After revealing that North Korea is operating a large facility to enrich uranium, experts now estimate it can produce one or two nuclear bombs a year.
The bomb dropped on Hiroshima was produced using 64.1 kg of highly enriched uranium, which had the explosive power of 15,000 tons of TNT. Fissile material capable of delivering that explosive power is considered one nuclear bomb. In 1945, technology allowed up to 70 percent uranium enrichment, but now 90 percent or higher is possible, meaning just 20 to 25 kg is enough to make a bomb.
But nuclear experts say that it is difficult to reach any solid conclusions about North Korea's uranium enrichment capabilities. Manufacturing capabilities vary according to the centrifuges. In the case of the old P-1 centrifuge, 2,000 can yield around 20 kg of highly enriched uranium annually. The upgraded P-2 centrifuges can apparently yield around 40 kg of HEU a year.
Siegfried Hecker, the co-director of the Center for International Security and Cooperation at Stanford University who estimated that North Korea could produce 40 kg of HEU annually, believes the North's centrifuges are closer to the P-2 models. There is also the possibility that North Korea has more centrifuges than the 2,000 it showed to Hecker. Another facility of the same scale would double North Korea's capability.
A nuclear scientist at Seoul National University said, "Considering North Korea's power supply situation, it would be difficult to operate the centrifuges all year long, so 20 kg of HEU, let alone 40 kg, is impossible."