Exploratory thermo-mechanical assessment of a pin of the Helium Cooled Pebble Bed breeding blanket concept with a modular pin monoblock design for the EU DEMO nuclear fusion reactor

Abstract

The Helium-Cooled Pebble-Bed (HCPB) Breeding Blanket (BB) concept is one of the two candidates for the driver blanket of the EU-DEMO nuclear fusion reactor. It shall adopt gaseous helium at 8.0 MPa as coolant and tritium carrier together with solid tritium breeder and neutron multiplier. With the aim of overcoming the critical issues that emerged during the DEMO pre-conceptual design phase, potential HCPB BB design variants are under development in the frame of the DEMO R&D. Among them, the concept envisaging a modular pin monoblock presents the advantages of having all the functional materials contained in a pin structure and of avoiding the need for a first wall, remarkably easing manufacturing. Hence, in this work, a campaign of thermo-mechanical scoping analyses aimed at assessing the performances of this novel BB concept is presented. Starting from a previous thermofluid-dynamic assessment presented in another work, different geometric layouts have been assessed in view of the rules prescribed by the RCC-MRx structural design code. In particular, a multi-scale analysis has been carried out assessing, in a first phase, the global thermo-mechanical performances of the equatorial region of the Central Outboard Blanket segment moving, in a second phase, to the detailed structural analysis of the pin internals. The results obtained from the investigation of two promising geometric configurations have been quite encouraging, showing the conceptual feasibility of this potential HCPB BB variant, and thus paving the way for future and more accurate pre-conceptual analysis.