Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[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

 

[SpunkyMonkey]

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

Thanks and nice orderly sequenced parsing of all that mess! I agree with what you say.

At some moments I get the feeling there may be a corner at the 'slime trail' (leaky flange) that runs the length of the trail, meaning one side of the trail angles up 90˚, but I'm not sure. But if so, that would probably be the metal of a hatch insertion into the PCV concrete. I'm already confident one side of the trail is painted metal of the hatch insertion, just not sure if it angles at 90˚ from the wall. :)

I'm now confident (due to the contrast-suppressed video that makes clear the same location during entry) that the little red and white objects are in fact on the floor in the hatch passageway near its opening. I guess we can't be sure when they got there, perhaps they fell from something during efforts to get a look into the crevice. But if they were there before the first post-tsunami inspections, they provide clear evidence that explosive forces did not blast through the crevice as such forces would surely not leave such small lightweight objects there.

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?

Yes, some kind of wind turbulence would explain the irregular and sometimes curved paths of the chips. I'd like to see what the camera probe looks like. I wonder how it maintained height as it extended, I presume it's on some rigid extension, but it also seems to have some range of flexibility in edging around the corners. And then the camera at its end rotates too. So it might be fairly sophisticated. Perhaps it has a small fan on it? Probably not, just thinking out loud.

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.

I think we're looking at the metal of the hatch insertion (probably not the hatch door). The paint appears to flake off that metal surface, and the concrete in that area is not painted.

 

[SpunkyMonkey]

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.

I'm confident that we saw misty water vapor in the Unit 1 shockwave (note the sliver-moon-shaped misty cloud that shoots upward biased to the left in the first instants of the explosion), consistent with a hydrogen-oxygen synthesis reaction. But that volume of water vapor was tiny compared to the Unit-3 mushroom cloud and it vanished in fractions of a second. The Unit-1 vapor also showed no signs of being hot.

So how would you account for the volume of persistent hydrogen-oxygen-synthesis vapor necessary to form the massive Unit-3 mushroom cloud? And why would the same reaction at Unit 1 produce such a relatively tiny amount of water vapor?

 

[mheslep]

Having 1000kg of H2 on hand to detonate and actually burning all 1000kg in the perfect 2:1 mix with rapidly accumulating H20 are two different things. Does a 50% burn still provide sufficient energy to explain all observed damage?

 

[westfield]

Thanks m'doc & etud't

<snip>

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

old jim

You and nearly everyone else here are way ahead of me when it comes to the real nitty gritty of chemistry.

I don't have the knowledge to do the math and this probably was covered previously as it's seems a fairly obvious thing to consider - All I know is there would be some energy potential in the heat & water of the SFP.

Would the U3 SFP be creating an appreciable amount of heat and steam at the time of the explosion and if so, can this play any meaningful part in the characteristics of the explosion?

 

[zapperzero]

I'm confident that we saw misty water vapor in the Unit 1 shockwave (note the sliver-moon-shaped misty cloud that shoots upward biased to the left in the first instants of the explosion), consistent with a hydrogen-oxygen synthesis reaction. But that volume of water vapor was tiny compared to the Unit-3 mushroom cloud and it vanished in fractions of a second. The Unit-1 vapor also showed no signs of being hot.

The thing in the unit 1 explosion video is the trailing edge of a rapidly decelerating shock front, made visible by atmospheric water condensation (there's a rather sharp pressure dip that "follows" the pressure spike, of course).

I miss the #3 explosion thread, boy do I.

 

[zapperzero]

Having 1000kg of H2 on hand to detonate and actually burning all 1000kg in the perfect 2:1 mix with rapidly accumulating H20 are two different things. Does a 50% burn still provide sufficient energy to explain all observed damage?

To your question: there is no way you'd get a partial H2 combustion in air.

This isn't a gasoline engine (even those have to be rather finely tuned to avoid "knocking" - the leaner the mix the worse the danger of detonation, as oxygen, not fuel, is the limiting factor).

 

[tsutsuji]

The 5th mid long term meeting was held yesterday: http://www.meti.go.jp/earthquake/nuclear/20120423_02.html

The 4th meeting (28 March 2012) : https://www.physicsforums.com/showpost.php?p=3838108&postcount=12764

The 3rd meeting (27 February 2012) has been translated into English on Tepco's website : http://www.tepco.co.jp/en/nu/fukushima-np/roadmap/conference-e.html

23 April government-Tokyo Electric mid and long term response committee, steering committee (5th meeting)

http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02a.pdf Agenda
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02b.pdf Participants

Document 1
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02c.pdf Abstract of the proceedings of 4th steering committee meeting

Document 2: Plant status
Document 2-1: Plant status
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02d.pdf Plant parameters
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02e.pdf Accumulated water storage status

Document 3 Study and execution of each special plan

3-1 Cooling by closed loop water injection
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02f.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02g.pdf Report on the results of mock-up experiment for the purpose of installing alternative RPV thermometers
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02h.pdf Measurement of unit 4 spent fuel pool inclination and desalination status

3-2 Treatment of accumulated water
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02j.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02k.pdf Plan to lay polyethylene pipes at water treatment facilites
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02m.pdf Progress status of subdrain purification test
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02n.pdf Plan to reduce volumes of groundwater seeping into units 1~4 buildings by groundwater bypass

3-3 Countermeasures to reduce environmental radiations
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02p.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02q.pdf Management of debris, cut down trees, generated by the response to the accident
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02r.pdf Plan to decontaminate the whole power plant premises
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02s.pdf Results of scattered debris survey
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02t.pdf Sinking of zeolite sandbags and checking of the results
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02u.pdf Operational achievements of seawater closed loop purification system
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02v.pdf Results of evaluation of additional releases from reactor building's primary containment vessels
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02w.pdf Evaluation of yearly radiation exposure at plant premises boundary
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02x.pdf Sampling survey of fish and shellfish in the 20 km range from Fukushima Daiichi nuclear power plant
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02y.pdf Measures to improve monitoring posts' environment

3-4 Improvement of working conditions
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02z.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02aa.pdf Plan to turn Fukushima Daiichi NPP's seismic isolated building (part of it) into an area outside the radiation management area
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02bb.pdf Test run of screening and decontamination facility for vehicles at Fukushima Daiichi NPP

3-5 Countermeasures for spent fuels pools
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02cc.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02dd.pdf Debris removal work, reactor building top part, unit 3
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02ee.pdf Debris removal work, reactor building top part, unit 4
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02ff.pdf Results of unit 3 underwater survey into spent fuel pool for the purpose of debris removal
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02gg.pdf Unit 4 spent fuel pool debris map

3-6 Preparations for fuel debris removal
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02hh.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02jj.pdf Execution of onsite survey as part of "Development of remote controlled decontamination techniques inside buildings"
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02kk.pdf Onsite survey into unit 2 reactor building basement torus room

3-7 treatment and disposal of radioactive waste
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02mm.pdf Schedule

Document 4
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02nn.pdf roadmap progress (abstract)

23 April 2012 government-Tokyo Electric mid and long term response committee, technical development progress headquarters (5th meeting) (http://www.meti.go.jp/earthquake/nuclear/20120423_01.html )

http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01a.pdf Agenda

Document 1
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01b.pdf Abstract of the proceedings of 4th meeting

Document 2-1
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01c.pdf Orientation of evaluation of achievements and revisions of research and development projects (draft)

Spent fuel pool countermeasures working team

Evaluation of long term soundness of fuel assemblies removed from spent fuel pools
Document 2-2-1 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01d.pdf Project evaluation (draft)
Document 2-2-2 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01e.pdf Project achievements, etc. in fiscal 2011 (JAEA)

Machinery and equipment development etc. sub-working team

Development of remote controlled decontamination techniques inside buildings
Document 2-3-1 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01f.pdf Project evaluation (draft)
Document 2-3-2 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01g.pdf Project achievements, etc. in fiscal 2011 (Toshiba, Hitachi GE, Mitsubishi Heavy Industries)

Development of techniques to determine PCV leakage points
Document 2-4-1 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01h.pdf Project evaluation (draft)
Document 2-4-1 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01j.pdf Project achievements, etc. in fiscal 2011 (Toshiba, Hitachi GE, Mitsubishi Heavy Industries)

Development of techniques to repare PCV
Document 2-5-1 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01k.pdf Project evaluation (draft)
Document 2-5-2 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01m.pdf Project achievements, etc. in fiscal 2011 (Toshiba, Hitachi GE, Mitsubishi Heavy Industries)

Development of techniques to survey inside PCV
Document 2-6-1 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01n.pdf Project evaluation (draft)
Document 2-6-2 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01p.pdf Project achievements, etc. in fiscal 2011 (Toshiba, Hitachi GE, Mitsubishi Heavy Industries)

Development of techniques to evaluate soundness of RPV/PCV
Document 2-7-1 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01q.pdf Project evaluation (draft)
Document 2-7-2 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01r.pdf Project achievements, etc. in fiscal 2011 (Toshiba, Hitachi GE, Mitsubishi Heavy Industries)

Development of techniques to manage debris criticality
Document 2-8 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01s.pdf Fiscal 2012 plan for development of techniques to manage debris criticality

Reactor inside status grasping and analysis sub-working team
Upgrading of accident progression analysis for the purpose of grasping reactor inside status (implementation of user tuning type)
Document 2-9-1 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01t.pdf Project evaluation (draft)
Document 2-9-2 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01u.pdf Project achievements, etc. in fiscal 2011 (Toshiba)

Upgrading of accident progression analysis for the purpose of grasping reactor inside status (structural model type)
Document 2-10-1 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01v.pdf Project evaluation (draft)
Document 2-10-2 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01w.pdf Project achievements, etc. in fiscal 2011 (Institute of Applied Energy)

Characterization and preparation of treatment of fuel debris sub-working team

Characterization using mock-up debris and development of debris treatment techniques
Document 2-11-1 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01x.pdf Project evaluation (draft)
Document 2-11-2 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01y.pdf Project achievements, etc. in fiscal 2011 (JAEA)

Construction of plan for material accountancy of fuel debris
Document 2-12-1 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01z.pdf Project evaluation (draft)
Document 2-12-2 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01aa.pdf Project achievements, etc. in fiscal 2011 (Tepco)

Treatment and disposal of radioactive waste working team

Development of techniques for treatment and disposal of secondary radioactive waste generated by contaminated water treatment
Document 2-13-1 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01bb.pdf Project evaluation (draft)
Document 2-13-2 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01cc.pdf Project achievements, etc. in fiscal 2011 (JAEA)

Development of techniques for treatment and disposal of radioactive waste
Document 2-14-1 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01dd.pdf Project evaluation (draft)
Document 2-14-2 http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01ee.pdf Project achievements, etc. in fiscal 2011 (JAEA)

Document 3
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01ff.pdf Results of public appeal for technical catalogue for equipments and machinery (etc.) for fuel debris removal toward decommissionning of Fukushima Daiichi NPP units 1~4

Document 4
http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_01gg.pdf Activities of the remote control technical task force

 

[SpunkyMonkey]

The thing in the unit 1 explosion video is the trailing edge of a rapidly decelerating shock front, made visible by atmospheric water condensation (there's a rather sharp pressure dip that "follows" the pressure spike, of course).

Thanks! You're probably right. A nice example of that phenomenon is seen here. Does this imply that Unit 1 was a detonation, or can this condensation happen with subsonic shockwaves?

 

[zapperzero]

Thanks! You're probably right. A nice example of that phenomenon is seen here. Does this imply that Unit 1 was a detonation, or can this condensation happen with subsonic shockwaves?

Gaaah. I really wish that thread hadn't been wiped out.

The nice condensation cloud happens during transitions from super- to sub-sonic or viceversa (google transonic shock and you'll find a few beautiful pictures). Your picture is also very educational by the way, as you can see the pressure front has moved on (the white circle on the water has a much bigger radius than the wispy white cloud).

 

[tsutsuji]

http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02ff.pdf Results of unit 3 underwater survey into spent fuel pool for the purpose of debris removal

Page 3/6
2. Surveyed locations (representative)

Page 4/6
3. Survey results

Page 5/6
4. Summary
* With this survey, we could check part of the status of the fallen debris inside pool and part of the status of the fallen FHM. Also, although it is only a tiny part, we could check the fuel and at the checked location no fuel handle deformation, etc. was observed.
* With this survey, we could not check the whole fallen debris status. In the future, depending on the reactor building debris removal status, we plan to intermittently perform more surveys.

 

[tsutsuji]

Page 6/6
(Reference) Outline of Fuel Handling Machine

 

[tsutsuji]

http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02gg.pdf Unit 4 spent fuel pool debris map

Page 3/4
Unit 4 SFP debris distribution map

 

[SpunkyMonkey]

http://www.meti.go.jp/earthquake/nuclear/pdf/120423/120423_02ff.pdf Results of unit 3 underwater survey into spent fuel pool for the purpose of debris removal

Thanks tsutsuji!

Looks like the track guide of the FHM is located (identified as '3' on the overhead map photo above) about right where we'd expect it to be, implying that the crane was just slightly dislodged from its track and fell straight down from where it was, still largely in its original east-west orientation.

 

[MadderDoc]

<..>
Would the U3 SFP be creating an appreciable amount of heat and steam at the time of the explosion and if so, can this play any meaningful part in the characteristics of the explosion?

Unless we will introduce assumptions of something quite out of the ordinary about the pool (e.g. a leak/sloshing/siphoning event that had drained most of its water, or re-criticality), the pool could not have been a meaningful source of steam in the context of the unit 3 explosion.

Assuming just its native state (1400 m3 water, and a decay heat of 0.54 MJ/s) the temperature of that amount of water could have increased by at most 8 ^oC/day. And the explosion happened less than 3 days after pool cooling stopped on March 11th. Over that period, the water in the pool would likely have become warm to the touch, but it would have been far from boiling.

 

[SteveElbows]

The 3rd meeting (27 February 2012) has been translated into English on Tepco's website : http://www.tepco.co.jp/en/nu/fukushima-np/roadmap/conference-e.html

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

It gets quite interesting from page 25 onwards because they have updated their model analysis of the 3 reactors. Here are notable changes from older versions:

Reactor 1 they have an assumption of leakage from in-core monitor guide tube, and leakage due to MS line flange damage.

Reactor 1 core melt diagrams show earlier progression to fully melted state & rev damage - now just 8.6 hours after SCRAM rather than 15 hours.

Reactor 2 they have the assumption that water in the torus room may have helped cool the S/C, which helps their simulation to produce pressure figures that are in better alignment with the measured data. Assumed D/W leakage now occurs much later, at about the time we see photo evidence of steam escaping from blowout panel.

Reactor 2 core melt & rpv damage analysis is still producing results where rev damage doesn't happen for a rather long period of time, its now even longer after the updated analysis, and more of the fuel remains in RPV.

Reactor 3 they have gotten their model to match the data better by putting in new assumptions about how HPCI was controlled by operators when it was in use. They still have a problem getting model results to match measured containment pressure during time when HPCI was in use, and they wonder whether this may be down to thermal stratification in the S/C.

Reactor 3 core & rpv damage analysis is much like reactor 2, now shows even greater lengths of time and lack of damage.

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.

 

[SteveElbows]

And this document about fuel removal difficulties has a few things that relate to recent discussions here:

http://www.tepco.co.jp/en/nu/fukushima-np/roadmap/images/m120314_01-e.pdf

Page 6 we see an example of how to fix leaks at the large equipment hatch, with diagram.

Page 17 we see a robot view up the north-east stairs of reactor 3, where there is much debris. Daylight can be seen through hole above. I attempt to relate this to recent discussion about black/hole area of reactor 3, and offer the suggestion that a stairwell in this area is involved.

 

[tsutsuji]

Page 6 we see an example of how to fix leaks at the large equipment hatch, with diagram.

I had seen that diagram a number of times, but I did not realize what this was about. As it was only this diagram without a narrative and without dimensions, not being aware that there was a trouble at unit 3 and that this was badly needed, I though it was just an example, of the kinds of technologies that might be needed if you want to enter the PCV with a robot or something.

 

[MadderDoc]

<..>
Reactor 2 they have the assumption that water in the torus room may have helped cool the S/C

Perhaps that is more like a fact than an assumption:

"From approximately 01:00 until around 02:00 on March 12, the shift team members
equipped with self-contained air breathing sets (self-air-set), small flashlights and rubber
boots went to the RCIC room on the first basement floor of the R/B of Unit 2 to inspect
the operating condition of the RCIC system. The RCIC room was flooded
and the water level was just below the upper edge of their rubber boots.
When they opened the door, water gushed out of the room and they could not go in."

"At approximately 02:10 that day (March 12th), members of the shift team with the same outfits as the previous
went to the RCIC room of the R/B at Unit 2. Though the level of water inside the room had risen,
the shift team members went inside to check the operating condition of the RCIC system.

"It was confirmed with Unit 2 at around 04:00 on March 12 that water level showed a
decrease for the condensate storage tank, the water source for the RCIC. Accordingly,
the shift team decided to change the water source for the RCIC from the condensate
storage tank to the S/C in order to maintain the water level of the condensate storage
tank and control increase in S/C water level."
accordingly..
"From around 04:20 to around 05:00 that day, some shift team members wearing the
level C outfits and full-face masks went to the RCIC room on the first basement of the
Unit 2 R/B. The RCIC room was flooded and the depth of water was up to about the
upper edge of the rubber boots the team members were wearing
and the temperature and humidity were high. "

 

[MadderDoc]

Page 17 we see a robot view up the north-east stairs of reactor 3, where there is much debris. Daylight can be seen through hole above. I attempt to relate this to recent discussion about black/hole area of reactor 3, and offer the suggestion that a stairwell in this area is involved.

The outline of the landing of that staircase at the fifth floor is somewhat north of the big black hole. I believe its outline can be made out from photos of the building top, but its state cannot be seen since too much debris has landed on top of it. I believe the view up to the sky has been enabled by yet another black hole in the fifth floor, east of that staircase landing, and close to the wall. This latter hole seems to have relatively clean edges, and to coincide with the position of some stationary equipment likely connected to a penetration of the 5th floor there. The equipment at the wall in that corner of the building was pushed out through the wall frames during the explosion, and could be seen hanging on to the wall outside apparently in defiance of gravity, before that platform for debris clearance came up.

 

[SteveElbows]

I speak of assumptions because this stuff is about modelling, and the assumptions they feed into the model. I do not doubt that there was water in the torus room.

 

[westfield]

Unless we will introduce assumptions of something quite out of the ordinary about the pool (e.g. a leak/sloshing/siphoning event that had drained most of its water, or re-criticality), the pool could not have been a meaningful source of steam in the context of the unit 3 explosion.<snip.

Cheers.

 

[MadderDoc]

Thanks tsutsuji!

Looks like the track guide of the FHM is located (identified as '3' on the overhead map photo above) about right where we'd expect it to be, implying that the crane was just slightly dislodged from its track and fell straight down from where it was, still largely in its original east-west orientation.

However note that '4' , photographed in a perpendicular to direction to '3', and at some distance from it, is the lower NW end of the north face of the bridge, which on the intact machine was mounted just above, and only a meter away from the track guide. Indeed the video of '4' shows the flange through which this corner was connected to the frame piece that is/was mounted on top of the track guide (albeit the mounting flange now looks sadly beaten up, de-bolted and without its partner)

 

[MadderDoc]

I speak of assumptions because this stuff is about modelling, and the assumptions they feed into the model. I do not doubt that there was water in the torus room.

Sorry, I think it was the pleonastic use of 'assumption' and 'may' in your expression that threw me off.

 

[westfield]

<snip>
I believe the view up to the sky has been enabled by yet another black hole in the fifth floor, east of that staircase landing, and close to the wall. This latter hole seems to have relatively clean edges, and to coincide with the position of some stationary equipment likely connected to a penetration of the 5th floor there. The equipment at the wall in that corner of the building was pushed out through the wall frames during the explosion, and could be seen hanging on to the wall outside apparently in defiance of gravity, before that platform for debris clearance came up.

U3. FL5, NE corner - large ducting right in the corner diving down into the floor & possibly the gravity defying equipment near it -

 

[westfield]

However note that '4' , photographed in a perpendicular to direction to '3', and at some distance from it, is the lower NW end of the north face of the bridge, which on the intact machine was mounted just above, and only a meter away from the track guide. Indeed the video of '4' shows the flange through which this corner was connected to the frame piece that is/was mounted on top of the track guide (albeit the mounting flange now looks sadly beaten up, de-bolted and without its partner)

The orientation marked "4" on that diagram is misleading.

In the video & still shot marked "4" we are viewing the vertical plane of the northern side of the bridge not the horizontal "top" of the bridge as the arrow tends to indicate. What we are seeing most of is the personnel "catwalk" with the driveshaft under it which is\was? bolted along the northern face of the FHM bridge proper.

In the video we only see a small glimpse of the main part of FHM bridge truss structure in the background, through the "catwalk" truss and possibly the FH Machine itself in the furthest background. It's very difficult to tell how "apart" the various sections of the whole FHM are but as Madder Doc mentioned, it's clear the heavy "end" piece shown in view "3" parted from this catwalk section in view "4".

Here is a quick diagram I made that didn't turn out that clear and features some terrible abuses of perspective & photoshop :)

Also, to be clear, it's comparing to Unit 2's FHM which is a little different but close enough for the purpose. There are just no decent images of the northern side of U3's FHM as it was.

PS - if this sort of post is getting just too off track then someone please say so - it is a bit of a messy thread at times and perhaps another thread for this sort of PCV hatch \ FHM \ Holes in floor type of discussion would be useful and make this sort of thing less disruptive to this thread? Perhaps rename & recycle the Unit 2 thread which is very quiet.