Dependence of the UO2-PuO2 pellet structure on fabrication parameters

The fabrication of fuel pellets with a given structure and certain properties requires detailed knowledge of the effects of the individual fabrication parameters. The correlation between some of these parameters and the pellet structure has been investigated with UO2-PuO2 pellets which were prepared by the so-called OCOM process. The most important results are: The fraction of open porosity decreases with increasing duration of the milling process due to enhancement of the sintering activity. The addition of an appropriate pore former gives the possibility for a well-defined reduction of the sintering density generally achieved as a result of the milling process. An increase of maximum pore size and an inhomogeneous distribution of pore volume has to be accepted. The O/M ratio cen be adjusted to a certain value by moistening of the sintering gas Ar/H2. The occurrence of cracks with this procedure can be avoided, if dry gas is fed during the cooling-down phase. (orig.)