The invention belongs to the technical field of preparation of
uranium trioxide, and particularly relates to a method of preparing high-activity
uranium trioxide by thermal denitration of
uranyl nitrate. The method comprises the following steps: step (1) evaporating and concentrating an
uranyl nitrate solution to obtain a concentrated
uranyl nitrate solution; step (2) conveying the concentrated
uranyl nitrate solution to a cooling crystallizer, cooling the concentrated
uranyl nitrate solution to a temperature below 40 DEG C, carrying out cooling
crystallization to form UO2(NO3)2.6H2O crystals,and returning a saturated solution to an
evaporation and concentration device in step (1); step (3) dehydrating the UO2(NO3)2.6H2O crystals obtained in step (2) by
microwave drying, and converting the UO2(NO3)2.6H2O crystals obtained in step (3) into UO2(NO3)2
powder; and step (4) generating the UO3 product in a
fixed bed by using the UO2(NO3)2
powder obtained in step (3) in a vacuum environmentthrough
microwave heating. The method has the advantages of short technological process, no generation of radioactive
ammonia-
nitrogen wastewater, good product activity and the like, increases the integral level of a
uranium purification and conversion technology in the
nuclear fuel cycle, and has obvious social and
economic benefits.