Merits of the refractory metals single crystals in application to the TFE [thermionic fuel element]

Development of a thermionic fuel element (TFE) with a long-term service life and a high electric power requires a substantiated choice and, in some cases, production of modern structural materials having improved operating characteristics. A number of such investigations, including material-scientific, technological and calculated-and-engineering developments have been performed. A number of modern structural materials on molybdenum, tungsten and niobium single-crystal bases have been developed and introduced into the TFE designs in the course of this work. This report covers the results of experimental and calculated investigations justifying the advantages of the above materials over similar polycrystallines. Usage of the single-crystal materials as a TFE part is shown to: increase the specific electric power by a factor of 1.5-2; provide geometric emitter stability for 10-year service life realization; reduce fuel component flow into the interelectrode gap through the emitter by 2 orders of magnitude and provide electrical output parameter stability during the service life; and provide normal operation of the elements of the gas fission product removal system