Nuclear Fission & Fusion Practice Questions

Question 1

3 marks

Nuclear reactions can be a source of energy.

(a)

Which nuclear process is the source of the energy radiated by the Sun?

A fission of uranium nuclei
B fusion of hydrogen nuclei
C burning of hydrogen gas
D alpha decay of helium nuclei

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(b)

Name two other types of nuclear reaction that release energy.

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Question 2

4 marks

A uranium-235 nucleus absorbs a neutron and undergoes fission.

$^{235}_{\ 92}\mathrm{U} + ^{1}_{0}\mathrm{n} \rightarrow\ ^{90}_{38}\mathrm{Sr} + ^{A}_{Z}\mathrm{Xe} + 2\,^{1}_{0}\mathrm{n}$

(a)

Determine the values of $A$ and $Z$ for the xenon (Xe) nucleus.

$A$ = ..............................................

$Z$ = ..............................................

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(b)

State what else is released in this fission reaction, apart from the two nuclei and the neutrons.

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(c)

Give one reason why the strontium and xenon nuclei produced must be handled and stored carefully.

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Question 3

3 marks

Nuclear fusion takes place naturally in stars.

(a)

When two small nuclei fuse, the mass of the nucleus produced is

A greater than the total mass of the two original nuclei
B equal to the total mass of the two original nuclei
C less than the total mass of the two original nuclei
D equal to the mass of one of the original nuclei

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(b)

State what happens to the mass that is lost in a fusion reaction.

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(c)

State one difference between nuclear fusion and nuclear fission.

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Question 0

6 marks

The diagram shows the first three generations of fissions in a sample of uranium-235. In this diagram every fission releases three neutrons and every neutron goes on to cause another fission.

(a)

Explain how the fission of one uranium-235 nucleus can lead to a chain reaction.

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(b)

Calculate the number of fissions that would take place in the 5th generation.

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(c)

Describe what would happen inside a nuclear reactor if the chain reaction were not controlled.

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Question 0

5 marks

The diagram shows the main parts of the core of a nuclear reactor.

(a)

Name a material that is commonly used as the moderator in a nuclear reactor.

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(b)

Explain why the neutrons released by fission need to pass through the moderator before the chain reaction can continue.

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(c)

Explain what happens to the rate of the chain reaction when the control rods are pulled further out of the core.

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Question 0

5 marks

In an experimental fusion reactor, pairs of hydrogen nuclei are fused together. In each fusion reaction the total mass decreases by $3.1 \times 10^{-29}\ \mathrm{kg}$ .

The decrease in mass, $m$ , appears as energy, $E$ , according to

$E = mc^2$

where $c = 3.0 \times 10^8\ \mathrm{m/s}$ .

(a)

Calculate the energy released in one of these fusion reactions.

energy = .............................................................. J

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(b)

Fusion releases large amounts of energy, but no fusion power station yet supplies electricity to the grid.

Explain why it is so difficult to build a practical, economic fusion power station.

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Question 0

5 marks

The table gives information about a nuclear power station and a gas-fired power station.

	Nuclear power station	Gas-fired power station
Carbon dioxide emitted while generating (g per kWh)	0	450
Electrical energy generated in one year (kWh)	$8.0 \times 10^{9}$	$8.0 \times 10^{9}$
Fuel used in one year (tonnes)	25	$1.1 \times 10^{6}$
Waste that stays hazardous for thousands of years	yes	no

$1\ \mathrm{tonne} = 1 \times 10^{6}\ \mathrm{g}$

(a)

Calculate the mass, in tonnes, of carbon dioxide emitted by the gas-fired power station in one year.

mass = .............................................................. tonnes

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(b)

Use the table to give two disadvantages of choosing the nuclear power station rather than the gas-fired power station.

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Question 0

6 marks

Inside a fusion reactor, a deuterium nucleus and a tritium nucleus fuse together.

$^{2}_{1}\mathrm{H} + ^{3}_{1}\mathrm{H} \rightarrow\ ^{4}_{2}\mathrm{He} + \mathbf{X}$

(a)

Determine the mass number and the atomic number of particle $\mathbf{X}$ , and name this particle.

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(b)

Explain why this reaction does not take place when deuterium and tritium gas are mixed at room temperature.

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(c)

The gas in the reactor is also squeezed to a very high pressure. Explain why a high pressure is needed.

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Question 0

6 marks

Nuclear fission and nuclear fusion are both nuclear reactions that release energy.

Compare nuclear fission and nuclear fusion.

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Question 0

6 marks

A country plans to close its last coal-fired power stations and to build a large new nuclear power station in their place. Some local residents have objected to the plan.

Evaluate the use of nuclear power stations for generating electricity.

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Question 0

8 marks

A nuclear power station contains a reactor in which uranium-235 undergoes fission.

the thermal power produced in the reactor core is $3000\ \mathrm{MW}$
each fission of a uranium-235 nucleus releases $2.9 \times 10^{-11}\ \mathrm{J}$ of energy
$1\ \mathrm{MW} = 1 \times 10^{6}\ \mathrm{W}$

(a)

Describe how the thermal energy produced in the reactor core is used to generate electricity.

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(b)

Calculate the number of fissions taking place in the core each second.

number of fissions per second = ..............................................................

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(c)

The electrical power output of the power station is $1100\ \mathrm{MW}$ .

Calculate the efficiency of the power station as a percentage.

efficiency = .............................................................. %

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Key Concepts of Physics

Motion & Forces

Conservation of Energy

Waves

Light & the Electromagnetic Spectrum

Radioactivity

Astronomy

Energy – Forces Doing Work

Forces & their Effects

Electricity & Circuits

Static Electricity

Magnetism & the Motor Effect

Electromagnetic Induction

Particle Model

Forces & Matter

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