Vol 65, No 9 (2018)

The current state and ways for improving the effectiveness of steam turbine units at nuclear power stations (NPS) are examined. The specifics of NPS turbines is described. The comparison of NPS steam turbine performance with the performance of steam turbines at thermal power stations (TPS) demonstrates that power units of NPSs are much poorer in effectiveness due to relatively low steam conditions at the inlet and the presence of wet steam already in the first stages of turbines. A decrease in the relative internal efficiency of NPS turbines results from the enhanced negative effect of wetness in the expansion process: in modern NPS turbines, more than two-thirds of the heat drop is spent in the two-phase region, while less than one fourth in TPS turbines. It is demonstrated that the effectiveness of NPS steam turbine units can be increased drastically in the future only through a considerable rise in the turbine inlet steam conditions. This can be achieved by using a heat carrier at supercritical conditions in the NPS reactor. The dependence of the effectiveness of NPS modern turbines on the turbine inlet steam conditions in the applicable pressure ranges of the saturated steam and vacuum in the condenser, as well as on the turbine exhaust area, is examined. For a 1000 MW turbine, increasing the inlet pressure from 6.0 to 8.0 MPa raises the turbine power and efficiency by 3.5%. At a condensing turbine outlet pressure ranging from 2.5 to 7.5 kPa and a constant velocity downstream of the last stage, the turbine power and efficiency can be increased by 7%. The importance of the exhaust area for the turbine effectiveness is revealed. Alternative designs of the flowpath in a low-pressure cylinder are analyzed. A unique configuration of a steam turbine unit with two-stage moisture separation is proposed. The comparison of high-speed turbines with low-speed ones was performed. It is demonstrated that the efficiency of the examined turbines is nearly the same within the accuracy of design calculations and the test results, and it is slightly higher for low-speed turbines due to lower losses with outlet velocity.

The article proposes a new concept for designing power plants operating on natural gas and involving means for fully removing carbon dioxide from the cycle in the liquid phase form in order to subsequently bind or bury it for reducing the emissions of greenhouse gases into the atmosphere. In contrast to means used in the conventional power plant process arrangements for capturing CO₂ from the combustion products, the proposed concept involves the need to develop fundamentally new power engineering technologies, in which the CO₂ utilization system is intrinsically built into the cycle structure already at the initial stage of power plant design and optimization of its parameters. As an example, the process flow diagram of a natural gas fired power plant generating electricity and heat is considered. The integral indicators characterizing the thermal efficiency of such a power plant are given and compared with the similar indicators of the operating or newly designed plants fitted with CO₂ capturing systems, the process arrangement of which implies direct emission of carbon dioxide into the atmosphere. The comparison is carried out for the average ratio between the generated electricity and heat that has historically been established in the climatic zone of central Russia. It is shown that the proposed cycle features high thermodynamic efficiency and competitiveness with respect to the same indicators of alternative systems for combined generation of electricity and heat. The article suggests versions of the CO₂ capturing system configuration that allows, with the modern technological level of equipment, the carbon dioxide emissions to be reduced down to 0.5–5.0% of the total amount produced in firing natural gas.

Hydrodynamics and heat transfer were investigated of an upward liquid metal flow through a rectangular channel having an aspect ratio of approximately 3 : 1 and one-sided heating under a coplanar magnetic field (MF). The flow in the cooling system’s cooling channel for a liquid metal blanket module of a Tokamak type thermonuclear reactor is simulated. Experiments were carried out in the mercury magnetohydrodynamic (MHD) test facility. Local heat transfer characteristics were measured using a probe technique. Two types of thermocouple probes were used: a lever-type pivoted probe for detailed measurements of velocity and temperature fields in a channel cross-section and a longitudinal probe for taking measurements along the heated zone in the channel. A correlation method was used for measuring local velocity. The distributions of averaged velocity and temperature, the distributions of dimensionless wall temperature along the cannel perimeter, and characteristics of flow temperature fluctuations are presented. The distributions of averaged and instantaneous wall temperatures along the channel were obtained. The effects caused by an increase in the intensity of temperature fluctuations in a coplanar magnetic field were revealed. It is the authors' opinion that natural convection is responsible for formation and separation of large-scale vortex structures, the axis of which is parallel to the magnetic field induction vector, at the heated wall. These vortices bring about temperature fluctuations that often exceed the level of turbulent fluctuations. The data on heat transfer should be considered in designing MHD cooling channels of a fusion reactor.

The article presents information on the validation and verification (V&V) of the first version (V1) of the EUCLID integrated code intended for safety analysis of operating or designed liquid metal (sodium, lead, or lead–bismuth) cooled reactors under normal operation and under anticipated operational occurrences by carrying out interconnected neutronics, thermal–mechanical, and thermal–hydraulic calculations. The list of processes and phenomena that have to be modeled in the integral code for correctly describing the above-mentioned operating conditions is given. Based on this list, the most high-quality experimental data are selected for carrying out the validation. It is shown that, for sodium cooled reactors, a significant number of experiments was carried out around the world on studying individual thermal–hydraulic processes and phenomena, which made it possible to perform validation of the thermal–hydraulic module. The validation of the code—as applied to description of processes that take place in fuel rods with oxide or nitride fuel and gas gap—is carried out against the results of post-pile investigations of fuel rods irradiated in fast sodium cooled research and power-generating reactors. The obtained results opened up the possibility to determine the errors of calculating such fuel rod parameters as release of gaseous fission products from the fuel and sizes of pellet and cladding in a limited range of burnup values. To perform validation of the neutronics module as applied to calculation of such parameters as power density distribution over the core and decay heat release, a sufficient number of experiments and benchmarks were selected. The results obtained from experimental operating conditions of a BN-600 reactor and startup conditions of a BN-800 reactor made it possible to estimate how correctly the integral code performs calculations of interconnected thermal–hydraulic and neutronic processes. Only a limited set of experimental investigations is available for heavy liquid metal cooled reactors. In view of this circumstance, programs for obtaining the lacking data are developed. To estimate the quality with which the experiments are modeled by means of the EUCLID/V1 integrated code, a procedure for evaluating the errors of calculation results is developed. In accordance with this procedure, the error of calculating the parameters playing the main role in the reactor safety assessment is evaluated.

The third part of this review1 discusses matters concerned with managing the flow-accelerated corrosion of power-generating equipment’s and pipelines' components. The importance of these matters tends to increase with increasing the capacity of power plant units and the time for which they have been in operation. The article considers the capabilities of object-oriented software packages aimed at providing information support to the personnel (PSSPs) in regard to scheduling in-service inspections for timely revealing cases of close-to-inadmissible flow-accelerated corrosion-induced thinning. The prospects of using PSSPs for minimizing the carryover of iron-containing products of general flow-accelerated corrosion into the process circuit of NPP units are shown. The list of parameters and characteristics necessary for numerically estimating the thinning rates and residual life of pipelines and equipment susceptible to flow-accelerated corrosion is determined. The possibility of using some PSSPs to predict the thinning of process circuit component walls taking into account the effect of cavitation and droplet impingement erosion on the metal is pointed out. The need to optimize the scheduling of in-service inspections of near-seam zones of welded connections used in the pipelines of the condensate–feedwater and wet steam paths of power units is substantiated. It is pointed out that work is underway for fitting the Russian NPP units with PSSPs able to define— based on calculation results, data of in-service inspections, and other information—a priority list of components to be subjected to first-priority or next scheduled in-service inspection and to schedule repair (or replacement) of components susceptible to intense thinning. It is shown that the use of stainless steels for making the components of pipelines and equipment operating in the secondary circuit of NPP power units is often an excessive measure for preventing the occurrence of inadmissible local flow-accelerated corrosioninduced thinning and for minimizing the concentration of iron in feed water. The prospects for comprehensively solving the flow-accelerated corrosion problems by implementing appropriate measures at the designing, construction, and operation stages are considered. The main topical practical objectives for coping with the problem of flow-accelerated corrosion in power engineering are formulated.

When untreated natural water is used in the reverse cooling systems with tower-shaped evaporative cooling stacks of thermal power plants, negative processes occur, namely sparingly soluble substance deposition onto heat-exchange surfaces, corrosion, sludging of flow paths, bio-fouling, etc., which significantly worsens the thermal efficiency of TPPs as a whole, leads to equipment deterioration, and worsening hydrodynamic performance. This paper is devoted to the study of the physicochemical structure of deposits formed in reverse cooling systems of thermal power plants using IR spectroscopy and elemental analysis. At the Kazan TPP-3 with a conjugated reverse cooling system, samples of deposits have been taken from the rotary chamber and the condenser tubes of a turbine as well as from the sprayers of a tower-shaped evaporative cooling stack. The analysis of IR spectra of the samples showed that the base of deposits in the tower-shaped evaporative cooling stack consists of calcium carbonate that includes iron compounds (mainly hematite Fe₂O₃), inorganic sulfates, silicates, magnesium carbonate. Dense parts of the deposits in the condenser of turbines consist of iron silicate with the impurities of other substances. The deposits in the reverse cooling system are most intensely formed in the areas with the highest heating temperature, such as turbine condensers and spraying nozzles in the tower-shaped evaporative cooling stack. At the Naberezhnye Chelny TPP, the deposits have been taken from a forechamber gate of the reverse cooling system. In total, four different samples of deposits that differ in appearance from each other have been chosen. As shown by infrared spectroscopy, the main part of deposits is formed by the corrosion products of metal structures coated with the layers of sparingly soluble compounds, including calcium and magnesium carbonates, iron oxides, silicates, and organic compounds, such as humic substances.

The imperfection of the approach to the fuel efficiency assessment of energy sources with the combined generation of electrical and thermal energy based on the specific fuel consumptions is shown; it is caused by the fact that the use of different methods for the separation of the total fuel consumption leads to ambiguous results. A simple and feasible technique for the comparative assessment of the system fuel efficiency of existing energy sources of different types is proposed. The technique is based on the combined use of two dimensionless criteria that are calculated based on the CHPP production activity parameters provided in the yearly reports. These criteria have a clear physical sense and do not require the separation of the CHPP total fuel expenses into components. Analytical calculation dependences that relate the values of the proposed criteria and the actual relative fuel conservation, which is calculated for each individual energy source with respect to the average fuel efficiency level that is actually achieved in the considered energy system, are presented. The proposed approach and the technique based on it make it possible to objectively assess and compare the actual fuel efficiencies of energy sources of different types in terms of relative fuel conservation. The practical importance of the developed technique is demonstrated for a specific case: the comparative analysis of the actual fuel efficiency at all heat supply sources of the Saratov Branch of PAO T Plus is performed based on the available reported data on the results of the production activity. The results are visualized in the form of a diagram representing the actual fuel efficiency of each CHPP (for each year) with respect to the average level achieved in this energy system during the operating period of 8 years. The presented materials can serve as a basis for the choice of rational ways to improve the CHPP fuel efficiency.