Separation of radioactive krypton from carbon dioxide and oxygen with molecular sieves

In the reprocessing of HTGR nuclear fuels, the off-gas cleanup system generates a stream containing about 1 percent krypton, 90+ percent CO2, and various amounts of O2, N2, and xenon. The krypton is radioactive and must be separated from the CO2 before it is bottled or zeolite-encapsulated for final disposal. A series of theoretical and experimental investigations to find the best method for separating CO2 and krypton under the required conditions showed that 5A molecular sieves near O0C and 1.01 x 105 Pa (1 atm) provided the most effective separation. Molecular sieves are powerful solid adsorbents for CO2 but weak adsorbents for krypton. For a typical expected CO2-O2-krytpon gas mixture, a molecular sieve bed adsorbs the CO2, allows the O2 to pass freely through the bed, and concentrates the krypton before it exits the bed. The process selected and investigated is called frontal analysis gas chromatography