Expert not convinced on NK nukes
From CNN National Security Correspondent David Ensor
Dr. Siegfried Hecker speaks with the Senate Foreign Relations Committee on Wednesday on Capitol Hill.
North Korea says it showed its 'nuclear deterrent' to an unofficial U.S. delegation.
North Korea is offering a deal that could halt its nuclear program in return for concessions from Washington.
WASHINGTON (CNN) -- A top American nuclear expert has told a U.S. Senate committee that North Koreans showed him a piece of radioactive metal in a glass jar when he visited that country, but said he could not say if it really was bomb-grade plutonium metal as they claimed.
Sigfried Hecker, former director of the Los Alamos nuclear research laboratory, was part of a private delegation that, at the invitation of North Korea, visited nuclear-related sites in that country, including a reprocessing facility at Yongbyon.
The North Koreans could well have a "rudimentary" bomb, he testified Wednesday, but without greater access, and other experts and instruments, he could not certify -- as the North Koreans apparently wanted him to do -- that they definitely have nuclear weapons.
The U.S. Central Intelligence Agency has estimated for some years now that North Korea probably has one or two nuclear weapons.
Hecker and former Ambassador Jack Pritchard told the Senate Foreign Relations Committee that they were shown the now-empty storage pools where 8,000 spent fuel rods once were stored.
They also were shown reprocessing facilities, which the North Koreans said had been used to reprocess the spent fuel rods into weapon-grade plutonium.
But Hecker said that to be sure of that statement, he would need to return to North Korea, gain access to more materials, and bring along other experts and instruments "that would allow us to make a more definitive assessment."
He said it was urgent that the United States and other countries not delay efforts to resolve the issue.
"Let's not forget just how devastating nuclear weapons are, how important it is to resolve these issues as quickly as we can," he said.
Senator Joseph Biden noted that "there's also a real and growing risk of a war on the Korean peninsula, rising out of miscalculation and miscommunication."
Pritchard said he and Hecker were told that North Korea does not have a program to use highly enriched uranium to produce a nuclear device, although Assistant Secretary of State James Kelly has said he was told by the Koreans in 2002 that they did have such a program.
Kelly said that admission came after he confronted the North Koreans with evidence collected by U.S. intelligence. Now Pyongyang is denying having made such an admission.
Pritchard quoted North Korean Vice Foreign Minister Kim Gye Gwan as telling the visitors that "time is not on the American side. As time passes, our nuclear deterrent continues to grow in quantity and quality."