Influence of plate material on the contact strength of Li4SiO4 pebbles in crush tests and evaluation of the contact strength in pebble–pebble contact

Lithium orthosilicate (Li4SiO4) pebbles are considered to be a candidate as tritium breeder in the helium cooled pebble bed (HCPB) blanket. Their contact strength is of concern since they might be crushed in the blanket under thermomechanical load. Crush tests for single pebbles are carried out to evaluate their strength. In these tests, single pebbles are crushed by a pair of parallel plates. In this way, the crush load, i.e., the maximum contact force between pebble and plates before failure of the pebble occurs, can be obtained. In this study, the influence of the plate material used in the crush tests on the crush load is investigated. Single Li4SiO4 pebbles are crushed by plates made of aluminum alloy (AL) and tungsten carbide (WC), respectively. Two corresponding crush load distributions are obtained. A probabilistic strength model is proposed to explain the influence of the plate material. Moreover, this model will be used to predict the contact strength of pebbles in pebble–pebble contact. The pebble–pebble contact strength can be used to investigate the influence of pebble failure on the thermomechanical response of the pebble beds.