- uploaded: Jun 20, 2012
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What Keeps Nuclear Weapons from Proliferating? Bill explains that the hardest step is making the proper type of uranium. Weapons and power plants require uranium that contains a greater amount of the isotope uranium-235 than found in natural uranium, which is mostly uranium-238. He outlines the key difficulty in separating the two isotope: They have nearly identical properties. He explains the two key methods for separation: Gas diffusion and centrifuges.