Categories of radioactive waste and emissions

Radioactive waste is categorised into high-, intermediate- and low-level waste. Spent nuclear fuel is categorised as high-level waste.

Radioactive waste arising from the use of nuclear energy is subject to the Nuclear Energy Act and waste arising from any other use of radioactive substances is subject to the Radiation Act. In the image (in Finnish), these main categories are divided further into subcategories according to the final destination of the radioactive waste.

​​​​​​​For the purpose of processing and storage of radioactive waste, it is appropriate to categorise waste according to the activity level into the following categories (STUK Guide YVL D.4):

• High-level waste requires very efficient radiation protection arrangements and usually also cooling. In this case, the activity concentration of the waste is higher than 10 GBq/kg. In Finland, spent fuel from nuclear reactors is categorised as high-level waste.
• The processing of intermediate-level waste requires efficient radiation protection arrangements, and the activity concentration of such waste is more than 1 MBq/kg but not more than 10 GBq/kg. For example, ion-exchange resin used for cleaning the primary circuit in a nuclear power plant is intermediate-level waste.
• Low-level waste can be can be processed without any special radiation protection arrangements, and the activity concentration in such waste is not more than 1 Mbq/kg. For example, mixed solid waste accrued during maintenance outages in nuclear power plants (so-called maintenance waste) is mainly low-level waste.

In time, when the nuclear facility is dismantled, this will result in corresponding low and intermediate-level waste.

For final disposal purposes, radioactive waste is often categorised into short- and long-lived waste. In short-lived waste, the half-life of the predominant radioactive material is not more than about 30 years (for example, strontium-90 and cesium-137 are included here). Their activity level is reduced to a safe level within a few hundred years. Low and intermediate-level radioactive waste arising from the operation of nuclear power plants is usually short-lived. Long-lived waste, such as spent fuel, contains substantial concentrations of radioactive materials, with a half-life of more than 30 years.

Radioactive and conventional waste

Because radioactive substances occur in people’s living environment, for example in building materials, it is important to define what is radioactive waste and what can be considered conventional waste. The starting point for any such definition is whether the waste can generate radiation doses that exceed the level considered insignificant. This way, activity concentration limits that define radioactive waste can be derived.

The International Atomic Energy Agency IAEA has given radionuclide-specific recommendations for limits. For the most significant radionuclides contained in nuclear waste, these limits are in the range of 0.1–10 Bq/g. The STUK Guide YVL D.4 contains the corresponding limits. The exemption values for other radioactive waste are specified in the STUK Guide ST 1.5.