Thermal-hydraulic design of a DCLL breeding blanket for the EU DEMO

Abstract

The thermal-hydraulic design of the breeding blanket, as the main thermal source for power conversion,reveals itself as a key issue to counteract the influence of the foreseen low overall plant availability on the cost of electricity. In the case of the Dual Coolant Lithium-Lead (DCLL), the decreased contribution of helium (non-breeding coolant) as thermal source in comparison with lithium-lead (breeding coolant) presents clear advantages, like less dependence on the long-term availability of He and lower recirculating power (recompression). The short operational range of temperature (300–550◦C) imposed by the use of RAFM steel is handled by adopting the Multi-Module Segment concept. This allows lower PbLi velocities by arranging in parallel the circuits of different modules. In consequence, the magnetohydrodynamic pressure drop and corrosion rates may be diminished. On the other hand, the high Péclet numbers validate the use of simpler computational codes to couple thermally both coolants, taking advantage of assuming that the heat transfer between the structure and the fluids is one-dimensional. A thermal-hydraulic one-dimensional code (PLATOON) has been developed for sensitivity analyses. The paper also addresses an assessment of the cooling of the radial stiffening plates and a preliminary study of the effects of the high heat generation gradient in the front poloidal PbLi channels.