Based on data reported to the International Atomic Energy Agency (IAEA) by 31 December 2019, 450 nuclear power reactors were in operation worldwide, totaling 398.9 GW(e) in net installed capacity, an increase of 2.5 GW(e) since the end of 2018. Nuclear power generated around 10% of the world’s electricity in 2019, or almost one third of all low carbon electricity, and was set to remain the second largest source of low carbon electricity after hydro power.

Source: IAEA

In 2019, 30 countries generated nuclear power and 28 were considering, planning, or actively working to include it in their energy mix. Four of these countries, Bangladesh, Belarus, Turkey and United Arab Emirates, were building their first nuclear plants, with the plants in Belarus and the UAE nearing completion.

Nuclear technology was first developed in the 1940s, and during the Second World War it was used for producing bombs. In the 1950s attention turned to the peaceful use of nuclear fission, controlling it for power generation. For more information, see page on History of Nuclear Energy.

Nuclear energy is defined as a source of power which is created from energy released by a nuclear reaction. Nuclear reactors serve three general purposes:

  • Civilian Reactors are used to generate energy for electricity and sometimes also steam for district heating;
  • Military Reactors create materials that can be used in nuclear weapons; and
  • Research Reactors are used to develop weapons or energy production technology, for training purposes, for nuclear physics experimentation, and for producing radio-isotopes for medicine and research.


The focus of this book is on the Civilian and Research Reactors.

According to Word Nuclear Association, as of March 2020, the status of Nuclear Power:

  • The first commercial nuclear power stations started operation in the 1950s;
  • Nuclear energy now provides about 10 percent of the world’s electricity from about 440 power reactors;
  • Nuclear is the world’s second largest source of low-carbon power (29 percent of the total in 2017); and
  • Over 50 countries utilize nuclear energy in about 220 research reactors. In addition to research, these reactors are used for the production of medical and industrial isotopes, as well as for training.

Civil nuclear power can now boast more than 17,000 reactor years of experience, and nuclear power plants are operational in 30 countries worldwide. In fact, through regional transmission grids, many more countries depend in part on nuclear-generated power; Italy and Denmark, for example, get almost 10 percent of their electricity from imported nuclear power.

Number of Operable Reactors Worldwide 2020

Source: World Nuclear Association

Around 10 percent of the world’s electricity is generated by about 440 nuclear power reactors. About 50 more reactors are under construction, equivalent to approximately 15 percent of existing capacity.

In 2018 nuclear plants supplied 2563 TWh of electricity, up from 2503 TWh in 2017. This is the sixth consecutive year that global nuclear generation has risen, with output 217 TWh higher than in 2012.

Nuclear Electricity Production 2019

Here is an view of World Electricity Production by 2017:

Twelve countries in 2018 produced at least one-quarter of their electricity from nuclear. France gets around three-quarters of its electricity from nuclear energy, Hungary, Slovakia and Ukraine get more than half from nuclear, whilst Belgium, Sweden, Slovenia, Bulgaria, Switzerland, Finland and Czech Republic get one-third or more. South Korea normally gets more than 30 percent of its electricity from nuclear, while in the USA, UK, Spain, Romania and Russia about one-fifth of electricity is from nuclear. Japan is used to relying on nuclear power for more than one-quarter of its electricity and is expected to return to somewhere near that level.

Nuclear Generation by Country 2018

The performance of nuclear reactors has improved substantially over time. Over the last 40 years the proportion of reactors reaching high capacity factors has increased significantly. For example, 62 percent of reactors achieved a capacity factor higher than 80 percent in 2018, compared to 28 percent in 1978, whereas only 7 percent of reactors had a capacity factor lower than 50 percent in 2018, compared to 20 percent in 1978.

Long-term Trends in Capacity Factors

The global demand for electricity will continue to intensify and in order to meet this demand, future electricity generation will need a range of options and these options must be low carbon if the global objective is to reduce greenhouse gas (GHG) emissions significantly.  The good news is that nuclear generation provides reliable supplies of electricity, with very low carbon emissions and relatively small amounts of waste that can be safely stored and eventually disposed of.

The reality is that each method opted to generate electricity, generates GHGs in varying quantities throughout the life cycle – construction, operation, and decommissioning.  Some generation methods such as coal fired power plants release the majority of GHGs when their carbon-containing fossil fuels are burnt, producing carbon dioxide (CO2). Others, such as wind power and nuclear power, give rise to much less emissions, these being during construction and decommissioning, or mining and fuel preparation in the case of nuclear.  Comparing the lifecycle emissions of electrical generation allows for a fair comparison of the different generation methods on a per kilowatt-hour basis. The lower the value, the fewer GHG emissions are released.

Here is an important consideration.  Nuclear power plants produce no GHG emissions during operation, and over the course of its life-cycle, nuclear produces about the same amount of carbon dioxide-equivalent emissions per unit of electricity as wind, and one-third of the emissions per unit of electricity when compared with solar.

Average life-cycle carbon dioxide-equivalent emissions for different electricity generators (Source: IPCC)

It should be kept in mind that nuclear technology is not just used to supply electricity to the grid; it is in a wide variety of other uses such as medicine, heating and space travel.  For instance:

  • Nuclear Medicine:  Nuclear medicine uses radiation to allow doctors to make a quick, accurate diagnosis of the functioning of person’s specific organs, or to treat them. Radiotherapy can be used to treat some medical conditions, especially cancer, using radiation to weaken or destroy particular targeted cells.
    • Tens of millions of patients are treated with nuclear medicine each year;
    • Over 10,000 hospitals worldwide use radioisotopes in medicine, and about     90  percent of the procedures are for diagnosis.  The most common radioisotope used in diagnosis is technetium-99, with some 30 million procedures per year, accounting for 80 percent of all nuclear medicine procedures worldwide; and
    • Modern industry also uses radioisotopes in a variety of ways. Sealed radioactive   sources are used in industrial radiography, gauging applications and mineral analysis.
  • Heat for Desalination: Heat from nuclear reactors can be used directly, instead or as well as being used to generate electricity. This heat can be used for district heating, as process heat for industry or for desalination plants, used to make clean drinkable water from seawater; and
  • Space Missions:  Radioisotope thermal generators are used in space missions. The heat generated by the decay of a radioactive source, often Plutonium-238, is used to generate electricity.  The Voyager space probes, the Cassini mission to Saturn, the Galileo mission to Jupiter and the New Horizons mission to Pluto all are powered by RTGs. The Spirit and Opportunity Mars rovers have used a mix of solar panels for electricity and RTGs for heat. The latest Mars rover, Curiosity, is much bigger and uses RTGs for heat and electricity as solar panels would not be able to supply enough electricity.

In the future electricity or heat from nuclear power plants could be used to make hydrogen. Hydrogen can be used in fuel cells to power cars, or can be burnt to provide heat in place of gas, without producing emissions that would cause climate change.

The cost advantage of nuclear power over other forms of power generation depends greatly on your location and specifically the availability of other resources around you. As many of the resources needed for power is exhausted or their byproducts are outlawed, nuclear power becomes a much more attractive alternative.  An example would be coal, which is only economically attractive in countries where carbon emissions are cost-free such as China, the USA , and Australia .  In fact, if environmental and health costs are included into the price of power produced by coal its market cost would double.  This places countries in a situation where either a large up-front-cost can be spent on building nuclear facilities or money can be saved by using resources available but will cause the environment to pay the ultimate price.

The bottomline is that nuclear energy is a highly controversial energy source that some see as a way to reduce GHG emissions while other see it as a threat to their safety.  However, the reality is that without human errors, accidents, or natural calamities, the nuclear reactors work very well and can go on for a long time.  Furthermore, once constructed, the nuclear power plant requires very few people to operate it.

The Organization for Economic Co-operation and Development’s Nuclear Energy Agency (OECD-NEA) has today launched a series of policy briefs that examine nuclear energy’s role in the post-pandemic economic recovery. The policy briefs, to which World Nuclear Association contributed, have four themes: building resilience; job creation; cost-effective decarbonization; and unlocking finance.

According to the World Nuclear Association as of June 11, 2020:

  • Nuclear reactors have a key role to play in many countries in ensuring that electricity supplies are maintained during the COVID-19 crisis.
  • Reactor operators have taken steps to protect their workforce and have implemented business continuity plans to ensure the continuing functioning of key business activities where appropriate.
  • Operations have been halted at some facilities, where necessary or deemed appropriate, to prevent the spread of the virus and protect workers. Some facilities have now restarted operations.
  • Nuclear technologies are also being used to detect and fight the virus.

Updated on 2 June 2020; and updated on 30 June 2020.

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