Thermal expansion behaviour of ZrO2-PuO2 fuels

Fuels based on ZrO2-PuO2 system are of interest in thermal reactors in which ZrO2 provides a refractory and stable matrix while PuO2 provides the required fissile species. Accurate measurement of the thermal expansion of fuel materials is important for the design of fuel elements. Studies are conducted with a push rod type of dilatometer upto a temperature of 11000C with compositions containing 5, 10 and 15% PuO2 without any calcia and with the same compositions containing 3.5, 5 and 6% CaO. The results show that the expansion coefficient depends upon the structure of the material. Both PuO2 and CaO promote the formation of face centred cubic solid solution at room temperature. It is seen that the coefficient of expansion increases gradually as the amounts of these additions are increased. All the compositions studied show a phase transformation accompanied by contraction and the contraction, as expected, is related to the amount of stabilizer addition. (auth.)