process for the manufacture of kernreactorsplijtstof usable or cylinders of splijtstofdioxyde sintered tablets and tablets or cylinders manufactured with this method.

摘要

1,148,478. Sintered oxides. COMMISSARIAT A L'ENERGIE ATOMIQUE. 2 Feb., 1968 [13 Feb., 1967], No. 5415/68. Heading C1A. [Also in Division G6] Sintered pellets of UO 2 , PuO 2 or ThO 2 or mixtures thereof, for use as nuclear fuel, are made by grinding the oxide(s) into powder, adding to the powder 1 to 7% by weight of a fatty acid salt as a sintering inhibitor, preferably zinc behenate or zinc stearate, cold-pressing the mixture into bodies, breaking the bodies into granules, coating the granules with the sintering inhibitor in a proportion between 0À2 and 1% by weight, cold-pressing the coated granules into pellets, and sintering the pellets in a reducing atmosphere at a temperature equal to or higher than 1500‹ C. In one example, a finely divided powder of zinc behenate is added to a finely divided UO 2 powder and pellet-shaped bodies of the UO 2 /zinc behenate powder are prepared in an hydraulic press under a pressure of about 1500 bars. The bodies are broken in a mill and only those that pass through a screen of 0À6 mm. but not one of 0À3 mm. are retained. These are coated with between 0À2 and 0À3% by weight of finely-divided zinc behenate in a conventional mixer and shaped by cold-pressing under a pressure between 4000 and 7000 bars to obtain pellets having the desired final shape, except that shrinkage is taken into account. The pellets are sintered for 3 hours in a reducing atmosphere at 1700‹ C. The density of the pellets is 90% of the theoretical density with 1% zinc behenate added during the first mixing step, 85% with 2À5 to 3% zinc behenate, and 80% with 5% zinc behenate. Such pellets are more suited to retain fission products without the cracks found in higher density pellets when subjected to high burn-up. The manufacture of annular pellets made of a mixed dioxide of enriched uranium and plutonium (U 0 . 8 , PU 0À2 )O 2 for use as fuel elements in a fast reactor is also described.