Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[zapperzero]

If there had been no explosion, would it have been possible to activate the #3 SFP cooling equipment? The primary containment of #3 seems to be leaking into the (former) service space, so if the building had not exploded it would have been filled with radioactive steam from the top down, through the fuel chute and stairwells.

There's water in the basement, too. Corium may be there as well. What matter, if it gets filled top-down or bottom-up? Is it somehow better that a larger fraction of radioactive steam may be released into the atmosphere, as compared to Unit 2?!

 

[zapperzero]

Well. a) Unit 2 and 3 do not vent through the same stack. b) to be consistent with the Japanese Government report to the IAEA, the inoperable vent in question would be one of the S/C side valves, i.e. a valve deep down in the bowels of the beast, in the basement floor of unit 2.

Well then I don't understand

 

[SteveElbows]

Well. a) Unit 2 and 3 do not vent through the same stack. b) to be consistent with the Japanese Government report to the IAEA, the inoperable valve in question would be one of the S/C side valves, i.e. a valve deep down in the bowels of the beast, in the basement floor of unit 2.

I went looking for which technical document I had seen which suggested explosion at 3 caused problems at 2. I did not find very much in the documents sent to IAEA. But I found something in the last report TEPCO did, which I think is only in Japanese so far:

http://www.tepco.co.jp/cc/press/betu11_j/images/110618l.pdf

Unfortunately I think that computer translation of this document is perhaps not good enough for this discussion, so I wait for a better translation. If anyone wants to have a go, try page 27 of that document.

 

[Jorge Stolfi]

There's water in the basement, too. Corium may be there as well. What matter, if it gets filled top-down or bottom-up? Is it somehow better that a larger fraction of radioactive steam may be released into the atmosphere, as compared to Unit 2?!

Sorry for my confused prose. I meant to say that the steam leaking from #2's containment may be cleaner than that leaking from #3, because #2's may be going through the suppression pool scrubber, while #3's seems to be going straight into the service space through the refueling pool. So, without the explosion, #3 may have been more off-limits than #2.

 

[MadderDoc]

If there had been no explosion, would it have been possible to activate the #3 SFP cooling equipment?

I think ultimately yes, but not right away, there might be some non-standard electrical repair needed. As the narrative is being sketched out before us, unit 3 is the bad guy contributing in some fashion to the demise of both unit 2 and unit 4. Swallowing that, if unit 3 had not exploded things might've developed in a much more benevolent direction.

The primary containment of #3 seems to be leaking into the (former) service space, so if the building had not exploded it would have been filled with radioactive steam from the top down, through the fuel chute and stairwells.

Fair enough, but there are caveats: this is assuming that the leaking was not caused by the explosion. It also assumes that the observed steam leaking is from containment vessel water, and not more trivially, water leaking from the sfp and into the hot space above the reactor and the containment vessel.

In contrasts, the leak of #2's primary containment seems to be in the suppression chamber, right? So the escaping steam is perhaps being scrubbed, with most its radioactivity going into the basement water rather than into the building's atmosphere. If that is true, then, without the explosion of #3, the contamination inside it could have been worse than that in #2. Does this make sense?

It does, and with the caveats above, it's plausible.

 

[zapperzero]

Sorry for my confused prose. I meant to say that the steam leaking from #2's containment may be cleaner than that leaking from #3, because #2's may be going through the suppression pool scrubber, while #3's seems to be going straight into the service space through the refueling pool. So, without the explosion, #3 may have been more off-limits than #2.

No, sorry for MY confused prose.

I meant there is undoubtedly contaminated water in unit #3 basement and it is undoubtedly giving off radioactive steam which is contaminating the lower levels.

 

[MadderDoc]

I went looking for which technical document I had seen which suggested explosion at 3 caused problems at 2. I did not find very much in the documents sent to IAEA. But I found something in the last report TEPCO did, which I think is only in Japanese so far:

http://www.tepco.co.jp/cc/press/betu11_j/images/110618l.pdf

Unfortunately I think that computer translation of this document is perhaps not good enough for this discussion, so I wait for a better translation. If anyone wants to have a go, try page 27 of that document.

Thanks Steve, perhaps this is where it's coming from, whatever it is. I agree the machine translation is probably not good enough to decide what that is, but it seems clear at least that in the timeline for unit 2 in this document, all reference to the unit 3 explosion has not been omitted. This is unlike the unit 2 timeline reproduced in the appendix to the Japanese government report to the IAEA, which in comparison appears to have been scrubbed of reference to unit 3. Otherwise, the two timelines appear to be quite similar at about this time between March 13th and 14th.

 

[MadderDoc]

Considering the recent abduction of our only decent explanation of the observed heat signature in thermographs from the unit 4 reactor pit (=the explanation that hot water was leaking from sfp to pit), I feel I have a pebble in my shoe.

I previously posted a mapping of the contents of the pool -- based on the two videos from the SFP4 -- showing the number of racks to be fairly close to an early estimate of the number of assemblies in storage in the pool, and that gave me some confidence that I had 'seen them all'.

Already then some other posters said they felt that estimate was too low, that it probably did not include the newly removed core assemblies. I did look at the video data again, and could find possible room in the blind angles for a few extra racks, but certainly not enough to hold a full core load -- and left the question there -- on the impression that there was sufficient uncertainty about the actual number of assemblies to not necessarily produce an overt inconsistency between the mapped rackspace and the estimated range of the number of assemblies.

However, ever since, it's been the higher estimate of the number of assemblies in the pool that has kept popping up, also in data released directly by Tepco, and consequently my confidence in having seen them all during the mapping of SFP4 has eroded. Otoh, I still can't see where the extra assemblies could be hiding in the pool. I would be happy to have my results corroborated or rejected by another mapping attempt made independently from my own. Absent that, I must say that I cannot exclude based on my mapping that some assemblies may still be in the reactor pit.

 

[joewein]

Sorry for my confused prose. I meant to say that the steam leaking from #2's containment may be cleaner than that leaking from #3, because #2's may be going through the suppression pool scrubber, while #3's seems to be going straight into the service space through the refueling pool. So, without the explosion, #3 may have been more off-limits than #2.

When I calculated the amounts of cesium in the ~105,000 t of water in TEPCO's data sheet (reactor basements, turbine basements, trenches and rad waste buildings, but not in SPFs), I was amazed at the comparison of the units:

• 1/2 of the cesium is in unit 2 alone
• Another 1/4 of the total is in the central rad waste building, but was mostly pumped out of the #2 basement and trench.
• Almost all of the rest is in unit 3.
• A little more than 1% is in unit 1
• About 0.1 % is in unit 4

That means:

• Unit 2 was 3x as dirty as unit 3
• Unit 3 is 50% bigger and 30x as dirty by volume as unit 1

I can understand why the water in #2 is much dirtier if the gas has been scrubbed through S/C water. But why is #3 so much dirtier than #1, when #1 melted down at a much hotter stage (after only 5 hours), when its isolation condenser was barely effective while the core isolation cooling system in #3 kept injecting water for 3 days or so?

I guess it must all be a function of the pressure before venting and its effects on the containment...

 

[zapperzero]

• Unit 2 was 3x as dirty as unit 3
• Unit 3 is 50% bigger and 30x as dirty by volume as unit 1

I can understand why the water in #2 is much dirtier if the gas has been scrubbed through S/C water. But why is #3 so much dirtier than #1, when #1 melted down at a much hotter stage (after only 5 hours), when its isolation condenser was barely effective while the core isolation cooling system in #3 kept injecting water for 3 days or so?

Well, Unit 3 is much bigger than Unit 1 in terms of installed capacity (460 vs. 780 MWe), so that could be a factor as well.

 

[SteveElbows]

However, ever since, it's been the higher estimate of the number of assemblies in the pool that has kept popping up, also in data released directly by Tepco, and consequently my confidence in having seen them all during the mapping of SFP4 has eroded. Otoh, I still can't see where the extra assemblies could be hiding in the pool. I would be happy to have my results corroborated or rejected by another mapping attempt made independently from my own. Absent that, I must say that I cannot exclude based on my mapping that some assemblies may still be in the reactor pit.

The temperatures shown on the thermal images were not generally very high really. So I am not really sure that we have clear signs of a big source of heat in the reactor area, but I admit some of the thermal images still interest me in this regard. Is it possible that we are just looking at the heat of steam that has blown in a northerly direction as it rises up from the pool? Or we are looking at water that is in the pit & reactor well area, but is not really very hot?

I have trouble imagining some fuel still being in reactor area, because diagram from the other day that showed work to inject water into reactor well & pit areas, seems to suggest that the core shroud has been removed and placed in the pit. I don't imagine them having any fuel in the area if shroud has been removed. It would be helpful if we knew more about the exact stage the shroud replacement work was at when disaster struck.

 

[SteveElbows]

Thanks Steve, perhaps this is where it's coming from, whatever it is. I agree the machine translation is probably not good enough to decide what that is, but it seems clear at least that in the timeline for unit 2 in this document, all reference to the unit 3 explosion has not been omitted. This is unlike the unit 2 timeline reproduced in the appendix to the Japanese government report to the IAEA, which in comparison appears to have been scrubbed of reference to unit 3. Otherwise, the two timelines appear to be quite similar at about this time between March 13th and 14th.

While we are waiting for full translation, here are some interesting press stories based on the document:

http://www.yomiuri.co.jp/dy/national/T110619002601.htm

http://search.japantimes.co.jp/cgi-bin/nn20110619x2.html

There are some interesting details covered by these stories, including the venting problem and some other things that went wrong as a result of explosions.

 

[zapperzero]

The temperatures shown on the thermal images were not generally very high really. So I am not really sure that we have clear signs of a big source of heat in the reactor area, but I admit some of the thermal images still interest me in this regard. Is it possible that we are just looking at the heat of steam that has blown in a northerly direction as it rises up from the pool? Or we are looking at water that is in the pit & reactor well area, but is not really very hot?

It could even be heat from nuclides in the RPV walls and shroud, for all we know.

 

[SteveElbows]

It could even be heat from nuclides in the RPV walls and shroud, for all we know.

Any ideas how we learn more about this issue in theory? I have no proper sense in my mind of how much heat something like the shroud may create months after shutdown.

 

[zapperzero]

Any ideas how we learn more about this issue in theory? I have no proper sense in my mind of how much heat something like the shroud may create months after shutdown.

I'm under the impression that some of the posters here may have first-hand experience with such issues...

 

[jim hardy]

to (was it M'doc?) thought about explosion below decks

Did something change atop unit 3 in the first week ?



.....24(? i think) March..........16 March

(ignore the label - it's nobody here.)


telephoto compression distorts perspective, so count rafters on the right side of main beam.

 

[zapperzero]

to (was it M'doc?) thought about explosion below decks

Did something change atop unit 3 in the first week ?



.....24(? i think) March..........16 March

(ignore the label - it's nobody here.)


telephoto compression distorts perspective, so count rafters on the right side of main beam.

Are you sure you're looking at the same section of beam?

 

[robinson]

Yes.

 

[biggerten]

While we are waiting for full translation, here are some interesting press stories based on the document:

http://www.yomiuri.co.jp/dy/national/T110619002601.htm

http://search.japantimes.co.jp/cgi-bin/nn20110619x2.html

There are some interesting details covered by these stories, including the venting problem and some other things that went wrong as a result of explosions.

Man. The guy gets the battery from his car to power the valve to release pressure so they can inject water in No. 3. While nuclear reactor buildings explode from time to time. And earthquakes. In the dark.

Desperate measures in desperate times. I thought my job was hard. Hah! I am humbled. These guys are true heroes.

 

[razzz]

In the YouTube http://www.youtube.com/watch?v=lJjbNw07OUA" just after 7 minutes he says the shroud replacement was complete in Unit 4, according to his GE connections.

 

[SteveElbows]

to (was it M'doc?) thought about explosion below decks

Did something change atop unit 3 in the first week ?

(ignore the label - it's nobody here.)


telephoto compression distorts perspective, so count rafters on the right side of main beam.

The red rings in this photo are simply wrong and misleading.

The photo on right actually shows the section of beam going all the way to the east end wall, not just to the position indicated by red ring in the left photo. The photo on right is shot from a lower angle, causing this mistake to be made.

Look at the more noticeable beam that goes south (going left on photo) and is near the bottom of the picture on the right. This is the same beam that is near the bottom of the left picture, not the one half-way up.

If you already know this, and were advising us to ignore the red rings, then I don't know what else is supposed to be different in these two pictures, nothing has changed at all.

Edited to add a picture showing how things actually line up, since I am not sure my words made sense.

 

[etudiant]

An interesting take on the prospects for nuclear in China.
A senior researcher of the NDRC (National Development and Reform Commission) was interviewed at some length by 'Business China' here: http://en.21cbh.com/HTML/2011-5-11/yOMTc1XzIxMDEyOA.html

Takeaway was: nuclear is less bad than the alternatives and besides, Japan relied on antiquated reactors, badly located.
There was a nice dig at the safety of large dams in the interview, a gutsy move given the political support lavished on the Three Gorges project.

 

[jim hardy]

""'If you already know this, and were advising us to ignore the red rings, then I don't know what else is supposed to be different in these two pictures, nothing has changed at all."""

i do get frustrated by my clumsiness with "Paint" .

Indeed as you point out the left red ring should be dragged down until it grazes the east end of the beam, as does the right red ring. They are misaligned.

the angle of sunlight is different between the photos so illumination of the floor below the beams changed..

The feature i am interested in is not the beams but something underneath them, namely that black circle inside the ring in Mar 16 photo on right.
To me it looks like a hole in the deck below.
It is not visible in later photos.
It does show briefly in a March 15th helicopter video as mentioned a few pages ago..
around 1:10
so if it's an optical illusion it was there on two days.


What i was after is opinion on whether the black circle looks to anybody else like a hole in the deck. I sometimes suffer from what Mark Twain called "excess of imagination."
There seems to be plenty of photo expertise here. Perhaps somebody has another early photo or some enhancement tools that'd nail it yea or nay.

original is , again, at
http://cryptome.org/eyeball/daiichi-npp3/daiichi-photos3.htm
twenty-third one down.


jh

 

[Borek]

Catching up to congratulate you for being the poster of the ten thousandth post to this thread!

This is not the first time we hit 10k, however, some posts were deleted/moved to other threads.

 

[MadderDoc]

<..>
Did something change atop unit 3 in the first week ?
.....24(? i think) March..........16 March
<..>

March 24th, yes.

Water was replenished to the pool over that period, so that's something that changed drastically, but probably not what you are hinting at.

I've found no evidence of structural changes in the remains of the roof metal structure since the explosion on March 14th, and also not between March 16th and 24th. I don't think there has been any such changes. If you've counted different number of beams in these two photos, there's probably one that has been missed. The slightly different angle could well make the beams closest to the camera hard to detect in these photos, then try counting from the other direction. I think you will find everything matches up.

Compared to the March 16th photo, the photo from March 24th features a readily apparent dark discoloration of beams, girders and pillars, assumedly from the recent fire on the evening of March 23rd:

 

[WhoWee]

Man. The guy gets the battery from his car to power the valve to release pressure so they can inject water in No. 3. While nuclear reactor buildings explode from time to time. And earthquakes. In the dark.

Desperate measures in desperate times. I thought my job was hard. Hah! I am humbled. These guys are true heroes.

Absolutely!

 

[MadderDoc]

<..>
The feature i am interested in is not the beams but something underneath them, namely that black circle inside the ring in Mar 16 photo on right. To me it looks like a hole in the deck below.
It is not visible in later photos.

I too can make it look like a circle, but I am pretty certain it's an illusion, To make it look like a circle I need to blend in certain dark areas which via other photos can be identified as parts of material objects, not holes.

It does show briefly in a March 15th helicopter video as mentioned a few pages ago..
around 1:10
so if it's an optical illusion it was there on two days.

The date attribution is wrong for this video. Actually there are two videos there combined, including the video from which your photo was taken, both videos are from March 16th.

 

[Jorge Stolfi]

The temperatures shown on the thermal images were not generally very high really. So I am not really sure that we have clear signs of a big source of heat in the reactor area.

Perhaps it is just heat from the sun that is stored in the water during the day and released at night.

 

[MadderDoc]

The temperatures shown on the thermal images were not generally very high really.

The heat signature from that part of the building has generally been about 30^oC, or appr. 30^oC above ambient. See:
http://gyldengrisgaard.dk/fuk/thermal/thermala.html

So I am not really sure that we have clear signs of a big source of heat in the reactor area, but I admit some of the thermal images still interest me in this regard. Is it possible that we are just looking at the heat of steam that has blown in a northerly direction as it rises up from the pool? Or we are looking at water that is in the pit & reactor well area, but is not really very hot?

The signature indicates that going to sleep there on a stretcher across the reactor well on a freezing cold night during March or April, would have involved sleeping in a tropically warm and steamy environment at 30+^oC. Certainly that needs an explanation.

 

[clancy688]

Sounds probably silly, but...

What's with heat transfer from the pool to the RPV? Even if the gate's inteact, it should conduct heat.

So if there's 90+ degrees on one side and 20 degrees on the other, the other side is probably getting hotter.

Catching up to congratulate you for being the poster of the ten thousandth post to this thread!

But we're still only the second largest thread in PF. https://www.physicsforums.com/showthread.php?t=63689" thread has 10560 posts.

400 posts to go for number one.

 

[MadderDoc]

Perhaps it is just heat from the sun that is stored in the water during the day and released at night.

No, that's not possible. I foolhardily got in early summer mode and introduced a flock of reasonably cold resistant fish in my pond in late April, observing that a series of sunny days had managed to drive the water up to 15^o. During the night weather changed, temperature dropped to the freezing point, and next morning the pond stood at 3^o and not a fish was alive. If only it were so easy to stack solar heat for the night during the cold spring of the north temperate zone. If only.

 

[MadderDoc]

Sounds probably silly, but...
What's with heat transfer from the pool to the RPV? Even if the gate's inteact, it should conduct heat.
So if there's 90+ degrees on one side and 20 degrees on the other, the other side is probably getting hotter.

Surely that's something that could be estimated. The estimation should take into account not only the heat gain through the relatively small gate area, but also the heat loss through the disproportionately much larger remaining area interfacing with a colder atmosphere and supposedly colder reactor and containment structures.

 

[jim hardy]

"""I too can make it look like a circle, but I am pretty certain it's an illusion,...""

thank you, that's what i was after - another opinion on the dark circle.

i can live with "it's ambiguous".

Indeterminate is after all a valid state.

thanks for the input.

 

[MadderDoc]

"""I too can make it look like a circle, but I am pretty certain it's an illusion,...""
thank you, that's what i was after - another opinion on the dark circle.
i can live with "it's ambiguous".
Indeterminate is after all a valid state.
thanks for the input.

Personally I wouldn't say it is ambiguous. During the flight the video camera scans across the area in question, and in only a few frames there's this appearance of a circle. Skipping forward and backwards frame by frame It seems clear to me this effect is caused by the camera's looking through changing 'windows' in the rightmost steam plume caused by its swirling motion in the wind. It is easy enough to select a few frames in which it looks like there is a circle, but that does not mean one can cast away the great majority of frames in which nothing like a circle appears and it rather looks like there is a duck, a frog, Aladdin's jinni or something else or nothing but steam there.

 

[joewein]

What's with heat transfer from the pool to the RPV? Even if the gate's intact, it should conduct heat.

Yes, but until recently the water level on the reactor pit side of the gate was low, until they realized this removed radiation shielding for the steam dryer and cut-up shroud and topped it up.

While the water was low only the lower portion of the gate area would have transferred heat and the reduced water depth would have reduced convective transfer.

In the YouTube http://www.youtube.com/watch?v=lJjbNw07OUA" just after 7 minutes he says the shroud replacement was complete in Unit 4, according to his GE connections.

I noticed that too and then I saw someone post here that they were 5 months into a 10 month shroud replacement job. Unit 4 had been shut down either on November 29 or 30, depending on the source. The 10 months overall seem plausible, given it took more like 15 months the first time they replaced a shroud in Japan, but end of November to mid March is only 3 1/2 months.

TEPCO says the shroud in the tool bay was cut, so presumably that's the old one that had been cut up under water using plasma cutters and lifted out.

Toshiba writes that they surface-decontaminate all the metals using oxalic acid before starting the replacement. I don't think there can be a huge amount of decay heat from activated isotopes in the RPV steel or there would be a lot of gamma too and people couldn't be working in there during the repairs.

 

[jlduh]

Sounds probably silly, but...

What's with heat transfer from the pool to the RPV? Even if the gate's inteact, it should conduct heat.

So if there's 90+ degrees on one side and 20 degrees on the other, the other side is probably getting hotter.
But we're still only the second largest thread in PF. https://www.physicsforums.com/showthread.php?t=63689" thread has 10560 posts.

400 posts to go for number one.

Not all data in this other long thread come from peer reviewed articles, it seems

Being more serious, it seems they are moving a huge crane close to Building N°1, it's currently on Tepco webcam:

http://www.netimago.com/image_213177.html

http://www.netimago.com/image_213178.html

 

[joewein]

The crane at unit 1 most likely is for putting up the metal frame and polyester cover around the damaged building. Preparation work for it started on May 13, according to TEPCO.

Here's their plan:
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110614e17.pdf

Recently TEPCO's workers have been practicing assembling and disassembling the cover at Onahama port. Assembly at Fukushima 1 unit is scheduled after disassembly is finished at Onahama.

 

[etudiant]

Now appear to have a pump unit on reactor 1. Photo survey or water injection? Anyone have any insight?

 

[joewein]

According to TEPCO, pool water injection is now done via the pool cleaning and cooling system at all units (unit 4 having been the last one to make the switch from concrete pumps on June 16).

I don't think they'll cast concrete foundations for the cover, otherwise they didn't have to go for this lightweight design. They'll use a more robust structure for the next layer, whenever that will arrive.

Camerawork is a good guess.

Oops, it's gone again!

EDIT: The crane is too small for erecting that cover, but it may be used for clearing the place for the other one.

 

[tsutsuji]

The crane at unit 1 most likely is for putting up the metal frame and polyester cover around the damaged building. Preparation work for it started on May 13, according to TEPCO.

It could be the crane assembled by the worker who removed his mask for smoking :

According to TEPCO, the worker in his 50s was helping put together a crane on the morning of June 15 as part of preparations to build an enclosure around the plant's No. 1 reactor.
http://mdn.mainichi.jp/mdnnews/news/20110616p2a00m0na008000c.html

 

[zapperzero]

Is this the crane? I can't see it on the TEPCO feed. Screenshot taken at 09:45 GMT

 

[zapperzero]

Also, a report by TEPCO on the fact-finding expedition inside reactor #2.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110622_02-e.pdf

EDIT: 430 mSv/h at the bottom of the stairs leading to the first basement level.

 

[SteveElbows]

Also, a report by TEPCO on the fact-finding expedition inside reactor #2.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110622_02-e.pdf

EDIT: 430 mSv/h at the bottom of the stairs leading to the first basement level.

The water is a sinister colour.

As for the crane around unit 1, its been doing stuff almost every day at unit 1 for some time now - often appears to be dangling a probe of some kind, though in locations that are not intuitive to me.

 

[tsutsuji]

http://www.meti.go.jp/press/2011/06/20110622004/20110622004.html : The NISA agreed today with the request made by Tepco on 8 June to store more water in the Process main building :

OP5100 mm -> OP5600 mm
1.4 m above 1st basement floor -> 1.9 m
14,200 m³ -> 15,700 m³

http://www.bloomberg.co.jp/apps/news?pid=90920019&sid=a45S9fQOTF3A : this provides 5 more days of storing capacity, beyond the former 29 June expected overflow date.

http://www.yomiuri.co.jp/science/news/20110622-OYT1T00687.htm : the flows in the reactors are set as follows :

unit 1 : 3.5 tons/hour.
unit 2 : 4 tons/hour
unit 3 : 10 tons/hour

 

[SteveElbows]

Yep, water levels are now such an issue that they've been reducing the amount pumped into the reactors in order to buy themselves a bit more time.

 

[tsutsuji]

http://www.asahi.com/national/jiji/JJT201106220097.html : The filtration efficiency of the absorption facility and the coprecipitation facility put together was found to be OK in the tests with highly contaminated water. The efficiency of the absorption facility is lower with highly contaminated water than during the tests with low contaminated water, but that is still high enough.

 

[Atomfritz]

Also, a report by TEPCO on the fact-finding expedition inside reactor #2.

http://www.tepco.co.jp/en/nu/fukushi...10622_02-e.pdf

EDIT: 430 mSv/h at the bottom of the stairs leading to the first basement level.

Thank you for the link.

This weird color of the water looks to me like rust. It's just the same color you get when you have various sorts of scrap metal rusting in aggressive water.
Remember there are many different metals there and this can boost the rusting speed to a nearly explosive pace.
Just think of how fast the Komsomoletsk dissolved due to the titanium-steel rusting catalytics.

The saturation of the water with whatever dissolved in it appears quite high, as it is completely opaque.

Hope they will publish a chemical and radiological analysis of that liquid soon.

And, when I looked at the picture in detail, I noticed that the water level originally has been a few cm higher.
And the water apparently was originally not that intensely saturated with that brown stuff, as you can barely recognize the original flooding mark.

Could an explanation for these observations be that there is an opening at the height of the water level where the water flows off to somewhere else?
Could the observation of a higher original water level be caused by a widening of such an initial opening, maybe because insulation or other debris in the way has been swept away by the water flow?

 

[joewein]

This weird color of the water looks to me like rust.

There should be plenty of rust, given how salty the water is. I saw one report that the salt contents of the liquid in the basements still is 50-80% of that of sea water. Also, the relatively high temperature from the decay heat will accelerate the reaction speed.

Once they pump out salty radioactive water, treat it and pump it back as almost clean water, this will lower the salt contents, but will probably take a very long time to bring the NaCl concentration down to levels comparable to fresh water, as it will just dilute and dilute it.

Anything already touched by salt water will keep a slight salt crust when the liquid level drops. Anything already rusty will continue to draw moisture from the air (rust seeks moisture), which will keep the rust growing. I can't help wondering what the basements will look like in say 5 years from now. Will there be any metal staircases left?

The salt water contamination and resulting corrosion also has implications for units 5 and 6, which TEPCO has not officially written off as not restartable yet, and for Fukushima Daini which TEPCO would also like to bring online again ASAP.

And, when I looked at the picture in detail, I noticed that the water level originally has been a few cm higher.

Perhaps some water was pumped from the turbine hall basement, since the reactor building basement and turbine hall basements are connected.


The 430 mSv/h at the bottom of the stairs was pretty interesting. TEPCO is talking about drilling holes through the floor to near the torus, to fill the space around it with a cement/sand mix. A bit like drilling a hole down into hell...

 

[robinson]

The water is a sinister colour.

Doesn't that give a pretty good idea of where the reactor and the fuel ponds are, at least for building 2? The containment is structure is hug!

 

[zapperzero]

The 430 mSv/h at the bottom of the stairs was pretty interesting. TEPCO is talking about drilling holes through the floor to near the torus, to fill the space around it with a cement/sand mix. A bit like drilling a hole down into hell...

And a bit like pouring concrete over the scene of an accident while the investigation is ongoing.
EDIT: Can't be helped, I suppose, not if they want closed loop cooling. But still.