Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[jim hardy]

Yet, in na'r an official document can you find reference to the explosion in unit 3, without being told implicitly that nothing but the possibility of a hydrogen explosion --an 'ex-ex-vessel' hydrogen explosion so to speak -- in the upper floors of the building has been found worth considering, but really hasn't, while it is all just 'believed to be' or 'assumed to be' what happened, nothing more, nothing less, and nothing is learned.

Are you hinting that what has not been said might speak volumes?

When the cameras get to the area of PCV flange then on to RPV upper and lower heads it'll end a lot of speculation.

 

[SpunkyMonkey]

Spunky & Madder I may be wrong but I'm fairly sure that once you get past roughly halfway into the plug penetration it transitions from square opening to round - so there are likely no corners \ floor \ walls once you are in there at the PCV hatch.

Notice at the last corner before the slime trail, the wall looks pretty flat. But maybe you're right and it goes to a circular passage there, I'm not 100% sure either way.

Update: consistent with your theory, I think the slime trail may be seen to curve upward in the first frames where we get a quick look down its length. Or that might be camera 'fish-bowl' distortion.

I may be wrong again but these do look quite like a PCV hatch and flange.
Looking Straight at hatch, along "wall" at hatch. across hatch to wall ---

I'm tempted to agree, and as such in viewing the 'hotspot' we're not really looking at a new place. I'm thinking maybe the burst of ccd snow is caused by the camera being closer to an unvisualized floor were highly contaminated water has pooled. That burst of snow has to mean something unique me thinks.

 

[MadderDoc]

Gentlemen, it is such a pleasure working with you. On reviewing the video using autogain, as inspired by Spunky's wonderfully improved video, and using westfield's directives along the route, I get the timeline below of the camera position relative to landmarks of the cavity wall.

Position A is at the outside wall of the concrete shield, B is at the first notch on the wall, C is a small notch in the wall which I would think is close to as far as the plug goes, when it is fully inserted. Behind C and deeper into the void, we are inside the room that was behind the plug in its normal position. At D not far from C, the room seems to narrow in considerably, which might mean we are now inside the cylindrical part of the hatch construction, and we could potentially now be seeing the lid of the hatch at some time during the approximately 2 minute sequence which follows, until the camera finally exits.

Entry times:
A: 0:54.4
B: 0:58.4
C: 1.07.8
D: 1.09.0

Exit times
D: 3:05.3
C: 3:08.0
B: 3:19.0
A: 3:31.2

To westfield: I suggest there might be a bottom insert in the metal portion of the hatch, such as to produce a horizontal floor inside it. I imagine that could be practical for equipment loading and unloading through the hatch, and the previously posted photo from that METI/industry document of an open hatch seen from inside of the PCV appears to have such an insert.

To Spunky: looking at these streaking particles, there are times I get this weird impression that they move as being taken by a wind, is it only my brain doing this, is it some kind of illusion, or is there a draught at the floor in that room?

To both of you: Could that yucky rusty patch be on such presumed horizontal floor inside the metal portion of the hatch?. I can't get away from Tepco's statement that the water is seen on a floor.

 

[MadderDoc]

Are you hinting that what has not been said might speak volumes?

In a way, maybe, similar to the curious incident of the dog (it didn't bark), in the short story Silver Blaze.

("Is there any point to which you would wish to draw my attention?" "To the curious incident of the dog in the night-time." "The dog did nothing in the night-time." "That was the curious incident," remarked Sherlock Holmes.)

When the cameras get to the area of PCV flange then on to RPV upper and lower heads it'll end a lot of speculation.

Well there's some way to go to get there yet, but they do seem to be building a platform, which could be suitable for such attempts.

(photo cropped from: http://www.sdnyw.cn/news/edit/UploadFile1/201231292418951.jpg)

The photo above, btw, establishes certainty about what is the dark shape we have seen in poorer photos, at the east side of the equipment pool, at the close end to the reactor area. It is not anything but a big hole in the fifth floor, apparently blown upwards from below. Previous photos from above would then suggest that the damage below goes as far as to the 3rd floor. The hole in the floor would seem to be a likely candidate for the apparent source of the black smoke event on March 21st, one week after the explosion. No close up photos have been published of the possibly related http://192.168.168.11/tepcowebcam/20110323180100.jpg

 

[MadderDoc]

<..>Could that yucky rusty patch be on such presumed horizontal floor inside the metal portion of the hatch?. I can't get away from Tepco's statement that the water is seen on a floor.

I've thought about, looked a bit more on this video, and perhaps the indications of Tepco matters less as regards which surface this water is seen, than as regards which type of damage is indicated. I may have just got a false impression of what Tepco intended to convey. Although I am still not quite sure what I see in the video, it seems a far cry from just a puddle in some rails, or a leaking gasket. I do understand the video might have given some pause for thought.

 

[MadderDoc]

You make a valid point. But how do you eat an elephant? One bite at a time.

Yeah, always. But how do you roach it... :-)

OK, water-filling to the fifth floor of these tormented structures. Plan B?

 

[SteveElbows]

For now I'm keeping an open mind on the reactor 3 equipment hatch video, since issues of scale as well as orientation play tricks on me.

Meanwhile there are a couple of good images of people visiting the upper floor of reactor 4 here, including the covered fuel pool and a view of the top of the reactor well.

http://photo.tepco.co.jp/library/120423_01/120423_03.jpg

http://photo.tepco.co.jp/library/120423_01/120423_04.jpg

 

[SteveElbows]

The photo above, btw, establishes certainty about what is the dark shape we have seen in poorer photos, at the east side of the equipment pool, at the close end to the reactor area. It is not anything but a big hole in the fifth floor, apparently blown upwards from below. Previous photos from above would then suggest that the damage below goes as far as to the 3rd floor.

The thing that was described a long time ago as 'snaggle tooth' and that I spent a while on debunking the idea that it was the top of containment?

From that photo I am not sure as it is a hole, it could be, but it could also be something that has melted/burnt. I believe there is a little bit of melted black substance hanging off the roof beams that are above this area, not sure if its related.

As for whether it has anything to do with the black smoke event, it might, but there isn't much that let's us take this idea much further.

edited to add picture where black stuff on roof beam can be made out.

 

[Rive]

... a big hole in the fifth floor, apparently blown upwards from below. Previous photos from above would then suggest that the damage below goes as far as to the 3rd floor.

We have some floorplans from U2 survey maps, so maybe we can find out something about the affected areas.

 

[westfield]

<snip>To westfield: I suggest there might be a bottom insert in the metal portion of the hatch, such as to produce a horizontal floor inside it. I imagine that could be practical for equipment loading and unloading through the hatch, and the previously posted photo from that METI/industry document of an open hatch seen from inside of the PCV appears to have such an insert.

<snip>

To both of you: Could that yucky rusty patch be on such presumed horizontal floor inside the metal portion of the hatch?. I can't get away from Tepco's statement that the water is seen on a floor.

When any of these PCV hatches are open I would be very surprised if there was not always some sort of cover to protect at least the seal seat on the flange if not the whole flange from damage and as you say, to make the hatch trafficable. We see such "bridges" in the Browns Ferry & the Onagawa equipment hatch images and in those it's clear the "bridges" would be removed when the PCV hatch is closed out.

Additionally, I don't think anything loose at all would be left in the shield plug void and I don't think there would be anything permanent that might tie or create possible interference with the concrete \ steel interface at operational temperatures.

So I'm only guessing but personally I wouldn't think there would be any sort of "step" mounted in the equipment hatch flange itself or near it. I've been reading about Onagawa NPP damage due to earthquake only. Quite eye opening.
Amongst that there is this ( taken from this report )

Onagawa PCV equipment hatch shield plug

How much it broke it's lock and moved

Shield plug movement mystery solved?

 

[HowlerMonkey]

Lots of combustible materials outside containment but within the buildings.

 

[jim hardy]

the dark shape we have seen in poorer photos,

great images guys, guess i haven't been keeping up."Snaggletooth" was a shadowy apparition in several early photos. I've seen no further hints of him since March last year.

old jim

 

[westfield]

The thing that was described a long time ago as 'snaggle tooth' and that I spent a while on debunking the idea that it was the top of containment?

From that photo I am not sure as it is a hole, it could be, but it could also be something that has melted/burnt. I believe there is a little bit of melted black substance hanging off the roof beams that are above this area, not sure if its related.

As for whether it has anything to do with the black smoke event, it might, but there isn't much that let's us take this idea much further.

edited to add picture where black stuff on roof beam can be made out.

<snip>Well there's some way to go to get there yet, but they do seem to be building a platform, which could be suitable for such attempts.

<snip>The photo above, btw, establishes certainty about what is the dark shape we have seen in poorer photos, at the east side of the equipment pool, at the close end to the reactor area. It is not anything but a big hole in the fifth floor, apparently blown upwards from below. Previous photos from above would then suggest that the damage below goes as far as to the 3rd floor. <snip>

Is that one of the platforms for the demolition work in your previous post?

You mean this hole in the floor adjacent to the DS pit was uncertain? ;) (March 30 2012 image)

Steve what was the date for the "black smoke" event? As you also noticed on aerial shots sometime between the March 20th and the 24th the roof truss directly over that hole seems to have taken on a sooty appearance. Edit : I'm not referring to the black sheet of roofing membrane or whatever it is.

Around March 20th 2011, Around Mar 23 and then Mar 30.

Re damage in U3 - if you watch the recent PCV equipment hatch clip there are several glimpses of more significant disarray on FL 1 than we have seen before. It's not so tidy down there. The reason I mention that in relation to the hole in FL5 floor is I was reading an interesting report last night that included some modeling of the U3 hydrogen dispersion and subsequent deflagration. That particular modeling placed the ignition source on 1FL of U3. I will try to find the link. I didn't bother at the time because I thought it would have been posted here already. It seemed quite authoritive. It was a reprt from Nisa or METI or someone like that.Is that modelling and the first floor ignition point something new?

 

[MadderDoc]

The thing that was described a long time ago as 'snaggle tooth' and that I spent a while on debunking the idea that it was the top of containment?

From that photo I am not sure as it is a hole, it could be, but it could also be something that has melted/burnt.

Yes, that was a fair alternative explanation. What finally clinches it for me as a hole is that in the new photo I can now clearly see the bent up rebar at the far side. But already the previous best photo of the location I felt strongly suggested a hole:

(crop, color-releveled & de-distorted, from http://photo.tepco.co.jp/library/111008_1/111008_05.jpg )

I believe there is a little bit of melted black substance hanging off the roof beams that are above this area, not sure if its related.

As for whether it has anything to do with the black smoke event, it might, but there isn't much that let's us take this idea much further.<..>

Oh Steve! We can do better, we can put to rest that idea once and for all :-)
The black substance was there on those roof beams with a quite similar attire in photos from the day before the first black smoke event, so it had nothing to do with any of those.

It appears to be some flexible material, and has always had a weird 'green-metallic' look. I have no idea how it got there, but would assume it came there as a result of the explosion. It can be fairly hypothesised, seeing the way it has been apparently closely draped around the beams that it may have been shaped by heat influence, either from landing there while the beams were still hot after the explosion, or from the heat influence of the massive amounts of steam that came out of the primary containment vessel during the first couple of days after the explosion.

 

[MadderDoc]

<..>Is that modelling and the first floor ignition point something new?

It is to me, at least (drool).

 

[westfield]

It is to me, at least (drool).

ok I will trawl through my browser history and try to find the link.
Don't ruin your shirt though, it was only a one or two page summary of the modelling in amongst a lot of other summaries.

Edit : While I look for that- I don't know if this report has been posted.
I had always wondered what happened to the roller door of the Unit 3 TB.

This emergency response report has lots of interesting details of the immediate on site actions that I'd never read in other reports, such as why they drove a truck through the Turbine Building roller door.

Edit Edit : Holy C*** - what are the odds two people would post a link to the same report at virtually the same time!

 

[MadderDoc]

Perhaps relevant to some of the current topics of discussion:
(from http://icanps.go.jp/eng/120224Honbun04Eng.pdf )

"At around 14:31 that day [March 13th 2011], a high radiation level of more than 300 mSv/h was detected north of the double-entry door of the Unit 3 R/B, white haze was observed inside the double-entry door and a level of 100 mSv/h was detected south of the double-entry door."

" Since white haze filled the first floor of the Unit 3
R/B and their APDs showed high readings at that time, they evacuated from the building."

 

[MadderDoc]

ok I will trawl through my browser history and try to find the link.
Don't ruin your shirt though, it was only a one or two page summary of the modelling in amongst a lot of other summaries.

Well, I'll be happy to read it if you can find it without too much trouble. Whereas there are signs of damage just about anywhere of unit 3, this damage seems to me to be centered about the 3rd,4th and 5th floor, and the primary containment. Hum. Perhaps centered is not the right word for such widespread destruction. Anyhow, not particularly centered about the 1st floor.

 

[westfield]

Well, I'll be happy to read it if you can find it without too much trouble. Whereas there are signs of damage just about anywhere of unit 3, this damage seems to me to be centered about the 3rd,4th and 5th floor, and the primary containment. Hum. Perhaps centered is not the right word for such widespread destruction. Anyhow, not particularly centered about the 1st floor.

This is the summary report - the summary about the U3 explosion modelling is around page 69. Quite a few other things in there as well. It says the full report will be posted here at METI soon

Edit : also a few pages before that , I hadn't seen that exact radiation map of U3 of around the equipment hatch before.
Am I mistaken or was that particular reading at the U3 equipment hatch shield plug left out of the previous map?

To be honest there are so many duplicate, updated and derivative reports around I often find it difficult to keep track.
I don't know how Tsutsuji san and other dedicated posters manage to keep tabs on it.
Kudos to them.

 

[SteveElbows]

That report is rather interesting. On page 56 it says that they have a new possible explanation for slower PCV pressure rises at reactor 2 than the model predicts - that seawater getting into the S/C room contributed to the slower rise of pressure!

 

[MadderDoc]

When any of these PCV hatches are open I would be very surprised if there was not always some sort of cover to protect at least the seal seat on the flange if not the whole flange from damage and as you say, to make the hatch trafficable. We see such "bridges" in the Browns Ferry & the Onagawa equipment hatch images and in those it's clear the "bridges" would be removed when the PCV hatch is closed out.

Additionally, I don't think anything loose at all would be left in the shield plug void and I don't think there would be anything permanent that might tie or create possible interference with the concrete \ steel interface at operational temperatures.

Cf this diagram, it appears to have a horizontal platform at the bottom, presumably made of steel. I don't think there would be anything like a concrete/steel interface there. In the diagram the level of the platform is marked to be at OP 10200, which is exactly the level of the first floor in Unit 2 at Daiichi (and presumably of unit 3 too) difficult to think it is a coincidence, and especially so, since it is from a publication dealing a.o. with possible repair methods of the leaking PCV hatches of Daiichi:

<..>
Shield plug movement mystery solved?

I don't think we would say solved :-), but now we know not say, 'it could not have happened that way' so it is a hypothesis fair as ever, that the plug was displaced by the earthquake. But to prove it, we would have to disprove other possible causes. I don't think we are quite there yet.

 

[westfield]

That report is rather interesting. On page 56 it says that they have a new possible explanation for slower PCV pressure rises at reactor 2 than the model predicts - that seawater getting into the S/C room contributed to the slower rise of pressure!

That may be based on this report

Edit : I tried to find a copy of "High-temperature leak characteristics of PCV hatch flange gasket,'' Nu cl. Eng. Des.,145, 375-386 (1993) " but could only find it behind a paywall.

Abstract

Small-model tests were performed to examine the integrity of the containment flange gasket in a severe accident. During a severe accident, containment structures suffer slow pressurization at relatively high temperatures. A realistic understanding of containment performance in such conditions is a major concern in developing an accident management strategy. This paper describes the results of experiments on the sealing capability of flange gaskets at high pressures and high temperatures. Silicone-rubber gaskets, which are used as the sealing material in BWR plant primary containment vessels (PCV) in Japan, were examined in small-model tests. The gaskets show sufficient sealing capability up to 225°C at 20 kgf/cm2. When applying the leakage characteristics specified in this paper to codes for severe accidents, the results should be examined carefully based on realistic heattransfer phenomena.

Copyright © 1993 Published by Elsevier B.V.Also in that report which was new to me, it's stated clearly that Units 1-3 SGTS's had backflow "dampers" while Unit 4 did not. (report page 70)

 

[westfield]

Cf this diagram, it appears to have a horizontal platform at the bottom, presumably made of steel. I don't think there would be anything like a concrete/steel interface there. In the diagram the level of the platform is marked to be at OP 10200, which is exactly the level of the first floor in Unit 2 at Daiichi (and presumably of unit 3 too) difficult to think it is a coincidence, and especially so, since it is from a publication dealing a.o. with possible repair methods of the leaking PCV hatches of Daiichi:

<snip>

I don't think we would say solved :-), but now we know not say, 'it could not have happened that way' so it is a hypothesis fair as ever, that the plug was displaced by the earthquake. But to prove it, we would have to disprove other possible causes. I don't think we are quite there yet.

Well in the case of that diagram and the photo you posted with it previously, before I subsequently posted my thoughts on the subject, does clearly show a step type thing in place right there on the flange. I really did not think that would be something they would mount in a situation like that, on such an important flange, it looks like it could be permanent (unless that guy there IS holding a spirit level on it). Seems my guess was wrong on that count and also I should pay more attention!

Edit: that was a downer for my 100th post :)
Another edit: One thing to note that does help in interpreting the hatch video - the back of the PCV hatch - vertical, concealing the concave shape of the hatch.

 

[jim hardy]

Old Snaggletooth, if it was ever any more than an apparition, would have been right about here aligned with center column.

i think the better resolution photos you guys are posting have pretty much obsoleted that hypothesis.

But i too still wonder about the relative vigor of unit 3 explosion compared to the others .
I did spend enough time looking into nucleonics of MOX, Americium and Hafnium to realize it's simply over my head. I could niether prove nor disprove anything except fast criticality was a very long shot.. Maybe if i'd been around Bigten and Flattop in my younger days.. I know nothing of fast reactors and little enough about thermal ones.
Atomic H2 density of steam even at 3200psi appeared insufficient for thermal recriticality. So did that of hydrogen gas. Zirconium hydride was over my head to figure out. Sea salt appears to be a mild poison and moderates to below hafnium's n-3n threshold..

that's why i decided to give up and await the NOVA show. I really do appreciate you guys sharing what you discover here. If it gets figured out you guys will do it.

So many riddles, so little time.
old jim

 

[tsutsuji]

This is the summary report - the summary about the U3 explosion modelling is around page 69. Quite a few other things in there as well. It says the full report will be posted here at METI soon

Edit : also a few pages before that , I hadn't seen that exact radiation map of U3 of around the equipment hatch before.
Am I mistaken or was that particular reading at the U3 equipment hatch shield plug left out of the previous map?

To be honest there are so many duplicate, updated and derivative reports around I often find it difficult to keep track.
I don't know how Tsutsuji san and other dedicated posters manage to keep tabs on it.
Kudos to them.

Nice find. I spent some time trying to find the japanese version on the NISA website, but finally, I guess that there is no Japanese version, and that this is English only, because here is what I found:

This Masaya Yasui presentation "Causes and Countermeasures:The Accident at TEPCO’s Fukushima Nuclear Power Stations" which you linked, was part of the following IAEA event:

http://www-pub.iaea.org/MTCD/Meetings/Announcements.asp?ConfID=43900 International Experts’ Meeting on Reactor and Spent Fuel Safety in the Light of the Accident at the Fukushima Daiichi Nuclear Power Plant, 19-22 March 2012 Vienna, Austria

http://www.scribd.com/collections/3...-at-the-Fukushima-Daiichi-Nuclear-Power-Plant All the presentations

Tepco's Kawano presentation page 45/76 : The Latest version of accident Timeline (Dec.22nd, 2011) English version will be on the following website soon: http://www.tepco.co.jp/en/press/corp-com/release/11122208-e.html [it is available now]

I've been reading about Onagawa NPP damage due to earthquake only. Quite eye opening.
Amongst that there is this ( taken from this report )

Onagawa PCV equipment hatch shield plug

How much it broke it's lock and moved

Shield plug movement mystery solved?

Nice find too. Yes it sounds like the plug movement mystery is solved. Let me translate a little bit :

http://www.tohoku-epco.co.jp/ICSFiles/afieldfile/2011/11/10/ab.pdf page 13/14 Onagawa NPP unit 2

The electrically operated step back shield doors, that have the purpose of shielding radiations, are electrically self-propelled concrete doors installed in the outer side of the nuclear reactor PCV. Also, they have no direct influence on the airtightness of the PCV itself.

It was confirmed that the locking system of the two electrically operated step back shield doors (hereafter "the aforesaid doors") located in the reactor building basement first floor were damaged as a consequence of the earthquake (12 March 2011).

One of the aforesaid doors moved by around 25 cm towards the outside and the other one moved by around 7 cm towards the outside, but as we confirmed that the aforesaid doors could be normally operated, we moved them back to their original position.

The aforesaid doors moved towards the outside as a consequence of the earthquake, but there is no consequence on their shielding function.

Contents of the response: we replaced the two damaged aforesaid doors' locking systems with new locking systems. (3 October 2011)

 

[MadderDoc]

<..>
But i too still wonder about the relative vigor of unit 3 explosion compared to the others .

Now, 1000 kg of hydrogen, the estimated amount of hydrogen exploding in the newest modelling approach on unit 3, would have plenty of vigor, I'd say. Hydrogen is really some explosive -- it is yielding a sharp short shock, which is deadly to most constructions.

Not surprisingly the researcher finds that 1000 kg hydrogen well exploded in the building could easily account for the damages to it. I think nobody should have a problem with that, it seems quite evident that hydrogen exploded in the building.

However, the quibble I have with the hydrogen explosion is not really one of vigour, it is one of volume.

If I may be slightly chemical, the net change of the number of molecules during a hydrogen explosion is negative. After the hydrogen explosion there was fewer molecules in the combustion gases than there was molecules inside the building that exploded. And if I may be slightly physical too, the volume of gas is proportional to the number of molecules in it. So there's the problem with the hydrogen explosion in the R/B of unit 3: it can't explain that a cloud emerged within seconds, with a volume manifold the volume of the building, and rose sky-high over the explosion site.

 

[etudiant]

While it is true that after the 2 H2 and the O2 molecules ( 3 molecules in all) combine, there are only 2 molecules of H2O left as a result, these residual molecules have the benefit of a good deal of energy released by the combination. There is plenty of energy to form an expanding cloud of steam from the reaction, even if the number of molecules is cut by a third.

 

[MadderDoc]

<..> One thing to note that does help in interpreting the hatch video - the back of the PCV hatch - vertical, concealing the concave shape of the hatch.

Right, and thanks for pointing it out. I hadn't realized that is in fact what the diagram is indicating.

So it's back to the hatch, ah, "To Sail the Cylindrical Sea". We may be close to cracking the code of that video, you know that? :-)

 

[MadderDoc]

<..>There is plenty of energy to form an expanding cloud of steam from the reaction, even if the number of molecules is cut by a third.

Please quantify your claim.

 

[jim hardy]

Thanks m'doc & etud't

There is plenty of energy to form an expanding cloud of steam from the reaction, even if the number of molecules is cut by a third.

i recall doing a back-of-envelope cipher . Making that much H2 into H2O released enough energy to make a cloud of steam roughly the volume of plume that rose over unit 3 .
It would have to transfer a lot of heat to boil additional water though.

So i put that in my list of possibilities and backed off from it needing a fission boost. Didn't rule out its having got one, though.

lessee here-- 1000kg of H2 is a half million moles

which would react with oxygen to make a half million moles of water = 9,000 kg = 19 thousand pounds X 27 cu ft/lb = ~515 thousand cubic feet of steam

which is a column ~80 ft diameter X 100 ft high. Probably there was more water involved than that because the column went so much higher.

check my arithmetic.
The energy released is not a difficult calc either and it allows more steam if you can get the heat transported into some water.
Like m'doc i am to date puzzled.

it can't explain that a cloud emerged within seconds, with a volume manifold the volume of the building, and rose sky-high over the explosion site.

plodding along, behind as usual. It's my asperger's.

old jim