Preparation Of Extremely Low Nitrogen Concentration Lithium By Fe-5at.%Ti Alloy Hot Trap

In the lithium loop of IFMIF (International Fusion Materials Irradiation Facility), the target value of the nitrogen concentration in lithium flow is designed to be <10 wt.ppm from the viewpoint of corrosion prevention. However, the optimum method for obtaining this extremely low nitrogen concentration lithium (<10 wt.ppm-N) has not yet been established. In this study, therefore, we aimed to investigate the hot trap method using Fe-5at.% Ti alloy grains and the nitrogen concentration measurement method for the extremely low nitrogen concentration in lithium. When lithium was handled in an argon atmosphere glove box (>99.9999 %), it was contaminated by nitrogen as an impurity of the cover gas. Therefore, the hot trap experimental pot sealed was placed in a vacuum exhaust glove box. In order to minimize nitrogen contamination, lithium sampling for nitrogen concentration measurement was carried out by scraping out lithium in a solid state. Then, nitrogen concentration was determined by the ammonia conversion method. As a result of the hot trap experiment under the above conditions, the nitrogen concentration in lithium was reduced from 43 to 10 wt.ppm by immersing Fe5at.%Ti grains (similar to 160 mu m) at 509 degrees C after 192 h, from 62 to 9.8 wt.ppm at 550 degrees C after 168 h, and from 65 to 9.9 wt.ppm at 557 degrees C after 144 h.