Uranium trioxide

In TBP extraction, the yeUowcake is dissolved ia nitric acid and extracted with tributyl phosphate ia a kerosene or hexane diluent. The uranyl ion forms the mixed complex U02(N02)2(TBP)2 which is extracted iato the diluent. The purified uranium is then back-extracted iato nitric acid or water, and concentrated. The uranyl nitrate solution is evaporated to uranyl nitrate hexahydrate [13520-83-7], U02(N02)2 6H20. The uranyl nitrate hexahydrate is dehydrated and denitrated duting a pyrolysis step to form uranium trioxide [1344-58-7], UO, as shown ia equation 10. The pyrolysis is most often carried out ia either a batch reactor (Fig. 2) or a fluidized-bed denitrator (Fig. 3). The UO is reduced with hydrogen to uranium dioxide [1344-57-6], UO2 (eq. 11), and converted to uranium tetrafluoride [10049-14-6], UF, with HF at elevated temperatures (eq. 12). The UF can be either reduced to uranium metal or fluotinated to uranium hexafluoride [7783-81-5], UF, for isotope enrichment. The chemistry and operating conditions of the TBP refining process, and conversion to UO, UO2, and ultimately UF have been discussed ia detail (40). 

As mentioned above, uranium trioxide exists in six weU-defined modifications with colors ranging from yeUow to brick-red. Of these phases, the y-phase has been found to be the most stable, however, other phases, especially a and 3, are also frequently used and studied. The stmcture of the a-modification is based on sheets of hexagons, whereas the 3-, y-, and 8-modifications contain an infinite framework. AH of these topologies have been fliUy described (105,106). They are a-brown, hexagonal 3-orange, monoclinic y-yeUow, rhombic 5-red, cubic S-brick red, triclinic and Tj-rhombic. 

Since the uranium from the milling process is still in an unusable form, the yellow cake is broken down once again. The uranium trioxide is reduced to uranium dioxide at veiy high temperatures. Refining of the product also takes place. Now the uranium product consists almost entirely of UO,. 

During routine operations to reduce the hexahydrate to uranium trioxide, an excessive amount of organic solution entered the denitrator pots and ignited. 

Uranium also combines with oxygen in various ratios. For instance, uranium dioxide (UO ) is a brownish-black powder that was once thought to be pure uranium. Uranium trioxide (UOj), a heavy orangish-powder, was once referred to as uranyl oxide. 

Another preparative method involves converting triuranium octaoxide to uranyl nitrate, U02(N0s)2, by treatment with nitric acid. Uranyl nitrate then is decomposed to uranium trioxide, UO3, which is reduced to the dioxide, UO2, with hydrogen. A fluidized bed of uranium dioxide is treated with hydrogen fluoride to produce uranium tetrafluoride, UF4, which then is treated with fluorine to form hexafluoride. The preparation should be done in copper apparatus. 

Elemental composition (anhydrous compound) U 60.41%, N 7.11%, O 32.48%. The compound may be identified by its physical properties and measured by gravimetric methods from its thermal decomposition to form uranium trioxide, UO3. The radioactivity may be measured by an alpha counter. 

How do the stability and acid-basic properties of the hydrates of chromium, molybdenum, tungsten, and uranium trioxides change ... 

The (IV) and (VI) are the important oxidation states and therefore tlie more important phases of the chemistry of uranium may be related to the two oxides UO> and UO3. uranium dioxide and uranium trioxide. A series of salts such as the chloride and sulfate, UC14 and U(S04)2 9H20 is... 

The aerosol by-products of exploded DU munitions are primarily the uranium oxides with varying dissolution rates. Uranium trioxide (UO3) is soluble like uranyl salts, and systemic absorption accounts for more than 20% of the exposure burden, with 20% of the excreted uranium being in the urine (Morrow et al, 1964, 1972, 1982). UO3, being soluble, has a fast dissolution rate (Type F), and is rapidly removed from the lung (half-life of 4.7 days). Uranium... 

Morrow, P.E., Gibb, F.R., Beiter, H.D. (1972). Inhalation smdies of uranium trioxide. Health Phys. 23 273-80. 

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