Development of Uranium Dioxide - Tungsten Cermet fuel Specimens for Thermionic Applications

The Lewis Research Center of the National Aeronautics and Space Administration initiated a project at Battelle Memorial Institute for the purpose of fabricating clad fuel pellet containment vessel assemblies. These assemblies house clad fuel pellets containing enriched fuel. Irradiation studies of these assemblies in the NASA Plum Brook Reactor will provide data required for the desigi of thermionic converter reactors being considered by NASA. Three major objectives were defined at the initiation of this project at Battelle. These were (1) to provide containment vessel assemblies for irradiation studies, (2) to identify the best fuel dispersion/cladding combination for the fueled pellets, and (3) to identify and optimize the most promising fabrication technique to the extent necessary to provide reproducible specimens. In addition to these major objectives, other goals were defined in relation to supporting studies required for the successful conclusion of this program. The approach for accomplishing these objectives involved the cooperation of various research and research support groups at Battelle. These groups contributed to the overall program by involvement in the following areas: (1) Preparation or procurement of various types of UO{sub 2} fuel particles; (2) Application of tungsten coating to the fuel particles; (3) Development of various powder-consolidation techniques for the fuel form including use of explosive methods and hot isostatic pressing; (4) Selection and evaluation of high-temperature claddings for the fuel form; (5) Development of techniques for cladding application to the fuel form; (6) Evaluation of candidate systems by thermal cycling; (7) Fabrication of irradiation containment vessels and the associated components; and (8) Conduction of appropriate supporting studies associated with welding and brazing of the containment vessel components. The objectives of this program were accomplished to the extent that two clad fuel pellet containment vessel assemblies were completed and forwarded to NASA for irradiation testing. In conjunction with this effort, a compatible fuel-cladding system was developed for the clad fuel pellet as well as a fabrication process. In addition'to the accomplishment of these major goals, other valuable information relating to the fabrication and assembly of the containment vessel components was developed