Tritium release behavior of Li4SiO4 pebbles with high densities and large grain sizes

Tritium release behavior from the Li4SiO4 pebbles with high densities (∼96%TD) and large grain sizes (100-300 μm) fabricated by a melt-based method (the M-OSi sample) was investigated through out-of-pile experiments. Another batch of Li4SiO4 pebbles with relatively low densities (∼86%TD) and small grain sizes (10-50 μm) fabricated by a wet method (the W-OSi sample) was used for comparative study. Comparing with the W-OSi sample, the temperature of tritium release from the M-OSi sample was found much higher. Moreover, the fraction of tritium gas released from the M-OSi sample was much larger, especially under helium purge gas. The big differences between the characteristics of tritium release from the two batches of samples can be explained reasonably by the effect of grain size, implying that the grain size played an important role in the tritium release behavior. This study can provide a guideline for optimizing the fabrication process of Li4SiO4 pebbles.