A Two-Column Method for the Separation of Kr and Xe from Process Off-Gases

Radioactive isotopes of xenon (Xe) and krypton (Kr) exist in the off-gases from the reprocessing of nuclear fuels. To meet regulations, at least the Kr needs to be removed from these off-gas streams. Two metal organic framework (MOF) materials were investigated to determine the removal efficiency and capacity of MOF materials for krypton recovery from air at noncryogenic temperatures. Our two-column breakthrough measurements on nickel dioxobenzenedicarboxylic acid and a partially fluorinated MOF with copper indicate that these materials can capture and separate parts per million levels of Xe and Kr from air. In a two-column system, the removal efficiency and adsorption capacity for Kr on these two MOFs were further increased upon removal of Xe on the first bed. These results show that there is a promising future for the use of MOFs for the removal of noble gas radionuclides from process off-gases during reactor operation or reprocessing of irradiated nuclear fuels.