(423b) Water Sorption/Desorption Characteristics in Electrorefiner Salt-Occluded Zeolites

Electrorefiners currently operating in the Fuel Conditioning Facility of Idaho National Laboratory contain radioactive, actinide-containing molten chloride salt. The primary components of this salt are LiCl and KCl in a eutectic composition. The salt also contains UCl₃, PuCl₃, and numerous fission products from processing irradiated sodium-bonded metal fuel from the Experimental Breeder Reactor-II. It has been proposed to occlude the salt into a zeolite such as zeolite-4A or Na-Y zeolite before eventual conversion into ceramic waste forms for permanent disposal. In this work, we studied the characteristics of the salt-occluded zeolite for hydration and if such hydration is reversible. Zeolite-4A with 20 wt% LiCl-KCl was found to absorb up to about 10 wt% water when in contact with 40^oC air at 20% relative humidity. As is the case with zeolite-4A without any occluded salt, essentially all of the moisture can be desorbed by heating the salt occluded zeolite-4A to 500^oC under flowing argon. However, the dehydration is accompanied by a small amount of HCl gas formation due to hydrolysis of the salt. HCl generation was measured continuously while the salt occluded zeolite was heated to 500^oC using an off-gas sparged auto-titrator. The amount of HCl generated ranged from about 0.3 to 0.5% of the total Cl contained in the salt for any given sample of salt occluded zeolite. The effect of temperature ramp rate and maximum temperature on the amount and rate of HCl generated was studied and will be reported.