Fusion Science and Technology / Volume 56 / Number 1 / July 2009 / Pages 80-84
Divertor and High Heat Flux Components / Eighteenth Topical Meeting on the Technology of Fusion Energy (Part 1)
A He-cooled divertor concept for DEMO has been pursued at the Forschungszentrum Karlsruhe (FZK) within the framework of the EU (European Union) power plant conceptual study since 2002. The design goal is to remove a DEMO-relevant heat flux of 10 MW/m2 at least. The current reference concept HEMJ (He-cooled modular divertor with jet cooling) relies on impingement cooling with high pressure helium (10 MPa, 600°C). This modular design employs small tiles made of tungsten, which are brazed to a thimble made of W-1%La2O3. The W finger units are connected to the main structure of ODS Eurofer steel. Machining tungsten is a challenging task due to its hardness and brittleness. It was found that EDM (electrical discharge machining) induce micro-cracks on the tungsten surfaces. Cutting techniques like turning, milling, grinding and the use of cutting wheels (CBN (cubic boron nitride) or diamond) carry the hope for manufacturing divertor tungsten parts with a high and repeatable quality. Further machining techniques development like pressing of tungsten plates is in process. In this contribution the status of the fabrication technology especially the machining of tungsten divertor parts will be outlined and the potential of mock-up quality improvement shall be discussed.