Question 61 : Thorium-232 is converted into uranium-233 in a/an __________ nuclear reactor.
1. heavy water moderated
2. thermal
3. fast breeder
4. enriched uranium
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Question 62 : Which of the following may not need a control rod ?
1. Liquid metal cooled reactor.
2. Fast breeder reactor.
3. None of these.
4. Candu reactor.
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Question 63 : Commercial power generation from fusion reactor is not yet possible, because
1. quantity of fuel required for initiating fusion reaction is prohibitively high.
2. it is difficult to control fusion reaction.
3. the fuel required (e.g. deuterium and tritium) is scarce.
4. it is difficult to initiate fusion reaction.
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Question 64 : The amount of a radioisotope remaining undecayed after a time equal to four times its half life, will be __________ percent.
1. 125
2. 25
3. 6.25
4. 150
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Question 65 : One 'amu' is equivalent to
1. 931J
2. 931 Mev
3. 9.31 MeV
4. 931 eV
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Question 66 : Which of the following may not need a moderator ?
1. Pressurised water reactor
2. Candu reactor
3. Fast breeder reactor
4. Homogeneous reactor
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Question 67 : Heat is generated in a nuclear reactor (thermal) by
1. absorption of neutrons in uranium atoms.
2. fusion of atoms of uranium.
3. fission of U-235 by neutrons.
4. combustion of a nuclear fuel e.g. uranium.
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Question 68 : The decay product of tritium (a beta emitter) is
1. lithium
2. deuterium
3. helium
4. hydrogen
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Question 69 : The time taken for a radioactive element to reduce to 50% of its original weight is __________ years, if its half life period is 12 years.
1. 24
2. 18
3. 6
4. 48
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Question 70 : The second underground nuclear test was conducted by India at
1. Narora
2. Pokhran
3. Jaisalmer
4. Kalpakkan
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