Aspects of dimensional control during manufacture of bronze self-lubricating bearings: J.P. Lagier et al (University of Paris, France)

Abstract

The tested divertor targets were designed by the NET Team with emphasis on a high overall melting temperature, which is attractive for off-normal operating conditions, providing a wide margin in passive safety. The mock-up samples were manufactured by Metallwerk Plansee. The high heat flux experiments were performed in the Electron Beam Test System of Sandia National Laboratories, the testing parameters were chosen to match NET/ITER requirements. The power density of electron beam testing was increased stepwise up to 14 MW/m2, the loading time was adjusted to reach steady-state temperature conditions – pulses of up to 500 s were applied. In addition the loading procedure was observed and recorded with an on-line diagnostics system. Numerical methods using known materials data of the refractory metals and the carbon armor were applied to estimate the general thermal response of the test pieces. The excellent agreement with the observed surface and bulk temperatures as well as the good resistance to heat fluxes up to 12.3 MW/m2 is rather promising for an application in future fusion devices. The observed surface temperature for the CC armored target was 1000°C at 6 MW/m2, and 2400°C at 14 MW/m2. However, for some CC-tiles an increased surface temperature was detected after continued loading at heat fluxes between 12.3 and 14 MW/m2. After 1000 loading cycles applied on a graphite tile brazed atop a heat sink of TZM/Mo.41Re neither a visible damage nor a change in the thermal response was observed; the steady-state surface temperature ranged between 1000 and 1050°C.