Displacement Gas Chromatography will be used at JET to extract pure T2 and D2 from mixtures of H2, HD, HT, D2, DT and T2. This method makes use of strong isotopic effects in the β-phase of the Pd-Qa system. Designed for a daily throughput of ∼20 moles of isotope mixtures, the system will incorporate four individual separation columns, each containing ∼ 5ℓ packing of palladium on a porous alumina substrate. The main parameters, operation seguences and design principles are discussed.