Radioactive isotopes of xenon were not detected in the atmosphere after North Korea’s nuclear test, Seoul’s Korea Institute of Nuclear Safety said Thursday.

Korea Institute of Nuclear Safety said radioactive xenon was not found in the first batch of samples collected using mobile collecting equipment in the East Sea on Wednesday.

Radioactive isotopes of various elements are released into the atmosphere following a nuclear test, and the material -- plutonium or uranium -- used in the explosive device can be determined by analyzing the proportion of xenon in the sample.

The Korea Institute of Nuclear Safety said that it would now analyze later samples for xenon.

However, as radioactive xenon isotopes have short half-lives, the likelihood of collecting the isotopes required to determine the material used in the latest nuclear test would drop with time.

Of the four radioactive xenon isotopes the Korea Institute of Nuclear Safety is looking for, the longest half-life is 12 days.

“Analysis of three batches of samples collected by two fixed-collecting equipments did not contain xenon,” a Korea Institute of Nuclear Safety official said, adding that later batches could contain xenon depending on the direction of the winds.

Radioactive xenon was not detected following North Korea’s second nuclear test in 2009. In 2006, radioactive isotopes of xenon were collected by the U.S.

By Choi He-suk
(cheesuk@heraldcorp.com)