Development and fabrication of ITER divertor cassette body

The ITER divertor cassette body is a large (>20 tonne) stainless steel structure that supports the plasma facing components (PFCs), delivers cooling water to them, and provides shielding for the vacuum vessel and magnets. It is also required to withstand electromagnetic loads and route cooling water through itself to remove nuclear heating. It is intended to be a full life component, accommodating several sets of PFCs for the life of ITER. The use of hot isostatically pressed (HIPped) castings for this component is under development by the US Home Team. HIP eliminates porosity due to shrinkage, greatly enhancing the reliability of castings. Because the size of the cassette body exceeds that of the largest HIP vessel in the world, the body is made up of segments which are welded together. Routing of water cooling in the body is accommodated by machined-in channels with welded-on cover plates. Several manufacturing development efforts are underway; including casting design and fabrication, segment welding, and cover plate welding. Current progress, results, and future plans are discussed.