What is Enriched Uranium?

Identification

• Enriched uranium refers to a processed product of the ore of the uranium 235 (U-235) isotope. Of all the isotopes of uranium, only U-235 has the characteristics necessary for sustaining the chain reaction that is central to useful nuclear fission.

Function

• Enriched uranium is used in both nuclear reactor power plants and in nuclear weapons.

Types

• Natural uranium has only 0.7-0.8% percent of the U-235 that is valuable in nuclear fission processes. Low grade enriched uranium of the type used for power generating nuclear reactors has been concentrated so that 3-4% of its make-up is made of U-235. Weapons grade uranium has been enriched until 90% or more of its content is made of U-235.

Features

• There are a handful of methods for enriching uranium. Thermal and gaseous diffusion works by forcing natural uranium through another substance and causing the desired U-235 to separate from the rest of the uranium ore. Gaseous diffusion was formerly the most common method of enriching uranium, and continues to account for roughly 1/3 of all uranium enriched today, but is being superseded by other methods.

  The main means of producing enriched uranium today is the gas centrifuge. It is more energy efficient than gas diffusion, and accounts for over half of all modern production. This process spins gaseous uranium around in cylinders, using centrifugal force to separate heavier isotopes from lighter ones.

  Laser techniques are gaining in popularity, with Separation of Isotopes by Laser Excitation (SILEX) expected to become commercially viable in the near future. Other methods, such as electromagnetic isotope separation and plasma separation, have either been used in the past or were experimented with, but are not used today.

Size

• It is estimated that there is approximately 2000 tons of enriched uranium (both reactor and weapons grade) in existence around the world.

Potential

• There is a process called downblending for turning highly enriched, weapons-grade uranium into low enriched, reactor-grade uranium. This is a major feature of the Megatons to Megawatts Program, which is aimed at securing from danger and converting to peaceful purposes the vast nuclear weapons stockpile of the former Soviet Union.