Диуранат аммония

Description

Ammonium diuranate (ADU) is a uranium cycle intermediate with the formula (NH4)2U2O7. Also known as “yellow cake” at a certain stage of uranium ore processing.

Basic Attributes

• CAS No.: 7783-22-4
• Chemical formula: H4N,O,U ((NH4)2U2O7)
• Molecular Weight: 624.130
• Exact weight: 624.134705
• EU number: 231-986-2
• UNII: 39Y3LFK95B
• PSA Specifications: 9

Physico-chemical characteristics

• Solubility in water: insoluble

Scope of application

The substance class is an intermediate product of uranium ore processing. Ammonium diuranate is precipitated by the addition of aqueous ammonium hydroxide after extraction of uranium with tertiary amines in kerosene; the precipitate is concentrated, centrifuged and then calcined to uranium oxide. Calcination produces purified solid oxide U3O8, known as yellowcake, the standard commercial form of uranium in the mining industry. ADU also serves as an intermediate in the manufacture of mixed oxide (MOX) fuel and as a feedstock for the production of uranium dioxide (UO2) and uranium tetrafluoride (UF4). Historically, ammonium diuranate was used as a black pigment for painting porcelain and as a chemical reagent when working with alkaloids.

The technological scheme for producing ADU refers to the refining of the so-called “yellow cake”: the uranyl sulfate or uranyl nitrate solution extracted from ore is purified by liquid extraction from impurities of associated metals, and then precipitated with ammonia. The resulting diuranate precipitate is separated from the mother liquor, washed and dried before calcination. The quality and uniformity of the precipitate at this stage directly affects the purity of the final uranium oxide supplied for further conversion into hexafluoride or dioxide for the production of nuclear fuel.

Storage and transportation conditions

As a compound of natural uranium, it belongs to the category of radioactive and chemically hazardous materials; storage and transportation are regulated by the standards for handling nuclear materials and radiation safety, with control of the tightness of the container, ventilation of the room and background radiation. Accounting and movement of shipments are subject to documentary support in accordance with the requirements for control over the circulation of nuclear materials.

Place in the uranium production cycle

Ammonium diuranate occupies an intermediate position between the extraction of uranium ore and the production of commercial natural uranium concentrate. At the mining and processing plant, the ore is crushed, leached with sulfuric acid or carbonate solutions, after which the uranium is extracted into the organic phase and transferred back into an aqueous solution for precipitation. The choice of ammonia precipitation is due to the availability of the reagent and the good filterability of the resulting precipitate compared to precipitation with sodium or magnesium hydroxide, used at individual enterprises to produce sodium or magnesium diuranate, respectively. After calcination of diuranate, technical uranium oxide is obtained, which is weighed, analyzed for impurity content and shipped to consumers - uranium conversion and enrichment plants. The exact mass according to the source is 624.134705.