Radioisotope Source Research Articles

Evaluation of lithium tetra borate glass-ceramics: Structural, physical and radiation safety properties using experimental and theoretical methods

By using the standard melt quenching method, samples of lithium borate glass-ceramics with a composition of 40Li2B4O7 + xLi2O +(50-x)NiO+5Gd2O3 + 5BaTiO3 (x = 10 (C1), 20 (C2), 30 (C3), 40 (C4) and 50 (C5) wt%) have been manufactured. The structural and physical characteristics of the prepared C1–C5 samples have been investigated. Using an Ultra Ge detector and a 133Ba (3 Ci) radioisotope source as well as theoretically using EpiXS software, the radiation shielding competence of the C1–C5 samples were examined. The XRD analysis showed large crystal particle sizes were formed in the C1 sample, where the amount of NiO in its structure was maximum and the amount of Li2O was minimum. The change in the NiO/Li2O ratio caused the crystal particle size in the structure to decrease. Additionally, it was observed that the particle size increased in the C4 structure. In addition, the C3 and C5 structures became completely amorphous. This doping in the structure caused the crystal structure of C3 and C5 to deteriorate. While increasing the amount of NiO in the structure gave positive results up to a certain value, increasing the Li2O structure disrupted the crystal structure. A range of 2.91–4.51 g/cm3 was observed in the density of the synthesized C1, C2, C3, C4, and C5 samples. The dense C1 sample proved to have the largest mass-attenuation coefficient (MAC). The results obtained from experiments agree with the theoretical ones. There are no differences in the trends of the MAC and linear attenuation (LAC) coefficient. For each given energy, the half-value layer (HVL) organized as (HVL)C5 > (HVL)C4 > (HVL)C3 > (HVL)C2 > (HVL)C1. Results revealed that glass-ceramics are one source of materials that can be used for radiation shielding.

Spectra measurement of 238Pu-13C source

The precise description of the neutron spectrum is crucial for the measurement of cross sections and well defined integral experiments. Radioisotope sources such as PuC are one of the most widely used neutron sources for different purposes. The neutron spectrum of this source was measured with narrow energy bins for energies greater than 1.3MeV in this experiment with the method of stilbene scintillation spectrometry and the NGA-01 system. The measured neutron spectrum was also compared to simplified simulations in MCNP6 with satisfactory agreement. Effect of the internal structure of the neutron source was tested thoroughly with simulations and is also presented here.

Sr-doped carbon matrices for use as electrodes in autonomous electrical energy sources

Relevance. The need to create new safe energy sources that can meet the needs of production and medicine where the use of traditional energy sources is impossible or unprofitable. Such sources may include radioisotope power sources, in which energy production is ensured by the natural decay of radionuclides. The most important components of current sources such as supercapacitors are electrode materials, the characteristics of which determine the electrophysical characteristics of radioisotope sources. This work proposes a method for synthesizing a carbon matrix doped with Sr for use as electrodes of radioisotope power sources. Aim. Development, mastery and optimization of a method for synthesizing electrodes of radioisotope power sources based on carbon materials doped with the Sr-90 radioisotope. Objects. Carbon material doped with a radioisotope simulant Sr-90 (Sr stable). Carbon matrices were obtained by carbonizing a resorcinol-formaldehyde resin doped with a stable strontium salt. Methods. Scanning electron microscopy, low-temperature adsorption-desorption of nitrogen, cyclic voltammetry, galvanostatic charge-discharge, impedance microscopy. Results. A carbon matrix doped with a stable strontium isotope was synthesized by the method of semi-carbonization followed by physical activation with carbon dioxide. The structure, porosity and electrochemical characteristics of the material were studied. It was established that physical activation has a positive effect on the development of the specific surface area and mesoporosity of the samples of the synthesized matrix, as a result of which its electrochemical characteristics are improved. The method of physical activation is proposed as the most preferable for the synthesis of a carbon matrix doped with strontium isotopes for use as electrodes of radioisotope power supplies.

Exposure Factors for Flexible Digital Detector Arrays

Exposure factors (R factors) provide guidance in gamma radiography applications. The exposure time is calculated for a specific source type, activity, thickness of steel, desired exposure factor for a target film density or pixel value, and source-to-detector distance (SDD). R factors to produce target film densities of 2.0, 2.5, 3.0, and 3.5 were published for M100, MX125, T200, AA400, and HS800 films. Digital R factors are now published for Carestream rigid and flexible digital detector array (DDA) products. The flexible DDA’s are bent repeatedly around curved surfaces for single wall viewing, as radiography codes and standards require that the detector be in direct contact with the weld whenever practical. The R factor tables are published along with the supporting data used to calculate them, which are provided in graphical format for each condition. Iridium, selenium, and cobalt radioisotope sources were utilized for the generation of the data. Radiographers utilize the tables provided to enter the R factor into a commercially available phone-based calculator to determine the exposure time required to obtain the target optical density or grey value through the base metal. R factors are meant to be a starting point only, as other factors related to the part geometry and technique impact the required exposure.

Single-layer Compton camera based on a 1 mm thick pixelated CDTE detectors

Compton camera is a novel γ-camera paradigm that relies upon the kinematics of Compton scattering for image reconstruction. A Conventional Compton camera uses two layers of sensors - the Absorber and the Scatterer. This work reports the proof of concept of a single-layer Compton camera (SLCC) where simultaneous Compton pairs events are registered in a single High-Z semiconductor sensor. The Hybrid pixel detector (HPD) is 1 mm thick, 256 x 256 square pixels with 55 μm pixel pitch CdTe sensor bonded to a Timepix3 readout ASIC. The superior spectroscopic imaging and fast timing capabilities of the Timepix3 readout ASIC coupled with a microscopic and highly pixelated CdTe enable simultaneous event detection of multi-energies occurring at multiple positions. The concept was exemplified by measuring the 122 KeV γ-ray emitted from a 57Co radioisotope source at two positions. Data were captured in the Timepix3 data-driven mode with the KATHERINE readout system via Gigabyte Ethernet data transfer. A bespoke Compton kinematics criterion algorithm implemented in Python 3 IDE was used for data analysis and Compton’s image reconstruction. Numerous events (5.2 million) were captured for 30-minute acquisitions. However, due to the thin nature of CdTe, fewer events (≈ 0.01 %) met the Compton event selection criteria. Nevertheless, the algorithm accurately pinpointed the radioisotope’s location, demonstrating proof of concept of the SLCC system.

Comprehensive modeling and characterization of the General-Purpose Heat Source Radioisotope Thermoelectric Generator for solar system missions

The radioisotope thermoelectric generator relies solely on radioactive decay for its energy and generates power through the thermoelectric effect. The General-Purpose Heat Source Radioisotope Thermoelectric Generator (GPHS-RTG) represents the RTG with the largest power and highest conversion efficiency ever built, and its energy supply supported four daring interplanetary missions (Galileo, Ulysses, Cassini, New Horizons). To explore the use potential of the GPHS-RTG in the solar system, its conservative application range and performance should be determined. In this work, a comprehensive model of the GPHS-RTG was developed, and its calculated results agreed well with Lockheed Martin’s test report (temperature relative error < 1 %). The study demonstrates that within the Earth orbit, the distance of the mission area from the sun and the angle of incidence sunlight significantly affect the thermoelectric performance and hot-junctions’ temperature. Moreover, conservative application ranges and their extending methods (changing coating material, thermal loading, and operational voltage) for GPHS-RTG at different attitudes in the solar system were determined for the first time by comparing the proportion of the hot-junction over-temperature area. The temperature distribution and its cause of formation in the axial and circumferential directions of the GPHS-RTG during solar system missions were revealed in the end. This work is valuable for future RTG design and mission planning.

Characterisation of neutron fields at the n-lab, a fast neutron facility at the University of Cape Town

The n-lab is a fast neutron facility based in the Department of Physics, University of Cape Town, offering collimated neutron beams produced by an MP 320 deuterium–tritium sealed tube neutron generator, and a 220 GBq americium–beryllium radioisotopic source. Characterisations of the spatial and energy distributions of the fast neutron beams were performed using an EJ-301 organic liquid scintillator detector and digital data acquisition system. Neutron energy spectra were obtained through unfolding analyses with MAXED, and a Monte Carlo approach to the propagation of uncertainties was implemented. Measurements of fluence and neutron emission rates were determined through the neutron activation of copper foils and subsequently used to validate the scaling of the unfolded neutron energy spectra.

Feasibility study on radioisotope-powered thermophotovoltaic/thermoelectric hybrid power generation system used in deep-sea: From design to experiment

This study aims to comprehensively examine the feasibility of a hybrid power generation system that integrates solar and thermoelectric technologies, with a focus on utilizing a radioisotope heat source (RHU) for deep-sea applications. The investigation encompasses the whole design process as well as rigorous testing procedures. The self-designed coupling device establishes a connection between the silicon photovoltaic (PV) cell and the bismuth telluride (Bi2Te3) thermoelectric modules (TEMs), therefore creating a photovoltaic-thermoelectric (PV-TE) hybrid system. The measuring platform incorporates the system to investigate the influence of varying light intensity (ranging from 400 to 1600 W/m2) on the electrical properties of the system, specifically focusing on three subgroups of PV cell temperature (20 °C, 25 °C, and 30 °C). The findings suggest that the enhanced performance of the photovoltaic (PV) cell and thermoelectric modules (TEMs) under identical PV cell temperatures may lead to an improvement in the electrical performance of the system due to variations in light intensity. Nevertheless, when the temperature of the photovoltaic (PV) cell increases, there is a gradual decline in the growth rate of the output power. The subsequent research provide evidence that there exist discrete mechanisms responsible for the reduction in intensity between thermoelectric modules (TEMs) and photovoltaic (PV) cells. The processes arise due to the impact of thermal effect on the photovoltaic materials and the increased temperature difference between hot and cold junctions of the thermoelectric modules (TEMs), respectively. Furthermore, a control group is incorporated by calculating the performance of the hybrid system under the same operating conditions as the single thermoelectric (S-TE) system. According to a comparative analysis comparing the Radioisotope Thermal-Photovoltaic-Thermoelectric (RTPV-TE) hybrid power production systems and the S-TE system, it has been shown that the former exhibits a potential increase in output power of up to 271% while operating under identical conditions. This work offers insights and methodologies for the design and measurement of RTPV-TE hybrid power generating systems in engineering application situations.

Devising an alternative technique to manufacture a radioisotope source of 60Co for irradiation device to ensure ornithological safety of aircraft flights

This paper reports an alternative technique for producing a source of hard gamma radiation with the 60Со isotope for the proposed device for radioactive irradiation of birds, which is also innovative in providing for ornithological aircraft flight safety. However, the high cost of producing a 60Со radionuclide source with activity sufficient to irradiate bird pests with a lethal or sterilizing dose poses a serious challenge. A solution to the problem of reducing the cost of a 60Со radionuclide source can be an alternative technique of its production outside the reactor. The results are characterized by the following features and distinctive peculiarities that make it possible to solve the problem under study: – an irradiation device with the radioactive isotope 60Со causes a lethal or sterilizing effect. This is much more effective in ensuring ornithological safety of aircraft flights compared to known methods of scaring away birds of prey, but is harmless to humans; – the production of 60Со radionuclide for the irradiation installation is carried out by thermal diffusion heating, which significantly reduces the cost of the source compared to the well-known methods of its production in a reactor and accelerator. The results obtained could find practical application in the field of civil aviation for ornithological flight safety, subject to compliance with national and international legislation. In addition, the proposed technique of manufacturing a 60Со radionuclide source, in addition to aviation ornithology, may find application in other sectors of industry, economics, and agriculture

Pore Forming Agent–Assisted Fabrication of Porous Platinum Vent Frits and Their Suitability Evaluation for Radioisotope Power Sources

Disc-shaped porous platinum sintered frits were fabricated employing a pore forming agent (PFA) via a powder-metallurgical process. Porous vent frits using several platinum-PFA compositions were prepared after characterizing the starting materials (platinum and PFA powders) for particle size (D50) and distribution (D10 to D90), morphology, Brunauer-Emmet-Teller surface area, density (apparent and tap), etc. The sintered platinum vent frits were extensively characterized to evaluate their suitability for application in terms of surface microstructure analysis by scanning electron microscopy, helium/air permeability parameters, and particulate filtration characteristics. This paper reports for the first time on the measurement of retention efficiency of vent frits for particulate sizes 0.3, 0.5, and 1 µm. The platinum frits made using 10 and 20 vol % PFA were found to be suitable as a vent hole filter for radioisotope power sources.

Exploratory study of betavoltaic nuclear battery using AlN P[sbnd]N junction

In most of the betavoltaic nuclear batteries, wide band semiconductors such as GaN and SiC have been used as an energy converter. But, the growth of these semiconductors are relatively expensive. In the present work, a new study was conducted on betavoltaic nuclear batteries. In this study, AlN betavoltaic nuclear battery driven by an 90Sr + 90Y radioisotope source was investigated. AlN is wide band semiconductor and economically viable. Then, by Monte Carlo simulation the effects of factors such as type of electrode, dimensions, thickness, and geometric model of PN junction on the battery efficiency were investigated. Finally, it was found that the cubical model has the highest amount of short circuit current, open circuit voltage, and battery efficiency. The value of short circuit current, open circuit voltage, and battery efficiency in this model are 406.05 nA, 5.43 V, and 5.16 %, respectively. In order to compare the efficiency of AlN betavoltaic nuclear battery with the efficiency of GaN and SiC betavoltaic nuclear batteries, first the optimal dimensions were investigated for each of GaN and SiC betavoltaic nuclear batteries and then based on the optimal dimensions obtained for GaN and SiC, the cubical model was investigated for them. The results of the simulations show that, the efficiency of AlN betavoltaic nuclear battery is 24 % more than GaN betavoltaic nuclear battery efficiency and 975 % more than SiC betavoltaic nuclear battery efficiency. Also, the efficiency of the AlN betavoltaic nuclear battery (simulated in this work) is about 130 % more than the efficiency of the GaN betavoltaic nuclear battery calculated by others.

Monte Carlo simulation-aided design of a thermal neutron generator system from 241Am-Be isotopic sources

Collimated thermal neutron beams are obtained from neutron extraction channels in nuclear reactors for various applications in research and technology, such as neutron imaging techniques (neutron radiography, neutron radioscopy, neutron tomography, and neutron-based autoradiography). Practical setups for neutron radiography using ion beams from particle accelerators and radioisotopic sources of fast neutrons have been also developed. However, only radioisotopic sources enable autonomous and transportable thermalization systems that can produce thermal neutron collimated beams. This work presents the performance results for a prototype of a compact system that generates a collimated beam of thermal neutrons using low-activity isotopic 241Am-Be sources. It was designed with the aid of Monte Carlo simulation using the PHITS v 3.17 program. Experimental measurements of the fluence of the neutron beam produced by the built prototype showed good agreement with the simulated values by the Monte Carlo method.

Analysis of the cancer occurrence related to natural radioactivity in the Rio Grande do Norte State, Brazil.

The state of Rio Grande do Norte, located in the Northeast region of Brazil, has areas of granites and pegmatites with minerals that have varying concentrations of uranium. Consequently, high concentrations of radon gas, a carcinogenic substance for humans, can occur. The present study aimed to assess the occurrence of cancer and its association with exposure to sources of natural radioactivity using geological and geophysical information in the aforementioned state. The spatial dependence of pulmonary, breast, stomach, leukemia, and skin cancer cases with the location of radioisotope sources were analyzed using geoprocessing tools. The geoprocessing analysis showed a differential pattern of uranium emission throughout the state, with the highest emission from areas with pegmatites outcrops. A spatial dependency of cancer cases was shown (Moran index: 0.43; p < 0.01). Moreover, a higher rate of natural radioactivity-cancer cases was associated with the high-intensity natural radioactivity areas: odds ratio:1.21 (95% CI 1.20; 1.23), following the same pattern when separately compared the different related types of cancer. These results highlight the importance of natural radioactivity as a public health problem in the Brazilian environmental scenario, confirming the need for further studies as the first toward understanding and implementing health management strategies mitigating the exposures, especially in areas of environmental risk.

Synthesis, Characterization, and Stability of Two Americium Vanadates, AmVO3 and AmVO4.

In search for chemically stable americium compounds with high power densities for radioisotope sources for space applications, AmVO3 and AmVO4 were prepared by a solid-state reaction. We present here their crystal structure at room temperature solved by powder X-ray diffraction combined with Rietveld refinement. Their thermal and self-irradiation stabilities have been studied. The oxidation states of americium were confirmed by the Am M5 edge high-resolution X-ray absorption near-edge structure (HR-XANES) technique. Such ceramics are investigated as potential power sources for space applications like radioisotope thermoelectric generators, and they have to endure extreme conditions including vacuum, high or low temperatures, and internal irradiation. Thus, their stability under self-irradiation and heat treatment in inert and oxidizing atmospheres was tested and discussed relative to other compounds with a high content of americium.

Prediction of Betavoltaic Battery Parameters

The approaches for predicting output parameters of betavoltaic batteries are reviewed. The need to develop a strategy for predicting these parameters with sufficient accuracy for the optimization of betavoltaic cell design without using the simple trial and error approach is discussed. The strengths and weaknesses of previously proposed approaches for the prediction are considered. Possible reasons for the difference between the calculated and measured parameters are analyzed. The depth dependencies of beta particles deposited energy for Si, SiC, GaN, and Ga2O3 and 20% purity 63Ni and titanium tritide as radioisotope sources are simulated using the Monte Carlo algorithm taking into account the full beta energy spectrum, the isotropic angular distribution of emitted electrons and the self-absorption inside the radioisotope source for homogeneously distributed emitting points. The maximum short circuit current densities for the same semiconductors and radioisotope sources are calculated. The methodology allowing the prediction of betavoltaic cell output parameters with accuracy no worse than 30% is described. The results of experimental and theoretical investigations of the temperature dependence of betavoltaic cell output parameters are briefly discussed. The radiation damage by electrons with the subthreshold energy and the need to develop models for its prediction is considered.

Evaluation of Radioactivity and Heavy Metals Content in a Basalt Aggregate for Concrete from Sicily, Southern Italy: A Case Study

In the present paper, an investigation on the natural and anthropic radioactivity and heavy metals content in a basalt aggregate for concrete from Sicily, Southern Italy, was performed as a case study. In particular, the evaluation of the specific activity of radium-226, thorium-232, potassium-40 and caesium-137 radionuclides was performed by using High-Purity Germanium (HPGe) γ-ray spectrometry, together with the estimation of several indexes developed to evaluate the radiological risk for the population related to radiation exposure, i.e., the alpha index (Iα), the radium equivalent activity (Raeq), the absorbed γ-dose rate (D) and the annual effective dose equivalent outdoor (AEDEout) and indoor (AEDEin). Moreover, measurements of the average heavy metals (arsenic, cadmium, copper, mercury, nickel, lead, antimony, thallium and zinc) concentrations in the analyzed sample were performed by using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Furthermore, with the aim to investigate any possible chemical pollution, the Enrichment Factor (EF), Geo-accumulation Index (Igeo), Contamination Factor (CF) and Pollution Load Index (PLI) were assessed. Finally, the identification of the source of the aforementioned radioisotopes of natural origin was carried out by X-ray diffraction (XRD), thus identifying the major mineralogical phases present in the investigated basalt aggregate for concrete.

A compact direction-sensitive fast neutron spectrometer

A compact neutron spectrometer is described, which consists of four square prisms of plastic scintillator capable of pulse shape discrimination, eight silicon photomultipliers and a high density polyethylene moderator. The device is capable, in principle, of spectroscopic measurements up to around 60 MeV, although extendable to higher energies, and is also able to discern the direction of neutron radiation impinging on the detector. Results from simulations using Geant4, together with measurements with neutrons from an 241Am-9Be radioisotopic source, are used to characterise the detector in both spectroscopic and direction-sensitive modes. Field applications of the detector are discussed.

Assessment of structural, physical properties as well as radiation safety competence of lithium borate glass-ceramics: Experimental and theoretical evaluation

Samples of lithium borate glass-ceramics with a composition of 40Li2B4O7 + xBi2O3 + (55-x) ZrO4 + 5CaWO4 (x = 10–50 wt%) have been fabricated via ordinary melt quenching route. The physical and structural features have been investigated. Radiation shielding competence has been examined experimentally using an Ultra Ge detector with the 133Ba (3 Ci) radioisotope source and theoretically via EpiXS software. X-ray diffraction showed that the structure of the B1 sample has large crystal particle sizes. However, the structure with the smallest amount of ZrO4 and the largest amount of Bi2O3 has become completely amorphous (sample B5). The density of the synthesized samples were noticed to change between 4.70 to 5.99 g cm−3 for B1 and B5 samples, respectively. The B5 sample with high density possessed the highest mass attenuation coefficient (MAC) among other samples. There is an agreement between experimental and theoretical data. The trend of the linear attenuation coefficient (LAC) is the same as that of the MAC. At any certain energy, the half-value layer (HVL) is arranged as; (HVL)B5 > (T1/2)B4 > (T1/2)B3 > (T1/2)B2 > (T1/2)B1. The mean free path (MFP) of the investigated samples is similar to that of the HVL. The recommended glass ceramics can be used as radiation shielding materials.

Development of hard X-ray spectrometer with full digital data acquisition for runaway electron studies at HL-2M

The development of hard X-ray (HXR) spectrometers with full digital data acquisition for runaway electron studies on the HL-2M tokamak is presented. Consisting of large-sized NaI:Tl detectors and high-performance multichannel analyzers, this system can realize the measurement of HXR with energies ranging from 0.5 to 10 MeV, and spectrum temporal resolution of 1 ms. An average energy resolution of 56 keV at 662 keV has been achieved at counts rates of about 100 kcps. The spectra data is acquired by a digital-based data acquisition system with fast digitization and software signal processing technology. The energy calibrations are performed by using several radioisotope gamma-ray sources, and the detection efficiencies are simulated by MCNP code. First experimental results from HL-2M Ohmic discharges are presented in this paper.

Gamma-ray anomaly detector for airborne surveys based on a machine learning methodology

Machine learning methods were used to develop an automated classification model for detecting gamma-ray spectra with anomalous (i.e., non-background) signatures collected during airborne surveys. Spectra were preprocessed with an altitude-based normalization procedure, followed by application of a digital filter to remove baseline and noise effects. Segments of the preprocessed spectra were then used as input patterns to piecewise linear discriminant analysis (PLDA). For use in building the classification model, a training set was constructed based on two data classes: (1) spectra containing various radioisotope signatures and (2) background spectra. Through the use of a piecewise linear discriminant based on seven separating boundaries, a general-purpose spectral anomaly detector was developed for use in the automated screening of large spectral datasets collected during airborne surveys. The intended application of the methodology is to aid first responders in locating lost or stolen radioactive sources or in managing other incidents in which radioactive material is released into the environment. In developing and testing the methodology, laboratory spectra, spectra collected during airborne surveys, and mathematically synthesized spectra were used. When applied to 17 airborne surveys in which known radioisotope sources were present, the anomaly detector was able to locate each source with high confidence. While false detections were observed at a rate of 3.7%, many of these were in the vicinity of the known source location but the radioisotope signature could not be visually observed in the spectrum. For false detections away from the source locations, elevated signatures from naturally occurring background components were typically observed.