Abstract
A study on the development of a continuous co-conversion process of Pu-U mixed nitrate solutions to oxide powder by using a microwave-heating direct-denitration process was performed to obtain more stable powder characteristics and an increased capacity. Basic characteristics of materials, such as water, uranium nitrate and oxides, for microwave were investigated by means of small microwave oven, and estimated on the basis of an experience obtained through 2-kg/batch denitration operations. A continuous denitration test equipment, capacity of which is 2.5kg/h, was designed, followed by the measurement of microwave adsorption efficiencies of water to know a characteristics of this equipment. Denitration tests were performed for cerium nitrate and uranyl nitrate solutions.
As a result, it was found that the microwave adsorption efficiency of this equipment was a little lower than 30%, and its capacity was 1.7kg/h when 500-g/l uranyl nitrate was fed. It was also revealed that the apparent property of the denitrate was similar to that produced by the batchwise equipment. Furthermore, several new materials, which are capable of being used as denitration trays, were investigated, and Si3N4 was found to be promising with regard to mechanical and chemical properties.
Based on these results, more detailed investigation will be carried out to design an improved equipment for the purpose of mass production.
