Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[MadderDoc]

To people drawing squares on the wall of Unit #4: beware that the floors inside do not have the same height.

The floors inside do probably not have the same height, however the upper three stock wall structural elements and with them the wall panels of the east wall of unit 4 do appear to me be of about the same stock-height and width.

The hole would be within the lower part of the structural element of the east wall, which I would call row3 column1. On the closeup produced by THawk of the lower part of this element (see attachment) it appears looking into it, that we have a horizontal floor structure somewhat elevated over the base of the wall element, confirming what you are saying.

Via the putative hole, according to my measuring stick one might be able to gain access to areas above as well as below that floor. And I reckon that would mean: gaining access to more or less the complete outside of the thick concrete walls surrounding the -- presumably stainless steel lined -- spent fuel pool inside.

The 3nd floor is level with the roof of the building in front, and its ceiling is very low, just matching the height of the "hole". In the post-explosion pics, the "hole" is all but hidden behind a pile of rubble from the façade. the 4rd floor is slightly taller, the two rows of panels on the service floor (5th) taller still.http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/povray/blueprint/un3_building_cut_N_2.png

Edit: fixed the floors above (3rd and 4th)

Thanks for the caveats, Jorge. I believe you must be speaking from the drawings of unit 3. in which the upper three floors from the top have heights of 7.90 m, 7.90 m, and 7.62 m. We can't be certain that unit 4 is quite the same, but so far I've not spotted any significant difference.

 

[jlduh]

Very interesting article Biffvernon. Concerning the generators, some details are given and assumptions already discussed here confirmed: most of them were in the BASEMENTS.

http://www.bloomberg.com/news/2011-04-25/japan-s-terrifying-day-saw-unprecedented-exposed-fuel-rods.html

“Most are located in generator rooms in basement 1 of the turbine buildings,” Arai said, pointing to a diagram in a Tepco brochure of the Dai-Ichi plant. The turbine buildings holding eight of the generators are about 140 meters from the seafront, another two generators were on the ground floor behind reactor 4, which was offline for maintenance. Three others were in and around reactor 6, which was also offline.

But an other information is kind of interesting also:

Seawater flooded the basements of turbine buildings and other sites, disabling 12 of the 13 back-up generators and destroying electrical switching units. Salt water shorted electric circuitry, depriving the reactors of power for cooling and triggering a nuclear disaster that Tepco was forced to combat with fire hoses and makeshift pumps.

“The level of flooding differed by building, but it was as high as 1.5 meters in one turbine room,” said Hikaru Kuroda, chief of Tepco’s nuclear facility management group.

So if this is confirmed, and as i personally imagined it based on the layout out of this basements, that seawater actually flooded the basements of the turbine buildings. Which means that a certain volume of the water that has been reported on site (contaminated then, of course) was in fact from the tsunami.

This is important in my opinion because if this confirms to be true, then it means that the figures we got concerning the "highly contaminated water" in the basements, when it was reported, were probably in fact the result of a dilution of the cooling water leaking from the reactors(with even higher contamination levels I am my opinion) into uncontaminated seawater from the tsunami resting in the basement after the wave withdraw.

I'm not sure that this picture was clear for everybody so that's why i enlighten it. Do others share this analysis?

 

[NUCENG]

Great thread! Long time lurker and first post.

Nice hack! Why are #5 & #6 so high? (up and down)?

Great finding & explanation!

This is just one more anomaly for unit 4. The core was offloaded into the SFP. If the reactor cavity was drained for the core shroud replacement and the gates to the spent fuel pool failed or leaked contaminated water would have drained from the spent fuel pool into the RPV and reactor cavity. However if the refueling belows and manhole are intact the water should not have drained into the drywell proper. To get to the suppression pool, it has to be filling the drywell to the point it overflows down the Drywell to Torus vent pipes to the suppression pool. For the torus to be that hot we should be offscale high on site from the spent fuel pool.

 

[Caniche]

Just a very simple question regarding methodology .
At what point does existing fallout from tests/accidents become "background radiation"
How far has "background" radiation increased in the last 50 years ? (as opposed to "natural " background radiation ,which seems to be confused and combined.)

 

[WhoWee]

Lurker with first question: how is it that the edge of the opening on right hand side is so very clean and sharp
--yet appears to have rebar curled back from it?
Or are those shadows from above, and a doorframe unmarred by the explosion?

Some of the lines appear to be shadows.

 

[MiceAndMen]

That's a mighty fine catch you have there, mate. They come very handy. EW _and_ NS sections of unit 3! On leafing further through the Tepco documents, I find there's a schematic floorplan of the service floor of unit 3 on page 28 in this pdf (see also attachment below, with the schematic tentatively x/y scaled):

http://www.pref.fukushima.jp/nuclear/info/pdf_files/100805-6.pdf​

A very nice find! I think we have the MOX fuel experiment in Unit 3 to thank for many of those documents.

For anyone who wants to do some spelunking (potholing), the following page has links at the top (above the first 3 pictures of buildings) that lead to collections of PDFs relating to nuclear power in Fukushima Prefecture. Google's translation service helped me to navigate through much of it.

http://wwwcms.pref.fukushima.jp/pcp_portal/PortalServlet?DISPLAY_ID=DIRECT&NEXT_DISPLAY_ID=U000004&CONTENTS_ID=10739

 

[PietKuip]

Very interesting article Biffvernon. Concerning the generators, some details are given and assumptions already discussed here confirmed: most of them were in the BASEMENTS.

http://www.bloomberg.com/news/2011-04-25/japan-s-terrifying-day-saw-unprecedented-exposed-fuel-rods.html

Why do they put generators in the basements and spent fuel in the attic?

So if this is confirmed, and as i personally imagined it based on the layout out of this basements, that seawater actually flooded the basements of the turbine buildings. Which means that a certain volume of the water that has been reported on site (contaminated then, of course) was in fact from the tsunami.

This is important in my opinion because if this confirms to be true, then it means that the figures we got concerning the "highly contaminated water" in the basements, when it was reported, were probably in fact the result of a dilution of the cooling water leaking from the reactors(with even higher contamination levels I am my opinion) into uncontaminated seawater from the tsunami resting in the basement after the wave withdraw.

I'm not sure that this picture was clear for everybody so that's why i enlighten it. Do others share this analysis?

I agree. Those "puddles" were probably diluted. But it is difficult to guess by how much - a factor of 2 or a factor of 100?

 

[MadderDoc]

Lurker with first question: how is it that the edge of the opening on right hand side is so very clean and sharp
--yet appears to have rebar curled back from it?
Or are those shadows from above, and a doorframe unmarred by the explosion?

They are not shadows from above (see attachment with another zoom in).

I think what you see is just how the building is built: steel reinforced concrete pillars and vertical girders producing a skeleton of rectangular fields, and to this skeleton plastered to its outside, a layer of rebar reinforced concrete. In case of an internal explosion, this outer layer tends to be blown away and apart where it is not protected from the inside, by the pillar girder structure. Therefore I'd say the very clean and sharp right hand side (except for the rebar!) is not a doorframe, is just the right pillar of that rectangular field.

Anyway, the apparent hole we have been looking at does not extend as far as to the right pillar you are looking at. If there has initially been a doorframe at the right side of the hole, then surely it is now completely gone, blown away by the later explosion.

 

[PietKuip]

Just a very simple question regarding methodology .
At what point does existing fallout from tests/accidents become "background radiation"
How far has "background" radiation increased in the last 50 years ? (as opposed to "natural " background radiation ,which seems to be confused and combined.)

Total ionizing radiation is hardly higher than 50 years ago. The natural internal radiation is due to potassium-40 and carbon-14 (which actually has gone down because of burning fossil fuel).

But most other radioactive isotopes in the environment are man-made. Their natural level is essentially zero.

 

[jlduh]

At what point does existing fallout from tests/accidents become "background radiation"

very good question indeed... I asked it myself several times when i heard sentences like "this is lower than natural background" (sure you heard it already ;o))

Well, i guess that after a certain memory time, artificial can become natural...

Pietkuip, concerning "basement and attic" architecture, i think Joe Neubarth already got the right answer here: "APS" or Aboslute Pure Stupidity...

Back to my remark about very probable dilution by residual seawater from tsunami (which factor is the question) of the first flows of contaminated cooling water leaking from reactors into the basements: this is important to consider for the analysis of I-131 levels/decay because as the volumes are now being pumped to the waste facility, the new leaking water in the basement could very well exhibit higher contamination levels (or levels not properly decaying) just because the initial dilution by this resting seawater is no more acting of course. This could be an alternate and simple explanation to why the decaying is not showing as it should be, even without re-criticality...

Just an idea to keep in mind, maybe?

 

[Dmytry]

Why do they put generators in the basements and spent fuel in the attic?

Because the control rooms etc, power lines (to reactor from turbine hall) are on the bottom, and the fuel is taken out of reactor from the top? Looks like cheapest placement. A lot of extra machinery to get fuel to the bottom.

 

[Pheesh]

Total ionizing radiation is hardly higher than 50 years ago. The natural internal radiation is due to potassium-40 and carbon-14 (which actually has gone down because of burning fossil fuel).

But most other radioactive isotopes in the environment are man-made. Their natural level is essentially zero.

To add to this:
http://en.wikipedia.org/wiki/Low-background_steel

 

[Caniche]

.

But most other radioactive isotopes in the environment are man-made. Their natural level is essentially zero.

:) If only we could train those sheep to just eat the organic stuff

 

[MadderDoc]

This looks about right , point being where we think there was a hole there is concrete
this is a close up of the hole after the explosion .
[PLAIN]http://img12.imageshack.us/img12/17/snapshot20110425222647.jpg[/QUOTE]

I don't agree,
I admit that in this photo the thin yellow line with which I have indicated the position of the pre-explosion hole has been extended below the red line at the bottom, but I am painfully aware that's from _imagination_, I have seen no visuals indicating that the putative pre-explosion hole actually did extend below the lower boundary of the hole after the explosion.

Where I have _reason_ to think there may have been a hole before the explosion, there is now just a (larger) hole.

[URL]http://gyldengrisgaard.dk/fuku_docs/unit4preexplosionhole_ext.jpg[/URL]

 

[razzz]

From the closeup, they didn't even use small #3 rebar in this knockout panel, they used wire mesh (which is like smooth large wire, sometimes spot welded at intersections) probably preformed/preshaped, stood up, and secured/spaced on the forms before pouring concrete. That smooth faced vertical, looks typical when you look at enough of the remaining verticals also separated from their adjoining walls/panels. Remember the exterior blue and white clouded walls were meant to separate in an explosion and they did and were designed to not disturb the vertical and horizontal main-framing when they depart. If there was framing for a door or something else was going on, I'm sure we'll get that answer eventually.

Compared to Chernobyl, in the long run, you can see why it is important to stop uncontrolled groundwater intrusions from carrying off contamination or possibly interacting with what's ever left of the cores. Chernobyl is still threatened by groundwater seepage (maybe also rain water) finding the corium and causing reactions, this current disaster you might start worrying every time high tide occurs.

An attempt to build an underground perimeter watertight wall to bedrock encircling all 4 units wouldn't surprise me. From there you could build an enclosure to further isolate the units provided you get cool down and Unit 4 pool doesn't collapse and make the area unworkable.

 

[RealWing]

This account of the 11th March contains a few useful bits of information gathered toghether.

http://www.bloomberg.com/news/2011-04-25/japan-s-terrifying-day-saw-unprecedented-exposed-fuel-rods.html

Of particular interest is the comments about the radiation levels on site:

"On two occasions radiation levels at Dai-Ichi reached 1 sievert an hour" (100 R.hr)!
(I recall that they had to evacuate the site on 2 occasions - I now see why!)

"Linked by a hot line to Tepco headquarters in central Tokyo, the three-story, white bunker had extra-thick walls and two filtration systems designed to keep out radiation. It was to become their new home."

"When the No. 3 reactor housing exploded on the morning of March 14, levels inside the bunker jumped as much as 12-fold, he said, checking dates and times in a pocket diary."

So - what is the source for these very high levels? One possibility is from a quantity of spent fuel (from the SFP's) being blown into the air during the explosions? Another is from the large cloud of radioactive gasses? I hate to think it might be a criticality event - but maybe should add it to the list?

Other possibilities??

 

[mscharisma]

... So - what is the source for these very high levels? One possibility is from a quantity of spent fuel (from the SFP's) being blown into the air during the explosions? Another is from the large cloud of radioactive gasses? I hate to think it might be a criticality event - but maybe should add it to the list?

Other possibilities??

Was actually wondering: are any of you keeping a list of unresolved questions? You know, for example, cause of the explosion/fire in #4, isotopes on the highly radioactive concrete piece, source of radiation jump in bunker, etc? I'm thinking it might be useful given that some info get to us so much later, or can you still "connect the dots" even without such a list?

 

[WhoWee]

They are not shadows from above (see attachment with another zoom in).

I think what you see is just how the building is built: steel reinforced concrete pillars and vertical girders producing a skeleton of rectangular fields, and to this skeleton plastered to its outside, a layer of rebar reinforced concrete. In case of an internal explosion, this outer layer tends to be blown away and apart where it is not protected from the inside, by the pillar girder structure. Therefore I'd say the very clean and sharp right hand side (except for the rebar!) is not a doorframe, is just the right pillar of that rectangular field.

Anyway, the apparent hole we have been looking at does not extend as far as to the right pillar you are looking at. If there has initially been a doorframe at the right side of the hole, then surely it is now completely gone, blown away by the later explosion.

A few shadows are visible.

 

[NUCENG]

Was actually wondering: are any of you keeping a list of unresolved questions? You know, for example, cause of the explosion/fire in #4, isotopes on the highly radioactive concrete piece, source of radiation jump in bunker, etc? I'm thinking it might be useful given that some info get to us so much later, or can you still "connect the dots" even without such a list?

That's a good idea. I wonder if there is a way to do that so it is avilable for reference without searching through over 5000 posts. Maybe Borek or Astronuc can help us find a way to do it.

 

[Astronuc]

Was actually wondering: are any of you keeping a list of unresolved questions? You know, for example, cause of the explosion/fire in #4, isotopes on the highly radioactive concrete piece, source of radiation jump in bunker, etc? I'm thinking it might be useful given that some info get to us so much later, or can you still "connect the dots" even without such a list?

Ultimately it comes down to:

1. How much and what fuel was damaged, and to what extent, in units 1, 2 and 3?

2. How much and what fuel was damaged, and to what extent, in Unit 4 SFP?

3. What damage is there to the containment structures of units 1, 2, 3 and 4?

4. What damage is there to the RPVs, feedwater systems, and all related piping systems of Units 1, 2, 3 and 4?

We won't know the answers until 1) the fuel is removed, 2) the contaminated water is removed from the containments, and 3) the containments are decontaminated sufficiently to inspect with high resolution cameras, if not in person.

 

[Emreth]

So if this is confirmed, and as i personally imagined it based on the layout out of this basements, that seawater actually flooded the basements of the turbine buildings. Which means that a certain volume of the water that has been reported on site (contaminated then, of course) was in fact from the tsunami.

This is important in my opinion because if this confirms to be true, then it means that the figures we got concerning the "highly contaminated water" in the basements, when it was reported, were probably in fact the result of a dilution of the cooling water leaking from the reactors(with even higher contamination levels I am my opinion) into uncontaminated seawater from the tsunami resting in the basement after the wave withdraw.

I'm not sure that this picture was clear for everybody so that's why i enlighten it. Do others share this analysis?

I think there were workers in the basements working on the electrical connections and there was no flooding at that point (maybe within couple weeks). Then one day ( i can't remember the exact date), they found some water about 30 cm deep, and two or three workers got irradiated through their boots until they realized it was contaminated water. The water level rose afterward. This suggests the water is not from tsunami/groundwater but is from the leaks and the radiation levels in that water are not highly diluted, at least not in the way you suggest.

Edit: Here's the link to the post.
https://www.physicsforums.com/showpost.php?p=3210380&postcount=1281

 

[mscharisma]

Ultimately it comes down to:

1. How much and what fuel was damaged, and to what extent, in units 1, 2 and 3?

2. How much and what fuel was damaged, and to what extent, in Unit 4 SFP?

3. What damage is there to the containment structures of units 1, 2, 3 and 4?

4. What damage is there to the RPVs, feedwater systems, and all related piping systems of Units 1, 2, 3 and 4?

We won't know the answers until 1) the fuel is removed, 2) the contaminated water is removed from the containments, and 3) the containments are decontaminated sufficiently to inspect with high resolution cameras, if not in person.

Understood. I was thinking, however, that it will take right around forever to get those ultimate questions answered (and who knows if we'll get to hear the full truth or when), so that it might be a good idea to keep a list of those "smaller" questions along the way and their answers as or if they emerge. Maybe those answers can at some point confirm or disprove the answers to the ultimate questions 1-4 above. Just a thought.

 

[rowmag]

yes yes of course Russian also uses word 'radioactivity'.
How do they call contamination with radioactive materials? The English word 'contamination' is not very specific, can be used for something contagious. Russian word is specific, made dirty, never used for viruses or bacteria.

The word used is 汚染, which I think has about the same range of meanings as the English word "contamination." (Can also be used in reference to chemical pollution or viruses and bacteria, for example.)

But that word was not used in the Japanese reply at the press conference. It (or rather, "contamination") was added in the translation to English.

 

[AntonL]

I found a google spreadsheet. The Water Level on Unit 4 is display. If the Level is correct, i don´t know
https://spreadsheets0.google.com/cc...ZDbX39YK-iFb0Iw&hl=ja&authkey=CP6ewJkO#gid=35

triumph61 this is a nice find, here we have all the published data tabulated in a spreadsheet thanks to the hard work of Masato Fujii http://twitter.com/toofuya

Browsing this data, I possibly discovered a unpublished problem for reactors 5 and 6.

Plot of water level and water temperature of reactor 6
[PLAIN]http://k.min.us/iliXFo.JPG
left axis reactor temp, right axis water level above reactor fuel, blue is for water, red-brown is for temperature
From this plot we can draw two conclusion
1) Reactor 6 water seems to be slowly leaking, either into the primary containment or to the outside (classic saw-tooth plot), and since cooling was re-established water has been replenished on three occasions. (or is there another explanation)
2) Reactor 6 cooling is a start stop operation

Assuming reactor diameter of 6 metres, then 1 metre change in level is 113 tonnes of water, thus the leak rate is about 50 to 70 tonnes a week

Also, from the spreadsheet data similar situation exists in reactor 5


One can see the effect of the water temperature rising as small peaks in the water level.

 

[MiceAndMen]

From this plot we can draw two conclusion
1) Reactor 6 water seems to be slowly leaking to the outside (classic saw-tooth plot), and since cooling was re-established water has been replenished on three occasions. (or is there another explanation)
2) Reactor 6 cooling is a start stop operation
3) similar situation exists in reactor 5

One can see the effect of the water temperature rising as small peaks in the water level.

Please label your axes. Which line goes with the numbers on the left, and which goes with the right? I did figure it out eventually - I think - but I shouldn't have had to.

What is the water level in relation to? Is the graph for the reactor or the SFP? Why does this graph represent a problem? Because water is disappearing and needs to be replenished?

 

[AntonL]

Please label your axes. Which line goes with the numbers on the left, and which goes with the right? I did figure it out eventually - I think - but I shouldn't have had to.

I am a MS-Excel anti-talent; left axis reactor temp, right axis water level above reactor fuel, blue is for water, red-brown is for temperature

What is the water level in relation to? Is the graph for the reactor or the SFP? Why does this graph represent a problem? Because water is disappearing and needs to be replenished?

Water should not be disappearing from the nuclear reactor, it is a closed loop cooling system

Furthermore, we are observing low level radiation in the ground water of Unit 5 and 6, possibly this is the source.

 

[MiceAndMen]

left axis reactor temp, right axis water level above reactor fuel, blue is for water, red-brown is for temperature

Water should not be disappearing from the nuclear reactor, it is a closed loop cooling system

Furthermore, we are observing low level radiation in the ground water of Unit 5 and 6, possibly this is the source.

Thanks, Anton.

 

[jlduh]

I think there were workers in the basements working on the electrical connections and there was no flooding at that point (maybe within couple weeks). Then one day ( i can't remember the exact date), they found some water about 30 cm deep, and two or three workers got irradiated through their boots until they realized it was contaminated water. The water level rose afterward.

Well, i know this is what has been said. But to tell you the truth, since the very beginning i know that these turbine buildings have basements below the platform level, I've been pretty sure, based on the images i saw of the tsunami flooding the plant, that it was almost impossible that these basements stayed dry with so much water outside at ground level. The description in this article just confirms this feeling. Now, why this story of water appearing suddenly in the basement floor? Well, i think there are two possibilities:

1) a cover up story from Tepco for reducing its responsbility when the 3 workers got caught with highly contaminated water in this place. Remember the context, Tepco was under pressure from the gov because the workers had not the appropriate suits and shoes. We learned after also that dosimeters were heavily missing for workers at the plant since the start of the operations after the tsunami, so a story like that is really a possibility to minimize their responsabilities in the medias.

2) it is a possible though that the specific place where this happened was a different room than the turbine building in itself (based on the images where one expert located it, that was i think an adjacent one) which could also explain the fact that there wasn't so much water at first. Also the article says that the levels in turbine reactors were not the same everywhere.

But i on't see the one with as much as 1,5 meters of water drying up like that after the tsunami, so anyway, there is something strange around this subject.

 

[biffvernon]

So - what is the source for these very high levels? One possibility is from a quantity of spent fuel (from the SFP's) being blown into the air during the explosions? Another is from the large cloud of radioactive gasses? I hate to think it might be a criticality event - but maybe should add it to the list?

Other possibilities??

In the recent Chris Busby (yeah, I know) interview, http://www.youtube.com/watch?v=x-3Kf4JakWI&feature=channel_video_title he certainly suggests criticality.

It is frustrating that TEPCO staff are not (presumably) allowed to join this forum! (There must be a few thousand of them at home). Some of them will have answers to a lot of our questions.

I can imagine one of them reading or musings and saying to himself, "Hole? What hole? That's just the washing line we hung out those dirty rags to dry on."

 

[jlduh]

To Anton L: your analysis is interesting with these curves on n° 5 and 6. Something to add to the list of mysteries. Could it be related to a normal variation in closed loop in relation with the level in the suppression chamber for example? In cold stop I don’t see two much how the SC would play a role if the water is at low temp, but…

Reactor n°6 doesn’t have a torus if I remember well (newer generation of BWR)?

 

[jlduh]

To all asking where to bring more political aspects around the accident, i remember that i started this thread to do that:

https://www.physicsforums.com/showthread.php?t=486089

A thread where I'm going to post this info from NHK saying that none at the government knew of any risk of hydrogen explosions at the reactors before it happened (should be a good political subject to revive this specific thread and post other political subjects!):

http://www3.nhk.or.jp/daily/english/26_10.html

So go there to talk about this!

 

[jlduh]

three interesting articles at ASAHI

One gives some bits of infos on the radiation (related to rumble and debris) subject:

http://www.asahi.com/english/TKY201104250130.html

The other one is about the strategy used by tepco to gradually fill (at least in reactor n°1, but maybe also in other ones) the containment vessels with water:

http://www.asahi.com/english/TKY201104250125.html

And the last one is about the seriousness of the leakage of contaminated water into the sea (compared already to the one of Sellafield):
http://www.asahi.com/english/TKY201104230223.html

 

[kujala]

The water level rose afterward. This suggests the water is not from tsunami/groundwater but is from the leaks and the radiation levels in that water are not highly diluted, at least not in the way you suggest.

Remember those two dead guys found in the basement of the number four turbine building?

They were killed by the tsunami waters, according to the pathologist.

How is this possible? The tsunami waters perhaps traveled at high speed through some tunnel into the basement and those two guys were killed immediately.

The tsunami waters can also fill the basements from outside in: first the tsunami waters mix with ground and groundwater and afterwards - perhaps after the level of groundwater has risen a little bit - this water can enter into the basements by infiltrating through the concrete.

In this latter situation the water levels rise more slowly in the basements.

So it is probably a mess where groundwater, tsunami waters and cooling waters have mixed and you cannot say which of these has happened in any particular spot (sub-drainage, basements, tunnels, trenches and so on).

TEPCO wants most of it to be tsunami waters, of course, because that way they can keep their belief that most of the cooling waters are still in the reactors.

 

[liamdavis]

Hmmm . . .

The northeast corner of Bldg 4 is odd, for sure. I don't believe it was the whole roof that lifted -- maybe the northeast corner might have had that effect. But if so, why?! What happened in the northeast corner of that building.

@liamdavis:

Maybe you could lend your expertise here, sir. Also, can you comment on your assessment of the possibility that the concussion and shock wave from the Bldg 3 explosion might have done structural damage to the northeast corner of Bldg 4 that wasn't readily visible from the outside. Perhaps after the blast at Bldg 3, the northeast corner of Bldg 4 was simply the weakest link.

Sir, to your post 4077 on P255, the northeast corner (bottom-left) appears to have been closest to the origin of the blast. The area closest would have been most closely coupled to the energy of the blast. SWAG mostly, and I apologize for the delayed response. I have been away and not been able to get on for a week. (50 pages to go)

 

[jlduh]

Well, i don't understand very well how difficult it is to imagine how tsunami water can have entered the basements of the turbine buildings. These ones are not designed to be water proof nor air tight, they are not part of the containment structure of the reactors. With the wave coming, some doors or panels may have (and probably have been) distorted or damaged...