I am puzzled as to where or who produced the U235 for the first nuclear pile. I read that graphite was used as a neutron moderator but only .7 % of natural uranium is U235.
He must have gotten it from Oak Ridge?. But I always thought that Oak Ride's uranium production came after the feasibility study that a pile was even possible. So where did the original batch come from ? Maybe from mass spectroscope or cyclotron but that wouldn't make enough uranium would it?