A nuclear power plant converts atomic energy into electrical energy. The atomic energy stored in radioactive fuel like Uranium, and Thorium. In a nuclear power plant, atomic energy transferred into thermal (heat) energy and the water converts into steam. After that working is the same as the thermal power plant. The difference between the thermal power plant and the nuclear power plant is the way to generate heat energy from the fuel. In a thermal power plant, Coal used as a fuel and in nuclear power plants, Uranium used as fuel.
Working of Nuclear Power Plant
In a nuclear power plant, the heat generated by means of nuclear fission. The radioactive elements used in this process. In most of the cases, Uranium (U235) and Thorium (Th232) used as fuel. The fission of 1 kg uranium produces heat which is equal to the heat produced by 4500 tons of high-grade coal. This is a great advantage of nuclear fuel. But it is a big challenge to control the amount of heat produced by fission in a nuclear reactor.
This large amount of heat transferred to the reactor coolant. Water, gas, or liquid metal used as a coolant. The high-temperature coolant used to convert the water into steam. But, the coolant contains a small amount of radioactive element. That’s why heat exchanger used to transfer the heat from coolant to water. The heat exchanger used to transfer the heat without getting a direct touch with coolant. This high-temperature steam used to rotate the steam turbine. The alternator and steam turbine connected with the same shaft and generates electrical energy.
1) Nuclear Reactor
In a nuclear reactor, atomic energy converted into thermal energy. The heat produced in the nuclear reactor. This heat produced by the fission process of a radioactive element like uranium and thorium. Once the fission is done, the process control by the chain reaction. Due to any reason, if the chain reaction fails or it is not in control, the result will be an explosion. It will create big damage to the entire plant and nearby places also.
A nuclear reactor is a pressure vessel. It contains fuel rods, moderator rods, and control rods. The fuel rods consist of radioactive elements. It releases a huge amount of energy when bombarded with slow-moving neutrons.
The moderator rods used to slow down the neutrons before they bombarded to the fuel rods. The graphite rods used as moderator rods.
The control rods used to control the chain reaction. It has the ability to absorb the neutrons and thus regulate the supply of neutrons for fission. Cadmium is a strong neutron absorber and is used as control rods. When the cadmium rods pushed in deep, it absorbs most of the fission neutrons.
Therefore, the neutrons available for the fission are less and the process slows down. As the cadmium rods pull out, the number of neutrons available for the fission increase and the intensity of the chain reaction increased. Hence, heat production also increased.
Types of Nuclear Reactor
There are two types of nuclear reactors. First is the Pressurised water reactor (PWR). In this type of reactor, produced heat transferred to the coolant with the help of a heat exchanger. Hence, in this case, radioactive elements and coolant cannot come in direct contact. But, in the case of Boiling water reactor (BWR), the heat exchanger is not used and heat transferred directly to the coolant. In this case, some amount of radioactive element comes in contact with the steam (from heat) and it may get damaged the turbine blade.
2) Heat exchanger
The heat exchanger used for transferring the heat from one medium to another medium. In a nuclear power plant, the heat exchanger used to transfer the heat from the coolant to the water. In the Boiling water reactor, the heat exchanger is not used.
The coolant used to transfer heat. The water, heavy water, gas (CO2, helium), liquid metal (Na) used as a coolant. The coolant transferred a large amount of heat from reactors and keep the reactor at a safe temperature. The coolant must be non-corrosive, high chemical and radiation stability, non-toxic, non-oxidising and it must not absorb neutrons.
4) Steam turbine
High-temperature and high-pressure steam passed to the turbine. In a steam turbine, thermal energy converted into kinetic energy. The steam turbine used in the nuclear power plant is almost the same as the turbine used in the thermal power plant.
The alternator and steam turbine both connected to the same shaft. Therefore, the alternator rotates at the speed of the turbine. Here, the kinetic energy of the turbine converted into electrical energy.
Site selection of the Nuclear Power Plant
1) Disposal of waste
The waste of radioactive fuel is dangerous for the health of a human being. So, it must be disposed of properly. This waste should be disposed of in the sea (quite away from the seashore) or buried in a deep trench. Therefore, the selected site has adequate arrangements for the disposal of radioactive waste.
2) Availability of water
The plant must be located where a large amount of water is available. for example, the plant placed near a river or sea-side.
3) Distance from the populated area
The plant must be placed far from the human-populated area. Because the radioactivity may spread through the wind or waterways. For precautions, the plant covered by the dome but for safety, purpose makes a proper distance from the populated area.
4) Transportation facility
During the installation of the plant, heavy equipment needs. Hence, choose the site where transportation is easily available.
- It requires less space compared to another power plant.
- It requires a very small quantity of fuel. So, fuel transportation cost is less.
- It does not require a large amount of water.
- It is not affected by weather conditions.
- Less manpower required compared to the thermal power plant.
- This type of plant is very economical for the bulk production of electrical energy.
- It ensures the reliability of the operation.
- The cost of transportation is less compared to the coal power plant.
- Easy to select the site location.
- Running charges are less as a small amount of fuel used for bulk power generation.
- It requires well-trained operators.
- It is not suitable for varying load conditions.
- Very high initial cost and maintenance cost.
- It has an adverse effect on the health of the population surrounding is the plant if radioactive waste is not carefully disposed of.
- The fuel is expensive and difficult to store.
- Erection and commissioning of plants require technical knowledge.
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