North Korea has apparently shut down its main nuclear reactor; a sign some fear could mean the Communist nation is gearing up to reprocess more nuclear weapons material. 

Both South Korea and the United States have confirmed that the main reactor at North Korea's Yongbyon nuclear power plant has been shut down.  Security experts say there are several reasons why that could have taken place. Officials are giving most weight to the fear that North Korea has completed the task of producing spent fuel rods laced with weapons-grade plutonium.  Additional possibilities for the shut down are less threatening - that the reactor ran into mechanical trouble or that North Korea is bluffing in an attempt to raise anxieties about its nuclear weapons program. 

In Washington on Monday, U.S. State Department spokesman Richard Boucher said whatever is happening in North Korea, it is important for the nation to return to the six-party talks, begun in late 2002 to seek a peaceful solution to the nuclear crisis.  Those talks, between North and South Korea, Russia, Japan and the United States stalled last June. 

"Obviously we have looked at the various courses of action available diplomatically but the most important thing is how are we going to solve this problem.  And the way to solve this problem is to go back to talks.  The way to solve the problem for the North Koreans is to go back to talks.  Running reactors or not running reactors, reprocessing, or not reprocessing is not going to get North Korea a solution to its troubles, it's not going to get them as the Secretary has said, the respect that they desire or the assistance that they need.  And so whatever is going on in North Korea, and I can't get in to the details, but I do say we follow developments at Yongbyon very closely," says Richard Boucher.

The Yongbyon complex houses a 5-megawatt reactor that generates spent fuel rods, which contain plutonium.  However the rods must be removed and reprocessed in order to extract the plutonium.  To do that, the reactor, which has been operating since November 2002, must be shut down. 

A U.S. scholar who recently visited North Korea said earlier this month that officials there are not prepared to return to the stalled talks until the United States apologizes for referring to North Korea as an "outpost of tyranny." U.S. Secretary of State Condoleezza Rice made the comment during her Congressional confirmation hearing in January of this year.  Selig Harrison, of the Washington based Center for International Policy said the apology or another gesture of respect could restart the talks.

"There has been a major policy shift in Pyongyang in recent weeks. The hard-line elements there are riding high. The army has increasingly asserted its control over nuclear policy. We have lost the opportunity that we have had for the past years to negotiate the type of step-by-step denuclearization agreement favored by China and South Korea but opposed by the Bush administration," says Selig Harrison.

U.S. officials say they are optimistic a peaceful, diplomatic solution can still be reached without accepting the preconditions demanded by the North Koreans.