High-purity titanium,zirconium, and hafnium in nuclear power

The use of high-purity (iodide) titanium, zirconium, and hafnium for obtaining building and absorbing materials for use in nuclear power is examined. The possibilities for iodide refining of these metals to remove impurities and the chemical composition, microstructure, and microhardness of iodide rods are presented. Regimes for chemical decontamination of raw materials and iodide refining of metals in commercial equipment are examined. It is shown that iodide refining makes it possible to use as raw materials the wastes and recyclables from metallurgical and rolled production of titanium, zirconium, and hafnium and to obtain from them under commercial conditions high-purity metals with multiple uses, including as components of a charge for smelting alloys to be used in nuclear power. Materials based on titanium, zirconium, and hafnium of consistent quality which are obtained using metal iodides will make it possible to extend the VVER service life to 60 years.     

Equilibrium pressures of hydrogen and deuterium dissolved in titanium,zirconium and hafnium at low concentrations

Equilibrium pressures of hydrogen and deuterium over titanium (420–970°C), zirconium (480–940°C) and hafnium (445–635°C) were measured in the pressure range from 0.013 to 133 Pa. The pressure-composition relationship obeyed Sieverts' law and the Sieverts' constants in the Arrhenius equation were derived. At constant atomic fraction the equilibrium pressures of deuterium were found to be 1.1 to 1.4 times as high as those of hydrogen for all three metals over the temperature range examined.     

Separation of zirconium and hafnium by solvent extraction using mixture of TBP and Cyanex 923

In this study, a new Zr/Hf separation procedure by solvent extraction is proposed. The method is based on using the mixture of TBP and Cyanex 923 as extractant in the organic phase. Several parameters including; TBP/Cyanex 923 volume ratio, extractant concentration in the organic phase, nitric acid and NaNO₃ concentration in aqueous phase have been investigated. The results demonstrate better condition respect to traditional TBP/HNO₃ process. Lower required acid concentration and more zirconium extraction are some advantages of the new separation process.     

Prospects for zirconium and hafnium supplies for nuclear power in Russia up to 2030

The prospects for supplying zirconium and hafnium-the main structural and prospective absorbing material for thermal reactors-are examined in accordance with the strategy for the development of nuclear power in our country up to 2030. The present situation concerning the use of Russian nuclear fuel is described. The characteristics of the main zirconium alloys used in domestic and foreign thermal reactors and the approximate requirements for baddeleyite and zirconium concentrates, the distribution of balance zirconium reserves, and the requirements of the nuclear industry for hafnium metal and hafnium compounds are presented. Translated from Atomnaya énergiya, Vol. 105, No. 4, pp. 190–194, October, 2008.     

Nondestructive nuclear-physical methods of determining the boron content in zirconium

A. A. Bochvar All-Union Scientific Research Institute of Standardization and Mechanical Engineering. Translated from Atomnaya Énergiya, Vol. 73, No. 6, pp. 497-498, December, 1992.     

Discovery of the astatine,radon, francium,and radium isotopes

Thirty-nine astatine, thirty-nine radon, thirty-five francium, and thirty-four radium isotopes have so far been observed; the discovery of these isotopes is described. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.     

Separation of hafnium from zirconium in hydrochloric acid solution with di(2-ethylhexyl)phosphoric acid by solvent extraction

The preparation of nuclear-grade zirconium and hafnium is very important for nuclear power. The separation of hafnium from zirconium in a hydrochloric acid solution by solvent extraction was investigated with di(2-ethylhexyl)phosphoric acid(D2 EHPA). The effects of hydrochloric acid concentration, extractant concentration,diluents, and temperature on the distribution coefficient of hafnium and zirconium were studied. The species extracted were ZrOA_2·2 HA and HfOA_2-2 HA. In this process, the separation factors varied with different diluents and followed the order octane hexane toluene chloroform.A high separation factor value of 4.16 was obtained under the conditions of a solution containing 0.05 mol/L HCl and0.01 mol/L D2 EHPA for the separation of hafnium from zirconium. The extraction reaction was endothermic.     

Comparative study of methods of the determination of Kearns parameter in zirconium

Various methods of Kearns “f” parameter evaluation were compared for their consistency and dependency on measurement cross section of the sample and variation in the microstructure across different cross sections. The study showed that, EBSD (Electron Back Scattered Diffraction) method is more consistent in comparison to X-ray based techniques for the “f” parameter determination especially in case of recrystallized microstructures.     

Diffusion of uranium in molybdenum,niobium, zirconium,and titanium

The diffusion of uranium was studied in molybdenum, niobium, zirconium, and titanium. The diffusion coefficients were determined by measuring the over-all activity of the residue of the sample, using the a-radiation of uranium enriched with the U²³⁵ isotope to 90% at temperatures 1500 to 2000° C (molybdenum, niobium) and 915 to 1200° C (zirconium, titanium). The temperature dependence of the diffusion coefficients was given by the equationsD _Mo ^U=7.60.10³ exp (–76 400/RT) cm²/sec;D _Nb ^U=8.90.10^–2 exp (–76 800/RT) cm²/sec;D _Zr ^U=7.77,10^–5 exp (–25 800/RT) cm²/sec;D _Ti ^U=4.90. t0^–4 exp (–29 300/RT) cm²/sec.The considerable differences between the diffusion mobilities and activation energies of molybdenum and niobium on the one hand and zirconium and titanium on the other were probably due to the effects of lattice defects, for example, excess vacancies arising in zirconium and titanium during polymorphic transformations.Translated from Atomnaya Énergiya, Vol. 19, No. 6, pp. 521–523, December, 1965Report read by G. I. Budker at the International Conference on High-Energy Accelerators (Frascati, Italy).     

Discovery of yttrium, zirconium, niobium, technetium, and ruthenium isotopes

Currently, thirty-four yttrium, thirty-five zirconium, thirty-four niobium, thirty-five technetium, and thirty-eight ruthenium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.     

Thermal transport properties of hafnium hydrides and deuterides

The thermal conductivities of δ′-, δ-, δ+ε-, and ε-phase hafnium hydrides and deuterides with various hydrogen isotope concentrations (HfH_x, 1.48 ? x ? 2.03; HfD_x, 1.55 ? x ? 1.94) were evaluated within the temperature range of 290-570 K from the measured thermal diffusivity, calculated specific heat, and density. The thermal conductivities of δ′-, δ-, δ+ε-, and ε-phase HfH_x and HfD_x are independent of the temperature within the range 300-550 K and are in the range 0.15-0.22 W/cm K and 0.17-0.23 W/cm K, respectively; these values are similar to and lower than the observed thermal conductivities of α-phase Hf. The experimental results for the electrical resistivities of δ′-, δ-, δ+ε-, and ε-phase HfH_x and HfD_x and the Lorenz number corresponding to the electronic conduction, obtained from the Wiedemann-Franz rule, indicated that heat conduction due to electron migration significantly influences the thermal conductivity values at high temperatures. On the other hand, heat conduction due to phonon migration significantly affects the isotope effects on the thermal transport properties.     

Cesium solubility,diffusion and permeation in zirconium carbide

To compare the relative effectiveness of ZrC vis-a-vis SiC as a fission product barrier in fuel structures for high temperature gas cooled reactor (HTGR) applications, a series of cesium infusion experiments on various ZrC powders, and ZrC coated graphite structures was performed to study the cesium solubility, diffusivity, and permeability of this coating material. The ZrC powder results yield a solubility of Cs in ZrC, S(ppm wt) = (1.7 × 10^?6) exp[229 kJ/RT], over the temperature range 1485–1896 K. The diffusion coefficient of Cs in ZrC is 10^?18–10^?16 m²/s over a similar temperature interval. The activation energy of diffusion is estimated to be ≈ 50 kJ/mole.The results of experiments in which both SiC and ZrC coated graphite samples were exposed to cesium are more difficult to interpret. The results support the conclusions of the ZrC powder experiments that ZrC is comparable to SiC as a diffusion barrier to cesium.     

Dislocations generated by zirconium hydride precipitates in zirconium and some of its alloys

The character of dislocations emitted during the precipitation of γ-zirconium hydride in zirconium, Zircaloy-2, Zr-1% Al and Zr-1% Cr has been determined. Contrast experiments in the transmission electron microscope have shown that the dislocations possess Burgers vectors ($\text{b}$) of the type $\text{1}\text{3}\text{a <11}\text{2}\text{?}\text{0>}$. Of the three possible $\text{b}$'s only one or two are observed associated with a given hydride needle, those giving a large component of $\text{b}$ along a direction perpendicular to the needle. Dislocation generation is thought to result from the dilatational misfit associated with the hydride needles. The creation of dislocations with $\text{b}$'s along the $\text{c-}\text{axis}$ is more difficult and the misfit strain along this direction is not relieved by plastic deformation.