Title: MOLTEN-SALT SOLVENTS FOR FLUORIDE VOLATILITY PROCESSING OF ALUMINUM-MATRIX NUCLEAR FUEL ELEMENTS
Abstract: The results of a search for molten-salt solvents for use in fluoride volatility processing of aluminum-matrix f'uel elements are presented.The solubility of aluminum fluoride in .various mixtures of fluorides was determined in order to estimate the feasibility and cost of processing methods.Sufficient data were accumulated to construct equilibrium phase diagrams of the solution systems, LiF-N~F-AlF3{ LiF-KF-AlF3, LiF-KJAlF6-MF2 (where MF2 is CaF2, SrF2, or ZnF2J, and KF-ZrF4-AlF3.New and revised phase diagrams were determined for the limiting binary systems of the alkali fluorides with AlF3 by use of a new visual method for determining the occurrence of liquidus transitions.This method provided several advantages not available in classical methods of obtaining liquidus data.For e.xample, it was observed for the first time that i..mm.iscible liquids are formed at high temperatures in AlF3-based systems.The temperatures at which such liquids form are, however, higher than is feasible for adoption in most current chemical technologies.Of the various materials evaluated as solvents for the volatility process, the greatest potential for application was displayed by the KF-ZrF4-AlF3 system.High solubility and good dissolution rates are afforded by the inexpensive solvent salt K2ZrF6• At operating temperatures, approximately 6oo 0 c, the AlF3 capacity of the solvent is in excess of 25 mole %.