250+ TOP MCQs on Radioactive Decay & Half Life – I and Answers

Power Plant Engineering Multiple Choice Questions on “Radioactive Decay & Half Life – I”.

1. Fast breeder nuclear reactors using enriched uranium as fuel may contain upto a maximum of __________ percent of U-235 (i.e. fissile material).
a) 15
b) 45
c) 65
d) 85
Answer: d
Clarification: Fast breeder nuclear reactors using enriched uranium as fuel may contain upto a maximum of 85 percent of U-235 (i.e. fissile material).

2. __________ have the same mass number, but different nuclear charge.
a) Isotones
b) Isobars
c) Isotopes
d) Isoemtropic
Answer: b
Clarification: Isobars have the same mass number, but different nuclear charge.

3. Atoms with same number of neutrons, but different number of nucleons are called __________
a) Isobars
b) Isotones
c) Isotopes
d) Isoters
Answer: b
Clarification: Atoms with same number of neutrons, but different number of nucleons are called Isotones.

4. The half-life period of a radioactive substance is best determined by counting the number of alpha particles emitted per second in a Geiger Muller counter from its known quantity. If the half-life period of a radioactive substance is one month, then?
a) it will completely disintegrate in two months
b) l/8th of it will remain intact at the end of four months
c) 3/4th of it will disintegrate in two months
d) it will completely disintegrate in four months
Answer: a
Clarification: The half-life period of a radioactive substance is best determined by counting the number of alpha particles emitted per second in a Geiger Muller counter from its known quantity. If the half-life period of a radioactive substance is one month, then it will completely disintegrate in two months.

5. Which of the following ores contains maximum percentage of uranium?
a) Rescolite
b) Thorium
c) Pitchblende
d) Carnotite
Answer: c
Clarification: Pitchblende contains the maximum percentage of Uranium.

6. Percentage of U-238 in natural uranium is around __________
a) 29.71
b) 99.29
c) 0.015
d) 0.71
Answer: c
Clarification: Natural Uranium contains around 0.015% of U-238.

7. Uranium ore is currently mined & concentrated at __________
a) Khetri
b) Alwaye
c) Ghatsilla
d) Jadugoda
Answer: d
Clarification: Uranium ore is currently mined & concentrated at Jadugoda.

8. Graphite is used in nuclear reactor as __________
a) lubricant
b) fuel
c) retarder of neutron velocity
d) insulation lining of the reactor
Answer: c
Clarification: Graphite is used in nuclear reactor as retarder of neutron velocity.

9. A fast breeder reactor employs __________
a) U-235 as a fuel
b) water as a coolant
c) graphite as a moderator
d) none of the mentioned
Answer: a
Clarification: U-235 is used as a fuel in a fast breeder reactor.

10. A radioactive isotope undergoes decay with respect to time following __________ law.
a) logarithmic
b) exponential
c) inverse square
d) linear
Answer: b
Clarification: A radioactive isotope undergoes decay with respect to time following exponential law.

11. U-235 content in enriched uranium, that is normally used in power reactors (e.g., at Tarapur atomic power plant), is about __________ percent.
a) 50
b) 3
c) 85
d) 97
Answer: b
Clarification: U-235 content in enriched uranium, that is normally used in power reactors (e.g., at Tarapur atomic power plant), is about 3 percent.

12. The half-life period of a radioactive element is 100 days. After 400 days, one gm of the element will be reduced to __________ gm.
a) 1/2
b) 1/4
c) 1/8
d) 1/16
Answer: d
Clarification: The half-life period of a radioactive element is 100 days. After 400 days, one gm of the element will be reduced to1/16 gm.

13. Which of the following is a non-fissile material?
a) Pu-239
b) U-235
c) U-232
d) Th-232
Answer: d
Clarification: Of the mentioned fuels, only Th-232 is the fissile nuclear fuel.

14. Fast breeder reactors are most usable in India, because of our largest __________ deposits.
a) Uranium
b) Plutonium
c) Thorium
d) None of the mentioned
Answer: c
Clarification: Fast breeder reactors are most usable in India, because of our largest Thorium deposits.

15. Which is the main ore of thorium?
a) Magnetite
b) Monazite Sand
c) Pitchblende
d) None of the mentioned
Answer: b
Clarification: Monazite Sand is the main ore of Thorium.