P2 - Nuclear Power Flashcards
What is the factor that decides how much energy is released in nuclear fission?
How heavy the nucleus is
What are the 2 most important fissile isotopes?
Uranium-235
Plutonium-239
What are isotopes?
Variants of an element that have the same number of protons and electrons but a different number of neutrons
What is nuclear potential energy?
Energy stored between the bonds holding the subatomic particles in the nucleus together
What is nuclear fission?
The process of splitting nuclei in order to collect energy and start a chain reaction
What is a fissile isotope?
An isotope that can maintain a nuclear chain reaction
What is a thermal neutron?
A neutron that moves at the same speed as air particles at room temperature
What are fission fragments?
The parts of a nucleus that have been split in nuclear fission
This is the radioactive waste
Describe how nuclear fission works
A thermal neutron strikes a nucleus of the fissile isotope
The mass number of the isotope goes up by 1 because of the thermal neutron making the nucleus unstable
The instability causes the nucleus to split into 2 fission fragments
The fission fragments shoot off at high speed
A few neutrons also shoot off
One neutron hits another nucleus
This is why the chain reaction occurs
What are the masses of fission fragments in comparison to the original nucleus?
One is a third of the mass and the other is 2 thirds of the mass
In nuclear power stations, how are some of the neutrons stopped so that the chain reaction does not go out of control?
Control rods soak up the neutrons
What are the 3 problems with nuclear fission as an energy source?
Disposal of waste is very hard and expensive to do
Cost of power plant and decommissioning is very high and it takes a long time
Risk of a major catastrophe like Chernobyl
What are the 3 problems with nuclear fission as an energy source?
Disposal of waste is very hard and expensive to do
Cost of power plant and decommissioning is very high and it takes a long time
Risk of major catastrophe
What is nuclear fusion?
The joining of 2 light nuclei to create a larger nucleus and release a large amount of energy
What are the 3 advantages of nuclear fusion?
More energy than fission
Doesn’t leave behind a lot of waste
Lots of hydrogen to use as fuel
What are the 2 disadvantages of nuclear fusion?
Can only happen at very high temperatures
You can’t hold the hydrogen at the high temperatures and pressures required for fusion in an ordinary container (very strong magnetic field is needed)
Describe the first stage of the life cycle of a star
They initially form from clouds of dust and gas and the force of gravity makes the gas and dust spiral in together to form a protostar
Describe the second stage of the life cycle of a star
Gravitational energy is transferred to heat and when the temperature gets high enough, hydrogen nuclei fuse together to form helium nuclei and give out massive amounts of heat and light
Describe the third stage of the life cycle of a star
The star enters a long stable period where the heat created by the nuclear fusion provides outward pressure to balance the force of gravity pulling everything inwards
The star maintains its energy output for millions of years due to the massive amount of hydrogen
In this stable period, it is called a main sequence star
Describe the fourth stage of the life cycle of a star
The hydrogen begins to run out and heavier elements such as iron are made by fusion of helium
The star swells into red giant if it is smaller and a red super giant if it is larger
It becomes red because the surface cools
Describe what happens to red giants next
It then becomes unstable and ejects its outer layer of dust and gas as a planetary nebula
This leaves behind a hot, dense solid core called a white dwarf that finally cools down to a black dwarf and eventually disappears
Describe the next stage that occurs in red super giants
They start to glow more brightly again as they undergo more fusion and expand and contract several times forming elements as heavy as iron in various nuclear reactions
Eventually, they explode in a supernova forming elements heavier than iron and ejecting them into the universe to form new planets and stars
Describe the final stage of red super giants
The supernova leaves an extremely dense core known as a neutron star
If this star is big enough, it will become a black hole
