Nuclear Energy Flashcards
What is nuclear energy?
Energy that originates from the nuclei of atoms.
What three types of reactions release nuclear energy?
- Radiation from nuclei (in the form of alpha, beta and gamma particles)
- Nuclear fission (from the splitting of a nucleus)
- Nuclear fusion (from the fusing of two nuclei)
What is nuclear fission?
The splitting of a large nucleus into two similar smaller nuclei with the release of neutrons and energy.
What is a chain reaction?
Fission creation in which at least one neutron is emitted in order to carry on the reaction.
What is the critical mass?
The minimum amount of fissile material required in order to sustain a chain reaction.
Explain how U-235 (uranium isotope) undergoes fission.
- A sufficient mass of uranium is brought together
- When a neutron strikes the U-235, it briefly turns into U-236. This is very unstable and will quickly undergo fission.
- The U-236 splits into krypton (Kr) and barium (Ba), along with three neutrons
- The neutrons carry most of the kinetic energy from the fission
- Each of these neutrons can cause a chain reaction which carries on automatically until it is slowed or stopped by human interaction
What does the critical mass of an isotope depend on?
- Density
- Temperature
- Shape
- Purity
What is radiative capture?
When a nucleus captures/absorbs a fast moving neutron.
Name the parts of a nuclear reactor. (7)
- Fuel rods
- Control rods
- Moderator
- Heat exchanger
- Pipes
- Turbines
- Shielding
What is the purpose of fuel rods?
The uranium fuel rods (which have a higher percentage of U-235) are used as the fissile material.
What is the purpose of control rods?
They are used around the fuel rods to absorb neutrons being emitted from the fuel rods. They are raised proportionally to control the chain reactions.
What is the purpose of the moderator?
It slows down fast neutrons and prevent radiative capture from happening.
What is the purpose of the heat exchanger?
The coolant carries the excess heat to the heat exchanger.
What is the purpose of pipes?
The cold water moves in sealed pipes through the heat exchanger and os converted to steam by the coolant energy.
What is the purpose of turbines?
They generate electricity.
What is the purpose of shielding?
It prevents radiation leaks.
State the advantages of nuclear fission power.
- Doesn’t emit greenhouse gases
- It produces massive amounts of energy very economically
- There will be no shortage pf nuclear fuel
- Reduces the need for fossil fuels
- Reactors can be used to create new elements for research and development
- Very low accident rate compared to other energy sources
State the disadvantages of nuclear fission power.
- Radioactive waste has a very long half-life and is expensive to store
- Reprocessing of fuel is hazardous and expensive
- If a major accident occurs there can be a large scale health hazard
What is nuclear fusion?
The joining of two small nuclei to create a larger single nucleus, with the release of energy.
What are the factors affecting fusion?
- Pressure
- Temperature
These are required in extreme amounts to overcome the repulsive coulomb force
What are the advantages of nuclear fusion?
- Little or no radioactive or harmful by-products are produced
- Significantly higher amounts of energy are released than any current technology
- The fuel required for fusion is relatively cheap and plentiful
What are the disadvantages of nuclear fusion?
There are no major disadvantages to speak of other than the difficulty in sustaining the reaction.
State some precautions for dealing with radiation.
- Reduce exposure to radiation as much as possible
- Increase shielding on radioactive isotopes and radioactive waste
- Warn the public about potential hazards
- Always wear protective clothing and do not smoke, eat or drink near ionising sources
What is background radiation?
Radiation from cosmic rays, the Earth’s crust and other radioisotopes
