Effect of oxygen potential on the sintering behavior of MOX fuel containing Am

The effect of oxygen potential on the sintering behavior of MOX fuel containing Am (Am-MOX) was investigated. Green pellets of Am-MOX were prepared by a conventional powder metallurgical technique. For Am-MOX fuel pellets sintered at various oxygen potential conditions, density measurement, microstructural observation and element analysis by EPMA were performed. The effects of oxygen potential on sintering behavior are evaluated from the viewpoints as follows, 1) effect of changing oxygen potential at the cooling process, 2) effect of changing oxygen potential at 1700degC by the amount of moisture and 3) effect of sintering temperature. 1) High density pellets having good structure were obtained due to oxygen potential change of sintering atmosphere from high oxygen potential to low oxygen potential at 800degC in the cooling process. 2) For the pellets sintered at -520 kJ/mol, -390 kJ/mol and -340 kJ/mol, the sintered density increases with increase of oxygen potential up to -390 kJ/mol (threshold oxygen potential), then decreases above the threshold oxygen potential. The differences of sintering behavior for Am-MOX pellets which were observed by changing the oxygen potential were attributable to the difference of pore structure, which was supposed to be caused by the valence state of Am in the oxides. 3) For the pellets sintered at 1500degC, 1600degC, 1700degC, the high dense pellets are obtained. Therefore, this results show the possibility of fabrication of good fuel pellets at lower temperature than 1700degC. (author)