Patent Number: 042785600
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing mixed crystals containing uranium and gadolinium for oxidic nuclear fuels. 2. Description of the Prior Art The increasing demand for UO.sub.2 nuclear fuel, to which gadolinium has been added, makes it more and more necessary to find a simple method of mixing gadolinium and uranium. The presently used methods are based almost exclusively on mixing gadolinium oxide (Gd.sub.2 O.sub.3) mechanically with UO.sub.2 powder. This presents not only mixing problems which are caused by the different densities and grain distributions of the two mixing partners but also the nuclear fuel pellet sintered from these mixed powders has considerable inhomogeneities, causing difficulty in attaining the required density approaching the theoretical density. SUMMARY OF THE INVENTION An object of the invention is to provide a method for incorporating and distributing the gadolinium finely and homogeneously into the oxidic nuclear fuel by effecting such distribution in mixed crystals containing uranium and gadolinium. The mixed crystals are converted to uranium and gadolinium oxides for nuclear fuel. With the foregoing and other objects in view, there is provided in accordance with the invention a method for manufacturing mixed crystals containing uranium and gadolinium for conversion into nuclear fuels, which comprises maintaining a body of an aqueous solution of ammonium carbonate at a pH of 9, introducing NH.sub.3, CO.sub.2 and a uranyl salt solution containing the desired gadolinium in dissolved form, said uranyl salt being selected from the group consisting of uranyl nitrate and uranyl sulfate, into the aqueous solution of ammonium carbonate to precipitate ammonium salts of gadolinium and uranium complexes and during precipitation lowering the pH9 of the body of aqueous solution down to 8.2, separating the precipitate from the body of solution, and converting the precipitate of complexes containing gadolinium and uranium to uranium and gadolinium oxides. Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in method for manufacturing gadolinium-containing nuclear fuels, it is nevertheless not intended to be limited to the details shown, since various modifications may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.