Sains Malaysiana 48(9)(2019): 2021–2028

http://dx.doi.org/10.17576/jsm-2019-4809-23

A Study on the Atmospheric Dispersion of Radionuclide Released from TRIGA MARK II Reactor using Gaussian Plume Model

(Suatu Kajian Penyebaran Atmosfera pada Radionuklid Terbebas daripada Reaktor TRIGA MARK II menggunakan Model Gaussian Plum)

JEYLEENNY RANTY JANSON¹*, SITI NUR AIN BINTI SULAIMAN¹, SUHAIMI BIN KASSIM², NUR SYAHIRAH BINTI MUSZAKHIR¹, FAIZAL MOHAMED¹, SYAZWANI MOHD FADZIL¹ & KHOO KOK SIONG¹

¹Nuclear Technology Research Centre, School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

²Reactor Technology Centre, Technical Support Division, Malaysia Nuclear Agency, 43600 Bangi, Selangor Darul Ehsan, Malaysia

Diserahkan: 8 April 2019/Diterima: 3 Julai 2019

ABSTRACT

TRIGA MARK II reactor is a research facility and site for neutron activation analysis. Should there be fuel rod damage for the first time, amongst its possible causes are human and environmental factor. Consequently, the study objectives were to determine types and released rates of radionuclides dispersed to air and deposited on land through core inventory using ORIGEN2 Code; to determine the concentrations of radionuclides released to air and deposited on land using Gaussian Plume Model; and to determine the exposure doses of radionuclides released to air and deposited on land using exposure dose equation. Core inventory identified types of radionuclides which were Br, I, Kr and Xe. The chosen radioisotopes of Br-83, I-131, Kr-85 and Xe-135 were based on its negative impact on human body system. The maximum released rate of Br-83 was 0.522×105 Bq/s; I-131 was 2.818×105 Bq/s; Kr-85 was 6.447×105 Bq/s and Xe-135 was 4.850×105 Bq/s, respectively. The maximum concentration in the atmosphere for Br-83 was 1.981 Bq/m3; I-131 was 0.062 Bq/m3; Kr-85 was 25.034 Bq/m3 and Xe-135 was 4.248 Bq/m3. The annual exposure doses for four selected radionuclides were 1326 μSv/yr (300 m), 119 μSv/yr (1000 m) and 7.463 μSv/yr (4000 m) for Category B, whereas for Category were 194 μSv/yr (300 m), 17.440 μSv/yr (1000 m) and 1.090 μSv/yr (4000 m), respectively. Conclusively, this study shows that in case of fuel rod damage on TRIGA MARK II reactor, radionuclide atmospheric dispersion at a distance of 300 m (Category B) was exceeding the standard annual exposure dose limit (1000 μSv/yr).

Keywords: Atmospheric dispersion; exposure dose; Gaussian Plume Model; TRIGA MARK II

ABSTRAK

Reaktor TRIGA MARK II merupakan sebuah insitut penyelidikan dan tempat untuk menjalankan analisis pengaktifan neutron. Sekiranya berlaku kerosakan rod bahan api buat pertama kalinya, antara sebab yang berkemungkinan adalah faktor manusia berserta persekitaran. Akibatnya objektif kajian adalah untuk menentukan jenis dan kadar pelepasan radionuklid yang tersebar ke udara dan mendap dalam tanah melalui inventori teras menggunakan Kod ORIGEN2; untuk menentukan kepekatan radionuklid terbebas ke udara dan mendap dalam tanah menggunakan Model Kepulan Gaussian; dan untuk menentukan dos dedahan radionuklid yang terbebas ke udara dan mendap dalam tanah menggunakan rumus dos dedahan. Inventori teras mengenal pasti jenis radionuklid yang terbebas berserta isotopnya iaitu adalah Br, I, Kr dan Xe. Radionuklid terpilih iaitu Br-83, I-131, Kr-85 dan Xe-135 adalah berdasarkan impak negatif terhadap sistem tubuh badan manusia. Kadar pelepasan maksimum masing-masing bagi Br-83 adalah 0.522×105 Bq/s; I-131 adalah 2.818×105 Bq/s; Kr-85 adalah 6.447×105 Bq/s dan Xe-135 adalah 4.850×105 Bq/s. Kepekatan maksimum di atmosfera bagi Br-83 adalah 1.981 Bq/m3; I-131 adalah 0.062 Bq/m3; Kr-85 adalah 25.034 Bq/m3 dan Xe-135 adalah 4.248 Bq/m3. Dos dedahan tahunan untuk empat radionuklid terpilih masing-masing adalah 1326 μSv/thn (300 m), 119 μSv/thn (1000 m) dan 7.463 μSv/thn (4000 m) bagi Kategori B manakala bagi Kategori D adalah 194 μSv/thn (300 m), 17.440 μSv/thn (1000 m) dan 1.090 μSv/thn (4000 m). Kesimpulannya, keputusan kajian menunjukkan sekiranya berlaku kerosakan rod bahan api pada reaktor TRIGA MARK II, penyebaran atmosfera oleh radionuklid pada jarak 300 m (Kategori B) adalah melebihi had dos dedahan piawai (1000 μSv/thn) yang dibenarkan.

Kata kunci: Dos dedahan; Model Kepulan Gaussian; penyebaran atmosfera; TRIGA MARK II

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