Fission reactions in nuclear power stations produce radioactive material, of which some is useful but most is hazardous radioactive waste. There are three categories of waste: High-level waste, Intermediate-level waste and Low-level waste.
HLW is very radioactive, made up of spent nuclear fuel and must be stored in concrete and steel in order to not leak the radiation. This type of waste does not remain high-level for very long. Within a few years, the activity has decreased and it is classed as intermediate-level waste.
Made up of elements of equipment such as fuel cladding, which are radioactive because they have been in the core of the reactor. Unlike HLW, intermediate-level waste is radioactive for tens of thousands of years. It is currently stored temporarily in Sellafield inside concrete and steel drums; politicians and scientists are still deciding what should be done with it in the long term (It must be secure for tens of thousands of years, without being able to leak any material).
Comprises of clothing, paper towels and medical equipment from hospitals and nuclear power stations. These items are slightly radioactive and cannot be buried with household waste; it is compacted and buried in special landfill sites.