Nuclear energy is a form of energy released by the nucleus, the heart of atoms, made up of protons and neutrons. It can be produced in two ways, by fission – splitting the nucleus of the atom into several parts – or by the fusion of several nuclei.
The nuclear energy used today in the world to generate electricity comes from nuclear fission, with the technology of generating electricity through fusion still in the research and development phase.
A radioactive nucleus is an unstable nucleus that will disintegrate and thus transform into another more stable nucleus or not.
This disintegration is a random, spontaneous and inevitable phenomenon (which cannot be prevented).
The disintegration is accompanied by the emission of a particle and electromagnetic radiation.
There are three types of radioactivity:
Beta radioactivity is a type of radioactive decay where a beta particle (electron or positron) is emitted. We speak of beta + radioactivity when a positron is emitted but we speak of radioactivity – when an electron is emitted.
Alpha radioactivity is radiation caused by alpha decay which is radioactive decay where an atomic nucleus ejects an alpha particle which transforms into another nucleus whose mass number is decreased by 4 and atomic number by 2 due to the missing alpha particle which is analogous to the helium 4 nucleus.
Gamma radioactivity is radiation caused by gamma decay. Most often, these decays accompany alpha or beta decays. Indeed, when it emits an alpha or beta ray, the nucleus becomes excited. During the emission of gamma electromagnetic radiation, the nucleus can therefore descend to a more stable state.
Nuclear energy: what to remember
Nuclear energy is a relatively recent invention that has been constantly evolving for the past century. This powerful, low-carbon energy is continuously available to meet our various energy needs. From the extraction of uranium ore through nuclear fission, to the production of electricity that powers our homes: here are the different stages that make up the uranium cycle.
How does nuclear energy work?
Uranium: a natural resource.
Uranium is present in its natural form in the earth’s subsoil. It is the 235 and 238 isotopes of the ore that are used in the nuclear combustion cycle. Uranium 235 represents 0.7% of the uranium present in the earth’s crust. It is particularly unstable, very rare, and fissile.
It is enriched prior to its use, by centrifugation or diffusion, and then concentrated in the form of Yellow Cake. Orano has greatly developed its expertise in uranium enrichment and ranks 3rd in the world. Uranium 238, much more present in nature, is said to be fertile. It accounts for 99.7% of the uranium share in the earth’s crust.
The enriched uranium, which looks like black powder, is compressed, once processed, in the form of 7-gram pellets stored in 4-meter-long metal tubes called “pencils”. Perfectly hermetic, they are then aggregated in the form of a fuel assembly.
What happens in a nuclear chain reaction?
When a nucleus of uranium 235 is bombarded by a neutron, it will absorb it and split into two parts. This is nuclear fission.
By splitting, this nucleus produces new neutrons which will in turn bombard other uranium 235 atoms and this cascade of fissions is called a chain reaction.
Did you know? 1g of uranium produces more heat than the combustion of a ton of oil
It is controlled and maintained at a constant level thanks to control rods which measure and regulate the number of neutrons.
This phenomenon generates a large amount of energy and heat. The nuclear reactor then comes into play to reuse this energy by heating the water which produces steam and activates the turbine. The latter, combined with an alternator, transforms it into electricity.
Known and lesser known applications of nuclear energy
Nuclear energy has many other applications besides producing electricity. If it has promoted great advances in terms of medical research, its contribution in the fields of the arts, archeology or food are still little known. Here are some examples…
1. In medicine, it makes it possible to make leaps forward in terms of prevention, diagnosis, treatment of diseases, radiotherapy, alpha therapy, cancer research, etc.
2. In the fields of agriculture and food, it contributes to the improvement of agricultural techniques, food preservation and nutrition. Nuclear radiation makes it possible, for example, to fight against bacteria and many viruses that could harm crops, but also to detect in the soil the elements most favorable to the development of certain crops. Or to find water in arid areas by detecting it in an extremely precise way.
3. It promotes the protection of the environment, and in particular the seabed, through studies on ocean acidification and plastic pollution.
4. It also plays a big role in the restoration of works of art and greatly facilitates the work of archaeologists. It makes it possible to date, identify and reconstruct the history of objects discovered during excavations.
The Principle of Binding Energy
Using state-of-the-art techniques, it is possible to measure the mass of a nucleus, that of an isolated proton or an isolated neutron. The mass of the nucleus is less than the sum of the masses of each of its nucleons (protons and neutrons). What happened to the missing mass? This mass defect corresponds to a latent energy that Einstein’s famous formula, E = mc2, allows us to calculate. This amount of energy serves as the cement to hold the constituents of the nucleus together: for this reason it is called binding energy. It corresponds to the energy that must be supplied to the nucleus to dissociate it into isolated nucleons.
The nuclei of medium mass atoms (iron, nickel) are the most strongly bound and therefore more stable than the heavy (uranium) or light (hydrogen) nuclei.
They are of two types
1. The splitting or breaking of a very heavy nucleus into two medium sized nuclei
It consists in breaking heavy nuclei, such as those of uranium 235 or plutonium 239, under the effect of the impact of a neutron. It transforms each nucleus into two other nuclei about twice as small. It is the energy released by this reaction that is used in nuclear power reactors; it appears in the form of heat and, as with thermal combustion, its conversion into electricity has a limited yield (nearly 35% for 2nd generation reactors, 37% in the case of the EPR).
2. The fusion of very light nuclei into a slightly heavier and more stable nucleus
It is this phenomenon that occurs in the heart of the Sun and stars, mainly by fusion of hydrogen nuclei into helium nuclei.
Nuclear energy and climate change
Nuclear power is a low-carbon source of energy because unlike coal, oil or gas power plants, nuclear power plants emit practically no CO₂. Nuclear reactors, which produce nearly a third of the world’s carbon-free electricity, are key to meeting climate change goals.
With the adoption of the Paris Agreement in 2015, almost all parties to the United Nations Framework Convention on Climate Change have agreed to prepare nationally determined contributions to control greenhouse gas emissions and contain the rise in average global surface temperature at the end of the century to 2°C above pre-industrial levels. Since then, a better scientific understanding of the considerable risks associated with a warming of 2°C and the growing concern of society have underlined the need for more urgent and ambitious action to avoid the worst impacts of climate change by limiting the temperature rise to 1.5°C
To achieve this goal, carbon (CO₂) emissions from electricity generation must be reduced to zero or near zero by mid-century even as global electricity needs continue to grow in transport, heating and electricity. ‘industry.
Nuclear power is a low-carbon energy source. In 2018, it produced around 10% of the world’s electricity. With the expansion of renewable energy sources and the shift from coal to gas, increased nuclear power generation has helped limit global CO₂ emissions to 33 gigatonnes in 2019. Clearly, nuclear power, a source of low-carbon, easy-to-dispatch electricity can play a leading role in the shift to clean energy.
As part of building capacity for energy systems analysis and planning, the IAEA (International Atomic Energy Agency) is helping Member States assess the role of nuclear energy in national climate change mitigation strategies through the Technical Cooperation Program and coordinated research projects. To this end, a comprehensive set of IAEA tools and methods are available to Member States.
Sources: PinterPandai, IAEA, Energy Information Administration (EIA)