Fission and nuclear energy
2026 editorial revision
Nuclear fission releases energy at the atomic scale that is incomparable with other energy sources used by humans.
Discovered in 1938, the fission of heavy nuclei, such as uranium and plutonium, is triggered by the capture of a neutron. The nucleus splits into two highly radioactive fragments, releasing energy and new neutrons.
Because of these neutrons, fission propagates from one uranium nucleus to another. This is the chain reaction which, when uncontrolled, results in an explosion (atomic bomb). The challenge for engineers in energy production is to control this reaction in reactors in order to spread the release of energy over months and years.
As a nuclear phenomenon, the fission of 1 gram of uranium-235 produces as much heat as the combustion of 1.6 tonnes of fuel oil or 2.8 tonnes of coal, which are chemical phenomena. Fission is an abundant and even virtually inexhaustible source of energy with the option of breeder reactors. Production units are powerful.
Nuclear energy does not emit greenhouse gases and does not contribute to global warming. Unlike wind and solar energy, it is not intermittent. For example, for its electricity production, Germany in 2019 emitted 208 million tonnes of CO2 equivalent, compared with 22.7 million in France, despite producing 5 times more renewable energy than France.
Very safe operation must be guaranteed to avoid accidents. Only developed countries, India and China have achieved this expertise.
Nuclear power also produces small volumes of highly radioactive waste, whose management requires the greatest care. This is the case in France. The public is not aware of it, but no sector has gone as far as the nuclear sector in reducing the volume of its waste and its hazardousness.
There is even an obligation to introduce sorting at source. This impressive source of energy, sought after by some and feared by others, cannot be placed in just anyone’s hands because the distinction between civilian and military nuclear power is a fine one. Access to nuclear power must be very strictly controlled, but it may be necessary to draw on the reserves stored in uranium atoms to meet the enormous demand from emerging countries. Most reactors under construction are now in Asia.
Fission and nuclear energy
Using the internal energy of the atomic nucleus to produce energy
© IN2P3
SUMMARY OF TOPICS COVERED
– The phenomenon of nuclear fission: Chain reaction, role of neutrons. A large amount of energy released. Fission products. Plutonium and minor actinides.
– Reactors: Reactor types: Pressurized water reactors (PWR), fast neutron reactors. Breeding. Reactor control.
– The nuclear fuel cycle: Uranium fuel. Enrichment and isotope separation. Use of plutonium and MOX fuel.
– Reactors of the future: Generations III (EPR) and IV. Generation IV reactor projects. Hybrid waste-burning reactors. Small modular reactors (SMRs).
– Military applications: Nuclear weapons: Nagasaki. Atomic tests. Atoms for Peace. Dismantling of arsenals.
– Nuclear proliferation: Proliferation pathways: Uranium enrichment. Weapons-grade plutonium. The case of Iran.
– Reactor safety: Principles of nuclear safety: Containment barriers. Reactor shutdown and cooling.
– Nuclear accidents: Accident scenarios: INES scale. Soviet accidents, Three Mile Island.
– Chernobyl accident (1986): Circumstances. Radioactive releases and contamination. Health consequences. Chernobyl today.
– Fukushima accident (2011): Causes and circumstances. Radioactive releases and contamination. Health consequences. Decontamination. Fukushima today.
– Nuclear fusion: ITER project.