Operations: the processing of natural uranium

The chemistry of uranium

The COMURHEX Malvési plant receives uranium from all over the world in the form of ore concentrates known as "yellow cake", or oxide, contained in steel drums. COMURHEX Malvési is the only reception point for natural uranium in France.

Upon its reception, the processing of uranium concentrate begins.

This operation is carried out in 2 coordinated stages at 2 industrial sites:

• The COMURHEX Malvési site
  • purifies the uranium ore concentrate to a very high level,
  • converts the uranium ore concentrate into uranium tetrafluoride (UF₄).
• The COMURHEX Pierrelatte site (in the Drôme region) transforms the uranium tetrafluoride into uranium hexafluoride (UF₆).

This processing gives the uranium concentrate the required purity for the production of nuclear fuel.

Production process

The transformation of ore concentrate into uranium tetrafluoride (UF₄) involves the following steps:

• Dissolution: after reception and inspection, the ore concentrate is dissolved in nitric acid to obtain uranyl nitrate.
• Purification: any impurities are removed from the uranyl nitrate solution in a purification column. On completion of this stage, the uranium satisfies the purity requirements for use in nuclear power plants.
• Precipitation and calcination: the "purified" uranyl nitrate solution is then concentrated; Ammonium diuranate is obtained by the injection of gaseous ammonia. This is calcinated in ultra-high temperature furnaces. A solid matter is produced - uranium trioxide (UO₃).
• Reduction and fluorination: the uranium trioxide is then reduced to uranium dioxide (UO₂) by passing through a furnace, and then transformed into uranium tetrafluoride (UF₄) upon contact with hydrofluoric acid. This is the final chemical transformation step carried out at the Malvési site.
• Transportation: the UF₄ is packed in a special container and transported to the Pierrelatte site.

The COMURHEX II project at Malvési

To meet the growing needs of its customers, in 2007 AREVA decided to renovate and modernize its industrial facilities for converting uranium concentrate into uranium hexafluoride (UF₆). The initiative, called the COMURHEX II project, will maintain AREVA’s position as market leader.

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

The COMURHEX II project at Malvési has embarked upon a new industrial construction of around 2,500 square meters meeting the latest structural standards. The construction will include:

• a unit for the drainage and dissolution of ore concentrates, designed to improve product containment,
• a purified uranium thermal denitration unit. The process will end the use of ammonia, and enable the recycling of nitric acid,
• the modification of the purification unit,
• the construction of a processing facility for refined materials issuing from the purification phase. When connected to the future capture center for prestocked discharge, the use of lagoons will cease,
• the construction of a new gas treatment system for the hydrofluorination unit,
• the installation of an industrial platform featuring, among other things, a control system to handle all of the water collected, as well as a closed-loop cooling water circuit.