Design of an external-fueled thermionic diode for in-pile testing.

Description of an external-fueled thermionic diode suitable for in-pile testing in a research reactor. The active electrode area is 94 sq cm. The 10-in. long, 1.5-in.-OD emitter body is tungsten 2% thoria. The fuel is contained in six 0.4-in.-diam holes equally spaced about the 0.5-in. central emitter hole. The collector is niobium-1% zirconium. The expected diode performance is 6 W/sq cm at 2000 K. In addition to following the constraints imposed by the in-pile testing and the electrically heated performance mapping prior to insertion in-pile, the diode will have end configurations prototypical of those anticipated for a flow-through, NaK-cooled, external-fuel thermionic reactor.