[en] Previous studies have shown that the natural radioactivity contained in building materials have significantly influenced the dose rates in dwelling. Exposure to natural radiation in building has been of concerned since almost 80 % of our daily live are spend indoor. Thus, the aim of the study is to assess the radiological risk associated by natural radioactivity in soil based building materials to dwellers. A total of 13 Portland cement, 46 sand and 43 gravel samples obtained from manufacturers or bought directly from local hardware stores in Peninsular of Malaysia were analysed for their radioactivity concentrations. The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in the studied building materials samples were found to be in the range of 3.7-359.3, 2.0-370.8 and 10.3-1,949.5 Bq kg^-1 respectively. The annual radiation dose rates (μSv year^-1) received by dwellers were evaluated for 1 to 50 years of exposure using Resrad-Build Computer Code based on the activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K found in the studied building material samples. The rooms modelling were based on the changing parameters of concrete wall thickness and the room dimensions. The annual radiation dose rates to dwellers were found to increase annually over a period of 50 years. The concrete thicknesses were found to have significantly influenced the dose rates in building. The self-absorption occurred when the concrete thickness was thicker than 0.4 m. Results of this study shows that the dose rates received by the dwellers of the building are proportional to the size of the room. In general the study concludes that concrete building materials; Portland cements, sands, and gravels in Peninsular of Malaysia does not pose radiological hazard to the building dwellers. (author)

[en] Rare-earth (RE) extraction activities in Malaysia produces 64000 to 75000 tonnes of low- level radioactive residue annually which contains thorium concentration above the regulatory clearance limit. Since thorium is considered as non-economic element, large volumes of these RE processed residues are commonly disposed of without treatment. This research aims to investigate the separation capability of thorium from aqueous waste through an electrosorption technique using a carbon-based electrode. The leachate solution obtained from the digestion of RE extraction residue was treated with the electrosorption technique. Several parameters such as the applied voltage potential (0.2V - 0.8V vs Ag/AgCl), ion competition, and initial concentration were investigated. The results showed that the adsorption of thorium ion (ThSO₄)₃ ^2- was dominant at higher positive voltage with the trend of Kd value was Th> Pr> Nd> La> Ce. The specific adsorption capacity obtained in this study ranged from 1.0 to 8.4 mg-Th/ g-Carbon. The adsorption of ((ThSO₄)₃ ^2- conforms to the Langmuir and Freundlich adsorp- tion isotherm models, while first and second pseudo order kinetic models were well fitted for the separation ofv(ThSO₄)₃ ^2- by carbon electrodes. Characterization of the electrode carbon after treatment reveals that the migration of (ThSO₄)₃ ^2- to the surface of the carbon electrode was due to the electrostatic forces followed by diffusion into the pores and bonding with the C1s group through ion exchange and chemical non-reaction profile. In general, this study found that the application of electrosorption technique with carbon- based electrode may reduce up to 40% volume of the radioactive residue. (author)

[en] A series of phosphorus (P) doped g-C₃N₄ (P-C₃N₄) electrodes are prepared via a facile hydrothermal - calcination synthesis method, using urea as precursor and phosphoric acid (H₃PO₄) as dopant. The successful incorporation of phosphate into the framework of g-C₃N₄ nanosheets was verified by FT-IR, FESEM and EDX characterizations. In terms of molecular conformation, the FT-IR spectra phosphate transmission peak at 954 cm^-1, tri-s- triazine transmission peaks at 800 cm^-1, N-H band transmission peak at 3365 cm^-1 affirms the formation of the synthesized electrodes. P atoms have been successfully introduced into the framework of g-C₃N₄ by forming P-N bond. The as-fabricated P-C₃N₄ electrodes were applied to electrosorption performance of Th(IV) in aqueous solution in comparison with open-circuit potential (OCP) and applied positive potential. Results reveal that the P-C₃N₄ exhibits that the applied potential accelerated the adsorption rate of P-C₃N₄. The potential on the electrode accelerated the mobility of thorium ions and concentrated them in the electrical double layer (EDL) by means of electrostatic force. This is mainly ascribed to that electron-rich P atoms, acting as electron donor, efficiently trap thorium ions and substantially suppress the recombination of charge carriers. This study paves the way for tailoring design and synthesis of P-C₃N₄ electrodes have been successfully applied for effective and should be a practicable candidate as sorbent material for Th(IV) ions removal from aqueous solution. (author)

[en] This paper presents the dose rates received by dwellers based on the finding of natural radioactivity concentration in Malaysia's Portland cement. A total of 13 samples were collected from various manufacturers and suppliers were analysed using a shielded HPGe gamma-ray spectrometer for 12 hours counting times. The activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K in the analyzed cement samples ranged from 14.0 - 70.5 Bq kg^-1, 15.8 - 58.8 Bq kg^-1 dan 81.9 - 382.9 Bq kg^-1 Bq kg^-1 respectively. The external cummulative dose was evaluated using Resrad-Build Computer Code for 1, 5, 10, 20 and 50 years through the direct exposure pathways. Two scenarios have been evaluated using Resrad-Build Computer Code and the result shows that dose rates received by dwellers for both scenarios were increased for each investigated years. However, the dose rates received by dwellers for the investigated years were still lower than the annual recomended limit of 1.5 mSv. Therefore, these studies suggest that the dose contribution of Malaysian Portland cement is lower than 100 mSv which is necessary to induce the stochastic effects as suggested by ICRP 103. (Author)

[en] Besides bricks, granites and sands cement is one of the main components of building materials Cement is made from a combination of rocks and soils which is known to contain natural radioactivity. The objectives of this study were to determine the level of natural radioactivity and associated radiological hazard caused by natural radioactivity in Malaysia's Portland cements. Portland cements samples were obtained from the manufacturers or bought directly from local hardware stores. Natural radionuclide concentrations of ²²⁶Ra (²³⁸U series), ²³²Th and ⁴⁰K were determined using gamma-ray spectrometry. Activity concentrations of ²²⁶Ra (²³⁸U series), ²³²Th and ⁴⁰K were found in the range of 7.76 - 82.91 Bq kg^-1, 9.79 - 49.37 Bq kg^-1 dan 81.89 - 377.10 Bq kg^-1 respectively. Radium equivalent were found in the range of 35.36 ± 0.60 to 135.94 ± 15.27 Bq kg^-1 while the average annual equivalent dose and internal hazard index were found in the range of 80 ± 2 to 300 ± 30 μSv year^-1 and 0.12 ± 0.00 to 0.56 ± 0.07 respectively. (author)

[en] Modern life style requires people to spend most of their time indoors either in a house or in the workplace. Most modern buildings are made from soil based material which may consist of low concentration of naturally occurring radioactive materials (NORM). It is known that one of the daughters of natural uranium is ²²⁶Ra which eventually produce radon (²²²Rn) gas. Recently, more evidence has linked lung cancer to exposure to high levels of radon and also to cigarette-smoking. Consequently, this research was conducted to study the radon emanation rates in different workplaces. The radon emanations in 27 rooms with three different dimension (54 m³, 210 m³ and 351 m³) and different building materials were determined for 96 hours using Sun Nuclear Radon Monitor. The radon emanations in the rooms studied were found to be in the range of 20.6 Bq m^-3 hour^-1 to 134.3 Bq m^-3 hour^-1.The increase in humidity was found to significantly increase the radon emanation rates in the building, whereas the increase in temperature will result the decrease of radon emanation rates. In addition, the findings shows that the radon emanation rates in building were higher during the night until early in the morning which is in agreement with the findings on humidity and temperature factors. (author)

[en] This research investigates the optimal enrichment value thorium ratio that can prolong the operating cycle period, improve fuel burnup and achieve optimal thorium conversion ratio. The analysis was performed using variety of U-235 enrichment values and Th:U ratios to determine the optimal enrichment value and thorium ratio that can prolong the operating cycle period, improve fuel burnup and achieve optimal thorium conversion ratio. The study was performed using simulation of isotropic Tristructural fuel compact (TRISO) for Gas Turbine Modular Helium Reactor (GT-MHR) reactor using MCNPX version 2.7. The results showed that the increasing of U-235 enrichment will result in a higher kinf initial value and be able to maintain criticality until the end of the burning period. The thorium conversion ratio decreased with increasing U-235 enrichment and decreased from 1.0 for U-235 enrichment 10 % and above. The increased enrichment of U-235 has slowing down the rate of neutron capture by U-238 and Th-232 lead to the decrease formation of Pu- 239, Pu-241 and U-233. In addition to that, the increased enrichment of U-235 will reduce radioactivity from actinides waste. In conclusion, the increase in fuel burnup was not affected by U-235 enrichment and Th:U ratio. Thus, the most practical fuel composition proposed is U-235 20 %, Th: U 70:30 as it can maintain criticality throughout burnup, achieve long operating cycle duration and high thorium conversion ratio value. (author)

[en] Medicinal and aromatic plants have been used for many decades all over the world in disease risk reduction claims, food supplements, treatment of illnesses, and medicinal remedies. Knowledge of the radioactivity levels in medicinal and aromatic plants is paramount for the protection of human health. The levels of primordial ²²⁶Ra, ²³²Th, and ⁴⁰K were specified in seven samples of different types of medicinal and aromatic plants consumed in Malaysia. The analysis employed a low background gamma-ray spectroscopy coupled with a Germanium detector with high purity. The measurements showed that the average radioactivity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in (Bq kg^-1 ±SD) dry weight were 6.32 ± 1.19, 5.02 ± 0.95, and 372.84 ± 15.05, respectively. The annual ingestion-related effective dose as well as excess lifetime cancer risk per adult individual member of the public for ²²⁶Ra, ²³²Th, and ⁴⁰K were estimated to be 0.0032 ± 0.0006, 0.0021 ± 0.0004, 0.0042 ± 0.0002 mSv y^-1, respectively, and 0.0125 x 10^-3 ± 0.0024, 0.0081 x 10^-3 ± 0.0015, and 0.0163 x 10^-3 ± 0.0007. The radiological hazard assessment revealed that the studied medicinal plant-based materials contain natural radioactivity levels that are within the internationally advisory limit. The radiological hazard related to the ingestion of natural radionuclides in medicinal and aromatic plants for adult consumption is insignificant. (author)

[en] In this study, 52 samples of ceramic materials were studied for ²²⁶Ra, ²²²Rn, ²³²Th and ⁴⁰K natural radionuclides using high-purity germanium detector and relevant radiological hazards parameters were also appraised. Furthermore, the long-term variations of the total effective dose equivalent (TEDE) and effects of wall thickness on TEDE were established and analyzed using RESRAD-BUILD computer code. The observed percentage variations of TEDE are 2% and 8% for ²²⁶Ra and ²³²Th, respectively, while no variation observed for external dose due to ⁴⁰K. The estimated indoor doses from the studied ceramic materials are all below the recommended maximum limit. (author)

[en] Comprehensive radiological survey and evaluation of heavy metal contamination were conducted in Chini Lake, which has been awarded a pristine title of Biosphere Reserve. The concentrations of ²²⁶Ra, ²²⁸Ra, and ⁴⁰K in sediments exceeded the average soil in Malaysia. Besides, the concentration of As, V, and Zn in sediments were greater than the Dutch/Malaysian target values. Results showed that the annual effective dose equivalent (AEDE) values of sediments were slightly higher than 1 mSv/y. The pollution indices indicated that the sediments were moderately to severely contaminated. Oral consumption of the lake water could cause substantial radiation-related health issues. (author)