Abstract:A comprehensive radiological survey was carried out in an open-cut slate stone quarry. The activity of 226Ra, 228Ra and 40 K in the ore samples were measured as 38 ± 5, 41 ± 6 and 869 ± 52 Bq kg1, respectively. Outdoor radon and indoor radon concentrations were measured from 37 ± 7 to 193 ± 11 Bq m−3 (77 ± 8 Bq m−3), and 49 ± 6 to 253 ± 23 Bq m−3 (131 ± 13 Bq m−3), respectively. The average indoor and outdoor gamma dose were measured as 116 and 84 nSv h− 1, respectively. The annual effective doses were estimat… Show more
“…The tracks can then be counted and analyzed to determine the radiation dose. Further details are extensively discussed in our previous publications [ [19] , [20] , [21] , [22] ]. Fig.…”
“…The tracks can then be counted and analyzed to determine the radiation dose. Further details are extensively discussed in our previous publications [ [19] , [20] , [21] , [22] ]. Fig.…”
“…Radon measurement was divided into two different methods of passive and active monitoring. The methodology of these measurements could be found in the previously published papers [16][17][18][19].…”
Background
The European Union council has introduced the basic safety standards (EU-BSS) for protection against the dangers arising from exposure to ionizing radiation by laying down a new radon reference level at workplaces. In this regard, all European state members must establish a national reference level based on all pre-defined requirements. After implanting the directive 2013/59/Euratom by European state members, new challenges have been revealed to mitigate radon appropriately in underground workplaces due to the exciting limitations (e.g., ventilation system, dust dispersion, air injection, etc.). Therefore, a conceptual design of an environmental radiological survey was defined and implemented by examining the hypothesis to find practical solutions following EU-BSS. The main objectives of this study were to identify the potential radon entry paths, utilize an optimized ventilation system, and carry on long-term radon monitoring in an operational underground manganese mine.
Results
The mullock rocks (the geological structure of the mine walls) contained a small amount of Ra-226 (2–4 Bq kg−1). On the other hand, the mine ore (black shale, underlayer black shale, and carbonate ore) has shown the highest concentration of Ra-226 (12–16 Bq kg−1) and the highest radon exhalation (1.2–1.6 mBq s−1 m−2). The surface radon exhalation from the mine walls was in the range of 0.7 ± 0.1 and 1.5 ± 0.2 mBq m−2 s−1. It was found that shortly after mining activity was undertaken, radon concentration increased dramatically with an average of about 5900 ± 420 Bq m−3 near the freshly broken walls. The optimized mobile mitigation system reduced radon concentration to 250 ± 41 Bq m−3 on average.
Conclusion
Apart from the fact that aged walls were involved in the radon accumulation, considering the mine ventilation performance and the total active surface area, the exhaled radon from the aged walls could not be the primary potential source of high radon concentration when mining activity was undertaken. According to the obtained results, the ores, recently fragmented during the course of mining operations, were the primary path. Therefore, after successfully identifying the radon entry path, radon concentration could be reduced to meet the EU-BSS requirement by implementing the developed mitigation system.
“…By taking into consideration the aforementioned criteria, a different range of ventilation rates from 0.3 to 4.3 h −1 (also reported by Zhou et al 8 and Agarwal et al 14 ) was considered and assessed in the current study. The radon source term as a key input parameter in the CFD software (ANSYS Fluent 2020 R1 based on the FVM) has also been measured by an accumulation chamber technique for samples of cement (comprehensively described in Kocsis et al 17 and Shahrokhi et al 18 ) before the simulations took into account the room geometry. To validate the simulation results, two pairs of common radon monitoring methods, namely NRPB and Raduet (as passive methods based on CR-39) as well as AlphaGUARD and RAD7 (as active methods), were also used to measure the indoor radon concentration under the aforementioned scenarios at various locations throughout the room.…”
Based on the European Union Basic Safety Standards to protect people against exposure to ionizing radiation, establishing and addressing the reference levels for indoor radon concentrations is necessary. Therefore, the indoor radon concentration should be monitored and control in dwelling and workplaces. However, proper ventilation and sustainability are the major factors that influence how healthy the environment in a building is for its occupants. In this paper, the indoor radon distribution in a typical naturally ventilated room under two scenarios (when the door is closed and open) using the computational fluid dynamics (CFD) technique was studied. The CFD code ANSYS Fluent 2020 R1 based on the finite volume method was employed before the simulation results were compared with analytical calculations as well as passive and active measurements. The average radon concentration from the CFD simulation was found to be between 70.21 and 66.25 Bq m−3 under closed and open-door conditions, respectively, at the desired ventilation rate of 1 ACH (Air Changes per Hour). Moreover, the highest concentrations of radon were measured close to the floor and the lowest values were recorded near to the inlet, resulting in the airflow velocity profile. The simulation results were in good agreement with the maxima of 19% and 7% compared to analytical calculations at different indoor air velocities in the open- and closed-door scenarios, respectively. The measured radon concentrations obtained by the active measurements also fitted well with the CFD results, for example, with a relative standard deviation of around 7% and 2% when measured by AlphaGUARD and RAD7 monitors at a height of 1.0 m above the ground in the open-door scenario. From the simulation results, the effective dose received by an individual from the indoor air of the workplace was also calculated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
