Radon mapping by retrospective measurements - an approach based on CDs/DVDs

Radon Exposure Assessment in Occupational and Environmental Settings: An Overview of Instruments and Methods

Radon is a naturally occurring noble radioactive gas that poses significant health risks, particularly lung cancer, due to its colorless, odorless, and tasteless nature, which makes detection challenging without formal testing. It is found in soil, rock, and water, and it infiltrates indoor environments, necessitating regulatory standards and guidelines from organizations such as the Environmental Protection Agency, the World Health Organization, and the Occupational Health and Safety Agency to mitigate exposure. In this paper, we present various methods and instruments for radon assessment in occupational and environmental settings. Discussion on long- and short-term monitoring, including grab sampling, radon dosimetry, and continuous real-time monitoring, is provided. The comparative analysis of detection techniques-active versus passive-is highlighted from real-time data and long-term exposure assessment, including advances in sensor technology, data processing, and public awareness, to improve radon exposure evaluation techniques.

Testing and Calibration of CDs as Radon Detectors at Highly Variable Radon Concentrations and Temperatures

The application of the compact disk (CD) method for radon measurements at mines, caves and other workplaces needs testing under highly variable exposure conditions. We present the results from a blind comparison of CDs exposed in the Laboratory of Natural Radiation (Saelices el Chico, Spain). During the exposure the temperature varied from 6.5 to 24.9 °C (average 12.6 °C) and the ²²²Rn activity concentrations varied from <10 Bq m⁻³ to 147 kBq m⁻³. Good correspondence was observed between the integrated ²²²Rn activity concentration determined by the reference instruments in the laboratory (122,500 ± 6100 kBq h m⁻³) and that assessed by analysis of the CDs at a depth 80 µm beneath the front surface (118,000 ± 12,000 kBq h m⁻³) and at a depth of 120 µm (106,000 ± 12,000 kBq h m⁻³). The theoretical modeling of the CD response under variable temperature and radon concentration suggested that the small bias is probably due to the time variation of the calibration factor because of the time variations of the temperature.

Identifying radon priority areas and dwellings with radon exceedances in Bulgaria using stored CD/DVDs

The implementation of the 2013/59/EURATOM directive in the part related to radon exposure imposes challenges for radon measurement methodology and radon survey design. Among them is the need to have estimates (preferably direct) of the annual average radon concentrations, which can be directly compared to the recommended reference levels. On this basis, the surveys should make possible the identification of dwellings with indoor radon above the reference levels and "radon priority areas" where significant proportion of the dwellings falls in this category. The performance of the CD/DVD method for radon measurements as a tool to address these issues is presented. A recent large scale field study based on the CD/DVD method that was carried out in the suburb area of Sofia, Bulgaria is described. Part of the studied area was affected in the past by the uranium mining and milling industry. In total 462 disks (CDs and DVDs) taken from 335 private dwellings from 10 districts in the region were analyzed. The results revealed the large heterogeneity in radon distribution in the area, with the percentage of dwellings with a ²²²Rn level above 300 Bq m^-3 ranking from about 7% to 74%. The district of Yana, for which this percent was 74, was identified as the area of highest radon priority in the region. The paper also discusses how prompt identification of dwellings with radon above the reference level by CD/DVDs can be incorporated within an integrated approach to the radon problem. Within this approach the radon hazard is identified shortly after the stakeholder's decision to test, which allows fast solution of the problem without waiting the long (and usually demotivating) one-year period needed for direct results by the commonly used prospective methods.

THE CD/DVD METHOD AS A TOOL FOR THE HEALTH PHYSICS SERVICE AND VENTILATION DIAGNOSTICS IN UNDERGROUND MINES

The CD/DVDs used as radon (222Rn) and thoron (220Rn) detectors can provide a sufficiently sensitive and cost-efficient option for passive radiation monitoring in underground mines. This note presents results of measurements made under real environmental conditions by CD/DVDs. Comparison with conventional diffusion chambers was made and good correspondence was observed. Correlation between 222Rn and 220Rn was studied by CD/DVDs and no signs for any correlation were observed. Dedicated study in a mine gallery showed that CD/DVDs can be successfully used for the purposes of ventilation diagnostics by identifying sources of air contaminated with radon.

Laboratory facility to create reference radon + thoron atmosphere under dynamic exposure conditions

Radon (²²²Rn) and thoron (²²⁰Rn) levels in the environment are typically subject to significant random and systematic variations. Creation in the laboratory of reproducible and controlled exposure conditions close to that in the real environment can be useful for testing ²²²Rn and ²²⁰Rn detectors and for research. In this report the design and performance of a novel laboratory facility with such functionality is presented. The facility allows the exposure of detectors under controlled dynamic as well as static activity concentrations of ²²²Rn and ²²⁰Rn (pure and mixed) and temperature. The temperature is measured and regulated within -15 °C ÷ +60 °C by a dedicated programmable thermostat. Different reference activity concentrations in the exposure vessel are made by regulating the flow-rate of the air that flushes ²²²Rn/²²⁰Rn activity from the sources towards the exposure vessel. Reference atmospheres that contain ²²²Rn, ²²⁰Rn or a specified ratio of the two can be created. Pilot experiments that demonstrate the feasibility of the approach are presented. They include follow-up of a pre-defined temperature profile (in the range -5 °C ÷ +35 °C), test of the correspondence between planned and measured ²²²Rn and ²²⁰Rn activity concentrations, follow-up of a pre-defined dynamic profile of ²²⁰Rn concentrations and test of the possibility to create mixed ²²⁰Rn/²²²Rn atmospheres (experimentally checked for ratio of the activity concentrations from 0.27 to 4.5). The results from the experimental tests are in agreement with the values obtained by the developed theoretical model. The proposed approach can be used to plan and create stationary and dynamic reference exposure conditions that are close to the real exposure regimes in the environment.

Energy-efficient reconstructions and indoor radon: the impact assessed by CDs/DVDs

Recent modelling suggests that the expense of energy-efficient building reconstructions can be the enhanced indoor radon levels and the related adverse health impact. Here we show that a couple of home-stored CDs/DVDs can be used to check by direct measurements whether a significant change in radon level occurred in the past after building reconstruction. Radon is continuously absorbed in the polycarbonate material of CDs/DVDs and its average concentration can be determined by etching alpha tracks at a certain depth in the disk. With two disks, one bought before and one after the reconstruction, a change in radon concentration can be detected retrospectively. Within a pilot study of 20 rooms in 16 buildings that underwent energy-efficient interventions years in the past, we observed significant increase in radon concentration (at 95% confidence level) in 35% of the cases, and no case with significant decrease. Direct indication of a radon problem emerged after some of the energy-efficient building interventions was observed. The CD/DVD based approach provides a tool for assessment of the effect of different energy-efficient reconstruction approaches on indoor radon in very short terms and could be useful for finding radon-safe energy-efficient options.

Application of polystyrene films for indoor radon dosimetry as SSNTD

In this study, the sensitivities and calibration factors of polystyrene (PS) to (220)Rn and (222)Rn have been investigated. The sensitivity of compact disks (CD/DVD) as thick polycarbonates (PC) to (220)Rn and (222)Rn has been also obtained by applying a new etching condition. Five different brands of X-ray radiology and MRI films with polystyrene base and four brands of CD/DVDs have been studied to assess their applicability as a passive detector for indoor radon monitoring. The comparison between the sensitivities of PS samples, CD/DVDs (as thick PC) and Lexan PC to (222)Rn and (220)Rn shows an improved sensitivity of PS over conventional PC currently being used as solid state nuclear track detectors (SSNTD). The sensitivity of X-ray radiology PS films to (222)Rn and (220)Rn was found to be 8.77±0.591 and 0.028±0.006 (cm(-2)kBq(-1)d(-1)m(3)). The sensitivities of MRI PS films to Rn-222 and Rn-220 was found to be 12.2±1.25 and 0.360±0.090 (cm(-2)kBq(-1)d(-1)m(3)). The CD/DVD PC found to have a sensitivity of 0.178±0.013 and 0.0024±0.00013 (cm(-2)kBq(-1)d(-1)m(3)) to (222)Rn and (220)Rn respectively.

Retrospective measurements of thoron and radon by CDs/DVDs: a model approach

An approach for retrospective measurements of thoron ((220)Rn) and radon ((222)Rn) by home-stored CDs/DVDs is proposed. It employs analysis of alpha tracks at two depths beneath the disk surface. The signal in the first one (69 µm) is due both to (220)Rn and (222)Rn, while the signal at the second (80 µm) is due only to (222)Rn. The second signal is used as to measure (222)Rn, as well as to determine and subtract 'the (222)Rn component' from the first signal. The remaining '(220)Rn component' is used to measure thoron. Numerical modelling is performed and the results show that simultaneous retrospective measurements of thoron and radon are possible over a wide range of environmental concentrations.

Logistic of surveys of retrospective radon concentrations by home-stored CDs/DVDs

Recently, a method for rather precise retrospective (222)Rn measurements, based on home-stored compact disks (CDs)/DVDs, has demonstrated a promising potential for wide application. In Bulgaria, pilot surveys have been initiated based on voluntarily provided CDs/DVDs. The results showed that large-scale surveys could be efficiently organised. However, several problems were identified and are discussed in the report. The first is the relatively small proportion of participants (30-50 %) that actually provided disks. Other addressed topics include the compatibility between results of different disks from one place, the accuracy of dating CDs/DVDs and the possibility for individual a posteriori calibration of each disk. The possibility to follow year-to-year variations by disks of different age is also discussed.