Sains Malaysiana 43(10)(2014): 1565–1571

Radiological Impact Assessment of Fukushima Daiichi Nuclear Accident on

Malaysian Marine biotas via Ocean Partway using Erica Code System

(Penilaian Kesan Radiologi terhadap Kehidupan Akuatik melalui Lautan Pasifik ke Malaysia

Akibat Bencana Nuklear Fukushima Daiichi dengan Kod-Sistem Erica)

HOH SIEW SIN¹, SUKIMAN SARMANI² & KHOO KOK SIONG¹*

¹School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia

²School of Chemical Sciences & Food Technology, Faculty of Science and Technology

Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia

Diserahkan: 3 September 2013/Diterima: 10 Februari 2014

ABSTRACT

Fukushima Daiichi nuclear disaster led to radioactive contamination crisis was resulted from a series of system failures, nuclear meltdown and radioactive material releases, following the 9.0 magnitude of earthquake and tsunami on March 11, 2011. The objectives of this study were; to investigate the movement of radionuclides based on oceanography and morphology of Pacific Ocean and Southeast Asia (Malaysia); to estimate the time for radionuclides to reach Malaysia and to calculate the amount of total absorbed dose rate for selected marine biotas namely benthic fish and pelagic fish. ERICA code system was used because it has the ERICA integrated approach to assess the radiation risk of biota. The estimations of radionuclide discharge from Fukushima Daiichi nuclear disaster were based on Cs-137 (half-life of 30.17 years), I-131 (half-life of 0.02 years). The parameters such as discharge rate of radionuclides (Bq/s), water depth (m), the distance between the target coast of Malaysia and radionuclide release point (m), the distance between the receptor and radionuclide release (m) and the velocity of the water/ocean currents (m/s) were studied. The results showed that the minimum estimated arrival time of radionuclides to reach Malaysia is located in Sandakan, Sabah, which is approximated at 4.82 years (Dec 2015) with an average of 5.039±0.310 years after the accident. Meanwhile, maximum estimated arrival time of radionuclides to Malacca is 5.87 years (Jan 2017) with an average of 5.527±0.480 years. The lowest estimated total absorbed dose rate by benthic fish is 0.0583 μGy/h with an average of (6.33±0.71) × 10-2 μGy/h in Malacca whereas the highest estimated total absorbed dose rate by benthic fish is 0.0751 μGy/h with an average of (7.11±0.57) × 10-2 μGy/h in Sandakan, Sabah. Pelagic fish in Malacca shows the lowest estimated total absorbed dose rate of 0.00149 μGy/h with an average of (1.62±0.18) × 10-3 μGy/h whereas Sandakan, Sabah showed the highest estimated total absorbed dose rate of 0.00193 μGy/h with an average of (1.83±0.15) × 10-3 μGy/h. The total absorbed dose rate and risk quotient of ERICA code system show that for all reference organisms, the probability of exceeding the selected screening dose rate of 400 μGy/h by aquatic biota is below the probability selected. Therefore, no measurable population of chronic exposure effects would occur at this stage. Nonetheless, a normal experimental analysis of fish samples should be performed in order to monitor the radiation effects to marine ecosystem.

Keywords: ERICA; Fukushima Daiichi nuclear disaster; marine biota; total absorbed dose rate

ABSTRAK

Kemalangan Loji Kuasa Reaktor Nuklear Fukushima Daiichi merupakan krisis pencemaran nuklear akibat kerosakan dan pelepasan bahan radiokatif akibat bencana gempa bumi bermagnitud 9.0 diikuti tsunami yang melanda Jepun pada 11 Mac 2011. Objektif kajian ini adalah; untuk mengkaji cara pergerakan radionuklid berdasarkan arus dan morfologi oseanografi Lautan Pasifik dan Asia Tenggara; menjangka masa pergerakan radionuklid ke Malaysia yang dibebaskan oleh kemalangan Reaktor Nuklear Fukushima Daiichi melalui perairan Malaysia dan mengira jumlah anggaran kadar dos terserap terhadap ikan bentik dan ikan pelagik. Kod sistem ERICA digunakan kerana ia mempunyai struktur berdasarkan Pendekatan ERICA Bersepadu untuk menilai risiko sinaran kepada biota. Radionuklid dianggap bebas daripada loji kuasa reaktor nuklear berdasarkan Cs-137 (separuh hayat 30.17 tahun) dan I-131 (separuh hayat 0.02 tahun). Parameter seperti kadar aktiviti radionuklid yang dibebaskan (Bq/s), kedalaman air (m), jarak antara sasaran pantai Malaysia dan tempat melepaskan radionuklid (m), jarak antara reseptor dengan tempat melepaskan radionuklid (m) dan kadar kelajuan air/arus pengairan lautan (m/s) telah dikaji. Hasil kajian menunjukkan jangkaan masa tercepat ketibaan radionuklid ke Malaysia adalah 4.82 tahun (Dis 2015) dengan purata 5.039±0.310 tahun bertempat di Sandakan, Sabah manakala jangkaan masa terlambat adalah 5.87 tahun (Jan 2017) bertempat di Melaka dengan purata 5.527±0.480 tahun. Jumlah anggaran kadar dos terendah terhadap ikan bentik mengikut jarak terjuah adalah 0.0583 μGy/j berpurata (6.33±0.71) × 10-2 μGy/j bertempat di Melaka manakala jumlah kadar dos tertinggi terhadap ikan bentik mengikut jarak terdekat adalah 0.0751 μGy/j berpurata (7.11±0.57) × 10-2 μGy/j di Sandakan. Ikan pelagik di Melaka mempunyai anggaran jumlah kadar dos terendah mengikut jarak terjuah iaitu 0.00149 μGy/j dengan purata (1.62±0.18) × 10-3 μGy/j manakala Sandakan mempunyai jumlah kadar dos tertinggi mengikut jarak terdekat iaitu 0.00193 μGy/j berpurata (1.83±0.15) × 10-3 μGy/j. Jumlah kadar dos terserap dan tahap risiko kod sistem ERICA  menunjukkan bahawa untuk semua rujukan organisma, kebarangkalian melebihi kadar dos terhad yang dipilih iaitu 400 μGy/j oleh biota akuatik adalah di bawah kebarangkalian yang dipilih. Oleh itu, tidak ada kesan pendedahan kronik kepada populasi yang dapat diukur pada peringkat ini. Walau bagaimanapun, penganalisian sampel ikan perlu dilakukan untuk memantau kesan sinaran terhadap ekosistem marin.

Kata kunci: Biota lautan; ERICA; jumlah kadar dos terserap; kemalangan Loji Kuasa Reaktor Nuklear Fukushima Daiichi

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*Pengarang untuk surat-menyurat; email: khoo@ukm.edu.my