Progress in the benchmark exercise for analyzing the lithiate breeder pebble bed thermo-mechanical behaviour

The Helium Cooled Pebble Bed (HCPB) Blanket is one of the reference concepts for the European Breeding Blanket Programme for DEMO. In the reference blanket module, alternate layers of lithiated ceramics and beryllium pebbles act, respectively, as tritium breeder and neutron multiplier. The thermo-mechanical behaviour of both the pebble beds and their performances in reactor relevant conditions are also dependent on the pebble size and cell geometries (bed thickness, pebble packing factor, bed thermal conductivity). Therefore, in the EU Fusion Technology Programme, several out-of-pile experimental test campaigns have been performed to determine these behaviours. Theoretical calculations have been also launched for the prediction of the thermal and mechanical performances of the pebble beds under different testing conditions. More recently, among the EU Associations involved in the ceramic breeder qualification, a benchmark exercise has been launched to select the pebble bed thermal mechanical constitutive models to be implemented in a FEM computer code. This paper describes the activities, carried out by ENEA and DIN, University of Palermo (I), for the first comparison with the results of the experiments carried out at HE-FUS 3 facility of ENEA Brasimone on the HELICA mock-up. The paper describes the test conditions and also presents the main experimental results and its first comparison with the theoretical calculations.