242-A evaporator vacuum condenser system

In order to study the mechanism of the condensation and feedwater system of nuclear power plant, some simplified mathematic models are presented. The controlling principle of condensation and feedwater control system is explained, and their controllers are designed. Matlab/Simulink module is used for the simulation, result shows that the water level control system of steam generator could make the feedwater flow rate well track the change of the steam flow rate, reduce the false action of the feedwater valve and make the water level keep invariant. The control system of the vacuum and condensate subcooling degree of the condenser could timely regulate the flow rate of cooling water. Thereby, the vacuum and condensate subcooling degree could be limited in certain range. The validity of the control system is proved which could provide reference for the design of the condensation and feedwater control system of nuclear power plant.

The cold-end system of a nuclear power plant is a key complex node connecting the power generation system with the variable environmental conditions, and its operation, economy, and stability have become the main obstacles to further improving the performance of the first and second circuits. The current research on the interactions between the cold-end system and the thermal cycle of nuclear power mainly adopts the micropower model, while the existing condenser model does not take into account the influence of the turbine exhaust resistance and exhaust flow and other factors on the condenser vacuum change caused by the change in the circulating water flow rate and temperature in determining the optimal vacuum. This ignores the interactions between the equipment and the interconnections between the parameters, which results in the reduction of the model’s accuracy. This paper takes a nuclear power unit as an example, adopts the “constant flow calculation” method to calculate the heat balance of the two-loop thermal system of the nuclear power plant, and constructs an integrated simulation model of the reaction environment variables, the cold-end system, and the thermal cycle. Taking the circulating water temperature and flow rate as variables, the errors of the separate condenser model and the coupled model in circulating water parameter changes were obtained under the condition of satisfying the thermal system operation, and the circulating water temperature and flow rate change ranges applied by the separate condenser model were analyzed in order to reduce the amount of calculations when the unit power error was 1%. The results show that the circulating water temperature is 4 °C, the applicable range of the circulating water flow rate is 42 m3/s to the rated flow rate, the applicable range of the circulating water temperature is 20 °C, the applicable range of the circulating water flow rate is 32.12 m3/s to the rated flow rate, the applicable range of the circulating water temperature is 26 °C, the applicable range of the circulating water flow rate is 38.63 m3/s to the rated flow rate, the applicable range of the circulating water temperature is 30 °C, and the applicable range of the circulating water flow rate is 45 m3/s to the rated flow rate. At a circulating water temperature of 26 °C, the applicable range of the circulating water flow is between 38.63 m3/s and the rated flow; at a circulating water temperature of 30 °C, the applicable range of the circulating water flow is between 45.64 m3/s and the rated flow.

Peptides presented by the major histocompatibility complex (MHC) are derived from the degradation of cellular proteins. Thus, the repertoire of these peptides (the MHC peptidome) should correlate better with the cellular protein degradation scheme (the degradome) than with the cellular proteome. To test the validity of this statement and to determine whether the majority of MHC peptides are derived from short lived proteins, from defective ribosome products, or from regular long lived cellular proteins we analyzed in parallel the turnover kinetics of both MHC peptides and cellular proteins in the same cancer cells. The analysis was performed by pulse-chase experiments based on stable isotope labeling in tissue culture followed by capillary chromatography and tandem mass spectrometry. Indeed only a limited correlation was observed between the proteome and the MHC peptidome observed in the same cells. Moreover a detailed analysis of the turnover kinetics of the MHC peptides helped to assign their origin to normal, to short lived or long lived proteins, or to the defective ribosome products. Furthermore the analysis of the MHC peptides turnover kinetics helped to direct attention to abnormalities in the degradation schemes of their source proteins. These observations can be extended to search for cancer-related abnormalities in protein degradation, including those that lead to loss of tumor suppressors and cell cycle regulatory proteins.

Multiple holdup equilibria and hydraulic gradients in stratified gas–liquid flows

Station blackout (SBO) accident is considered as one of the most significant design extension conditions (DECs), which has been extensively focused after the Fukushima Dai-chi accident. When the SBO accident occurs in the APR+ (Advance Power Reactor Plus), the PAFS (Passive Auxiliary Feedwater System), which is an advanced safety feature adopted in the APR+, should play a significant role to cool down the core decay heat without any operation of active safety systems. This study focuses on validation of the cooling and operational performance for the PAFS during the SBO transient with utilizing an integral effect test facility, ATLAS-PAFS. In order to simulate the SBO transient of the APR+ as realistically as possible, a pertinent scaling approach was taken into account. The initial steady-state conditions and the sequence of event in the SBO scenario for the APR+ were successfully simulated with the ATLAS-PAFS facility. In the transient simulation, major thermal-hydraulic parameters such as the system pressures, the collapsed water levels, the break flow rate, and the condensate flow rate at the return-water line were measured and investigated. Following the reactor trip at the initiation of the transient, the coolant inventory of the secondary system of the steam generator was reduced by the repeated opening and closing of the MSSV. When the collapsed water level reached 25% of wide range, the PAFS was actuated to cool down the primary system by the condensation heat transfer at the PCHX (Passive Condensation Heat Exchanger). The pressure and the temperature of the reactor coolant system continuously decreased during the heat removal by the PAFS operation. It points out that the PAFS can supply auxiliary feedwater to the steam generator and remove the core decay heat without any active system. From the present experimental result, it could be concluded that the APR+ has the capability of coping with the hypothetical SBO scenario with adopting the PAFS and proper set-points of its operation. This integral effect test data will be used to evaluate the prediction capability of existing safety analysis codes of the MARS, RELAP5 as well as the SPACE code and to identify any code deficiency for a SBO simulation with an operation of the PAFS.

Experimental research on reverse flow phenomenon in an equal-height-difference natural circulation system at low pressure

The reactor cavity cooling system (RCCS) for a very high temperature reactor (VHTR) represents a very important safety feature for achieving the defense in depth of the plant. An experimental facility was built for testing the heat transfer capability and phenomenology of this last heat sink designed for ensuring the cooling down of structural material of the vessel and of the concrete walls of the vessel cavity. This small scale facility was built using some of the scaling laws in order to resemble the main heat transport features in RCCS configuration. The natural convection phenomena and radiative heat transfer inside the cavity were represented. The experimental facility represents half of the vessel and of the reactor cavity with five stand pipes for cavity cooling using water as cooling fluid. Measurements were performed heating up the vessel surface temperature to an average temperature of 300 °C that is the average value in accident scenarios. Temperature measurements of the vessel surface temperature, the outer pipes surface temperature profile and inlet and outlet temperature of the cooling water were performed. Axial and radial temperature profiles of the air in the cavity were measured using a movable rack of 24 thermocouples. The results demonstrated the natural circulation phenomena. In addition Velocity measurement of the air inside the cavity were performed using particle tracking velocimetry techniques (PTV) determining the flow regime characteristics and the coupling with the temperature profile. The experimental test matrix of various flow rates in the cooling pipes were carried out.

This paper describes loss of coolant accident (LOCA) analyses of the Supercritical-pressure Water-Cooled Fast Reactor (Super Fast Reactor). The features of the Super Fast Reactor are high power density and downward flow cooled fuel channels for the improvement of the economic potential of the Super Fast Reactor with high outlet steam temperature. The LOCA induces large pressure and coolant density change in the core. This change influences the flow distribution among the downward flow parallel channels. It will affect the safety of the Super Fast Reactor. LOCA analysis of Super Fast Reactor is important to understand the safety features of the Super Fast Reactor. Keeping the flow rate in the core is important for the safety of the Super Fast Reactor. In LOCA, it is difficult to maintain an adequate flow rate due to the once-through coolant cycle and the downward flow cooled fuel assemblies. Therefore, the early actuation of the Automatic Depressurization System (ADS) and reduction of the maximum linear heat generation rates of the downward flow seed fuel assemblies and Low-Pressure Core Spray (LPCS) system are necessary for the Super Fast Reactor to cool the core under LOCA. Analysis results show that the Super Fast Reactor can satisfy the safety criteria with these systems.

Scoping analyses of the coupled thermal-hydrological-mechanical behaviour of the rock mass around a nuclear fuel waste repository

Aerobic treatment of black ripe olive processing streams to reduce biological contamination

Structural and technological studies of processes in which cadmium-sulfide nanowhiskers are synthesized in a quasi-closed volume by the method of vacuum evaporation and condensation are reported. It is demonstrated that the processes are in agreement with the classical vapor–liquid–crystal model. Micrographs of the objects in different formation stages are presented.

Effect of electron irradiation on the crystalline structure of hgte and hgl-xcdxte thin films

Multilayer organic and inorganic systems of thin solid films are widely used in novel optoelectronic devices. The required properties of the system depend on the morphology of the films and transition zone at interfaces. We studied the formation of deposits of fluorinated azo-dyes, polymethine, merocyanine and sulfur-terminated organic compounds (STOC) by evaporation and condensation in vacuum. The films were deposited on glass, silicon (Si), gold (Au) and polytetrafluoroethylene (PTFE) substrates. The influence of dye chemical structure and substrate on deposit morphology was studied using atomic force microscopy (AFM). Depending on the ratio between thermodynamic and kinetic processes, islands, crystalline aggregates or nano-structures were obtained. A difference in the morphology of the same dye solid, but deposited on various substrates was detected. Changes in the dye end or side groups caused variation in the morphology of the dye solid film. STOC formed a smooth film on the Au surface, while on the glass and PTFE it formed various islands. Thin films of the dyes in PTFE matrix exhibited unique stability to action of external factors. A new type of evaporable dyes with unsaturated reactive bond at the end was synthesized. Using new evaporation–activation–polymerization methods, the films with enhanced hardness and thermal stability were prepared from new dyes. Several dyes formed nano-micro-wires during the self-assembly process, in some cases between two neighboring Au strips. Adjusting the structure of the molecule by changing the end groups allows purposeful control of the deposit morphology on the selected surface.

Electrometallurgy Today, 2023, №01. SOVREMENNAYA ELEKTROMETALLURGIYA Quarterly scientific-technical and production journal. ISSN: 2415-8445, Since 1985. Text in Russian, contents and summaries in English. The journal presents the results of theoretical and experimental research carried out at the PWI in the field of electrometallurgy. Special attention is given to electroslag technology (electroslag melting, refining and casting). The journal is divided into the following main sections: electroslag technology; electron beam processes; plasma arc technology; vacuum arc remelting and vacuum induction melting; general problems of special electrometallurgy.

The gas-liquid membrane contactor generally used as a nonselective gas absorption enhancement device is innovatively proposed as a condenser for heat recovery in liquid-absorbent-based carbon capture. The membrane condenser is used as a heat exchanger to recover the latent heat of the exiting vapor from the desorber, and it can help achieve significant energy savings when proper membranes with high heat-transfer coefficients are used. Theoretical thermodynamic analysis of mass and heat transfer in the membrane condensation system shows that heat recovery increases dramatically as inlet gas temperature rises and outlet gas temperature falls. The optimal split mass flow rate is determined by the inlet gas temperature and the overall heat-transfer coefficient in the condensation system. The required membrane area is also strongly dependent on the overall heat-transfer coefficient, particularly at higher inlet gas temperatures. Mass transfer across the membrane has an insignificant effect on heat transfer and heat recovery, suggesting that membrane wetting may not be an issue when a membrane condenser is used for heat recovery. Our analysis provides important insights into the energy recovery performance of the membrane condensation system as well as selection of operational parameters, such as split mass flow rate and membrane area, thickness, and thermal conductivity.