Nuclear power is the generation of electricity from controlled reactions within the nucleii of atoms that release energy used to boil water, the steam from which drives a turbine to generate electricity . The International Atomic Energy Agency (IAEA) reports that, as of November 21, 2012, there are 437 nuclear power reactors in operation in 30 countries, plus Taiwan.
In addition to electricity generation, nuclear power is presently used to power over 150 marine vessels, both civilian and military; and two countries (Russia and the USA) have deployed nuclear powered spacecraft. Because it does not result in the emission of greenhouse gases, nuclear power has received increased support in recent years as an alternative to fossil fuels to mitigate global warming.
The severe damage to several nuclear reactors at the Fukushima Daiichi plant in Japan in March 2011, following a devastating earthquake and tsunami, has led to increased attention to safety issues related to nuclear power. Research has been undetaken for many decades into nuclear fusion (an alternative form of nuclear energy to fission), which theoretically could generate significant power without many of the environmental concerns connected to fission. Ancient Greek philosophers first developed the idea that all matter is composed of invisible particles called atoms. If it were ever possible to control at will the rate of disintegration of the radio elements, an enormous amount of energy could be obtained from a small amount of matter. Albert Einstein developed his theory of the relationship between mass and energy one year later. James Chadwick discovered the neutron in 1932, and soon thereafter in 1934 physicist Enrico Fermi conducted experiments in Rome that showed neutrons could split many kinds of atoms.
In the fall of 1938, German scientists Otto Hahn and Fritz Strassman fired neutrons from a source containing the elements radium and beryllium into uranium (atomic number 92).
Hahn and Strassman contacted Lise Meitner in Copenhagen before publicizing their discovery. Scientists throughout the world began to believe a self-sustaining chain reaction might be possible.
Fermi and his associate, Leo Szilard, suggested a possible design for a uranium chain reactor in 1941. Early in 1942, a group of scientists led by Fermi gathered at the University of Chicago to develop their theories. On the morning of December 2, 1942, the scientists were ready to begin a demonstration of Chicago Pile-1. A major goal of nuclear research in the mid-1950s was to show that nuclear energy could produce electricity for commercial use. Chernobyl (Ukraine 1986) where the destruction of the reactor by steam explosion and fire killed 31 people and had significant health and environmental consequences.
Fukushima (Japan 2011) where three old reactors (together with a fourth) were written off and the effects of loss of cooling due to a huge tsunami were inadequately contained. The first two accidents led to significant changes in the regulation and operation of nuclear power plants and in a slowing of construction starts for new plants.
The worldwide mix of primary fuels used to generate electricity has changed a great deal over the past four decades. From the early 1970s to the early 1990s, nuclear power steadily grew around the world with brief periods of relatively slow growth following the accidents at Three Mile Island (North America, 1979) and Chernobyl (Former Soviet Union, 1986), as the nuclear industry absorbed the lessons learned from both accidents. The International Atomic Energy Agency (IAEA) reports that, as of October 1, 2012, there are 435 nuclear power plant units with an installed electric net capacity of about 370 GW, which are in operation in 30 countries, plus Taiwan. The three contruction starts in 2012 occurred in Russia, South Korea, and the United Arab Emirates. The nations that have permanently shutdown the most reactors at the United Kingdom (29), the United States (28),  Germany (27), and France (12). The share of total electricity generation provided by nuclear power plants varies widely, as show in the figure below. The United States has more nuclear capacity and generates more electricity from nuclear power than any other nation. There are currently 104 operable commercial nuclear reactors at 65 nuclear power plants in 31 states.


The last new reactor to come on-line in the United States was the Tennessee Valley Authority's (TVA) Watts Bar 1 reactor in Tennessee, in February 1996. Nine European countries generated over 30% of their electric power from nuclear sources in 2010. Recent issues in European energy policy include a reassessment of nuclear power following the accident at Japan's Fukushima nuclear facility in March 2011. Germany currently generates about a quarter of its electricity from nuclear power, yet announced plans to decommission its more than 20 gigawatts of nuclear capacity by 2022. The true costs of nuclear power is a topic of significant disagreement between different scholars and between advocates for and against use of nuclear power. Research seems to show promise; one test installation in Yonkers, NY, can produce 200kw by using gas created in the operations of a wastewater treatment plant. Another 64 reactors under construction in 14 countries which if operational today would increase the worldwide electrical generation capacity of nuclear power by 17%.
Safety concerns about the release of radiation were highlighted by accidents at Three Mile Island in the United States (1979) and at Chernobyl in Ukraine (1986 when Ukraine was part of the Soviet Union), and recently, in Fukushima, Japan (2011). The time horizon for commercially viable nuclear fission electricity generation is highly uncertain and likely to be many decades away if acheivable. They were surprised to find lighter elements, such as barium (atomic number 56), in the leftover materials.
Their model consisted of uranium placed in a stack of graphite to make a cube-like frame of fissionable material. By November 1942, they were ready for construction to begin on the world’s first nuclear reactor, which became known as Chicago Pile-1. Fermi ordered the control rods to be withdrawn a few inches at a time during the next several hours. Most early atomic research focused on developing an effective weapon for use in World War II. The AEC authorized the construction of Experimental Breeder Reactor I at an experimental facility near Arco, Idaho. On August 27, 1956, the Calder Hall nuclear power plant in northern England, with a net electrical output of 50 MW was connected to the national grid.
The first commercial electricity-generating  plant powered by nuclear energy was located in Shippingport, Pennsylvania. Apart from the initial deaths, the number of deaths resulting from the accident is unclear and a subject of considerable controversy. The long term impact of the Fukushima is not yet clear, but already Germany, Switzerland, Italy, and Austria have resolved to reduce or eliminate their reliance on nuclear power in the aftermath of that event. Coal continues to be the fuel most widely used for electricity generation, although generation from nuclear power increased rapidly from the 1970s through the 1980s, and natural-gas-fired generation grew rapidly in the 1980s and 1990s. Worldwide Nuclear Electricity Generation and Nuclear reactor construction starts, 1951 – 2011. Since then, nuclear power capacity has remained relatively stable throughout most of the world, with the exception of rapidly developing countries in Asia. Further, there 64 reactors under construction with an installed capacity of 62 GW are under construction in 14 countries.
Nuclear power reactors world-wide, in operation and under construction, as of November 21, 2012 according to the International Atomic Energy Agency (IAEA) Power Reactor Information System.
Since 1990, the share of the nation's total electricity supply provided by nuclear power generation has averaged about 20%, with increases in nuclear generation that have roughly tracked the growth in total electricity output.
While Germany, Switzerland, Italy, and Austria have resolved to reduce or eliminate their reliance on nuclear power in the aftermath of that event, France plans to continue its current extensive nuclear program, as does the United Kingdom.
Switzerland generates over a third of its electricity from nuclear sources, but has decided to halt development of new facilities. Countries within the EU must consider EU-wide energy goals, which include a 20% decrease in greenhouse gas emissions by 2020 (from 1990 levels).


Belgium, Bulgaria, the Czech Republic, France, Hungary, Slovakia, Slovenia, Sweden, and Switzerland use nuclear energy for over 30% of their electricity generation.
Comparing the cost of nuclear power to other sources of electricity adds additional areas of disagreement.
One hundred and forty reactors have been permanently shut down since the beginning of commercial nuclear power in the 1950s; another 3 are in long term shut down.
Other concerns relate to the long term safety of spent fuel, and the diversion of reactor fuel for use in weapons.
British physicist Ernest Rutherford was called the father of nuclear science because of his contribution to the theory of atomic structure. The amount of uranium needed to make a self-sustaining chain reaction is called a critical mass. The pile was erected on the floor of a squash court beneath the University of Chicago’s athletic stadium.
The work was done under the code name Manhattan Project which led to the two atomic bombs used in August 1945 against Japan to bring World War II to an end. The reactor generated the first electricity, around 100 kilowatts of power, from nuclear energy on December 20, 1951. However France plans to continue its current extensive nuclear program, as does the United Kingdom, and new plants are being planned in other parts of the world. The use of oil for electricity generation has been declining since the mid-1970s, when oil prices rose sharply. The post-Fukushima (March, 2011) impacts on Japan's nuclear capacity and elsewhere is still evolving. The NRC approved Southern Company's application to build and operate two new nuclear reactors at the Vogtle nuclear plant, near Augusta, Georgia, which already houses two operating reactors. Germany, which ranked second in both total and nuclear generation in 2010, has announced plans to phase out nuclear generation by 2022. Existing plants will be permitted to operate until the end of their lifetime, effectively phasing out nuclear power in that country by 2034. Because nuclear power does not emit greenhouse gases, the loss of the nuclear component in the generation portfolio in some countries will make it harder for them to meet the national commitments that have been made in support of this EU-wide goal. Fermi and his group had successfully transformed scientific theory into technological reality.
However, some scientists worked on making breeder reactors, which would produce fissionable material in the chain reaction. Light-water reactors like Shippingport use ordinary water to cool the reactor core during the chain reaction.
Every country which operates nuclear power plants has a nuclear safety inspectorate and all of these work closely with the IAEA. Nuclear generating capacity additions began in the 1950s and now top 370 gigawatts worldwide. Four new nuclear reactors (Vogtle Units 3 and 4 and Summer Units 2 and 3) are expected to come on-line between 2016 and 2017.
Italy and Austria do not have commercial nuclear reactors; however, in a recent referendum, Italy voted against new nuclear construction, and Austria has decided to end their imports of electricity generated from nuclear sources by 2015. Meitner and Frisch thought the barium and other light elements in the leftover material resulted from the uranium splitting — or fissioning. Nuclear power provided slightly more than 19% of electricity and about 8% of all energy consumed in the United States. However, when she added the atomic masses of the fission products, they did not total the uranium’s mass.



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