Fission and fusion Flashcards

1
Q

What does natural uranium contain?

A
  • Natural uranium consists of two isotopes, Uranium-258 and Uranium-235.
    • The ‘enriched uranium’ used in fuel in a nuclear power station contains a greater proportion of the uranium-235 isotope than occurs naturally.
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2
Q

When does fission occur?

A
  • Fusion occurs when a large unstable nucleus is split up and energy released as heat.
    • The heat is used to boil water to produce steam.
    • The pressure of the steam acting on the turbine blades make it turn
    • The rotating turbines turns the generator, producing electricity.
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3
Q

What happens when uranium fissions?

A

When uranium fission, a chain reaction starts. A nuclear bomb is an example of a chain reaction that is not controlled.

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4
Q

What happens to uranium-235 in a nuclear power station?

A
  • In a nuclear power station, atoms of uranium-235 are bombarded with neutrons. This causes the nucleus to split, releasing energy.
  • Extra neutrons emitted cause further uranium nuclei to split. This is described as a chain reaction and produces a large amount of energy.
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5
Q

What happens in the diagram?

A
  • A neutron is absorbed by the nucleus of a uranium-235 atom.
  • the nucleus is now less stable than before.
  • It splits into two parts and releases energy.
  • Several neutrons are also produced - these may go on to strike the nuclei of other atoms causing further fission reactions.
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6
Q

How can the output of a nuclear reactor can be controlled?

A
  • A graphite moderator between the fuel rods slows down the fast-moving neutrons emitted during fission. Slow-moving neutrons are more likely to be captured by other uranium nuclei.
  • Boron control rods can be raised or lowered. Boron absorbs neutrons, so fewer neutrons are available to split more uranium nuclei. This controls the rate of fission.
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7
Q

Fusion bombs

A

Fusion bombs are started with a fission reaction which creates exceptionally high temperatures.

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8
Q

When does nuclear fussion happen?

A
  • Nuclear fusion happens when two light nuclei fuse together releasing large amounts of heat energy.
  • In stars, fusion takes place under extremely high temperatures and pressures.
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9
Q

What does fusion require?

A
  • Fusion requires extremely high temperatures which have proved difficult to achieve and to manage safely on Earth and so its use for large-scale power generation remains a dream.
  • Research in this area is very expensive so it is carried out as an international joint venture to share costs, expertise and benefits.
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10
Q

How succesful are attempts to replicate fusion conditions?

A
  • So far attempts to replicate these condition safety on Earth has been unsuccessful.
  • Scientists are still trying to solve the safety and practical challenges presented.
  • Cold Fusion is still not accepted as realistic since any results output impossible to verify so far.
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