What is a nuclear reactor?

               A team of scientists in Chicago, USA, led by the famous physicist Enricho Fermi, first successfully managed to control nuclear fission. Fission, in physics, is the process of splitting of heavy atomic nuclei into two or more fragments. Under his direction, the ‘so called’ atomic pile or reactor was first established in 1942 to release nuclear energy in a controlled way.

               Do you know what nuclear reactors are? These are the key units in nuclear power stations. In other words, a nuclear reactor is a device for producing nuclear energy in a controlled manner where fission takes place. The nuclei of uranium are used as the main fuel to induce the split that releases a large amount of heat energy.

               Broadly, there are three types of reactors – thermal, fast-breeder and fusion. In thermal reactors the efficiency of fission process is increased by slowing down or sending out neutrons in the core by using moderators such as carbon or graphite. They surround the neutron–absorbing rods in the reactor, made out of boron to release heat energy.

               Fast breeding reactors have no moderators. In these cases, neutrons bring about fission and mixtures of plutonium and uranium oxide are used as fuel. While in operation, uranium is converted into plutonium. The plutonium is extracted and reused later as fuel. It is called fast breeder because it produces more plutonium than it consumes. Fast breeder reactors can extract about 60 times the amount of energy from uranium that thermal reactors do.

               Fusion reactors are not yet in commercial production. Instead of splitting heavy atom, they force very light atoms together.

              In all nuclear reactors, there is a coolant system in which ordinary water or gas like carbon dioxide is used. The heat produced in the reactors turns the water or gas into steam that drives generators to produce electricity.

              The advantages of nuclear energy are that it produces a large amount of useful energy from a very small amount of fuel and does not produce gases contributing to the “Green House Effect”. The disadvantages are that the harmful radio-active nuclear waste that it produced is difficult to store and there is always a risk of accident if something goes wrong.