What effect are the control rods intended to have on the average kinetic energy and number of fission neutrons in a thermal nuclear reactor?
Average kinetic energy of fission neutrons
Number of fission neutrons
A
unchanged
unchanged
B
reduced
unchanged
C
unchanged
reduced
D
increased
reduced
- AQA - A-Level Physics - Question 31 - 2019 - Paper 2
Question 31
What effect are the control rods intended to have on the average kinetic energy and number of fission neutrons in a thermal nuclear reactor?
Average kinetic energy ... show full transcript
Worked Solution & Example Answer:What effect are the control rods intended to have on the average kinetic energy and number of fission neutrons in a thermal nuclear reactor?
Average kinetic energy of fission neutrons
Number of fission neutrons
A
unchanged
unchanged
B
reduced
unchanged
C
unchanged
reduced
D
increased
reduced
- AQA - A-Level Physics - Question 31 - 2019 - Paper 2
Step 1
Average kinetic energy of fission neutrons
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Answer
The control rods are made of materials that absorb neutrons, which reduces the number of neutrons available to continue the fission reaction. As the reaction is slowed down, the average kinetic energy of the fission neutrons remains unchanged because the principle of thermal equilibrium is maintained.
Step 2
Number of fission neutrons
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Answer
The introduction of control rods decreases the number of fission neutrons available, as they capture some of the neutrons that would otherwise contribute to further fission reactions. Therefore, the number of fission neutrons is reduced.