Abstract
The purpose of this study is to evaluate the effective dose of radon by radon exposure by measuring the concentration of radon in university lecture room. The measurement of radon concentration was made in two lecture rooms on the first floor of reinforced concrete structure from March to May, 2018. On weekends when there was no use of the lecture room, it was measured for 24 hours in a closed state for 12 hours before measurement, and continued for 12 hours in 12 hours and 12 hours in continuous for 5 weeks. The indoor radon concentration was measured by a radon meter and an analysis program, and the indoor radon concentration per unit time was converted in real time. The annual effective dose and the continuously measured radon concentration due to radon inhalation were analyzed for mean and standard deviation, coefficient of variation, indoor radon concentration range, and quartile range. The closed lecture room radon concentration was estimated to be $67{\sim}81.8Bq{\cdot}m^{-3}$ (mean $74.5{\pm}6.65Bq{\cdot}m^{-3}$) and the effective dose per year was $0.289{\sim}0.353mSv{\cdot}y^{-1}$. The average radon concentration in normal operation was $26.6{\sim}54Bq{\cdot}m^{-3}$ (mean $40.2{\pm}8.34Bq{\cdot}m^{-3}$), which was 54% lower than the closed room. The mean radon concentration was $48.3{\pm}5.94Bq{\cdot}m^{-3}$ before the start of the academic year, $31.3{\pm}6.64Bq{\cdot}m^{-3}$, the average radon concentration was $41.9{\pm}9.64Bq{\cdot}m^{-3}$, $0.115{\sim}0.233mSv{\cdot}y^{-1}$. Radon concentration $32.2{\sim}54Bq{\cdot}m^{-3}$ (average $45.7{\pm}5.2Bq{\cdot}m^{-3}$) at 18:00 o'clock without the lecture at 09:00 the following day, quaternary range $43.9{\sim}48.8Bq{\cdot}m^{-3}$, annual effective dose $0.190{\sim}0.211mSv{\cdot}y^{-1}$ respectively. Radon concentration was $26.6{\sim}40Bq{\cdot}m^{-3}$ (average $31.3{\pm}6.64Bq{\cdot}m^{-3}$) from 09:00 am to 18:00 pm, which was reduced by 68.5% compared to the classroom without class, and the quartile range was $28.3{\sim}33.8Bq{\cdot}m^{-3}$, and annual effective dose was $0.122{\sim}0.146mSv{\cdot}y^{-1}$. The average radon concentration in the lecture room was 10 min resting time ($31.8{\pm}6.54Bq{\cdot}m^{-3}$) after lecture 50 minutes, 10 minutes resting time ($32.3{\pm}7.18Bq{\cdot}m^{-3}$) after 1 hour and 50 minutes lecture, and $0.008{\sim}0.013mSv{\cdot}y^{-1}$. The average indoor radon concentration of $40.2{\pm}8.92Bq{\cdot}m^{-3}$ for 2 hours and 50 minutes of continuous use in classroom, the annual effective dose of $0.01{\sim}0.016mSv{\cdot}y^{-1}$ for 50 minutes or 1 hour 50 minutes, indoor radon concentration and annual effective dose of about 30% respectively. The radon concentrations in the lecture room were measured at lower levels than the indoor radon concentration control standards, and the hazard coefficients from the radon inhalation in these environments were evaluated to be lower than the population mean life time cancer risk.