Sylvie Willis
Uranium is the primary fuel for nuclear reactors, and it is mined and refined into a usable fuel. Uranium oxide, also known as yellowcake, is not directly usable as nuclear fuel and requires further processing. Uranium is enriched to increase the concentration of the fissile isotope U-235, which only makes up 0.7% of natural uranium. The enriched uranium is then converted into uranium dioxide powder, which is formed into small fuel pellets. These pellets are then loaded into fuel rods, which are grouped into fuel assemblies. The amount of uranium required depends on the type of reactor, with a 1000 MWe pressurized water reactor requiring approximately 27 tonnes of uranium per year.
| Characteristics | Values |
|---|---|
| Percentage of natural uranium that is fissile | 0.7% |
| Isotope of uranium that is fissile | Uranium-235 (U-235) |
| Percentage of U-235 in most reactor fuel | 3-5% |
| Percentage of U-235 in highly enriched uranium | 20% or more |
| Percentage of U-235 in low-enriched uranium | 0.711-20% |
| Percentage of U-235 in depleted uranium | 0.711% or less |
| Percentage of U-235 burned in CANDU reactors | 6.5% |
| Number of fuel rods in a fuel assembly | 90-200+ |
| Number of fuel pellets in a 1000 MWe pressurized water reactor per year | 18 million |
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What You'll Learn
- Uranium oxide is refined to uranium dioxide, which is usable as nuclear fuel
- Uranium oxide is converted to uranium hexafluoride gas, then enriched
- Uranium is mined using in-situ leaching, without disturbing the ground
- Uranium is refined and enriched before being loaded into a nuclear reactor
- Uranium oxide is processed to make fuel pellets for nuclear reactors
Uranium oxide is refined to uranium dioxide, which is usable as nuclear fuel
Uranium is the primary fuel for nuclear reactors and is found in rocks and seawater. Uranium oxide, often referred to as "yellowcake", is one of the first steps towards making nuclear fuel. However, it is not directly usable as fuel for a nuclear reactor and requires additional processing. Only 0.7% of natural uranium is "fissile", or capable of undergoing fission—the process by which energy is produced in a nuclear reactor.
The uranium oxide is refined to uranium dioxide, which is usable as nuclear fuel. This refined uranium dioxide can be used as fuel for reactors that do not require enriched uranium. The uranium dioxide powder is pressed to form small fuel pellets, which are then heated to make a hard ceramic material. These pellets are then inserted into thin tubes called fuel rods, which are grouped together to form fuel assemblies.
The number of fuel rods used to make each fuel assembly varies from 90 to over 200, depending on the type of reactor. A 1000 MWe pressurized water reactor requires about 27 tonnes of uranium—approximately 18 million fuel pellets housed in over 50,000 fuel rods—each year. In contrast, a coal power station of equivalent size requires over two and a half million tonnes of coal to produce the same amount of electricity.
For most reactor types, the concentration of the fissile U-235 isotope needs to be increased to between 3.5% and 5%. This process is called enrichment and requires the uranium to be in a gaseous form. The balance of the uranium oxide is converted into uranium hexafluoride, a gas at relatively low temperatures.
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Uranium oxide is converted to uranium hexafluoride gas, then enriched
Uranium is mined and refined into uranium oxide concentrate, often referred to as "yellowcake". This is achieved through a process called in-situ leaching, where water injected with oxygen or another oxidizing solution is circulated through the uranium ore, extracting it. However, this yellowcake product is not directly usable as fuel for a nuclear reactor and requires additional processing.
Only 0.7% of natural uranium is fissile, or capable of undergoing fission, the process by which energy is produced in a nuclear reactor. The fissile form of uranium is uranium-235 (U-235), which makes up 0.7% of natural uranium. The remainder is uranium-238 (U-238). For most kinds of reactors, the concentration of fissile U-235 needs to be increased to between 3% and 5%. This is done through a process called enrichment, which requires the uranium to be in a gaseous form.
To convert the solid uranium oxide into a gas, it is transformed into uranium hexafluoride, which is a gas at relatively low temperatures. This conversion is done at a separate conversion plant. The uranium hexafluoride is then fed into centrifuges, which separate the uranium into two streams: one enriched in uranium-235, and the other consisting of "tails" with a lower concentration of uranium-235, known as depleted uranium (DU). This enriched uranium hexafluoride is the product of this stage of the nuclear fuel cycle.
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Uranium is mined using in-situ leaching, without disturbing the ground
Uranium is the main fuel for nuclear reactors. In order to make the fuel, uranium is mined and goes through refining and enrichment before being loaded into a nuclear reactor. Uranium is mined using conventional mining methods, as well as in-situ leaching, also known as solution mining or in-situ recovery (ISR).
In-situ leaching is a process that involves leaving the ore in the ground and recovering the minerals by dissolving them and pumping the solution to the surface. This method does not disturb the ground and is considered environmentally friendly. It is also used to extract other minerals such as copper and gold. In-situ leaching is achieved by drilling boreholes into the ore deposit and pumping a leaching solution into the deposit, which dissolves the ore. The solution is then pumped to the surface and processed. This process is often used for deposits that are too deep or thin to be mined using conventional methods.
The uranium solution from the mines is separated, filtered, and dried to produce uranium oxide concentrate, often referred to as "yellowcake". This is the first step towards making nuclear fuel. However, the uranium oxide product is not directly usable as fuel for a nuclear reactor, and additional processing is required. The uranium oxide is refined to uranium dioxide, which can be used as fuel for reactors that do not require enriched uranium. For most reactors, the concentration of the fissile U-235 isotope needs to be increased through enrichment, which requires the uranium to be in a gaseous form. This is achieved by converting the uranium oxide to uranium hexafluoride, a gas at low temperatures.
The enriched uranium is then transported to a fuel fabrication plant where it is converted to uranium dioxide powder. This powder is pressed to form small fuel pellets and heated to make a hard ceramic material. These pellets are then inserted into thin tubes called fuel rods, which are grouped together to form fuel assemblies. About 27 tonnes of uranium, or around 18 million fuel pellets, are required annually for a 1000 MWe pressurized water reactor.
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Uranium is refined and enriched before being loaded into a nuclear reactor
Uranium is a common mineral found in rocks and seawater. It is used as a fuel for nuclear reactors. Uranium undergoes a series of processes before it can be used as a fuel in nuclear reactors. Firstly, it is mined from the ground using conventional mining techniques or a method called in-situ leaching. In this method, water injected with oxygen or another oxidizing solution is circulated through the uranium ore, extracting the uranium. The uranium solution is then pumped to the surface. The ore is crushed in a mill, and water is added to produce a slurry of fine ore particles. This slurry is leached with sulfuric acid or an alkaline solution to dissolve the uranium, leaving the remaining rock and other minerals undissolved.
The uranium solution from the mines is then separated, filtered, and dried to produce uranium oxide concentrate, often referred to as 'yellowcake'. Yellowcake is further processed to obtain the desired form of uranium suitable for nuclear fuel production. The milling process converts yellowcake to uranium dioxide, which can be used as fuel for reactor types that do not require enriched uranium. For most reactor types, the uranium oxide is converted to uranium hexafluoride, a gas at low temperatures. This conversion is necessary because the enrichment process requires the uranium to be in a gaseous form.
The uranium hexafluoride gas is then fed into centrifuges, which separate the uranium-235 from the uranium-238 isotope. Uranium-235 is the only naturally occurring fissile isotope, capable of undergoing fission, the process by which energy is produced in a nuclear reactor. The enrichment process increases the concentration of uranium-235 from 0.7% in natural uranium to between 3% and 5%, which is the level used in most reactors.
The enriched uranium is then transported to a fuel fabrication plant. Here, it is converted to uranium dioxide powder, which is pressed to form small fuel pellets. These pellets are heated to make a hard ceramic material. The pellets are then inserted into thin tubes called fuel rods, which are grouped together to form fuel assemblies. These fuel assemblies are then loaded into the nuclear reactor, where they remain for several years.
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Uranium oxide is processed to make fuel pellets for nuclear reactors
Uranium is the main fuel for nuclear reactors and can be found in many places worldwide. Uranium oxide, produced in a uranium mill, cannot be directly used as fuel for a nuclear reactor and requires additional processing. Only 0.7% of natural uranium is fissile, or capable of undergoing fission, the process by which energy is produced in a nuclear reactor. The isotope of uranium that is fissile is uranium-235 (U-235), which is used as fuel by most nuclear reactors. The concentration of U-235 needs to be increased to between 3% and 5% for use in most reactors.
Uranium is mined and goes through refining and enrichment before being loaded into a nuclear reactor. Uranium is found in small amounts in most rocks and even in seawater. Uranium oxide is first refined to uranium dioxide, which can be used as fuel for reactors that do not require enriched uranium. The uranium dioxide powder is then pressed to form small fuel pellets, which are then heated to make a hard ceramic material. These pellets are encased in metal tubes to form fuel rods, which are arranged into a fuel assembly ready for introduction into a reactor.
The uranium oxide is converted to uranium hexafluoride, a gas at relatively low temperatures, to increase the uranium-235 concentration. The uranium hexafluoride is reconverted to produce enriched uranium oxide. The enriched uranium oxide is then converted to uranium dioxide powder, which is used to make the fuel pellets.
Each nuclear fuel pellet, not much larger than a sugar cube, contains as much energy as a tonne of coal. About 27 tonnes of uranium, or around 18 million fuel pellets housed in over 50,000 fuel rods, is required each year for a 1000 MWe pressurized water reactor.
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Frequently asked questions
This depends on the type of reactor and the enrichment process used. For most reactors, the concentration of the fissile U-235 isotope needs to be increased to between 3% and 5%.
Uranium oxide is first refined to uranium dioxide, which can be used as fuel for reactors that do not require enriched uranium.
The balance of uranium oxide is then converted into uranium hexafluoride, a gas at relatively low temperatures, through a process called conversion.
The conversion to uranium hexafluoride is necessary for the enrichment process, which requires the uranium to be in a gaseous form.
The enriched uranium hexafluoride is reconverted to produce enriched uranium oxide, which can then be fabricated into fuel pellets for use in nuclear reactors.
