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Under Kim Jong Il, North Korea declared itself a nuclear weapons state in 2006, when it first tested a nuclear bomb underground. A second test came in 2009. Still, it's believed North Korea's stockpile of nuclear bombs is small. And in something of a surprise, Pyongyang has voluntarily refrained from making plutonium and more bombs for the past four years.
NPR's Mike Shuster has that story.
MIKE SHUSTER, BYLINE: Reliable details about North Korea's nuclear weapons are hard to come by, but here's what is believed to be the case. The North Koreans currently hold between four and 10 nuclear bombs. All of them are made from plutonium, which the North has manufactured since the early 1990s. There's currently no plutonium left in their stockpile. It's all been turned into bombs.
North Korea does have more than 100 tons of fresh nuclear fuel rods that could be inserted into an active nuclear reactor. That could produce more plutonium. But, says Joel Wit, an expert on North Korea at the Johns Hopkins School of Advanced International Studies, North Korea hasn't done that.
JOEL WIT: Essentially, over the past few years, they haven't produced any.
SHUSTER: Why they haven't produced more plutonium is something of a puzzle.
WIT: They haven't restarted this reactor that was shut down under President Bush, although they threatened to do it many times. So if they did restart it, they could load it up with these fuel rods.
SHUSTER: North Korea has agreed to shut down its plutonium production a couple of times over the past 20 years. Each time, negotiations with the U.S. and North Korea's neighbors broke down, and Pyongyang took steps to restart its nuclear program - except this last time.
Dan Sneider, a Korea expert at Stanford University's Asia-Pacific Research Center, believes there could be several reasons.
DAN SNEIDER: First of all, the reactor is old and has problems. Secondly, it may well be that they have decided to move on to uranium enrichment over plutonium as bomb material, and that they have decided to - basically, to sell the plutonium reactor for whatever they could get from it, in a international-negotiating sense.
SHUSTER: Last year, North Korea disclosed that it had developed secretly a gas centrifuge facility to enrich uranium. It is not certain whether the facility has enriched any uranium - either highly enriched uranium for bombs or, as the North Koreans assert, low enriched uranium for reactor fuel.
And then, says Dan Sneider, there is the issue of their work on making a nuclear warhead that could be fitted into the nose cone of a missile.
SNEIDER: This is, I think, the matter of greatest concern for people who are watching the North Korean nuclear program; that is that - their progress towards miniaturizing a warhead sufficient to be able to marry it to the ballistic missiles that they are also developing.
SHUSTER: For much of this year, North Korea has not hidden its desire to see international negotiations restart over its nuclear activities. There have been several sets of lower-level talks between U.S. and North Korean diplomats.
The Obama administration has proceeded with extreme caution. If Pyongyang now shows as much eagerness for talks as Kim Jong Il did before he died, it could be an early, important sign of the new leadership's approach to nuclear bargaining, says Joel Wit.
WIT: It'll be an early indicator of stability in North Korean policy and also, stability in decision-making.
SHUSTER: At the same time, there's talk that North Korea is planning a long-range missile test, and possibly another underground nuclear test, in 2012. That, too, would be an early indicator of where North Korea's nuclear weapons program is headed.
Mike Shuster, NPR News.
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