Development of Liquid Lithium Target of 7Li(p,n)7Be Reactions for Accelerator Based BNCT Irradiation System

摘要

A feasibility study of using a liquid lithium target was performed. The candidate configurations for the neutron generation target was adapted for the ~7Li(p,n) ~7Be assuming a proton beam which is 30 mm in diameter and with an energy and current of up to 3 MeV and 20 mA, respectively. The flowing film of liquid lithium was 0.5 mm-thick with 50 mm width and 50 mm length. The shapes of the nozzle and concave back wall, which creates a stable flowing film jet, were decided based on water experiments. The flowing film on the concave wall is a windowless type target. A lithium hydrody namic experiment was carried out to observe the liquid lithium flow behavior and to investigate the stability of the lithium target. The flowing film of liquid lithium was found to be feasible at temperatures below the liquid lithium boiling saturation of 342 degrees Celsius at the surface pressure of 1×10~(-3) Pa. Using a test liquid lithium circulating loop, it was found that a stable film flow on a concave back wall can be expected at a velocity of up to 30 m/sec. At present, proto-type lithium circulating loop for practical BNCT irradiation system was built and is under examination.