Measurement of Separative Characteristics of Thermal Diffusion Column for Argon Isotope Separation

Abstract

Performances of separation of 36Ar and 40Ar isotopes were measured by changing feed rate, cut and/or hot wire temperature in a 950 mm-height thermal diffusion column with an inner tube of 7.5 mm radius and a hot wire of 0.3 mmφ in the axis. The column was operated at 0.1 MPa, and feed flow rate and cut were regulated in a good reproducibility with three sets of thermal mass flow controllers for feed and upper and lower draw-offs. The temperature of the Mo hot wire was controlled by the density of an electric current based on the relation between the temperature and an electric resistance of the wire. Abundance ratio of 36Ar to 40Ar was measured with the Q-pole mass filter, whose outputs being calibrated by means of a double-focused mass spectrometer. The data obtained were compared with analytical results of a separative analysis based on numerical solution of axisymmetric convection-diffusion equation. The co- efficient of diffusion and the thermal diffusion constant were obtained through the Lennard-Jones 12-6 (L-J) or the generalized Dymond-Alder (D-A) potentials. The measured dependences of separation factor and separative power on feed rate, cut and/or temperature difference between hot wire and cold wall surfaces were predicted fairly well by the D-A potential rather than by the L-J potential, although the measured separative power was a little smaller than analytically predicted one.