Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[PietKuip]

Again we two possibilities

a. Nuclear explosion ala Gunderson
b. Steam explosion by flash boiling

I think we can discard Gunderson nuclear explosion, that to me is the wildest speculation for a fuel pool that was fairly sparsely packed. It contained 548 spent fuel assemblies with an estimated heat load of 200kW (compare this to SPF 4 with 1535 fuel assemblies and a heat load 2000 to 2400kW)

There was also fresh fuel in the same #3 pool. Which to me seems a risky thing to do. A nuclear explosion cannot be excluded.

Do we know how big this spike was in absolute terms, or was it just 12 times the normal background level in the seismic refuge building?

This is all we know:
"When the No. 3 reactor housing exploded on the morning of March 14, levels inside the bunker jumped as much as 12-fold, [Kazuma Yokota] said, checking dates and times in a pocket diary. "
http://www.bloomberg.com/news/2011-04-25/japan-s-terrifying-day-saw-unprecedented-exposed-fuel-rods.html

 

[Jorge Stolfi]

The basic premise of a spent fuel pit is you build it so criticality is impossible. You do that by two different means:

I understand that that the original arrangement was safe because of its low density, but after re-racking with close-packed assemblies they had to rely on absorbers. It seems they use them even in the casks, out of concern for possible criticality --- even though the casks have no moderating water and hold much less fuel.

BWR's don't use borated water like PWR's do so if they use poison it's either those Boraflex plastic inserts or boron bearing steel racks.

Others have mentioned boral (same boron carbide powder as boraflex but in an aluminum matrix instead of silicone plastic). IIRC TEPCO uses boral in the casks. On the other hand it is the first time I hear of borated steel in the SFP. I know it is used in reactor control rods; but also in SFPs?

Zircalloy starts reacting significantly with water at 800C, right?Aluminum melts at <700C and silicone should decompose into gas + silica ash well before that. So if #4's explosion was due to H2, it must have come from the SFP, and therefore some of the neuron absorbers must have collapsed. (Would that be visible in the movie? The heads of the assemblies are a feet or two away from the fuel, so they would remain relatively cool, no?)

The last obstacle is the lack of moderator. A couple of days ago I proposed that, once the fuel becomes partly dry, the water level inside the racks could begin to oscillate due to delayed feedback between rising level and increased steam production. That could be a mechanism for first getting rid of the boral and then returning water to the scene, independent of external spraying.

Note also that keff = 0.95 does not allow an exponenially increasing fission chain reaction, but still it means that the natural level of spontaneous fission is amplified by 1/(1 - 0.95) = 20 times. How significant is that?

 

[swl]

Something else, could someone tell me what is the title of this parameter (Unit 1)

https://spreadsheets.google.com/spr...ZDbX39YK-iFb0Iw&hl=ja&authkey=CP6ewJkO#gid=41

FPCスキマーサージタンクレベル (mm)

FCP Skimmer Surge Tank Level (mm)

 

[TCups]

REGARDING THE EXPLOSIONS OF BOTH UNITS 1 AND 3 - DID STEAM FLASH OCCUR?

I think you described Unit 1's explosion perfectly, at least the water flashing to steam part. See beginning at 32 seconds http://www.youtube.com/watch?v=OFt1OHU1u9s"

Hey, I think razzz is right. There was a steam flash at Unit 1, too, just a lot smaller volume of water flashed to steam. Excellent observation, IMO, razzz. Thank you.

Q: Why the difference between the relatively small steam flash at Unit 1 and the massive steam flash at Unit 3?

A: The difference may have been:
1) the explosion in the drywell at Unit 1 and the amount of rapid turbulence venting from the fuel transfer chute or concrete plug "burp" or both caused in SFP3 vs only an overhead hydrogen explosion in Unit 1
2) the total amount of thermal energy stored in SFP3 > SPF1 before the explosion.

Obviously these aren't mutually exclusive, and it seems to me, both were probably the case.

@anton:
Brilliant analysis on the thermodynamics of the steam flash at Unit 3, Anton! I am glad there is someone here at PF with the brains to help back up at least some of my wild speculation and off-the-wall theories. Thank you, sir.

 

[razzz]

REGARDING THE EXPLOSIONS OF BOTH UNITS 1 AND 3 - DID STEAM FLASH OCCUR?



Hey, I think razzz is right. There was a steam flash at Unit 1, too, just a lot smaller volume of water flashed to steam. Excellent observation, IMO, razzz. Thank you.

Q: Why the difference between the relatively small steam flash at Unit 1 and the massive steam flash at Unit 3?

A: The difference may have been:
1) the explosion in the drywell at Unit 1 and the amount of rapid turbulence venting from the fuel transfer chute or concrete plug "burp" or both caused in SFP3 vs only an overhead hydrogen explosion in Unit 1
2) the total amount of thermal energy stored in SFP3 > SPF1 before the explosion.

Obviously these aren't mutually exclusive, and it seems to me, both were probably the case.

@Anton:
Brilliant analysis on the thermodynamics of the steam flash at Unit 3, Anton! I am glad there is someone here at PF with the brains to help back up at least some of my wild speculation and off-the-wall theories. Thank you, sir.

I'm just guessing but the wild card in Unit 3 is the MOX fuel.

 

[MadderDoc]

Explosion Unit 3 – Putting it together.
<..>somewhere near the surface the what is left over from the >100^oC hot water would convert to steams and boiling would only be apparent near the surface of the water. <..>

Stop there. Just because a volume of water is above 100^oC, doesn't mean that this water can all convert to steam. The liquid to vapour transition for water is strongly endothermic (energy demand 2257 MJ/ton).

If you have 1 ton of water at, say, 110^oC at atmospheric pressure, this unstable system has energy only to convert itself to a mixture of 980 kg liquid water and 20 kg water vapour at 100^oC. If you extend this to a sfp of 1400 m³, about 30 tons of water vapour could be produced.

Problem is, as I see it, that this amount of vapour is insufficient to explain the size of the mushrooming cloud and the apparent size of its lifting capability.

 

[TCups]

REGARDING THE HIGH SPIKE OF MEASURED RADIATION ASSOCIATED WITH UNIT 3'S EXPLOSION

This is all we know:
"When the No. 3 reactor housing exploded on the morning of March 14, levels inside the bunker jumped as much as 12-fold, [Kazuma Yokota] said, checking dates and times in a pocket diary. "
http://www.bloomberg.com/news/2011-04-25/japan-s-terrifying-day-saw-unprecedented-exposed-fuel-rods.html

Could there be another plausible explanation? For example:

Could the spike in measured radiation levels be explained by the explosive release of volatile iodine and cesium (or other highly radioactive isotopes) from the explosion and venting of the contents of the drywell of Unit 3, lofted by the associated steam flash? I believe there were smaller spikes in measured radiation during controlled venting. It would seem to make sense that explosive venting would be a much larger spike.

Could some of the contents of SFP3 also have been damaged by an explosion and steam flash and also lofted and scattered, perhaps also contributing to the spike?

 

[artax]

Having previously not understood the mechanism for instantaneous conversion of water to steam and the possible resulting high energy explosion, I now do see that it's possible. The PRINCIPLE section of this page:- http://en.wikipedia.org/wiki/Boiler_explosion. explains.
However I think that for the explosion of unit three to be due to a steam explosion, it would mean there had been a catastrophic failure of the pressure vessel to produce so much steam instantly.
I think this has been ruled out due to the radioactivity and isotopes found.

Do we have an approximate figure for the power of that explosion...based on the dimensions of the rising cloud...or the fact that it was heard 30 miles away?

 

[TCups]

Stop there. Just because a volume of water is above 100^oC, doesn't mean that this water can all convert to steam. The liquid to vapour transition for water is strongly endothermic (energy demand 2257 MJ/ton).

If you have 1 ton of water at, say, 110^oC at atmospheric pressure, this unstable system has energy only to convert itself to a mixture of 980 kg liquid water and 20 kg water vapour at 100^oC. If you extend this to a sfp of 1400 m³, about 30 tons of water vapour could be produced.

Problem is, as I see it, that this amount of vapour is insufficient to explain the size of the mushrooming cloud and the apparent size of its lifting capability.

Yes, clearly a large amount of energy is required for phase change from water at 100ºC to steam at 100ºC (the old chemist seems to remember the heat of transition is 880Kcal/mole), but water will boil to water vapor at room temp in a vacuum (ie, from a rapid drop in pressure). Agitating heated water at the bottom of the pool, bringing it to the top of the pool, would have occurred (ie, a rapid decrease in the pressure). Consider also not vaporization but atomization of water droplets resulting from a drywell explosion, then combined with mixing the atomized water droplets with a secondary hydrogen explosion in the upper building.

Regrets that I cannot provide the calculations or perhaps even a very detailed description, but it seems that there may have been several factors contributing to the rapid production of steam. Also, I don't know that flashing of tons of water to steam were involved, though again, I fall short of PF standards in not being able to provide the calculations needed to support a reasonable estimate of the volume of water which may have flashed to steam in the explosion at Unit 3.

 

[Rive]

Whichever is correct or a combination of both, does not necessarily account for the spectacular vertical column, something else must have happened, and we need a barrel pointing to the sky, this barrel is the spent fuel pool.

I'm still skeptic about the SFP. The first (hydrogen) explosion most likely 'cleared' the roof and most of the walls (like on U4). But the vertical column still moved a lot of (new) debris/dust. Where is the source of that dust/debris? The SFP has no such severe structural damages, it cannot supply so much material.

So we are searching for a barrel and a hole too. The NW corner has both of them. IMO that part is more logical source than the SFP.

Ps.: I cannot discard the possibility of criticality accident in SFP#3, but the energy release of such accident has a hard upper limit - there are no structural damages in the SFP itself.

 

[MadderDoc]

I think you described Unit 1's explosion perfectly, at least the water flashing to steam part. See beginning at 32 seconds http://www.youtube.com/watch?v=OFt1OHU1u9s"

I think the steam cloud whose condensed top we can see rising swiftly to dissipate over unit 1 is just from the hot humid air produced by the hydrogen explosion.

This air mass is rising because it is hot and humid, i.e has a lower density than atmospheric air. It is swiftly dissipating because the amount of water from the hydrogen explosion was not huge, and it is white/colorless, because contained in it was after all only air and steam.

Unit 3 that is another story.

 

[SteveElbows]

Any reaction welcome:

2. Take a look at the attached image from the unit 4 SFP.

I explained what is labelled on that picture as being damaged grid & damaged vertical row in the past. This is not actually damage to the fuel assembly storage racks, it is actually handles/lugs that are part of the racks themselves (as opposed the the fuel handles), handles that protrude above the rest of the rack. And so when viewed from that angle at that low resolution, it can appear like a distortion to the grid.

If you watch the 2nd, longer unit 4 fuel pool video then you can see these more clearly, along with other features.

edit - I attach an image from the 2nd video that shows these handles clearly.

 

[AntonL]

Stop there. Just because a volume of water is above 100^oC, doesn't mean that this water can all convert to steam. The liquid to vapour transition for water is strongly endothermic (energy demand 2257 MJ/ton).

If you have 1 ton of water at, say, 110^oC at atmospheric pressure, this unstable system has energy only to convert itself to a mixture of 980 kg liquid water and 20 kg water vapour at 100^oC. If you extend this to a sfp of 1400 m³, about 30 tons of water vapour could be produced.

Problem is, as I see it, that this amount of vapour is insufficient to explain the size of the mushrooming cloud and the apparent size of its lifting capability.

Do not think the the upward moving column of dust as a shotgun propulsion but rather as an atmospheric thermal of sucking up the dust. when the steam condenses back to water droplets the stored heat is released into the air causing more heating and updraughts. (same process as in cumulus clouds that have up drafts of high enouh velocity for tennis sized hail stones)

 

[jlduh]

TEPCO has only "repaired" the reactor water level sensor A. Sensor B is the old one. A is reported as "Off scale" (water level lower than 5 m below the "former" top of fuel) .

Nisa is saying no need to inject as much water in N°1 if fuel has fallen to the very bottom of RPV...

http://www3.nhk.or.jp/daily/english/13_26.html

NISA: no need to flood No.1 reactor
An official of Japan's nuclear safety agency has suggested that a nuclear fuel meltdown at one of the damaged Fukushima reactors means that filling the reactor's container with water may be meaningless.

Hidehiko Nishiyama told reporters on Friday that melted rods at the bottom of the No. 1 reactor are being cooled by a small amount of water.

Whata are your opinions about that? Can some calculations be made (i imagine that they consider that most of the heat could be removed by steam production if there is no real flow except the leaks (which might be important though...).

But... we see no steam coming out, so it's only leak flow that would cool the melted core?

I'm getting lost.

 

[MadderDoc]

Yes, clearly a large amount of energy is required for phase change from water at 100ºC to steam at 100ºC (the old chemist seems to remember the heat of transition is 880Kcal/mole), but water will boil to water vapor at room temp in a vacuum (ie, from a rapid drop in pressure). Agitating heated water at the bottom of the pool, bringing it to the top of the pool, would have occurred (ie, a rapid decrease in the pressure).

However true that is there is still no free lunch as regards the heat of transition.
It must be served, or you will not have any vapour no matter how much you tune down the pressure.

Consider also not vaporization but atomization of water droplets resulting from a drywell explosion, then combined with mixing the atomized water droplets with a secondary hydrogen explosion in the upper building.

I am not sure what you are saying there. The problem I see is one of size of cloud and one of lifting capability. Water in tiny droplets do not take up much space, and do not contribute to lift.

Regrets that I cannot provide the calculations or perhaps even a very detailed description, but it seems that there may have been several factors contributing to the rapid production of steam. Also, I don't know that flashing of tons of water to steam were involved<..>

OK, so you don't know that flashing of tons of water to steam was involved. However you do know, I believe, that 'something' propelled a diversity of heavy objects 100s of meters into the air. If a huge amount of water vapour rising didn't do it, what did?

 

[SteveElbows]

That was definitely not a function of wind.

Wind was clearly blowing to the SE at that point.

Steam (presumably) was spewing straight out of #3, sideways, toward the north, and then getting blown by the wind out to sea, towards the SE.

I feel that you are ruling out weather phenomenon too definitively here. Failure to take into account a range of weather phenomenon has caused repeated wild speculation over the last week, based on live feed images. There is now a danger that if something really does change, we may miss it because we are so used to these false stories caused by live feed images.

As you can see, people are mostly not too surprised to hear of stuff coming from the north end of the building. Perhaps it would be helpful for you to review a video that was shot early on, and shows an area where this stuff is likely to be coming from:

http://www.youtube.com/user/modchannel

Check out the above at around 3:08, 3:23 and 3:48 for a view of what was escaping from the north side in the past.

 

[AntonL]

Nisa is saying no need to inject as much water in N°1 if fuel has fallen to the very bottom of RPV...

http://www3.nhk.or.jp/daily/english/13_26.html
Whata are your opinions about that? Can some calculations be made (i imagine that they consider that most of the heat could be removed by steam production if there is no real flow except the leaks (which might be important though...).

But... we see no steam coming out, so it's only leak flow that would cool the melted core?

I'm getting lost.

"Feed and Bleed" or "Chernobyl by Drip Feed" whatever you want to call it continues by the NISA comment, closed loop cooling is the only way forward.

@NISA and @Tepco if you run out of creative thinking please enlist as many specialists from around the world, to brain storm, analyse and come up with viable solution. At the moment your direction remind me of silk paper blowing in the wind.

 

[MadderDoc]

Do not think the the upward moving column of dust as a shotgun propulsion but rather as an atmospheric thermal of sucking up the dust. when the steam condenses back to water droplets the stored heat is released into the air causing more heating and updraughts. (same process as in cumulus clouds that have up drafts of high enouh velocity for tennis sized hail stones)

Right, exactly. A cumulus cloud needs no barrel, it has direction 'up' due to gravity and it has considerable lifting properties. So why invoke a need for a barrel in the case of the unit 3 cloud?

 

[clancy688]

Q: Why the difference between the relatively small steam flash at Unit 1 and the massive steam flash at Unit 3?

A: The difference may have been:
1) the explosion in the drywell at Unit 1 and the amount of rapid turbulence venting from the fuel transfer chute or concrete plug "burp" or both caused in SFP3 vs only an overhead hydrogen explosion in Unit 1
2) the total amount of thermal energy stored in SFP3 > SPF1 before the explosion.

I don't know if that has probably something to do with the different explosions in Unit 1, 2 and 3, but I just recently discovered that Unit 1 had a totally different emergency cooling system compared to Unit 2 and 3.
And because of that, Unit 1 probably had far less water and steam at time of its explosion than Unit 2 and 3 at time of theirs.

Both images are taken from this Caltech presentation: http://www.galcit.caltech.edu/~jeshep/fukushima/ShepherdFukushima30April2011.pdf


According to these images, it's normal under emergency cooling conditions that the Drywell in Units 2 and 3 is filled with hot steam.

 

[smartie18]

Who knows what really happened there actually. I heard so many conspiracy theries about the Japan thing that I am almost starting to believe some of them. It's weird that the Japanese would let something like that happen.

 

[zapperzero]

I think you described Unit 1's explosion perfectly, at least the water flashing to steam part. See beginning at 32 seconds http://www.youtube.com/watch?v=OFt1OHU1u9s"

I see part of a shock front there, going up as if from a large cannon barrel or the tailpipe of a bike when it misfires. I also see a lot of debris/dust/smoke going to the sides and nothing going upwards. No steam until very late on.

If you look closely, you can see the roof going up, as a black spot in the middle of the cloud of dust. The shock front must have passed through it, but not whatever else was beneath, creating conditions for that nice disk to be visible.

If I squint just right, I think I also see some orange light, just before the shock front goes up, obscuring everything. Hey, that's no steam explosion! Must've been Osama.

EDIT: I am not implying there was some sort of barrel involved. Just what it looks like. Of course, the shock front is almost hemispherical, perhaps a bit flattened at the top (the lighter debris and dust travels with it, very visibly marking the parts going outwards; upwards, we have just condensation from compression for a while, then nothing).

EVEN LATER EDIT: The nice condensation disk tells us the shock front was supersonic.

 

[Borek]

However true that is there is still no free lunch as regards the heat of transition.
It must be served, or you will not have any vapour no matter how much you tune down the pressure.

I just did some back of the envelope calculations. To cool down water by 1 deg C one have to change 0.186% of that water into gas.

This is just to give some number to make further discussion easier.

 

[artax]

From a bit of reading I would estimate the unit 3 blast to be less than 10 GJ, based on the Flixborough disaster (60GJ) and the Glennan Barracks bombing (4GJ) though this is somewhat a wild guess as some channelling of the blast at unit 3 could have prevented nearby building damage.

 

[AntonL]

Problem is, as I see it, that this amount of vapour is insufficient to explain the size of the mushrooming cloud and the apparent size of its lifting capability.

Look at this video of US soldiers blowing up a jungle cocaine factory,

Pillar and mushroom development after a small scale military explosion
http://topdocumentaryfilms.com/cocaine-submarines/
[PLAIN]http://k.min.us/in6Hxg.JPG

concerning lifting capacity, all held up by air being a couple of degrees warmer
[URL]http://www.abqballoonrides.com/images/2008_NJFOB.jpg[/URL]

 

[MadderDoc]

Having previously not understood the mechanism for instantaneous conversion of water to steam and the possible resulting high energy explosion, I now do see that it's possible. The PRINCIPLE section of this page:- http://en.wikipedia.org/wiki/Boiler_explosion. explains.
However I think that for the explosion of unit three to be due to a steam explosion, it would mean there had been a catastrophic failure of the pressure vessel to produce so much steam instantly.

If instrument readings can be trusted, the PV had already failed on March 13th. At the time of the explosion, the PV was leaking, held a pressure about 4 bar, while the CV held about 5 bar, and the CV probably had within it the major part of the water contained in the combined system. So it could well also have been a catastrophic failure of the containment vessel. While a steam explosion from the CV couldn't likely have left the PV quite untouched, we cannot conclude that such an event would necessarily lead to the PV spewing all its content into the air.

I think this has been ruled out due to the radioactivity and isotopes found.

Yes, I've been told that before, albeit so far with no proper reference to this allegedly conclusive analysis. :-) (I'm sure my scepticism is showing.)

 

[SteveElbows]

That's either due to local weather at night (as discussed before), or because they fill the SFP's at night and this is creating a lot of fog. Or even both.
It would make sense to fill up the SFP's at night in the latter case; makes for a safer working environment during daytime, doesn't it.

The question of putting water in the pools at night has come up several times before. But the official updates give times for pumping & spraying at various pools, and these times indicate that it is extremely rare for any of this stuff to be done during hours of darkness.

 

[artax]

I must say I assumed some channelling of unit 3 explosion, or barrel if you like, due to the large piece that is propelled perfectly vertically, and falls almost where it rose from,... though probably slightly (though imperseptibly) to the right (or Southeast) due to the wind, the cloud however moves with the wind, due to it's low density.
That large piece must have been directly ballanced on the balloons centre if we're simply talking bouyancy! and what is it? the floor above the SFP?

 

[SteveElbows]

If I squint just right, I think I also see some orange light, just before the shock front goes up, obscuring everything. Hey, that's no steam explosion!

When you say orange light, do you mean the fireball to the south of the building that's clearly visible?

 

[zapperzero]

When you say orange light, do you mean the fireball to the south of the building that's clearly visible?

I circled it in the attachment. It's to the south I think, yes.

 

[AntonL]

I just did some back of the envelope calculations. To cool down water by 1 deg C one have to change 0.186% of that water into gas.

This is just to give some number to make further discussion easier.

or to cool the volume of the SFP by 1^oC would release .596 GJ

 

[TCups]

However true that is there is still no free lunch as regards the heat of transition.
It must be served, or you will not have any vapour no matter how much you tune down the pressure.

Understood. I was attempting to say that the total amount of heat required for phase change is a constant, but that it would not be correct to think that all of it must be applied instantly, or that very high temperatures are necessary to supply the heat of transition. Heat energy continues to be stored in water undergoing heating at 100ºC even though the temperature does not appear to change. There can be a huge difference in the total energy stored in two pools of water, each at 100ºC and each under the same pressure, unless I misunderstand the concept of the heat of transition and phase change.

Edit: Reference added - http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/phase.html

I am not sure what you are saying there. The problem I see is one of size of cloud and one of lifting capability. Water in tiny droplets do not take up much space, and do not contribute to lift.

True, but tiny droplets of water require less total thermal energy (although not per unit volume) than a massive pool of water requires in order to undergo the phase change. Is it not possible that atomized water droplets intermixed with burning hydrogen + oxygen might be efficiently heated and turned into additional steam during the hydrogen explosion itself?

OK, so you don't know that flashing of tons of water to steam was involved. However you do know, I believe, that 'something' propelled a diversity of heavy objects 100s of meters into the air. If a huge amount of water vapour rising didn't do it, what did?

In part, perhaps the hydrogen explosion itself, of course, but I strongly suspect a steam explosion based on what I see, even if I don't "know". I suppose that it is sort of like the old joke about the prostitute (do you know it?) . . . I presume that we have already established, by its characteristics that a large component of the explosion of Unit 3 was a steam explosion. So now, we are just haggling over the "price" (and source) of thermal energy required to fuel it. Anton gave some reasonable calculations, I believe.

Edit: Reference added - http://en.wikipedia.org/wiki/Water_vapor#Lifting_gas

Lifting gas
Due to its low molecular weight, water vapor is a lifting gas under STP conditions; however, it is limited by the low amount of water vapor which can exist in the air at a given point in time. High enough temperatures to maintain a theoretical "steam balloon" yield approximately 60% the lift of helium and twice that of hot air.[9]


Potential sources of thermal energy I can see are these:

1) thermal energy stored in the water of SFP3 transferred from decay heat of spent fuel rods in the pool,
2) thermal energy transferred from burning hydrogen in the building above SFP3,
3) thermal energy from the RPV transferred by explosive venting of steam and hot (radioactive) gasses from the drywell or upper "wet well" or both,
4) thermonuclear energy from sudden criticality occurring in the unspent fuel in SFP.

And say, don't I remember a passive emergency cooling system that operates without electric power driven by a steam turbine that circulates through a cooling pool? Was such a mechanism in operation at Unit 3? Would that have been in any way related to heating SFP3 (ie, was initial emergency cooling of the Unit 3 core at the expense of additional heating of SFP3 or is another water reservoir used for this emergency system, if it was used)?

Are there any other substantial sources of thermal energy that I have not considered?

I remember some earlier, detailed discussion about the calculation of energy released with the explosion of Unit 3 and, I believe that the final conclusion was that it could not even be estimated to within an order of magnitude with any reasonable accuracy. (sigh)

Edit by Borek: TCups, I corrected quote tags so that it is obvious what is a quote and what was your answer. If something is wrong, please contact me by PM and I will correct it again.

 

[artax]

this is one of the best shots without TV channel stuff covering bit up! could do with some contrasting though

http://www.youtube.com/watch?v=RxAHoxEvv7Y&feature=related

 

[jlduh]

Concerning SFP's and plugs, did we already have a clear statement about this subject: are the SFPs normally plugged with concrete removable roofs (some kind of anti-missile protection i think?)?At n°1 i don't see the SFP (maybe under the crane?), so is it plugged with these?

What about N°2 (which we don't see)?

N°3 we know that there is none currently, but what about before the explosion?

For N°4, even if it had some in normal use, it was getting fuel reloading so probably no plug anyway, which is consistent with what we see now.

Again, this subject is fuzzy to me. We can imagine that at N°3 for example, if there was some plug the explosion could be explained much differently.

I was really thinking that SFPs should have plugs for safety (missiles) reasons (which is a problem if cooling is stopped as gases are captured by the way!)

Could this explain the big hole above N°3 SFP, and maybe some big chunks of concrete thrown in the air?

 

[zapperzero]

The question of putting water in the pools at night has come up several times before. But the official updates give times for pumping & spraying at various pools, and these times indicate that it is extremely rare for any of this stuff to be done during hours of darkness.

Well, some nights the plant's all lit up and steam's coming out. Other nights it's pitch black.

 

[elektrownik]

No, there is no protection on SFP, they are open.