Thermal characterization of molten salt systems

This report fulfills Level 3 Milestone No. M31SW050702 titled “Complete
Final Report of Thermal Analysis Study” for FY 2011 within the Department of
Energy (DOE) Work Package No. FTIN11SW0507 titled “Fundamental
Properties of TRU-Bearing Chloride Salt”. This work package falls under the
Fuel Cycle Research & Development (FCR&D) Program 1.02.03.11 titled “ROK
Feasibility Study”. (It was formerly in FCR&D Program 1.02.03.05 titled
“Fundamental Science and Methods Development”.)
The phase stability of molten salts in an electrorefiner (ER) may be adversely
affected by the buildup of sodium, fission products, and transuranics in the
electrolyte. Potential situations that need to be avoided are the following: (1) salt
freezing due to an unexpected change in the liquidus temperature, (2) phase
separation or non-homogeneity of the molten salt due to the precipitation of
solids or formation of immiscible liquids, and (3) any mechanism that can result
in the separation and concentration of fissile elements from the molten salt. Any
of these situations would result in an off-normal condition outside the established safety basis for electrorefiner (ER) operations.
The stability (and homogeneity) of the phases can potentially be monitored
through the thermal characterization of the salts, which can be a function of
impurity concentration. This report describes the experimental results of typical
salts compositions, which consist of chlorides of potassium, lithium, strontium,
samarium, praseodymium, lanthanum, barium, cerium, cesium, neodymium,
sodium and gadolinium chlorides as a surrogate for both uranium and plutonium,
used for the processing of used nuclear fuels.