Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[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 ..?

 

[fluutekies]

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.

Assuming non-criticality and no vigorous boiling, only the volatile content of the pool will enter completely into the atmosphere: H2O condensed as steam, all noble gasses, H2, O2, N2 etc .
If the pH of the pool is below 8, also HI, I2 will (partly) leave. Hopefully TEPCO added either sodium borate or neutralized the boric acid with lye to avoid acidifcation of the pool.
All metals, either as oxides or salts (ions) can not leave with the steam. But if a typhoon sucks up the water from the pool and disperse it with the wind, then it's a different story ...

 

[MadderDoc]

The recent data from the analysis of water from SFP4 would seem to me to be strong evidence of leaking. Taking account of the decay of iodine-131, the data for all three measured isotopes indicates that the pool has lost half of the content of soluble matter it had 14 days ago.
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110429e13.pdf

 

[zapperzero]

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 ..?

Most probably it's water - the pools are not exactly cold. The noble gasses have all left by now. Could be hydrogen, depending on how hot those rods still are, but I doubt it. At 500 C or so, there'd be many more bubbles, no?

It doesn't really matter anyway because there's no containment where H2 from the pools can accumulate and eventually explode.

 

[NUCENG]

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 see at least 16 fuel assemblies that appear to be totally intact in ther right corner of the fuel rack in the center of the picture. Bright shiny lifting bails (the diagonals you see) could be fresh fuel or used or spent.

I do see slabs and pieces of some kind of debris laying on tops of the bundles and in the bottom of the pool laying on top of what look to be cross members.

The racks along the wall to the left are not fuel racks. The ones at the top are too large and the ones with some sort of round caps are definitely not fuel.

The seven roughly cruciform shapes between the central rack and the fuel rack in the upper right may be control rod blades. The small lifting bail of a blade appears to be there.

In the central rack I see four positions in the corner at the top and five on the left side that appear to be empty. There may be some discoloration of these cells that may indicate heat and possibly melting down of fuel in those positions, I do not know which.

The other positions in that rack and in the other two racks visible may contain damaged fuel, or fuel assemblies with debris , or even just debris. Are their shadows in the pool such that only a few lifting bails appear shiny. Probably not because the tops of the racks look shiny and unmelted and intact.

I do not see any deformation or off kilter indications of an explosion that pushed stuff around. I would expect to see distortions and bent structures or even gaps if I was looking for conclusive evidence of explosion. Before you jump down my throat, that is not proof of no explosion, just a lack of proof that there was an explosion IN THIS CLIP.

I see debris moving around indicating turbulence or convection. Did they measure temperature of the pool? Were they pumping water into the pool? Probably not because the clarity of debris-filled water would probably not be so clear if they were spraying water through the debris over the pool.

I have stayed out of the photo interpretation game pretty much because it is simply too easy to see what we want to see. One of my first posts asked for people to let me know when they spotted Osama ibn Laden.

When you are performing photo reconnaissance and interpretation remember the observer who was aked what color the barn was. A good analyst would reply, "It is red, on this side."

 

[zapperzero]

Did they measure temperature of the pool? Were they pumping water into the pool?

My bet is this is the camera that was attached to the rig they used to get a water sample.