The nuclear powered reconnaisance drone was a piece of technology created by the Russians during their Stargate Program.
The Russians managed to have built several of them, for the purpose of leaving them on planets for long term observation. They can remain operational for as long as ten years. When one such drone went to the Water planet, the Water-based life form was able to use the drones to power the Stargate, which could cease the American Stargate Program. Fortunately, they were able to shut down the drone. (SG1: "Watergate")