hankyoreh

By Lee Keun-yong, science correspondent

The Nuclear Safety and Security Commission (NSSC) said that as of 3pm on Feb. 14, two days of detection efforts had failed to find any radioactive isotopes following North Korea's Feb. 12 nuclear test. The samples were taken from the area near the DMZ and the East Sea.

The NSSC conducts detection efforts to determine whether a nuclear test has taken place, as various radioactive isotopes that cannot normally be found in nature are produced when an atomic device explodes. The primary isotopes are four varieties of xenon, which have half-lives between nine hours and 12 days.

According to the NSSC, a total of six air samples were taken, five using two fixed land-based detectors and another using a mobile detector on a ship, but no xenon was found in any of them. Two samples were also gathered by a mobile airborne detector, but analysis found no particulate radionuclides such as cesium. Particulate radionuclide analysis looks for isotopes attached to yellow dust and other forms of fine dust.

An NSSC source said the chance of radioactive isotopes leaking into the atmosphere was very slim when a nuclear test is conducted underground, adding that sample collection would also be complicated by the isotopes dissipating into the air.

"We do have an outstanding xenon detector with the 'Sauna-2,' so if we can just get a sample, I think we'll be successful with the detection," the source said.

The NSSC plans to continue its detection efforts through the weekend, conducting additional analysis on second and third samples taken by aircraft that arrived on Feb. 14.

It also announced that it was using another isotope detector at the Korea Atomic Energy Research Institute to check for the presence of krypton, with results to come around the weekend.

In principle, the proportions of xenon and krypton should be able to show whether an atomic device used plutonium or highly enriched uranium. However, experts said that even if both isotopes are detected, the amounts would most likely be too small to identify the material used.

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