Japan detected a trace amount of
xenon-133 during a monitoring flight over Japan the day after North
Korea carried out its third nuclear test on Feb. 12, the science
ministry said Thursday.
The radioactive material amounting to 1.9 millibecquerels per cubic meter of air was detected from samples collected at an altitude of 300 meters off the coast of Aichi Prefecture, central Japan.
This was the first time that Japan has detected xenon-133 since it boosted its radiation monitoring activities in response to North Korea's nuclear test.
Japanese Self-Defense Forces aircraft carried out the operation based on forecasts on the diffusion of radioactive materials from the site of the nuclear test. The forecasts were made by the W- SPEEDI II emergency dose predicting system.
Xenon-133, whose half-life is five days, is released into the environment not only by an atomic explosion but from nuclear power plants under operation and medical institutions.
Japan detected up to 6.7 millibecquerels per cubic meter of air even before the March 2011 meltdowns at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear power plant, ministry officials said.
The ministry does not know whether the newly detected radioactive xenon has anything to do with the North Korean nuclear test, the officials added.
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