Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[razzz]

A lay person's questions: What information is available about the approximate weight of the structure under normal operating conditions? Are the foundations (and other relevant parts of the structure) really designed to handle some 7000 tons of added weight?

You'll just have to take the news release at face value and that TEPCO/Japan knows what they are doing.

I'm sure the foundation on bedrock can handle the weight and the vessel can hold the water, it's any earthquakes and explosions that are hard to factor.

 

[AntonL]

SPF-4 and Hydrogen Production

The puzzle how the Hydrogen in reactor 4 building was generated has not been solved.

That the fuel pool boiled dry such that overheated Zirconium steam reaction could take place
is very improbable due to the mass of water involved and not enough heat available to boil it
away. https://www.physicsforums.com/showthread.php?p=3244793#post3244793"
(We can also discard the idea of double decking as postulated in that post)

Furthermore should the pool have boiled dry this would contradict the Tepco analysis of
SFP-4 water and their conclusion that fuel rod damage is slight. (possible some fuel rods
broken by falling objects into the pool)

We have not discussed the possibility of radiolysis of water into Hydrogen an Oxygen.
[PLAIN]http://k.min.us/in0vfm.JPG
(extracted from Light Water Reactor Hydrogen Manual by Allen L Camp et al)
Under normal circumstance when the water is not boiling the Hydrogen and Oxygen
recombine shortly after the radiolysis event and as such of no concern, however once the
water is boiling the H2 and O2 are carried away by the steam and the amount of Hydrogen
produced for a 3300MW(Th) reactor is tabulated below
[PLAIN]http://k.min.us/jn0vjq.JPG

Now SPF-4 contained the full load of reactor 4 fuel and 106 days old (nearly 10⁷ seconds
at time of explosion, and assuming a Hydrogen production rate of 0.001 Kg/s and scaled
down to 2380MW would result in 62kg of Hydrogen being produced in 24 hours but as the
pool boiled for at least 48 to 60 hours some 120 to 150kg of Hydrogen would have been
released.

Is this enough for the damage we observe?

 

[pdObq]

Think of an explosion as air moving away in every direction radiating from the explosion centre. Once the expansion caused by heating phase is over, the air keeps on moving due to kinetic energy, this results in a under pressure at the explosion centre

below simulation of an hydrogen explosion at a hydrogen refuelling station, an under pressure immediately follows the over pressure.

@NUCENG: of course the pressure front can go supersonic. It's called a detonation. Obstacles (choked flow) can make a reaction front go supersonic even if it was not, in the beginning.

Now, fwiw, my take on implosion:

a. I don't see it in the video
b. fancy mechanisms are not required to cave in such a building. A regular explosion inside will do.
c. blast waves can be reflected off nearby buildings. Perhaps this is what you are seeing?
d. Long pulse duration + high overpressure is a recipe for serious vacuum. Light debris may get sucked back in, then ride up the thermal (fireballs are good at radiating heat)

http://www.gexcon.com/handbook/GEXHBcontents.htm

esp. chapters 7 (detonation) and 10 (gas explosions in buildings).

PreS: I think I am spending too much time in writing a post reply. I just got timed out again and lost all that I had written. And this time I didn't do the ctrl-c. ARGH! So I try to be quicker and more concise this time...

Yes, that handbook seems like a nice resource. There is also a wikipedia article on the deflagration to detonation transition, http://en.wikipedia.org/wiki/Deflagration_to_detonation_transition, that cites that handbook. There are also a lot more combustion and explosion related articles on wikipedia.

That handbook also has a section on explosion relief panels/walls. So, my conclusion is that the metal walls of the unit 1 service floor really did help to minimize the damage from the explosion, whether it was intended or not. The concrete pillars and wall panels in units 3 and 4 did not serve that function and maybe even made the explosion worse by back-reflecting the blast wave into the building and by making it go super-sonic if it hadn't already been (see zapperzeros comment about obstacles).

As an aside regarding the damage to the wall panels below the service floor on unit 3 looking from the east: It almost looks like when the upper part of the wall flew apart, it peeled away with it also the lower panels as the whole thin outer concrete wall seems to have shared one large rebar mat.

 

[unlurk]

Daily plot from Hirono station

http://www.fnet.bosai.go.jp/waveform/view.php?plot=1day&code=HRO&comp=Z&tm=2011031500&LANG=en

I missed that!

It shows some activity at 6:13 and 20 seconds for about five seconds but KSK reported no data that day and there is nothing from the 14th to compare it to.

But this renews hope that the data may yet be out there.

Thanks zapperzero
Thanks Ms Music

 

[NUCENG]

A lay person's questions: What information is available about the approximate weight of the structure under normal operating conditions? Are the foundations (and other relevant parts of the structure) really designed to handle some 7000 tons of added weight?

Containment flooding is an anticipated plant configuration for severe accidents. I will see if I can find information as to whether that is considered as a configuration for which the plant is seismically qualified. What may not be considered is potential damage to the structure from the earthquake and explosions. During initial consideration of containment flooding in March the NRC personnel reported concerns about flooding with potential damage. I don't remember an explanation why they were concerned

edit: I checked two US plant Safety Analysis Reports : a BWR-3 Mk1, and a BWR-4 Mk1. Both include a containment flooded load case for seismic qualification.

 

[elektrownik]

I don't remember an explanation why they were concerned

Earthquake

Another question: unit 1, they are injecting 8m^3/h of water, on current RPV pressure and temperature water should be liquid, and it looks correct becouse there is no steam from unit 1 on live web cam, so where this water go ? If there wouldn't be leak it should fill RPV a long time ago...

 

[~kujala~]

Paper warning of Fukushima nuke plant risks draws attention on Net

http://english.kyodonews.jp/news/2011/05/89638.html

 

[NUCENG]

Earthquake

Another question: unit 1, they are injecting 8m^3/h of water, on current RPV pressure and temperature water should be liquid, and it looks correct becouse there is no steam from unit 1 on live web cam, so where this water go ? If there wouldn't be leak it should fill RPV a long time ago...

Not the RPV. I was referring to flooding the containment (drywell) around the RPV. The theory is that by flooding the containment it may fill the RPV through any pipe breaks or holes that may exist and are preventing filling the RPV directly.

 

[ernal_student]

Containment flooding is an anticipated plant configuration for severe accidents. I will see if I can find information as to whether that is considered as a configuration for which the plant is seismically qualified. What may not be considered is potential damage to the structure from the earthquake and explosions. During initial consideration of containment flooding in March the NRC personnel reported concerns about flooding with potential damage. I don't remember an explanation why they were concerned

edit: I checked two US plant Safety Analysis Reports : a BWR-3 Mk1, and a BWR-4 Mk1. Both include a containment flooded load case for seismic qualification.

Thanks for the detailed explanation! I recall reading about concerns in the case of flooding but until now didn't have enough information to put that in perspective.

 

[ernal_student]

Paper warning of Fukushima nuke plant risks draws attention on Net

http://english.kyodonews.jp/news/2011/05/89638.html

Story accessible at the link below (unfortunately the link shown above requires the viewer to be a client of Kyoudou News Agency):

http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/05/07/20110507p2g00m0dm054000c.html

The paper itself is here:

http://ci.nii.ac.jp/els/110002066513.pdf?id=ART0002195281&type=pdf&lang=en&host=cinii&order_no=&ppv_type=0&lang_sw=&no=1304756220&cp=

 

[NUCENG]

Paper warning of Fukushima nuke plant risks draws attention on Net

http://english.kyodonews.jp/news/2011/05/89638.html

This is one of the issues I have been researching as discussed in the Fukushima Management and Government Performance thread. Professor Takagi wrote his paper in 1995 and it was certainly true at that time. However it appears that NISA initiated reevaluations ofseismic design basis in 2006 (better late tjan never). In 2008 TEPCO apparently performed that evaluation and, according to WNA, upgraded the seismic qualification at Fukushima to 600 Gal which is greater than the peak ground acceleration during the March 11, 2011, quake.

 

[elektrownik]

Not the RPV. I was referring to flooding the containment (drywell) around the RPV. The theory is that by flooding the containment it may fill the RPV through any pipe breaks or holes that may exist and are preventing filling the RPV directly.

Yes, I know, I was asking about RPV in general, why it is not filled wit water yet, if there are leaks from RPV to drywell it also should be filled now, I think that water is leaking from RPV and drywell in some way, because if they are injecting 8m3/h and there is no steam from unit 1 then this mean that water must leak...

 

[NUCENG]

Story accessible at the link below (unfortunately the link shown above requires the viewer to be a client of Kyoudou News Agency):

http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/05/07/20110507p2g00m0dm054000c.html

The paper itself is here:

http://ci.nii.ac.jp/els/110002066513.pdf?id=ART0002195281&type=pdf&lang=en&host=cinii&order_no=&ppv_type=0&lang_sw=&no=1304756220&cp=

Unable to open the Takagi paper. Can you check that link?

 

[PietKuip]

In 2008 TEPCO apparently performed that evaluation and, according to WNA, upgraded the seismic qualification at Fukushima to 600 Gal which is greater than the peak ground acceleration during the March 11, 2011, quake.

How could Tepco have upgraded the seismic stability of their plant?

I would regard it as impossible the modify the concrete and steel construction physically. Maybe they just accepted that design criteria should be 600 gal. Without being able to do much about it, other than shutting down the reactors.

"The design basis acceleration for both Fukushima plants had been upgraded in 2008, and is now quoted at horizontal 441-489 Gal for Daiichi and 415-434 Gal for Daini. The interim recorded data for both plants shows that 550 Gal was the maximum for Daiichi, in the foundation of unit 2 (other figures 281-548 Gal), and 254 Gal was maximum for Daini. Units 2, 3 and 5 exceeded their maximum response acceleration design basis in E-W direction by about 20%. Recording was over 130-150 seconds. (Ground acceleration was around 2000 Gal a few kilometres north, on sediments.)"
http://www.world-nuclear.org/info/inf18.html

 

[ernal_student]

Unable to open the Takagi paper. Can you check that link?

I just opened it again from the link I posted and did not encounter any problem. Please try again.
You can also get to that same link by way of this link:
http://ci.nii.ac.jp/lognavi?name=nels&lang=en&type=pdf&id=ART0002195281

 

[Borek]

Think of an explosion as air moving away in every direction radiating from the explosion centre. Once the expansion caused by heating phase is over, the air keeps on moving due to kinetic energy, this results in a under pressure at the explosion centre

But it has nothing to do with the condensation. That's all I wrote. You even quoted me on it.

 

[Borek]

If H2 and O2 gas and H2O gas were at the same temperature and pressure after the reaction as before then the volume should be reduced to 2/3

At STP it is wrong, for reasons so obvious I feel ashamed pointing that out.

Call it nitpicking if you like

 

[~kujala~]

I guess you all noticed this: Miroslav Lipar who is in charge of IAEA reactor status summary has made these more thorough explanations of the reactor status after the general summary page:

http://www.slideshare.net/iaea/technical-briefing-11-0505

The more thorough summary begins on page 4.

For every unit they now have some guesses about the leakings:

Unit 1:
Reactor Pressure Vessel is assumed to be leaking most probably through connected recirculation system (Pump seal LOCA).
Exiting gap in PCV is assumed (On-going injection of nitrogen gas has not led to increase of pressure in PCV)

Unit 2:
Reactor Pressure Vessel is assumed to be leaking most probably through connected recirculation system (Pump seal LOCA).
Containtment is believed to be damaged.

Unit 3:
Reactor Pressure Vessel is assumed to be leaking most probably through connected recirculation system (Pump seal LOCA).
The leak elevation is about -1500 from the top of the active fuel (level of ejectors of RCPs).
Containtment is believed to be damaged.

 

[PietKuip]

I guess you all noticed this: Miroslav Lipar who is in charge of IAEA reactor status summary has made these more thorough explanations of the reactor status after the general summary page:

http://www.slideshare.net/iaea/technical-briefing-11-0505

The more thorough summary begins on page 4.

That is a tremendous improvement in the IAEA reporting!

There are no power spikes, no significant neutron flux, and no short-lived isotopes at any of the units (no La-140). At the moment. And there is a caution to keep an eye on this.

 

[NUCENG]

How could Tepco have upgraded the seismic stability of their plant?

I would regard it as impossible the modify the concrete and steel construction physically. Maybe they just accepted that design criteria should be 600 gal. Without being able to do much about it, other than shutting down the reactors.

"The design basis acceleration for both Fukushima plants had been upgraded in 2008, and is now quoted at horizontal 441-489 Gal for Daiichi and 415-434 Gal for Daini. The interim recorded data for both plants shows that 550 Gal was the maximum for Daiichi, in the foundation of unit 2 (other figures 281-548 Gal), and 254 Gal was maximum for Daini. Units 2, 3 and 5 exceeded their maximum response acceleration design basis in E-W direction by about 20%. Recording was over 130-150 seconds. (Ground acceleration was around 2000 Gal a few kilometres north, on sediments.)"
http://www.world-nuclear.org/info/inf18.html

You may be right. We may have here another example of conflicting information. I provided a link to the WNA statement that TEPCO had upgraded the seismic qualification to 600 Gal in 2008. I would assume that this was done by reanalysis, not physical modifications or there would have been some discussion of the mods. There is usually added margin in any design and it is not unusual to "sharpen the pencil" to show that a small increase in the PGA was acceptable. I had also seen reports of the lower number of 449 Gal. Either way, they were doing something between 2006 and 2008 to reevaluate the seismic risk. Absolutely, they should have been doing that periodically over the last 30+ years.

There have been cases where a building, once erected showed unexpected sesitivity to winds or other loading or was later found to be more vulnerable to seismic forces. I think that either the Sears Tower or Hancock building in Chicago was featured in a documentary about this kind of post-construction engineering. Active dampening can sometimes be added after construction. My guess is that the reanalysis was paper only, but that doesn't mean it was wrong. If it was still short of the actual event, it doesn't sound like it was much of a problem since the diesels started and ran until the tsunami hit.

 

[jim hardy]

[q]There are no power spikes, no significant neutron flux, and no short-lived isotopes at any of the units (no La-140).[/q]

i think they got control of criticality early on.

i think i'd use CO2 rather than nitrogen to inert atmosphere. it's heavy so will stay in the vessel up to level of leak and not mix so much with air..

 

[yakiniku]

I don't recall seeing mention of the data published on April 23rd by the Center for the Promotion of Disarmament Non-Proliferation Japan. It contains data for a number of radioactive isotopes that might be interesting from the CBTO Takasaki station in Gunma:

http://www.cpdnp.jp/pdf/110427Takasaki_report_Apr23.pdf

http://www.ctbto.org/verification-regime/featured-stations/types/radionuclide/rn38-takasaki-japan/page-1-rn38/

 

[StrangeBeauty]

I guess you all noticed this: Miroslav Lipar who is in charge of IAEA reactor status summary has made these more thorough explanations of the reactor status after the general summary page:

http://www.slideshare.net/iaea/technical-briefing-11-0505

The more thorough summary begins on page 4.

For every unit they now have some guesses about the leakings:

thx for the resource. Is this the first time that 'those in charge' have officially admitted they have pictures of a crack in #3 primary containment (pg 6 "Images of Unit 3 show crack in the primary containment")? I believe others (e.g. NRC) have referenced this, but I haven't seen this picture as of yet.

Also the marine monitoring portion of the presentation from the same date is here:
http://www.slideshare.net/iaea/marine-briefing-11-0505-hn-rev

 

[elektrownik]

I don't recall seeing mention of the data published on April 23rd by the Center for the Promotion of Disarmament Non-Proliferation Japan. It contains data for a number of radioactive isotopes that might be interesting from the CBTO Takasaki station in Gunma:

http://www.cpdnp.jp/pdf/110427Takasaki_report_Apr23.pdf

http://www.ctbto.org/verification-regime/featured-stations/types/radionuclide/rn38-takasaki-japan/page-1-rn38/

Interesting, there are Xe data also on page 7

 

[NancyNancy]

It was suggested that I share this here. A couple of people had mentioned #4 looked like it was falling over or it is an optical illusion of the wide angle lens on the TBS camera. I am not totally convinced it is the camera since there is no oddity on the opposite side of the camera. I also have a screen shot that shows even further right of #4, everything is totally vertical. #3 isn't leaning, as if there was a distortion, it would gradually get worse rather than being sudden in one spot only. I marked up a couple of images to explain what I was seeing. TEPCO also moved the watering crane that has been on the south side of #4 to the corner of #4 on the land side about 4 hours ago. I don't have a screen shot yet but the person who saw it is reliable. I am hoping to get a screen shot of that once it is daylight again. Another concern to add to this is that TEPCO employees were telling a couple of different Japanese reporters I have spoken to that the stability of #4 was a big concern. This was about 2 weeks ago. The concern was the building framework instability and the impact it is having on the SFP. There were plans to pour concrete columns underneath and also a plan to put a steel framework underneath. There is already damage to the frame work on both the north and south sides.
Image of all reactors and towers http://www.houseoffoust.com/fukushima/sinking.jpg
Close up of 4 http://www.houseoffoust.com/fukushima/sinking5_6a.jpg
4 with lines tracing the building framework http://www.houseoffoust.com/fukushima/sinking5_6b.jpg
large image of reactors with vertical lines http://www.houseoffoust.com/fukushima/sinking2.jpg
web page of all of this http://www.houseoffoust.com/fukushima/r4sinking.html

 

[elektrownik]

I look into data and I see Tc99m for example, half-life 6h it was detected in big concentration (100 000 - 600 000 uBq/m^3) on 3.16, 3.21, 3.22, 3.29, 3.30 and last time when it was detected it was only ~3000 on 4.9,
For Xe133: 3.16 - 400 Bq/m^3, 3.17 - 50 Bq/m^3, 3.21 - 62 Bq/m^3, 3.22 - 30 Bq/m^3,
What this mean ?

 

[StrangeBeauty]

I too think that #4 looks like it's leaning in these images, but I am not convinced that's it not an optical distortion of some form. The low resolution also hinders analysis. Does anyone have recent images from a different angle to compare? A satellite image would be good.

Welcome Nancy... Thanks for the images you have posted on your site.

...TEPCO also moved the watering crane that has been on the south side of #4 to the corner of #4 on the land side about 4 hours ago. I don't have a screen shot yet but the person who saw it is reliable.

evidence please? A picture would be good :)

...TEPCO employees were telling a couple of different Japanese reporters I have spoken to that the stability of #4 was a big concern...

link please? The collapse of the building would be a very bad development...

 

[Jorge Stolfi]

It was suggested that I share this here. A couple of people had mentioned #4 looked like it was falling over or it is an optical illusion of the wide angle lens on the TBS camera. I am not totally convinced it is the camera since there is no oddity on the opposite side of the camera

Nancy, there are a few things in those images you must take into account:

(1) The camera is a bit tilted. Your 'vertical' lines are a bit off; check carefully the tower, you should tilt them clockwise by a couple of pixels at each end.

(2) There is, definitely, radial distortion of the barrel type, stronger in the high-zoom images. Check that the vertical edges of #2 seem to be leaning counterclockwise, as much as #4 seems to be leaning clockwise. Because of that, the 'vertical' in the corner where #4 is should be tilted even more clockwise.

(3) The upper edge of the South wall of building 4 is damaged and has been displaced down by 1-2 meters, and there is a large foreign object sticking out of the roof at the NE corner (on the far side of the building, near the center of its outline on the photo). Thus the pink lines you drew to show the outline of the building are incorrect. The top of the building is actually almost level with the camera, so the outline at the top is very nearly a single straight line from the upper left corner to the upper right corner (like that of #2).

(4) There is some dark obstacle (a tree?) near the base of the right edge of #4 in tht photo. That obstacle gives the impression that the right edge is more tilted than it really is.

(5) The pillar at the NW corner, that defines the left edge of the building in the photo, was damaged too. Its middle part bulges out by a meter or two. What you see in the webcam is only the upper half of that pillar, which therefore seems to be tilted.

Thus I think that the "leaning over" is an illusion due to the unlucky combination of effects, all conspiring to tilt the outline of #4 clockwise.

 

[elektrownik]

You can see red concrede pump on live cam now...

 

[dh87]

i think i'd use CO2 rather than nitrogen to inert atmosphere. it's heavy so will stay in the vessel up to level of leak and not mix so much with air..

CO₂ is toxic, even at pretty low levels (2%), not that anyone should be breathing the atmosphere, and CO₂ will acidify the water.

 

[turbo]

CO₂ is toxic, even at pretty low levels (2%), not that anyone should be breathing the atmosphere, and CO₂ will acidify the water.

Another reason to use nitrogen is that is generally readily available in liquid form. You can get a large volume of nitrogen gas from an amount of liquid nitrogen that is easily transported by truck.

 

[DSamsom]

You can see red concrede pump on live cam now...

And it seems the smoke from reactor 3 is black (and thick). Look at this short excerpt from the live feed.

http://goo.gl/JBdwI

 

[ascot317]

And it seems the smoke from reactor 3 is black (and thick). Look at this short excerpt from the live feed.

http://goo.gl/JBdwI

I don't see much there. It's dark. Looks "normal" to me.

 

[DSamsom]

I don't see much there. It's dark. Looks "normal" to me.

Hm, this array of screenshots from apparently (can't verify) a few hours ago doesn't look very 'normal' or am I mistaken

http://twitpic.com/4unrpd

 

[unlurk]

Hm, this array of screenshots from apparently (can't verify) a few hours ago doesn't look very 'normal' or am I mistaken

http://twitpic.com/4unrpd

No. 3 blew up again.

The live cam seems to verify it.Edited

 

[ascot317]

Hm, this array of screenshots from apparently (can't verify) a few hours ago doesn't look very 'normal' or am I mistaken

http://twitpic.com/4unrpd

That black smoke (if it is black smoke) could be comming from #4.

I'm sceptical about interpreting low resolution pictures at night.

 

[elektrownik]

Interesting unit 3 have big temperature and cooling problems, they are injecting 9m^3/h but last data show that after litle drop temperature was increasing again

 

[biffvernon]

In this video:
http://www.youtube.com/watch?v=9BN0teWjt3Y&feature=player_embedded#at=44

the smoke seems to be coming from both #3 and #4

 

[MadderDoc]

Here is an annotated version of the Air Photo Service snapshot of reactor #3, from nearly above:

[PLAIN]http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/povray/blueprint/foto/edited/out/reactor3-Z-3-c-A-i.png

To the best of my knowledge:

(A) Outline of the service floor, out to the outer surface of the building.
(B) Stairwell (?).
(C) Elevator shaft.
(D) Spent-fuel pool. The North edge is guessed, the East edge may be a bit off.
(E) Steam-dryer storage pool (= equipment pool). The South edge is guessed.
(F) Overhead crane (outline of upper surface).
(G) Winch box of the overhead crane.
(H) E-W and N-S cuts through the reactor axis (as in blueprints).
(I) Estimated broken edge of service floor slab.
(J) Grappling attachment for the containment cap?<..>
Higher resolution images:
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/povray/blueprint/good/un3_foto_exploded_Z_1.png
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/povray/blueprint/good/un3_foto_exploded_Z_2.png
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/povray/blueprint/good/un3_foto_exploded_Z_3.png
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/povray/blueprint/foto/edited/out/reactor3-Z-3-c-A-e.png (annotated version of the latter)

Here is another stab of it (a higher resolution image is attached):
[URL]http://gyldengrisgaard.dk/fuku_docs/20110324_down_3thumb.jpg[/URL]
1) Approximate location of apparent kink in the northern boom of the overhead crane (as if it is bent or broken)
2) Approximate location of fire with grey/black smoke on March 21st-22th. Soot on roof girders and wall concrete structure. At floor below, dark shape or possibly crack in service floor.
3) Signature of heat on the winch, and possibly a burn through of the southern boom in this location
4) Missing rails on the top of this section of the southern boom.
5) Areas in which the booms have sunk into the concrete deck of the service floor, extending the NW broken region of the floor.

 

[Uagrepus]

Thanks MadderDoc,
I came to a similar result based on a thermo pic of No.3. (Drawn 19.04.11).

http://i54.tinypic.com/2iie3pw.jpg

Edit by Borek: image was too large, replaced by the link.

 

[PietKuip]

...TEPCO employees were telling a couple of different Japanese reporters I have spoken to that the stability of #4 was a big concern...

link please? The collapse of the building would be a very bad development...

These concerns were made public by Tepco in their "plan". The stability of the #4 SFP was listed as a priority problem. They want to do something about within 3 months.

I read something about reinforcing the construction with steel pillars.

 

[zapperzero]

It's morning (a rare fog-less one). The live cam shows no fire or smoke.
On other nights, I have seen similar... uhh... transients, I guess you might call them.
It's just steam (water vapor), they seem to be doing some/most of their pumping with the Putzmeister at night, plus it tends to be colder so more condensation is to be expected.
I'm beginning to get annoyed with all the fringe theories (even my own).

Sorry for starting up the "omg #4 is crooked" thing, guys :/. Need to do more lurking.

 

[Dmytry]

Interesting unit 3 have big temperature and cooling problems, they are injecting 9m^3/h but last data show that after litle drop temperature was increasing again

In my opinion, there would be intermittent criticality, in at least one of the reactors but possibly in all 3.
It is known that bottom of reactor 3's PV is at 150 Celsius. That implies fuel laying on the bottom of PV in a lump. It is unclear what happens to control rods but one thing for certain - the fuel won't be laying evenly between control rods, and it won't be mixed evenly with damaged control rod's material (which has dramatically smaller density than uranium dioxide).

It is known that they have been urged to use borated water (by French and by NRC, French even gave them the boron), so the re-criticality is a concern. This concern is not something that goes away with time.

The cooling water is leaking, which means that they are losing boron, and eventually they will run out of boron, at which point cooling could become impossible as non borated cooling water would cause criticality.
The boron in question is not ordinary boron, but enriched boron-10 which is not readily available.

 

[elektrownik]

Can you look on this ? : http://www.cpdnp.jp/pdf/110427Takasaki_report_Apr23.pdf pages 4,5,6,7

 

[StrangeBeauty]

These concerns were made public by Tepco in their "plan". The stability of the #4 SFP was listed as a priority problem. They want to do something about within 3 months.

I read something about reinforcing the construction with steel pillars.

Ah thanks -- I see this from the Roadmap doc:

(Unit 4) Installation of supporting structure under the bottom of the pool.

which is different from the entire building being at risk (not believing that at this point, just asking the question based on the photos we have atm). Sounds like Nancy was referring to something else (a convo between reporters and tepco officials).

 

[Dmytry]

which is different from the entire building being at risk (not believing that at this point, just asking the question based on the photos we have atm).

Who gives a bleep about the 'entire building' being omfg at risk? The SFP is the only thing that matters. if SFP floor falls out, this can make a level 8 on the scale from 0 to 7 where 7 is Chernobyl.

 

[biffvernon]

It's morning (a rare fog-less one). The live cam shows no fire or smoke.
On other nights, I have seen similar... uhh... transients, I guess you might call them.
It's just steam (water vapor), they seem to be doing some/most of their pumping with the Putzmeister at night, plus it tends to be colder so more condensation is to be expected.
I'm beginning to get annoyed with all the fringe theories (even my own).

Sorry for starting up the "omg #4 is crooked" thing, guys :/. Need to do more lurking.

So why would they do the Putzmeister pumping at night. Someone tweeted the suggestion it was so people didn't see and become concerned at the sight, but really? That sounds a bit too conspiracy-like even for TEPCO.

 

[GJBRKS]

So why would they do the Putzmeister pumping at night. Someone tweeted the suggestion it was so people didn't see and become concerned at the sight, but really? That sounds a bit too conspiracy-like even for TEPCO.

Temperature conditions at night make it easier for the steam to rise and escape ?

(which is actually strange as temperature inversions occur more often at nighttime :

http://apmru.usda.gov/aerial/Publications/2008 Pubs/Fritz Low level Inversions 2008.pdf

It would however create more atmospheric stability , so better results from spraying

)

 

[StrangeBeauty]

Who gives a bleep about the 'entire building' being omfg at risk? The SFP is the only thing that matters. if SFP floor falls out, this can make a level 8 on the scale from 0 to 7 where 7 is Chernobyl.

Of course the SPF is all that matters at #4 although the RPV is probably fairly radioactive itself. But don't you think the entire building collapsing would at least cause the SPF to spill much of its contents? Hopefully the way the building is engineered it's a very unlikely scenario.

 

[zapperzero]

(which is actually strange as temperature inversions occur more often at nighttime

Hmm. Inversion layers are good, sort of, because anything caught beneath them doesn't travel far. The zone around the plant is already contaminated, no?