Sains Malaysiana 52(1)(2023): 271-280

http://doi.org/10.17576/jsm-2023-5201-22

Penentuan Kepekatan Keradioaktifan Radionuklid Semula Jadi dan Indeks Bahaya Sinaran pada Musim Hujan dari Tanah di Kawasan Sekitar Kemudahan Simpanan Jangka Panjang (LTSF) Bukit Kledang, Perak

(Determination of Natural Radionuclide Radioactivity Concentration and Radiation Hazard Index during the Rainy Season from the Soil in the Area Around the Long-Term Storage Facility (LTSF) Bukit Kledang, Perak)

MOHD IZWAN ABDUL ADZIZ¹ & KHOO KOK SIONG^1,2,*

¹Jabatan Fizik Gunaan, Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

²Pusat Penyelidikan Teknologi (NUKLEAR), Fakulti Sains dan Teknologi, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

Recieved: 22 April 2022/Accepted: 30 September 2022

Abstrak

Kajian dan pemantauan yang dilakukan terhadap taburan dan penentuan aktiviti keradioaktifan radionuklid semula jadi boleh dijadikan panduan dan rujukan serta amat berguna terutamanya ketika berlakunya dedahan sinaran yang tinggi dan tidak terancang daripada sumber antropogenik dan kemalangan nuklear global. Sampel tanah permukaan dari 12 lokasi yang telah dikenal pasti di sekitar kawasan kemudahan repositori telah diambil untuk dijalankan kajian analisis penentuan kepekatan keradioaktifan dan indeks bahaya sinaran. Pengukuran kepekatan radioaktif dalam sampel tanah dilakukan dengan menggunakan sistem pembilangan spektrometer gama yang dilengkapi dengan pengesan High Purity Germanium (HPGe). Keputusan yang diperoleh menunjukkan kepekatan radioaktiviti ²³⁸U adalah berjulat antara 17.83 - 31.80 Bq kg^-1, ²³⁴Th adalah berjulat antara 23.18 - 40.64 Bq kg^-1, ²²⁶Ra adalah berjulat antara 20.09 - 32.80 Bq kg^-1, ²²⁸Ra adalah berjulat antara 21.20 - 38.88 Bq kg^-1 dan ⁴⁰K adalah berjulat antara 9.11 - 51.39 Bq kg^-1 dengan nilai purata masing-masing adalah 21.45 Bq kg^-1, 28.17 Bq kg^-1, 24.00 Bq kg^-1, 27.43 Bq kg^-1 dan 24.01 Bq kg^-1. Nilai kepekatan radioaktiviti radionuklid tersebut didapati setara dengan nilai yang pernah dilaporkan dalam kajian terdahulu di Semenanjung Malaysia. Nilai purata yang diperoleh bagi keempat-empat parameter Indeks Bahaya Radiasi iaitu aktiviti bersamaan radium (Ra_eq), kadar dos luaran (D), dos berkesan tahunan dan indeks bahaya luaran (H_ex) masing-masing adalah 66.37 Bq kg^-1, 29.13 nGy j^-1, 20.16 μSv dan 0.18. Nilai yang diperoleh ini adalah rendah berbanding nilai purata dunia dan nilai piawaian yang diguna pakai secara global iaitu masing-masing adalah 370 Bq kg^-1, 57nGy j^-1, 480.00 μSv dan 1.0. Perbandingan dengan kajian sebelum ini juga mendapati nilai bagi keempat-empat parameter adalah rendah dan setara. Ini menunjukkan tahap bahaya radiasi di kawasan sekitar kajian adalah selamat untuk orang ramai.

Kata kunci: Bahan radioaktif semula jadi; kemudahan repositori; musim hujan; spektrometer gama; tanah

Abstract

Continuous research and monitoring on the distribution and determination of these natural radionuclides' activity as a guide and reference and are very useful, especially in an accidental exposure. Surface soil samples from 12 locations that have been identified around the repository facility area were taken for the study. Radioactive concentrations in soil samples were measured using a gamma spectrometer counting system equipped with an HPGe detector. The results obtained showed that the radioactivity concentration of ²³⁸U ranged between 17.83 - 31.80 Bq kg^-1, ²³⁴Th ranged between 23.18 - 40.64 Bq kg^-1, ²²⁶Ra ranged between 20.09 - 32.80 Bq kg^-1, ²²⁸Ra ranged between 21.20 - 38.88 Bq kg^-1 and ⁴⁰K ranged between 9.11-51.39 Bq kg^-1 with average values ​​of 21.45 Bq kg^-1, 28.17 Bq kg^-1, 24.00 Bq kg^-1, 27.43 Bq kg^-1, and 24.01 Bq kg^-1, respectively. The values obtained from this study were low or equivalent to the values previously reported in previous studies. It was also found that the mean/mean values obtained for the four parameters of the Radiation Hazard Index, namely radium equivalent activity (Ra_eq), external dose rate (D), annual effective dose and external hazard index (H_ex) were 66.37 Bq kg^-1, 29.13 nGy h^-1, 20.16 μSv and 0.18, respectively. These obtained values are low compared to the world average values and the values of globally applied standards (370 Bq kg^-1, 57nGy h^-1, 480.00 μSv & 1.0, respectively). Comparison with previous studies also found that the values for all four parameters were low and equivalent. This indicates that the level of radiation hazard in the area around the study is safe for the public.

Keywords: Gamma spectrometer; natural radioactive material; soil; repository facility; wet season

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^*Corresponding author; email: khoo@ukm.edu.my