Nuclear_Power_Plant

Prepared by: Nimesh Gajjar

Introduction

A generating station which converts heat energy produced by nuclear materials to electrical energy.

1 Kg Uranium = 4500 tons of high grade coal.

Nuclear Fusion

• Nuclear fusion is the combining of two nuclei with low masses to form one nucleus of larger mass.

• Nuclear fusion reactions are also called thermonuclear reactions.

Nuclear Fusion cont.

• Fusion reactions exist in stars.• Our sun is a good example of

a thermonuclear (fusion) reaction.

• It is almost impossible to create fusion reactions on earth since they need temperatures above one million degrees Celsius in order to take place.

Nuclear Fusion cont.

Nuclear Fission

• Nuclear fission is the process of splitting a nucleus into two nuclei with smaller masses.

• Fission means “to divide”

When unstable heavy nucleus is

bombarded with high energy neutrons, it

splits in to two fragments more or less of

equal mass. This process is known as

“Nuclear Fission”.

Nuclear Fission Animation for Science.mp4

Fission cont.

• Only large nuclei with atomic numbers above 90 can undergo fission.

• Products of fission reaction usually include two or three individual neutrons, the total mass of the product is somewhat less than the mass of Uranium-235.

Chain Reaction

• A chain reaction is an ongoing series of fission reactions. Billions of reactions occur each second in a chain reaction.

Chain Reaction cont.• On earth, nuclear fission reactions

take place in nuclear reactors, which use controlled chain reactions to generate electricity.

Chain Reaction cont.A chain reaction refers to a process in which

neutrons released in fission produce an

additional fission in at least one further

nucleus. This nucleus in turn produces

neutrons, and the process repeats. If the process

is controlled it is used for nuclear power or if

uncontrolled it is used for nuclear weapons

Uncontrolled chain reactions take place

during the explosion of an atomic bomb.

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. Not all nuclear fuels are used in fission chain reactions

Classification of Reactor

On the basis of neutron energyFast reactorThermal reactor

On the basis of fuel usedNatural fuelEnriched uranium

On the basis of moderator usedWater moderatedHeavy water moderatedGraphite moderatedBeryllium moderated

On the basis of coolant usedWater cooled reactorGas cooled reactorLiquid metal cooled reactorOrganic liquid cooled reactor

Components of Nuclear Power Plant

AP1000 Loop Animation.swf

Nuclear Reactor

Use as an energy source for the generation of electrical energy.

A nuclear reactor is a cylindrical pressure vessel and houses fuel rods of uranium, moderator and control rods.

The fuel rods consist of the fission materials and release huge amount of energy when bombarded with slow moving neutrons.

By pulling out the control rods, power of the nuclear reactor is increased, whereas by pushing them in, it is reduced.

The heat produced in the reactor is removed by the coolant, generally a sodium metal.

nuclear.swf

• The nuclear reactor is fueled by uranium dioxide and moderated by water.

• The nuclear reaction produces heat. The reaction is controlled by controlled rods.

• The coolant pump drives water through the reactor, where the nuclear reaction increases the coolant (in most cases water) temperature.

• The steam is generated in the heat exchanger/boiler.

• The high pressure steam drives the turbine, which in turn drives the generator. (usually at 1800 rpm)

• The condenser condenses the steam to water, which is pumped back into the Heat exchanger.

nuclearAnimation1.swf

how_nuclear_plants_work.swf

Types of Reactors

1. Pressurized water reactor, (PWR)

2. Boiling water reactor, (BWR)

3. Gas cooled reactor, (GCR)

4. CANDU reactor, (CANDU)

5. Fast breeder reactor

Pressurized water reactor (PWR)

PWR.mp4

PWR cont….

•In this reactor fuel used is enriched uranium.

•Water is used both as a moderator & coolant.

••Water is kept at a high pressure so that it cannot boil within reactor.

•Coolant water is passed to heat exchanger where another feed water is converted to steam.

•A pressurize and surge tank maintain the constant pressure in water system. Since water passing through reactor becomes radioactive, the entire primary circuit with heat exchanger has to shielded.

Boiling water reactor (BWR)

02fb6ba6fc.gif

BWR cont….

• In this reactor fuel used is enriched uranium.

• Water is used both as a moderator & coolant.

• Steam is generated within the reactor so heat exchanger is not required.

• The heat released by the nuclear reaction is absorbed by the water and the steam is generated in reactor itself.

• Feed water enters the reactor tank below to pass through fuel element in the core as coolant and also as moderator.

Gas Cooled Reactor

• Gas is used as a coolant.

•(a) Gas Cooled Graphite Moderated (GCGM) Reactor uses carbon dioxide gas as a coolant.

•(b) High Temperature Gas Coolant (HTGC) uses Helium gas as a coolant.

•The carbon dioxide is circulated through the core, reaching 650 oC it is passed through to the heat exchanger.

Canadian‐Deuterium‐Uranium Reactor (CANDU)Heavy water cooled and moderated Reactor

•This reactor is useful for countries which do not produce enriched uranium.

• Enrichment of uranium is costly and this reactor uses natural uranium as fuel and heavy water as a moderator.

•The CANDU reactor design has been developed since the 1950s in CANADA.

•Control rods are not required in this reactor.

•Reactor control is achieved by varying moderator level in reactor

LIQUID METAL FAST BREEDER REACTOR (LMFBR)

• In this reactor, sodium in a primary loop is pump through the reactor core.

• This sodium collects the heat and transfers it to a secondary loop in the heat exchanger, which converts into steam.

• Then steam drives the turbine and produce electricity.

• Two heat transfer circuits…. Radio active sodium does not come in contact with steam circuit.

• This types of reactor also produces more fissile material then it consumes, so it is called a “Breeder Reactor”.

Advantages of NPP

1. Space: A nuclear power plants needs less space compared to other power plant of equal size.2. Performance: They are well suited (Economical) to meet large power demands.3. Fuel: Since the fuel consumption is very small as compared to type of power plants. Therefore, there is a saving in cost of the fuel transportation.4. Operation: The operation of the plant is more reliable.5.Condition: It is not affected by the adverse weather condition. It can be operated in any type of weather condition6. Capacity: high7. Expenditure: The expenditure on metal structures piping, storage mechanisms is much lower for this plant then a coal burning power plant.8. Clean: There is some greenhouse gas emission associated with the life cycle of uranium, as gases are emitted as it is mined and transported etc. However this is significantly, nuclear power would be “carbon‐zero” if the uranium were mined and transported in a more efficient way.9. Efficient: It can produce significant quantities of electricity, up to about 2GW. They are generally comparable in output to coal plants.10. Reliable: they run constantly, rather than turning on and off to meet base load demand.

Disadvantages of NPP

1. Waste: High radioactive waste is very dangerous. A sophisticated method of storing the waste for this period of time must be designed.

2. Terrorism: Nuclear power plant would be very tempting target to anyone wanting to disrupt the power supply and destruct an entire region.

3. Cost: These types of plants are very expensive to install and run. The fuel is expensive and difficult to recover.

4. Health of worker: Working conditions in nuclear plants are always harmful to health of the workers.

5. Staff : highly qualified staff is required6. Maintenance: Maintenance charges are high due to lack of standardization.

Moreover, high salaries of specially trained personal employed.7. Pollution: The fission by products is generally radioactive and may cause a

dangerous amount of radioactive pollution.8. Disposal: The disposal of the product, which is radioactive, is a problem. They

have either to be disposed off in a deep trench or at a common disposal point to which wastes are transported.

9. Load: Plants are not well suited for varying loads, as the reaction does not respond to the load fluctuation efficiently.

Nuclear Fission & POWERNuclear Fission & POWER

• Currently about 103 Currently about 103

nuclear power plants in nuclear power plants in

the U.S. and about 435 the U.S. and about 435

worldwide.worldwide.

• 17% of the world’s 17% of the world’s

energy comes from energy comes from

nuclear.nuclear.

435 nuclear plants worldwide.

Today

Half of today’s plants will be too old to operate.*

(assuming 40-year lifespan)

By 2025

In reality, total operating capacity will decrease, not increase