Safety of nuclear laboratories and plants

The terms "nuclear laboratories" and "nuclear plants" are commonly used to refer to all basic nuclear facilities other than reactors and facilities for the long-term storage of radioactive waste.

These installations include

• Nuclear fuel cycle plants: uranium enrichment, fuel fabrication and irradiated fuel processing plants;

• nuclear industry research laboratories and defense-related laboratories;

• facilities for processing, packaging and storing radioactive waste, treating radioactive effluents and maintaining contaminated materials;

• plants manufacturing radioelements for medical or industrial use;

• particle gas pedals and ionization systems (sterilization of food and medical products, in particular).

With the exception of gas pedals and ionizers, radioactive materials, including fissile materials, passing through these facilities undergo physical and chemical transformations through a variety of processes. For example, in fuel cycle facilities, the main transformations are as follows: fluorination of uranium in the form of uranium hexafluoride (UF ₆ ); enrichment of uranium in the isotope 235 by diffusion of uranium hexafluoride through porous barriers or by ultracentrifugation; defluorination-oxidation of enriched uranium hexafluoride ; sintering-sheathing of enriched uranium oxide, possibly combined with recycled plutonium oxide, to obtain fuel elements; shearing-nitric dissolution of irradiated fuel elements; solvent separation of uranium, plutonium and fission products, and packaging of these materials.

Nuclear laboratories and plants generally comprise several units in which radioactive materials undergo specific processing; such units will hereafter be referred to as workshops. The various workshops in the nuclear laboratories and plants under consideration are highly diverse:

• the processes used and the physico-chemical form (gases, liquids, powders, sintered products, sheathed solids) of the radioactive materials used;

• the nature of the radionuclides and chemical elements present (fissile isotopes, fission products, activation products, hydrogen, hydrofluoric acid, etc.).

A nuclear facility can be considered safe when the measures taken for its design, construction, operation and decommissioning ensure :

• firstly, in normal operation, to protect workers and members of the public from ionizing radiation