The processing of mineral monazite to produce thorium (Th) and rare earth elements may create a radiological impact if the processing and residue are not properly or safely managed. Malaysian Atomic Energy Licensing Board (AELB) categorized monazite as a radioactive material because the concentration of thorium in the mineral is higher than 1Bq/g. Therefore, the current study aimed to determine the separation percentage of thorium from Malaysian monazite and to assess the radiological impact of thorium during various stages involved in the processing. In this study, monazite was digested by hot sulphuric acid followed by selective precipitation of thorium using ammonia. Neutron Activation Analysis (NAA) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) techniques were used to determine thorium. The result of the study showed that the average concentration of thorium in Malaysian monazite ore was 17,990.5 ± 1,239.3 ppm. After digestion, 46.56 % of thorium was recovered and about 97.68 % of thorium was separated as thorium hydroxide from the obtained sulphate leach solution. The study also indicated that less than 3% of Thorium entered in the rich rare earth elements filtrate during the separation. The calculated maximum dose that could be received by workers and public from the monazite ore were 61.91 ± 4.27 mSv/y and 54.24 ± 3.73 mSv/y respectively. However, during the processing of 25 g the monazite ore, the worker and public will receive a lower dose in the range of 0.01 -0.72 and 0.01 -0.63mSv/y respectively. Based on the results, useful suggestions on how to improve thorium recovery and how to minimize the radiological impact as a whole are provided. Keywords: thorium, monazite, radiological impact, separation, dose AbstrakPemprosesan mineral monazit untuk menghasilkan torium (Th) dan unsur nadir bumi boleh menyebabkan impak radiologi sekiranya pemprosesan dan residu tidak diuruskan dengan baik. Lembaga Perlesenan Tenaga Atom Malaysia (AELB) telah mengkategorikan monazit sebagai bahan beradioaktif kerana kepekatan torium dalam mineral adalah tinggi iaitu melebihi 1Bq/g. Oleh itu, tujuan utama kajian ini adalah untuk menentukan peratus pengasingan torium daripada bijih monazit dan menilai impak radiologi torium dalam beberapa peringkat yang terlibat dalam pemprosesan. Dalam kajian ini, asid sulfurik telah digunakan untuk menghadam monazit dan diikuti dengan pemendakan terpilih torium menggunakan ammonia. Teknik Analisis Pengaktifan Neutron (NAA) dan Induktif Plasma Pendua -Spektrometri Jisim (ICP-MS) telah digunakan untuk menentukan kandungan torium. Hasil kajian menunjukkan purata kepekatan torium dalam bijih monazit Malaysia adalah 17,990.5 ± 1,239.3 ppm. Selepas penghadaman, peratus mendapatkan torium adalah 46.56 % dan 97.68 % torium telah diasingkan sebagai torium hidroksida daripada larutan larut lesap sulfat. Kajian juga menunjukkan kurang daripada 3 % torium terdapat dalam turasan unsur nadir bumi semasa pengasingan. Dos maksimum yang boleh diterima oleh pekerja dan orang awam daripada...

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Solvent extraction is a powerful separation technique in the preparation of nuclear grade thorium. In this study, monazite thorium concentrates produced from Malaysian monazite were used. Thorium was extracted from an aqueous nitric acid medium with TBP (30%) in kerosene and Aliquat-336 (10%) in kerosene, respectively. Constant experimental conditions were used for the extraction in terms of the molarity of nitric acid, concentration of extractants in kerosene, organic/aqueous volumetric ratio, mixing time, and contact time between phases. The stripping process was carried out with distilled water. The determination of thorium and rare earth elements (REEs) in the monazite thorium concentrates and aqueous solutions were performed by using inductively coupled plasma mass spectrometry (ICP-MS). The concentrations of thorium in the thorium concentrate samples were in the range of 11.58 -83.56%. Three stages of extraction and three stages of stripping were carried out for the extraction of thorium from the REEs in the nitrate solution. The results of the study showed that the thorium extraction efficiency was in the range of 60.96 -99.75% using TBP (30%) in kerosene and Aliquat-336 (10%) in kerosene. Thorium was stripped from the loaded TBP (30%) in kerosene and Aliquat-336 (10%) in kerosene at an average stripping percentage of 89.04% and 75.75%, respectively. The stripped aqueous solutions were analysed, and it was shown that the thorium content was in the range of 29.49 -91.28%. This study indicated that both extractants can be successfully used to recover thorium from REEs, but in order to increase the purification of thorium, the extraction and stripping process cycle should be increased.Keywords: thorium, rare earth elements, solvent extraction, monazite thorium concentrate Abstrak Pengekstrakan pelarut adalah teknik pengasingan yang kuat digunakan untuk mengasingkan torium bergred nuklear. Dalam kajian ini, pekatan torium monazit yang dihasilkan daripada monazit Malaysia telah digunakan. Torium diekstrak daripada medium akues asid nitrik dengan TBP (30%) dalam kerosin dan Aliquat-336 (10%) dalam kerosin. Kondisi eksperimen digunakan iaitu molariti asid nitrik, kepekatan pengekstrak dalam kerosin, nisbah isipadu organik/akues, masa percampuran dan masa sentuhan antara fasa dikekalkan. Proses pelucutan dilakukan menggunakan air suling. Torium dan unsur nadir bumi (REEs) dalam pekatan torium monazit dan larutan akues ditentukan menggunakan spektrometri jisim plasma gandingan teraruh (ICP-MS). Kepekatan torium dalam sampel pekatan torium ditentukan adalah dalam julat 11.58 -83.56%. Tiga peringkat pengekstrakan dan pelucutan dilakukan untuk mendapatkan torium dari REEs dalam larutan nitrat. Hasil kajian menunjukkan kecekapan pengekstrakan torium adalah dalam julat 60.96 -99.75% menggunakan TBP (30%) dalam kerosin dan Aliquat-336 (10%) dalam kerosin. Torium telah dilucutkan daripada muatan TBP (30%) dalam kerosin dan Aliquat-336 (10%) dalam kerosin dengan purata peratus pelucutan masing -masing adalah 89.04...

Coal-fired power plants and industrial waste (IW) incinerators increasingly dispose large amounts of fly ash that cause environmental contamination by toxic heavy metals. This study aimed to investigate the concentration of heavy metals and measure the specific activity of naturally occurring radioactive materials (NORM) that remain in the fly ash of coal power plants and industrial incinerators. Ash samples were collected from the Kapar and Jana Manjung coal-fired power plants and the Kualiti Alam industrial incinerator in Malaysia. The concentrations of As,

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