Abstract
Inhaled radon status in the laneways of some Chinese stone-coal mines is a cause of concern. In this study, computational fluid dynamics simulations were employed to investigate three flowrates of the dilution gas (2.5, 5, and 7.5 m3/s) and radon distributions at realistic breathing levels (1.6, 1.75, and 1.9 m). The results showed that there are obvious jet-flow, backflow, and vortex zones near the heading face, and a circulation flow at the rear of the laneway. A high radon concentration area was found to be caused by the mining machinery. As the ventilation rate increased, the radon concentrations dropped significantly. An airflow of 7.5 m3/s showed the best dilution performance: The maximum radon concentration decreased to 541.62 Bq/m3, which is within the safe range recommended by the International Commission on Radiological Protection. Annual effective doses for the three air flowrates were 8.61, 5.50, and 4.12 mSv.
Highlights
222 Rn has recently drawn much attention, due to its radioactivity in underground workplaces which can cause over-exposure in miners [1,2]. 222 Rn is widely found in underground rocks as a product of uranium decay and can diffuse from rock pores to the working space during mining operations
Al-Zoughool et al [7] assessed several studies on the radon exposure of uranium miners in six countries (U.S.A., Australia, Canada, France, Germany, and Czech Republic): the exposure of radon inhalation ranged from 7.6–595.7 working level months (WLM), which was much higher than the threshold limit of 4 WLM prescribed by the International Commission on Radiological Protection (ICRP) [8]
The results showed that there were greater radon concentrations in stone-coal mines without auxiliary ventilation
Summary
222 Rn has recently drawn much attention, due to its radioactivity in underground workplaces which can cause over-exposure in miners [1,2]. 222 Rn (radon; Rn) is widely found in underground rocks as a product of uranium decay and can diffuse from rock pores to the working space during mining operations. The typical value of radon concentrations of stone-coal mines in China was, suggested to be 1500 Bq/m3 , which is three times the lower limit of the action level (500 Bq/m3 ). The high uranium content of the mineral nodules and lack of effective ventilation are the major reasons that radon exceeds the limit in laneways of stone-coal mines. There are three main auxiliary ventilation systems used in coal mine laneways: Forcing ventilation systems, exhaust ventilation systems, and mixed ventilation systems (a forcing ventilation system together with an exhaust ventilation system); the forcing ventilation system being the most commonly used [17,18,19] It is, important to understand airflow behavior in the laneway to select proper ventilation parameters to maintain radon concentrations at a reasonable level. The study results are helpful for obtaining a better understanding of the complex airflow characteristics and radon dispersion under auxiliary ventilation and provides reliable guidance and education for the design of effective radon dilution systems
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