The FUBR-1B irradiation experiment: Tritium release and physical stability of solid breeder materials

The FUBR-IB irradiation experiment in EBR-II has provided important information on the irradiation behavior of candidate lithium solid breeder materials in a high energy neutron spectrum. The solid breeder materials include Li2O, LiAlO2, Li2ZrO3, Li8ZrO6 and Li4SiO4 pellets and LiAlO2 spheres. The irradiation behavior of the materials was characterized for the temperature range from 400 to 900 degree C. The amount of tritium/helium retained by the solid breeder materials, as well as swelling and physical stability, was determined for specimens removed after the first period of irradiation. LiAlO2, Li2ZrO3, and Li8ZrO6 exhibited excellent dimensional stability during irradiation while the dimensional stability of Li2O was found to be dependent on the as-irradiated microstructure. Measurements of the amount of retained tritium characterize the ability of the solid breeder to release tritium. These results are compared to measurements of tritium retention made on similar closed capsule experiments and extend the data to burnups as high as 1.6 x 1021 at/cc. Water vapor, in the form of T2O, was found to have a pronounced effect on the irradiation behavior of Li2O and LiAlO2. 6 refs., 2 figs., 5 tabs