The theory for recovery of deuterium from water isotope mixture by thermal diffusion in countercurrent-flow inclined Frazier scheme has been developed and investigated. The equations for the optimal angles of inclination and the corresponding best performances were derived. Considerable improvement in performance is obtained when the Frazier scheme is operated at the optimal angle of inclination. Further improvement can be achieved if the operation is conducted in countercurrent flow, instead of being in cocurrent flow.
