Comparative study of full-scale thin double-layered annulus beds loaded with ZrCo, Zr0.8Hf0.2Co and Zr0.8Ti0.2Co for recovery and delivery of hydrogen isotopes

Metal hydride bed is a necessary component for deuterium–tritium fusion energy under development in International Thermonuclear Experimental Reactor (ITER), which is used for rapid and safe recovery/delivery of hydrogen isotopes. In the present work, full-scale thin double-layered annulus beds loaded with ZrCo, Zr0.8Hf0.2Co and Zr0.8Ti0.2Co were fabricated. The corresponding hydrogen storage behaviors including hydrogen recovery/delivery and cycling properties of the three beds were systematically investigated and compared. It was found that all the three fabricated beds could reach the hydrogen storage target of 17.5 mol. Compared with ZrCo bed and Zr0.8Hf0.2Co bed, Zr0.8Ti0.2Co bed exhibited superior hydrogen delivery properties in terms of higher hydrogen delivery amount, faster delivery rate and better cyclic delivery performance, which could deliver 17.06 mol H2 (∼94.7% of total capacity) at 450 °C within 31.8 min holding at the critical delivery rate of 20 Pa m3/s. Although the hydrogen delivery amount gradually decreased during the recovery/delivery cycles, which was revealed to be caused by the characteristic disproportionation of ZrCo based alloy, significant improvement had been gained for Zr0.8Ti0.2Co bed relative to ZrCo bed and Zr0.8Hf0.2Co bed. In addition, the industrial computed tomography (ICT) results showed that the thin double-layered annulus bed owned good structural stability during the hydrogen recovery/delivery cycles. In view of its beneficial hydrogen recovery and delivery performances, the Zr0.8Ti0.2Co bed with thin double-layered annulus configuration appeared to be a potential option for hydrogen isotopes recovery and delivery in ITER if the anti-disproportionation property could be further enhanced.