms "window width" and "window level"? If so, go back on every image and look carefully at the color bar on the left to determine where the "center" temperature is, the total spread of high and low temperatures displayed, and the absolute values assigned to each color. Some things that look "hotter" just because they are more toward the red end of the spectrum in one image are not necessarily hotter than something green in the next image, when you check the scale.

I confess I haven't gone frame by frame through your analysis and questions, but at a glance, I can tell you that you have to be very careful comparing one image to the other. The time lapsed during the acquisition of the image and the color scale ascribed to the image vary significantly, I believe.

Even when looking at small variations, a color contrast illusion can make simple observation inconclusive and misleading. How much detail is being offered in the IR?

P. S. Does anybody have specs? Most modern IR is digitally enhanced to account for wave distortion like observatory (digital) astronomical observation.

 

[TCups]

Even when looking at small variations, a color contrast illusion can make simple observation inconclusive and misleading. How much detail is being offered in the IR?

Yes. The bright colors look impressive on the web and on TV sound bytes, but at least in medical imaging, color scales are seldom used. Monochrome or grayscale are preferred. Either a very big difference with a wide window can look like a very small difference with a narrow window.

In imaging, "detail" is usually reserved for spatial resolution. Some of the IR images seemed to have wide windows, little overall difference in the color scale, and a lot of detail. Some of the color images appear to "bloom" with the colors used and all detail is lost.

I will try to go through the IR mages later (tonight is the NCAA basketball finals, after all).

You can see, though, that all of these images have been windowed and leveled so as to identify the single hottest point on the image, which is the annotated temperature on the labels.

 

[razzz]

After dousing with water, I think the point is that there are hot spots where there should be no hot spots. Everything around the pool should be ambient temp. Even inside the pool it's inconsistent.

 

[M. Bachmeier]

Yes. The bright colors look impressive on the web and on TV sound bytes, but at least in medical imaging, color scales are seldom used. Monochrome or grayscale are preferred. Either a very big difference with a wide window can look like a very small difference with a narrow window.

In imaging, "detail" is usually reserved for spatial resolution. Some of the IR images seemed to have wide windows, little overall difference in the color scale, and a lot of detail. Some of the color images appear to "bloom" with the colors used and all detail is lost.

I will try to go through the IR mages later (tonight is the NCAA basketball finals, after all).

You can see, though, that all of these images have been windowed and leveled so as to identify the single hottest point on the image, which is the annotated temperature on the labels.

Yes thank you I forgot (NCAA), see you later:), but thank you+.

 

[denislaurent]

Same question about Pressure & Temperature in Unit#1 vessel.

In fact, Tepco release 2 vessel pressure data (A & B).
They are consistent until March 26 (end of massive cooling)
But they are now diverging, with PA showing the same trend than in D/W and S/C
but PB continuously climbing for now one week+.

It would be good to know the exact location of the sensors.

Please note too that radiation level in drywell is not continuously decreasing
as for units #2 and #3.

Has somebody more information / Hypothesis ?

 

[Jorge Stolfi]

what is going on with core pressure in number 1? It doesn't deem to correlate with temperature readings?

I have no idea; I just write down the TEPCO numbers.

Actually I still do not know how and where those temperatures are measured. I GUESS that they are readings of thermocouples attached to the ouside of (or embedded into) the wall of the reactor's pressure vessel. I have read claims that the "dry"well too is being sprayed with water, is that right? If so the numbers may be meaningless...

 

[M. Bachmeier]

I have no idea; I just write down the TEPCO numbers.

Actually I still do not know how and where those temperatures are measured. I GUESS that they are readings of thermocouples attached to the ouside of (or embedded into) the wall of the reactor's pressure vessel. I have read claims that the "dry"well too is being sprayed with water, is that right? If so the numbers may be meaningless...

P. S. Temperature could be reasonably calculated at a given distance re analogue.

With plants in excess of 40 years old there would be analogue gauges, much of which could survive strong pressure variances, being that high pressure gauges are liquid filled and stainless steel. The real question is if those gauges are ported by pressure lines to be (parallel) accessible (outside of intolerable hazard) for interpretation.

 

[MadderDoc]

It is reported that the cause of the unit 4 building damage was a H2 explosion caused by overheating of the discharged fuel in the U4 spent fuel pool. To the best of my knowledge, there is no photgraphic evidence of the explosion. Something that has troubled me since the first pictures of the Unit 4 damage on 16March, was whether there actually was a loss of inventory in the U4 spent fuel pool. Attached is a markup of the first photograph that was released on 16 March showing the U4 buiding damage. One can find the photo on Reuters site. This photo was taken before any water injection/spray in Unit 4. Perhaps, I'm missing something, but it sure looks to me like there was still significant water in the fuel pool on March 16. Anyone have an alternative speculation?

Some specks of lights, reminicent of reflections in a water surface, can be seen at about 1:33 in this video from March 16th, supporting your contention;

(The attachment below is just to show where to look. For the proper experience, one must watch the video.)

If not by force of hot fuel in a dried up SFP, the damage to unit 4 would seem to me to have been caused by hot fuel being stashed somewhere _else_ up there.

For what it is worth, webcam photos the day unit 4 was destroyed:
http://www.gyldengrisgaard.dk/tepcowebcam/tepweb20110315.html
We are looking in from the south. It is readily apparent that all damage done to the south face of unit 4 occurred in the morning between 6 and 7 am -- at 6 am the buiding looks quite fine, while at 7 am it is a total wreck, and the sky above it is swarming with choppers.

 

[Jorge Stolfi]

Now it is my turn at hallucinating: In this image (previously posted by AntonL) I see a couple of smashed fuel assemblies. Rods, the square envelope, even the handle at the top. (Disclaimer: I just had wine for dinner...)

 

[AtomicWombat]

MECHANISM FOR CASK TRANSFER OF NEW AND SPENT FUEL RODS?
It would make more sense to put the dry cask in a small pool, pumped dry, then flood the small pool, then open the cask underwater, then transfer the new rods directly to the reactor core underwater. It would also seem logical to transfer the spent rods under water to a flooded small pool, containing an open cask, then to close and decontaminate the exterior of the cask before the crane takes it back for loading on the truck. Just guessing.

These videos help illustrate the transfer of spent fuel rods to a dry cask - the first one seems to relate to Mark I BWRs:
http://www.youtube.com/watch?v=rh6FeQWuhCs"
http://www.youtube.com/watch?v=fkz-3e-BYSk"
http://www.youtube.com/watch?v=cisdwv5lPwk&feature=related"
http://www.youtube.com/watch?v=CjGD2oL9fJ8&feature=related"
http://www.youtube.com/watch?v=-gzyvh0cPN4&feature=related"
http://www.youtube.com/watch?v=gS9sJHp0q2c&feature=related"
http://www.youtube.com/watch?v=qj4gZogu_BI&NR=1"
http://www.youtube.com/watch?v=nNmtV-ljFWg&feature=related"
http://www.youtube.com/watch?v=qJmXfWA3m_U&NR=1"
http://www.youtube.com/watch?v=AQIo1-8H3Ww&NR=1"

 

[TCups]

Now it is my turn at hallucinating: In this image (previously posted by AntonL) I see a couple of smashed fuel assemblies. Rods, the square envelope, even the handle at the top. (Disclaimer: I just had wine for dinner...)

Conservatively, even the much older spent fuel rods would very soon reach a temperature of several hundred ºC once removed from the pool and exposed to air. Somehow, I recall the figure of a heat up rate of 1ºC per second if the rod is removed from the water. If those were fuel rods and if they were exposed to air since the explosion, then the IR thermal imagery would almost certainly show them as the hottest thing in the image, I suspect. I could be wrong, though . . .

 

[MadderDoc]

BLAST DAMAGE AT UNIT 3



@ MadderDoc, Fred, et. al.:

Re: New video. Attached is a screenshot from the viedo with and without annotations of what I think I see. As ever, I say the blast came out of the primary containment, through failed seals on the transfer ("cattle") chute gate. But then, it is all too easy to see what you expect to see and want to see. Comments?

http://i306.photobucket.com/albums/nn270/tcups/Screenshot2011-04-04annotated.png

http://i306.photobucket.com/albums/nn270/tcups/Screenshot2011-04-04at50940PM.png

Agreed except looking at other pictures rather than having been blasted from below, the bent girders seem to me to have been hit heavily by something coming from above. Looking for a blast from below I think the area of the SPF is the only candidate. Perhaps during the assumed hydrogen explosion, the SPF pit came to act like a barrel for the blast, shooting the parked FHM high in the air, only to come down on the north end of the building, just about where those girders were.

 

[TCups]

It could well be so.

 

[AntonL]

Spread of radioactivity 4 to 7 April - these are relative values as actual is not known

[PLAIN]http://www.dwd.de/bvbw/generator/DWDWWW/Content/Oeffentlichkeit/KU/KUPK/Homepage/Aktuelles/Sonderbericht__Bild5,templateId=poster,property=poster.gif