N. Korea likely to test nukes again: scientist

VIENNA (AP) -- A U.S. scientist who visited a secret North Korean nuclear site last year says Pyongyang may seek to launch a third atomic test to enable it to develop a small fissile warhead that can be carried by a missile.

Siegfried Hecker -- who first revealed news of a previously clandestine North Korean uranium enrichment plant -- also expanded on details of that facility on Friday. He said it was more advanced than Iran's enrichment operation, and could be re-engineered to turn out enough fissile material to make two nuclear weapons a year.

The North tested nuclear devices in 2006 and 2009 based on plutonium -- like enriched uranium, a potential source of fissile warhead material.

North Korea dismantled or mothballed much of its plutonium producing capacity several years ago as part of now shattered commitments to denuclearize in exchange for economic and political concessions from the U.S. and other global or regional powers.

Before that, however, the North amassed enough plutonium for up to seven bombs.

At a lecture Friday, Hecker said Pyongyang remains committed to having a nuclear deterrent and may want to launch a test at least one more time to progress from developing a small and sophisticated missile warhead from the basic weapon it now has.

``The second test was a necessity because the first one didn't work well,'' Hecker said. While the North now has the knowledge to make ``a rudimentary plutonium bomb ... they would need one more nuclear test'' to develop a modern missile warhead, he said.

Hecker said that the North has appeared to shut down its plutonium production for good after dismantling its Yongybon reactor and mothballing other facilities four years ago, but expressed concern about the enrichment program that he revealed last year.

In a confidential report obtained last week by The Associated Press, the International Atomic Energy agency said the enrichment plant contained about 2,000 centrifuges and the North Koreans had told Hecker's group that the machines were setup to produce low-enriched uranium, used for reactor fuel. North Korea has a small research reactor fueled by low-enriched uranium.

But Hecker on Friday said that -- if reconfigured -- the facility could churn out up to 40 kilograms of 90 percent highly-enriched and weapons grade uranium each year. That would be enough material for two nuclear bombs.

He did not discount speculation that North Korea had helped Iran develop Tehran's larger uranium enrichment program -- an activity that has led to four sets of U.N. Security Council sanctions over fears Tehran could use the program to make fissile weapons-grade material.

But Hecker noted that Pyongyang's program was more advanced than Iran's, with the North Koreans using more efficient centrifuges than the Islamic Republic, which appears not to have progressed in its advanced centrifuge manufacture beyond the testing stage.