Development of a chromatographic separation process for krypton and nitrogen

The final step in purification of the off-gas from nuclear fuel re-processing facilities requires the removal of radioactive Kr from an atmosphere of N2. The objective of this study was to develop an efficient adsorption process for this separation. A pilot separation unit based on the chromatographic principle was designed and constructed using a column 120 cm x 5.5 cm i.d. packed with H-mordenite. This adsorbent was shown to offer the best compromise between cost and performance in preliminary screening studies. Performance tests were run for different flow-rates and injection pulse sizes in order to determine the optimum conditions for the desired separation. The pilot unit was also tested for continuous operation to check whether the steady-state condition could be maintained. The unit was shown to be capable of handling a flow-rate of 2.5 L/min of mixture (2000 ppm Kr in N2) on a continuous basis, with almost complete separation of Kr