A method is presented for calculating the basic technological parameters of rectification systems for separating tritium-containing mixtures of hydrogen isotopes with intermediate homomolecular isotopic exchange stages. The method of independent determination of the concentrations was used in simulating the rectification process. The liquid-vapor equilibrium problem was solved with a correction for the nonideality of the mixtures. Heat release due to tritium decay is taken into account in the heat balance equations. The quantum-statistical method was used to calculate the equilibrium constants for simulating the homomolecular isotopic exchange. The CRYDIST computer code implementing this method is used to determine the optimal parameters of the apparatus for separative processing of two isotopic mixtures with different composition and including two low-temperature rectification columns and two homomolecular isotopic exchange units.