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.