Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[tsutsuji]

Cf this diagram,

The diagram with blue arrows is from http://www.meti.go.jp/english/earthquake/nuclear/decommissioning/pdf/20120315_02_004.pdf page 5/19.

But where did you find the diagram without blue arrows and with dimensions ?

http://www.tepco.co.jp/fukushima1-np/images/c12304_5.jpg
Fukushima Daiichi unit 1, from http://www.tepco.co.jp/fukushima1-np/c12304-j.html

http://www.tepco.co.jp/fukushima1-np/images/b13201_6.jpg
Fukushima Daiichi unit 3, from http://www.tepco.co.jp/fukushima1-np/b13201-j.html

http://www.tepco.co.jp/fukushima1-np/images/cb2006_3.jpg
Fukushima Daiichi unit 3, from http://www.tepco.co.jp/fukushima1-np/cb2006-j.html

http://www.tepco.co.jp/fukushima1-np/images/b13500_05.jpg
Fukushima Daiichi unit 3, from http://www.tepco.co.jp/fukushima1-np/b13500-j.html

And now I'm wondering why they call that step thing "scaffolding".

Perhaps because they don't know that it is called a "step" in English. I wish I could find a Japanese version to know how they call it in Japanese. There is one word in Japanese, 足場 litterally "foot-place". My dictionary translates it as "scaffolding, footing, foothold, beachhead"

 

[Rive]

... foothold...

Very thanks for the pictures.

On the first attached picture I've marked the area which can be that 'foothold', and a line on the containment wall, which I think can be identified on the video.

I think the device used was an endoscope taped on a stick, which limits the accessible area: an assumed accessible area is marked on the second picture. The area applies also to the ground side, but that part is crowded.

 

[westfield]

The diagram with blue arrows is from

<snip>

Perhaps because they don't know that it is called a "step" in English. I wish I could find a Japanese version to know how they call it in Japanese. There is one word in Japanese, 足場 litterally "foot-place". My dictionary translates it as "scaffolding, footing, foothold, beachhead"

The PCV Equipment hatch images are a very helpful find tsutsuji, thankyou.

Re - translation of "scaffolding. Ok, thanks again. I had that feeling it was a translation thing but I also wondered if it also indicated a temporary item.

Edit : If I may asnwer on behalf of madderdoc who first linked it - the PCV equipment hatch image without the blue lines is here at METI

 

[tsutsuji]

Edit : If I may asnwer on behalf of madderdoc who first linked it - the PCV equipment hatch image without the blue lines is here at METI

Can you please check again and tell which page number. Because this is the same pdf where I find the picture with blue lines (page 5/19).

I found the Japanese version of the Toshiba/Hitachi-GE/Mitsubishi Heavy Industries document with the blue lines : http://www.meti.go.jp/earthquake/nuclear/pdf/120227_01h.pdf (it is from the 27 February workshop: https://www.physicsforums.com/showpost.php?p=3787196&postcount=12416 ). The Japanese wording for the step is 常設足場 : permanent/normally installed step/foothold.

 

[SpunkyMonkey]

Sfp3 fhm

Here's a collage from this SFP3 video. I see what I think may be railing with metal fencing from the trolley, as pointed to on the right. And what might be the bottom of the trolley platform just above / beside the smashed-down crane bridge.

Any ideas on what's the large flat object that's smashed down across the crane's bridge? This is a pretty dramatic aspect. An easy guess is that it's a panel of the exterior wall. But it's difficult to understand why it would be there, since I believe most of the upper-deck wall panels got blown outwards and turned to rubble. So why, if it is a wall panel, would a wall panel be found on the north end of the pool? But if it's not a wall panel, what the heck is it? It seems to big to be the trolley. Perhaps some east-side wall panels fell inward. And yet there seems to be other large objects on top of this possible 'wall panel'. What a mess to figure out!

 

[SpunkyMonkey]

http://www.tepco.co.jp/fukushima1-np/images/cb2006_3.jpg
Fukushima Daiichi unit 3, from http://www.tepco.co.jp/fukushima1-np/cb2006-j.html

Great photos tsutsuji, thanks!

The probe camera makes the passageway seem much longer than it is. Curiosity, seeing the hatch passage better at the moment only makes me more confused about the video therein .

 

[MadderDoc]

Some interesting stuff there.
http://www.tepco.co.jp/en/nu/fukushima-np/roadmap/images/m120314_02-e.pdf

Sometimes looking at this stuff, I wonder if it in the end will be the data that validates the model or it will be the other way around. Or, perhaps, they might come to be seen as validating each other. However, to be fair not likely as all gigo. Data may be inaccurate, but the data sets do seem to contain information. Similarly, the models may not reproduce reality, or data, on all accounts, but they also do not seem outrageously detached from it.

An interesting example fom that presentation is the attempt to reproduce the pressure data of the PCV of unit 3. The natural trend for this parameter during the accident was to increase, by the accumulation of decay heat. By interventions, such as PCV cooling, or venting of steam from the PCV, that trend could be temporarily reversed, only to have the system picking up pressure again, when cooling, or venting was aborted.

The start of such downtrend episodes are neatly and appropriately presented in the diagram below, where the blue arrows are coming _down_, while their abortion, such as to go back to an increase of pressure is marked with the blue arrows coming _up_. And although arrow text is in Japanese, it is all about vents, their start and stop, respectively. When the occurence of vents are considered model assumptions the text ends with two glyphs parentesized, saying 'assumed' in Japanese. Those unmarked would then be those considered by the modellers to be factually known.

I can see there is some issues still to be resolved.

It is impressive to see how the model manages to distance itself from the Unit 3 explosion:

- First, the model starts out a S/C vent in the early morning of March the 14th, when data says nothing was vented.

- Then, at 11.01, at the time of the explosion, the model has nothing relevant happening, nothing worth a blue arrow -- while the data says a sudden major vent occurred.

-Finally, when data says the reactor picked up pressure some hours after the explosion, the model is let to assume the S/C vent it started in the morning has now been stopped.

Whilst I do not rule out the possibility of substantial quantities of fuel remaining in RPV at reactors 2 & 3, I think they are well aware that their analysis in this regard is probably out of whack with reality.

Yes, agreed. Perhaps it will be in the next version.

 

[SpunkyMonkey]

The gate in the SFP3 cask faces south in the only photo I have of it...

I don't understand what the SFP cask is, can you show that photo? Is it a fuel rack? I thought they eventually put fuel in dry casks, but I didn't know there are casks in the pool but have seen this noted here and there w/o imagery.

BTW, could what we are seeing there close under the surface be the _bottom_ frame of the trolley, that one with the wheels? I feel I have been everywhere else high and low on the FHM looking without finding a match, only this stout frame remains, it is so well hidden, that I can't see enough to dismiss it as a possibility.

Did you have in mind the thing I point to in my collage above as the trolley's base frame? It's not a perfect match for anything caught in the limited pre-tsunami imagery we have, but it's intuitively close. Now more than ever I agree with being confused as heck about where the FHM parts are. I still these parts have strong signals of being the upper deck, but how what looks like the bottom frame of the trolley can be deep down, but the upper deck above water. I just have to shrug my shoulders and say WTF?!

Certainly the FHM in Unit 3 took a horrendous beating!

 

[MadderDoc]

Great photos tsutsuji, thanks!

The probe camera makes the passage way seem much longer that it is. Curiosity, seeing the hatch passage better at the moment only makes me more confused about the video therein .

OK, so using measures from the diagram, now with regained trust from those fine photos, we have this cylindrical room of the hatch clearly defined. Geometrically, it is a cylinder of height 0.90 m. and diameter 3.050 m, lying at its side, and it has a horizontal insert to produce a platform, which according to the diagram is at a height of 0.385 above the lowest part of the cylinder. And with a bit of math .. inside he hatch we'll have approximately 7 m2 of hatch inner plate to potentially look at, about 8 m2 cylindrical wall, and 1.8 m2 floor platform. Most of which, according to Tepco, we have not seen in the video, although again according to Tepco we do see parts of the platform, or floor.

Also, I am pretty sure, we see parts of the cylindrical wall as well as parts of the inner plate. Starting with the inner plate, we see it most closely in connection with the filament like artefacts. The inner plate presumably has been painted with the same paint as the rest of the room but it has degraded differently due to heat, presumably. From there we also see the inner plate meeting the wall and/or the floor (I believe we see examples of both). One might expect a similar peel off of paint at the walls and perhaps at the platform close to the inner plate, but wet corrosion there steals the show. We see a patch of something looking as cracked steel, all rusted up and wet, I believe that is on the floor, but it cannot definitely be said to be a crack, it could be just a bad wet rust problem looked upon up close. Alien looking stuff, for sure.

The slit at the floor between the platform and the inner plate produces a narrow trench, where water from a leaking flange would run into and accumulate, connected to the trough like cavity under the platform, where water would similarly accumulate. The scope does not enter the latter cavity, but it appears to have high interest in the corrosion along the slit at the inner plate. My 0.02.

Edit: corrected depth of hatch 0.4 m --> 0.9 m and affected areas.

 

[westfield]

Can you please check again and tell which page number. Because this is the same pdf where I find the picture with blue lines (page 5/19).

<snip>

. The Japanese wording for the step is 常設足場 : permanent/normally installed step/foothold.

Why yes it does have the blue marking, my apologies for the wild goose chase.
I've subsequently discovered that when the image is extracted from the PDF it has no blue marking on it.

At the risk of posting the same thing again, click on the thumb for the extracted image at it's best resolution without markings:

 

[MadderDoc]

I don't understand what the SFP cask is, can you show that photo? Is it a fuel rack? I thought they eventually put fuel in dry casks, but I didn't know there are casks in the pool but have seen this noted here and there w/o imagery.

Sorry, I meant to write 'cask area' It is a box like area in the corner of the pool, which is used for transporting 'stuff' in and out of the pool, such that the stuff is always kept either under water, or inside a cask, for radiation shielding. During the operation the cask is placed in the cask area.

The photo I refer to is this one

Did you have in mind the thing I point to in my collage above as the trolley's base frame? It's not a perfect match for anything caught in the limited pre-tsunami imagery we have, but it's intuitively close.

Edit: No, not that one, I have no idea what those fragments are, FHM parts is fair game.

The trolley deck I am talking about is that one the video you made of, the thing looked at from the concrete pump over the pool. It has several platforms, the main structure of most can be made out so-and-so, at least enough to make one doubt that they could be what we see in that position of the pool.
The waggon the machine with the grabbler is traveling on east west over the pool is however just too much out of sight in photos for that. It would have a stout structure, and it would have cut-outs for mounting wheel boxes and such underneath, all of that could have come off so there remains only the basic frame of that waggon. So I thought maybe that could be it.

 

[SpunkyMonkey]

OK, so using measures from the diagram, now with regained trust from those fine photos, we have this cylindrical room of the hatch clearly defined. Geometrically, it is a cylinder of height 0.40 m. and diameter 3.050 m, lying at its side, and it has a horizontal insert to produce a platform, which according to the diagram is at a height of 0.385 above the lowest part of the cylinder. And with a bit of math .. inside he hatch we'll have approximately 7 m2 of hatch inner plate to potentially look at, about 3.5 m2 cylindrical wall, and 0.8 m2 floor platform. Most of which, according to Tepco, we have not seen in the video, although again according to Tepco we do see parts of the platform, or floor.

Revisiting the video with the photos now in mind it's pretty clear. Obviously westfield was right that the wall is curved, but moreover that its curvature probably explains the wall / floor impression. The camera enters at the curved painted wall with the leaky flange (slime trail) in sight then probably scrolls down and left to the concrete floor, in which case the moment of footage Tepco calls floor is floor, which brings things to right.

Now I'm wonder if the 'new room' is looking back at the back side of the plug. Notice that the trough there seems to be flat and the 'change of scene' could be the camera quickly panning 180˚. That trough is not the slime trail.

EDIT: or the 'new room' might be looking almost straight up toward the hatch-door seam. Just not sure.

 

[tsutsuji]

I've subsequently discovered that when the image is extracted from the PDF it has no blue marking on it.

Thanks for solving the mystery.

it is a cylinder of height 0.40 m. and diameter 3.050 m,

Does that mean that the x and y-axis scales are different ?

Also on the other diagram here : http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120419_03-e.pdf the grey part seems to be about one third of the diameter (it looks like 1 m instead of 0.40 m). Don't you think it could be "900" mm (0.90 m) instead of 0.40 ?

 

[westfield]

<snip>

During the operation the cask is placed in the cask area.

The photo I refer to is this one
http://192.168.168.11/daiichigrab/unit3/f1-27.jpg

<snip>.

MadderDoc could you check that Cask area image link - it's not working for me and it appears to point to a private IP address range.

 

[Rive]

Still about the shield plug video: the spherical distortion and the shaking makes it a mess. After removing them, it's much more better (the result is under it's way up to the youtube). I think the rusty-wet part is where the internal steel door meets its frame. The falling paint (?) chips are removed from the steel door.

Ps: the video is available here:

At 1:09 the cam enters the circular area of the hatch, and around 1:13 it bangs to the steel door and stops moving at that direction. Around 1:20 the door and frame fitting can be seen first time on the upper-left corner: the concrete there has a strange bluish colour, maybe becouse of the temperature?

Around 1:25 the cam turning and sliding down on the circular part. At 1:55 it's 'climbing' upward on the door: you can see that the upper part of the image is moving strange: it's because the upper part is actually the vertical door, while a lower parts are the almost horizontal part of the circular opening. The deshaker does not handles well when the different parts of the image has different relative speeds.

Around 2:20 the cam is moved upward, facing right and checking the fitting between the door and the frame. This is the part when the small chips flying.

After that not much left: the floor with wet parts can be seen for a moment as the cam is pulled out. Then the run for the low dose.

I think that's it, more or less.

Ps.: it's worth to watch the video at highest resolution and full screen.

 

[MadderDoc]

MadderDoc could you check that Cask area image link - it's not working for me and it appears to point to a private IP address range.

Right. Here it comes:

 

[westfield]

Here's a collage from <snip>
I see what I think may be railing with metal fencing from the trolley, as pointed to on the right.

<snip>. What a mess to figure out!

Re - the mesh you mention - While it's all over the place in the SFP -
given that we do know we are looking at the end of the "Catwalk" that runs along the northern length of the FHM bridge it may be more likely it's mesh from the "catwalk" rather than the FHM proper, the trolley part.

I look at it as the FHM & the FHM bridge as I'm not familiar with what they are called.
They probably have cute nicknames in the business.

I need to look at that clip again - I've only looked at the truss\driveshaft so far.

 

[westfield]

Right. Here it comes:

<image snipped>

Is that the right image? I don't see a cask loading area there. Great piccy though.

Here's a picture of one prepared earlier by tcups (not a fukushima one)

Or here in the SE corner of the pool if this was Unit 3

 

[MadderDoc]

<..> Don't you think it could be "900" mm (0.90 m) instead of 0.40 ?

You are absolutely right. Thank you.

 

[MadderDoc]

Or here in the SE corner of the pool if this was Unit 3
http://s1185.photobucket.com/albums/z360/fukuwest/misc/?action=view&current=1312012042605_28_05.jpg

Yes, 'tis, but that is not where the cask area is.

I have attached a marked up version of that other photo, which I believe is pointed along the west wall of the SFP3 towards its NW corner. Marked up is the outline of what I believe is the gate to the cask area. My clue was the horizontal X structure at its bottom which I see as the cask support. X always marks the spot :-)

It got clinched only recently, when we were told in no uncertain terms by Tepco that the cask area is in the NW corner -- which was where I had this photo figured out to be from, from combining information from other photos of the pool taken during the MOX refueling & a previous photo tour.

 

[SpunkyMonkey]

Re - the mesh you mention - While it's all over the place in the SFP -
given that we do know we are looking at the end of the "Catwalk" that runs along the northern length of the FHM bridge it may be more likely it's mesh from the "catwalk" rather than the FHM proper, the trolley part.

The mesh is very close to the catwalk-railing screen we see on Unit-2 that you posted. But I don't see the same screen on the U3 crane except possibly on the trolley as I showed. Perhaps there are photos that show that mesh screening along the U3 catwalk?

Where is this mesh all over the SFP? I don't recall seeing it before.

The trolley deck I am talking about is that one the video you made of, the thing looked at from the concrete pump over the pool. It has several platforms, the main structure of most can be made out so-and-so, at least enough to make one doubt that they could be what we see in that position of the pool.

Sure it could be a lower deck of the trolley, but I believe the contents there are shaped closer to upper-deck contents.

Sorry, had this second quote attributed to westfield.

 

[MadderDoc]

<..>
Any ideas on what's the large flat object that's smashed down across the crane's bridge?

No, but it has two features which may aid an ID. Along its top, which is well sprinkled with rubble, can be seen three regular cylindrical shapes at regular intervals (wheel pins is my first impression, but those are not always right). Also at the top, but on the side of the object that is facing the camera, there is a regular pattern bright/dark/bright /dark etcetera . The dark fields could represent just cavity in the dark, but they could also be fair dinkum darker surface fields. Considering the regularity the object displays it is not likely a chunk of the wall.

closeup to top of object:

from the distance, and at a different angle:

 

[MadderDoc]

Still about the shield plug video: the spherical distortion and the shaking makes it a mess. After removing them, it's much more better (the result is under it's way up to the youtube).<..>
Ps: the video is available here:

Thank you, you done a fine job there, it so much less straining to eye and brain.

<..> the concrete there has a strange bluish colour, maybe becouse of the temperature?

I think it could be blue pigment from the peeled off paint. Some blue pigments are surprisingly resistant to harsh conditions, including high temperatures. I think we see several signs of a previously applied blue layer of paint on surfaces of the room.

Ps.: it's worth to watch the video at highest resolution and full screen.

Yes indeed, and thank you again.

 

[SpunkyMonkey]

No, but it has two features which may aid an ID. Along its top, which is well sprinkled with rubble, can be seen three regular cylindrical shapes at regular intervals (wheel pins is my first impression, but those are not always right). Also at the top, but on the side of the object that is facing the camera, there is a regular pattern bright/dark/bright /dark etcetera . The dark fields could represent just cavity in the dark, but they could also be fair dinkum darker surface fields. Considering the regularity the object displays it is not likely a chunk of the wall.

Nice images, you can really bring out the details! Right, I don't think this is a wall. I have to say the easiest thing to guess it is is what was on top of the bridge span it is rather on top of now, the trolley. But were there enough trolleys to account for all them that I'm seeing, lol!

Though as you note the trolley had a couple levels, but if that big object is the lower level and the object I suspect is the upper level actually is the upper deck, then it seems maybe they were torn apart. As odd as that sounds, I don't know what to expect at this point. The bridge is in much worse shape than I'd have expected. And how about the crane's ladder entangled with a roof girder! That mess is like a surreal bad dream!

Still about the shield plug video: the spherical distortion and the shaking makes it a mess. After removing them, it's much more better (the result is under it's way up to the youtube). I think the rusty-wet part is where the internal steel door meets its frame. The falling paint (?) chips are removed from the steel door.

Ps: the video is available here:

Nice, thanks for posting! It gives a better feeling for the actual structures as you enter the curved area.

At 1:55 it's 'climbing' upward on the door: you can see that the upper part of the image is moving strange: it's because the upper part is actually the vertical door, while a lower parts are the almost horizontal part of the circular opening.

Exactly! That's what I was trying to describe before, that the camera there is in a 'corner', at the bottom of the screen is a surface that's 90˚ to the surface on top of the screen, and the 'slime trail' is in the corner of these two surfaces. It's just an impression, and it seems stronger in your deshaked video.

 

[westfield]

Yes, 'tis, but that is not where the cask area is.

I didn't phrase that very well. I was saying that IF that image was of U3's SFP (and not some other NPP) then it would be in the SW corner of that SFP. I wasn't neccesarily saying it is unit 3 SFP - The image is from the NHK video you linked to earlier.

I have attached a marked up version of that other photo, which I believe is pointed along the west wall of the SFP3 towards its NW corner. Marked up is the outline of what I believe is the gate to the cask area. My clue was the horizontal X structure at its bottom which I see as the cask support. X always marks the spot :-)

It got clinched only recently, when we were told in no uncertain terms by Tepco that the cask area is in the NW corner -- which was where I had this photo figured out to be from, from combining information from other photos of the pool taken during the MOX refueling & a previous photo tour.

I'm fairly sure the "X" is a reflection of the roof bracing as is the almost vertical line - with the ceiling lights reflected in it.
Maybe it's me but I still can't see anything like a cask loading area in that image.

I'll come straight out with it at my peril, I may end up looking a right wally :)
I know Tepco indicated the U3 SFP cask loading area in the NW corner of the SFP in the recent debris map.
This was a surprise to me because I was sure the only other diagram TEPCO has shown us has the cask area on the Eastern side. That diagram was published by Tepco months ago and I haven't found it again yet. Does anyone remember it or have it?

It was also a surprise to me because I've never seen any alleged image of Unit 3's SFP with the cask area in the NW or NE corner.
Are lots of alleged Unit 3 SFP images wrong, mislabelled? I don't know. I have 3 alleged U3 images showing the cask area in the SE corner.

This is what I'm trying to get to the bottom of.

Finally if U3 SFP cask area was in the NW corner where did it go, it's not a lightweight structure.

For reference Unit 4 SFP - looking to NW corner, cask loading area marked - underwater view of the cask loading area - overhead view of cask area

 

[westfield]

The mesh is very close to the catwalk-railing screen we see on Unit-2 that you posted. But I don't see the same screen on the U3 crane except possibly on the trolley as I showed. Perhaps there are photos that show that mesh screening along the U3 catwalk?

Where is this mesh all over the SFP? I don't recall seeing it before.

Sure it could be a lower deck of the trolley, but I believe the contents there are shaped closer to upper-deck contents.

Sorry, had this second quote attributed to westfield.

Sorry, I said "all over the SFP" but meant all over the FHM, not literally though. - The mesh is on the lower half of all personel walkways and in some areas as machinery guard, there's a lot of it - we don't see a lot of it because images of the northern side of the U3 FHM\Bridge are few and far between.

 

[MadderDoc]

Improving the models (was Re: Japan Earthquake..)

Some interesting stuff there.
This one deals with how to improve modelling to establish core damage etc.
http://www.tepco.co.jp/en/nu/fukushima-np/roadmap/images/m120314_02-e.pdf

This appears to be saying that the model, latest ver., has been tailored to simulate the RPV pressure, and because of that, RPV pressure is well simulated.

 

[SteveElbows]

This appears to be saying that the model, latest ver., has been tailored to simulate the RPV pressure, and because of that, RPV pressure is well simulated.

My understanding of this, based on the limited info available, is that the 2nd graph is a much better fit than the first one because they have now taken account of the fact that operators were manually controlling the HPCI in a manner different to the original assumption. I think I read more about this mode of operation somewhere, will have a look when I find time.

 

[SteveElbows]

My understanding of this, based on the limited info available, is that the 2nd graph is a much better fit than the first one because they have now taken account of the fact that operators were manually controlling the HPCI in a manner different to the original assumption. I think I read more about this mode of operation somewhere, will have a look when I find time.

OK pages 14 to 19 of this document should shed light on their thinking and modified analysis.

http://210.250.7.21/en/press/corp-com/release/betu11_e/images/111222e16.pdf

So a combination of the way the HPCI was operated (e.g. flow rate), other spraying operations, and ruling out the idea of steam leak from HPCI caused them to change their analysis.

 

[westfield]

No, but it has two features which may aid an ID. Along its top, which is well sprinkled with rubble, can be seen three regular cylindrical shapes at regular intervals (wheel pins is my first impression, but those are not always right). Also at the top, but on the side of the object that is facing the camera, there is a regular pattern bright/dark/bright /dark etcetera . The dark fields could represent just cavity in the dark, but they could also be fair dinkum darker surface fields. Considering the regularity the object displays it is not likely a chunk of the wall.

closeup to top of object:

from the distance, and at a different angle:

If you imagine this on the other side of the FHM and with the "stops" torn off it's not a bad match to this.
We can't see if there's a middle wheel in this image which would have helped.

 

[MadderDoc]

My understanding of this, based on the limited info available, is that the 2nd graph is a much better fit than the first one because they have now taken account of the fact that operators were manually controlling the HPCI in a manner different to the original assumption. I think I read more about this mode of operation somewhere, will have a look when I find time.

My understanding it that whereas the model includes code to model behaviour during automatic HPCI operation, it has no code for manual operation. So, during the period of manual operation of the HPCI, for which the modellers have no model, the code is just set to roughly reproduce the actual RPV pressure measurements. Of course one can then say that the 'RPV pressure is well simulated' during that period, but it does seem a bit too pretentious for my taste, and is liable to leave the false impression that the model has been improved by the exercise.

 

[SpunkyMonkey]

There appears to be some large heavy-metal debris in the NE quadrant of SFP3 (the video is motion stabilized and so the frame moves):

"www.youtube.com/watch?v=95mB2B65ZVM&hd=1" ​

This is an area close to the object I suspect is the trolley's upper deck. One only gets the briefest glimpse, and for the life of me I can't make out what those objects are. But I'm sure I can see machined shapes, especially on a piece of debris at approximately 4 o'clock if you imagine a clock face over the video screen. The brief view is clear enough that someone who worked there or who just saw it in a photo could probably recognize it.

Here's a video clip where I attempt to outline some of these heavy-metal objects so you can see which objects I refer to.

 

[MadderDoc]

OK pages 14 to 19 of this document should shed light on their thinking and modified analysis.

http://210.250.7.21/en/press/corp-com/release/betu11_e/images/111222e16.pdf

So a combination of the way the HPCI was operated (e.g. flow rate), other spraying operations, and ruling out the idea of steam leak from HPCI caused them to change their analysis.

Yes, thank you. What I get, of what they did to their analysis is that "the quantity of water injected by the HPCI system was adjusted through the test line to prevent unnecessary halt of the HPCI system due to the reactor water level (L-8)". Which seems fair enough, seeing that was their narrative of what the operator was trying to achieve. The rub, of course, lies in the lack of definition in 'enough to prevent unnecessary halt'. How much is that? Anyway, in the same document we see the result of that flow adjustment in this figure:

Funny how the adjustment of flow needed under the stated criterium: "what it takes to prevent unnecessary halt of the HPCI system due to the reactor water level (L-8)" seems to be identical to the adjustment that would have been needed under the criterium "what it takes to bring the modeled RPV pressure down to the level suggested by the measured data".

 

[SteveElbows]

My understanding it that whereas the model includes code to model behaviour during automatic HPCI operation, it has no code for manual operation. So, during the period of manual operation of the HPCI, for which the modellers have no model, the code is just set to roughly reproduce the actual RPV pressure measurements. Of course one can then say that the 'RPV pressure is well simulated' during that period, but it does seem a bit too pretentious for my taste, and is liable to leave the false impression that the model has been improved by the exercise.

I feel you have made unsafe assumptions here. I do not claim that their model is perfect, and obviously they are looking to change code & variables so that the output of the model more closely matches the actual data. But I don't think they just threw away proper code and fudged stuff to give suitable results, I find it more likely that they did actually make changes to the model or fed a more sophisticated set of data into the model.

Although they are obviously interested in getting the model analysis to match the measured data, I believe their priority is to be able to use the model to test assumptions about the state of various facilities at the plant. They would also like to make the model better for future use. Neither of these things is well served by simply fudging stuff to get a match, as opposed to improving the code used by the model or the data that's fed into it.

We see an example of this later in the document, when they move on to issues of containment pressure of reactor 3. They still can't get their model to match the measured data, so they have to think about what other factors may be involved, with the hope of modelling these factors later on and getting better results. They did not simply fudge things at this point to give a nice clean match between model and measured data.

In another document mentioned recently in this thread, we see that they are looking at improving the core melt model, since they know that the model is vastly oversimplified compared to the realities inside the reactor pressure vessel. But since they lack much in the way of real data about the state of the cores, this is not going to be so easy. I already ranted in the past at how their model seems to give wrong results in terms of RPV damage occurring/time of this occurring, and I speculated that this may be because they have made wrong assumptions about how much decay heat and how much water cooling was available at key points for reactors 2 and probably 3. But until they actually have far more detailed evidence that state of melted fuel & RPV is much worse than model results, I doubt they really know how far away their model is from reality.

 

[clancy688]

I already ranted in the past at how their model seems to give wrong results in terms of RPV damage occurring/time of this occurring, and I speculated that this may be because they have made wrong assumptions about how much decay heat and how much water cooling was available at key points for reactors 2 and probably 3. But until they actually have far more detailed evidence that state of melted fuel & RPV is much worse than model results, I doubt they really know how far away their model is from reality.

I think they've come to the same conclusions themselves. To quote from the recently posted document: "However, calculation results show no damage on RPV."
But on the last page they seem to be convinced that there's at least some of the fuel left the RPV.
So I'd interpret the "However" phrase as "There may be something wrong with the model since it doesn't show any RPV damages, but we're convinced there are."
Of course I can be mistaken, but that's at least what it sounds like to me. Moreover, you all know the radiation readings from the Unit 2 PCV. Is it possible that there are such high readings if there's absolutely no fuel escape? That should be obvious to TEPCO as well.

 

[MadderDoc]

I feel you have made unsafe assumptions here. I do not claim that their model is perfect, and obviously they are looking to change code & variables so that the output of the model more closely matches the actual data. But I don't think they just threw away proper code and fudged stuff to give suitable results, I find it more likely that they did actually make changes to the model or fed a more sophisticated set of data into the model.

Although they are obviously interested in getting the model analysis to match the measured data, I believe their priority is to be able to use the model to test assumptions about the state of various facilities at the plant. They would also like to make the model better for future use.

Perhaps. In the present case, though, they did nothing to the model, only fed new data to it. Perhaps I am too cynical in thinking that it is not coincidental that that made the model match the measured data to perfection. Perhaps they truly just fed the data they assumed to be most likely, in an effort to validate the model and hoorah, it came out exactly reproducing the measured data, the modeller's wet dream.

Neither of these things is well served by simply fudging stuff to get a match, as opposed to improving the code used by the model or the data that's fed into it.

We see an example of this later in the document, when they move on to issues of containment pressure of reactor 3. They still can't get their model to match the measured data, so they have to think about what other factors may be involved, with the hope of modelling these factors later on and getting better results.

Yeah, right. :-) And in that process all discrepancies are equal but some discrepancies are more equal than others. In their latest model of the PCV pressure of unit 3, I see they have meticulously made assumptions of S/C vent operations matching every remaining unexplained significant change in pressure trends -- except the precipitous pressure drop at the time of the explosion, and the curious incident of the S/C vent some hours earlier.

They also seem to have gotten into trouble by assuming a lower decay heat than in previous attempt. Now the model undershoots, appears insensitive to interventions, and cannot reproduce the measured pressure increase rates in the PCV.

Although this latest version produces a much poorer fit than the previous attempt they seem quite happywith it, except they have one outstanding issue, an unexplained pressure increase in the initial phase under RCIC operation, which they seem to speculate might be fixable by assuming S/C stratification.

 

[MadderDoc]

There appears to be some large heavy-metal debris in the NE quadrant of SFP3 (the video is motion stabilized and so the frame moves):

"www.youtube.com/watch?v=95mB2B65ZVM&hd=1" ​

This is an area close to the object I suspect is the trolley's upper deck. One only gets the briefest glimpse, and for the life of me I can't make out what those objects are. But I'm sure I can see machined shapes, especially on a piece of debris at approximately 4 o'clock if you imagine a clock face over the video screen. The brief view is clear enough that someone who worked there or who just saw it in a photo could probably recognize it.

Here's a video clip where I attempt to outline some of these heavy-metal objects so you can see which objects I refer to.

I think those are parts of the roof covering, they seem to have been caught above the level of the pool, and be of low thickness. You can see them from another angle later in the video. Straight underneath them there are more parts of the FHM than you can point a stick at, here, there and everywhere there are glimpses of cross beamed greenish structures through all that stuff hunkering above. In a way it was predictable all along that there would big objects to find in the east end of the pool. Otherwise, what kept us from seeing the water surface, what dampened the heat signature. Certainly Tepco would have a pretty good picture of what is in the east end of the pool, but we have to date not been let in on it. Maybe they think we are not interested in that end of the pool? But we are, we are.

 

[MadderDoc]

If you imagine this on the other side of the FHM and with the "stops" torn off it's not a bad match to this.
We can't see if there's a middle wheel in this image which would have helped.

Right, it is not a bad match at all. It would be reasonable to think the other side is similar but that side is well hidden in all photos. Anyone got drawings of a classical Toshiba FHM? ;.)

We should also be cautious to accept those tree wheel pins, and we can certainly not exclude that e.g. the one of the middle is just a piece of rubble caught in our minds fabrication. Maybe they all are? It is difficult to not see pins after first having seen them, though.

 

[SpunkyMonkey]

I think those are parts of the roof covering, they seem to have been caught above the level of the pool, and be of low thickness. You can see them from another angle later in the video. Straight underneath them there are more parts of the FHM than you can point a stick at,

Right, but I'm referring to those underneath objects, which are clearly not roof girders or sheathing strips. I outline them here. The one object at about 4 o'clock could be identifiable had we the right pre-tsunami photo or an FHM expert on hand.

In a way it was predictable all along that there would big objects to find in the east end of the pool. Otherwise, what kept us from seeing the water surface, what dampened the heat signature.

Lol, that's exactly what I said on another forum, that in hindsight it should have been obvious that something large (and what else if not the FHM) is filling the pool given that something obscures the full heat signature and that roof debris 'floats' over the western half of the pool as can be seen with a "www.youtube.com/watch?v=zOthckEvROk#t=4s" . All that debris couldn't be floating on water, lol.

 

[SteveElbows]

I think they've come to the same conclusions themselves. To quote from the recently posted document: "However, calculation results show no damage on RPV."
But on the last page they seem to be convinced that there's at least some of the fuel left the RPV.
So I'd interpret the "However" phrase as "There may be something wrong with the model since it doesn't show any RPV damages, but we're convinced there are."
Of course I can be mistaken, but that's at least what it sounds like to me. Moreover, you all know the radiation readings from the Unit 2 PCV. Is it possible that there are such high readings if there's absolutely no fuel escape? That should be obvious to TEPCO as well.

I agree, I am sure they already thought for a long time that the model results are wrong on this, as soon as evidence came out which made no RPV damage seem implausible.

However in the early days they tried to stick to models that didn't show much damage at 2 & 3, and talk as if this was real, and this formed part of a wider picture of positivity which damaged TEPCOs credibility by being so out of whack with reality. Gradually other peoples analysis along with new facts from the ground meant they had to come onboard with public conclusions that the cores were worse than first indicated.

At this point I think they would still like to lean towards more positive assumptions until evidence kills such assumptions, but they would probably like these core melt models to show something more realistic. But how far to go? I think its fair enough that they have assumed there is still some fuel in the RPV based on temperature of RPV as water spraying from several sources was adjusted over time, but I would not care to estimate quite what percentage of the core remains there or anywhere else. They did not avoid admitting that all of reactor 1s fuel melted according to their model, but when it comes to a question of percentages in the other reactors I am not sure I would trust estimates at this point anyway, so I don't know what they should aim for if they are tinkering with input parameters.

Certainly I don't find it easy to talk much more about these models or assumptions without actually being able to see the models in detail themselves, or even run them with different data. I moan about the potential for decay heat & water injection rates & time periods for reactor 2 to be all wrong and to have resulted in the bad model results, but without actually being able to adjust some of the data to compensate for the potential flaws I speculated about, and see what the results are, I cannot test my ideas properly. Id love to know for example how much they would need to tamper with the timescale for how long they assume water was not removing heat from reactor 2 for, to get a result that indicated say 50% fuel melted and left the RPV.

 

[MadderDoc]

Certainly I don't find it easy to talk much more about these models or assumptions without actually being able to see the models in detail themselves, or even run them with different data. I moan about the potential for decay heat & water injection rates & time periods for reactor 2 to be all wrong and to have resulted in the bad model results, but without actually being able to adjust some of the data to compensate for the potential flaws I speculated about, and see what the results are, I cannot test my ideas properly. Id love to know for example how much they would need to tamper with the timescale for how long they assume water was not removing heat from reactor 2 for, to get a result that indicated say 50% fuel melted and left the RPV.

Now I doubt that timescale would be a parameter for the model. I should think to produce RPV damage one would have to change other parameters or change the set of assumptions such as to affect that time scale.

My basic issue with the Unit 2 model is that it does not assume RPV damage at about midnight between March 14th and March 15th, although RPV damage is suggested by the data: - we see the RPV pressure fluctuations come to a final halt, while drywell pressure and cams increase suddenly.

Hence the model leaves this abrupt D/W pressure increase unexplained -- in the previous, as well as in the latest version of the model. In the previous version the model didn't produce a pressure increase at all, however the latest version has in some unknown way been made to produce it.

As regards the sudden D/W pressure drop in the morning of March 15th, the latest version now assumes that the D/W pressure dropped due to D/W failure, which seems to be a reasonable assumption.

 

[SpunkyMonkey]

Btw, it's curious to note how perfectly the model of a Mark I meltdown by Ott et al happens to correspond to Unit 3's RPV pressure data:

After I graphed this remarkable correspondence I found that this sudden RPV pressure drop at Unit 3 shown above was attributed to manual activation of a pressure relief valve, so I dropped this graphic from my argument for a primary-containment explosion.

Would there be any way to falsify Tepco's claim that this perfect replication of the predicted Mark I melt-through RPV pressure data was just a coincidental artifact of manual operations?

For reference:

 

[zapperzero]

I don't see how there could be a melt-through that does not dramatically affect the pressure in the drywell.

 

[SteveElbows]

Now I doubt that timescale would be a parameter for the model. I should think to produce RPV damage one would have to change other parameters or change the set of assumptions such as to affect that time scale.

I wasn't meaning to imply that I thought there was one time parameter they would need to change.

I was talking about how I consider that a possible major reason why their core melt analysis is wrong, is that they have not used an appropriate timescale when considering how much decay heat was not dealt with by injected water. I ranted about some of the detail of this some weeks ago but cannot find my post right now, I shall dig up the relevant chart and then talk more about what I mean.

 

[MadderDoc]

I don't see how there could be a melt-through that does not dramatically affect the pressure in the drywell.

My thought too. That would force us to reject melt through, and accept as per default that the RPV pressure dropped due to the opening of a SRV, since the pcv pressure did increase but not drastically. However, a complicating factor is that primary containment vessel venting was initiated in close connection to the observed depressuring of the reactor vessel, which would have suppressed the pcv pressure increase.

 

[SteveElbows]

OK I found my original reactor 2 decay heat rant:

https://www.physicsforums.com/showthread.php?p=3837167

Since I didn't get much feedback about this at the time, and my post was rather long and perhaps badly worded, I will make another attempt now.

I have paid more attention to the situation at reactor 2 than reactor 3 so that's the one I pick on for this example. Please see the attached graphs which come from http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_07-e.pdf

So my issue is with the timescale used to calculate the decay heat that needed to be dealt with at reactor 2 during the time that water level was dropping and alternative water injection could not be confirmed.

For the start time they used 13:25 on the 14th. The water level actually started to fall before this time, 13:25 is when they officially declared that there was a new incident that required notification according to the regulation, the incident being a drop in coolant level. Water level actually started dropping at 12:00. I suppose so long as the figure they used for amount of water in the reactor actually matched what was in the reactor at 13:25, and not the higher amount that was present at 12:00 or before, then this issue shouldn't be a problem. But seeing as how the amount of heat removal by water they have used in the second graph is identical for reactors 2 & 3, I have some doubts as to whether they have done this stuff correctly. I will do some more checking into the detail of this.

My bigger issue is with the end time. I went into detail on this in my previous post about the issue, but basically I have concerns that they chose the earliest possible moment for water injection beginning, and seem to have assumed that from this moment onwards there was enough water being injected to cover all heat produced from this time onwards. Given the numerous issues they encountered when injecting water at the reactor, especially in the first hours after starting this operation, I have big concerns that they are missing a load of uncooled decay heat from their model, and that's why its producing inaccurate results in regard to RPV damage etc. Its no wonder their model shows this, seeing as how the 2nd graph shows that decay heat was more than dealt with by the water that was in the reactor, leading to all of the water that surrounded the fuel being used up, but some being left below the bottom of the fuel.

 

[MadderDoc]

OK I found my original reactor 2 decay heat rant:

https://www.physicsforums.com/showthread.php?p=3837167

Since I didn't get much feedback about this at the time, and my post was rather long and perhaps badly worded, I will make another attempt now.

I have paid more attention to the situation at reactor 2 than reactor 3 so that's the one I pick on for this example. Please see the attached graphs which come from http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_111130_07-e.pdf

So my issue is with the timescale used to calculate the decay heat that needed to be dealt with at reactor 2 during the time that water level was dropping and alternative water injection could not be confirmed.

For the start time they used 13:25 on the 14th. The water level actually started to fall before this time, 13:25 is when they officially declared that there was a new incident that required notification according to the regulation, the incident being a drop in coolant level. Water level actually started dropping at 12:00. I suppose so long as the figure they used for amount of water in the reactor actually matched what was in the reactor at 13:25, and not the higher amount that was present at 12:00 or before, then this issue shouldn't be a problem. But seeing as how the amount of heat removal by water they have used in the second graph is identical for reactors 2 & 3, I have some doubts as to whether they have done this stuff correctly. I will do some more checking into the detail of this.

My bigger issue is with the end time. I went into detail on this in my previous post about the issue, but basically I have concerns that they chose the earliest possible moment for water injection beginning, and seem to have assumed that from this moment onwards there was enough water being injected to cover all heat produced from this time onwards. Given the numerous issues they encountered when injecting water at the reactor, especially in the first hours after starting this operation, I have big concerns that they are missing a load of uncooled decay heat from their model, and that's why its producing inaccurate results in regard to RPV damage etc. Its no wonder their model shows this, seeing as how the 2nd graph shows that decay heat was more than dealt with by the water that was in the reactor, leading to all of the water that surrounded the fuel being used up, but some being left below the bottom of the fuel.

Sorry I did not pay attention when you first raised the issue. As regards evaluating the potential for fuel damage this method is of course deeply flawed. Standing alone it looks like a typical piece of corporate science, suggesting, albeit not claiming a particular conclusion that does not quite follow from the information presented. The question here is of course: so what happened after?

I think the model we were looking at would be highly sensitive to the assumptions made as to how much water reached the core right after the rpv was depressurised, and sea water injection was being attempted. A few m3 here and there could mean the difference between having a melt-down and having a melt-through. In the latest version of the model which has no rpv damage, adjustments seem to have been made to produce a subtly higher water level in the RPV during those fateful hours.

 

[MadderDoc]

SRV question

I read somewhere in a Fukushima accident analysis, that a manually opened safety relief valve would shut due to the sheer weight of the valve, once the pressure drops below about 0.3-0.4 MPa.

What status would that leave the valve in? Would it just reopen on renewed pressure build-up, or would it need another manual actuation to become open ?

 

[SpunkyMonkey]

My thought too. That would force us to reject melt through, and accept as per default that the RPV pressure dropped due to the opening of a SRV, since the pcv pressure did increase but not drastically. However, a complicating factor is that primary containment vessel venting was initiated in close connection to the observed depressuring of the reactor vessel, which would have suppressed the pcv pressure increase.

Though the Ott et al melt-through model I just posted says RPV pressure drops to equalize with the containment. Isn't that's pretty much what happened (albeit containment pressure was a bit higher thereafter)?

When the SRV was opened, was it never closed again? If so, is that usual as a risk-mitigation strategy under the circumstances? Wouldn't it just be opened for a period? Is there a standard protocol for this action? RPV pressure never rebounded, but was like a flat tire forever thereafter.

 

[MadderDoc]

Though the Ott et al melt-through model I just posted says RPV pressure drops to equalize with the containment. Isn't that's pretty much what happened (albeit containment pressure was a bit higher thereafter)?

I see what you mean, yes, but I think that effect could be produced also by a leak in the reactor above the fuel level.

When the SRV was opened, was it never closed again? If so, is that usual as a risk-mitigation strategy under the circumstances? Wouldn't it just be opened for a period? Is there a standard protocol for this action? RPV pressure never rebounded, but was like a flat tire forever thereafter.

Yes, it seems we ended up eventually with a RPV that couldn't build up pressure, however, when that state was reached is not immediately clear, hence my interest in the inherent properties of a manually opened SRV.