MANUFACTURING DEVELOPMENT OF LOW-ACTIVATION VANADIUM ALLOYS

General Atomics is developing manufacturing methods for vanadium alloy s as part of a program to encourage the development of low activation alloys for fusion use. The culmination of the program is the fabricati on and installation of a vanadium alloy structure in the DIII-D tokama k as part of the Radiative Divertor modification. Water-cooled vanadiu m alloy components will comprise a portion of the new upper divertor s tructure. The first step, procuring the material for this program has been completed. The largest heat of vanadium alloy made to date, 1200 kg of V-4Cr-4Ti, has been produced and is being converted into various product forms. Results of many tests on the material during the manuf acturing process are reported. Research into potential fabrication met hods has been and continues to be performed along with the assessment of manufacturing processes particularly in the area of joining. Joinin g of vanadium alloys has been identified as the most critical fabricat ion issue for their use in the Radiative Divertor Program. Joining pro cesses under evaluation include resistance seam, electrodischarge (stu d), friction and electron beam welding. Results of welding tests are r eported. Metallography and mechanical tests are used to evaluate the w eld samples. The need for a protective atmosphere during different wel ding processes is also being determined. General Atomics has also desi gned, manufactured, and will be testing a helium-cooled, high heat flu x component to assess the use of helium cooled vanadium alloy componen ts for advanced tokamak systems. The component is made from vanadium a lloy tubing, machined to enhance the heat transfer characteristics, an d joined to end flanges to allow connection to the helium supply. Resu lts are reported.