Overview of the sensitivity of Ge- and Al-doped silicon dioxide optical fibres to ionizing radiation

This paper reviews the thermoluminescence sensitivity of Ge- and Al- doped SiO2 optical fibre subjected to various ionizing radiations. It is found that the Ge- doped SiO2 optical fiber has the thermoluminescence response superior to Al-doped SiO2 optical fibre at certain energy and dose range in alpha, beta, photon and electron irradiation. High thermoluminescence intensity per unit dose goes to photon and electron irradiation than alpha and beta irradiation of lower energy. This probably due to the linear energy transfer that influence the dose deposition in the material as incident ionizing radiation striking the surface of Ge- and Al- doped SiO2 optical fibre. However, both doped SiO2 optical fibres show good linearity at studied dose range. It has been proven by researchers providing great potential as a dose absorbed measuring devices especially in radiotherapy energy and dose rang

Radiological dose assessment due to hypothetical nuclear power plant operation in Mersing, Johor, Malaysia

Malaysia has considered for some time to adopt nuclear power to cater to the increasing demand of electricity following other developed Asian countries such as Japan, Korea, and China. In implementing a nuclear power plant, strict regulations and guidelines by the International Atomic Energy Agency (IAEA) and International Commission on Radiological Protection (ICRP) must be fulfilled before any construction license is given for a new nuclear power program. One of the assessments include the estimation of potential radiological risks to both humans and environment from routine and accidental release of radioactive effluent from the nuclear power plant (NPP). In this work, simulations of radionuclide dispersion from a hypothetical NPP site in Mersing, Johor will be presented. The simulation was performed based on the Lagrangian atmospheric dispersion model using the HYSPLIT software. The radioactive effluent release rate was approximated to the value found in the Fukushima Dai-ichi accident in 2011. Meteorological data of 2017 were utilized in this study. Simulation results showed that the dispersion of radioactive effluent from the hypothetical NPP can potentially affect areas around Johor Bahru district, Singapore, and even some areas in Indonesia

Photon signature analysis using template matching

We describe an approach to detect improvised explosive devices (IEDs) by using a template matching procedure. This approach relies on the signature due to backstreaming ? photons from various targets. In this work we have simulated cylindrical targets of aluminum, iron, copper, water and ammonium nitrate (nitrogen-rich fertilizer). We simulate 3.5 MeV source photons distributed on a plane inside a shielded area using Monte Carlo N-Particle (MCNP TM) code version 5 (V5). The 3.5 MeV source gamma rays yield 511 keV peaks due to pair production and scattered gamma rays. In this work, we simulate capture of those photons that backstream, after impinging on the target element, toward a NaI detector. The captured backstreamed photons are expected to produce a unique spectrum that will become part of a simple signal processing recognition system based on the template matching method. Different elements were simulated using different sets of random numbers in the Monte Carlo simulation. To date, the sum of absolute differences (SAD) method has been used to match the template. In the examples investigated, template matching was found to detect all elements correctly

The thermoluminescence response of doped SiO2 optical fibres subjected to fast neutrons

This paper describes a preliminary study of the thermoluminescence (TL) response of doped SiO2 optical fibres subjected to 241AmBe neutron irradiation. The TL materials, which comprise Al- and Ge-doped silica fibres, were exposed in close contact with the 241AmBe source to obtain fast neutron interactions through use of measurements obtained with and without a Cd filter (the filter being made to entirely enclose the fibres). The neutron irradiations were performed for exposure times of 1-, 2-, 3-, 5- and 7-days in a neutron tank filled with water. In this study, use was also made of the Monte Carlo N-particle (MCNPTM) code version 5 (V5) to simulate the neutron irradiations experiment. It was found that the commercially available Ge-doped and Al-doped optical fibres show a linear dose response subjected to fast neutrons from 241AmBe source up to seven days of irradiations. The simulation performed using MCNP5 also exhibits a similar pattern, albeit differing in sensitivity. The TL response of Ge-doped fibre is markedly greater than that of the Al-doped fibre, the total absorption cross section for Ge in both the fast and thermal neutrons region being some ten times greater than that of Al

A new insight into the temperature induced molecular aggregations in tris(8-hydroxyquinoline) metals

Abstract Annealing of tris(8-hydroxyquinoline) gallium (Gaq3) film at various temperatures in dry N2 atmosphere has shown the existences of four different phases of molecular aggregations before the burning out of the film at about 310 °C. The first three phases, up to 235 °C, are amorphous molecular aggregations, while the fourth one at 255 °C is a crystalline structure, very likely α-polymorph. The photoluminescence (PL) intensity was increased to about five times greater than that of the pristine film at 235 °C, while the PL peak was blue shifted consistently. Although a small contribution of Rayleigh scattering cannot be excluded at high temperatures when crystallites appear, the PL blueshift was mainly attributed to the nanostructured molecular aggregations followed by enhanced PL intensity. These new findings can be a common characteristic of organometallic complexes at varied annealing temperatures. The presented results open a new route of fabricating highly emissive thin films of amorphous nanostructure, which are specifically important for organic light emitting diode (OLED) based displays

Direct and indirect entrance surface dose measurement in X-ray diagnostics using nanoDot OSL dosimeters

This study investigated the suitability of nanoDot optically stimulated luminescence (OSL) dosimeters for entrance surface dose (ESD) measurements in common X-ray diagnostics. OSL dosimetry system supplied by Landauer Inc, (Glenwood, IL, USA) consisting of nanoDot OSL dosimeters and microStar reader were used. ESDs were measured with nanoDots placed on whole-body anthropomorphic phantom (for direct measurements) and in free air without backscatter material (for indirect measurements) in accordance with the IAEA Technical Report Series No. 457. Measurements were carried out in five X-ray projections including AP abdomen, AP chest, PA chest, AP thoracic spine and AP skull. The mean ESD for each projection was evaluated from multiple measurements with three different field sizes. Mean ESDs (direct measurements) for AP abdomen, AP chest, PA chest, AP thoracic spine and AP skull were 4.3 mGy, 0.7 mGy, 0.3 mGy, 6.8 mGy and 2.8 mGy respectively. While in the case of indirect measurements, the corresponding mean ESD values were 4.8 mGy, 0.7 mGy, 0.2 mGy, 7.2 mGy and 3.7 mGy respectively. The results were found to be within IAEA and European Commission (EC) diagnostic reference levels (DRLs) range. The percentage difference of the ESDs measured by direct and indirect methods in all projections were between 0 to 40%. It was affirmed that nanoDot OSL dosimeter is a good candidate for ESD measurement in common radiographic examinations, while taking into account the effect of energy dependence

Analysis of photon scattering trends for material classification using artificial neural network models

In this project, we concentrate on using the Artificial Neural Network (ANN) approach to analyze the photon scattering trend given by specific materials. The aim of this project is to fully utilize the scatter components of an interrogating gamma-ray radiation beam in order to determine the types of material embedded in sand and later to determine the depth of the material. This is useful in a situation in which the operator has no knowledge of potentially hidden materials. In this paper, the materials that we used were stainless steel, wood and stone. These moderately high density materials are chosen because they have strong scattering components, and provide a good starting point to design our ANN model. Data were acquired using the Monte Carlo N-Particle Code, MCNP5. The source was a collimated pencil-beam projection of 1 MeV energy gamma rays and the beam was projected towards a slab of unknown material that was buried in sand. The scattered photons were collected using a planar surface detector located directly above the sample. In order to execute the ANN model, several feature points were extracted from the frequency domain of the collected signals. For material classification work, the best result was obtained for stone with 86.6% accurate classification while the most accurate buried distance is given by stone and wood, with a mean absolute error of 0.05

Thermoluminescence responses of photon- and electron-irradiated lithium potassium borate co-doped with Cu+Mg or Ti+Mg

New glasses Li2CO3–K2CO3–H3BO3 (LKB) co-doped with CuO and MgO, or with TiO2 and MgO, were synthesized by the chemical quenching technique. The thermoluminescence (TL) responses of LKB:Cu,Mg and LKB:Ti,Mg irradiated with 6 MV photons or 6 MeV electrons were compared in the dose range 0.5–4.0 Gy. The standard commercial dosimeter LiF:Mg,Ti (TLD-100) was used to calibrate the TL reader and as a reference in comparison of the TL properties of the new materials. The dependence of the responses of the new materials on 60Co dose is linear in the range of 1–1000 Gy. The TL yields of both of the co-doped glasses and TLD-100 are greater for electron irradiation than for photon irradiation. The TL sensitivity of LKB:Ti,Mg is 1.3 times higher than the sensitivity of LKB:Cu,Mg and 12 times less than the sensitivity of TLD-100. The new TL dosimetric materials have low effective atomic numbers, good linearity of the dose responses, excellent signal reproducibility, and a simple glow curve structure. This combination of properties makes them suitable for radiation dosimetry

Determination of out-core fuel burnup in TRIGA PUSPATI

The investigation was conducted on the out-core neutron flux and burn-up at irradiated fuel stored in TRIGA PUSPATI research reactor tank. This is required to examine whether the thermal and/or fast neutron flux can influence burn-up of the irradiated fuel stored in the same vicinity of the reactor core, the fuel rack being located 1 m above the core. MCNPX code was used to simulate fast and thermal neutron flux for the reactor operating at 750 kW. In this work, the computational model was created using MCNPX version 2.7 with the evaluated nuclear data file for thermal neutron scattering law data (ENDF7) cross-section data library and using a 10 cm x 10 cm x 10 cm mesh model. The results showed that the axial distribution for thermal neutrons occurred at energy lower than 1 x 10-6 MeV. Thermal neutron traveled at the maximum distance of 78 cm due to thermalization by moderator. Based on the maximum distance traveled by the thermal neutron, the thermal neutron did not reach the storage rack located 1 m from the core, hence there was no burn-up occurring at the irradiated fuel since burn-up can only occur in the thermal neutron region. For fast neutron, the axial distribution energy was higher than 1 x 10-6 MeV and traveled more than 158 cm. The reaction time for the fast neutron was too short to result in burn-up due to its fast travel

Characteristics of multihole collimator gamma camera simulation modeled using MCNP5

This paper describes the characteristics of the multihole collimator gamma camera that is simulated using the combination of the Monte Carlo N‐Particles Code (MCNP) version 5 and in‐house software. The model is constructed based on the GCA‐7100A Toshiba Gamma Camera at the Royal Surrey County Hospital, Guildford, Surrey, UK. The characteristics are analyzed based on the spatial resolution of the images detected by the Sodium Iodide (NaI) detector. The result is recorded in a list‐mode file referred to as a PTRAC file within MCNP5. All pertinent nuclear reaction mechanisms, such as Compton and Rayleigh scattering and photoelectric absorption are undertaken by MCNP5 for all materials encountered by each photon. The experiments were conducted on Tl‐201, Co‐57, Tc‐99 m and Cr‐51 radio nuclides. The comparison of full width half maximum value of each datasets obtained from experimental work, simulation and literature are also reported in this paper. The relationship of the simulated data is in agreement with the experimental results and data obtained in the literature. A careful inspection at each of the data points of the spatial resolution of Tc‐99 m shows a slight discrepancy between these sets. However, the difference is very insignificant, i.e. less than 3 mm only, which corresponds to a size of less than 1 pixel only (of the segmented detector)