Marie Curie doubt, the Curies sought to isolate polonium and radium in pure form. Pitchblende is a complex mineral; the chemical separation of its constituents was an arduous task. The discovery of polonium had been relatively easy; chemically it resembles the element bismuth, and polonium was the only bismuth-like substance in the ore. Radium, however, was more elusive; it is closely related chemically to barium, and pitchblende contains both elements. By 1898 the Curies had obtained traces of radium, but appreciable quantities, uncontaminated with barium, were still beyond reach. The Curies undertook the arduous task of separating out radium salt by differential
Operation Sandstone month. A "Fat Man" core required about of plutonium, of which 21% fissioned. Plutonium production fell off during 1946 due to swelling of the reactors' graphite neutron moderators. This is known as the Wigner effect, after its discoverer, the Manhattan Project scientist Eugene Wigner. These reactors were also required for the production (by irradiation of bismuth-209) of polonium-210, which was used in the initiators, a critical component of the nuclear weapons. Some of bismuth-209 had to be irradiated for 100 days to produce 600 curies of polonium-210, a little over . Because polonium-210 has a half-life of only 138 days,