Effect of NO_x and Water Variations on Iodine Loading of AgZ

Abstract

Reprocessing of used nuclear fuel will result in the release of several volatile radionuclides that need to be removed from facility off-gas streams before their release to the environment. Iodine, one of these radionuclides, is expected to be primarily released in the dissolver off-gas stream as iodine (I2) or methyl iodide (CH3I). Sorbents that target I2 and CH3I removal from the DOG stream will need to adsorb iodine under elevated temperatures and in the presence of water vapor and nitrogen oxides (NOx). Previous studies examining the adsorption of CH3I and I2 in the presence of NOx gases by silver-exchanged mordenite (AgZ), a zeolite mineral considered for use in this application, have resulted in slightly inconsistent conclusions.This study characterizes the effects of water vapor, nitric oxide (NO), nitrogen dioxide (NO2), and operating temperature on the adsorption of both I2 and CH3I by AgZ. These effects were determined through the performance of designed factorial experiments allowing the resolution of each variable's effect on iodine loading capacity. These factorial experiments also provide an assessment of whether the variables of interest may have interactions with each other that affect iodine capture by AgZ. The experiments were performed by exposing thin sorbent beds of AgZ to iodine-bearing feed streams. In total, 16 tests were completed.

Analysis of Organoiodide Adsorption Mechanisms

“…Recent studies by ORNL confirm that water plays less of a role in CH 3 I sorption than initially thought, despite a significant difference in observed loading rates, depending on whether water is present in the gas feed stream. Greaney et al (2020) found no statistical difference observed in the loading capacity of AgZ for CH 3 I from dry and humid gas streams. The findings of Greaney et al (2020) broadly align with the findings of Chebbi et al (2021).…”

“…Greaney et al (2020) found no statistical difference observed in the loading capacity of AgZ for CH 3 I from dry and humid gas streams. The findings of Greaney et al (2020) broadly align with the findings of Chebbi et al (2021).…”

Abatement of radioiodine in aqueous reprocessing off-gas

“…Apparent mass gain measured with the TGA is confirmed with neutron activation analysis (NAA) at the High Flux Isotope Reactor at Oak Ridge National Laboratory. Detailed methods can be found in other works ( Greaney et al, 2020 ; Greaney et al, 2021 ).…”

Off-Gas Design and Testing from Advanced Chlorination Process

“…The capture of I species and 3 H was investigated at Oak Ridge National Laboratory in earlier studies. (Greaney et al 2020, Jubin et al 2019. Silver mordenite was identified as an optimal trap for I species.…”