Uranium

Synonyms

Uranium metal: Uranium compounds; UN2979 (Uranium metal); Uranium and compounds;

Category

Radionuclides

Description

Metal: Silver-white, malleable, ductile, lustrous solid (Weakly radioactive); [NIOSH] Soluble in H2O or dilute acids: uranium nitrate, sulfate, chloride, fluoride, & acetate; Relatively insoluble: uranium dioxide, uranyl oxide, & uranium octoxide; [ACGIH]

Sources/Uses

Enriched uranium is used as fuel in nuclear power plants and submarines. [Sullivan, p.1269] Mineral deposits containing uranium include pitchblende, uraninite, autunite, uranophane, and coffinite. Natural uranium contains over 99% U-238 (T1/2 = 4.47 billion years). Enriched uranium for commercial fuel contains 2-3% U-235 (T1/2 = 700 million years). Higher percentages of U-235 are used in fuel for submarines and in nuclear weapons (usually over 90%). Depleted uranium is less radioactive than natural uranium. It is used by the military for bullets, missiles, and tank armor. [EPA] Uranium ore is produced from underground and open-pit mines. From the ores, uranium mills produce yellowcake, which is a complex mixture containing 80-96% uranium. The yellowcake is used to produce nuclear fuel. [PMID 14691274 ] In the nuclear fuel cycle, yellowcake is converted into uranium hexafluoride gas, which is fed through centrifuges repeatedly to separate isotopes until uranium is enriched. The low-level enriched uranium is used for nuclear fuel while the highly enriched can be used in nuclear weapons. [BBC News] "The two principal natural isotopes are uranium-235 (0.7 percent of natural uranium), which is fissile, and uranium-238 (99.3 percent of natural uranium), which is fissionable by fast neutrons and is fertile." [NRC Glossary]

Comments

The BIER IV Committee of the National Academy of Sciences, National Research Council, found that "there is little convincing epidemiological evidence that serious renal disease has occurred in human populations as a result of chronic low-level exposure nor of increased rates of malignant tumors." [Sullivan, p. 1272] Uranium causes acute tubular necrosis in animal experiments, but the case for kidney disease in humans after chronic occupational exposure is unclear. [LaDou, p. 422] Acute renal failure in humans has been reported rarely. No chronic renal disease has been documented. [Rosenstock, p. 574] Studies of uranium and other underground miners in the 1950s showed increased rates of lung cancer in workers heavily exposed to radon decay products. [Rosenstock, p. 732] Absorption through intact skin may occur: Uranyl nitrate; uranyl fluoride; uranium pentachloride; uranium trioxide (uranyl oxide); and uranium hexafluoride; Urine concentrations are less than 0.02 ug/24 hours as background and 100 ug/L in workers exposed to at least 50 ug/cu m; [HSDB] "The toxicity of uranium varies according to its chemical form and route of exposure. On the basis of the toxicity of different uranium compounds in animals, it was concluded that the relatively more water-soluble compounds (uranyl nitrate hexahydrate, uranium hexafluoride, uranyl fluoride, uranium tetrachloride, uranium pentachloride) were the most potent renal toxicants." [ATSDR ToxProfiles] "Fourteen epidemiologic studies have been conducted of more than 120,000 workers at uranium processing, enriching, metal fabrication, and milling facilities. These studies overall found no cancer to be significantly increased." [Boice, p. 274] "Our results support previous estimates that the depleted uranium levels inhaled during the 1991 friendly fire incidents likely do not cause long-term adverse pulmonary health effects." [PMID 23887699]
Most Important Radionuclide: U-238
Source: Mined from natural deposits (99.3% U-238)
Half-Life: 4.5 billion years
Specific Activity: 0.00000034 Ci/gm
Decay Mode: Alpha, Spontaneous Fission
GI Absorption: 0.2% to 5%
Lung Clearance Half-Time: Days for UF6, UO2F2, and UO2(NO3)2; Weeks for UO3, UF4, and UCl4; Years for UO2 and U3O8;
Critical Organ: Kidney
Internal Toxicity: Very High
Annual Limit on Intake: 0.00004 mCi
Radiation Energy (MeV): Alpha 4.2 (75%); Alpha 4.15 (25%) + daughters;
Radiation Accidents: 1 accident involving 1 person exposed to U-235; 1 incident of "Meltings of Radioactive Materials"; [See Glossary for references.] See "Radiation, ionizing."

Reference Link #1

Biomedical References

Uranium in urine = 200 ug/L at end of shift; [ACGIH]

Insufficient data

Yes

0.2 mg/m3, as U

0.6 mg/m3, as U

0.05 mg/m3, as U (sol. compds), 0.25 mg/m3, as U (insol. compds)

10 mg/m3, as U

Excerpts from Documentation for IDLHs

Other animal data: No grossly observable signs or symptoms were induced in mice, rats, guinea pigs, rabbits, or dogs following the first day of exposure to 20 mg/m3 of UF6 (13.5 mg U/m3), UO2F2 (15.5 mg U/m3), UCl4 (12.5 mg U/m3), or UO2(NO3)2×H2O (9.5 mg U/m3) [Wilson et al. 1953]. \ Human data: None relevant for use in determining the revised IDLH.

Explanatory Notes

60% of soluble uranium is cleared by urinary excretion within 24 hours. 7 mg as an acute dose is the threshold for acute kidney injury. The National Academy set 3500 micrograms/liter of urine as the short-term exposure limit. [Gollnick, p. 744-6]

Kidney: 1-6 days; bone: 300 days; [TDR, p. 1204]

Reference Link #2

burn readily

Yes

Confirmed Human

Diseases

Occupational diseases associated with exposure to this agent:

• Acute tubular necrosis

Processes

Industrial Processes with risk of exposure:

• Glass Manufacturing
• Metal Extraction and Refining
• Mining

Activities

Activities with risk of exposure:

• Glassblowing