The preformation factor of alpha-decay process in compound nuclei is microscopically proposed with a new perspective. The formation of alpha particle inside the parent nuclei is considered as a quantum-mechanical state which is yielded from a certain interaction among the valance nucleons. This interaction is very similar to that one responsible for the formation of the quasi-bound states in many-body system. This introduced microscopic perspective might give more insight to the understanding of the nuclear structure in the compound nuclei.
The main component of most building materials in Malaysia is rocks. These rocks have been found to naturally contain U-238, Th-232 and K-40. In order to estimate the radiological impact to the dweller, the level of radionuclides present in various building materials available in Malaysia were analyzed using gamma spectrometry. The radiation hazard indexes were calculated based on the above results. The results showed that the activity concentration of natural radionuclides U-238, Th-232, K-40 were between 19.0 Bq/kg – 42.2 Bq/kg, 16.5 Bq/kg –28.8 Bq/kg and 243.3 Bq/kg – 614.2 Bq/kg respectively. On the whole the radionuclides concentrations were still below the global average of 50 Bq/kg, 50 Bq/kg and 500 Bq/kg for U-238, Th-232 and K-40 respectively. The radiation hazard indexes of the building materials were also lower than the maximum value suggested.
At present, soil and mineral based building material such as bricks are one of the main components in building construction in Malaysia. This building material is a direct source of radiation exposure since it contains naturally occurring radioactive materials (NORM). In this study, clay brick samples used were obtained from 7 factories in Selangor and Johore, Malaysia. The activity concentrations of 226 Ra, 232 Th and 40 K in these samples of clay bricks were determined using a comparative method and was analysed using gamma spectrometry with HPGe detector. The mean values of activity concentrations for 226 Ra, 232 Th and 40 K were found to be in the range of 39.04 ± 0.88 Bqkg-1 - 73.61 ± 5.32 Bqkg-1, 43.38 ± 2.60 Bqkg-1 - 73.45 ± 1.51 Bqkg-1, and 381.54 ± 11.39 Bqkg-1 - 699.63 ± 15.82 Bqkg-1, respectively. The radiation hazard of NORM in the samples was estimated by calculating the radium equivalent activity (Raeq), external hazard index (Hex) and internal hazard index (Hin). Radium equivalent activity (Raeq) determined was in the range of 151.90 Bqkg-1 - 194.22 Bqkg-1 which is lower than the limit of 370 Bqkg-1 (equivalent to 1.5 mSvyr-1 ) recommended in the NEA-OECD report in 1979, whereas external hazard index (Hex) and internal hazard index (Hin) were between 0.20 – 0.26 and 0.52 - 0.71 respectively. The annual effective dose rate exposure to a dweller received from the clay bricks was calculated to be in the range of 0.35 ± 0.18 mSvy-1 - 0.43 ± 0.09 mSvy-1.
Concentrations of Natural Occurring Radioactive Material (NORM) and terrestrial gamma radiation have been shown to be associated with certain lithology and soil types. An attempt was made to statistically predict and validate environmental gamma radiation dose rates based on limited number of actual field measurements using sodium iodide (NaI(Tl)) detector. Statistical analysis including the correlations between the actual and predicted dose were made based on 32 different lithology and soil type combinations. Results of field measurements, have shown that more than 50% of the predicted data were not significantly different from the actual measured data. The interpolation method in GIS was used to produce an isodose map based on the prediction equation. A correlation of multiple regression on the predicted versus lithology and soils dose rates gave relationships of DP = 0.35 DL + 0.82 DS – 0.02, r2 = 0.736. A predicted isodose map was subsequently plotted base on 4 dose rates classes, ranging from 0.1 – 0.3 μSvhr-1.
The concentrations of Naturally Occurring Radioactive Material (NORM) and their corresponding terrestrial gamma radiation have been shown to be associated with certain lithology and soil types. A possible relationships among gamma radiation levels, and the lithology and soil types make it possible to predict ionizing radiation level of an area that cannot be directly measured. A study was carried out to statistically predict and validate environmental gamma radiation dose rates based on actual field measurements using a sodium iodide detector. Results obtained showed that the predicted dose rate (Dp) may be determined using a multiple correlation regression equation, Dp = 0.35DL + 0.82 Ds – 0.02, that integrates dose rates contributed by different lithological structures (DL) and soil types (Ds). Statistical analysis on 32 different lithology and soil type combinations showed that more than 50% of the predicted data were not significantly different from the data measured in the field. A predicted isodose map was subsequently plotted base on 4 dose rate classes ranging from 0.1 – 0.3 μSv h-1.
Selain daripada batu-batu kecil, batu kerikil dan pasir, simen merupakan salah satu bahan penting untuk membina bangunan. Simen diperbuat daripada campuran batuan dan tanah dan diketahui secara semulajadinya mengandungi radionuklid tabii. Kajian ini bertujuan untuk menentukan aras keradioaktifan tabii serta menilai hazard sinaran yang berpunca daripada radionulid tabii di dalam simen Portland di Malaysia. Sampel simen Portland diperolehi dari kilang pengeluar simen atau dibeli di pasaran tempatan. Kepekatan radionuklid tabii bagi 226Ra (siri 238U), 232Th dan 40K ditentukan dengan menggunakan spektrometri sinar gama. Hasil kajian mendapati julat kepekatan aktiviti bagi 226Ra (siri 238U), 232Th dan 40K masing-masing adalah 7.76 – 82.91 Bq kg-1, 9.79 – 49.37 Bq kg-1 dan 81.89 – 377.10 Bq kg-1. Purata nilai kesetaraan radium berada dalam julat 35.36 ± 0.60 hingga 135.94 ± 15.27 Bq kg-1 manakala julat purata bagi dos setara tahunan dan indeks hazard dalaman adalah masing-masing ialah 80 ± 2 hingga 300 ± 30 μSv tahun-1 dan 0.12 ± 0.00 hingga 0.56 ± 0.07.
Penggunaan bahan binaan yang mengandungi bahan radioaktif tabii (NORM) yang tinggi boleh meningkatkan kadar dos dedahan kepada penghuni di dalam sesebuah bangunan. Kebimbangan terhadap impak radiologi kepada penghuni menyebabkan perlunya dilakukan penilaian hazard radiologi yang berpunca daripada bahan binaan. Sehubungan itu, objektif kajian ini adalah untuk menentukan aras keradioaktifan tabii dalam bahan binaan di Malaysia serta menilai risiko radiologi yang diterima oleh penghuninya. Sebanyak 46 sampel pasir, 43 sampel kerikil dan 13 sampel simen Portland telah dianalisis menggunakan sistem spektrometri sinar gama. Hasil kajian mendapati kepekatan aktiviti bagi ketiga-tiga sampel bahan binaan berada pada julat 4.4 Bq kg-1 hingga 354.9 Bq kg-1, 2.4 Bq kg-1 hingga 263.9 Bq kg-1 dan 15.1 Bq kg-1 hingga 1931.7 Bq kg-1 bagi masing-masing 226Ra, 232Th dan 40K. Pengiraan kadar dos dedahan dalam bangunan mendapati semua sampel menghasilkan dos di bawah nilai 1500 μSv tahun-1, iaitu jumlah had dos yang disyorkan bagi bahan binaan. Hasil analisis ke atas nilai indeks aras perwakilan sinar gama, indeks hazard luaran dan indeks hazard dalaman mendapati sebahagian sampel memberikan bacaan melebihi nilai satu, iaitu had yang ditetapkan bagi bahan binaan. Penilaian risiko radiologi kepada penghuni dengan menggunakan kod komputer Resrad-Build mendapati kadar dos dedahan yang berpunca daripada simen Portland, pasir dan batu kerikil meningkat pada setiap tahun sepanjang tempoh 50 tahun.
Combination of magnetic and biocompatible materials to form core-shell nanomaterials has been widely used in medical fields. These core-shell magnetic biomaterials have a great potential for magnetic fluid hyperthermia (MFH) treatment to remedy cancer. The aims of this study were to investigate the production of core-shell cobalt ferrite/polycaprolactone (CoFe2O4/PCL) nanomaterials with different ratios of cobalt ferrite to caprolactone, to study the effects of using polymer in reducing the agglomerations between particles and to determine the structure, morphology, thermal and magnetic properties of these core-shell nanomaterials. The core-shell nanomaterials were produced by in situ polymerization method. The formation of the CoFe2O4/PCL was investigated by means of Fourier transform infrared spectroscopy (FTIR), x-ray diffractometer (XRD) and transmission electron microscopy (TEM). Its thermal properties were determined by using thermogravimetric analyzer (TGA). The vibrating sample magnetometer (VSM) was used to reveal the magnetic properties. The results for the XRD and FTIR spectra demonstrated the formation of cobalt ferrite and polycaprolactone in core-shell nanomaterials. From the TEM results, it was seen that the core-shell CoFe2O4/PCL nanomaterials were best formed at a ratio of CoFe2O4 to monomer caprolactone mixtures of 1:4.
A Monte Carlo simulation of the Malaysian nuclear reactor has been performed using MCNP Version 5 code. The purpose of the work is the determination of the multiplication factor (k eff ) for TRIGA Mark II research reactor in Malaysia based on Monte Carlo method. This work has been performed to calculate the value of k eff for two cases, which are the control rod either fully withdrawn or fully inserted to construct a complete model of the TRIGA Mark II PUSPATI Reactor (RTP). The RTP core was modeled as close as possible to the real core and the results of k eff from MCNP5 were obtained. When the control-fuel rods were fully inserted, the k eff value indicates the RTP reactor was in the subcritical condition with a value of 0.98370 ± 0.00054. When the control-fuel rods were fully withdrawn the value of k eff value indicates the RTP reactor is in the supercritical condition, that is 1.10773 ± 0.00083.