Technical Accomplishments of the Thermionic Fuel Element Verification Program

Abstract

The Thermionic Fuel Element Verification Program (TFEVP) was created to demonstrate the technological readiness of a Thermionic Fuel Element (TFE) suitable for use as the basic element in a thermionic reactor having an electric power output in the 0.5‐ to 5‐MWe range and a full‐power life of seven years. The TFEVP has made significant progress in developing components capable of withstanding the required neutron fluence (4 × 1022 n/cm2, E > 0.1 MeV) and the required burnup (5.3%). Technology developed under the TFEVP also supports the 5‐ to 40‐ kWe thermionic systems currently of interest to the Strategic Defense Initiative Organization and the United States Air Force. The fast‐neutron flux in certain 5‐ to 40‐kWe systems is nearly an order of magnitude less than that in 0.5‐ to 5‐MWe systems. Component technology that has been developed for 0.5‐ to 5‐MWe systems will thus be suitable for use in long‐life, high‐performance, 5‐ to 40‐kWe systems. Components that are being developed by the TFEVP include insulator seals, sheath insulators, fueled emitters, cesium reservoirs, and interconnective TFE components. In addition, the TFEVP has created a preliminary 2‐MWe‐system design and has evaluated converter performance under various conditions. Six integrated TFEs have also been tested. The TFEVP has encountered and surmounted problems in developing and testing long‐life TFEs. The emphasis of the US thermionic reactor development effort has shifted to the development of a 40‐kWe thermionic space nuclear power supply. The TFEVP will be closed out by the end of fiscal year 1994, with the closeout optimized for yielding the maximum overall program benefit‐to‐cost ratio. Information gained during the closeout will be very useful to the development of 40‐kWe and other thermionic systems.