The Research Of The Application Of Nanometer Technique In Pellet Manufacture

Improving gradually fuel burn-up is one of the paths which can lower the expense on fuel cycle cost for light water reactor. In the high burn-up condition, because of more fission gases releasing from fuel pellets, the pressure in fuel columns will increase;because of air bubble expanding, interactions between pellets and cladding (PCI) will increase. These are the main problems which relate the safe operation of nuclear fuel and which can be solved effectively byimproving quality of UO₂ pellets.In the present paper ,it is studied how and why small addition of nanometer-size powder of alumina and silica improves the quality of the pellets. Results show that the small additives can accelerate effectively the growth of grain size in the course of sintering and improve effectively the thermal stability of the pellets. If excessive nanometer power is added in, otherwise, the density increase of the pellets will be retarded in the course of sintering, so more crack will appear on the surface of pellets. The correlation of the grain size and addition of nanometer powder isn't linear. The grain size will increase sharply at the level of 20-30μg/g, then it will increase tardily and decrease after the maximum point. Although the adding content with which maximal grain size achieved is different in pellets with different performance, the trend influenced by addition is coincident.The addition of the nanometer powder with different granularity has the similar influence on grain size. The mechanism that small addition of nanometer powder can accelerate the growth of grain is liquid phase occurred in sintering zone.