Influence of ventilation on the reduction of the radon concentration in an underground research facility

The concentration of radon in an underground research facility (URF) was measured by setting up 12 sampling points in the URF and with 3 different measurement methods. All the methods were calibrated in the radon laboratory of the No. 6 Institute of Nuclear Industry. The accumulation of radon in the URF was observed before a ventilation system was applied. The reduction of radon concentration in the URF by 1-hour ventilation was also observed. Experimental result indicates that the concentration of radon in the URF increased from 15 to 50 Bq·m⁻³ in 5 days without ventilation, and decreased to less than 10 Bq·m⁻³ with 1-hour ventilation. Applying the average working time of 4 hours per day of the workers in the URF, the additional effective dose is 0.75 msv·y⁻¹ when 1 hour ventilation is applied before entering the URF and 13 mSv·y⁻¹ without ventilation. These figures strongly suggest that for the health of the workers, ventilation in such underground research facilities is needed.