(477e) Iodine Adsorption in Reduced Agz and Ag-Aerogel in Presence of Water and NOX

Reprocessing used nuclear fuel (UNF) generates several volatile radioactive species, including ³H, ¹⁴C, ⁸⁵Kr, and ¹²⁹I, along with significant amount of water vapor and NO_X into the off-gas streams. The presence of water vapor and NOx impacts the performance of the adsorbents for capturing the radioactive gases, especially, the Ag-containing adsorbents for iodine adsorption. In this study, the iodine adsorption performance of reduced Ag mordenite (Ag⁰Z) and Ag functionalized silica aerogel (Ag⁰-aerogel) in the presence of water and NO_X were investigated experimentally and analytically. Through thin-bed adsorption experiments, uptake curves of I₂ on Ag⁰Z and Ag⁰-aerogel were obtained in gas streams containing I₂, H₂O, and NOx. Through chemical analyses of the iodine-loaded adsorptions including scanning electron microscopy (SEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and X-ray absorption fine structure (XAFS), the binding information of Ag with I₂, H₂O and NO_X during the adsorption process were obtained. Several chemical reactions occurred during the process forming silver iodide, silver nitrates and silver sulfate (in Ag⁰-aerogel). Their chemical compositions were also determined. It was found that the oxidation of Ag by H₂O and NO_x occurs much faster than the iodine adsorption process due to the much higher concentration of H₂O and NO_X. As a result, the iodine adsorption performance of Ag⁰Z and Ag⁰-aerogel decreased significantly.