Short-lived Progeny Research Articles

A review of radiation doses and associated parameters in Western Australian mining operations (2020-23)

Government policies have stimulated the Western Australian (WA) mining industry to position itself as a significant global supplier of critical minerals, including lithium and rare earths. In WA the lithology that supports these minerals is often associated with elevated concentrations of naturally occurring radioactive materials (NORMs) and the increase in the number of mining operations pursuing the minerals has witnessed a commensurate increase in the number of workers potentially exposed to the radiation emitted from the NORMs. The regulatory framework for radiation protection in WA mining operations underwent significant change with the implementation of the Work Health and Safety Act 2020 and Work Health and Safety (Mines) Regulations 2022 which both came into effect on the 31 of March 2022. Under the new framework mining operations identified as having workers who were likely to receive annual effective doses (EDs) from NORMS above one mSvy-1are referenced asrelevant mines (RM). RMs are required to submit an annual report of the estimates of EDs)received by their workforce to the mining regulatory authority (WorkSafe WA: Mines Safety). This research provides an overview of the new legislative framework and updates the information in Ralph and Cattani (2022J. Radiol. Prot.42012501) to include data derived from annual occupational EDs submitted by RMs in the three-year period spanning 2020-21, 2021-22 and 2022-23. In 2022-23, 38 mining operations were identified as RMs, an increase of ten from 2021-22 which in turn had increased by six from the 2020-21 reporting period. The mean annual ED reported for the three-year period was 1.0 mSv, the level at which regulatory intervention should be considered. The maximum ED was 4.9 mSv, just below the threshold of 5 mSv above which exposed workers are considered Designated Workers and are subject to focused monitoring. The collective effective annual dose of the mine worker population reached an historical maximum of 2339 man mSv in 2022-23. Analysis of the three main exposure pathways confirms that inhalation of long-lived alpha emitting radionuclides in dust remains the most significant contributor to worker EDs. Inhalation of radon-222 and radon-220 and their short-lived progeny, once considered as a negligible contributor to worker annual EDs is the second most significant exposure pathway. A declining trend in the number of samples collected per worker is highlighted as requiring remediation to provide confidence in the reported annual EDs. The transition to the new legislative framework for radiation protection in mines has been supported by the publication of guidance materials which have been widely endorsed by the industry.

Activity concentration of indoor radon and its short-lived progeny (218Po, 214Pb, and 214Po) and their effect on atmospheric ionization rate in Sana'a, Yemen

Exposure to ionizing radiation inside houses, especially radionuclides of radon and its progeny, poses serious health risks that can be exacerbated when inhaled as a result of interaction with human lung tissue. Also, air ionization is mainly due to these radionuclides. Therefore, accurate measurements of radon activity concentrations and its short-lived progeny are required to assess dose and environmental pollution and estimate ionization rates in indoor environments. For this purpose, we employed a previously tested and approved reliable method, following the three-count procedure. This method is based on airborne radon progeny sampling on polycarbonate membrane filters and alpha counting using a passive α-dosimetry technique with CR-39 detectors. The method also relies on a PC-based software we developed for solving mathematical equations and calculating all the necessary physical quantities. In this study, the concentrations of radon and individual short-lived radon progeny were measured in 20 houses in Sana'a, Yemen. Measurement conditions and meteorological variables were considered. The average activity concentrations of 222Rn, Equilibrium-Equivalent Concentration (EEC), 218Po, 214 Pb, and 214Po were 73.1 ± 6.0, 29.2 ± 2.4, 44.4 ± 3.6, 30.5 ± 2.5, and 23.2 ± 1.9 Bq.m-3, respectively. The calculated average unattached fractions f1(218Po), f2(214 Pb), and fp were found to be 0.24, 0.04, and 0.07 % respectively. The annual average values of ion-pair production rate caused by 222Rn and their progeny and air ion concentration, were 27.25 ions.cm-3s-1 and 1829 ions.cm-3 respectively. The annual effective dose was estimated to be 1.93 ± 0.16 mSv.y−1, well lower than the recommended 10 mSv.y−1.

Timescale of radium and alkaline earth cations ascent in the trees: Use of isotopic (228Ra/226Ra) ratio

Due to its short-lived progeny, including gaseous radon isotopes that can be inhaled and its significant transfer into vegetation, radium poses a substantial concern in radiation risk assessment. Although the transfer of Ra from soil to plants has been previously documented, the distribution and speciation of radium within the plant tissues, particularly within trees, remain unclear. The temporal dimension of Ra transfer is also poorly known. Therefore, the transfer of radium and others alkaline earth cations in beech trees was investigated through the analysis of fine (<2 mm) roots and leaves corresponding to tree organs with a life cycle limited to one season. This study was conducted at the experimental Montiers (INRAE-Andra site, France) and Strengbach watershed (OHGE site, France) beech-forested site. The activity of 226Ra and the isotopic ratio (228Ra/226Ra) were measured in roots and leaves using gamma spectrometry. Additionally, the concentration of alkaline earth cations (Mg, Ca, Sr, and Ba) was measured, to better constraint the mechanism of alkaline earth cation transfer through the xylem. The retention of these cations within the trees increases with the mass of the element, following the order Mg < Ca < Sr ≈ Ba < Ra, i.e.: light alkaline earth cations are more efficiently transferred from roots to leaves than heavy one. Our results suggest that these cations maintain their hydration shell during their ascent in stems and a low pH ion-exchange process rather than a complexation process with carboxylic group occurs.The decay of the (228Ra/226Ra) isotopic ratio over time during transfer within the trees allows us to quantify the slow Ra translocation from roots to the leaves, ranging from 1 to more than 16 years. This duration increases with the age of the trees. Hence, radioactive decay of Ra provides particularly valuable timescale information that is usually difficult to assess for Ca or other alkaline earth cations.

Estimation of Radon/Thoron and their progeny concentration in some dwellings and exhalation rates from soils of Samana city, Patiala

The study of indoor pollutants and radioactive nuclides imposes importance on human health as we spend most of our time indoors. Out of all the natural radioactive elements, Radon-222 and Radon220 are present in large abundance indoors. Both are radioactive and decay to various short-lived progenies by emitting high-energy alpha particles, so inhalation of such gases can harm the human body in various ways. In the present report, the concentration of Rn-222 and Rn-220 and its progenies are estimated from some dwellings of Samana city of Patiala district, Punjab. Pin-hole dosimeters with DRPS and DTPS were employed in 15 houses in the study area to measure indoor Rn-222 and Rn-220 concentrations. The concentration of Rn-222 ranges between 401.96 Bq/m3 and 27.36 Bq/m3 with mean value of 138.82 Bq/m3, and the concentration of Rn-220 varies from 222.2 Bq/ m3 to 50 Bq/m3 with the mean weight of 131.12 Bq/m3. The average inhalation dose was also calculated from the results and was found to have an average value of 2.19 mSv per year. The average weight of radon concentration was below the ICRP recommendation of 200-300 Bq/m3 but the value is above these limits at some locations. Radon and thoron emission rates from soil samples near to the dwellings was also calculated.

Behavior of 222Rn, 220Rn and their progenies along a daily cycle for different meteorological situations: Implications on atmospheric aerosol residence times and Rn daughters' equilibrium factors

The correct assessment of the radiological hazard from radon and daughters, external and internal doses, residence times and equilibrium factors, implies the need to properly determine 222Rn (radon), 220Rn (thoron) and their respective short-lived progenies (214Pb and 214Bi, and 212Pb and 212Bi, respectively), where the precise measurements of both progenies are quite complex due to their very short half-lives. In addition, it is important to study the temporal behavior of all these radionuclides along daily cycles. Therefore, the aim of this study was to analyze the temporal evolution of radon, thoron and their progenies, and of their activity ratios along daily cycles for two different meteorological situations (synoptic and mesoscale processes). Radon and thoron were measured using a radon monitoring system, while their respective progenies were collected onto atmospheric filters using an ASS-500 sampler, and then measured by gamma-ray spectrometry. Furthermore, the different relationships between the concentrations of radionuclides and the different meteorological variables of interest (temperature, ABL height, and speed and direction of the wind) were found. Finally, the atmospheric aerosol residence times and Rn daughters’ equilibrium factors were estimated for each sampling carried out along the two daily cycles, finding results consistent with previous studies.

Experimental Setups for In Vitro Studies on Radon Exposure in Mammalian Cells-A Critical Overview.

Naturally occurring radon and its short lived progeny are the second leading cause of lung cancer after smoking, and the main risk factor for non-smokers. The radon progeny, mainly Polonium-218 (218Po) and Polonium-214 (214Po), are responsible for the highest dose deposition in the bronchial epithelium via alpha-decay. These alpha-particles release a large amount of energy over a short penetration range, which results in severe and complex DNA damage. In order to unravel the underlying biological mechanisms which are triggered by this complex DNA damage and eventually give rise to carcinogenesis, in vitro radiobiology experiments on mammalian cells have been performed using radon exposure setups, or radon analogues, which mimic alpha-particle exposure. This review provides an overview of the different experimental setups, which have been developed and used over the past decades for in vitro radon experiments. In order to guarantee reliable results, the design and dosimetry of these setups require careful consideration, which will be emphasized in this work. Results of these in vitro experiments, particularly on bronchial epithelial cells, can provide valuable information on biomarkers, which can assist to identify exposures, as well as to study the effects of localized high dose depositions and the heterogeneous dose distribution of radon.

Influence of Dose Conversions, Equilibrium Factors, and Unattached Fractions on Radon Risk Assessment in Operating and Show Underground Mines.

This paper compares the results of measurements taken in the underground workings of active and tourist mines. In these facilities, the aerosol size distributions of ambient aerosols at key workplaces and the distributions of radioactive aerosols containing radon decay products were determined. Based on these studies, dose conversions used for dose assessment and unattached fractions were determined. In addition, radon activity concentrations and potential alpha energy concentrations of short-lived progeny were also measured in the mines to determine the equilibrium factor. The dose conversions varied between 2-7 mSv/(mJ × h × m-3). The unattached fraction measured in active coal mines ranged from 0.01-0.23, in tourist mines from 0.09-0.44, and in the tourist cave it was 0.43. The results showed significant discrepancies between the effective doses determined from current recommendations and legal regulations and those determined from direct measurements of parameters affecting exposure.

History of Radon Research

The original research is created out of the learning of history. Radon research has been performed from the beginnings of 20 century, right after discovery of uranium radioactivity. In this review, the history of radon research in atmosphere in the period from the beginnings to 1980s was mainly described at the viewpoint of health physics (health effects) including measuring methods, properties of radon short-lived progeny and the dose estimation. Radon in the uranium mine air and in water of the spa has been described a little. Radon long-lived progeny, thoron (radon-220) and thoron progeny were not described excluding something in connection with radon-222, and actinon (radon-219) was not mentioned at all.

Environmental Gamma Dose Rate Monitoring and Radon Correlations: Evidence and Potential Applications

Gamma emitting radionuclides naturally present in the Earth’s crust and the radon exhaled by soil in the atmosphere with its short-lived progeny are two of the main contributors to the environmental gamma dose rate that typically characterizes an outdoor measurement site. The present work aims to investigate variations in the environmental dose-rate time series originated by different natural phenomena, such as weather and seismic events, which can modify the radon concentration in the air. The data analyzed here were acquired over a five-year period using a Reuter–Stokes high-pressure ionization chamber placed in the ENEA Casaccia Research Center (Rome, Italy), from November 2013 to December 2018. The detector was set to take a single measurement of the equivalent ambient dose H*(10) every 15 min, thereby collecting more than 184,000 values over the five-year period under consideration. The detector’s sensitivity to the short-lived radon progeny was verified in a preparatory study performed by means of simultaneous radon flux measurement on field. Variations induced by meteorological events as well as variations potentially induced by seismic events were investigated by implementing different data analysis techniques. In the latter case, a retrospective preliminary study was conducted, applying the ARFIMA class of models in order to test the method’s potential. The analysis techniques, results and potential applications are presented and discussed in this article.

A straightforward approach for assessing the effectiveness of membrane materials as radon (222Rn) barriers

ABSTRACT The ubiquitous presence of the radioisotope radon (222Rn) and its short-lived progeny (218Po, 214Pb, 214Bi, 214Po) is challenging in two respects: (i) Radon is a major issue regarding health-related problems due to potentially elevated radiation exposure of humans in dwellings, and (ii) due to the mobility of radon the short-lived progeny may cause complications in radionuclide detection in laboratories. Polymer membranes are an appropriate means for effectively preventing unwanted radon migration. However, most of the published literature focusses on robust membranes made for the large-scale sealing of dwelling substructures. Membranes that are suitable (at small-scale) for sealing purposes in radionuclide detection applications are only rarely discussed. In this paper, we present a straightforward practical approach that allows the effectiveness of any membrane to be assessed for any purpose related to radon sealing. Executing the approach requires only (i) a suitable container with inlet and outlet ports, (ii) a mobile radon detector, and (iii) any type of radon source material. The approach provides a tool that allows testing any available membrane for its applicability as radon barrier sheeting.

MEASUREMENT OF RADON CONCENTRATION IN SOIL SAMPLES OF MAZAT AND KAFI-HABU MINING SITES, PLATEAU, NIGERIA

Radon and its short-lived progenies contributed significantly to natural background radiation. Long-term exposure to such radiation increases the probability of lung cancer to persons. To assess the radiological hazards associated with the inhalation of radon gas from ore dust in Mazat and Kafi-Habu mining sites of Plateau, Nigeria, 12 soil samples from an abandoned tailing dump ground were collected and analysed for radon using RAD-7 electronic detector. The dose rate of each sampling point was directly measured using RADOS RDS -120 portable survey meter. The results gave a mean radon concentration ranging from 771.51 ± 21.9 Bq/m3 to 5666.13 ± 28.8 Bq/m3 with 3451.13 ± 42.9 Bq/m3as the average value for all measurements. The average concentration of measurements from Mazat and Kafi-Habu is 3671.6 ± 41.2 Bq/m3 and 3010.16 ± 46.5 Bq/m3 respectively. The average values obtained from the analysis are significantly higher than the upper limit of 300 Bq/m3 set by the International Commission on Radiological Protection (ICRP) suggesting quick remediation on the host communities. The geometrical mean value of Dose Rate (DR) and Annual Effective Dose Equivalent (AEDE) were 870 nGy/hr and 1.04 mSv/yr respectively. Again, these values are above the global average limits of 59 nGy/hr and 1 mSv/yr. The result indicates that miners working in those sites and dwellers of the study areas are at higher risk of getting exposed to radon and need to employ protective measures. This work is useful in monitoring and control of radon level for the on-site workers and the

Radioactive Thoron 220Rn Exhalation From Unfired Mud Building Material Into Room Air of Earthen Dwellings

Thoron (220Rn), an isotope of radon with a strong α-decay energy, and its short-lived metallic progeny can pose an elevated lung cancer hazard in room air when unfired-soil derived building materials are used in earthen dwellings. Changes in moisture content and density influencing the thoron exhalation rate from earthen materials into room air were studied in the laboratory with terra rossa from a village on the Ðồng Văn Karst Plateau Geopark, Việt Nam, where ethnic minorities construct traditional dwellings with unfired terra rossa walls and floors. Our results show that the thoron exhalation rate from mud surfaces depends on (i) the content of radioactive parental nuclides in mineral components; (ii) the moisture content of mud where ∼5–10 weight % water maximizes the 220Rn exhalation rate; and (iii) the density of dry mud as primarily controlled by internal macroscopic voids, fractures, and porosity. Additional time-series of 220Rn exhalation data from an interior mud wall of a terra rossa-built house under different seasonal and weather conditions show that the temperature is influencing thoron exhalation via the water vapor pressure deficit (VPD) in air and the associated amount of atmospheric moisture adsorbed onto indoor mud surfaces. Our data suggest that occupants of “mud house” earthen dwellings in northern Việt Nam are exposed to an increased thoron geohazard during cooler weather, low VPD, and high relative humidity in air. Detailed studies are needed to evaluate the thoron geohazard for inhabitants of mud-built dwellings in other climates and geological terrains.

Investigating the detection of underground nuclear explosions by radon displacement

A novel approach is proposed to detect underground nuclear explosions (UNEs) through the displacement of natural radon isotopes (222Rn and 220Rn). Following an explosion, it is hypothesized that the disturbance and pressurization of the sub-surface would facilitate the movement of radon from the depth of the UNE towards the surface resulting in increased soil gas activity. The resulting signal may be magnified by a factor of 2.0–4.9 by the decay of radon to its short-lived progeny. Increases in background activity may be useful for identifying locations to perform additional measurements, or as a detectable signal at monitoring stations. To validate this hypothesis, radon detection instrumentation was deployed at the Dry Alluvium Geology (DAG) site of the Source Physics Experiment (SPE) at the Nevada National Security Site (NNSS). Natural fluctuations in the soil gas activity due to barometric pumping, and the lower yield of the chemical explosions (1–50 t) made it difficult to confirm a displacement of radon from the explosions, and further study to validate the proposed hypothesis is recommended.

Modeling of the Distribution of Radon and Its Decay in a Traditional Hammam: Dose to Adult Members of the Public

Radon and its descendants are the main causes of lung cancer in non-smokers. Therefore, the study of the behavior of radon and its descendants in indoor air is of the highest importance, in ordre to limit the risk of radiation dose due to inhalation of indoor air by members of the public. This article focuses to study the effect of meteorological parameters on the concentration and distribution of radon and its descendants inside a traditional Hammam by using CFD simulation. The results of modeling are qualitative and show that the concentration and distribution of radon and its descendants decrease when the ventilation rate increases, as well as, as the temperature increases; however, it increases with the increase relative humidity. Moreover, the committed equivalent doses due to ²¹⁸Po and ²¹⁴Po radon short-lived progeny were evaluated in different tissues of the respiratory tract of the members of the public from the inhalation of air inside the traditional Hammam. The influence of the activity of ²¹⁸Po and ²¹⁴Po and mass of the tissue on the committed equivalent doses per hour of exposure was investigated. The annual effective dose due to radon short-lived progeny from the inhalation of air inside the traditional Hammam by the members of the public was investigated.

Alpha Spectrometry of Radon Short-Lived Progeny in Drinking Water and Assessment of the Public Effective Dose: Results from the Cilento Area, Province of Salerno, Southern Italy.

Radon is a naturally occurring radioactive gas present in the hydrosphere, lithosphere and atmosphere abundantly. Its ionizing radiation provides the largest human internal exposure by inhalation and ingestion to natural sources, constituting a serious health hazard. The contribution to total exposure is mainly due to inhalation, as ingestion by food or drinking water is typically very small. However, because of public health concerns, the contributions from all these sources are limited by regulations and remedial action should be taken in the event that the defined threshold values are overcome. In this paper, the first campaign of measurements to control the radon activity concentration in drinking water from public water supplies in the province of Salerno, south Italy, is described. The results represent a main reference for the area, as it was never investigated before. The purpose of this survey was to contribute to data compilation concerning the presence of radon-222 in groundwater in the Campania region and to determine the associated risk for different age groups. The maximum radon activity concentrations and the related total annual public effective dose turned out to be lower than the threshold values (100 Bq/l and 0.1 mSv/y, respectively) indicated by international guidelines and the national regulation, showing that the health risks for public consumption can be considered negligible.

Cost-effectiveness of radon remediation programmes in the UK in the 2020s

Radon, a gaseous radioactive decay product of naturally-occurring uranium is widely distributed in the environment in rocks and soils and, in certain circumstances, can accumulate in the built environment. Initial studies confirmed a direct link between exposure to both radon gas and its short-lived radioactive progeny, and increased lung-cancer incidence, and demonstrated that radon levels in domestic housing can be sufficiently high to expose occupants to increased risk of lung-cancer. Subsequent studies worldwide have shown that it is cost-effective to detect and reduce domestic radon levels in order to reduce this risk.Recent advances in the early detection of lung-cancer, coupled with the development of improved treatment procedures, have progressively improved survival from the disease, with the numbers surviving at 5 years doubling over recent years, during which period the real costs of lung cancer treatment have risen by around 30%. In the meantime, however, in addition to radon and tobacco-smoke, other airborne pollutants have been identified as risk-factors for lung-cancer. This paper reviews both these actual developments and anticipated future trends, and concludes that since these advances in diagnosis and treatment of lung-cancer have had only a modest effect on cost-effectiveness, it is still important to conduct radon monitoring and remediation programmes. While the general increase in life-expectancy improves the cost-effectiveness of radon remediation programmes significantly, reducing tobacco-smoking incidence reduces that cost-effectiveness but with the overall benefit of reducing radon-related lung-cancers. The challenge remains of encouraging affected householders to remediate their homes to reduce radon levels.

Occurrence and Geochemistry of Lead-210 and Polonium-210 Radionuclides in Public-Drinking-Water Supplies from Principal Aquifers of the United States.

On the basis of lifetime cancer risks, lead-210 (210Pb) and polonium-210 (210Po) ≥ 1.0 and 0.7 pCi/L (picocuries per liter), respectively, in drinking-water supplies may pose human-health concerns. 210Pb and 210Po were detected at concentrations greater than these thresholds at 3.7 and 1.5%, respectively, of filtered untreated groundwater samples from 1263 public-supply wells in 19 principal aquifers across the United States. Nationally, 72% of samples with radon-222 (222Rn) concentrations > 4000 pCi/L had 210Pb ≥ 1.0 pCi/L. 210Pb is mobilized by alpha recoil associated with the decay of 222Rn and short-lived progeny. 210Pb concentrations ≥ 1.0 pCi/L occurred most frequently where acidic groundwaters inhibited 210Pb readsorption (felsic-crystalline rocks) and where reducing alkaline conditions favored dissolution of iron-manganese- (Fe-Mn-) oxyhydroxides (which adsorb 210Pb) and formation of lead-carbonate complexes (enhancing lead (Pb) mobility). 210Po concentrations ≥ 0.7 pCi/L occurred almost exclusively in confined Coastal Plain aquifers where old (low percent-modern carbon-14) groundwaters were reducing, with high pH (>7.5) and high sodium/chloride (Na/Cl) ratios resulting from cation exchange. In high-pH environments, aqueous polonium (Po) is poorly sorbed, occurring as dihydrogen polonate (H2PoO3(aq)) or, under strongly reducing conditions, as a hydrogen-polonide anion (HPo-). Fe-Mn- and sulfate-reduction and cation-exchange processes may mobilize polonium from mineral surfaces. Po2+ occurrence in low-to-neutral-pH waters is attenuated by adsorption.

Modelling of radon hazards in underground mine workings

For many years, the legal regulations governing radiation protection were primarily concerned with artificial radioactivity, omitting in practice the hazards associated with the occurrence of natural radioactivity in non-nuclear industry. Meanwhile, materials with enhanced concentration of natural isotopes can pose serious radiation risks. A spectacular case is the hazard posed by short-lived radon progeny in underground mine workings. This hazard is significant even when radium isotope concentration in the rocks is at the natural level, and the main reason is relatively poor ventilation of mine workings.The current study contains a description of a developed model that includes a mathematical pattern of the ventilation network and possible radon sources. The model takes into account radon exhalation, generation of radon and its short-lived progeny, losses due to radioactive decay and diffusion of particles and their gravitational deposition; finally, it enables the estimation of doses to miners on the basis of recommended conversion factors. In addition the influence of size distributions of radioactive aerosols on dose conversion factors is discussed. To check and calibrate the model, measurements of radon concentration and potential alpha energy concentration of its decay progeny in an underground hard coal mine were performed during the mining operation.

Measurement of radon, thoron and their daughters in the air of marble factories and resulting alpha-radiation doses to the lung of workers.

Concentrations of radon (222Rn) and thoron (220Rn) were measured in the air of different marble factories by using a nuclear track technique. The influence of the marble dust nature and ventilation on radon and thoron concentrations was investigated. It was observed that measured radon and thoron concentration ranged from 310 to 903Bqm-3 and 6 to 48Bqm-3, respectively. In addition, alpha-activities due to the unattached and attached fractions of 218Po and 214Po radon short-lived progeny were evaluated in the marble factories studied. Committed equivalent doses due to the attached and unattached fractions of 218Po and 214Po nuclei were evaluated in the lung tissues of marble factory workers. The dependence of the resulting committed equivalent dose on the concentration of the attached and unattached fractions of the 218Po and 214Po radionuclides and mass of the tissue was investigated. The resulting annual committed effective doses to the lung of marble factory workers due to the attached and unattached fractions of the 218Po and 214Po radionuclides were calculated. The obtained results show that about 80% of the global committed effective doses received by workers in the studied marble factories are due to the attached fraction of the 218Po and 214Po radon short-lived daughters from the inhalation of polluted air. Male workers spending 8h per day (2080h per year) in a marble factory receive a maximum dose of 34.46mSvy-1 which is higher than the (3-10mSvy-1) dose limit interval given by the ICRP. Good agreement was found between data obtained for the average effective dose gotten by using this method and the UNSCEAR and ICRP conversion dose coefficients.

Passive radon monitors with part-time sensitivity to radon

The recent European directive 59/2013 set reference levels for radon at working places. Since usually the personnel spend only part of the day (e. g. 8 h) at work, it is useful to have passive radon monitors that are sensitive only within a certain time window (e. g. the working hours). This work proposes a conceptual design of such a monitor and tests the feasibility of the approach. The design is based on a solid state nuclear track detector (SSNTD) that rotates over a radon absorber during the monitored period of the day. The SSNTD (Kodak Pathe LR-115 type II) has an energy window that makes it insensitive to 222Rn and 220Rn progeny plated-out on the surfaces. It only registers alpha particles of the absorbed 222Rn and its short-lived progeny 218Po, which is achieved by optimization of the absorber thickness. The absorber construction is further optimized to decrease the inertia of the signal. The modeling and the pilot experimental results show that with a composite absorber consisting of a stack of Makrofol N foils with thickness of less than 7 μm each, the inertia of the signal is less than 20 min. The estimated minimum detectable activity concentration (MDAC) for the proposed 222Rn monitor is about 15 Bq m−3 for year-long working time exposure (2000 h/year) or 60 Bq m−3 for 3- month exposure period (500 h).