A LevelPhysicsOCRTopic Questions6. Particles & Medical Physics6.10 Nuclear Fission & Fusion

Nuclear Fission & Fusion (OCR A Level Physics)

Topic Questions

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1a2 marks
a)
Explain the function of the control rods and the moderator in a nuclear fission reactor.

[2]

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1b6 marks
b*)
Some nuclear fission reactors use uranium-235 as fuel. In the future, there is possibility of using hydrogen-2 as fuel in fusion reactors.

Here is some information and data on fission and fusion reactions.

  Fission reactor Fusion reactor
Typical reaction straight n presubscript 0 presuperscript 1 space plus space straight U presubscript 92 presuperscript 235 space rightwards arrow space Ba presubscript 56 presuperscript 144 space plus space Kr presubscript 36 presuperscript 89 space plus space 3 straight n presubscript 0 presuperscript 1 straight H presubscript 1 presuperscript 2 space plus space straight H presubscript 1 presuperscript 2 space rightwards arrow space straight H presubscript 1 presuperscript 3 space plus space straight H presubscript 1 presuperscript 1
Approximate energy produced in each reaction 200 MeV 4 MeV
Molar mass of fuel material uranium-235: 0.235 kg mol–1 hydrogen-2: 0.002 kg mol–1

 

•    Describe the similarities and the differences between fission and fusion reactions.

•    Explain with the help of calculations, which fuel produces more energy per kilogram.

[6]

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2a2 marks
a)
A researcher is doing an experiment on a radioactive solution in a thin glass tube.
The solution has two radioactive materials X and Y.
The table below shows some data on these two materials.

  Material X Material Y
Half-life 10 minutes 10 hours
Particles emitted Alpha Beta-minus
Daughter nuclei Stable Stable

The solution has the same number of nuclei of X and Y at the start.

i)
State and explain which material has the greatest activity at the start.

[1]

ii)
State why it is dangerous for the researcher to handle the test tube with bare hands.

[1]

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2b5 marks
b)
Carbon-14 open parentheses straight C presubscript 6 presuperscript 14 close parentheses is produced in the upper atmosphere of the Earth by collisions between nitrogen nuclei and fast-moving neutrons.
The nuclear transformation equation below shows the formation of a single carbon-14 nucleus.

straight N presubscript 7 presuperscript 14 space plus space straight n presubscript 0 presuperscript 1 space rightwards arrow space straight C presubscript 6 presuperscript 14 space plus space straight X

i)
State the proton number of particle X.


proton number = .......................................................... [1]

ii)
Use the data below to determine the binding energy per nucleon of the 146C nucleus.

Write your answer to 3 significant figures.

•    mass of neutron = 1.675 × 10–27 kg
•    mass of proton = 1.673 × 10–27 kg
•    mass of straight C presubscript 6 presuperscript 14 nucleus = 14.000 u
•    1 u = 1.66 × 10–27 kg





binding energy per nucleon = ................................... J per nucleon [4]

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3a2 marks
a)
Fig. 21 shows stable and unstable nuclei of some light elements plotted on a grid. This grid has number of neutrons N on the vertical axis and number of protons Z on the horizontal axis.

q21a-paper-2-june-2019-ocr-a-level-physics
Fig. 21

The key on Fig. 21 shows whether a nucleus is stable, emits a beta-plus particle or emits a beta-minus particle to become stable.

For Z = 7, suggest in terms of N why an isotope may emit

i)
a beta-minus particle
[1]
ii)
a beta-plus particle.
[1]

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3b8 marks
b)
Inside a nuclear reactor, fission reactions are controlled and chain reactions are prevented.
A typical fission reaction of the uranium-235 nucleus (straight U presubscript 92 presuperscript 235) is illustrated below.

straight n presubscript 0 presuperscript 1 space plus space straight U presubscript 92 presuperscript 235 space rightwards arrow Cs presubscript 55 presuperscript 141 space plus space Rb presubscript 37 presuperscript 93 space plus space 2 subscript 0 superscript 1 straight n

The neutron triggering the fission reaction moves slowly. The neutrons produced in the fission reaction move fast.

i)
Describe what is meant by chain reaction.

[2]

ii)
Explain how chain reactions are prevented inside a nuclear reactor.
[2]
iii)
The energy released in each fission reaction is equivalent to a decrease in mass of 0.19u.
A fuel rod in a nuclear reactor contains 3.0% of uranium-235 by mass.
Estimate the total energy produced from 1.0 kg of fuel rod.
molar mass of uranium-235 = 0.235 kg mol–1
1u = 1.66 × 10–27 kg

energy = .......................................... J  [4]

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4a2 marks

Stars produce energy by nuclear fusion.
One particular fusion reaction between two protons (begin mathsize 16px style H presubscript 1 presuperscript 1 end style) is shown below.

straight H presubscript 1 presuperscript 1 space space space plus space space space straight H presubscript 1 presuperscript 1 space space space space rightwards arrow space space space straight H presubscript 1 presuperscript 2 space space space plus space space space straight e presubscript plus 1 end presubscript presuperscript 0 space space space plus space space space straight v

In this reaction 2.2 MeV of energy is released.

a)
Only one of the particles shown in the reaction has binding energy.
Determine the binding energy per nucleon of this particle. Explain your answer.

[2]

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4b2 marks
b)
Explain why high temperatures are necessary for fusion reactions to occur in stars.

[2]

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4c3 marks
c)
A gamma photon in a star can spontaneously create an electron-positron pair.
Calculate the maximum wavelength of a gamma photon for this creation event.





maximum wavelength = ......................................... m [3]

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