Xenon at Fukushima not result of ‘critical’ nuclear reactions: TEPCO
TOKYO (Kyodo) — Tokyo Electric Power Co. said Thursday the detection of radioactive xenon at its stricken Fukushima Daiichi power plant, indicating recent nuclear fission, was not the result of a sustained nuclear chain reaction known as a criticality, as feared, but a case of “spontaneous” fission.
“It is not leading to instability of the reactor or a rise of the radiation level outside,” the utility known as TEPCO said, adding that it does not expect the incident to impact its goal of attaining a stable condition of the plant’s troubled reactors called cold shutdown.
The plant operator said it has judged that spontaneous fission, which it says occurs at a constant rate, has generated xenon-133 and xenon-135 at its crisis-hit No. 2 reactor, as a criticality would have resulted in the recording of concentration levels 10,000 times higher.
The data at hand match estimated levels of xenon produced by sporadic fission of curium-242 and curium-244 inside melted fuel, it said.
It also cited as evidence supporting its view the detection of xenon even after it poured boric-acid solution to absorb neutrons necessary for a fission reaction, and a lack of abnormal rises in the reactor’s temperature or pressure.
Xenon, which was found Tuesday from gas collected from the No. 2 reactor’s primary containment vessel, is believed to have leaked out of the fuel’s cladding tubes due to their meltdown, it said, adding that it plans to continuously monitor gas inside the furnace.
The nuclear crisis at the plant, the world’s worst in 25 years, erupted in the wake of the March 11 earthquake and tsunami, and resulted in the meltdown of nuclear fuel in the six-reactor power complex’s Nos. 1 to 3 reactors.
When it revealed Wednesday that it had detected xenon at the No. 2 reactor, it touched on the possibility that melted fuel inside the reactor may have temporarily gone critical.
(Mainichi Japan) November 3, 2011
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Xenon can’t be caught by filter,what did they measure ?
Though Iodine 131 has been measured at variety of locations in Japan to show Fukushima went back to recriticality state,
it was the first time for Tepco to admit that reactor 2 has gone back to recriticality today.
Cf,a very insightful comment to the blog.
2011/11/01 at 11:27 am
There’s no I-131, it’s all decayed, disappeared, gone. The Lab must be worng
At their press conference of 11/2/2011 AM, Tepco admitted there is the possibility that reactor 1 and 3 may be in recriticality as well.
The Nuclear Agency describes it as “temporary spontaneous fission”, but Tepco clearly admitted that there has been “small” recriticality on and off since months ago, they noticed the fact finally because they checked the filter on 10/28/2011.
This time, Tepco sounds more honest than The Nuclear Agency.
However, their explanation does not make sense as always.
1) There is no filter at reactor 1 and 3. How do they know they may be in recriticality to measure xenon 133 and 135 ?
2) Xenon is noble gas,which can hardly be caught by a filter.What did they think they caught on the filter ? Why did they quit deceiving us all of a sudden ?
3) They explained they are injecting boric acid to the container vessel,but there is no container vessel. Where are they trying to inject it ?
JP PM Noda flew to France this evening.
No wonder, it is time to abandon this country,like Noda.
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Yet another view:
Xenon means recent fission in reactor 2
Tepco claims level in gas too small to affect shutdown effort
Tokyo Electric Power Co. said Wednesday that some of the melted fuel in reactor 2 at the Fukushima No. 1 nuclear plant may have triggered a brief criticality event.
Although the Nuclear and Industrial Safety Agency said there have been no drastic changes in the reactor’s temperature and pressure level, and the reactor itself is stable overall, the discovery may mean the goal of Tepco and the government to achieve cold shutdown of all three crippled reactors by the end of the year may not be possible.
Suggesting that criticality, or a sustained nuclear chain reaction, may have occurred temporarily, or partially, Tepco said one hundred thousandth of a becquerel per cubic centimeter of xenon-133 and xenon-135 was detected in gas samples.
Xenon-133 and xenon-135 are materials created through nuclear fission, and are not usually detected even when a reactor is in operation, as fuel rods are covered with zirconium. This means fission may have occurred in the melted fuel.
As the half-life of these two materials is short — five days for xenon-133 and nine hours for xenon-135, the xenon was probably created recently, but may not have been detected earlier.
Tepco injected boric acid, which can prevent fission, into the reactor Wednesday morning.
Tsuyoshi Misawa, a reactor physics and engineering professor at Kyoto University’s Research Reactor Institute, said that if Tepco’s data are correct, “it’s clear that the detection (of xenon-133 and -135) comes from nuclear fission.”
“This amount of xenon would not be detected unless there was a certain degree of fission chain reaction,” so it is highly possible criticality took place, Misawa said.
Tepco will conduct detailed research on the gas survey to confirm if the data are accurate.
Yoshinori Moriyama, a NISA spokesman, said there is a possibility fission started from some small pieces of melted fuel. But the fission was probably small and partial, he said, adding, “large-scale fission was unlikely.”
He explained that most of the fuel core and control rods, which act to stop fission, may have melted together, so it is hard to imagine that a major criticality accident occurred.
Tepco spokesman Junichi Matsumoto said the test results suggest that either small-scale fission occurred in the melted fuel, or conditions to trigger criticality were temporarily met for some other reason.
He said the same thing could also happen at reactors 1 and 3.
But because the reactor’s temperature and pressure level have not changed, the fission would not have been large-scale, Matsumoto said, adding it would not thwart Tepco’s schedule for achieving a cold shutdown at the reactors.
Goshi Hosono, the minister overseeing the nuclear crisis, also said Wednesday evening that as the reactor status has remained stable, “we can achieve cold shutdown by the end of the year.”
But Misawa said the latest development demonstrates the reactor is still not completely under control, suggesting a cold shutdown remains a long way off.
While continuing to aim for a cold shutdown by year’s end, NISA’s Moriyama said the important thing is to bring the reactors to a safe and stable status rather than meeting the deadline.
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Further views and discussion over at EX-SKF:
Xenon in Reactor 2: TEPCO Now Says “Spontaneous Fission” of Curium
On the other hand, the Nuclear and Industrial Safety Agency, who was skeptical of criticality yesterday, now says, “We cannot rule out the possibility of localized criticality.”
OK it’s a “good cop, bad cop” routine, or a “covering all the bases” approach. If both “spontaneous fission” and “criticality” are mentioned in the same news, the Japanese government/TEPCO can say “See, we told you, either way.”
And this, from ENENEWS:
By ENENEWS STAFF
New fission raises “startling questions” says NYT — Koide: Harmful radioactive material in danger of leaking after a re-criticality
“The three reactors — together with spent fuel rods stored at a fourth damaged reactor — have been leaking radioactive material since the initial disaster, and new episodes of fission would only increase their dangers.”
According to Hiroaki Koide, assistant professor at Kyoto University’s Research Reactor Institute, “Re-criticality would produce more harmful radioactive material, and because the reactors are damaged, there would be a danger of a leak.”
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AND… yet another take on all of this from The New York Times:
Fears of Fission Rise at Stricken Japanese Plant
By HIROKO TABUCHI
Published: November 2, 2011
TOKYO – Nuclear workers at the crippled Fukushima power plant raced to inject boric acid into the plant’s No. 2 reactor early Wednesday after telltale radioactive elements were detected there, and the plant’s owner admitted for the first time that fuel deep inside three stricken plants was probably continuing to experience bursts of fission.
The unexpected bursts — something akin to flare-ups after a major fire — are extremely unlikely to presage a large-scale nuclear reaction with the resulting large-scale production of heat and radiation. But they threaten to increase the amount of dangerous radioactive elements leaking from the complex and complicate cleanup efforts, raising startling questions about how much remains uncertain at the plant, the site of the world’s worst nuclear disaster since Chernobyl.
Read the entire article at:
Cs-134 and 137 from Fukushima are already 95% of Chernobyl
The total contamination from Fukushima has been revised so many times by Tepco and the government, it is almost impossible to know “the lastest” truth.
Probably this is what they intended to do.
However, mixing the analysis of nature.com and IRSN, even if its only Cs, the contamination situation is already as bad as Chernobyl.
Thinking about Fukushima has ZERO hope to settle down, it is likely to be way worse in future.
According to the assumption, the total emission of Cs-137 is 74% of Chernobyl.
The total emission of Cs-134 and -137, it’s already 95% of Chernobyl. (Cs-134 needs to be assumed from the ratio of Cs-137)
This only focuses on Cesium. Taking other radioactive materials into consideration,now may be the point of Fukushima to catch up with Chernobyl.
Radioactive Disaster Debris Arrives in Tokyo from Iwate Prefecture
I’ve told you already that the one and only contractor who can burn according to the Tokyo Metropolitan government specs (which was clearly designed so that there would be nobody else) is a TEPCO’s subsidiary.
NHK reports that the first container from Miyako City in Iwate Prefecture arrived by rail in JR Tokyo container terminal in Shinagawa-ku, Tokyo at 7AM on November 3. It was promptly transported to one of the contractors selected by the Metropolitan government, and the debris was sorted, and crushed into smaller pieces. Flammable debris will go to the TEPCO’s subsidiary (Tokyo Rinkai Recycle Power) located on the landfill and be burned after November 6, and non-flammable debris will be simply buried in the same landfill.
According to NHK, they did measure radiation at the contractor’s site, by putting a bit of the debris in a lead box and measuring the radiation. If you say to yourself “WTF..” you are not alone.
Acticle continues at:
NO, AMANO, IT IS NOT DEMAND THAT HAS RISEN. IT IS THE NECESSITY BY THE IAEA AND THE NUCLEAR POWER INDUSTRY FOR MORE INTENSE MARKETING OF A PRODUCT THAT IS TOO COSTLY, OBSOLETE, AND IMMEASURABLY DANGEROUS TO THE HEALTH AND WELL-BEING OF THE PLANET.
Atomic power demand rises despite Fukushima
NEW YORK — Yukiya Amano, head of the International Atomic Energy Agency, said Tuesday demand for atomic energy around the world is on the rise, although the nuclear crisis in Japan triggered by the March earthquake and tsunami has dented growth.
“Despite the accident, the IAEA’s latest projection is that the number of operating nuclear reactors in the world will continue to increase steadily in the coming decades, although less rapidly than was anticipated before the accident,” the agency’s director general said in his report to the 66th U.N. General Assembly.
Most of the growth will occur in countries such as India and China that already have operating nuclear power plants, he said.
Read more of this tripe at:
The costly fallout of tatemae and Japan’s culture of deceit
Regardless, the awful truth is: “We Japanese don’t lie. We just don’t tell the truth.”
This is not sustainable. Post-Fukushima Japan must realize that public acceptance of lying got us into this radioactive mess in the first place.
For radiation has no media cycle. It lingers and poisons the land and food chain. Statistics may be obfuscated or suppressed as usual. But radiation’s half-life is longer than the typical attention span or sustainable degree of public outrage.
As the public — possibly worldwide — sickens over time, the truth will leak out.