By Lee Tae-hoon
A lawmaker of the governing Grand National Party (GNP) claimed Tuesday that North Korea conducted its third nuclear test this year, noting that an unusually high level of a rare gas’s radioactive isotope was detected in an eastern coastal town near the inter-Korean border on May 15.
“Xenon-135 is a radioactive element produced only by nuclear fission. And what is also certain is that the gas came from North, considering the direction of the wind and air currents at the time,” Rep. Kim Seon-dong said.
Kim said the Korea Institute of Nuclear Safety (KINS) detected 2.45 mBq/m3 of xenon-133 and 10.01 mBq/m3 of xenon-135, the highest level recorded since the state-run nuclear regulatory body began operating Swedish Unattended Noble Gas Analyzers (SAUNA).
“The concentration ratio of the noble gas at its monitoring station in Geojin, Gangwon Province had remained below 0.55 since 2007, but suddenly jumped to 4.085 at 2:07 a.m. on May 15,” he said.
The Korea Institute of Nuclear Safety (KINS) confirmed that it detected a high concentration of xenon-135, but declined to comment further on the possibility of a nuclear test.
“Our job is analyzing data, not drawing a conclusion to such a complicated matter,” an official of the KINS said, complaining that lawmaker Kim compromised classified information to back his claim.
Many believed only the U.S. forces have the ability and means to detect the radioactive fission products on the Korean Peninsula.
The official, asking for anonymity, said that the military ruled out the possibility of a nuclear test in the North in late May as no major seismic activity was spotted at the time.
However, Lee Chun-ho, an aide to Rep. Kim, told The Korea Times that the government is believed to have detected an earthquake with magnitude 3 or lower three times on May 12.
On May 12, the North’s state-run newspaper the Rodong Sinmun reported that Pyongyang successfully carried out a nuclear fusion reaction to help develop clean energy.
Lee suspects that the Korean and U.S. intelligence agencies may have intentionally covered up the truth as they do not want to acknowledge the North’s technological breakthrough.
Kim Tae-woo, a senior researcher at the Korea Institute for Defense Analyses, also told the paper that such a high level of xenon-135 and 133 could have only been produced as a result of a nuclear test.
However, professor Hwang Il-soon, a nuclear materials scientist at Seoul National University, raised the possibility that the North could have intentionally leaked the noble gas that it stored from past nuclear tests or reprocessing.
“Given that only xenon was detected and no major seismic activity was spotted, the North may have released xenon it had kept to make others believe it had conducted a nuclear test,” Hwang said.