Nuclear power plant
- A generating station in which nuclear energy is converted into electrical energy is known as a “Nuclear power station”.
1) Selection of site:
➢ Sufficient water should be available.
➢ Proper disposal of radio active waste must be done.
➢ Site should be away from populated area.
2) Schematic arrangement of Nuclear power station.
3) Main equipment:
(i) nuclear reactor:
It is an apparatus in which nuclear fuel (U235) is subjected to nuclear fission. Controls the chain reaction that starts once the fission is done. If the chain reaction is not controlled, the result will be an explosion due to the fast increase in energy released.
• Reactors
Reactor of nuclear power is similar to the furnace of a steam power plant . The heat liberated in the reactor due to nuclear fission of the fuel is taken up by the coolant circulating through the reactor core. The nuclear reactor mainly consist of fuel, core, moderator shield, reflector, reflector vessel, control rods and coolant.
➢ Types of fuel used:
(a) Nature uranium:
Natural uranium is used as fuel and heavy water or graphite is used as moderator.
(b) Enriched uranium :
The uranium contains 5 to 10 % of U235 and ordinary water can be used as moderator.
➢ Types of moderator used:
(a) Graphite
(b) Beryllium
(c) Water
➢ Types of coolant used:
(a) Gas cooled
(b) Water cooled
(c) Liquid metal cooled
(d) Organic liquid cooled
➢ Type of core:
(a) Homogenous:
In this reactor fuel and moderator represent a uniform mixture such as an aqueous solution of uranium salt.
(b) Heterogeneous:
In such reactors fuel rod are inserted in moderator. A fuel elements are generally arranged in some regular order forming a lattice.
➢ Moderator:
It slows down neutrons before they bombard the fuel rods.
➢ Control rods:
The control rods are of cadmium or boron and are inserted into the reactor.
Cadmium or boron is strong neutron absorber and thus regulates the supply of neutrons for fission.
➢ Reflectors:
This completely surround the reactors core and help to bounce escaping neutrons
back into the core.
➢ Reactor core:
This contains a no. of fuel rods made of fissile material.
➢ Fast breeder reactor:
A Fast breeder reactor is a small vessel in which the necessary quantity of enriched
uranium or plutonium is kept without moderator. The vessel is surrounded by fairly thick blanket of depleted fertile uranium. The fertile uranium absorbs neutrons from the fissile material and gets converted into fissile material. The reactor core is cooled by liquid metal. U238 can be converted to PU239; then later can be used in other thermal or fast breeder reactor.
➢ Breeding ratio:
Ratio of no. of secondary fuel atoms formed to the no. of primary fuel atoms consumed preceding ratio is equal to or greater than unity.
➢ Heat exchanger:
The coolant gives up heat to the heat exchanger which is utilized in raising the
steam. After giving up heat, the coolant is again fed to the reactor.
➢ Steam turbine:
The stem produced in the heat exchanger is led to the steam turbine through a value after doing a useful work in the turbine. The steam is exhausted to condenser.
➢ Condenser :
The condenser the steam which is fed to the heat exchanger through the feed water pump.
➢ Alternator :
The steam turbine driver the alternator which converts mechanical energy into
electrical energy. The o/p from the alternator is delivered to the bus bars through
transformer, C.B. and isolators.
Fuels heated to 1690 ± 10℃ , boiling point 3000℃ , electrical resistivity 18𝜇 Ω cm.
➢ Fission :
The breaking up of nuclear of heavy atoms into two nearly equal parts with release
of huge amount of energy is known as nuclear fission. The release of huge amount of heat energy during fission is due to mass defect. This mass defect is converted into heat energy according to “relation of E =mc^2”
Where, C =velocity of light = 3× 10^8m/sec
➢ Fusion :
The process of combination of two light nuclei to form a relatively heavier nucleus
is known as fusion. The common between two process is that it releases very large amount
of energy. But, there are many differences in the mechanism of the two processes.
▪ Fission involver braking up of a heavy nucleus into lighter nucleus. Fusion involves
combining of two lighter nuclei into one heavier nucleus.
▪ The links of the fission process are neutrons. While the links of a fusion process are
protons.
▪ Fission processed best with thermal neutrons where thermal means room temp. fusion
proceeds best with thermal particles where thermal means temp. of millions ok “K”.
Reactor of nuclear power is similar to the furnace of a steam power plant . The heat liberated in the reactor due to nuclear fission of the fuel is taken up by the coolant circulating through the reactor core. The nuclear reactor mainly consist of fuel, core, moderator shield, reflector, reflector vessel, control rods and coolant.
➢ Types of fuel used:
(a) Nature uranium:
Natural uranium is used as fuel and heavy water or graphite is used as moderator.
(b) Enriched uranium :
The uranium contains 5 to 10 % of U235 and ordinary water can be used as moderator.
➢ Types of moderator used:
(a) Graphite
(b) Beryllium
(c) Water
➢ Types of coolant used:
(a) Gas cooled
(b) Water cooled
(c) Liquid metal cooled
(d) Organic liquid cooled
➢ Type of core:
(a) Homogenous:
In this reactor fuel and moderator represent a uniform mixture such as an aqueous solution of uranium salt.
(b) Heterogeneous:
In such reactors fuel rod are inserted in moderator. A fuel elements are generally arranged in some regular order forming a lattice.
➢ Moderator:
It slows down neutrons before they bombard the fuel rods.
➢ Control rods:
The control rods are of cadmium or boron and are inserted into the reactor.
Cadmium or boron is strong neutron absorber and thus regulates the supply of neutrons for fission.
➢ Reflectors:
This completely surround the reactors core and help to bounce escaping neutrons
back into the core.
➢ Reactor core:
This contains a no. of fuel rods made of fissile material.
Types of nuclear rectors.
➢ Fast breeder reactor:
A Fast breeder reactor is a small vessel in which the necessary quantity of enriched
uranium or plutonium is kept without moderator. The vessel is surrounded by fairly thick blanket of depleted fertile uranium. The fertile uranium absorbs neutrons from the fissile material and gets converted into fissile material. The reactor core is cooled by liquid metal. U238 can be converted to PU239; then later can be used in other thermal or fast breeder reactor.
➢ Breeding ratio:
Ratio of no. of secondary fuel atoms formed to the no. of primary fuel atoms consumed preceding ratio is equal to or greater than unity.
➢ Heat exchanger:
The coolant gives up heat to the heat exchanger which is utilized in raising the
steam. After giving up heat, the coolant is again fed to the reactor.
➢ Steam turbine:
The stem produced in the heat exchanger is led to the steam turbine through a value after doing a useful work in the turbine. The steam is exhausted to condenser.
➢ Condenser :
The condenser the steam which is fed to the heat exchanger through the feed water pump.
➢ Alternator :
The steam turbine driver the alternator which converts mechanical energy into
electrical energy. The o/p from the alternator is delivered to the bus bars through
transformer, C.B. and isolators.
Fuels heated to 1690 ± 10℃ , boiling point 3000℃ , electrical resistivity 18𝜇 Ω cm.
➢ Fission :
The breaking up of nuclear of heavy atoms into two nearly equal parts with release
of huge amount of energy is known as nuclear fission. The release of huge amount of heat energy during fission is due to mass defect. This mass defect is converted into heat energy according to “relation of E =mc^2”
Where, C =velocity of light = 3× 10^8m/sec
➢ Fusion :
The process of combination of two light nuclei to form a relatively heavier nucleus
is known as fusion. The common between two process is that it releases very large amount
of energy. But, there are many differences in the mechanism of the two processes.
▪ Fission involver braking up of a heavy nucleus into lighter nucleus. Fusion involves
combining of two lighter nuclei into one heavier nucleus.
▪ The links of the fission process are neutrons. While the links of a fusion process are
protons.
▪ Fission processed best with thermal neutrons where thermal means room temp. fusion
proceeds best with thermal particles where thermal means temp. of millions ok “K”.
Advantages of Nuclear power plants
➢ The amount of fuel required is quite small. So, there is a considerable saving in the cost
of fuel transportation. Low maintenance.
➢ A nuclear power plant requires less space as compared to any other type of same size.
➢ It has low running charges.
➢ Reliable and economical for bulk generation.
Disadvantages of Nuclear power plants
➢ Nuclear power plants are not suitable for varying loads. As reactors cannot be easily
controlled.
➢ It is difficult to make the casing of the reactor, such as high temp. neutron bombarding.
➢ The disposal of the products which are radio active is a major problem.
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