Uranium-silicide (U3Si), which are the candidate nuclear fuel for research and test reactors, were studied to determine the effect of carbon on the peritectoid reaction. The three different kinds of alloys having trace, 1500 and 3000 ppm carbon were prepared by the are-melting, followed by the homonization heat treatment and the peritectoid heat treatment. Through the microstructure observation using the optics and scanning electron microscopy, the behaviors of the introduced carbon were examined and the U3Si rim thickness was measured for the peritectoid reaction rate.
As the results of these experiments, carbon compounds were appeared to have a shape of particle in regions of the Uss and U3Si compare to U3Si2 and some of the particles were observed to have the facet plane in SEM image. The carbon ompounds were determined as UC by X-ray diffraction analysis.
The U3Si rim thickness has grown slowly with the carbon content and was shown to have a linear relation with the square root of the peritectoid heat treatment time. These relations were discussed by establishing a diffusion model and inducing the diffusion equation. The linear relation was confirmed by the induced equation and found to be a function of DㆍΔC(Si) in U3Si. The calculated DㆍΔC values were decreased with increasing carbon content. Therefore it was assumed that the carb on in the alloy would give a retarding effect to atomic diffusion in U3Si peritectoid reaction. Also this effect was indirectly confirmed by the hardness measurement of samples with various heat treatment times.
