OPTIMUM FEED POINT FOR ISOTOPE SEPARATING THERMAL-DIFFUSION COLUMN

A relation satisfied by an optimum feed point (axial height l(opt): a dimensionless height from the bottom), which maximize separation factor (and, then, separative power), was derived based on an approximate column constants in terms of operating condition such as temperature difference between hot and cold walls Delta T, feed flow rate F, pressure P, and cut theta as well as geometrical condition of thermal diffusion column for isotope separation. The value of l(opt) is obtained through Newton iterative solution of this relation. As for an ordinary cold-wall (T-c=288 K) thermal diffusion column separating H-2-HT (Tracer level: 7.3x10(-10)) mixture, the authors got l(opt)=similar to 0.2 for operating conditions that Delta T=1,000 K, F=5 x 10(-5) m(3) (i.e. 50 cm(3))/min (at 0.1 MPa, 288 K), and theta=0.5. The optimum point obtained through a rigorous two-dimensional analysis by changing parametrically the feed point was l(opt)=similar to 0.17, and the optimum point can, therefore, be predicted well even by the present simple model. Moreover, the optimum feed position exists closely near the point where the radially averaged HT-concentration coincides with the feed mole fraction.