​Preliminary steady state and transient thermal analysis of the new HCPB blanket for EU DEMO reactor

•Thermal analysis is presented for the first time for the new HCPB blanket of the updated EU DEMO.•Transient thermal behavior under DEMO pulsed operation is reported for the first time for a solid breeder blanket concept.•Transient Ex-VV LOCA is reported for the first time with detailed finite element model for a solid breeder blanket concept.•Sensitivity analysis of thermal contact conductance of pebble-wall on blanket temperatures is presented for the first time.

This paper reports the thermal analyses of a new version of the Helium Cooled Pebble Bed (HCPB) blanket developed in Karlsruhe Institute of Technology (KIT) for the updated European fusion DEMO reactor. The blanket thermal behavior under DEMO typical pulse operation has been investigated, which serves as input to the structural analyses. The impact of thermal contact conductance between pebble beds and wall on blanket temperatures has been analyzed. The result shows that the thermal contact conductance has a sensitive influence on the temperature of Be pebble bed while exerts a limited influence on that of lithium orthosilicate pebble bed and EUROFER. The lack of contact may cause a local overheating of the Be pebbles, hindering the tritium extraction capability of the purge gas. The transient thermal analysis of the blanket after ex-vessel loss-of-coolant accidents has been studied, finding the FW will not melt under assumed conditions. The analysis of two soft plasma shutdown schemes after Ex-VV LOCA suggested that non-disruptive plasma shutdown should be as quickly as we can manage to reduce the high temperature reaching on the FW.