Radiogenic decay was the process by which radiogenic particles lost energy.
The detonation of a Druoda series 5 long-range tactical armor unit on a planetary surface in 2375 left high concentrations of radiogenic decay. (VOY: "Warhead")
In 2376, the rate of radiogenic decay on the Vaadwaur homeworld allowed the USS Voyager to determine that the planet had been bombarded 892 years prior. (VOY: "Dragon's Teeth")