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Nuclear and particle physics

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Question 6

In a nuclear reactor, the fission of a uranium-235 nucleus (92235U^{235}_{92}\text{U}92235​U) can be triggered by a slow-moving neutron.

a.

Explain how a chain reaction is sustained in a nuclear reactor and how control rods are used to limit the rate of energy release.

[3]
b.

The energy released in each fission reaction is equivalent to a decrease in mass of 0.21 u0.21\text{ u}0.21 u. A fuel rod in the nuclear reactor contains 4.5%4.5\%4.5% of uranium-235 by mass.

Estimate the total energy produced from the fission of all the uranium-235 in a 1.2 kg1.2\text{ kg}1.2 kg fuel rod.

Give your answer to an appropriate number of significant figures.

Data:

  • molar mass of uranium-235 = 0.235 kg mol−10.235\text{ kg mol}^{-1}0.235 kg mol−1
  • 1 u=1.66×10−27 kg1\text{ u} = 1.66 \times 10^{-27}\text{ kg}1 u=1.66×10−27 kg
  • Avogadro constant NA=6.02×1023 mol−1N_A = 6.02 \times 10^{23}\text{ mol}^{-1}NA​=6.02×1023 mol−1
  • speed of light in vacuum c=3.00×108 m s−1c = 3.00 \times 10^8\text{ m s}^{-1}c=3.00×108 m s−1
[6]

Nuclear and particle physics Questions

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