Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[MadderDoc]

Unit 4 spent fuel pool

I don't understand Tepco's recent announcement, that no cracks was found in the concrete wall surrounding the SFP of Unit 4.
I thought it to be a ~horizontal crack in that wall, the man in this previously released photo is pointing his hand gadget at. I still can't see what else it could be.

 

[zapperzero]

I assume we are also in the same ballpark, method-wise. The measurements are made from the thought that they represent the movements of a detonation shock/flame front. Can you think of them as perhaps representing something else?

Same method, yes. But no... can't think of anything else.

That would imply measuring to ill-defined points in the shadow of the building and the developing plumes, it doesn't seem immediately promising to me. What would that measurement be good for?

It's unclear, yes. But it would give you another measure of how fast the shock front was. Does it take one frame to reach that other corner, or two?

 

[Uagrepus]

I'd say the strong impression is one of building collapse, i.e. the roof appears to come down, so that the building seems to be shrinking in the vertical direction.

Indeed. Looking at the roof-anchor in the picture (true?), the roof collapsed in the south region also in the first stage of the explosion. The big vertical mushroom afterwards "cleaned" that area then.

After 14 months - is there any consensus if there were at least one or two explosions??
There are indications for two different events in my opinion. The hydrogen burns in the east side of unit 3, where it must have been in high concentrations after the leakage near the lid. In the west-side the hydrogen consentrations should have been lower, but with more oxygen there a bit more explosive (the west-wall was blown away, the east-wall remains partially).

Like at the lid of a cooking pot, the hydrogen escapes in an angle when under high pressure. Sorry for my english, look at my next picture:

Could this be an explanation for the fireballs (1A, 1B) in south-east and north-east? The enormous mushroom developed in the geometrical middle between those two fireballs from the perspective of the video. This is at the same time the location of the SPF. The heavy vertical blast (2) seems to be a secondary event, initialized by 1A and 1B. If it is not related to the SPF itself (but I think so), the only explanation that comes to my mind is the more explosive H2/O2-Concentration in the west-side of unit 3.

 

[MadderDoc]

Uagrepus, thanks for your well-argued reply. I read it mainly thinking yes,yes, yes. Rather than going into some detail of difference, I'll add the thought, that the sudden development of a leak in the primary containment top (say, a manhole in the PCV lid sprang open) might go a long way explaining the whole thing. The expected outcome of such occurrence would be a jet of H2 and steam, shortly followed by a whoosh of steam and superheated water, all making its way, up, through whatever passageway it could find through the concrete shield plugs and gate areas.

(To that. add the fair assumption in consistence with consensus, that previous hydrogen leakage had made a chemical hydrogen bomb out of the building, and it suddenly exploded)

 

[MadderDoc]

Same method, yes. But no... can't think of anything else.

The method assumes that the burning airmass is stationary. How did the airmass get there?

It's unclear, yes. But it would give you another measure of how fast the shock front was. Does it take one frame to reach that other corner, or two?

I can't see how it can be done to be of any use. Mind the perspective.

 

[SteveElbows]

I don't understand Tepco's recent announcement, that no cracks was found in the concrete wall surrounding the SFP of Unit 4.
I thought it to be a ~horizontal crack in that wall, the man in this previously released photo is pointing his hand gadget at. I still can't see what else it could be.

Given that the published title of that photo was 'The original place of installation of air-conditioning ducts', I assume he is pointing at where the ducts were originally present. I certainly don't see enough detail in that photo to even begin to assume that we see any cracks there.

 

[MadderDoc]

Given that the published title of that photo was 'The original place of installation of air-conditioning ducts', I assume he is pointing at where the ducts were originally present. I certainly don't see enough detail in that photo to even begin to assume that we see any cracks there.

Wonderful :-) You are one rock of skepticism.

Here's another photo from another angle showing a bit more detail (in upper right in the photo), of the left end of the alleged crack:

 

[zapperzero]

The method assumes that the burning airmass is stationary. How did the airmass get there?

It is only stationary in that the center remains fixed. Otherwise, the shock front would be pushing hydrogen-laden air ahead of it and leaving steam behind, until there was no more hydrogen left.

I can't see how it can be done to be of any use. Mind the perspective.

Yes, it's not very clear.

 

[MadderDoc]

It is only stationary in that the center remains fixed. Otherwise, the shock front would be pushing hydrogen-laden air ahead of it and leaving steam behind, until there was no more hydrogen left.

Should measurement then not be from the center, to the edge, rather than from edge to edge? Does air in front of a detonation shockwave 'know' that the shockwave is coming?

 

[Rive]

Here's another photo from another angle showing a bit more detail (in upper right in the photo), of the left end of the alleged crack:
[/QUOTE]
Where were these photos taken? The recent announcement was only about checking the walls around and supporting the fuel pools as I recall.

 

[SteveElbows]

Recently I have been speaking on the thread about reactor 2 releases, about this TEPCO report on total radiation estimates. We heard about the totals, but there are some interesting details in the full report. It doesn't sound like TEPCO are going to translate the full document, so this is an appeal for help in translating interesting bits.

http://www.tepco.co.jp/cc/press/betu12_j/images/120524j0105.pdf

A good starting point would be the table on page 9 which shows estimated releases of different substances during a range of different time periods/events. Not hard to understand most of it without proper translation, apart from the notes column.

Anyway I think this table should be of particular interest because for once it does not stop looking at detail after the explosions have finished, the dates March 16th to March 29th are represented here! For example reactor 3 gets some credit for some notable releases on march 16th and march 19th.

Those with an interest in weather may like many of the diagrams later in the report, and MadderDoc may be amused to note that when they talk about non-vent releases from containment, they use a thermal image of reactor 3 to acknowledge the issue. There are some diagrams of the engineering detail of potential weak-spots but they aren't very good resolution and we've seen at least some of them before.

 

[MadderDoc]

Where were these photos taken? The recent announcement was only about checking the walls around and supporting the fuel pools as I recall.

They are from the west wall of the pool, 4th floor, the same wall section which the recent announcement is showing a lower portion of in a sharp angle, the photo bottom right in
http://2.bp.blogspot.com/-e4hpgfA9W...jMc2lWo/s1600/fukushimareactor4SFPMay25-7.JPG

(The photos are from the original survey of Unit 4 damages done in Nov. 2011, source:
http://photo.tepco.co.jp/en/date/2011/201111-e/111110_01e.html)

 

[MadderDoc]

<..>http://www.tepco.co.jp/cc/press/betu12_j/images/120524j0105.pdf<..>
Anyway I think this table should be of particular interest because for once it does not stop looking at detail after the explosions have finished, the dates March 16th to March 29th are represented here! For example reactor 3 gets some credit for some notable releases on march 16th and march 19th.

Those with an interest in weather may like many of the diagrams later in the report, and MadderDoc may be amused to note that when they talk about non-vent releases from containment, they use a thermal image of reactor 3 to acknowledge the issue. There are some diagrams of the engineering detail of potential weak-spots but they aren't very good resolution and we've seen at least some of them before.

Actually those engineering details I found pretty interesting, or at least, new. Indeed there was a scent of what the Tepco cat could tell.

Otherwise, I got just the scent of the bones of the same old whale, the data from the monitoring posts. Apparently Tepco has set out to put a label and some figures on any major signal from that data series, however the soup of words that came out of it defies their own reasonable efforts to translate or express it in plain English in such manner as to be well taken internationally.

 

[Rive]

The previously mentioned press visit videos are now out: http://photo.tepco.co.jp/en/date/2012/201205-e/120526-01e.html

They have found a water inflow to the U3 buildings: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120526_01-e.pdf

And a survey about U1, without any immediate revelations: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120525_06-e.pdf

Some fuel will be removed from U4 pool in July: http://www3.nhk.or.jp/daily/english/20120528_09.html

 

[Rive]

(The photos are from the original survey of Unit 4 damages done in Nov. 2011, source:
http://photo.tepco.co.jp/en/date/2011/201111-e/111110_01e.html)

It's hard to put these pictures together, but the curved wall on this photo: http://gyldengrisgaard.dk/fuku_docs/111110_06.jpg
suggests that the wall section here: http://photo.tepco.co.jp/library/111110/111110_12.jpg belongs to the 'neck' between the pool and the well.

This section is marked as 'checked' in the 'soundness' document. And you are right, that line on the wall looks like a crack.

The only thing I can think is that the crack was smaller than 1mm and there was no danger of rebar corrosion... They can be right with these but even so it won't make me happy.

 

[MadderDoc]

It's hard to put these pictures together, but the curved wall on this photo: http://gyldengrisgaard.dk/fuku_docs/111110_06.jpg
suggests that the wall section here: http://photo.tepco.co.jp/library/111110/111110_12.jpg belongs to the 'neck' between the pool and the well.
This section is marked as 'checked' in the 'soundness' document. And you are right, that line on the wall looks like a crack.


The only thing I can think is that the crack was smaller than 1mm and there was no danger of rebar corrosion... They can be right with these but even so it won't make me happy.

You are right about the location. The pixel resolution of these images is about 10 mm and we see rust stain originating from one area of the crack. The crack in the wall was visible already in the first images I saw from the 4th floor of Unit 4, but it didn't really bother me, since cracks in a steel reinforced concrete building after an explosion was sort of what I expected to see. I take note of it only because the recent announcement seems inconsistent with already acquired knowledge. My brain works like that, sorry. Here's a detail from the first image of the wall as it looked in June 2011:
http://gyldengrisgaard.eu/fuku_docs/110611_05_detail.jpg
source Tepco, at http://photo.tepco.co.jp/en/date/2011/201106-e/110611-03e.html


Footage from the most recent press tour shows scaffolding and a ladder leading to the area of the crack, I guess they may have been puttying it.
http://gyldengrisgaard.eu/fuku_docs/Unit4_4th_scaffold.png

 

[Rive]

The pixel resolution of these images is about 10 mm and we see rust stain originating from one area of the crack.

The image resolution does not matter much for this one: on a photo every crack will look much wider than it really is due the painting/surface pieces of the concrete will be dislocated much wider range than the distance between the main bodies. This can be measured with probes only.

The rust also can be originated from rebars or anything close to the surface. Its presence does not mean that the structure is in danger in depth.

I think this is the point where we won't get enough information from the pictures to move further. However it's worrying that these cracks are not mentioned in the documents, even if they are thought to be safe/too small/irrelevant.

Ps.: about the press visit video: funny, now they have some heavy machinery on the top level and much more stuff 'missing' there than on the previous photos...

 

[Rive]

... the fireballs (1A, 1B) in south-east and north-east?

Based on the remnants of U4 top section, the double fireballs IMHO are most likely originated from between north/south wall and roof, and not necessarily from the corners. I think the suggested concentration differences are not necessary to explain the result.

It appears to me that these walls (and their weak/nonexistent connection to the roof) are the weak points of the secondary containment of this reactor type.

 

[turi]

[...]
And a survey about U1, without any immediate revelations: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120525_06-e.pdf[...]

Thanks for the link. Does anyone know what the vertical orange "thing" in the unprocessed image is? The processed image doesn't have such an artifact. What kind of processing is done anyway? Adjustment for the distance of the radiation source from the camera?

 

[MadderDoc]

The image resolution does not matter much for this one: on a photo every crack will look much wider than it really is due the painting/surface pieces of the concrete will be dislocated much wider range than the distance between the main bodies. This can be measured with probes only.

The rust also can be originated from rebars or anything close to the surface. Its presence does not mean that the structure is in danger in depth.

I think this is the point where we won't get enough information from the pictures to move further. However it's worrying that these cracks are not mentioned in the documents, even if they are thought to be safe/too small/irrelevant.

I of course agree on all points above. So there's a document which includes photos for apparent documentation which are totally unsuitable as evidence for or against cracks in the context of the inquiry, but it is perfectly alright with Tepco if the reader will conclude from looking at the photos that there are no cracks there at all. In fact that appears to be the intention of the document. I am not worried about that crack, but I don't like to be bs'ed.

 

[MadderDoc]

Unit 3 explosion (was Re: Japan Earthquake: nuclear plants)

I think the suggested concentration differences are not necessary to explain the result.

Something is necessary to explain the particular damages of the SE corner of the roof.

 

[Uagrepus]

Based on the remnants of U4 top section, the double fireballs IMHO are most likely originated from between north/south wall and roof, and not necessarily from the corners.

I agree, that the leaking containment in the middle between north and south wall was most likely the origin of large amounts of hydrogen and steam in Unit3 and makes the difference to Unit4. But if hydrogen leaks from there, we get automatically concentration gradients, because the concrete plug is not in the center of the building the three or more leakage beams might have been directed.

From looking at the earliest initial frames I suggest this timeline of the combustion:

1.) There is already H2 in the building on several floors. ("chemical hydrogen bomb building")
2.) Around the concrete-lid beams of H2 and steam escape directed to the service floor.
3.) Somewhere in the building H2 ignites.
4.) The roof begins to collapse and parts of the west-wall are blown away on several floors (no fireballs/flames there, H2 explodes with an excess of O2 inside the building)
5.) While the roof is collapsing, the high-concentrated H2 in the east half of the upper floor combusts in a fireball, now having contact to enough fresh air outside the building.
6.) A steam explosion/flash boil over the SFP is triggered (unsure, unconfirmed).

Just a hypothesis, not more.

 

[MadderDoc]

I agree, that the leaking containment in the middle between north and south wall was most likely the origin of large amounts of hydrogen and steam in Unit3 and makes the difference to Unit4. But if hydrogen leaks from there, we get automatically concentration gradients, because the concrete plug is not in the center of the building the three or more leakage beams might have been directed.

From looking at the earliest initial frames I suggest this timeline of the combustion:

1.) There is already H2 in the building on several floors. ("chemical hydrogen bomb building")
2.) Around the concrete-lid beams of H2 and steam escape directed to the service floor.
3.) Somewhere in the building H2 ignites.
4.) The roof begins to collapse and parts of the west-wall are blown away on several floors (no fireballs/flames there, H2 explodes with an excess of O2 inside the building)
5.) While the roof is collapsing, the high-concentrated H2 in the east half of the upper floor combusts in a fireball, now having contact to enough fresh air outside the building.
6.) A steam explosion/flash boil over the SFP is triggered (unsure, unconfirmed).

Ad 2-3. Hydrogen jets are prone to autoignition and detonation speed flame front propagation at ignition.
Ad 4. It is unlikely that the west-wall, as regards the concrete pillars were blown away by an explosion,considering how orderly they fell. More likely the concrete pillars were left temporarily standing while the panels were blown away, only to tumble to the ground in good order, in connection with the total collapse of the roof.
Ad 5. An ignited hydrogen jet directed at the SE corner inside the building could have caused the special damage to the roof structure there, initiated the collapse of the roof, and provided for the escape of the hydrogen seen burning outside the building.
Ad 6. Providing special conditions for an eruption of steam and water from the SFP adds complexity unnecessarily. Steam and water would erupt from the PCV in the heels of hydrogen by physical necessity due to the pressure drop, if 2) is initiated by a sudden development of a PCV leak.

An additional assumption would seem to be needed for the final touch, namely that the SE corner was hit by roof covering fragments that had been lifted to great heights by the mushroom cloud forming eruption.

 

[Rive]

Something is necessary to explain the particular damages of the SE corner of the roof.

All I'm telling is that on the south and north side of the buildings the top of the wall is not fixed to roof beams, so:
- in case of an internal explosion the connection between the N/S wall top and the roof would be the first to give up (and release the last breaths of a fireball)
- without the pull of the roof beams the columns of N/S walls would most likely break and fall almost immediately.

Sorry, I don't have enough time to completely walk this around, so I'm just trying to add some pieces :-(

 

[MadderDoc]

Thanks for the link. Does anyone know what the vertical orange "thing" in the unprocessed image is? The processed image doesn't have such an artifact. What kind of processing is done anyway? Adjustment for the distance of the radiation source from the camera?

It is also not clear to me what is going on there. However they appear to be able to combine measurements to produce a 3D representation of the air dose rate in the building. With that in hand they would be able to subtract from 2D measurements of surfaces, the fraction of gamma that is received from the air , such as to be able to discern gamma emitting surfaces more clearly through the air contamination 'fog'.

The vertical orange thing otoh, clearly an artefact, but would not seem to be explainable by air dose. It might be a camera error, at the edges of the field, which can also be corrected for, by combining measurements from the rotating camera.

 

[Rive]

1.) There is already H2 in the building on several floors. ("chemical hydrogen bomb building")
2.) Around the concrete-lid beams of H2 and steam escape directed to the service floor.
3.) Somewhere in the building H2 ignites.
4.) The roof begins to collapse and parts of the west-wall are blown away on several floors (no fireballs/flames there, H2 explodes with an excess of O2 inside the building)
5.) While the roof is collapsing, the high-concentrated H2 in the east half of the upper floor combusts in a fireball, now having contact to enough fresh air outside the building.
6.) A steam explosion/flash boil over the SFP is triggered (unsure, unconfirmed).

Just a hypothesis, not more.

Point two would match nicely with the maybe-starting of events at frame -2. Overpressure building up fast inside the building might be enough to explain some unexpected, but less dramatic changes on the webcam picture.

For point five: if there is a continuous leakage then you can give all the H2 on the upper/lower floors to the initial blast and still there will be enough 'new' Hydrogen/steam for the mushroom. And such kind of flame would give you that kind of constant heat what the blast can't (source of the heat marks on the roof components?).

 

[MadderDoc]

All I'm telling is that on the south and north side of the buildings the top of the wall is not fixed to roof beams, so:
- in case of an internal explosion the connection between the N/S wall top and the roof would be the first to give up (and release the last breaths of a fireball)
- without the pull of the roof beams the columns of N/S walls would most likely break and fall almost immediately.

Sorry, I don't have enough time to completely walk this around, so I'm just trying to add some pieces :-(

Indeed the north wall at least would have seemed to have been blown out quite early complete with pillars, wall panels, dragging the north part of the roof construction with it. judge this from the way parts of it ended up outer face up on top of the RW building and leaving beams pointing upwards in the remains of the roof on top of the building. Apparently the northern edge of the roof construction was fixed better to the wall, than it was to the rest of the roof construction. Assumedly the same holds true for the south end. The SW corner of the roof construction does seem to have been fractured in much the same manner as seen along the north wall, while of course the SE corner is different.

 

[MadderDoc]

Point two would match nicely with the maybe-starting of events at frame -2. Overpressure building up fast inside the building might be enough to explain some unexpected, but less dramatic changes on the webcam picture.

For point five: if there is a continuous leakage then you can give all the H2 on the upper/lower floors to the initial blast and still there will be enough 'new' Hydrogen/steam for the mushroom. And such kind of flame would give you that kind of constant heat what the blast can't (source of the heat marks on the roof components?).

The PCV is a limited source of hydrogen. Its content would be enough for a decent temporary flare and the explosion of the building, but you wouldn't be able to build the mushroom cloud on the basis of the amount of steam that could be produced by it's emptying itself of hydrogen, and its combustion. However, likely the water in the PCV would be flash boiling once the hydrogen pressure were to be relieved, which would make up for a massive temporary source of steam.

 

[MadderDoc]

Good view, best seen so far, of the SE corner of Unit 3, from recent press package:
http://photo.tepco.co.jp/library/120528_01/120528_35.jpg

 

[Yamanote]

Many new photos and videos:

http://photo.tepco.co.jp/en/index-e.html