Nuclear energy comes from the binding energy that is stored in the center of an atom and holds it together. Releasing this energy can be achieved through two different processes, fissions and fusion, the first one refers to nuclei of atoms splitting into several parts and is the process through which nuclear energy is harnessed today, whilst the second one refers to nuclei of atoms fusing together and its technology is still at the R&D phase. (Source: iaea.org)
Nuclear power is a clean and efficient low carbon energy that offers many benefits for the environment because its power plants don’t burn any materials and thus, produce no combustion by-products and release no greenhouse gases. Consequently, nuclear energy helps protect air quality and mitigate climate change. (Source: nucleargepower.com)
How it works
In a nuclear power plant low-enriched uranium fuel is used to produce electricity through the fission process. Uranium fuel consists of small, hard ceramic pellets, that are packaged into long, vertical tubes; bundles of this fuel are inserted into a nuclear reactor where the fission happens generating heat, the heat produced is used to boil water into steam that is then used to turn a turbine that drives generators to produce electricity, as illustrated below. (Source: nucleargepower.com)
When hit by a neutron, the nucleus of an atom of uranium splits into a barium nucleus, a krypton nucleus and two or three neutrons.
These extra neutrons will hit other surrounding uranium atoms, which will also split and generate additional neutrons in a multiplying effect, thus generating a chain reaction in a fraction of a second, the fission’s reaction is shown by the following figure. (Source: iaea.org)
A single uranium pellet, slightly larger than a pencil eraser, contains the same energy as a ton of coal, 3 barrels of oil, or 17,000 cubic feet of natural gas. (Source: nucleargepower.com)
Types of nuclear power reactors
There are various types of nuclear reactors from which we can cite the following:
Pressurized water reactor (PWR)
Most common type of reactors, with about 300 operable reactors for power generation and several hundred more employed for naval propulsion.
In this type of reactors, water is heated in the core and pressurized to prevent it from turning into steam, this hot radioactive water flows through tubes in a steam generator, which is a giant cylinder filled with nonradioactive water (or clean water). The hot radioactive water from the reactor core eventually brings the clean water to a boil and turns it into steam, that is then used to power a turbine to generate electricity. (Source: eia.gov)
Boiling water reactor (BWR)
In a boiling-water reactor, the reactor core heats water, which turns directly into steam in the reactor vessel, the steam is then used to power a turbine generator. (Source: eia.gov)
The two reactor types stated above and other reactor types are detailed in the following table. (Source: world-nuclear.org)
Reactor type | Main countries | Number | Fuel | Coolant | Moderator |
Pressurized water reactor (PWR) | USA, France, Japan, Russia, China, South Korea | 305 | enriched UO2 | Water | Water |
Boiling water reactor (BWR) | USA, Japa, Sweden | 62 | enriched UO2 | Water | Water |
Pressurized heavy water reactor (PHWR) | Canada, India | 49 | natural UO2 | Heavy water | Heavy water |
Advanced gas-cooled reactor (AGR) |
UK | 12 | natural U (metal), enriched UO2 | Co2 | Graphite |
Light water graphite reactor (LWGR) |
Russia | 12 | enriched UO2 | Water | Graphite |
Fast neutron reactor (FBR) | Russia | 2 | PuO2 and UO2 | Liquid sodium | None |
Nuclear power data
According to the IEA at cop28 world energy outlook fuel report:
- Over the past 50 years, the use of nuclear power has reduced CO2 emissions by over 60 gigatonnes – nearly two years’ worth of global energy-related emissions.
- Nuclear power is the second-largest source of low-carbon electricity today, with 452 operating reactors providing 2700 TWh of electricity in 2018, or 10% of global electricity supply.
- The nuclear fleet in advanced economies is 35 years old on average and many plants are nearing the end of their designed lifetimes. Given their age, plants are beginning to close, with 25% of existing nuclear capacity in advanced economies expected to be shut down by 2025.
- Electricity generation from nuclear reactors decreased by around 4% in 2020. Major reductions took place in the European Union (-11%), Japan (-33%) and the United States (-2%). The decline in Europe resulted from depressed electricity demand, temporary shutdowns for scheduled and unscheduled maintenance, and permanent shutdowns.
- In 2021 nuclear power rebounds and increases 2% in 2021, reversing only half of the decline in output that took place in 2020. (Source: iea.org)
According to the World Nuclear Performance Report 2021, Nuclear reactors generated a total of 2553 TWh in 2020, down from 2657 TWh in 2019. (Source: world-nuclear.org)
Nuclear electricity production up to 2020 is shown in the figure below.
The following figures give nuclear energy data in some European countries. (Source: World nuclear performance report 2021)
