Concentrating low-level tritiated water through isotope exchange

Trapping of tritium on polymers with specific functional groups was investi gated as a means of treating waste streams containing low levels of tritium . Chemical exchange of tritium with hydrogen on the functional group was us ed as the mechanism for trapping. The polymers tested include Aurorez polyb enzimidazole resin bends, Chelex 100 resin beans, Duolite GT-73, microcryst alline cellulose, ann polyethylenimine. The tests were performed under simu lated operating conditions on water obtained fi om the Radioactive Liquid W aste Treatment Facility at Los Alamos National Laboratory. Tritiated water front the Tritium Systems Test Assembly is discharge to this plant. Polyeth ylenimine is a water- soluble polymer that was tested using a stirred membr ane cell with art ultrafiltration membrane. All of the polymers except poly ethylenimine took up tritium from the water. Polybenzimidazole demonstrated the highest tritium uptake. The results are explained on the basis of the type of functional group, hydrogen bonding, and rigidity of the molecular s tructure of the polymer. The theoretical calculations indicate that signifi cant isotope discrimination requires high-frequency modes with hydrogen bon ding contribution and support the experimental findings. Modeling suggested trends that may lean to structures that are more efficient in trapping tri tium.