Experimental Investigations on the Thermal and Mechanical Behavior of Single Size Beryllium Pebble Beds

For the next generation fusion reactors with a ceramic breeder blanket the use, as a neutron multiplier, of either a binary bed of large (≈ 2 mm) and small (≈ 0.1–0.2 mm) beryllium pebbles or a single size bed made of 1 mm or 2 mm pebbles is foreseen. The heat transfer parameters of such a binary pebble bed, namely the thermal conductivity and the heat transfer coefficient to the containing wall, have been investigated in the experimental devices PEHTRA and SUPERPEHTRA and have been reported in the companion paper at this workshop.¹ In the present paper the results of analogous investigations for the single size beryllium pebble bed are shown and equations are given to correlate the heat transfer parameters.