Tritium localisation and release from the ceramic pebbles of breeder

Magnetic field (MF) effects on the radiolysis and tritium release from Li4SiO4 (FZK) and Li2TiO3 (CEA) ceramic pebbles were investigated. The tritium chemical forms in Li4SiO4 were estimated by means of lyomethods. In the case of the neutron fluence Fn⩽1018 n m−2, the tritium is mostly in the T+ form, but in the case of Fn≈1025 n m−2, the T+ form accounts for 86–95% of the tritium. A high subsurface concentration of tritium is characteristic of a separate pebble and correlates with the distribution of radiation-induced defects. The MF increases the radiolysis of Li4SiO4 by 20–25%. Irradiation with electrons to 1000 MGy at 1200 K increases the grain size by 5–10%, decreasing the parameters of tritium release. The increased grain size was observed for the Li4SiO4 pebbles irradiated in EXOTIC-8. A considerable tritium detention (up to 40%) was observed after annealing to 1120 K in the MF of 2.4 T.