Aim for FiveEnvironmental Science

Analyze an environmental problem doing calculations

Spent fuel from a nuclear plant

  • Unit 6
  • 10 points
  • About 24 minutes

You can use a calculator on this question, just like on exam day.

You work through an environmental scenario using numbers: set up and solve calculations (showing your work), then explain the science and propose solutions. Several of the 10 points come from the calculations, usually one for the setup and one for the answer. On the exam: Question 3 of 3 in the 70-minute free-response section (Section II is 40% of the exam score).

The question

A nuclear power plant stores its spent fuel rods in pools of water and steel casks at the plant site. The stored spent fuel contains 24 kg of cesium-137, a radioactive isotope with a half-life of about 30 years.

Suggested time: 24 minutes

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Part (a)

2 points

Calculate the mass of cesium-137, in kg, that will remain after 90 years. Show your work.

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Part (b)

2 points

Calculate the number of years it will take for the 24 kg of cesium-137 to decay until only 0.75 kg remains. Show your work.

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Part (c)

2 points

Fission of 1 kg of uranium-235 releases about 8.0 × 10¹³ J of energy. Burning 1 kg of coal releases about 2.4 × 10⁷ J. Calculate the mass of coal, in metric tons, that would release the same amount of energy as the fission of 1 kg of uranium-235. Show your work. (1 metric ton = 1,000 kg)

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Part (d)

1 point

Explain why nuclear power is classified as a nonrenewable energy source.

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Part (e)

1 point

Describe how a nuclear power plant uses fission to generate electricity.

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Part (f)

1 point

Describe one environmental advantage of generating electricity with nuclear power instead of coal.

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Part (g)

1 point

Spent fuel also contains plutonium-239, which has a half-life of about 24,000 years. Describe one challenge of storing waste that contains plutonium-239.

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