Thermo-hydraulical and thermo-mechanical analysis of the HCLL-TBM breeding unit

The Helium Cooled Lithium Lead (HCLL) blanket is one of the two breeding blanket concepts under development in the European Union and for which Test Blanket Modules (TBM) are planned in ITER. The HCLL-TBM consists of a steel box reinforced by an internal grid with Breeder Units inserted in the modular array (cells) defined by the grid. In each BU, cooling plates are used to extract the heat from the breeder/multiplier (Pb-17Li). This paper presents the latest design of the HCLL-TBM according to the new dimensions of the space available for the module in the ITER equatorial ports. The performances of the proposed design are evaluated by means of detailed FE models of one BU and the corresponding box structure. The new models allow a better estimate of the heat recuperation effect between the different cooling elements, so that the coolant bulk temperature can be calculated along each flow path. As we show in the paper, this is necessary to achieve a correct design of the He cooling circuit. Detailed temperature and stress field distributions in each part of the structure have been obtained for nominal and accidental load conditions. The results of the FE calculations are analyzed with respect to thermal-hydraulics and thermomechanical stresses in order to verify the compliance with the established design criteria (maximum temperature in the structural material and SDC-IC rules). Also, the operating parameters are discussed in view of the DEMO-relevance of the proposed TBM design. Finally, possible improvements and modifications of the current design are proposed. (orig.)