Quick recall · 143 cards
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Two radioactive materials A and B have decay constants 10λ and λ, respectively. If initially, they have the same number of nuclei, then the ratio of the number of nuclei of A to that of B will be 1/e after a time
A · 1/(10λ)
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One of the features of the fission process is that it:
A · A) Leads to a chain reaction
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What is the primary result of a fission reaction?
A · A) Heavy nuclei split into lighter nuclei
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Which of the following material is used to construct the control rod in the nuclear reactor?
(a) Cadmium
(b) Copper
(c) Graphite
(d) None of the above
A · Cadmium
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Where is Kakrapar’s atomic power station located?
(a) Andhra Pradesh
(b) Gujarat
(c) Madhya Pradesh
(d) None of the above
B · Gujarat
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Where was the first nuclear power plant planted?
(a) Bombay
(b) Andhra Pradesh
(c) Madhya Pradesh
(d) None of the above
A · Bombay
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What is the role of the moderator in the nuclear power station?
(a) Absorb the neutrons
(b) Accelerate the neutrons
(c) Slow down the neutrons
(d) Absorb the energy
C · Slow down the neutrons
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Nuclear reactors are used for:
(A) to produce heat for thermoelectric power
(B) to produce fissionable material
(C) to propel ships, submarines, aircrafts
(D) all of these
D · all of these
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Atomic spectra is also known as:
B · b) line spectra
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Which of the following is the \( \alpha \)-line of Balmer series?
C · c) longest wavelength with n2=3
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If uncertainty in the position of an electron is zero, the uncertainty in its momentum will be:
D · d) infinite
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Which of the following is a correct relation according to Heisenberg’s Uncertainty principle?
C · c) \( \Delta x \cdot \Delta p \geq \frac{h}{4\pi} \)
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What is the definition of half-life in radioactive decay?
A · The time taken for half of the radioactive nuclei to decay
Half-life is defined as the time required for half of the radioactive nuclei in a sample to decay.
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Which of the following best describes the half-life of a radioactive isotope?
A · It is constant and independent of the initial amount of the isotope
The half-life of a radioactive isotope is a constant characteristic property and does not depend on the initial quantity or external conditions.
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If a radioactive sample has a half-life of 10 hours, how much of the sample remains after 30 hours?
A · \( \frac{1}{8} \) of the original amount
After each half-life, half of the remaining sample decays. After 3 half-lives (30 hours), remaining amount is \( \left( \frac{1}{2} \right)^3 = \frac{1}{8} \).
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Which of the following is the correct mathematical expression for half-life \( T_{1/2} \) in terms of decay constant \( \lambda \)?
A · \( T_{1/2} = \frac{\ln 2}{\lambda} \)
The half-life \( T_{1/2} \) is related to the decay constant \( \lambda \) by \( T_{1/2} = \frac{\ln 2}{\lambda} \).
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If the decay constant of a radioactive substance is doubled, what happens to its half-life?
A · It becomes half
Since \( T_{1/2} = \frac{\ln 2}{\lambda} \), doubling \( \lambda \) halves the half-life.
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Refer to the diagram below showing the decay curve of a radioactive sample. What does the time interval between points A and B represent?
A · One half-life
The time interval between points where the quantity halves corresponds to one half-life.
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The radioactive decay law is expressed as \( N = N_0 e^{-\lambda t} \). What does \( N_0 \) represent?
A · Initial number of radioactive nuclei
\( N_0 \) is the initial number of radioactive nuclei present at time \( t=0 \).
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Using the radioactive decay law \( N = N_0 e^{-\lambda t} \), what is the fraction of nuclei remaining after time \( t = T_{1/2} \)?
A · \( \frac{1}{2} \)
At time equal to half-life, half of the nuclei remain, so the fraction is \( \frac{1}{2} \).
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Refer to the decay curve below. What is the approximate decay constant \( \lambda \) if the half-life is 5 hours?
A · \( 0.1386 \ \text{hr}^{-1} \)
Decay constant \( \lambda = \frac{\ln 2}{T_{1/2}} = \frac{0.693}{5} = 0.1386 \ \text{hr}^{-1} \).
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Activity \( A \) of a radioactive sample is defined as:
A · Number of decays per unit time
Activity is the rate at which nuclei decay, i.e., number of decays per unit time.
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If the activity of a radioactive sample is \( A = \lambda N \), what happens to the activity when the number of nuclei \( N \) is halved?
A · Activity is halved
Activity is directly proportional to the number of nuclei, so halving \( N \) halves the activity.
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Refer to the activity vs time graph below. What does the slope of the curve represent?
A · Decay constant \( \lambda \)
The slope of the natural logarithm of activity vs time graph equals \( -\lambda \), the decay constant.
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The activity of a radioactive sample is 1000 Bq. After one half-life, what will be the activity?
A · 500 Bq
Activity decreases by half after one half-life, so it becomes 500 Bq.
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If the initial quantity of a radioactive substance is \( N_0 \), what is the remaining quantity after \( n \) half-lives?
A · \( N_0 \times \left( \frac{1}{2} \right)^n \)
After \( n \) half-lives, the remaining quantity is \( N_0 \times \left( \frac{1}{2} \right)^n \).
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Calculate the remaining quantity of a radioactive sample after 3 half-lives if the initial quantity was 80 g.
B · 20 g
Remaining quantity = \( 80 \times \left( \frac{1}{2} \right)^3 = 80 \times \frac{1}{8} = 10 \) g.
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Refer to the decay curve below. If the initial quantity is 100 units, what is the quantity at time \( t = 2T_{1/2} \)?
A · 25 units
After 2 half-lives, remaining quantity is \( 100 \times \left( \frac{1}{2} \right)^2 = 25 \) units.
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The decay constant \( \lambda \) is related to half-life \( T_{1/2} \) by which of the following expressions?
A · \( \lambda = \frac{\ln 2}{T_{1/2}} \)
The decay constant is the inverse relation of half-life: \( \lambda = \frac{\ln 2}{T_{1/2}} \).
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If the half-life of a radioactive isotope is 8 hours, what is the decay constant \( \lambda \)?
A · \( 0.0866 \ \text{hr}^{-1} \)
Using \( \lambda = \frac{\ln 2}{T_{1/2}} = \frac{0.693}{8} = 0.0866 \ \text{hr}^{-1} \).
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Refer to the graph below showing activity vs time for two different isotopes. Which isotope has the shorter half-life?
A · Isotope A (steeper decay)
A steeper decay curve indicates a larger decay constant and thus a shorter half-life.
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The SI unit of activity is:
A · Becquerel (Bq)
The SI unit of activity is Becquerel (Bq), which equals one decay per second.
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Which of the following units is NOT used to measure radioactivity?
A · Sievert (Sv)
Sievert measures radiation dose equivalent, not radioactivity itself.
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Which instrument is commonly used to measure the activity of a radioactive source?
A · Geiger-Müller counter
A Geiger-Müller counter detects and measures ionizing radiation, thus measuring activity.
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Which of the following is an application of half-life in medicine?
A · Determining dosage and timing of radiopharmaceuticals
Half-life helps determine how long a radioactive tracer remains active in the body for medical imaging or treatment.
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In archaeology, the half-life of Carbon-14 is used for:
A · Dating ancient organic materials
Carbon-14 dating uses its known half-life to estimate the age of archaeological samples.
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Refer to the diagram below showing radioactive decay used in nuclear medicine. What is the significance of choosing isotopes with short half-lives?
A · They minimize radiation exposure time to patients
Short half-life isotopes decay quickly, reducing radiation exposure while providing effective imaging.
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A radioactive isotope has a half-life of 4 hours. If the initial activity is 1600 Bq, what is the activity after 8 hours?
A · 400 Bq
After 2 half-lives (8 hours), activity = \( 1600 \times \left( \frac{1}{2} \right)^2 = 400 \) Bq.
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A sample has a decay constant \( \lambda = 0.1 \ \text{day}^{-1} \). What is its half-life?
A · \( 6.93 \ \text{days} \)
Half-life \( T_{1/2} = \frac{\ln 2}{\lambda} = \frac{0.693}{0.1} = 6.93 \) days.
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Refer to the decay curve below. If the initial activity is 5000 Bq and the half-life is 3 hours, what is the activity after 9 hours?
A · 625 Bq
After 3 half-lives (9 hours), activity = \( 5000 \times \left( \frac{1}{2} \right)^3 = 625 \) Bq.
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A radioactive sample decays to 12.5% of its original quantity in 15 hours. What is its half-life?
A · 5 hours
12.5% = \( \left( \frac{1}{2} \right)^n \) implies \( n=3 \) half-lives. So, \( T_{1/2} = \frac{15}{3} = 5 \) hours.
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A radioactive isotope decays with half-life T. A sample is placed in a detector with dead time τ. If the initial activity is A_0 and A_0 τ ≈ 1, what is the observed count rate immediately after measurement starts?
A · A_0 / (1 + A_0 τ)
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Which of the following best defines nuclear fission?
A · Splitting of a heavy atomic nucleus into two lighter nuclei with the release of energy
Nuclear fission is the process where a heavy nucleus splits into two lighter nuclei, releasing energy.
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Which of the following nuclei is commonly used as fuel in nuclear fission reactions?
A · Uranium-235
Uranium-235 is a fissile isotope commonly used as fuel in nuclear reactors and weapons.
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What is the primary cause of the nucleus splitting during nuclear fission?
A · Absorption of a neutron
The nucleus splits when it absorbs a neutron, making it unstable and causing fission.
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Which of the following statements about nuclear fission is correct?
B · It releases energy due to mass defect and conversion to energy
Energy released in fission comes from the mass defect converted to energy according to \( E=mc^2 \).
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Refer to the diagram below showing a nuclear fission chain reaction.
What happens immediately after the absorption of a neutron by a Uranium-235 nucleus?
A · The nucleus splits into two smaller nuclei and emits more neutrons
Absorption of a neutron causes the Uranium-235 nucleus to become unstable and split, releasing neutrons and energy.
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In a nuclear fission chain reaction, what is the role of the emitted neutrons?
A · They initiate further fission events by colliding with other fissile nuclei
Emitted neutrons from one fission event cause further fission in other nuclei, sustaining the chain reaction.
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Which of the following best describes a self-sustaining nuclear fission chain reaction?
A · Each fission event causes exactly one more fission event on average
A self-sustaining chain reaction occurs when each fission produces one neutron that causes another fission, maintaining the reaction.
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Refer to the diagram below illustrating a nuclear fission chain reaction.
If the average number of neutrons from each fission that cause further fission is greater than 1, what will happen to the reaction?
A · The reaction will become supercritical and increase exponentially
If more than one neutron from each fission causes further fission, the reaction grows exponentially (supercritical).
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Which condition is necessary for a nuclear fission chain reaction to be sustained?
A · The system must be critical, meaning exactly one neutron from each fission causes another fission
Criticality means the chain reaction is self-sustaining with one neutron causing another fission on average.
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Which of the following terms describes a nuclear reactor operating with a chain reaction that is increasing in rate?
A · Supercritical
A supercritical reactor has a chain reaction that increases exponentially due to more than one neutron causing fission.
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Refer to the diagram below showing neutron population over time in different reactor states.
Which curve represents a critical state?
A · The horizontal line where neutron population remains constant
In a critical state, neutron population remains steady over time, represented by a horizontal line.
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Which of the following factors does NOT affect the criticality of a nuclear reactor?
A · Color of the reactor core
The color of the reactor core has no physical effect on criticality, unlike neutron absorption, fuel enrichment, and moderation.
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Which neutron energy range is most effective in sustaining a fission chain reaction in Uranium-235?
A · Thermal (slow) neutrons
Thermal neutrons have low energy and a higher probability of inducing fission in U-235 nuclei.
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What is the primary purpose of a neutron moderator in a nuclear reactor?
A · To slow down fast neutrons to thermal energies to sustain the chain reaction
Moderators reduce neutron speed, increasing the likelihood of fission in fissile material.
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Refer to the neutron interaction diagram below.
Which process is shown when a neutron collides elastically with a light nucleus and loses energy?
A · Neutron moderation
Elastic collisions with light nuclei slow neutrons down, a process called moderation.
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Which of the following best explains why control rods are used in nuclear reactors?
A · To absorb excess neutrons and regulate the chain reaction rate
Control rods absorb neutrons, preventing too many fissions and controlling the reaction.
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Which of the following correctly describes the source of energy released in nuclear fission?
A · Conversion of mass defect into energy according to \( E=mc^2 \)
Energy released in fission comes from the mass difference between reactants and products converted to energy.
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Refer to the energy release graph below showing energy distribution in a typical fission event.
Which form accounts for the largest portion of energy released?
A · Kinetic energy of fission fragments
Most energy released appears as kinetic energy of the fission fragments (daughter nuclei).
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Which of the following is NOT an application of nuclear fission chain reactions?
A · Solar energy generation
Solar energy generation does not involve nuclear fission; it relies on nuclear fusion in the sun.
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Which of the following best describes the role of nuclear reactors?
A · To control nuclear fission chain reactions to produce usable energy
Nuclear reactors sustain controlled fission chain reactions to generate heat and electricity safely.
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Which of the following is a primary method used to control the rate of nuclear fission in reactors?
A · Insertion or removal of control rods
Control rods absorb neutrons and regulate the chain reaction rate by their position in the reactor core.
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Refer to the reactor control mechanism illustration below.
What is the function of the control rods shown in the diagram?
A · Absorb neutrons to slow or stop the chain reaction
Control rods absorb neutrons, reducing the number available to cause fission and thus controlling the reaction.
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Which material is commonly used as a moderator in nuclear reactors to slow down neutrons?
D · Both A and C
Both heavy water and graphite are used as moderators to slow neutrons effectively.
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Which of the following is a major safety hazard associated with nuclear fission chain reactions?
A · Release of radioactive materials due to uncontrolled reactions
Uncontrolled fission reactions can release harmful radioactive materials, posing serious safety hazards.
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Which safety measure is used to prevent a nuclear reactor from going supercritical accidentally?
A · Automatic insertion of control rods during abnormal conditions
Automatic control rod insertion helps shut down or slow the reaction to prevent supercriticality.
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Which of the following best describes the process of nuclear fission?
A · Splitting of a heavy nucleus into two lighter nuclei with the release of energy
Nuclear fission involves the splitting of a heavy nucleus into two lighter nuclei, releasing a significant amount of energy.
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In nuclear fission, which particle initiates the splitting of the nucleus?
C · Neutron
A neutron initiates nuclear fission by colliding with a heavy nucleus, causing it to split.
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Which of the following statements about nuclear fission is correct?
B · Fission releases energy due to conversion of mass into energy according to \( E=mc^2 \)
Energy released in fission comes from the mass defect converted into energy as per Einstein's relation \( E=mc^2 \).
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Refer to the diagram below showing a nuclear fission chain reaction schematic. Which part of the diagram represents the neutrons that sustain the chain reaction?
A · Neutrons released from fission fragments
Neutrons released from fission fragments are the ones that can initiate further fission events, sustaining the chain reaction.
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In a nuclear chain reaction, what happens when the number of neutrons produced per fission event is exactly one on average?
B · The reaction is critical and self-sustaining
When exactly one neutron per fission causes another fission, the chain reaction is critical and self-sustaining.
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Which of the following best describes a supercritical state in a nuclear reactor?
C · Neutron population increases exponentially
In a supercritical state, each fission produces more than one neutron that causes further fission, leading to exponential increase in neutron population.
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Refer to the diagram below showing a nuclear chain reaction flow. Which step corresponds to the neutron-induced fission event?
A · Neutron absorption by fuel nucleus
Neutron absorption by the fuel nucleus triggers the fission event, releasing energy and more neutrons.
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What is critical mass in the context of nuclear fission?
A · Minimum mass of fissile material needed to sustain a chain reaction
Critical mass is the minimum amount of fissile material required to maintain a self-sustaining chain reaction.
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Which factor does NOT affect the critical mass of a fissile material?
D · Ambient temperature
Ambient temperature has negligible effect on critical mass compared to shape, density, and neutron reflectors.
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Refer to the diagram below showing different configurations of fissile material. Which configuration is most likely to have the smallest critical mass?
B · Spherical shape
A sphere has the smallest surface area to volume ratio, minimizing neutron leakage and thus requiring the smallest critical mass.
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Which of the following describes the term 'neutron economy' in a nuclear reactor?
A · Balance between neutron production and losses in the reactor
Neutron economy refers to the efficient use of neutrons, balancing production and losses to sustain the chain reaction.
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What is the primary role of a moderator in a nuclear reactor?
B · Slow down fast neutrons to thermal energies
The moderator slows down fast neutrons to thermal energies, increasing the probability of fission in fissile nuclei.
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Refer to the diagram below illustrating the neutron moderation process. Which part of the diagram shows the neutron losing energy through collisions?
B · Moderator atoms
Moderator atoms collide with fast neutrons, slowing them down to thermal energies.
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Which of the following materials is commonly used as a moderator in nuclear reactors?
B · Graphite
Graphite is a common moderator material because it effectively slows down neutrons without absorbing them significantly.
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How does increasing neutron absorption by control rods affect neutron economy in a reactor?
B · Reduces neutron economy by removing neutrons from the chain reaction
Control rods absorb neutrons, reducing the number available to sustain the chain reaction, thus reducing neutron economy.
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Which of the following correctly describes the energy released during nuclear fission?
A · Energy is released as kinetic energy of fission fragments and as gamma radiation
Energy released in fission appears as kinetic energy of the fragments, neutrons, and gamma radiation.
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Refer to the energy release graph below for a typical fission reaction. At which point is the maximum energy released?
B · During the splitting of the nucleus
Maximum energy is released during the splitting of the nucleus when the mass defect converts to energy.
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Which of the following is NOT a common application of nuclear fission energy?
D · Solar energy harvesting
Solar energy harvesting is unrelated to nuclear fission; it uses photovoltaic or thermal processes.
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Which method is commonly used to control the rate of a nuclear chain reaction in a reactor?
B · Adjusting the position of control rods
Control rods absorb neutrons and adjusting their position controls the reaction rate.
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Refer to the diagram below showing a control rod insertion mechanism. What is the effect of fully inserting the control rods into the reactor core?
B · Decrease neutron flux and reaction rate
Fully inserted control rods absorb more neutrons, reducing neutron flux and slowing the reaction.
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Which of the following is a consequence of a reactor becoming supercritical unintentionally?
B · Rapid increase in power output potentially causing damage
An unintentional supercritical state causes rapid power increase, risking damage or meltdown.
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Which of the following is a major safety hazard associated with nuclear fission reactors?
B · Radiation release due to core meltdown
Core meltdown can release harmful radiation, posing a major safety hazard.
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Refer to the diagram below showing safety systems in a nuclear reactor. Which component is primarily responsible for emergency shutdown?
B · Control rods
Control rods are inserted rapidly during emergency shutdown to absorb neutrons and stop the chain reaction.
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Which radioactive byproduct of nuclear fission is a major concern for long-term nuclear waste management?
C · Cesium-137
Cesium-137 is a highly radioactive fission product with a long half-life, posing long-term waste management challenges.
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Which of the following measures reduces the risk of a nuclear accident in a reactor?
B · Incorporation of multiple redundant safety systems
Multiple redundant safety systems ensure safe operation and reduce accident risk.
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Assertion (A): Delayed neutrons are essential for the controllability of nuclear reactors.
Reason (R): Delayed neutrons have longer lifetimes allowing slower changes in reactor power.
Choose the correct option:
A · Both A and R are true, and R is the correct explanation of A.
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Which of the following best describes the basic principle of a nuclear reactor?
A · Conversion of nuclear energy into electrical energy through controlled fission
A nuclear reactor operates by controlling nuclear fission to convert nuclear energy into electrical energy.
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In a nuclear reactor, what is the primary purpose of the moderator?
B · To slow down fast neutrons to sustain the chain reaction
The moderator slows down fast neutrons to thermal energies, increasing the probability of fission and sustaining the chain reaction.
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Which of the following statements correctly explains the concept of criticality in a nuclear reactor?
C · The reactor sustains a constant chain reaction with neutron production equal to neutron loss
Criticality means the chain reaction is self-sustaining, with neutron production balanced by neutron losses.
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Which type of nuclear reactor uses heavy water as a moderator and coolant?
C · Canada Deuterium Uranium (CANDU) Reactor
CANDU reactors use heavy water (deuterium oxide) as both moderator and coolant.
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Which of the following reactors is designed to produce more fissile material than it consumes?
C · Fast Breeder Reactor (FBR)
Fast Breeder Reactors generate more fissile material (usually plutonium-239) than they consume, by converting fertile material.
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Refer to the diagram below showing a schematic of a Pressurized Water Reactor (PWR). Which component labeled in the diagram is responsible for controlling the rate of the nuclear reaction?
B · B: Control Rods
Control rods absorb neutrons and regulate the fission rate in the reactor core.
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In the nuclear fission process, which particle initiates the chain reaction by colliding with the fissile nucleus?
C · Neutron
Neutrons initiate fission by colliding with fissile nuclei, causing them to split and release energy.
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Which of the following best describes a chain reaction in nuclear fission?
A · A single fission event producing multiple neutrons that cause further fission events
A chain reaction occurs when neutrons from one fission event cause further fission events, sustaining the reaction.
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Refer to the graph below showing neutron population versus time in a nuclear reactor. What does the flat region of the graph indicate?
B · Critical state
A flat neutron population indicates a critical state where the chain reaction is steady and self-sustaining.
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Which component of a nuclear reactor is primarily responsible for housing the fuel rods where fission occurs?
B · Reactor Core
The reactor core contains the fuel rods where nuclear fission reactions take place.
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Which of the following is NOT a typical component of a nuclear reactor?
C · Steam turbine
The steam turbine is part of the power plant but not the reactor itself; the reactor includes fuel rods, control rods, and moderator.
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Refer to the schematic diagram below of a nuclear reactor core. Which labeled part is the coolant that removes heat from the core?
D · D: Coolant
Coolant circulates through the core to remove heat generated by fission in the fuel rods.
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Which safety mechanism in a nuclear reactor is designed to rapidly shut down the chain reaction in case of emergency?
B · Insertion of control rods
Control rods absorb neutrons and can be fully inserted to quickly stop the chain reaction.
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Which of the following is a primary function of the containment structure in a nuclear power plant?
B · To prevent release of radioactive materials to the environment
The containment structure is a robust barrier designed to contain radioactive materials in case of accidents.
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Refer to the safety mechanism layout diagram below. Which component labeled is responsible for emergency core cooling?
B · B: Emergency Core Cooling System (ECCS)
The ECCS provides rapid cooling to the reactor core during emergency conditions to prevent meltdown.
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Which of the following control mechanisms helps maintain reactor stability by adjusting neutron absorption dynamically during operation?
B · Chemical shim (boric acid concentration)
Chemical shim involves varying boric acid concentration in the coolant to absorb neutrons and control reactivity.
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Which nuclear fuel is most commonly used in light water reactors?
A · Uranium-235
Uranium-235 is the primary fissile fuel used in most light water reactors.
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Which stage of the nuclear fuel cycle involves the reprocessing of spent fuel to extract usable fissile material?
C · Reprocessing
Reprocessing involves chemically treating spent fuel to recover fissile materials like plutonium and uranium.
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Refer to the flowchart below depicting the nuclear fuel cycle. Which process follows 'Enrichment' in the cycle?
A · Fuel Fabrication
After enrichment, uranium is fabricated into fuel rods for use in reactors.
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Which factor primarily affects the thermal efficiency of a nuclear power plant?
B · Temperature difference between heat source and sink
Thermal efficiency depends mainly on the temperature difference between the reactor heat source and the condenser sink, following Carnot principles.
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Which of the following methods is commonly used to improve the efficiency of nuclear power plants?
B · Increasing turbine inlet temperature
Increasing turbine inlet temperature improves thermal efficiency by increasing the work output of the turbine.
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Refer to the diagram below showing energy flow in a nuclear power plant. Which stage corresponds to the conversion of thermal energy into mechanical energy?
C · C: Steam turbine operation
The steam turbine converts thermal energy of steam into mechanical rotational energy.
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Which of the following is a major environmental concern related to nuclear power plants?
B · Radioactive waste disposal
Radioactive waste disposal poses long-term environmental and health risks due to its radioactivity.
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Which method is commonly used to manage high-level radioactive waste from nuclear reactors?
B · Deep geological repository
Deep geological repositories isolate radioactive waste underground to prevent environmental contamination.
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Which of the following nuclear reactor types uses thorium as a fertile material instead of uranium?
C · Thorium Reactor
Thorium reactors use thorium-232 as fertile material, which is converted into fissile uranium-233.
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Which advantage is associated with breeder reactors compared to conventional reactors?
B · Ability to generate more fissile fuel than consumed
Breeder reactors produce more fissile material (e.g., plutonium-239) than they consume, improving fuel utilization.
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Refer to the schematic diagram below of a breeder reactor. Which labeled part is responsible for converting fertile material into fissile fuel?
B · B: Blanket Zone
The blanket zone surrounds the core and contains fertile material (e.g., uranium-238) that is converted into fissile material by neutron capture.
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Which of the following best describes the primary function of a nuclear reactor core?
B · To sustain a controlled nuclear fission chain reaction
The reactor core contains the nuclear fuel where the controlled fission chain reaction occurs, producing heat.
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In a nuclear reactor, what is the role of the moderator?
B · To slow down fast neutrons to thermal energies
The moderator slows down fast neutrons produced during fission to thermal energies, increasing the probability of further fission reactions.
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Which of the following statements about nuclear reactors is correct?
A · A reactor can operate without a moderator if it uses fast neutrons
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Which type of nuclear reactor uses heavy water as a moderator and coolant?
C · Canadian Deuterium Uranium (CANDU) reactor
CANDU reactors use heavy water (deuterium oxide) as both moderator and coolant, allowing use of natural uranium fuel.
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Which of the following reactors is designed to produce more fissile material than it consumes?
C · Fast Breeder Reactor (FBR)
Fast Breeder Reactors generate more fissile material (usually plutonium-239) than they consume by converting fertile material (like uranium-238).
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Refer to the diagram below showing a schematic of a Pressurized Water Reactor (PWR). Which component is responsible for transferring heat from the reactor core to the steam generator?
B · Primary coolant loop
In a PWR, the primary coolant loop circulates water under high pressure to transfer heat from the reactor core to the steam generator.
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Which component of a nuclear power plant is primarily responsible for converting mechanical energy into electrical energy?
B · Generator
The generator converts mechanical energy from the turbine into electrical energy.
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In a nuclear power plant, what is the main function of the containment building?
B · To contain radioactive materials and prevent their release
The containment building is a robust structure designed to contain radioactive materials in case of an accident.
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Refer to the block diagram below of a nuclear power plant. Identify the component labeled 'X' which converts steam energy into mechanical energy.
B · Turbine
In the block diagram, component 'X' is the turbine, which converts steam energy into mechanical rotational energy.
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Which of the following isotopes is commonly used as nuclear fuel in thermal reactors?
C · Uranium-235
Uranium-235 is the fissile isotope commonly used as fuel in thermal reactors due to its ability to sustain chain reactions with thermal neutrons.
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In a nuclear chain reaction, the term 'criticality' refers to which condition?
C · The reaction is self-sustaining with a constant neutron population
Criticality means the chain reaction is self-sustaining with each fission event causing exactly one more, keeping neutron population constant.
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Refer to the graph below showing neutron population versus time during different reactor states. Which curve represents a supercritical state?
B · Curve B (increasing neutron population exponentially)
A supercritical state is characterized by an increasing neutron population, leading to an exponential increase in fission reactions.
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Which material is commonly used in control rods to regulate the fission chain reaction in a nuclear reactor?
B · Boron or Cadmium
Control rods are made of neutron-absorbing materials like boron or cadmium to control the rate of fission reactions.
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What is the primary purpose of the emergency core cooling system (ECCS) in a nuclear reactor?
B · To remove decay heat and prevent core meltdown during accidents
ECCS provides cooling to the reactor core during emergency shutdowns to prevent overheating and core damage.
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Refer to the diagram below of a nuclear reactor safety system. Which component labeled 'Y' is designed to absorb excess neutrons during an emergency shutdown?
B · Control Rods
Control rods absorb excess neutrons and are inserted fully during emergency shutdowns to stop the chain reaction.
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Which stage of the nuclear fuel cycle involves the chemical processing of spent fuel to separate usable fissile material?
C · Reprocessing
Reprocessing chemically separates usable fissile materials like plutonium and uranium from spent fuel for reuse.
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Which of the following is a major challenge associated with nuclear waste management?
C · Long-term storage and containment of high-level radioactive waste
High-level radioactive waste remains hazardous for thousands of years, requiring secure long-term storage solutions.
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Refer to the flowchart below depicting the nuclear fuel cycle. Which process is represented by the arrow labeled 'B' that follows the reactor operation stage?
B · Spent fuel reprocessing
After reactor operation, spent fuel undergoes reprocessing to recover usable materials.
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Which of the following factors most directly affects the thermal efficiency of a nuclear power plant?
B · Temperature difference between the steam and condenser
Thermal efficiency depends on the temperature difference between the heat source (steam) and sink (condenser), following thermodynamic principles.
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Refer to the efficiency curve below of a nuclear power plant. At what approximate temperature difference does the plant achieve maximum efficiency?
C · 300°C
The efficiency curve peaks around a temperature difference of 300°C, indicating optimal thermal efficiency at this point.
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Which of the following is a significant environmental concern associated with nuclear power plants?
B · Thermal pollution of nearby water bodies
Nuclear plants release large amounts of heat into nearby water bodies, causing thermal pollution which can affect aquatic ecosystems.
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Which application of nuclear reactors is NOT related to power generation?
A · Production of medical isotopes
Production of medical isotopes is an application of nuclear reactors but is not related to power generation.
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Refer to the diagram below showing environmental impacts of a nuclear power plant. Which labeled effect corresponds to radioactive waste release?
B · B: Radioactive waste release
Label B indicates radioactive waste release, which is a key environmental concern specific to nuclear plants.
