Hirotake Moriyama

Electrochemical investigation of uranium β-diketonates for all-uranium redox flow battery

Abstract The redox flow battery using uranium as the negative and the positive active materials in polar aprotic solvents was proposed. In order to establish the guiding principle for the uranium compounds as the active materials, the investigation of uranium β-diketonate complexes was conducted on (i) the solubility of active materials, (ii) the electrode reaction of U(VI) and U(IV) β-diketonate complexes and (iii) the estimation of the open circuit voltage of the battery. The solubilities of higher than 0.8 mol dm −3 of U(VI) complexes and higher than 0.4 mol dm −3 of a U(IV) complex were obtained in the solvents. The electrode reactions of U(pta) 4 , UO 2 (dpm) 2 , UO 2 (fod) 2 and UO 2 (pta) 2 were first studied and the redox potentials of uranium β-diketonates were thermodynamically discussed. The open circuit voltage is estimated more than 1 V by using Hacac or Hdpm. The larger open circuit voltage is expected when a ligand with the larger basicity is used.

Tritium recovery from liquid metals

Abstract Liquid breeder materials have many inherent advantages over solid breeder materials, and the liquid metals pure lithium and Pb-17Li alloy are expected to be potential candidate materials. This paper reviews recent work on tritium recovery from the two candidate materials, and discusses the implications of the work for successful future development. The physical and chemical properties of these two materials are also discussed in order to make the similarities and differences clear.

Analysis of Adsorption Behavior of Cations onto Quartz Surface by Electrical Double-layer Model

In a study of the adsorption behavior of cations onto quartz, the distribution coefficient of a variety of cations was determined using the batch method, and using the titration method, the surface charge densities of quartz in a number of electrolyte solutions. The two values thus determined were analyzed applying the electrical double-layer model, from which optimum parameter values were derived for double-layer electrostatics and intrinsic adsorption equilibrium constants. Based on these parameter values, the mechanism of cation adsorption is discussed: A key factor governing this mechanism proved to be the hydration behavior of cations. Consideration of the Coulomb interaction between the adsorbate ions and adsorbent surface led to the finding of a simple rule governing in common the adsorption equilibrium constants of different metal ions.

Molten salts in fusion nuclear technology

In the field of fusion nuclear technology, much interest lies in the use of molten salts. In some innovative design studies, the use of molten fluoride, especially the LiF–BeF2 mixture called Flibe, has been suggested as the primary loop coolant because of its inherent advantages such as high temperature stability and low electrical conductivity. The use of molten salts has also been suggested for the chemical processing of tritium. Together with the physical and chemical properties of molten salts, recent studies on the use of molten salts in fusion nuclear technology are reviewed and discussed, and issues are addressed for successful future development.

In-situ luminescence measurement of irradiation defects in lithium oxide

Abstract An in-situ luminescence measurement was performed in lithium oxide bombarded with 2 MeV He+ ions. The luminescence spectra were obtained in the temperature range from 300 to 850 K. During the ion bombardment, the luminescence peaks of broad widths were observed near 260, 380 and 510 nm and the equiliblium peak intensities decreased with increasing temperature. Another peak at 340 nm appeared above 550 K. After the ion bombardment, the 380 and 340 nm peaks were observed on the light irradiation of 310 and 260 nm, respectively, and were attributed to the F+ and F0 centers. The other peaks at 260 and 510 nm might be associated with the impurities such as hydroxides. The present technique is very useful to study the behaviours of irradiation defects under bombardment.

Solubility measurement of zirconium(IV) hydrous oxide

The solubility of zirconium(IV) hydrous oxide was measured in the hydrogen ion concentration (pHc) range from 1 to 13 at 25 °C. The experiment was carried out with I=0.1, 0.5 and 1.0 mol/dm3 (M) of NaClO4 solution. The concentration of Zr was measured by ICP-MS after separating the aqueous phase from the solid phase by ultrafiltration methods. Some differences between the obtained values and literature data were observed due to the size distribution of chemical species. In the lower pHc region, the size distribution of filtrate species was investigated by different pore-size filtration in the range of 3 k to 100 kDa NMWL (nominal molecular weight limit) membranes. The solubility values of mononuclear species were obtained by the Flory model, and by using the specific ion interaction theory (SIT) for ionic strength corrections and the known literature value of the hydrolysis constant β1°, the tentative value of the solubility product (Ksp°) was determined to be −56.94±0.32.

Thermodynamics of reductive extraction of actinides and lanthanides from molten chloride salt into liquid metal

For the development of a pyrochemical group-partitioning process of actinides and lanthanides, the equilibrium distributions of these elements were measured in some typical binary phase systems of molten salt and liquid metal. A LiCl-KCl mixture was selected as the salt phase, and Zn and Bi were examined as the metal phase. Generally speaking, actinides were more reducible and extractable from the salt phase into the metal phase than lanthanides, and the group partitioning of these elements was feasible in these systems. However, the separation factors which were the ratios in the distribution coefficient between actinides and lanthanides were found to be different in different systems due to different alloying energies. The thermodynamic quantities of actinides and lanthanides were evaluated from the equilibrium distributions and discussed in some detail.

An application of actinide elements for a redox flow battery

The electrochemical properties of U, Np, Pu and Am were discussed from the viewpoint of cell active materials. From the thermodynamic properties and the kinetics of electrode reactions, it is found that neptunium in the aqueous system can be utilized as an active material of the redox flow battery for the electric power storage. A new neptunium redox battery is proposed in the present article: the galvanic cell is expressed by The neptunium battery is expected to have more excellent charge and discharge performance than the current vanadium battery, whereas the thermodynamic one of the former is comparable to the latter. For the development of a uranium redox flow battery, the application of the redox reactions in the non-aqueous solvents is essential.

Equilibrium distributions of actinides and lanthanides in molten chloride salt and liquid zinc binary phase system

As one of the basic investigations on the group partitioning of actinides and lanthanides by the pyrochemical reductive extraction system, their distribution behavior in a binary phase system of molten chloride and liquid zinc was studied at 873 and 1073 K. Generally speaking, actinides were a little more easily reduced and extracted from the salt phase into the metal phase than lanthanides. However, the separation factors which were the differences in the distribution coefficient between actinides and lanthanides were not so large even at the lower temperature at which those were larger and the group partitioning of these elements seemed less attractive in this system. The present results were much the same as those in the LiFBeF2/Zn system and the effect of the selection of the salt phase on the separation factors were hardly observed. For some details, the thermodynamic quantities of actinides and lanthanides in the system were calculated from the equilibrium distributions and discussed.

Electronic absorption spectra of lanthanides in a molten chloride. I. Molar absorptivity measurement of neodymium(III) in molten eutectic mixture of LiCl-KCl

Abstract In order to enhance the basic understanding of the chemical constitution of lanthanides and actinides in molten salts, a new apparatus for high-temperature absorption spectrometry was developed. For the first experiment, by changing the concentration of NdCl3, the electronic absorption spectra of Nd(III) in LiCl–KCl eutectic at 873 K were measured in the wavelength region of 290∼890 nm. The molar absorptivities of detectable transitions were precisely determined.