Plasma melting of uranium dioxide

Experiments were conducted with the plasma remelting of UO2 and remelted UO2 was compared with the initial tablets of UO2. Remelting by means of plasma heating is feasible and the nuclear cleanness of the product is virtually unaffected by the material of the electrodes and the crucible. Ceramographic analysis indicates that plasma remelting resulted in a marked reduction in initial porosity and consequently in an increase in density. This fact was also confirmed by means of X-ray diffraction which indicated that the volume of the elementary cell decreases. The oxygen index of remelted UO2 is slightly higher than that of initial UO2; the value of this index could be reduced by using more suitable atmospheres (e.g. argon -hydrogen). (author)