Measurement of thermal conductivity of Li2TiO3 pebble bed by laser flash method

Highlights: • The thermal conductivity of Li₂TiO₃ pebble bed has been successfully measured by the laser flash method. • The thermal conductivity of Li₂TiO₃ pebble bed until 500 °C increased with increasing measuring temperature. • The thermal conductivity of Li₂TiO₃ pebble bed at more than 500 °C was saturated to 1.3 W/m/K. • The specific heat and thermal diffusivity of Li₂TiO₃ pebble bed were adopted up to 700 °C due to chemical reaction and pebble connection. -- Abstract: In order to verify the performance and safety of the solid-type breeding blanket concept, the thermal conductivity of the pebble bed is required as an essential parameter for design and analysis of the blanket. The hot wire, hot disk, guarded hot plate, and laser flash method are considered as measurement technique for the thermal conductivity of pebble bed. This study aims at the provision of the thermal conductivity of Li₂TiO₃ pebble bed, which is one of the candidates for tritium breeder material in the solid-type breeding blanket. The laser flash method was adopted due to its advantages compared with other methods, such as high accuracy and repeatability, easy sample preparation, absolute measurement technique, and so on. In this method, the thermal diffusivity is directly measured by the laser flash system, and then the thermal conductivity is obtained by multiplying density and specific heat to the measured thermal diffusivity. The thermal conductivity of the Li₂TiO₃ pebble bed with packing factor of 57% increased with increasing temperature up to 500 °C and was saturated to 1.3 W/m/K at more than 500 °C.