Zirconium Tetrachloride, Fundamental Chemistry and Nuclear Fuel Cycle

Zirconium alloys are used in the United States as cladding materials in nuclear reactors. The purification of Zr is of relevance due to the large amount of spent nuclear fuel produced every year (2,000 metric tons per year and rising), of which 25% corresponds to radioactive zirconium cladding. Through the recovery and reuse of Zr, estimated savings of $40 million per year are estimated due to the high cost of hafnium-free nuclear grade zirconium, and also due to the minimization of nuclear waste disposal requirements. Several chemical approaches have been proposed for the recovery and purification of Zr. Historically, a chloride volatility process has been preferred, which consists of the reaction between chlorine gas and irradiated cladding to produce zirconium tetrachloride and several other chloride species, which can be separated based on their different boiling/sublimation points, and then the purified zirconium tetrachloride is subsequently reduced to nuclear grade metallic zirconium. However, previous work has shown impurities in the tetrachloride product due to the presence of alloying elements (Fe, Sn, Nb, Cr, Ni), fission products (e.g. 137Cs, 90Sr), and activation products (e.g. 125Sb, 60Co, 93mNb). This dissertation expands on the fundamental properties of solid and gaseous zirconium tetrachloride, a significantly understudied compound. Then, experimental set-ups are developed for laboratory scale chlorination reactions of non-irradiated zirconium alloys and characterization of their chloride products. The data provided allows for the optimization and demonstration of a process that is highly selective for the separation of zirconium tetrachloride, and therefore yield high purity zirconium.