Tokyo Electric Power Co. announced Wednesday that there is the possibility that criticality, a sustained nuclear chain reaction, had occurred "temporarily" and "locally" in the No. 2 reactor of the stricken Fukushima No. 1 nuclear power plant. It detected radioactive xenon-133 and xenon-135, products of uranium or plutonium fission, in gases collected Tuesday from the reactor.
Because the half life of xenon-133 is 5.25 days…











