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How many nukes in North Korea's arsenal? (Part I)
Lee Wha Rang

North Korea claims that it has no nuclear weapons and that it has no plan to make nuclear weapons but it will fight back with nukes if the United States and its allies attacked. It is now accepted that North Korea has the technical expertise and the parts to make nuclear weapons. What is not clear is if North Korea has any nuclear weapons already assembled and ready to go. Or how many nukes can North Korea hustle up in case of war.

The US CIA says North Korea may have one or two or up to five "crude" nukes. Some intelligence sources of South Korea, Russia and China cite a larger number - as high as 100 nukes or more. How can the intelligence estimates vary so widely? In order to answer this question, one needs to trace the history of North Korea's nuclear program and study the basics of nuclear bomb design principles.

Contrary to the common belief, the only reactor North Korea received from the Soviets was a tiny 0.1 megawatts thermal (MWt) reactor at Yongbyon. This reactor went into operation in early 1960s. Its primary function was isotope production for biomedical research.

A few years before its collapse, the Soviet Union agreed to build two nuclear reactors for power generation, about 1,000 megawatts electric (MWe) each, provided that North Korea joined the Nuclear Non-Proliferation Treaty (NPT). Accordingly, North Korea joined the NPT but it never got the reactors. Unable to find other sources, North Korea designed and built a 5MWe reactor on its own. This reactor, code-named Reactor I, was based on a 1950 MAGNOX technology (graphite moderator, aluminum-magnesium clad natural uranium fuel , CO2 gas cooling). The reactor was completed in 1984 and activated in February 1987 under Prof. Ha Kyong Won, a Korean physicist educated in the United States. This reactor can generate more than 30 MWt of energy.

A 50 MW MAGNOX-type reactor (Reactor II) was started in 1984. N Korea built a military nuclear complex next to this reactor. This complex was completed in 1989 and the reactor was tentatively activated in 1992. A 200 MWe MAGNOX-type reactor was started at Taechon, 60 miles north of Pyongyang in 1988. A 600-800 MWe reactor was also started at Taechon. A third reactor, 635 MWe, based on a German design was under construction at Simpo. The completion of these reactors was on hold in accordance with the 1994 Agreed Framework until the current nuclear crisis began. It is believed that North Korea is working to complete these reactors post haste..

A plutonium separation facility ("Radiological Research Lab") was built at Yongbyon in 1987. This plant is capable of handling several hundreds of tons of fuel a year, enough to handle fuel from all of the reactors. The plutonium factory for the nuclear weapons is a single story building constructed on top of the main plutonium reprocessing facility, deep underground. In 1993, N Korea completed a second plant, doubling its capacity for plutonium production to more than 100 lbs per year.

It is believed that North Korea removed about 30 lb of plutonium from Reactor I in 1988, and 60 lbs more in 1989-1991. If these figures are correct, North Korea would have about 90 lbs of plutonium. According a Russian source, North Korea bought 120 lb of plutonium from a former Soviet block country in 1992. In addition, North Korea may have acquired additional nuclear materials or nuclear weapons from the former Soviet republics. North Korea has conducted several hundred "cold explosion" tests of nuclear bombs. In a "cold" explosion, an actual nuclear bomb, with a limited amount of fissile matter, is detonated.

In addition to the plutonium bomb, North Korea is believed to have perfected an implosion uranium bomb design. This design requires only enriched uranium and no plutonium is used. The Pakistani bomb is of a similar design. North Korea has a large reserve of uranium ores and enriched uranium for nuclear bombs can be produced in large volume using small devices that can be hidden in underground chambers. Bomb grade uranium can be made by separating out U-235 by mass separation or charge separation. In the latter method, laser beams ionized U-235 atoms and high-voltage fields extract U-235 ions. The former method separates U-235 using centrifugal force.

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