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| Nuclear Reactors |
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| A nuclear reactor is a device for obtaining and using the energy from a controlled nuclear chain reaction. Controlled means the rate or speed of the nuclear fissions can be changed by the operator. Most reactors are constructed in a similar manner. The six main parts of a nuclear reactor are fuel, moderator, control rods, coolant, heat exchanger, and safety shields. |
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| The fuel in a nuclear reactor is slightly enriched uranium oxide pellets. It is inserted into long rods. Nuclear energy is released from the fuel through a chain reaction. |
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Nuclear Reactor producing heat energy |
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| The moderator is a material that slows the neutrons released during nuclear fission. To keep a chain reaction going, the speed of the neutrons must be reduced. The neutrons must be moving at a speed that allows them to be captured by the other nuclei in the fuel. Graphite, a form of carbon, is one type of moderator. It surrounds the cans containing the fuel. Ordinary water, heavy water, and beryllium can also be used as moderators. Heavy water contains an isotope of hydrogen that is heavier than ordinary hydrogen. |
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| Control rods regulate the rate of fission in the fuel. They absorb any excess neutrons not required to keep the chain reaction going. Control rods are made of boron or cadmium alloyed with aluminium or steel. These materials absorb neutrons. By pushing the rods into the reactor or pulling them out, the fission rate is controlled. Pushing the rods all the way in stops the fission reaction. |
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| The coolant removes heat energy from the reactor. Examples of coolant are water, carbon dioxide, and liquid metals. Liquid sodium is one kind of metal used as a coolant. As coolant is pumped through spaces in the reactor, it absorbs heat released from fission. The coolant carries the heat to the heat exchanger. |
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| Safety shields are necessary to protect people from the nuclear radiation produced by a reactor. Nuclear radiation can produce burns, cancer, loss of hair, vomiting and destruction of blood cells. An overdose can cause death. Strict safety regulations are enforced to protect workers and the general public from dangers of radiation. Lead and thick concrete walls are used as shields for reactors. |
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| A radiation badge is worn by those working with radioactive materials. The film inside blackens when exposed to gamma rays. The amount of blackening shows the level of radiation to which the wearer has been exposed. |
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