Some time before the expedition visited the planet so had Genii built a nuclear power stations, but abandoned it since. In 2008 it was Teyla and Ronon been on the planet after hearing from one of Teyla's contacts there was the old technology on the planet. Argan and Zelenka managed to stop the meltdown, and the population of the planet was saved from disaster. (ATL: "Stargate Atlantis: Meltdown")