Condensation of uranium hexafluoride in supersonic Laval nozzle flow

Condensation, by homogeneous nucleation, of UF6 carried in a mixture of argon and methane was studied experimentally in a continuously operating supersonic Laval nozzle. The onset of condensation was detected by Rayleigh light scattering. Measurements of static pressure in the nozzle, together with the equations of isentropic flow, permitted the determination of the relation between the pressure of UF6, P-k, and the temperature, T-c, at the observed onset of condensation. The experiments addressed conditions of condensation onset in the range 80 < T-c < 160 K and 0.1 P-k < 3.0 Torr. We found that there was no influence of the pressure of the carrier gas argon, which ranged from 3.5 to 68 Torr at onset points, on the onset of condensation. The dependence of the supersaturation ratio on temperature at the onset could be expressed by a straight line as deduced by P.P. Wegener and B.J.C. Wu from the classical theory of homogeneous nucleation [Adv. Colloid Interface Sci. 7, 325 (1977)]. These results indicate that supersonic expansion in the nozzle formed single-component droplets of UF6 in a mixture of UF6, CH4, and Ar under the experimental conditions studied herein.