Alternator

The alternator is a rotating machine consisting of a rotor and a stator allowing the mechanical energy from the turbine to be transformed into electrical energy. The rotor is put into rotation by the mechanical power from the turbine, and turns at 1,500 rpm inside the stator, which is static. The electricity is produced in triphase at a frequency of 50 Hz in accordance with grid requirements. The current is modified by a transformer to amplify its voltage from 20 kV to 400 kV, and to lower its intensity from 48,000 A to 2,000 A.
Cold source

The heat flowing through the condenser is dissipated into the environment acting as the cold source. Water circulates in the tertiary circuit at a flow rate of approximately 50 m³/s. This water is drawn from a river or the sea and filtered. The circuit is said to be "open" when the tepid water is returned to its source after exiting the condenser. It is said to be "closed" when the water releases its heat to the ambient air in a cooling tower before returning to the condenser. About 1 m³/s of water evaporates in this process, forming a cloud plume.
Compaction

The metal structural waste from the shearing of fuel elements (sections of cladding, fuel assembly nozzles, etc.) is conditioned as slabs by compaction using a 2,500 ton press and stacked in stainless steel containers referred to as standard compacted waste containers (CSD-C).
Concentration

The extracted uranium ore, put into solution by a chemical attack reaction, undergoes purification and concentration. These chemical treatments allow the natural uranium to be isolated from all the other minerals, including its radioactive decay products. The solution obtained is precipitated to form a solid with high content in uranium (U3O8), referred to as yellowcake.
Condenser

The condenser turns the steam exiting the turbine into liquid water. The near vacuum draws in the steam at a rate of approximately two tons per second and allows its liquefaction upon contact with tubes cooled by the tertiary circuit. The liquid water is then degassed, preheated, and pumped back to the steam generators to begin a new cycle in the secondary circuit.
Construction of core

A typical reactor core consists of around 200 Fuel Assemblies (FA), each measuring 4 m in length and weighing 750 kg. These assemblies spend three to five years in the core and are moved at periodic intervals, to move them closer to the center as they are exhausted. Their arrangement also takes other constraints into account: alignment with the control and shutdown rods, interfaces between the different assemblies, irradiation of the pressure vessel, etc.
Conversion

The natural uranium is purified then transformed into uranium hexafluoride (UF6) to allow gas enrichment at low temperature. This conversion is carried out in two stages: the first one consists in transforming the uranium concentrate (U3O8) into uranium tetrafluoride (UF4) by dissolution then hydrofluorination; the second one is to transform the UF4 into UF6 by the addition of fluorine.
Counter-reactions

There are two types of self-stabilizing counter-reactions in the nuclear reactor: the moderating effect of the water in the reactor coolant system and the Doppler effect which has an impact on the absorption of neutrons by uranium 238. These spontaneous phenomena allow the power of the core to be reduced quasi-instantaneously if its temperature increases, and to increase it if the temperature decreases. They allow the power to be stabilized at a constant value and to thwart any possible runaway events without external intervention.
Deactivation in centralized pools

The spent Fuel Assemblies (FA) must be placed in interim storage prior to their processing in order to reduce their power and radioactivity. They remain in this way in centralized pool in the reprocessing plant for 5 to 7 years on average, under 9 meters of water. Underwater interim storage allows the fuel to be contained and cooled, while absorbing radiation and controlling the degradation of fuel assemblies with a view to their subsequent processing.
Deactivation in reactor pool

After passing through the reactor several times until its potential is exhausted, the fuel is put into interim storage in a pool of borated water in the fuel building of the reactor for a year and a half to five years. The water allows the absorption of radiation and the evacuation of heat, and the boron prevents the chain reaction from restarting. This period allows the radioactivity and the thermal power of the fuel to decrease, to allow for its dry transport for processing and recycling.
Deep geological disposal

Geological disposal, currently in the project phase, is envisaged for High Level Waste (HLW) and Long Lived Intermediate Level Waste (ILW-LL). This waste comes from the processing of spent fuel and reactors: - vitrified or compacted waste; - technological waste; - conditioned liquid effluents; - other radioactive waste which has been present in nuclear reactors.
Enrichment

Natural uranium essentially contains two isotopes, 235U (0.7 %) and 238U (99.3 %). Enriching the uranium consists in increasing its content in 235U. This operation is performed by ultracentrifugation in a cascade arrangement: under the effect of centrifugal acceleration, the heaviest molecules are pushed out to the edge, inducing isotopic separation. For current pressurized water reactors, the content in the isotope 235 of uranium is raised to between 3 % and 5 %.
Environment

Effluents can pose radiological, chemical and bacteriological risks. After treatment, they are controlled then discharged into the environment. The discharges are subject to regulatory limits not to be exceeded in order to protect the environment and health. Controls are carried out in the environment: samples of air, water, soil, organic matter, etc.
Extraction

Uranium is very commonly found in the Earth's crust and is naturally occurring in different forms. Each deposit is unique and requires specific techniques to extract the ore: - underground or open-pit mining; - in-situ leaching: this technique consists of circulating an oxidizing solution via injection wells in the mineralized layer, which selectively dissolves the uranium. The solution obtained is then pumped back to the surface and sent to the processing plant.
Extraction - Separation

The dissolution solution, obtained from spent fuel excluding structural elements, is processed to separate the recyclable materials from final waste. Three flows are generated as a result: - Uranium (U): around 95 % by weight; - Plutonium (Pu): around 1 % by weight; - Fission Products (FP) and Minor Actinides (MA): around 4 % by weight.
Fission

Fission, induced by the collision between a neutron and the nucleus of a fissile atom, is the splitting of the nucleus of an atom into two to four fragments known as "Fission Products" (FP). This phenomenon releases energy, transformed into heat, as well as several neutrons. These neutrons will in turn be able to induce new fissions: this is known as a chain reaction.
Formation of planets

The planets are formed from the matter present in a disk of dust and gas surrounding a young star, known as a protoplanetary disk. The dust particles aggregate to form planetesimals, which merge together to form protoplanets. They can in turn become planets, through the continuous and heterogeneous accretion of matter.
Fuel fabrication

The enriched uranium hexafluoride (UF6) is transformed into uranium dioxide (UO2) powder by defluorination. This powder is compacted then sintered to form pellets of enriched UO2 , which will then be inserted into zirconium tubes known as rods. Alternatively, depleted uranium and plutonium may be used as Mixed OXides (MOX), a substitute for enriched UO2. 264 rods containing around 300 pellets each, are combined in a metal structure to form a Fuel Assembly (FA).
General public - Associations

Citizens, either individually or grouped as associations or trade unions, participate in discussions on nuclear. They contribute to radioactivity measurements carried out in the environment, independently of industrial stakeholders. Public authorities organize information committee on a regular basis to discuss news relating to local industrial sites. The main strategic orientations, such as the construction of new reactors, are the subject of public engagement supervised by the CNDP, a national public debate commission.
High-voltage transmission

The transmission of electricity over long distances requires high voltages to limit losses. This network consists of two stages: - extra high-voltage power lines allow the transmission of electricity between regions or countries or to large urban areas. They operate at a voltage of 225 kV or 400 kV; - high-voltage power lines allow the distribution of electricity at regional or local level. They supply electricity to heavy industries or rail transport. They operate at a voltage of 63 kV or 90 kV.
Interim storage of recyclable materials

Different recyclable materials are placed in interim storage: - the Depleted Uranium (DU) resulting from the uranium enrichment step. It contains less than 0.4 % of 235U. One of its uses is the fabrication of MOX (Mixed OXides of uranium and of plutonium) fuel; - the Reprocessed Uranium (RepU) from the used fuel. It contains around 1 % of 235U. It can be re-enriched, and is then qualified as Enriched Reprocessed Uranium (ERU) and used in reactors.
Interim storage of technological waste

Technological waste is stored in areas physically marked on the ground when on their production site. Storage follows the precautionary principle regarding the risks it faces, such as: - Fire: prevention, detection, and extinguishing; - Ionizing radiation: exposure duration, distance, and shielding; - Chemistry: containment and separation of chemically incompatible materials. A physical inventory of technological waste ensures its traceability.
Interim storage of waste

The vitrified and compacted waste standard containers (CSD-V and CSD-C) are put into interim storage on their production site awaiting geological disposal. Although they only account for 3 % of the volume of all waste generated by French nuclear activities, they account for 99 % of the radioactivity.
Législator

The national legislator is responsible for establishing and implementing regulations governing nuclear activities. This role is carried out at both the European and national levels and involves various tools and bodies to address nuclear issues and challenges, such as: - HCTISN: High council for transparency and information on nuclear safety; - OPECST: Parliamentary office for scientific and technological assessment; - Parliamentary committees; - Advisory councils to public authorities from safety authorities.
Low-voltage distribution

Low-voltage distribution is used for the transmission of electricity over short distances. This network consists of two stages: - medium-voltage power lines allow electricity to be distributed at local level from substations to customers. They operate at a voltage between 15 kV and 30 kV; - low-voltage power lines are the smallest of the network. They supply electricity to the electrical sockets in our homes. They operate at a voltage of 230 V or 400 V.
Means of control

Control of the chain reaction requires continual balancing of the production of neutrons by fissions, the production of new fissions by neutrons, and losses of neutrons. To do this, neutron absorbers are used in different forms: boron dissolved in water concentration varying according to needs, gadolinium mixed with uranium in the fuel or different solid elements in the control rods.
Motor-driven reactor coolant pump

The transfer of several gigawatts of heat between the very compact core of the reactor and the steam generators requires a high flow rate to keep the water in the liquid state. Around 5 to 7 m3 of water passes through the reactor core every second. Three to four motor-driven pumps are necessary to maintain this flow rate, with one for each steam generator, constituting a corresponding number of "loops". Each of these machines weighing 100 tons and measuring 8 m in height consumes around 6 MW of electricity.
Nuclear safety authority

The nuclear safety authority plays the role of regulator for nuclear power, medical, and research sectors. Acting on behalf of the State, it ensures the oversight on safety and radiation protection by granting operating licenses for civilian nuclear facilities and conducting inspections, planned or unplanned. As part of its informational role, it issues public opinions and decisions. The authority records incidental and accidental events to be rated on the International Nuclear Events Scale. It also produces an annual report on the overall state of civilian nuclear safety and radiation protection in France.
Pressurizer

The pressurizer is a system which allows the water in the reactor coolant system to be kept in liquid form, despite a temperature in excess of 300 °C. It is placed on one of the loops of the reactor coolant system and keeps it a pressure of 155 bar. It also serves as an expansion vessel to absorb the dilatation of the water or its compression under variations in load. It is also equipped with valves to protect the reactor coolant system against overpressure.
Nucleosynthesis

Nucleosynthesis is the formation of chemical elements. This primordial process is at the origin of the presence of hydrogen and of helium in the universe. In stars, these elements fuse together to produce elements of the Mendeleev periodic table up to iron. Explosions and collisions of stars produce the extreme conditions allowing the fusion of lighter elements to create heavy elements, such as uranium.
Shearing - Dissolution

After their stay in the pool, the spent Fuel Assemblies (FA) are sheared before being immersed in nitric acid to dissolve the nuclear material. The dissolution solution produced in this way is sent to the extraction/separation workshops. Metal structural elements (sections of cladding and fuel assembly nozzles) are separated and sent for compacting.
Steam generator (single-phase leg)

The steam generator allows the heat generated by the reactor core to be removed and thus the reactor coolant system to be cooled. Its single-phase leg (reactor coolant system) consists of a multitude of U-shaped tubes through which the liquid water at a temperature of 324 °C coming directly from the reactor circulates. When it comes into contact with the two-phase leg, this water transfers its heat to the secondary cooling system. It comes out of the tubes at 289 °C before being pumped back into the reactor and heated up again.
Steam generator (two-phase leg)

The steam generator makes it possible to produce the steam to drive the turbine. Its two-phase leg (secondary cooling system) consists of water in two phases: liquid and gaseous. The liquid water is injected into the steam generator at 230 °C and 70 bar. When it comes into contact with the single-phase leg, this liquid water vaporizes recovering the heat from the reactor coolant system. The steam comes out of the steam generator at 284 °C before making its way to the turbine.
Supervision - Record-keeping

Radioactive waste disposal centers are designed to be passively safe once closed and thus do not require any intervention on the part of future generations. In addition, actions are in progress to transmit and keep records for these centers for at least three to five centuries. Beyond this, solutions are being considered to come up with ways of transmitting this information over longer periods.
Surface disposal

Surface disposal is reserved for Very Low Level Waste (VLLW) and Short Lived Low and Intermediate Level Waste (LILW-SL). This waste results mainly from the operation, the maintenance and the decommissioning of nuclear power plants, fuel cycle facilities, research centers and, to a far lesser extent, from the medical sector. France has three surface disposal centers: two are in operation - one specially for LILW-SL, and the other specially for VLLW and waste from non-nuclear power activities; the third is in the monitoring phase.
Thermal energy

100,000,000,000,000,000,000 fissions consume 0.05 grams of uranium. This is the number of reactions which occur every second, releasing 3,800 MW of thermal power. This is generated in the fuel and then transferred to the cooling water in the core via 200 km of rods.
Training, Research and Expertise

Training, research, and expertise encompass a wide range of activities, from fundamental sciences to humanities. These efforts are undertaken by industry professionals, public institutes, and universities, focusing particularly on nuclear safety, radioprotection, and the effects of ionizing radiation on workers, the public, and the environment. The International Commission on Radiological Protection (ICRP) issues recommendations laying the basis for most of international standards and national regulations in radiation protection.
Turbine

The turbine transforms the thermal energy produced by the steam generators into mechanical energy. The expansion of the steam first allows the thermal energy that it carries to be converted into kinetic energy which is captured by a series of rotors. The rotors then drive the shaft line of the generator. Upon exiting the turbine, the steam is then liquefied and continues its cycle in the steam-water system.
Vitrification

The Fission Products (FP), the shearing and dissolution fines, as well as the Minor Actinides (MA) are calcined then mixed with molten glass before being poured into stainless steel containers referred to as standard vitrified waste containers (CSD-V) offering safe and chemically stable conditioning for several tens of thousands of years.
Waste conditioning

Technological waste resulting from the operation of nuclear facilities is conditioned for interim storage or disposal. The conditioning processes can take several forms: compaction, concrete encapsulation, cementation, bituminization, sand embedding, incineration, or melting. These wastes are sorted according to their chemical nature, radiological characteristics and transportation regulations to their disposal sites. Upon arrival, the wastes are repackaged following the same criteria.
Did you know?

France's total electricity production amounts to around 500 TWh a year, nearly 70 % of which comes from nuclear energy. In addition to this, more than 20 % of the electricity comes from renewable energies (hydroelectric, wind, and solar power), fossil fuels and, to a lesser extent, from bioenergies. However, as electricity only accounts for a fifth of the energy consumed in France, fossil energies still represent over half of its energy mix, which is still very carbon-intensive.