Sains Malaysiana 47(5)(2018): 1017–1023 http://dx.doi.org/10.17576/jsm-2018-4705-18 Radiological Dose Assessment of Natural Radioactivity in Malaysian Tiles Using Resrad-Build Computer Code (Penilaian Dos Sinaran Keradioaktifan Tabii dalam Jubin di Malaysia Menggunakan Kod Komputer Resrad-Build) AZNAN FAZLI ISMAIL*, SHITTU ABDULLAHI, SUPIAN SAMAT & MUHAMAD SAMUDI YASIR ABSTRACT This research reports the annual effective dose of dwellers based on the fnding of natural radioactivity concentrations in Malaysian tiles. A total of 30 tiles samples obtained from the manufacturer or bought directly from local hardware store. Natural radioactivity was analyzed using gamma spectrometry system for 12 h counting times. The activity concentration of 226 Ra, 232 Th, and 40 K in the analyzed samples ranged from 37.50 – 158.05 Bq kg -1 , 42.22 – 80.19 Bq kg -1 and 349.46 – 750.18 Bq kg -1 , respectively. The determined radium equivalent activity was below than the recommended limit of 370 Bq kg -1 . The external dose received by dwellers due to natural radionuclides in tiles were projected for 1, 5, 10, 20 and 50 years through six exposure pathways using Resrad-build computer code. The results showed that the annual effective dose received by dwellers increased for the investigated timelines but still lower than the annual recommended limit of 1500 µSv. The simulation result also indicates that radon gas was the primary radiation exposure which contributes 80-94 % from the total radiation exposure to dwellers. Keyword: Annual effective dose; natural radionuclides; Resrad-Build computer code; tiles ABSTRAK Kajian ini melaporkan kadar dos yang diterima oleh penghuni bangunan berdasarkan kepekatan radionuklid tabii dalam jubin di Malaysia. Sebanyak 30 sampel jubin telah diperoleh daripada pengeluar atau dibeli secara terus daripada kedai. Kepekatan aktiviti radionuklid tabii dianalisis menggunakan sistem spektrometri sinar gama dengan masa pembilangan selama 12 jam. Kepekatan aktiviti 226 Ra, 232 Th, dan 40 K dalam sampel masing-masing berada dalam julat 37.50 – 158.05 Bq kg -1 , 42.22 – 80.19 Bq kg -1 dan 349.46 – 750.18 Bq kg -1 . Nilai aktiviti kesetaraan radium yang ditentukan adalah di bawah had yang disyorkan ititu 370 Bq kg -1 . Dos dedahan tahunan yang diterima oleh penghuni bangunan berpunca daripada radionuklid tabii dalam jubin telah ditentukan menggunakan kod komputer Resrad-build bagi 1, 5, 10, 20 dan 50 tahun melalui enam laluan dedahan. Keputusan kajian mendapati kadar dos dedahan tahunan yang diterima oleh penghuni meningkat bagi tempoh masa yang dikaji tetapi masih rendah daripada had dos tahunan yang dicadangkan iaitu 1500 μSv. Hasil simulasi juga menunjukkan gas radon adalah sumber dedahan sinaran utama yang menyumbang 80-94% daripada jumlah dedahan sinaran kepada penghuni bangunan. Kata kunci: Dos dedahan tahunan; jubin; kod komputer Resrad-build; radionuklid tabii INTRODUCTION Studies of natural radiation background considered relevant because it is the primary source of exposure to human kind. About 90% of radiation exposures come from natural sources such as terrestrial radiation, cosmic radiation, and radon gas. The exposure of the public to natural radiation sources has been estimated to result in an annual effective dose equivalent of 2.4 mSv (UNSCEAR 2000). The building material is one of the sources or radiation exposures to dwellers. Knowledge of radiation levels in buildings is clearly of fundamental importance in the assessment of population exposure, as the majority of individuals spend most time indoors. Building materials can cause signifcant gamma dose indoors, due to their natural radionuclide content (Trevisi et al. 2012). Though building materials act as radiation attenuator from outdoor radiation, they also contribute to the radiation dose to dwellers, if the building materials used contain a high concentration of natural radioactivity. For this reason, there are many research which reports the natural radionuclide content of building materials over the world. Various studies carried out by other researchers showed that the indoor dose rate would accordingly elevate to the natural radioactivity concentration in building materials (Al-Zahrani 2017; Nisha et al. 2016; Raghu et al. 2017; Senthilkumar et al. 2014; Trevisi et al. 2012). In addition to that, the knowledge on the level of natural radioactivity in building materials is imperative to assess the possible radiological hazard to dwellers and to develop standard and guidelines for the local authority.