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Fission and fusion

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Question 11

A nuclear reactor uses the energy released from the nuclear fission of plutonium-239, symbol 94239Pu^{239}_{94}\text{Pu}94239​Pu.

a.

How many neutrons are in a nucleus of plutonium-239?

  • A: 94
  • B: 145
  • C: 239
  • D: 333
[1]
b.

The diagram shows the process of nuclear fission.

Diagram showing a single small black dot representing an incoming neutron with an arrow pointing to a large circle. To the right of the large circle, five arrows point outwards: two of these lead to medium-sized circles representing products, and three lead to small black dots representing released neutrons.

State the terms used to describe the original large nucleus before fission, and the smaller nuclei produced after fission.

[2]
c.

Explain how this fission process can lead to a self-sustaining chain reaction.

[2]
d.

Describe the purpose of the control rods in a nuclear reactor.

[2]
e.

What is the purpose of the moderator in a nuclear reactor?

[1]
f.

In some historical reactor designs, the tips of the control rods entering the core were made of graphite (a moderator). Suggest why fully inserting these control rods could cause a temporary, dangerous increase in the fission rate.

[2]

Fission and fusion Questions

  1. IGCSE
  2. /Physics
  3. /Fission and fusion