Design, fabrication and testing of a helium cooled module

Helium cooling has been shown to be very attractive from safety considerations as a coolant for ITER. However, there is a concern that use of helium will result in large manifolds and large pumping power. The purpose of this task was to design, fabricate and test a helium cooled divertor module for ITER relevant heat flux conditions. The General Atomics divertor module was designed for 10MWm-2 and the width and length were selected such that the module could be tested in the helium loop and electron beam facility at Sandia National Laboratory, Albuquerque, NM. Design analysis shows that the required pumping power can be reduced by a factor of 45 by using heat transfer enhancement associated with extended surfaces. This analysis resulted in a module with macro fins of 1mm pitch and 0.4mm thickness. The module was fabricated from dispersion strengthened copper by an electric discharge machining process. It had a heat flux surface 25mm wide and 80mm long. The module was tested at Sandia National Laboratory, confirming the desing predictions. At the highest heat flux of 10MWm-2, the pumping power required was less than 1% of the power removed, and the peak surface temperature was about 400 C. (orig.)