HYDROGEN PERMEATION BARRIERS FOR BIMODAL REACTORS

BIMODAL SPACE NUCLEAR POWER SYSTEMS WHICH COMBINE BOTH THERMAL PROPULSION AND ELECTRIC POWER GENERATION CAPABILITIES IN A SINGLE INTEGRATED POWER AND PROPULSION PLATFORM HAVE RECENTLY EMERGED AS STRONG CANDIDATES FOR FUTURE MILITARY AND COMMERCIAL SPACE APPLICATIONS. FOR PROPULSION, THE REACTOR HEATS HYDROGEN WHICH IS EXHAUSTED THROUGH A NOZZLE TO PROVIDE PROPULSIVE THRUST. THERMAL ENERGY FROM THE REACTOR IS ALSO CONVERTED TO ELECTRICITY BY IN-CORE OR OUT-OF-CORE ENERGY CONVERTERS. ONE ISSUE OF CONCERN IN A BIMODAL SYSTEM IS THE POTENTIAL FOR HYDROGEN PERMEATION INTO ENERGY CONVERSION COMPONENTS. AT BIMODAL REACTOR TEMPERATURES, HYDROGEN WILL PERMEATE THROUGH THE REFRACTORY METAL STRUCTURES DEGRADING THE OPERATIONAL CAPABILITIES OF IN-CORE THERMIONIC CONVERTERS, OR HEAT PIPES USED TO TRANSMIT HEAT FROM THE REACTOR TO THE OUT-OF-CORE ENERGY CONVERTERS. THIS PROJECT WILL DEVELOP AND DEMONSTRATE A HYDROGEN PERMEATION BARRIER USING A TRILAYER ASSEMBLY WITH A THERMALLY CONDUCTIVE POROUS POWDER METAL LAYER BETWEEN TWO CONTAINMENT WALLS. HYDROGEN THAT PERMEATES THROUGH THE FIRST CONTAINMENT WALL IS VENTED FROM THE POROUS POWDER METAL TO THE VACUUM OF SPACE PRIOR TO PERMEATION INTO CRITICAL COMPONENTS. HYDROGEN PERMEATION RESISTANT COATING WILL ALSO BE EVALUATED.