Introduction
Uranium hexafluoride (UF6) is a critical component in the nuclear fuel cycle. It is used to extract uranium from ore for use in nuclear reactors and for other nuclear energy applications. UF6 is a crystalline, inorganic, and colorless gas, composed of six fluorine atoms bonded to a uranium atom. It has a molecular weight of 352.03 g/mol and a density of 5.59 g/cm3. It is very reactive, both physically and chemically, and is corrosive to many metals.
Properties
Uranium hexafluoride is an incredibly dangerous material. From an environmental standpoint, UF6 reacts readily with water to form hydrofluoric acid, hydrogen fluoride and uranyl fluoride, all of which are toxic. The gas also has a boiling point of -14.8°C and a freezing point of -79.3°C, making environments where it is handled highly cold, even in the summer months. In addition, UF6 is a very heavy gas, making it difficult to handle in a non-industrial setting.
Production of UF6
Uranium hexafluoride is produced by combining various forms of uranium (e.g., UO2, UO2F2, U3O8, UC2, UCF4) with fluorine gas (F2). For most commercial applications, UF6 is produced in a gaseous-phase reaction between the uranium and fluorine gases via a fluorination reaction. This reaction is carried out in a closed bomb using a two-stage process. In the first stage, unreacted components are heated and reacted inside a steel bomb, forming several fluorides. In the second stage, these intermediates react further with UF6, forming the required UF6 and an inflammable gas, HF. The UF6 is then cooled and allowed to condense at a temperature <195K (–79.3°C).
Uses
Uranium hexafluoride is used in several areas of the nuclear fuel cycle. In the first step, UF6 is used in the gaseous diffusion process to concentrate the natural uranium ore. The UF6 is then further enriched further to produce low-enriched uranium fuel for nuclear energy applications. UF6 is also used for producing enriched uranium for weapons applications and for producing fluoride-based fuels for some experimental nuclear reactors.
Safety
Uranium hexafluoride is an exceptionally toxic material and requires extreme safety precautions during handling, storage and shipping. All personnel handling UF6 must be adequately trained and outfitted in the appropriate Personal Protective Equipment (PPE). Additionally, the storage containers for UF6 must be made of high-strength stainless, aluminum, or nickel steel. Transport vehicles transporting UF6 must also be equipped with reinforced tanks that are resistant to both gunfire and explosions. Any leaks in the UF6 containers must be contained using appropriate absorption materials, such as activated charcoal filters and sweeping products.
Conclusion
Uranium hexafluoride is an extremely dangerous material, but it is an integral part of the nuclear fuel cycle, so it must be handled with extreme caution and diligence. The production, handling, storage and shipping of UF6 requires specialized knowledge, equipment and procedures to ensure the utmost safety of personnel and the environment. Without proper use and disposal of UF6, the health and safety of those involved can be put at risk.
