Refractory Metal Wicks for Extended Lifetime in AMTEC Power Systems

51029-98-I Refractory Metal Wicks for Extended Lifetime in AMTEC Power Systems--Creare, Inc., Etna Road, P.O. Box 71, Hanover, NH 03755-0071; (603) 643-3800 Dr. Michael G. Izenson, Principal Investigator Mr. Robert A. Hickin, Business Official DOE Grant No. DE-FG02-98ER82559 Amount: $74,955 Alkali Metal Thermal to Electric Conversion (AMTEC) is a key technology for radioisotope-heated power systems planned for spacecraft missions to the outer planets or high-radiation Earth orbits. AMTEC power converters need internal wick structures comprised of evaporator, artery, and condenser components to circulate liquid sodium using capillary forces. However, there is no existing technology to fabricate wicks that can operate at high temperature for long times during these missions. The objective of this project is to develop wicks for AMTEC power converters that are micromachined from refractory metals. These micromachined, capillary wicks will: (1) be fabricated from refractory metals to achieve a 15-year lifetime at the high operating temperatures of the alkali metal cells, (2) be micromachined with small capillary features (2-3 micron dimensions) for high capillary head and operation at temperatures from 1100-1200 degrees Kelvin, and (3) operate with a low temperature difference between the heat source and the evaporation site for good thermal control. In Phase I, refractory metals will be bonded in porous and foil forms, capillary features will be micromachined into the structure using a laser, and the performance (capillary head and permeability) of the evaporator will be evaluated. Commercial Applications and Other Benefits as described by the awardee: The micromachined capillary wick benefits DOE and NASA by enabling spacecraft radioisotope power systems with a 15-year life and up to one-third the weight of current thermoelectric systems. This technology could also benefit DoD (Air Force) by enabling power conversion systems to operate in high-radiation orbits. Commercial applications include spacecraft thermal management systems, cooling for portable electronics, chemical sensor arrays and thermal batteries._