ADU method named after the intermediate ammonium diuranate is a widely used process. The main disadvantage is poor thermal conductivity.

ADU powder is calcined in H2, which is first decomposed into U3O8 and then reduced to U2O2. The process flow is as follows: UF6 is heated to about 70℃, sent to a hydrolysis tank to react with deionized water, and then mixed with dilute ammonia water in the reaction tank to obtain ADU slurry. Aging, filtering, washing and drying to obtain ADU powder. Under negative pressure, it is sent to a rotary reduction furnace for defluorination and reduction to UO2 powder.

Uranium dioxide block is prepared by traditional powder metallurgy process, which includes crushing, granulating, forming, sintering and machining. Among them, milling, forming and sintering are the most noteworthy. Generally speaking, there are three main milling methods: ADU method, AUC method and IDR method.