North Korea shuts down its main nuclear reactor

North Korea shut down a main nuclear reactor on Monday at Yongbyon. Officials worldwide suspect the reactor was shut down to allow for extraction of spent fuel rods. Once spent fuel rods that are rich in plutonium are extracted from a shut-down reactor, they can be processed to yield the high-purity plutonium necessary for manufacturing an atomic weapon.

U.S. officials initially pointed out the reactor could have been shut down for non-threatening reasons. It may have experienced mechanical difficulties, or North Korea may simply have bluffed, having no spent fuel rods to remove.

On Tuesday, North Korea confirmed the reactor was shut down to remove fuel rods for weapons processing. USA Today quoted North Korea's ambassador to the UN, Han Sang-ryol, saying the measure was taken to "increase its deterrent against a possible U.S. attack."

"The ball is in the U.S. court," Han said. "We asked the United States to change its hostile policy. Then we can believe the United States and enter the disarmament process. If the U.S. policy is normal and friendly, [North Korea] will feel safe."

North Korea has blamed harsh words from the United States for its reluctance to conduct talks regarding its nuclear program. Most recently, US Secretary of State Condoleezza Rice called North Korea an "outpost of tyranny," enraging Kim Jong-il, the leader of North Korea.

The CIA estimates that North Korea has between two and six nuclear weapons in its arsenal, and told USA Today that additional plutonium gained from the reactor is enough for six more.