Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Krikkosnack]

I would expect those in the water being discharged in the ocean.

The measurements are mostly for volatiles such as Cs and I isotopes, which easily get out. Cs is also a decay product of Xe, which makes it easier to transport. On the other hand, Xe-137 has a very short half-life.

I would expect any fuel particles to be local to the plant, and discharge water.

Any failure from the spent fuel pool might pose a risk of release of less volatile fission products, if temperatures were high enough.

I'd be looking for Np-239 in the water, as well as isotopes of Eu, Ce, Ba, La, Y, Zr.

https://sites.google.com/site/analysisfukushima/
The isotope data were removed from English version.
The two versions are the same as each other from page 1 to page 10.
However the isotope data from page 11 are removed in English version.
You can see the isotope names and its data in Japanese version.
Please read the data from page 12 to page 14, which indicate the radioactivity at south discharge channel of nuclear reactor in Hukushima.
The data from page 15 to page 16 are the radioactivity at north discharge channel.
Please investigate them.


what already found (in bold) from different sources of information [PP=Power Plant]
http://www.rri.kyoto-u.ac.jp/NSRG/seminar/No110/Iitate-interim-report110404.pdf

Barium

Ba-137m - 2.552 minutes
Ba-139 - 82.7 minutes
Ba-140 - 12.74 days
Ba-141 - 18.27 minutes
Ba-142 - 10.6 minutes

Cobalt

Co-56 - 78.76 days
Co-57 - 270.9 days
Co-58 - 70.8 days
Co-60 - 5.27 years

Cesium

Cs-134 - 2.062 years (PP/air/soil sample)
Cs-134m - 2.90 hours
Cs-135 - 2.3E6 years
Cs-136 - 13.1 days (soil sample)
Cs-137 - 30.0 years (PP/air/soil sample)
Cs-138 - 32.2 minutes

Iodine

I-123 - 13.2 hours
I-125 - 60.14 days
I-129 - 1.57E7 years
I-130 - 12.36 hours
I-131 - 8.04 days (PP/air/soil sample)
I-132 - 2.30 hours (soil sample)
I-133 - 20.8 hours
I-134 - 52.6 minutes
I-135 - 6.61 hours

Lanthanum

La-140 - 40.272 hours
La-141 - 3.93 hours
La-142 - 92.5 minutes

Molybdenum

Mo-93 - 3.5E3 years
Mo-99 - 66.0 hours

Neptunium

Np-237 - 2.14E6 years
Np-238 - 2.117 days
Np-239 - 2.355 days
Np-240 - 65 minutes
Np-240m - 7.4 minutes

Plutonium

Pu-238 - 87.74 years
Pu-239 - 24065 years (soil sample)
Pu-240 - 6537 years (soil sample)
Pu-241 - 14.4 years
Pu-242 - 3.76E5 years
Pu-243 - 4.956 hours
Pu-244 - 8.26E7 years

Ruthenium

Ru-103 - 39.28 days
Ru-105 - 4.44 hours
Ru-106 - 368.2 days
Ru-97 - 2.9 days

Strontium

Sr-85 - 64.84 days
Sr-87m - 2.81 hours
Sr-89 - 50.5 days
Sr-90 - 29.12 years
Sr-91 - 9.5 hours
Sr-92 - 2.71 hours

Technetium

Tc-101 - 14.2 minutes
Tc-99 - 2.13E5 years
Tc-99m - 6.02 hours

Tellurium

Te-125m - 58 days
Te-127 - 9.35 hours
Te-127m - 109 days
Te-129 - 69.6 minutes (soil sample)
Te-129m - 33.6 days (soil sample)
Te-131 - 25.0 minutes
Te-131m - 30 hours
Te-132 - 78.2 hours (soil sample)
Te-133 - 12.45 minutes
Te-133m - 55.4 minutes
Te-134 - 41.8 minutes

Uranium

U-232 - 72 years
U-233 - 1.59E5 years
U-234 - 2.445E5 years
U-235 - 7.03E8 years
U-236 - 2.34E7 years
U-237 - 6.75 days
U-238 - 4.47E9 years
U-240 - 14.1 hours

Xenon

Xe-131m - 11.9 days
Xe-133 - 5.245 days
Xe-133m - 2.188 days
Xe-135 - 9.09 hours
Xe-135m - 15.29 minutes
Xe-138 - 14.17 minutes

Zirconium

Zr-93 - 1.53E6 years
Zr-95 - 63.98 days
Zr-97 - 16.90 hours

 

[Jorge Stolfi]

The loss of neutron absorber would not affect the decay heat in the spent fuel pool. ... Of course there is some spontaneous emission of neutrons from some TU nuclides, e.g., Pu-240 and 242, but they are such low level that they would only contribute on the order of watts.

Thanks for the reply. I understand that.

The neutron aborber loss is strictly a concern about criticality or re-criticality, particularly where reinsert fuel is placed in the spent fuel pool.

But that is the point. The absorbers are designed into spent-fuel storage pool because without them criticality woud be a real risk, isn't that so?

And, while spontaneous fission is an insignificant source of heat, even a momentary sub-critical chain reaction could cause a steam explosion, could it not?

I recall that famous accident where someone was trying to demonstrate a sub-critical chain reaction with two chunks of plutonium...

 

[Cire]

The problem is that any equipment used to handle the water (pumps, pipes etc) will rapidly become highly radioactive especially if the water is reinjected.

The radioactive contaminants must be removed and stored prior to reinjecting the water. It's a very tricky problem.

You run the effluent out of the reactors into the water processing facility/ship then pump it back to the plant. Depending on temperatures you run it through appropriate radiator/coolers before it gets to the ship.

 

[Cire]

So to reach the 4% lower flammability limit in 8000 m^3 requires only 0.04*8000*0.09 ~ 29 kg of hydrogen. So a much smaller amount of zirconium oxidation is required (about 660 kg). I suspect this is a small fraction of the total zirconium in the SFP.

I agree the number they released didn't sound right.

 

[Cire]

1) by the principle of differential pressure which would be required to lift the crane vertically, the primary force came upward, from the spent fuel pool and the propellant was vaporized water -- steam -- rather than hydrogen gas in the upper portion of the building.

To add to the confusion remember that a shock wave (a pressure wave) can reflect off of surfaces. You could have a shock wave originate up in the roof area, pass through the machinery breaking it from its mounts, strike the floor and rebound.

It would probably look externally like the roof bouncing up then a column shooting up through it a few milliseconds later.

This paper is modeling shock waves but I thought the shadowgraphs were interesting if we think of them as SFP's. From the images in the paper its not hard to imagine how the shock wave could have displaced most of the water and moved the fuel around.

http://www.personal.psu.edu/lnl/papers/AIAA-2007-4307.pdf

 

[Dmytry]

The real question is: How the hell would it reach detonation limit, 18%, without getting ignited first? You can explain it when it's leaking from the reactor, having cooled down sufficiently, but there's zirconium burning in steam (and air) there, at more than 1000 degrees Celsius or so, I'd guess hot pieces of oxide flying around, etc.
From 4% to 18% it is deflagration, not detonation.
See this:
http://www.iaea.org/ns/tutorials/regcontrol/appendix/app9344.htm
and check wikipedia etc:
http://en.wikipedia.org/wiki/Hydrogen_safety

I'm really kind of confused. I just can't believe in hydrogen detonation in reactor 4. Does not compute. I don't believe in nuke steam explosion in SPF either.

 

[TCups]

To add to the confusion remember that a shock wave (a pressure wave) can reflect off of surfaces. You could have a shock wave originate up in the roof area, pass through the machinery breaking it from its mounts, strike the floor and rebound.

It would probably look externally like the roof bouncing up then a column shooting up through it a few milliseconds later.

This paper is modeling shock waves but I thought the shadowgraphs were interesting if we think of them as SFP's. From the images in the paper its not hard to imagine how the shock wave could have displaced most of the water and moved the fuel around.

http://www.personal.psu.edu/lnl/papers/AIAA-2007-4307.pdf

It is doubtful that a piece of machinery that travels on a set of tracks was "mounted" to the floor. More likely, it rolls on wheels and was not mounted.

It seems impossible, IMO (certainly not an expert opinion), for sufficient energy from a blast to 1) be reflected off the inner roof of Bldg 3, then reflected off the bottom of the SFP3, and then, lift the FHM hundreds of feet in the air. IMO, that energy came from water rapidly expanding to water vapor (ie, conversion of thermal energy stored in the water from potential to kinetic energy via phase change from liquid to gas).

 

[AntonL]

Simply gone critical after it was damaged then covered by water. Nothing really outstanding, http://www.johnstonsarchive.net/nuclear/radcrit.html" are common.

Fuel in pool: 1331 spent fuel assemblies and 204 brand new assembles and some of them simply gone critical.
I already can hear Gunderson reporting that unit 4 is an open air reactor.

However let's analyse SPF 4
Capacity = 1425 m³ http://www.nisa.meti.go.jp/english/files/en20110406-1-1.pdf"

Decay Heat:
2000kW for spent fuel from unloaded reactor last operation 29 Nov 2010 (can be calculated)
+ 400kW long term stored spent fuel (estimated on the high side)
2400kW total

Assuming SPF4 was at 30^oC
To raise 1425m³ by 70^oC using 2.4MW it would take 48 hours
so SPF 4 has started to boil somewhere between March 13 afternoon to March 14 morning.

The pool is about 11 metres deep,
so to boil away 1 metre or 1425/11= 129.5m³ of water using a 2.4MW heater 33.8 hours
I cannot find the detail drawing that was posted here before to confirm the depth so I took depth of SPF 7

From earthquake (3pm 11/3) to unit 4 explosion (6am 15/3) if I can calculate correctly are 87 hours,
thus about (87-48)/33.8 = 1.2 metres of water would have boiled away at time of explosion.
that is the 4 metre fuel rods have 5.8m water covering them -
so where does the Hydrogen come from??

Helicopter crews on 17 March reported spotting water in SPF4 thus they concentrated on
dropping water on unit 3 - proof that there is ample water in the pool.

Spraying water into unit 4 was only started on March 20 at 9:40 thus
at time of explosion 6am 15/3 water level -1.2m
10am 20/3 114 hours later a further level drop of 3.4 metres due to boiling
thus when water spraying started on 20March the level was down 4.6 mtres
excluding leakage or spillage, this leaves the 4 metre fuel rods 2 metres under water.
Tepco set their priorities correctly and started spraying water at the right time.

http://www.nirs.org/reactorwatch/accidents/6-1_powerpoint.pdf" that the storage capacity of all fuel pools at Fukushima as 8310 fuel assemblies,
that is 1444 fuel assemblies can be stored at each units 2 to 5, based on SFP volume.

However, SPF4 had 1331+204 = 1535 fuel assemblies stored which is more than stated capacity! http://www.nisa.meti.go.jp/english/files/en20110406-1-1.pdf"

Therefore we can speculate that Tepco double layered at least two or three spent fuel racks,
this would explain the early exposure of fuel to air, hydrogen generation, fuel damage etc.
and we can speculate that two or three racks worth of spent fuel may be destroyed.

Debunk that.
Have I solved the hydrogen, spent fuel pool water mystery?

Now, should my calculation and speculation be proven true, Tepco needs to do a lot of explanation.

 

[elektrownik]

Fuel in pool: 1331 spent fuel assemblies and 204 brand new Tepco needs to do a lot of explanation.

There was something about "re-racking" in SFP #4 in tepco presentation...

 

[Dmytry]

There was something about "re-racking" in SFP #4 in tepco presentation...

Yep.

Really, this attitude about criticality is how you get one of those accidents:
http://www.johnstonsarchive.net/nuclear/radcrit.html
Some wise *** thinks that criticality is impossible unless you can prove it is possible, which you can't because you don't know how they re-racked their spent fuel pool, and how the pellets from the top fuel fell to the bottom, etc. Which you can't prove without numerical simulation.
How's about, for a change, someone proves criticality is impossible? The way it should be when you're considering safety. Until then - it could of simply gone critical because of re-racking, end of story. Physics is not court of justice. The open air nuclear reactor, that's how it has to be called, until they prove it isn't open air nuclear reactor.

This is example of safety by lack of proof of unsafety:
http://www.johnstonsarchive.net/nuclear/radevents/1999JAP1.html
"the facility did not have a procedure for dealing with criticality events", a facility dealing with 18% u235 solution, for god's sake. I can vividly imagine the managers there going like "but there is no proof criticality is possible" and all around going sceptical if someone proposes that they need procedure for dealing with criticality. Until one day it happened. I can imagine someone debunking the possibility of criticality in the very vat where it happened, by forgetting the neutron reflection from cooling water around the tank.

 

[shogun338]

Radiation has risen to high levels above the spent-fuel pool at reactor No. 4 and its temperature is rising, the nuclear safety agency said Wednesday, indicating the fuel rods have been further damaged and emitting radioactive substances.
The radiation level 6 meters above the spent-fuel storage pool at the crippled Fukushima No. 1 nuclear plant was measured at 84 millisieverts per hour Tuesday. Normally, it's 0.1 microsievert.

The temperature of the pool was 90 degrees, compared with 84 before it caught fire on March 15 in a suspected hydrogen explosion, the agency said.

"It's quite an amount," figured Hidehiko Nishiyama, a spokesman for the Nuclear and Industrial Safety Agency. http://search.japantimes.co.jp/cgi-bin/nn20110413x1.html

 

[elektrownik]

Also I still don't understand why is there so much heat in unit 4 core location... This picture is from 12/4 but you can see this on all thermal images... Maybe they were refueling it ?
[PLAIN]http://img34.imageshack.us/img34/7302/39280875.jpg

 

[TCups]

Yep.

Really, this attitude about criticality is how you get one of those accidents:
http://www.johnstonsarchive.net/nuclear/radcrit.html
Some wise *** thinks that criticality is impossible unless you can prove it is possible, which you can't because you don't know how they re-racked their spent fuel pool, and how the pellets from the top fuel fell to the bottom, etc. Which you can't prove without numerical simulation.
How's about, for a change, someone proves criticality is impossible? The way it should be when you're considering safety. Until then - it could of simply gone critical because of re-racking, end of story. Physics is not court of justice.
This is example of safety by lack of proof of unsafety:
http://www.johnstonsarchive.net/nuclear/radevents/1999JAP1.html

What of those two cask-carrier trucks seen in initial photos parked in back of Bldg 3, 4, only one visible with its cask aboard? Might the position of the FHM in Bldg 4 indicate that it had been moved out of the way to permit the larger overhead crane to be used to transfer something at that end of the building into or from the SFP or cask transfer pool?

Speculation for sure, but perhaps even suggesting that a last ditch desperate effort was made to move "something" after the quake but before the arrival of a tsunami?

Bldg 4 remains an enigma to me. The explosion there destroyed more of the lower building than the explosion at Bldg 3 and yet more of the roof's superstructure in Bldg 4 was preserved. The fire(s) have not been adequately explained, either. And it was Bldg 4 that required a dozer to clear debris (and metal plates to be laid?) before the hose crane could be brought into place over SFP4.

 

[elektrownik]

Also this is strange that tepco only tell us about fire, there was no pictures, videos or news about explosion, only about fire...

 

[sp2]

Umm, forgive me, but how do you possibly know any of this without knowing rates of leakage, or amounts sloshed out in the quake (not to mention more water sloshed out in later quakes, and likely changes in leakage rates over time, etc.)?
Also not to mention that we have no idea if there was water in the pool when TEPCO said there was, and, if so, how much.
Forgive me, but it seems to me you're building your whole analysis there on a mind-boggling set of unsupported assumptions.

Please correct me if I'm missing some things.

Also, is vertical stacking of spent-fuel rods something that's actually done? (Or even can be done?) I thought re-racking referred to cramming in the extra assemblies on the bottom of the pool with the rest?
Is that wrong?

Thanks.

Fuel in pool: 1331 spent fuel assemblies and 204 brand new assembles and some of them simply gone critical.
I already can hear Gunderson reporting that unit 4 is an open air reactor.

However let's analyse SPF 4
Capacity = 1425 m³ http://www.nisa.meti.go.jp/english/files/en20110406-1-1.pdf"

Decay Heat:
2000kW for spent fuel from unloaded reactor last operation 29 Nov 2010 (can be calculated)
+ 400kW long term stored spent fuel (estimated on the high side)
2400kW total

Assuming SPF4 was at 30^oC
To raise 1425m³ by 70^oC using 2.4MW it would take 48 hours
so SPF 4 has started to boil somewhere between March 13 afternoon to March 14 morning.

The pool is about 11 metres deep,
so to boil away 1 metre or 1425/11= 129.5m³ of water using a 2.4MW heater 33.8 hours
I cannot find the detail drawing that was posted here before to confirm the depth so I took depth of SPF 7

From earthquake (3pm 11/3) to unit 4 explosion (6am 15/3) if I can calculate correctly are 87 hours,
thus about (87-48)/33.8 = 1.2 metres of water would have boiled away at time of explosion.
that is the 4 metre fuel rods have 5.8m water covering them -
so where does the Hydrogen come from??

Helicopter crews on 17 March reported spotting water in SPF4 thus they concentrated on
dropping water on unit 3 - proof that there is ample water in the pool.

Spraying water into unit 4 was only started on March 20 at 9:40 thus
at time of explosion 6am 15/3 water level -1.2m
10am 20/3 114 hours later a further level drop of 3.4 metres due to boiling
thus when water spraying started on 20March the level was down 4.6 mtres
excluding leakage or spillage, this leaves the 4 metre fuel rods 2 metres under water.
Tepco set their priorities correctly and started spraying water at the right time.

http://www.nirs.org/reactorwatch/accidents/6-1_powerpoint.pdf" that the storage capacity of all fuel pools at Fukushima as 8310 fuel assemblies,
that is 1444 fuel assemblies can be stored at each units 2 to 5, based on SFP volume.

However, SPF4 had 1331+204 = 1535 fuel assemblies stored which is more than stated capacity! http://www.nisa.meti.go.jp/english/files/en20110406-1-1.pdf"

Therefore we can speculate that Tepco double layered at least two or three spent fuel racks,
this would explain the early exposure of fuel to air, hydrogen generation, fuel damage etc.
and we can speculate that two or three racks worth of spent fuel may be destroyed.

Debunk that.
Have I solved the hydrogen, spent fuel pool water mystery?

Now, should my calculation and speculation be proven true, Tepco needs to do a lot of explanation.

 

[Dmytry]

What of those two cask-carrier trucks seen in initial photos parked in black of Bldg 3, 4, only one visible with its cask aboard? Might the position of the FHM in Bldg 4 indicate that it had been moved out of the way to permit the larger overhead crane to be used to transfer something at that end of the building into or from the SFP or cask transfer pool?

Speculation for sure, but perhaps even suggesting that a last ditch desperate effort was made to move "something" after the quake but before the arrival of a tsunami?

Bldg 4 remains an enigma to me. The explosion there destroyed more of the lower building than the explosion at Bldg 3 and yet more of the roof's superstructure in Bldg 4 was preserved. The fire(s) have not been adequately explained, either. And it was Bldg 4 that required a dozer to clear debris (and metal plates to be laid?) before the hose crane could be brought into place over SFP4.

Yep. Same here. It is an excellent point that the wall blew too much in the building 4.
I'm totally puzzled. I'm starting to think there was a steam explosion, that blew through the floor of spent fuel pool. But the thing is, given delayed neutrons and given negative temperature coefficient ('cause of Doppler broadening of U-238 neutron capture) and negative void coefficient, the criticality does not imply kaboom. Perhaps if it gone critical thanks to the fuel pellets that fell down when zirconium cladding on the top burnt off, boiled happily self regulating with the void coefficient, but some instability happened (e.g. boiling on one side making increased pressure on other side collapsing the voids).
All that is speculation, but it seems to me the burden of proof that it can't happen should be on whoever designed (and re-racked) those spent fuel pools. They just shouldn't re-rack stuff without having a proof that it is safe.

 

[TCups]

Yep. Same here. It is an excellent point that the wall blew too much in the building 4.
I'm totally puzzled. I'm starting to think there was a steam explosion, that blew through the floor of spent fuel pool.

That hypothesis "doesn't hold water" so to speak. If the floor of the SFP4 were holed, then there would be no way or purpose in trying to keep water added to SFP4.

As earlier, though, I can put a cask in what looks like a cask transfer pool adjacent to the SFP4 and perhaps that was the "link" to lower floors. But Fred has pointed out even that hypothesis doesn't seem to match the external pattern of the blast damage to Bldg 4.

http://i306.photobucket.com/albums/nn270/tcups/Picture30-4.png

 

[Dmytry]

That hypothesis "doesn't hold water" so to speak. If the floor of the SFP4 were holed, then there would be no way or purpose in trying to keep water added to SFP4.

you could keep 'pouring' water into sieve for PR purposes.

As earlier, though, I can put a cask in what looks like a cask transfer pool adjacent to the SFP4 and perhaps that was the "link" to lower floors. But Fred has pointed out even that hypothesis doesn't seem to match the external pattern of the blast damage to Bldg 4.

http://i306.photobucket.com/albums/nn270/tcups/Picture30-4.png

We're already in conspiracy land on the blast damage...

 

[AntonL]

Radiation has risen to high levels above the spent-fuel pool at reactor No. 4 and its temperature is rising, the nuclear safety agency said Wednesday, indicating the fuel rods have been further damaged and emitting radioactive substances.
The radiation level 6 meters above the spent-fuel storage pool at the crippled Fukushima No. 1 nuclear plant was measured at 84 millisieverts per hour Tuesday. Normally, it's 0.1 microsievert.

The temperature of the pool was 90 degrees, compared with 84 before it caught fire on March 15 in a suspected hydrogen explosion, the agency said.

If you read my earlier post in this thread this pool must have been boiling since March 14 latest, It has a 2 to 2.4 MeggaWatt heater in it and that boils 67 to 81 Tons of water a day, Tepco are adding 120 Tonnes a day.

Tepco/NISA/NSC are not forthright with the data they provide, it is being squeezed out of Tepco little by little and released to the public even at a reduced rate. After releasing this data today, they will release some more related bad news soon.

Furthermore, for the first time since the accident the weather will not be working for Tepco, 3 days of winds blowing inland are being forecast for Sunday, Monday and Tuesday see http://www.windfinder.com/forecast/fukushima_nuklear_power_plant. As long as the winds where blowing to the USA there was no great problem, but now things look different, and they need to prepare and get explanation for the nuclear cloud that will be blowing inland soon, so it is announced that SFP4 is about to boil and things will be worse than previously thought.

 

[bytepirate]

what i don't understand (one thing out of many, i admit) is:
- explosion and fire in #4 at 15th and 16th
- *nothing* for 4 days
- start of spraying on 20th

is it possible, that the explosion was *not* a hydrogen explosion?
is it possible, that enough hydrogen for an explosion has been generated *under water* (maybe due to the re-racking?)
what has burned? if the zircaloy burned, would it stop burning before its all used up? *if* all zircaloy burned away, wouldn't the release be much larger?

#4 is very strange (#1 as well ... and i am far from grasping, what exactly happened to #2. and #3...)

 

[shogun338]

Cask for 38 fuel assembly BWR Type
Provide by Tokyo Electric Power Compay ---I don't know why there showing a pic of the cask . There talking about trying to remove the spent fuel with a crane or another large machine into a new cooling pool now so maybe this has something to do with it . They could put some of the older cooler fuel into these . --- Tepco said it is planning to move the spent fuel rods out of the storage pools at reactors 1 through 4 so they can be moved to a safer location, although details on when and how haven't been decided yet.

Some of the options Tepco is considering include pulling the rods out with a crane or building a special structure nearby to pull them out.
http://search.japantimes.co.jp/cgi-bin/nn20110413x1.html

 

[AntonL]

Umm, forgive me, but how do you possibly know any of this without knowing rates of leakage, or amounts sloshed out in the quake (not to mention more water sloshed out in later quakes, and likely changes in leakage rates over time, etc.)?
Also not to mention that we have no idea if there was water in the pool when TEPCO said there was, and, if so, how much.
Forgive me, but it seems to me you're building your whole analysis there on a mind-boggling set of unsupported assumptions.

Please correct me if I'm missing some things.

Also, is vertical stacking of spent-fuel rods something that's actually done? (Or even can be done?) I thought re-racking referred to cramming in the extra assemblies on the bottom of the pool with the rest?
Is that wrong?

Thanks.

I am presenting the best case neglecting possible leakage and spillage. If the pool was ever completely dry unit 4 would be in a greater mess than it is now,

OK vertical stacking may be a figment of my imagination, but if hydrogen developed that all racks were exposed, that is the pool would be empty, and water was only added 5days later that does not make sense, my explanation seems a bit more realistic.

 

[bytepirate]

Cask for 38 fuel assembly BWR Type
Provide by Tokyo Electric Power Compay ---I don't know why there showing a pic of the cask . There talking about trying to remove the spent fuel with a crane or another large machine into a new cooling pool now so maybe this has something to do with it . They could put some of the older cooler fuel into these . --- Tepco said it is planning to move the spent fuel rods out of the storage pools at reactors 1 through 4 so they can be moved to a safer location, although details on when and how haven't been decided yet.

Some of the options Tepco is considering include pulling the rods out with a crane or building a special structure nearby to pull them out.
http://search.japantimes.co.jp/cgi-bin/nn20110413x1.html

from http://search.japantimes.co.jp/cgi-bin/nn20110413x1.html :
"The temperature was rising and we don't know the water level of the pool, so we thought it would be safer to pour water," said NISA's Nishiyama said.

what is the 'FPC skimmer level', that they publish? i assumed, that this is the waterlevel in the SFP...

 

[TCups]

Cask for 38 fuel assembly BWR Type
Provide by Tokyo Electric Power Compay ---I don't know why there showing a pic of the cask . There talking about trying to remove the spent fuel with a crane or another large machine into a new cooling pool now so maybe this has something to do with it . They could put some of the older cooler fuel into these . --- Tepco said it is planning to move the spent fuel rods out of the storage pools at reactors 1 through 4 so they can be moved to a safer location, although details on when and how haven't been decided yet.

Some of the options Tepco is considering include pulling the rods out with a crane or building a special structure nearby to pull them out.
http://search.japantimes.co.jp/cgi-bin/nn20110413x1.html

The "picture" I attached was my PhotoShop alteration of where it appeared the overhead crane would leave a cask for loading/unloading in the accessory pool. Please excuse me for not being more specific that the illustration was part of my hypothesis, not a known fact.

http://i306.photobucket.com/albums/nn270/tcups/Picture30-4.png

As for "conspiracy land for blast damage" -- well, maybe I am a conspirator, but I am starting from pictures of what I believe to be accurate. These include the location of what appears to be the accessory "cask" pool on the working diagram I have, the location shown for the FHM when the overhead crane is in use, the pattern of external damage to the building including the access tunnel and lower floors below the service access floor for the SFP and reactor containment, etc.

 

[PietKuip]

If you read my earlier thread this pool must have been boiling since March 14 latest, It has a 2 to 2.4 MeggaWatt heater in it and that boils 67 to 81 Tons of water a day, Tepco are adding 120 Tonnes a day.

Tepco/NISA/NSC are not forthright with the data they provide, it is being squeezed out of Tepco little by little and released to the public even at a reduced rate. After releasing this data today, they will release some more related bad news soon.

They prepared for telling the worst news as early as several weeks ago: http://www.bbc.co.uk/news/science-environment-12762608"

 

[Jorge Stolfi]

The real question is: How the hell would it reach detonation limit, 18%, without getting ignited first?

Perhaps the rising steam and/or initial hydrogen combustion removed most of the oxygen from the atmosphere inside pool and just above it?

And what about criticality or near-criticality in the #4 SFP, after loss of the neutron-absorbing baffles? Can we rule that out?

 

[gmax137]

Also, is vertical stacking of spent-fuel rods something that's actually done? (Or even can be done?) I thought re-racking referred to cramming in the extra assemblies on the bottom of the pool with the rest?
Is that wrong?

Thanks.

I have never heard of vertical stacking - that 23 feet of water above the assemblies is there for shielding when they move the fuel into the rack. If you had a rack on top of a rack, then the top of the fuel assembly being moved into the top rack would be nearly out of the water. No way they would do that, I just can't believe it.

All of the re-racking I've seen is to fill what was open space with more racks or to squeeze the assemblies closer together in a 'tighter' rack.

 

[Jorge Stolfi]

Also, is vertical stacking of spent-fuel rods something that's actually done? (Or even can be done?) I thought re-racking referred to cramming in the extra assemblies on the bottom of the pool with the rest?

These docs were posted by user bythepirate :
http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/29/064/29064415.pdf
http://www.irss-usa.org/pages/documents/11_1Alvarez.pdf

These docs (Czech and US) indeed talk only about using a more compact arrangement of fuel assemblies within each rack, packed solid against each other instead of the original very open arrangement.

However "re-racking" is a general term and may include other bright ideas. And even if re-racking at Fukushima was single-layer, they may have used two layers too. Is the estimate above correct (capacity 1444 after re-racking, actual contents 1535)?

 

[cphoenix]

Another thing that makes a hydrogen detonation less plausible: There are still panels attached in the top row at building 4. Even at building 1, all panels were blown clean off the top two rows. It's hard to see how hydrogen could have exploded with enough force to damage concrete but left panels intact near the roof.

Meanwhile, something stripped concrete away from rebar in the below-decks row (third from top). That didn't happen even in building 3. And I haven't seen anything that looks like soot. I'd speculated that it was oil vapor that exploded, not hydrogen; that could have been heavier than air, and created a below-decks explosion. But I'd think that would leave soot.

I haven't seen any video of building 4 exploding. Someone else posted that they hadn't either. So, thinking outside the box...

What if building 4 did not actually explode? Is it plausible that most or all of the damage was mechanical, from aftershocks?

In the third-from-top row (the upper below-decks row) there are panels that appear to be made of rebar-reinforced concrete. Some of those panels have rebar exposed around the edges, and flat concrete left in the middle. It's hard to imagine that an explosion would do that. But twisting the beams that the panels were mounted between might crumble the panels from the edges in.

Are there any observations that would contradict the quake-damage theory for building 4?

 

[Dmytry]

These docs were posted by user bythepirate :
http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/29/064/29064415.pdf
http://www.irss-usa.org/pages/documents/11_1Alvarez.pdf

These docs (Czech and US) indeed talk only about using a more compact arrangement of fuel assemblies within each rack, packed solid against each other instead of the original very open arrangement.

However "re-racking" is a general term and may include other bright ideas. And even if re-racking at Fukushima was single-layer, they may have used two layers too. Is the estimate above correct (capacity 1444 after re-racking, actual contents 1535)?

can they lay extra fuel horizontally?

 

[Dmytry]

Another thing that makes a hydrogen detonation less plausible: There are still panels attached in the top row at building 4. Even at building 1, all panels were blown clean off the top two rows. It's hard to see how hydrogen could have exploded with enough force to damage concrete but left panels intact near the roof.

Meanwhile, something stripped concrete away from rebar in the below-decks row (third from top). That didn't happen even in building 3. And I haven't seen anything that looks like soot. I'd speculated that it was oil vapor that exploded, not hydrogen; that could have been heavier than air, and created a below-decks explosion. But I'd think that would leave soot.

I haven't seen any video of building 4 exploding. Someone else posted that they hadn't either. So, thinking outside the box...

What if building 4 did not actually explode? Is it plausible that most or all of the damage was mechanical, from aftershocks?

In the third-from-top row (the upper below-decks row) there are panels that appear to be made of rebar-reinforced concrete. Some of those panels have rebar exposed around the edges, and flat concrete left in the middle. It's hard to imagine that an explosion would do that. But twisting the beams that the panels were mounted between might crumble the panels from the edges in.

Are there any observations that would contradict the quake-damage theory for building 4?

that none of the aftershocks was even remotely strong enough to so effectively destroy something that withstood original quake?

 

[clancy688]

A little bit offtopic:

I heard, that La Hague in france emits several hundred PBq Krypton-85 every year. In my opinion, Krypton-85 is not dangerous to human health, because it's a noble gas and as such very volatile (= doesn't contaminate areas / humans). Furthermore, it has a very short half time in the human body. Is that correct? Or are there errors?

Because 300 PBq Krypton-85 every year sounds a bit much - if it would pose a hazard to human health.

 

[bytepirate]

These docs were posted by user bythepirate :
http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/29/064/29064415.pdf
http://www.irss-usa.org/pages/documents/11_1Alvarez.pdf

These docs (Czech and US) indeed talk only about using a more compact arrangement of fuel assemblies within each rack, packed solid against each other instead of the original very open arrangement.

However "re-racking" is a general term and may include other bright ideas. And even if re-racking at Fukushima was single-layer, they may have used two layers too. Is the estimate above correct (capacity 1444 after re-racking, actual contents 1535)?

the common spent fuel pool has an area of 12m*29m and can take 76 racks (90 assemblies each). makes a rough estimate of a size of 2m*2m for each rack (based on the picture on page 11 of http://www.nirs.org/reactorwatch/accidents/6-1_powerpoint.pdf)
the SFP in #4 has 11m depth and contains 1425m³, thus the area is roughly 129m² -> 32 racks -> 2880 assemblies (?). maybe the racking is more dense in the common SFP?

a *very* speculative thesis:
+ after the quake they tried to re-insert the core to the RPV
- why should they do this?
- two workers were found dead in #4
+ the crane stuck, when the core was directly above the RPV
- covered by water, but not very much
+ water boiled away
+ the core produced hydrogen and an explosion
+ the core fell into the RPV
+ the fire after the explosion has been caused by something else


this would explain the thermal images, that show heat in the place of the RPV.
and this would explain the 4 day 'silence' between explosion and spraying.

but i have to admit, that i am not convinced ;-)

 

[razzz]

Another thing that makes a hydrogen detonation less plausible: There are still panels attached in the top row at building 4. Even at building 1, all panels were blown clean off the top two rows. It's hard to see how hydrogen could have exploded with enough force to damage concrete but left panels intact near the roof.

Meanwhile, something stripped concrete away from rebar in the below-decks row (third from top). That didn't happen even in building 3. And I haven't seen anything that looks like soot. I'd speculated that it was oil vapor that exploded, not hydrogen; that could have been heavier than air, and created a below-decks explosion. But I'd think that would leave soot.

I haven't seen any video of building 4 exploding. Someone else posted that they hadn't either. So, thinking outside the box...

What if building 4 did not actually explode? Is it plausible that most or all of the damage was mechanical, from aftershocks?

In the third-from-top row (the upper below-decks row) there are panels that appear to be made of rebar-reinforced concrete. Some of those panels have rebar exposed around the edges, and flat concrete left in the middle. It's hard to imagine that an explosion would do that. But twisting the beams that the panels were mounted between might crumble the panels from the edges in.

Are there any observations that would contradict the quake-damage theory for building 4?

cphoenix brings up a good point about how concrete appears fractured by impact and not by explosion. Impact from pieces of a motor or tank or some other hard materials in flight hitting a concrete panel would not pulverized standard mix concrete. Lightweight concrete maybe would pulverize, like used for floors since rebar is not normally placed in lightweight concrete flooring applications. Flexing motions usually don't disturb reinforce concrete (bridges: flex, expand and contract like crazy).

Back many posts, read that summary of worst case scenarios where seawater interactions were not discussed and another conclusion (in this day in age) that the properties of hydrogen in particular conditions was not fully understood (yet). Steam or super-heated steam mixing with hydrogen along with some other gases or fuels makes for many variables.

Even one damaged rod in a pool via debris impacting let alone low water level(s) leading to exposed fuel would ruin your whole day.

Overhead cabling tram system is the only way to work and avoid the radiation and preform the heavy lifting required.

I believe the air blast nukes were less contaminating, only because the plume or mushroom cloud ejected higher into the atmosphere since in a controlled burst you could wait for optimum weather conditions.

 

[elektrownik]

a *very* speculative thesis:
+ after the quake they tried to re-insert the core to the RPV
- why should they do this?
- two workers were found dead in #4
+ the crane stuck, when the core was directly above the RPV
- covered by water, but not very much
+ water boiled away
+ the core produced hydrogen and an explosion
+ the core fell into the RPV
+ the fire after the explosion has been caused by something else
QUOTE]

Why ? To slow down vaporization of water from sfp ? Fresh fuel which was removed from core has bigger temperature than old fuel, so if they believe that they can restore cooling systems they want to slow down vaporization by removing some fuel from overpacked sfp...