Control of O/M ratio in the fabrication of FBR fuel pellets, (2)

The fabrication of FBR fuel pellets with low O/M ratio from the coprecipitated powder is reported together with the determination of the change of O/M ratio during the storage in glove boxes with air atmosphere and during the grinding process with water. The sintering of pellets was performed in 95% N2-5% H2 gas at the flow rate of 20 l/min and at 17000C for 4 hours. The thermodynamical prediction of the final O/M ratio after sintering was made from Woodleg's data and the calculation of equilibrium partial pressure of oxygen in the atmosphere. The relation between O/M ratio and equilibrium oxygen pressure is shown in a figure. The O/M ratio was obtained by both thermogravimetric and X-ray diffraction methods. The results are summarized in a table. The agreement between the results by both methods is good. The relation between the lattice parameter and the O/M ratio is also shown in a figure. The drift of O/M ratio under various conditions was also investigated. The results are shown in some figures, indicating that the O/M ratio of all pellets drifted near 1.98. (Aoki, K.)