Out-of-pile tritium release experiments of lithium orthosilicate pebbles

Lithium orthosilicate(Li4SiO4) pebbles are considered as the candidate tritium breeders of Chinese helium cooled solid breeder test blanket module(CH HCSB TBM).The post-irradiation annealing experiments of lithium orthosilicate ceramic pebbles,made by freezen-sintering process,have been performed in CAEP.The samples were purged with 100mL/min mixed gas of He +1% H2,heated at a constant rate of 5K·min-1 in a reactor tube.The results showed that tritium was released mainly as tritium gas(HT+T2),the proportion was about 70% except that in free tritium released out before annealing,and there were two tritium release peaks from 400℃～700℃.On the other hand,percentage of tritiated water(HTO+T2O) was less than 20%,and released at lower temperature region of 300℃～500℃.Tritium remained in the pebbles was less than 1% after 800℃ in annealing experiments,so Li4SiO4 pebbles made by freezen-sintering process have favorable tritium release performance,and have potential application in fusion reactor solid blanket system.

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