Radiological dose assessment of natural radioactivity in Malaysian tiles using resrad-build computer code

This research reports the annual effective dose of dwellers based on the finding 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 226Ra, 232Th, and 40K 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

Penentuan kepekatan radionuklid tabii dan indeks bahaya radiologi akibat penggunaan Condisoil® ke atas penanaman Hibiscus cannabinus (Kenaf)

Kajian ini bertujuan menentukan kepekatan aktiviti radionuklid tabii (226Ra, 228Ra dan 40K) dalam tanah, air dan tumbuhan serta faktor pemindahan daripada tanah kepada tumbuhan dan indeks bahaya radiologi akibat penggunaan Condisoil®. Sebanyak 4 sampel tanah, 14 sampel air dan 4 sampel tumbuhan telah dianalisis menggunakan sistem spektometri sinar gama. Keputusan kajian mendapati julat kepekatan aktiviti 226Ra, 228Ra dan 40K dalam sampel tanah yang menggunakan Condsoil® masing-masing adalah 13.8 - 17.6, 15.7 - 21.0 dan 44.5 - 57.7 Bq kg-1. Julat kepekatan aktiviti 226Ra, 228Ra dan 40K dalam sampel tumbuhan pula masing-masing adalah 5.0 - 18.5, 0.1 - 1.5 dan 42.7 - 321.8 Bq kg-1. Bagi sampel air, julat kepekatan aktiviti bagi radionuklid 226Ra, 228Ra dan 40K masing - masing adalah 0.3 - 0.9, 0.3 - 3.9 dan 1.4 - 11.6 Bq L-1. Julat faktor pemindahan radionuklid 226Ra, 228Ra dan 40K daripada tanah ke tumbuhan masing-masing adalah 0.42 - 0.71, 0.01 - 0.08 dan 0.85 - 5.34. Penilaian bahaya radiologi mendapati indeks kesetaraan radium berada di bawah nilai had yang dicadangkan iaitu 370 Bq kg-1. Sehubungan dengan itu, kajian ini mendapati penggunaan Condisoil® sebagai bahan penambahbaikan tanah tidak menyebabkan pertambahan radionuklid tabii ke dalam alam sekitar serta tidak mendatangkan risiko bahaya radiologi kepada manusia

Pengekstrakan dan penulenan torium oksida (ThO2) daripada mineral monazit

Monazit merupakan mineral fosfat yang mengandungi unsur nadir bumi, torium dan uranium dalam kepekatan tertentu. Kepekatan torium dalam monazit di Malaysia dilaporkan sekitar 2,525.0 - 40,868 ppm dan berpotensi digunakan sebagai bahan api untuk kegunaan reaktor nuklear torium. Sehubungan dengan itu, kajian ini bertujuan mengkaji proses pengekstrakan dan penulenan torium oksida (ThO2) daripada monazit tempatan. Proses pengekstrakan dan penulenan ThO2 dibahagikan kepada empat peringkat iaitu proses penghadaman, pengasingan, pengekstrakan pelarut dan pengkalsinan. Pencirian sampel telah dilakukan melalui analisis spektrometri jisim gandingan plasma teraruh (ICP-MS), analisis termogravimetri (TGA), pembelauan sinar-X (XRD) dan mikroskopi pengimbas elektron dengan spektroskopi serakan tenaga sinar-X (SEM-EDS). Proses penghadaman telah menghasilkan larutan larut lesap monazit ((Th,REE,U)(SO4)2) yang mengandungi sehingga 99.77 ± 7.84 mg torium. Unsur nadir bumi (La, Ce, Nd, Pr, Sm, Eu dan Gd) telah diasingkan daripada torium pada peratusan 96.73%. Manakala larutan Th(NO3)4 dan ThO2 yang dihasilkan masing- masing berketulenan 97.10 ± 0.74% dan 98.85 ± 0.69%. Sehubungan dengan itu, kajian ini menunjukkan bahawa pengekstrakan dan penulenan ThO2 daripada monazit tempatan boleh dilakukan melalui proses pengekstrakan berperingkat

Peningkatan kecekapan pemisahan air menggunakan g-C3N4 yang disinar gama

Dalam kajian ini, kesan sinar gama ke atas bahan semikonduktor g-C3N4 kGy (0.1 kGy dan 0.5) dibincangkan dan dibandingkan dengan sampel yang tidak disinar untuk melihat perbezaanya. Bahan g-C3N4 disintesis dari urea melalui proses pempolimeran haba pada suhu 520°C. Struktur dan morfologi g-C3N4 dianalisis dengan menggunakan pembelauan Sinar- X (XRD), spektroskopi transformasi Fourier inframerah (FT-IR), mikroskop pengimbas elektron pancaran medan dengan spektroskopi tenaga sinar-X (FESEM-EDX), spektroskopi cahaya nampak - ultraungu (UV-Vis) dan ketumpatan arus (LSV). Sinar gama telah mengubah struktur ikatan g-C3N4 dan mengurangkan sela jalur iaitu daripada 2.80 eV kepada 2.72 eV. Di samping itu, sampel g-C3N4 yang disinar pada 0.1 kGy menghasilkan prestasi lima kali ganda lebih tinggi iaitu daripada 3.59 μAcm-2 kepada 14.2 μAcm-2 pada 1.23 V lawan Ag/AgCl dalam larutan elektrolit 0.5 M Na2SO4 (pH7). Kesimpulannya, keputusan kajian menunjukkan bahan semikonduktor yang dirawat dengan sinar gama berpotensi untuk meningkatkan fotoelektrokimia (PEC) pemisahan air

Kajian keberkesanan pengekstrakan torium daripada larutan asid hidroklorik menggunakan Di(2-Etilheksil) asid fosforik (D2EHPA)

Pengekstrakan torium daripada larutan akueus torium tetraklorida (ThCl4) telah dilakukan dengan menggunakan larutan organik Di-(2-etikheksil) asid fosforik dalam kerosen (D2EHPA/K). Objektif kajian ini adalah untuk menentukan parameter kepekatan organik dalam pelarut dan masa campuran optimum yang mempengaruhi kecekapan pengekstrakan. Campuran torium - nadir bumi hidroksida ([Th-RE](OH)4) daripada sumber kepekatan monazit tempatan dilarutkan dalam asid hidroklorik (HCl) pada kepekatan 3 dan 4 molariti. Larutan akueus [Th-RE](OH)4 ini dicampurkan dengan pelarut organik D2EHPA/K pada kepekatan berbeza iaitu 10%, 20% dan 30%. Sebatian diaduk selama 5 hingga 20 min sebelum fasa larutan akueus dan organik dipisahkan. Kepekatan torium sebelum dan selepas pengekstrakan dianalisis menggunakan Spektrometri Jisim Plasma Gandingan Teraruh (ICP-MS). Keputusan kajian mendapati peningkatan kepekatan torium dalam larutan akueus (Th-RE)OH4 dalam julat 119.40 ± 3.43 – 121.13 ± 3.18 ppm berbanding sebelumnya. Kecekapan pengekstrakan optimum bagi torium ialah 99.8%, menggunakan D2EHPA/K pada kepekatan 30%. Keputusan kajian juga mendapati masa optimum bagi proses campuran dan pemisahan torium dalam larutan akueus kepada fasa organik masing - masing adalah 5 min. Sehubungan dengan itu, kajian ini membuktikan D2EHPA berpotensi untuk digunakan sebagai agen pengekstrakan torium daripada larutan asid hidroklorik

Investigation of activated carbon adsorbent electrode for electrosorption-based uranium extraction from seawater

To support the use of nuclear power as a sustainable electric energy generating technology, long-term supply of uranium is very important. The objective of this research is to investigate the use of new adsorbent material for cost effective uranium extraction from seawater. An activated carbon-based adsorbent material is developed and tested through an electrosorption technique in this research. Adsorption of uranium from seawater by activated carbon electrodes was investigated through electrosorption experiments up to 300 minutes by changing positive potentials from +0.2V to +0.8V (vs. Ag/AgCl). Uranium adsorption by the activated carbon electrode developed in this research reached up to 3.4 g-U/kg-adsorbent material, which is comparable with the performance of amidoxime-based adsorbent materials. Electrosorption of uranium ions from seawater was found to be most favorable at +0.4V (vs. Ag/AgCl). The cost of chemicals and materials in the present research was compared with that of the amidoxime-based approach as part of the engineering feasibility examination

Modification of Clinoptilolite as a Robust Adsorbent for Highly-Efficient Removal of Thorium (IV) from Aqueous Solutions

The natural zeolite has been modified with sulphate and phosphate. The adsorption of thorium from the aqueous solutions by using the natural and modified zeolites has been investigated via a batch method. The adsorbent samples were characterized by X-ray Diffraction (XRD), N2 adsorption–desorption (BET), Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDX). Modification of natural zeolite with sulphate and phosphate was found to increase its adsorption capacity of thorium but reduced its specific surface area (SBET). The adsorption experiments were expressed by Langmuir, Freundlich and Dubinin–Radushkevitch (D–R) isotherm models and the results of adsorption demonstrated that the adsorption of thorium onto the natural and modified zeolites correlated better with the Langmuir isotherm model than with the Freundlich isotherm model. The maximum adsorption capacity (Qo) was determined using the Langmuir isotherm model at 25 °C and was found to be 17.27, 13.83, and 10.21 mg/g for phosphate-modified zeolite, sulfate-modified zeolite, and natural zeolite, respectively. The findings of this study indicate that phosphate-modified zeolite can be utilized as an effective and low-cost adsorbent material for the removal of thorium from aqueous solutions

Radiological risk assessment of concrete building materials in Peninsular Malaysia

The use of building materials containing high concentration of naturally occurring radioactive material (NORM) may result in the increase of radiation dose rate inside the building. The assessment of radiological hazard in building materials is necessary due to the concern of radiological impact to its dwellers. Thus, the objectives of this study were to determine the level of natural radioactivity in Malaysia’s building materials and to assess the associated radiological risk among dwellers. A total of 46 sands, 43 gravels and 13 Portland cement samples have been analysed using a gamma spectrometry system. Activity concentrations of 226Ra, 232Th and 40K were found to be in the range of 4.4 Bq kg-1 to 354.9 Bq kg-1, 2.4 Bq kg-1 to 263.9 Bq kg-1 and 15.1 Bq kg-1 to 1931.7 Bq kg-1, respectively. The indoor dose rates were found to be lower than 1500 μSv year-1, which is the recommended limit for building materials. A few samples were found to have high values of the representative gamma level index, external hazard index and internal hazard index compared to the suggested value of one. The radiological risk assessments to dwellers using Resrad-Build computer code showed that the dose rates for the Portland cement, sand and gravel increased annually over a period of 50 years

Determination of indoor doses and excess lifetime cancer risks caused by building materials containing natural radionuclides in Malaysia

The activity concentrations of 226Ra, 232Th, and 40K from 102 building materials samples were determined using a high-purity germanium (HPGe) detector. The activity concentrations were evaluated for possible radiological hazards to the human health. The excess lifetime cancer risks (ELCR) were also estimated, and the average values were recorded as 0.42 ± 0.24 × 10−3, 3.22 ± 1.83 × 10−3, and 3.65 ± 1.85 × 10−3 for outdoor, indoor, and total ELCR respectively. The activity concentrations were further subjected to RESRAD-BUILD computer code to evaluate the long-term radiation exposure to a dweller. The indoor doses were assessed from zero up to 70 years. The simulation results were 92 ± 59, 689 ± 566, and 782 ± 569 μSv y−1 for indoor external, internal, and total effective dose equivalent (TEDE) respectively. The results reported were all below the recommended maximum values. Therefore, the radiological hazards attributed to building materials under study are negligible. Keywords: Annual effective dose, Excess lifetime cancer risk, External dose, Internal dose, Total effective dose equivalen

Ultra-effective modified clinoptilolite adsorbent for selective thorium removal from radioactive residue

Abstract This study investigated the efficacy of using phosphate-modified zeolite (PZ) as an adsorbent for removing thorium from aqueous solutions. The effects of various factors such as contact time, adsorbent mass, initial thorium concentration, and pH value of the solution on the removal efficiency were analyzed using the batch technique to obtain optimum adsorption condition. The results revealed that the optimal conditions for thorium adsorption were a contact time of 24 h, 0.03 g of PZ adsorbent, pH 3, and a temperature of 25 °C. Isotherm and kinetics parameters of the thorium adsorption on PZ were also determined, with equilibrium studies showing that the experimental data followed the Langmuir isotherm model. The maximum adsorption capacity (Qo) for thorium was found to be 17.3 mg/g with the Langmuir isotherm coefficient of 0.09 L/mg. Using phosphate anions to modify natural zeolite increased its adsorption capacity. Furthermore, adsorption kinetics studies demonstrated that the adsorption of thorium onto PZ adsorbent fitted well with the pseudo-second-order model. The applicability of the PZ adsorbent in removing thorium from real radioactive waste was also investigated, and nearly complete thorium removal was achieved (> 99%) from the leached solution obtained from cracking and leaching processes of rare earth industrial residue under optimized conditions. This study elucidates the potential of PZ adsorbent for efficient removal of thorium from rare earth residue via adsorption, leading to a reduction in waste volume for ultimate disposition