Nuclear Power Plant (GS3 S&T, Nuclear Energy)
- Nuclear power plants are a type of thermal power plant that use the process of nuclear fission in order to generate electricity.
Nuclear Fission
- Nuclear fission is the process of splitting a heavy atomic nucleus into two smaller nuclei, releasing energy in the form of heat, light, and radiation.
- Radioactive atoms (or isotopes) are used in nuclear fission.
- Uranium-235 (U-235) and plutonium-239 (Pu-239) are commonly used isotopes for fission.
- U-235, an extremely rare isotope of the heavy metal uranium, is the most commonly used nuclear fuel.
Radioactive Atoms (or Isotopes)
- Radioactive atoms are atoms that have an unstable nucleus and undergo spontaneous nuclear (radioactive) decay.
- The atom whose composition of protons and neutrons is such that it does not allow the nucleus to hold itself together is termed unstable.
- Radioactive decay is the process by which an unstable atomic nucleus loses its energy by emitting radiation.
How is Nuclear Fission Takes Place?
- The nuclear fission is initiated by subjecting a U-235 or Pu-239 nucleus to neutrons.
- The nucleus immediately absorbs an extra neutron, becomes unstable, and breaks into two lighter atoms, and a few extra neutrons.
- This process releases what is known as atomic energy.
- The fission of a U-235 or Pu-239 atom produces about 2 to 3 new neutrons.
- If these new neutrons are absorbed by other U-235 or Pu-239 atoms, it creates an exponentially growing chain reaction.
- Such chain reaction releases large amounts of energy.
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Basic Steps on How a Nuclear Power Plant Works
Nuclear Reactor
- The nuclear reactor is the heart of the nuclear power plant. It is where nuclear fission takes place.
- Fuel (U-235 or Plutonium-239) is placed into the reactor vessel along with a small neutron source.
- The neutrons start a chain reaction where each atom that splits releases more neutrons that cause other atoms to split.
- Each time an atom splits, it releases large amounts of energy in the form of heat.
Nuclear Reactor Coolant
- A nuclear reactor coolant is a substance that transfers heat away from the reactor core and carries it to the steam generator.
- It is circulated past the reactor core to absorb the heat it generates.
- Commonly used coolants are water, liquid sodium, heavy water, helium, and carbon dioxide.
Steam Generator
- The steam generator is a heat exchanger that uses the heat from the nuclear reactor to boil water.
- The boiling water turns into steam.
Turbine
- The steam then turns a turbine.
- The turbine is connected to a generator, which produces electricity.
Condenser
- The steam from the turbine is then condensed back into water.
- The water is then pumped back to the steam generator to start the process over again.
Neutron Moderator
- A neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction.
- Commonly used moderators include regular (light) water, solid graphite, and heavy water.

Some of the Safety Features of a Nuclear Power Plant
Control rods
- Control rods are used to control the rate of the nuclear reaction.
- They are made of materials that absorb neutrons.
Emergency Shutdown Systems
- Emergency shutdown systems are designed to automatically shut down the nuclear reactor in the event of an emergency.
Containment Building
- The containment building is a thick concrete structure that surrounds the nuclear reactor.
- It is designed to prevent the release of radiation in the event of an accident.
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