(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 NOX 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 NOX 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 NOX 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 NOx occurs much faster than the iodine adsorption process due to the much higher concentration of H2O and NOX. As a result, the iodine adsorption performance of Ag0Z and Ag0-aerogel decreased significantly.