Nuclear energy is an emissions-free energy source derived from splitting atoms in a purpose-built reactor to vaporize water. This steam is then forced into a turbine system, creating motion that generates electricity. Particle physics, which led to the discovery and development of nuclear energy, originated around the turn of the twentieth century and matured during the World War II (1939–1945) era.
According to the World Nuclear Association (WNA), nuclear energy offers many benefits, including a reliable, carbon-free solution to global energy needs, increased energy independence among the nations that use it, and economic benefits, including job creation and international development. However, it also has significant drawbacks, including dangerous radioactive waste byproducts and the potential for serious accidents, such as the 1986 explosion at the Chernobyl Nuclear Power Plant in Ukraine. As of January 2020, nuclear energy accounts for approximately 10 percent of the world's overall electricity production.
Nuclear energy first became possible in the early twentieth century when scientists discovered ways to split atoms. Understanding that this process released tremendous amounts of energy, researchers turned their focus to harnessing its power in controlled ways. The 1930s and 1940s saw major advancements in nuclear technology, but at the time, researchers were largely focused on developing nuclear weapons. Scientists working on a U.S. government project during World War II (1939–1945) created the first atomic bombs. In 1945, atomic bombs were dropped on the Japanese cities of Hiroshima and Nagasaki, prompting Japan's unconditional surrender and ending the war.
Meanwhile, scientists also developed reliable techniques to harness the heat from nuclear reactions and use it for everyday power generation applications. Known as nuclear fission, this process splits the heavy nucleus of an atom into two lighter nuclei. Controlled nuclear fission causes a relatively slow, cascading chain of nuclear reactions, which take place in a carefully structured, regulated, and safe environment.
Traditional power generation processes rely heavily on the heat energy released by the burning of fossil fuels. The resultant hot gases and steam propel magnetically charged turbine blades to produce an electrical current. Nuclear fission reactors produce electricity in a similar manner. Fuel rods loaded with radioactive material—mainly uranium and plutonium—lie at the core of the reactors. Nuclear reactions produce heat that vaporizes water to steam, which is then fed into electrical generators. To avoid overheating, the reactors are cooled using fluids such as water or gases such as carbon dioxide. Without such a cooling system, the metallic fuel rods can become hot enough to melt, spilling their radioactive contents into the reactor. This, in turn, can yield reactive gases capable of causing explosions and breaches in the reactor walls and surrounding containment vessels, which are usually made of steel. In a worst-case scenario, a complete meltdown can occur and release large amounts of dangerous radiation into the surrounding environment.
Partial meltdowns are also possible. For example, the metallic fuel rods can crack open and release some radioactive elements into the reactor. In dire cases, plant operators purposely vent radioactive gases into the surrounding air in an attempt to prevent explosive breaches of the reactor and its containment vessel.
The International Atomic Energy Agency (IAEA) was founded in 1957 with the sponsorship of the United Nations (UN). Its mandate is to work with UN member states and other partners to promote the peaceful use of nuclear technologies.
According to the IAEA, 450 nuclear reactors in thirty countries were operational for power generation purposes as of June 2019. The ten nations with the largest numbers of nuclear power generation facilities were the United States (97), France (58), China (45), Japan (37), Russia (36), South Korea (25), India (22), Canada (19), Ukraine (15), and the United Kingdom (15).
Nuclear power plants are expensive to design and build because of the many necessary safeguards that prevent radioactive releases. In addition, a country seeking to build a nuclear power plant must be able to source personnel with high levels of technological expertise and have access to fissionable materials such as uranium. It also needs adequate capabilities to store and dispose of radioactive waste, which can remain toxic for very long periods of time.
Notably, three countries with highly developed economies do not maintain nuclear power generation facilities. Italian voters decided to phase out its existing nuclear power plants in a 1987 referendum, and the last Italian nuclear facility ceased operations in 1990. Australia and Ireland both passed laws in the late 1990s banning nuclear power facilities within their borders.
The WNA is a voluntary membership association founded to represent the interests of the world's nuclear power industry. According to the WNA, there were about fifty nuclear power reactors under construction as of January 2020, with the largest number of projects located in China, India, Russia, and the United Arab Emirates. During the early 2010s, Germany, Italy, and Switzerland all decided to abandon plans to relaunch or expand their nuclear power capacities.
Many nuclear power reactors in developed economies are now decades old, and several of them are retired (taken out of service) each year. For example, the WNA notes that eighty-nine reactors were retired worldwide between 1998 and 2018. However, they were more than offset by the ninety-eight reactors that began operating during that same period.
As of 2018, France leads all countries in the proportion of electricity derived from nuclear energy and generates 72 percent of its total electricity with nuclear reactors. Slovakia (55 percent), Ukraine (53 percent), and Hungary (51 percent) are also very nuclear dependent. In contrast, the United States (19 percent), Russia (18 percent), Japan (6 percent), and China (4 percent) all fall at the lower end of this spectrum despite having relatively large numbers of nuclear reactors. In 2018, the United States produced the most nuclear energy of any country (805 terawatt-hours), followed by France (379 terawatt-hours).
Since its inception, the nuclear power industry has struggled with waste storage and disposal issues. Radioactive wastes from uranium mining, fuel processing, and nuclear reactor operations are all troublesome environmental and public safety issues. For example, spent nuclear fuel is highly toxic and must be isolated and contained for millennia. Every country that uses nuclear power grapples with the political and technical challenges associated with securing these materials for long time periods.
Yet, despite these issues, nuclear power has recently resurged in the context of the ongoing public debate about climate change. Because nuclear power is capable of continuously supplying large-scale electrical grids without burning carbon-rich fossil fuels, some advocates hail it as a possible solution to the current global warming crisis. However, it does pose other significant environmental and ecological challenges, as its byproducts include not only radioactive waste but also spent reactor fuel. Furthermore, when a nuclear power plant is decommissioned, reactor equipment is contaminated and the land must be mitigated to reduce its radioactivity and make it safe for other applications.
On the whole, nuclear energy continues to be a divisive issue. Critics tend to focus on the industry's safety and waste disposal challenges and gravitate toward natural, renewable power sources like solar and wind as replacements for fossil fuels. Nuclear power advocates tout its reliability and its carbon-free, climate-friendly aspects. They generally consider past accidents to be unique incidents that are unlikely to repeat. Some supporters also believe public perception of nuclear energy continues to be clouded by misconceptions and erroneous associations with nuclear weapons.
Nuclear power poses danger in three main ways. First, equipment malfunctions and human error can cause serious operational breaches with catastrophic potential. Second, severe weather, geological events like earthquakes and tsunamis, and other uncontrollable natural factors can also damage nuclear power equipment and cause large-scale environmental contamination. Finally, nuclear technology carries an inherent risk of weaponization. States that do not currently possess nuclear weapons could covertly develop them under the guise of nuclear power generation, then wield them as deterrents and threats to rivals and enemies. Iran, for example, has drawn scrutiny from the international community, with many outside states suspecting it has secretly engaged in such activities under the guise of a uranium enrichment program for electricity generation applications. Other countries that currently or formerly had nuclear weapons, such as India and South Africa, also used nuclear energy programs for electricity to access technology and resources to develop nuclear weapons.
As of 2020, the nuclear power industry has seen three major accidents that have had profound impacts on public opinion. The first occurred in 1979 when a reactor at the Three Mile Island nuclear plant in Pennsylvania suffered a partial meltdown due to equipment malfunctions, design problems, and operator error. Though a widespread disaster was averted, some radiation leaked into the environment. Subsequent studies have found possible links between the incident and cases of thyroid cancer among people in the affected area.
In 1986, a catastrophe occurred at the Chernobyl Nuclear Power Plant near the city of Pripyat, Ukraine, which was then a member state of the Soviet Union. A botched test resulted in a cooling system shutdown that sparked explosions, fires, and finally a complete meltdown of the reactor core. Dozens of plant workers and emergency responders died immediately or within a few months due to acute radiation poisoning, and hundreds of thousands of nearby residents were permanently evacuated from the area. Radiation from the Chernobyl release has been blamed for higher cancer rates among the populace most exposed to the radioactive plume ejected by the accident. In 2016, the UN's World Health Organization (WHO) published a thirty-year retrospective on the Chernobyl disaster. According to the agency, higher rates of thyroid cancer were a point of serious concern, especially among the children and adolescents in the exposure area who drank milk contaminated with radioactive iodine.
In 2011, another serious incident occurred, this time in Japan. A tsunami sparked by an earthquake swept the Japanese coastline, killing nineteen thousand people. The Fukushima Daiichi Nuclear Power Plant was swamped and lost the main and backup power sources for its cooling system. A series of meltdowns and explosions released radioactive materials into the air. Ultimately, seawater was pumped into the plant to cool the overheated reactors. By that point, more than one hundred thousand people had been evacuated from the area. According to the WNA, three plant personnel were killed during the earthquake and tsunami. However, few deaths or sicknesses were subsequently attributed to the radiation releases.
The Fukushima disaster prompted additional nuclear safety reforms around the world. In some quarters, it also dampened the enthusiasm for nuclear power that had steadily risen during the late 1990s and early 2000s as nuclear power was revisited as a climate-friendly alternative to fossil fuels.