Chapter 27 - Nuclear energy Flashcards
What is the binding energy of a nucleus?
The energy required to separate the nucleus into its constituent protons and neutrons.
To remove a nucleon from the nucleus, we must do work against the strong force.
Binding energy = Energy given out when nucleons come together to form a nucleus.
What is the mass defect of a nucleus (Δm)?
The difference between the mass of the separated nucleons and the mass of the nucleus.
The mass difference is explained quantitatively by E = mc^2.
What is the equation for the mass defect of a nucleus (Δm)?
Δm = Zm(protons) + (A-Z)m(neutrons) - m(nucleus)
What is the relationship between binding energy and mass defect?
E = Δmc^2
where E is binding energy and Δm is mass defect.
At what numbers of nucleons in the nucleus does nuclear fusion and fission occur?
The higher the number of nucleons in the nucleus, the higher the binding energy and the more stable the nucleus.
Nuclear fusion applies to nuclei with A < 50.
Nuclear fission applies to nuclei with A > 50.
What is induced fission?
When uranium isotope (Uranium-235) is bombarded with slow-moving neutrons, splitting the nucleus into two smaller nuclei, releasing energy and producing two neutrons which can then collide with more U-235 isotopes causing further fission events (chain reaction).
What is the critical mass?
The minimum mass of a fissile material necessary to achieve a self-sustaining fission chain reaction.
The larger the surface area to mass ratio of the fissile material…
The larger the surface area to mass ratio of the fissile material (e.g. U-235), the more likely the neutrons are to escape (and not cause further fission).
What is the equation for the energy released during fission?
E = Δmc^2
For a chain reaction to occur, the mass of the fissile material must be…
…greater than the critical mass.
What are the fuel rods in a thermal nuclear fission reactor?
The rods which contain the fissile material.
What is the role of the moderator in a thermal nuclear fission reactor?
Give an example of a moderator used in thermal nuclear fission reactors.
To slow down the fission neutrons so they can cause further fission.
The moderator atoms should be as close to the mass of the neutrons as possible to be most effective.
Water can be used as a moderator.
What is the role of the control rods in a thermal nuclear fission reactor?
To absorb neutrons in order to control nuclear fission reactions. They are moved in and out to alter the rate of fission. The further the control rods are pushed in, the slower the rate of fission.
What is the role of the coolant in a thermal nuclear fission reactor?
To transfer heat from the reactor to the heat exchanger where steam is produced to drive turbines.
The coolant must flow easily and not be corrosive.
What are the safety features of nuclear fission reactors?
- The reactor vessel is encased in thick steel to absorb beta and gamma radiation and neutrons from the reactor core.
- Control rods can be fully submerged in the core as part of an emergency shut-down system.
- Fuel rods are inserted and removed from the reactor by remote handling devices as they emit radiation before (alpha) and after use (beta and gamma).
