MCQs on Power Systems

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01․ Gas coolled reactor
use heavy water as coolant as well as moderator.
use coolant at pressure of 14-28 Kg/cm2 and at temperature of 700°-800° c.
use CO2. or helium as coolant and graphite the moderator.
both B and C.

As gas cooled reactor employs a gas as coolant instead of water. This type reactor employs CO2 or helium gas as coolant graphite as moderator. The gas is circulated at a temperature of 14-25 Kg/cm2 and at a temperature 700°C - 800°C. through the reactor core and the heat ex-changer by means of blower or a gas compressor.

02․ A sodium graphite reactors use
a mixture of sodium and graphite as coolant.
a mixture of sodium and graphite as moderator.
sodium as coolant and graphite as moderator.
sodium as moderator and graphite as coolant.

Sodium graphite reactor uses slightly enriched uranium alloy or uranium carbide clad with stainless steel as fuel, graphite as moderator and liquid sodium as coolant. Liquid sodium used as coolant in fast reactors which have large heat release from a small core, high heat transfer capability and low vapor pressure. Graphite used as a moderator because of it is simple to fabricate and handle and does not pose any containment problem.

03․ In boiler water reactor (BWR)
enriched uranium is used as fuel.
there is danger of radioactive contamination of steam.
the feed water acts both coolant and a moderator.
all of above.

Boiling water reactor is used enriched uranium as fuel and water is used as both moderator and coolant. The steam is generator at the top and after passing through turbine and condenser returns to the reactor. In view of direct cycle, there is danger of radioactive contamination of steam, therefore more elaborate safety measures are to be provided for piping and turbine.

04․ The thermal efficiency of BWR is
equal to that of PWR.
greater than that of PWR.
less than that of PWR.
none of the above.

The BWR include a small size pressure vessel, high steam pressure, simple construction and elimination of heat ex-changer circuit resulting gain in thermal efficiency (30 % in comparison to 20 % for a PWR reactor).

05․ In a nuclear reactor, chain reactor is controlled by introducing
brass rods.
cadmium rods.
iron rods.
graphite rods.

Chain reaction is controlled either by removing in the fuel rods by or inserting neutron absorbs materials. The material use for control rods must have very high absorption capacity for neutrons. The commonly used materials for control rod are cadmium, hafnium or boron.

06․ Which material is used in controlling chain reaction in a nuclear reactor
Heavy water.

Boron have very capacity of absorption neutrons.

07․ Critical mass is
maximum mass of fissionable material required to sustain a chain reaction.
minimum mass of fissionable material required to sustain chain reaction.
a mass of fissionable material required to stop a chain reaction.
none of these.

The minimum mass required to sustain a chain is called the critical mass of fissionable material.

08․ Nuclear power plant are used as
peak load plants.
base load plants.
intermediate load plants.
none of above.

The operating cost of nuclear power plants is quite low and once the installation is completed the loading of the power plant will have no effect on the generation cost. Therefore, a nuclear power plant is always operated as a base load plant.

09․ The conversion ratio of breeder reactor are
less than 1.
greater than 1.
none of above.

Fast breeder reactors can convert more fertile material to fissile material and therefore net fuel consumption is much less as a matter of fact more fissile material could be produced than would be consumed by it. So conversion ratio is greater than 1.

10․ Which of following materials can be used as coolant
Heavy water.
Any of above.

A coolant transfers heat produced inside the reactor to heat ex-changer for further utilization in power generation. The good coolant should not absorb neutrons, should be non oxidizing, non toxic and non corrosive and have high chemical and radiation stability and good heat transfer capability. Air, helium, hydrogen CO2, light and heavy water, molten sodium and lithium are used as coolant.