Preliminary thermo-mechanical assessment of the Top Cap region of the Water-Cooled Lead-Ceramic Breeder Breeding Blanket alternative concept

The Water -Cooled Lead Lithium (WCLL) and the Helium -Cooled Pebble Bed (HCPB) Breeding Blanket (BB) concepts are the two candidates currently poised to be chosen as the driver blanket for the EU DEMO reactor. Nevertheless, new variants are emerging with the aim of overtaking the potential showstoppers arisen during the WCLL and HCPB BB pre -conceptual design phase. Then, an intense campaign of exploratory studies has been launched in EU to investigate the potential performances of such alternative concepts. Among them, the Water -Cooled Lead -Ceramic Breeder (WLCB) BB concept is one of the most promising. It has been conceived as a trade-off (i.e. an hybrid concept) between WCLL and HCPB BB concepts, trying to take and integrating the best features of both. Since in the reference WCLL geometric layout the Top Cap (TC) region was identified as particularly critical from thermal and mechanical standpoints, so requiring specific design studies, also in the WLCB conceptual design activities a dedicated campaign of analysis has been necessary to preliminarily size the TC region components. Hence, in this paper, the preliminary thermo-mechanical assessment of the TC region of the WLCB BB alternative concept is presented. First, an initial geometric layout has been set-up on the basis of the main features of the reference WCLL BB TC region. Then, thermal analysis under nominal conditions has been performed and the results have shown that modifications were necessary to ensure the compliance with the thermal requirements of the structural material. Finally, once obtained an acceptable geometric layout, mechanical analyses were carried out in order to verify the fulfilment of the RCC-MRx structural design criteria, also considering an off -normal load case. The results showed that this variant is very promising in terms of structural behaviour, whereas further design iterations are necessary to lower the temperature of the breeder zone.