MCQs on Power Systems

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01․ The function of reflector is to
stop the chain reaction.
bounce back most of the neutrons that escape from the fuel core.
reduce the speed of the neutrons.
none of above.

As the reflector completely surrounds the reactor core within the thermal shielding arrangement and hilts to bounce escaping neutrons back into the core. This conserves the nuclear fuel as the low speed neutrons thus returned are useful in continuing the chain reaction.

02․ Generation of of one watt needs about ______________ fission per second
3.1 × 106.
3.1 × 107.
3.1 × 1010.

One fission of U235 causes a release of 200 MeV of energy. Now 200 MeV energy is equal to 3.2 × 10-11 Joules or watt seconds. So 1 watt requires 1 / (3.2 × 10-11 ) = 3.1 × 1010 fission per second.

03․ The average thermal efficiency of a modern nuclear power plant is about
30 %.
40 %.
60 %.
80 %.

The thermal efficiency is the ratio of gross electrical MW to thermal MW. This relates to the difference in temperature between the steam from the reactor and the cooling water. It is often 30 - 37 %.

04․ Graphite is use din nuclear plant as a / an

Properties of material to be used reflector are same as those for its use as a moderator. Graphite is simple to fabricate and handle and does not pose any containment problem.

05․ Which of the following is not a secondary nuclear fuel
None of above.

Secondary fuel nuclear power plant are plutonium (Pu239) and uranium (U233). Natural uranium (U235) is the parent material.

06․ One fission of U235 releases energy of
200 MeV.
335 MeV.
435 MeV.
525 MeV.

Generally we assumed that fission of U235 causes a release of 200 MeV of energy.

07․ One Kg of natural uranium gives energy equivalent to about
100 Kg of coal.
1000 Kg of coal.
5000 Kg of coal.
10500 Kg of coal.

All the atoms of 1 Kg of pure uranium were fissioned, the energy released would be equivalent to that contained in 3 × 106 Kg of coal with a calorific value of 6000 KCal/Kg. Though natural uranium contains only U235. If fission efficiency is 50 % (i.e. only half of the total atoms take past in fission) fission of 1 Kg of natural uranium would give energy equivalent to ( 0.7 × 3 × 106 × 0.5/100 ) or 10500 Kg of coal.

08․ In nuclear chain fission reaction each neutron causing fission produces
no new neutron.
one new neutron.
less than one new neutron.
at least one new neutron.

The splitting of heavy bucleus into two or more smaller nuclei is termed nuclear fission. The process of fission is always accompanied by the ejection of two or more neutrons and liberation of very fast energy.

09․ In a nuclear reator thermal energy is obtained from
fusion of radioactive material.
fission of radioactive material.
burning of fuel rods in oxygen.
all of above.

Nuclear fuel is subjected to nuclear fission in nuclear reactor and the energy released in the process is utilized to heat the coolant which may in turn generate steam or be used in a gas turbine.

10․ Critical mass of the fuel is the amount required to make the multiplication factor
equal to factor.
more than 1.
less than 1.

Critical mass of the fuel is the amount required to make the chain reaction at a steady state as the reaction will continue. So the multiplication factor will be one.