By Jung Sung-ki
Staff Reporter
South Korean authorities have failed to confirm the authenticity of North Korea's May 25 nuclear test as no radioactive material has been found over the East Sea, officials said Thursday.
Normally, radioactive materials such as krypton-85 and xenon-135 are released after a nuclear test ― krypton-85 remains in the air for several decades as clear evidence of a test.
In October 2006, a U.S. WC-135 reconnaissance plane detected radioactive materials over the East Sea a couple of days after Pyongyang conducted its first nuclear test.
In that context, some experts question if the North really did conduct a test.
Other military officials and experts say radioactive materials may have spread rapidly and been dispersed after the test due to strong winds.
There is also the hypothesis that North Korea might have revamped its underground test facility to prevent radioactive leaks.
``It is expected to take more time to confirm the nuclear test,'' a military source said, asking not to be named. ``But unless krypton-85 is detected, it will be difficult for the international community to confirm the alleged test.''
South Korea has been checking air samples for radioactive material at a military facility in Dongducheon, north of Seoul.
The latest nuclear test by the North, the second of its kind in two-and-a-half years, has sparked debate on the Stalinist state's nuclear capability. Estimates of the size of the explosion vary from 1 to 2 kilotons, to as high as 10 to 20 kilotons.
The higher estimate would match the power of the bombs America dropped on Hiroshima and Nagasaki in Japan in 1945 to end World War II.