Malaysian Journal of Analytical Sciences Vol 22 No 3 (2018): 446 - 451

VENTILATION EFFECT ON THE Radon-222 ANNUAL EFFECTIVE DOSE inSIDE Gua Gajah and Gua Penyu CAVES, Kompleks Gua Kota Gelanggi, Pahang, Malaysia

(Kesan Pengudaraan Kepada Dos Berkesan Tahunan Radon-222 dalam Gua Gajah dan Gua Penyu, Kompleks Gua Kota Gelanggi, Pahang, Malaysia)

Nazree Ahmad¹*, Junaidah Md Sani¹,Nur Hafilah Muslim¹, Nur Amirah Alias¹, Ahmad Saat²

¹Faculty of Applied Sciences

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

²Institute of Science,

Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia

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

Received: 4 December 2016; Accepted: 1 December 2017

Abstract

A study to determine the concentration and emanation rate of Radon-222 were done inside Gua Gajah and Gua Penyu limestone caves, Kompleks Gua Kota Gelanggi, Pahang, Malaysia to find the link between ventilation and annual effective dose. Gua Gajah has two major openings and features uneven earth surface unlike Gua Penyu which has single entrance and smooth passage way. Dosimeters with CR-39 solid state nuclear track detector (SSNTD) were distributed 15 m apart. For emanation rates, dosimeters were embedded about 5 cm into cave floor while for concentration measurements, they were placed 1 m above ground. The control samples were placed in front of the main entrance. The samples were left and collected after 30 days. Every CR-39 samples were etched with 6M NaOH solution with 70 ᵒC for 6 hours in water bath and observed under microscope of 200x linear magnifications to calculate tracks densities. Results indicated that the average Radon-222 emanation rate inside Gua Gajah was higher than that of Gua Penyu. On the other hand, the average concentration of Radon-222 inside Gua Gajah was lower than that of Gua Penyu. The average annual effective dose of Radon-222 in Gua Gajah and Gua Penyu was 0.084 mSv yr^-1and 0.12 mSv yr^-1,respectively. These findings point out that ventilation contributed by cave openings plays an important role in reducing the indoor radon gas accumulation, thus lowering the annual effective dose.

Keywords: emanation rate, radon gas, radon concentration

Abstrak

Kajian bagi mengukur kepekatan dan kadar pemancaran Radon-222 telah dijalankan dalam gua-gua batu kapur Gua Gajah and Gua Penyu, Kompleks Gua Kota Gelanggi, Pahang, Malaysia untuk mencari hubungan di antara pengudaraan dengan dos berkesan tahunan. Gua Gajah dengan dua laluan utama menunjukkan mukabumi tidak sekata manakala Gua Penyu hanya mempunyai satu laluan masuk dan rata. Dosimeter dengan pengesan jejak nuklear keadaan pepejal CR-39 (SSNTD) diletakkan berjarak 15 m satu sama lain. Dosimeter untuk kadar pemancaran ditanam 5 cm ke dalam lantai gua manakala bagi pengukuran kepekatan, dosimeter diletakkan 1 m di atas lantai gua. Sampel kawalan diletakkan di hadapan laluan masuk utama. Kesemua sampel ditinggalkan dan dikutip selepas 30 hari. Setiap sampel CR-39 kemudiannya dicelup dalam rendaman panas larutan 6M NaOH pada 70 ᵒC selama 6 jam sebelum dicerap di bawah microskop 200x pembesaran linear untuk menentukan kepadatan trek. Hasil menunjukkan purata kadar pemancaran Radon-222 dalam Gua Gajah lebih tinggi berbanding Gua Penyu. Sebaliknya, purata kepekatan Radon-222 dalam Gua Gajah lebih rendah berbanding Gua Penyu. Dos berkesan tahunan Radon-222 untuk Gua Gajah dan Gua Penyu masing-masing ialah 0.084 mSv yr^-1dan 0.12 mSv yr^-1. Penemuan ini menunjukkan kesan pengudaraan daripada bukaan gua memainkan peranan penting dalam mengurangkan penumpukan radon gas dalaman seterusnya merendahkan nilai dos berkesan tahunan.

Kata kunci: kadar pemancaran, gas radon, kepekatan radon

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