Hydrogen isotopic separation by a cryogenci distillation process is an essential processing step in the tritium removal facility of the heavy water reactor. Analysis of cryogenic distillation as a method for accomplishing this separation was carried out using numerical methods to simulate the required multi-component separation of the six isotopic forms of molecular hydrogen. To prove the versatility of the computer program, parametric investigations to study the effect of design and operating variables on the composition of the product stream were carried out for the case of separating hydrogen isotope.