Katsuhiro Fuchinoue

Fabrication development and preliminary characterization of Li2TiO3 pebbles by wet process

Lithium titanate (Li 2 TiO 3 ) has attracted attention of many researchers because of easy tritium recovery at low temperature, high chemical stability, etc. The application of small Li 2 TiO 3 spheres has been proposed in some designs of fusion blanket. Although, the wet process and sol-gel method are the most advantageous as a fabrication method of Li 2 TiO 3 pebbles from points of mass production, and of reprocessing necessary for effective use of resources and reduction of radioactive wastes. However, the fabrication of Li 2 TiO 3 pebbles by the wet process has not been established. Therefore, in this study, fabrication development and preliminary characterization of Li 2 TiO 3 pebbles by the wet process were performed, noting the aging and sintering conditions in the fabrication process of gel-spheres. At the best condition. Li 2 TiO 3 pebbles with the target density of 80-85%T.D. were obtained.

Isotope separation factor and isotopic exchange rate between hydrogen and deuterium of palladium

An isotopic exchange experiment was performed using a Pd particle bed for a fundamental study of hydrogen isotope separation. The isotope separation factor and the rate constant of the isotopic exchange reaction between gaseous deuterium and hydride were determined from fitting numerical calculations to experimental effluent curves of the Pd bed. The separation factors under the condition of a dilute deuterium concentration were correlated with the relation of αH − D =exp(−0.121 + 228/T) and were independent of the total hydrogen pressure. The rate-determining step of the overall isotopic exchange reaction at T > 300K was diffusion in the pore of Pd particles. The step at T < 300K was estimated to be diffusion in the β-phase Pd, although there is a little possibility of isotopic exchange reaction based on Bonhoeffer-Farcus mechanism. The height equivalent to a theoretical plate, HETP, was correlated as a function of the interstitial fluid velocity in the bed.

Hydrogen Isotope Separation by Displacement Chromatography with Palladium

In order to establish a lab-scale hydrogen isotope separation system, experimental and numerical studies were performed by means of displacement chromatography of protium and deuterium using a bed of spongy palladium particles. The inlet deuterium concentration of 5.0% D or 54.9% D was prepared for the experiment. The equations of the material balance of deuterium in the bed and the isotopic exchange rate between protium and deuterium were simultaneously solved. The contributions of isotopic exchange reaction on Pd surfaces, diffusion in the solid and axial dispersion in the interstitial of the Pd bed to overall mass transfer were taken into consideration in the equations. The numerical calculation results fitted to the experimental data. They predicted well the maximum deuterium concentration in the effluent and the shape of the displacement band. In the calculations, we used the values of the concentration-dependent isotope separation factor and the isotopic exchange rate constant determined in our prev...

Fabrication development of Li2O pebbles by wet process

Lithium oxide (Li 2 O) is one of the best tritium breeding materials. A small sphere of Li 2 O is proposed in some designs of fusion blankets, Recently, reprocessing technology on irradiated ceramic tritium breeders was developed from the viewpoint of effective use of resources and reduction of radioactive wastes, The wet process is advantageous for fabricating small Li 2 O pebbles from the reprocessed lithium-bearing solutions. Preliminary fabrication tests of Li 2 O pebbles by the wet process were carried out. However, the density of the pebbles obtained was only 55%. Therefore, process improvement tests were performed in order to increase the density of Li 2 O pebbles fabricated by this method. The improved process yielded Li 2 O pebbles in the target range of 80-85% T.D.

Hydrogen isotope separation based on isotopic exchange in palladium bed

A continuous hydrogen isotope separation system using twin beds of metals or alloys is here proposed. The isotope separation system called a twin-bed periodically counter-current flow (TB-PCCF) is analytically and experimentally investigated. Palladium and LaNi 4.7 Al 0.3 were selected based on experimental data of the isotope separation factor and the isotopic exchange rate. Numerical calculations by a plate model revealed effectiveness of the TB-PCCF method which is composed of an enriching column packed with Pd particles and a stripping column packed with LaNi 4.7 Al 0.3 particles. A preliminary experiment was performed at the condition where absorption and desorption cycles are repeated between room temperature and 473K for Pd and 363K for LaNi 4.7 Al 0.3 at the total reflux, and it showed possibility of the hydrogen isotope separation.

Hydrogen isotope separation using particle beds of LaNi3Al2 hydride

Abstract An experimental study was carried out for evaluating the performance of hydrogen isotope separation using an LaNi3Al2 hydride bed. The isotope effect in the uptake of hydrogen isotopes and the rate constants of hydriding and isotopic exchange between hydrogen and deuterium are given as indications of its effectiveness. These values were determined on the basis of the comparison of experimental data with numerical solutions to the material balance equation for hydrogen or deuterium in a bed. The uptake of deuterium is larger than that of hydrogen below 200 °C. The activation energy of the rate constant of isotopic exchange is 31.8 kJ mol−1, while that of the hydriding rate constant increases with increasing hydrogen concentration in the influent stream. The height equivalent to a theoretical plate in the LaNi3Al2 bed above 200 °C is comparable with that in a Pd bed.