Monday, February 17, 2014

Describe the main energy transformations that take place in a nuclear power station

Power plants that depend on atomic energy don't operate that differently from a typical coal-burning power plant. Both heat water into pressurized steam, which drives a turbine generator. Where the two plants are dissimilar is in the method which is used to heat the water into steam. While a coal-burning power plant burns fossil fuels, nuclear plants depend on the heat that occurs during nuclear fission, when one atom splits into two (see sections 8.4.1 and 8.4.2).
The splitting of a single U-235 atom releases approximately 200 MeV (million electron volts). This may not seem like much, however, a pound of highly-enriched uranium is equal to one million gallons of gasoline. This shows the superior efficiency that nuclear power-production has in comparison to fossil-fuels.
To turn the energy produced through nuclear fission into electrical energy, the energy must be controlled so that it can be effectively and safely used to heat water into steam.
Enriched uranium is typically formed into inch-long (2.5-cm-long) pellets, each with approximately the same diameter as a dime. The pellets are then arranged into long rods, which are then gathered into large bundles. The bundles are submerged in water inside a pressure vessel. The water acts as a coolant, and without it, the uranium would eventually overheat and melt.

Nuclear_Power_Plant.JPG

The uranium bundle acts as an extremely high-energy source of heat. It heats the water and turns it to steam. The steam drives a turbine, which spins a generator to produce power. The diagram above shows the step-by-step process which occurs within a nuclear power plant. Once the water has been heated by the enriched uranium metal, the energy transfers that take place are identical to that within a coal-burning power plant.

Energy Transfers:
- Water is heated by heat energy created through nuclear fission
- Energy is lost to surroundings
- Steam turns a turbine (heat energy transformed into kinetic energy)
- Energy is lost to friction
- Turbine powers a generator
- Energy is lost to friction
- Energy is transformed into electrical energy

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