About radioactive categories
Radioactive waste is generally classified on the basis of how much radiation it emits, on the form of radiation it emits, and on the length of time for which it will continue to emit radiation.
The purpose of classification is to ensure that radioactive waste is handled, stored and disposed of in ways that are appropriate to its characteristics.
Radioactive wastes are described as low level, intermediate level, or high level depending on the levels of radiation they emit. Radioactive wastes can also be categorised as short-lived or long-lived depending on the length of time over which they emit radiation.
Short-lived radioactive materials have a half-life of less than about forty years. This means that half the unstable atoms in short-lived radioactive materials will change into the stable decay product in less than forty years. Long-lived radioactive materials have a half-life of greater than forty years.
Australia has adopted a nationally uniform system for the classification of radioactive waste, based on the International Atomic Energy Agency General Safety Guide, Classification of Radioactive Waste .
The Australian classification scheme, developed by the Australian Radiation Protection and Nuclear Safety Agency is set out in the following table.
Low level waste
Contains enough radioactive material such that it is not exempt from regulatory control. Low level waste may include short-lived materials at higher activity concentration levels and long-lived materials at low activity concentration levels. Low level waste is suitable for near-surface disposal.
Intermediate level waste
Waste that requires greater containment and isolation from the environment than can be provided by near-surface disposal facilities. Intermediate level waste is differentiated from low level waste due to its content—particularly long-lived radionuclides. Intermediate level waste needs little or no provision for heat dissipation during storage and disposal.
High level waste
Waste that requires further containment and isolation than intermediate level waste. High level waste may generate such significant quantities of heat by radioactive decay that provision for heat dissipation is required, or it may contain large quantities of long-lived radionuclides. Australia possesses no high level radioactive waste.
For more information about radiation, see Radiation and radioactive waste.