N. Korean official tells U.S. 'time is not on your side'
The U.S. suspects Yongbyon (pictured here) is being used to reprocess spent nuclear fuel rods.
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 private American delegation that visited North Korea in recent days was shown the nuclear spent fuel storage pond at Yongbyon and found it empty, reinforcing North Korea's claims to have taken the spent fuel and reprocessed it into bomb-grade plutonium.
"The storage pond was empty. There are no spent fuel rods there," said former Ambassador Jack Pritchard, a member of the delegation.
Pritchard said the message to the United States from a North Korean vice minister was that "time is not on your side. As time goes by, we are increasing our arsenal."
At a news briefing at the Brookings Institution, Pritchard said, "Are they bluffing? I don't think so."
The visit by a nuclear scientist, two U.S. Senate aides and a retired diplomat was the first since North Korea restarted the Yongbyon reactor and others and expelled U.N. inspectors from the International Atomic Energy Agency in late 2002.
The private delegation, which was not sponsored by the U.S. government, was shown the reprocessing facility at Yongbyon, which was not operating at the time of the visit. North Korean officials said the 8,000 fuel rods all had been reprocessed between January and June of 2003.
North Korea has said it is building additional nuclear weapons with the material.
Fuel rods are used as the source of nuclear energy in a reactor. As fuel is burned in the reactor, uranium is fissioned as part of a controlled chain reaction.
As a result, the fuel is withdrawn from the reactor and over time becomes "spent fuel." Spent fuel rods are extremely hot and highly radioactive as a result of the new radioactive elements created by the fissioning process.
Those spent fuel rods can be reprocessed to remove the uranium and plutonium. The process involves cooling the fuel rods in storage ponds near the reactor for several months.
The material can then be used to produce nuclear bombs.
The Central Intelligence Agency estimates that North Korea already had one or two nuclear weapons before international monitors were thrown out of the spent fuel storage facility in December 2002.