Areva - Reference Document 2016

GLOSSARIES 1. Technical glossary

> Pressurizer Equipment used to create andmaintain pressure in the primary cooling system of a pressurized water reactor (PWR) at a level designed to prevent the primary cooling water from reaching the boiling point. The pressurizer functions at a temperature that is higher than the rest of the cooling system and is where liquid/steam balance is achieved. > PWR (pressurized water reactor) Nuclear reactor moderated and cooled by light water maintained in the liquid state in the core through appropriate pressurization under normal operating conditions. > Pyrolysis Thermal decomposition of a solid fuel (biomass, coal, etc.) in the absence of oxygen to produce other products (gas and matter). > Radiation Also referred to as “ionizing radiation”, designates a release and transmission of energy or matter in thermal luminescent, electromagnetic or corpuscular form. > Radiation protection, radiological protection Set of rules, procedures and means for prevention and monitoring aimed at preventing or reducing employee and environmental exposure to the harmful effects of radiation. > Radiferous material Material containing daughter products of uranium, including solid radiumand radon, which is released in gaseous form. > Radioactive decay Spontaneous transformation of a radionuclide into another nuclide, accompanied by particle emission. > Radioactive half-life The time it takes for half of the nuclei of a given radionuclide to disintegrate in a quantity of matter. At the end of that time, the radionuclide’s radioactivity has decreased by half. No external physical action can modify the half-life of a radioelement, except its “transmutation” into another radionuclide, through neutron capture, for example. The radioactive half-life is thus a physical characteristic of a given radionuclide. > Radioactive material Radioactive substance for which an immediate or later use is planned or foreseen, after treatment if required. > Radioactive substance Substance containing natural or manmade radionuclides whose activity level or concentration warrants radiation protection measures. > Radioactive waste Waste consisting of radioactive substances for which there are no plans for further use.

> Radioactive waste disposal In France, this consists of placing radioactive waste in a facility especially designed to isolate them permanently from man and the environment, in accordance with the principles laid down in the Environmental Code. > Radioactive waste disposal in a deep geologic formation Disposal of radioactive waste in a specially designed underground facility in accordance with the principle of retrievability. > Radioactivity Phenomenon in which a nuclide is transformed, releasing radiation. Radioactivity may be natural or artificial (manmade). The radioactivity of an element gradually decreases over time as the unstable nuclei dissipate. > Radon Radioactive gas (222 isotope) resulting from the natural decay of the uranium and thorium contained in the ground. It reaches the atmosphere through natural cavities and cracks in the ground and may build up in caves, cellars, homes, etc. if not sufficiently vented. > Reactor, nuclear reactor Nuclear facility in which controlled nuclear reactions are conducted, producing heat that is used to make steam. The steam activates a turbine, which drives an electric generator. > Reactor coolant pump Motor-driven pump that circulates the water in the primary cooling system of a pressurized water reactor. It turns at close to 1,500 rotations per minute, pumping about 20,000 cubic meters of water per hour. > Reactor core Consists of the nuclear fuel inside the reactor vessel, arranged in such a way that the fission chain reaction can be maintained. > Reactor vessel A thick steel container enclosing the reactor core and the control systems for the fission chain reaction. The primary cooling water circulating in the reactor vessel is heated by recovering the energy produced. > Recycling of used nuclear fuel After a reactor residence time of three to four years, the used nuclear fuel must be unloaded. At that time, about 96% of the fuel materials are reusable (95% uranium and 1% plutonium), while 4% are fission products andminor actinides (final waste). Treatment consists of separating the reusable radioactive materials from the final radioactive waste contained in the used fuel (which are packaged for disposal) for purposes of recycling. Recycling allows for significant conservation of natural resources. > Radionuclide Atom that emits ionizing radiation. > Reactor system Family of reactors presenting common general characteristics.

379

2016 AREVA REFERENCE DOCUMENT