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How do radioactive materials power atomic batteries for remote instruments?

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Labeled diagram showing the process of a nuclear power plant with a pressurized-water reactor. Water circulates through the reactor core, heats to produce steam in a steam generator, which drives a turbine connected to an electric generator. Steam is then cooled in a condenser using water from a cooling tower, which releases nonradioactive water vapor. Control rods, pumps, and transmission lines are also indicated. — nuclear power Schematic diagram of a nuclear power plant using a pressurized-water reactor.

Radioactive materials power atomic batteries—often called radioisotope thermoelectric generators (RTGs)—by utilizing the heat generated during the process of radioactive decay.21

In these devices, a radioactive isotope serves as a high-temperature heat source. This heat flows through a thermoelectric converter to a heat sink, which is maintained at a lower temperature. The resulting temperature differential across the converter produces direct current electricity, a phenomenon known as the Seebeck effect.234

Because thermoelectric materials are relatively immune to nuclear radiation, these batteries are highly reliable for remote or isolated applications where maintenance is impossible, such as in spacecraft, deep-ocean data collection, and weather monitoring stations. Alpha-emitting isotopes are typically preferred for these power sources because they require significantly less shielding than beta- or gamma-emitting isotopes. Common isotopes used for this purpose include plutonium-238, which provides a long-lasting and dependable energy supply.215