Development of a powder milling technique for making high density ThO2--UO2 pellets (LWBR development program)

Powder milling procedures were investigated to establish a method for preparing THO2--UO2 mixed powders suitable for fabrication into high density pellets when cold pressed and sintered at temperatures between 17000C and 18000C using standard commercial equipment. Powder activation was accomplished by co-micronizing the 2 oxides in a small commercial micronizer. The conventional pressure distribution to the micronizer was modified to permit its successful application to the milling of these fine powders. Particle size and surface area of the starting powder and the powder feed rate to the mill were critical parameters in achieving a fully activated co-micronized powder. This technique was used to activate all the binary oxide powder used in the fabrication of the binary fuel pellets for the LWBR core