Fast Hybrid Thermionic Blankets with Actinide Waste Fuel

Abstract

Basic performance analyses of a fast thermionic blanket driven by a deuterium-tritium fusion reactor with a wall loading of 2.25 MW/m2 (1014 incident neutron/cm2ṡs) is discussed. The basic thermionic element has been evaluated with some modifications from the German Incore-Thermionic-Reactor Project.During this study, highly enriched UO2 fuel is replaced by the following actinide waste materials:1. 244CmO22. (241AmO2 + 243AmO2) corresponding to the isotopic composition of the nuclear waste materials produced in light water reactors3. natural UO2.The calculated high emitter heating values P for converters with 244CmO2 as nuclear fuel are adequate for efficient thermionic conversion, P > 90 W(thermal)/cm2. Those values with AmO2 fuel are also still in the range of interest [P > 40 to 50 W(thermal)/cm2] whereas they are rather low for thermionic hybrid blanket with natural uranium [P = 15 to 20 W(thermal)/cm2].With the incorporation of a Li2O block beyond the thermionic region, a self-sustaining tritium production will be guaranteed.The main disadvantage of a thermionic blanket remains the high-production costs of the thermionic elements so that they have to compete with the high overall system efficiency of a thermionic blanket for its ultimate feasibility.