Gas centrifuge technology (GCT) is a method of enriching mined uranium to levels at which it can be used to generate nuclear power. The process provides an efficient, stable and scaleable way to consistently and safely produce the type of uranium the nuclear power industry requires. GCT uses highly engineered centrifuges to separate different isotopes of uranium, thereby producing an enriched form that is ideal for use in a nuclear reactor.
In fact, GCT is a well-proven technology that is now positioned to establish itself as the global standard process for enriching uranium. Through continual research, development and engineering expertise, the process is becoming ever more reliable and efficient.
Before GCT, uranium enrichment was a significantly less efficient process. Various technologies have been employed historically to enrich uranium. These include a laser process, electromagnetic separation and liquid thermal diffusion. However the only other technology still in use today is the gas diffusion separation process.
As a measure of GCT’s comparative efficiency, modern centrifuges used in GCT consume less than 2% of the energy that was needed to run the old gas diffusion process. Without doubt, advanced centrifuge technology is clearly regarded as the future of uranium enrichment.
What is GCT?
GCT works by increasing the concentration of the isotope U235 in the uranium. This isotope is less stable than the much more prevalent U238, and it is this relative instability that makes U235 suitable for use in the chain reaction known as nuclear fission that is key to the nuclear power generation process. The enrichment process increases the concentration of U235 from its naturally-occurring percentage of around 0.7%, to between 4% and 6% (depending on the requirements of the customer).
What happens during GCT?
GCT technology uses sophisticated centrifuges to produce uranium with an increased concentration of U235 isotopes. Mined uranium is converted into a gas called Uranium Hexafluoride (UF6). This gas is then pumped into a centrifuge, containing a rotor which spins at high speed in a vacuum casing.
As a result of the centrifuge’s spinning motion, the heavier U238 molecules are forced to the outside of the centrifuge, while the lighter U235 molecules tend to congregate in the middle. A counter current of the UF6 within the centrifuge enhances the separation process.
The two types of UF6 are then drawn off in separate places – producing two streams of product, one enriched (known as product) and one depleted (known as tails).
The centrifuge cascade
GCT technology uses highly engineered centrifuges to produce uranium with an increased concentration of U235 isotopes. The actions of a single centrifuge are not enough to produce the level of enrichment needed, and so the centrifuges are employed in series. Enriched UF6 from one centrifuge is passed along the cascade, and as it passes forward the levels of enrichment – known as the assay – increase. The depleted UF6 is passed back along the cascade for reprocessing, to achieve high efficiency from the cascade.
To deliver more throughput of material, the centrifuges are also connected in parallel in an industrial plant. This arrangement of centrifuges in series and in parallel is known as a cascade. An arrangement of several cascades may be used in a uranium enrichment plant to produce a single U235 assay. One of the key advantages of GCT is that the modular nature of the technology allows enrichment plants to scale up or down as the market demands.
Why does uranium need to be enriched?
Uranium produced by mining contains less than 1% of an isotope called U235. Because it is less stable than the much more prevalent U238 isotope, U235 is the isotope which nuclear power reactors use for nuclear fission.
In its naturally occurring state, uranium contains about 99.3% of U238, with the remaining 0.7% made up of U235. In order to produce uranium that is fit for the purpose of energy generation in a commercial nuclear reactor, uranium needs to have its concentration of U235 increased to between 4% and 6%. It is only at this concentration that the nuclear reaction which occurs in the nuclear power generation process can be initiated and sustained.
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