Sonic cesium supply for bi-modal thermionic reactors

Abstract

Recently proposed bimodal thermionic nuclear space power systems are attractive due to the benefits of the dual mode of operation. One of the key technologies that needs to be developed is a reliable cesium source for the thermionic converters. Significant quantities of hydrogen will permeate into the interelectrode gap of the converters during the propulsion mode of operation. This hydrogen must be removed from the interelectrode gap to allow efficient operation of the converters. Hydrogen pressures in unvented thermionic systems could exceed one atmosphere or more in less than one hour of operation, while detrimental effects have been observed with pressures of only 0.001 atmosphere. A Sonic Cesium Source (SCS) was designed to continuously sweep large quantities of contaminate gases from the interelectrode gap. A proof-of-principal device was designed and fabricated, based on the SCS conceptual design. The proof-of-concept device used water as the working fluid, and purged hydrogen from the system. The device incorporated the major features of the SCS, including maintaining pressures and temperatures in three different regions; returning condensate against a large pressure gradient; and venting non-condensible gas. The next major step is to demonstrate venting of hydrogen from a SCS operating with cesium.