radioactive waste

radioactive waste (nuclear waste) Any solid, liquid, or gaseous waste material that contains radionuclides (radioactive atomic nuclei). These wastes are produced in the mining and processing of radioactive ores, the normal running of nuclear power stations and other reactors, the manufacture of nuclear weapons, and in hospitals and research laboratories. Because high-level radioactive wastes can be extremely dangerous to all living matter and because they may contain radionuclides having half-lives of many thousands of years, their disposal has to be controlled with great stringency.

High-level waste (e.g. spent nuclear fuel) requires to be cooled artificially and is therefore stored for several decades by its producers before it can be disposed of. Intermediate-level waste (e.g. processing plant sludge and reactor components) is solidified, mixed with concrete, packed in steel drums, and stored in special sites at power stations before being buried in concrete chambers in deep mines or below the seabed. Low-level waste (e.g. solids or liquids lightly contaminated by radioactive substances) is disposed of in steel drums in special sites in concrete-lined trenches. In the UK, a company (Nirex Ltd) was set up by the nuclear industry and the government in 1988 to handle the disposal of low-level nuclear waste, which is disposed of at an underground site at Driggs in Cumbria. There are also nuclear reprocessing plants at Dounreay (Scotland) and Sellafield in Cumbria. Formerly, low- and intermediate-level wastes were disposed of in the Atlantic deeps, in steel drums cast in concrete, but this practice was banned by international agreement in 1983.