The binding energy per nucleon of a nucleus varies with its mass number.

PHYSICS · Multi-part · A Level · Physics · Nuclear physics · Nuclear physics

Problem

The binding energy per nucleon of a nucleus varies with its mass number. (i) Draw a qualitative graph showing the variation of binding energy per nucleon with mass number from

A = 1

A = 240

. (ii) Using this graph, explain why energy is released both when a heavy nucleus undergoes fission and when light nuclei undergo fusion. (iii) The average binding energy per nucleon is

7.6\,\text{MeV}

for

^{235}\!\text{U}

8.8\,\text{MeV}

for a typical fission fragment around

A \approx 118

1.1\,\text{MeV}

for deuterium and

7.1\,\text{MeV}

for

^{4}\!\text{He}

. Calculate the energy released per nucleon for (a) the fission of

^{235}\!\text{U}

into fragments of mass number

\approx 118

, and (b) the fusion of deuterium into helium-4. Hence decide which of the two processes is more energy efficient on a per-nucleon basis.

Related theory

Nuclear Fission
Nuclear Reactions
Nuclear Binding Energy
Mass defect and binding energy
Nuclear physics
Nuclei
Mass energy equivalence

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