Some remote Soviet navigation beacons ran on heat from radioactive decay.

Electricity from a temperature difference

A thermoelectric generator turns a persistent heat source into electrical current. Inside it, heat warms one side of a set of thermoelectric materials while the other side stays cooler. The resulting temperature difference nudges electric charges through the materials, producing electricity—quietly, with no moving turbine and no combustion.

In a radioisotope-powered unit, the heat comes from radioactive atoms breaking down. That process continues without a reactor’s controlled chain reaction, but it also produces radiation. The generator’s job is therefore twofold: supply useful heat to the conversion system and keep radiation contained behind protective shielding.

Power where a delivery truck cannot go

Remote navigation beacons need electricity to keep transmitting, often in places where routine maintenance or fuel deliveries are difficult. A long-lived heat source could power a beacon for years without a crew making regular trips to refill it. That was the engineering tradeoff: the equipment was heavy and required careful containment, but it could provide dependable power in isolation.

Thermoelectric conversion is not especially efficient, so this kind of generator is best suited to modest, steady loads rather than high-power machinery. A beacon’s simple, continuous need for electricity fit that limitation better than a device that had to start and stop or draw large bursts of power.

When containment fails

The generator’s heat can remain noticeable even after a beacon has been abandoned, but warmth is not a measure of how safe the unit is. Radioactive decay produces both heat and radiation; shielding reduces the radiation that escapes. If the shielding is lost or compromised, a seemingly inert piece of equipment can become dangerous to approach or handle.

That is why abandoned units pose a problem beyond lost infrastructure: their power source does not simply go cold when the beacon stops working. The same steady decay that once kept a remote signal alive can continue to make an unprotected generator a serious radiation hazard.