Wet granulation of mixed oxide powders de-nitrated by the microwave heating

Kato, Yoshiyuki 

Performance of wet granulation for MOX powder de-nitrated by the microwave heating de-nitration method was investigated in order to fabricate MOX fuel pellets for FBR at an extremely simplified process. An agitating granulator equipped with three blades and a chopper was used and the performance was evaluated. Characteristics of raw powder and granules were evaluated from SEM observation, granulometry and flow-ability measurement. We could obtain the granules of 120-140 m in diameter from the raw powder of several micron in a narrow range of water addition ratio 12.5-13.5 wt% with a flow-ability 73 and a product yield 90%. Specific surface area which is the index of sintering performance was almost same as the one of raw powder. When the ratio was 9 wt%, flow-ability did not change from the one of raw powder 30 and no granule was observed. It was estimated from an additional experiment that the reason was capillaries (or voids) in the raw powder. When the ratio was larger than 14 wt%, flow-ability saturated and product yield decreased. This narrow range of water addition ratio and strong binding force were successfully understood based on the standard theory of granulation supposing a pendular state and Gorge method.