Thermomechanical behaviour of ceramic breeder pebble stacks for HICU

This paper reports on the thermomechanical behaviour of small pebble beds or pebble stacks in order to lay out irradiation test specimens. Uniaxial compression tests (UCTs) of the pebble stacks with relatively small diameters are performed at 27 and 800 °C i.e. the maximum irradiation temperature. The H/D ratio of the specimens influences the thermomechanical behaviour because of the friction between the pebbles and the steel tube. The results are compared with the thermomechanical data obtained from standard UCTs, which apply for larger pebble-beds. The outcome of the comparison will be used for the detailed design of the constrained pebble-beds in the high fluence irradiation. In addition, the compatibility between the ceramic breeder materials and the containment is studied. It has been shown that platinum has the best compatibility at 800 °C for both the lithium meta-titanate and lithium ortho-silicate ceramics.