[en] Results are presented for the fourth major campaign for quantifying krypton removal from simulated High-Temperature Gas-Cooled Reactor reprocessing off-gas by the Krypton Absorption in Liquid CO₂ (KALC) process. This process utilizes the high solubility of krypton in liquid CO₂. Mass transfer experiments for the absorption, fractionation, and stripping operations of the KALC process indicate that the addition of N₂ and CO do not alter the mass transfer characteristics exhibited by O₂ and krypton in the basic CO₂--O₂--Kr system. Decontamination factors for xenon in the absorber and stripper were several orders of magnitude less than those for krypton under similar conditions. Indications are that the fate of xenon is controlled by the heat input to the stripper reboiler. Experiments on the solubility of O₂ and CO indicate that CO is more soluble than O₂ at temperatures below -21⁰C