Tritium release kinetics from Li2TiO3 pebbles as prepared by soft-wet-chemistry

Lithium meta titanate pebbles has been prepared from agglomeration-sintering powders which were obtained by Li-Ti-peroxo-complex solution precursor (Li2TiO3 dissolved at room temperature in H2O + 40% H2O2 and stabilized with citric acid). Through this wet route Li2TiO3 pebbles with high density(∼92% of T.D.) has been obtained and the tritium release behavior has been tested `in-pileʹ by the EXOTIC-8.9 experiment (∼440 days of irradiation at full power in the high neutron flux of HFR-Petten). Tritium residence times (τ) in the pebbles has been measured during irradiation between 550 and 400 °C and He + 0.1%H2 purge gas composition. By a thermally activated process (activation energy=111 kJ/mol) with 410 °C as minimum temperature the tritium residence time is found to be about 1 day, which places this specimen in a good ranking position among those tested by the EXOTIC-series. A clear increase of the tritium release rate has been observed by increased H2 concentration (up to 1%) in the He purge. Out-of-pile ramp-annealing tritium desorption (TPD) tests on short-time irradiated pebbles has been also performed by various devices and conditions. The kinetic parameters from the TPD investigation gave consistent results with those characterizing the equilibrium times of tritium release rate after the gas composition and temperature transients imposed on the specimen during the in-pile experiment.