HIGH CREEP STRENGTH THERMIONIC EMITTER

PERFORMANCE AND LIFETIMES OF THERMIONIC SPACE NUCLEAR POWER SYSTEMS ARE LIMITED BY DEFORMATION OF THE CHEMICAL VAPOR DEPOSITION-TUNGSTEN (CVD-W) EMITTER. THIS LIFE-LIMITING PHENOMENON IS ATTRIBUTABLE ALMOSTENTIRELY TO SWELLING OF THE NUCLEAR FUEL. HIGH STRENGTH EMITTER MATE-RIALS HAVE BEEN IDENTIFIED WHICH WOULD ELIMINATE EMITTER DEFORMATION AS A DESIGN CONSTRAINT. THE EMITTER BEING DEVELOPED IN THIS STUDY IS EXPECTED TO RETAIN ALL OF THE REQUIRED CHARACTERISTICS OF THE PRESENT CVD-W EMITTER: COMPATIBILITY WITH CESIUM AND NUCLEAR FUEL, THERMIONICEMISSION PROPERTIES, AND MATERIAL JOINING CHARACTERISTICS. THIS HIGH STRENGTH, LOW CREEP RATE MATERIAL IS ANTICIPATED TO HAVE A TESTING DATA BASED ON WHICH TO PREDICT PERFORMANCE. THE MATERIAL HAS BEEN SUCCESSFULLY FABRICATED IN ANNOTHER MATRIX MATERIAL (WHICH IS NOT SUITED TO THE THERMIONIC APPLICATION). IN THIS EFFORT, THE FEASIBILITY OF FABRICATING THE HIGH STRENGTH MATERIAL INTO A CVD-W MATRIX IN THE GEOMETRY OF INTEREST TO THERMIONIC SYSTEMS IS BEING ESTABLISHED. TUNSTEN METAL IS BEING VAPOR DEPOSITED ONTO A HIGH-CREEP STRENGTH WIRE REINFORCEMENT AND, SUBSEQUENTLY, METALLOGRICALLY EXAMINED TO DEMONSTRATE THE FABRICABILITY OF THE PROPOSED EMITTER CONCEPT. WHEN SUCCESSFUL, THE HIGH STRENGTH EMITTER WOULD ALLOW HIGHER EMITTER TEMPERATURES, WHICH IN TURN WOULD PRODUCE HIGHER POWER OUTPUT AND/OR LOWER SYSTEM MASS.