Process by which an element's content of a fissile isotope is increased. For example, the fissile uranium 235 content of natural uranium is 0.7% and the non-fissile uranium 238 content is 99.3%. To make it utilisable in a pressurized water reactor, the proportion of uranium 235 is increased to around 3 or 4%.

Several non-proliferation agreements have been signed since 1969. They prohibit nuclear weapons countries from transferring know-how to other countries. The other signatory States agree not to acquire a nuclear deterrent capability. Few countries have not signed these accords (North Korea and Iran).

Nuclide that releases energy when consumed by fission in a reactor. By extension, product containing fissile materials that supplies energy in the reactor core by sustaining the chain reaction. A 1,300 MWe pressurized water reactor holds about 100 metric tons of fuel, which is regularly replaced by section.

The system encompassing the nuclear steam supply system and the fuel-related facilities, as well as the equipment required for the system’s operation and safety. A “conventional island” consists of the alternating current turbogenerator coupled to the nuclear island, along with the equipment required for its operation.

(See also "SAFETY ANALYSIS REPORT") In the nuclear industry, nuclear safety covers measures taken at every stage of the design, construction, operation and final shutdown of a facility to ensure operational safety, to prevent incidents, and to limit their effects. - RFS - Règles Fondamentales de Sûreté (fundamental safety rules): safety rules for licensed nuclear facilities setting forth requirements for compliance with French regulations. - RGE - Règles Générales d'Exploitation (general operating rules): document that describes the prescribed operating boundaries of the facility and identifies operations important for safety. It describes measures to be taken during operations in the event of a breach of normal operating boundaries.