Calibrations, testing and irradiation of radiation meters
Radiation Act (859/2018) defines that radiation measurements must be performed with a method suitable for the purpose and proved reliable. The results of the measurements must be metrologically traceable to the International System of Units. The radiation meter or measuring instruments must be appropriately calibrated.
STUK provides calibration and testing services for dose and activity quantities of ionizing radiation. The purpose of the calibration is to enable reliable and internationally comparable radiation measurements in Finland. For this purpose, STUK maintains the necessary measurement standards.
Services offered
The most common meter type-specific services are presented below. The content of the service can be modified according to the usage of the meter and what kind of radiation need to be measured. Obviously, the measurement capability of the meter has to be taken into account. A certificate pursuant to ISO 17025 is provided for the services.
In calibration, the meter reading is compared to a reference level and the meter is assigned with a calibration coefficient that is recorded in the calibration certificate. The meter reading is multiplied by the calibration coefficient to give the actual measurement result. Please note that as a rule, we do not adjust the meters.
For meters intended for rescue operations and civil defence an inspection is usually sufficient.
The laboratory can also irradiate various components to the desired dose with different radiation qualities.
Measurements and tests can also be carried out at places of use of radiation.
The prices of the services are provided in STUK's Service price list.
Radiation meters for radiotherapy are usually calibrated in terms of absorbed dose to water in 60Co gamma radiation beam. Calibration can be performed either for the ionization chamber or, for the entire measurement chain, i.e. ionization chamber, electrometer and measurement cable. Information about the collecting voltages of the ionization chamber and the measurement settings of the electrometer (for example, high range and charge measurement) are required for the calibration. If needed, calibration can also be done in terms of air kerma for 60Co gamma radiation.
Radiation meters used in x-ray diagnostics and interventional radiology are calibrated for standardized x-ray qualities. The customer can choose the calibration qualities based on, for example, the tube voltages. The applied radiation qualities depend strongly on the use of the meter.
Typical measurement quantities and radiation qualities:
- conventional ionization chambers: air kerma, RQR radiation qualities (40–150 kV)
- mammography meters: air kerma, MAM radiation qualities (25–35 kV)
- KAP meters: air kerma-area product, RQR radiation qualities (40−150 kV)
- CT chambers: air kerma-length product, RQT radiation qualities (100−150 kV)
All available x-ray qualities are shown in the X-ray qualities table (.pdf).
A typical calibration of protection meter is performed with 137Cs-gamma radiation in terms of ambient dose equivalent (H*(10)) and at different dose rates (typically three dose rates are used). The meters can also be calibrated with 60Co and 241Am gamma radiation sources, with ISO narrow-spectrum and ISO high air kerma rate (ISO 4037:2019) x-ray qualities as well as beta and neutron radiation sources. The radiation qualities used depend on the purpose of the meter.
Several different planar sources are in use for calibration of the surface contamination meters. The customer can choose from them the radionuclides used for calibration. The calibration quantity is the surface emission rate.
Available radiation qualities:
Gamma, beta, alpha, neutrons (.pdf)
X-ray qualities (.pdf)
For meters intended for self-acting protection measures (e.g. housing companies' civil defence shelters), an inspection of the operating condition is usually sufficient instead of calibration. Detailed information about the inspection can be found in the Radiation and Nuclear Safety Authority Regulation on Measurements of Ionizing Radiation (STUK S/7/2021). An inspection certificate is issued for the meter.
In licensed practices, meters must often be calibrated, and an inspection of the operating condition is not an adequate measure. In the inspection, the meter reading is compared to a reference value in different measurement ranges and the linearity of the meter and alarm functions are checked. The inspection is performed using 137Cs gamma radiation.
Radon measuring instruments are used for integrated, continuous or spot measurements (for example, track-etch detectors, semiconductor detectors, ionization chambers and LUCAS chambers). The calibration of radon (222Rn) and thoron (220Rn) measuring instruments is performed by comparing the instrument reading with the known activity concentration of radon in the air (222Rn or 220Rn gas). Exposures of 222Rn of different lengths of time at the desired radon concentration (without calibration) can also be performed, for example, for alpha-track detectors.
In irradiation, the target is irradiated to a certain predetermined dose, and an irradiation certificate is issued for this. Irradiation can be performed with 137Cs, 60Co and 241Am gamma radiation sources and with ISO narrow-spectrum and ISO high air kerma rate (ISO4037:2019) x-ray qualities, as well as beta and neutron radiation sources.
Available radiation qualities:
Gamma, beta, alpha, neutrons (.pdf)
X-ray qualities (.pdf)
Calibrations and measurements can also be carried out at the place of use of radiation as agreed. Standardization tests of x-ray diagnostic equipment and irradiation of radiation meters, biological samples and electronic components are also carried out. These will be agreed separately with the customers.
Ordering and delivery of services
Services provided by the Radiation Metrology laboratory can be ordered by free-form email. The order must specify the following:
- the service to be ordered (calibration/testing/irradiation, radiation quality, quantity or a brief explanation of the radiation or equipment to be measured with the meter)
- customer’s contact information and invoicing information
- meter delivery and return method (brought and picked up, sent by post/courier)
- other relevant meter-related data
You can use this email to order:
[email protected]
Email link with order form: [email protected]
Please note that we do not usually adjust the meters.
The type and serial number of the meter must be identifiable and the meter must be in working order in accordance with the instructions for use.
The delivery time for calibration, inspection, testing and irradiation services is usually from one week to four weeks. A certificate or report is issued for the services (PDF). In addition, a sticker is affixed to the calibrated meter indicating the date of calibration and the number of the calibration certificate.
A fee is charged for the services according to STUK's valid service price list.
Delivery address for meters:
Radiation and Nuclear Safety Authority
Radiation Metrology laboratory
Jokiniemenkuja 1
01370 Vantaa, Finland