Nuclear power plant - construction, working, advantages with PDF

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Nuclear power plant - construction and working

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Introduction

What comes to your mind when you hear the term ” Nuclear power plant “? You probably might be thinking about something horrible.

But that’s not what you think. You would be surprised to know that Nuclear energy is the second-largest source of low carbon electricity with a share of 10% of the global electricity supply produced by 452 reactors around the globe.

– Source IEA (2019), Nuclear Power in a Clean Energy System, IEA, Paris

Nuclear power plants have a bunch of good things up their sleeve, like it does not produce greenhouse gases, has a very low carbon footprint, and many more…

What is a nuclear power plant?

A nuclear power plant is a type of power plant which produces electricity with the heat generated by the nuclear fission reaction in the nuclear reactor. This heat is then used to convert water into steam which is then used to drive the turbine, eventually generating electric power.

A nuclear power plant is similar to a steam power plant except that in place of a boiler a nuclear reactor is used to generate steam.

Before starting off with the construction and working of the nuclear power plant, let’s understand the nuclear fission process which takes place in the nuclear reactor.

What is meant by nuclear fission?

Nuclear fission is the process in which a heavy nucleus like Uranium or Plutonium is split into lighter nuclei of approximately equal mass along with the release of a large amount of energy.

The Uranium 235 on itself is a stable atom, however, when hit with a neutron the Uranium 235 atom absorbs the neutron and becomes Uranium 236 which is unstable, and thus, it spontaneously splits into Krypton 92 and Barium 141.

This reaction results in the release of 3 neutrons along with a large amount of energy (i.e. 1MeV). These 3 neutrons further hit the other Uranium 235 atoms and the chain reaction goes on.

It is necessary that the chain reaction must be controlled or else an accident might occur. In nuclear a reactor control rods and moderators are present for a controlled reaction to take place.

So what are Fuel rods, control rods, and moderators?

Fuel rod – The fuel rod in the nuclear reactor is a tube made up of zirconium alloy within which small ceramic pellets of uranium oxide are placed. The fuel rods are placed inside the reactor core and submerged in the moderator.

Moderator – A moderator is used to slow down the energy of the neutrons in the nuclear reactor which is produced by the fission process. Normal water or heavy water is used as a moderator and also acts as a coolant.

Control rod – Just as the name suggests, the control rods are used to control the fission reaction. The control rods absorb the excess neutrons present in the moderator and thus any further fission reaction is prevented. These rods are made up of Boron or Cadmium. The control rods and can be lowered or raised into the reactor accordingly to control the fission reaction.

Did you know?

A complete fission of 1 kg of Uranium is equivalent to 2.7 million kg of Coal

– source European Nuclear society (https://www.euronuclear.org/)

Construction of nuclear power plant

The following are the major components of nuclear power plant:

Nuclear reactor
Heat exchanger / Steam generator
Steam turbine
Alternator / Generator
Condenser
Cooling tower

Nuclear power plant image source – U.S.NRC., Public domain, via Wikimedia Commons

Nuclear reactor

The nuclear reactor is the most important part of the nuclear power plant, you can call it the heart of the power plant. The nuclear reactor is the place where the heat is generated by nuclear fission of the radioactive elements.

The nuclear reactor is enclosed in meters deep of steel-reinforced concrete building.

The heat generated from the nuclear fission is passed on to a working fluid which could either be a gas or liquid.

The nuclear reactor consists of the reactor core within which the fuel rods, control rods, and the moderator are present.

There are two basic types of nuclear reactors:

1. Boiling water reactor (BWR) – In the BWR the feed water is allowed to boil in the reactor itself and is converted into steam. This steam is then directly passed through the steam turbine to produce electrical energy.

The BWR has a disadvantage which is that the water comes directly in contact with the fuel rods, thus there may be a possibility of the water carrying radioactive particles.

2. Pressurized water reactor (PWR) – In the PWR as the name suggests, the water in the reactor is pressurized so that it doesn’t convert into steam. This water is used to absorb the heat and deliver it to the feed water in a heat exchanger.

The feedwater is then converted into steam and sent to the turbine. In PWR there are 2 separate circuits as compared to the single circuit of the BWR. Since the coolant and the feed water do not mix there is no problem of radioactive particles in the feed water. The figure above shows the PWR nuclear power plant.

Heat exchanger / Steam generator

The heat from the working fluid is given up in the heat exchanger to the water which is to be converted into steam.

Steam turbine

The steam turbine is used to convert the kinetic energy of the steam into rotational mechanical energy.

Alternator / Generator

The steam turbine is coupled to the alternator or generator. The function of the generator is to convert the rotational mechanical energy of the steam turbine into electrical energy.

Condenser

The steam from the turbine is sent to the condenser wherein the steam is cooled and converted into water.

Cooling tower

The hot cooling water coming out of the condenser after absorbing heat from the steam is sent to the cooling tower. The cooling tower is a huge structure wherein the hot cooling water is cooled and sent back again to the condenser.

Image source

Working of Nuclear power plant

The nuclear fission reaction of the heavy element Uranium (U 235) generates a large amount of heat inside the nuclear reactor.

This heat is then transferred to the coolant. The coolant is then passed through the heat exchanger where it gives up the heat to the feed water, resulting in the conversion of water into saturated steam.

Then, the steam generated is sent to the steam turbine where it is allowed to expand. The expansion causes the steam turbine to rotate.

Since the steam turbine is coupled to the alternator / generator the rotational energy of the turbine is converted into electrical energy.

The energy produced is then stepped up with the help of a transformer and then transmitted to the load centers.

The steam which exits the turbine is sent to the condenser where it is converted into water and is pumped back to the heat exchanger/steam generator where it is again converted into steam and the cycle goes on…

Advantages of Nuclear power plant

The following are the advantages of nuclear power plant:

The nuclear power plant produces isotopes that have different applications.
Nuclear power plants do not produce greenhouse emissions as compared to other conventional power plants.
Nuclear power plants are more reliable.
Since a very small quantity of uranium is required, fuel transportation and storage is not a problem.
Operating costs are less.

Disadvantages of Nuclear power plant

The following are the disadvantages of nuclear power plant:

The initial capital cost is high.
The used fuel is highly radioactive. Thus, special processes are required for its disposal.
Also, the waste products from the plant must be treated before disposing off.
High maintenance cost.
As compared to fossil fuels, uranium is found in some countries and has a lot of regulations regarding its use.

Some FAQ regarding nuclear power plant

What is the difference between a steam power plant and a nuclear power plant?

The major differences between steam and nuclear power plants are:

The initial investment required is very high for nuclear power plants as compared to the steam power plant.

However, nuclear power plants have low operating costs than steam power plants.

Nuclear power plants have a more reliable operation than steam power plants.

Space required for the storage of fuel is very less in a nuclear power plant when compared to a steam power plant.

How nuclear power plant works?

The nuclear power plant works by using the heat generated during the fission reaction of the nuclear fuel in the nuclear reactor to convert the feed water into steam. This steam is then expanded in a steam turbine and with the help of an alternator, electrical energy is generated.

Which is the first Nuclear power plant in India?

The Tarapur Atomic Power Station (TAPS) located near Boisar in the Palghar district of Maharastra state was the first nuclear power plant of India.

– source NTI.org

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So that’s a brief on Nuclear power plant – its construction and working. Do let us know your thoughts on this topic in the comments.

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Nuclear power plant – construction, working, advantages with PDF

Introduction