Chemistry - Nuclear Energy

Introduction

• Nuclear reactions release tremendous amount of energy (known as nuclear energy), which are being used to produce electricity in a nuclear power plant.

• The nuclear energy normally produced by nuclear fission, nuclear fusion, and nuclear decay.

• In 1938, German chemists Otto Hahn, Fritz Strassmann, and the Austrian physicist Lise Meitner conducted the experiments in which the products of neutron-bombarded uranium. As result of this experiment, the relatively tiny neutron split the nucleus of the massive uranium atoms into two roughly equal pieces and released massive energy.

• The nuclear experiments of Otto Hahn and his colleagues are popular as nuclear fission.

Nuclear Fission

• The process of nuclear fission produces free neutrons and gamma photons, while doing this also releases a very large amount of energy.

• Nuclear fission is an exothermic reaction, which can release large amounts of energy in the forms of electromagnetic radiation as well as kinetic energy.

• Nuclear fission, sometimes, can occur naturally (i.e. without neutron bombardment) as a type of radioactive decay.

Types of Nuclear Fission

• Following are the major types of Nuclear Fission −

  • Chain Reaction and

  • Fission Reaction

Let’s discuss them in brief −

Chain Reaction

• When one single nuclear reaction causes one or more subsequent nuclear reactions, it is known as chain reaction.

• Such chain reaction increases the possibility of a self-propagating series of nuclear reactions.

• The nuclear chain reactions release million times more energy per reaction than any other chemical reaction; therefore, it is also known as explosive or uncontrolled chain reaction.

• When a heavy atom experiences nuclear fission, it normally breaks into two or more fission fragments. During the process, several free neutrons, gamma rays, and neutrinos are emitted, and ultimately a large amount of energy is released.

• Following are the two examples of chain reaction −

  • ²³⁵U + → neutron Fission fragments + 2.4 neutrons + 192.9 MeV

  • ²³⁵Pu + → neutron Fission fragments + 2.9 neutrons + 198.9 MeV

• In atom bomb, chain reaction technology is used, as it required consistent source of energy.

Fission Reactions

• The fission reaction in which neutrons (produced by fission of fuel atoms) are used to induce yet more fission for the release of sustainable energy, is known as fission reactions.

• Such reactions are slow and controllable; therefore, also known as controlled chain reaction.

• The power (electricity) producing nuclear reactor is an ideal example of controlled chain reaction.

• Based on the properties and type of usages, fission/controlled chain reaction is classified as −

  • Power reactors

  • Research reactors

  • Breeder reactors

• These power reactors generally convert the kinetic energy of fission products into heat; further, the heat is used to heat a working fluid that drives a heat engine, which ultimately generates mechanical or electrical power.

Basic components of Nuclear Reactor

• Following are the essential components of a nuclear reactor −

  • Nuclear fuels − Such as Uranium (²³³U, ²³⁵U), thorium (Th²³²), plutonium (Pu²³⁹).

  • Moderators − Used to control the emitted neutrons. E.g. heavy water, beryllium, graphite, etc.

  • Coolant − It is used to cool the reactor. E.g. water, steam, helium, CO₂, air, molten metals, etc.

  • Control rods − It is used to run and stop the fission reaction. E.g. cadmium or boron rods are used for such purpose.

Nuclear Fusion

• The process by which two light nuclei are fused to form a heavy nucleus is known as nuclear fusion; during this process, a tremendous amount of energy is being released known as nuclear energy.

• The best example of nuclear fusion is – hydrogen bomb.

• A hydrogen bomb is about 1,000 times more powerful than an atom bomb.