Thermo-mechanical evaluation of a water cooled high heat flux unit for the K-DEMO divertor

In a conceptual study of the Korean fusion demonstration reactor (K-DEMO), a water cooled divertor concept applying tungsten monoblock design was primarily considered. As an extension of the study, the purpose of this paper is to find out the design concept meeting the thermomechanical stability for a water cooled high heat flux (HHF) unit through the fluid structural interface (FSI) analysis. The target peak heat flux requirement of 10 MW/m2 and nuclear heating induced by neutrons are considered as heat loads on a HHF unit. In order to find the design concept satisfying the thermal requirement, operating within materials´ own maximum allowable temperature ranges, steady state thermohydraulic analyses were performed as varying design parameters such as the size of tungsten monoblocks, the thickness of reduced activation ferritic and martensitic (RAFM) tube, and the speed of water coolant. Then, thermal stress was estimated through finite element analysis considering the temperature distribution obtained from thermohydraulic analysis and a pressure boundary condition on the RAFM tube. Consequently, the design parameters in which an HHF unit can be operated as satisfying thermal and structural requirements are proposed through the parameter study.