Yuki Edao

Engineering Validation and Engineering Design of Lithium Target Facility in IFMIF/EVEDA Project

Abstract EVEDA Lithium Test Loop (ELTL) has been designed and constructed, has operated a liquid lithium flow test facility with the world’s highest flow rate and has succeeded in generating a 100-mm-wide and 25-mm-thick free-surface lithium flow along a concave back plate steadily at a high speed of 20 m/s at 300°C for the first time in the world. This result will greatly advance the development of an accelerator-based neutron source to high energy and high density, one of the key objectives of the fusion reactor materials development under the BA (Broader Approach) Activities. Recent related engineering validation and engineering design of the lithium facility has been evaluated.

Experiment on recovery of hydrogen from fluidized Li17Pb83 blanket

Development of an efficient tritium recovery method is indispensable in order to compose a liquid blanket system of a D-T fusion reactor in the near future. Here, tritium recovery using a bubbling tower is focused on, and the behavior of H transfer between fluidized lithium-lead (Li-Pb) and gas bubbles of Ar-H2 or pure Ar is examined analytically and experimentally under isothermal conditions. Gas of Ar-H2 or pure Ar is injected into fluidized Li-Pb through an I-shape nozzle made from SS-316. Time variations of the H2 concentration in gas bubbles that come out from fluidized Li-Pb are measured by gas chromatography. Mass-transfer coefficients to correlate rates of H atom transfer between Li-Pb and gas bubbles are obtained by fitting analytical equations to experimental results. The solution is derived under conditions where H transfer between bubbles and liquid Li-Pb is limited by diffusion in the Li-Pb boundary layer. The parameters such as bubble diameter and terminal rising velocity which are used in order to derive analytic formula are estimated from balance among several forces such as gravity, surface tension, inertia force and so on. The behavior of hydrogen transfer at gas-liquid interfaces in liquid blanket is investigated in terms of the mass-transfer coefficient obtained under various conditions.

Experimental investigation on feasible bioreactor using mechanism of hydrogen oxidation of natural soil for detritiation system.

A passive reactor for tritium oxidation at room temperature has been widely studied in nuclear engineering especially for a detritiation system (DS) of a tritium process facility taking possible extraordinary situation severely into consideration. We have focused on bacterial oxidation of tritium by hydrogen-oxidizing bacteria in natural soil to realize the passive oxidation reactor. The purpose of this study was to examine the feasibility of a bioreactor with hydrogen-oxidizing bacteria in soil from a point of view of engineering. The efficiency of the bioreactor was evaluated by kinetics. The bioreactor packed with natural soil shows a relative high conversion rate of tritium under the saturated moisture condition at room temperature, which is obviously superior to that of a Pt/Al2O3 catalyst generally used for tritium oxidation in the existing tritium handling facilities. The order of reaction for tritium oxidation with soil was the pseudo-first order as assessed with Michaelis-Menten kinetics model. Our engineering suggestion to increase the reaction rate is the intentional addition of hydrogen at a small concentration in the feed gas on condition that the oxidation of tritium with soil is expressed by the Michaelis-Menten kinetics model.

Correlation of rates of tritium migration through porous concrete

Abstract What affects tritium migration through porous concrete walls coated with a hydrophobic paint is reviewed from the viewpoint of tritium safety. Being taken into consideration of multi-structural concrete composed of aggregates, sand, water and cement which contents are CaO, SiO2, Al2O3, Fe2O3, MgO, CaSO4 and so on, tritium path is discussed in terms of the HTO diffusivity and adsorption coeffcient on porous walls. Measures to predict rates of tritium leak from laboratory walls to the environment and residual tritium amounts in concrete are estimated based on previous data. Three cases of accidental or chronic tritium release to laboratory air are discussed using the diffusion-adsorption model.

Measurement of Tritium Penetration Through Concrete Material Covered by Various Paints Coating

Abstract The present study aims at obtaining fundamental data on tritium migration in porous materials, which include soaking effect, interaction between tritium and cement paste coated with paints and transient tritium sorption in porous cement. The amounts of tritium penetrated into or released from cement paste with epoxy and urethane paint coatings were measured. The tritium penetration amounts were increased with the HTO exposure time. Time to achieve a saturated value of tritium sorption was more than 60 days for cement paste coated with epoxy paint and with urethane paint, while that for cement paste without any paint coating took 2 days to achieve it. The effect of tritium permeation reduction by the epoxy paint was higher than that of the urethane. Although their paint coatings were effective for reduction of tritium penetration through the cement paste which was exposed to HTO for a short period, it was found that the amount of tritium trapped in the paints became large for a long period. Tritium penetration rates were estimated by an analysis of one-dimensional diffusion in the axial direction of a thickness of a sample. Obtained data were helpful for evaluation of tritium contamination and decontamination.