Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Borek]

I am a chemist.

First, it's thermal production of H2 and O2 not radiological.
2 molecules of water produce one molecule of O2 and 2 molecules of H2
a similar reaction takes 2H2O +Zr -> ZrO2 + 2H2

The purely thermal reaction produces H2 and O2 in equal proportions. This reaction is likely what caused the explosion that blew the torus at Unit 2

Judging from the diagram posted earlier

https://www.physicsforums.com/attachment.php?attachmentid=34079&d=1302058688

you need around 12% oxygen by volume for the explosion. Seems unlikely in the conditions present inside. Thermal decomposition of water needs fast separation of products, otherwise they react back.

 

[artax]

Why the reddish color of the debris cloud? It only last a few seconds then fads in real time.

Some of the videos were seriously contrast enhanced due to the distance shot and telephoto lens so the orange will probably be artificial. Though colour can reveal a lot about the chemistry, I suspect simple confined hydrogen explosion full of particles of concrete/dust.

This image... (or rather the second image with dust plume) though clearly shows how truly vertical that large slab is projected upwards, and that the sideways, (towards us and to the left) is purely an illusion created by the wind taking the lightweight dust to the southeast.
What explosion could project so perfectly vertically... I can only think of the concrete containment vessel again! it's the only thing shaped like the combustion chamber of a rocket. So did it fall back down on the building itself?
Sorry I'm having trouble ggrabbing the image I want from razzzz's post earlier.
watch this vid instead, the tower is directly in line with the buildings diagonal so marks the middle of the building. watch the 'slab' ...

 

[Borek]

The N2 gas and steam would have a constant partial pressure at a given temperature. So as the total pressure rises due to steam Nitrogen, Hydrogen and Oxygen, the partial pressure of Hydrogen would increase from zero before the fuel damage to some new value. and the partial pressure of oxygen would increase from a low inerted pressure to its new value, but at half the rate of the hydrogen. Volumetrically the same relationship is present. Does the containment ever reach an explosive or ignition concentration if the % of oxygen is insufficient for ignition and continues to decrease? What am I missing?

I have the same problem with yuriwho post, I don't see how the mixture can get past lower explosive limit.

 

[AntonL]

500 m**3/day is about 500 tons, about double the daily water used for reactor cooling at the 150 liter/min rate indicated by the NISA. Suggests this leak is drawing on more than just reactor 2.

Does anyone have any idea of how a thin slurry of irradiated reactor fuel could be stored?
Maybe freeze it in place and wait a few years for decay?

I doubt that anyone would want to store a slurry or solution of fission products or fuel.

I would recommend that it be chemically processed in much the same way normal fuel is fabricated. Basically, one simply precipitates the solution. The precipitate is dried, then calcined and finally vitrified, possibly with a glass additive. The solid can then be stored permanently in a geological repository.

One possibility would be to recover the fuel, or fissile and fertile material.

But, In the fukushima case the precipitate would be mostly sea salt. Can salt be vitrified?

 

[AntonL]

OK I agree with the equation for Zr-H20 reaction, but that yields only ZrO2 which is a solid and H2 gas.

Radiologial or Thermal whatever the source, isn't the equation:
2H2O -> 2H2 + O2

I remember PV = NRT where N is in moles. If you are releasing two molecules of Hydrogen gas for each molecule of oxygen, then the partial pressure of hydrogen increases at twice the rate of Oxygen in a constant volume with both gasses at the same temperature.

The N2 gas and steam would have a constant partial pressure at a given temperature. So as the total pressure rises due to steam Nitrogen, Hydrogen and Oxygen, the partial pressure of Hydrogen would increase from zero before the fuel damage to some new value. and the partial pressure of oxygen would increase from a low inerted pressure to its new value, but at half the rate of the hydrogen. Volumetrically the same relationship is present. Does the containment ever reach an explosive or ignition concentration if the % of oxygen is insufficient for ignition and continues to decrease? What am I missing?

If it does reach an explosive point without air inleakage, it begs the question of why NRC requires BWR MK1 containments to be inerted. Are we sure the Japanese inert their plants? There are tanks on the Fukushima site that look like our liqiud nitrogen storage tanks at US BWRs.

I have the same problem with yuriwho post, I don't see how the mixture can get past lower explosive limit.

With all the dissolved oxygen in the water that has been pumped into the reactor a substantial amount could have been accumulated by now as gas

http://docs.engineeringtoolbox.com/documents/841/oxygen_solubility_fresh_sea_water.pdf

http://www.engineeringtoolbox.com/oxygen-solubility-water-d_841.html

 

[MadderDoc]

That's not what I mean. There are large pieces thrown up a long way up but they might be the large sections of the trusses above the SFP that are missing, which I would expect to be much lighter than FHM. It's about the mass really. I find it more plausible that the FHM got blasted sideways in the first explosion towards the north wall, destroying the wall and itself.
Again like I said I might be wrong, no need to get defensive or dismissive.

The FHM and trusses could, I presume, be in the SFP, otherwise the NW corner for either or both is my focus. Attached are a few photos from the MOX loading of the reactor number 3, on 21 August 2010 so we know what we're looking for. More photos from the occasion at:
http://www.gyldengrisgaard.dk/20100821_daiichi03/

 

[NUCENG]

With all the dissolved oxygen in the water that has been pumped into the reactor a substantial amount could have been accumulated by now as gas

http://docs.engineeringtoolbox.com/documents/841/oxygen_solubility_fresh_sea_water.pdf

http://www.engineeringtoolbox.com/oxygen-solubility-water-d_841.html

That may be the answer. I'll look, but I thought they performed containment flood AFTER the explosions? I agree there is free oxygen in containment since flooding now. The explosions may have compromised containment integrity (at least in unit 2 allowing air inleakage.

But with pressure in containment before the explosions where did the oxygen come from to support a belief that a detonation came from the drywell? It is the chicken and the egg question. Did containment failure allow the explosions or did the explosions cause contaiment failure?

Has anybody seen a good detailed timeline based on the plant reports?

 

[Borek]

With all the dissolved oxygen in the water that has been pumped into the reactor a substantial amount could have been accumulated by now as gas

Good point, I forgot about it. Still, I wonder if at the temperatures present and in the presence of ionizing radiation hydrogen would not react with oxygen and create water - without an explosion. It is all in kinetics.

 

[TCups]

Correct me If I'm not understanding this right: flash heating of water lead to fast vaporisation ie: cold watter on a hot pan. What you are suggesting is that the steam pressurized escaping the Primary containment entering the pool full of watter would flash heat the (large amount of) water in the pool ? Just like inserting a really hot metal blade into water?

Now isn't the suppression pool working exactly on the principle of cooling hot steam or gaz with water ?

as far as temperature are concerned we have a max pressure in the drywell of 0.490 MPa (75psi) does this value is consistent with a steam temperature hot enough to flash boil the pool ?

|Fred:

Not cold water. The water in the SFP is absolutely pure and still. The spent fuel is (pre)heating the water in the pool. The water in the pool could have been at the boiling point temperature but not vigorously boiling. Maybe superheated isn't the term, but certainly very, very hot.

In the example I mentioned, heating water in a clean flask, the boiling chip is not a catalyst. It is just a rough surface that is a rough surface to initiate vaporization. Sometimes beer glasses use laser etching on the bottom of the glass to make the CO2 come out of solution.

Not saying that there aren't small rough surfaces on the fuel rod assemblies. But in a very pure, very hot pool of water, already at or very near the boiling point, a hot blast of any sort would 1) raise the surface temperature and 2) agitate the entire pool. In the presence of burning hydrogen + oxygen, a large amount of water could be quickly converted to steam. And although the SFP isn't shaped like a rocket nozzle, it is a deep, vertical structure. Recall also that the initial blast blows the roof off over the SFP.

BTW, one of the earlier posts did confirm that the dozer work was to clear high level waste and another confirms that pieces of radioactive fuel rod have been found large distances from the pool.

Did those come from the core of the reactor or from the SFP? My vote is SFP and the only vertical blast out of the SFP would have to come from steam.

Water at 100C degrees does not boil. Water at 100C begins a phase change. The heat of transition is 880 cal/gr (been a long time -- correct me if I am wrong), or once 1ml water gets to 100C, another 880 cal is needed to turn that 1ml into steam at 100C. That is why live steam has so much more energy than hot water.

The hot fuel in the still pool could have already supplied most or all of the heat of transition without the water actively boiling. After all, Bldg 4 didn't look like a boiling tea kettle emitting steam before the explosion. It is reasonable to believe that a very large amount of thermal energy was stored in the SFP water, and that a hot explosion that raised the temp of and severely agitated that pool tipped the reaction. The rapid phase change from liquid to gas means a massive increase in volume, and a huge vertical steam plume.

 

[artax]

I don't think it is possible to get the sort of steam explosion you are talking about with a large body of water at or near it's boiling point.
I think the sort of meltdown and water table/steam explosion is a bit of a myth (if you're thinking along those lines)
Someone mentioned earlier... the first time I saw hot lava flowing into water I was surprised to see there wasn't any explosion.

The heat of vapourisation for water is just too high, like it's heat capacity, (precisely why it's so good for cooling)
Only microwaves can deliver this sort of threoughout volume and 'to every molecule', energy transfer instantaeneously.

Still got to be hydrogen to me, or a confined biuld up of steam with vessel failure to give such a large blast.

Sorry mate!

There's an interesting article here

http://www.ieer.org/comments/Daiichi-Fukushima-reactors_IEERstatement.pdf

 

[NUCENG]

With all the dissolved oxygen in the water that has been pumped into the reactor a substantial amount could have been accumulated by now as gas

http://docs.engineeringtoolbox.com/documents/841/oxygen_solubility_fresh_sea_water.pdf

http://www.engineeringtoolbox.com/oxygen-solubility-water-d_841.html

Re: AntonL #3051, NUCENG #3053 BOREK #3054


As promised. I looked at the TEPCO sequence of events and JAIF Plant Status reports.

Explosions were reported on 3/12, 3/14, and 3/15, Unit 4 was damaged about the 15th or 16th.

Seawater had been injected into RPVs on Units 1 and 3.

Seawater injection into containment was still being planned/considered on 3/16.

TEPCO is still reporting no coolant leakage into containment on all units. ?

Conclusion: Sea water injection into contaiment followed explosions and therefor oxygen dissolved in seawater could not have been responsible for creating an explosive mixture inside containment. The only remaining possibility would have been containment failures from the earthquake, but since there was a high pressure in containment, it would be tough to get air inleakage. Unless I missed something about the mixture of steam, oxygen, hydrogen, and nitrogen in containment, I just don't see an condition that could lead to an explosion inside containment.

 

[artax]

have a read of this!

http://www.nytimes.com/2011/04/06/world/asia/06nuclear.html?_r=4&hp

(according to a confidential assessment prepared by the Nuclear Regulatory commission...)"The document also suggests that fragments or particles of nuclear fuel from spent fuel pools above the reactors were blown “up to one mile from the units,” and that pieces of highly radioactive material fell between two units and had to be “bulldozed over,” presumably to protect workers at the site. The ejection of nuclear material, which may have occurred during one of the earlier hydrogen explosions, may indicate more extensive damage to the extremely radioactive pools than previously disclosed. "

 

[TCups]

I don't think it is possible to get the sort of steam explosion you are talking about with a large body of water at or near it's boiling point.
I think the sort of meltdown and water table/steam explosion is a bit of a myth (if you're thinking along those lines)
Someone mentioned earlier... the first time I saw hot lava flowing into water I was surprised to see there wasn't any explosion.

The heat of vapourisation for water is just too high, like it's heat capacity, (precisely why it's so good for cooling)
Only microwaves can deliver this sort of threoughout volume and 'to every molecule', energy transfer instantaeneously.

Still got to be hydrogen to me, or a confined biuld up of steam with vessel failure to give such a large blast.

Sorry mate!

There's an interesting article here

http://www.ieer.org/comments/Daiichi-Fukushima-reactors_IEERstatement.pdf

No worries, artax. I may well be wrong. My difficulty is that I can't match up the photographic evidence, which says:

1) vertical blast from unit 3 following a fireball at the SE corner
2) blast damage over the SE corner is over the SFP3
3) crane and roof girders are still intact and apparently on top of the location of the top plug of the primary containment
4) something that looks a lot like a heavy piece of machinery has gone almost straight up and crashed almost straight down back onto Bldg 4, which IF it is a FHM rather than the plug, then the vertical blast must come out of the SFP, not the primary containment
5) the quality and quantity of the blast at Unit 3 look fundamentally different from the blast at Unit 1 (although different construction) and the proposed hydrogen blast at Bldg 4 (same construction)

None of this excludes a blast originating in the primary containment; in fact, in my opinion, a blast did come from the primary containment, except that the blast was

1) not vertical but instead sidewise into the region of the SFP through the transfer chute.
2) associated with a secondary vertical blast coming from the SFP, and
3) possibly associated with a third blast component in the lower floors of Building 3
4) questioned because of a viable mechanism for ignition of gas within the primary containment atmosphere.

So my difficulty is correlating the pictures with a vertical blast, which all agree occurred, as coming from the mouth of the primary containment, which the photos don't seem to support, or as coming from the spent fuel pool, for which my explanation of a superheated steam blast seems to be inadequate.

Something doesn't fit -- either my interpretation of the photographic evidence (very possible) or my explanation of the etiology of a vertical steam explosion from SFP (also very possible) is wrong. So, either way, I am wrong, I suppose.

Better minds than mine are still pondering. But (sigh), I fear it may all be wasted mental gymnastics given the sum of mounting problems and the implications for the "big picture" at Fukushima.

 

[ian_scotland]

watch this vid instead, the tower is directly in line with the buildings diagonal so marks the middle of the building. watch the 'slab' ...

I don't know if this is of any help to people, but I've an image that may correlate the unit 3 vertical explosion debris visible in the video to the whole Fukushima Daiichi plant layout:

https://www.physicsforums.com/attachments/34094

OK, that attachment failed :-(
How do I attach the image?

 

[artax]

I'm like you, just want to know what happened and work out the consequences, it's just frustrating when you know they're not telling us everything.
That vertical component of the blast has me dumbfounded if the plug didn't blow.
I've searched the web for some other group or engineer that's tried to analyse the blast at unit 3, because it was enormous, and filmed from 30km away!
Seriously are you sure the plug is intact?
That large piece that comes back down on the roof, or the sw/ne axis of reactor 3 was so perfectly vertical it must have a mechanism of almost bullet/barrel like accuracy.
I can see there's no tell tale hole in the roof girders, so it does look like an SPF blast, blowing the roof off.
Anyway, hopefully they'll tell us one day!
PS have you seen the slowed down/zoomed in/de-shaked version of the JFK's assassination? Truely Shocking!

 

[artax]

I don't know if this is of any help to people, but I've an image that may correlate the unit 3 vertical explosion debris visible in the video to the whole Fukushima Daiichi plant layout:

https://www.physicsforums.com/attachments/34094

OK, that attachment failed :-(
How do I attach the image?

click on 'new reply' (bottom left), below where you type in your message, there's a box saying manage attachments, click...browse your pic, upload and close window... submit reply.

 

[ian_scotland]

attached image attempt 2 :-)Thanks Artax :-)

 

[timeasterday]

Anyway, hopefully they'll tell us one day!

I wonder if we will ever know? I mean, doing any kind of forensic analysis is going to be pretty much impossible for any person on site due to radioactivity. Robots might be able to get in certain areas but may be hampered by debris. Getting large stuff off the top to examine the status of the reactor containment and adjacent pools would require a large crane but nobody is going to be able to secure the rigging on the objects being lifted. Or maybe you just try to hook a cable on stuff and drag it off instead of lifting. I just cannot comprehend the task of cleaning up the site or if they choose that path - securing everything for entombment.

 

[Jorge Stolfi]

{Re red color of dust cloud:} Some of the videos were seriously contrast enhanced due to the distance shot and telephoto lens so the orange will probably be artificial. Though colour can reveal a lot about the chemistry, I suspect simple confined hydrogen explosion full of particles of concrete/dust.

I don't think it is color processing. The buildings did not become reddish.

It is not sunlight either because the time is 11am.

Perhaps they are red-hot glowing particles (=sparks). Note that to have an H2 explosion one must have zirconium at >1000C.

 

[NUCENG]

More new pictures:

http://cryptome.org/eyeball/daiichi-npp3/daiichi-photos3.htm

 

[Jorge Stolfi]

Re the reddish color of the dust cloud: Perhaps it is also the tar in the roofing material: pulverized by the exposion, heated by the steam and H2 combustion, finally coming in contact with oxygen and burning up.

 

[Jorge Stolfi]

Forgive me for going back to the "hallucination" pic:

I had suggested that item (7) could be the water in/out pipes of the spent-fuel pool.

Could be ventilation ducts, but a pic of the reactor's working floor shows only square-section ventilation ducts.

On the other hand, a while ago I saw an NHK framegrab where two guys were debating over a one-foot-tall cutaway 3D model of the SPF. (Sorry, cannot find it now.) Besides the array of fuel assemblies at the bottom, it showed also the two water pipes. *In that model* they were round and painted dull gray. One came inthrough the side, then bent down and ended a couple of meters beloe the water level. The other one came in through the bottom, went up almost to the top, then made two right angles and went back down, siphon-like, almost to the bottom.

 

[AntonL]

By the size of what is falling from the explosion pillar (right hand side) I would imagine it to be roof sheeting.

 

[Jorge Stolfi]

PS. Also about item (1): one objection to them being fuel rods is that in the assembly they are held together by several horizontal "spacer" plates, which are missing in the pic.

However, AFAIK the spacer plates are made od steel (MP < 1500C) and the tubes of zircalloy (MP ~1800C). We know that some of the fuel in the SFP #4 was heated to at least 1000C (only way to make enough hydrogen for the explosion in #4). If heating continued past that point, eventually the steel plates would melt leaving the tubes loose. Is that correct?

The outer square jacket is made of zircalloy, correct? If so it would have protected the rods from corrosion (very little steam inside it, not renewed) until the sleeve itself got busted.

 

[Astronuc]

I don't think it is color processing. The buildings did not become reddish.

It is not sunlight either because the time is 11am.

Perhaps they are red-hot glowing particles (=sparks). Note that to have an H2 explosion one must have zirconium at >1000C.

Hydrogen is generated in a corrosion reaction between Zircaloy and water at 300°C. The higher the temperature, the faster the reaction. To have a hydrogen explosion, one only need H₂ + O₂ with something like a 15% concentration. Below that one gets a fast burn or deflagration.

Also, one doesn't necessarily need O₂ as the oxidizer for a hydrogen explosion. Chlorine gas (Cl₂) mixed with H₂ makes for a pretty good explosion. If there was H₂ produced from the Zr + 2 H₂O => ZrO₂ + 2H₂ reactions, and seawater release Cl₂, then I wonder if an H₂ + Cl₂ => 2 HCl reaction in the top of the RPV would be possible.

 

[TCups]

have a read of this!

http://www.nytimes.com/2011/04/06/world/asia/06nuclear.html?_r=4&hp

(according to a confidential assessment prepared by the Nuclear Regulatory commission...)


"The document also suggests that fragments or particles of nuclear fuel from spent fuel pools above the reactors were blown “up to one mile from the units,” and that pieces of highly radioactive material fell between two units and had to be “bulldozed over,” presumably to protect workers at the site. The ejection of nuclear material, which may have occurred during one of the earlier hydrogen explosions, may indicate more extensive damage to the extremely radioactive pools than previously disclosed. "

Yes, I noted that earlier. The dozer work was necessary before they could bring the crane into spray water at Unit 4.

The confidential report suggests the source of the rods was from "one of the earlier hydrogen explosions". My vote would be Unit 3 as the most likely candidate.

An earlier post referred to differential pressures in an explosion. Hydrogen exploding inside an upper building containment might blow pieces of the roof upward, but is unlikely to blow rods in the bottom of a SFP upward. And that, in my mind, includes hydrogen of origin from dry rods in a SFP.

And so, as ever, in my mind, I keep coming back to steam as the villain and vertical explosion from SFP3 as the vector that ejected fuel rods. And we still don't know for sure if fuel rods are seen atop the NE corner of Bldg 3, which might again implicate the "ballistic" FHM model.

 

[Astronuc]

PS. Also about item (1): one objection to them being fuel rods is that in the assembly they are held together by several horizontal "spacer" plates, which are missing in the pic.

However, AFAIK the spacer plates are made od steel (MP < 1500C) and the tubes of zircalloy (MP ~1800C). We know that some of the fuel in the SFP #4 was heated to at least 1000C (only way to make enough hydrogen for the explosion in #4). If heating continued past that point, eventually the steel plates would melt leaving the tubes loose. Is that correct?

The outer square jacket is made of zircalloy, correct? If so it would have protected the rods from corrosion (very little steam inside it, not renewed) until the sleeve itself got busted.

The spacer grids are fabricated from Zircaloy-2 strip (outer perimeter) and Zircaloy-2 ferrules. There is an Inconel spring shared between pairs of ferrules.

The outer channel (square box with round corners, with width of ~5.3 inches/134 mm) is fabricated from Zircaloy-2 or Zircaloy-4. Hydrogen can be produced by corrosion of Zr by steam at 300°C, although it's expected that without proper cooling the core temperatures were several hundred degrees greater.

 

[WhoWee]

The spacer grids are fabricated from Zircaloy-2 strip (outer perimeter) and Zircaloy-2 ferrules. There is an Inconel spring shared between pairs of ferrules.

The outer channel (square box with round corners, with width of ~5.3 inches/134 mm) is fabricated from Zircaloy-2 or Zircaloy-4. Hydrogen can be produced by corrosion of Zr by steam at 300°C, although it's expected that without proper cooling the core temperatures were several hundred degrees greater.

Just to be clear, wouldn't the Hydrogen normally have been vented under such circumstances if it wasn't for the damage from outside forces?

 

[artax]

under normal operating temperatures you don't get hydrogen produced (<300C)

 

[Astronuc]

Just to be clear, wouldn't the Hydrogen normally have been vented under such circumstances if it wasn't for the damage from outside forces?

The hydrogen should have been vented up the tall stacks and in a way that it didn't explode. There is certainly something abnormal about the hydrogen detonations/deflagration.

There is apparently unknown damage within the containments. Unit 2 seems to have a very significant leak, and if they are adding water and not able to maintain a certain level in the RPVs or containment, then there is some significant leak or leaks somewhere - whether it's ruptured duct work or cracks in the reinforced-concrete containment structures and steel liners/pipes.