Experimental measurements for the effective thermal conductivity of pebble beds with uncertainty analysis

The lithium ceramic pebble bed is a vital functional component of solid blankets in fusion reactors to realize tritium breeding. The effective thermal conductivity of the lithium ceramic pebble bed is a key thermal property which has a significant impact on the design and analysis of the fusion blanket. An experimental platform including a test section and a helium loop was designed to measure the effective thermal conductivity. The test section was based on the principle of the hot wire method and the helium loop was designed to satisfy different experimental conditions. For the Li2TiO3 and the Li4SiO4 pebble bed, experiments were performed in the presence of stagnant helium at atmospheric pressure. An increase of the effective thermal conductivity was detected in the temperature range RT-400 °C and the results were compared with numerical results. For the binary glass pebble beds with different diameter ratios, experiments were performed at room temperature in the presence of stagnant helium and air. The effective thermal conductivity was found strongly dependent on the packing factor.