The duration that radioactive waste remains hazardous varies significantly depending on the specific type and isotopic composition of the material. Low-level radioactive waste, which includes contaminated laboratory equipment, clothing, and operational tools, typically loses its radioactivity and decays to safe background levels within a few decades. In contrast, high-level radioactive waste, primarily consisting of spent nuclear fuel rods and byproducts from atomic reactors, contains long-lived fission products and actinides like plutonium-239 and uranium-235. These highly radioactive materials can remain dangerously toxic and emit hazardous ionizing radiation for hundreds of thousands to millions of years, requiring ultra-secure, multi-barrier deep geological disposal repositories to isolate them permanently from the human biosphere and natural water tables.