Steven M. Frank

SALT-ZEOLITE ION-EXCHANGE EQUILIBRIUM STUDIES FOR A COMPLETE SET OF FISSION PRODUCTS IN MOLTEN LiCl-KCl

Abstract This paper presents results of experiments and modeling for ion exchange of LiCl-KCl-based molten salts with zeolite-A. The experiments examined the equilibrium distributions of various nuclear fuel fission products between the molten salt and zeolite phases. In addition to data that were collected in previous studies, new experiments were run using ternary salts (LiCl-KCl-YCl3, LiCl-KCl-LaCl3, and LiCl-KCl-PrCl3) and quaternary salts (LiCl-KCl-CsCl-NdCl3 and LiCl-KCl-CsCl-SrCl2). All contacting experiments were conducted at 500°C with a salt-zeolite contacting period of 24 h to allow for equilibrium to be reached. The developed equilibrium model assumes that there are ion-exchange and occlusion sites, both of which are in equilibrium with the molten salt phase. A systematic approach in estimating the total occlusion capacity of the zeolite-A was developed. The parameters of the model, including the total occlusion capacity of the zeolite-A, were determined from fitting the entire set of experimental data available between previous studies and the current one. Experiments involving ternary salts were used to estimate the parameters of the model, while those involving quaternary salts were used to validate the model.

Selective Separation of Cs and Sr from LiCl-Based Salt for Electrochemical Processing of Oxide Spent Nuclear Fuel

Abstract Electrochemical processing technology is currently being used for the treatment of metallic spent fuel from the Experimental Breeder Reactor-II at Idaho National Laboratory. The treatment of oxide-based spent nuclear fuel via electrochemical processing is possible provided there is a front-end oxide reduction step. During this reduction process, certain fission products, including Cs and Sr, partition into the salt phase and form chlorides. Both solid state and molten LiCl-zeolite-A ion exchange tests were conducted for selectively removing Cs and Sr from LiCl-based salt. The solid-state tests produced in excess of 99% removal of Cs and Sr. The molten state tests failed due to phase transformation of the zeolite structure when in contact with the molten LiCl salt.