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Radon Calibration Laboratory

  • The Federal Office for Radiation Protection (BfS) operates an accredited calibration laboratory for quality assurance of radon and radon progeny measurements.
  • Beside calibrations the laboratory offers type tests and comparison tests for measurement devices. Furthermore, it carries out scientific investigations on the metrological background, evaluation and improvement of measuring methods.

Radon Calibration Laboratory

Head

Dr. Udo Gerstmann, Sebastian Feige

Technical laboratory management

Dr. Martin Dubslaff

Quality Management Representative

Dr. Felice Friedrich-Kees

Address

Bundesamt für Strahlenschutz
Radon-Kalibrierlaboratorium UR 1
Köpenicker Allee 120-130
10318 Berlin
Deutschland

Contact by e-mail

cal-radon@bfs.de

Reliable statements on radon and radon progeny concentrations are only possible on the basis of measurements. These measurements require a high quality in performance and evaluation, especially when they are used to compare them with each other. In that regard, measurement devices shall be calibrated periodically.

During calibration the measured value of the instrument to be calibrated is compared to the measured value of a reference measurement instrument (standard). The aim is to determine the deviation from the standard and the uncertainty of this deviation. Thus, the calibration of the measurement instrument can be traced back to the national primary standard via a chain of standards.

BfS Radon Calibration Laboratory

The Radon Calibration Laboratory for devices determining the exposure to radon and radon progenies is an essential element for assuring the quality of measurements in the field of radiation protection. It is part of the BfS Coordinating Office for the Monitoring of Elevated Natural Radioactivity in Berlin.

The calibration laboratory is the recognized metrological reference for

Quality assurance

Radon calibrating laboratory Radon calibrating laboratory with stainless steel containers0.4-cubic-metre stainless-steel containers in the Radon Calibration Laboratory with computer-controlled measuring and dosage system

Besides the calibration of measurement devices an extensive program for quality assurance is performed to ensure a national quality standard for the measurement of radon and radon progenies. The program is focused on

  • measuring bodies, which are appointed by the competent authority, and bodies for the measurement of radon at workplaces, which are recognised by the BfS,
  • users offering a regular calibration service of measurement devices, and
  • device manufacturers to evaluate the metrological properties conformity of their measurement devices with international stated normative requirements.

An interlaboratory comparison and proficiency testing is operated regularly for exposimeter (integrating non-electronic measuring instruments (also callt passive radon monitors).

The offers for quality assurance of measurements of radon-222 and radon-222-progenies are used by both national and international laboratories and institutions.

Technique and equipmentShow / Hide

The Calibration Laboratory is accredited according to norm DIN EN ISO/IEC 17025 at the German Accreditation Body (DAkkS GmbH) for the measurands activity concentration of radon-222 in air (CRn) and potential alpha-energy concentration (PAEC) of the short-lived radon-222 progenies (PAEC). These measurands are traceable to national primary standards at national metrology institutes, for instance Physikalisch-Technische Bundesanstalt PTB.

The Radon Calibration Laboratory consists of the following areas:

  • Laboratory for the measurand activity concentration of radon-222 in air,
  • Laboratory for the measurand potential alpha-energy concentration of the short-lived radon-222 progenies, and
  • Physical-technical laboratories.
Radon atmospheres

For the calibration of measurement devices as well as scientific and technical investigations radon-222 atmospheres are generated and characterised by reference measurements. For this pupose several stainless steel containers can be used with volumes of

  • 0.4 cubic metres,
  • 11 cubic metres ("Radon chamber" with climate control) and
  • 30 cubic metres ("PAEC chamber" with both climate and aerosols control as well).

Another calibration container is used for setting up the reference atmosphere. It features a certified volume of 0.17 cubic metres and is operated with radon-222 activity standards in order to ensure the traceability of the measurand "activity concentration of radon-222 in air".

Calibration of radon measurement devicesShow / Hide

The activity concentration of radon-222 in the calibration containers is adjusted to a pre-determined value by a single injection of radon-222 gas. A computer-controlled dosage system compensates the natural decay continuously. Thus the radon activity concentration can be kept constant.

Part of the Calibration Service Laboratory with PAEC chamber Calibration Service Laboratory with PAECView of Calibration Chamber for "Potential Alpha Energy Concentration of Short-lived Radon 222 Derivative Products" (PAEC) with facilities for metering and measuring aerosols.

Reference measurement and ambient conditions

The radon-222 activity concentration as well as the climate parameters (temperature, relative humidity and air pressure) are monitored continuously. Additionally, manual sampling can be performed for each radon atmosphere. The measurement results of several measurement methods are compared for quality assurance.

All measurement values obtained during the tests are recorded. Thus, the repeatability and traceability are ensured.

Traceability and measurement uncertainty

The measurand activity concentration of radon-222 is traceable to national standards via a radon-222 activity standard and a certified volume. The best measurement uncertainties in calibrations are given in the annex of the accreditation certificate.

Calibration of devices measuring radon-222 progeniesShow / Hide

The calibration of measurement devices for radon-222 progenies is technical more sophisticated than those of radon gas measurement devices. A variety of additional parameters that influence the measurement of short-lived progenies have to be accounted for and monitored including:

  • Particle concentration and particle size distribution of the aerosol,
  • Relation between the aerosol-attached part and the unattached part of the short-lived progenies,
  • Temperature, relative humidity, and air pressure,
  • Flow velocity and degree of turbulence of the air in the chamber, and
  • Measuring position within the chamber.

The calibration of devices measuring radon progenies is conducted in a chamber with a large volume of 30 cubic meters. This provides a suitable surface to volume ratio to reduce the influence of interfering parameters like adsorption to the chamber surface. Thus, the homogeneity of the reference conditions within the chamber volume is ensured.

Technical equipment

All relevant parameters are detected by sensors and logged automatically for calibration and quality assurance purposes. Furthermore, the parameters of the radon-222 progeny atmosphere can be adjusted and/or kept constant during the calibration process. The following technical facilities are used:

  • Aerosol generators with different principles of operation and particle size distribution,
  • Device for dosing aerosols continuously,
  • Flow-through source containing radium-226 for continuous compensation of radon-222 losses due to radioactive decay,
  • Cleaning circuit to reduce the aerosol concentration,
  • In-wall heating and cooling elements, and
  • Adjustable fan assembly.
Main measurement parameters and their range of adjustment
Measurement parameterRange of adjustment
Radon-222 activity concentration50 to 50,000 becquerel per cubic metre
Potential alpha-energy concentration of the short-lived radon-222 progenies (PAEC)0.3 to 150 Micro-Joule per cubic metre
Particle concentration of the aerosol200 to 50,000 particles per cubic centimetre
Equilibrium factor0.1 to 0.9
Unattached fraction of PAEC1 to 60 per cent
Air temperature-2 to 40 degrees Celsius
Relative humidity10 to 95 per cent
Air pressureAtmospheric pressure (not adjustable)
Air flow (turbulence)0 to 1 metre per second

Radon progeny measurement devices are calibrated for the measurand potential alpha-energy concentration of the short-lived radon-222 progenies. This requires the determination of the activity concentrations of these progenies in the reference atmosphere, respectively.

Application of the combined mesh-filter probe

For this purpose the air of the radon-222 progeny atmosphere is conveyed with a constant volume flow rate through a combined mesh-filter probe. The fraction of the short-lived radon-222 progeniesa, which are attached to aerosols, are deposited to the filter. The free (unattached) fraction is adsorbed to the wire mesh.

The radon progenies collected at the filter and the mesh, respectively, decay according to the natural law of radioactive decay and emit alpha particles. The activities of the alpha-emitting nuclides are determined in periodic time intervals with corresponding detectors. The associated graphic representation is denominated as decay curve.

Immediately after sampling the decay curves of the alpha radiation on filter and mesh are measured, respectively. An algorithm is used to deduce the potential alpha-energy concentration and unattached part of the short-lived radon-222 progenies.

Traceability and measurement uncertainties

The measurand potential alpha-energy concentration of the short-lived radon-222 progenies is traceable to the national standard of the German National Metrology Institute Physikalisch-Technische Bundesanstalt (PTB) via a radium-226 source.

PublicationsShow / Hide

Improvement of methods

The quality assurance program ensures a constant striving for the further development of methods. Scientific investigations are performed in regard to metrological basics as well as to the evaluation and development of measurement methods.

This is to provide the ability to act promptly on current issues.

BfS service: quality assurance of radon measurement devices and devices measuring radon progenies

The BfS Radon Calibration Laboratory offers the following:

  • Calibration of measurement devices measuring radon-222 and its short-lived progenies for the mearesurands activity concentration of radon-222 in air and potential alpha energy concentration of the short-lived radon-222 progenies in air,
  • Calibration of passive, integrating radon-222 measurement devices,
  • Testing of metrological properties of measurement devices and methods.

Calibration of electronic radon-222 measurement devices and its short-lived progeniesShow / Hide

The Radon Calibration Laboratory of the Federal Office for Radiation Protection is accredited according to DIN EN ISO/IEC 17025 by the Deutsche Akkreditierungsstelle (DAkkS) for the calibration of devices measuring

  • the activity concentration of radon-222 in air (CRn)
  • the potential alpha energy concentration of the short-lived radon-222 progenies (polonium-218; lead-214; bismuth-214) in air (Cp).

The measurands are traced back to the national standards. The best measurement uncertainties for calibrations are indicated in annex of the accreditation certificate.

For calibration the measurement instrument is exposed to a radon-222 atmosphere with defined values of the measurand as well as potentially influencing factors. The indication of the calibration object is compared to the reference value.

The costs for calibration services are charged according to the list of fees and charges.

Calibration exposure of measurements systems for radon-222 based on exposimetersShow / Hide

The integrating non-electronic measurement devices (exposmeters, also known as passive radon measurements instruments) are exposed to a radon-222 atmosphere within a container for a certain time. The radon-222 activity concentration is tyically adjusted to values within the range of 0.4 to 12 kilobecquerel per cubic metre and aimed to be constant.

  • Measurement range: 30 to 20,000 kilobecquerels per cubic metre multiplied by the number of hours
  • Best measurement uncertainty of the reference measurement (2σ, standard uncertainty multiplied with a coverage factor k=2): ± 5 per cent

The costs for calibration exposure services will be charged according to the list of fees and charges. If the exposure is performed for a legally required proficiency testing, fees are charged, too.

Testing of the metrological properties of measurement systemsShow / Hide

Investigations of radon-222 and radon-222 progeny measurement system properties influence of external parameters on the displayed values and testing of measurement methods will be conducted upon request.

Costs will be charged according to the time involved.

State of 2023.07.26

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