Nuclear fission avoids using large quantities of fossil fuel for energy but is very contentious because it produces radioactive waste.

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Thermoelectric coupling uses heat from the decay of a radioactive fuel (as opposed to the full-scale nuclear fission which powers a reactor on Earth) as its energy source.

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Reactors that exploit nuclear fission (in which energy is generated by splitting uranium atoms) have produced thousands of tonnes of spent fuel and other radioactive by-products.

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