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In the present work, nanocomposites of polyvinyl alcohol (PVA) and sodium iodide (NaI) nanoparticles have been prepared by casting technique. PVA has been doped by different percentage of sodium Iodide (0, 1, 2, 3 and 4 wt. %). The structural, electrical and optical properties of polymer electrolytes have been investigated. The experimental results showed that the D.C electrical conductivity increases with increase the sodium iodide nanoparticles concentrations. The activation energy of D.C electrical conductivity decreases with increase of sodium iodide nanoparticle concentrations. At low frequency, the variation of dielectric constant and dielectric loss with frequency shows the presence of material electrode inter-face polarization processes. The exponent factor found is between 0.98 and 0.086 and obeys the universal power law. The optical properties of samples are investigated in the wavelength range from 200 nm to 1100 nm at 300 K using UV-Vis spectroscopy. The absorbance, extinction coefficient, refractive index and reflectance of PVA doped with NaI increase with increasing of doping percentages except the transmittance. The real and imaginary parts of dielectric constants and optical conductivity are increasing with increase sodium iodine concentration. From direct allowed transition the optical energy gap decreases from 4.27 eV (for pure PVA) to 4.22 eV (for PVA+40%NaI). [ABSTRACT FROM AUTHOR]

The attenuation coefficients and building up factor (BF) of two different specimens of organic compound (paraffin wax) and sodium chloride structures were measured using gamma rays from radioactive sources (124Am, 137Cs, 226Ra) with energies (60, 662, 186, 242, 295, 352, 609, 1120, 1765) keV respectively. These two samples were measured with a gamma ray integrated computer spectrometer (ICS). This system is controlled by a computer using a custom-written programme and is linked to a sodium iodide activated thallium detector that measures just 1.5 inches by 1.5 inches. The radioactive source and detector were placed in the same room as the specimen. There was a 900-second accumulation time. With the (USX PCI) software, we were able to calculate the photopeak, net area, and FWHM of photopeak. Measured data was compared to the ICRU Report 44 value. When an organic compound and sodium chloride are combined, the attenuation coefficients are less than 7% different from what would be expected in human tissue. Results from this study suggest that the materials used for dosimetry could also be used to create tissue phantoms that accurately represent the biological tissues under investigation. [ABSTRACT FROM AUTHOR]

Thallium doped sodium iodide scintillation detector is the most widely used scintillation detector in gamma spectrometry. Unfortunately, sodium iodide reaches insufficient energy resolution for many applications. This fact has led manufacturers to develop scintillators with better energy resolution such as LaBr3:Ce and CeBr3. The energy resolution of LaBr3:Ce is about 3 times better and the resolution of CeBr3 is about 2 times better than the resolution of NaI:Tl. On the other hand, the production costs is still a disadvantage of these newer scintillators. The paper deals with energy resolution functions comparison of the 1.5 inch NaI:Tl, CsI:Tl, LaBr3:Ce, and CeBr3 scintillation detectors. The measurements and analysis to find the best fitting functions for energy resolution were performed. [ABSTRACT FROM AUTHOR]

In the present work, albedo factor is calculated for various tissue substitutes by using multiple backscattering of gamma photons. Reflected gamma photons emitting from a 137Cs source having energy of 662 keV from the target have been recorded by sodium iodide scintillation detector with crystal size 3 inch. by 3 inch. placed at an angle of 180° to the target. From experiments, it observed that, the albedo factor is varies with the depth target depth (thickness) of the tissue equivalent materials and their Zeff. The experimentally determine values of total multiply back-scattered flux are in good agreement with theoretically generated flux by using a M.C. simulation code. Also for accurate and précised experimental results, application of response function is implemented on the recorded spectrums. [ABSTRACT FROM AUTHOR]

The present study illustrates the solid polymer electrolyte (SPE) films based on hydroxypropyl methylcellulose (HPMC) complexed with different inorganic dopants. Pure HPMC and various compositions of complexed films of HPMC with different dopants, like sodium iodide (Nal), cadmium chloride (CdCl2), and ceric ammonium nitrate (NH4)2Ce(NO3)6 (CAN) were prepared by solution cast method using double distilled water as solvent. The prepared samples were gamma irradiated with different dose of 20, 60 and 100 kGy. Direct current (dc) conductivity was measured in the temperature range of 313-383K. The magnitude of conductivity was found to increase with increasing concentration of the salt, temperature and for higher dose of gamma radiation. All systems exhibits Arrhenius behavior, and was determined from the plots obtained for all the systems. HPMC:Nal (5:4) exhibits the maximum ionic conductivity at 313 K for un-irradiated samples. Whereas after 100 kGy gamma irradiation, HPMC:CdCl2 (5:4) and HPMC:CAN (5:2) exhibits a slightly higher conductivity value compare to that of HPMC:Nal un-irradiated samples. [ABSTRACT FROM AUTHOR]

The glasses of the batch xPbO: 10BaO: (90-x)B2O3: 0.2Gd2O3 (x = 40,45,50 mol %) were prepared by melt-quench technique. The work emphasizes on gamma ray shielding effect on doped lead glasses. The role of Boron is significant as it acts as better neutron attenuator as compared with any other materials, as the thermal neutron cross-sections are high for Gadolinium, 0.2 mol% is chosen as the optimum concentration for this matrix, as higher the concentration may lead to further increase as it produces secondary γ rays due to inelastic neutron scattering. Shielding effects were studied using Sodium Iodide (NaI) - Scintillation Gamma ray spectrometer. It was found that at higher concentration of lead oxide (PbO) in the matrix, higher the attenuation which can be co-related with density. Infra-red (I.R.) spectra reveals that the conversion of Lose triangles to tight tetrahedral structure results in enhancement of shielding properties. The Differential Scanning Calorimeter (D.S.C.) study also reveals that the increase in glass forming range increases the stability which in-turn results in inter-conversion of BO3 to BO4 units such that the density of glass increases with increase in PbO content, resulting in much stable and efficient gamma ray shielding glasses. [ABSTRACT FROM AUTHOR]

Asian Rare Earth (ARE) is a locally incorporated company that operated a mineral processing operation to extract rare earth element. ARE has received much attention from the public since the beginning of their operation until the work of decommissioning and decontamination of the plant. Due to the existence of Naturally Occurring Radioactive Material (NORM) in the residue, the decommissioning and disposal was done by the company in collaboration with the Perak State Government and the Atomic Energy Licensing Board (AELB). The main objective of this study is to review the level of compliance of the existing Radiation Protection Regulations enforced by AELB particularly in the achievement of allowed exposure dose limit. The next objective was to study the impact of the construction of the Mukim Belanja Repository to workers and public. This study was conducted by analyzing documents that were issued and conducting the area monitoring using a Geiger Muller detector (GM) and Sodium Iodide (NaI(Tl)) survey meters. The measurements were made at 5 cm and 1 m from the ground surface at 27 measurement stations. The external doses measured were within the background levels of the surrounding area. The annual effective dose using the highest reading at 5 cm and 1 m from ground surface by GM detector was calculated to be 1.36 mSv/year and 1.21 mSv/year respectively. Whereas the annual effective dose using the highest reading at 5 cm and 1 m from ground surface by using NaI(Tl) detector was calculated to be 3.31 mSv/year and 2.83 mSv/year respectively. The calculated cancer risks from the study showed that the risk is small compared with the risks derived from natural radiation based on global annual radiation dose to humans. This study therefore indicated that the repository is able to constrain the dose exposure from the disposed NORM waste. The study also revealed that the construction of the repository has complied with all the rules and regulations subjected to it. The exposed dose received by the radiation and the public workers during the construction of the repository were below the annual limit i.e. 20 mSv/year and 1mSv/year respectively. [ABSTRACT FROM AUTHOR]

The Compton scattering is able to determine the signature of land mine detection based on dependency of density anomaly and energy change of scattered photons. In this study, 4.43 MeV gamma of the Am-Be source was used to perform Compton scattering. Two detectors were placed between source with distance of 8 cm and radius of 1.9 cm. Detectors of thallium-doped sodium iodide NaI(TI) was used for detecting gamma ray. There are 9 anomalies used in this simulation. The physical of anomaly is in cylinder form with radius of 10 cm and 8.9 cm height. The anomaly is buried 5 cm deep in the bed soil measured 80 cm radius and 53.5 cm height. Monte Carlo methods indicated the scattering of photons is directly proportional to density of anomalies. The difference between detector response with anomaly and without anomaly namely contrast ratio values are in a linear relationship with density of anomalies. Anomalies of air, wood and water give positive contrast ratio values whereas explosive, sand, concrete, graphite, limestone and polyethylene give negative contrast ratio values. Overall, the contrast ratio values are greater than 2% for all anomalies. The strong contrast ratios result a good detection capability and distinction between anomalies. [ABSTRACT FROM AUTHOR]

Sodium ion (Na+) based solid polymer electrolyte (SPE) has been prepared using solution cast technique with distilled water as solvent and Methylcellulose (MC) as a polymer host. Methylcellulose polymer was chosen as the polymer host due to the abundance of lone pair electrons in the carbonyl and C-O-C constituents, which in turn provide multiple hopping sites for the Na+ conducting ions. Variable compositions of sodium iodide (NaI) salt were prepared to investigate the optimum MC-NaI weight ratio. Results from Electrical Impedance Spectroscopy (EIS) technique show that pure methylcellulose has a low conductivity of 3.61 x 10-11 S/cm. The conductivity increases as NaI content increases up to optimum NaIcomposition of 40 wt%, which yields an average conductivity of 2.70x10-5 S/cm. [ABSTRACT FROM AUTHOR]

We have developed low background CsI(Tl) and NaI(Tl) crystals to search for weakly interacting massive particles as well as to verify the origin of the annual modulation signal observed by the DAMA/LIBRA experiment. Extensive studies about the contamination mechanisim of 137Cs in CsI powder lead to the growth of ultra-low-background CsI(Tl) crystals. Similar approaches for NaI(Tl) crystals have been applied to reduce internal backgrounds to less than 0.5 counts/kg/day/keV. Status and understanding of backgrounds and background reduction in NaI(Tl) crystals will be discussed. [ABSTRACT FROM AUTHOR]

Several large NaI(Tl) detectors, produced by different companies, have been operated in the Canfranc Underground Laboratory (LSC) in the frame of the ANAIS (Annual modulation with NaI Scintillators) project devoted to the direct detection of dark matter. A complete background model has been developed for a 9.6 kg detector (referred as ANAIS-0 prototype) after a long data taking at LSC. Activities from the natural chains of 238U and 232Th, and 40K in the NaI(Tl) crystal were evaluated applying different methods: discrimination of alpha particles vs beta/gamma background by Pulse Shape Analysis for quantifying the content of the natural chains and coincidence techniques for 40K. Radioactive contaminations in the detector and shielding components were also determined by HPGe spectrometry. Monte Carlo simulations using Geant4 package were carried out to evaluate their contribution. At high energies, most of the measured background is nicely reproduced; at low energy some non-explained components are still present, although some plausible background sources have been analyzed. The 40K content of the NaI(Tl) crystal has been confirmed to be the dominant contributor to the measured background with this detector. In addition, preliminary results of the background characterization, presently underway at the LSC, of two recently produced NaI(Tl) detectors, with 12.5 kg mass each, will be presented: cosmogenic induced activity has been clearly observed and is being quantified, and 40K activity at a level ten times lower than in ANAIS-0 has been determined. [ABSTRACT FROM AUTHOR]

The radiation is an essential phenomenon in daily life. There are various amounts of radioactivite substances in the underground and the earth was irradiated by this substances. Humans are exposed to various kind of radiation from these sources. The travertines are usually used as a coating material in buildings. In this study, the photon attenuation coefficients of some travertines have been measured using a gamma spectroscopy with NaI(Tl) detector. The measurements have been performed using 60Co source which gives 1173 and 1332 keV energies gamma rays and 137Cs source which gives 662 keV energy gamma rays and the results will be discussed. [ABSTRACT FROM AUTHOR]

The soil on the earth's crust is a source of continuously exposure to human beings. The amount of radioactivity in soil depends upon the type of soil and its uses. Amasya is located on the inside of the Department of the Central Black Sea. Amasya is situated between 34° 57′ 06″ - 36° 31′ 53″ east longitudes and 41° 04′ 54″ - 40° 16′ 16″ north latitudes. In this study, the concentration of naturally occurring radionuclides (40K, 226Ra, 232Th) was measured in some soil samples collected in Amasya region using gamma spectrometer system which contains NaI(Tl) and 16k Multichannel analyser at the Süleyman Demirel University-Gamma Spectroscopy Lab in Isparta (Turkey). [ABSTRACT FROM AUTHOR]

Although the plaster is one of the oldest known synthetic building materials, nowadays, it is used as interior coating of walls and ceilings of buildings. Thus measuring its radiation shielding properties is vital. For this purpose, radiation absorption properties of different plaster samples in this study. The measurements have been performed using gamma spectrometer system which connected to 3" × 3" NaI (TI) detector. [ABSTRACT FROM AUTHOR]

We examine gamma-ray and optical data of GRB 091024, a gamma-ray burst (GRB) with an extremely long duration of T90≈1020 s, as observed with the Fermi Gamma-Ray Burst Monitor (GBM). We present spectral analysis of all three distinct emission episodes using data from Fermi/GBM. and compare the optical and gamma-ray light curves of this event. We find that the optical light curve is highly anti-correlated to the prompt gamma-ray emission, with the optical emission reaching the maximum during an epoch of quiescence in the prompt emission. We interpret this behavior as the reverse shock (optical flash). [ABSTRACT FROM AUTHOR]

Radioactive tracer 82Br in the form of KBr-82 with activity ± 1 mCi has been injected into steel pipeline to qualify the extent dispersion of water flowing inside it. Internal diameter of the pipe is 3 in. The water source was originated from water tank through which the water flow gravitically into the pipeline. Two collimated sodium iodide detectors were used in this experiment each of which was placed on the top of the pipeline at the distance of 8 and 11 m from injection point respectively. Residence time distribution (RTD) curves obtained from injection of tracer are elaborated numerically to find information of the fluid flow properties. The transit time of tracer calculated from the mean residence time (MRT) of each RTD curves is 14.9 s, therefore the flow velocity of the water is 0.2 m/s. The dispersion number, D/uL, for each RTD curve estimated by using axial dispersion model are 0.055 and 0.06 respectively. These calculations are performed after fitting the simulated axial dispersion model on the experiment curves. These results indicated that the extent of dispersion of water flowing in the pipeline is in the category of intermediate. [ABSTRACT FROM AUTHOR]

The uptake of naturally occurring thorium, radium and potassium by sawi (Japanese Mustard) from disused tin mining was studied. Both soil and sawi sample were collected from a vegetable farm located 15 km from Kuala Lumpur, Malaysia where the farm has been operating for 22 years on a disused tin mining. By using a gamma spectroscopy system, the transfers of radionuclides from soil to plants were investigated. The highest values of radionuclides in the soil was K-40 which is 52.8 Bq kg-1 and the lowest was Ra-226 which is 6.51 Bq kg-1. The activity of Th-232 is 18.5 Bq kg-1. The activity of radionuclides in the sawi sample shows higher values as compared to the soil sample. The highest values of radionuclides in the sawi were K-40 which is 446 Bq kg-1 and the lowest was Ra-226 which is 17.5 Bq kg-1. The activity of Th-232 is 65.2 Bq kg-1. The concentration of radionuclides in soils and plants can be used for the determination of soil-to-plant transfer factors. The soil to plant transfer factors (TF) were calculated and observed to be 2.68 for radium-226, 3.52 for thorium-232 and the highest which is 3.97 for potassium-40. [ABSTRACT FROM AUTHOR]

The DAMA/NaI experiment (≃ 100 kg highly radiopure NaI(Tl)) at the Gran Sasso National Laboratory of the I.N.F.N. had the unique feature to effectively investigate the presence of Dark Matter particles in the galactic halo by exploiting the model independent annual modulation signature. A total exposure of more than 105 kg × day, collected over seven annual cycles, has pointed out at 6.3 σ C.L. an effect which satisfies all the many peculiarities of the signature. Neither systematics nor side reactions able to account for the observed effect were found. No experiment whose result can be directly compared in a model independent way with the experimental one of DAMA/NaI is available so far. Searches in space experiments are not in contradiction with DAMA/NaI. Several (but still few with respect to the possibilities) corollary model dependent quests for the candidate particle have also been carried out; others are in progress. At present the second generation DAMA/LIBRA set-up (≃ 250 kg highly radiopure NaI(Tl)) is in data taking deep underground. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Since 1995, there have been great advances and extremely exciting results in the search for brown dwarfs and extrasolar giant planets. In the formation of their spectra, the far wings of the alkali resonance lines, especially Na I and K I, play an extraordinary role. Model atmospheres are necessary in order to calculate synthetic spectra and colors and to derive reliable parameters and the atmospheric chemical composition for such objects. Using alkali resonance line profiles [1] and [2], the differences in the synthetic spectra compared to earlier results [3], [4] will be outlined. Besides the line formation process dependent on the effective temperature and the chemistry in the atmosphere will be discussed. For the synthetic spectra, the general purpose stellar atmosphere code PHOENIX [5] is used. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Recently, the Long Term Storage Facility (LTSF) in Bukit Kledang, Perak, Malaysia, has been upgraded to repository facility upon the completion of decontamination and decommissioning (D&D) process. Thorium waste and contaminated material that may contain some minor amounts of thorium hydroxide were disposed in this facility. This study is conducted to determine the concentrations of gross alpha and gross beta radioactivities in soil samples collected around the repository facility. A total of 12 soil samples were collected consisting 10 samples from around the facility and 2 samples from selected residential area near the facility. In addition, the respective dose rates were measured 5 cm and 1 m above the ground by using survey meter with Geiger Muller (GM) detector and Sodium Iodide (NaI) detector. Soil samples were collected using hand auger and then were taken back to the laboratory for further analysis. Samples were cleaned, dried, pulverized and sieved prior to analysis. Gross alpha and gross beta activity measurements were carried out using gas flow proportional counter, Canberra Series 5 XLB - Automatic Low Background Alpha and Beta Counting System. The obtained results show that, the gross alpha and gross beta activity concentration ranged from 1.55 to 5.34 Bq/g with a mean value of 3.47 ± 0.09 Bq/g and 1.64 to 5.78 Bq/g with a mean value of 3.49 ± 0.09 Bq/g, respectively. These results can be used as an additional data to represent terrestrial radioactivity baseline data for Malaysia environment. This estimation will also serve as baseline for detection of any future related activities of contamination especially around the repository facility area. [ABSTRACT FROM AUTHOR]

Solid polymer electrolyte films based on Hydroxypropylmethylcellulose (HPMC) complexed with Sodium Iodide (NaI) were prepared using solution cast method. The dissolution of the salt into the polymer host and the micro structural properties of pure and NaI complexed HPMC polymer electrolyte films were confirmed by X - Ray diffraction (XRD) studies. The XRD results revealed that the amorphous domains of HPMC polymer matrix was increased with increase in the NaI salt concentration. The degree of crystallanity and crystallite size is high for pure HPMC samples. Direct current (dc) conductivity was measured in the temperature range of 313-383k. Temperature dependence of dc electrical conductivity and activation energy regions data indicated the dominance of ion type charge transport in these polymer electrolyte films. [ABSTRACT FROM AUTHOR]