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Japan Earthquake: nuclear plants

by gmax137
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MadderDoc
#13195
May11-12, 03:54 AM
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Quote Quote by jim hardy View Post
<..>
i often try to rule things out.
When the "three minutes after" satellite photo came out showing what looks like that same plume,

i set out looking for what could have heated pool that quickly.

That path seemed implausible. I dont even know if they actually were the same plume.
So i decided to wait it out.
Trying to put myself in your situation at the time you saw this photo, I imagine you'd have a possible case of nearly exposed fuel on March 16th in your mind. The satellite photo would have seemed to you to have possible repercussions to that, indicating a possible case of nearly exposed fuel already shortly after the explosion on March 14th, and then, a possible case of pool involvement in the Unit 3 explosion, the explanation of which 'hydrogen explosion' you felt was in miss of something.

As I recall, I came out from the curious incident of the pool on March 16th with no clear conception of what it was about, except for an intuitive feeling of bait and switch. I had that feeling arranged to reinforce a possible case of the presence of an unwillingness to admit PCV involvement in the Unit 3 explosion. Pool involvement, I believe, was not something I really thought of until it occurred to me that other people did. But then it just became a case for me of accommodating that possibility. To me that seemed pretty straightforward, seeing the energetics of flashing large quantities of water into steam in a short instant it left pool involvement with only a tiny probability of a case of criticality, bordering to the impossible according to experts, which I have to trust in such matters.

That the plume came from someplace other than spent fuel pool is certainly not ruled out.
In respect to the never-ending circle of expanding knowledge along with language to express it ..

I suggest we can say less conservatively, that the plume from the building, at least for a part of that plume, did in fact come from someplace else, i.e. the PCV. Evidence, also evidence from a very early stage indicates this to be the case, no evidence appears to contradict it. The only inconsistency it produces is with Tepco's estimate on March 16th, which appeared to be, that the plume in its entirety was caused by evaporation of water from the pool.
jim hardy
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May11-12, 09:10 AM
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Thanks for 'walking in my shoes'. I find it helpful in my troubleshooting to ask myself "What would make a rational person say that? Just what was the picture in his mind right then ?"

....pool involvement with only a tiny probability of a case of criticality, bordering to the impossible according to experts
I watched the TV news video that morning and thought it had to be the SFP. I even emailed Arnie Gundersen to ask if those racks had boraflex and could go fast critical on loss of moderator.. i think i set him off on a tangent.
But as i learned more about their pools and about fast fission cross sections i too decided it wan't the pool.
Photos have since confirmed.

part of that plume, did in fact come from someplace else, i.e. the PCV.
So next i looked into recriticality on reflood as described in ORNL and European BWR studies.
But Morbius made a pretty strong case against thermal recrificality and his credentials are awesome.
So next i looked into low enrichment Pu with U reflector.
And into Hafnium cross section at high energy(~10mev)
And what i found out is i don't know enough about fast reactor physics to make meaningful calculations. So i can't put a number on it. I admit defeat.
You could be right.
But for me that train of thought is too speculative to make any strong assertions.

As i said on another forum i'll have to wait for photographs of reactor head.

What's that "evidence from a very early stage " you mention ?
Probably i looked at it (i was obsessive back then) and tucked away in the 'unresolved observations' basket , and would like to know what facet it was that has retained your attention.

That was a very clearly communicated post, by the way . With my Asperger's i had to study it but it parsed quite well. Thanks !


old jim
mheslep
#13197
May11-12, 10:38 AM
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Quote Quote by jim hardy View Post
...
But Morbius made a pretty strong case against thermal recrificality and his credentials are awesome.
Sorry, do you recall roughly when and in what thread was that part posted? This thread?
zapperzero
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May11-12, 11:17 AM
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Quote Quote by mheslep View Post
Sorry, do you recall roughly when and in what thread was that part posted? This thread?
That would be the explosion thread, now lost to time and incompetence. Sorry. Some people here may have copies of the Google cache before it expired or other such things - there is a discussion earlier in this thread wrt the demise of that thread. It was closed for moderation and never reopened. There is no backup at PF.

Morbius (aka Gregory Greenman iirc) was arguing, based on his extensive experience designing nukes and on some calculations he did, that unmoderated recriticality is impossible in reactor fuel, in any configuration, that moderated criticality is only possible in a 50/50 "matrix" configuration of fuel/(light)water, that there is no way that such a configuration could have been achieved with melted fuel.

He also stated that there is no way that the neutron-reflecting properties of either water surrounding fuel or reactor steel and other metals could have changed this.

At the time, I was obsessing over the possibility of pulsating criticality in reactor 3, which I saw as a way to explain some of the readings we saw in the first few weeks.

The issue of spent fuel in the pools was only marginally touched upon, I believe.

I present this along with pre-emptive apologies for any inexact info, both to you and to Morbius. It has been a rather long time and my memory is not getting better.
jim hardy
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May11-12, 11:27 AM
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Sorry, do you recall roughly when and in what thread was that part posted? This thread?
It was in the 'Unit 3 explosion' thread which is no longer with us.
Would have been within a very few days of June 12 2011.

He ran a Monte Carlo program and said , to best of my recollection, 'corium' couldn't go if it has less than 10% enrichment because it lost the optimal geometry of an assembled core.
Monte Carlo is outside my experience base. All i know is it's a sophisticated neutronics program used by genuine experts.
I accepted his opinion as a solid data point. for uranium.


old jim

zz posted while i was typing. He has a better memory for detail than i do.

we dont disagree, thanks zz i worry about anything i do from memory.
zapperzero
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May11-12, 11:37 AM
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Quote Quote by jim hardy View Post

we dont disagree, thanks zz i worry about anything i do from memory.
De nada, I do too.
MadderDoc
#13201
May11-12, 02:18 PM
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Quote Quote by jim hardy View Post
It was in the 'Unit 3 explosion' thread which is no longer with us.
Would have been within a very few days of June 12 2011.

He ran a Monte Carlo program and said , to best of my recollection, 'corium' couldn't go if it has less than 10% enrichment because it lost the optimal geometry of an assembled core.
Monte Carlo is outside my experience base. All i know is it's a sophisticated neutronics program used by genuine experts.
I accepted his opinion as a solid data point. for uranium
IIRC, his challenge to criticality theoreticists is to postulate a credible mechanism for getting the fuel arranged as it is in the core and with no control rods between them, and submerged in water.

As regards the fuel in the SFP, that leaves afaics only the possibility of some disturbance overturning racks causing fuel to rearrange and come back to rest in the right positions for the criticality to happen. While not impossible, the probability of such occurrence is too low to take a theory about it seriously until one can say that one has examined and exhausted all other options for explanation.

As regards the fuel in the core, jim hardy did bring up a mechanism involving control rod melt-away in a degrading core during a LOCA. Criticality could then happen on subsequent reflooding of portions of un-melted fuel assembly parts being still in their original positions however now devoid of control rod material between them.
This would seem to me a much more likely contender for a criticality theory.

But, however much a theory of a criticality event makes a lot of exciting energy available for destruction -- the Unit 3 reactor, it must be assumed, at the time of the explosion was already shock full of hydrogen and accumulated energy in hot water, the system had already in it plenty enough of energy available for its own destruction. An assumption of criticality then becomes just one of many possible triggering factors, for its particular quality: energy, there is no need.
MadderDoc
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May11-12, 02:46 PM
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Quote Quote by jim hardy View Post
What's that "evidence from a very early stage " you mention ?
I was thinking of the visual evidence from Tepco's intensive helicopter surveys on March 16th. Although in written sources Tepco comes over as saying that the plume in its entirety was due to water evaporated from the SFP , even this lousy video shot taken during the mission leaves no doubt that the reality of the situation was, shall we say, a bit more complex. Note the clear visibility of the steam plume out of the equipment pool. Surely Tepco would have noticed the presence of that plume, which certainly is not steam produced by water evaporated from the SFP many meters away. In fact, views like this would have suggested to me that the plume in its entirety might have very little to do with the spent fuel pool. Tepco, alas, curiously appears to have reported to NISA the opposite judgement, that it was all coming out from there.
jim hardy
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May11-12, 09:07 PM
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this one looking opposite direction also has appearance of steam coming out nearer reactor.



this one it's hard to say. Reactor would be centered on fourth column.


not sure where i got this one. Top one is from Cryptome, [EDIT: add] http://cryptome.org/eyeball/daiichi-...hi-photos3.htm , twenty-third one down. It's worth loading the zipped full resolution ones from link at top of that page..[end edit]



Thanks, it had not occured to me to localize the sources of the steam. Guess i'm intimidated by not knowing the piping there.

...........................................................

BTW - that control rod meltaway and recriticality scenario is not my creation. It's the subject of NUREG CR-5653.
which has this great line: "... the operations staff may be very surprised..."
It's bad science to go looking for things that support one's preconceived notions.
Mea culpa. The enormity of that explosion set me off looking for reasons to believe it got a fission boost.




old jim
jim hardy
#13204
May11-12, 10:40 PM
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challenge to
...postulate a credible mechanism for getting the fuel arranged as it is in the core and with no control rods between them, and submerged in water.....


Experiments to investigate the phenomena of core melt progression in prototypical BWR core geometries have been carried out in the Annular Core Research Reactor (ACRR) at Sandia National Laboratories (one BWR test) and at the CORA out-of-pile facility9 at the Kernforschungszentrum Karlsruhe (KfK) in the former Federal Republic of Germany (six BWR tests). The first of these was the DF-4 experiment," conducted within the ACRR in November 1986. The test apparatus, placed within the cylindrical region surrounded by the ACRR annulus, included a control blade arm, channel box walls, and 14 fresh fuel rods. The apparatus was dry, but the 20inch (50-cm) long test section was supplied from below with a steam flow representative of BWR boiloff conditions.
When the DF-4 fuel rod cladding was heated beyond the runaway zirconium oxidation temperature, the energy release associated with oxidation accelerated the temperature escalation. Much of the clad melted at 2125 K (3365F) and relocated downward; the remainder was converted to and remained in place as ZrO2, which has a much higher melting point ([4900'F]2978 K).
The control blade in the DF-4 experiment melted earlier than expected and progressively and rapidly relocated downward. Subsequently, the reactor was shutdown to terminate power generation within the test assembly fuel rods before fuel melting could begin. In a post-test crosssection, the relocated control blade material was found in the form of an ingot at the very bottom of the test section, which was below the bottom of active fuel. Both the control blade and the channel box wall portions of the DF-4 test section were more than 90% destroyed due to melting and relocation during the experiment, but the fuel pellet stacks were predominantly still standing. Relocated cladding blocked the base of the fuel rod regions of the experiment.

Figure 3.7-15 illustrates the results of the DF-4 experiment, extrapolated to the same portion of the core that is represented in Figure 3.7-14. (Here the water rods, which were not included in the DF-4 experiment, have been assumed to relocate in the same time frame as the channel box walls.) The ramifications of these standing fuel pellet stacks in the absence of control blades with respect to the potential for criticality if water were to be introduced at this point in an actual accident sequence should be obvious.

Figure 3.7-15 You'll have to look at the document for i dont know how to copy the figure here. Its descriptor says it all, though. jh
Relocation of control blades and channel box walls leaves on U02pellets encased in thin Zr02sheaths sic
http://pbadupws.nrc.gov/docs/ML0210/ML021080117.pdf

so i could niether prove nor disprove it happened, only that it's deemed possible by credible sources..

old jim
jim hardy
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May11-12, 11:49 PM
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ps

Nureg CR-5653 was hard to find but it seems available here:

http://www.findthatfile.com/download...4077748&t=hPDF

12 meg , takes a while .
rmattila
#13206
May12-12, 01:19 AM
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There's also one report by the Nordic nuclear safety group on the issue of BWR recriticality:

http://www.nks.org/scripts/getdocume...11010111119589
zapperzero
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May12-12, 02:39 AM
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Fwiw, i had proposed a mechanism where there is thermal inversion in the melt (ceramic ends up on the bottom) then the melt breaches in the bottom head and is blown down into the water which was supposed to exist on the PCV's bottom, as in the report you provided.

This would result in a steam explosion, of course, and would also create a bed of small ceramic fragments which when re-flooded might (I thought) go critical and provide the fluctuating radiation and heat levels we were seeing at the time as well as the periodic spikes of Iodine in the water.

Morbius chewed me over for thinking that it's even remotely possible for a debris bed to self-arrange into a favorable geometry.
MadderDoc
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May12-12, 05:26 AM
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Quote Quote by jim hardy View Post
<..>Thanks, it had not occured to me to localize the sources of the steam. Guess i'm intimidated by not knowing the piping there.
Oh, you'll be excused, but not so with Tepco. You must imagine you are Tepco's man on board the helicopter. Localizing the sources of the steam is part of you mission and you know exactly what is where in the reactor building.

Now, how could you possibly come to the conclusion from your views of Unit 3 from the air (only bleakly represented by the scraps we've been handed), that e.g. this scene of the plumes rising over Unit 3 is all about its having a problem of evaporating water from its SFP -- and not at all about its having a problem of a leaking reactor?



NISA Relase March 16 12:30:
-"White smoke was seen rising from the vicinity of Unit-3 at around 8:30, Mar. 16. Damage to the containment vessel of the unit is suspected."
(Bait: There may be a serious situation, it is being investigated)

NISA Release March 16 19:00:
-"White smoke was seen rising from the vicinity of Unit-3 at around 8:30, Mar. 16. TEPCO estimates that failing to cool the SFP has resulted in evaporation of pool water,
generating steam."
(Switch: We have now evaluated the situation. The white smoke is just steam from the SFP. But that is also a serious matter you can worry about. It may eventually boil dry.)

Next day, reinforcement. In all media: "There is an urgent need for watering the SFP"
jim hardy
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May12-12, 09:13 AM
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I guess i can excuse them for wanting to know what they had before going public.

That Atlantic article from last year said "Unfortunately, Welch couldn't share the specifics of the missions his team flew. The cone of secrecy around Fukushima extends far and wide."
http://www.theatlantic.com/technolog...ushima/237981/
One would think by now there'd be a Nova show about it.

The line you quoted : "Damage to the containment vessel of the unit is suspected." is i think 'execuspeak' for the unmentionable. Media sure missed it.

old jim
MadderDoc
#13210
May12-12, 09:56 AM
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Quote Quote by jim hardy View Post
<..> wanting to know what they had before going public<..>
That's not good enough when you are two days after the explosion in the unit and you have just handed a photo out to the press showing the unit was steaming already by the morning of yesterday.
MadderDoc
#13211
May12-12, 11:17 AM
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Quote Quote by jim hardy View Post
<.>
The line you quoted : "Damage to the containment vessel of the unit is suspected." is i think 'execuspeak' for the unmentionable. Media sure missed it.
Journalists are as a breed inquisitive, but what could they do, with counterparts moving about the map confusing as crabs and barely more outspoken than oysters.

The media did seem ready to blow. Media temper flares on March 16th Tepco press conference. But then next day we were at war with Poolasia, and news from the front naturally took focus.

Edit: After the first day of the war the generals could declare victory in the first few battles:
"Holding a midnight press conference, TEPCO is cautiously optimistic efforts with
helicopter drops and water cannons had some success cooling the spent fuel rod pool at the #3 Fukushima reactor.
"We were able to see some steam," says an official, "its fair to say that the spraying was somewhat effective." "

So the war with Poolasia which was started because Poolasia was steaming, was now being won because Poolasia was steaming.
jim hardy
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May12-12, 01:07 PM
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Journalists are as a breed inquisitive, but what could they do, with counterparts moving about the map confusing as crabs and barely more outspoken than oysters.
Oysters? Confusing? Counterparts?
you have to be blunt with me. I am more obtuse than normal people and miss social cues. It's called Asperger's.



The experts were caught flat-footed .. some of their emails are still floating around.
http://list.ans.org/pipermail/ncsd-f...il/000020.html

i think Tepco's scurrying about was from a genuine lack of knowledge compounded with shock and disbelief . Probably official pressure to quell panic, too.

I spent a lifetime working in a plant . Certainly i had a hard time acceptng that one of these things is capable of what it did.
But i've got over that and as i've said so many times - i'm ready for that Nova show.

A calm scholarly presentation would be welcome. Nobody needs tabloids screaming end of the world scanarios, though. And that's what would have happened last year.

We're ready now, IMHO.

old jim


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