The National Institute for Nuclear, Biological, and Chemical Protection, under the European project 16ENV10 MetroRADON (the European metrology program for innovation and research, EMPIR), has developed unique equipment for the testing of measuring devices at low-level radon activity concentrations. The equipment consists particularly of an airtight low-level radon chamber (LLRCH) with an inner volume of 324 liters; a Rn-222 type RF 5 flow-through source with a Ra-226 activity of 4.955 kBq developed by Czech Metrological Institute within the above-mentioned project; and a pressure vessel as a radon-free air source. The mass flow controller of the Bronkhorst EL-Flow type is a part of the apparatus and ensures the requested airflow through the radon source—partialized if necessary—through the chamber. The homogeneity of the atmosphere in the chamber is ensured by means of a continuously regulated fan (airflows in the range of 0.1–3.5 m·s⁻¹ can be established). Another important chamber component is the measuring device of climatic conditions, since temperature, air pressure, and relative humidity must be determined. The construction of the equipment allows the time-stable radon activity concentration to be maintained at a precise level for several days. Radon concentration values can be arbitrarily and continuously set in the range from 100 Bq·m⁻³ to 300 Bq·m⁻³.

An interlaboratory comparison for European radon calibration facilities was conducted to evaluate the establishment of a harmonized quality level for the activity concentration of radon in air and to demonstrate the performance of the facilities when calibrating measurement instruments for radon. Fifteen calibration facilities from 13 different European countries participated. They represented different levels in the metrological hierarchy: national metrology institutes and designated institutes, national authorities for radiation protection and participants from universities. The interlaboratory comparison was conducted by the German Federal Office for Radiation Protection (BfS) and took place from 2018 to 2020. Participants were requested to measure radon in atmospheres of their own facilities according to their own procedures and requirements for metrological traceability. A measurement device with suitable properties was used to determine the comparison values. The results of the comparison showed that the radon activity concentrations that were determined by European calibration facilities complying with metrological traceability requirements were consistent with each other and had common mean values. The deviations from these values were normally distributed. The range of variation of the common mean value was a measure of the degree of agreement between the participants. For exposures above 1000 Bq/m³, the variation was about 4% for a level of confidence of approximately 95% $\left(k=2\right)$. For lower exposure levels, the variation increased to about 6%.

At least 10 % of inhabitants in the Czech Republic are supplied with water from private sources (private wells, boreholes). With the increasing cost of water, the number of people using their own sources of drinking water will be likely to increase. According to the Decree of the State Office for Nuclear Safety about the Radiation Protection 307/2002 as amended by Decree 499/2005, the guideline limit for the supplied drinking water (‘drinking water for public supply’) for radon concentration is 50 Bq·l⁻¹. This guideline does not apply to private sources of drinking water. Radon in water influences human health by ingestion and also by inhalation when radon is released from water during showering and cooking. This paper presents results of measurements of radon concentrations in water from private wells in more than 300 cases. The gross concentration of alpha-emitting radionuclides and the concentrations of radium and uranium were also determined.

A collection of personal protective equipment (PPE), suitable for use in case of accident in nuclear facilities or radiological emergencies, was gathered at the National Institute for Nuclear, Chemical and Biological Protection, Czech Republic. The shielding characteristics of the various PPE materials were measured via narrow geometry spectral attenuation measurements with point radionuclide sources covering a broad range of photon energies. Photon relative penetration and attenuation for relevant energies of the spectra were the principal experimentally determined quantities for tested PPE. Monte Carlo simulations in the MCNPX™ code were carried out to determine photon attenuation for respective energies in the tested PPE, and the results were compared to those determined experimentally. Energy depositions in a unit volume of an ORNL phantom were simulated in a radioactive aerosols atmospheric environment to determine effective doses both for the whole body and in various organs in the human torso during exposure to different dispersed radioactive aerosols while wearing one of the PPE protecting against X- and gamma-ray. This work aimed to determine the effective dose and its decrease for individual PPE protecting against X- and gamma-ray.

Knowledge of the active size distribution of radon daughters is one of the main parameters for determining the effective dose from inhalation of short-term radon decay products. However, this parameter is crucial for accurately determining an effective dose; there are currently very limited possibilities for determining it. This paper describes the laboratory validation of a method for determining the activity size distribution of radon decay products using the Dekati ELPI+ cascade impactor and the Graded Screen Array Diffusion Battery (GSA DB). Using nuclear track detectors placed on individual impaction plates of the cascade impactor, the equivalent equilibrium activity concentration of individual size classes can be determined in the range from 17 nm to 10 μm. A diffusion battery was used to detect smaller particles in the unattached fraction area. The presented method can further refine the knowledge of the activity size distribution of radon decay products in different types of workplace atmospheres. Workplaces with higher radon concentrations differ significantly in the size distribution of aerosol particles, radon activity concentration, and equilibrium equivalent activity concentration.