NUCLEAR POWER PLANT

NUCLEAR POWER PLANT

If nuclear fission reaction is made to occur in a controlled manner, then the energy released can be used for constructive purposes like electricity generation. The arrangement or equipment used to carry out fission reaction under controlled conditions is called a nuclear reactor. The energy produced in a controlled manner can be used to produce steam which can run turbines and produce electricity. This arrangement is employed in a nuclear power plant to generate electricity.

BLOCK DIAGRAM: 

EXPLANATION:

Functioning of Nuclear power plant:

Nuclear power plants generate steam to drive electric turbines by circulating liquid through a nuclear reactor. The reactor produces heat through the controlled fission of atomic fuel. Normally the fuel for power reactors is slightly enriched uranium.

Detailed process of power generation in a thermal power plant:

(i)Nuclear Reactor:

It is an apparatus in which nuclear fuel (U235) is subjected to nuclear fission. It controls the chain reaction that starts once the fusion is done. If the chain reaction is not controlled, the result will be an explosion due to the fast increase in the energy released.

A nuclear reactor is a cylindrical stout pressure vessel and houses fuel rods of Uranium moderator and control rods. The fuel rods constitute the fission materials and release huge amount of energy when bombarded with slow moving neutrons. The moderator consists of graphite rods which enclose the fuel rods. The control rods are of Cadmium and are inserted in the reactor. Cadmium is strong neutron absorber and thus regulates the supply of neutrons for fission. When the control rods are pushed in deep enough, they absorb most of fission neutrons and hence few are available for chain reaction, which therefore stops. However, hence they are being withdrawn, more and more of these fission neutrons cause fission and hence the intensity of chain reaction is increased. Therefore by pulling out the control rods, power of nuclear reactor is increased, whereas by pushing them in, it is reduced. In actual practice, the lowering or raising of control rods is accomplished automatically according to the requirement t of load. The heat produced by the reactor is removed by the coolant, generally a sodium metal. The coolant carries heat to the heat exchanger.

Types of reactor:

 After the enzyme and the carrier system have been chosen, decision needs to be taken on reactor design, which can be any one of the following four types:

(a) Batch reactor: It is the simplest type of reactor. The immobilized enzyme is placed in a container with the reactants, and the reaction is allowed to proceed until the desired level of conversion is reached. Some stirring or agitation of reaction mixture is also required. Many modifications of these reactors have been designed to simplify recovery and reuse of the enzyme composite.

(b) Continuously stirred reactors: These types of reactors employ a stirred tank, to which reactants are continuously added and products continuously withdrawn.

(c)Fluidized-bed reactor:            In these reactors, enzyme system is fluidized by the upward flowing of substrate solution. This helps in eliminating any plugging of enzyme system, although small duration of contact may be insufficient for the desired conversion. This can be overcome by decreasing velocity of solution by different methods.

Glucose isomers and lactase have been shown to double their efficiency due to fluidization when compared with fixed beds.

(d)Fixed bed reactors: These are most widely used for large scale commercial operations. Different companies use these reactors for enzymes like

(I) Aminocylase

(II) Glucose isomers and

(III) Lactase.

These reactors will keep on dominating the large scale commercial application due to their.

(I) High efficiency and

(II) Ease and simplicity of operation.

There are many types of fixed bed reactors including those with packed bed of particular material to which enzyme is coupled.

(ii)Heat Exchanger:

The coolant gives up the heat to the heat exchanger which is utilised in raising the steam. After giving up heat, the coolant is again fed to the reactor.

(iii)Steam Turbine:

The steam produced in the heat exchanger is led to the steam turbine through a valve. After doing a useful work in the turbine, the steam is exhausted to the condenser. The condensers condense the steam which is fed to the heat exchanger through feed water pump.

(iv)Alternator:

The steam turbine drives the alternator which converts mechanical energy into electrical energy. The output from the alternator is delivered to the bus bars through transformers, circuit brakers and isolators.

THE NUCLEAR FUEL CYCLE:

The nuclear fuel cycle is the series of industrial processes which involve the production of electricity from uranium in nuclear power reactors.  Uranium is a relatively common element that is found throughout the world. It is mined in a number of countries and must be processed before it can be used as fuel for a nuclear reactor.

Fuel removed from a reactor, after it has reached the end of its useful life, can be reprocessed to produce new fuel.

The various activities associated with the production of electricity from nuclear reactions are referred to collectively as the nuclear fuel cycle. The nuclear fuel cycle starts with the mining of uranium and ends with the disposal of nuclear waste. With the reprocessing of used fuel as an option for nuclear energy, the stages form a true cycle.

ADVANTAGES:

1. They can be located very conveniently near the load centers.

2. Does not require shielding like required in nuclear power plants.

3. Unlike nuclear power plants whose power production method is difficult, for thermal             power plants it is easy if compared.
4. Transmission costs are reduced as they can be set up near the industry.
5. The portion of steam generated can be used as process steam in different industries.
6. Steam engines and turbines can work under 25% of overload capacity.
7. Able to respond changing loads without difficulty.

DISADVANTAGES:

1. Large amounts of water are required.
2. Great difficulties experienced in coal handling and disposal of ash.
3. Takes long time to be erected and put into action.
4. Maintenance and operating costs are high.
5. With increase in pressure and temperature, the cost of plant increases.
6. Troubles from smoke and heat from the plant.

SITE SELECTION PARAMETERS:

The following points should be kept in view while selecting the site for a nuclear power station.

(i)Availability of Water:

As sufficient of water is required for the cooling purposes, therefore the plant site should be located where ample quantity of water is available.

(ii) Disposal of Waste:

 The waste produced by fission in nuclear power station is generally radioactive which must be disposed off properly to avoid health hazards. The waste should either be buried in a deep trunch or disposed off in a sea quite away from the sea shore. Therefore the site selected for such a plant should have adequate arrangement for the disposal of radioactive waste.

(iii)Distance from populated areas:

 The site selected for a nuclear power station should be quite away from the populated areas as there is a danger of presence of radio activity in the atmosphere near the plant. However, as a precautionary measure, a dome is used in the plant which does not allow the radioactivity to spread by wind or underground waterways.

(iv)Transportation Facilities:

 The site selected for a nuclear power station should have adequate facilities in order to transport the heavy equipments during erection and to facilitate the movement of workers in the plant. From the above mentioned factors it become apparent that ideal choice for a nuclear power station would be near sea or river and away from thickly populated  areas.

STATUS OF NUCLEAR POWER PLANT:

Nuclear power stations
Power station	State	Total capacity (MW)
Kaiga	Karnataka	880
Kakrapar	Gujarat	440
Kalpakkam	Tamil Nadu	440
Narora	Uttar Pradesh	440
Rawatbhata	Rajasthan	1180
Tarapur	Maharashtra	1400
Kudankulam	tamilnadu	2400
jaitpur	maharashtra	3200
pati sonapur	orissa	6000
saurashtra	gujarat	2800

CONCLUSION:

            After study of the nuclear power plant we conclude that the nuclear power generation is more efficient than the other power plant so with help of small amount of the nuclear material like uranium and thorium we can generate a large amount of the electricity but more safety precautions are required than other power plant and the major problem is that the waste of nuclear material disposal is so difficult and it is also do effect on the ecology.

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HYDRO POWER PLANT

HYDRO POWER PLANT

Worldwide, hydropower plants produce about 24 percent of the world's electricity and supply more than 1 billion people with power. The world's hydropower plants output a combined total of 675,000 megawatts, the energy equivalent of 3.6 billion barrels of oil, according to the National Renewable Energy Laboratory. There are more than 2,000 hydropower plants operating in the United States, making hydropower the country's largest renewable energy source

BLOCK DIAGRAM: 

        Hydroelectricity is one of the main forms of energy in use today. Its use is being promoted in many countries of the world as a renewable and non-polluting source of energy. The industrialized nations of the world have drawn flak in recent times for releasing high concentrations of green house gases into the atmosphere. The regulations of the Kyoto Protocol are making things tougher. Hence greater interest is being shown in making use of non-polluting energy sources.

 

EXPLANATION: FUNCTIONING OF HYDRO POWER PLANT:  Hydroelectricity is produced in a hydroelectric power plant. In this plant, the water is released from a high location. The potential energy present in the water is converted into kinetic energy, which is then used to rotate the blades of a turbine. The turbine is hooked to the generator which produces electricity.   COMPONENTS:    RESERVOIR: The basic requirement of a hydro electric power plant is a good reservoir where large quantity of water is stored during flood season and used during dry season.    DAM: Most hydropower plants rely on a dam that holds back water, creating a large reservoir. Often, this reservoir is used as a recreational lake, such as Lake Roosevelt at the Grand Coulee Dam in Washington State.    PENSTOCK: A pipe between the surge tank and the power house is known as pen stock. A pen stock is a conductor that takes water from the reservoir to the power house. Usually steel, RCC pipes are used. Penstocks are usually equipped with head gates at the inlet which can be closed during the repair of penstocks.     INTAKE: Gates on the dam open and gravity pulls the water through the penstock, a pipeline that leads to the turbine. Water builds up pressure as it flows through this pipe.    TURBINE: The water strikes and turns the large blades of a turbine, which is attached to a generator above it by way of a shaft. The most common type of turbine for hydropower plants is the Francis Turbine, which looks like a big disc with curved blades. A turbine can weigh as much as 172 tons and turn at a rate of 90 revolutions per minute (rpm), according to the Foundation for Water & Energy Education (FWEE).     POWER HOUSE: A power house houses the turbine and the generator. The turbine rotates the turbine shaft which in turn rotates the generator shaft, which is coupled to the turbine shaft. Thus the turbine converts hydraulic energy into mechanical energy and the generator converts mechanical energy into electrical energy. The power house is usually at the foot of the dam.    GENERATORS: As the turbine blades turn, so do a series of magnets inside the generator. Giant magnets rotate past copper coils, producing alternating current (AC) by moving electrons.     TRANSFORMER: The transformer inside the powerhouse takes the AC and converts it to higher-voltage current.    POWER LINES: Out of every power plant come four wires: the three phases of power being produced simultaneously plus a neutral or ground common to all three.     OUTFLOW: Used water is carried through pipelines, called tailraces, and re-enters the river downstream.    SURGE TANK: Surge tank is a small additional storage facility near the power house. It is required when there is considerable distance between the power house and the reservoir. When the distance is more non-uniform water intake to the power house results in the bursting of penstocks. In the absence of surge tank, the excess water rushes at the lower end causing the penstock to burst. However in the presence of a surge tank and can be used whenever there is any water shortage. Thus the surge tank acts as a shock absorber or a pressure regulator tank. TYPES OF HYDRO POWER PLANT:  1. Impoundment: An impoundment facility, typically a large hydropower system, uses a dam to store river water in a reservoir. The water may be released either to meet changing electricity needs or to maintain a constant reservoir level. 2. Diversion: A diversion, sometimes called run-of-river, facility channels a portion of a river through a canal or penstock. It may not require the use of a dam. 3. Pumped Storage: When the demand for electricity is low, a pumped storage facility stores energy by pumping water from a lower reservoir to an upper reservoir. During periods of high electrical demand, the water is released back to the lower reservoir to generate electricity. Sizes of Hydro power Plants: Facilities range in size from large power plants that supply many consumers with electricity to small and micro plants that individuals operate for their own energy needs or to sell power to utilities. 1. Large Hydro power plant: Although definitions vary, DOE defines large hydropower as facilities that have a capacity of more than 30 megawatts. 2. Small Hydro power plant: Although definitions vary, DOE defines small hydropower as facilities that have a capacity of 0.1 to 30 megawatts. 3. Micro Hydro power plant: A micro hydropower plant has a capacity of up to 100 kilowatts (0.1 megawatts).                                                                    ADVANTAGES: 1. Once a dam is constructed, electricity can be produced at a constant rate. 2. If electricity is not needed, the sluice gates can be shut, stopping electricity generation. The water can be saved for use another time when electricity demand is high. 3. Dams are designed to last many decades and so can contribute to the generation of electricity for many years / decades. 4. The lake that forms behind the dam can be used for water sports and leisure /          pleasure activities. Often large dams become tourist attractions in their own right. 5. The lake's water can be used for irrigation purposes. 6. The build up of water in the lake means that energy can be stored until needed, when the water is released to produce electricity. 7. When in use, electricity produced by dam systems do not produce green house gases. They do not pollute the atmosphere.     DISADVANTAGES: 1. Dams are extremely expensive to build and must be built to a very high standard. 2. The high cost of dam construction means that they must operate for many decades to become profitable. 3. The flooding of large areas of land means that the natural environment is destroyed. 4. People living in villages and towns that are in the valley to be flooded, must move out. This means that they lose their farms and businesses. In some countries, people are forcibly removed so that hydro-power schemes can go ahead. 5. The building of large dams can cause serious geological damage. For example, the building of the Hoover Dam in the USA triggered a number of earth quakes and has depressed the earth’s surface at its location. 6. Although modern planning and design of dams is good, in the past old dams have been known to be breached (the dam gives under the weight of water in the lake). This has led to deaths and flooding. 7. Dams built blocking the progress of a river in one country usually means that the water supply from the same river in the following country is out of their control. This can lead to serious problems between neighbouring countries. 8. Building a large dam alters the natural water table level. For example, the building of the Aswan Dam in Egypt has altered the level of the water table. This is slowly leading to damage of many of its ancient monuments as salts and destructive minerals are deposited in the stone work from ‘rising damp’ caused by the changing water table level. SITE SELECTION PARAMETERS: 1) Availability of Water Since the primary requirement for a hydro electric power station, is the availability of huge amount of water such plants should be built at a place (e.g. River, canal) where adequate water is available at a good head. 2) Storage of Water There are wide variations in water supply from a river or canal during the year. This makes its necessary to store water by constructing a dam in order to ensure the generation of power through out the year. The storage helps in equalizing the flow of water so that any excess quantity of water at a certain period of the year can be made available during times of very low flow in the river. This leads to the conclusion that site selected for hydro electric plant should provide adequate facilities for erecting a dam and storage of water. 3) Cost and Type of Land The land for the construction of plant should be available at a reasonable price. Further, the bearing capacity of the soil should be adequate to withstand the installation of heavy equipment. 4) Transportation Facilities The site selected for the hydro-electric plant should be accessible by rail and road so that necessary equipment and machinery could be easily transported. It is clear from the above mentioned factors that ideal choice of site for such a plant is near a river in hilly areas where dam can be conveniently built and large reservoirs can be obtained. STATUS OF HYDRO POWER PLANT: Sr. no. Power Plant State Commissioned Capacity (MW) year of commission 1 Baira siul Himachal Pradesh 180 1981 2 Loktak               Manipur 105 1983 3 Salal-I Jammu & Kashmir 345 1987 4 Tanakpur Uttarakhand 120 1992 5 Chamera-I                       Himachal Pradesh 540 1994 6 Salal-II                Jammu & Kashmir 345 1996 7 Uri-I Jammu & Kashmir 480 1997 8 Rangit Sikkim   60 1999 9 Chamera-II Himachal Pradesh 300 2004 10 Indira Sagar Madhya Pradesh 1000 2005 11 Dhauliganga-I Uttarakhand  280 2005 12 Dul Hasti Jammu & Kashmir  390 2007 13 Omkareshwar Madhya Pradesh  520 2007 14 Teesta-V Sikkim  510 2008 CONCLUSION: After studding hydro power plant we conclude that hydro power plant is easy way to produce electricity. In hydro power plant installation cost is high, but after it constructs its maintenance cost is low. It can easy to start & easy to stop. If water is available for whole year then it is very efficient power plant.  Use below link for more information : http://en.wikipedia.org/wiki/Hydroelectricity  * * * * * * *