Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[LabratSR]

Discovery Channel Special on Japan's Nuclear Crisis TONIGHT - 10:00pm eastern April 28, 2011 http://dsc.discovery.com/tv-schedules/special.html?paid=1.14144.26383.0.0

 

[Reno Deano]

The radiation measurment rose after the start of N2 injection. N2 injection will do 2 things 1) stir up the contents of wherever it's being injected; and 2) create void space.

Void space in the water will reduce shielding from the radiation sources. Stirring could spread the radiation around.

All this is speculation. I don't even know whether the N2 is injected into the RPV or dry-well.

This could be the source of high radiation increase fresh water and the Oxygen 16 to Nitrogen 16 activation via fast neutrons. Though short lived the resultant gama from its decay is very strong.

Radioisotope 16N is the dominant radionuclide in the coolant of pressurized water reactors or boiling water reactors during normal operation. It is produced from 16O (in water) via (n,p) reaction. It has a short half-life of about 7.1 s, but during its decay back to 16O produces high-energy gamma radiation (5 to 7 MeV).

 

[Reno Deano]

Toshiba web page describing what happens during a core shroud replacement.

http://www.toshiba.co.jp/nuclearenergy/english/maintenance/replace/shroud03.htm

Initially the RPV is filled with water. In later stages, the RPV is empty. It sounds like a milling machine works underwater and takes off metal at some point to reduce the radiation. The shavings are then removed to the equipment pool. That may explain the thermal images we saw that implied the reactor well was hot.

http://www.irpa.net/irpa10/cdrom/00584.pdf

Further describes the chemical and mechanical decontamination at Unit 2 when its core shroud was replaced years ago.

What I don't understand is if it's possible to decontaminate the inside of a reactor this way, why is it necessary to put decommissioned reactors into SAFSTOR mode for decades? Why not just decontaminate them, cut them up into pieces, and dispose of them?

Decontamination of the RPV interior surface just removed radioactive surface corrosion/wear particles adhered to it. The RPV is still irradiated/radioactive and shielding is still needed for workers on the support platform.

 

[Astronuc]

This how it's supposed to work -

http://www.world-nuclear-news.org/RS_Browns_Ferry_hit_by_major_storms_2804112.html

TVA said it had never experienced anything like the passage of several storm systems through its 80,000 square mile service area. Each one caused more damage to transmission lines until over 100 transmission elements were knocked out and some 677,000 homes left without power.

The three boiling water reactors at TVA's Browns Ferry nuclear power plant in Alabama shut down automatically with cooling systems powered by "a combination of offsite transmission and on-site diesel generators." However, the shutdown was notified as an 'unusual event' to the Nuclear Regulatory Commission "when the normal and alternate power supplies for essential equipment were unavailable for more than 15 minutes." TVA stressed that "safety systems performed well."

They have one line intact, and their 8 EDGs are available.

 

[Jorge Stolfi]

A message to Jorge Stolfi: as you spent a good time in the modelization of the buildings and reviewed some of the drawings available, if you have a chance to modelize also the turbine buildings maybe you could do a rough estimate of the volume that can be contained in the basements of the turbine buildings (so below the level of the platform ground)? .

For that one would need diagrams of the turbine building, with reliable dimensions and/or scale. It was already so hard to get those reactor blueprints, and they are still missing many important details...

Moreover I will be rather busy until next week. Anyway, if you manage to get the blueprints, computing the rom volumes by hand is much easier than modeling them with POV-Ray (which in fact does not have a 'volume' function).

 

[MiceAndMen]

Decontamination of the RPV interior surface just removed radioactive surface corrosion/wear particles adhered to it. The RPV is still irradiated/radioactive and shielding is still needed for workers on the support platform.

Thanks, I see that now. Even though the workers were able to work without respirators, they still needed a bunch of lead shielding before they could go inside.

 

[WhoWee]

This how it's supposed to work -

http://www.world-nuclear-news.org/RS_Browns_Ferry_hit_by_major_storms_2804112.html

They have one line intact, and their 8 EDGs are available.

This should be part of the national news coverage - along with the storm damage and human toll.

 

[MiceAndMen]

Discovery Channel Special on Japan's Nuclear Crisis TONIGHT - 10:00pm eastern April 28, 2011 http://dsc.discovery.com/tv-schedules/special.html?paid=1.14144.26383.0.0

I would rate it 4/10 based on the fact that I watched it with someone who has not been following the situation as closely as I have, and she was more confused about the entire situation after watching it than she was before.

I saw some photos that I don't recall seeing yet anywhere else. Other than that... meh. It served up the "Fukushima 50" as heroes and perpetuated the myth of workers cutting a hole in the side of Unit 2 after Unit 3 exploded. It did pose a few unanswered and insightful questions about the future of the entire area around the plant.

About a third of it dealt with the general devastation left behind by the earthquake and tsunami. That part was actually interesting, even though it was obviously influenced by the presence of a young and attractive American woman who was up the coast trying to save the whales. She was touched that some of the Japanese people they encountered offered her and her companions food to eat on their treacherous hike away from the coast in search of a ride to the airport.

They had comments from Lochbaum and a few others. Thankfully they did not talk to Gundersen. The show as a whole was not a scientific look into the problems at Fukushima Daiichi. It was more of a "human interest" piece so typical of American television. The message at the end was, "They will eventually get it sorted out."

Better than nothing I guess. If you didn't see it you didn't miss much.

 

[robinson]

Due to my diligence in following this topic I spotted many mistakes made in the broadcast.

 

[I_P]

A few new photos - debris clean-up operation, T-hawk, robots, salvage in exclusion zone:

http://cryptome.org/eyeball/daiichi-npp13/daiichi-photos13.htm"

 

[ernal_student]

Greetings from a first time poster! I found this forum by googling "physicsforums" with "forensic analysis" after someone had alerted me to its existence, and I have taken the time to read (well, in many cases perhaps just skim) all 5000+ posts here. I am impressed by both the educated speculation that is naturally based on limited evidence and the honest critique of all speculation in accordance to the principles of the scientific method. According to Google this thread has been mentioned in other forums as a high quality resource, and I would like to express my appreciation for the time and expertise people have been offering to make it such.

Since I have nothing of substance to post at this time I will permit myself to recede into the background and keep reading along.

 

[UNECCS]

Well if they take questions, we need the contact addresses of those two to send them questions to ask

I guess two men was Japanese.

 

[~kujala~]

http://www.foxbusiness.com/industries/2011/04/18/japan-nuclear-agency-reactor-building-4s-basement-filled-meters-water/

"It was the first time that the agency released the extent of flooding in any of the reactor buildings. The flooding situation in the Nos. 1-3 reactor buildings is not known, Nishiyama said.<..> Nishiyama also said the basement of the turbine building of the No. 4 reactor also has about a meter of water."

Okay, thanks MadderDoc.
So it was +80 cm, < 60 mSv/h in the basement of the turbine building.
And now +500 cm, 100 mSv/h in the basement of the reactor building.

 

[biffvernon]

A few new photos - debris clean-up operation, T-hawk, robots, salvage in exclusion zone:

http://cryptome.org/eyeball/daiichi-npp13/daiichi-photos13.htm"

I think the first picture gives a good view of where the staircase leading to the 'hole' on #4 was.

 

[~kujala~]

So TEPCO says SFP 4 is not leaking:

The company checked the reactor facilities, suspecting water might be leaking from the pool, but cannot confirm water leakage into the bottom structures of the reactor building.

If we take the best option and guess that RPV is not leaking either the question remains where has this +500 cm/100 mSv/h of water in the basement come from?

I can think of two possibilities:
1. It's the result of all the sprayed water into the SFP that has missed the target or overflown.
2. Some of it might be tsunami waters coming from outside in.

 

[Jorge Stolfi]

I think the first picture gives a good view of where the staircase leading to the 'hole' on #4 was.

It also shows that what appeared to be some Dark Goo streaming down the wall from the terrace is actually a bunch of cables. Some random comments about this old photo, based on the blueprints:
[PLAIN]http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/povray/blueprint/foto/edited/out/reactor4-S-1-A-i.png
(A larger version is http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/povray/blueprint/foto/edited/out/reactor4-S-1-A-e.png" .)

A - Wall sections pushed out by the explosion. Same pattern on the other side of the entrance gallery. (Why only the sections on the far end of the gallery?)

B - Markings left by the external staircase. It seems that the staircase was still there after the earthquake but before the explosion. Where did it go? is it buried under the rubble, or was it removed by workers early on?

C,D,E - Approximate levels of floors 5 (service), 4, and 3, respectively.

F - Outline of the SFP projected on the south face. The SFP cavity begins about 6.4 meters north of the south façade, and its internal dimensions are ~ 13.2 m E-W, ~10 m N-S. These numbers are my estimates assuming the drawings I have are correctly scaled. One of the drawings gives the total depth of the SFP as 13.020 meters.

G - Original locations of pillars 2, 3, and 4 on the South face. (Pillars 2 and 4 are aligned with the tracks of the FHM and probably are there to help support the SFP. Pillar 3 is aligned with the reactor axis. Pillar 4 was twice as wide as the others.)

H - apparently, the original location of the Mysterious Green Box, that seems to have disappeared after the earthquake, uncovering the Door With Mickey Mouse Ears.

I - A huge grenish "closet", flush against that wall. The dark bands above it, leading to the terrace, are bundles of cables or pipes. Is that the Mysterious Green Box? Too big for that?

 

[jlduh]

Ok Jorge, i was just asking in case you would have some more prints or data. I only have two sketches that have been posted here maybe a month ago, especially one that i captured from an NHK news program which is a transversal cut of the all building (East/West).

Could you confirm me two numbers:

1) the depth of the floor basement in the reactor building, below the line of the platflorm ground? (probably n°1 is different because it is a different reactor, but 2 to 4 should be similar). It should be something like 11 meters i think but maybe you can confirm this. The depth of the basement of T/B seems aligned with the one of the R/B so this info could help me to check and scale the sketch i captured on the NHK.

2) seen from the top, and also for scaling purposes, the exact outside dimensions of the R/B 1 to 4 (1 is a little bit smaller maybe)?

I will see if i can try to estimate some rough volume of the basements we are talking about.

 

[razzz]

Hey Jorge Stolfi, you seem to know your building elevations so...if the RPV cap at the join to the vessel leaks and vents, what level or plane would it be projecting or slicing through in relation to Unit 3? Or if you cut the Unit 3 down to the elevation level with the RPV flange (like cap removed), what would it look like on your modeling?

 

[rowmag]

Indeed, Tepco's having the theory, that water may have overflowed from the reactor cavity into the SFP after an explosion damaged the gate certainly implies that Tepco must know the cavity to be water-filled at the time of explosion. The theory seems to be fed by a suspicion that water fed to the SFP now overflows back into the reactor. One cannot have it both ways, I think, unless the same explosion which so very fortunately damaged the gate such that a disastrous fire could be averted, unfortunately also made the reactor leak. Good news/bad news.

Here's a link to Yomiuri's English translation of the original article:
http://www.yomiuri.co.jp/dy/national/T110428006723.htm

TEPCO's theory certainly explains a lot of things. But I am still curious:

What is not discussed is how this squares with their earlier measurements of the water contamination, which indicated insufficient fuel rod damage to explain hydrogen generation. Could those measurements now be explained by dilution, since the water volume is now effectively much bigger (including the reactor vessel, and possibly the equipment storage pool on the other side if that gate was also damaged) than was being considered before (just the SFP)? Or can you get hydrogen generated before the zircaloy heats up enough to crack?

Anyone? (NUCENG? Astronuc?)

 

[elektrownik]

So TEPCO says SFP 4 is not leaking:



If we take the best option and guess that RPV is not leaking either the question remains where has this +500 cm/100 mSv/h of water in the basement come from?

I can think of two possibilities:
1. It's the result of all the sprayed water into the SFP that has missed the target or overflown.
2. Some of it might be tsunami waters coming from outside in.

cant confirm but can't deny also... so who know, I don't believe in miracles, if they were injecting 70t per day and it was ok so why they chang it to 200t per day now ? Tsunami water shouldn't enter reactor building, it should be sealed, also I don't think that so much water missing SFP during injection, also water is radioactive so it can't be from tsunami

 

[AntonL]

Indeed, Tepco's having the theory, that water may have overflowed from the reactor cavity into the SFP after an explosion damaged the gate certainly implies that Tepco must know the cavity to be water-filled at the time of explosion. The theory seems to be fed by a suspicion that water fed to the SFP now overflows back into the reactor. One cannot have it both ways, I think, unless the same explosion which so very fortunately damaged the gate such that a disastrous fire could be averted, unfortunately also made the reactor leak. Good news/bad news.

Here's a link to Yomiuri's English translation of the original article:
http://www.yomiuri.co.jp/dy/national/T110428006723.htm

This new "Tepco theory" I think is boulevard like speculation by Yomiuri, it has not been echoed by any other main stream news agency. "Explosion saves us from a meltdown" is a spectacular headline that would have made the world circuit if indeed true.
Also note that Tepco made three public statements in April negating Yomiuri claims http://www.tepco.co.jp/en/news/topics/topics-e.html

By the way if the theory is true then that would mean that about 900 tons of water was boiled away 87 hours, or that the spent fuel pool has a heat source of 10.35 MW (about 4 times as much as all estimates). Furthermore, that means all 1331 spent + 204 new fuel rods were uncovered and as a result most of them would be damaged which contradicts the http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1302781546P.pdf" that most of the fuel rods are not damaged

 

[AntonL]

Jorge - great work you doing

It also shows that what appeared to be some Dark Goo streaming down the wall from the terrace is actually a bunch of cables. Some random comments about this old photo, based on the blueprints:
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/povray/blueprint/foto/edited/out/reactor4-S-1-A-e.png

A - Wall sections pushed out by the explosion. Same pattern on the other side of the entrance gallery. (Why only the sections on the far end of the gallery?)

The shock-wave could set up a standing waves in the refueling tunnel resulting in an uneven damage distribution

F - Outline of the SFP projected on the south face. The SFP cavity begins about 6.4 meters north of the south façade, and its internal dimensions are ~ 13.2 m E-W, ~10 m N-S. These numbers are my estimates assuming the drawings I have are correctly scaled. One of the drawings gives the total depth of the SFP as 13.020 meters.

This does not tie up with the published capacity = 1425 m³ http://www.nisa.meti.go.jp/english/files/en20110406-1-1.pdf"

 

[elektrownik]

SFP #4 underwater video ! http://www.tepco.co.jp/en/news/110311/images/110428_1.zip
We can see that upper parts of fuel sets are melted

 

[clancy688]

SFP #4 underwater video ! http://www.tepco.co.jp/en/news/110311/images/110428_1.zip
We can see that upper parts of fuel sets are melted

Um, sure...? It does look damaged. And half of the racks seem to be empty, which contradicts the "the SFP was overfilled" informations we have.
But I don't think that either of us knows how racks in a SFP look like... I'd like to hear Astronucs or NUCENGs opinion on this. What did TEPCO say?

Image for all who are to lazy to download the vid:

 

[zapperzero]

B - Markings left by the external staircase. It seems that the staircase was still there after the earthquake but before the explosion. Where did it go? is it buried under the rubble, or was it removed by workers early on?

Tsunami.

 

[|Fred]

SFP #4 underwater video ! http://www.tepco.co.jp/en/news/110311/images/110428_1.zip
We can see that upper parts of fuel sets are melted

I don't know about we... I do not know what I 'am seeing. But surely experts will
(sorry clancy688 about double post.. You're faster with the keyboard)

[PLAIN]http://img4.imageshack.us/img4/9593/snapshot20110429134921.jpg

 

[ceebs]

Um, sure...? It does look damaged. And half of the racks seem to be empty, which contradicts the "the SFP was overfilled" informations we have.
But I don't think that either of us knows how racks in a SFP look like... I'd like to hear Astronucs or NUCENGs opinion on this. What did TEPCO say?

Image for all who are to lazy to download the vid:

Does it fit with the number of rod assemblages that TEPCO has published as being in the pool?

 

[Astronuc]

Um, sure...? It does look damaged. And half of the racks seem to be empty, which contradicts the "the SFP was overfilled" informations we have.
But I don't think that either of us knows how racks in a SFP look like... I'd like to hear Astronucs or NUCENGs opinion on this. What did TEPCO say?

Image for all who are to lazy to download the vid:

I'll look at the video later. The rack in the center and the one to the left look like they have damaged fuel, but it's so murky. I would guess that the shinier bails (the handles) that are intact may be fresh fuel.

Unfortunately, the camera is not close enough to see the details of the upper tie plates, and the water is still relatively murky. It would be nice to have a map of the SFP racks so we know at what we're looking.

As far as I know, SFP had 1331 assemblies, so they still had room (see below - Unit 4 SFP capacity = 1590 assys). That was supposed to be a temporary situation since after the repair they would have put 548 assemblies back in the core.

Unit 2, 3 & 4 ponds are about 12 x 10 metres, with 1240, 1220 and 1590 assemblies capacity respectively (unit 1 is about 12 x 7 m, 900 assemblies). Unit 4 pond contains a total 1331 used assemblies (783 plus full fuel load of 548), giving it a heat load of about 3 MW thermal, according to France's IRSN, which in that case could lead to 115 cubic metres of water boiling off per day, or about one tenth of its volume. Unit 3's pool contains 514 fuel assemblies, unit 1 has 292 and unit 2 has 587, giving it a heat load of 1 MW. There is no MOX fuel in any of the ponds.

Ref: http://www.world-nuclear.org/info/fukushima_accident_inf129.html

In Unit 4, 204 assemblies were fresh fuel, so there is not heat from those. I'm not sure how IRSN estimated the heat load. They may have been somewhat conservative.

I understand that TEPCO was behind on getting spent fuel out of the common pool and into dry cask storage, and therefore were behind in getting fuel out of the SFPs, primarily from Unit 4.

 

[zapperzero]

Um, sure...? It does look damaged. And half of the racks seem to be empty, which contradicts the "the SFP was overfilled" informations we have.

Disclaimer: I am not a nuclear engineer, nor do I play one on TV. That being said, new fuel bundles have a handle on top and an end cap that it is attached to (the bright diagonal lines you see, oriented approximately vertically on some fuel bundles are the handles).

Some of those handles (and the caps of the bundles themselves) seem melted, in particular those in the rack that is partly visible in the bottom right corner, while others are simply not visible above the tops of the racks. I believe they call that "total meltdown"?.

One bundle in particular (upper left corner in the middle rack) looks as if someone/something punched a hole through its cap, although the handle is intact). Interesting?

Next to that middle rack, there is a "free-standing" bunch of seven bundles, of a different design (or maybe just in a different stage of meltdown). These are interesting as well, because they seem to be out of alignment with each other, suggesting that something has picked them up and set them back down none too carefully. The explosion, maybe?

There is one other thing in this picture that is not right at all. Some of the racks seem to be flush with the pool wall. Should they not be some distance off, so that the water can stop radiation, as in any other pool I have ever seen in a picture?

 

[MadderDoc]

<..>
2) seen from the top, and also for scaling purposes, the exact outside dimensions of the R/B 1 to 4 (1 is a little bit smaller maybe)?

I will see if i can try to estimate some rough volume of the basements we are talking about.

For a rough estimate of the length and width of buildings, the plant layout map should be able to yield data of sufficient precision:
http://gyldengrisgaard.dk/fuku_docs/plant/

Good estimates of the W and L of the reactor buildings might be of great utility to others, so do not hesitate to post them.

 

[zapperzero]

Is this Cherenkov light, or just heat?

 

[MadderDoc]

Hey Jorge Stolfi, you seem to know your building elevations so...if the RPV cap at the join to the vessel leaks and vents, what level or plane would it be projecting or slicing through in relation to Unit 3? Or if you cut the Unit 3 down to the elevation level with the RPV flange (like cap removed), what would it look like on your modeling?

From drawings we've seen, the level of the RPV flange would be close to the level of the floor below the service deck. I believe it is what is called the 4th floor of the building.

 

[rowmag]

Next to that middle rack, there is a "free-standing" bunch of seven bundles, of a different design (or maybe just in a different stage of meltdown). These are interesting as well, because they seem to be out of alignment with each other, suggesting that something has picked them up and set them back down none too carefully. The explosion, maybe?

Those are control rods, are they not?

NHK news tonight pointed out some debris that can be seen on top of the fuel assemblies in this video (right of, and down from, center of zapperzero's image), but didn't point out anything else as being of interest. (Not sure they have had an expert look at it yet, though.)

 

[GJBRKS]

Is this Cherenkov light, or just heat?

This is once again just enough 'peek-aboo' to let us know they have the authority ,
but too little to see what's going on...
I'm beginning to get desinterested ...

 

[MadderDoc]

Re Jorge's estimate of the SFP cavity dimensions, yielding a volume ~1690 m³

This does not tie up with the published capacity = 1425 m³ http://www.nisa.meti.go.jp/english/files/en20110406-1-1.pdf"

The NISA number is given as the water volume of the pool. It may be the equivalent of the SFP concrete cavity minus volume of steel liner minus volume of equipment installed inside the pool (e.g. heat exchangers).

 

[zapperzero]

A video dated April 22 with images from the emergency centre and from the reactor grounds:

Via http://ex-skf.blogspot.com/"

 

[Dmytry]

I'll look at the video later. The rack in the center and the one to the left look like they have damaged fuel, but it's so murky. I would guess that the shinier bails (the handles) that are intact may be fresh fuel.

Unfortunately, the camera is not close enough to see the details of the upper tie plates, and the water is still relatively murky. It would be nice to have a map of the SFP racks so we know at what we're looking.

As far as I know, SFP had 1331 assemblies, so they still had room (see below - Unit 4 SFP capacity = 1590 assys). That was supposed to be a temporary situation since after the repair they would have put 548 assemblies back in the core.

Ref: http://www.world-nuclear.org/info/fukushima_accident_inf129.html

In Unit 4, 204 assemblies were fresh fuel, so there is not heat from those. I'm not sure how IRSN estimated the heat load. They may have been somewhat conservative.

I understand that TEPCO was behind on getting spent fuel out of the common pool and into dry cask storage, and therefore were behind in getting fuel out of the SFPs, primarily from Unit 4.

why put fresh fuel into SPF anyway? Fresh fuel is much more reactive, and requires more boron...

 

[jlduh]

cant confirm but can't deny also... so who know, I don't believe in miracles, if they were injecting 70t per day and it was ok so why they chang it to 200t per day now ? Tsunami water shouldn't enter reactor building, it should be sealed, also I don't think that so much water missing SFP during injection, also water is radioactive so it can't be from tsunami

I have posted recently a message based on an article already posted where it was confirmed by a plant operator there just after the tsunami that the water flooded the basements of the turbine buildings (he talked about a max of 1,5m in one of the buildings). So there weren't not sealed, or no more sealed. The water from the tsunami can have diluted the water from the reactor of the SFP.

Now the tsunami water cannot explain a rise in the last weeks from a level of 80cm to a level of 5m of course (if measured at the same spot, which we don't know about).

 

[rowmag]

I'll look at the video later. The rack in the center and the one to the left look like they have damaged fuel, but it's so murky. I would guess that the shinier bails (the handles) that are intact may be fresh fuel.

Is the thing on the upper left of center a fuel rack, or something else? The square holes seem larger than those on the one in the lower middle (the one with shiny bails visible in it).

 

[jlduh]

Those are control rods, are they not?

To me that "cross" design looks like control rods, i agree, but Astro will probably give his opinion on that.

 

[AntonL]

A video dated April 22 with images from the emergency centre and from the reactor grounds:

Via http://ex-skf.blogspot.com/"

more than just the control centre
a complete tour of the plant with new views from car level

 

[Varon]

I wonder why CNN no longer reports about the nuclear plants.. guess it's no longer serious and problems almost solved. (?)

 

[~kujala~]

Now the tsunami water cannot explain a rise in the last weeks from a level of 80cm to a level of 5m of course (if measured at the same spot, which we don't know about).

It's not the same spot, 80 cm from the turbine building [1] and 500 cm from the reactor building [2].
[1] http://search.japantimes.co.jp/cgi-bin/nn20110329a1.html
[2] http://www.foxbusiness.com/industries/2011/04/18/japan-nuclear-agency-reactor-building-4s-basement-filled-meters-water/

As for the waterproof systems I think the reactor buildings should be waterproof (but nobody knows if they still are) whereas the turbine buildings probably are not. It costs a lot of money to make waterproof systems everywhere and nuclear industry wants to save money, of course.

 

[jlduh]

I wonder why CNN no longer reports about the nuclear plants.. guess it's no longer serious and problems almost solved. (?)

Well, i can confirm that here in France, the medias have completely left this subject out. They just mentioned the 25 Anniversary of the Thernobyl accident and of course the various events and protests in relation with this. But Fukushima has disappeared from their scope. I guess they would probably show some images if some new explosions were happening. As i said in other places, radioactivity is invisible and complex, so this is not good for medias audiences...

More surprising the french IRSN has completely stopped (since almost one month) to report what is going on at Fukushima, except in a weekly basis but more for the french citizens leaving in Japan. So basically difficult, outside of this forum (and because we all now have recorded the links to where to go to compile infos) to follow what is going on there...

 

[MadderDoc]

[PLAIN]http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/povray/blueprint/foto/edited/out/reactor4-S-1-A-i.png
(A larger version is http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/povray/blueprint/foto/edited/out/reactor4-S-1-A-e.png
<..>
B - Markings left by the external staircase. It seems that the staircase was still there after the earthquake but before the explosion. Where did it go? is it buried under the rubble, or was it removed by workers early on?

The video taken on March 11th shortly after the tsunami shows a large portion of the staircase to be still on the building, except the uppermost part of the staircase which is missing. The video does not give a view to the lowermost part of the staircase close to the ground level to see whether is has sustained any damage, but it would be reasonable to expect at least some damage to it since this part of the staircase was inundated by tsunami water with floating debris.

H - apparently, the original location of the Mysterious Green Box, that seems to have disappeared after the earthquake, uncovering the Door With Mickey Mouse Ears.

After having exhausted as good as I think I can other possibilities to explain the combined visuals of Mysterious Green Box and Mickey Mouse, I end up with that the Green Box is a piece of equipment Tepco had affixed to the outside wall, and Mickey Mouse is the jagged hole remaining in the wall after something forcefully made this piece of equipment come off the wall.

The tsunami as the culprit for this cannot be excluded, however this is rather high up on the wall, so I find it most reasonable to categorize the coming off of the Green Box, as earthquake damage.

I - A huge grenish "closet", flush against that wall. The dark bands above it, leading to the terrace, are bundles of cables or pipes. Is that the Mysterious Green Box? Too big for that?

If you mean the apparent green box standing at the _foot_ of the wall, I think it is about the right size (I estimate the dimensions of the green box to be about 4 x 4 x 2 m). If the scenario of earthquake damage making the box come off is assumed, this is one of the places it could have ended up. It might initially have fallen down more or less vertically during the earthquake, taking with it the upper part of the staircase. The tsunami waters could then have made the box end up in this corner, behind other debris.

 

[etudiant]

Separate question.
Assuming that the SFPs are largely intact and only need to be topped up periodically, what does this mean for the environment?
About 250 tons of water are being boiled off daily. Is that steam a carrier for significant radioactive contaminants or is it pretty clean?
The question will take on additional interest as the summer winds and taifun season approach.

 

[zapperzero]

Is that steam a carrier for significant radioactive contaminants or is it pretty clean?

Common sense would suggest that it is not clean, but rather laden with whatever can be dissolved from the fuel rods or "steam-cleaned" off the inner walls (mainly Cesium which is an alkali, but also other things like Technetium, even Uranium directly from the rods).

 

[MadderDoc]

Those are control rods, are they not?

NHK news tonight pointed out some debris that can be seen on top of the fuel assemblies in this video (right of, and down from, center of zapperzero's image), but didn't point out anything else as being of interest. (Not sure they have had an expert look at it yet, though.)

For comparison purposes, here's a photo looking into the SFP of unit 3 during its refueling in 2010. It appears to have been taken in a place in the pool roughly equivalent to where the the imagery from SFP4 was taken (I believe close to the FPM)

 

[etudiant]

Common sense would suggest that it is not clean, but rather laden with whatever can be dissolved from the fuel rods or "steam-cleaned" off the inner walls (mainly Cesium which is an alkali, but also other things like Technetium, even Uranium directly from the rods).

Just as you say.
The question is whether the ongoing gradual decay mobilizes material incremental material, or whether the 'steam cleaning' already experienced will have pretty much purged the pools by now.

 

[fluutekies]

For comparison purposes, here's a photo looking into the SFP of unit 3 during its refueling in 2010. It appears to have been taken in a place in the pool roughly equivalent to where the the imagery from SFP4 was taken (I believe close to the FPM)

http://gyldengrisgaard.dk/daiichigrab/unit3/f1-26.JPG

Here is another view into a SFP: http://allthingsnuclear.org/post/3964225685/possible-source-of-leaks-at-spent-fuel-pools-at

What are the disks between the casks?
In the TEPCO video rising gas bubbles can be noticed: H2 from Zr-alloy? Or degassing of the UO2 pellets from the rods like Xe, Kr ..?