In this article, I will share with you the methods used to enrich uranium in nuclear power plants.
If you know how the energy is produced in a nuclear power plant then you already know that uranium is an important part of this process.
Uranium is the fuel that is used with Plutonium to create the chain reaction that leads to the production of heat that is used to drive the steam turbine.
For more information on how the process happens read the article below.
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The uranium that is used in nuclear fission can either be enriched or not.
Some nuclear reactors e.g pressure water reactor uses enriched uranium because of the reaction it provides.
Enriched uranium provides the perfect chain reaction because it’s more stable than natural uranium and very compatible with most of the coolants used in nuclear reactors.
The enrichment of uranium increases the concentration of uranium-235 which increases the reaction capacity.
In some cases, the reaction with the natural uranium (U-235) doesn’t take place and the only way to make the reaction happen is to enrich the uranium.
The process of enriching uranium to contain a higher content of U-235 is called the concentration of uranium enrichment.
Methods used in uranium enrichment;
1. The diffusion method.
This method of enrichment of uranium is based on the principle that molecular gases with a lower weight penetrate through a porous barrier faster than heavy molecular gases.
In this method of enrichment, a separating stage for gaseous diffusion is used.
Non-saturated uranium Hexa-fluoride is used for gaseous diffusion.
The difference in mass in these gases is what enables them to diffuse.
The molecule weight of U235F6 is 349 and that of U238F6 is 352, these two mixtures are fed into the gap between the porous barrier.
Since U238F6 molecules are heavier than U235F6 molecules, U-235 being lighter will pass through the barrier quicker as enriched uranium of U235F6 and U238F6 will pass out of the barrier as a depleted product.
2. Thermal diffusion method of uranium enrichment.
In this method of uranium enrichment, a column of two concentric pipes is used.
The pipes are filled with UF6 liquid and space is left between the two pipes.
Since this method uses heat, One pipe is kept at a higher temperature than the other.
The temperature difference will make the liquid start rising along the hot wall of the pipe and falling along to cold wall.
The principle of convection heat transfer enables the heavy part of the liquid to remain on the cold wall while the lighter liquid rises on the hot wall.
In the same way, when boiling water, the cold water remains at the bottom while the hot water rises to the top.
So, the light liquid that is U235F6 will be on the hot side while the heavy liquid of U238F6 will remain on the cold side.
Thermal diffusion will take place during the circulation of these liquids within the pipes.
The U235F6 is obtained as enriched uranium.
3. Electromagnetic method.
This method is based on the principle that when ions move at equal velocities along a straight line in the same direction and are passed through a magnetic field, they are acted upon by forces perpendicular to the direction of ion movement and the field.
A gaseous compound of uranium is fed into the ion source where they are ionized first before they are passed to the separation chamber.
The ionization happens with the help of ion bombardment and the ions come out of the ionization source in form of a narrow beam after passing through a chamber of sitos.
The narrow beam of ions enters a separation chamber where the magnetic field is applied.
Since the ions will be moving at the same velocities, in a straight line and in the same direction the magnetic field disperses the ions in different directions due to their difference in mass.
Uranium-235 ions will be collected at the collectors while the Uranium-238 ions will be left on the magnetic field line.
Uranium-235 ions will be collected as the enriched uranium.
4. Concentration method.
This method is based on the fact that when two mixture gases with different weights are rotated in a centrifuge at very high speeds, the heavier gas will be obtained near the walls of the centrifuge while the light gas will be at the centre.
UF6 is fed into the centrifuge and then rotates at a very high speed this will leave the light gas of U235F6 at the centre of the centrifuge and its extraction will be done to separate these isotopes.
Uranium enrichment is quite expensive and that is why not all nuclear reactors use enriched uranium.
Thanks for reading, if you have any questions leave your comment. See you in the next one.
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