Uranium soluble compounds

URANIUM. SOLUBLE COMPOUNDS (ASU) u Synonyms vary depending upon specific compound Uranyl nitrates combustibles. Uranium hexa-nuoride water Properties vary depending upon specific compound ... 

Uranium Purification. Subsequent uranium cycles provide additional separation from residual plutonium and fission products, particularly zirconium— niobium and mthenium (30). This is accompHshed by repeating the extraction/stripping cycle. Decontamination factors greater than 10 at losses of less than 0.1 wt % are routinely attainable. However, mthenium can exist in several valence states simultaneously and can form several nitrosyl—nitrate complexes, some for which are extracted readily by TBP. Under certain conditions, the nitrates of zirconium and niobium form soluble compounds or hydrous coUoids that compHcate the Hquid—Hquid extraction. SiUca-gel adsorption or one of the similar Hquid—soHd techniques may also be used to further purify the product streams. 

Insoluble compounds Soluble compounds Turpentine Uranium (natural)... 

Soluble Compounds Animals repeatedly exposed to dusts of soluble uranium compounds in concentrations from 3 to 20mg/m died of pulmonary and renal damage both feeding and percutaneous toxicity studies on animals indicated that the more soluble compounds are the most toxic. In animals, effects on the liver are a consequence of the acidosis and azotemia induced by renal dysfunction. ... 

The 2003 ACGIH threshold limit value-time-weighted average (TLV-TWA) for uranium (soluble and insoluble compounds, as U) is 0.2 mg/m with a short-term excursion limit (STEL) of 0.6mg/mk... 

Grinberg, A.A., Nikolskaya, L.E., Petrzhak, G.I., Ptitsyn, B.V and Filinov, F.M. (1957) Preparation of slightly soluble compounds of quadrivalent uranium using rongalite. J.Anal. Chem. Tranl. Zh.Anal. Khimi., 12, 89-91. 

One site of deposition for the soluble compounds (uranyl nitrate, uranium tetrachloride, uranium hexafluoride) in animals was the skeleton, but accumulation was not seen in bone at levels below 0.25 mg U/m over a period of 2 years in rats exposed to soluble compounds (uranyl nitrate, uranium tetrachloride, uranium hexafluoride) in one study. The insoluble compounds (uranium hexafluoride, uranium dioxide) were found to accumulate in the lungs and lymph nodes after the inhalation exposure. For uranyl nitrate exposure, no retention was found in the soft tissues. Accumulation of uranium was also found in the skeleton (Stokinger 1953). The amount distributed in the skeleton has been reported to be 23 5% of the intake in dogs (Morrow et al. 1972) 28-78% in rats (Leach et al. 1984) and 34-43% in guinea pigs (Leach et al. 1984). A biological half-time of 150-200 days (Ballou et al. 1986) or 70 days (Morrow et al. 1982) in the skeleton has been reported following inhalation exposure to soluble uranium compounds (e.g., uranium hexafluoride). 

Ingested uranium is excreted mostly in the feces urinary excretion is generally low. The biological halftimes of soluble uranium compounds (uranium hexafluoride, uranyl fluoride, uranium tetrachloride, uranyl nitrate hexahydrate) are estimated in days or weeks those of the less soluble compounds (uranium tetrafluoride, uranium dioxide, triuranium octaoxide) are estimated in years. No information is currently available on the excretion of dermally absorbed uranium. Transdermally absorbed uranium is expected to behave identically to uranium compounds absorbed through the lungs and the gastrointestinal tract. 

Evidence also suggests that the toxicity of uranium varies according to the route of exposure and to its compounds. This finding may be partly attributable to the relatively low gastrointestinal absorption of uranium compounds. Only <0.1-6% of even the more soluble uranium compounds are absorbed in the gastrointestinal tract. On the basis of the toxicity of different uranium salts in animals, it was concluded that the relatively more water-soluble salts (uranyl nitrate hexahydrate, uranyl fluoride, uranium pentachloride) were primarily renal and systemic toxicants. The less water-soluble compounds (uranium trioxide, sodium diuranate, ammonium diuranate) were of moderate-to-low toxicity, while the insoluble compounds (uranium tetrafluoride, uranium dioxide, uranium peroxide, triuranium octaoxide) were... 

The effects of uranium in animal experiments were also compound-dependent, the more water-soluble compounds (e.g., uranyl nitrate) causing much greater renal toxicity than insoluble compounds (e.g., uranium dioxide) when the dose contained equivalent amounts of uranium. ATSDR has determined that the toxicity database for uranium justifies the derivation of separate MRLs for soluble and insoluble forms of uranium for certain durations and routes of exposure. This is based on toxicokinetic evidence that absorption of uranium (and concentration in target tissue) is significantly greater during exposure to the more water-soluble compounds. Soluble forms include uranyl fluoride, uranium tetrachloride and uranyl nitrate hexahydrate insoluble forms include uranium tetrafluoride, uranium dioxide, uranium trioxide, and triuranium octaoxide. Where the database is not extensive enough to allow separate MRLs, the MRL for the soluble form should be protective for health effects due to all forms of uranium. 

An MRL of 4x10 mg U/m has been derived for intermediate-duration inhalation exposure (15-364 days) to soluble compounds of uranium. 

The oxidation-reduction potential of water is important in controlling the mobility of uranium. In anoxic waters where the aquatic environment is reductive, U(VI) will be reduced to U(IV) (e.g., changed from a soluble compound to an insoluble one). The U(IV) will be deposited into the sediment due to the insolubility of the resulting U(IV) salts (Allard et al. 1979 Herczeg et al. 1988). Mobilization and... 

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