Radiological assessment of radon-222 in Gua Gajah, Pahang, Malaysia

The purpose of this study is to determine the indoor radon-222 concentration and its emanation in Gua Gajah and to estimate radiological risks due to radon-222 by assessment of its annual effective dose. Radon is a natural radioactive substance which comes from the decay series of Uranium-238. Once it was inhaled in high concentration, it may harm human health and it may cause lung cancer. In order to study the levels concentrations of radon-222, 22 dosimeters by using the passive technique were prepared. All of these dosimeters were used with CR-39 as the solid state nuclear track detector (SSNTD) and have been distributed in the cave according to the appointed place. The samples were then being exposed to the environment in the cave for 30 days starting from March 2015 until April 2015. After 1 month, all the SSNTDs were etched with 6N NaOH solution with 70°C for 6 hours in water bath. Once being etched, all of them were washed thoroughly with tap water for an hour. Then, they were left to dry before the tracks on it were counted under 200x microscope magnification. The obtained results from this study have shown that the average of concentration of radon in Gua Gajah was 3.31±1.44 Bq.m-3 and it is varied from 4.08±3.60 Bq.m-3 to 2.66±0.93 Bq.m-3. While the emanation rate of radon in this cave was varied from 2.53±0.17 Bq.m-2. day-1 to 0.23±0.07 Bq.m-2.day-1. The average of radon emanation rate was 1.24±0.12 Bq.m-2.day-1. Further, the average annual effective dose in this study was 0.084±0.036 mSv.y-1. The value shows that the workers and visitors have not in danger condition since it was not exceeded the referred value by ICRP (1994) that is 20mSv.y-l for workers and ImSv.y-1 for occasional users (visitors).