Experimental and numerical analysis of thermoelectric magnetohydrodynamic driven liquid lithium flow in open channels for fusion applications

Controlled fusion;liquid lithium;thermoelectric Magnetohydrodynamics;plasma facing component

Xu, Wenyu

关键词: Controlled fusion;    liquid lithium;    thermoelectric Magnetohydrodynamics;    plasma facing component;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/78620/XU-DISSERTATION-2015.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The concept of using molten metal as a plasma facing material (PFM) has been widely considered, and liquid lithium, among many choices, has attracted a lot of research interests in recent years. Compared to the traditional solid plasma facing component (PFC) a liquid lithium PFC may effectively lower the erosion and thermal stress while transferring heat and prolonging the lifetime limit of the PFCs. The liquid lithium surface can also suppress the hydrogen isotopes recycling and absorb the impurities in fusion reactors. The Lithium/Metal Infused Trench (LiMIT) concept successfully demonstrated that the thermoelectric effect can drive liquid lithium flow within horizontally placed metallic open trenches when an external magnetic field is transverse to the trench walls. Experiments at the University of Illinois have yielded experimental lithium velocities of 0.22±0.03 m/s under a magnetic field of 0.059T, and a similar experiment on HT-7 tokamak measured 0.037±0.005 m/s lithium flow velocity. Experiments and simulations have been performed to investigate this type of thermoelectric driven lithium flow in open trenches and the relation between different parameters such as external heat flux, magnetic field, cooling rate, trench geometry, etc.The application of this concept for fusion reactors has been twofold. One application is to use this concept for a flowing liquid lithium divertor. The trenches can be placed at the bottom of the tokamak along the poloidal direction so that lithium can be driven by the toroidal field to flow across the strike point. Experiments have been done on Magnum-PSI and DeVEX to investigate the plasma-lithium surface interactions for this thermoelectric driven trench flow. Lithium flows at the velocity that is calculated from the theory while some phenomena, such as lithium dry-out and lithium ejection, will need further investigation. Another application is to build these trenches on the inner wall to use flowing lithium as a plasma facing surface, which requires the lithium to flow along an arbitrary angle. Capillary force within the narrow width trenches is utilized to achieve this goal. The pumping effect from the thermoelectric force is expected to overcome the gravity and drive the lithium flow. A new LiMIT design with narrow vertical trenches was manufactured, and this type of flow was proven in experiments.