Experimental investigation of tritium release from LiAlO2 and absorption into Zr

• Water formation reaction on LiAlO 2 was observed above 450 °C. • T diffused from inner LiAlO 2 grain is considered to occur water formation reaction. • Redox reaction rate of H 2 O on Zr increased above 700 °C. • T release peak from the 700 °C-preheated LiAlO 2 with Zr was observed at 200, 800 °C. • Mass transfer resistance of Zr oxide layer is considered to deteriorate above 700 °C. Tritium (T) production using a high-temperature gas-cooled reactor (HTGR) has been proposed to arrange initial T inventory for nuclear fusion reactors. For the establishment of this method, the behavior of T in a Li-loading rod (Li-rod), which contains LiAlO 2 and zirconium (Zr), needs to be understood. In this study, a powdered LiAlO 2 sample was heated in H 2 containing Ar gas flow to observe water formation reaction. Then, a powdered Zr sample was heated in humid Ar gas flow to investigate the temperature dependence of H 2 O reduction rate on the Zr. Finally, a Zr-mixed LiAlO 2 sample, which had been neutron-irradiated in the Kyoto University Research Reactor (KUR), was preheated at 700 °C in a sealed quartz tube, and then heated in Ar gas flow to observe the release behavior of T from the sample. Released gaseous T (HT, T 2 ) and tritiated water vapor (HTO, T 2 O) were separately collected using a pair of bubblers installed upstream and downstream of a copper oxide (CuO) bed, and the tritium concentration in each bubbler was measured using a liquid scintillation counter. Based on the results, it is suggested that LiAlO 2 should be in advance heated in reduction atmosphere to remove adsorbed water and unstable oxygen to suppress the release of T in chemical form of HTO, and Li-rod should be operated at higher temperatures over 700 °C to decrease the mass transfer resistance by an oxide layer on Zr.