Forefront Of Displacement Chromatography Separation Of Hydrogen Isotopes

High purity tritium is significant nuclear material, and hydrogen isotopes separation is very crucial to the manufacture and application of nuclear weapon. Otherwise, hydrogen isotopes separation is also one of the key technologies for the deuterium-tritium nuclear fuel cycling and exhaust gas handling of future fusion reactor. Large amount of the deuterium-tritium fuel unburned can be reused in reactor through hydrogen isotopes separation procedure. And the environment release of tritium can be controlled by it, too.In this research based on the theory of frontal displacement chromatography (FDC) method, gas of hydrogen isotopes loading with argon has been separated by a chromatography column which was made from a 4.45m long coiled copper pipe with a size ofΦ10×1 and 164.64g palladium loaded on alumina (Pd-Al2O3, with palladium content of 46.2 wt.%) filled in. The hydrogen isotope separation by FDC is realized by the displacement between light hydrogen atoms and heavy hydrogen atoms. And the lighter hydrogen isotope in the feed gas has been used as displacement gas. The output gas from the end of the column has been analyzed by quadrupole mass spectrograph (QMS). Outflow curves were plotted and the deuterium enrichment factor and recovery ratio were calculated.Effects of column temperature, flow rate, hydrogen isotopes content and deuterium/protium ratio of the feed gas on the separation efficiency have also been systematically investigated. The results obtained are as follows:(1) Feed gas of (5±0.1)%H2-(5±0.1)%D2-(90±0.1)%Ar was separated at 30℃,0℃,-10℃,-20℃,-60℃five different temperatures, all at the flow rate of 15mL (NTP)/min. When the column temperature is 30℃, the deuterium enrichment factor and deuterium abundance are 1.52 and 60.37%, respectively. While at-60℃, they are 180 and 99.44%, respectively. At temperatures below 0℃, good separation efficiency can be achieved, and the deuterium abundance of the product gas and recovery ratio are larger than 98% and 40%, respectively.(2)At 10mL (NTP)/min,15mL (NTP)/min,20mL (NTP)/min,30mL (NTP) /min,40mL (NTP)/min five different flow rates, feed gas of (5±0.1)%H2-(5±0.1)%D2-(90±0.1)%Ar was separated, all at the column temperature of-20℃. The deuterium enrichment factor are all between 64 and 85, and the recovery rate of deuterium and the deuterium abundance of product gas are about 60% and 98.7% respectively. But the higher flow rate the fewer separation time. Separation time is 8044min at the flow rate of 10mL(NTP)/min, and while at 40mL(NTP)/min, it is only 2308min. (3) Feed gas with hydrogen isotopes content of 10%,50%,100%(The deuterium/protium ratio are all 1:1.)was separated at the flow rate of 10mL(NTP)/min and the column temperature of-20℃. Deuterium enrichment factors are 85,113,104 in turn. And the recovery rate of deuterium are 57.11%,57.82%.50.37% in turn. The deuterium abundance are all about 99%. But the volume of separated feed gas decreased as the hydrogen isotopes content increases.(4) Feed gas with deuterium/protium ratio of 1:9,1:1,9:1 (The hydrogen isotopes contents are all about 10%.) was separated at the flow rate of 15mL(NTP)/min and the column temperature of-60℃. The deuterium/protium ratio has significant influence on the deuterium enrichment factor. With the increase of the deuterium/protium ratio, the deuterium enrichment factor increases notably. When the deuterium/protium ratio reaches 9:1 or 1:9, the corresponding deuterium enrichment factor will be 11 and 870, respectively. The deuterium abundance are 99.43%,99.44%,99.58% in corresponding turn, and the recovery rate of deuterium are 47.38%,63.08%,66.39% in turn.The experiment results indicate that hydrogen isotopes can be effectively separated by FDC method, and the main factors affecting the separation effect are temperature of the column and deuterium/protium ratio. The deuterium enrichment factor and deuterium abundance of the product gas increases remarkably as the column temperature decreases; the deuterium/protium ratio has significant influence on the deuterium enrichment factor. The deuterium enrichment factor decreases rapidly while the deuterium/protium ratio increases. It showed that FDC is more applicable to separate the feed gas of low deuterium and or tritium content; the flow rate of the feed gas has no obvious effect on the separation effect, and it can obtain higher separation efficiency at properly higher flow rate. FDC method has several advantages such as simple separation process, large enrichment factor, no extra displacement gas, small amount of tritium containing exhaust gas and low energy consuming. Therefore, FDC technology has a potential application for the large-scale hydrogen isotope separation in future fusion reactor.