Analysis and radiation dose assessment of 222Rn in indoor air at schools: Case study at Ulju County, Korea

222Rn exists in nature in the form of a rare radioactive gas. In terms of environmental radiation, issues regarding 222Rn have persisted because of its radiological hazardousness. Ulju County is one of the regions of Ulsan metropolitan city, with a population of 227,699. Ulju County has the highest density of industrial complexes in Korea. In this study, 222Rn radioactivity concentration was measured and analyzed in 57 schools in Ulju County using 114 passive LR-115 type detectors to secure radiological safety and confirm basic information for reduction of resident exposure to 222Rn. The effective dose of 222Rn was assessed to find the actual risk of the concentration surveyed in schools to human beings. The dose depended on four factors: subjects, 222Rn concentration, dose coefficient, and time. The individuals subjected to dose estimation were classified into three types: students, teachers, and office workers. The subjects had different dwelling locations and times. The findings demonstrate that the radiological hazard to students and workers at schools in Ulju County owing to 222Rn is negligible in terms of 222Rn activity recommendation level.