Operations

How to contact or ask a question to AREVA T&D (Transmission & Distribution)? How to contact or ask a question to AREVA T&D (Transmission & Distribution)?

If you have any question to ask about the Transmission & Distribution operations of the AREVA group, please contact directly the AREVA T&D Contact Center by clicking here.

How does nuclear energy help combat the greenhouse effect? How does nuclear energy help combat the greenhouse effect?

Nuclear power is part of the answer to the threat of climate change. Nuclear-generated electricity does not emit carbon dioxide (CO2), the main cause of the greenhouse effect and global warming.

Nor does using electricity in the home, in industry or for transportation emit greenhouse gases.

It is interesting to note that France's energy choices have given it one of Europe's lowest CO2 emission rates per capita. Nuclear power prevents an estimated 1.8 billion tons of CO2 emissions worldwide every year, including some 800 million tons in Europe, or the equivalent of emissions from 200 million automobiles.

What's the EPR? What's the EPR?

The EPR is based on long proven pressurized water reactor (PWR) technology. It uses Uranium oxide fuel slightly enriched in U235, up to 5%, or mixed uranium and plutonium oxide fuel (MOX). Its net electrical power is in the range of 1,600 MWe.

The EPR is the result of a joint venture between Framatome* and Siemens KWU whose nuclear activities have since been merged to form Framatome ANP*.

It has the following advantages over its predecessors:
- its performance levels have been greatly improved, resulting in increased competitiveness,
- it includes a considerable number of advanced technological features that make it extremely safe,
- operation and maintenance are simplified,
- it provides solutions to sustainable development issues, notably by generating less waste and effluents.

* Now AREVA NP

To learn more:
Download the publication: The EPR, a strategic choice
Read the press kit: The EPR, the advanced nuclear reactor (October 2004)
View the 3D video clip about EPR
Week picture: Olkiluoto, Finland's fifth reactor and AREVA's first EPR

What is nuclear energy? What is nuclear energy?

Nuclear energy is the product of powerful forces that hold together protons and neutrons, the building blocks of the atom's nucleus. Some large nuclei can split into two smaller nuclei when they are hit by a neutron, releasing some of that energy in the form of a strong burst of heat.

During this reaction, called fission, two or three neutrons and radiation are released. Nuclear reactors use fission energy. When neutrons hit nature's only fissile atom, uranium 235 (U235), its nuclei split, producing heat that is converted into electricity.

What is a fuel assembly? What is a fuel assembly?

Nuclear fuel makes up the reactor core and is the reactor's source of energy. The heat it supplies is produced by a series of fissions of uranium enriched to 4% in the 235 isotope (versus the 0.7% found in nature).

The uranium is contained in highly elaborate fuel assemblies designed to control the nuclear fission reaction and for good thermal contact with the primary water.

The fuel is advanced technology designed to comply with stringent reactor safety requirements. Special precautions must be taken during its fabrication due to the presence of fissile materials.

A reactor may contain from 150 to 200 fuel assemblies, depending on its rated capacity. Every 12 or 18 months, one third or one fourth of the "spent" fuel assemblies in the reactor core are replaced with "fresh" assemblies.

The total residence time of an assembly in the reactor vessel is three or four years.

How does a nuclear power plant work? How does a nuclear power plant work?

This question relates more generally to how electric power companies operate. The AREVA group designs and builds reactors and supplies nuclear fuel products and services to electric power companies all over the world, but it is not involved in electric power distribution, which is provided by specialized companies such as EDF in France.

There are three types of power plants: fossil fuel plants, hydroelectric plants and nuclear plants. All three are based on the same concept: turning a turbine connected to an alternator that generates electricity. What differentiates them is how the turbine is driven.

In hydroelectric plants, water from a dam activates the turbine. In conventional fossil fuel plants coal, natural gas or oil is burned to convert the water into steam to drive the turbine. Nuclear plants replace those fossil fuels with uranium nuclei.

What are fission and the chain reaction? What are fission and the chain reaction?

Nuclear power plants operate with naturally-occurring uranium, a relatively abundant metal found in the earth's crust.

In its natural state, uranium is a mixture of two atoms or "isotopes": 99.3% is uranium 238 (U238) and 0.7% is uranium 235 (U235). Only U235 is fissile, its nucleus capable of splitting into several smaller nuclei.

When the nucleus of a U235 atom is bombarded by a neutron, it splits into two new smaller nuclei, or fission products. The fission process releases energy in the form of heat along with three new neutrons. These "new" neutrons will, in turn, split other U235 atoms, creating more neutrons that split more U235 atoms, and on and on in a chain reaction.

It is this chain reaction that makes nuclear power plants operate. The large amount of heat it releases in the reactors is used to heat water, converting it to steam just like a conventional boiler, which activates a turbine that drives an alternator that generates electricity.

How is reactor power controlled? How is reactor power controlled?

Reactor operations can be precisely controlled.
To start the reactor up, shut it down and operate it at various power levels, the chain reaction is modulated by inserting control rods into the reactor core.

The control rods contain neutron-absorbing boron or cadmium to slow down or stop the chain reaction.

The reactor's power can be varied by inserting the control rods at varying depths into the uranium fuel assemblies.

In the event of off-normal operating conditions, the controls rods are completely inserted into the reactor core, stopping the chain reaction in two seconds.

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