UO2 fuel pellet microstructure modification through impurity additions

The thermal densification of UO2 pellets containing small amounts of the sintering aids Ti, V, Nb and Ca + Ti has been studied to determine the changes in grain size and pore size distribution. Additive levels above 0.5 mol% greatly increased the grain size and increased the size of the fine porosity, but also reduced the sintered density. A comparison was made between the microstructure of fuel whose density had been reduced by this means and that produced by the addition of small amounts of the known density suppressants, Ba and Sr. (orig.)