MCQs on Power Systems

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01․ In a pressurized water reactor
the coolant water boils in the reactor core.
heavy water is used as both coolant and moderator.
water is used at high pressure so that it is available is liquid from at about 280° C.
both B and C.

Pressurized water reactor is a thermal reactor using enriched uranium oxide, clad in zinc alloy as fuel. Water under pressure is used both as coolant and moderator. Sometimes heavy water is used both as moderator and coolant. A pump circulates water at high pressure (as high as 140 Kg/cm2) round the core so that water in liquid state absorbs heat from the uranium and transfer it to the boiler.

02․ Half life is defined as
the time required for one half of isotope to decay.
the time required for full of atoms in a specimen disintegrate.
the time required to spiliting of a heavy nucleus.
none of above.

Half life or half life period of a radio active isotope is the time required for one half of the isotope to decay.

03․ Thermal shielding is provided to
prevent the reactor wall from getting heated.
absorb the fast neutron.
protected the operating personal from exposure to radiations.
all of the above.

The purpose of shielding is to give protection from the deadly α rays as wall as neutron given off by the process of fission with the reactor. A good shielding system absorbs radiations before they are emitted to the surroundings. Since the coolant flows over the shielding to take away the heat.

04․ Which of following statement are false
A thermal reactor needs a moderator material.
In a nuclear reactor, multiplication factor is kept almost equal to one.
Nuclear power plants are used as peak load plants only.
In nuclear power plants, chain reaction is controlled by cadmium rods.

Nuclear power plants are used as base load plants because the loading of power plant will have effect on the generation cost.

05․ In what from the initial energy will be released for the 200 MeV per fission by a neutron in a slow thermal nuclear reactor
heat energy.
electromagnetic radiations.
kinetic energy and sound energy.
kinetic energy of particles and electromagnetic radiation.

Energy from the fission of uranium nucleus is released mainly as the kinetic energy of the neutrons and the energy of gamma radiations i.e. electromagnetic radiations.

06․ The radiation shield for a nuclear power reactor for biological safety is provided by having the reactor
encased by thick concrete wall.
encased thick metal wall.
immersed in water pool.
isolated from outside word with strong magnetic field.

The whole of the reactor is enclosed in a biological shield to prevent the escape or leak away of fast neutrons, slow neutrons, β - particles and γ - rays as these radiations are very harmful for living organisms. So thick concrete walls is used for this purpose.

07․ The power output of a nuclear power station is proportional to
square root of the rate at which fission reaction occurs.
square of the rate at which fission reaction occurs.
the rate at which fission reaction occurs.
none of above.

The power output of nuclear power station is proportional to fission reaction rate.

08․ A thermal power station needs space
less than that required by atomic power station of the same output.
less than that required by hydro-power station of same capacity.
less than that required by a gas turbine power plant of same output.
less than that required by the diesel power station of same output.

Hydro power station is required large area due to reservoir, dam.

09․ What is the approximate efficiency of a normal thermal power station
30 - 40 %.
45 - 55 %.
20 - 25 %.
60 - 70 %.

In a thermal power station, more than 50 % of total heat of combustion is lost as heat rejected to the condenser and this loss is unavoidable as heat energy cannot be converter into mechanical energy without drop in temperature, and the steam in condenser is at the lowest temperature. This is the reason that the approximate efficiency of a power plant is 30 to 40 %.

10․ On which one of the following cycles does a modern steam power plat work
Otto cycle.
Carnot cycle.
Rankine cycle.
Bell - Coleman cycle.

Rankine cycle is used to predict the performance of steam power plant. The Rankine cycle is an idealized thermodynamic cycle of a steam power plant that converts thermal of a thermal power plant that converts thermal energy to mechanical energy.