Effective Thermal Conductivity Measurement of the Candidate Ceramic Breeder Pebble Beds by the Hot Wire Method

The effective thermal conductivity of the pebble beds is one the most important design parameters for pebble bed solid breeder blanket. In the framework of IEA Implementing Agreement on Solid Breeder Subtask Group, measurement of pebble bed thermal conductivity by the hot wire method were defined as one of tasks to provide comparative information on the effective thermal conductivity of candidate ceramic pebble beds for DEMO blanket designs and ITER breeding blanket design. The authors previously reported the preliminary result of the pebble bed thermal conductivity for Li₂O, Be and Al₂O₃. This paper presents the result of Li₂TiO₃, Li₂ZrO₃ (1 mm diameter) from CEA, and Li₄SiO₄ (0.25 - 0.63 mm diameter) from FZK.

Observation was compared to the correlations, SZB model and HM model. Contact area fraction was obtained by correlation fitting, of which the value is 4.9×10⁻³ for Li₂TiO₃, Li₂ZrO₃ (the same value as Li₂O) and 1×10⁻⁶ for and Li₄SiO₄.