t a concentration of only 0.7%; Urenco used the Zippe method to separate the fissile isotopes U235 from non-fissile U238 by spinning UF6 gas at up to ~100,000RPM.[16] His pioneering research led to the improvement of the Zippe method, which at that time, was an emerging technology whose publications were classified by the Soviet Union.[16] Khan's leading-edge research in metallurgy brought laurels