The solid, liquid, or gaseous substances and materials that contain radionuclides that remain after the mining of radioactive ores, the reprocessing of nuclear fuels, the operation of nuclear reactors, the manufacture or decommissioning of nuclear weapons, and the waste from hospitals and research laboratories. The radionuclides may be highly radioactive and have very long half-lives presenting a danger to all living organisms. Their disposal is therefore highly regulated. Radioactive waste is classified as being either high-level, intermediate-level, or low-level waste. High-level waste includes spent nuclear fuel from nuclear power stations and is first required to be cooled for very long periods of time before being disposed of. Intermediate-level waste arises from the reprocessing of nuclear fuels and includes sludges, liquid, and the equipment used in the reprocessing. The waste is solidified, mixed with concrete, and packed into steel drums. It is stored in deep geologically stable mines. Low-level waste arises from materials used in the everyday activities of nuclear reprocessing, hospitals, and research laboratories, and includes liquids and solids. It is packed into steel drums and disposed of in special concrete-lined landfill sites. In the UK, these sites are under the authority of the UK Nuclear Decommissioning Authority that manages the site at Drigg near the UK reprocessing plant at Sellafield in Cumbria.
https://www.nda.gov.uk/ Official website of the UK Nuclear Decommissioning Authority.