Multi-dimensional numerical analyses for the IFMIF target jet flows

The characteristics of liquid lithium (Li) plane jet target flowing with free surface along a concave wall were studied using a multi-dimensional thermal-hydraulic code, FLOW-3D, as part of the design activity of the International Fusion Materials Irradiation Facility (IFMIF) that started in February 1995. The IFMIF will provide high flux, high energy (∼14 MeV) neutron irradiation field for testing and development of low-activation and damage-resistant fusion materials by deuteron-Li reaction in the target. The Li target flows at high velocity (≤ 20 m/s) in vacuum, and should adequately remove the intense deuteron beam power (≤ 10 MW). The two-dimensional hydraulic analyses of the flows around the exit of contraction nozzle to form the jet clearly showed the mechanism how the depth-wise velocity profile develops in the jet. The pressure distribution in the nozzle was found to be influenced by a depth-wise static pressure distribution developed in the jet on the concave back-wall, and to accelerate the flow near the free surface but decelerate near the back-wall. The results agreed well with the data obtained from water simulation experiments. Furthermore, effects of three-dimensional convection due to high-temperature region after beam irradiation in centrifugal force field was clarified by means of two-dimensional calculations. The temperature rise at the jet free surface was found too small to cause any thermal instability in the target flow. (author)