UPSC 2017 CDS II GK Paper

In a nuclear reactor, the reaction is controlled, while in nuclear bombs, the reaction is uncontrolled. For stopping the chain reaction in a nuclear reactor, control rods are used. Control rods are made of materials such as Boron, Hafnium, or Cadmium, which have a property called high neutron absorption cross-section. In a nuclear reactor, all the operating reactors are ‘critical’, while there is no question of ‘criticality’ in case of a nuclear bomb. A nuclear reactor is a machine where electricity and heat energy are generated by utilising the power of atoms. In this mechanism, nuclear chain reactions are produced, controlled and contained releasing a tremendous amount of energy. This controlled energy is used in electricity generation and radioactive isotopes production. All the operating nuclear reactors are ‘critical’. When the reactors are running at a constant power level, they are said to be in a ‘critical condition’. In a nuclear bomb, there is a nuclear device having massive destructive power coming from uncontrolled fusion and fission reactions.