Hasil untuk "Plasma physics. Ionized gases"

Kattathu J. Mathew, Amy E. Hixon, Matthew Higginson

Tatsuyoshi Saijo, Tatsuyoshi Saijo, Tatsuyoshi Saijo

Nuclear waste repository siting presents an unprecedented intergenerational challenge: decisions made today will affect approximately 5,000 future generations over 100,000 years. Contemporary approaches in Finland, Sweden, and France rely almost exclusively on present-generation perspectives in societal decision-making. While achieving varying degrees of local acceptance through institutional trust and economic compensation, these processes implement no systematic exercises where current residents adopt future generations’ temporal viewpoints. Future Design (FD) offers a complementary framework by activating futurability—the capacity to experience present happiness through pursuing future generations’ wellbeing. FD employs dual perspective-taking: temporal (through integrated Past Design, Present Design, and Future Design exercises) and spatial (host-beneficiary dialogue). This cultivates three forms of pride: achievement pride from confronting civilization’s waste challenge, collective pride in community contribution, and anticipatory pride imagining descendants’ evaluation. Unlike compensation-based acceptance, pride-based acceptance emerges intrinsically through perspective-taking. Rigorous pilot testing comparing FD and non-FD deliberations is essential, with ethical safeguards ensuring transparency and genuine openness to rejection. Integrating FD into repository siting can help demonstrate what current generations owe future generations: not merely engineered safety, but proven concern.

Mariam, Mariam, Manish Joshi et al.

IntroductionA significant quantity of radioactive iodine is expected to be released following severe nuclear reactor accidents. Recent studies have shown that among various species expected, iodine oxides (IxOy) are less explored but play a crucial role in nuclear safety assessments due to their impact on source term evaluation. Therefore, this study was designed to generate and characterize iodine oxides in a laboratory scale setup.MethodsExperiments were conducted at room temperature and ambient relative humidity using an I2 concentration of ∼1 ppm and an O3 concentration of ∼30 ppm inside a controlled chamber. The reaction kinetics were determined by continuously monitoring O3 concentration. While many previous studies have relied on the radioactive iodine tracers and gamma spectroscopy, this study adopts an alternative approach by analysing ozone decay as a proxy for iodine oxidation. The generated iodine oxide aerosols were characterized for their physical and chemical properties. Impactors and gross samplers were used to collect aerosols, giving particle mass size distribution and total mass concentration, respectively. Particle morphology and chemical composition were determined using a scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS).Results and discussionThe reaction kinetics showed that ozone decay followed first-order kinetics with a high correlation (R2 > 0.99). The particles were found to have I2O5 chemical species with varied shapes, from small porous cloud-like structures to large rod-shaped particles. The findings provide valuable insights into iodine oxidation under environmentally relevant conditions, bridging knowledge gaps in source term estimation and contributing to the enhancement of accuracy of the modeling codes for nuclear safety applications.

Yesim Kutlu, Ivan Spasov, Svetlomir Mitkov et al.

The advanced thermal-hydraulics sub-channel tool CTF has been in the process of continuous development and improvement by Oak Ridge National Laboratory (ORNL) and North Carolina State University (NCSU). In recent years, there has been considerable progress in code development, including new functionalities, application-specific correlations, various multi-physics applications, built-in pre- and post-processors, improved solvers, parallelization, and extensive testing. VVER applications are part of these activities. NCSU has been cooperating with the Institute for Nuclear Research and Energy (INRNE) on CTF development, verification, and validation for VVER core modeling and simulation. This article presents an overview of these CTF studies for VVER applications. Several test cases are considered, which include pure thermal-hydraulic problems as well as multi-physics simulations at the nodal and pin level. On the single physics side, thermal-hydraulic CTF solutions have been compared against measured data for rod bundle, fuel assembly, and full core, as well as code-to-code vs. FLICA4 solutions. CTF was tested in the simulation of the TVSA-5T VVER mini-assembly experiments and in the full-core steady-state calculation for the ongoing OECD/NEA Rostov-2 benchmark. For the TVSA-5T calculations, CTF was coupled with the uncertainty analysis tool Dakota and utilized to propagate uncertainties of input and boundary conditions to output quantities of interest for thermal-hydraulic parameter investigations. The CTF results and measured data obtained from this experimental setup were compared for validation. To produce reliable pin-resolved reference solutions for multi-physics model testing the high-fidelity continuous energy Monte Carlo-based neutron transport codes MCNP6.2 and Serpent 2.2.0 were separately coupled with the CTF sub-channel code. Coupled models of a VVER-1000 fuel assembly were tested in comparisons between MCNP/CTF and Serpent/CTF results. Coarse-mesh multi-physics solutions for a full core have been obtained with the coupled COBAYA/CTF, COBAYA/FLICA4, and PARCS/CTF codes. These solutions have been compared against steady-state plant data and code-to-code for transients. High-fidelity pin-resolved solutions with SERPENT/CTF serve as reference solutions in a steady state. The outcomes from the various studies of single-physics and multi-physics cases used for CTF verification and validation met the initial expectations both qualitatively and quantitatively. The results of the numerical verification and experimental validation are in good agreement with the corresponding reference data.

Shenyang Hu, Yulan Li, R. Matthew Asmussen

A mesoscale model is developed to study silver (Ag) dissolution in Cast Stone (CS) matrix containing silver mordenite (AgM) particles. The model captures microstructure-dependent thermodynamic and kinetic properties, including multispecies diffusion, redox reactions, and Ag precipitation. Simulations show that Ag-rich precipitate formation at the AgM/CS interface slows dissolution by reducing chemical potential gradients and diffusivity, while oxidation reactions enhance Ag release by increasing retention around unreacted reagents (e.g., slag, cement). Smaller AgM particles dissolve more rapidly due to shorter diffusion paths. This model offers a mechanistic framework to assess how microstructure and redox chemistry influence Ag retention and can be integrated with geochemical speciation models for multiscale performance evaluation of nuclear waste forms.

Manoj K. Deka, Balaram Pradhan, Apul N. Dev et al.

In this study, the effects of pressure anisotropy and viscosity on the propagation of shock waves in spin-polarized degenerate quantum magnetoplasma are studied under the influence of the streaming energy of ion beams. The effects of different suitable plasma parameters on the shock wave’s potential profile are studied using the steady state solution of the Zakharov–Kuznetsov–Burgers (Z–K–B) equation, as well as the numerical simulation of the governing non-linear Z–K–B equation. First-order analysis of the non-linear wave propagation depicted a new beam-induced stable mode whose Mach number may be subsonic or supersonic depending on the anisotropic pressure combination in the presence of different spin density polarization ratios. This is the first observation of this new beam-induced stable mode in ion beam plasma, apart from the other existing modes of ion beam plasma systems, namely, the fast beam mode, the slow beam mode, the inherent ion acoustic mode, and the coupled mode, which also has unique propagation characteristics compared to the other modes. The spin density polarization ratio of spin-up and spin-down electrons have an unprecedented effect on the polarity and the direction of propagation of different shock wave modes in such plasma systems. Apart from the spin effect, anisotropic pressure combinations, as well as the viscosity of ions and ion beams, also play an outstanding role in controlling the nature of propagation of shock waves, especially in the newly detected beam-induced stable mode, and depending on the viscosity parameters of ions and ion beams, both oscillatory and monotonic shock waves can propagate in such plasma.

Ming Ding, Chunwei Yang, Yifan Bai et al.

The flat linear induction pumps (FLIPs) are a class of driving devices that converts electromagnetic energy into mechanical energy of pumped liquid metal, which are widely used in the field of energy power and chemical industries. The end effects and wall eddy current effect of FLIPs can significantly reduce the pump head and energy conversion efficiency. In this paper, the longitudinal and transverse end effects of FLIPs caused by the finite length of the core were analyzed, and the analytical expressions of the electromagnetic field in the electromagnetic air gap were given. Based on the mathematical analysis of the end effects and the T-shaped equivalent circuit of the rotary induction motor, an equivalent circuit model was established, considering two kinds of end effects and wall eddy current effects. The calculation methods of main characteristic parameters, such as head and energy conversion efficiency, were given. The accuracy of the analytical model was validated by comparing the calculation results with the open experimental data. The work can provide a rapid analysis method for improving the energy conversion efficiency and working performance of FLIPs.

Achraf Hani, Karim Saber, Alyen Abahazem et al.

This paper focuses on the determination of and improvement in the energy efficiency of plasma jets. To achieve this goal, an equivalent electrical model of a discharge reactor was developed, incorporating variable electrical parameters. The evolution of these parameters was determined by a mathematical identification method based on the recursive least squares algorithm (RLSA). The good agreement between the measured currents and those calculated using our electrical circuit, as well as the significant shapes of the estimated parameters, confirmed the accuracy of the parameter estimation method. This allowed us to use these parameters to determine the energy delivered to the reactor and that used during the discharge. This made our reactor controllable at the energy level. Thus, the ratio between these two energies allowed us to calculate the energy efficiency of plasma jets at each discharge instant. We also studied the effect of the applied voltage on efficiency. We found that efficiency was increased from 75% to 90% by increasing the voltage from 6 kV to 8 kV. All the results found in this work were interpreted and compared with the discharge behavior. This proposed model will help us to choose the right operating conditions to reach the maximum efficiency.

Shingo Tamaki, Yuuki Ohtani, Sachie Kusaka et al.

IntroductionBoron Neutron Capture Therapy (BNCT) is a promising cancer therapy. At present, development of accelerator based neutron source (ABNS) is underway to be utilized as a neutron source instead of nuclear reactor. However, it is known that the neutron field formed with accelerators have different characteristics depending on kinds of accelerators. We thus have to characterize the field before practical use.MethodIn the authors’ group, various neutronics characterization devices have been developed for our p-Li based BNCT machine named CSePT. In this paper, three neutron intensity monitor foils with an isomer production reaction for several tens to 800 keV of the p-Li neutrons were proposed, i.e., 107Ag, 115In and 189Os.Result and DiscussionFrom the experimental test results, two activation foils of 107Ag and 115In were confirmed to be a possible candidate as the monitor. However, the isomer production cross sections of them should be examined for practical use.

Boudewijn Philip van Milligen, Teresa Estrada, Benjamin Carreras et al.

We study the effect of the rotational transform profile on the L–H confinement transitions in the neutral beam-heated plasmas in the TJ-II stellarator. The rotational transform profile in the vacuum is determined by the external coil currents but is modified by the plasma current, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>I</mi><mi>p</mi></msub></semantics></math></inline-formula>. We find that L–H confinement transitions systematically occur when the configuration and plasma current are such that a low-order rational is placed in the plasma edge region, with a distribution centered around <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>ρ</mi><mo>=</mo><mn>0.8</mn><mo>±</mo><mn>0.05</mn></mrow></semantics></math></inline-formula>. It is suggested that magnetohydrodynamic turbulence plays an important role in triggering the L–H transitions at TJ-II.

Howard E. Sims, Robin M. Orr

It is generally accepted that radiolysis of water on the surface of PuO2 by alpha particles is the source of H2 which can cause pressurisation in sealed storage containers if the material is not adequately conditioned before packing. The mechanisms for this have not been discussed in detail previously. Radiolysis mechanisms of bulk water are summarised and then applied to water at the surface of PuO2. It is shown that the radiolysis processes occurring on timescales of less than 1 ps after energy deposition could have an impact on the storage behaviour of the PuO2 and the potential gas volume generated. Some of the radiolysis products are highly reactive and would be expected to react with plutonium at the surface, affecting the usual water radiolysis processes. A corollary of this observation is that the surface should not be considered a completely crystalline PuO2 solid. It is also highlighted that whilst there are significant uncertainties in the radiolysis process at the PuO2 surface there are also significant uncertainties in H2 formation mechanisms in bulk water. Finally, methods to model the radiolysis process at the surface and the prospects for predictive models are briefly discussed with suggestions for future areas of development.

Ferrine Gianne G. Reyes, Jason P. Licerio, Aian B. Ontoria et al.

Nitrides of aluminum (Al) and titanium (Ti) mixtures have long been studied and used as commercial coatings because of their high hardness and high oxidation resistance due to the formation of an alumina layer on the coating surface. To fully understand the contribution of Al and Ti to the properties of the film, a combinatorial deposition approach was employed using half-disk targets. Film growth was carried out using a magnetron sputtering system powered by a 13.56 MHz radio frequency power supply with varying argon (Ar) and nitrogen (N₂) gas ratios. Depending on the location of the substrate relative to the target, atomic percent gradients of 0.60–0.70 Al and 0.30–0.40 Ti across the substrate surface were obtained from energy dispersive X-ray spectral analysis. X-ray diffraction peaks at 43.59°, 74.71° (face-centered cubic), and 50.60° (wurtzite) confirmed the presence of aluminum titanium nitride (AlTiN) mixtures, with an increasing amount of wurtzite phase at higher Al concentrations. For all samples, cauliflower-like nanograins were obtained and samples of the 80:20 Ar:N₂ gas pressure ratio showed the smallest grain size among the three gas ratio combinations. The 80:20 Ar:N₂ films revealed a relatively high hardness compared to the other gas ratios. All thin films exhibited good adhesion to 304 stainless steel substrates.

F. Bok, H. C. Moog, V. Brendler

Xavier Gaona, Bernd Grambow, Taishi Kobayashi et al.

Timur S. Batukaev, Igor V. Bilera, Galina V. Krashevskaya et al.

The task of CO₂ decomposition is one of the components of the problem associated with global warming. One of the promising directions of its solution is the use of low-temperature plasma. For these purposes, different types of discharges are used. Microwave discharge in liquid hydrocarbons has not been studied before for this problem. This paper presents the results of a study of microwave discharge products in liquid Nefras C2 80/120 (petroleum solvent, a mixture of light hydrocarbons with a boiling point from 33 to 205 °C) when CO₂ is introduced into the discharge zone, as well as the results of a study of the discharge by optical emission spectroscopy and shadow photography methods. The main gas products are H₂, C₂H₂, C₂H₄, CH₄, CO₂, and CO. No oxygen was found in the products. The mechanisms of CO₂ decomposition in the discharge are considered. The formation of H₂ occurs simultaneously with the decomposition of CO₂ in the discharge, with a volumetric rate of up to 475 mL/min and energy consumption of up to 81.4 NL/kWh.

Jürgen Guljakow, Walter Lang

This work aims to provide information about the deposition of gold via bipolar high-power impulse magnetron sputtering (HIPIMS) in order to identify suitable process parameters. The influences of voltage, pulse length and the kick-pulse on an argon–gold plasma during a bipolar high-power impulse magnetron sputtering deposition process were analysed via optical emission spectroscopy (OES) and oscilloscope. The voltage was varied between 700 V and 1000 V, the pulse length was varied between 20 µs and 100 µs and the process was observed once with kick-pulse and once without. The influence of the voltage on the plasma was more pronounced than the influence of the pulse width. While the intensity of several Au I lines increased up to 13-fold with increasing voltages, only a less-than linear increase in Au I brightness with time could be identified for changes in pulse length. The intensity of excited argon is only minimally affected by changes in voltages, but follows the evolution of the discharge current, with increasing pulse lengths. Contrary to the excited argon, the intensity emitted by ionized argon grows nearly linearly with voltage and pulse length. The reverse polarised pulse mainly affects the excited argon atoms in the plasma, while the influence on the ionized argon is less pronounced, as can be seen in the the spectra. Unlike the excited argon atoms, the excited gold atoms appear to be completely unaffected by the kick-pulse. No ionization of gold was observed. During the pulse, a strong rarefaction of plasma takes place. Very short pulses of less than 50 µs and high voltages of about 1000 V are to be preferred for the deposition of gold layers. This paper offers a comprehensive overview of the gold spectrum during a HIPIMS process and makes use of optical emission spectroscopy as a simple measuring approach for evaluation of the reverse polarized pulse during a bipolar process. Future uses of the process may include the metallization of polymers.

Mike Machielsen, Joey Rubin, Jonathan Graves

Electromagnetic perturbations of a magnetized plasma cause induced charges and currents, collectively known as the plasma response. In the frequency domain, this response is a non-local functional of the electric field. The associated integral kernel, known as the conductivity kernel, is well known in wave-number space, assuming the special case of a homogeneous plasma with a given Maxwellian background distribution function. It is used in this form by many full-wave codes. However, it may be more advantageous to solve the wave problem using a finite element model because of its attractive meshing flexibility. In this paper an exact solution for the conductivity kernel is derived in configuration space, to our knowledge for the first time in 3D. It is valid to all orders in Larmor radius, and up to arbitrary cyclotron harmonic. Future finite element models can be easily constructed using this kernel, which is shown in two simple examples. The model includes mode conversion as well, demonstrated by the second example.

Masaaki Okubo

A review is presented to integrate fluid engineering, heat transfer engineering, and plasma engineering treated in the fields of mechanical engineering, chemical engineering, and electrical engineering. A basic equation system for plasma heat transfer fluids is introduced, and its characteristics are explained. In such reviews, generally, the gap between fundamentals and application is large. Therefore, the author attempts to explain the contents from the standpoint of application. The derivation of formulas and basic equations are presented with examples of application to plasmas. Furthermore, the heat transfer mechanisms of equilibrium and nonequilibrium plasmas are explained with reference to the basic equation system and concrete examples of analyses.

Jennifer Yao, Shalini Tripathi, Bruce K. McNamara et al.

Introduction: This study aims to develop a microgram-scale microfluidic electrochemical cell (E-cell) for investigating the redox behavior of uranium oxide (UO2). The traditional bulk electrochemical methods may require shielded facilities to investigate the hazardous materials, e.g., spent nuclear fuel, due to high radiation levels. Microfluidic E-cells offer advantages such as reduced radiation exposure, control over fluid flow rates, and high-throughput capabilities.Methods: The design of the E-cell considers electrode morphology, adhesion to a thin membrane, electrode configuration, and vacuum compatibility. Three techniques, including FIB-SEM lift-out, Au coating, and polyvinylidene fluoride (PVDF) binder, are explored for fabricating and attaching microgram quantities of UO2 as working electrodes. The PVDF binder method proves to be the most effective, enabling the creation of a vacuum-compatible microfluidic E-cell.Results and discussion: The PVDF binder method demonstrates successful electrochemical responses and allows for real-time monitoring of UO2 electrode behavior at the microscale. It offers chemical imaging capabilities using in situ SEM/EDS analysis. The technique provides consistent redox outcomes similar to bulk electrochemical analysis.Conclusion: The development of a microgram-scale microfluidic electrochemical cell using the PVDF binder technique enables the investigation of UO2 redox behavior. It offers a low-risk approach with reduced radiation exposure and high-throughput capabilities. The technique provides real-time monitoring and chemical imaging capabilities, making it valuable for studying spent nuclear fuel systems and material characterization.

A. Mathews, J. Terry, S. Baek et al.

The role of turbulence in setting boundary plasma conditions is presently a key uncertainty in projecting to fusion energy reactors. To robustly diagnose edge turbulence, we develop and demonstrate a technique to translate brightness measurements of HeI line radiation into local plasma fluctuations via a novel integrated deep learning framework that combines neutral transport physics and collisional radiative theory for the 33D - 23P transition in atomic helium with unbounded correlation constraints between the electron density and temperature. The tenets for experimental validity are reviewed, illustrating that this turbulence analysis for ionized gases is transferable to both magnetized and unmagnetized environments with arbitrary geometries. Based on fast camera data on the Alcator C-Mod tokamak, we present the first two-dimensional time-dependent experimental measurements of the turbulent electron density, electron temperature, and neutral density, revealing shadowing effects in a fusion plasma using a single spectral line.