Site activities: uranium conversion

The second step in the conversion of uranium concentrate

COMURHEX Pierrelatte converts the uranium tetrafluoride (UF₄), originating from COMURHEX Malvési, into uranium hexafluoride (UF₆). This constitutes the second step in the conversion of uranium concentrate, also known as "yellow cake", originating from the mining sites.

UF₆ changes from a solid state into a liquid or gaseous state with only slight changes in temperature. Thus, UF₆, which is a gas at 65 ºC, is in the right form to be enriched using gaseous diffusion or centrifugation.

COMURHEX Pierrelatte also recycles the uranium contained in various materials produced during the conversion process:

• Impure uranium salts of varying degrees of complexity, with or without other chemically inert substances
• Pure uranium metals and alloys
• Impure ore concentrates
• Uranium trapped on ion exchange resins

The plant also converts (recycled) processed uranium originating from the uranium hexafluoride (UF₆) treatment. Once enriched in the future Georges Besse II plant, the uranium will be used to produce new fuels for pressurized water reactors.

Production process

• Electrolysis: Fluorine, a necessary raw material in the production of UF₆, is produced continuously by hydrofluoric acid electrolysis. Electrolysis separates the hydrogen molecules from the fluorine present in the hydrofluoric acid.
• Fluorination of UF₄: UF₆ is produced by bringing fluorine gas into contact with UF₄ powder. The chemical reaction takes place at ultra high temperatures in a flame reactor.
• Storage: Hot UF₆, in liquid form, is stored in containers that are certified for transport (type "48Y"). Once filled, the containers are put in storage for several days so that the UF₆ can refreeze and crystallize. They can then be handled in a manner that is completely safely.
• Transportation: The weighed and inspected UF₆ containers are shipped to uranium enrichment plants.

Fluorine production

COMURHEX Pierrelatte produces the fluorine needed for its conversion operations. Thanks to expertise gained through experience, this plant is now the premier gaseous fluorine producer in Europe.

It has developed a number of fluorine products used in the nuclear energy sector, as well as in the automobile industry.

• Nitrogen fluoride, used in the automobile industry to treat plastic materials and seal gas tanks
• Chlorine trifluoride, which is used:
  • to clean the barriers in the gaseous diffusion enrichment process in the company's enrichment plants,
  • in its ultra-pure form, for manufacturing microprocessors.

COMURHEX II: meeting the world's growing energy needs

To meet the growing needs of its customers, market leader AREVA decided in 2007 to renovate and modernize its industrial facilities for converting uranium concentrate into uranium hexafluoride (UF₆). The project was dubbed COMURHEX II. Annual production capacity should reach 15,000 metric tons of uranium by 2012 and 21,000 metric tons over the long term.

By implementing proven practices and technological innovations, COMURHEX II will offer enhanced production performance, a further reduction in environmental impact, and improved plant safety.

The COMURHEX II project in Pierrelatte comprises:

• a new hydrofluoric acid storage unit with containment and additional safety devices,
• new electrolysis fluorine production systems applying the latest advances in electrolysis technology,
• a new UF₄ and UF₆ fluorination unit using tried and trusted technologies alongside some new systems developed in this project,
• enhanced gas treatment processes with increased efficiency, enabling reductions in reagent used and waste produced, in turn decreasing fluorine production by 50% and potassium consumption by 60%,
• a new liquid discharge treatment system which will produce less waste.