Fabrication of a He-cooled divertor module for DEMO reactor

One current design of the divertor for a fusion reactor like DEMO uses He-cooled thimble-like tungsten, which is covered by sacrificial tungsten tile. Each thimble has to be connected with a supporting unit made from ferritic steel. This paper describes the development of joining techniques between tungsten thimbles and steel supporting units. Paper also provides an evaluation of simple geometries up to more complex conical interlocks filled with cast copper. Four candidates tungsten alloys (WL10, W-single crystal, W–Cu composite and chemical vapour deposited (CVD) tungsten) were experimentally checked by ‘non-isothermal’ heating to characterize the thermal gradient in the range 600 °C (for joint) and more than 1000 °C (for thimble top) using a special testing procedure. Basing on the test results, several mock-ups were manufactured for future high heat flux testing in a helium loop.