North moved nuclear research site

North Korea has been experimenting with uranium refining in a state research lab near Pyeongyang, possibly using lasers to separate the key isotopes needed for developing nuclear weapons. The laser method is a process that can be accommodated in a limited space.

The information, obtained by U.S. intelligence, was relayed to key Seoul officials after the trip by Assistant Secretary of State James Kelly to Pyeongyang earlier this month, intelligence and diplomatic sources in Seoul said Friday. At the talks in Pyeongyang, the North admitted to having continued its nuclear development program after agreeing to suspend it. The sources, insisting on anonymity, said the information was communicated to South Korean officials by visiting U.S. officials, not by Mr. Kelly, sometime around Oct. 10.

Seoul's Foreign Minister Choi Sung-hong said in the National Assembly on Friday that the government had much of the information admitted to by Pyeongyang before Mr. Kelly's trip.

The state laboratory is believed to be in the National Science Institute at Pyeongseong, on the outskirts of Pyeongyang. North Korea experts characterized the institute, established in 1952, as the center of scientific research in the North. The center of North Korea's nuclear program had been at Yeongbyeon, further north in North Pyeongan province, where limited international inspections had been conducted on plutonium reprocessing facilities.

The Korean officials, echoing charges made in Washington on Thursday, said assistance from Pakistan was key to the research activities at Pyeongseong, with which Mr. Kelly confronted North Korean officials in Pyeongyang. Pakistan, the sources said, is believed to have supplied uranium enriching technology and received key ballistic missile technology from the North in return.

The Pakistan embassies in Washington and Seoul rejected the suggestion of any involvement in the North's nuclear program.

"It is incorrect and malicious in nature," the Embassy of Pakistan in Seoul said in a statement.

The research lab's facility is believed to use a combination of laser separation and centrifuges in separating the uranium isotope needed as material in nuclear warheads. Lasers are used to selectively excite an isotope in the uranium ore, much of which is then removed to form the enriched material. The process is reportedly cheaper and more easily hidden than other separation methods.

Both Seoul and Washington believe that the enrichment technology the North Koreans are trying to develop is not yet at the point where weapons could be produced, the sources said. One speculated that that fact may have influenced Washington to say it seeks a peaceful resolution of the matter.

by Oh Young-hwan, Kim Min-seok