Abstract
Liquid metal breeding blankets are extensively studied in nuclear fusion. In the main proposed systems, the Water Cooled Lithium Lead (WCLL) and the Dual Coolant Lithium Lead (DCLL), the liquid metal flows under an intense transverse magnetic field, for which a magnetohydrodynamic (MHD) effect is produced. The result is the alteration of all the flow features and the increase in the pressure drops. Although the latter issue can be evaluated with system models, 3D MHD codes are of extreme importance both in the design phase and for safety analyses. To test the reliability of COMSOL Multiphysics for the development of MHD models, a method for verification and validation of magnetohydrodynamic codes is followed. The benchmark problems solved regard steady state, fully developed flows in rectangular ducts, non-isothermal flows, flow in a spatially varying transverse magnetic field and two different unsteady turbulent problems, quasi-two-dimensional MHD turbulent flow and 3D turbulent MHD flow entering a magnetic obstacle. The computed results show good agreement with the reference solutions for all the addressed problems, suggesting that COMSOL can be used as software to study liquid metal MHD problems under the flow regimes typical of fusion power reactors.
Highlights
In the nuclear fusion framework, the breeding blanket is a key system devoted to power extraction, shielding and tritium production
Among the different designs of the blanket, in the Water-Cooled Lithium-Lead (WCLL) breeding blanket of DEMO [1] and in the WCLL test blanket module of ITER, the liquid, electrically conducting LiPb is adopted as working fluid to address the above-mentioned functions
Tritium transport mechanisms [3,4,5] are influenced by the magnetic field; a detailed solution of magnetohydrodynamics is necessary, and it is obtainable with 3D multiphysics models for the breeding blanket
Summary
In the nuclear fusion framework, the breeding blanket is a key system devoted to power extraction, shielding and tritium production. The intense magnetic field used in fusion reactors to confine the burning plasma has a strong influence on the flow behavior, producing a magnetohydrodynamic (MHD) effect. The presence of the external magnetic field produces an additional MHD pressure drop, and rougher MHD studies can predict the ∆p [2], other phenomena, such as turbulence and buoyancy-driven convection, have a drastic impact on blanket performance and require a deeper analysis. In the first problem, the non-isothermal condition is due to differentially heated boundaries, while in the second case, temperature gradients are produced by internal heat generation Both conditions are typical in breeding blanket systems, where strong temperature gradients and intense volumetric heat generation are present
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