• WCLL
• Fusion
• Breeding
• Blanket
• DEMO
• Energy
• CFX
• CFD
• Tokamak
• Design

The conceptual design of Demonstration Fusion Power Reactor (DEMO) is developed under the leadership of EUROfusion Consortium Agreement with EU H2020 funds. The breeding blanket is a key nuclear component of Demonstration Fusion Power Reactor (DEMO), being in charge of the power extraction, the tritium fuel sustainability and the vacuum vessel radiation shielding. An attractive breeding blanket concept is the Water-Cooled Lithium-Lead Breeding Blanket (WCLL), which is considered a candidate option.

Starting from the experience exploited during previous studies, a new conceptual design has been proposed and is been developed as a multi-module box concept based on DEMO 2015 specifications. The layout of the module is based on horizontal (i.e. radial-toroidal) water cooling tubes in the Breeding Zone (BZ) and on PbLi flowing in radial-poloidal directions. Therefore, besides the caps zone, the central equatorial module is composed by 14 segments having the same geometry.

Within the framework of the DEMO R&D activities, a computational thermal and fluid-dynamic model is developed to investigate the thermal-hydraulic efficiency; to evaluate the temperature distribution in the structures and the thermal field and flow path in the breeding zone. Three-dimensional meshes are set-up, reproducing a toroidal-radial slice of the central equatorial module. It includes six breeder channels in the toroidal direction and one breeder cell in poloidal direction. Solid structures (EUROFER97 and tungsten) and fluid domains (PbLi and coolant) are considered, exploiting the ANSYS CFX (ver. 15.0) solver based on the volume finite method.

Different analyses are carried out changing the mass flow rate distributions in the cooling tubes; the first wall heat load addressing the module performance when limiting temperature conditions are considered and finally the tubes and baffle plate layout in order to optimize the thermal field in the module.

The first series of calculations highlighted where allowable limits are not met and possible criticalities in the PbLi flow paths (i.e. stagnant or low flow zone) giving hints for enhancements of baffle plate geometry and for the layout of the tubes in the breeding zone. The last simulation demonstrates reduced operating temperatures of PbLi and structures, about 30°C below the tolerable limits and enhanced flow rates and temperatures of coolant in the different arrays of the breeding zone.