The physical metallurgy of the metal uranium and its alloys

The thesis presents some aspects of the physical metallurgy of uranium which are relevant to its use as a reactor fuel. Creep and swelling of the fuel may he influenced by the presence of impurity phases. In PART I, techniques have therefore been developed to identify inclusions by 1) metallographic examination of uranium to which the elements normally present as impurities, have been intentionally added, 2) metallographic classification of inclusions in cast uranium, 3) extraction of inclusions followed by examination of the residues. Inclusions have been classified into seven main types and their occurrence, form and chemical nature have been summarised together with their etching and optical characteristics. PART II describes the structural effects due to dilute additions of aluminium, iron, chromium, niobium, titanium, vanadium and zirconium. Emphasis is placed on their grain refining capacity during heat treatment because of the need to eliminate surface wrinkling of a fuel during irradiation. The differing degrees of beta-stabilisation obtained by the use of some of these elements may influence the extent of grain refinement. Data are presented on the uranium-rich ends of the uranium-aluminium and uranium-iron constitutional diagrams. PART III is an investigation into the creep properties of uranium and uranium alloys after various heat treatments using a sagging bar technique. PART IV examines the preferred orientation induced in uranium and uranium alloys by rolling and extrusion. A geiger counter technique is used to give a quantitative assessment. The various textures are all of a single or multiple (hke) types. Preferred orientation is undesirable in a reactor fuel because of irradiation growth, but it has been shown that beta heat treatment can substantially remove the texture.