| Popis: |
As a result of elevated radon levels, the high number of visitors and a number of employees who spend the majority of their working hours in the cave (tour guides, train drivers, maintenance workers), Postojna Cave has been investigated more systematically in the last decade. In 1995, the Ministry of Health required the cave management to implement permanent radon monitoring in the cave and yearly dose estimates for the employees. Due to the specific work regime in the cave, primarily depending on the number of daily visitors, and seasonal variations in radon concentrations, an optimal methodology for measurement was sought. The five locations, selected in 1996 along the guided path, were reduced to only two in 1998. Radon concentration is being permanently measured at these two locations. The measurements are performed with etched-track detectors and continuous monitors for radon and radon progeny recording. In the beginning, etched-track detectors were exposed monthly all year round. In addition, measurements using continuous devices were performed four times a year for about one-week each season. The yearly measuring programme was eventually optimised, at present comprising: three-month exposures of etched-track detectors and two 7-10 day measurements using continuous devices. In this paper, the results of radon measurements and dose estimates based on recent methodology will be presented. |
