Nuclear energy Flashcards
What is are the sources of energy from the nuclear reactions?
- radioactive decay=
form of alpha or beta particles or gamma rays. - nuclear fusion=
the fusing of hydrogen nuclei in the sun releases enormous amounts of light + heat, some which we receive on earth. - nuclear fission=
uranium nuclei are split by slow-moving neutrons in a nuclear reactor, resulting in the release of enormous amounts of thermal energy.
What is nuclear power used for and what is the waste?
- the power is a highly effective way at producing electrical energy.
- less nuclear fuel is needed compared to coal, oil or gas, to produce the same amount of electrical energy.
- nuclear power stations do produce radioactive nuclear waste that needs to be dealt with. Some of it stays radioactive for thousands of years.
What are the advantages + disadvantages of using nuclear energy for electricity?
ADVANTAGES:
- nuclear power stations don’t produce CO2, so they do not contribute to global warming.
- supplies of nuclear fuel will last longer than supplies for fossil fuels.
DISADVANTAGES:
- it is difficult and expensive to store nuclear waste safely.
- an accident at a nuclear power station can spread radioactive material over a large area.
- many think that these power stations are dangerous so do not want new ones to be built.
What is nuclear fission?
- a large unstable nucleus, splits into 2 smaller ones.
- it produces 2 daughter nuclei.
- it also releases energy.
- the daughter nuclei are also radioactive.
- for example, the fission of uranium-235 releases a large quantity of energy which is used to heat water in power stations.
How can a chain reaction be controlled?
- use a different material to absorb one of the neutrons.
- this slows the reaction because there are fewer neutrons to cause more nuclei to undergo fission.
What is the most useful to the generation of energy in a power station?
The thermal energy from nuclear fission.
What is a moderator?
A material (often graphite or water) that is used to slow down the flow of neutrons so that the fission of the uranium- 235 nuclei can occur.
The moderator doesn’t absorb the neutrons.
How do control rods work in nuclear power stations?
- they absorb neutrons.
- if the control rods are pushed down into the core, more neutrons are absorbed and the chain reaction slows down.
- if they are pulled out, fewer neutrons are absorbed and the chain reaction speeds up.
What is nuclear fusion?
The joining of smaller nuclei to form a larger nuclei.
- fusion reactions release energy.
- obtaining a continuous supply of energy from the fusion is more difficult than obtaining energy from fission.
How does nuclear fusion link to stars?
- during that stable period of a star’s life, vast quantities of hydrogen nuclei are converted into helium nuclei by nuclear fusion. This is the source of energy for stars.
What are the difficulties for nuclear fusion?
- nuclei need to get very close to each other for fusion to happen.
- under normal circumstances, the positive charges on nuclei repel each other. This is known as electrostatic repulsion.
- very high temperatures and pressures are needed for the nuclei to overcome this repulsion.
- these high temps and pressures are difficult to produce in a power station.
What’s the difference between fission and fusion?
- In fusion hydrogen nuclei fuse to produce helium nuclei whereas nuclear fission uranium- 235 splits into 22 smaller nuclei and 2 or 3 neutrons.
- nuclear fusion requires very high temperatures and pressures whereas nuclear fission requires a slow-moving neutron to be absorbed.
- both processes release large quantities of energy.
