Kimikazu Moritani

Discharge electrolysis in molten chloride: formation of fine silver particles

Abstract A relatively stationary discharge was generated in molten chloride utilizing a simple apparatus and successfully achieved at electrolysis. Fine silver particles were obtained using a LiCl-KCl-AgCl eutectic melt in an argon atmosphere. SEM observations of the silver particles showed them to be almost spherical and the size to be strongly dependent on the experimental conditions. This new kind of discharge electrolysis is expected to be adopted as a new method for metal powder production.

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.

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.

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.

Chemical behaviors of tritium formed in a LiF-BeF2 mixture

Chemical behaviors of tritium formed in a LiF-BeF2 mixture were studied using a radiometric method. Most of tritium was found to be present in the T+ and T− states under no thermal treatment. The distribution of tritium in chemical states was explained by considering hot atom reactions and radiation chemical reactions. Tritium behaviors in a molten LiF-BeF2 mixture were also studied at 873 K. In presence of hydrogen, the isotopic exchange reaction which is TF + H2 → HT + HF was observed to occur probably in the salt phase.

In situ luminescence measurement of irradiation defects in ternary lithium ceramics under ion beam irradiation

For the performance assessment of fusion reactor solid breeder materials, the production behavior of irradiation defects in some candidate materials of Li2TiO3, Li2ZrO3 and Li2SnO3 was studied by an in situ luminescence measurement technique under ion beam irradiation. The luminescence was observed to be composed of multiple luminescence bands and the temperature dependence of the luminescence intensity was measured under He+ or H+ ion beam irradiation. The production mechanism of irradiation defects was discussed by comparing the present results with those previously obtained for Li2O. The effects of irradiation defects on tritium recovery kinetics and material stability were pointed out.

Reductive extraction behaviour of actinide and lanthanide elements in molten salt and liquid metal binary phase systems

Abstract In support of the development of a pyrochemical group-partitioning process of actinides and lanthanides, the equilibrium distributions of these elements were measured in some binary phase systems of molten salt and liquid metal. An LiF—BeF2 mixture was selected as the salt phase and Bi, Sn, Cd and Zn were examined as the metal phase. In general, actinides were more easily reduced and extracted from the salt phase into the metal phase than were lanthanides. Group partitioning is thus feasible. In different partitioning systems a systematic difference in the separation factor between actinides and lanthanides was observed. The difference is attributable to the difference in alloying energies in the metal phase. The thermodynamic quantities of solute elements in the metal phase were evaluated from the present analysis. Some regularities were inferred from the analysis which are theoretically interesting and helpful to estimate unknown distribution coefficients.

Thermodynamic Properties of Lanthanides and Actinides for Reductive Extraction of Minor Actinides

The excess thermodynamic quantities of lanthanides and actinides in molten salts and liquid metals were studied for reductive extraction of minor actinides. The excess enthalpies and entropies of those elements in the molten chloride phase were found to be correlated with the ionic radii of metal ions possibly due to complex formation. In the liquid metal phase, on the other hand, the excess enthalpies were explained with Miedemas atomistic model and the excess entropies were explained with the vibrational entropy due to alloy formation. Using these correlations and models, some missing values of the excess thermodynamic quantities were evaluated and the separation factors of minor actinides from lanthanides were calculated in different reductive extraction systems. The higher separation factors were obtained in the system using aluminum or gallium than in the system using bismuth or cadmium as the liquid metal phase.

Behavior of several lanthanide and actinide elements in a molten salt/liquid metal extraction system

Abstract The extraction behavior of several lanthanide and actinide elements in the reductive-oxidative extraction process in a molten salt/liquid metal system is described. The equilibrium distributions of the elements are affected by metal composition as well as by salt composition. The effect of salt composition is due to the formation of complex compounds in the salt phase. The influence of metal composition is the result of intermetallic compounds in the metal phase. The extraction rates of the elements from the salt phase to the metal phase were also studied from the standpoint of mass transfer and chemical reaction at the interface between the two phases.

The effect of salt composition on reductive extraction of some typical elements from molten LiF-BeF/sub 2/ salt into liquid bismuth

The distribution coefficients of thorium and radium between molten LiF-BeF/sub 2/ and liquid bismuth solutions were measured at 600/sup 0/C in support of the processing of the molten-salt breeder reactor (MSBR) fuel. The increasing mole fraction of LiF in the salt phase from 40 to 70 mol% resulted in the rapid decrease of the distribution coefficient of thorium and in the slow decrease of that of radium. A comprehensive correlation of distribution behavior with salt composition is given by taking into account the formation of complex ions. The equilibrium distribution data affirm that thorium and radium exist mainly as Li/sub 2/ThF/sub 6/ and RaF/sub 2/, respectively, in the salt phase. It is suggested that the lower mole fraction of LiF in the fuel salt is effective in the MSBR fuel processing.