THERMAL-RADIATION IN GAS CORE NUCLEAR-REACTORS FOR SPACE PROPULSION

A diffusive model of the radial transport of thermal radiation out of a cylindrical core of fissioning plasma is presented. The diffusion ap proximation is appropriate because the opacity of uranium is very high at the temperatures of interest (>3000 K). We make one additional sim plification of assuming constant opacity throughout the fuel. This all ows the complete set of solutions to be expressed as a single function . This function is approximated analytically to facilitate parametric studies of the performance of a test module of the nuclear light bulb gas-core nuclear-rocket-engine concept, in the Annular Core Research R eactor at Sandia National Laboratories. Our findings indicate that rad iation temperatures in range of 4000-6000 K are attainable, which is s ufficient to test the high specific impulse potential (approximately 2 000 s) of this concept.