Contribution of Selangor and Johor clay bricks towards the natural radioactivity exposure to dweller

Abstract

ABSTRACT 

At present, soil and mineral based building material such as bricks are one of the main components in building construction in Malaysia. This building material is a direct source of radiation exposure since it contains naturally occurring radioactive materials (NORM). In this study, clay brick samples used were obtained from 7 factories in Selangor and Johore, Malaysia. The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in these samples of clay bricks were determined using a comparative method and was analysed using gamma spectrometry with HPGe detector. The mean values of activity concentrations for ²²⁶Ra, ²³²Th and ⁴⁰K were found to be in the range of 39.04 ± 0.88 Bqkg^-1 - 73.61 ± 5.32 Bqkg^-1, 43.38 ± 2.60 Bqkg^-1 - 73.45 ± 1.51 Bqkg^-1, and 381.54 ± 11.39 Bqkg^-1 - 699.63 ± 15.82 Bqkg^-1, respectively. The radiation hazard of NORM in the samples was estimated by calculating the radium equivalent activity (Ra_eq), external hazard index (H_ex) and internal hazard index (H_in). Radium equivalent activity (Ra_eq) determined was in the range of 151.90 Bqkg^-1 - 194.22 Bqkg^-1 which is lower than the limit of 370 Bqkg^-1 (equivalent to 1.5 mSvyr^-1) recommended in the NEA-OECD report in 1979, whereas external hazard index (H_ex) and internal hazard index (H_in) were between 0.20 – 0.26 and 0.52 - 0.71 respectively. The annual effective dose rate exposure to a dweller received from the clay bricks was calculated to be in the range of 0.35 ± 0.18 mSvy^-1 - 0.43 ± 0.09 mSvy^-1.

ABSTRAK 

Bahan binaan berasaskan tanah dan mineral seperti batu bata kini telah menjadi sebagai komponen utama pembinaan bangunan di Malaysia.Bahan binaan ini merupakan sumber langsung dedahan sinaran kerana ia mengandungi bahan radioaktif tabii (NORM). Kajian ini menggunakan  batu bata tanah liat yang diperolehi dari 7 kilang di Selangor dan Johor.  Kepekatan aktiviti  ²²⁶Ra, ²³²Th dan ⁴⁰K dalam sampel batu bata tanah liat ditentukan menggunakan kaedah bandingan dan dianalisis mengggunakan spektrometri gama dan pengesan  HPGe. Nilai min kepekatan aktiviti bagi masing-masing ²²⁶Ra, ²³²Th dan ⁴⁰K berada dalam julat 39.04 ± 0.88 Bqkg^-1 - 73.61 ± 5.32 Bqkg^-1, 43.38 ± 2.60 Bqkg^-1 - 73.45 ± 1.51 Bqkg^-1, dan 381.54 ± 11.39 Bqkg^-1  - 699.63 ± 15.82 Bqkg^-1. Hazard sinaran NORM dalam sampel dianggarkan dengan mengira aktiviti setara radium (Ra_eq), indeks hazard luaran (H_ex) dan indeks hazard dalaman (H_in). Aktiviti setara radium (Ra_eq) didapati dalam julat 151.90 Bqkg^-1 - 194.22 Bqkg^-1 yang mana lebih rendah daripada had yang disarankan dalam laporan NEA-OECD pada tahun 1979 iaitu 370 Bqkg^-1 (setara dengan 1.5 mSvth^-1), manakala bagi indeks hazard luaran (H_ex) dan dalaman (H_in)  pula masing-masing didapati antara  0.20 – 0.26 dan 0.52 - 0.71. Kiraan menunjukkan bahawa kadar dos dedahan berkesan tahunan yang diterima oleh penghuni bangunan dari batu bata tanah liat berada dalam julat  0.35 ± 0.18 mSvth^-1- 0.43 ± 0.09 mSvth^-1.