Physics
Nuclear reactors used to produce electricity are based on

Nuclear fission
Superconductivity
Nuclear fusion
Cold fusion

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Physics
Radiocarbon is produced in the atmosphere as a result of

Action of solar radiations particularly cosmic rays on carbon dioxide present in the atmosphere.
Collision between fast neutrons and nitrogen nuclei present in the atmosphere.
Action of ultraviolet light from the sun on atmospheric oxygen.
Lightning discharge in atmosphere.

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