Tungsten Alloy Divertor Concept with Helium Jet Cooling

Helium-cooled, refractory metal heat sinks are being considered for the divertor sections of several fusion energy reactors. One type of helium cooling, jet impingement, has shown promise for high heat flux applications. However, because of the small size of the units (1.5-2 cm), a large number of these heat sinks would be needed for the divertor section of a reactor. Recently, a mid-size helium-jet-cooled configuration, with good heat flux accommodation potential, has been designed. The system is comprised of concentric tungsten tubes in a ¿T-shaped¿ configuration. This project will advanced net-shape refractory-metal forming techniques to enable the fabrication of this improved helium cooled tungsten divertor concept. In Phase I, impingement-cooled and straight-bore tungsten heat sinks were fabricated and tested. Preliminary high-heat-flux testing demonstrated that a tungsten heat sink with helium-impingement cooling provided ~20% greater reduction in average surface temperature compared to a straight-bore tungsten heat sink under the same heat flux. In Phase II, a mid-size helium-impingement-cooled divertor configuration will be developed and fabricated to withstand heat fluxes up to 10 MW/m2. To determine the Phase II design, initial studies will be conducted to determine trade-offs between ease of fabrication, thermal induced stresses/strains, and thermal performance. Manufacturing techniques will be optimized and improvements will be thoroughly characterized using metallographic and material properties testing techniques. Commercial Applications and Other Benefits as described by the awardee: Compared to other helium cooling techniques, such as the porous heat exchanger configuration, the jet-impingement cooling method could significantly simplify the fabrication of helium cooled refractory metal heat sinks and improve long term reliability and performance. In fusion reactors, the technology would allow higher operating temperatures, which could result in increased power conversion efficiency. The techniques developed to produce the helium-jet-cooled tungsten divertor also should be applicable to such components as x-ray targets, crucibles for semiconductor crystal growth, rocket hardware, and wear and thermal protection coatings.