Ricerc@Sapienza

The breeding blanket is a critical component of a fusion reactor that involves the use of liquid metal (LM) as working fluid. One of the most challenging engineering issues in the blanket design is the necessity to account for the interaction between the electrically conductive LM and the magnetic field employed to confine the plasma. The LM is distributed to the blanket elementary cells composing the Breeding Zone (BZ) through a poloidal manifold. Breeder collectors are foreseen at blanket extremities to distribute it to and retrieve it from the BZ. From a geometrical point of view, the bottom outboard collector is the most complex, and it is where the 3D magnetohydrodynamic (MHD) effects are expected to contribute more to the pressure drops and flow distribution. The pressure drop increase, due to the MHD drag, is magnified when the channels are coupled with electroconductive walls. Moreover, there are considerable head losses located in correspondence with the connections between the manifold channels and the collector and near the collector feeding pipe, due to the 3D electric currents generated by velocity gradients in the stream-wise direction. In the framework of the development of the fusion reactor industrial demonstrator DEMO by the EUROfusion consortium, this project aims to investigate the 3D MHD flow numerically in complex geometrical elements, representing a simplified but realistic model of the bottom outboard collector and its connection with the spinal manifold. The main goals are the overall pressure drop estimate, the identification of the most relevant flow features, the evaluation of the 3D electric currents impact on the pressure drop and the study of electro-coupling phenomena between the channels including flow distribution. Parametric analyses on the position of the feeding orifice, the wall conductivity and the inlet velocity are performed to have a preliminary assessment of different breeding blankets concepts.