8.3 Nuclear Energy

Notes

Nuclear power plants use fission, the splitting of uranium-235 atoms, to release heat. The heat makes steam that turns a turbine.

• Advantages: produces electricity with almost no $CO_2$ emissions during operation, high energy output from small amounts of fuel, and steady (baseload) power.
• Disadvantages: radioactive waste that stays dangerous for thousands of years, high construction costs, risk of accidents and security concerns, uranium mining impacts, and thermal pollution from cooling water.
• Notable accidents: Three Mile Island (US, 1979), Chernobyl (Ukraine, 1986), Fukushima (Japan, 2011).
• A half-life is the time for half of a radioactive sample to decay. After one half-life 50% remains; after two, 25%.
• Spent fuel is stored in cooling pools and dry casks; the US has no permanent national repository.
• People disagree about nuclear power: some see it as an important low-carbon option, others emphasize waste, cost, and safety.
• Fusion, joining nuclei, is not yet commercially available.
• Example: a sample with a half-life of 30 years starts at 80 g. After 60 years, 2 half-lives, 20 g remains.