U.S. World War II U235 isotope separation: E. O. Lawrence and Philip H. Abelson.
"' To sustain my argument that sufficient separated U235 had been produced by 17 July 1944 to enable a nuclear fission weapon detonation on that date at the Port Chicago Naval Magazine it has been necessary to discover corresponding documentary attestations to authenticate that either 74 kg or 59 kg U235 had been separated during 1943. Study of the many published books of the Manhattan Project historical literature yields no attestation that any quantity of U235 had been separated during 1943. The author's task has been to satisfactorily confute that universally accepted precept of the Manhattan Project historical literature. Information published in this chapter will show that Philip H. Abelson, working at the United States Naval Research Laboratory with the liquid thermal diffusion uranium isotope separation method, did separate the U235 isotope during 1943 in quantity sufficient to permit the detonation of at least one Mark II bomb utilizing 9 kg U235 by 17 July 1944."