What is Nuclear Energy ?
Nuclear Energy is the energy of the Nucleus, or core of an atom. Atoms make up everything in the universe, and are held together with great force.
In a process called fission, atoms are broken apart, and energy is released. Atoms of uranium, a common element that can be mined from the Earth, are used in nuclear reactors. In fission a tiny particle called a neutron hits a uranium atom and the atom splits. This releases more neutrons, and generates a chain reaction. That reaction releases huge amounts of energy. Nuclear energy is also produced when two atoms join to become a new atom. This process is called fusion.
What is the structure of an atom ?
It is important to get an idea of the structure of an atom to understand how nuclear energy is produced. An atom is not the smallest particle of matter. The outer part of an atom consists of a cloud- often called shell or orbit- of particles called electrons, while inside this 'cloud' is the inner core of the nucleus. The nucleus is again made up of particles called protons and neutrons.
There are even smaller particles moving around in atoms. These super small particles can be found inside the protons and neutrons. They are usually known as nucleons and quarks. Protons have positively charged, while electrons have negatively charged, and neutrons have no charge at all.
Who discovered nuclear fission ?
It was in the early 1930's, that scientist discovered that atom is made up of proton and neutron particles, in addition to electrons.
In 1938, two German scientists, Otto Hahn and Fritz Strassman and physicist Lise Meitner of Australia, discovered that they could split the nucleus of a uranium atom by bombarding it with neutrons. This is called fission. As the uranium nucleus split, some of its mass was converted to heat energy. The next step was in 1942, when Enrico Fermi of Italy, noticed that the fission of one uranium atom gave off more neutrons which could in turn split other uranium atoms, starting a chain reaction. This meant that enormous amounts of energy could be produced by this process of nuclear fission.
Otto Hahn and Enrico Fermi both Nobel prizes for their work.
Why is uranium used for nuclear fission?
Uranium is one of the heaviest of all naturally occurring elements, It occurs in most rocks in concentrations of two to four parts per million. Uranium occurs in seawater, and can be recovered from the oceans. Like other elements, uranium occurs in several slightly differing forms known as 'isotopes'. The isotope U-235 is important, because under certain conditions it can readily be split, yielding a lot of energy.
When the nucleus of a U-235 atom is hit by a moving neutron it splits in two, and releases some energy. Two or three additional neutrons are also thrown off. It enough of these expelled neutrons cause the nuclei of other U-235 atoms to split, releasing further neutrons, a fission 'chain reaction' can be achieved. Hence uranium is widely used in nuclear experiments.
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