Characteristics and sinterability of MOX powder prepared by the microwave heating denitration method

Asakura, Koichi; Kato, Yoshiyuki ; Furuya, Hirotaka

UO, PuO and MOX (mixed oxide of U and Pu) powders were prepared by the MH (microwave heating de-nitration), ADU (Ammonia diuranate) and OX (oxalate) methods. The BET specific surface area, avarage particle size by air permiation method, bulk density, tap density, angle of repose, angle of spatula and cohesiveness of these powders were measured. The degree of surface roughness was evaluated from the ratio of BET surface area to the one calculated from average particle size and then flowability was evaluated on the basis of Carr's theory. These results were compared for the different powders and preperation methods as a parameter of calcination temperature. The degree of surface roughness in MH-MOX powder was larger than in ADU-UO powder and smaller in OX-PuO powder. These results could be understood using the concpt of Httig and Tamman temperatures commonly cited in ceramics materials. As already reported for the general papers, the flowabilities of MH-MOX and ADU-UO powders also decreased with increase of compressibility, and their absolute values were below 50 points. According to Carr's theory, the brderline between free-flowing and non-free-flowing powders is from 60 to 69 points. It is, therefore, necessary for the mixed powder of MH-MOX powder, ADU-UO powder and dry recycled MOX scrap powder to be granulated to provide a free flowing feed to the pelletizing press in the MOX pellet fabrication process.