Erin Holland, Erin Holland, Matthew A. Higginson
et al.
Nuclear forensic science aims to correlate measurable parameters to the processing history of nuclear materials to support law enforcement investigations. Controlled studies on elemental fractionation with processing are valued on materials of known provenance to validate methods and signatures. There is need to understand how useful current applied techniques are when applied to thorium materials. In this study, we discuss the potential nuclear forensic signatures in thorium materials and report an academic study processing a monazite ore of known provenance through a historic industrial process to thorium dioxide. The measurements traced a variety of ‘fingerprint’ material properties and impurities through the processing route. It was shown that radiometric methods, relative rare earth element abundances, impurities, radiochronometry and microscopy were useful for characterising the material.
María Victoria Villar, Katerina Cernochova, Jaime Cuevas
et al.
Most safety cases for radioactive waste disposal consider a temperature limit of 100°C for the clay buffers. Given that being able to tolerate higher temperatures would have significant advantages, the work package HITEC of the EURAD project aimed at determining the influence of temperature above 100°C on buffer properties, trying to establish if the safety functions are unacceptably impaired. A synthesis of the state of knowledge on the thermo-hydro-mechanical and chemical behaviours of different buffer materials at different temperatures is presented, along with the progress made in this area during HITEC. The changes in the properties of the preheated material and the hydromechanical properties of bentonite at high temperatures were assessed. To cover the first instance, bentonite was heated at 150°C in dry and wet conditions for different periods of time up to 2 years. The clay mineralogy was significantly preserved. The slight changes observed in the other properties were opposite depending on the heating conditions: in the case of evaporation, the cation exchange capacity, specific surface area, sorption coefficients, and sometimes swelling pressure decreased. These changes likely resulted from the strong drying induced by the elevated temperatures. Bentonite was also subjected to hydration under a thermal gradient in field and laboratory tests. No post-mortem structural modifications of the smectite were observed; however, dissolution and precipitation of species occurred, conditioned by the type of bentonite and hydration water. These processes were accompanied by the modification of the exchangeable cation complex. Determination of the hydromechanical properties of expansive clay at elevated temperatures is challenging owing to experimental and interpretation issues. In most cases, a reduced swelling pressure was obtained when the temperature increased, particularly at higher dry densities. These results may have been affected by the experimental protocols, use of bentonite or purified smectite, and exchangeable cations. Even at the highest temperatures, bentonite can fill voids and develop large swelling pressures at high densities. Thermo-hydro-mechanical models were developed or upgraded during the project to include thermal phenomena and dependencies and were applied to the simulation of new laboratory thermo-hydraulic tests in cells.
To explore the potential of plasma technology in regulating seed germination, this study compared the effects of direct treatment with needle-plate electrodes using DC and pulse power supplies, and indirect treatment with plasma-activated water on the growth characteristics of <i>Bromus inermis</i> seeds. By comparing different pulse power parameters, including voltage, pulse width, frequency, and duration, it was found that treatments at 15 kV, 2500 ns, 6 kHz, and 10 min significantly increased the surface hydrophilicity and germination performance of the seeds. The best conditions for DC power supply were 15 kV and 10 min. Indirect treatment with plasma-activated water (15 kV, 10 min) effectively broke the seed dormancy by regulating active nitrogen oxygen particle components, increasing the germination percentage by 50%. Analysis of antioxidant enzyme activity showed that in seedlings the activities of superoxide dismutase (SOD) and peroxidase (POD) increased by 75% and 21%, respectively, after treatment, revealing the mechanism of oxidative stress response induced by plasma. This study provides theoretical and technical references for the application of plasma technology in enhancing seed vitality and agricultural practices.
Self-consistent, one-dimensional quasineutral screw-pinch equilibria are constructed within a hybrid model that couples fluid electrons with kinetic ions governed by the Vlasov equation. The equilibria depend on the radial coordinate perpendicular to the cylindrical axis and include an axial background magnetic field. Adopting a three-parameter ion distribution function depending on the energy and the canonical momenta conjugate to the two ignorable coordinates, the problem is reduced to a set of four quasilinear ODEs which are solved numerically. Both static equilibria and equilibria with macroscopic ion sheared velocities are obtained. The pressure of the electron fluid is isotropic and the electron contribution to the current density is parallel to the magnetic field, while the kinetic ions are associated with a non-gyrotropic pressure tensor. By means of the solutions the various equilibrium quantities are calculated and the impact of the free parameters on the equilibrium characteristics is examined.
This paper focuses on the passive residual heat removal system of a typical large advanced pressurized water reactor, analyzing its design, performance, and reliability during station blackout conditions combined with the failure of the auxiliary feedwater steam-driven pumps. The study employs modeling of passive safety systems and utilizes response surface methodology to evaluate system behavior during severe accident scenarios. Such comprehensive analysis contributes to ensuring the safe operation and advancement of nuclear power plants. The best-estimate program VITARS is used to analyze and calculate accident scenarios, with sensitivity analysis conducted based on preliminary thermal-hydraulic calculations to optimize parameter selection and simplify the response surface model structure, thereby streamlining the analysis process. An artificial neural network is employed as a surrogate model for complex thermal-hydraulic calculations, significantly improving analysis efficiency. The findings indicate that the passive residual heat removal system has zero failure probability under normal uncertainty ranges within 72 h. Even under extreme conditions, such as delayed opening of the steam generator’s safety valve, the system maintains reactor safety with a failure probability of only 0.035%.
Parthkumar Rajendrabhai Patel, Parthkumar Rajendrabhai Patel, Amit Kumar
et al.
With the growing emphasis on safety in next-generation reactors, along with the necessity to practically eliminate large doses to the public from severe accidents, a mechanistic assessment of such accidents becomes very important problem. The present manuscript attempts to address the source term assessment, focusing on the release behaviour of the aerosol from the roof-slab leak paths post-Core Disruptive Accident (CDA) conditions (known as interface source term or cover gas source term). Following a CDA, after possible Na leak through the gap between rotating plugs and major components, the cover gas space could be in contact with the containment atmosphere through these open leak paths. Additionally, the impact of sodium slug to roof-slab could have caused roof-slab cooling line failure. The present study assesses the release behaviour of the aerosols from the roof-slab leak paths, with respect to aerosol size under various cases of roof-slab cooling line failure. Sodium aerosols are used as representative aerosols for studying the radionuclide (RN) aerosol release behaviour. The assessment indicates that most of the aerosol leaking from roof-slab leak paths are of the diameter between 5 and 25 μm, with leak rates peaking in the range of 17–23 μm. Furthermore, with respect to air ingress concern, it is observed that the air ingress from the containment atmosphere was found only in the annular leak paths and it is not mixing into cover gas. However, this ingress was limited to the annular leak path only. It is seen that higher leak rates are observed in the case of complete failure of the roof-slab cooling system. Hence, it is important to maintain the roof-slab bottom plate temperatures within limits to avoid larger aerosol leak rates.
A vacuum arc is an electrical discharge, in which the current is supported by localized cathode heating and plasma generation in minute regions at the cathode surface called cathode spots. Cathode spots produce a metallic plasma jet used in many applications (microelectronics, space thrusters, film deposition, etc.). Nevertheless, the cathode spot is a problematic and unique subject. For a long time, the mechanisms of spot initiation, time development, instability, high mobility, and behavior in magnetic fields have been described by approaches that caused some controversy. These spot characteristics were discussed in numerous publications over many years. The obscurity and confusion of different studies created the impression that the cathode spot is a mysterious phenomenon. In the present work, a number of typical representative publications are reviewed with the intention of clarifying problems and contradictions. Two main theories of cathodic arcs are presented along with an analysis of the experimental data. One of the approaches illustrates the cathode heating by Joule energy dissipation (volume heat source, a sharp rise in current density, etc.), nearly constant cathode potential drop, and other certain initial conditions. On the other hand, a study using a mathematically closed approach shows that the spot initiation and development are determined not by electron emission current rise but by a rise in arc power density, affecting heat sources including the energy of ion flux to the cathode (surface heat source).
The famous Hill’s solution describing a spherical vortex with nested toroidal pressure surfaces, bounded by a sphere, propelling itself in an ideal Eulerian fluid, is re-derived using Galilei symmetry and the Bragg–Hawthorne equations in spherical coordinates. The correspondence between equilibrium Euler equations of fluid dynamics and static magnetohydrodynamic equations is used to derive a generalized vortex type solution that corresponds to dynamic fluid equilibria and static plasma equilibria with a nonzero azimuthal vector field component, satisfying physical boundary conditions. Separation of variables in Bragg–Hawthorne equation in spherical coordinates is used to construct further new fluid and plasma equilibria with nested toroidal flux surfaces, featuring respectively boundary vorticity sheets and current sheets. Finally, the instability of the original Hill’s vortex with respect to certain radial perturbations of the spherical flux surface is proven analytically and illustrated numerically.
Samira Amiri Khoshkar Vandani, Lian Farhadian, Alex Pennycuick
et al.
This work explores the polymerization of sodium 4-styrenesulfonate (NaSS) inside filter paper using dielectric barrier discharge (DBD) plasma and its application in the environmental field. The plasma-based technique, performed under mild conditions, solves common problems associated with conventional polymerization inside porous materials. The polymerization process was monitored using Fourier-transform infrared (FTIR) spectroscopy, which confirmed the consumption of double bonds, particularly in NaSS samples containing the optimal concentration of crosslinker divinyl benzene (DVB) (0.25% wt). Our work demonstrates the effectiveness and promise of DBD plasma as a substitute polymerization approach, especially for those in porous materials.
This study assesses the plasma sheath formation on the night side of the Moon when exposed to highly energetic ambient plasma. The calculations indicate that the secondary electron emission (SEE) due to highly energetic plasma electrons leads to the formation of the inverse sheath around the positively charged lunar surface on the night side, where a traditional Debye sheath with a high negative surface potential is anticipated. Analytical formulation of Debye sheath and inverse sheath formation is given considering Maxwellian plasma and secondary electrons and cold ions. For a given SEE yield, a temperature regime is predicted where the inverse sheath is possible.
Tatiana Habib, Ludovica Ceroni, Alessandro Patelli
et al.
Gold nanoparticles have been extensively studied due to their unique optical and electronic properties which make them attractive for a wide range of applications in biomedicine, electronics, and catalysis. Over the past decade, atmospheric pressure plasma jets in contact with a liquid have emerged as a sustainable and environmentally friendly approach for synthesizing stable and precisely controlled dispersions. Within the context of plasma jet/liquid configurations, researchers have explored various power sources, ranging from kHz frequencies to nanopulse regimes. In this study, we investigated the effects of coupling two distinct power supplies: a high-voltage micropulse and a radio frequency (RF) generator. The variations within the plasma induced by this coupling were explored by optical and electrical measurements. Our findings indicated a transition from a bullet plasma propagation mechanism to a capacitive coupling mechanism upon the introduction of RF energy. The impact on the production of metal nanoparticles was also examined as a function of the radio frequency power and of two distinct process gases, namely helium and argon. The characterization of gold nanoparticles included UV-visible spectroscopy, dynamic light scattering, and scanning electron microscopy. The results showed that the size distribution depended on the type of process gas used and on the power supplies coupling. In particular, the incorporation of RF power alongside the micropulse led to a decrease in both average particle size and distribution width. The comparison of the different set up suggested that the current density can influence the particle size distribution, highlighting the potential advantages of the use of a dual-frequency atmospheric pressure plasma jet configuration.
The properties of non-thermal atmospheric pressure plasma jets (APPJs) make them suitable for industrial and biomedical applications. They show many advantages when it comes to local and precise surface treatments, and there is interest in upgrading their performance for irradiation on large areas and uneven surfaces. The generation of charged species (electrons and ions) and reactive species (radicals), together with emitted UV photons, enables a rich plasma chemistry that should be uniform on arbitrary sample profiles. Lateral gradients in plasma parameters from multi-jets should, therefore, be minimized and addressed by means of plasma monitoring techniques, such as electrical diagnostics and optical emission spectroscopy analysis (OES). This article briefly reviews the main strategies adopted to build morphing APPJ arrays and ultra-flexible and long tubes to project cold plasma jets. Basic aspects, such as inter-jet interactions and nozzle shape, have also been discussed, as well as potential applications in the fields of polymer processing and plasma medicine.
Magnetic reconnection (MR) is a fundamental process in space and laboratory plasmas. The appearance of high power lasers opens a new way to investigate MR under the relativistic condition. In this paper, relativistic collisionless MR driven by two ultra-intense lasers and a pair of asymmetric targets is studied numerically via the kinetic simulations. The static magnetic fields produced by the electron vortex structures with opposite magnetic polarities approach each other driven by the magnetic pressure and the density gradient. The antiparallel magnetic fields annihilate accompanied with the topological variation and the corresponding magnetic field energy is being dissipated to the kinetic energy of the nonthermal charged particles. Besides the outflows along the current sheet, a fast particle bunch is accelerated perpendicularly contributed by the displacement current.
Samuel A. Walker, Mauricio E. Tano, Abdalla Abou-Jaoude
et al.
Molten salt reactors (MSRs) are innovative advanced nuclear reactors that utilize nuclear fuel by dissolving it in a high-temperature liquid salt. This unique feature differentiates MSRs from other types of reactors and allows for enhanced safety and economic performance. The liquid fuel also entails several multiphysics effects that can complicate reactor design and operation. One primary effect termed here as depletion-driven thermochemistry is a driving force in altering the multiphysics behavior of the reactor. Essentially, depletion-driven thermochemistry is the effect that fuel depletion has on changing the chemical redox potential of the fuel salt over time. As the fuel is consumed, the redox potential shifts toward a more oxidizing state. Without active control, the changing chemistry due to depletion increases corrosion thereby limiting reactor component lifetimes. Additionally, the changing redox potential of the fuel salt alters the vapor pressures of chemical species dissolved in the fuel salt. Changing vapor pressures of species in the fuel salt is an important parameter to understand when off-gassing volatile species during normal reactor operation, and for source term characterization during accident scenario transients. The present work represents a fundamental step toward modeling and coupling the driving physics (i.e., neutronics and chemistry) involved in altering the redox potential in an MSR. Here, the neutronic code Griffin models the depletion of the fuel-salt system, while the chemical equilibrium code Thermochimica calculates the thermochemical state of the isotopic inventory, using the Molten Salt Thermodynamic Database - Thermochemical (MSTDB-TC). These two codes are tightly coupled to predict the impact of fuel depletion in altering the chemistry in MSR systems. Redox potential control methods are discussed and can be modeled using this multiphysics approach. The vapor pressures of chemical species that could be extracted to an off-gas system, as determined by the reactor’s thermochemical state, are examined. The neutronics-chemistry coupling developed in this work is expected to have potential application for analyzing corrosion, source term evolution, and material safeguards in MSR systems. Lastly, suggestions for areas of further improvements of the models to expand these capabilities by incorporating other coupled physics effects is provided.
Oxygen is one of the key reaction partners for many redox reactions also in the context of nuclear waste disposal. Its solubility influences radionuclides’ behavior, corrosion processes and even microbial activity. Therefore, a reliable calculation of the solubility of molecular oxygen in aqueous solutions is relevant for any safety assessment. Available geochemical speciation and reactive transport programs handle these data very differently. In some codes, the hypothetical equilibrium between dissolved oxygen and water is used to balance redox reactions. Equilibrium constants are given in “temperature grids” for up to 573.15 K. In other cases, temperature functions for the solubility of gaseous oxygen in water are given, without any reference to a valid temperature range. These settings become even more complicated when used in the context of modeling equilibria in high-saline solutions applying the Pitzer formalism. This raised the question about the experimental foundation of equilibrium constants given in such data files and their validity for the solubility of molecular oxygen in saline solutions. For this article, a thorough literature review was conducted with respect to the solubility of molecular oxygen in pure water and saline solutions. From these primary experimental O2 solubility data a temperature-dependent Henry’s law function as well as temperature-dependent binary and ternary Pitzer ion-interaction coefficients were derived. An internally consistent set of thermodynamic data for dissolved oxygen is presented, along with statements about its validity in terms of temperature and, as far as Pitzer interaction coefficients are concerned, of solution composition. This self-consistent activity-fugacity model containing thermodynamic data, Henry’s law temperature equation, and Pitzer interaction coefficients is capable of providing a more accurate description of redox transformations, allowing a reduction of conservatism in safety assessment calculations, not only in the context of a nuclear repository. The model reproduces well the reliable experimental data available, and is capable to predict the oxygen solubility in complex solution media. The temperature functions used to describe Henry’s constant and the Pitzer interaction coefficients are consistent with the implementation in commonly used geochemical computational programs, allowing direct use without further modification.
Shatadru Chaudhuri, Asesh Roy Chowdhury, Basudev Ghosh
In physical reality, the phenomena of plasma physics is actually a three-dimensional one. On the other hand, a vast majority of theoretical studies only analyze a one-dimensional prototype of the situation. So, in this communication, we tried to treat the quantum electron–ion plasma in a full 3D setup and the modulational stability of envelope soliton was studied in a quantum electron–ion plasma in three dimensions. The Krylov–Bogoliubov–Mitropolsky method was applied to the three-dimensional plasma governing equations. A generalized form of the nonlinear Schrödinger (NLS) equation was obtained, whose dispersive term had a tensorial character, which resulted in the anisotropic behavior of the wave propagation even in absence of a magnetic field. The stability condition was deduced ab initio and the stability zones were plotted as a function of plasma parameters. The modulational stability of such a three-dimensional NLS equation was then studied as a function of plasma parameters. It is interesting to note that the nonlinear excitation of soliton took place again here due to the balance of nonlinearity and dispersion. The zones of contour plots are given in detail.
This paper describes the design and operation of a low-cost plasma applicator based on a patented, swirled-type dielectric barrier discharge configuration with a treatment width up to 300 mm. Differences from earlier plasma applicators include: blown cylindrical dielectric barrier discharge, combining the functional properties of the plasma jet systems, arc and corona discharge blown in a single type of universal applicator, and the possibility of treating large areas of samples with cold plasma generated in a certain type of specific process gas mixture chosen according to the type of desired effect. We tested the effect of the plasma on a few materials such as cotton and linen fabrics, glass wafers and printing cardboard, proving that the generated plasma can easily make hydrophilic or hydrophobic surfaces. We also tried the plasma’s sterilizing effect on <i>Escherichia coli</i> (<i>E. coli</i>) bacteria. The results suggest that our plasma system can be successfully applied to medical and biological fields as well, where the removal of bacteria and their fragments is required.