Advanced Water Reactor Program. The second fuel loading for the EBWR is planned as ThO/sub 2/--UO/sub 2/. Some properties of ThO/sub 2/-- UO/sub 2/ systems are presented. Fast Power Breeder Reactor Program. The development of casting techniques for EBR-1, Mark III extrusion billet cores are described. The investigation of methods for the remote refabrication of irradiated reactor fuels was undertaken with the objective of designing, constructing, and testing techniques and equipment for the refabrication of EBR-II fuels. Advanced Engineering and Development. From observations amd photographs made during disassembly operations, and from chemical, metallographic, and density measurements, it was possible to reconstruct the probable physical structure of the core after the meltdown of the EBR-1 core. A boiling experiment was performed to give preliminary information as to whether thermal decomposition or volatility would complicate the use of H/sub 3/PO/sub 4/ solution in boiling reactors. Due to the possible use of Mg as a cladding material a few preliminary corrosion tests were made with distilled water. Cylindrical, NaK-filled Zr irradiation capsules, which suddenly broke open during decanning operations following irradiation, were examined in an effort to determine the role of irradiation in these unexpected failures. Production, Treatment, and Properties of Materials. Elastic …