... continued from pg 42 [Review of Radon]
has decreased with time, being approximately 1,800 Bq m−3 in the year 1972, 300 Bq m−3 in 1990, and 100 Bq m−3 in 2000 (Koja et al. 2021). Therefore, this paper aimed to provide updated information on radon exposure to non-uranium underground miners based on review of more recent publications on measurements of radon and radon progeny concentrations in active underground non- uranium mines (i.e., mines in operation with ventilation on) found in the literature in recent two decades (2000 to present).
In Canada, mining associated with the nuclear fuel cycle (i.e., uranium) falls under the regulatory authority of the Canadian Nuclear Safety Commission (CNSC) and is subject to requirements for monitoring and reporting information on radiation doses to workers. Other types of mining are regulated by the provincial and territorial authorities. For CNSC-regulated uranium mining activity, miners’ dose records (including radon doses) have been reported to the National Dose Registry (NDR) since 1955. However, exposure monitoring for non-uranium mining activities using a licensed dosimetry service and reporting doses to the NDR is not required. In the most recent “Report on occupational radiation exposures in Canada 2008–2018” (Health Canada 2021), dose records were only available for workers with uranium mining activities (there were 629 underground workers in uranium mines in 2018; they were uranium mine underground miners, underground workers for maintenance, and other underground personnel). To fill the data gaps for large numbers of workers employed in various non-uranium mines, radon exposures to Canadian non-uranium mine workers were estimated with radon exposure information from literature review, assuming Canadian non-uranium mines operating under similar conditions to the averages from many other non-uranium mines around the world.
REVIEW OF RADON CONCENTRATIONS IN UNDERGROUND NON-URANIUM MINES
Radon gas contributes relatively little to the dose to the lung. The inhalation of the short-lived solid radon decay products and subsequent deposition on the walls of the airway epithelium of the bronchial tree deliver most of the radiation dose to humans. The equilibrium factor, F, between radon and its short-lived progeny in underground mine atmospheres can be very unstable and vary in space and time in the range of 0.1–1.0 (Chen and Harley 2020). Therefore, some radon measurements in mines were direct measurements of radon progeny concentration in working level (WL) (1 WL = 2.08 × 10−5 J m−3) or potential alpha energy concentration (PAEC, in units of J m−3). For the purpose of comparison with residential radon gas measurements, measurement results of radon progeny concentrations were converted to radon gas concentration in the units of Bq × m−3 using the equilibrium factor F = 0.38 determined from multiple simultaneous radon gas and radon progeny measurements performed in a total of 173 underground mines of various mining types in 18 countries (Chen and Harley 2020). Therefore, 1 J m−3 of radon progeny concentration was converted to 4.76 × 108 Bq m−3 of radon gas concentration (1 μJ m−3 = 476 Bq m−3). Due to the importance of F factor in radon dose calculation, current review also collected information of measured F factor whenever available in the literature.
https://journals.lww.com/health-physics/Fulltext/2023/04000/A_Review_of_Radon_Exposure_in_Non_uranium.2.aspx