Experimental tests and thermo-mechanical analyses on the HEXCALIBER mock-up

Within the framework of the R&D activities promoted by European Fusion Development Agreement on the helium-cooled pebble bed test blanket module to be irradiated in ITER, ENEA Brasimone and the Department of Nuclear Engineering of the University of Palermo performed intense research activities on the modelling of the thermo-mechanical behaviour of both beryllium and lithiated ceramics pebble beds, which are envisaged to be used, respectively, as neutron multiplier and tritium breeder. In particular, at the DIN a thermo mechanical constitutive model was developed for both lithiated ceramics and beryllium pebble beds and it was successfully implemented on a commercial finite element code to analyze the experimental results of the ENEA test campaigns on TAZZA, HELICHETTA and HELICA mock-ups. The paper presents the preliminary theoretical–numerical study performed at the DIN to support the experimental investigations on the HEXCALIBER mock-up, a more complex test section set-up by ENEA to investigate the thermo-mechanical behaviour of mutually interacting pairs of beryllium and lithium orthosilicate pebbles beds. In particular, after the descriptions of the HEXCALIBER mock-up and its finite element model, the numerical predictions of temperatures and/or contact pressures in the pebble beds, in the structural materials and in the helium coolant are presented and critically discussed.