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:
