P 5.1 What is Radioactivity ?

This question is about ionising radiation. Ionising radiation affects atoms.

Complete the labels on diagram of an atom.

This question is about ionising radiation.

Ionising radiation affects atoms.

What is the effect of ionising radiation hitting an atom?

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Read the following article.

Write down words or phrases from the article that mean the following:

breaks down over time .............

produces ionising radiation .............

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The three types of ionising radiation from radioactive materials travel different distances.

Write alpha, beta and gamma in the boxes to show how far each type of ionising radiation travels through the body.

Which two statements explain why the ionising radiation “destroys the tumour”?

• ... can break molecules into this.

• ... gets stronger over time.

• ... is produced from the electrons in atoms.

• can be destroyed using acid.

• ... kills living cells.

Which statement explains why the radioactive material decays at the same rate both inside and outside the body?

• The movement of the body speeds up the decay.

• The heat from the body increases the radioactivity.

• The decay is not affected by chemicals in the body.

• The body shields the radioactive material form light.

For brachytherapy to be effective:

the radioactive material must remain in the tumour long enough for the tumour to be destroyed

the activity must be low after that time.

One particular tumour will have to be treated for 6 months to be destroyed.

A doctor has a choice of three different substances to treat the tumour.

Each substance gives out the same type of radiation.

Which substance should the doctor use to treat this tumour?

Justify your answer. [3 Marks]

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There are many arguments for and against nuclear power.

Some people are worried about the materials left over as waste from nuclear power stations.

Three of the materials left over are caesium-134, technetium-99 and zirconium-93.

They have very different half-lives.

What is half-life?

• The time taken for the radioactive material to completely change into another material.

• The time taken for a radioactive material to become safe.

• The time taken for half of the radioactive material to decay.

Caesium-134 has a half-life of about 2 years.

Technetium-99 has a half-life of about 200 000 years.

Zirconium-93 has a half-life of about 1.5 million years.

Samples of each material start with the same activity.

Which material will take the longest time for its activity to halve?

Which material will take the shortest time for its activity to halve?

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Another material often left over from nuclear power stations is strontium-90.

The graph below shows how strontium-90 decays.

How long does it take strontium-90 to decay to a quarter of its starting activity?

Use the graph.

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