Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[cphoenix]

I wrote:

While I'm at it, let me float a new hypothesis for building 4:

1) Fuel abruptly went critical near the bottom of the pool. (Even a mild aftershock might have shifted geometry.)

(list continues, describing a steam bubble and water hammer causing steam explosion in the building below the pool.)

Assuming that http://www.asahi.com/english/TKY201104140125.html is correct, and the water sample rules out any disintegration of fuel rods, then this is no longer plausible. I've added that note to the original post.

 

[Jorge Stolfi]

I understood from your original proposal that the criticality was occurring above the water layer where the boron was lost. But if the water was lost here as well I don't see how criticality could occur.

I do not have a definite proposal; I am just looking for ways that chain fission could have happened in the SFP (which could explain why the explosion happened earlier than predicted by decay heat alone).

Suppose the top half of the assemblies got hot enough to melt the top half of the boral baffles. Then we got a layer of 1535 half-assembles, densely packed without neutron absorbers, sitting above a layer of water. By the above reasoning, that water would behave like a neutron moderator+reflector, with somewhat less than 50% efficiency (for being on one side only of the fuel).

The problem with this idea is that the still-intact lower halves of the boral plates would absorb a large part of the neutrons that enter the water, before they had the chance to emerge. Would enough of them survive to produce significant fission?

The idea may have a better chance if the assemblies got completely uncovered for a while, lost the entire boral baffles, then got partly or totally submerged again. But that did not happen, did it? Water injection into the SFP only began after the explosion, right?

Or perhaps the explosion of #3 jostled the seals of the SFP door in #4, allowing water to flow from the reactor pool to refill the SFP, where the assemblies had already been exposed...

Anyway, note that the water-around-is-enough observation applies also to a molten fuel mass in a reactor core. Will the molten absorbers (steel?) float over the molten/compacted fuel? Or sink below it? Or get mixed with it?

 

[AntonL]

A new batch of pictures (some of them taken on April 14, 2011) is available at http://cryptome.org/eyeball/daiichi-npp8/daiichi-photos8.htm

and these solve the mystery of the "ballistic" fuel handling machinery in unit 3, submerged in SPF3
[PLAIN]http://k.min.us/imMKhK.JPG

 

[ottomane]

and these solve the mystery of the "ballistic" fuel handling machinery in unit 3, submerged in SPF3

Any idea what the half round concrete plate may be (top half of the pic, left of the middle)?

 

[Dmytry]

I do not have a definite proposal; I am just looking for ways that chain fission could have happened in the SFP (which could explain why the explosion happened earlier than predicted by decay heat alone).

Suppose the top half of the assemblies got hot enough to melt the top half of the boral baffles. Then we got a layer of 1535 half-assembles, densely packed without neutron absorbers, sitting above a layer of water. By the above reasoning, that water would behave like a neutron moderator+reflector, with somewhat less than 50% efficiency (for being on one side only of the fuel).

The problem with this idea is that the still-intact lower halves of the boral plates would absorb a large part of the neutrons that enter the water, before they had the chance to emerge. Would enough of them survive to produce significant fission?

The idea may have a better chance if the assemblies got completely uncovered for a while, lost the entire boral baffles, then got partly or totally submerged again. But that did not happen, did it? Water injection into the SFP only began after the explosion, right?

Or perhaps the explosion of #3 jostled the seals of the SFP door in #4, allowing water to flow from the reactor pool to refill the SFP, where the assemblies had already been exposed...

Anyway, note that the water-around-is-enough observation applies also to a molten fuel mass in a reactor core. Will the molten absorbers (steel?) float over the molten/compacted fuel? Or sink below it? Or get mixed with it?

what if an aftershock makes a wave. then the water in the wave boils violently, pushing water down, and amplifying the wave. That can be expected to happen even without criticality. Would take numerical simulation to demonstrate, of course.

 

[ian_scotland]

From the latest cryptome images, http://cryptome.org/eyeball/daiichi-...hi-photos8.htm

Is it just me, or does the semicircular item with a stepped edge look a bit like the half of the concrete plug that usually sits over over the reactor?

It is of course difficult with possible perspective and scale unknowns

Edit1... AntonL you beat me to it !

Edit 2 the actual plug appears to be approx 6.5m radius. Can anyone identify something to scale from in the photo?

 

[rowmag]

Okay, thx.
Interesting video. Doesn't look as if there's much damage inside of Unit 4... oO

That's what the professor is saying at the end of the video. "What kind of explosion destroyed the building, but left the crane looking relatively unscathed? Very surprising."

Edit to add: Watching the video again, the term he uses is "fuel exchanging machine" (I guess what folks here call the "FHM"), not "crane."

 

[Dmytry]

That's what the professor is saying at the end of the video. "What kind of explosion destroyed the building, but left the crane looking relatively unscathed? Very surprising."

the same kind of explosion that blew all the wall panels from the floor 1 but left 2 out of 4 panels standing on floor 4? (western wall) The kind of explosion that didn't happen where the crane is?

 

[TCups]

and these solve the mystery of the "ballistic" fuel handling machinery in unit 3, submerged in SPF3
[PLAIN]http://k.min.us/imMKhK.JPG[/QUOTE]

Sure looks like part of a big green machine in SPF. Maddening that there isn't a wider field of view. The round thing looks to be too small to be part of the primary containment plug, but it's hard to get an absolute scale from this perspective.

 

[ottomane]

Edit 2 the actual plug appears to be approx 6.5m radius. Can anyone identify something to scale from in the photo?

The white roof panels - aren't they 70cm wide? Not sure anymore.

I have problems to correlate this pic with the other areal pics of R3.

 

[TCups]

The white roof panels - aren't they 70cm wide? Not sure anymore.

I have problems to correlate this pic with the other areal pics of R3.

Funny, too that exposed rebar seems to be partially in and partially out of the pool. How does that happen?

Hey Anton! I've got it! The FHM broke in two pieces and one of them fell back into the SFP! Amazing!

 

[Dmytry]

What is the chimney height and reactor height? We can estimate velocity of rising air there, in reactor 3 explosion video. Hell, we can probably estimate blast energy in kt.

 

[TCups]

What is the chimney height and reactor height? We can estimate velocity of rising air there, in reactor 3 explosion video. Hell, we can probably estimate blast energy in kt.

Dmytry:

http://www.houseoffoust.com/fukushima/blueprint.html

Take your pick. The "chimney" is either the depth of the SFP or the "neck" of the reactor's primary containment, depending on whether one believes the vertical blast originated from the SFP or the primary containment, I suppose.

Surprisingly, in the drawing, they are about the same size, so it may not be that much different.

 

[M. Bachmeier]

What is the chimney height and reactor height? We can estimate velocity of rising air there, in reactor 3 explosion video. Hell, we can probably estimate blast energy in kt.

You could also look at the audio file to try and confirm the energies.

This is my best guess alignment of audio to video with the middle blast corresponding to the visible explosion. Best estimate of camera distance 2.25 KM.

Video Link :

Audio wave table :

 

[M. Bachmeier]

You could also look at the audio file to try and confirm the energies.

This is my best guess alignment of audio to video with the middle blast corresponding to the visible explosion. Best estimate of camera distance 2.25 KM.

Video Link :

Audio wave table :

Also audio file in ac3 format:

 

[tsutsuji]

The same Video but better . Sorry for my English

At the end of the video Professor Kazuhiko Kudo of Kyushu University says he is surprised to see that the fuel handling machine at unit 4 looks intact, while other parts of the building have suffered important damage.

 

[TCups]

Also audio file in ac3 format:

MB:

Confused -- what happened to the third "boom" in the original audiovideo file? Was it cropped from the beginning of the video? Was there really a third boom or was the original sound track altered by the news production crew? Do you think there were really only two blasts?

 

[M. Bachmeier]

MB:

Confused -- what happened to the third "boom" in the original audiovideo file? Was it cropped from the beginning of the video? Was there really a third boom or was the original sound track altered by the news production crew? Do you think there were really only two blasts?

Sorry you hear the third and second boom, but the first got cut with audio alignment. There was more to the video than was available in the clip I had available.

You can tell it was thrown back together because the audio potion is only 12.77 seconds and the video is approx. 13.25. There's also no way to be sure about distance, but if you like here's the alignment from first boom and visual, but it doesn't seem to match as well.



Bear in mind youtube remixes so audio may not match as nicely.

P.S. it makes more sense for the first explosion to be somewhere in containment, the second would be oxygen and hydrogen +, and the third from the SFP. This would also explain why a large object (FHM?) would appear to be on a delayed trajectory from first visible blast. The second blast column would shroud the third directional explosion inside.

 

[TCups]

Sorry you hear the third and second boom, but the first got cut with audio alignment. There was more to the video than was available in the clip I had available.

You can tell it was thrown back together because the audio potion is only 12.77 seconds and the video is approx. 13.25. There's also no way to be sure about distance, but if you like here's the alignment from first boom and visual, but it doesn't seem to match as well.



Bear in mind youtube remixes so audio may not match as nicely.

So, if the "two boom" synched audio/video match you first posted is correct -- it does seem to match the video -- sharp fireball blast (from the primary containment?), secondary blast of the whole building just a bit lower pitch (accumulated hydrogen in Bldg 3 exploding), a continuous background rumble (of the rising vertical steam/smoke column?), and mechanical transients at the end (falling metal debris?), then what was the first boom, in your opinion? Was it real (some sort of internal explosion within the building not seen by the camera), or perhaps an artifact left from editing the sound track from the original TV news production (overlaying the audio of the first boom and following sounds again, matched to the visual of the first explosion, but sounding like a second boom then a third?) or something else?

 

[M. Bachmeier]

So, if the "two boom" synched audio/video match you first posted is correct -- it does seem to match the video -- sharp fireball blast (from the primary containment?), secondary blast of the whole building just a bit lower pitch (accumulated hydrogen in Bldg 3 exploding), a continuous background rumble (of the rising vertical steam/smoke column?), and mechanical transients at the end (falling metal debris?), then what was the first boom, in your opinion? Was it real (some sort of internal explosion within the building not seen by the camera), or perhaps an artifact left from editing the sound track from the original TV news production (overlaying the audio of the first boom and following sounds again matched to the visual of the first explosion, but sounding like a second boom?) or something else?

Sorry look at edit above. First explosion inside containment. Second hydrogen +, and third from SFP.

 

[Bob S]

I'm trying to analyze more in detail this video to get some information about what flew in the sky ... mainly on its mass. Maybe someone can help me too.
http://energheia.bambooz.info/index.php?option=com_content&view=article&id=170%3Areactor-3-explosion-enhanced-view&catid=60%3Avideo&Itemid=85&lang=it

Some notes:
Take a look on the right side of the reactor 3 and follow the hard material falling down near the tower

1) at the time 0:16 there is an explosion of flammable material that expands almost sideways
2) immediately something shoot oneway directed upward the material as a recoil of the weapon (very strange, like a cannonball!)
3) about the time 0:21 comes to its maximum height
4) at the time 0:32 comes around on the ground near the tower under the law of gravitation http://en.wikipedia.org/wiki/Equations_for_a_falling_body

You state that the time to max elvation is 5 sec, and the time to fall is an additional 11 sec (meaning high drag force). This implies that the terminal (falling) velocity is low. Could you do a frame by frame analysis the determine the maximum elevation, the final velocity before it hits the ground, and the approximate dimensions of the object?
The drag force for an object in air is (for turbulent drag)
F= \frac{1 }{2 } \rho AC_dv^2

The terminal (falling) velocity is given by

\frac{1 }{2 } \rho AC_dv^2=mg

where ρ is the density of air, A is the cross-sectional area, C_d is the drag coefficient, v is the velocity, and mg is the gravitational force.

Here is an example. A golf ball has a terminal falling velocity of 36 meters per second. A golf ball shot straight upward at 100 meters per second will hit the ground in 10.9 seconds, with a final velocity of only 34 meters per second.

Bob S

 

[Rive]

What if the second and third explosions are just the echoes of the first one? Is it possible? Do we have any reflecting surface around (maybe the other units)? WIth distance in match with the delays? Can it be identified based on the recording?

 

[M. Bachmeier]

So, if the "two boom" synched audio/video match you first posted is correct -- it does seem to match the video -- sharp fireball blast (from the primary containment?), secondary blast of the whole building just a bit lower pitch (accumulated hydrogen in Bldg 3 exploding), a continuous background rumble (of the rising vertical steam/smoke column?), and mechanical transients at the end (falling metal debris?), then what was the first boom, in your opinion? Was it real (some sort of internal explosion within the building not seen by the camera), or perhaps an artifact left from editing the sound track from the original TV news production (overlaying the audio of the first boom and following sounds again, matched to the visual of the first explosion, but sounding like a second boom then a third?) or something else?

To address your other points. 1) there are five distinct sounds in the audio file. a) an event that is decaying at the start of the video (possibly steam escape). b) first explosion. c) second (highest peak energies) d) third (possibly from SFP). e) combined roar and or additional steam escaping. Each audio element is unique and I've found no evidence of clipping/ pasting or the like. Doesn't mean somebody isn't smarter than me though.

I also have a stretched and pitch adjusted version of the audio file where distinct echos from each blast follow between reports. All this would be very difficult to fake while rushing to get the scoop. Seems some of the file sizes are too large to upload here.

 

[Dmytry]

Dmytry:

http://www.houseoffoust.com/fukushima/blueprint.html

Take your pick. The "chimney" is either the depth of the SFP or the "neck" of the reactor's primary containment, depending on whether one believes the vertical blast originated from the SFP or the primary containment, I suppose.

Surprisingly, in the drawing, they are about the same size, so it may not be that much different.

sorry, I meant the literal chimney tower. I want to see the velocity of that rising air, and it's size, and roughly estimate its kinetic energy or it's temperature.
Ok i'll use horizontal size of reactor and assume the video's aspect ratio never got messed with.

For the pieces falling out: they look like they have been carried up by updraft. They reach terminal velocity while falling, which is smaller than velocity of rising air, meaning they would of been carried up by rising air.

 

[|Fred]

and these solve the mystery of the "ballistic" fuel handling machinery in unit 3, submerged in SPF3
http://k.min.us/imMKhK.JPG

well , would be nice to get the video.. as is I'm not able to figure out what I'm looking at or rather how to relate it to other available material

 

[Jorge Stolfi]

the same kind of explosion that blew all the wall panels from the floor 1 but left 2 out of 4 panels standing on floor 4? (western wall)

The top 2 rows of panels belong to the same storey. The floor level of that storey is the top edge of the reactor and of the SFP.

The kind of explosion that didn't happen where the crane is?

An object located near the "center" of a gas explosion presumably would be squeezed hard but not displaced by the explosion. Besides the roof frame of #4 was hardly damaged by the explosion (which blew through it); and the crane seems to be a lot heavier than that frame, even heavier and sturdier than the concrete pillars.

 

[rowmag]

The top 2 rows of panels belong to the same storey. The floor level of that storey is the top edge of the reactor and of the SFP.
An object located near the "center" of a gas explosion presumably would be squeezed hard but not displaced by the explosion. Besides the roof frame of #4 was hardly damaged by the explosion (which blew through it); and the crane seems to be a lot heavier than that frame, even heavier and sturdier than the concrete pillars.

The naive impression I get looking at the building is that the main blast was on the level below the top floor. Could something else have blown up besides hydrogen? Are there any gas or fuel tanks on the 4th floor? Going back to the original (day of blast) speculation of lubricating oil fire, is lubricating oil explosive? (Maybe if it gets aerosolized for some reason?)

Seems hard to believe anything explosive would be present in a reactor building on purpose. Though, since the reactor was undergoing core shroud replacement, which apparently involves welding (according to the link given by MiceAndMen), might oxy-acetylene welding equipment have been temporarily located there?

 

[GJBRKS]

Perhaps that this helicopter video with longshots and closups of the reactor insides can help identify some locations (4:21 27th march)

 

[tadjik]

Assuming that http://www.asahi.com/english/TKY201104140125.html is correct, and the water sample rules out any disintegration of fuel rods, then this is no longer plausible. I've added that note to the original post.

In my vision, high concentrations in Iodine, cesium, and fission product can be due to either :
1) remaining fission in leaking used fuel rods (which are numerous and active in SFP #4)
2) cricality in any part of the stored fuel
3) contamination by rain
They indicate the concentration are high (220 000 Bq for 1 kg), but not so tremendous after all.
Do we have an idea of the magnitude the concentration would be in each of the 3 hypothesis ?
For me, the 3 can ruled out, but beetween 1 an 2 ?

 

[elektrownik]

The naive impression...

No way, explosion was too big for oil, this could be only steam and hydrogene. This is nuclear reactor and there is not much explosive things becouse it would be danger to keep them inside reactor building. But we don't know many things about unit 4 explosion, there is no video so we can't say how the explosion was.

 

[rowmag]

No way, explosion was too big for oil, this could be only steam and hydrogene. This is nuclear reactor and there is not much explosive things becouse it would be danger to keep them inside reactor building.

What about welding equipment for the core shroud replacement that was underway at the time? Acetylene tanks, for example?

 

[Cire]

What about welding equipment for the core shroud replacement that was underway at the time? Acetylene tanks, for example?

You wouldn't have enough acetylene in a welding tank to approach the lower ignition point based on the volume of that structure.

One large full welding tank at the most could handle about (guesstimate) 450 FT^3 of space. Much more then that and you'll have problems with ignition.

I've been wondering if there was any common piping between the reactors that could have transferred hydrogen from one facility to the other.. Via the stack or otherwise.

 

[rowmag]

I've been wondering if there was any common piping between the reactors that could have transferred hydrogen from one facility to the other.. Via the stack or otherwise.

Perhaps the underground cabling conduits?
(Latterly of contaminated water fame.)

 

[tavella]

If I understand correctly, you are assuming that a dose rate that would accumulate 50 mSv per year is dangerous. But this is not the case.

A person could probably accumulate 1 mSv in 1 second without danger. That is a dose rate of over 30,000 Sv per year.

1mSv/sec is 86 Sv/day. 10 Sv/day is considered absolutely lethal.

 

[elektrownik]

I've been wondering if there was any common piping between the reactors that could have transferred hydrogen from one facility to the other.. Via the stack or otherwise.

I don't think so, it is nuclear reactor, all pipes, tunels, etc. must be leak secure this would be too danger to connect reactors with open tunels for example, in case of leak in one reactor all would be floded with radioactive water.

I will stay with my theory:
They move some fuel from SFP to core after cooling faliture to gain some time and slow down vaporization of water from SFP until (as they believe)cooling would be restored. And explosion was in core not in SFP...

 

[Borek]

1mSv/sec is 86 Sv/day.

Right, but that happens only if you stay for all day in the same place. That's not what cphoenix meant.

 

[TedNugget]

Regarding the 6th photo that shows all the rebar and what appears to be a plug laying just below the number 15 on the time readout.

http://cryptome.org/eyeball/daiichi-npp8/daiichi-photos8.htm

I offer this cut and paste from another forum.
The writer has had a full Navy Nuclear Career and worked for a couple decades+ in the US Nuclear industry. From his posts I judge him to be intelligent, knowledgeable, conservative and more balanced than simple pro-industry.
My own knowledge is nada.
So take this with appropriate skepticism.

- - - - - -
However, it would seem worthy to paste here at this time.
- - - - - -

(It is called the) "shield plug, I agree. IMO the Drywell head and Reactor Pressure Vessel head are still bolted on. Unit 3 had Reactor Pressure and Drywell Pressure indicated after the explosion.

It looks to me like it could be part of a concrete shield plug. We call these the cookies. Smaller to larger diameter stacked concrete shield plugs are normally located on top of the Drywell Head, and stack up flush with the Refuel Floor.

I believe containment pressures, according to what I have heard (not seen printed) may have been as high as 120 psig. Most Mark 1s in the US have a 56 psig Design Pressure. It is conjectured that 2x design pressure results in stretched Drywell Head closure studs. Resulting in self - venting of the Containment inside the Reactor Building. Steam coming from the shield plugs should be observable and Reactor Bldg Area Radiation Monitors should alarm.

MELCOR analysis study of Peach Bottom was computer modeled in the 1990s - predicting that beyond design basis severe accident the Mark 1 fails at the Drywell Head Seal at 132 psi.

http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/26/012/26012080.pdf

Page 9, MELCOR model calculated DW Pressure reached a max of 910 kpa = 132 psi. With variation centering very nearly on 120 psi.

Evidently dead nuts accurate. So our procedures throw in a substantial margin and require us to vent to maintain below 56 psig. Japanese didn't do this, or couldn't without power. This is in contrast to US plants which can vent under any condition. Air / Nitrogen operated containment vent valves can be operated with a SCBA bottle and an air regulator without ANY station power.

If containment venting doesn't occur, pressure builds. Once the flange and head get separated, the Drywell pressure will vent off through the clearance. (Self venting ) This would produce steam escaping with zirc water reaction generated Hydrogen.
Note all three Reactor Buildings appeared to explode on the Refuel Floor.
IMO - purely conjecture - some Hydrogen still trapped below the shield cookies, probably went off and lifted them up."

 

[MiceAndMen]

RE: BUILDING 4, CASK TRANSFER POOL & FUEL ROD ASSEMBLY LOCATION(S), AND CURRENT THERMAL IMAGES

A second diagram found here, source: PowerPoint Presentation - "Anatomy of a Tragedy: Fukushima Dai-lchi March 2011", downloaded from UCS website, here:

http://www.ucsusa.org/nuclear_power/nuclear_power_risk/safety/disaster-at-fukushima-anatomy.html

. . . this diagram:
http://i306.photobucket.com/albums/nn270/tcups/Picture3-1.png

and the previous schematic:
http://i306.photobucket.com/albums/nn270/tcups/Picture63.png

would both seem to confirm the location of a separate, gated "Cask Transfer Pool" (CTP) in addition to the larger Spent Fuel Pool (SFP) in the Mark 1 BWR design.

I don't think you can point to a couple of diagrams and conclude they represent "the Mark 1 BWR design". For instance, slide 7 in Lochbaum's powerpoint presentation shows the operating rector buildings 1, 2 and 3 have a diameter. The buildings in question are not round, however. On slide 24 there is a diagram that more closely resembles the ubiquitous GE color marketing drawing of a Mark I secondary containment. It does indeed show a cask storage area with gates, but I submit that that area is within the overall volume of the SFP. I have attached a picture that depicts the arrangement of the refueling floor at Oyster Creek for comparison. The NE corner of the SFP has just such a walled-off compartment for fuel casks. The Oyster Creek floor plan also shows the travel path for casks being transported in and out. Note that the equipment hatch is about 90 feet away from the cask storage area in the SFP, in the SE corner of the building.

If you want to call that a separate pool, fine, but the distinction at Oyster Creek is tenuous at best. I think you are relying too much on a few generic Mark I building drawings floating around the net. The Oyster Creek blueprint fragment is prima facie evidence that the layout of a reactor building can and does differ from the diagrams everyone is using to "prove" their points.

It is also known and documented and posted here, some weeks back that the pneumatic seals for the transfer gates were electric-powered and that failure of the seals results in significant leakage from the SFP to the upper primary containment of the RPV, which could explain the presence of warm water in the region of the open primary containment of Unit 4 on current thermal images:

It is not known at all. You have posited electric-powered pneumatic seals for the reactor-cavity/SFP connecting passage, but I don't recall seeing any other documentation that confirms that. Even if there are designs that use such seals, that would not automatically mean that they were used at Fukushima Daiichi. In the other Oyster Creek drawings I have, there is no reference whatsoever to pneumatic seals of any kind.

 

[razzz]

You could also look at the audio file to try and confirm the energies.

This is my best guess alignment of audio to video with the middle blast corresponding to the visible explosion. Best estimate of camera distance 2.25 KM.

Video Link :

Audio wave table :

Good effort MB.

 

[Jorge Stolfi]

I've updated my plots of #Fukushima reactor variables to NISA release 95 (15/apr 15:00) : http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/Main.html

I have added markers showing the approxiamte times of black/grey smoke events in #3 (even though those may have been related to the SFP rather than the reactor proper). So far only those events between mar/21 and mar/24 are marked. Were there any other?

 

[Atomfritz]

Adding to this the (i presume by now ascertained) fact that the level measurement monitors the level in the downcomer, not in the core, and the possibility that at least the upper temperature measurement monitors the temperature of the core vessel close to the feedwater inlet (=area affected by the inflow through feedwater lines), this currently leaves us very little on which to base estimates on the state of the cores. As I see it, it could be that only a little part (if any) of the water injected in the reactor vessel actually ends up cooling the core. ...Is there some way to ascertain that the water injected in the reactor vessel actually reaches the core?

Afaik no.
Imagine of a large crust insulating the circulating hot corium in the lower part of the reactor, letting swim maybe some feet of slowly boiling water until these broken reactor interconnections that cause the water level not rise higher. This makes sure that you won't measure much more than 400 degs even if the lower part of the vessel is already glowing bright, almost white, imminently before rupturing.

Besides the roof frame of #4 was hardly damaged by the explosion (which blew through it); and the crane seems to be a lot heavier than that frame, even heavier and sturdier than the concrete pillars.

Looks to me that it will eventually settle down a bit, ripping pool cracks open, and crushing the brittle Zirconiumoxide rod hulls, making a really big nuclear fart.
I hope this won't happen.

Regarding the 6th photo that shows all the rebar and what appears to be a plug laying just below the number 15 on the time readout.

Castor plug?
Looks too small to me to be a reactor plug. If any, then one of the lower ones.

Hey Anton! I've got it! The FHM broke in two pieces and one of them fell back into the SFP! Amazing!

This is what I also see. Could be like in a Hollywood movie.
This will assure for some dramatic possibilities.

In a russian forum mentioned in some other post here some apparently very knowledgeable people say that even recriticality issues could theoretically not be excluded, considering the changed fuel geometry after having been hammered and compacted by the impact of the FHM.

At the end of the video Professor Kazuhiko Kudo of Kyushu University says he is surprised to see that the fuel handling machine at unit 4 looks intact, while other parts of the building have suffered important damage.

Yes, it's working well. It's redesignated function now seems being a SFP plug-in radiation shield. Amazing!

 

[Jorge Stolfi]

I believe containment pressures, according to what I have heard (not seen printed) may have been as high as 120 psig. Most Mark 1s in the US have a 56 psig Design Pressure.[/I][/B]

The max recorded pressure I have seen for #3's drywell is 637 kPa ~ 6.3 bar, on mar/13 09:10. That was just when the RPV pressure started falling very fast from 7341 kPa to below 500 kPa: http://www.nirs.org/reactorwatch/accidents/conditionoftheplants313317.pdf

The max recorded pressure in #1's drywell was 940 kPa, on mar/11 ~23:30, from this plot: https://www.physicsforums.com/showthread.php?p=3225222&highlight=missing#post3225222

The max recorded pressure in #2's drywell was 750 kPa, just before an "explosion noise" was heard and pressure dropped suddenly to 155 kPa: http://www.nirs.org/reactorwatch/accidents/conditionoftheplants313317.pdf

However, beware that those numbers do not come directly from TEPCO, but from data compilations by other people.

 

[rowmag]

I will stay with my theory:
They move some fuel from SFP to core after cooling faliture[...]

Without electricity?

 

[SayaX]

Some New pictures released today of the reactors (Japanese website) for anyone interested:

http://mainichi.jp/select/wadai/graph/20110415_2/2.html

 

[TCups]

I don't think you can point to a couple of diagrams and conclude they represent "the Mark 1 BWR design". For instance, slide 7 in Lochbaum's powerpoint presentation shows the operating rector buildings 1, 2 and 3 have a diameter. The buildings in question are not round, however. On slide 24 there is a diagram that more closely resembles the ubiquitous GE color marketing drawing of a Mark I secondary containment. It does indeed show a cask storage area with gates, but I submit that that area is within the overall volume of the SFP. I have attached a picture that depicts the arrangement of the refueling floor at Oyster Creek for comparison. The NE corner of the SFP has just such a walled-off compartment for fuel casks. The Oyster Creek floor plan also shows the travel path for casks being transported in and out. Note that the equipment hatch is about 90 feet away from the cask storage area in the SFP, in the SE corner of the building.

If you want to call that a separate pool, fine, but the distinction at Oyster Creek is tenuous at best. I think you are relying too much on a few generic Mark I building drawings floating around the net. The Oyster Creek blueprint fragment is prima facie evidence that the layout of a reactor building can and does differ from the diagrams everyone is using to "prove" their points.
It is not known at all. You have posited electric-powered pneumatic seals for the reactor-cavity/SFP connecting passage, but I don't recall seeing any other documentation that confirms that. Even if there are designs that use such seals, that would not automatically mean that they were used at Fukushima Daiichi. In the other Oyster Creek drawings I have, there is no reference whatsoever to pneumatic seals of any kind.

Thanks, Mice & Men. A thoughtful critique is always helpful

I don't have much of an engineering background - a year of ME/Automotive, and I don't claim to be a structural engineer or nuclear engineer. But I don't think it implies anything on the scale of a bad hallucinogenic trip would be required to imagine a difference, perhaps like the first vs the second variations on a theme of the Mark I design. In fact, if one considers the likelihood that SFP storage space was at a premium at Fukushima, and what the photographic and video evidence since day 1 have shown, I don't think variation 2 is much of a stretch at all.

Maybe that presumes too much, but it seems at least to me to fit the visual evidence and might help explain some of the things I and others seem to be struggling to understand.

As for the seals, I didn't make it up out of thin air. I believe this was discussed in some detail back around post 600 or so. See reference:

http://allthingsnuclear.org/post/3964225685/possible-source-of-leaks-at-spent-fuel-pools-at

And as for a the couple of diagrams, I will claim responsibility for having given the impression that perhaps I had only looked at two diagrams. Instead, I have scoured almost every diagram, photograph, and reference posted here since day one, as well as all the other reasonable sources I could find in the process of coming up with several of my wild conjectures.

Does one of these look like what we have been seeing at Fukushima Unit 3 & 4 to anyone else? I think I commented on the apparent incongruity of the elevator shaft on one of the earlier diagrams. I believe the Fukushima photographs pretty clearly demonstrate the alternate position of the elevator shaft and access tunnels in version 2.

Oyster Creek:

http://i306.photobucket.com/albums/nn270/tcups/Picture1-6.png

Fukushima (?):

http://i306.photobucket.com/albums/nn270/tcups/Picture2-6.png

 

[ceebs]

I googled around a bit and found a few other items of interest regarding the core shroud replacement program at Fukushima Daiichi. My understanding is that the "core shroud" is a cylindrical wrapper that surrounds the fuel core inside the reactor pressure vessel (RPV).

looking further at this I came across this That I haven't noticed here

http://www.nirs.org/factsheets/bwrfact.htm"

The core shroud is a large stainless steel cylinder of circumferentially welded plates surrounding the reactor fuel core. The shroud provides for the core geometry of the fuel bundles. It is integral to providing a refloodable compartment in the event of a loss-of-coolant-accident. Extensive cracking of circumferential welds on the core shroud has been discovered in a growing number of U.S. and foreign BWRs. A lateral shift along circumferential cracks at the welds by as little as 1/8 inch can result in the misalignment of the fuel and the inability to insert the control rods coupled with loss of fuel core cooling capability. This scenario can result in a core melt accident. A German utility operating a GE BWR where extensive core shroud cracking was identified estimated the cost of replacement at $65 million dollars. The Wuergassen reactor, Germany's oldest boiling water reactor, was closed in 1995 after wary German nuclear regulators rejected a plan to repair rather than replace the reactor's cracked core shroud.

 

[AtomicWombat]

The plans for relocating the capital of Japan is an old story. The timeline at http://www.mlit.go.jp/kokudokeikaku/iten/English/background/index.html starts in the 1950s, but in old times, emperors changed the location of their capital quite often : http://en.wikipedia.org/wiki/Capital_of_Japan

It's a very sensible idea, but now is NOT the time to rush it.

 

[AtomicWombat]

What is the chimney height and reactor height? We can estimate velocity of rising air there, in reactor 3 explosion video. Hell, we can probably estimate blast energy in kt.

I did this before using 2 methods. I think the most convincing is timing how long the heavy junk takes from the explosion until it returns to roof level again - it's 14-15 seconds. Half this 7-7.5 sec and then use Newton's Laws distance = 0.5*g*t^2 gives around 245-280 metres from memory.

 

[rowmag]

Re: moving the capital:

It's a very sensible idea, but now is NOT the time to rush it.

This hasn't been discussed in the Japanese press at all. If anyone had brought it up, their political opponents would be gleefully roasting them over the fire with it (this is already happening with other disaster-related statements), so I doubt it is being discussed. My vote is against ITAR-TASS getting the big scoop ahead of any other news agency in the world.

 

[shogun338]

The US Department of Energy facility storing melted fuel from the Three Mile Island nuclear plant has not done enough to address crumbling concrete modules encasing the radioactive material, the US Nuclear Regulatory Commission said in a letter made public Friday.

The DOE facility at the Idaho National Laboratory holds the damaged fuel from unit 2 of the Three Mile Island Plant, which, in 1979, suffered a partial meltdown of the core, leading to the US' worst nuclear accident. http://www.platts.com/RSSFeedDetailedNews/RSSFeed/ElectricPower/6002873