Nuclear Power Plant | Fuel, Working, Types, Advantages, Disadvantages

Table of Contents

A nuclear power plant is a thermal power station where nuclear fuel is used to generate the heat which converts water into steam. This steam is further used to run the turbine. This turbine is connected to an alternator which converts mechanical energy of turbine into electrical energy. It works on Rankine cycle.

In a nuclear power plant cost of fuel used is very less in comparison to total production cost hence they are used as base load stations. Base load is the minimum level of power demand on an electrical grid over a period of time, for example a week or a month. Power plants that do not change their power output quickly, such as large coal or nuclear power plants are generally used as base load power stations.

In a nuclear power plant, a reactor is used to generate energy from nuclear fuel. Which is analogous to the furnace of coal based thermal power plant. A nuclear reactor is the place where nuclear fission happens and vast amount of energy is released.

Nuclear fuel

Nuclear fuel is a material which can be used for nuclear fission reaction in a nuclear reactor. When nuclear fission happens, an atom splits into two atoms and a large amount of heat is generated.

Uranium (235) and Plutonium (239) are two common nuclear fuels. Uranium is a heavy metal and is present in a very huge quantity on earth. It has two isotopes Uranium (238) and Uranium (235). Isotopes are atoms of same element with a different number of neutrons.

Only Uranium (235) can be used for fission process and it is only 0.7% of total Uranium available. The process of obtaining, refining and using nuclear fuel is known as nuclear fuel cycle.

Working of nuclear reactor

A nuclear reactor is basically composed of three main elements fuel rods, control rods and moderator. In a nuclear reaction fuel atom gets bombarded with neutron. This process splits the atom into two atoms, with a large amount of heat generation.

The purpose of moderator is to covert energy neutrons generated in fission process to the thermal neutrons. Some energy of energy neutrons is absorbed by moderator. Only thermal neutrons can be used to carry on further fission process. Generally, water or heavy water is used as a moderator.

Control rods are used to absorb excess neutrons generated during fission process. Otherwise the fission process will become uncontrollable and reactor will melt down.

Types of nuclear reactors

Boiling water reactor (BWR)
Pressurized water reactor (PWR)
Pressurized heavy water reactor (PHWR or CANDU)
Gas cooled reactor
Fast neutron reactor
Light water graphite reactor

Boiling water reactor (BWR)

Boiling Water Reactor

The same water which is used to carry away heat from the nuclear reactor is used to drive turbine. In case of some leak in turbine, pump, condenser or any pipe the radioactive water will create problems.

Pressurized water reactor

The water which carries away heat from reactor transfers its heat to water driving turbine through a heat exchanger. The water which carries heat from the reactor is pressurized so that it does not convert to steam. This type of reactor uses Uranium (235) with 3% to 4.5% enrichment.

Pressurized heavy water reactor

This type of reactor is same as pressurized water reactor, the only difference is that it uses heavy water as moderator and coolant. This heavy water is a good moderator like normal water but has very poor ability to absorb neutrons. It means we have a greater number of thermal neutrons to continue the fission process. Which ultimately gives us freedom to use Uranium (235) at its natural concentration i.e. 0.7%.

Pressurized heavy water reactor is also known as CANDU. CANDU stands for Canada Deuterium Uranium.