| 摘要 |
<p>1,047,399. Fuel materials. UNITED KING- DOM ATOMIC ENERGY AUTHORITY. Nov. 23, 1964 [Nov. 25, 1963], No. 46564/63. Heading G6C. A nuclear fuel, suitable in particular for a high temperature gas-cooled reactor, comprises a mixture of uranium and plutonium sesquicarbides. The sesquicarbide is the stable phase in a uranium-plutonium-carbon system up to a temperature which varies from 1670‹ C. when the uranium-plutonium atomic ratio is 95: 5 to 1720‹ C. when the said ratio is 90: 10. In the absence of free carbon, the sesquicarbide would be the stable phase up to higher temperatures than those quoted, but when the fuel is in the form of small (i.e. about 250 microns diameter) " kernels," the coatings of these kernels usually possess a thin inner layer of carbon. The mixed sesquicarbides may be prepared by any of the known methods, e.g. by arc-melting the metals in the appropriate quantities with carbon, by " plunge sintering " in the manner described in Specification 914,153, or by reacting together uranium and plutonium dioxides and carbon in the requisite proportions. By way of example, 12À75 gm. of uranium metal and 2À25 gm. of plutonium metal in the form of small cubes having sides about 3 mm. long were placed, together with 1À50 gm. of graphite, also in the form of 3 mm. cubes, in the hearth of an arc furnace. The mixed charge was melted and caused to react by striking an arc between the charge and a graphite electrode in an atmosphere of argon. After 1 min. the arc was switched off and the charge allowed to cool, the resulting button of material being turned over and remelted, this being repeated six times to ensure the uranium-plutonium-carbon alloy was homogeneous. The product was found to be a mixed uranium-plutonium dicarbide. The mixed dicarbide was then transferred to a vacuum furnace and heated to about 1700‹ C. for a period of 6 hours at a pressure of 10<-5> mm. of mercury. Subsequent metallographic examination of the material from the vacuum furnace showed it to be a dispersion of graphite in a continuous matrix consisting of a solid solution of uranium and plutonium sesquicarbides.</p> |
