Quantify the Extent of Physisorption on Silver Based Sorbents under VOG Conditions

US regulations govern release limits for volatile radionuclides contained in the gaseous effluents of used nuclear fuel reprocessing facilities. Of the four volatile radionuclides that are most restricted by the release limits (3H, 14C, 85Kr, and 129I), 129I will require the greatest degree of abatement. Within a reprocessing facility, the vessel off-gas stream will likely contain 1%–5% of the total iodine at parts per billion (ppb) concentrations. Studies conducted by the authors have now investigated both I2 and methyl iodide (CH3I) adsorption by two silver-bearing sorbents, hydrogen-reduced silver-exchanged mordenite (Ag0Z) and silver functionalized aerogel (AgAerogel) at a range of concentrations up to 1,000 ppb. Throughout this suite of tests, and particularly in the case of CH3I adsorption tests, there was a significant discrepancy in the amount of iodine recovered on sorbent beds compared to the amount of iodine that was believed to be delivered to the test system.