Tritium release performance of neutron-irradiated core–shell Li2TiO3-Li4SiO4 pebbles

• Tritium release form and temperature range from neutron-irradiated core–shell Li 2 TiO 3 -Li 4 SiO 4 were obtained through out-of-pile tritium release experiments. • Micro-CT revealed the three-dimensional structure and the distribution of abundant interconnected pores of core–shell Li 2 TiO 3 -Li 4 SiO 4 pebbles, which contributed to the lower temperature tritium release. • The desorption activation energies of 0.63 eV and 1.64 eV, along with the diffusivity of 3.73 × 10 -6 exp(−1.35 eV/kT) m 2 /s for core–shell Li 2 TiO 3 -Li 4 SiO 4 pebbles, were calculated and compared to previously reported values. To enhance the mechanical strength of Li 4 SiO 4 and reduce its sensitivity to carbon dioxide and water, advanced tritium breeder core–shell Li 2 TiO 3 -Li 4 SiO 4 was designed and fabricated by graphite bed method. The 1:1 phase ratio between Li 2 TiO 3 and Li 4 SiO 4 was confirmed by X-ray diffraction (XRD) and Rietveld refinement. Scanning electron microscopy (SEM) revealed that submicron-sized Li 2 TiO 3 grains aggregated at the grain boundaries of Li 4 SiO 4 . Micro-computed tomography (Micro-CT) distinctly illustrated the shell-structure and the three-dimensional distribution of internal pores, aligning with the original design requirements and expectations. Neutron irradiation and out-of-pile tritium release experiments were conducted to evaluate the tritium release performance. Temperature-programmed desorption tritium release spectra exhibited two distinct release peaks, occurring at approximately 312 and 478 °C. The corresponding desorption activation energies were calculated using varying heating rates, yielding values of 0.63 eV and 1.64 eV, respectively. Isothermal desorption experiments indicated that complete release of residual tritium can be achieved at temperatures exceeding 400 °C. The tritium release rate-controlling process was found to be primarily diffusion of tritium through the crystal, with an effective diffusivity of 3.73 × 10 -6 exp(−1.35 eV/kT) m 2 /s.