The radioactivity of building materials and ash
Radiation exposure from building materials
The radiation exposure arising from construction products is examined if the radiation exposure is suspected to be higher than the reference value. The reference value for the radiation exposure of the population caused by construction products used in housing construction is 1 millisievert a year, although in such a way that the radiation dose from the cesium 137 in the construction products is at maximum 0.1 millisieverts a year.
The party subject to the reporting obligation is the one who manufactures, imports or transfers to Finland a construction product that complies with the EU Construction Products Regulation. The construction products to be examined are:
- a building’s framework manufactured from mineral-based raw materials;
- construction products whose primary raw material consists of crushed rocks, gravel or sand which contains granite or other granitoids, such as granodiorite, tonalite or gneiss;
- construction products whose raw material consists of intermediate or by-products or waste generated by industries which exploit ash or mineral-based natural raw materials.
The survey begins by measuring the activity concentrations of uranium-238, thorium-232, potassium-40 and caesium-137 in the construction product in a laboratory using high-resolution gamma spectrometry. If the measurement is carried out elsewhere than at STUK, the party responsible for the reporting sends the results of the measurement to STUK's regulatory control of natural radiation without delay.
If the measurement result meets the condition set for the intended use of the construction product in section 13 of STUK Regulation S/6/2022, the radioactivity of the product does not restrict its use for the intended purpose. In other words, the radiation exposure caused by the construction product is below the reference value.
If the condition is not met, the construction product can often still be used in construction. However, in such cases, a more detailed description of the radiation exposure caused by the product must be prepared and the radioactivity recorded in its product information. STUK's regulatory control of natural radiation sends additional information to the person responsible for this practice.
• STUK-B-STO 32 (pdf) (Markkanen M.) Radiation Dose Assessments for Materials with Elevated Natural Radioactivity. STUK, Helsinki 1995.
• CEN/TR 17113:2017. Construction products – Assessment of release of dangerous substances – Radiation from construction products – Dose assessment of emitted gamma radiation.
• Tables to estimate the dose rate caused by filling gravel and crushed rock in different situations (in Finnish only).
In addition to the natural radioactive substances, the construction product, especially in fly ash, may contain the isotope cesium-137 from the Chernobyl nuclear power plant accident. The radiation dose caused by it is assessed separately from the construction product, and it has a separate reference value. The maximum concentration of cesium-137 in concrete is 50 Bq/kg, so the concentration of cesium-137 in the fly ash used in concrete must be taken into account in the survey.
Activity concentration measurements carried out elsewhere than at STUK as well as reports on radiation exposure of the population caused by construction products are sent to STUK at the following address: lsv (at) stuk.fi
Obligations of combustion plants and radioactivity of ash
The use of peat and coal-fired power plants, the maintenance of boilers and their decommissioning are activities that are subject to the obligation to investigate natural radiation exposure.
Natural radioactive substances accumulate in the ash from combustion plants burning peat, coal or wood-based fuel. For further processing of the ash, the natural radionuclides of the ash must be investigated in order to know that the ash is suitable for the intended use in terms of its radioactivity. By investigating the radioactivity of the ash, it can be ensured that the use of the ash in construction products, fertilizers or landfill, for example, does not cause exposure that exceeds the reference values to the public. STUK Regulation S/6/2022 (sections 6 and 13) sets out the conditions for assessing whether ash is suitable for forest fertilizers, construction products or landfills without further clarification. If the conditions for the intended use of the ash are not met, the population exposure must be investigated and it must be demonstrated to STUK that the exposure caused by the ash is below the reference values in the chosen use.
STUK recommends repeating the radioactivity test for ash from the combustion of peat, coal and wood-based material if the composition of the fuel changes significantly or every 5–10 years.
Reporting the exposure to natural radiation
Reports on the exposure of combustion plants to natural radiation must be submitted to STUK using the form:
Electronic form for combustion plants for the assessment of natural radiation exposure (Formbox, in Finnish)
- Radiation Act 859/2018 (Finlex)
- Government Decree on Ionizing Radiation 1034/2018 (Finlex)
- Decree of the Ministry of Social Affairs and Health on ionizing radiation 1044/2018 (Finlex)
- Radiation and Nuclear Safety Authority Regulation on Practices that Cause Exposure to Natural Radiation STUK S/6/2022 (Stuklex)
- Radiation and Nuclear Safety Authority Regulation on Measurements of Ionizing Radiation STUK S/7/2021 (Stuklex)
- Radiation and Nuclear Safety Authority Regulation on Exemption Levels and Clearance Levels STUK SY/1/2018 (Stuklex)
- Radioactivity of ash from bioenergy production (julkari.fi, in Finnish)
- REGULATION (EU) No 305/2011 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL
laying down harmonised conditions for the marketing of construction products and repealing Council Directive 89/106/EEC (eurlex)
- Building materials and ash - measurements (stuk.fi, service pages only in Finnish and Swedish)
- Obligation to investigate exposure to natural radiation, NORM (stuk.fi)