Plutonium is a silvery-grey radioactive actinide metal with the symbol Pu and the atomic number of 94. Plutonium was first synthesized in 1940 by Glenn Seaborg an Edwin McMillan at the University of California by bombarding U-238 with deuterons which are nuclei of deuterium containing a neutron and a proton. Following its synthesis, plutonium-244 was discovered in minute quantities in the natural environment.
Radium is a chemical element with the symbol Ra and an atomic number of 88. It was discovered in 1898 by Marie and Pierre Curie. They extracted it from uranium ore. Twelve years later, Marie Curie and Andre Debierne isolated the pure metallic form of radium by electrolysis from radium chloride. It was given the French name radium from Latin radius or ray. The curie unit of radioactivity was named for Marie Curie and is based on the radioactivity of Ra-226.
Radon is a tasteless, colorless, odorless elemental noble gas in the family with helium, neon, argon, krypton and xenon. Its chemical symbol is Rn and it has an atomic number of 86. It is the densest noble gas and one of the densest gases that exist. As with the other noble gases, radon is chemically inert and rarely forms compounds with other substances. It was discovered in 1900 by Friedrich Ernst Dorn as a gas given off by radium.
When enriched uranium is used in nuclear reactors, the exhausted fuel consists mainly of U-238 with small amounts of U-235, plutonium and minor actinides such as neptunium, americium, curium, berkelium, californium, einsteinium, and fermium. There are commercial facilities in France, the United Kingdom and Japan for reprocessing spent fuel. Reprocessing is also carried out at nuclear weapons facilities. Reprocessing is currently carried out in eleven countries.
When uranium metal is processed to increase the proportion of U-235, a byproduct of the process is a great deal of uranium metal containing smaller amounts of U-235 than the natural proportion of 0.72 %. This byproduct is known as “depleted” uranium(DU). The U-238 in DU emits alpha particles which contain 2 protons and 2 neutrons. These alpha particles only travel a few centimeters in open air and can be blocked by a sheet of paper or plastic, a layer of clothing.
When uranium metal is processed to increase the proportion of U-235, a byproduct of the process is a great deal of uranium metal containing smaller amounts of U-235 than the natural proportion of 0.72 %. This byproduct is known as “depleted” uranium. To produce 1 pound of 10% enriched uranium, 24 pounds of uranium must be processed leaving 23 pounds of deplete uranium. Depleted uranium usually contains from 0.2 % to 0.4 percent U-235. Processes have been developed to recover more U-235 from the deplete uranium as the price of uranium has risen. Deplete uranium metal is 1.67 times as dense as lead and almost as dense as gold or tungsten. In a powdered or vaporized state, it is highly flammable.
The U-238 in depleted uranium emits alpha particles which contain 2 protons and 2 neutrons. These alpha particles only travel a few centimeters in open air and can be blocked by a sheet of paper or plastic, a layer of clothing or even human skin. Their primary danger to human health lies in their danger when inhaled or swallowed.
Depleted uranium is store near the uranium processing facilities. It is mainly stored in steel cylinders in a crystalline solid form of uranium hexafluoride (UF6). Each cylinder contains about 14 tons of UF6. As of 2008, there were about 760,000 tons of UF6 in the US in Kentucky and Ohio. These stores of UF6 pose an environmental threat because the UF6 can interact with water moisture in the air to produce solid uranyl fluoride(UO2F2) and hydrogen fluoride(HF) gas both of which are highly toxic. Fortunately, the solid UO2F2 tends to plug leaks in the steel cylinder which would allow the HF gas to escape.
In the 1970, research on the use of depleted uranium as a projectile was begun in response to developments in armor plating for tanks. It has also been used as armor plating because of its density.
Armor piercing incendiary ammunition is currently in use by the U.S. military. In calibers of 20 to 30 mm, it is fired from tanks, armored personnel carriers, jet fighters, helicopters and naval vessels. Long thin penetrators made of depleted uranium are fired from tanks to defeat armored tanks and other vehicles. When they penetrate the armor of a tank, they can disintegrate, catch fire and burn everything inside the vehicle. Grenades, cluster bombs and mines were also developed by the U.S. military but they are no longer used.
There are minor civilian uses for depleted uranium such as shielding for radiographic cameras, chemical reagents, detectors in high energy physics and other scientific and industrial application. Other civilian uses for depleted uranium that have been discontinued include coloring agents for glass and ceramics, trim weights in aircraft and keels in sailboats.
Depleted uranium penetrator of a 30 mm round:
If the concentration of uranium in the ore from underground mines or open pit mines is too low to be processed in the mill, the heaps of ore are subjected to leaching liquids such as acids, alkaline chemicals or peroxide solutions. The liquid flows down through the heap and dissolves uranium minerals. The liquid runs down a layer of plastic under the heap and collects in pools.
Uranium is mined in 20 countries with a world annual production in the range of 60,000 tons. Just 10 mines in six countries provide over half of the total world production of uranium ore. These six countries produce over 85% of the annual mined uranium in the world.
Uranium is mined all over the world. There a number of different techniques that have been developed to extract uranium from various types of sources.
Uranium is a common element. It forms compounds with many other elements and is present in a wide variety of minerals. Four common geological processes distribute uranium minerals in many different forms across the earth. Only a few of the many minerals are considered suitable for extraction to obtain useful uranium and only a few of their deposits are currently exploited. .About one third of the worlds uranium resources are in the form of unconformity-related deposits.
