From the extraction of uranium to the fuel fabrication
Open sky uranium mine quarry near Arlit (Niger)
© AREVA ©
The front-end of the nuclear cycle is the name given to the various stages ranging from the extraction of uranium ore in mines to the introduction of fuel assemblies in reactors.
The content in uranium of uranium ores is low and generally does not exceed a few percent. Mines are often located far from industrial sites. To avoid unnecessary transports of large tonnages over long distances, an initial concentration of uranium is carried out in close proximity to mining sites.
After drying, the concentrates of uranium have the appearance of a bright yellow powder commonly called “yellow cake”. The yellow cake contains about 750 kg of uranium per ton, which facilitates the transport from the mine to the conversion plant. The picture shows the “Yellow cake” on a filter strips to the treatment plant of the Society of Mining Jouac (Haute-Vienne) in french Limousin.
© PHILIPPE LESAGE /AREVA ©
After a treatment which varies from one site to another, uranium is concentrated into a bright yellow powder, called “yellowcake”. The yellow cake contains about 750 kg of uranium per ton.
After transport, the next step is purification. Although already, concentrated the “cake” should be refined in order for uranium to get rid of impurities, for the preparation of the fuel.
For most existing reactors, natural uranium is not convenient and should be enriched in isotope 235. The industrial processes of isotope separation requires uranium to be in the form of uranium hexafluoride UF6, a fluorine gaseous compound. This uranium compound has the property of being able to pass easily from solid to liquid and gaseous states. Below 65 ° C it is liquid which facilitates the transport, above 65 ° C, it becomes gaseous and ready for enrichment. These operations of refining and conversion take place in France on the sites of Malvési, then Pierrelatte.
Containers of uranium hexafluoride
Uranium hexafluoride containers of stored at the EUDODIF Georges Besse enrichment plant on the site of Tricastin in France. Once purified, uranium has been converted into this chemical compound, liquid below 65 C (which facilitates its transport) and gaseous above this temperature. The gaseous form is required to enrich uranium in the fissile isotope 235 at the enrichment plant.
© AREVA/Taillat Jean-Marie ©
The final operation of isotope separation, by far the most complex, costly and strategic, is described elsewhere.
In 2000 the annual production in France was of 17,725 tons of raw uranium and 2,422 tons of enriched uranium (it has not varied much since). This would allow supplying fuel for 100 reactors of 1,000 megawatts.
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