The Determination of Radon/Thoron Exhalation Rate in an Underground Coal Mine-Preliminary Results.

The objective of this work was to perform a series of measurements of radon and thoron exhalation in the underground workings of an experimental coal mine. In the years 2012-2015, experiments on underground coal gasification were carried out in a coal mine, which caused, among other effects, damage to rock mass. Afterward, periodic increases in the concentration of potential alpha energy (PAEC) of radon decay products in the air were found, which could pose a hazard to miners. The question posed was whether the gasification experiment resulted in the increased migration of radon and thoron. If so, did it increase the radiation hazard to miners? The adaptation of the existing instrumentation to the specific conditions was conducted, and a series of measurements were made. It was found that the measured values of radon and thoron exhalation rates ranged from 3.0 up to 38 Bq·m-2·h-1 for radon and from 500 up to 2000 Bq·m-2·h-1 for thoron.

Radon Concentrations in Dwellings in the Mining Area-Are There Observed Effects of the Coal Mine Closure?

The article presents the results of radon research, carried out in the area of the mining commune in the Upper Silesian Coal Basin (USCB), Poland. Past investigations in the 1990s on radon concentrations in buildings, located within the mining area, showed that the indoor radon concentrations measured in the area affected by mining were higher than in buildings located outside that area. Currently, all underground hard coal mines within the boundaries of the observed commune have been closed. In 2020, after the closure of the last active mine, radon measurements were started again. The current results of indoor radon concentrations were compared with the archival results from the 1990s. It was found that the radon concentration increased significantly in the basements of buildings where measurements were made in 1990, 2020, and 2021: the maximum values were 260 Bq/m3, 644 Bq/m3, and 1041 Bq/m3, respectively. Therefore, these questions were posed: Do the mine closure processes increase radon migration? How long is the period of the occurrence of changes in radon concentrations in buildings after the cessation of mining operations?

Application of TLD devices for radon and thoron PAEC measurements in air is the concept of "total PAEC" useful?

The calibration of monitors of radon decay products is a difficult task, and even more so in the case of monitors detecting the products of thoron decay. An important issue here is the lack of primary standards, both in relation to the products of radon as well as thoron decay. In Poland, for many years, measurements of potential alpha energy concentration (PAEC) were carried out with the application of special devices, called ALFA probes. These in turn featured thermo-luminescent detectors (TLD), the readout of which provided information about the potential alpha energy, with no dependence on equilibrium or other factors alike. In this paper, we propose modifying this technique, which had been used only for measurements of products of radon decay. We specifically examine how it can be used to allow simultaneous measurements of radon and thoron PAECs. In employing the method, the idea is to use two sets of TL detectors in the same device during and after sampling. The first set of detectors is used to store the energy of alpha particles during the course and for a short while after the sampling, up to 5 h after its end. Using this method, the first set of detectors holds respectively the full and partial PAECs of products of radon and thoron decay. After that, the first set of TLDs is replaced with a second one. These are then left in the device for another 55-60 h. This set contains only the PAEC from thoron decay products. Afterwards, it is necessary to subtract thoron PAEC from the first set result and add it to the result provided by the second set in order to estimate the PAEC for the products of thoron decay. On a practical level, using such a procedure can potentially difficult during underground or field monitoring nevertheless. This is why another approach can be adopted as well. This is specifically to leave the device for 60 h after sampling without any changes, the original set of TLDs providing a "total" PAEC readout - this being a sum of radon and thoron PAECs. In this paper, we will explore the value of using such a readout for the measurement that is carried out.

The correction factors for UD802 dosimeters irradiated with different radiation energies and at different incidence angles.

Many laboratories around the world work on the issue of protection against ionising radiation. It is a very broad topic, covering both the protection of members of the public and workers exposed to ionising radiation, based on personal or environmental monitoring. Thermoluminescence detectors are commonly used for this purpose, which is accepted in most countries. The entire process of dose evaluation with such dosimeters can be divided into several steps. Undoubtedly, one of the most important steps is the calibration procedure. The calibration should be performed in conditions as similar as possible to those experienced during the exposure. Moreover, the calibration is performed using only the Cs-137 source. This article presents results of Panasonic UD-802 irradiation dosimeters in different radiation fields generated by Cs-137, Kr-85, Sr-90/Y-90 and an x-ray tube, series N, and at different angles such as 0°, 30°, 60°, 90°. On the basis of the obtained results, the calibration coefficients and correction factors were determined in relation to calibration based on Cs-137 or Sr-90/Y-90 irradiated at 0°.

Multivariate statistical approach on distribution of natural and anthropogenic radionuclides and associated radiation indices along the north-western coastline of Aegean Sea, Greece.

A comprehensive radiological survey using multivariate statistical analysis was carried out to evaluate the distribution of 40K, 232Th, 226Ra, 235U, and 137Cs, and associated radiation indices in beach sand samples of the coastal area of the Aegean Sea. The activity concentration of selected radionuclides was measured and no clue of recent migration of radiocaesium by not only precipitation but also through an indirect way, such as ocean runoff, was found. As part of radiological risk assessment, external radiation hazard index, radium equivalent activity, effective dose, and absorbed dose rate were estimated. Pearson correlation, cluster, and PCA analysis were used by processing observed radiological parameters to determine the correlation between the radiological parameters and locations. Pearson correlation shows a strong association between all parameters and activity of 226Ra and 232Th. A spatial distribution map was provided to a distinct visual representation of the distribution of radionuclide contents in the study area.

Radiological Assessment of Indoor Radon and Thoron Concentrations and Indoor Radon Map of Dwellings in Mashhad, Iran.

A comprehensive study was carried out to measure indoor radon/thoron concentrations in 78 dwellings and soil-gas radon in the city of Mashhad, Iran during two seasons, using two common radon monitoring devices (NRPB and RADUET). In the winter, indoor radon concentrations measured between 75 ± 11 to 376 ± 24 Bq·m-3 (mean: 150 ± 19 Bq m-3), whereas indoor thoron concentrations ranged from below the Lower Limit of Detection (LLD) to 166 ± 10 Bq·m-3 (mean: 66 ± 8 Bq m-3), while radon and thoron concentrations in summer fell between 50 ± 11 and 305 ± 24 Bq·m-3 (mean 115 ± 18 Bq m-3) and from below the LLD to 122 ± 10 Bq m-3 (mean 48 ± 6 Bq·m-3), respectively. The annual average effective dose was estimated to be 3.7 ± 0.5 mSv yr-1. The soil-gas radon concentrations fell within the range from 1.07 ± 0.28 to 8.02 ± 0.65 kBq·m-3 (mean 3.07 ± 1.09 kBq·m-3). Finally, indoor radon maps were generated by ArcGIS software over a grid of 1 × 1 km2 using three different interpolation techniques. In grid cells where no data was observed, the arithmetic mean was used to predict a mean indoor radon concentration. Accordingly, inverse distance weighting (IDW) was proven to be more suitable for predicting mean indoor radon concentrations due to the lower mean absolute error (MAE) and root mean square error (RMSE). Meanwhile, the radiation health risk due to the residential exposure to radon and indoor gamma radiation exposure was also assessed.

The analysis of results of radon/thoron measurements performed with the use of nuclear track detectors.

Radon has been identified as one of the most important hazards, causing lung cancer. The most important isotope of radon is222Rn (3.83 d), while thoron220Rn (55 s) is treated as the less important isotope due to its short half-life. The radon/thoron hazard for people is related to inhalation of their decay products, but usually, only measurements of radon gas are done in dwellings. For such a purpose nuclear track detectors are used in most of the cases. Since several years simultaneous measurements are done to estimate thoron contribution to indoor radon and thoron exposure with the use of track detectors, too. Typically, a set of two detectors are applied and thoron concentrations are calculated on the basis of discriminative calculations. Unfortunately, very often results of these surveys are not accurate due to underestimation of the lower limit of detection (LLD) for thoron in the presence of elevated radon concentrations. Therefore an analysis of thoron LLDs in relationship to radon concentrations is presented.

A method for the simultaneous measurement of radon and thoron PAEC concentrations in air using a TLD monitor.

The idea of using a device with thermo-luminescent detectors (TLD) for the simultaneous measurement of radon (Rn-222) and thoron (Rn-220) decay products' concentrations was invented and developed in the Silesian Centre for Environmental Radioactivity at the Central Mining Institute, Katowice, Poland. The results of a preliminary analysis of the technical applicability, the required minimum period of air sampling and the optimised time schedule proved that such measurements can provide information about the potential alpha energy concentrations (PAECs) of radon and thoron decay products (TnDP).Following the analysis, preliminary measurements were performed at several locations-in a thoron chamber, in dwellings and even outdoors. Surprisingly, the maximum PAEC of the TnDP in the basement of a twin house in the Upper Silesia region was as high as 0.68 ± 0.15µJ m-3. This paper presents the results of those measurements.

High level of natural ionizing radiation at a thermal bath in Dehloran, Iran.

It has been proven that more than half of the exposure to natural background radiation originates from radon isotopes and their decay products. The inhalation of radon and its decay products causes the irradiation of respiratory tracts, thus increasing the risk of lung cancer. In this study, the concentrations of radon and thoron in thermal baths at a spa in Dehloran (Iran) were investigated. The concentrations of dissolved 226Ra in samples of water from thermal baths were also measured. Additionally, the activity concentrations of abundant naturally occurring radionuclides in farmland soils irrigated with water from hot springs was measured and compared with other soil samples irrigated with water from other sources to estimate possible radioecological effects of natural radiation staff, patients and tourists at the spa are exposed to. In addition, the search for a link between the concentration of naturally occurring radionuclides in soil and the use of water from hot springs for irrigation was one of the main goals of the study. The activity concentrations of three major naturally occurring radionuclides in soil samples were measured; the ranges for 40K, 226Ra and 228Ra were 101 ± 8 to 240 ± 12, 276 ± 7 to 322 ± 12 and 20 ± 7 to 80 ± 10 Bq.kg-1, respectively. Higher activity concentrations of 226Ra and 228Ra were recorded in soil samples irrigated with hot spring water. The water from the same spring was used in all thermal baths so concentrations of dissolved 226Ra in water samples from different thermal baths were approximated to also be 0.42 ± 0.20 Bq.l-1. The indoor radon concentrations in the private thermal baths over a period of 45 days (including both occupied and vacant time) were measured to be between 1880 ± 410 and 2450 ± 530 Bq.m-3 and the radon concentrations in the spa galleries were measured to be between 790 ± 135 and 1050 ± 120 Bq.m-3, however, thoron concentrations were below the detection limit. The ventilation and centralized heating systems at the spa under investigation are inefficient so the radon concentrations in the therapy rooms and baths are high. The maximum radiation doses originating from the inhalation of radon for tourists and the staff were estimated to be 0.13 and 5.5 mSv.yr-1, respectively, which is slightly over the national limit in Iran (5 mSv.yr-1). The exposure duration was estimated 15 and 1468 h per year for visitors and workers, respectively.

Long term changes in the concentration of radium in discharge waters of coal mines and Upper Silesian rivers.

According to the latest guidelines of the International Atomic Energy Agency (IAEA, 2016), coal mining is one of the most important contributors to occupational exposure. Coal mining contributes about 45% of the total annual collective dose obtained by workers due to the exposure at places of working. One of the sources of exposure in mining are formation brines with elevated concentrations of natural radionuclides, the most common are radium 226Ra and 228Ra. Radium isotopes often occur in formation waters in underground collieries in the Upper Silesian region (USCB) in Poland. Significant amounts of radium remain underground in the form of radioactive deposits created as a result of spontaneous deposition or water treatment. This phenomenon leads to the increase of radiation hazard for miners. The remaining activities of 226Ra and 228Ra are released into the rivers with mine effluents, causing the contamination of bottom sediments and river banks. The results of radioactivity monitoring of effluents and river waters are presented here to illustrate a trend of long-term changes in environmental contamination, caused by mining industry in the Upper Silesian Region.

Sample volume optimization for radon-in-water detection by liquid scintillation counting.

Radon is used as environmental tracer in a wide range of applications particularly in aquatic environments. If liquid scintillation counting (LSC) is used as detection method the radon has to be transferred from the water sample into a scintillation cocktail. Whereas the volume of the cocktail is generally given by the size of standard LSC vials (20 ml) the water sample volume is not specified. Aim of the study was an optimization of the water sample volume, i.e. its minimization without risking a significant decrease in LSC count-rate and hence in counting statistics. An equation is introduced, which allows calculating the ²²²Rn concentration that was initially present in a water sample as function of the volumes of water sample, sample flask headspace and scintillation cocktail, the applicable radon partition coefficient, and the detected count-rate value. It was shown that water sample volumes exceeding about 900 ml do not result in a significant increase in count-rate and hence counting statistics. On the other hand, sample volumes that are considerably smaller than about 500 ml lead to noticeably lower count-rates (and poorer counting statistics). Thus water sample volumes of about 500-900 ml should be chosen for LSC radon-in-water detection, if 20 ml vials are applied.

Natural radioactivity in drinking underground waters in Upper Silesia and solid wastes produced during treatment.

Content of (226)Ra, (228)Ra and uranium isotopes in waters from subsurface aquifers was studied. The sampling points were chosen for having the elevated natural content of iron and manganese. Measurements of radium were made by LSC, while uranium was measured by alpha spectrometry. Waste sludge was measured by gamma spectrometry and three-stage BCR sequential extraction was performed. Radon activity concentration in the air at water treatment plants was determined and dose adsorbed by staff was calculated.

Application of zeolites for radium removal from mine water.

For removal of radium from saline waters in Upper Silesian mines, several methods of purification have been developed. The most efficient one is based on application of barium chloride, which was implemented in full technical scale in two Polish coal mines several years ago. Very good results of purification have been achieved-the removal efficiency exceeding 95% of the initial activity. Another possibility for the removal of different ions from salty waters and brines is the application of zeolites. We found that technique as a very promising method for removal of not only radium isotopes from mine waters but also other ions (barium, iron, manganese). Treatment of several various water samples has been done to assess the removal efficiency for natural radionuclides. Preliminary results show very good effects for radium isotopes as well as for barium ions. In the paper, a short description of laboratory results of the purification of mine waters with application of synthetic zeolites is presented.

Radium removal from mine waters in underground treatment installations.

The underground mining of hard coal is widespread in the Upper Silesian Coal Basin (southern Poland). In deep mines, inflows of highly mineralised waters containing radium isotopes are numerous. These waters cause severe damage to the natural environment due to the salinity, but additionally radioactive pollution occurs. The region is densely populated, therefore mitigation methods are very important. The method of radium removal has been applied in full technical scale in two coal mines with very good results--in one of the mines radium-bearing waters are treated at the rate of approximately 0.1 m3 s(-1), while in another mine salty waters are purified at the rate of 0.1 m3 s(-1). The purification takes place in special underground galleries without any contact of the mining crew with the radioactive deposits produced during the process. As a result, release of radium is significantly lower, more than 200 MBq of 226Ra and 228Ra remains underground each day.

Geophysical methods in radon risk studies.

The results of the studies presented in the paper have shown that in the Upper Silesian Region in Poland, radon indoor concentration levels depend first of all on the geological structure of the subsurface layers. The essential factors influencing radon migration ability are the mining-induced transformations of a rock mass. In some cases, significant variations of radon potential have been found at sites featuring similar geological structures and experiencing comparable mining effects. To find out the causes of these variations, studies involving geophysical methods such as electrical resistivity profiling (PE) and electrical resisitivity sounding (VES) were used. These studies have shown that the measurements made using the electrical resistivity method can be helpful in evaluating radon potential of both the tectonically disturbed areas and the mining-transformed ones.