Chain Reactions Reignited At Fukushima After Tsunami, Says New Study (MIT)

[flamingdem]

http://www.technologyreview.com/blog/arxiv/26738/

Radioactive byproducts indicate that nuclear chain reactions must have been burning at the damaged nuclear reactors long after the disaster unfolded

-- Original paper:
Tetsuo Matsui's original paper (9 pages with calculations), the link is this: http://arxiv.org/PS_cache/arxiv/pdf/1105/1105.0242v1.pdf

Nuclear reactors produce radioactive by-products that decay at different rates. One common by-product is iodine-131 which has a half life of about 8 days while another is cesium-137 with a half life of about 30 years.

When a reactor switches off, the iodine decays more quickly so the ratio between these two isotopes changes rapidly over a period of days. That's why measuring this ratio is a good way to work out when the nuclear reactions terminated.

There are some complicating factors, however. The most important of these is that the ratio of iodine-131 and cesium-137 to start with depends on how long the reactor has been operating and so is not constant.
That's because, after a reactor has been switched on, the levels of iodine-131 reach an equilibrium on a timescale similar to its half life of about 8 days.

But cesium-137, with a half life of 30 years, takes much longer to reach equilibrium. To all intents and purposes, the levels of cesium-137 in a reactor continue to grow steadily during the timescales over which reactors are usually operated. MORE AT LINK

[flamingdem]

1. Translations + more information from Tetsuo Matsui (Arnie G of Japan) via ex-skf blogger

Recriticality at #Fukushima I Nuke Plant: Japanese Researcher Says Nuclear Chain Reaction May Have Reignited Long After Tsunami Disabled the Plant

Tetsuo Matsui is a professor at University of Tokyo's Institute of Physics. On May 2, he submitted his paper titled "Deciphering the measured ratios of Iodine-131 to Cesium-137 at the Fukushima reactors" to arXiv.org, in which he says "The data of the water samples from the unit-4 cooling pool and from the sub-drain near the unit-2 reactor show anomaly which may indicate, if they are correct, that some of these fission products were produced by chain nuclear reactions reignited after the earthquake." (quote taken from his paper)

Chain nuclear reactions reignited = recriticality

That is what some of the non-mainstream researchers like Japan's Hiroaki Koide of Kyoto University and the US's Arnie Gundersen of Fairewind Associates have been saying all along, that there may have been recriticality in some of the reactors at Fukushima I Nuclear Power Plant.

Now the Japanese mainstream Tokyo University professor is saying it. TEPCO's and the Japanese government's acknowledgement can't be that far away. (And no doubt it will be presented as "it's nothing, it's safe.")

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From The Physics arXiv Blog at Technology Review at MIT (5/9/2011):

Chain Reactions Reignited At Fukushima After Tsunami, Says New Study: Radioactive byproducts indicate that nuclear chain reactions must have been burning at the damaged nuclear reactors long after the disaster unfolded

..... Today, Tetsuo Matsui at the University of Tokyo, says the limited data from Fukushima indicates that nuclear chain reactions must have reignited at Fuksuhima up to 12 days after the accident.

Matsui says the evidence comes from measurements of the ratio of cesium-137 and iodine-131 at several points around the facility and in the seawater nearby. He has calculated what the starting ratio must have been by assuming the reactors had been operating for between 7 and 12 months.

He says the ratios from drains at reactors 1 and 3 at Fukushima are consistent with the nuclear reactions having terminated at the time of the earthquake.

However, the data from the drain near reactor 2 and from the cooling pond at reactor 4, where spent fuel rods are stored, indicate that the reactions must have been burning much later.

"The data of the water samples from the unit-4 cooling pool and from the sub-drain near the unit-2 reactor show anomaly which may indicate, if they are correct, that some of these fission products were produced by chain nuclear reactions reignited after the earthquake," he says.

These chain reactions must have occurred a significant time after the accident. "It would be difficult to understand the observed anomaly near the unit-2 reactor without assuming that a significant amount of fission products were produced at least 10 - 15 days after X-day," says Matsui.

So things in reactor 2 must have been extremely dangerous right up to the end of March.

[Mnemosyne]

2. K&R for more visibility. n/t

[intaglio]

3. visibility kick

[flamingdem]

4. thanks for kicking me ..

lol!

[madokie]

5. Kick back to the top

Thanks for the info :hi:

[Melissa G]

6. kick n/t

[ReturnoftheDjedi]

7. according to our local experts, this is impossible.

:sarcasm: