Carbon Diffusion.
Abstract
In the STAR-C out-of-core space nuclear power system, heat is radiated from a graphite core onto the emitter/hot shoe of thermionic converters. Carbon evaporates from the surface of the core and condenses on the emitter/hot shoe. There is concern that this carbon may diffuse through the emitter/hot shoe, reaching the emitter surface. This may alter the work function of the emitter and degrade electrical output. In this work, a carbon source was placed directly facing an uncoated, chemical vapor deposition (CVD) polycrystalline tungsten specimen. The bare work function of the back side of the tungsten specimen (not facing the carbon source) was measured before testing. Both the carbon source and tungsten specimen were heated and a fluence of carbon was allowed to deposit onto the adjacent tungsten surface. Under accelerated conditions, a fluence corresponding to 255 days of operation, at the STAR-C system operating conditions, was deposited onto the tungsten specimen. Work function measurements of the back side of the tungsten revealed no detectable change in the bare work function.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1996
- Accession Number
- ADB219965