Radioactive waste is a term used for certain substances that are radioactive and that are no longer useful. Most radioactive waste is a by-product of operating nuclear power plants. A small amount also comes from hospitals, which use radioactivity for certain treatments. In some cases, research labs also produce radioactive waste. Nuclear weapons also produce radioactive waste. Radioactive waste is dangerous to the environment, and there are many regulations about transporting it, handling it, and processing it in such a way that the dangers are reduced.