Japan Earthquake: Nuclear Plants at Fukushima Daiichi

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The Fukushima Daiichi nuclear plant is facing significant challenges following the earthquake, with reports indicating that reactor pressure has reached dangerous levels, potentially 2.1 times capacity. TEPCO has lost control of pressure at a second unit, raising concerns about safety and management accountability. The reactor is currently off but continues to produce decay heat, necessitating cooling to prevent a meltdown. There are conflicting reports about an explosion, with indications that it may have originated from a buildup of hydrogen around the containment vessel. The situation remains serious, and TEPCO plans to flood the containment vessel with seawater as a cooling measure.
  • #5,881
pdObq said:
<..>The steel roof girders (C) also seemed deformed due to melting to me around where the reactor should be. But that could in principle also be due to the forces during the explosion, not necessarily due to the heat. Concerning the rust on them, I think it makes sense that that comes from the steam from the reactor.

unit3_rust_roof.jpg

If rust is attributed solely to steam, how come there is rust to the south and not to the north?
 
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  • #5,882
MadderDoc said:
unit3_rust_roof.jpg

If rust is attributed solely to steam, how come there is rust to the south and not to the north?
That's one thing I was also wondering about while I was writing and looking at the picture, but I didn't know how to call the two plumes, so I left that to other posters ;) .

Yes, the north plume should also lead to rust which does not seem to be there. Unless it is only on the underside of the girders for that plume. Or the two plumes have different temperatures? Another possibility could be that the rust was already there before the explosion, and came from the humidity over the SFP, so that it was more severe in that place of the roof?
 
  • #5,883


pdObq said:
<..>That the explosion at unit 1 went relatively graceful thanks to these panels can be seen from the fact that the wall steel structure is basically still standing. Unit 2 also seems to have blowout panels, as the whole in the wall looks rather clean (see first attached picture).

Unit 3 and 4 did actually have blowout panels similar to unit 2 and at the same positions in their east wall as in unit 2.

<..> my question is basically if the upper walls in unit 3 had been the same as in unit 1, would the damage have been less severe?

In unit 4, I think the damage might well have been less severe, however with unit 3 I am not so sure. With the strong upward vector involved in the unit 3 explosion, a lighter construction might have allowed even more heavy objects to go ballistic and come back down hard on the building.
 
  • #5,884
pdObq said:
Yes, the north plume should also lead to rust which does not seem to be there. Unless it is only on the underside of the girders for that plume. Or the two plumes have different temperatures? Another possibility could be that the rust was already there before the explosion, and came from the humidity over the SFP, so that it was more severe in that place of the roof?

Another possibility is that steel girders to the south have been exposed to strong heat and therefore rust more easily.
 
  • #5,885
jlduh said:
What is happening inside N°3 right now? Do people with access to live feed of TBS see something special on the images (more steam for example?).

The live stream is on currently but it is close to pitch dark, there's nothing to see. There appears to have been nothing going on today out of the ordinary, judging by the webcams.
 
  • #5,886
If you look on thermal images of unit 3, but they don't give them science 26th, you can see that there are 4 sources of heat (so steam also) around core location
 
  • #5,887
After weeks of almost constant westerly winds, the weather is not so helpful today.

[URL]http://www.zamg.ac.at/pict/wetter/sonderwetter/fuku/20110505_I-131_FUKU.gif[/URL]

http://www.zamg.ac.at/wetter/fukushima/
 
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  • #5,888


pdObq said:
As far as I understand, in unit 1 the wall panels from the service floor upward are designed as blowout panels
I do not think that we ca assume that they were designed as such. There uper side walls were not concrete reinforced

Unit 2 & 3&4
Share a more similar design and likely an identical upper side walls.
 
  • #5,890
jlduh said:
An article describing the situation, and a picture of what you describe (they eat with their suits...). No more a plant but a "battlefield" as one worker describes it...

http://www.fresnobee.com/2011/04/20/2357627/doctor-warns-japan-nuke-workers.html




Read more: http://www.fresnobee.com/2011/04/20/2357627/doctor-warns-japan-nuke-workers.html#ixzz1LQjG0NFE

http://www.netimago.com/image_196912.html

Well, that really sucks. The internal doses are not being measured and not being minimized. The dosimeter's dose is the lowest bound. Furthermore, things like Sr-90 stay in bones for life; a lot larger exposure per ingested amount than Cs-137
 
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  • #5,891
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110504e13.pdf this document describes how Tepco propose to cool reactor 1

-----------------------

I have found this interesting slide presentation by Prof. Joseph Shepherd last updated 30 April
http://www.galcit.caltech.edu/~jeshep/fukushima/ShepherdFukushima30April2011.pdf and video of his lecture of 30 March can be found here http://www.galcit.caltech.edu/~jeshep/fukushima/ - his explanations are very easy to follow and I recommend to listen to this lecture.
 
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  • #5,892
jlduh said:
This second video with the second theory (hydrogen explosion reflected from the stronger walls of Unit 3 into the SFP triggering a prompt critical explosion is interesting.


http://www.youtube.com/watch?v=2onC01URt9c&feature=iv&annotation_id=annotation_31501

I found the full study mentionned in this video concerning the possibility that there was a Nuclear explosion at Chernobyl , it is here:

Estimation of Explosion Energy Yield at Chernobyl NPP Accident
SERGEY A. PAKHOMOV and YURI V. DUBASOV


http://www.springerlink.com/content/d71710g0012116x4/fulltext.pdf

Wouldn't there be a detectable signature of a critical explosion? Perhaps using the nonproliferation sensors on GPS satellites.
http://www.fas.org/spp/military/program/masint/pr96103.html
 
  • #5,893
For me the fact that the blast coming from #3 is immensely more powerful than the unit 1 blast is inescapable.

Also, the unit 3 blast was vectored by either the SPF or the concrete containment structure of the reactor.

The fact that the number 3 reactor to be seems intact and the "hole" through the roof debris is over where the sfp should be tells me that the blast was vectored by the sfp structure.

That blast could not have been vectored or contained by marginally stronger building walls.
 
  • #5,894


pdObq said:
As far as I understand, in unit 1 the wall panels from the service floor upward are designed as blowout panels, i.e. they are meant to blow out easily in case of a hydrogen explosion on the service floor. ... Unit 2 also seems to have blowout panels ... At unit 3&4 however, they apparently changed the construction of the walls above the service floor, and used reinforced concrete pillars instead of the steel structure and reinforced concrete "panels" in between... if the upper walls in unit 3 had been the same as in unit 1, would the damage have been less severe?

As others have observed, units #2--#4 seem to be fairly alike in the construction of the upper storey walls, including the presence of knockout panels. In views of the East side of #4 one can see that one of the panels popped off rather neatly, while the others were torn off the pillars.

As the state of #4 shows, two pop-out panels made little difference to the outcome. I guess they are useful only for steam leaks, when pressure increases slowly; not against explosions.

Woud it have helped if the walls were like those of #1? My guess is no. Note that the explosion in #4 was violent enough to shatter the massive concrete pillars on the south side, even though the roof above offered a path of lesser resistance.

Moreover, I would guess that part of the explosion in #4 occurred in floors 3 and 4, below the service floor. Yet there are only a few relatively small openings between the floors. Presumably the hydrogen had time to spread through the whole building before it ignited. The fact that we see no damage to the lower floors of #1 probably means that the explosion happened when most of the hydrogen was still in the service area.
 
  • #5,895
MadderDoc said:
If rust is attributed solely to steam, how come there is rust to the south and not to the north?
By default, hot steam is invisible. It becomes visible only when it's cooled down. And when it's cooled down it looses most of its corrosive power too.

I can't edit pictures here, I will draw those release paths tomorrow.

pdObq said:
As far as I understand, in unit 1 the wall panels from the service floor upward are designed as blowout panels ... At unit 3&4 however, they apparently changed the construction of the walls above the service floor, and used reinforced concrete pillars instead of the steel structure and reinforced concrete "panels" in between...

So, my question is basically if the upper walls in unit 3 had been the same as in unit 1, would the damage have been less severe?
U1 had no concrete over the service floor: the wall panels were steel, screwed (?) to the steel pillars. U2 - U4 has concrete pillars and concrete panels. My bet is that the destruction could be less severe without concrete, even with the more powerful reactors inside. But I don't know.

By the available pictures some reactors in the US (with MK1 containment - I've looked only for those) has pure metal upper parts. I'll check tomorrow.

Regarding the explosion of U3: I think the first few frames shows as the building is blowing up like a balloon, and the fire/flash just belongs to the weakest point of the building.
 
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  • #5,896
MadderDoc said:
Another possibility is that steel girders to the south have been exposed to strong heat and therefore rust more easily.

Indeed, the steel girders should be covered with paint and anti-rust primer. The rust we see may indicate that the paint was removed not much after the explosion. Perhaps by fire (remeber the black smoke?), or superheated steam?
 
  • #5,897
unlurk said:
The fact that the number 3 reactor to be seems intact and the "hole" through the roof debris is over where the sfp should be tells me that the blast was vectored by the sfp structure.

Note that the heavy crane was parked right above the reactor at the time of the explosion, and was hardly displaced by it. That may be the reason why the central part of the roof remained relatively intact (and even attached to one of the pillars)
 
  • #5,898


pdObq said:
Although I have been following this thread for a while, I have one question which I haven't seen addressed yet, although it might already have been discussed somewhere in the 5000+ posts. Sorry, if that is the case.

As far as I understand, in unit 1 the wall panels from the service floor upward are designed as blowout panels, i.e. they are meant to blow out easily in case of a hydrogen explosion on the service floor. That the explosion at unit 1 went relatively graceful thanks to these panels can be seen from the fact that the wall steel structure is basically still standing. Unit 2 also seems to have blowout panels, as the whole in the wall looks rather clean (see first attached picture).

At unit 3&4 however, they apparently changed the construction of the walls above the service floor, and used reinforced concrete pillars instead of the steel structure and reinforced concrete "panels" in between (see second attached picture of unit 4). Now, I am wondering if those were still supposed to have the function of "blowout panels", or if they just thought "oh, let's make those upper walls a bit more sturdy" without taking into account that a hydrogen explosion on the service floor will be much more devastating, as there is no easy way out any more. Indeed the explosion at unit three was much worse than at unit 1, destroying the walls completely on three sides of the building, and even kicking out concrete panels below the service floor. In addition, the stuff flying around was much heavier and caused more damage than in case of unit 1.

So, my question is basically if the upper walls in unit 3 had been the same as in unit 1, would the damage have been less severe? And are those reinforced concrete panels a Japanese "upgrade", which turned out to actually make things worse? Do other reactors of this type built e.g. in the US still have blow out panels like unit 1 (From the cut out drawings from GE it looks like both Mark I and Mark II containments have blowout-able upper wall structures).

[Both images taken from houseoffoust]


Yes, I saw also that on Mark I reactors (and maybe Mark II, not sure) that the name used was "blow out panel", which supposes some "intention" by design, but...

I found an original study (1986) on this subject of "secondary containment", didn't read it yet (I'm behind a lot of readings to do...) but it seems very well documented. It's called "The role of BWR MK I secondary containments in severe accident mitigation" an you can get the pdf from this page:

http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=6957980
 
  • #5,899
|Fred said:
I do not think that we ca assume that they were designed as such. There uper side walls were not concrete reinforced

AntonL said:
I have found this interesting slide presentation by Prof. Joseph Shepherd last updated 30 April
http://www.galcit.caltech.edu/~jeshep/fukushima/ShepherdFukushima30April2011.pdf [...] - his explanations are very easy to follow and I recommend to listen to this lecture.

Nice slides indeed. And in case of unit 1 he also calls the walls above the serivce floor blow out panels, so it really seems they were designed to easily fly away in case of an explosion to reduce pressure and limit further damage.
 
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  • #5,900


jlduh said:
Yes, I saw also that on Mark I reactors (and maybe Mark II, not sure) that the name used was "blow out panel", which supposes some "intention" by design, but...

I found an original study (1986) on this subject of "secondary containment", didn't read it yet (I'm behind a lot of readings to do...) but it seems very well documented. It's called "The role of BWR MK I secondary containments in severe accident mitigation" an you can get the pdf from this page:

http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=6957980
Interesting, thanks for the link, I will take a look at it later.
 
  • #5,901


Jorge Stolfi said:
As others have observed, units #2--#4 seem to be fairly alike in the construction of the upper storey walls, including the presence of knockout panels.

I would assume so too, in principle. Just that for u2 that one panel came out very easily there, and doesn't really look like concrete to me. Are there any high-res images of that side of reactor building 2 around? One could probably also check the wall structure on pictures taken inside in better days.

Jorge Stolfi said:
In views of the East side of #4 one can see that one of the panels popped off rather neatly, while the others were torn off the pillars.

As the state of #4 shows, two pop-out panels made little difference to the outcome. I guess they are useful only for steam leaks, when pressure increases slowly; not against explosions.

I would expect them to pop out most easily in an explosion, not necessary for steam leaks. The fact that they don't seem to come off easily and that their rebars seems to connect to the outside of the pillars, makes me wonder if those concrete panels were still intended as "blowout panels". I don't understand what you mean by "two pop-out panels made little difference to the outcome" in unit 4.
 
  • #5,902


pdObq said:
I would assume so too, in principle. Just that for u2 that one panel came out very easily there, and doesn't really look like concrete to me. Are there any high-res images of that side of reactor building 2 around? One could probably also check the wall structure on pictures taken inside in better days.



I would expect them to pop out most easily in an explosion, not necessary for steam leaks. The fact that they don't seem to come off easily and that their rebars seems to connect to the outside of the pillars, makes me wonder if those concrete panels were still intended as "blowout panels". I don't understand what you mean by "two pop-out panels made little difference to the outcome" in unit 4.

The generic BWR design has two blowout panels on the refueling floor. They are ddesigned to open at low pressures (inches of water) during steam leaks or breaks or during negative pressures such as a tornado. The idea that they would most readily blow out in an explosion does not take inertia into account. A very rapid pressurization (explosion) does not give the panel enough time to move out and open the vent path before overpressurizing the remainder of the walls. In short the blowout panels are not useful during a hydrogen explosion.
 
  • #5,903
only of minor importance, but i just stumbled upon a TEPCO data correction:

http://translate.googleusercontent.com/translate_c?hl=en&ie=UTF-8&sl=ja&tl=en&u=http://www.tepco.co.jp/cc/press/betu11_j/images/110424c.pdf&prev=_t&rurl=translate.google.com&twu=1&usg=ALkJrhjytyTZ377D7zoeIKPy33m2_59b-Q

maybe interesting for jorge (the obviously wrong #3 CAMS(B) readings are corrected).
 
  • #5,904
Jorge Stolfi said:
Note that the heavy crane was parked right above the reactor at the time of the explosion, and was hardly displaced by it. That may be the reason why the central part of the roof remained relatively intact (and even attached to one of the pillars)


I'm now going to search for seismic data from the times of the explosions.

I may have missed it but I don't think it has been presented here yet.

Japan is loaded with seismic sensors, it should be possible to compare amounts of energy released in the blasts in different units.
 
  • #5,905


pdObq said:
Are there any high-res images of that side of reactor building 2 around? what you mean by "two pop-out panels made little difference to the outcome" in unit 4.

http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/povray/blueprint/foto/drone/hcrop/reactor2-W-1.png
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/povray/blueprint/foto/drone/hcrop/reactor4-W-2.png

Those are from the great Air Photo Service set. Bot are views from East looking West. The East blow-out panel in #4 is the fourth from left, second from top. Note the clean edges.
 
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  • #5,906
I have made a graph of the I-131/Cs-137 ratio in Tepco's press releases https://spreadsheets.google.com/spr...EdE5IbzlocmczREZ2Z3Y0TEk2WVdwUVE&hl=en&gid=1".

The yellow points are measurements in air. The trend of the ratio is consistent with the 8-day halflife of I-131.

The concentrations in water have a much larger spread. I will see if I can make sense of it. There is also the problem of the reliability of the numbers. There are many minor errors (in dates, for example). Sometimes there is clearly an error in the exponent. I made an emendation on April 7, where the concentrations of the particulate cesium isotopes were obviously wrong. Such errors are then reproduced in every graph that Tepco publishes, for example in http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110413e9.pdf

There are more places where I suspect copying errors. And maybe I made a copying error myself somewhere. But why is not Tepco publishing such graphs?? Are not they analyzing their own data themselves?
 
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  • #5,907


NUCENG said:
...
This is what I understood from what you mentioned a few weeks back. But, (and this is pdObq question) to your knowledge
Was the design of the UNIT 1 meant to be weak permissive for explosion on this floor to be less damaging to the containment bellow ?
 
  • #5,908
unlurk said:
<..>the unit 3 blast was vectored by either the SPF or the concrete containment structure of the reactor.

I assume you restrict to those two options because you've seen a big cloud rising vertically, so you are looking for something that could serve as a vertical 'barrel' to produce this dramatic effect.

However, the vectoring of such a cloud needs no barrel. The cloud is mainly steam, hot steam, it forms a mass that is much lighter than atmospheric air. Once released, hot steam rises vertically 'all by itself', as a piece of styrofoam does when it is released under water.
 
  • #5,909
unlurk said:
Japan is loaded with seismic sensors, it should be possible to compare amounts of energy released in the blasts in different units.
Brilliant idea! I am very curious.
 
  • #5,910
yes unit 1 is different, 2,3,4 have one blow panel on the turbine building side, you can see it for unit 2, also there was some ir image posted here where those blow panels were visible. Unit 1 reactor hall wall and roof is the same like 2,3,4 roof, steel construction with concrede without steel in concrede, 2,3,4 construction is concrede with steel rods inside (http://en.wikipedia.org/wiki/Reinforced_concrete)
 

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