4.4 Nuclear Fission and Fusion Flashcards

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1
Q

what is nuclear fission?

A

the splitting of large, unstable nuclei to form smaller more stable nuclei (+the emission of spare neutrons).

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2
Q

what usually needs to happen to induce fission?

A
  • the unstable nuclei must absorb a neutron
  • spontaneous fission (where no neutron absorption occurs) is rare
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2
Q

give an example of a fissionable isotope.

A

uranium - 235

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3
Q

what is the consequence of an uncontrolled chain reaction?

A
  • the rate of fission events becomes to high and results in the production of too much energy
  • this can lead to a nuclear explosion
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3
Q

alongside two smaller nuclei, what else is emiited in a fission reaction?

A
  • two or three neutrons
  • gamma rays
  • energy
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4
Q

what form of energy do all fission prodcucts have?

A

kinetic energy.

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5
Q

what are the three main components of the core a nuclear reactor?

A
  1. fuel rods
  2. control rods
  3. moderator
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5
Q

what takes place during a chain reaction in a nuclear reactor?

A
  • an unstable nucleus absorbs a neutron
  • the nucleus undergoes fission and releases 2 or 3 further neutrons
  • these induce more fission, which results in a chain reaction
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6
Q

what is the role of the moderator in a nuclear reactor?

A

to slow down the neutrons so they are travelling at speeds which allow them to be absorbed by fissile nuclei and cause fission.

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7
Q

how is the chain reaction in a fission reactor kept under control?

A
  • control rods are positioned in between the fuel rods
  • the rate of fission is controlled by moving these rods up and down
  • the lower the rods are inserted, the slower the rate of fission
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8
Q

what term is used to describe nuclei in which fission can be induced through the absorption of slow neutrons?

A

fissile nuclei

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9
Q

what is nuclear fusion?

A

the joining of two light nuclei to produce a heavier nuclei and release energy.

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10
Q

name two isotopes of hydrogen which are commonly used in nuclear fusion.

A

deuterium and tritium

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11
Q

which releases more energy, nuclear fission or nuclear fusion?

A

nuclear fusion.

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12
Q

explain the difficulty of generating energy through nuclear fusion.

A

fusion requires very high temperatures which in itself requires large quantities of energy and also requires casing which can withstand them.

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13
Q

explain why nuclear fusion is currently not a viable way to produce energy on earth.

A

with current equipment/techniques, the energy required is greater than the energy produced, resulting in a net energy loss.