Thermal fatigue of HIPed W/Cr–bronze divertor small scale mock-ups

Thermal fatigue is one of the key factors governing the lifetime of the divertor plate. Tungsten is a promising candidate to cover the surface of the divertor plate in the design of the international thermonuclear experimental reactor (ITER). The W/Cr–bronze divertor small scale mock-ups were manufactured by hot isostatic pressing (HIPing) technique. Thermal fatigue tests of W/Cr–bronze divertor mock-ups have been carried out by an electron beam facility. The mock-ups were tested under a cyclic surface heat flux of 9 MW m−2 for 1000 cycles. The electron beam was loaded on the mock-up surface for 20 s and unloaded for 20 s, alternately. The flow rate of water coolant was 0.1 L s−1. The 0.3 mm diameter NiCr–NiSi thermocouples were used to monitor the temperature distribution of the mock-up. It was found that the maximum temperature of the tungsten surface was about 400 °C. The saturated temperature at the joint of tungsten and Cr–bronze was 160 °C. The surface and the W/Cr–bronze joint of the mock-up did not show any damage during the thermal fatigue test up to 1000 cycles. A critical cooling flow rate Lc exists under a certain heat flux for a certain cooling system. The agreement between the experimental results and calculated temperature distributions was good.