Progress of Qualification Testing for Full-Scale Plasma-Facing Unit Prototype of Full Tungsten ITER Divertor in Japan

National Institutes for Quantum and Radiological Science and Technology (QST) reports progress of research and development of a full-tungsten (W) Divertor Outer Vertical Target (OVT) for ITER. Under a framework of a W divertor qualification program, QST manufactured 7 full-scale plasma-facing units (PFUs) as prototypes. Through the manufacturing, (i) all joint surfaces in four PFUs with a casted Cu interlayer successfully passed the ultrasonic testing (UT) and (ii) the profile tolerance of surface in target part of PFUs stayed within ± 0.25 mm. (iii) Moreover QST succeeded in demonstrating a durability for high heat flux (HHF) testing of the repetitive heat load of 10 MW/m2 × 5000 cycles and 20 MW/m2 × 1000 cycles in close collaboration with the ITER organization (IO-CT) and the Russian Domestic Agency (RFDA). These results demonstrated the capability of Japanese industry to produce the PFU of full-W ITER divertor to meet the technical requirements