P2.6 - Energy From The Nucleus Flashcards
Which radioactive isotopes undergo fission?
Uranium-235
Plutonium-239
What is nuclear fission?
The splitting of a nucleus and the release of two or three neutrons.
What is a chain reaction in fission?
A chain reaction occurs in a nuclear reactor when each fission causes further fission.
How is a chain reaction in a nuclear reactor controlled?
Control rods absorb fission neutrons to ensure that only one neutron per fission goes on to produce further fission.
What does water do in a nuclear reactor?
Water slows down fission neutrons and acts as a coolant for the fuel rods.
How is radiation contained in the reactor?
The core is made of thick steel and enclosed in thick concrete.
What is nuclear fusion?
The process of forcing two nuclei close enough together so they form a single larger nucleus.
How can nuclei be made to fuse?
Making two light nuclei collide at very high speed.
Where does the Sun’s energy come from?
Nuclear fusion occurs in the Sun’s core which releases energy.
Why is it difficult to make a nuclear fusion reactor?
- A reactor needs to be at a very high temperature before nuclear fusion can take place.
- The nuclei fused are difficult to contain.
What is produced when hydrogen nuclei fuse?
“Heavy hydrogen”
What is produced when two “heavy hydrogen” nuclei fuse?
A helium nucleus
Why does nuclear fusion only take place at high temperatures?
The two nuclei will repel each other but if they are going fast enough, they can overcome the force of repulsion.
Give three advantages of using nuclear fusion for energy.
- The fuel needed is readily available as heavy hydrogen and is present in sea water.
- The product, helium, is a harmless inert gas.
- The energy released can be used to generate electricity.
What is radon gas?
An alpha-emitting isotope that can seep into houses in certain areas.
What happens to nuclear waste?
Nuclear waste is stored in secure facilities after unused radioactive isotopes are recovered.
Why is the Chernobyl disaster unlikely to be repeated?
- Most reactors have a different design.
- Chernobyl didn’t have a high-speed shut down system.
- Operators at Chernobyl ignored safety instructions.
What three things does the effect of radiation on living cells depend on?
- Type and amount of radiation
- Whether the source is inside or outside the body.
- How long the cells are exposed.
How do workers at risk of ionising radiation reduce their exposure?
- Keeping far away from the source of radiation.
- Spending as little time as possible in ‘at-risk’ areas.
- Shielding themselves from radiation.
What is a galaxy?
A collection of billions of stars held together by their own gravity.
What was the universe like before stars and galaxies were formed?
The universe was a dark patchy cloud of hydrogen and helium.
Which force caused the formation of stars and galaxies?
Gravity
When did quarks and electrons form in the Big Bang?
After 0.1s from radiation
When did neutrons and protons form following the Big Bang?
After 100s.
When did hydrogen and helium atoms form following the Big Bang?
After 100,000 years
When were the first stars and galaxies formed?
After a few billion years.
What is a protostar?
A gas and dust cloud in space that can go on to form a star.
What are the stages in the life of a low mass star?
- Protostar
- Main sequence star
- Red giant
- White dwarf
- Black dwarf
What are the stages in the life of a high mass star?
- Protostar
- Main sequence star
- Red supergiant
- Supernova
- Neutron star
- Black hole if there is enough mass
What is a supernova?
The explosion of a supergiant after it collapses.
How does a protostar form?
- The particles in a cloud are pulled together by their gravitational pull.
- The clouds merge and become more concentrated.
What happens at the end of the main sequence of a star like the Sun?
They swell out, cool down and turn red. Light elements fuse to form heavier elements.
What happens at the end of the red giant stage?
- When there are no more light elements, fusion stops.
- Due to its own gravity, the star collapses in.
- It heats and turns from red to a white dwarf.
What happens at the end of the red supergiant stage?
- The star collapses.
- The matter surrounding the star’s core compresses the core.
- The compression suddenly reverses in a cataclysmic explosion.
What elements are formed inside stars?
Elements up to the mass of iron are formed inside stars as a result of nuclear fusion.
What chemical elements are formed in supernovas?
Elements heavier than iron are formed in supernovas.
Why does the Earth contain heavy elements?
The Solar System was formed from the debris of a supernova.
Why aren’t elements heavier than iron formed in stars by nuclear fusion?
Too much energy is needed.
What evidence is there that the Solar System formed from the remnants of a supernova?
Uranium could only have been made in a supernova because of the energy needed.
