Malaysian Journal of Analytical Sciences Vol 22 No 3 (2018): 483 - 490

DOI: 10.17576/mjas-2018-2203-16

 

 

 

The Assessment OF INDOOR Radon-222 Concentration and Emanation Rate at Gua Penyu, Pahang

 

(Penilaian Kepekatan dan Kadar Pancaran Dalaman Radon-222 di Gua Penyu, Pahang)

 

Junaidah Md Sani¹*, Nuramirah Alias ¹, Nazree Ahmad ¹, Ahmad Saat ²

 

¹Faculty of Applied Sciences,

Universiti Teknologi MARA Cawangan Pahang, 26400 Bandar Tun Abdul Razak Jengka, Pahang, Malaysia

²Institute of Science,

Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia

 

*Corresponding author:  ajun@pahang.uitm.edu.my

 

 

Received: 4 December 2016; Accepted: 1 December 2017

 

 

Abstract

The indoor Radon-222 concentration and emanation rate in Gua Penyu, Gua Gelanggi Complex, Pahang were measured using Solid State Nuclear Track Detector CR-39 (SSNTD CR-39) to evaluate the air quality and radiological exposure in this recreational cave. A total of 20 SSNTD CR-39 dosimeters were placed inside the cave at about 15 m apart each. 10 dosimeters were embedded 5 cm into cave floor to determine emanation rate, while the other 10 dosimeters were placed at one meter above the floor level for concentration measurement. The control samples were placed outside the cave 15 m from the main entrance. These SSNTD CR-39 samples were left for a month before undergone etching process with NaOH solution (6 M) at 70 °C for six hours. The radon concentration and emanation rate were both determined from the track density in each CR-39 (1cm ´ 1cm) sampling. The results showed that the radon emanation rates varied between 0.030 ± 0.004 Bqm^-2day^-1 and 0.120 ± 0.017 Bqm^-2day^-1 with the average rate of 0.080 Bqm^-2day^-1. The radon concentration was between 3.72 ± 1.60 Bqm^-3 and 7.89 ± 2.10 Bqm^-3 with the average of 4.8 Bqm^-3. These values were lower compared to indoor concentration allowed by the International Commission on Radiation Protection (ICRP) 2009 that is 200 – 300      Bqm^-3. The annual effective dose were found to range between 0.09 mSv.y^-1 and 0.20 mSv.y^-1 which was lower than recommended value 3 to 10 mSv.y^-1 put forth by the ICRP 1993. Hence, this recreational cave is safe to be visited by public.

 

Keywords:  limestone cave, emanation rate, indoor radon

 

Abstrak

Kepekatan dan kadar pancaran dalaman Radon-222 dalam Gua Penyu, Kompleks Gua Gelanggi, Pahang telah diukur menggunakan Pengesan Jejak Nuklear Keadaan Pepejal CR-39 (SSNTD CR-39) untuk menilai kualiti udara dan pendedahan radiologi dalam gua rekreasi ini. Sejumlah 20 dosimeter SSNTD CR-39 telah ditempatkan dalam gua ini setiap satu berjarak kira-kira 15 m. 10 dosimeter telah dibenamkan 5 cm ke dalam lantai gua untuk penentuan kadar pancaran, manakala 10 dosimeter lain ditempatkan pada satu meter di atas aras lantai untuk pengukuran kepekatan. Sampel kawalan ditempatkan di luar gua 15 m  hadapan pintu masuk utama. Sampel SSNTD CR-39 ini ditinggalkan selama sebulan sebelum melalui proses punaran dalam larutan NaOH (6M) pada 70 °C selama enam jam. Kepekatan dan kadar pancaran radon keduanya ditentukan dari ketumpatan jejak dalam setiap sampel (1 cm ´ 1cm) CR-39.  Hasil kajian menunjukkan bahawa kadar pancaran radon berada antara 0.030 ± 0.004 Bqm^-2hari^-1 dan 0.120 ± 0.017 Bqm^-2hari^-1 dengan purata 0.080 Bqm^-2hari^-1. Kepekatan radon antara 3.72 ± 1.60 Bqm^-3 and 7.89 ± 2.10 Bqm^-3 dengan purata 4.8 Bqm^-3. Nilai-nilai ini lebih rendah berbanding nilai dalaman 200 - 300 Bqm^-3 yang dibenarkan oleh Jawatankuasa Perlindungan Radiasi Antarabangsa (ICRP) 2009. Didapati dos berkesan tahunan berada antara 0.09 mSv.tahun^-1 dan 0.20 mSv.tahun^-1 lebih rendah berbanding dengan nilai tahunan yang disyorkan oleh ICRP 1993 iaitu 3 hingga 10 mSv.tahun^-1. Justeru, gua rekreasi ini adalah selamat dikunjungi oleh orang awam.

 

Kata kunci:  gua batu kapur, kadar pancaran, radon dalaman

 

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