1. Which of the following has high fission percentage?
a) Pu239
b) U233
c) U235
d) U234
Explanation: U235 has higher fission percentage in comparison to others. U235 is only fissionable nuclear fuel found in nature, Pu239 and U233 are produced artificially. They are fissionable.
2. Reactors used for converting fertile materials to fissile materials are called _____
a) research and development reactor
b) production reactor
c) power reactors
d) slow reactors
Explanation: Research and development reactors are used for testing new reactor designs and research. Production reactors are used for converting fertile materials into fissile materials and Power reactors are used for generation of electrical energy.
3. Which statement about fast reactor is true?
a) These reactors are big in size so not easier to shield
b) Fast reactors can convert fertile materials to fissile materials
c) Fast reactors are easy to control
d) Heat transfer and cooling is very easy and simple
Explanation: Fast reactors can convert more fertile material to fissile materials with the result that the net fuel consumption for such reactors is much less. These reactors are small and compact and so easier to shield. Heat transfer and cooling problems in the core are accomplished due to high power density
4. In which part of nuclear power plant steam is produced?
a) Boiler
b) Heat exchanger
c) Chamber across the reactor
d) Air preheater
Explanation: There is no boiler in nuclear power plant. The heat energy released in the reactor during nuclear fission is utilised to heat the coolant. This coolant is circulated through the heat exchanger to produce steam.
5. What is the main function of moderator?
a) It absorb the extra neutrons
b) It divert extra neutrons
c) It slow down the speed of fast neutrons
d) It absorb the heat energy caused by nuclear reaction
Explanation: Neutrons rejected during the fission process at a very high velocity of about 1.5 × 107 m/s. For more effective use in nuclear reactor it is desirable to slow down the fast neutrons to speed corresponding to the speed of molecules of gas at normal temperature and pressure. This is accomplished with the help of moderator.
6. Which of the following material is not used as moderator?
a) Oxygen
b) Ordinary water
c) Heavy water
d) Graphite
Explanation: At present the common moderator materials used are graphite, ordinary water and heavy water. Oxygen is not suitable to use due to its low density and the consequent small number of collision.
7. Which of the following part of nuclear reactor is used to control the rate of reaction.
a) Moderator
b) Control rods
c) Reflector
d) Coolant
Explanation: In a reactor the chain reaction is to be maintained at steady value during the operation of reactor. Also the reactor must be able to shutdown automatically under emergency conditions. All these requires control rods for control of reactor so as to prevent the melting of fuel rods, disintegration of coolant and destruction of reactor as the amount of energy released is enormous.
8. Which of the following is the most essential requirement of control rod material?
a) It must be light weight
b) It must be cheap
c) It must have high absorption capacity for neutrons
d) It must be very reflective to neutrons
Explanation: The function of control rod is to control the rate of nuclear reaction by absorption extra release neutrons. Chain reaction is controlled either by removing or inserting neutron absorbing materials. The materials used for control rods must have very high absorption capacity for entrance
9. Which of the following can be used as both as coolant and moderator ?
a) Helium
b) Molten sodium
c) Lithium
d) Ordinary water
Explanation: A good coolant should not absorb neutrons, should be non-oxidizing, non-toxic, non corrosive, should have high chemical and radiation stability and good heat transfer ability. Ordinary water is used as both as coolant and moderator in boiling water reactor and pressurized water is used as both as coolant and moderator in pressurized water reactor.
10. In thermal reactors control is very easy in comparison to other reactors.
a) True
b) False
Explanation: In thermal reactor control his very easy because of relatively low power densities and longer in neutron lifetime.