Development of ITER divertor plate with annular swirl tube and tungsten rods

Development of divertor high heat flux components is one of the key issues to realize fusion experimental reactors such as ITER. JAERI has been developing the divertor components to meet the ITER design. In the reference design of the ITER divertor, CFC monoblocks on a swirl cooling tube with pressurized water flow are adapted for the lower part of the vertical target. To increase reliability, an annular flow concept of the CFC monoblocks with concentric feed and return has been proposed and developed. A critical heat flux (CHF) testing has shown the no degradation of CHF of the annular swirl tube in comparison with the conventional swirl tube which indicates its applicability to the ITER divertor cooling. Large-scale vertical target mock-ups have been fabricated and tested in an ion beam test facility. The mock-ups have successfully withstood a heat load of 20 MW/m2, 15 s for more than 1000 cycles. Thus it is demonstrated that the vertical target with the annular tube can be applicable to the ITER divertor plate. For upper part of the vertical target, the W/Cu hot pressing method has been also developed to improve the reliability and to reduce the cost. Thermal cycle test was performed on the W/Cu hot pressing divertor mock-up to investigate the durability of the joining interface. As a result, the surface temperature has shown almost constant throughout the experiment, and no degradation of the thermal response was found through 3000 cycles at 5 MW/m2, which corresponds to the ITER operational conditions for upper part of the divertor. (author)