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A nuclear reactor is a facility in which nuclear chained reactions are initiated and controlled. There are various types of nuclear reactors, but the most common uses are for producing electric power and for ship propulsion. The concept is fairly simple; the heat from the nuclear reaction is used to heat up water, then the steam spins some turbines in order to generate electricity.
The idea is that when a large fissile atomic nucleus, such as uranium 235 or plutonium 239 absorbs a neutron, the nucleus splits into two lighter nuclei, along with the emission of other neutrons and gamma radiation. These new neutrons are later absorbed by other large nuclei and the process is happening all over again. The problem is that some neutrons are too fast, and might burst out of the reactor or cause damage. These neutrons are dealt with filters called moderators which reduces the velocity of the neutrons that pass through. In today's nuclear reactors, as moderators, it is used: water (75% of the world's nuclear reactors), solid graphite (20% of the world's reactors) and heavy water (5% of the world's reactors). Of course, other materials have been proposed but these are only in experimental stages.
The core of the reactor (where the nuclear reactions take place) emits an enormous quantity of thermal energy (heat) and therefore needs to be cooled. What do they use in order to cool the reactor ? The answer might surprise you - WATER. It's as simple as that. Sometimes, in certain conditions and in certain types of reactors, they might use a gas or a liquid metal or molten salt. Whatever the coolant may be, it is circulated past the core in order to absorb the heat that is produced. The heat is carried away from the reactor and is then used to generate steam.
The key components common to most nuclear reactors are:
- Nuclear fuel
- Nuclear reactor core
- Neutron moderator
- Coolant
- Control rods
- Reactor vessel
- Boiler feedwater pump
- Steam generators
- Steam turbine
- Electrical generator
- Spent fuel pool
- Nuclear safety systems
- Containment building
- Control room
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