Fission & Fusion (Edexcel IGCSE Physics (Modular): Unit 2)

The control rods control the reaction in a nuclear reactor by

The diagram shows the main parts of a nuclear reactor.

Draw a line linking each part of the reactor with its main function.

The first one has been done for you. 

In a fission reaction, energy is transferred from the nuclear store of the particles to which store?

Explain the role of the moderator in a fission reaction.

Explain, in terms of neutrons, what is meant by controlled nuclear fission. 

A student finds this representation of nuclear fission on a website.

Describe what happens when nuclear fission of uranium occurs. 

The daughter nuclei move off with high speed.

Name the energy store that gives them high speed.

The diagram shows the main parts of a nuclear reactor. 

In the nuclear reactor uranium−235 nuclei undergo fission in a controlled chain reaction.

Describe nuclear fission and how the chain reaction is controlled.

Use terms from the diagram to help you.

Name the energy store that is filled after the nucleus splits in a fission reaction.

How does the shielding improve safety?

 In a nuclear reactor, a uranium-235 nucleus absorbs a neutron and fission occurs.

Complete the equation below that shows a typical fission reaction.

Explain how nuclear fission can lead to a chain reaction.

The diagram shows a nuclear reactor.

(i) On the diagram, label the control rods and the shielding.

(2)

(ii) Explain why the shielding is needed.

(2)

The diagram shows the fuel used in some nuclear reactors.

The fuel is contained inside spheres.

The silicon carbide layer of each sphere is designed to contain the fission products for at least one million years.

(i) Give the name of a fuel that could be used.

(1)

(ii) Explain what is meant by the term fission products.

(2)

(iii) Explain why it is important to contain these fission products for such a long time.

(2)

The graphite layer in every fuel sphere acts as a moderator.

(i) State the function of the moderator in a nuclear reactor.

(1)

(ii) The nuclear reactor also contains boron control rods.

Explain why it is dangerous to remove most of the control rods from the reactor.

(2)

The diagram shows a neutron colliding with a nucleus of uranium-235, producing a number of products.

Name the process shown in the diagram.

Explain how the process shown in the diagram can lead to a chain reaction.

This process releases energy.

Explain the energy transfer taking place in this reaction.

The energy released in this process can be used in a nuclear power station.

(i) The pressurised water acts as a coolant. It also acts as a moderator.

What is the purpose of a moderator?

(1)

(ii) Complete the chart below to show the main useful energy transfers in a nuclear power station.

(4)

Nuclear power stations use a uranium isotope as fuel. 

The table shows information about three isotopes of uranium. 

(i) Complete the table by filling in the missing numbers. 

(2)

(ii) Explain what is meant by the term half-life. 

(2)

(iii) Suggest why uranium-238 is the most common isotope of uranium.

(1)

What are the products of the fission of uranium nuclei?

The diagram shows the reactor in a nuclear power station. 

(i) What is the purpose of the moderator? 

(1)

(ii) Describe what happens in the reactor when a control rod is removed.  

(2)

There have been several accidents at nuclear power stations. The most serious accident caused an explosion in the reactor. This explosion spread material from inside the reactor to the surrounding area.

Explain why it is difficult to make the surrounding area safe again after a serious nuclear accident. 

Nuclear fission occurs in nuclear reactors.

Describe the process of nuclear fission in the reactor, including the material used in the fuel rod. Explain what happens to the energy released.

Explain the role of the moderator and the control rods. Suggest materials which would be suitable to use for each one.

Explain how a chain reaction can occur in the reactor.

Which of the following statements about nuclear power is incorrect? 

Which of the following statements about nuclear fusion is incorrect?

Energy and mass can be converted using the equation: 

Fusion and fission are examples of when this conversion process occurs.

A particular fusion reaction that can occur is:

In this reaction:

• Mass of reactants m_R = mass of helium−3 + mass of helium−4

• Mass of product m_P = mass of beryllium−7

• Energy is released

State and explain which quantity is greater, m_R or m_P.

The difference in mass of the reactants and products was found to be 2.8 × 10^–30 kg.

The speed of light is 3.00 × 10⁸ m/s.

Calculate the amount of energy released. Give the unit.