Energy from the nucleus Flashcards
What is nuclear fission?
Nuclear fission is the splitting of an atomic nucleus.
What are the two fissionable isotopes in common use in nuclear reactors?
What do the majority of nuclear reactors use?
Uranium-235 and Plutonium-239
Uranium-235
What is naturally occurring uranium?
What do most nuclear reactors and how much uranium-235 does this contain?
Naturally occurring uranium is uranium-238 which is non-fissionable.
Most nuclear reactor used enriched uranium that contains 2-3% uranium-235.
What must happen for fission to occur?
What happens in the process of fission?
(4)
1) For fission to occur, the uranium-235 or plutonium-239 must absorb a neutron.
2) The nucleus then splits into two smaller nuclei.
3) Then two or three neutrons are emitted and energy is released.
4) The energy released in such a nuclear process is much greater the energy released in a chemical process such as burning.
What is a chain reaction?
A chain reaction occurs when each fission event causes further fission events, in a nuclear reactor the process is controlled, so one fission neutron per fission goes on to produce further fission.
What is nuclear fusion?
Nuclear fusion is the process of forcing two nuclei close enough together so they form a single large nucleus.
How can nuclear fusion be brought about?
Where does fusion release energy in space?
Nuclear fusion can be brought about by making two light nuclei collide at very high speed.
Fusion is the process by which energy is released in stars.
What are the problems with producing energy from nuclear fusion?
1) Nuclei approaching each other will repel one another due to their positive charge.
2) To overcome this the nuclei must be heated to very high temperatures to give them enough energy to overcome the repulsion and fuse.
3) The reaction must be contained in a magnetic field because of the extremely high temperatures.
What is the major source of background radiation?
Where does it come form?
What type of nuclear radiation does it emit and why is this a hazard?
The major source of background radiation is radon gas which seeps through the ground from radioactive substances in rocks deep underground.
Radon gas emits alpha particles which is a hazard if it is breathed in.
What other sources of background radiation are there other than radon gas?
Other sources of background radiation include cosmic rays from outer space, food and drink, air travel and nuclear weapons testing.
What are medical sources of background radiation?
Medical sources of background radiation include x-rays, as these have an ionising effect, as well as radioactive substances.
What can be removed from nuclear fuel rods from nuclear reactors and why are they removed?
What must be done to the remaining nuclear waste?
Uranium and plutonium are removed from used fuel rods from nuclear reactors, as these substances can be used again.
The remaining radioactive waste must be stored in secure conditions for many years.
What should workers at nuclear reactors do to reduce exposure to nuclear radiations? (3)
1) Keep as far as possible from sources of radiation.
2) Spend as little time as possible exposed.
3) Shield themselves with materials such as concrete and lead.
How and when do most scientists believe the universe was created?
What was the universe like at first? what happened in the first few minutes?
Most scientists believe the earth was created by the Big Bang about 13 billion years ago.
At first the universe was a hot glowing ball of radiation, in the first few minutes, the nuclei of the lightest elements formed.
What happened as expanded over millions of years?
As the universe expanded over millions of years, its temperature fell and uncharged atoms were formed.
