Q1. What is the process by which a heavy nucleus splits into two or more lighter nuclei?
a) Nuclear fusion
b) Nuclear decay
c) Nuclear fission
d) Nuclear transmutation
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Correct Answer: c) Nuclear fission
Explanation: Nuclear fission is a nuclear reaction in which the nucleus of an atom splits into two or more smaller nuclei, along with the release of energy. This process is typically induced by bombarding the nucleus with neutrons and is utilized in nuclear power plants and nuclear weapons.
Q2. Which of the following elements is commonly used as a fuel in nuclear fission reactions?
a) Carbon
b) Uranium
c) Silicon
d) Oxygen
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Correct Answer: b) Uranium
Explanation: Uranium, particularly uranium-235 (^235U), is commonly used as a fuel in nuclear fission reactions due to its ability to undergo fission when bombarded with neutrons. Nuclear reactors utilize uranium fuel rods to sustain controlled fission reactions, generating heat to produce electricity.
Q3. Which of the following particles is released during the nuclear fission of uranium-235?
a) Neutrons
b) Electrons
c) Protons
d) Alpha particles
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Correct Answer: a) Neutrons
Explanation: In nuclear fission reactions, neutrons are typically released when a heavy nucleus such as uranium-235 undergoes fission. These neutrons can then collide with other uranium nuclei, initiating a chain reaction that results in further fission events and the release of additional neutrons and energy.
Q4. What is the term used to describe the minimum amount of fissile material needed to sustain a nuclear chain reaction?
a) Fission threshold
b) Critical mass
c) Fusion limit
d) Reactor core
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Correct Answer: b) Critical mass
Explanation: Critical mass refers to the minimum mass of fissile material required to sustain a nuclear chain reaction under specific conditions. If the mass is below the critical mass, the reaction will not be self-sustaining. Achieving and maintaining critical mass is essential for the operation of nuclear reactors and weapons.
Q5. Which of the following is NOT a product of nuclear fission reactions?
a) Neutrons
b) Gamma rays
c) Helium nuclei
d) Fission fragments
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Correct Answer: c) Helium nuclei
Explanation: Nuclear fission reactions primarily produce neutrons, along with fission fragments (smaller nuclei resulting from the fission process) and gamma rays (high-energy electromagnetic radiation). Helium nuclei, also known as alpha particles, are not typically produced in nuclear fission reactions, but they may be emitted in subsequent decay processes.
Q6. What is the primary source of energy in nuclear fission reactions?
a) Mass defect
b) Binding energy
c) Kinetic energy
d) Potential energy
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Correct Answer: b) Binding energy
Explanation: In nuclear fission reactions, the primary source of energy is the conversion of nuclear binding energy into kinetic energy of the fission fragments and neutrons. When a heavy nucleus undergoes fission, the resulting fragments have a slightly lower combined mass than the original nucleus, and this mass difference is converted into energy according to Einstein’s equation, E=mc².
Q7. Which of the following materials is commonly used as a moderator in nuclear reactors to slow down neutrons?
a) Graphite
b) Lead
c) Iron
d) Aluminum
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Correct Answer: a) Graphite
Explanation: Graphite is commonly used as a moderator in nuclear reactors to slow down neutrons produced during nuclear fission reactions. Slowing down neutrons increases their likelihood of causing further fission events in fissile materials such as uranium-235, facilitating a sustained chain reaction. Other materials, such as heavy water (deuterium oxide), can also serve as moderators.
Q8. What is the purpose of control rods in nuclear reactors?
a) To absorb excess neutrons and regulate the rate of the chain reaction
b) To generate electricity directly from nuclear reactions
c) To shield the reactor core from radiation
d) To cool down the reactor core
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Correct Answer: a) To absorb excess neutrons and regulate the rate of the chain reaction
Explanation: Control rods are used in nuclear reactors to control the rate of the nuclear chain reaction by absorbing excess neutrons. By adjusting the position of the control rods within the reactor core, operators can regulate the number of neutrons available to sustain the chain reaction, thereby controlling the reactor’s power output.
Q9. Which of the following statements about nuclear fission reactors is true?
a) They rely on the fusion of hydrogen nuclei to generate energy.
b) They produce no radioactive waste.
c) They utilize the heat generated by nuclear fission to produce electricity.
d) They are completely safe and pose no risk of accidents.
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Correct Answer: c) They utilize the heat generated by nuclear fission to produce electricity.
Explanation: Nuclear fission reactors harness the heat generated by nuclear fission reactions to produce steam, which drives turbines connected to generators to generate electricity. This process is similar to conventional power plants fueled by coal or natural gas, but the heat source in nuclear reactors is the controlled fission of uranium or other fissile materials.
Q10. Which of the following nuclear fission products is typically used as nuclear fuel in breeder reactors?
a) Plutonium-239
b) Xenon-133
c) Krypton-85
d) Iodine-131
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Correct Answer: a) Plutonium-239
Explanation: Plutonium-239 (^239Pu) is a fissile material produced as a byproduct of nuclear fission reactions, particularly in reactors fueled by uranium-238. Breeder reactors utilize plutonium-239 as nuclear fuel by converting non-fissile uranium-238 into plutonium-239 through neutron capture and subsequent radioactive decay, thereby maximizing the use of nuclear fuel resources.