Radon-222 concentration rate and emanation rate by using cr-39 solid state nuclear track detector at Gua Penyu

Radon-222 is a naturally radioactive substance that is been produced from the decay of Uranium-238. It is colorless, odorless and present in earth crust. Radon gas has been measured at Gua Penyu in Kota Gelangi to determine the concentration and emanation rate of radon gas in this cave. Radon concentration has been measured using passive dosimeters which is SSNTD CR-39. A total of 20 dosimeters were placed and distributed in this cave. 10 dosimeters were embedded into the ground and another 10 were placed 1 m from the ground for a period of one month which started from 6 March 2015 and end on 10 April 2015. After the exposure time, the SSNTD CR-39 sheet were removed and chemically etched in NaOH solution (6M at 70°C for 6 hours) in a constant temperature bath. They were then washed under tap water and dried prior to microscope inspection. The number of track density were be counted to measure the rate concentration. Radon gas concentration rate were found to have an average value of 4.77±0.6 Bqm-3. The concentration rate was much lowered compared to indoor concentration allowed by USEPA Action Limit which was 148 Bqm-3.The radon emanation from the ground of cave have an average value 0.08 Bqm-2 day-l. The average of annual effective dose rate is 0.12 mSvyear-1 and below recommended value by ICRP which was 3 - 10 mSvyear- l . All the measured value is in safe range. Thus, this cave is safe to be visited.