Classification of Radioactive Waste The classification of radioactive waste plays a crucial role in how it is finally stored.

Radioactive waste may be solid, liquid or gaseous and is classified according to its activity and half-life. It may be low-, intermediate- or high-level radioactive waste (LLW, ILW or HLW respectively) and short- or long-lived waste.

Low- and intermediate-level waste (LLW, ILW) in Austria mainly results from medicine, industry and research as well as from the decommissioning of old facilities. This waste primarily includes radionuclides with half-lives that do not exceed 30 years (for example cesium-137 or strontium-90). Low- and intermediate-level waste may also contain a limited amount of long-lived radionuclides. This type of waste does not give off warmth and is usually stored in near-surface final repositories or repository mines (final repository for low- and intermediate-level radioactive waste).

Besides low- and intermediate-level radioactive waste medicine mostly produces very short-lived wastes. The half-life of the radionuclides contained in this type of waste is less than 100 days. This waste is stored until the radioactivity decays to a level where it can be cleared and released from regulatory control. It can then be disposed of in a regular landfill and does not need to be stored in a final repository.

High-level radioactive waste (HLW) and spent fuel elements arise from nuclear power plants and nuclear research reactors. These types of radioactive waste generate heat, thus, the general consensus is that they must be stored in deep geological repositories. This guarantees a safe enclosure for several hundreds of millennia. As Austria does not operate any nuclear power plants and the spent fuel elements of Vienna University of Technology’s research reactor will be sent back to their supplier (US Department of Energy) according to contract, no high-level radioactive waste or spent fuel elements will need to be stored in a final repository in Austria.