11/02/2011, 00.00
JAPAN
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Fukushima: alarm over possible nuclear fission

Presence of 133 or 135 Xenon gas detected in N.2 reactor damaged by the earthquake and tsunami. The management company has raised the alarm, and began to inject boric acid into nuclear reactors to avert the danger of nuclear fission. It will take 30 years to drain the system completely.
Tokyo (AsiaNews / Agencies) – The alarm of a possible nuclear fission has been raised in Fukushima overnight. The Nippon Agency for Nuclear Safety (NISA) is carrying out tests and controls to determine if xenon isotopes 133 or 135 have really been released in the containment vessel of the N.2 reactor of the nuclear power plant damaged by the earthquake and tsunami of 11 March last. Xenon is a gas usually released during the fission process. The alarm was launched by TEPCO (Tokyo Electricity Power Company), which operates the plant. TEPCO is injecting boric acid into the damaged reactor as a precaution.

The presence of Xenon 133 and 135 alone is not proof that the partially melted fuel roods are in a critical condition, with a self-sustaining chain reaction that could lead to fission. The presence of neutrons are necessary in the fission process, which in this case, could have been generated not by the fission process itself, but by the activities of so-called ' neutron 'emitters’ or secondary reactions in nature.

The Nisa said that the release of xenon is very recent, and in small quantities, all of which tend to reassure against an emergency. The agency also stressed that at present there are no variations in temperature or pressure, but either ways the decision was taken to inject boric acid to prevent a reaction. According to an official report of the Japan Atomic Committee it will take at least 30 years to complete the decommissioning of Fukushima, and arrive at a complete remediation. The beginning of the removal of the radioactive material is expected in 2012. TEPCO said that the cold shutdown program for the reactors continues, and should be completed within the year.
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