Kinetic analysis of tritium release from irradiated biphasic lithium ceramics Li$_4$SiO$_4$-Li$_2$TiO$_3$ with different phase ratios

This paper analyzes the kinetics of tritium release from biphasic Li$_2$TiO$_3$/Li$_4$SiO$_4$ lithium ceramics using thermal desorption spectroscopy after neutron irradiation at the WWR-K reactor. Samples with different Li$_2$TiO$_3$ contents (25 mol% and 35 mol%) in the Li$_4$SiO$_4$ main phase, fabricated by the KALOS process at the Karlsruhe Institute of Technology, were irradiated at a low temperature and a thermal neutron flux of 2 × 1013 n/(cm²·s) during 21.5 effective full power days until accumulating a fluence of 3.7 × 1019 n/cm².
The experimental results confirm the significant influence of phase composition on the processes of tritium release. The analysis allowed us to develop a reasonable mechanism of tritium release during linear heating up to 1173 K.
Tritium was found to be uniformly distributed throughout the ceramic volume and its release is closely related to the microstructural characteristics of the material. Key factors affecting the process include the presence and distribution of traps and defects interacting with the external surface of the sample. The release process of these traps is determined by the transport of tritium to the boundaries, followed by desorption mainly in the form of HT molecules and has three main peaks.
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Samples with 25 mol% Li$_2$TiO$_3$ showed high activation energy values, indicating the presence of more stable traps and complex tritium transport pathways. With an increased Li$_2$TiO$_3$ content of 35 mol%, a decrease in activation energy was observed, indicating a faster desorption process, probably due to changes in microstructure or the number of active defects facilitating tritium release at lower temperatures.