Nuclear Power Station

Modern world requires large quantity of power at cheap cost. Industrialization and the gradually increasing living standard of human beings has increased to such an extent that the required energy becoming thrice in decade. Nowadays this required demand of power is fulfilled by major contribution of fossil fuels such coal, oil, etc. The studies had estimated and proved  that stock of these fossil fuels will no longer be sufficient and available to fulfill the very fast increasing demand of energy as the reserves of these resources in the world are limited and these will be exhausted soon.With the vision of increase in demand power, an important source of prosperity. For this we need to understand the atomic physics.

Modern World Electricity Requirement - A view from Shanghai

 Atomic Physics

An atom is the smallest particle of a chemical element that can exist. An  atom can be visualized as the tiny solar system of which the the matter is composed. An atom consists of positively charged nucleus surrounded by number of negatively charged electrons. The nucleus contains two types of particles, namely protons and neutrons. Each proton carries unit positive charge while neutrons are uncharged or neutral particles.A normal atom is generally electrically uncharged due to the fact that the number of electrons on the orbits is equal to the number of protons in the nucleus. Thus any addition of electron to the neutral atom makes atom, negatively charged. While recombination of electron to an atom it absorbs energy. Similarly any subtraction of electron will make the atom positively charged, while liberating an electron from atom it releases some energy.This is the most basic of Nuclear Power Generation which we should learn proficiently if we want to gain knowledge of Nuclear Power Station. 

Nuclear Fission

When an unstable heavy nucleus is bombarded with high energy neutrons then it splits into two elements of lower mass number. It also releases huge amount of energy with separation of two or three neutrons at high speed ( 2 × 10⁷ m/sec ). This process is known as fission and the two elements which have separated due to fission have smaller mass number and called as fission products.The fission is always associated with the release of tremendous amount of heat energy which is very important for power development.

Chain Reaction

We already discussed on the above paragraph that how fission take place so now we will discuss about the Chain Reaction. When a slow moving neutron is bombarded on the fuel rods which splits the atom into two parts usually negatively charged electron and two or three neutrons.Each fission ed nucleus ejects two or three neutrons which again hit the remaining fuel and accelerate the splitting process. While separating the electrons, energy is released by the atom. If this process is continuous then it is known as chain reaction.

Working of Nuclear Power Station

Nuclear Power Station (Tarapur)

In nuclear power plant, Uranium U²³⁵ or Thorium T²³² takes the place of oil, coal and gas to be the fuel used to heat water and produce steam.A nuclear reaction (Chain Reaction) occurs when Uranium atom splits into smaller particles in a chain reaction that produces large amount of heat.The heat producing fission process is controlled in reactors. The core of the reactor contains the Uranium fuel. The fission process take place within the fuel assemblies in the reactor and fuel is shaped and located in such a manner that the heat production within the reactor is uniform.The reaction is controlled by control rods.Control rods, located inside the fuel assembly are made of material which absorb neutron. In addition to control rods, operator use Boron dissolved in the coolant to absorb neutrons to the fission process. The nuclear energy released by fission heats the water or coolant that flows through and the fuel assemblies. In nuclear plants the coolant prevents the core of the reactor from becoming excessively hot and also carries heat energy from the reactor to steam turbine. In nuclear power plant, a vessel known as a pressure keeps the primary side at high temperature to prevent the boiling yet allowing water temperature to reach 500℃. Heat from the primary side water is transferred to the secondary through the steam turbine. Since the secondary water is at a lower pressure than the primary side, the secondary side water boils and steam become steam which rotates the steam turbine.

Main Components of Nuclear Power Station

Nuclear Reactor

1. Reactor Core :- The reactor core is that part of nuclear power plant where fission chain reaction is made to occur and where fission energy us liberated in the form of heat for operating power conversion equipment. The core of the nuclear reactor consist of an assembly of fuel rod, control rod, coolant and moderator. The fuel element are made of plates or rods of Uranium or Thorium.
2. Reflector :- A  reflector is usually a plate around the core to reflect back some of the neutrons that leak out from the surface of the core.It is generally made of same material as the moderator.
3. Control rods :- It is also known as control mechanism used to start the nuclear chain reaction when the reactor is started from cold. The chain reaction should be maintained at steady state condition at the required level. It is also use to shut down the reactor automatically under emergency condition.
4. Moderator :- The moderator is a material which reduces the kinetic energy of fast neutron to slow neutron and this is done in a fraction of second.The function of moderator is to increase the probability of reaction.
5. Coolant :- The main purpose of coolant in the reactor is to transfer the heat generated in the reactor to heat exchanger where steam is generated.
6. Shielding :- The reactor is a source of intense radiation activity and these radioactive produced are very harmful to human life. Hence the reactor is shielded. The common radiation from the reactors are α rays, β rays, γ rays and fast electrons.