In a nuclear reactor, self-sustained chain reaction is possible, because:
More neutrons are released in each of the fission reactions.
The neutrons immediately take part in the fission process.
The fast neutrons are slowed down by graphite.
Every neutron released in the fission reaction initiates further fission.
Which of these statements are correct?
Correct Answer:
(B) 1 and 3
Nuclear reactor, formerly known as atomic pile (molecular furnace) uses Uranium - 235 or Plutonium-239 as fuel. When this fissile atomic nucleus absorbs a neutron, it may undergo nuclear fission. The heavy nucleus splits into two or more lighter nuclei, releasing kinetic energy, gamma radiation, and free neutrons. To reduce the speed of neutrons in this reaction H2O (light water), D2O (heavy water), graphite or beryllium oxide are used as the moderator. This whole process is called self-sustained chain reaction, so statement 1 and 3 are correct.
Ques: 2
Which statement is not associated with nuclear fission:
Correct Answer:
(B) Energy generation in stars.
Nuclear fission is a type of reaction in which a heavy atomic nucleus splits into fragments of roughly equal mass releasing huge amount of energy. In contrast, nuclear fusion occurs when two or more smaller atoms fuse together to form a heavier atom releasing large amount of energy. Neutron induced nuclear reaction, nuclear reactors producing electricity and atom bomb are based on the nuclear fission reactions whereas energy generation in stars is due to nuclear fusion.
Ques: 3
Consider the following statements about nuclear fusion reactors:
They work on the principle of fission of heavy nuclei.
They usually have Tokamak design.
They operate at very high temperature.
Of these:
Correct Answer:
(C) Only ii and iii are correct
Nuclear fusion reactors work on the principle of fusion of two light nuclei. So, statement (i) is incorrect. Nuclear fusion reactions are also called ‘Thermonuclear reactions’ because they operate at very high temperature. Usually, nuclear fusion reactors have Tokamak design.
Ques: 4
The difference between nuclear reactor and atom bomb is that:
Correct Answer:
(B) The chain reaction in nuclear reactor is controlled
The chain reaction process used in nuclear reactors and atom bombs both release vast amount of energy, but the manner in which the energy is controlled and utilized is different in both the cases. In nuclear reactors, the reaction is moderated and controlled for peaceful purpose, while in nuclear bombs the reaction is uncontrolled.
Ques: 5
With reference to the radioactivity, which of the following statements is/are correct?
Radioactivity is a nuclear property.
Hydrogen bomb is prepared on the principle of nuclear fission.
Select the correct answer using the codes given below.
Codes:
Correct Answer:
(A) Only 1
Radioactivity is a nuclear phenomenon. It is the process of spontaneous emission of alpha, beta and gamma radiations from the nuclei of an atom. Hence, statement 1 is correct. Statement 2 is incorrect as hydrogen bomb is prepared on the principle of nuclear fusion.
Ques: 6
The working principle of atom bomb is nuclear fission of uranium and the working principle of hydrogen bomb is–
Correct Answer:
(A) nuclear fusion of deuterium.
losion of bomb involving hydrogen gas
explosion involving dynamite and T.N.T.
Ans. (a)
Exp: Hydrogen bomb's enormous explosive power results from an uncontrolled, self-sustaining chain reaction in which isotopes of hydrogen (deuterium and tritium) combined under extremely high temperature and pressure to form helium in a process known as nuclear fusion.
Ques: 7
Enriched Uranium is -
Correct Answer:
(B) Natural uranium in which radioactive U235 isotope is increased artificially.
'Enriched Uranium' is a type of uranium in which the proportion of the uranium-235 isotope has been increased from the natural level by the process of isotope separation.