Atomic Energy Research Articles

Role of independent research at AERB for ensuring safety of nuclear facilities in India.

The mission of Atomic Energy Regulatory Board (AERB) of India is to ensure that the use of ionising radiation and nuclear energy in India does not cause unacceptable impact on the workers, members of the public and to the environment. AERB has the mandate to carry out detailed safety review for the siting, construction, commissioning, operation and decommissioning of nuclear and radiation facilities established within the country. To deliver and maintain a strong, credible and technically sound regulation, AERB has established the Safety Research Institute (SRI) at Kalpakkam with a robust technical infrastructure and wide knowledge base. This paper highlights the independent safety research activities carried out at SRI and its role to support and facilitate the decision-making process by AERB at various stages of regulatory review for ensuring safety of the nuclear facilities in India.

Methodology for shielding design and evaluation for container scanners.

There has been an increase in the use of high energy photon beam for container scanners in many countries for multi purposes such as detecting high atomic number materials which might be nuclear materials, drugs, high explosive materials and other contrabands etc. High energy photon beams generally 6 and 9 MV can be used for scanning such materials. However, it is important to ensure that radiation level beyond the container scanner installation is within the permissible dose limit specified by the national competent authority for the protection of public and radiation workers. In this paper, challenges in the biological shielding during the installation of high energy X-ray system for scanning vehicles containing suspected materials are discussed. The purpose of the present study is to develop a methodology for shielding design and evaluation for container scanner installations. The basic concept pertaining to shielding evaluation of radiotherapy installations provided in National Council on Radiation Protection and Measurements (NCRP)/International Atomic Energy Agency (IAEA) reports are referred, and appropriately used to calculate optimized shielding thicknesses requirements for container scanner installation. Workload is estimated based on number of containers scanned, machine ON time and dose rate at 1m. The shielding evaluation includes use of beam stopper in the primary beam, scattering by heterogeneous metallic scrap materials or any other suspected materials contained in the vehicle and their impact on the thickness of shielding walls. A model lay out plan to be used for installation of container scanner is developed. A methodology for shielding evaluation for various protective walls and ceiling of this model is also discussed. The study provides basic requirement for designing a structural room for installing 9MV container scanner from radiological safety view point.

Influence of a plasma focus device on the structural and optical properties of highly conductive AZO thin films

In the present work, we deposited Al-doped ZnO (AZO) thin films on microscope glass slides at different pressures (5, 10, 20, and 30 mTorr) using an EAEA-PFD (Plasma Focus Device of the Egyptian Atomic Energy Authority) without any extra heat treatment. Argon gas provided the radiant energy needed to form a crystalline AZO film. This study investigated the deposition and features of AZO thin films. The impact of changes in work pressure on the microstructure, morphology, and optical attributes of AZO films was reported. The results demonstrated that varying the work pressure significantly affects the microstructure, morphology, crystallinity, optical absorbance, and optical energy gap. The microstructure and morphology were evaluated through XRD and scanning electron microscopy (SEM). The optical properties were analyzed using a UVvis double-beam spectrophotometer within a wavelength range from 300 to 1100 nm. XRD patterns indicating a zinc-blende structure and the Williamson–Hall approach were used to estimate the structural parameters. The estimated trend in the particle size of the AZO film demonstrates a decrease from 82 ± 5 nm to 48 ± 5 nm as the pressure increases. The calculated energy gap, Egopt, increases from 3.53 eV to 3.69 eV with increasing work pressure. The conductivities in terms of both optical and electrical decreased with increasing work pressure of the AZO films.

Transfer functions for QA/QB international regulatory limits for the safe transport of radioactive materials.

This paper presents a proposed revision of the International Atomic Energy Agency (IAEA) transport regulations, related to the A1 and A2 limit values used to determine the radioactive transport classification. Based on the "Q system", a novel methodology was introduced to derive QA and QB values related to scenarios involving external exposure from a distant source. These values are key parameters that respectively represent the total effective dose and total equivalent dose to the skin, from all primary and secondary particles contributing to radiation exposure. The International Working Group (WG A1/A2) is established and associated with the TRANSSC Technical Expert Group on Radiation Protection (TTEG-RP). A review of the A1 and A2 values is performed in response to identified limitations within the existing Q system. The followed approach is based on Monte Carlo simulations that enabled the development of transfer functions aimed at reducing computational time and increasing the flexibility of dose evaluations for any radionuclide with known particle emission spectra. This method allows updating the QA and QB values to account for future data evolutions (decay data, fluence-to-dose conversion coefficients) and standardizing the calculation of regulation limits across all referenced radionuclides and scenarios related to external exposure. The transfer functions are established using three Monte Carlo simulation codes - FLUKA, Geant4, and MCNP - and address the previous limitations of the "Q system", reflecting the latest ICRP recommendations and improvements in calculation techniques. The results of the WG show consistent agreement across the codes, with minor discrepancies observed at low primary energies due to statistical uncertainties and different handling of stopping power for electrons/positrons in the codes. This revised approach aligns with current standards and recommendations, ensuring that the radiological consequences of transport accidents are acceptable for the new A1 and A2 limits from a radiological protection perspective.&#xD.

Tertiary Magmatism in Northwestern Kalimantan: Probability of Volcanic Hazard to The Nuclear Power Plant Site Candidate at Gosong Beach, Bengkayang Regency

Gosong Beach in Bengkayang, West Kalimantan, is selected as a potential Nuclear Power Plant (NPP) site candidate. Volcanic and intrusive rocks are found in the radius of 150 km from it. Based on IAEA (International Atomic Energy Agency) standard, the main assessment target is volcanic rock that is younger than 10 Ma. However, there are Tertiary volcanic and intrusive rocks next to and cover a wide area around the NPP site that show volcanic activities over the Tertiary period. Therefore, it is necessary to investigate this group of rocks to understand its characteristics. This study aims to characterize the geochemistry and petrology of the Tertiary volcanic and intrusive rocks found in northwestern Kalimantan. The fieldwork was conducted to observe and to take Serantak volcanic rocks, Bawang dacite, Niut volcanics, and Sintang intrusion samples. The XRF and micro-XRF analyses were conducted to characterize the geochemical aspect, while petrography and AMICS analyses were conducted to characterize the mineralogical aspect. The result shows that Serantak volcanic rocks, Bawang dacite, Niut volcanics, and Sintang intrusion are derived from tholeiitic to calc-alkaline as a product of mantel partial melting in the subduction zone which go through fractional crystallization. The volcanic activity was initiated by the rise of primitive parental magma from partial melting in the shallow-depth subducted crust as indicated by the garnet-free HREE pattern, the enrichment of LILE and LREE, and the depleted HREE. The Tertiary magmatism in northwestern Kalimantan was found in a small activity with a small impact on the NPP candidate site at Gosong Beach, Bangkayang.

Uranium standards in drinking water: An examination from scientific and socio-economic standpoints of India.

The detection of uranium in drinking water has ignited concerns among the public, regulators, and policymakers, particularly as around 1% of the 55,554 water samples in India have shown uranium levels surpassing the 60µg/l guideline established by the Atomic Energy Regulatory Board (AERB) based on radiological toxicity. Further, the Bureau of Indian Standard (BIS), has given a limit of 30µg/l, which is derived from World Health Organization (WHO) guidelines. Besides the chemical and radiological aspects associated with uranium, factors such as technological constraints in water purification, waste management, environmental factors, and socio-economic conditions significantly influence these guideline values, which are often overlooked. This manuscript explores the variations in approaches for establishing guideline values and highlights the uncertainties arising from dependence on various variables such as intake and usage patterns, inter- and intra-species distinctions, and epidemiological data. A critical analysis indicates that adherence to global guidelines may result in some undesirable environmental issues. By considering factors such as population dynamics, socio-economic conditions, and geological influences, we suggest that limit of 60µg/l for uranium in drinking water is appropriate for India.

Incorporating Noncovalent Interactions in Transfer Learning Gaussian Process Regression Models for Molecular Simulations.

FFLUX is a quantum chemical topology-based multipolar force field that uses Gaussian process regression machine learning models to predict atomic energies and multipole moments on the fly for fast and accurate molecular dynamics simulations. These models have previously been trained on monomers, meaning that many-body effects, for example, intermolecular charge transfer, are missed in simulations. Moreover, dispersion and repulsion have been modeled using Lennard-Jones potentials, necessitating careful parametrization. In this work, we take an important step toward addressing these shortcomings and show that models trained on clusters, in this case, a dimer, can be used in FFLUX simulations by preparing and benchmarking a formamide dimer model. To mitigate the computational costs associated with training higher-dimensional models, we rely on the transfer of hyperparameters from a smaller source model to a larger target model, enabling an order of magnitude faster training than with a direct learning approach. The dimer model allows for simulations that account for two-body effects, including intermolecular polarization and charge penetration, and that do not require nonbonded potentials. We show that addressing these limitations allows for simulations that are closer to quantum mechanics than previously possible with the monomeric models.

An exploration of the regulatory regime of the Indian nuclear industry

India has always attached great importance to the development of its nuclear industry. India's nuclear industry started early with the establishment of the Atomic Energy Commission (AEC) in 1948 and the Department of Atomic Energy (DAE) in 1954. The current management system in India is that the Prime Minister exercises the highest decision-making power, the Atomic Energy Commission assists the Prime Minister in decision-making; the Department of Atomic Energy is in charge of the nuclear industry; research and development institutions and state-owned enterprises under the Department of Atomic Energy implement specific decisions. The characteristics of India's nuclear industry system are: direct supervision by the Prime Minister and full safeguards; high degree of centralisation and unified management; integration of the military and civilian sectors and the use of the civilian sector as a cover for the military; and adherence to the “"three-step” nuclear energy development route. India's remarkable achievements in the face of a prolonged international embargo are attributable to the nuclear industry management system that has been in place in India for more than 60 years, which is worthy of our reference.

Effect of strain on the photoelectric properties of molybdenum ditelluride under vacancy defects: a DFT investigation.

This study explores the impact of deformation on the electrical and optical characteristics of monolayer cadmium telluride (MoTe2) with vacancies, using the foundational principles of density functional theory. It was discovered that both strain and imperfections alter the electrical characteristics of monolayer MoTe2. Under VTe-MoTe2, a direct-to-indirect band-gap transition occurs. In DTe-MoTe2, the band-gap value reduces dramatically, the conduction band changes downward, and the carrier concentration rises. The DVTe-induced band gap state is closer to the Fermi energy level than the VTe-induced band gap state. In this paper, DTe-MoTe2 is chosen for tensile deformation. The results show that the band-gap value tends to decrease by increasing tensile deformation. When the stretching value reaches 10%, the lower bound of the conduction band and the top of the valence band overlap, and the system is converted from a semiconductor to a metal. Considering the density of states, the missing state MoTe2 is mainly contributed by the participation of Te-s, Te-p, and Mo-d orbitals. In terms of optical qualities, the absorption and reflection peaks are red-shifted and blue-shifted, respectively. It is hoped that these effects on the optoelectronic properties will be widely applied. In this study, we utilize the generalized gradient approximation plane-wave pseudopotential method, incorporating Perdew-Burke Ernzerhof (PBE) generalized functions and following the fundamental principles of the density functional theory framework. A 3 × 3 × 1 supercell was constructed as an undoped model based on a MoTe2 monolayer, which consists of 9 Mo atoms and 18 Te atoms. The vacuum flat plate was set to 15Å along the z-direction to avoid interactions between the monolayers. For electronic structure calculations, the energy cutoff was set to 450eV. Each model's computational process and structural optimization were carried out using the Monkhorst-Pack specialized K-point sampling approach. Crystal optimization computations used a 3 × 3 × 1 Monkhorst-Pack K-point grid for molybdenum ditelluride monolayers and a 9 × 9 × 1K-point grid for electronic system analysis, analyzing state density and optical characteristics, respectively. For the structural optimization, the convergence requirements for maximum force, maximum atom displacement, maximum stress, and energy change were defined at 0.03eV/Å, 0.001Å, 0.05 Gpa, and 1.0 × 10-5eV/atom, respectively.

Regional Workshop on Optimization of Protection in Pediatric Interventional Radiology in Latin American and Caribbean Countries.

The purpose of this article is to describe the activities developed within the framework "Regional Workshop on Optimization of Protection in Pediatric Interventional Radiology in Latin American and Caribbean countries," developed between October 16th and 19th of the year 2023 in the city of San José, Costa Rica. The workshop was carried out as part of a joint work between the Pan American Health Organization (PAHO) and the World Health Organization (WHO), in cooperation with the International Atomic Energy Agency (IAEA). The main objective of the regional workshop was to gather the experiences and future work planning among participants in the Optimization of Protection in Pediatric Interventional Radiology in Latin America and the Caribbean (OPRIPALC) program. It involved professionals from 14 centers across 11 countries in the region, along with 4 experts from PAHO/WHO/IAEA. The work modalities during the workshop consisted of keynote presentations, individual presentations, group work, and general discussions. An online survey was carried out after the workshop, with the objective of knowing the opinion of the event participants and determining the impact and projection of the OPRIPALC program. During the workshop the centers had to present their experiences: the use of the DOLQA dose management system was presented and work was done on the consensus document on good practices. The activities, topics and organization of the workshop were valued positively by the participants. There is unanimity among the centers that the OPRIPALC program has had a positive impact and they wish to continue actively participating in the next biennium.

Regional Workshop on Optimization of Protection in Pediatric Interventional Radiology in Latin American and Caribbean Countries.

The purpose of this article is to describe the activities developed within the framework "Regional Workshop on Optimization of Protection in Pediatric Interventional Radiology in Latin American and Caribbean countries," developed between October 16th and 19th of the year 2023 in the city of San José, Costa Rica. The workshop was carried out as part of a joint work between the Pan American Health Organization (PAHO) and the World Health Organization (WHO), in cooperation with the International Atomic Energy Agency (IAEA). The main objective of the regional workshop was to gather the experiences and future work planning among participants in the Optimization of Protection in Pediatric Interventional Radiology in Latin America and the Caribbean (OPRIPALC) program. It involved professionals from 14 centers across 11 countries in the region, along with 4 experts from PAHO/WHO/IAEA. The work modalities during the workshop consisted of keynote presentations, individual presentations, group work, and general discussions. An online survey was carried out after the workshop, with the objective of knowing the opinion of the event participants and determining the impact and projection of the OPRIPALC program. During the workshop the centers had to present their experiences: the use of the DOLQA dose management system was presented and work was done on the consensus document on good practices. The activities, topics and organization of the workshop were valued positively by the participants. There is unanimity among the centers that the OPRIPALC program has had a positive impact and they wish to continue actively participating in the next biennium.

Scalable Ab Initio Electronic Structure Methods with Near Chemical Accuracy for Main Group Chemistry.

This study evaluates the precision of widely recognized quantum chemical methodologies, CCSD(T), DLPNO-CCSD(T), and localized ph-AFQMC, for determining the thermochemistry of main group elements. DLPNO-CCSD(T) and localized ph-AFQMC, which offer greater scalability compared to canonical CCSD(T), have emerged over the past decade as pivotal in producing precise benchmark chemical data. Our investigation includes closed-shell, neutral molecules, focusing on their heat of formation and atomization energy sourced from four specific small molecule data sets. First, we selected molecules from the G2 and G3 data sets, noted for their reliable experimental heat of formation data. Additionally, we incorporate molecules from the W4-11 and W4-17 sets, which provide high-level theoretical reference values for atomization energy at 0 K. Our findings reveal that both DLPNO-CCSD(T) and ph-AFQMC methods are capable of achieving a root-mean-square deviation of less than 1 kcal/mol across the combined data set, aligning with the threshold for chemical accuracy. Moreover, we make efforts to confine the maximum deviations within 2 kcal/mol, a degree of precision that significantly broadens the applicability of these methods in fields such as biology and materials science.

Tailoring Mott-Schottky RuO2/MgFe-LDH Heterojunctions in Electrospun Microfibers: A Bifunctional Electrocatalyst for Water Electrolysis.

Hydrogen is a fuel of the future that has the potential to replace conventional fossil fuels in several applications. The quickest and most effective method of producing pure hydrogen with no carbon emissions is water electrolysis. Developing highly active electrocatalysts is crucial due to the slow kinetics of oxygen and hydrogen evolution, which limit the usage of precious metals in water splitting. Interfacial engineering of heterostructures has sparked widespread interest in improving charge transfer efficiency and optimizing adsorption/desorption energetics. The emergence of a built-in-electric field between RuO2 and MgFe-LDH improves the catalytic efficiency toward water splitting reaction. However, LDH-based materials suffer from poor conductivity, necessitating the design of 1D materials by integration of RuO2/ MgFe-LDH to enhance catalytic properties through large surface areas and high electronic conductivity. Experimental results demonstrate lower overpotentials (273 and 122mV at 10mAcm-2) and remarkable stability (60h) for the RuO2/MgFe-LDH/Fiber heterostructure in OER (1m KOH) and HER (0.5m H2SO4) reactions. Density functional theory (DFT) unveils a synergistic mechanism at the RuO2/MgFe-LDH interface, leading to enhanced catalytic activity in OER and improved adsorption energy for hydrogen atoms, thereby facilitating HER catalysis.

RPV top and bottom break SBLOCA with passive emergency core cooling system using ATLAS test facility

A SBLOCA test, named as C2.1 in the frame of the OECD/NEA ATLAS3 project, using a passive emergency core cooling system (PECCS) was performed by Korea Atomic Energy Research Institute (KAERI). In the test, two simultaneous 2-inch equivalent breaks occurred at top and bottom nozzles of the reactor pressure vessel of ATLAS test facility. The main purpose of the test is to investigate thermal hydraulic transient behavior in a reactor coolant system (RCS) during a SBLOCA scenario and to evaluate the effectiveness of PECCS. From the observation on thermal hydraulic phenomena during the test, the test period was divided into three characteristic phases such as pressure plateau, safety injection, and clad temperature re-increase phases. Continuous inventory loss of the primary loop through two break nozzles led to a primary system pressure decrease and a clad temperature increase. Even though high-pressure safety injection tanks (HPSITs) were actuated in an early stage of the pressure plateau phase, safety injection from HPSITs, however, were not actually injected. Safety injection flows from the HPSITs and SITs were practically injected to the downcomer only after the opening of automatic depressurization valves (ADVs). With a continuous decrease of a primary system pressure, low-pressure (LP) injection was started. However, LP injection could not change the increasing trend of the clad temperatures. Post-test calculations were performed using MARS-KS 1.4, and calculation results were compared with those of the test.

Assessment of soil moisture on radon levels, radon exhalation, natural radioactivity, and radiological risks in offices and laboratories in GAEC

This study investigates the influence of moisture on soil radon exhalation, natural radioactivity in soil, and indoor radon concentrations in offices and laboratories at the Ghana Atomic Energy Commission (GAEC) and their associated radiological risks to workers. Radon exhalation rates were determined using the Sealed Can method. CR-39 SSNTD detectors were used to measure indoor radon concentrations. Gamma spectroscopy using HpGe detector was used to determine the activity concentrations of U-238, Ra-226, Th-232, and K-40 in the soil samples. The results showed mean concentrations of 14.3 ± 2.0 Bq/kg (CI 95%: 10.0–18.0) for U-238, 145.0 ± 10.0 Bq/kg (CI 95%:123.0–167.0) for K-40, 31.5 ± 6.0 Bq/kg (CI 95%: 24.0–39.0) for Th-232, and 15.6 ± 2.0 Bq/kg (CI 95%:14.0–29.0) for Ra-226. The results showed mean surface and mass exhalation rates of 6.9 ± 2.3 × 10−4 Bq/m2/h1 (CI 95%: 5.7 × 10−4 –12.6 × 10−4) and 2.4 ± 0.4 (CI 95%: 1.9–4.2) nBq/kg1/h1 respectively. The findings revealed mean indoor radon concentrations of 93.0 ± 10.0 Bq/m3 (CI 95%: 88.0–98.0), 111.0 ± 12.0 Bq/m3 (CI 95%: 102.0–119.0) and 145.0 ± 13.0 Bq/m3 (CI 95%: 135.0–155.0) in the offices, laboratories, and basements respectively, with laboratories and basements exceeding the WHO reference level of 100 Bq/m3. A strong inverse relationship between moisture levels and exhalation rates (r = −0.8) was observed, leading to a negative correlation (r = −0.3). Between the moisture levels and indoor radon levels. The research findings indicated a mean annual effective dose of 0.6 mSv/yr. (CI 95%: 0.5–0.6) to the workers, which is well below occupational and public dose limits. The lung cancer cases of workers were computed which ranged from 0.9 × 10−8 to 1.2 × 10−8 cases per million people per year, which is less than the limit range of 170–230 per million people per year recommended by ICRP but remaining with safe radiological limits for workers. This study identified moderate radon exposure risks at the GAEC, exceeding the WHO recommendation. The correlation and trend analysis demonstrate strong relationships between moisture, exhalation rates, radium, and indoor radon.

Hydrogen Adsorption, Migration and Desorption on Amorphous Carbon: A DFT and AIMD Study

Physisorption is the general dominating adsorption mode on pure carbonaceous materials. In this study, we examined if chemisorbed hydrogen can be accomplished without incorporating metals on carbon surfaces. We constructed two 100-atom amorphous carbon models with different microenvironments (42% 2-fold, 52% 3-fold, and 6% 4-fold coordinated carbon atoms and 18% 2-fold and 82% 3-fold, respectively) using ab initio molecular dynamics (AIMD) simulations to mimic activated carbon samples in reality. The structural, energetic, electronic structure and kinetic properties of hydrogen adsorption, migration, and desorption on the amorphous carbon surfaces were analyzed using density functional theory (DFT) and AIMD calculations, which showed that: (1) hydrogen molecules could spontaneously dissociate on the convex side of 2-fold coordinated carbon atoms. Physisorption of hydrogen molecules mainly took place on 3-fold coordinated carbon atoms. (2) Regarding the multiple hydrogen adsorption, the entire amorphous model could uptake around 156 hydrogen atoms with the adsorption energy per hydrogen atom about -0.70 to -0.60 eV at high hydrogen pressure. In addition, we found that the average individual adsorption energy of a single hydrogen atom on different carbon atoms could be used as a quick prediction for the saturated hydrogen adsorption energy. (3) The migration barrier of a hydrogen atom between two adjacent carbon atoms was about 2 eV at both low and high hydrogen coverage, indicating that hydrogen mobility on this designed amorphous carbon model was low. The desorption of a hydrogen molecule can take place at 300 K using AIMD calculation, but not for atomic hydrogen desorption. In this work, we demonstrated that hydrogen chemisorption could take place on this designed amorphous carbon without the decoration of metal particles to enhance hydrogen adsorption amounts. The materials design to balance hydrogen chemisorption, migration, and desorption shall be considered in the future.

New features in Franck–Hertz experiment with argon: experiment and Monte Carlo simulation

In this work, a homemade apparatus was built to perform the Franck–Hertz experiment with argon. The lowest energy state and the higher energy state of argon can be excited by the Franck–Hertz experiment. The excitation energies of the argon atom are measured by using the setup. The obtained higher excitation energy of argon atoms is 13.73 ± 0.28 eV, for the mixture of higher energy states 3s 23p 53d and 3s 23p 54p. A plate capacitor model was constructed to simulate the inelastic collisions between electrons and argon atoms using the Monte Carlo method. The simulated current curve and electron energy distribution agrees with that of Franck–Hertz experiments, especially the features of higher excited state. The Monte Carlo simulation indicates the deformed electron energy distribution results from the change in excitation proportion of energy levels during the collisions of electrons and argon atoms. Moreover, the new features in Franck–Hertz curve are ascribed to the higher excitation states of argon atoms. The experimental setup has been applied to undergraduate physics experiment teaching in college. Students can perform the Franck–Hertz curve measurement of not only the lowest excited state, but also the higher excited states of argon. In addition, students can do the Monte Carlo simulations for the experimental Franck–Hertz curves and gain a better understanding of electron-argon atom collisions in the experiment. The new designed experiment will make students more familiar with the quantum behavior in atomic physics and quantum mechanics course.

Superior moderate-strength Pd–Pt/Al-based composite tailored for dehydrogenation of perhydroacenaphthene

Pd–Pt-based catalysts are promising for the dehydrogenation of perhydroacenaphthene (PHAN) molecules, yet their effectiveness is hampered by strong adsorption of the product C12H8 and limitations under extreme conditions. Herein, utilizing a relational model involving d-band center, sub-surface coverage, and H atom and C12H8 adsorption energies, the most dehydrogenation-prone crystal facet was identified. Following this, employing Mulliken charge and Sabatier principle, we screened positively charged Pd–Pt/111_O2(Al) surface with moderate interaction strength through the calculation of interaction energy between the chosen Pd–Pt surface and thermally stable MgAl2O4(111) terminal surfaces. Crucially, an extensive examination into reaction mechanisms, microkinetics, and the variation in interaction strength between support and active components at 873.15 K and 3 MPa was conducted. It was observed that the rate-determining step for PHAN molecules on the Pd–Pt/111_O2(Al) surface was C12H19* + * → C12H18* + H*, with a rate of 2.57 × 10-23 s−1. The dehydrogenation of C12H10 to C12H8 proved more favorable than from C12H20 to C12H10, with the latter strengthening support and active components, unlike the weakening effect of the former. This work offers essential foundational support for the development of excellent performance catalysts and the dehydrogenation process of superior heat sink fuels.

Design and simulation of sun position sensors for space applications: A comparative study.

Sun position sensors are used in space applications as part of the attitude determination and control system. The aim of this work is to describe the design process of single and dual axis sun position sensors based on a photodiode array detector and a window to limit and direct the light that reaches the detector. The design process involves choosing the sensor architecture, modeling its output, and then evaluating the model through simulation. Six architectures, with different configurations and geometries for both the detector and window, were modeled and compared. To evaluate the model and performance of the sensor, a program was developed, and simulations were made varying the window height and size as well as the photodiode size. From the simulations performed, we concluded that for each design, the key factors that influence the sensitivity and field of view performance are the window height and window or photodiode size, depending on the sensor configuration. From the comparison across architectures, the detector configuration, as well as the window geometry, influences the sensitivity and linearity of the response for similar conditions of operation. The two-quadrant detector configuration offers a better sensitivity than the triangular photodiode configuration. For a better linearity of the output, a square window is preferred. This comparative study is part of the development of new products for space applications by the National Atomic Energy Commission and contributes to the Argentinian National Space Plan.

Design and simulation of sun position sensors for space applications: A comparative study.

Sun position sensors are used in space applications as part of the attitude determination and control system. The aim of this work is to describe the design process of single and dual axis sun position sensors based on a photodiode array detector and a window to limit and direct the light that reaches the detector. The design process involves choosing the sensor architecture, modeling its output, and then evaluating the model through simulation. Six architectures, with different configurations and geometries for both the detector and window, were modeled and compared. To evaluate the model and performance of the sensor, a program was developed, and simulations were made varying the window height and size as well as the photodiode size. From the simulations performed, we concluded that for each design, the key factors that influence the sensitivity and field of view performance are the window height and window or photodiode size, depending on the sensor configuration. From the comparison across architectures, the detector configuration, as well as the window geometry, influences the sensitivity and linearity of the response for similar conditions of operation. The two-quadrant detector configuration offers a better sensitivity than the triangular photodiode configuration. For a better linearity of the output, a square window is preferred. This comparative study is part of the development of new products for space applications by the National Atomic Energy Commission and contributes to the Argentinian National Space Plan.