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Nuclear Power Plant By-

Nuclear power plant

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Page 1: Nuclear power plant

Nuclear Power Plant

By-

Page 2: Nuclear power plant

Introduction to nuclear power• Uranium was discovered in 1789 by Martin Klaproth, a

German chemist, and named after the planet Uranus.

• The science of atomic radiation, atomic change and nuclear fission was developed from 1895 to 1945, much of it in the last six of those years

• Over 1939-45, most development was focused on the atomic bomb

• From 1945 attention was given to harnessing this energy in a controlled fashion for naval propulsion and for making electricity

• Since 1956 the prime focus has been on the technological evolution of reliable nuclear power plants.

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What is nuclear energy?

• Power plants use heat to produce electricity. Nuclear energy produces electricity from heat through a process called fission. Nuclear power plants use the heat produced by fission of certain atoms.

1. Nuclear fission nucleus of atom is split into parts,

produces free neutrons and energy

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Nuclear Reactions • Nuclear reactions deal with interactions between

the nuclei of atoms including of nuclear fission and nuclear fusion

• Both fission and fusion processes deal with matter and energy

• Fission is the process of splitting of a nucleus into two "daughter" nuclei leading to energy being released

• Fusion is the process of two "parent" nuclei fuse

into one daughter nucleus leading to energy being released

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1.Fission Reaction• A classic example of a

fission reaction is that of U-235:

• U-235 + 1 Neutron 2 Neutrons + Kr-92 + Ba-142 + E

• In this example, a stray neutron strikes an atom of U235. It absorbs the neutron and becomes an unstable atom of U-236. It then undergoes fission. These neutrons can strike other U-235 atoms to initiate their fission.

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2.Fusion Reactions •A classic example of a fusion reaction is that of deuterium (heavy hydrogen) and tritium which is converted to Helium and release energy. p + p He + n + .42 MeV

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Nuclear Reactors

A nuclear reactor is a device that permits a controlled fission chain reaction. In the reactor, neutrons are used to cause a controlled fission of heavy atoms such as Uranium 235 (U-235). U-235 is a uranium isotope used to fuel nuclear fission reactors.

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Reactor is inside a large containment building

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CLASSIFICATION OF REACTORS• The nuclear reactors can be classified as

follows :• 1. Neutron Energy. Depending upon the

energy of the neutrons at the time they are captured by

• the fuel to induce fissions, the reactors can be named as follows :

• (a) Fast Reactors. In such reactors fission is brought about by fast (non moderated) neutrons.

• (b) Thermal Reactors or Slow Reactors. In these reactors the fast moving neutrons are slowed down by passing them through the moderator.

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PARTS OF A NUCLEAR REACTOR• A nuclear reactor is an apparatus in which

heat is produced due to nuclear fission chain reaction.

• 1. Nuclear Fuel• 2. Moderator• 3. Control Rods• 4. Reflector• 5. Reactors Vessel• 6. Biological Shielding• 7. Coolant.

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NUCLEAR FUEL Nuclear fuel is any material that can be consumed to derive nuclear energy.

The most common type of nuclear fuel is fissile elements that can be made to

undergo nuclear fission chain reactions in a nuclear reactor

The most common nuclear fuels are 235U and 239Pu. Not all nuclear fuels

are used in fission chain reactions

fuel Thermal conductivity K-cal/m. hr°C

Specific heatkcal/kg °C

Density kg/m3 Melting point(°C)

Natural uranium

Uranium oxide

Uranium carbide

16.3

1.8

20.6

0.037

0.078

-

19000

11000

13600

1130

2750

2350

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CONTROL RODS

Control rods made of a material that absorbs neutrtons are inserted into the bundle using a mechanism that can rise or lower the control rods.. The control rods essentially contain neutron absorbers like, boron, cadmium or indium.Control rods should possess the following properties :

1. They should have adequate heat transfer properties.2. They should be stable under heat and radiation.3. They should be corrosion resistant.4. They should be sufficient strong and should be able to shut down the reactor almost instantlyunder all conditions.5. They should have sufficient cross-sectional area for the absorption.

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MODERATOR• In the chain reaction the neutrons produced are

fast moving neutrons. • These fast moving neutronsare far less effective

in causing the fission of U235 and try to escape from the reactor.

• To improve the utilization of these neutrons their speed is reduced.

• It is done by colliding them with the nuclei of other

• material which is lighter, does not capture the neutrons but scatters them.

• Each such collision causes loss of energy, and the speed of the fast moving neutrons is reduced. Such material is called Moderator.

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A moderator should process the following properties :• 1. It should have high thermal conductivity.• 2. It should be available in large quantities in pure

form.• 3. It should have high melting point in case of

solid moderators and low melting point in case of liquid moderators. Solid moderators should also possess good strength and machinability.

• 4. It should provide good resistance to corrosion.• 5. It should be stable under heat and radiation.• 6. It should be able to slow down neutrons.

• Ex-Graphite, heavy water and beryllium are generally used as moderator.

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Reflector• The neutrons produced during the fission process will

be partly absorbed by the fuel rods, moderator, coolant or structural material etc.

• Neutrons left unabsorbed will try to leave the reactor core never to return to it and will be lost.Such losses should be minimized.

• It is done by surrounding the reactor core by a material called reflector which will send the neutrons back into the core.

• Generally the reflector is made up of graphite and beryllium.

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REACTOR VESSEL• It is a strong walled container housing the cure of the

power reactor. • It contains moderator, reflector, thermal shielding and

control rods.BIOLOGICAL SHIELDING• Shielding the radioactive zones in the reactor roan

possible radiation hazard is essential to protect, the operating men from the harmful effects.

• During fission of nuclear fuel, alpha particles, beta particles, deadly gamma rays and neutrons are produced.

• A protection must be provided against them. Thick layers of lead or concrete are provided round the reactor for stopping the gamma rays.

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Safety Is Engineered Into Reactor Designs

Containment Vessel1.5-inch thick steel

Shield Building Wall3 foot thick reinforced concrete

Dry Well Wall5 foot thick reinforced concrete

Bio Shield4 foot thick leaded concrete with1.5-inch thick steel lining inside and out

Reactor Vessel4 to 8 inches thick steel

Reactor Fuel

Weir Wall1.5 foot thick concrete

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Cladding• The material that the fuel

rods are made out of is called cladding.

• It must be permeable to neutrons and be able to withstand high heats.

• Typically cladding is made of stainless steel or zircaloy.

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The Pressurized Water Reactor (PWR)• The Pressurized Water Reactor is a superior nuclear

reactor design and it is the mostly widely used reactor type.

• In this reactor, water in the primary loop, that includes the reactor vessel and a heat exchanger in the steam generator, is isolated from water in the steam loop, that includes the steam generator, the steam turbine, and the condenser.

• The water in the primary loop is pressurized so that it doesn’t boil and can run at a higher temperature than in a BWR.

• The Pressurized Water Reactor or PWR is safer than the BWR because all the radioactive material is in the primary loop and within the containment building.

• The PWR is also more efficient than the BWR because it converts more of the thermal energy into output energy and dumps less waste energy to the environment. This is a more modern reactor than the Boiling Water Reactor.

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The Pressurized Water Reactor (PWR)

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• This diagram shows the big picture view of energy transformations in a boiling water nuclear reactor.

• The thermal energy released in the reactor vessel boils the water in the vessel and converts the water into steam, the steam drives the steam turbine, and the steam turbine drives the electric generator.

• , it is cooled down and condenses as water in the condenser and goes back again to be heated up in the reactor vessel.

• The radioactive primary loop includes the reactor vessel, the turbine, and the condenser. The cooling loop that goes to the cooling tower is not radioactive and the electric generator is not radioactive. This type of reactor is a “Boiling Water Reactor” or BWR because it boils water in the reactor core to make steam.

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STEAM TURBINE

A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into useful mechanical

Various high-performance alloys and superalloys have been used for steam generator tubing.

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COOLANT PUMPThe coolant pump pressurizes the coolant to pressures of the orderof 155bar. The pressue of the coolant loop is maintained almost constant with the help of the pump and a

pressurizer unit.

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FEED PUMPSteam coming out of the turbine, flows through the condenser for condensation and recirculated for the next cycle of operation. The feed pump circulates the condensed

water in the working fluid loop.

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CONDENSERCondenser is a device or unit which is used to condense vapor into liquid.The objective of the condenser are to reduce the turbine exhaust pressure to increase the efficiency and to recover high qyuality feed water in the form of condensate & feed back it to the steam generator without any further treatment.

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COOLING TOWER

Cooling towers are heat removal devices used to transfer process waste heat to the atmosphere.Water cirulating throughthe codeser is taken to the cooling tower for cooling and reuse

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SITE SELECTION• 1. Availability of water.• 2. Distance from load center.• 3. Distance from populated area.• 4. Accessibility to site.• 5. Waste disposal.

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NUCLEAR POWER STATION IN INDIA

(i) Tarapur Nuclear Power Station:-• It is India’s first nuclear power plant. It has been built

at Tarapur 60 miles north of Bombay with American collaboration.

• It has two boiling water reactors each of 200 mW capacity and uses enriched uranium as its fuel.

(ii) Rana Pratap Sagar (Rajasthan) Nuclear Station. • It has been built at 42 miles south west of Kota in

Rajasthan with Canadian collaboration. It has two reactors each of 200 mW capacity and uses natural uranium in the form of oxide as fuel and heavy water as moderator.

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(iii) Kalpakkam Nuclear Power Station. • It is the third nuclear power station in India

and is being built at about 40 miles from Madras City.

• It has two fast reactors each of 235 mW capacity and will use natural uranium as its fuel.

(iv) Narora Nuclear Power Station.• It is India’s fourth nuclear power station and

is being built at Narora in Bullandshahar District of Uttar Pradesh. This plant will initially have two units of 235 mW each and provision has been made to expand its capacity of 500 mW

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(v) Kakarpar Nuclear Power Plant.This fifth nuclear power plant of India is to be located at Kakarpar near Surat in Gujarat. This power station will have four reactors each of 235 mW capacity.(vi) Kaiga Atomic Power Plant. • The sixth atomic power plant will be

located at Kaiga in Karnataka.• Kaiga is located away from human

habitation and is a well suited site for an atomic power plant. It will have two units of 235 mW each

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ADVANTAGES OF NUCLEAR POWER PLANT

• 1. Space requirement of a nuclear power plant is less.

• 2. A nuclear power plant consumes very small quantity of fuel.

• 3. There is increased reliability of operation.• 4. Nuclear power plants are not effected by adverse

weather conditions.• 5. Nuclear power plants are well suited to meet large

power demands. They give better performance at higher load factors (80 to 90%).

• 6. Materials expenditure on metal structures, piping, storage mechanisms are much lower for a nuclear power plant than a coal burning power plant.

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DISADVANTAGES• 1. Initial cost of nuclear power plant is higher as

compared to hydro or steam power plant.• 2. Nuclear power plants are not well suited for

varying load conditions.• 3. Radioactive wastes if not disposed carefully

may have bad effect on the health of workers and other population.

• 4. Maintenance cost of the plant is high.• 5. It requires trained personnel to handle

nuclear power plants.