Fission and Fusion
5 marks · NormalThe energy released in both fission and fusion reactions has important consequences for their use as energy sources.
Explain how energy is released in the process of uranium-235 fission, mentioning both the particles produced and how energy is distributed among them.
Describe one advantage and one disadvantage of using nuclear fusion, compared to nuclear fission, for providing electricity.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) —
(b) —
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Marking points
M1 (a) · 1 mark · States that uranium-235 absorbs a neutron and splits.
A1 (a) · 1 mark · Mentions that two lighter (daughter) nuclei, neutrons, and gamma radiation are produced.
A2 (a) · 1 mark · Explains that most energy is carried away by kinetic energy of daughter nuclei, some by kinetic energy of neutrons, and some by gamma radiation.
B1 (b) · 1 mark · Gives one valid advantage (e.g., fusion produces no long-lived radioactive waste, fuel is abundant, etc).
B2 (b) · 1 mark · Gives one valid disadvantage (e.g., extremely high temperatures needed, hard to control, not yet commercially viable).
Worked solution
a) In uranium-235 fission, a neutron is absorbed by the nucleus, making it unstable. The nucleus splits into two lighter nuclei (such as barium and krypton), releases more neutrons, and gamma radiation. Most of the energy is carried away by the kinetic energy of the two daughter nuclei, with some energy given to the neutrons and some as gamma radiation.
b) Advantage: Fusion fuels are abundant and fusion does not create high-level radioactive waste. Disadvantage: Achieving the required temperature/pressure is difficult and currently not practical for generating electricity on Earth.