NUCLEAR AND HYDEL POWERPLANTS
1. Define Fission?
Fission is the process that occurs when a neutron collides with the nucleus of certain of heavy atoms, causing the original nucleus to split into two or more unequal fragments which carry-off most of the energy of fission as kinetic energy.This process is accompanied by the emission of neutrons and gamma rays.
2. Define nuclear fusion?
Nuclear fusion is the process of combining or fusing two lighter nuclei into a stable and heavier nuclide. In this case large amount of energy is released because mass of the product nucleus is less than the masses of the two nuclei which are fused.
3. Write the types of nuclear radiations?
The five types of nuclear radiations are :
(i) Gamma rays (or photons) : electromagnetic radiation.
(ii) Neutrons : uncharged particles, mass approximately 1.
(iii) Protons : + 1 charged particles, mass approximately 1.
(iv) Alpha particles : helium nuclei, charge + 2, mass 4.
(v) Beta particles : electrons (charge – 1), positrons (charge + 1), mass very small.
4. Define Nuclear Reactor?
A nuclear reactor is an apparatus in which nuclear fission is produced is the form of
a controlled self-sustaining chain reaction.
5. Write the Essential components of a nuclear reactor?
Essential components of a nuclear reactor are:
(i) Reactor core (ii) Reflector
(iii) Control mechanism (iv) Moderator
(v) Coolants (vi) Measuring instruments
6. What are the factors are consider to selecting the site for Nuclear power plant?
Following factors should be considered while selecting the site for a nuclear power plant: (i) Proximity to load centre
(ii) Population distribution (iii) Land use
(iv) Meteorology (v) Geology
(vi) Seismology (vii) Hydrology
7. What are the advantages of nuclear power plant?
1. It can be easily adopted where water and coal resources are not available.
2. The Nuclear power plant requires very small quantity of fuel. Hence fuel transport cost is less.
3. Space requirement is very less compared to other power plant of equal capacity.
4. It is not affected by adverse weather condition.
8. Define Surge tank?
A surge tank is a small reservoir or tank in which the water level rises or falls to reduce the pressure swings so that they are not transmitted in full to a closed circuit.
9. Write the purpose of Draft tube?
A draft tube serves the following two purposes:
1. It allows the turbine to be set above tail-water level, without loss of head, to facilitate inspection and maintenance.
2. It regains, by diffuser action, the major portion of the kinetic energy delivered to it from the runner
10. What is the Element of Hydel Power Plant?
Elements of Hydel Power Plant:
1. Water reservoir, 2. Dam, 3. Spillway,
4. Pressure tunnel,5. Penstock, 6. Surge tank,
7. Water turbine,8. Draft tube, 9. Tail race,
9. Step-up transformer,11. Power house.
11. Write the Advantages of Hydro-electric power plants?
1. Water is a renewable source of energy. Water which is the operating
fluid, is neither consumed nor converted into something else,
2. Water is the cheapest source of energy because it exists as a free gift of nature. The fuels needed for the thermal, diesel and nuclear plants are exhaustible and expensive.
3. There is no ash disposal problem as in the case of thermal power plant.
12. Define Governing Mechanism?
When the load on the turbine changes, the speed may also change. (i.e., without load the speed increases and with over load, the speed decreases). Hence, the speed of the runner must be maintained constant to have a constant speed of generator. This is done by controlling the quantity of water flowing on the runner according to the load variations. This speed regulation is known as governing and it is usually done automatically by a governor.
13. Define Francis water turbine?
The modern Francis water turbine is an inward mixed flow reaction turbine. It operates under medium heads and also requires medium quantity of water.
14. Write the advantages of small Hydro-power plant (SHP)?
a) Readily accessible source of renewable energy,
b) Can be installed making use of water head as low as 2 m and above,
c) Does not involve setting up of large dams,
d) Least polluting.
15. Differentiate propeller and Kaplan turbine?
In the propeller turbine the runner blades are fixed and non-adjustable. In Kaplan turbine, which is a modification of propeller turbine the runner blades are adjustable and can be rotated about the pivots fixed to the boss of the runner.
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