Equipment for Testing Measuring Devices at a Low-Level Radon Activity Concentration

Abstract

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.

Low-Level Radon Activity Concentration—A MetroRADON International Intercomparison

“…For the radon monitors comparison measurement, we used an infrastructure which enabled us to maintain the long-term stable radon atmosphere. In particular, the equipment consisted of an airtight low-level radon chamber (LLRCH), a humidifier, a flowthrough source of Rn-222 type RF 5 (Prague, Czech Republic), a mass flow controller of the Bronkhorst ® EL-Flow type (Bethlehem, PA, USA), an aerosol filter and an air pressure vessel as the source of radon-free air [6].…”

Approximate sequential Bayesian filtering to estimate 222Rn emanation from 226Ra sources using spectral time series

“…For the problem at hand, a stochastic differential equation (SDE) is needed to express the (time-varying) uncertainty associated with the latent continuous variable η (t). This can be seen as an application of the latent-force models introduced in Alvarez et al (2009), whose link with Bayesian filtering was previously established in and Hartikainen and Särkkä (2012). The specific choice of SDE is subjective but allows the properties of the resultant functions to be constrained, and can be used to encode prior knowledge (Särkkä and Solin, 2019).…”

“…The system is thus modeled to follow the combined SDE given in Eqs. ( 8)-( 11) in terms of the Itō stochastic integral (Särkkä and Solin, 2019;Hartikainen and Särkkä, 2012).…”

“…emitting 222 Rn) to be used to estimate the resulting activity concentration of 222 Rn in a closed volume, by measuring the activity of residual SLP in the source to quantify the 222 Rn emanation. In recent years, there has been a trend towards the use of dynamic calibration conditions for 222 Rn (e.g., Fialova et al, 2020), eliminating the need for the long build-up period associated with static conditions. However, it has been demonstrated that emanation from most materials demonstrates a strong dependence on humidity and temperature as a result of changes in diffusion properties (Janik et al, 2015; F. Mertes et al: Approximate sequential Bayesian filtering to estimate 222 Rn Stranden et al, 1984;Zhou et al, 2020), which generally results in a correlation between emanation and environmental parameters.…”

Development of 222Rn Emanation Sources with Integrated Quasi 2π Active Monitoring

“…Generally, state-of-the-art methods to quantify the 222 Rn emanation from solid sources (in a primary way, i.e., not using 222 Rn concentration measurement devices that require calibration) rely on measuring activity ratios of 226 Ra and the residual γ-ray emitting 222 Rn progeny, 214 Pb and 214 Bi, inside an emanation source to deduce the steady-state release of 222 Rn or, equivalently, a partitioning coefficient of 222 Rn between the free volume and the source volume [ 16 , 18 , 22 ]. The basis of this method is the conservation of the total amount of 222 Rn nuclei that are generated by the source, which can either emanate from the source or decay within the source, which is expressed by the following first order kinetics.…”