Photograph: Magnox reactor graphite and stainless steel support strut (non-active) © Steve Barlow

Radioactive waste is generated as a by-product in several industrial sectors that use radioactive materials. This includes electricity production, nuclear fuel manufacture and reprocessing, research and development, nuclear medical applications and the defence industry. Like all other wastes, the industry attempts to reuse and recycle these radioactive materials but eventually there will be wastes for which there is no further use. These wastes will be disposed of where there are disposal facilities available, or stored pending the availability of such facilities.

Radioactive wastes are categorised according to their radioactivity and consequential heat output. The categories are:

Low level waste

Waste that only has low levels of radioactivity but is not suitable for disposal as ordinary household waste. It may be solid or liquid and includes soil, rubble and building materials from nuclear sites and protective clothing that has been worn in nuclear facilities.

intermediate level waste

Waste with more activity than low level waste but less activity and heat generating capacity than high level waste. Intermediate level waste can be solid or liquid and comes from the operation and decommissioning of nuclear power stations, reprocessing of nuclear fuel and other uses of radioactive materials. Liquid intermediate level waste will be converted to a solid by mixing with materials such as cement to make a stable product for onward storage and disposal.

high level waste

This is the most active of the waste classes, containing the fission-products remaining as a result of reprocessing spent nuclear fuel. This waste is converted into a glass product for onward storage and disposal by the process of vitrification. These fission-products decay rapidly with the consequence that this waste emits significant heat which needs to be considered when planning storage and disposal. Spent nuclear fuel which is not reprocessed and which is disposed of directly, will also be classed as high level waste.

In the UK disposal facilities are available to deal with low level waste but there are no disposal facilities to deal with intermediate level or high level wastes. Within industry and government circles, intermediate and high level wastes are jointly referred to as higher-activity wastes. A small fraction of low level waste not suitable for the existing disposal routes is also included within this description.