Nuclear Fission and Fusion Flashcards
What is nuclear fission?
When an atomic nucleus splits up to form two smaller nuclei. This releases a lot of energy.
What is a use of nuclear fission?
Generating electricity
What two atoms are usually used in nuclear power stations?
Uranium-235 or plutonium-239
What happens during nuclear fission?
A slow-moving neutron is absorbed into the nucleus. This makes the nucleus unstable causing it into two new smaller nuclei which are both radioactive.
What happens during a chain reaction?
When nuclear fission happens, two or three neutrons can be released which can go on to hit other nuclei causing them to split and release more neutrons.
How does a nuclear power station work?
Nuclear fission takes place in the reactor which releases heat energy. This heats the coolant which pumped into the boiler to heat water into steam. This steam drives the generator.
What do the control rods do in a nuclear reactor?
They absorb neutrons do that there are less neutrons about to case fission. This stops the reaction from happening too quickly and the reactor overheating.
What is the main problem with nuclear power?
The disposal of waste. The waste is highly dangerous and is difficult and expensive to dispose of.
Why is nuclear power expensive despite the fuel being cheap?
Cost of building the power plant and final commissioning.
What is nuclear fusion?
When two nuclei join together to create a larger nucleus.
Why are scientists trying to make nuclear fusion reactors?
Because fusion releases a lot more energy and doesn’t leave behind a lot of radioactive waste.
What is the main barrier to making fusion reactors?
The reaction has to take place at millions of degrees and an extremely strong magnetic field.
What do stats start life as?
Clouds of dust and gas.
What is a protostar?
When clouds of ist and had spiral together due tithe force of gravity.
Why does the temperature rise in a protostar?
The gravitational energy that pulls the gas and dust together is transferred I to heat energy.
What are main sequence stars?
A long stable period for a stat where heat is created by nuclear fusion provides an outward pressure to balance gravity.
What happens when a main sequence star runs out of hydrogen for fusion?
It starts to fuse helium and then increasingly heavy elements up to Iron.
What happens when a star the size of the Sun dies?
It will expand into a red giant as the surface cools. The red giant then becomes unstable and ejects its outer layers of dust and gas as a planetary nebula leaving behind a hot, dense solid core called a white dwarf. The white dwarf cools into a black dwarf and eventually fades out of sight.
What happens when stars larger than the sun die?
They expand into Red Super Giants which are much bigger and burn much longer than Red Giants. The Red Super Giants explode into supernovas which eject elements into the Universe to form new planets and stars. The core left behind is either a neutron star or a black hole,
