Analysis of the anticipated transient without scram (ATWS) initiated by emergency power mode through the full scope simulator

The integrity of the reactor coolant system is severely challenged as a result of an Emergency Power Mode – ATWS event. The purpose of this paper is to simulate the Anticipated Transient without Scram (ATWS) using the full scope simulator of Angra 2 Nuclear Power Plant with the Emergency Power Case as a precursor event. The results are discussed and will be used to examine the integrity of the reactor coolant system. In addition, the results were compared with the data presented in Final Safety Analysis Report (FSAR – Angra 2) in order to guarantee the validation of the methodology and from there analyze other precursor events of ATWS which presented only plausibility studies in FSAR – Angra 2. In this way, the aim is to provide and develop the knowledge and skill necessaries for control room operating personnel to ensure safe and reliable plant operation and stimulate information in the nuclear area through the academic training of new engineers. In the presented paper the most severe scenario is analyzed in which the Reactor Coolant System reaches its highest level of coolant pressure. This scenario is initiated by the turbine trip jointly with the loss of electric power systems (Emergency Power Mode). In addition, the failure of the reactor shutdown system occurs, i.e., control rods fail to drop into the reactor core. The reactor power is safely reduced through the inherent reactivity feedback of the moderator and fuel, together with an automatic boron injection. Several operational variables were analyzed and their profiles over time are shown in order to provide data and benchmarking references. At the end of the event, it was noted that Reactor shutdown is assured, as is the maintenance of subcriticality. Residual heat removal is ensured.

Power mode of axisymmetric high-speed combined extrusion of bimetallic road milling picks

The article presents a simplified three-stage model of the transition from a flat to axisymmetric deformation during high-speed, combined extrusion of bimetallic road milling picks. The transition is based on the principle of equality of areas, according to which the area of a figure during a flat deformation is replaced by an equal area of a circle. In this case, it is assumed that the kinematically possible field of the slip lines remains unchanged. This approach makes it possible to reduce the number of necessary calculations and at the same time maintain a high degree of correctness of the obtained equations. The first stage shows the transition to a special case of a flat problem, in which a stepped rectangular part is extruded from the original square blank, in which one of the sides is equal to the square side of the original blank. At the second stage of the transition, a flat-step part having square sections along its entire length is extruded from the original square-section blank. Directly at the third stage, the final transition to the axisymmetric deformation of the cutter is formed, in which the area of the square is replaced by the equal area of the circle. The dependences obtained because of solving the axisymmetric problem can be recommended for calculations in the industrial implementation of the technology of high-speed combined extrusion of bimetallic milling picks.

Reactive power control

The article investigates the methods of control of reactive power modes. It is shown that ensuring the efficiency of electricity transmission and distribution is inseparable from setting and solving problems related to reducing electricity losses in networks. Moreover, one of the most effective ways to reduce electricity losses, as well as improve its quality at the terminals of electrical receivers is to compensate for reactive power, which is carried out using various compensating devices. It is shown that the control of the reactive power mode is carried out in accordance with the Methodology for calculating the fee for the flow of reactive energy between the power transmission organization and its consumers. It is shown that the indicator of economically advantageous value of the level of reactive energy consumption can be cos φз, the value of which is predetermined. The procedure for controlling the reactive power mode contains two main stages: the stage of determining the magnitude of the possible reduction of the current cos φ above the set and the stage of determining and implementing control effects aimed at eliminating possible deviations. Preferably, it is preferable to focus on those methods that are based on the study of forecast estimates, which constitute the source information for management decisions. It is expedient to use adaptive methods of exponential smoothing as a basis for operative forecasting of electric loading. Reactive power mode is controlled by compensating units. It is shown that the control of voltage modes in the power supply system significantly affects the modes of reactive power consumption. In this regard, it is advisable to comprehensively solve the problem of reactive power control both by controlling the compensating units and the impact on the voltage regimes of the power supply system. In the calculation model, the reactive load of the distribution network is given by its static characteristics, which can be the basis for regulating the reactive load. To implement regulation in the power supply centers of electrical networks, technical means are provided on the basis of changing the transformation coefficient or generating reactive power by counter-voltage regulation.

Estimation of stator and rotor forms distortions influence on operating parameters of a hydrogenerator

The field calculation was carried out using finite element method of the Ansys Maxwell software package and verification in the Matlab Simulink software. It should be noted that there are several regulatory documents that describe criteria for permissible distortion of the rotor shape, where the air gap between the stator and the rotor at diametrically opposite points should not differ from each other by more than ± 20% from the average value equal to their halfsum. In this work, a calculation was carried out covering this interval of diameter change; an analysis was carried out considering change in range of ± 35% of the air gap’s width’s value. Results of the research showed that a change in a value of the air gap up to 10% would make a significant contribution to magnitude of magnetic field induction, which increases the value of main losses in a core of magnetic circuit of the generator. Also, there is a significant decrease in voltage (from 25 to 50%) of a nominal voltage in nominal power mode, which requires increase in current in field magnetizing coil, leading to ohmic losses’ increase in rotor’s windings.

УДОСКОНАЛЕННЯ ПРОЕКТУВАННЯ ТЕХНОЛОГІЧНОГО ПРОЦЕСУ ТОЧНОГО ОБ’ЄМНОГО ШТАМПУВАННЯ ВИДАВЛЮВАННЯМ НА ОСНОВІ РОЗВИТКУ ЕНЕРГЕТИЧНОГО МЕТОДУ БАЛАНСУ ПОТУЖНОСТЕЙ

Improvement of technology design in precision forging process based on development of energy method with power balance and development of recommendation with the rational use of systematized based on kinematic modules in complex configuration to make calculated schemes for power mode assessments and shaping of part in cold forging extrusion process with subsequent software implementation are considered. Methodology. Energy method of power balance is considered based on kinematic module method that will be systematized the results of investigation for expanding in cold forging extrusion process with the definition of the power mode in deformation and features of semi-finished product shaping to make hollow and rod parts with flange such as sleeves and glasses. Results. Development results of recommendation with the rational use of systematized based on kinematic modules in complex configuration to make calculated schemes including with the ability to quickly take into account changes in the configuration of the tool have been determined. This made it possible to define the several factors for controlling the shaping of the semi-finished product in combined and sequential combined cold forging extrusion processes. Scientific novelty. Energy method of power balance is considered such as an effective method of preliminary analysis to determine the area of rational use in cold forging process based on process technology design to make complex parts. Practical significance. Software product development with extended systematization based on kinematic modules, complex of calculation models in cold forging extrusion with power mode assessments and to predict shaping of part and defect formation such as dimple defect will contribute more active implementation in the manufacturing industry for combined cold forging extrusion processes.

Preparation of Metal Nitride Particles Using Arc Discharge in Liquid Nitrogen

A simple process to synthesize metal nitride particles was proposed using submerged arc discharge plasma in liquid nitrogen. Gibbs standard free energy was considered for the selection of the nitride-forming materials. In this study, titanium (Ti) and aluminum (Al) electrodes were used as raw materials for nitride particle preparation. Liquid nitrogen acted as a dielectric medium as well as a nitridation source in this process. A copper electrode was also used as a non-reactive material for comparison with the reactive Ti and Al electrodes. As the operating conditions of the experiments, the arc discharge current was varied from 5 A (low-power mode) to 30 A (high-power mode). The formation of titanium nitride (TiN) and aluminum nitride (AlN) was confirmed in the particles prepared in all experimental conditions by X-ray powder diffraction (XRD). The observation using a field emission scanning electron microscope (FE-SEM) and a field emission transmission electron microscope (FE-TEM) indicated that the synthesized TiN particles showed a cubic morphology, whereas AlN particles containing unreacted Al showed a spherical morphology. The experiments using different metal electrode configurations showed that the anode generated most of the particles in this process. Based on the obtained results, a particle formation mechanism was proposed.

Generation of High Peak Power Mode-Locked Green Pulses Based on WS2 and EOM: Experiment and Theory

Based on an as-prepared high-quality WS2 film and an electro-optic modulator (EOM), a dual-loss-modulated low repetition rate mode-locking laser at 0.53 μm with high peak power is presented for the first time. The laser characteristics versus the pump power are investigated experimentally and theoretically. At a pump power of 10.67 W, the shortest pulse duration of 305 ps can be measured, corresponding to the highest peak power of 931 kW, which is much higher than those of the single passive modulated lasers with WS2-SA. A simple rate equation simulation was used to describe this dual-loss-modulated mode-locking green laser based on WS2 and EOM. The results of the numerical simulation are basically in accordance with the experimental values.

Power Mode of High-Speed Combined Extrusion of Flat Bimetallic Road Milling Picks

The paper presents a mathematical model developed for calculating the force effect on the punch in the process of high-speed combined hot extrusion of bimetallic road milling picks under plane deformation conditions. To solve the problem, the process is divided into two phases: acceleration phase and braking phase, which consists of two stages. A distinctive feature of the acceleration phase is that it allows the analysis of reverse extrusion, in the process of which the metal flows in the opposite direction to the punch stroke. A method for calculating the force acting on the punch at each phase of the process of plastic flow of a bimetallic workpiece into a matrix cavity with three deformation zones is presented in the paper. While solving the problem in a quasi-static formulation and proceeding from the conditions of the minimum power of internal forces, equations have been obtained for calculating the optimal field parameters aopt, bopt, gopt, depending on the elongation coefficients l and the friction coefficient m. The equations obtained within the framework of the developed model are quite correct, since they allow determining the minimum force acting on the punch. The considered calculation model and equations can be used in the development of industrial technology for high-speed combined hot extrusion of flat-step bimetallic road milling picks.

Simulation for Battery Electric Vehicle using MATLAB

Electric cars (EVs) are probable to be an opportunity power mode of transportation for the destiny because it has shown a wonderful capability to lessen the intake of petroleum based and different excessive CO2 emitting transportations fuels. on this look at, the additives of the BEVs device had been mentioned and a version of BEV at the MATLAB-Simulink platform was simulated. Furthermore, the applicable electric system additives in addition to its corresponding equations for verification had been recognized. moreover, all simulation effects were taken into consideration. This look at affords a basis for added researches.