How is uranium enriched in U-235?

Answer 1

Many methods are known now.

1. Large scale methods: centrifugation and gaseous diffusion

2. Small scale methods: thermal diffusion, nozzle expansion, laser separations, electromagnetic separation, ion exchange separation, etc.

Answer 2

Separation of isotopes can only be done by physical means, using the slight difference in weight or density from the majority U-238. Uranium can be made gaseous as uranium hexafluoride. There are two methods: gaseous diffusion which was used in the Manhattan Project in WW2 and has continued after the war for many years, and centrifuge operation which was developed in Europe and uses much less electrical power. A long chain of many centrifuges is required, the more you have the higher the quality of the U-235 produced.

Answer 3

Uranium occurs in nature primarily as about 99.3% 238U and about 0.7% 238U. This natural mix will not produce a chain reaction, no matter how pure it is or how much of it there is. This is because fission of 238U has a small yield neutrons that will cause fission. Since 235U has a relatively rich yield, if the amount of 235U is increased sufficiently, the resulting mix can produce a chain reaction, with each fission event causing more fission events until the whole is consumed.

Enriching uranium is a process of separating out 238U selectively in greater quantities than 235U. This is a much more difficult operation than doing a typical chemical separation of different elements, since the things being separated are nearly identical chemically.

The original method of separation depended on the fact that when a fluid containing uranium was heated, the 235U would tend to concentrate closer to the heat source. This was replaced by gas diffusion, a method that depended on the fact that UF6 gas containing atoms of different isotopes would diffuse through semipermeable membranes at different rates, producing different concentrations of isotopes.

Later diffusion techniques depend on centrifugal force, which prefers to send the heavier molecules of UF6, which have the 238U in them, outward in a centrifuge.

There are a number of other, mostly experimental, processes of enrichment. These involve the use of lasers, electromagnetism, plasma, and so on.

Answer 4

Uranium contains to isotopes U235 in small quantity and U238 in larger quantity. the ist isotope is used to produce plutonium and hence atomic bomb, the separation of U235 from mixture in maximum purity this is known as uranium enrichment.

Answer 5

- centrifuging

- gaseous diffusion

- thermal diffusion

- laser separation

- ion exchange

- electromagnetic

- nozzle