Migration of Metallic Fission Products in Reactor Oxide Fuels

The fission-product elements molybdenum and ruthenium were added to uranium and uranium-plutonium oxide by a co-precipitation technique. Heat treatment of these materials in a simulated reactor thermal gradient causes migration and coagulation of the metals to form inclusions up to a maximum size of 10 m. Inclusions of large diameters between 5 and 10 µm do not migrate noticeably by diffusion. Their migration rate is different from that of pores in a temperature gradient.