Study on the Characteristics of the Ion Exchange of Zeolite 4A in a Molten LiCl System

An advanced spent fuel management process using a molten LiCl salt for the purpose of reducing spent oxide fuel to a metallic form generates a waste salt containing alkali, alkaline-earth, and some rare-earth fission products. A periodic removal of the high heat-generating Cs and Sr should be accomplished to reuse the salt since a recycling of the LiCl waste salt to a process stream is required to decrease the total amount of waste to be disposed of. In this study, zeolite 4A was proven to have desirable properties for the removal of the Cs and Sr elements from an LiCl molten salt phase, and the ion-exchange characteristics of zeolite in the molten salt were investigated. The adsorption of the Cs and Sr elements in an LiCl molten salt reaches nearly a constant value after 2–4 h of contact with the zeolite. The salt-occluded zeolite was produced in an LiCl molten salt, and then its ionexchange and salt occlusion properties were studied experimentally. The result indicates that zeolite 4A occluded between 10 and 11.5 salt molecules, and the salt-occluded zeolite was found to be a very effective molecular sieve for sorbing the Cs and Sr in the LiCl waste salt.