Nuclear Fission & Fusion Practice Questions

Complete the sentence.

Nuclear fission is the splitting of a large and ______ nucleus.

Name one element that is used as a nuclear fuel in a fission reactor.

Tick the box to show what the nucleus must usually absorb before fission takes place.

Particle absorbed	Tick (✓)
an electron
a neutron
a proton
a gamma ray

Name the particle labelled A in Figure 1.

The two nuclei labelled B are roughly equal in size.

State one other thing, not shown in Figure 1, that is emitted during this fission event.

The particles labelled C leave the fission event moving very quickly.

Explain how the particles labelled C can lead to a chain reaction.

All of the fission products in Figure 1 have kinetic energy.

What does this tell you about the energy of the products compared with the energy of the original uranium nucleus and neutron?

Explain why the control rods are needed in a nuclear reactor.

Describe what would happen to the chain reaction if the control rods were pushed further into the reactor core.

The explosion caused by a nuclear weapon is also due to fission.

Give one way in which the chain reaction in a nuclear weapon is different from the chain reaction in a nuclear reactor.

Complete the sentence.

Nuclear fusion is the joining of two ______ nuclei to form a heavier nucleus.

The total mass of the two hydrogen nuclei is greater than the mass of the helium nucleus formed.

Explain how this leads to the release of energy.

A student says:

"Fusion happens when two atoms join together."

Give one reason why this statement is not correct.

Compare nuclear fission and nuclear fusion in terms of the nuclei involved in each process.

Fission of a uranium nucleus does not usually happen on its own.

State what is meant by spontaneous fission and explain why nuclear reactors do not rely on it.

In a fission reactor the fuel rods become very hot even though no chemical burning takes place.

Explain why the fuel rods get hot.

Figure 3 shows the start of a chain reaction. Each circle represents a uranium nucleus that undergoes fission and each arrow represents a neutron.

Using Figure 3, explain why the energy released by this chain reaction increases very rapidly with time, and state how this is prevented in a nuclear reactor.