TEPCO disclosed the latest result of the analysis of the gas coming from the Containment Vessel of Reactor 2 at Fukushima I Nuclear Power Plant, along with the result of the analysis done on October 28, 2011 when the gas management system started operating in Reactor 2.
There was no xenon or krypton detected on October 28. Then they were there in the analysis on November 1.
From TEPCO's handout for the press (11/2/2011), from November 1 to November 2,
Krypton-85 (half life 10.8 years) went from 3.6 x 10^-3 to 5.3 x 10^-1, 100-fold increase
Xenon-131m (half life 12 days) went from to 5.3 x 10^-4 to 6.1 x 10^-4
Xenon-133 (half life 5 days) went from 6.5 x 10^-6 to below detection limit
Xenon-135 (half life 9 hours) went from 1.3 x 10^-5 to 1.7 x 10^-5.
The unit is Bq/cubic centimeter. According to wiki, "About three atoms of krypton-85 are produced for every 1000 fissions (i.e. it has a fission yield of 0.3%)". It sure looks like a nuclear chain reaction happening, i.e. re-criticality, the possibility of which TEPCO's Matsumoto has already admitted.
Result of November 1, 2011:
Result of November 2, 2011:
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23 comments:
In natually occuring nuclear reactors, when the fission increases it is due to the uranium being cooled to make it more reactive, so this is likely the corium entering the water table and cooling to the point of re-criticality. The cooler the mass the more reactive it becomes until it peaks and then the mass is hot enough to impede such reaction, and the cycle repeats.
oh btw- in naturally occuring nuclear reactors, the reactions like this can last for a million years, literally.
could you define what a naturally occurring nuclear reactor is or provide a link on where we can read up on it?
Wiki is your friend (sort of):
http://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor
I can't remember the source - I read that about 6 month ago and forgot to bookmark it -
Re-Criticality is quite common, and under normal circumstances, it will not lead to an enduring chain-reaction automatically; because if you want to have an ongoing chain-reaction, you have to be in a kind of data frame that allows reaction but prevents over-reaction. Having too much fast or slow neutrons will result in stopping the chain-reaction that can only occur within a defined frame.
But this is about a reactor, where every single fuel rod has a well defined position, based on age, use and composition of the fuel rod.
Since we have a mess in- and outside the reactor core, those calculations can't be done anymore.
So you have to guess what's happening because you don't know about the real situation inside - and you'll not know for a long time...
"oh btw- in naturally occuring nuclear reactors, the reactions like this can last for a million years, literally."
Seems safe to say a corium can re-shape itself, as energetic as the material is.
Anon@12:14, I think you are a bit off the mark. The temperature of the uranium is more or less irrelevant. Its the presence of water that acts as a neutron moderator that creates (one of) the conditions for a sustained chain reaction. There is plenty of water in the reactor buildings, so the corium doesn't need to drop into the water table to find a moderator. If the corium did melt through the concrete floors into the dirt and then into the water table, there would be other telltale signs that would tip us off (massive steam explosion might be one, but certainly burning concrete and much smoke would be obvious signs). I've also read that the water table isn't an underground lake of water that corium plops into, rather it is a gradual saturation of the soil, and therefore the image of corium dropping into a pool of water isn't realistic.
Can somebody explain the change in Cs-137 from October to November?
There was a huge steam explosion reported by the onsite workers where the cracks in the ground were spewing super-radioactive steam, and the video from reactor 2 looking like it blew up again with the huge steam/smoke release a few days ago before the detected recriticality if you've been following any of this, and we aren't talking about a controlled sustained reaction, it's a big lump of corium, that was cooled by the water table afterwhich it re-reacted just like natural nuclear reactors, a lump of uranium-containing material, cools whereas the neutrons being emitted internally are close enough to cause a fission chain reaction which continues until it is too hot due to expansion and then the criticality stops until the cycle repeats for as long as the corium material contains enough uranium for this to occur. In this case, it's an active core's worth of material which is likely much more than any known naturally occuring nuclear reactor which as the wiki-link points out can run for hundreds of thousands of years in a simple cool and react scenerio. To stop this reaction they will have to fish the corium out of the water table by tunneling under it and removing it with robot sleds.
The corium obviously can melt it's own cavity tube which would fill up with water from various fissure points overhead as it sunk, so it's formed a deep well of water, and from the reports of the hundreds of tons of water GUSHING into the bottoms of the stricken reactor facilities I'd say this exactly what's occuring.
@anon at 5;44PM, I wouldn't put too much trust in that report about cracks in the ground spewing radioactive steam. I happen to know the original source of that "information", Kouta Kinoshita, independent journalist cum activist measuring radiation in soil all over Japan.
He wrote on his post that he heard it from a government official who had heard about it from somewhere and was worried. Kinoshita simply said he was relating this official's word to his readers. The on-site workers who tweet did not reported such a phenomenon. But someone took Kinoshita's post out of context and wrote up an English post without citing the original source and as if it were a fact, which was carried by a US site, and someone in Japan read it at this US site, and so on - a positive feedback loop.
For those of you unable to click the unclickable link above this wiki definition of the reaction that took place at the detected natural nuclear reactor.
"The natural nuclear reactor formed when a uranium-rich mineral deposit became inundated with groundwater that acted as a neutron moderator, and a nuclear chain reaction took place. The heat generated from the nuclear fission caused the groundwater to boil away, which slowed or stopped the reaction. After cooling of the mineral deposit, the water returned and the reaction started again. These fission reactions were sustained for hundreds of thousands of years, until a chain reaction could no longer be supported.
Fission of uranium normally produces five known isotopes of the fission-product gas xenon; all five have been found trapped in the remnants of the natural reactor, in varying concentrations. The concentrations of xenon isotopes, found trapped in mineral formations 2 billion years later, make it possible to calculate the specific time intervals of reactor operation: approximately 30 minutes of criticality followed by 2 hours and 30 minutes of cooling down to complete a 3-hour cycle.[4]
It is estimated that nuclear reactions in the uranium in centimeter- to meter-sized veins consumed about five tons of 235U and elevated temperatures to a few hundred degrees Celsius.[3][5] Most of the non-volatile fission products and actinides have only moved centimeters in the veins during the last 2 billion years.[3] This offers a case study of how radioactive isotopes migrate through the Earth's crust.[6]"
This shows us that the current Fukushima reaction models that of known naturally occuring nuclear reactors,it points out that in nature these amounts of Uranium do not occur in combination with a close water table and an amount of fissable material which will sustain itself for much longer than the "year-cold shutdown" predicted by the TEPCO experts, with the data available on the amount of U235 we could predict based upon the natural reactor model that this reaction will occur much longer in cycles for at least (http://geology.about.com/od/geophysics/a/aaoklo.htm) 16 million years @ a million years per 5 tons of 4% UR235 minus 20 tons for oxidation and dispersion through surrounding rock matrix. Cold shut down in a year? No way- try 16 million years for each 80 ton corium blob to fully react into a cold-shutdown mode in this manner. Can you spell evacuation?
Yeah whatever- anyone can see the videos of the huge steam releases at reactor #2. Using the natural nuclear reactor model, the reason why seems simple. let's not overcomplicate this, you have 100 tons of nuclear fuel, which melted, formed up into a blob on the bottom of the concave reaction vessel, it melted through the bottom of the reactor onto the floor which it melted through, and was at least 100' into the ground, upon reaching the water table large cycle-like releases of radioactive steam have been detected at the site, scaring the workers. This will not just go away, it will have to be dealt with, that means physical removal of the melted cores form the water table unless Toyko wants to be breathing toxic radioactive steam for the rest of Japan's existance. A million years is a looong time 16 million is even longer, that estimate is based upon emperical data from similar reactors which have already gone full-cycle. Pay attention to history Japan, you already ignored the ancient Tsunami warning stones which told you not to build below certain altitudes, I'd say this disaster is a civic engineering mistake, don't build Nuclear reactors below the Tsunami lines on large earthquake prone fault-lines with previously recorded 9.0 quakes in the past 300 years as Fukushima is.
deception is so peculiar to Japanese.
Deception about Tsunami risks, deception about power plants that are built to resist earthquakes, and now deception about the health effect of fukushima. Next is the deception about the actual safety of Fukushima remains.
None of these are insignificant. What does it take for Japanese to stop deception? Will the Japanese deceive them self until their disappearance? yes, they are willing to kill them self because this deception ability is more important to them than them-self.
We should nuke the reactor.
Give it a rest with the natural reactor nonsense. This situation is nothing like Oklo, and if it were critical (self-sustaining critical, like Oklo) we wouldn't be seeing bits of Xenon, we'd be seeing a whole shitstorm of radionuclides, not to mention radiation off the charts in the whole area. A bit of paranoia is a great life-saving mechanism, but the above is not even quack science. Cooling uranium has nothing to do with criticality or fissioning. The role of water is a neutron moderator (i.e. it slows neutrons down to the point where they interact with other atoms). Imagining a blob of fuel plopping into a pool of water, then cooling so that it can "go critical" is not a great use of grey matter.
I'm thinking energetic fast neutrons fissioning U-238 or plutonium-239.
TEPCO's gas measurements are unreliable like everything else from TEPCO.
Likely cores are fissioning within other reactors/spent fuel pools. No 'moderator' in core melt other than leftover control rod material. Water is not likely to be inside core materials which is probably a blob of molten material as in Chernobyl. Xenon-135 is neutron poison which might be only thing that is keeping recriticality from running away. All the cores, etc. are open to the air, BTW. When TEPCO talks about 'pressure' it is lying. There is no pressure.
TEPCO could find the cores by way of a simply plumbing tool that takes video images of insides of pipe. There is a light and a camera at the end of a flexible probe that can be pushed into a pipe.
Not our TEPCO which would rather have ministers drink water on TV.
TEPCO needs to pump solids into the reactors as a barrier against radiation and to cut back the amount of water leaking into ground and being vaporized. Sand, boron, bentonite, iron, etc.
Denial and poking fun at/of the facts won't change them, wake up and get out of the radiation-lands. People are a natural resource too, they support higher offices through their labors, when they are gone, there is no higher office needed in that area anymore. Save the people.
New attraction coming soon to Fukushima: Super Radioactive geysers. Maybe it'll be a tourist thing? Oh that's what the tents are for, sweathouses! Gotta love that innovation! I wonder what happens to all that steam? Does it just go up into the atmosphere through giant smoke stacks? those existing ones look like hypervelocity thrust vectoring nozzles, wow I'll bet those can throw the radioactive steam to very high altitudes. = more fallout. too bad.
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