 Hello everyone, this is Shila Ratna Bansode from Walchand Institute of Technology, Solarpur. Today we are going to see the topic introduction to nuclear power plants. As we all know, the major portion of the electricity being supplied in India is from thermal power plant, that is cold based thermal power plant. Then comes the hydro power plant. But the demand for electricity cannot be met by merely these two plants. That's why we need to go for the third type of power plant or the third type of generation of electricity that is based on nuclear fuel, which is called as nuclear power plant. Learning objectives. At the end of this session, students will be able to explain the construction and working of nuclear power plant. Now, before starting any of a nuclear power plant of any capacity, what are the basic requirements that are to be considered? That is, the site selection criteria that needs to be considered before starting any nuclear power plant. First, there should be availability of water. Ample quantity of water should be available for steam generation required in nuclear power plant. Second, the location away from the populated area. As nuclear fuel is being involved in the generation of electricity, the area in and around the power plant gets radioactive. So, for safer conditions, it should be away from highly populated areas. Facilities for the disposal of radioactive products. After the fusion process, there is generation of radioactive waste, which needs to be disposed perfectly or easily. So, there should be enough facility to dispose the radioactive products. For the operation of these kinds of plants, there should be skilled and trained labor so that there should not be any kind of dangerous events take place because of the unskilled labor. The working of nuclear power plant is based on the process of nuclear fusion. In this, uranium-235 nuclei is used on which a neutron is bombarded Because of the bombarding of the neutron on the uranium-235, which is the most unstable nuclear fuel, barium and krypton are formed as byproducts along with emission of three neutrons. So, when a neutron is bombarded on an unstable uranium nuclei, it gets split into three neutrons and into barium and krypton as byproducts. These three neutrons in turn get bombarded with another three uranium nuclei by generating three neutrons each. And this process goes on and on and during this process or due to the splitting of the uranium nuclei, there is large amount of energy generated which can be used for generation of steam. As this reaction goes on and on till the uranium nuclei gets totally exhausted, this reaction is called as chain reaction or as the splitting of uranium-235 nuclei takes place, it is also called as fission process. And this is the reaction that is responsible for generation of steam in nuclear power plants. Now, let's have a look on how a nuclear power plant works. As far as nuclear power plants are concerned, there are two types of power plants. First, the boiling water reactor type and the second, pressurized water reactor type. Let us have a look at the boiling water reactor. Let us see the elements. This is the reactor core fuel elements. These are the control rods filled with water, turbine, generator, condenser and cooling system. As you can see, when a neutron is bombarded on the uranium fuel, the chain reaction starts and because of this, large amount of energy is released. Because of this energy, the water surrounding the uranium fuel starts getting heated and steam is generated. This steam is allowed to pass over the turbine which rotates the turbine at the desired rpm. This turbine rotates the generator generating electricity. The steam that passes over the turbine is allowed to flow into the condenser where it is cooled and it is again passed to the reactor core. Because of the heat exchange between the steam that is coming out of the turbine and the condensate or the cooling water, the cooling water temperature increases whereas the steam gets converted into water. This water is fed back to the reactor whereas the hot water because of the cooling effect or due to the heat exchange effect is sent back to the cooling tower and this cycle is repeated. This is how any nuclear reactor works or a boiling water reactor works. As the water inside the reactor core boils, it is called as boiling water reactor. There is no additional circuit provided in this. This is the direct circuit where water is directly converted into steam. The disadvantage of this type of boiling water reactor or a nuclear reactor is that the water that directly comes in contact with the nuclear fuel is allowed to get converted into steam and this comes in contact with the turbine. If and so, if there is any maintenance purpose, the plant is shut down and maintenance of turbine is to be carried out, the turbine also gets radioactivity affected. Thus, insulation needs to be provided on this side from the reactor core to the turbine for safety purpose which adds to the additional cost. So, the elements that comes in contact with this steam gets radioactively affected. This is how your boiling water reactor works. Now, let us see how a pressurized water reactor works. This is a reactor uranium fuel, control rods. This is the heat exchanger, the circuit, turbine generator, condenser and cooling. You can see the names, the control rods, the nuclear reactor. This is the additional thing that comes into picture that is steam generator. This is the thing which supplies steam to the turbine, the generator. This is the condenser. This is the feed pump which supplies cooling water. And this is the pump which supplies the hot condenser to be cooled to the cooling tower. Here, when it is bombarded with a nuclear neutron of uranium-235 bombarded by the neutron, chain reaction takes place which allows to generate steam as we have seen in thermal porbulant. But in pressurized water reactor, in the reactor core, high pressure is maintained so this water does not get converted into steam rather its temperature is increased. This high temperature water is allowed to flow into the steam generator. Due to the bombardment of neutrons on the uranium fuel, this water gets heated but it does not get converted into steam rather this hot water is used to generate steam in the steam generator. This is because high pressure is maintained in the reactor core. When the hot water enters into the steam reactor or steam generator, from this circuit water is supplied. There is heat exchange between the hot water and the cold water being supplied where this cold water or water in the secondary circuits gets heated and gets converted into steam. So, this water in the primary circuit does not get converted into steam rather it is helpful for generation of steam. The water in the secondary circuit gets converted into steam. Because of heat exchange, this water's temperature decreases and it is again fed to the reactor core whereas the water in the secondary circuit comes in contact with this hot water and it gets converted into steam. This steam is allowed to flow over the turbine which in turn rotates and generates electricity by rotating the generator. The steam that flows over the turbine is allowed to flow into the condenser. In the condenser, heat exchange between this hot steam and cold water takes place and the temperature of this steam is reduced by converting it into water. This cold water is again fed back to the steam generator. Because of the heat exchange, the water in the condenser is heated up and it needs to be cooled for further cooling process and it is allowed to flow to the cooling tower. This is how a pressurized water reactor works. The benefit of this over boiling water reactor is that the water that comes in contact with the uranium fuel is not allowed to flow into the turbine or it is not directly converted into steam. Rather, another water is used to generate steam. So, this part of the nuclear plant does not get affected by radioactivity. So, maintenance of this part can be easily done without any external coating needed. Plus, as high pressure is maintained in the core reactor, the thickness of these walls is more as compared to boiling water reactor. So, this is how a pressurized water reactor works. Now, let us see what are the advantages of nuclear power plant. Response to changing load is good. It easily responds to the high and low load demand as and when required throughout the day. Easy start and stop facility by just controlling the nuclear fusion process. Problem of smoke and ash is not present as burning of coal or any other fossil fuel is not involved. No requirement of fuel or rather no requirement of fossil fuels. Thank you.