THE’enrichment ofuranium It is a fundamental process so much for the production of nuclear energy as for military applications, Like atomic bombs. But what exactly does it mean “enriched”? And why is this productive step so fundamental? THE’enriched uraniumobtained mainly for gaseous centrifugation, it is a mixture of uranium isotopes with a greater percentage of the isotope Uranium-235the only one of the three useful to support the reactions behind nuclear reactors. The issue of uranium enrichment is of geopolitical current affairs, as demonstrated by the recent events concerning the Iran nuclear programmonitored for years by the international community as technology to enrich uranium for civil purposes (energy production) is the same that can be used to produce it for military purposes.
What is the enriched uranium and what it is for
THE’natural uranium It is mainly composed of three isotopes: Uranium-238 (about 99.27%), Uranium-235 (about 0.72%) e Uranium-234 (less than 0.01%). Only the Uranium-235 is fissilethat is, it is the type of uranium useful to support one chain reaction. This type of reaction is the one at the basis of the functioning of nuclear reactors to fission, but also of atomic bombs.
During the enrichment process we try to isolate the isotope Uranium-235 from the other isotopes, increasing the percentage. Based on the percentage of Uranium-235 that is obtained with enrichment, different are obtained types of uranium:
- Low enrichment uranium (Leu – Low Enriced Uranium), composed for less than 20% of Uranium-235. This type of uranium typically contains a percentage between the 3% and the 5% of this isotope and normally it is used for i Commercial fission reactors to light water;
- Low enrichment uranium with high concentration (Haleu – High-Assay Low-enricted uraiium), containing a percentage of Uranium-235 between the 5% and the 20%. In this type of uranium, the greater degree of enrichment than Leu is necessary for the functioning of the Small Modular Reactors (SMR), i.e. the reduced power and dimensions reactors, currently the development or construction phase to produce energy in a safer and modular way.
- High enrichment uranium (Heu – High Enriced Uraraium), composed for over 20% of Uranium-235. This type of uranium is mainly used for the manufacture of nuclear weapons. Heu can also be used for other niche applications, in particular to feed fission reactors used on board ships and in the medical field.
Theoretically, for a nuclear weapon it is necessary to uranium containing at least 20% of Uranium-235, but in practice the percentage of Uranium-235 used for the production Of bombs nuclear is at least of the85%. This is linked to the fact that plus the enriched uranium And the lower the mass required to give life to the fission reactions: since it is a argument to be launched, in fact, in Massa it is extremely important and a greater enrichment is preferred to maximize lightness.
How to get the enriched uranium
The uranium enrichment process is very complex due to the chemical properties of the isotopes of uranium. The Uranium-235 isotope has one minor of the Uranium-238 of little more than1%: for this reason the division between these two “variants” of the same element is so difficult to carry out. There are two fundamental methods to enrich Uranium:
- Gaseous centrifugationor the method more efficient and currently more used. This method uses the centripetal force Created by cylinders that rotate quickly on themselves to separate the Uranium-235 molecules from those of Uranium-238. Thanks to the rotation, the heaviest molecules of Uranium-238 remain outside the cylinder, while the lighter ones of Uranium-235 concentrate inside.
- Gaseous diffusionor the first method used, but now obsolete. This system uses the properties of some membranes To separate the isotopes. In fact, these membranes allowed the passage of Uranium-235, blocking a part of the Uranium-238.
Some are currently being experimented techniques use laser to allow chemical reactions to take place ionization Only in Uranium-235 molecules. These methods are still proving more efficient than centrifugesbut raise concerns about nuclear proliferation.
What is done with the gap of the enrichment: the depleted uranium
The waste of the uranium enrichment process is thedepleted uraniumcontaining a percentage of Uranium-235 isotope much lower than the natural uranium. The depleted uranium is very densethat is, it has a very high weight With the same volume than other elements, almost twice more than lead. Also, it does not emit radiationindeed it is capable of absorb them. For this, it is used in many sectors as a layer of shielding In the medical sector or how counterweight in the sector aerospace, aeronautical or oil.
