GB821639A - Improvements in fissionable materials for use in nuclear reactors and in the methodsof manufacturing such materials - Google Patents

Abstract

A fissionable material for nuclear reactors is constituted by an alloy of uranium with from any amount above 0 and up to a maximum of 2% of one or more of aluminium, zirconium, chromium, titanium and vanadium, the addition metal or metals forming a fine dispersion in the mass of uranium. The alloy may include one only of the above metals and also a further metal, differing from the first, chosen from zirconium, niobium, molybdenum, technecium, ruthenium, rhodium, tin and antimony in amount above 0 and up to 1%. The addition may be made to uranium in several steps, the whole being melted under a vacuum of 10-4 to 10-5 mm. of mercury, the melt being heated to about 1500 DEG C for a time sufficient to ensure full dissolution and degassing. The first addition metal may be alloyed with uranium that has been produced by reduction of UF4 with calcium, magnesium or other reducing agent. The addition metal may be used as such or as a compound that is itself reducible. The second addition metal may then be added. The alloy is subjected to heat treatment to reduce the grain size of the dispersed phase by heating under a vacuum of about 10-3 mm. of mercury at a temperature above 1000 DEG C but below the melting point, the period of heating being 200-300 hours where metal or metals of the first group are used alone or about 50 hours where a metal of the second group is also present. The alloy is quenched in a cold oil bath, still under vacuum and is then further heated at a temperature about 600 DEG C, near the upper limit of stability of the ortho rhombic phase of uranium for about 10 minutes, to cause precipitation of the addition as a fine dispersion.