Apparatus for separating and recovering Kr-85

An economical Kr-85-separating and recovering apparatus is provided for enriching a gas containing Kr-85 discharged from a nuclear reactor. The apparatus comprises Kr-85-enriching means including a pair of alternately operable Kr-85 adsorbing and desorbing columns using activated carbon, means for liquefying the enriched gas delivered from the column, and distillating means for separating Kr-85 from the discharged gas which returns to the recirculating piping so that there is no leakage of Kr-85 outside the apparatus. In embodiments, an enriching apparatus is designed so that argon gas containing 100 ppm of Kr-85 can be treated at a rate of flow of 1 Nm3/h to obtain 2 Nm3 per year of argon gas containing 5% Kr-85. Kr-85 is adsorbed with activated carbon under a pressure of 1 atm at a temperature of 200C for 400 hours, and is desorbed under a pressure of 10 torr at a temperature of 200C at a rate of flow of 0.5 Nm3 for 400 hours. After twenty cycles of operation (about one year), 120 Nm3 of argon gas containing 0.1% by volume of Kr-85 is introduced into the liquefying and distilling apparatus. The concentration of Kr-85 may preferably be below 0.3%. In this apparatus, the mixed gas of krypton and argon is liquefied with liquid nitrogen, and argon gas is evaporated in the distillation column. The discharged gas from the separation column still contains 100 ppm of Kr-85, and therefore is recirculated. (Iwakiri, K.)