Diurnal and seasonal variations of radon levels, effects of climatic conditions, and radon exposure assessment in a former uranium metal production facility

• Published in: Health physics (1958) Vol. 74; no. 5; p. 568
• Main Authors: Merrill, E A, Akbar-Khanzadeh, F
• Format: Journal Article
• Language: English
• Published: United States 01.05.1998
• Subjects: Climate; Humans; Occupational Exposure; Ohio; Periodicity; Radiation Monitoring; Radon - analysis; Seasons; Uranium; Weather; Ohio
• ISSN: 0017-9078
• DOI: 10.1097/00004032-199805000-00004

Storage of radon-producing material in two silos and two waste pits is one of the major environmental and occupational issues at a former uranium production facility, now a Superfund site. In addition, up to 100 metric tons of thorium is stored on the northeast side of the site. Concentrations of radium up to 17,600 Bq g(-1) (477,000 pCi g(-1)) or higher for silos and up to 45 Bq g(-1) (1,200 pCi g(-1)) for waste pits have been reported. This study was conducted to identify factors and climatic conditions that contribute to higher radon levels and to assess workers' exposure at the site. Data covering a 12-mo period were compiled from monitoring hourly real-time radon levels at indoor (within 3 buildings) and outdoor (at 14 on-site and 2 off-site monitoring stations) locations and from hourly site-specific meteorological information. The ranges of radon levels were as follows: 1.8-3,655 Bq m(-3) (0.05-98.8 pCi L(-1)) outdoor on-site, 3.7-329 Bq m(-3) (0.1-8.9 pCi L(-1)) outdoor off-site, and 1.8-111 Bq m(-3) (0.05-3.0 pCi L(-1)) indoor on-site. Only radon levels in the vicinity of the storage silos were significantly higher than levels off-site. Radon concentrations showed diurnal variations, with maximum levels occurring in the early morning and minimum levels in the afternoon. Seasonal variation was also observed, with radon levels higher during the summer through early fall and lower during the late winter through spring. Wind speed, relative humidity, and wind direction appeared to be the most significant predictors of radon concentration. The estimated radon dose to workers, calculated by using exposure models and annual average levels of radon in the work area, was below recommended exposure limits. These results suggest that the emission control methods at this site have been effective in maintaining environmental radon contamination and workers' exposure at acceptable levels.