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The core of a thermal nuclear reactor contains a number of components that are exposed to moving neutrons - AQA - A-Level Physics - Question 4 - 2017 - Paper 2
Question 4
The core of a thermal nuclear reactor contains a number of components that are exposed to moving neutrons. 0 4 . 1 State what happens to a neutron that is incident ... show full transcript
Worked Solution & Example Answer:The core of a thermal nuclear reactor contains a number of components that are exposed to moving neutrons - AQA - A-Level Physics - Question 4 - 2017 - Paper 2
Step 1
State what happens to a neutron that is incident on the moderator.
Answer
When a neutron collides with the moderator, it undergoes elastic collisions with the atoms of the moderator material. This causes the neutron to lose kinetic energy, effectively slowing it down. The moderation process is crucial for achieving an optimal neutron speed that favors fission reactions.
Step 2
State what happens to a neutron that is incident on a control rod.
Answer
When a neutron encounters a control rod, it is absorbed into the material of the control rod. This process effectively stops the neutron and reduces the number of neutrons available for sustaining the fission process, thus controlling the reaction rate.
Step 3
Describe what happens in the process.
Answer
In the fission process, a slow-moving neutron collides with the nucleus of a fissile material (such as Uranium-235). This collision can cause the nucleus to become unstable and split into two smaller nuclei, along with the release of additional neutrons and a substantial amount of energy. The released neutrons can then initiate further fission events, leading to a chain reaction, which is harnessed for energy production in nuclear reactors.
Step 4
State the source of this waste and discuss some of the problems faced in dealing with the waste at various stages of its treatment.
Answer
The main source of radioactive waste in a thermal nuclear reactor comes from the spent nuclear fuel that is removed after it has been used in the reactor. This waste is highly radioactive and poses significant challenges in terms of safety and storage.
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Outline of how waste is treated: Initially, the spent fuel is cooled in a spent fuel pool for several years to allow for the decay of short-lived isotopes. After this cooling period, the waste can be either reprocessed to extract usable elements or stored in dry casks.
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Problems faced in dealing with the waste: A major issue is the long-term storage of high-level waste, which remains hazardous for thousands of years. Another complication is public concern and opposition to the disposal methods. To overcome these problems, developing deep geological repositories that can safely contain the waste away from human contact is considered a potential solution. Continuous research and investment in new technologies for waste management are also critical for improving safety and efficiency.