Depleted of uranium Lena Hassan Odeh An- Najah university- Nablus -Palestine

Text Discussion: References.. - Basic Information - Atomic Structure - Fact - What is uranium? - Where does uranium come from? - What are the properties of uranium? -Is uranium radioactive? - Uranium Uses - is depleted uranium? References..

Basic Information Name: Uranium Symbol: U Atomic Number: 92 Atomic Mass: 238.0289 a mu Melting Point: 1132.0 °C Boiling Point: 3818.0 °C Number of Protons/Electrons: 92 Number of Neutrons: 146 Classification: Rare Earth Color: silver

Uranium is a silvery-white metal.

Atomic Structure Number of Energy Levels: 7 First Energy Level: 2 Second Energy Level: 8 Third Energy Level: 18 Fourth Energy Level: 32 Fifth Energy Level: 21 Sixth Energy Level: 9 Seventh Energy Level: 2

Fact Date of Discovery: 1789 Discoverer: Martin Klaproth Name Origin: After the planet Uranus Uses: fuel for nuclear reactors

What is uranium? Uranium is a radioactive element that occurs naturally in low concentrations (a few parts per million) in soil, rock, and surface and groundwater. It is the heaviest naturally occurring element, with an atomic number of 92. Uranium in its pure form is a silver-colored heavy metal that is nearly twice as dense as lead.

In nature, uranium atoms exist as several isotopes: primarily uranium-238, uranium-235, and a very small amount of uranium-234. (Isotopes are different forms of an element that have the same number of protons in the nucleus, but a different number of neutrons).

Where does uranium come from? Uranium occurs naturally and can be found in low levels within rocks, soil and water. It is found within the earth crust and is often found combined with other elements as it is unstable. So uranium found everywhere in nature and particularly in rocks, soil, water, and air, as well as in all plants, animals, and humans.

Uranium has been mined in Canada, the southwest United States, Australia, parts of Europe, the former Soviet Union, South Africa, Niger and elsewhere.

What are the properties of uranium? - uranium is a silvery white with atomic number 92 , weakly radioactive metal. - Uranium metal has very high density, 65% more dense than lead.

- Uranium in ores can be extracted and chemically converted into uranium dioxide such as in the olive-green-colored. And other chemical forms usable in industry and used for nuclear fuel.

- Three additional isotopes of uranium are not naturally present but can be produced by nuclear transformations. These are uranium-232, uranium- 233, and uranium-236. Like the natural uranium isotopes, these three also decay by emitting an alpha particle. All uranium isotopes are radioactive.

-. The half-life of uranium-238 is about 4 - The half-life of uranium-238 is about 4.5 billion years, which means it is not very radioactive. In fact, its very long half-life (and thus low radioactivity) is the reason uranium still exists on the earth.

- Uranium-fluorine compounds are also common in uranium processing, with uranium hexafluoride (UF6) and uranium tetra fluoride (UF4) being the two most common. In its pure form, uranium is a silver-colored metal.

Is uranium radioactive? All isotopes of uranium are radioactive, with most having extremely long half-lives. Half-life is a measure of the time it takes for one half of the atoms of a particular radionuclide to decay into another nuclear form. Each radionuclide has a characteristic half-life.

Half-lives vary from millionths of a second to billions of years Half-lives vary from millionths of a second to billions of years. Because radioactivity is a measure of the rate at which a radionuclide decays (for example, decays per second), the longer the half-life of a radionuclide, the less radioactive it is for a given mass.

The half-life of uranium-238 is about 4 The half-life of uranium-238 is about 4.5 billion years, uranium-235 about 700 million years, and uranium-234 about 25 thousand years.

Uranium atoms decay into other atoms, or radio nuclides, that are also radioactive and commonly called "decay products." Uranium and its decay products primarily emit alpha radiation, however, lower levels of both beta and gamma radiation are also emitted.

The total activity level of uranium depends on the isotopic composition and processing history. A sample of natural uranium (as mined) is composed of 99.3% uranium-238, 0.7% uranium-235, and a negligible amount of uranium-234 (by weight), as well as a number of radioactive decay products.

In general, uranium-235 and uranium-234 pose a greater radiological health risk than uranium-238 because they have much shorter half-lives, decay more quickly, and are thus "more radioactive.

Uranium Uses Uranium is of great importance as a nuclear fuel. Nuclear fuels are used to generate electrical power, to make isotopes, and to make weapons. Much of the internal heat of the earth is thought to be due to the presence of uranium and thorium. Uranuim-238, with a half-life of 4.51 x 109 years, is used to estimate the age of igneous rocks. Uranium may be used to harden and strengthen steel.

What is depleted uranium? Depleted uranium is created during the processing that is done to make natural uranium suitable for use as fuel in nuclear power plants or for nuclear weapons.

Natural uranium contains about 99 Natural uranium contains about 99.3 percent of the isotope uranium-238 and 0.7 percent of the fissionable isotope uranium-235. Although uranium- 235 is the rarer of the uranium isotopes, it is the one that most readily undergoes nuclear fission and is thus the most useful for common nuclear applications. Therefore, to use uranium, the proportion of the uranium-235 isotope found in natural uranium must be increased. This process of increasing the fraction of uranium-235 in natural uranium is called enrichment.

The uranium enrichment process results in two streams of uranium: one containing greater than 0.7 percent uranium-235, and one containing less than 0.7 percent uranium-235. Depleted uranium is that uranium containing less than 0.7 percent of uranium- 235. Depleted uranium is slightly less radioactive than natural uranium because some of the uranium- 235 has been removed.

Depleted uranium :- is uranium whose isotopic composition has been changed by removal of the 235U and 234U such that the fraction of 238U increases. In the past it was called by the names Q-metal, depletalloy, and D-38, but these have fallen into disuse.

Since depleted uranium contains at least three times less uranium-235 than natural uranium, it is weakly radioactive and an external radiation dose from depleted uranium is about 60% of that from the same mass of uranium with a natural isotopic ratio. Depleted uranium behaves in the body as does natural uranium.

At standard temperature and pressure (STP) it is a very dense metal solid. Due to its high density the main uses of depleted uranium include counterweights in aircraft, radiation shields in medical radiation therapy machines and containers for the transport of radioactive materials. The military uses depleted uranium for defensive armor.

DU is considered both a toxic and radioactive hazard that requires long term storage as low level nuclear waste. DU is relatively expensive to store but relatively inexpensive to produce or obtain.

Production and availability Natural uranium metal contains about 0.71% U- 235, 99.28% U-238, and about 0.0054% U-234. In order to produce enriched uranium, the process of isotope separation removes a substantial portion of the U-235 for use in nuclear power, weapons, or other uses. The remainder, depleted uranium, contains only 0.2% to 0.4% U-235. Because natural uranium begins with such a low percentage of U- 235, the enrichment process produces large quantities of depleted uranium

Depleted uranium is produced during the uranium enrichment process Depleted uranium is produced during the uranium enrichment process. In the United States, uranium is enriched through the gaseous diffusion process in which the compound uranium hexafluoride (UF6) is heated and converted from a solid to a gas. The gas is then forced through a series of compressors and converters that contain porous barriers.

Because uranium-235 has a slightly lighter isotopic mass than uranium-238, UF6 molecules made with uranium-235 diffuse through the barriers at a slightly higher rate than the molecules containing uranium-238. At the end of the process, there are two UF6 streams, with one stream having a higher concentration of uranium-235 than the other.

The stream having the greater uranium-235 concentration is referred to as enriched UF6, while the stream that is reduced in its concentration of uranium-235 is referred to as depleted UF6. The depleted UF6 can be converted to other chemical forms, such as depleted uranium oxide or depleted uranium metal.

Most of the depleted UF6 produced in the United States is stored at the locations where it was produced as a product of the gaseous diffusion enrichment process.

In addition to gaseous diffusion, other methods can be used to enrich uranium, producing depleted uranium as a by-product. The most common enrichment process used outside of the United States is gas centrifuge enrichment. Laser-based enrichment processes are also under development.

References Arfsten D. P., Still K. R., Ritchie G. D. (2001). "A review of the effects of uranium and depleted uranium exposure on reproduction and fetal development". Toxicol Ind Health 17 (5–10): 180–91. doi:10.1191/0748233701th111oa. PMID12539863 Jump up Domingo J. L. (2001). "Reproductive and developmental toxicity of natural and depleted uranium: a review". Reprod Toxicol 15 (6): 603–9. doi:10.1016/S0890-6238(01)00181-2 PMID 11738513.  Briner W., Murray J. (2005). "Effects of short-term and long-term depleted uranium exposure on open-field behavior and brain lipid oxidation in rats". Neurotoxicology and Teratology 27 (1): 135–44. doi:10.1016/j.ntt.2004.09.001. PMID 15681127

http://www.epa.gov/radiation/radionuclides/uranium. html  (Associated Press, August 12, 2006, free archived copy at: http://www.commondreams.org/headlines06/0812- 06.htm most recently visited November 1, 2006)  The International Legality of the Use of Depleted Uranium Weapons: A Precautionary Approach, Avril McDonald, Jann K. Kleffner and Brigit Toebes, eds. (TMC Asser Press Fall-2003)