Liquid Thermal Diffusion

Liquid Thermal Diffusion during the Manhattan Project

“…58 On September 8, the Lewis committee conveyed to Conant the same concerns regarding cost, steam requirements, and long equilibrium times as they had in January, but they did favor the S-1 Committee and the Manhattan District supporting their work on improving the efficiency of the LTD process. 59 Apparently such support was never forthcoming.…”

“…Each column was connected to a reservoir that held from 3 to 170 kg of UF 6 whose vapor pressure when heated drove UF 6 into the column. 64 Because UF 6 is poisonous and was under high pressure in the reservoirs, all tasks related to its handling were performed in a separate building designed to minimize risks; this ''transfer room'' served as a facility for transferring UF 6 from shipping cylinders to the reservoirs, controlling pressures, and metering material. 65 The resurrection of Manhattan District interest in liquid thermal diffusion had an almost comedic flavor.…”

“…Competition between the thermal diffusion of the fluid and the ''ordinary'' diffusion of its isotopes through each other will lead, exponentially, to equilibrium between the two after some hours or days. 16 The theory of thermal diffusion was first developed by the Swedish mathematical physicist David Enskog (1884Enskog ( -1947 in 1911 and the English mathematical physicist Sydney Chapman (1888Chapman ( -1970 in 1916, 17 its experimental proof was established by Chapman and F.W. Dootson in 1917.…”

“…20 Abelson adopted this approach; he heated the inner tube with steam, cooled the outer tube with circulating water, and introduced the fluid into the narrow annular space between them-a process that really was a combination of gaseous and liquid diffusion and hence usually called simply thermal diffusion. 21 Figure 2 shows the inner steam-heated tube and the concentric outer watercooled tube. The time to achieve equilibrium between the thermal and ordinary diffusion of the gas depends upon the difference in temperature between the two Fig.…”

“…A run with UF 6 in a 12-foot column in April 1941 yielded a small separation of the uranium isotopes, but it was roughly equal to the probable error of measurement. 29 The prospects for fission-based power were coming under considerable official scrutiny by the S-1 Committee in the spring of 1941. Bush had requested that the National Academy of Sciences appoint a committee to review possible military aspects of nuclear fission, and the Committee on Atomic Fission, under the chairmanship of Arthur H. Compton, submitted its first report on May 17; others would follow in July and November.…”