- #3,676
Maxion
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elektrownik said:New thermal images, very bad, so hot: http://www.mod.go.jp/j/approach/defense/saigai/tohokuoki/kanren/230414.pdf
Please not the scale of the temperature. Nothing is very hot.
elektrownik said:New thermal images, very bad, so hot: http://www.mod.go.jp/j/approach/defense/saigai/tohokuoki/kanren/230414.pdf
Look at the right column: some temperatures are rising quite a bit.Maxion said:Please not the scale of the temperature. Nothing is very hot.
tsutsuji said:A research team from Kyoto, Hiroshima, Kokugakuin, Nihon universities presents its "Interim Report on Radiation Survey in Iitate Village area conducted on March 28th and 29th" : http://www.rri.kyoto-u.ac.jp/NSRG/seminar/No110/Iitate-interim-report110404.pdf. It includes a gamma ray radionuclide analysis of soil samples.
AntonL said:Can someone please be so kind and repost the link to the large cross-sectional plan of the nuclear reactor that was posted some time ago, not the GE handout - I tried very hard and cannot find it
bytepirate said:#4 was undamaged after #3 exploded: http://www.digitalglobe.com/downloads/featured_images/japan_earthquaketsu_fukushima_daiichi_march14_2011_dg.jpg
bytepirate said:this one? http://fukushimafaq.wikispaces.com/Reactor+Blueprints
bytepirate said:#4 was undamaged after #3 exploded: http://www.digitalglobe.com/downloads/featured_images/japan_earthquaketsu_fukushima_daiichi_march14_2011_dg.jpg
Most of those pictures do not point to fuel rods, which are slightly less than 0.5 inch in diameter. The top images show a 9x9 fuel assembly.Krikkosnack said:Fuel Rods of the reactor 4... are really those?
http://www.houseoffoust.com/fukushima/rods.html
That smoke is continuous with the smoke towards bottom right of picture towards the trees. I guess just an eddy a few moments earlier from the #3 plume.clancy688 said:Doesn't it look like as if there's white smoke coming from the eastern (sea) side of unit 4?
MEXT reported on measurements of strontium-89 (half-life: 50.5 days) and strontium-90(half-life: 28.8 years) in three samples taken in one village in the Fukushima prefecture on 16 March. The activities in soil for Sr-89 ranged from 13 and 260 Bq/kg and for Sr-90 between 3.3 and 32 Bq/kg. Sr-90 was also distributed globally during nuclear weapons' testing in the atmosphere, typical global levels of Sr-90 in surface soils are in the order of one to a few becquerel per kg. Strontium was also measured in plant samples in four others villages, with values ranging from 12 to 61 Bq/kg for Sr-89 and 1.8 to 5.9 Bq/kg for Sr-90.
The decay heat was stronger in the cores of Units 1, 2 and 3, because they had recently shutdown (May 11). They then lost cooling on May 12-13. Unit 4 had been shutdown for about 100 days (Nov 30, 2010 - Mar 11, 2011), so the decay heat was significantly diminished. However, there is still heat on the order of 0.2% of operating power, or about 3.7 MW. That is still a significant amount of heat.georgiworld said:I wonder if someone can clear something up for me. From the beginning I thought Reactor 4 posed the most danger since the fuel in it, both spent and unspent, were outside of containment. Since then most attention has focused on the three other reactors and the possible breaching of the RPV with a concomitant oozing of corium .
There have now been reports of fires at number 4, which has refocused attention on it and which concerns me greatly.
As I understand it, the decay heat that is emanating from the spent fuel has created the need for a great deal of water to be added in order to remain cool. While this effort appears to have worked since there remains water in the pool, the amount of heat generated maybe too much to deal with and the excess heat has found another outlet.
Now what I'd like to know is could this heat be melting the unspent fuel rods? Is that what is on fire?
Are we looking at an open-air reactor with widespread dissemination of radiation?
Can anyone reassure me that this is not the case.
AntonL said: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 30oC
To raise 1425m3 by 70oC 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.
I don't believe the fuel necessarily melted. It certainly did have contact with the coolant, then seawater. Various chemical reactions are possible well below melting temperatures. It is certainly likely that the Zr-alloy cladding was several corroded (oxidized), which is the source of hydrogen. The oxidation could have proceeded to cladding rupture and perforation (breach), and possibly fracture or cracking. If cracking occured, particularly axial splits, then the fuel has intimate contact with the coolant, and it is possible that the ceramic fuel oxidized, possibly to the point where particles of fuel dropped out and settled to the bottom of the core, or perhaps in the regions below the core.SayaX said:Hi all. I've been reading quietly, but I wanted to contribute here since I've been keeping up with the disaster through the Japanese media.
This was posted shortly ago, I don't know if it's good news or not. But curious what people think of it. The translations are my own and while it's not perfect (I'm not a professional or a native speaker), the news is about an hour old.
The spent fuel pool racks are design to prevent criticality. There is neutron absorber material present. IF somehow that neutron absorber material was lost, then there would be a chance of criticality. The configuration of the pool is important. It's not clear to me where the fresh fuel was located with respect to the reinsert and discharge fuel.georgiworld said:Thank you Astronuk, as always your technical assessment is spot on.
My question however is not about what happens to the cladding of the spent fuel but what effect the heat will have on the unspent fuel which was stored in SPF#4. Now while the decay heat was greater in the reactors that were operational at the time of the incident, it was contained in the RPF.
My fear is that the unspent fuel in the SFP of #4 will go critical. Is that possible?
I think it gone critical before, after geometry change due to the fire. The geometry has to be specifically designed as to avoid criticality. The pool was re-racked to higher capacity.georgiworld said:Thank you Astronuk, as always your technical assessment is spot on.
My question however is not about what happens to the cladding of the spent fuel but what effect the heat will have on the unspent fuel which was stored in SPF#4. Now while the decay heat was greater in the reactors that were operational at the time of the incident, it was contained in the RPV.
My fear is that the unspent fuel in the SFP of #4 will go critical. Is that possible?
michael200 said:Let's please stop this discussion about "double layers" of fuel in the SFP. The depth of the fuel pool is about 40 ft and the height of a fuel assembly in the SFP racks is about 14 ft. Plant technical specifications require a minimum water level of about 20 ft above irradiated fuel in the SFP. This technical specification requirement could never be met if two fuel assembilies were stacked on top of each other. The very idea of such a thing would be impractical.
When a utility increases the capacity of the SFP, they do it by replacing the exisiting used fuel storage racks in the SFP with racks that allow the fuel to be placed closer together (higher density). The geometry is analyzed and possible change to the neutron absorber panels in the fuel racks are changed to preclude criticality of the assemblies in the SFP.
Back to loss of inventory in the U4 SFP: AntonL's boiloff calculations look pretty good. There probably was also several feet (maybe 3-4 ft total) of SFP inventory loss due to pool sloshing during the earthquake. However, the inventory boiloff plus the inventory loss from sloshing wouldn't explain uncovery of the irradiated fuel in the U4 SFP. It is possible that the earthquake caused a leak in the spent fuel pool (perhaps in the gate plugs that are removed when performing refueling operations between the reactor and the SFP). Such a leak, if large, would explain the additional inventory loss. However, the limited photos of the damage to the U4 reactor indicate that there was a VERY hot fire with explosions in the lower levels of the U4 reactor building. How H2 generation and ignition at the elevation of the U4 refuel floor caused this lower building destruction is beyond me.
why would the valve between reactor 4's suppression pool and the common exhaust stack be open?AntonL said:Ok, michael200, I take your point on doubling up so let's forget it. Thanks for sort of agreeing with my boiloff calculation and let's asume there was no leak in pool otherwise Tepco could not have waited until the 20th to replenish water, because should there have been a significant leak fuel exposure would have resulted before then.
But where does the Hydrogen come from for the explosion, forum members here agree that the explosion centre was lower down in the building on the north side, which does make sense because of the observed damage.
For that scenario I can also give a very imaginative explanation. When unit 3 was vented, could unit 4 have pumped hydrogen steam into unit 3. Unit 3 and 4 share a common exhaust stack and there was no power for fans to work to aid the exhaust procedure, Furthemore, we do not know if there are any dampers in the system and if installed I would imagine they fail open when power is lost.
Lets assume unit 3 pumped unit 4 full of steam and hydrogen, this would then be into the suppression chamber, then H2 will leak into the primary containment chamber, it would not immediately escape to the roof, as there is a seal between the reactor vessel and PCV so that PCV is not flooded during fuel transfer. The Hydrogen could have leaked out through the access hatch which would not have been sealed due to the maintenance taking place, This access hatch is on the ground floor, which is the right level for a lower explosion centre. The only question why the long delay between units 3 and 4 exploding.
@TCups have you considered that the access hatch could also have leaked at unit 3, this could explain a second and third explosion. Explosion 1 roof area, due to shock wave and vibration of the building the access hatch leaks and PCV burps through access hatch, now more hydrogen in lower building resulting in explosion 2, same happens again explosion 3 and PCV has lost a lot of pressure and the process stops, looking at the devastation on lower northern side this could work, also watch the video to the north the dust cloud expands more than to the south
Earthmover said:
Krikkosnack said:Fuel Rods of the reactor 4... are really those?
http://www.houseoffoust.com/fukushima/rods.html
Dmytry said:The criticality is not hell on Earth event. In all the mess, it could even be going on somewhere unnoticed. It's not necessary a kaboom, even though it might be a kaboom.
Hi all,AntonL said:Lets assume unit 3 pumped unit 4 full of steam and hydrogen...
Dmytry said:why would the valve between reactor 4's suppression pool and the common exhaust stack be open?
javadave said:Is this article correct in that TEPCO could cool the reactors within days if they flooded them with water?
Borek said:I don't see physics behind the idea. Flooding with water won't help, as water will get heated and evaporate, so there will be a need to constantly add more. It won't be much different from what they do now.
And it won't be shorter, as the problem is not with the heat that is already there - heat is still produced and will be produced for months to come.