ИСТИНА

Three major steps exist in creating an atomic weapon based on plutonium: Reactor irradiation of uranium: 238U + n 239U 239Np 239Pu Separation and purification of Pu and conversion to metal Devising the weapon. Of these, the second is the messiest and most resource-consuming. For the USSR, copying from the US (achieved through espionage) occurred in the first and third steps the creation of Pu in nuclear reactors and in devising the weapon but, curiously, was minimal in Pu separation and chemical conversion processes. Why? And how were the US and USSR approaches constrained by historic developments, wartime exigencies, and Pu chemistry?