Development of Manufacturing Technology for High Purity Low Activation Vanadium Alloys

"Vanadium alloys are promising candidate low activation materials for structural components of fusion reactors. Establishment of industrial infrastructure is, however, remaining to be a critical issue because of lack of other large scale commercial application. In the present study, technologies for large scale manufacturing of high purity V-4Cr-4Ti alloy were developed by improving the present commercial production processes of vanadium metal, and optimizing alloying, plating, sheeting and wiring techniques. Efforts were focused on reducing carbon, nitrogen and oxygen impurities, which are known to deteriorate workability, weldability and radiation resistance of vanadium alloys. Especially, improvements were made in atmospheric control during calcination, aluminothermic reduction, vacuum arc remelting, and hot forging and rolling. A medium size (30kg) high purity V-4Cr-4Ti ingot was produced and designated as NIFS-HEAT-1. The specimens produced out of the ingot are being submitted to Round-robin tests by Japanese universities. Two larger ingots of 166kg in total weight were produced recently (NIFS-HEAT-2(A) and (B)). By these efforts, technology for fabricating large V-4Cr-4Ti alloy products with < 100ppm C, ~100ppm N and 100~200ppm O was demonstrated.