Uranium

Natural uranium is made up of:

Isotope	Percentage Composition	Half Life	Radioactive decay particles
U-238	99.2742%	7.038×10⁸ years	and
U-235	0.7204%	7.038×10⁸ years	and
U-234	0.0054%	245,500 years	and

	Because of the relatively short half life of the U-234 compared to the other two isotopes about half of the activity of a naturally occurring uranium sample is made up of counts from the decay of that isotope. That is true even though it makes up the tiniest proportion of the uranium isotopes.
	Enriched Uranium: Because U-235 is used for fission in nuclear reactors and nuclear weapons, natural uranium is enriched in U-235 by separating the isotopes out by mass to produce a sample that has about 2% to 4% U-235.
	Weapons grade enrichment results in about 90% U-235! This type of Uranium has to be carefully monitored and stored so that a critical mass is not reached until required.

Depleted Uranium: The byproduct of enrichment is called depleted uranium or DU.

It is mainly made up of of the isotope uranium-238 (U-238). It contains less than one third as much U-235 and U-234 as natural uranium. Therefore the external radiation dose from DU is about 60 percent of that from the same mass of natural uranium.

Another less common source of DU is reprocessed spent nuclear reactor fuel rods. This can be distinguished from DU produced as a byproduct of uranium enrichment by the presence of U-236 (half life 2.342×10⁷ years). This is not naturally found on Earth despite its long half life. It is the isotope that is produced in nuclear reactors by firing neutrons at U235. It very readily undergoes fission - but some atoms of it remain that have not undergone fission and can be used to identify spent fuel rods.

DU is used for its very high density of 19.1 g/cm³.

Civilian uses include:

counterweights in aircraft. Aircraft that contain depleted uranium trim weights (such as the Boeing 747–100) may contain between 400 to 1,500 kg of DU. This application is controversial because the DU may enter the environment if the aircraft were to crash. The metal can also oxidize to a fine powder in a fire. Its use has been phased out in many newer aircraft. Boeing and McDonnell-Douglas discontinued using DU counterweights in the 1980s. Depleted uranium was released during the crash of El Al Flight 1862 on 4 October 1992, in which 152 kg was lost, but an extensive study concluded that there was no evidence to link depleted uranium from the plane to any health problems.

radiation shielding in medical radiation therapy and industrial radiography equipment, and

the manufacture of containers used to transport radioactive materials.

Military uses include:

defensive armour plating and

armour-piercing projectiles.

Depleted uranium munitions are controversial because of unanswered questions about potential long-term health effects.

DU is less toxic than other heavy metals such as arsenic and mercury, and is only very weakly radioactive because of its long half-life.^. While all radiation exposure has risks, no conclusive epidemiological data have correlated DU exposure to specific human health effects such as cancer (there are always so many other factors that can trigger it - and the effect takes decades not months or years) .

However, the UK government has attributed birth defect claims from a 1991 Gulf War combat veteran to DU poisoning, and studies using cultured cells and laboratory rodents continue to suggest the possibility of leukemogenic, genetic, reproductive, and neurological effects from chronic exposure. Data is still being collected on its effects.

See this article in Medical News Today.