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.
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.
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°.
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.
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