PHYS 199M Lecture Notes - Lecture 16: Edwin Mcmillan, Fissile Material, Isotope Separation
18 Nov 2016
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Toward criticality: bohr"s identification of 235u as the actor in slow neutron fission was shown to be correct experimentally. The neutron absorption cross section in graphite was fairly modest, suggesting that a reactor based on graphite moderator could work. Annoyed with szilard for pressuring him not to, he was talked out of it by pegram. This turned out to be a critical decision. In germany, bothe had done a similar experiment but measured a much larger cross section (probably due to impurities) The germans concluded that heavy water was the only way forward. Eka-osmium : princeton physicist louis turner had an interesting theoretical insight: if 238u did capture a neutron, it would form a new isotope 239u. Energetic considerations suggested that this would be unstable against beta decay and form a new element. Similar energetic consideration suggested that 239np would also beta decay into something called eka-osmium .
