Die chemischen Grundlagen des Hydrolyseverfahrens zur Herstellung spärischer Kernbrennstoffteilchen

Abstract

The preparation of UO$_{2}$ microspheres by the Hydrolysis Process is based on the solidification of droplets of a concentrated uranyl " nitrate solution in hot oil. The uranyl nitrate is complexed by urea and partly hydrolized by adding solid hexamethylentetramine. The temperature depending solidification reaction of the metastable solution is a continuous polymerisation of [(U0$_{2}$ (OH)$_{2}$)$_{n}$ UO$_{2}$]$^{2+}$ ions forming kolloidal UO$_{2}$(OH)$_{2}$. The crystallite size of the spherical gel particles is increased by washing with hot water. Heat treatment of the washed and dried particles in reducing atmosphere leds to UO$_{2}$ with excellent sintering behaviour. The process was also successfully applied to the preparation of ThO$_{2}$ and (U,Th)O$_{2}$ microspheres