Conceptual design of a He-cooled divertor with integrated flow and heat transfer promoters. (PPCS subtask TW3-TRP-001-D2) Part II: Detailed Version

This report represents a summary of our knowledge after little more than one year of development of a helium-cooled divertor. The design goal is to reach at least 10 MW/m 2 at a reasonable pumping power for a fusion powerplant operating under DEMO conditions. In the first part, design requirements for the divertor are given and the current design using low-activation materials is described. In the second part, materials choice and promising tungsten alloy materials are pointed out. In view of the operation temperature window defined, materials choice for the divertor components is limited, i.e. tungsten for the thermal shield in the form of small tiles, W-1%La 2 O 3 for the thimble, and high-temperature ODS for the back bone structure. To broaden the operating temperature window of the divertor for obtaining a larger safety margin in the design, further development of tungsten alloys as thimble material is required. Promising methods (EDM, ECM and PIM) are identified for the fabrication of pin and slot arrays from tungsten, which need to be further developed. In the third part, computational fluid dynamics (CFD) analyses and thermomechanical finite element (FE) simulation calculations are covered. Comparisons of the pressure loss calculated by the CFD programs with first results of the pressure loss measurement performed at EFREMOV are made, the results are discussed. FE simulations revealed opportunities for the improvement of the design. The last part deals with the planning of experimental devices to confirm the theoretical findings. To validate the CFD programs, helium experiments are planned to be performed in the helium blanket test loop HEBLO at FZKIIMF III in the middle of 2004 using a single finger test mock-up of 10:1 in scale. For the high-heat-flux tests, a large helium loop is planned to be constructed at the EFREMOV Institute in St. Petersburg, Russia. Planning and specification of the experiment programmes are under way. The overall results as presented by this study confirm that the investigated helium-cooled divertor concept HEMPIHEMS has a sufficient potential for resisting the specified heat load of 10 MW/m 2 at a reasonable pumping power. The concept is feasible.