Application of sidestream recycle to the separation of hydrogen isotopes by cryogenic distillation

Withdrawal of a sidestream from an isotopic separation distillation column followed by equilibration of species and reinjection is a technique for reducing the required number of columns and hence reducing tritium inventories in fusion-energy fuel processing systems. Measurements have been made with a single column and the three-component H₂-HD-D₂ system withdrawing streams of essentially pure H₂ and D₂. This was followed by single column measurements with the full HDT system and a column inventory of ca 16.8 moles (H/D/T=0.043/0.528/0.429). Rather pure T₂ (ca. 98.7 mol%) was produced as one of the products. This would previously have required two separate distillation columns with an inventory of ca. 16 moles of T₂ as compared with 7.2 moles of T₂ in these experiments. The dynamic response of the H-D system was followed using in situ laser Raman spectroscopy to obtain product compositions and column composition profiles