NUCLEAR, BIOLOGICAL AND CHEMICAL WEAPONS
February 19, 2009: South Korean intelligence efforts in the north appear to have uncovered information about a secret North Korean underground factory that is producing nuclear weapons using enriched Uranium. North Korean first admitted it had such a program, when the U.S. made the accusation in 2002, but then insisted that it had no such program. Nevertheless, the U.S. insisted that a uranium weapons program violated the 1994 agreement in which North Korea agreed to shut down their plutonium fueled nuclear weapons program in return for billions of dollars worth of aid. In response to that, North Korea resumed its plutonium program, and detonated (more or less) a plutonium bomb in 2006. South Korea and the U.S. both still believe North Korea has kept its uranium bomb program going as well, but were unsure as to where the North Korean were hiding it. Now it is believed the underground plant is in the same area as the above ground plutonium plant in Youngbyon.
North Korea has long been installing military installations in large underground bunkers, often dug into the sides of mountains. North Korea has lots of mountains for this. North Korea has become so good at this, that they sell their expertise to other countries. Iran is a current client. Meanwhile, the U.S. is still interested in negotiating with North Korea about shutting down the uranium program, but currently North Korea denies that such an operation even exists.
If North Korea decides to test a uranium based bomb, it would probably be an underground test, like the 2006 plutonium bomb. But there is no way to prevent some radioactive gases from such a test from escaping into the atmosphere. The U.S. has special aircraft that can fly off the coast of North Korea and pick up samples of these gases, and analyze them to determine if the bomb was fueled by uranium or plutonium.
The earliest nuclear weapons used uranium, but soon switched to the more efficient plutonium. But enriched uranium is easier to produce for nations new to nuclear weapons manufacturing.