Page 33 - Curriculum Visions Dynamic Book

Reactor
Uses of nuclear energy
The image of nuclear energy is clouded with the experience of how the energy can be released for destructive purposes (such as the atomic bombs dropped on Japan in order to end World War II, see page 38) and how some dangerous radioactive materials can sometimes escape (as was the case at Chernobyl, see page 37). Indeed, the need for very powerful bombs during World War II encouraged politicians to fund nuclear research in the first place.
The first fission reactor was created by a team led by Enrico Fermi in Chicago in 1942. His team used natural uranium,
which is mostly uranium-238. However, only the more rare uranium-235 can be made to react. Thus, they discovered that
to make the reaction work successfully they needed to produce concentrated uranium-235 (“enriched uranium”), or they needed to use plutonium.
Although some of this material has been used for weapons, the vast majority is now used for making electricity. Nearly one-
fifth of the world’s electricity is generated by nuclear means, making it one of the world’s most important energy supplies. It is expected that although nuclear energy programmes have slowed down in some countries, the adoption of nuclear energy
in the developing world – especially in countries that have little coal or oil of their own – will cause the world use of nuclear energy to be responsible for one-quarter of the world’s electricity needs by the end of the century.
 The core of a reactor contains fuel rods, a moderator and control rods. The purpose of the fuel rods is to provide the fissionable material. However, without a moderator material (such as graphite), the neutrons created
by fission would move too fast to be captured by the remaining fuel. The moderator slows down the neutrons so that the likelihood of capture by a nucleus is high. Control rods, on the other hand, serve to stop the fission process. They are made of materials that absorb (not just slow down) neutrons, so that the neutrons cannot be captured by more nuclei.
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