Design of a core-length thermionic fuel element for electrical heating

Abstract

This paper describes the design of an electrically heated version of a core‐length Thermionic Fuel Element (TFE) with advanced features, as is suggested by the designation Advanced Thermionic Inititative (ATI). The advanced features include a high‐strength emitter structure to be fabricated by Space Power, Incorporated. This structure consists of a cylindrical emitter, 15 mm diameter and 254 mm long of Chemically Vapor Deposited (CVD) tungsten, reinforced with tungsten‐hafnium carbide wire wound over a CVD tungsten core with additional CVD tungsten incorporating and bonding the wire into the emitter. The emitter surface is CVD tungsten, deposited from tungsten chloride resulting in the desirable crystal orientation of 〈110〉. It is possible to design a reactor with core‐length TFEs so that it can be electrically tested prior to fueling. The program is focussed on the design and fabrication of a single core‐length TFE with current collection at both ends which will be tested in a reactor. In parallel with this effort is the design, fabrication, and testing of an unfueled, electrically heated prototype. The intent is to make the electrically heated converter as similar as possible to the fueled one, while providing for accurate emitter and collector temperature measurement.