Mitigation of three water supplies with high radon exposure to the employees

Abstract

A comprehensive survey to determine the occupational radiation exposure in water supplies and spas was conducted in the federal state of Upper Austria. The study comprises 45 water supplies. The limit for radon exposure of 6 MBq h m(-3) was exceeded by two water supplies (WS 33 and WS 42). In one water supply (WS 29), the level of 2 MBq h m(-3) was exceeded. These water supplies were mitigated. Prior to mitigation the main radon sources were identified. Mitigation measures were: evacuation of the outlet air of the vaporiser by means of a fan, installation of a fan in the exhaust air duct of the compensating reservoir, sealing of drain shafts and mechanical ventilation of the office. In all water supplies, the radon exposure was reduced to below 0.8 MBq h m(-3) at a cost of approx. euro 750 to euro 1000.

Measurement strategies for radon in indoor air of waterworks – a review

“…Besides the values for the 222 Rn activity concentration in indoor air of waterworks, other results and relevant information are presented, which are the used methodology for the determination of 222 Rn in air, the activity concentrations of 222 Rn in water, the equilibrium factor F applied for dose calculation, and the annual effective dose of the staff. The maximum values reported in these studies were more than 50000 Bq m À3 (Marinko et al, 2004) for 222 Rn in air, 1200 Bq I À1 (Trautmannsheimer et al, 2003) for 222 Rn in water and 56 mSv y À1 (Ringer et al, 2008) for the annual effective dose of the waterworks staff.…”

“…This literature review on studies directly associated with 222 Rn measurements in waterworks, covering more than 800 waterworks in nine regions, shows that 222 Rn can exhale in large amounts through open water surfaces in this working area and cause a significant dose contribution for the staff. For the 222 Rn activity concentration in indoor air of waterworks, values higher than 50000 Bq m À3 were documented in the literature (Marinko et al, 2004) and annual effective doses as high as 56 mSv y À1 were reported (Ringer et al, 2008).…”

“…During visits at waterworks, it could be helpful to start with active measurements (as conducted by Fisher et al, 1996;Hingmann et al, 2001;Vaupotic, 2002;Ringer et al, 2008;Nagels et al, 2009;Stietka et al, 2014). Such short-term measurements À preferably conducted with a high-efficiency active device with a display operated in flow mode (e.g.…”

“…For the proof of effectivity of the set dose reduction measures, it is necessary to repeat the measurements after a remediation process (e.g. Ringer, 2008). In case of high annual effective doses, the repeat of measurement after remediation is enshrined in the national act or ordinance, e.g.…”

“…Additionally to the 222 Rn measurement devices, a dose rate meter is frequently used as a supplementary instrument in waterworks (Ringer et al, 2008). It can help to identify water filters enriched with 226 Ra, which could be a source of 222 Rn emanation.…”