Verification of the Mathematical Model and Numerical Investigation into the Thermal–Hydraulic Parameters of Fuel Assemblies Containing Microspherical Fuel Elements

The article presents the results from numerical investigations into the hydrodynamics and temperature field in the KLT-40S reactor’s fuel assembly (FA) in the case of using microspherical fuel elements as nuclear fuel. The simulated FA has the same overall dimensions as the existing FA containing fuel rods, due to which it can be accommodated in the reactor core without the need of modifying the reactor design. The specific feature of an FA with micro fuel elements (MF FA) is the need to set up radial flow of coolant through the bed of micro fuel elements, which is achieved by using distribution and collection headers. The numerical simulation was carried out using the ANSYS Fluent computer code. The mathematical model implemented in the code has been refined and verified against the experimental data obtained by the authors on a model experimental setup whose design is similar to that of the considered FA containing micro fuel elements. Radial flow of coolant through the pebble bed is arranged in the model installation. The numerical and experimental data on pressure loss and temperature distribution in the bed estimated at different values of coolant mass velocity mass are compared with each other. The design of an FA containing micro fuel elements for the KLT-40S reactor is proposed. It has been found that almost purely radial flow of coolant can be set up with the perforation parameters (cross-section coefficients) higher than those mentioned in the literature. The serviceability of such a fuel assembly is demonstrated. The distributions of temperature, excess pressure, and coolant velocity and current lines are obtained. The perforation parameters of jackets confining the bed of micro fuel elements are presented.     

Experimental Determination of Numerical–Analytical Model Coefficients of Electrophysical Processes in Silicon Power Devices

A method has been presented of experimental determination of numerical–analytical model coefficients describing electrophysical processes in silicon power devices that does not use “transistance” (the effect of on-again modes) to decrease loss of power in a device. It has been demonstrated that experimental determination of the coefficients allows one to dispense with numerical solutions of the fundamental systems of equations of semiconductors and use a low-level model for solution of practical problems related to the maximum permissible current loads of silicon power devices in regimes specified by a customer.     

Wavelet-based Analysis of Impulse Grounding Resistance–Experimental Study of the “A”-type Grounding System

This article presents the results of experimental investigation concerned with the “A”-type grounding system's impulse characteristics, which are utilized for grounding of high-voltage transmission line towers. The investigation results point to the presence of high-frequency components in voltage and current signals that are not caused by tower footing response to the impulse current. Additionally, both surge generator coupling and measuring circuit remain their main source. High-frequency components of signals are extracted from voltage and current signals by means of the discrete wavelet transform. In addition to being external influence results, the extracted components have very low energy content as well as short duration. The discrete wavelet transform analysis application has validated the existence of external influences.     

The Study of Scaling Prevention in Recirculating Ash Disposal System by the Treatment of Make up Water with Flue Gas

<正> In this paper, we discussed the reason of scaling in the recirctilating ash disposal sys tern of No. 7 and No. 8 boiler in Huangtai Power Station. When we use the supersatu ration level of CaCO3 to represent the seal ing driving force, it is seen that the scaling tendency of water is dependent on activity product f2[Ca2-]f2[CO32]. Therefor, if we want to prevent scaling in ash disposal system, we must decrease and remove the concentration of Ca2- and/or CO32 . But in consideration of the particular condition of re circulating ash disposal system; the free CaO in ash particles will gradually dissolve in water and the concentration of Ca2- in slurry will continuously increase. Hence, it is more difficult to get rid of Ca2- from slurry water than to remove CO32 . Basing upon the calculation of material balance, it shows that the main source of the carbonic species which bring into system is from make-up water, consquently. If we only acidify the make up water and then decarbonize them, we may decrease and     

The forecast of the development of the market for gas turbine equipment in the years 2013–2021 (review)

The data are given, according to which, 12521 power-generating gas turbines will be manufactured in 2011–2021. More than 32% of these turbines will be made by Solar, while products made by General Electric will account for 41% (in terms of money). Servicing of gas turbine units provided by firms manufacturing them will gain wide acceptance.     

Three-dimensional optimal multi-level Monte–Carlo approximation of the stochastic drift–diffusion–Poisson system in nanoscale devices

The three-dimensional stochastic drift–diffusion–Poisson system is used to model charge transport through nanoscale devices in a random environment. Applications include nanoscale transistors and sensors such as nanowire field-effect bio- and gas sensors. Variations between the devices and uncertainty in the response of the devices arise from the random distributions of dopant atoms, from the diffusion of target molecules near the sensor surface, and from the stochastic association and dissociation processes at the sensor surface. Furthermore, we couple the system of stochastic partial differential equations to a random-walk-based model for the association and dissociation of target molecules. In order to make the computational effort tractable, an optimal multi-level Monte–Carlo method is applied to three-dimensional solutions of the deterministic system. The whole algorithm is optimal in the sense that the total computational cost is minimized for prescribed total errors. This comprehensive and efficient model makes it possible to study the effect of design parameters such as applied voltages and the geometry of the devices on the expected value of the current.     

Water chemistry of the system for cooling the electrical generator’ stator of the power unit at a thermal power station

Results from studies of the water chemistry used in the system for cooling the stator windings of alternators used in supercritical-pressure power units are presented, and a solution is suggested using which the standardized pH value of cooling water is maintained in the range 8.0–9.0. It is shown that addition of NaOH in the water cooling system when a drop of pH value occurs cannot fully satisfy the requirements of the operating circular due to low buffer properties of aqueous medium.     

Development of Design for Circulating Water Intake Structure in Thermal Power Plant

SummaryThispaperintroducesthedesigndevelopmentinthefields0fcirculatingwater(C.W.)intakestructuredesignedbyEastChinaElectricPowerDesignInstitute(ECEPDI).Therearemanymethodssuchascaissonmeth0d,sinkingwellmethod,floatingcaiss0nmeth0d,andexterior-protectedconstructionfoundationmethodetc.f0rC.W.pumph0usedesign.Therearejackingsteelpipetunnel,jackingR.C.pipetunnel,shieIdtunnelandfl0atingpipetunneletc.f0rdesignofdiversionpipe.Thefl0atingcaiss0nc0nstructionofC.W.pumphouseisfirstusedinChina.1.…     

Improving the accuracy of multisided travelling wave determination of location of a fault in a power line by means of the difference–distance-measuring technique

The double-ended travelling wave method of determination of location of a fault in electrical networks has significant errors due to changes in the propagation velocity of electromagnetic waves. We have developed a travelling wave method of improving the accuracy of location of a fault determination in power transmission lines that is based on navigation algorithms. The method is applicable to lines with branches. The distance to fault determination for the developed method is up to twice as accurate as the double-ended travelling wave location of a fault method. The accuracy of the developed method is less influenced by external factors (change of sag, soil resistance, the instantaneous value of the current at the fault time) than is the accuracy of the double-ended travelling wave location of a fault method. The proposed method allows reducing the errors in determining distance to the location of a fault, and its accuracy is less affected by external factors. The developed method can be incorporated into existing and prospective devices based on travelling wave methods of location of a fault determination.     

Strategies for improving resilience of regional integrated energy systems in the prevention–resistance phase of integration

he construction of integrated energy systems can help improve energy efciency and promote global energy transition. However, in recent years, the occurrence of extreme natural disasters has brought certain threats to the safe and stable operation of the integrated energy system. Thus, it is necessary to improve the ability of the integrated energy system to resist disasters, reduce disaster losses, and restore energy supply as soon as possible, i.e., improve its resilience. Considering the infuence of pre-disaster prevention measures and disaster-time operational measures on system disaster resilience and the correlation between the two, this paper proposes a system hardening strategy based on three-layer robust optimization. The upper layer formulates the optimal hardening strategy of the system before the disaster event occurs, the middle layer identifes the failed elements in the worst disaster situation, while the lower layer realizes the system operational optimization by coordinating the energy storage charging and discharging plan of each subsystem. The strategy can reduce the total supply shortage of the integrated energy system and improve the fexibility of the system in the pre-disaster prevention and disaster resistance integration stages.     

Strong correlation effects in the (5,5)@(10,10) double-walled carbon nanotubes in the framework of the t–J model

Double-walled carbon nanotubes are coaxial nanostructures composed of exactly two single-walled carbon nanotubes, one nested in another. This unique structure offers advantages and opportunities for extending our knowledge and application of the carbon nanomaterials family. An emphasis is placed on the double wall physics that contributes to these structures’ complex inter-wall coupling of electronic and optical properties. The susceptibility tensor of double-walled carbon nanotubes of the “armchair” type the ABAB packing of layers is investigated theoretically in the weak and strong correlation regime. We calculated the spin and charge susceptibility tensor for of the (5,5)@(10,10) double-walled carbon nanotubes using the random-phase approximation in the weak correlation regime. The relationship with the Heisenberg limit (large U/t) is discussed. Our results show that the susceptibility spectra of the (5,5)@(10,10) double-walled carbon nanotubes shift peaks to lower energies with increase in the correlation parameter of the t–J model \((U\ge t)\). These results show that electronic correlation effects should be taken into account in theoretical studies of double-walled carbon nanotubes. We discuss the relevance of our results for the \(\hbox {C}_{20}\) and \(\hbox {C}_{60}\) fullerens and (5,5) nanotubes.     

Multiple-Input–Multiple-Output Linear-Quadratic Control of the Energy Production of a Synchronous Generator in a Nuclear Power Plant

—A multiple-input–multiple-output linear-quadratic servo controller is proposed for a synchronous generator operating in a nuclear power plant that keeps the active power at the desired level and performs reactive power reference tracking using the reactive power demand from a central dispatch center. The controller design was based on the locally linearized version of a previous non-linear dynamical model of the synchronous electrical generator [1 Anderson, P., and Fouad, A., Power-Systems-Control and Stability, Ames, IA: The IOWA State University Press, Chap. 4, 1977. [Google Scholar], 2 Fodor, A., Magyar, A., and Hangos, K.M., Control-oriented modeling of the energy-production of a synchronous generator in a nuclear power plant, Energy, . 39, pp. 135–145, 2012.[Crossref], [Web of Science ®] , [Google Scholar]], the parameters of which have been identified using measured data from Paks Nuclear Power Plant (Hungary). The method can easily be applied to any industrial power plant generator connected to the electrical grid after estimating its parameters. The proposed observer-based multiple-input–multiple-output state feedback controller is a linear-quadratic servo controller with very good reference tracking and disturbance rejection properties, which were confirmed by simulation experiments.     

Investigation of microwave dielectric properties in the BaO–Nb2O5–P2O5 system

BaNb₂P₂O₁₁ and Ba₃Nb₂P₄O₁₈ compounds with corner-sharing NbO₆ octahedra and PO₄ tetrahedra were prepared by a conventional solid-state reaction method. The crystal structure and microstructure were investigated by X-ray powder diffraction and field emission scanning electron microscope, respectively. The microwave dielectric properties were measured using a network analyzer. Both ceramics were sintered at a relatively low temperature of 1150 °C and had a relative density of ～96%. Compared to Ba₃Nb₂P₄O₁₈, BaNb₂P₂O₁₁ had a higher permittivity of 31.7. However, the quality factor of BaNb₂P₂O₁₁, was smaller than Ba₃Nb₂P₄O₁₈. Furthermore, the effect of the crystal structure on the microwave dielectric properties was investigated.     

Jiles–Atherton Hysteresis Approach in Analyzing the Effect of Field Suppression in Saturated Iron-core Superconducting Fault Current Limiters

Saturated iron-core superconducting fault current limiters (SISFCL) are becoming more popular in the recent years due to their ability of reliable, effective and instantaneous fault limiting. With a superior performance than conventional current limiting methods, the SISFCL is finding its application in modern transmission lines and distribution system. In the SISFCL, the iron core is forced into saturation using a superconducting coil carrying DC current. During a fault in the system, the high fluxes set up in the AC coils interact with the DC flux, thereby reducing the flux density abruptly. This sudden change in the flux density induces a high voltage across the DC coil, which may damage the DC current source as well as the superconducting material. As a protective measure, a field suppressor unit is used that disconnects the DC supply following a fault. In this paper, a mathematical model of the SISFCL is developed considering hysteresis and the effects of the field suppressor unit have been analyzed. The paper also aims to highlight the effects on the performance of SISFCL with varying hysteresis loops of the core material.     

On technical requirements for Arc Suppression Reactors in the distribution circuit of 6–35 kV

Development of the technical requirements for arc suppression reactors (ASRs) used for the capacitive current compensation of the single-phase earth fault is a critical task. The corresponding GOST (State Standard) 19470–74 “Oil-Filled Arc Suppression Reactors. Technical Requirements” is no more valid; automatically controlled reactors (with adjustable spacing controlled by magnetic biasing) are the mainstream; and completely new reactor designs, with the capacitor adjustment in particular, have become available. The standard guide for the earth-fault current compensation [1], not taking into account new technologies, has become obsolete. This paper considers the current criteria for the ASR application in the 6- to 35-kV networks and proposes new ones. It is proposed to use the residual earth-fault current, but not the ASR detuning coefficient, as the major criterion for capacitive current compensation of the single-phase earth fault; in this case, new requirements for the ASR and the network conditions characterized by active phase-to-ground and harmonics content currents are specified taking into account the electrical safety regulations. The problem of capacitance asymmetry is considered absolutely and relatively, and it is shown that the use of ASRs controlled by magnetic biasing allows omitting the network balancing and limitation of the asymmetry voltage at the level of 0.75% of the phase voltage. It is proposed to take into account these recommendations during development of an earth-fault current compensation guide and general technical requirements for ASRs and automatic tuning systems.     

Optimization of the range of asynchronous motors with the dimensions 100–132 with combined windings

The theoretical foundations for creation of a new type of intelligent energy-saving asynchronous electric motor with combined windings are described. The results of theoretical studies and computer modeling, as well as a method of manufacturing a range of such motors, are given.     

Feasibility of intravoxel incoherent motion in the assessment of tumor microvasculature and blood–brain barrier integrity: a case-based evaluation of gliomas

Magnetic Resonance Materials in Physics, Biology and Medicine - To evaluate the feasibility of intravoxel incoherent motion (IVIM) in assessing blood–brain barrier (BBB) integrity and...