Figure 1. This spent nuclear fuel is placed in a cold pool to cool. 
The term nuclear waste is often used to refer to spent nuclear fuel. This term is general, as there are many different types of nuclear waste, but refers to any radioactive waste substance that is produced from industrial processes, including nuclear power plants. Nuclear waste is also produced at hospitals and other medical facilities.
Spent nuclear fuel is specifically high level waste, but it is the waste that many think of. There are many different grades of nuclear waste. Generally, the more radioactive the waste, the less there is of it. The categories of waste are:
- Exempt waste: This type of waste is also referred to as very low level waste. This type of waste is any material that has so little radioactivity, and thus poses no threat. Waste of this kind includes concrete from decommissioned nuclear power plant buildings.
- Low level waste: This type of waste is generated by facilities that use radioactive isotopes. This includes the nuclear power industry, but also includes medical facilities (such as hospitals or radiology clinics) that use medical isotopes to assess and treat diseases like cancer. The radioactivity from low level waste is far less intense than from spent fuel, but the volume is much greater.
- Intermediate level waste: This waste has sufficient radiation that it requires shielding and needs to be handled more carefully than low level waste. There is much less intermediate level waste than low level waste. This type of waste includes the metal around the fuel pellets if the fuel is reprocessed.
- High level waste: This waste is the used fuel and the material that has been drawn out of the used nuclear fuel.
Exempt waste, as the name implies, isn't monitored as radioactive waste, but the rest of the types are. Different levels of waste have different laws proscribing how each level is to be handled.
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