Fukushima recriticality Nov 2011

[auroraglacialis]

Remember that old news about Nuclear meltdowns in Japan? Well its back in Mainstream News. The reason is, that TEPCO has confirmed that there is fission going on in the reactor #2. Elevated concentrations of gases that have a halflife of only days are proof of that. This is in line with the strangely elevated levels of radioactive Iodine measured over the past months. Official statement say that it happens only in some pockets of the completely molten fuel and there is no danger of a more widespread recriticality, but they look for signs of recriticality in the other reactors as well now, while dumping boronic acid on the fissioning reactor in the hope of stopping the reaction. Can we trust this assessment? I think at least the Japanese won't do so, given how the information policies played out regarding this topic so far. Also TEPCO still does not have a visual on the molten core, so they do not know yet how it looks like, where it is and in what shape it is. So the assessments made can only be made from deduction of instrument readings.

Tepco Detects Nuclear Fission at Fukushima Station - Bloomberg

Tokyo Electric Power Co. detected signs of nuclear fission at its crippled Fukushima atomic power plant, raising the risk of increased radiation emissions. No increase in radiation was found at the site and the situation is under control, officials said.

The company, known as Tepco, began spraying boric acid on the No. 2 reactor at 2:48 a.m. Japan time to prevent accidental chain reactions. Tepco said it may have found xenon, which is associated with nuclear fission, while examining gases taken from the reactor, according to an e-mailed statement today.

“Given the signs, it’s certain that fission is occurring,” Junichi Matsumoto, a general manager at Tepco who regularly talks to the media, told reporters in Tokyo today. There’s been no large-scale or sustained criticality and no increase in radiation, he said.

Fission taking place in the reactor can lead to increases in radiation emissions and raises concerns about further leaks after another radioactive hot spot was discovered in Tokyo on Oct. 29. It’s possible there are similar reactions occurring in the No. 1 and No. 3 reactors, the other cores damaged at the station, Matsumoto said.

“Melted fuel in the No. 2 reactor may have undergone a sustained process of nuclear fission or re-criticality,” Tetsuo Ito, the head of Kinki University’s Atomic Energy Research Institute, said by phone.
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[general assessment]
The radioactive cesium that flowed into the sea from the plant was 20 times the amount estimated by Tepco, according to the Institute for Radiological Protection and Nuclear Safety, which is funded by the French government.

The oceanic study estimates 27,000 terabecquerels of radioactive cesium 137 leaked into the sea from the plant. The

Fukushima station may have emitted more than twice the amount of radiation than estimated by the Japanese government at the height of the Fukushima accident, according to another study by the Atmospheric Chemistry and Physics journal.