912,282. Nuclear fuel. UNITED STATES ATOMIC ENERGY COMMISSION. June 1, 1960 [June 2, 1959; April 18, 1960], No. 19447/60. Drawings to Specification. Class 39 (4). A plutonium alloy which has been stabilized in the delta allotropic form is freed from voids and cracks and is changed in physical characteristics by compression to at least the lowest of its transformation pressures in order to convert the delta form partially to the alpha form. The alloys are useful as nuclear fuels. Stabilization of plutonium in the delta allotropic form is effected by heating and rapidly cooling the alloy. Suitable alloying metals are aluminium, zinc, zirconium, indium, cerium, erbium, hafnium, scandium, dysprosium, thulium, lutetium, and thallium. If the content of alloying metal is below a certain amount, the delta form is not retained at room temperature. In order to effect the change to the alpha form, which is of increased density and hardness, the alloy is compressed hydraulically in a cylinder, using glycerine as the hydraulic fluid. With plutonium-cerium alloys there are two transformation pressures, one corresponding to the formation of the beta phase, and the other to the formation of the alpha phase. If the alloy contains more than a certain amount of delta stabilizing metal, there will be a return to the delta form on release of the pressure. Graphs are provided showing for various alloys the volume change with increasing pressure, the variation of transformation pressure with percentage of alloying metal, and the effect of compression on the density and hardness of the alloys.
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