Tritium release from lithium orthosilicate ceramic pebbles irradiated with low thermal-neutron fluences was studied using out-of-pile annealing experiments. It was found that the tritium produced in Li4SiO4 pebbles was released mainly as tritiated water vapor. The diffusion coefficients of tritium in the crystal grains at 450 to 600K were obtained by isothermal annealing tests, and the Arrhenius relationship was:

D(cm2/s) = 1 x 10-7exp[-40300/RT]

C.Xiao, X.Gao, M.Kobayashi, K.Kawasaki, H.Uchimura, K.Toda, C.Kang, X.Chen, H.Wang, S.Peng, X.Wang, Y.Oya, K.Okuno: Journal of Nuclear Materials, 2013, 438[1-3], 46-50