Talk-Polywell.org

I might be missunderstanding something, but did somebody here seriously believe that there was a nuclear explosion of some sorts?
LOL

http://www.youtube.com/watch?v=MMB2VR0087w
I'm all ears.

I've been looking at the list of isotopes that TEPCO started releasing from March 24th. And I have a question concerning the BA-140, LA 140 Cerium-140 decay chain.

heres the source info from the water in the turbine room @#3:

http://www.tepco.co.jp/en/press/corp-co ... 503-e.html



Barium 140 half life is 12.8 days, Barium 140 decays to lanthunum 140 (half life of 40.5 hours) which then decays to the stable cerium 140.

http://energyfromthorium.com/tech/physics/decay2/

The ratio of Ba to La seems to suggest fission occurring after March 12th, roughly. But then if you look at the sample from March 26th

http://www.nisa.meti.go.jp/english/file ... 27-1-5.pdf

The ratio of Ba to La still suggests recent fission. Lets guess and say around March 14th.

If we then look at Technetium99m (Tc99m, half life of 6.02 hrs.) we see this present in samples from both the 24th and the 26th.

Does this not suggest fission as recently as 60 hrs from the time the sample was taken? If we assume that 45% of the fuel rods in Reactors #2&3 were uncovered, and 45% then "fell on the floor" of the reactors, are we talking the possibility of low level recriticality in reactors 2 & 3 ?

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I like the p-B11 resonance peak at 50 KV acceleration. In2 years we'll know.

No, who said that?

What was said was that the reactor vessel had most likely popped ... as in over-pressure failure and breached containment. If you examine the video you'll see the amount of concrete debris that gets airbourne (tall, narrow, gray plume) is more than just the few roof panels that reactor1's hydrogen explosion, (white smoke), tossed around. There is also a bright orange/yellow flame deep down in the building that is not consistent with hydrogen explosion explanation.

Ok, that makes more sense.
So when the reactor vessel blows that is simply a pressure explosion. How would that explain the flames?
They still have not sent in any darn robots yet?

With a volume that "hot", would a robot work? Remember, the Space Shuttle main computer has processer equivalent to the old intel 286 generation because anything with smaller features is too subject to derangement by radiation.

Does any robot in Japan have features the size of a 286? Would even THAT size stand up to the radiation described in some of the publicatios (>1 Sv/hr)?

Sometime lower tech is better than higher tech, but if you have none...

After watching this video, I have a hole different level of appreciation for the stability of that nuclear power plant. It seems really hard to compete with forces like that...



Uhm, no. I dont know where you are getting these ideas from.
People constantly bring their laptops, ipods and other computers to the ISS with them.
The Space Shuttle computers were updated several times during the lifetime of the Shuttles. The last update brought a full glass cockpit. You think that you can run that on 286 CPUs? I doubt it.
I heard that until recently many systems were using 486 CPUs, because they are very robust and still onyl require passive cooling, but 286? I am sure not.
Also, there are actually robots that were specifically developed to work in nuclear power plants in case of an accident. If anything, you should be able to shield them sufficiently.

Criticality would imply nuclear explosion- at least on a tiny scale- that is what is happening in a normal active nuclear reactor. . Under the proper conditions this could result in a lot of steam pressure building up and result in an explosion, or at least contribute to an ongoing chemical explosion.Certainly a similar steam explosion could occur from the decaying fuel rods after shutdown. There would not be any direct color from this steam explosion. If some pieces of fuel rod were pulverized, at a temperature of ~ 1200 degrees C they would probably be glowing ~ yellow. But they would not be part of the explosion unless some remarkable brief conditions were met that led to nuclear fission. I suspect this would be extremely difficult at uranium concentrations of less than 5 percent. If they were MOX fuel rods though, I have no idea how the plutonium would respond.
But, my point is that the yellow glow at the base of the explosion has many possible explanations without needing participation by the core or core steel container. Again, the radiation surge would have been huge and persistent if the core was disrupted and dispersed. I would be more suspicious that the spent fuel rod storage tank could have been disrupted than the 6 inch(?) thick stainless steel reactor vessel. If so, there should be spent fuel rods scattered around the floor of the containment building and once again the radiation readings would tell the story.

The differential decay ratios mentioned above are interesting, though I'm not sure how many scenarios could result in the ratios. I do wonder about the shutdown design of the reactor. If the fuel rods are reaching temperatures of ~ 1200 degrees C, then the aluminum alloy(?) control rods would possibly be melting and slumping to the base of the reactor. Would this allow the fixed fuel rods to start active (at least on a low but significant level) neutron driven fission? This seems an obvious design consideration, but surely it was addressed in the design!. Boron injection might mitigate this, but only if the solution covered the rods (or if the fuel rods also melted and pooled in the base of the reactor and mixed with the boron left behind as the solution evaporated.

Dan Tibbets

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To error is human... and I'm very human.

I think "criticality" in a powerplant merely means a sustained nuclear reaction while in an nuclear bomb it means a run-away nuclear reaction. Same basic reaction, different rates, by MANY orders of magnitude! I suspect that if the core COULD go bomb-type critical, they wouldn't have to worry about evacuating the nearest 20 km because the plant would have already evacuated that region for them.

http://en.wikipedia.org/wiki/Criticality_accident

Can it go up like a bomb? Let's see, now. Lots of molten heavy isotopes around, more than critical mass, heavy ones sink, light ones float. Will a critical mass find itself in proximity to some moderator (water?). Best to hope that this combination doesn't happen. Can it go up like a bomb? If fissile material is out of control and melting whichever way it wants to, why might it not go up like a bomb? 'All you have to do' is accumulate a 50kg lump of U235. A core in melt down might do that for you, no?

Oh, I know the answer to this one:

http://www.youtube.com/watch?v=JzqdHkpXuy4

I dont think it can go up like a bomb. Remember, building nuclear bombs is hard. The iranians have been trying for years without success. The North Koreans have not had much either.

Dan,
I am not sure what you mean in the lead sentence. Criticality would imply a neutron induced self sustaining balanced power reaction. Not growing (supercritical) or declining (sub-critical).

Wrong fuel type and wrong geometry. Power plants use slow fuels, hence the need for moderators. Weapons use fast fuel, and have dense geometry. Two different animals.

A weapon is a fast neutron induced supercritical event in a fast fuel. The closest thing to it in a slow fuel plant is called "prompt criticality". Going prompt can induce a pressure transient explosion if there is a mechanical failure of the containment (vessel or components).
When a slow fuel core slags, and loses geometry, it can be setup for a prompt critical event. Reactor vessel designs are inclusive of prompt criticality events. The envisioned (and days of old tested event) was the ejection of control rods. When a core slags, it loses geometry controls, and thus can lose neutron damping and power up. In extreme cases you could go prompt. Loss of geometry is a BAD thing, it has no rules other than no control.