The behavior of the 210Pb during the recycling of selected waste in the metallurgical industry.

Contemporary trends in the metal industry are based on zero-waste and a closed circular economy. Such an approach has encouraged the industry to search for new methods of metal production using unconventional sources of them instead of high-priced raw materials. Waste from some industry sectors e.g. residues, slag, stack dust, etc. may be a economically interesting input material for other sectors of industry. There are at least two benefits reusing waste in such a way - the reduction of disposal costs and reduction of the environmental and health impact of industry. However, industrial waste or by-products are often classed as naturally occurring radioactive materials (NORM). The behavior of a lead isotope 210Pb - a naturally occurring radioactive nuclide - was investigated in this work. The analyzed metallurgical process is based on the recycling of waste from niobium and tantalum production, which were then used in tin and lead production. Behavior of 210Pb in particular stages of a process may lead to the enrichment of this radionuclide in the final product - distilled lead. The concentrations of 210Pb in the input material, final product as well as generated by-products and waste were determined.

Radon Exposure in the Underground Tourist Route-Historic Silver Mine in Tarnowskie Góry, Poland.

An assessment of the exposure of workers and tourists to radon in the underground tourist route of the Historic Silver Mine in Tarnowskie Góry was carried out. The study was conducted over a one-year period to capture seasonal variations in radon concentrations. CR-39 track detectors were used to measure radon concentrations, which were exposed in the mine during the following periods: 9 February 2021-19 May 2021, 19 May 2021-26 August 2021, 26 August 2021-25 November 2021 and 25 November 2021-3 March 2022. The annual average radon concentration along the tourist route was 1021 Bq m-3. The highest measured concentration was 2280 Bq m-3 and the lowest concentration was 80 Bq m-3. Based on the measured concentrations, effective doses were calculated, assuming that employees spend 1350 h a year in underground areas and that the time of visiting the mine by tourists is ca. 1 h. The average annual effective dose a worker would receive is approximately 2.5 mSv, and a tourist below 2 µSv. The dose limit expressed as the annual effective dose is 1 mSv for members of the general public and 20 mSv for occupational exposure.

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?

Long term behaviour of radium rich deposits in a lake ecosystem.

Behaviour of radionuclides released into environment is crucial for further evaluation of any kind of possible effects. Possibility of observation how does a radionuclide behave in natural environment is limited to very few post accidental areas. However, valuable observation can be collected at areas where enhanced concentration of natural radionuclides is presented caused by activity of non-nuclear industry. One example is area affected by release of radium rich brines from coal mines (Upper Silesia, south of Poland) that let one observe radium and its decay product behaviour in freshwater ecosystem from long-term perspective. Selected as long-term observatory site former mine water reservoir allowed identification of processes leading to accumulation of radium in bottom sediments and observation of its further behaviour from 17-years-time perspective. New data were collected during two-years monitoring campaign and compared with archive data on radioactivity in water and sediments collected in 1999. Radium-barium co-precipitation process was identified as main source of sediments heavy contamination, however, radium chemical form resulted from this process is insoluble and not easy migrate to other environmental compartments, what was proved by low 226Ra and 210Pb transfer to water measured under laboratory condition and to biota observed on site. As barium is not always present in mine radium rich brines a discussion is launched what would happen when such waters are released into environment based on simple laboratory experiment. In main conclusion is underlined that the current radium activity concentration in sediments is lower than expected only considering radioactive decay. Distribution of 226Ra, 228Ra and 210Pb in sediment profiles suggest that bio- or mechanical turbation (e.g. local flood) is responsible for significant 226Ra deficiency observed.

Testing of the radon tightness of beakers and different types of sealing used in gamma-ray spectrometry for 226Ra concentration determination in NORM.

The presence of radium is common in the natural environment. However, some human activities lead to the production of large amounts of waste and by-product containing elevated concentrations of radium. Several methods for the determination of radium isotopes exist. The common use of gamma-ray spectrometry is justified by several of its advantages: it is a non-destructive method, easy, it is a time- and cost-effective procedure of preparing a sample and provides a reasonable time of measurement. The major disadvantages of direct measurements of radium are its weak yields γ-line 186.2 keV (3.59%) and, additionally, an interference with 235U direct line 185.7 keV. There is an indirect method of measuring radium. The method uses the daughter radionuclides of radon: 214Pb and 214Bi. The problem is radon escape from the measurement container. The article describes the tests of radontightness of various types of containers and different types of sealing. In frame of performed measurements, not sufficient tightness of typical containers used in laboratories was found.

The self-absorption correction factors for 210Pb concentration in mining waste and influence on environmental radiation risk assessment.

The radioactive lead isotope 210Pb occurs in waste originating from metal smelting and refining industry, gas and oil extraction and sometimes from underground coal mines, which are deposited in natural environment very often. Radiation risk assessment requires accurate knowledge about the concentration of 210Pb in such materials. Laboratory measurements seem to be the only reliable method applicable in environmental 210Pb monitoring. One of the methods is gamma-ray spectrometry, which is a very fast and cost-effective method to determine 210Pb concentration. On the other hand, the self-attenuation of gamma ray from 210Pb (46.5 keV) in a sample is significant as it does not depend only on sample density but also on sample chemical composition (sample matrix). This phenomenon is responsible for the under-estimation of the 210Pb activity concentration level often when gamma spectrometry is applied with no regard to relevant corrections. Finally, the corresponding radiation risk can be also improperly evaluated. Sixty samples of coal mining solid tailings (sediments created from underground mining water) were analysed. Slightly modified and adapted to the existing laboratory condition, a transmission method has been applied for the accurate measurement of 210Pb concentration . The observed concentrations of 210Pb range between 42.2 ÷ 11,700 Bq·kg-1 of dry mass. Experimentally obtained correction factors related to a sample density and elemental composition range between 1.11 and 6.97. Neglecting this factor can cause a significant error or underestimations in radiological risk assessment. The obtained results have been used for environmental radiation risk assessment performed by use of the ERICA tool assuming exposure conditions typical for the final destination of such kind of waste.

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.