Alzheimer's Research and Therapy

For substantiating liquid metal cooled reactor plants, the EUCLID/V2 integrated code is being developed, and its verification and validation are carried out for certifying it at the Scientific and Technical Center for Nuclear and Radiation Safety (NTC NRB). One of the integrated code’s main parts is the severe accident block, which includes the SAFR module for calculating the destruction of fuel pins, fuel assemblies (FAs) and the entire core, as well as the HEFEST-FR module for calculating the melt retention and cooling down in the sodium-cooled reactor core catcher. The HEFEST-FR module implements the possibility to perform 2D simulation of the structural elements and fuel melt behavior in liquid metal cooled reactors. In accordance with the NTC NRB requirements, for the HEFEST-FR module to be used as part of the EUCLID/V2 code for analyzing the safety of fast reactors, it must be validated with the use of available experimental data; the validation shall be accompanied with an uncertainty and sensitivity analysis and assessment of the calculation result error. The article presents the results obtained from verification of the EUCLID/V2 integrated code HEFEST-FR module through solving the analytical problem of settling a stationary temperature of a homogeneous bounded cylinder uniformly heated from below with boundary conditions of the third kind and through solving the Stefan single-phase problem, as well as the results of validating the HEFEST-FR module based on the SCARABEE BF1 experiment. It is shown that the average absolute value by which the numerical calculation deviates from the analytical solution of the problem of settling a stationary temperature of a homogeneous bounded cylinder uniformly heated from below with boundary conditions of the third kind makes approximately 1.1 K. The maximum relative deviation of the results of calculations carried out using the computer program from the results of analytical solution of the Stefan problem (determination of the melt front) makes 0.46%. An assessment of the errors of modeling using the melt retention module as part of the EUCLID/V2 code (HEFEST-FR) based on the BF1 test of the SCARABEE experiment has shown that the temperature calculation error lies in the interval [‒82.3; 182.5] K, and the error of calculating the radial heat flux lies in the interval [‒55.2; 31.2] kW/m2.

Reducing greenhouse gas emissions remains a topical issue in fundamental and applied scientific research, including in terms of analyzing developed and applied CO2 capture technologies. The main focus is on methods of carbon dioxide burial in stable geological formations, absorption, filtration, etc. The absorption of carbon dioxide during photosynthesis is usually associated with terrestrial biota, although aquatic organisms have a higher productivity of photosynthesis. The use of microalgae as photosynthetic agents is determined mainly by their value for obtaining high-quality food and feed additives, pharmaceutical products, and biofuels, but it is important to consider their effectiveness in the associated absorption of CO2. When producing products with a long carbon sequestration period, this method can be included in the list of effective carbon capture technologies. To estimate the specific energy costs for CO2 absorption, proven cultivation methods were considered: open-plane cultivators (microalgae Arthrospira platensis, growth rate from 20 to 40 g/m2 per day on dry matter) and cylindrical closed photobioreactors (microalgae Chlorella vulgaris, growth rate 0.7 g/dm3 per day in dry matter). Based on experimental results of microalgae cultivation under conditions of elevated CO2 concentrations, it is shown that specific energy consumption is in the range from 27 to 768 GJ/t when cultivating A. platensis microalgae and from 59 to 373 GJ/t in microalgae cultivation of C. vulgaris. The greatest energy costs are required for heating and lighting microalgae plantations as well as for separating biomass from the culture liquid for microalgae with small cell sizes. Specific energy consumption can be reduced by maximizing the use of natural light and waste heat from industrial facilities and optimizing biomass collection systems.

A mathematical model of a high-temperature cylindrical reactor for heterogeneous pyrolysis of methane during its filtration through a moving layer formed by granules of carbonized wood is presented. The carbon matrix was modeled by spheres of the same diameter with a simple cubic packing. The carbon matrix was heated through the reactor wall. Preheated methane was fed into the lower part of the reactor. The process of pyrocarbon formation as a result of heterogeneous pyrolysis of methane was described by one gross reaction taking into account hydrogen inhibition and changes in the reaction surface. It was assumed that the rate of pyrocarbon deposition is directly proportional to the partial pressure of methane. The system of two-dimensional, nonstationary differential equations describing the operation of the reactor in a cyclic mode with periodic unloading of a portion of carbon–carbon composite and synchronous loading of carbonized wood granules was solved numerically using the DIFSUB algorithm. The reactor radius and operating parameters (specific mass flow rate of methane, carbon composite unloading frequency) were varied in calculations. Based on the obtained results, the dependences of the quality of the carbon–carbon composite (average density and maximum density spread), the composition of the hydrogen-containing gas mixture at the reactor outlet, the degree of methane conversion, the reactor productivity for carbon composite and hydrogen on the operating parameters, and the reactor radius were analyzed. Data are provided on energy consumption for heating methane and carbonized granules loaded into the reactor as well as for compensation of the endothermic effect accompanying methane pyrolysis.

Various design versions of the rotor of hydro-steam turbines (HSTs) and their application fields are reviewed. It is shown that the design with nozzles arranged over the periphery has certain shortcomings resulting in a decreased energy efficiency, including a thermodynamically unjustified increase of pressure at the nozzle inlet, which results in excessively high velocities in the nozzle “throat,” a short period of time for which the evaporating medium resides in the nozzle divergent part, and poor aerodynamic characteristics of the peripheral area, which cause increased friction losses during the impeller rotation in a two-phase medium. A hydro-steam turbine impeller design with helical nozzle-channels is proposed. Such design has features that create prerequisites for increasing the turbine efficiency, including a longer time for which the medium resides in the nozzle, a possibility to obtain aerodynamically smooth lateral and peripheral surfaces of the impeller, and better conditions for moisture separation from the medium surrounding the rotating impeller. The conditions under which superheated water enters the impeller are considered, and statements on shaping the impeller profile part are formulated. A procedure for determining the nozzle-channel divergent part’s camber line shape is proposed proceeding from the minimal force interaction between the liquid phase fragments and channel walls. An algorithm for determining the areas of the channel divergent part’s cross sections when the velocity increase and pressure decrease patterns become monotonic in nature as the flow moves from the inlet to the outlet is developed. A solid-state 3D model of the HST four-nozzle impeller obtained in designing the turbine is presented.

Currently, power facilities that operate turbine lubrication and control systems using fire-resistant oil only use fire-resistant fluids from foreign manufacturers (Reolube-OMTI, Reolube 46RS, and Fyrquel-L). The impossibility of domestic production of fire-resistant oil is connected with the loss of a special industrial raw material base in Russia in the 1990s. Restoring the entire technological cycle is not a matter for the immediate future. To maintain the operational readiness of oils used in process equipment, extend their service life, and reduce the volume of replacement, it is necessary to organize a high-quality cleaning process. For this purpose, the All-Russia Thermal Engineering Research Institute developed technology for the comprehensive cleaning of fire-resistant liquids and created equipment for its implementation at energy facilities. The results are presented of the analysis of complex cleaning and restoration of oils with their draining from the oil system and “on the go.” The quality indicators of the oils in both variants have been significantly improved—the acid number, deaeration and demulsification time, moisture content, and corrosive aggressiveness of the oil have been reduced, the industrial purity class has been lowered, etc.—and values for individual indicators have been achieved that meet the requirements for fresh oils. It has been shown that it is advisable to carry out complex oil cleaning “on the go,” which helps to clean the oil system from accumulated deposits due to the simultaneously occurring process of sludge dissolution and also allows to significantly reduce the rate of degradation of the restored oil under operating conditions.

The effect of dimensionless operating parameters (Reynolds (Re) and Prandtl (Pr) numbers) on the dimensionless heat-transfer coefficient (Nusselt (Nu) number) is examined in a liquid metal flow in a round tube. The Nu number dependences at Pr $$ \ll $$ 1 (liquid metals) are often presented as Nu = f (Pe), where Pe = Re Pr is the Peclet number. The simplified dependence for Nu relies very much on the fact that determination of the dependence Nu = f (Re, Pr) from the experiments with liquid metal coolants is a challenging matter since such experiments involve great difficulties. Moreover, the measurement error in in such experiments is 10–20% or higher, which is comparable with the deviation of the Nusselt number under the effect of the Prandtl number. In addition, when making experiments under earthly environment conditions, the effect of natural convection on the experimental results cannot be eliminated. In this work, to study the dependence of the Nusselt number on the Prandtl number, a series of calculations of a liquid metal flow in a round tube at a constant Peclet number was performed using the direct numerical simulation (DNS) technique. The predictions demonstrate an increase in the Nusselt number by approximately 10% as the Prandtl number drops from Pr = 0.025 (mercury) to Pr = 0.005 (liquid sodium) at Pe = 125. The influence of the Pr number on the Nu number decreases (in percentage terms) as the Pe number increases.

The prospects for achieving carbon neutrality in economically developed countries that are members of the Organization for Economic Cooperation and Development (OECD) and other countries are examined. An analysis of the energy and land use structure in these countries was carried out. Scenario assessments of the dynamics of changes in carbon indicators of the study economies have been developed, and a comparison has been made with forecasts from leading global energy agencies. It has been shown that, at the current rate of decarbonization and development of the carbon capture and storage (CCS) industry, it is impossible for countries in both groups to fulfill their commitments to achieve climate neutrality in 2050–2070; this goal cannot be achieved before the end of this century. The central challenge in achieving climate neutrality is the rapid and large-scale implementation of CCS technologies in all their possible manifestations. Using a set of global climate system models, calculations of the global average temperature (GAT) were performed for the proposed scenarios, and their results were compared with other works. Despite the fact that climate change occupies almost a leading place on the global agenda, the actual results of efforts in this area are far from those declared, and it is now impossible to cap warming to within 1.5°C. The key task is to minimize the time the global climate system remains in the dangerous extreme zone (above 1.5°C), which will require the emergence of a global economy with negative greenhouse gas (GHG) emissions.

Heat exchange during condensation of freons has been studied quite well; however, various flow regimes of the steam-condensate mixture may arise during condensation inside heat-exchange pipes. There is a large amount of experimental data on the condensation of freons inside pipes with different internal diameters. However, the results obtained by different authors are contradictory, and experimental dependencies can give a high error in the event of a discrepancy between the calculated and actual flow regimes of the steam-condensate mixture. Due to the difficulty of identifying these modes for each such case, reliable recommendations for the calculation and design of heat exchangers must be based on experimental data. In order to obtain such materials, an experimental stand was developed and manufactured, allowing the study of condensation processes of various working fluids in a horizontal cooled tube. The working section of the stand was a copper pipe with an external diameter of 32 mm and a wall thickness of 2 mm, built into an external steel pipe with a diameter of 45 × 3 mm with an annular gap of 3.5 mm. Five chromel-copel thermocouples were installed in the gap to measure the water temperature; they were led to the measuring instruments through the wall of the outer pipe. Thermocouples were also installed in the copper pipe wall. The stand’s thermocouples were precalibrated, and the freon and cooling water consumption was determined by the differences on the flow diaphragms with an error not exceeding 1.5%. The temperatures of cooling water and condensing freon R142b along the length of the heat-exchange pipe were obtained for some flow regimes with different parameters of the working fluid at the pipe inlet. A sharp decrease in the local heat-transfer coefficient along the length of the heat-exchange pipe during complete condensation is shown and is especially significant at its inlet section. The obtained data will be used in the design of heat exchangers with condensation of R142b freon in horizontal pipes.

An analysis is performed of the phosphate water chemistry of a high-pressure drum boiler. In Russia, water chemistries with purely phosphate alkalinity and phosphate-and-alkali water chemistry are now mainly used at power plants equipped with drum boilers. One of the main quantitative parameters determining the maintenance of phosphate water chemistries is the ratio of sodium and phosphate concentrations. Calculated dependences of the ratios of pH, the concentration of phosphate, and the sodium-to-phosphate concentration are given. A relationship is found between such ratios and the domains where acid–phosphate corrosion, the hydrogen embrittlement of metal, and alkali cracking occur. It is shown that at concentrations of phosphate below 2.5 mg/dm3, the chloride and sulfate concentrations in boiler water must be monitored to avoid the hydrogen embrittlement of metal. Dependences are presented for the pH and sodium-to-phosphate concentrations at different temperatures. Results are presented from industrial tests of purely phosphate alkalinity water chemistry during the startup and normal operation of a boiler. Analysis of the chemistry of a high-pressure drum boiler water shows that the concentration of phosphate in the pure compartment of a drum has almost no effect on the pH, but the concentration of phosphate in the drum’s salt compartment affects it strongly. Attention should therefore mainly be given to the pH prescribed by the relevant standard when managing the water chemistry in the pure compartment. It is shown that phosphate hideout is often observed when starting power units equipped with high-pressure boilers, so mono- and disodium phosphate solutions are used to maintain the pH and concentrations of phosphate. An analysis of the quality of boiler water during a startup shows there was a drop in the concentration of phosphate in the boiler water and a rise in the sodium-to-phosphate concentrations, so a hideout occurred. The possibility of identifying deviations when monitoring phosphate water chemistry is thus demonstrated, based on an analysis of sodium-to-phosphate ratios of concentrations.

An Erratum to this paper has been published: https://doi.org/10.1134/S0040601524110016

Abstract—An analysis of the relationships for calculating the thermal properties of liquid lead (hereinafter referred to as lead) was carried out, and the method for determining its heat capacity over a wide range of temperatures, including at high values, was chosen. This is especially important for numerical studies to justify the safety of designed reactor installations with liquid metal coolants, such as BREST-OD-300 and BR-1200. Measuring the properties of lead at temperatures close to the boiling point is often difficult due to the lack of reliable methods and materials that can withstand temperatures above 2273 K. At present, theoretical approaches to calculating the properties of simple liquids based on phonon theory are being actively developed. Such approaches can be used to derive semiempirical relations for the heat capacity of liquid lead that would allow physically correct extrapolation of the data to the high-temperature region. In this regard, the aim of this work is to obtain a relationship for calculating the heat capacity of liquid lead from its melting point to its boiling point based on modern theoretical approaches. To achieve the set goal, the following tasks were solved. Firstly, an analysis of the works of various authors was carried out and empirical formulas were selected that make it possible to reliably calculate the heat capacity at a constant volume cv (isochoric heat capacity) for a lead coolant from the melting point to 1500 K. Secondly, based on them, using phonon theory, an approximating formula was constructed, thanks to which it is possible to physically correctly extrapolate the properties of lead to the boiling point (2022 K).

Structural endurance testing of rotor blades is the most important stage of perfecting newly developed blade systems for gas turbine units (GTUs). Obtaining the values of a blade’s structural endurance (fatigue) limit allows designers to evaluate the vibration reliability of a GTU’s blade system. Experimental data also provide an opportunity to verify calculated models of blades. Specialists at the Power Machines company are now working on a line of new GTUs that includes the GTE-170 gas turbine unit. The rotor blades of the GTE-170 unit’s axial compressor and gas turbine, manufactured according to original equipment design documents, are currently being studied for structural endurance on the TsKTI Research and Production Association (NPO) fatigue testing stand. Blade vibration is excited on the stand by applying a variable-frequency electromagnetic field to the area around the tip of a blade. The blade’s limit of structural endurance is determined proceeding from the readings from strain gauges glued in the zones of maximum vibration stresses. Fatigue tests of more than 300 blades used in 14 stages of axial compressors and four gas turbine stages have been run on the stand. The resulting data show that the rotor blades of the GTE-170 unit’s axial compressor and gas turbine have high vibration reliability. Based on results from comparative fatigue tests, it has been determined how replacing the grade of steel and redesigning a blade’s profile affect its vibrational strength. Stand test results have confirmed the need to perform experimental studies of the structural endurance of both newly developed and updated blades when changing their material and redesigning their profiles.

More accurate evaluation of the energy loss as a consequence of fluid leaks through the clearances between the rotor and stator of turbine machines is a topical problem, which can be solved through more accurately assessing the shroud clearance area by applying a leak flow normal cross section. The article presents the results obtained from measurements of gas dynamic parameters in the low-pressure cylinder (LPC) of a high-capacity steam turbine in the last stage tip zone with improved active protection of the rotor blades against erosion. Flow traversing results have confirmed that, near the stage top at the outlet from the radial clearance between the blade row cylindrical shroud and fins of a three-chamber ledgeless seal (i.e., with the same clearances), the wet steam (two-phase medium) leak direction differs from the axial direction in the turbine and is mainly governed by the working medium swirling in the diaphragm nozzle vane channels and mutually opposite influence of rotation of the shroud and of the main flow from the running cascade channels. The leak flowrate is evaluated by using the flow parameters at the seal outlet and the gas dynamics equation with taking into account the medium compressibility. In estimating the two-phase medium flowrate, the following corrections were calculated: the flowrate coefficient increment caused by the flow dispersity, a correction characterizing the influence of initial wetness and the phase slip ratio. Taking into account the coefficients and corrections is conductive to more accurate description of flow through the seals. The wet steam leak flowrate assessment is approximate in nature because it was carried out proceeding from a simplified physical model describing the two-phase medium outflow. With the jet flowing out at an angle of 35° with respect to the circumferential velocity positive direction, the leak flowrate from the shroud seal at the nominal load expressed in fractions of the wet steam medium flowrate through the LPC last state amounted to $$\overline {{{G}_{{{\text{shr}}}}}} $$ = 0.017. The obtained study results are used in designing the wet steam stages of the LPCs of advanced turbines for thermal and nuclear power plants.

The role of solar and wind energy in the current processes of decarbonization of the Russian electric power industry is considered. The issues of the formation and further development of renewable energy, which can make up a significant share of the country’s energy balance thanks to the legislation introduced to stimulate its implementation, are discussed. The rates of commissioning of renewable energy-generation facilities (hereinafter referred to as renewable generation) by region are analyzed, and trends towards reducing capital expenditures in the construction of both solar and wind grid power plants are assessed. An important feature of renewable generation is its stochastic nature, which can cause certain problems when transmitting energy to electrical networks and requires the adoption of special measures to increase the share of renewable energy sources in electrical networks and additional costs to ensure it. Abroad, where a significantly greater path has been taken in the development of the industry, the introduction of grid energy-storage devices, methods for converting surplus energy generated by renewable sources into various useful products and other measures are widely discussed as such measures. In Russia, the overall share of RES in the energy balance is still quite small, but it has already reached threshold values in some regions, at which several pilot projects are being implemented using electric energy-storage devices in both network and autonomous systems. The article provides estimates of the contribution of grid solar and wind power plants to replacing energy from traditional sources and reducing greenhouse gas emissions, and examines the problems and prospects for further development of the industry, primarily from the point of view of the need to reconstruct the grid infrastructure.

The purpose of the study was development of a technology for the extraction of a carbon-rich concentrate suitable for use as an energy fuel from solid products of municipal waste pyrolysis (SPMWP). To do this, the effect of reagents and different flotation conditions on the yield and quality of the carbon-rich concentrate was investigated. The results are presented of the experimental study into the features of the SPMWP flotation process. A relationship has been established between the SPMWP fraction size, the yield of carbon-rich concentrate, and its quality. The fact has been demonstrated that SPMWP flotation characteristics can be improved by ultrasonic dispersion of flotation agents in water and production of concentrates containing, depending on the size distribution of SPMWP particles, from 60 to 67% of combustible matter. Thermogravimetry and differential scanning calorimetry methods have revealed that the combustible matter of the concentrate consists of 65% carbon and 35% volatile carbon-containing compounds. According to the results of X-ray phase analysis, the main water-soluble salts of SPMWP are chlorides of potassium, sodium, and calcium sulfate. As to its heating value (q = 18.4 MJ/kg), the obtained combined concentrate is comparable to coal and can be considered as a renewable energy source since, according to forecasts, the annual increase in the amount of municipal solid wastes (MSWs) will be from 1 to 7%. A schematic diagram of material flows for processing 100 t of SPMWP has been constructed on the basis on the results of performed studies. An additional economic effect can be obtained by using hydroseparation at the stage of municipal waste sorting to separate crushed glass, as a result of which large SPMWP particles may be sent to flotation after grinding.