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

Bis(tetraphenylarsonium) hexachloridozirconate(IV) acetonitrile tetrasolvate

The bis(tetraphenylarsonium) hexachloridozirconate(IV) salt, (AsPh4)2[ZrCl6] (Ph = C6H5), was prepared more than 25 years ago [Esmadi & Sutcliffe (1991). Indian J. Chem. 30 A, 99–101], but its crystal structure was never reported. By following a similar experimental procedure, the compound was synthesized and its crystal structure was investigated as a acetonitrile tetrasolvate, (As(C6H5)4)2[ZrCl6]·4CH3CN, by single-crystal X–ray diffraction. The [ZrCl6]2− anion adopts a slightly distorted octahedral coordination sphere, with Zr—Cl bond lengths of 2.4586 (6), 2.4723 (6), and 2.4818 (5) Å, and Cl—Zr—Cl angles ranging from 89.602 (19) to 90.397 (19)°

Zirconium chloride molecular species: combining electron impact mass spectrometry and first principles calculations

Zirconium tetrachloride was synthesized from the reaction between zirconium metal and chlorine gas at 300 °C and was analyzed by electron impact mass spectrometry (EI-MS). Substantial fragmentation products of ZrCl4 were observed in the mass spectra, with ZrCl3 being the most abundant species, followed by ZrCl2, ZrCl, and Zr. The predicted geometry and kinetic stability of the fragments previously mentioned were investigated by density functional theory (DFT) calculations. Energetics of the dissociation processes support the most stable fragment to be ZrCl3 while the least abundant are ZrCl and ZrCl2