A possible test procedure for thermionic fuel elements

Thermionic fuel elements (TFE) are thermionic energy converters (TEC) combined with a nuclear charge. TFEs are meant to be power sources on deep space missions and other purposes where solar energy is not usable at all, or the power level available from the sun is too low. A TFE consists of two coaxial metal tubes with a small space in between which is the interelectrode gap (IG). The IG contains a vapor of metallic cesium. This is the TEC unit. The heat energy required to heat the emitter is taken from a nuclear charge, often uranium dioxide. If the emitter is the inner tube and the collector is the outer tube, the uranium dioxide is located inside the inner tube of the TEC. When the uranium dioxide is inactivated it is rather harmless to handle. When the reaction has been initiated, the core becomes highly radioactive. Thus, it is not a preferable method to test the TFEs on Earth by starting the reaction. When testing TFEs, the nuclear charge located in the middle of the TFE is replaced with an electric heater element.