S. Korea struggling to confirm N. Korea's nuclear detonation: officials

By Sam Kim
SEOUL, June 9 (Yonhap) -- South Korea is struggling in its weeks-long effort to
produce scientific evidence confirming that North Korea detonated a nuclear
device on May 25, officials said Tuesday.
North Korea, which conducted its first underground atomic test in 2006, said last
month it set off another underground nuclear explosion, drawing condemnation from
around the world.
The Korea Institute of Nuclear Safety (KINS) has since led the South Korean
efforts to detect radioactivity in air particles blowing from the North, but
failed to find xenon and krypton, two gases that are generated following nuclear
testing or reprocessing.
"Chances of finding them are getting slimmer as time lapses," Kim Si-sun, a
government official who oversees the KINS project, said by phone. "We may even
have to end our search this week."
Sung Ki-tak, a researcher at the National Fisheries Research and Development
Institute (NFRDI), said efforts to find traces of radioactive material in the sea
have also produced little in the way of results.
"We have not found a meaningful amount of radioactivity in the East Sea," he
said. NFRDI began its second round of maritime searches last Friday, but it is
unlikely to be more successful than the first one which took place shortly after
the test.
North Korea is believed to have conducted its nuclear test in Poongkye-ri, North
Hamgyong Province, on the east coast. The blast created a shock that registered
4.52 in magnitude on the Richter scale, according to the Vienna-based
Comprehensive Nuclear-Test-Ban Treaty.
The communist country produced a magnitude 4.1 tremor with its first test, which
was apparently conducted at the same site that is more than 300 kilometers away
from the border with South Korea.
"A variety of factors may be making it hard for us to detect radioactivity," Kim
said, citing the distance, changes in wind direction and an explosion that may
have been smaller than North Korean scientists had hoped for.
"It was conducted underground, which limits the amount of radioactive material
emitted into the air," he said.
The United States, which condemned the test but has yet to make a final
confirmation, has reportedly flown a WC-135 aircraft over the East Sea in its own
effort to detect radioactivity.
The U.S. confirmed the first test less than a week after the North set off the
explosion in October 2006. South Korea has yet to obtain an aircraft capable of
performing a similar mission, Kim said.
As the search for radioactivity continues, some South Korean analysts have raised
speculation that North Korea may have detonated a pack of conventional bombs to
simulate a nuclear explosion.
North Korea, which they say is trying to raise the stakes in its
denuclearization-for-aid negotiations with the outside world, has test-fired a
series of short-range missiles since the test and appears to be assembling an
intercontinental ballistic missile.
A South Korean defense official, who spoke on customary condition of anonymity,
said it seems unlikely that North Korea faked a nuclear test because it has
already demonstrated its ability to conduct one.
"But we may never have scientific evidence that the second explosion indeed
involved a nuclear device," he said. The South Korean military has been operating
its own facility north of Seoul to find traces of radioactive material that could
come from the North.
South Korea acquired its own equipment to detect radioactivity in air particles
shortly after the first North Korean nuclear test. The technology is mobile and
involves a small crew who has operated along the east coast since the second
test.
samkim@yna.co.kr
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