A method for the production of sintered uranium dioxide, in particular for nuclear reactors become denser

摘要

A sintered body of high density containing uranium dioxide ore as mixture thereof with, preferably 10-30% plutonium dioxide, for use as a fuel element in a fast neutron reactor, is obtained by heating a compressed body of uranium dioxide, or mixture thereof with plutonium dioxide, to at least 1300 DEG C. in an atmosphere consisting of carbon dioxide, or a mixture thereof with carbon monoxide. If CO2 alone is used the maximum sintering temperature is 1550 DEG C. The CO/CO2 volumetric ratio may range from 1:100 to 100:1. The preferred range for a 10% PuO2, 90% UO2 being 1:100 to 1:10 and for a 30% PuO2 70% UO2 from 1:20 to 1:1, during sintering at 1400 DEG -1600 DEG C. A sintered body having a metal / oxygen atomic ratio 1,98 to 2.02:1 is produced by cooling in a reducing atmosphere, preferably a CO/CO2 atmosphere of volumetric composition range 1:10 to 100:1 although hydrogen or hydrogen containing water vapour may be used. The density of the sintered product, depends upon sintering time and attains a maximum value and diminishes thereafter. Optimum times, determined by experiment, are between 3-6 hours. Thus in Example 1 a mixture of 10% plutonium dioxide 90% uranium dioxide were ball milled and polybutyl methacrylate in toluene were added as a binder. After drying the granules were double pressed into pellets, which were heated at 400 DEG C. then to 1500 DEG C. in a CO2 atmosphere, and maintained at 1500 DEG C. for 4 hours. The resulting pellets had a theoretical density of 96% and had an oxygen/metal ratio of 2,14/1. Other examples refer to the use of CO/CO2 mixtures during sintering and H2 or H2 and water vapour during cooling. Specification 881,883 is referred to.