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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.
> Radionuclide
Atom that emits ionizing radiation.
> 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 system
Family of reactors presenting common general characteristics.
> 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.
2016 AREVA
REFERENCE DOCUMENT
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