|Radiation Information Network's||Depleted Uranium|
Depleted Uranium (DU)
Natural uranium is made up mostly of Uranium 238 (99.2745% by atom percent ) and Uranium 235 (0.72% atom percent). While both uranium isotopes have long half-lives, because U-235 has a shorter one, in one ton of natural uranium, there is 320 mCi of U-238 and 14 mCi of U-235. There is a small amount of U-234 in natural uranium too at 0.0055% atom percent.
Removing most of the usable U-235, to be used for weapons or nuclear reactor fuel, creates depleted uranium. DU is made into a metal, and due to the high density, very useful for shielding and weapons.
Due to the use of DU in weapons and shielding over the last 15 years, there has been some press on health hazards that are alleged to be due to the DU.
From the DOE "Guide of Good Practices for Occupational Radiological Protection in Uranium Facilities", is a good description of uranium processing:
The process of reducing uranium ore to metal begins with the discovery and mining of uranium in ore bodies. Most medium grade ore consists of oxides of uranium, of which carnotite is predominant. Although some ore is mined using in situ leach techniques, most is hard-rock mined with a small amount removed by open pit mining. Uranium ore is milled by crushing, leaching, extracting, and precipitating, usually to ammonium diuranate, commonly called yellow cake. The radioactivity of this product is low because the decay products have been stripped away and it is in an unenriched form. The yellow cake is purified and converted to UF4 and then further fluorinated to uranium hexafluoride (UF6). Gaseous diffusion enrichment changes the uranium isotopic, but not the chemical, composition of the gas. The UF6 is hydrolyzed to uranyl oxyfluoride, which is precipitated with an ammonia solution to ammonium diuranate. This precipitate is filtered or centrifuged, dried, and calcined. The uranium compound is reduced to UO2 powder, which is pelletized, sintered, and encapsulated in tubes for reactor usage.
U-238 which is most of DU decays by:
234U is long lived (2.4E5 years), so DU would not have much in the way of decay products beyond that.
The Health Physics Society members have provided a good resource on uranium and DU in their Ask the Expert section:
The World Health Organization has provided a good set of resources on DU ammunition
Uranium has some special chemical and biological characteristics: since natural uranium has a low specific activity, chemical damage to the kidneys is likely to be more limiting than radiation damage. If U-235 is concentrated for fuel or weapons, it is called enriched. Normally radiation damage to the lung and kidney are considered if exposure is to enriched uranium.
Isotope: Uranium-235 (235U)
Isotope: Uranium-238 (238U)
The Agency for Toxic Substances and Disease Registry (ATSDR), part of U.S. Department of Health and Human Services, Public Health Service statement on how can uranium affect health:
All uranium mixtures (natural, depleted, and enriched) have the same chemical effect on your body. Large amounts of uranium can react with the tissues in your body and damage your kidneys. The radiation damage from exposure to high levels of natural or depleted uranium are not known to cause cancer
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