Management of radon in tunnel drilling

According to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) report in 1982, radiation from radon contributes about 50% of all natural radiation sources to the public. The situation is worse in Hong Kong where large area is granitic containing larger amount of uranium when compared to the global mean. Radon level can therefore be on the high side during tunneling especially where poor ventilation is envisaged. This article includes realistic field study of radon in tunnel under construction. A maximum concentration of over 30,000 Bq/m3 was recorded (1 Becquerels per cubic meter is equivalent to 0.027 pico Curies/L). Radon concentration in tunnel environment is found to be related to groundwater ingress, ventilation provision and geology. A review of the current statutory control in Hong Kong is done as well as its comparison with other countries' practices. In fact, the situation can be improved through education, adopting control legislation and more specifically, having a suggested radon management plan in every tunnel drilling project.