Liquid PbLi atomization in vacuum for tritium and heat recovery

摘要

The feasibility of liquid metal atomization in vacuum is studied by analysis and verified by experiment. Simultaneous tritium and heat recovery in vacuum from liquid lithium–lead (PbLi) has been previously proposed, where hot and tritium–rich PbLi is transformed into small droplets in vacuum, with the tritium then released by advection and the heat radiated away. Both mechanisms aimed to reduce the tritium permeation and membrane corrosion. The key hurdle is the atomization of liquid metal in vacuum by a large diameter nozzle. Conventional sprays function in air or other gases but not in vacuum. Therefore, an instability is applied that occurs at the velocity inflection in a parallel flow. The velocity inflection is generated by superimposing rotation on a liquid jet with a dedicated swirl nozzle. This can function in vacuum. An experiment using a low–temperature melting alloy (GaInSn) is performed in vacuum, using nozzle diameters of 0.7 mm, swirl angles 67°, and flow velocities of 3 and 5 ms−1. The instability that arises when using GaInSn at room temperature resembles that of PbLi at 400–500 °C, can be used as a proxy. The observed mean droplet Feret diameter was 0.31 mm at 3 m/s jet velocity and 0.23 mm at 5 m/s. These results support the feasibility of small droplet formation from a large diameter nozzle in vacuum. Further experiment must be performed to fully verify the droplet formation and proposed tritium and heat extraction method.