Nuclear Power Plants & Nuclear Reactors
Table of Contents:
Nuclear Power in the World Today
The first commercial Nuclear Power Station started operation in the 1950s. There are now over 440 commercial Nuclear Power Reactors operating in 30 countries, with 377,000 MWe of total capacity. They provide about 14% of the world's electricity as continuous, reliable base-load power, and their efficiency is increasing. 56 countries operate a total of about 250 research reactors and a further 180 nuclear reactors power some 140 ships and submarines.
Today, the world produces as much electricity from nuclear energy as it did from all sources combined in 1960. Civil nuclear power can now have over 14,000 reactors years of experience and supplies almost 14% of global electricity needs, from reactors in 30 countries. In fact, many more than 30 countries use nuclear-generated power.
Principle of Operation
A nuclear plant works on a similar way as that of a thermal power plant, the main difference is that the fuel used to generate heat for the production of steam to drive the turbines that produce electricity. A nuclear plant uses Uranium or Plutonium as a fuel for heat production through fission reaction. The heat energy is used to boil the water for the production of steam in a steam generator.
The fuel inside the reactor is a metal called Uranium. Uranium exists as an isotope in the form of U235 which is unstable. When the nucleus of an atom split, the neutrons released hit other atoms and split them in turn. More energy is released each time another atom splits. This is called ‘chain reaction’.
During the nuclear fission process U235 splits into two fragments of approximately equal size. About 2.5 neutrons are released and a large amount of energy (200 Million electron volt, Mev) is produced. The neutrons produced move at a very high velocity of 1.5 X 107 m/s and fission other nucleus of U235. Thus the fission process and release of neutrons take place continuously throughout the remaining material.
Control rods limit the number of fuel atoms that can split. They are made up of a material that absorbs neutrons. To turn on the reactor some rods are pulled out. The rods are made of boron or cadmium.