Question about Fukushima in 2016

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ladajo
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Re: Question about Fukushima in 2016

Postby ladajo » Fri Mar 25, 2016 8:20 pm

I can't reconcile that -- a view of criticality as a continuum -- to the Slotin accident at Los Alamos (criticality by fleetingly and accidentally joining the two halves of the demon core) and the Cecil Kelley centrifuge accident (criticality by centrifuge).


This is a terminology issue only. In the business, "critical" means at power equilibrium where K-effective = 1 and power is stable.
In the case of both your cited accidents, they were dealing with fast fuel, processed and shaped (Slotin), and in-processing/not formed (Kelley). This would imply prompt criticality events which is a super-critical condition demonstrated by rapid uncontrolled power rise. They both made mistakes regarding the mass/geometry, Slotin probably knowing he was playing with fire, whereas Kelley not so much. In any event, the power transient in both cases required up-power, which by definition is "super-critical". It doesn't really matter to me how it is portrayed in media, beit wikipedia, movies, or news articles, that is for laymen and zombies.
To be fair, the term "criticality" actually encompasses all three conditions, sub, stable, and super. It not just limited to stable, or to super.
But be sure, that in both accidents, the fuel masses were in supercritical conditions, and it is doubtful that they stabilized. A rapid up then a rapid down.
Think of it like playing with a light dimmer where you spin it from off to max and then back to off.
If you want to read up on a really fun prompt critical accident, read up on SL-1. It was part of our former "expeditionary nuclear power" program back in the day. I have been to the former site, sobering. I think there are some videos floating around somewhere on it as well. I like to call it the "don't play with control rods unless you are sure" accident. Kind of similar to Chernobyl.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

ladajo
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Re: Question about Fukushima in 2016

Postby ladajo » Fri Mar 25, 2016 8:25 pm

My point is that does not apply to tons of corium slag which will remain hot accordingly to the rules of the decay chain (at at Fukushima so hot it cannot be approached by man or machine, at least for years).


Yes, corium plays by its own rules, which are not the same as a constructed core form. That said, plants are designed with corium in mind, and it is really unlikely that corium would sustain enough hunger to eat its way out to raw earth. The bigger issue is the unrestrained water dumping that went on without consideration to leakage and runoff. But even that is not actually as bad as folks think. Most all the stuff you see in the news and web is about trace levels, not harm levels. But they tend to leave that bit out. Trace meaning that you can id the isotope signatures to a probable source. It is done all the time, not just for nuclear stuff. Oil is a good example.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)

What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

paperburn1
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Re: Question about Fukushima in 2016

Postby paperburn1 » Sat Mar 26, 2016 10:07 pm

The real worry you should have about a power plant. /https://www.funker530.com/nuclear-plant-officer-murdered-in-belgium-security-pass-stolen/
It was only a matter of time, but i still think evil do not know what they are up against.
I am not a nuclear physicist, but play one on the internet.

KitemanSA
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Re: Question about Fukushima in 2016

Postby KitemanSA » Sun Mar 27, 2016 2:37 am

CharlesKramer wrote:
KitemanSA wrote:
CharlesKramer wrote:And what makes fission scary: no off switch!

False. Fission definately DOES have an off switch

Definitely has an off switch... meaning control rods?

My point is that does not apply to tons of corium slag which will remain hot accordingly to the rules of the decay chain (at at Fukushima so hot it cannot be approached by man or machine, at least for years).
So where do you think all the neutron absobing material from the control rod went?

Also, how much concrete does the coreum have to burough through and what happens to all that material?

ladajo
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Re: Question about Fukushima in 2016

Postby ladajo » Sun Mar 27, 2016 1:23 pm

The true bottom line here for the slag is that while it operates under a different regime than a core construct, it is still beholden to fuel mass density / geometry. The more it reacts with surrounding materials, be they structural or containment, the more it loses in regard to the mass / geometry argument. It will reach a point where it is no longer considered to be in a power range operating mode, and that has already happened. It does not take long for it to lose the mass/geometry argument. I would say it is done more or less when the slag finds its first real concrete boundary. It is highly likely at this point to accumulate sufficient contaminants and loss of geometry to dictate loss of self sustainability reaction rates, and by definition become 'shut down' where reactions are dominated by natural decay verses burn up.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)

What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

CharlesKramer
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Re: Question about Fukushima in 2016

Postby CharlesKramer » Mon Mar 28, 2016 12:01 am

KitemanSA wrote:where do you think all the neutron absobing material from the control rod went?
Also, how much concrete does the coreum have to burough through and what happens to all that material?

Are you saying the China Syndrome is baloney because, in a worst case meltdown, the melting stops because:

-- molten fuel melts and mixes with control rods, metal containment, and the cement around the containment?

-- the resulting salg is neutron poisoned, diluted, and no longer contains the right geometry for fission?

That certainly sounds like a good idea (a last ditch failsafe) but Fukushma seems like a close case.

I'm surprised in the post-Chernobyl world (where sand -- by luck -- diluted and vitrified the core) sand (or sand + boron or something) wasn't required to automatically mix in. I would think the Fukushima slag would be easier to deal with if a little more diluted.
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hanelyp
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Re: Question about Fukushima in 2016

Postby hanelyp » Mon Mar 28, 2016 2:58 am

In a well designed fission reactor facility the core catcher basin is designed to spread out a molten core, the better to both send the fuel sub-critical by geometry, and for passive cooling. Both are facilitated by more surface area. Not every facility necessarily has such a design, or even a basin to catch the corium in a total melt down. Absent a functional catch basin the worst realistic case scenario would be molten material reaching the water table and producing a steam explosion.
The daylight is uncomfortably bright for eyes so long in the dark.

ladajo
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Re: Question about Fukushima in 2016

Postby ladajo » Mon Mar 28, 2016 12:20 pm

In the case of the Fulushima design, they have three/technically four layers of baskets. The final is the subfoundation which is meters thick (on purpose).

Even if a slag made it to dirt, the likelihood of it staying as a singular mass goes significantly down due to the uneven densities it would encounter. As it tried to work its way down it would probably start to lose bits here and there as it flowed around rocks and what not. I am unaware of any testing done on various soil/underlayment compositions. It is still fun to imagine a smoking glowing hole dropping down into the dark depths of the earth's crust... :)
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)

What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

paperburn1
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Re: Question about Fukushima in 2016

Postby paperburn1 » Mon Mar 28, 2016 8:10 pm

I am not a nuclear physicist, but play one on the internet.

CharlesKramer
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Re: Question about Fukushima in 2016

Postby CharlesKramer » Tue Mar 29, 2016 7:47 am

Corium slag must make a complicated chemical soup. It starts with fuel and cladding at thousands of degrees... then add steel containment... then cement. In Fukushima add some salt (ocean) water. In Chernobyl add sand. And then the decay chain of the fuel. Then all that mess transmuting from neutrons.

I doubt if anyone has modeled the result (even of a theoretical homogeneous mixture). Guess we'll know in a few hundred (or thousand years) what Fuku-shimium looks like.
Last edited by CharlesKramer on Sat Apr 02, 2016 1:11 am, edited 1 time in total.
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ladajo
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Re: Question about Fukushima in 2016

Postby ladajo » Tue Mar 29, 2016 12:52 pm

The studies done on core slags have shown that mass and geometry are the drivers. There have been a number for contained in the primary containment, and leakers. These have been both mods/sims and live tests with real cores. To my knowledge, a study has never been done looking at an escape from containment to the environment. I believe the assessment is that this is so unlikely, that it does not warrant the expense.
None of the five known accidents have seen slag escape beyond containment to the environment. Contaminated cooling water, gases, and in the case of Japan and Russia, core fragments (Japan from the cooling pools, Russia from the core explosion), but not slag burn through.

Here is a good summary done in 2000 by LANL. Some of our (U.S.) fun testing was done at NRTS. You should check those out for sure. Technically you could argue there were more than "five" accidents, but I don't count the ones that were started on purpose, no matter how "fun" they got. :)

https://www.orau.org/ptp/Library/accidents/la-13638.pdf
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)

What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

paperburn1
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Re: Question about Fukushima in 2016

Postby paperburn1 » Tue Mar 29, 2016 3:03 pm

How would the core flow in real life? the link I posted earlier has many photos of the Corium.
I am not a nuclear physicist, but play one on the internet.

ladajo
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Re: Question about Fukushima in 2016

Postby ladajo » Tue Mar 29, 2016 3:19 pm

It is gravity driven. Paths are determined by least resistance. When encountering something it will go around if it can, and/or eat it if possible.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)

What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

KitemanSA
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Re: Question about Fukushima in 2016

Postby KitemanSA » Wed Mar 30, 2016 12:46 am

CharlesKramer wrote:I doubt if anyone has modeled the result (even of a theoretical homogeneous mixture). Guess will know in a few hundred (or thousand years) what Fukushimium looks like.
TEPCO plans to have units 1 thru 4 to green fields in ~ 40 years. They actually plan to START with coreum removal ops in the early 20s.

krenshala
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Re: Question about Fukushima in 2016

Postby krenshala » Thu Mar 31, 2016 1:34 pm

Considering the parks at ground zero in both Nagasaki and Hiroshima, I wouldn't be that surprised if they manage to do so.


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