Question

Describe the two competing methods that were used to separate Uranium 235 from Uranium 238, and identify which of the two methods ended up being used, and why. Be as specific as possible in your descriptions. (At least 2 paragraphs, 2-3 sentences per paragraph.)

Answer 1

solution:

The differences in chemical properties are very slight between uranium isotopes; the only effective means of separating them is to use the difference in mass between the 2 isotopes (uranium-238 and uranium-235). The uranium-235 isotope is actually lighter than the uranium-238 isotope.

GASEOUS DIFFUSION

• All the molecules in a gas are in movement, striking the wall of the container in which they are confined.
• The lighter molecules are the fastest, thus statistically they will strike the wall more often.
• If this wall is porous, the lighter molecules will come through it more frequently than the heavier molecules.
• The isotopes are thus separated, and this separation yields enrichment.

Using this principle, enrichment is carried out in successive stages: gaseous UF₆ is pushed by a compressor through a cascade of diffusers containing porous diffusion barriers. The gas is enriched in uranium-235 hexafluoride at each passage (1,400 in all).

New AREVA has conducted uranium enrichment by gaseous diffusion at the Georges Besse EURODIF Production plant, located at the Tricastin nuclear site (France) for more than 30 years. The production shutdown of this plant has started on May 2012. This plant is gradually being replaced by the Georges Besse II plant.

CENTRIFUGATION

• Gaseous UF₆ is introduced into a cylinder turning at very high speed in a vacuum in an air-tight chamber.
• Under the effect of the centrifugal force, the heavier molecules are sent to the edge of the tube.
• The gas enriched in the lighter uranium-235 isotope in the center of the tube rises. The gas richer in heavier uranium-238 descends.
• The enriched and depleted products are recovered at the 2 ends of the tube, the top and bottom.

Centrifugation is the highest performance technology available today. It offers better guarantees in terms of energy savings, controlling environmental impact and also competitiveness. It is already used in many countries around the world.

In the late 1980’s, advances in the resilience of carbon fiber materials made centrifugation the leading uranium enrichment technology.

Proven on an industrial scale since 1992 in Germany, the Netherlands and the United Kingdom, the centrifuge technology developed by ETC with its TC12 model, used at the Georges Besse II plant, offers the best cost-effectiveness, energy savings and technical reliability and the lowest environmental impacts.

The agreement found between URENCO and its shareholders in 2003 and completed in July 2006 enables AREVA to access centrifugation technology. This process has been in use in the Georges Besse II plant in Tricastin, France, started production in April, 2011 and which is scheduled for full production capacity in 2016.