U.S. nuclear expert Siegfried Hecker has said that a uranium enrichment facility he was shown in North Korea seemed intended for civilian use, a claim which ties in with plans the North revealed earlier to build an experimental light-water reactor.
But the New York Times quoted U.S. Defense Secretary Robert Gates as saying such a claim cannot be trusted. "South Korea and the U.S. are confident that the North Korean centrifuges are for military purposes," a diplomat said. And a South Korean government official said, "South Korean and U.S. intelligence authorities have concluded that North Korea is not capable of building a light-water reactor. It seems to have shown the construction site to make it look like the centrifuges are designed to enrich uranium for power generation rather than for weapons production."
Enriching natural uranium to 3-5 percent produces fuel for light-water reactors. But enriching it to more than 90 percent yields the ingredients for a nuclear bomb. It is up to North Korea how much it intends to enrich the uranium, and it is difficult to judge the purpose based solely on the centrifuges.
The U.S. believes Iran has used this strategy to cloak its uranium enrichment activities, insisting on its right to peaceful energy production. Despite opposition from the West and the International Atomic Energy Agency, Iran restarted its uranium enrichment facility in Natanz in 2006, stressing it was a "peaceful activity intended for electricity production.