Radiation measurements and approvals
Radiation is measured for a variety of reasons, and there are different types of radiation detectors in use. In all measurements, it is important to use a right kind of measuring instrument for the purpose and to ensure that the instrument is in working order and calibrated. The measurement result must also be interpreted correctly. Some radiation measurements require separate approval.
Radiation measurements are carried out to protect workers when monitoring exposure conditions or individual doses. Measurements are also needed for quality assurance of the use of radiation and in health care when determining the radiation exposure of patients. In addition, radon measurements are carried out to assess the exposure of both workers and the general public. In order for the measurement results to be reliable, radiation measurements must be made with a suitable, intact and calibrated radiation detector that is in full working order. In addition to radiation measurements, computational methods are also used to determine radiation exposure. For more detailed information on the requirements for radiation meters is available in the Radiation and Nuclear Safety Authority Regulation on Measurements of Ionizing Radiation STUK S/7/2021.
Selecting a suitable radiation meter
When selecting a radiation meter, ensure that it is capable of measuring the type of radiation and the dose rate in question and that the energy range of the meter is suitable. The characteristics of the radiation meter must be suitable for the application, and the prevailing environmental conditions must not influence the measurement result in unpredictable ways.
The suitability of the radiation meter has to be verified particularly carefully when measuring pulsed radiation, very high dose rates or low-energy radiation. Typically, a single radiation meter type is not suitable for measuring all types and qualities of radiation. For example, a dose rate meter cannot be used for determining surface activity caused by radioactive contamination.
Calibration and condition monitoring
Radiation meters must be properly calibrated. Calibration means determining a calibration factor for the radiation meter, i.e. the ratio between the value indicated by the radiation meter and the value of the measured quantity. Calibration also involves determining uncertainty for the calibration coefficient. Radiation meters are calibrated in a laboratory that has traceability to international radiation measurement standards. A radiation meter has to be calibrated before it is put into operation. Thereafter, the calibration will be carried out at least once in every five years, unless otherwise specified at the time of approval of the measurement method or operations.
Stricter requirements have been set for the calibration intervals of meters used in healthcare and radon measurements. The calibration interval of a field instrument used for measuring medical exposure may not exceed two years. The calibration interval of measuring instruments used for dose calibration of radiotherapy equipment used for external radiotherapy may not exceed three years, and the same calibration interval applies to the radiation sources and measuring instruments used for calibration of radiation sources in brachytherapy. The calibration interval of a meter and measurement system for airborne radon concentration and radon exposure may not exceed two years.
Calibration might need to be repeated more frequently if the meter is adjusted or problems are detected in its operation. Initial calibration by the manufacturer is often sufficient for commissioning a radiation meter.
During calibration, the meter reading is usually not adjusted. The true value of the quantity of radiation is obtained by multiplying the meter reading by the calibration factor. The calibration factor may depend on the radiation quality to be measured. Therefore, the calibration has to be performed for the energy range for which the meter will be used.
The operating condition of the meter must be checked regularly between the calibrations. This includes checking the general condition of the meter and a functional test using a suitable radiation source.
Accuracy of measurements in radiation and dosimetry
All measurements are subject to uncertainty. Their impact on the measurement result is assessed in a measurement uncertainty estimate. The measurement uncertainty estimate indicates how well the measurement result describes the actual value of the measured quantity and what factors affect the measurement uncertainty.
Approval of radon measurements
Radon measurements carried out to assess occupational or public exposure or to ensure safety require an approval from the Radiation and Nuclear Safety Authority. The prerequisite for approval is that the equipment used for measurements meets the requirements laid down in the Radiation Act and the decrees and regulations issued on the basis thereof, and that the equipment has been appropriately calibrated. The calibration of the equipment must be valid at the time of measurement.
Form: Application for approval of radon measurement (in Finnish)
The test report based on the measurement must be compliant with the standard. The calibration factor determined during calibration must be taken into account when reporting the results of radon measurements. The actual radon concentration in respiratory air is obtained by multiplying the result given by the radon measuring device by the calibration factor.
More information on measuring radon
Approved radon measurements
The Radiation and Nuclear Safety Authority (STUK) has granted several different operators an approval to carry out radon measurements. The approvals are in force for a limited period and must use the meter or measurement method for which the approval has been applied for.
Table 1. Alpha track radon detectors with a valid approval and calibration.
Organization | Appliance type | Approval expiration date | Approval |
AlphaRadon Teo |
Alpha track radon detector | 5 Nov 2024 | Homes and workplaces |
Eurofins Radon Testing Sweden AB |
Alpha track radon detector | 8 Feb 2028 | Homes, workplaces: detection of exceedance of action limit values or maximum values |
Radonova Laboratories AB |
Alpha track radon detector Radtrak2 |
14 Feb 2029 14 Feb 2029 |
Homes and workplaces |
STUK – Radiation and Nuclear Safety Authority | Alpha track radon detector | 22 Dec 2026 | Homes and workplaces |
*) Distributor stated by the holder of the approval decision.
Table 2. Portable alpha track radon detectors with a valid approval and calibration, intended for measuring radon exposure.
Organization | Appliance type | Approval expiration date | Approval |
AlphaRadon Teo |
Alpha track radon detector | 1 Feb 2029 | Occupational radon exposure of workers |
Radonova Laboratories AB |
Alpha track radon detector |
14 Feb 2029 14 Feb 2029 14 Feb 2029 |
Occupational radon exposure of workers |
*) Distributor stated by the holder of the approval decision.
Table 3. Continuously operating radon concentration measuring instruments with a valid approval and calibration.
Organization/Approval | Appliance type | Approval expiration date | Serial number of the measuring instrument |
A-Insinöörit Suunnittelu Oy /Homes and workplaces | Corentium Pro | 24 Nov 2026 | 2700006989 2700013944 |
BlueForServices Oy (Suomen radonkeskus) /Homes and workplaces | Corentium Pro | 2 Feb 2026 |
2700006209 |
Brado Oy /Homes and workplaces | Corentium Pro | 10 Feb 2028 | 2700008938 |
City of Helsinki /Workplaces | Corentium Pro | 14 Mar 2028 | 2700005664 2700005659 |
PBM Rakennustutkimus /Homes and workplaces | Corentium Pro | 30 Sep 2026 | 2700011801 |
RadonFix Suomi Oy /Workplaces | Corentium Pro | 12 Jan 2029 | 2700006435 2700006311 2700006400 2700006416 2700007460 2700008227 2700005785 2700006666 2700006830 2700006277 2700008638 2700006936 |
Radonova Laboratories AB /Homes and workplaces | SPIRIT | 1 Feb 2028 | 70B3D5D7202C0084 |
Ramboll Finland Oy /Homes and workplaces | Corentium Pro | 4 Feb 2025 | 2700008695 |
Ramo Pro Oy /Workplaces | Corentium Pro | 31 Jan 2029 | 2700005872 2700005160 |
Suomen Radonpalvelut /Workplaces | AlphaGuard PQ2000 | 24 Feb 2027 | EF0323 |
Sustera Radon Consulting Oy /Workplaces | Corentium Pro | 26 Jan 2028 | 2700005569 |
Finnish Institute of Occupational Health/ Homes and workplaces | AlphaGuard PQ2000 | 18 May 2027 | AG000312 |
Bulletin on radon measurements with Corentium Pro measuring instruments (in Finnish)
Approval of dosimetry services
Dosimetry service providers who provide measurement services for individual dosimetry of workers, must apply for approval from the Radiation and Nuclear Safety Authority. An approval has to be sought for the dosimetry service itself and for the measurement methods used for individual dose monitoring.
The application for approval must demonstrate that the requirements laid down in the Radiation Act and in the decrees and regulations issued on the basis thereof are met. This can be demonstrated, for example, by calibration certificates, test reports and measurement uncertainty estimates.
An unsolicited application should be sent by e-mail to STUK's registry: stuk(at)stuk.fi, with "Approval of individual monitoring service" in the subject field.
Table 4. Approved dosimetry services.
Organization | Field of activity | Expiration date | Measurement methods |
Doseco Oy | Use of radiation | Until further notice | TLD, DIS |
Fortum Nuclear Power and Heat Oyj | Nuclear power plant | Until further notice | TLD |
Radiation and Nuclear Safety Authority in Finland, Environmental Radiation Surveillance | Use of radiation | Until further notice | Determination of dose from internal radiation exposure: direct measurements with HPGe detectors, measurements from urine samples |
Teollisuuden Voima Oy | Nuclear power plant | Until further notice | TLD |
Fees for radiation practices regulation