Design activities toward the achievement of the conceptual phase of the EU-TBM sets

Abstract

Europe is developing two reference tritium breeder blanket concepts that will be tested in ITER under the form of Test Blanket Modules (TBMs): the helium–cooled lithium–lead (HCLL) which uses the liquid Pb–16Li as both breeder and neutron multiplier and the helium–cooled pebble-bed (HCPB) with lithiated ceramic pebbles as breeder and beryllium pebbles as neutron multiplier. Both concepts are using the EUROFER reduced activation ferritic–martensitic steel as structural material and pressurized helium technology for heat extraction. In view of the conceptual design review, design activities of the TBM sets have been focused on specific areas. The convergence of TBMs design, developed in their pre-conceptual phase by different European Fusion laboratories, has been sought in order to optimize fabrication and maintenance in ITER port #16. The structural strength of the helium back manifold of both TBMs is now based on the HCLL stiffening rod concept proposed in 2010. Through iterations between the nuclear analyses and design, the radiation shield design reaches a good compromise between its shielding performances versus manufacturing. A shield-to-TBM attachment has been implemented which complies with constraints related to thermal expansion under operating conditions and mechanical strength to handle dynamic loads such as major disruptions and seismic event. A full set of thermomechanical, hydraulic and structural analysis of the TBM sets has been carried out. They cover the loads selected as design drivers in the conceptual phase along with exploration of operational domain in terms of helium cooling conditions versus RCC-MRx code criteria compliance. The analysis results show that thermal loads are the main design driver for most of TBM sub-components. Pressure loads are also a design driver for the TBM stiffening grids under in-TBM loss of coolant accident. From the analyses carried out for the shields, the most demanding scenario has been demonstrated to be the baking mode. For these internal pressure loads, the capacity checks carried out have demonstrated the feasibility and potential of the shield design proposed.