Elution chromatography for hydrogen isotope separation is numerically analyzed under conditions where a H-2-HD-D-2 mixture is injected into a palladium particle bed followed by an inert gas purge. When an isotopic mixture of a nearly equal atomic molar fraction of protium and deuterium is developed in the bed with an inert gas purge, effluent concentration bands of each hydrogen species exhibit several characteristics different from ones expected from the Gaussian distribution function. The characteristics are a D-2 band with the highest peak, a HD band with a moderate peak, and a H-2 band drawing a broader or plateau-like curve and having a shoulder around its back end. They are well revealed by the present calculation model. The calculation model is applied to elution chromatography of the six-component hydrogen isotopes using a Pd bed to simulate the isotope separation system of an experimental fusion reactor.