Moisture Separator Reheater Research Articles

Numerical investigation on heat transfer and pressure drop characteristics of moisture separator reheater with porous media method

The geometry structure of the Moisture separator reheater is very complex, which makes it almost impossible to calculate the whole domain and analyze the physical characteristics. To get the three-dimensional physical property distribution of the moisture separator reheaters, the porous media method is used to simplify the geometry. The 1-dimensional and 3-dimensional coupling theory is adopted into the calculation, for the primary side inside the finned tubes is iterated as the one-dimensional distribution, and the secondary side outside the finned tubes are treated as three dimensional. The whole process of conducting the porous media methods is illustrated with the value. Both the calculated and experimental results of the pressure drop are about 10 kPa in the 1st and 2nd reheaters. The calculation results provide a design and safety evaluation of the moisture separator reheater, as the three-dimensional physical distribution is got through the porous media calculation. With different input parameters such like the arrangement of the finned tubes, the calculated results of heat transfer and pressure drop will be different, and the calculated results are helpful to the design and optimization of the finned tube reheaters. This will help design a set of finned tube parameters.

Electromagnetic Testing of Moisture Separation Reheater Tube based on Multivariate Singular Spectral Analysis

Moisture separator reheater (MSR) tubing systems are an important part of a pressurized-water power plant to increase the efficiency of the heat transfer rate. The MSR tubes are finned tubes which are made of ferritic stainless steel (SS439) with a high strength and corrosion resistance characteristics. However, corrosion can appear along with the fins after a long period of operation of the MSR tubes that requires nondestructive testing (NDT) of the MSR tubes’ periodically. Electromagnetic testing (ET) is an efficient NDT method for the inspection of far-side corrosion in the MSR tubes. However, the ET sensor signal is affected by signal noise from the fins. Material degradation that make it challenging to inspect and evaluate the corrosion. In this study, we proposed three ET methods, including magnetic flux leakage testing, eddy current testing and partial saturation eddy current testing, and incorporated with a multivariate singular spectral analysis (MSSA) filter to improve the detectability of the corrosion in the MSR tubes. The proposed MSSA filter was compared with the multivariate wavelet transform filter and Gabor transform filter, and the results showed more efficient and stable results of the MSSA filter in the extraction of the corrosion signal.

On the Use of Thermal Energy Storage for Flexible Baseload Power Plants: Thermodynamic Analysis of Options for a Nuclear Rankine Cycle

AbstractThe intermittency of wind and solar energy can disrupt the dynamic balance utilities must maintain to meet fluctuating demand. This work examines the use of thermal energy storage (TES) to increase the operational flexibility of a baseload power plant and thus incentivize renewable energy and decarbonize the grid. A first and second law thermodynamic model of a nuclear power plant establishes the impacts of TES on the capacity factor and thermal efficiency of the plant. Four storage options, which are distinguished by the location within the cycle where steam is diverted for charging and whether discharge of the TES is via the primary or a secondary Rankine cycle, are considered. TES is compared to steam bypass, which is an alternative to provide baseload flexibility. TES is significantly better than steam bypass. The storage option with the greatest thermodynamic benefit is charged by diverting superheated steam at the outlet of the moisture separator/reheater (MSR) to the TES. The TES is discharged for peaking power through an optimized secondary cycle. TES increases the capacity factor as much as 15% compared to steam bypass at representative charging mass flowrates. The storage option that diverts steam from the steam generator to charge the TES and discharges the TES to the primary cycle extends the discharge power to a lower range and does not require a secondary cycle. In this case, the capacity factor and efficiency are as much as 8% greater than that of steam bypass.

Steam reheater with helical tube bundle for wet steam turbine

Since steam heat exchangers, used at steam cycle of Russian nuclear power stations, were designed while the knowledge about the separation and the heat exchange processes was limited, deviations between its empirical and theoretical characteristics occur. This limitation also determined application of heating pipes with simple straight shape rather than curved. This study explores a steam heat exchanger with helical heating pipes. It was shown that the model may work stably within the range of parameters, simulating work conditions of the moisture separator and steam reheater at Leningrad nuclear power plant. The experiment included processing of pure water steam as well as mixture of steam and nitrogen. It was obtained a relationship between empirical the heat transfer coefficient and the steam mass flow rate. It was noted that presence of incondensable gas does not affect significantly the heat transfer from the coils, processing high pressure steam.

Heat transfer in coiled type superheater of moisture separator-reheater of turbines at the nuclear power plant

The reheating part of the moisture separator-reheater (MSR) of nuclear power plant (NPP) steam turbine occupies a significant part of MSR volume and requires large consumption of metal. The superheating of low pressure steam provides by the high pressure steam condensation. This steam supplies partly from turbine inlet and partly from turbine stage bleeding because of two superheater stages. The significantly less heat transfer intensity at the single-phase side of reheater comparatively with condensation side requires intensification of heat transfer from the heated-steam. For such goal the different methods can be used: for instance the cross flow of the coiled tubes and finning of straight tubes bundles. Also is perspective the usage of artificial roughness in form of small “moons” and other types of artificial roughnesses.

Test Verification of Wave-Plate Separation Element for Moisture Separator Reheater

The separation characteristics and pressure drop characteristics of the saturated wet steam through the corrugated plate separation element are verified under the actual operating conditions of the moisture separator reheater (MSR) for PWR nuclear power units. The saturated wet steam which meets the requirements are provided by using a large thermal hydraulic test bench, and the pressure drop and residual humidity are obtained when the wet steam flows through the test piece. The results show that the critical flow rate of re-entrainment is high, and when the inlet steam dryness is not greater than 86% and the inlet flowrate is less than the critical flowrate, the residual humidity is not greater than 0.1%, the separation efficiency is of 99% or more, and the pressure drop is not greater than 7 kPa. The design requirements of more than 99% steam dryness and less than 14kPa pressure drop are satisfied. It is with good separation and pressure drop characteristics.

Signal analysis of a bobbin-type integrated hall sensor array in electromagnetic testing for moisture separator reheater tubes

Signal analysis of a bobbin-type integrated hall sensor array in electromagnetic testing for moisture separator reheater tubes

Heat transfer characteristics in super-low finned-tube bundles of moisture separator reheaters

Abstract Experimental investigation on the heat transfer characteristics of superheat vapor through a new designed moisture separator reheater with “super-low” finned-tube bundles for Generation III+ nuclear power plant, was carried out based on a 5*30 tube bundle test section. Impacts of the vapor mass flow rates are analyzed on the heat transfer characteristics of superheat vapor through the finned-tube bundle. A group of experiments are reviewed on single-phase fluid flowing across the triangular super-low finned-tube bundles whose fin heights are less than 2.75 mm and ratios of fin height to fin diameter are from 0.05 to 0.15. Combining the presented experimental data with the other open published data for single-phase turbulent gases flowing across triangular super-low finned-tube, a new heat transfer correlation is proposed for the MSRs super-low finned-tube bundles, which shows better accuracy and has wider Reynolds number range in application.

Nondestructive testing of moisture separator reheater tubing system using Hall sensor array

This paper presents a nondestructive testing system for inspecting the moisture separator reheater (MSR) tubing system in a nuclear power plant. The technique is based on partial saturation eddy current testing in which a Hall sensor array is used to measure the radial component of the electromagnetic field distributed in the tubes. A finned MRS tube of ferritic stainless steel (SS439) with artificial, flat–bottom hole-type defects was used in the experiments. The results show that the proposed system has potential applications in the MSR system or ferromagnetic material tubes in general, which could detect the artificial defects of about 20% of the wall thickness (0.24 mm). Furthermore, the defect volume could be quantitatively evaluated.

Root cause analysis of the folding deformation for the expansion joint in the nuclear power station

In the nuclear power station, the expansion joint of moisture separator re-heater (MSR for short) was founded locally folding deformation under the outage condition. Folding deformation increasing will lead expansion joint leak, it would cause emergency stop when leaking seriously. To solve these problems, this paper analysis mainly on three aspects: the material organization performance, the expansion joint installation and the stress characteristic of expansion joint. Both the verticality deviation in the process of installation and the material hardness value exceed standard are the root cause of these problems. At the end of the paper, the improvements have been put forward for this problem.

F214 湿分分離性能向上のための液滴径粗大化機構に関する研究(OS9 熱・流動(4))

The moisture separator reheater (MSR) is a facility which is used to improve the thermal efficiency for the nuclear power plant. We have been developing the technique to improve moisture separation efficiency of MSR using wire-mesh combined with wave-shaped vanes. The goal of this study is to clarify the wire-mesh configurations which can minimize the exit moisture by droplet diameter measurement under a dispersed flow condition which was made by air and water from a spray nozzle. The results showed that droplet diameters were increased as the number of layer was increased. Within our experiment range, the wire-mesh configuration which has more than three layers yields the increase of the droplet diameter. Besides, although the increasing flow velocity caused generation of small droplets, it was indicated that the velocity range which keeps droplets coarse, can expand using means of increasing layer of the mesh.

Optimization of a moisture separator reheater

The optimization of component size aimed to minimize the weight and volume is an important issue to a nuclear power plant design. The optimization algorithm is applied to determine the optimum structural and operation parameters of components in order to reduce the difficulty of manufacture and transport of large components in those nuclear power plants with high powers. A preliminary optimal design is performed on the moisture separator reheater of Qinshan I nuclear power plant in this paper. A self-adapting multi-complex-shape algorithm has been developed and coupled with the thermal mathematical model of the moisture separator reheater, written in C#. The steady-state thermal mathematical model of moisture separator reheater is used to estimate the weight of moisture separator reheater according to the variation of a given number of structural and operation parameters. Then, the thermal mathematical model coupled with the self-adapting multi-complex-shape algorithm permits a set of best structural and operation parameters of the moisture separator reheater to be determined. The results clearly show that there is plenty of potential to improve the design of moisture separator reheater, while satisfying the structural and performance constraints. The results can also help both designers and operators to make a more convenient selection of the structural and operation parameters of moisture separator reheater.

EVALUATION OF PH CONTROL AGENTS INFLUENCING ON CORROSION OF CARBON STEEL IN SECONDARY WATER CHEMISTRY CONDITION OF PRESSURIZED WATER REACTOR

The effect of various pH agents on the corrosion behavior of carbon steel was investigated under a simulated secondary water chemistry condition of a pressurized water reactor (PWR) in a laboratory, and the steel’s corrosion performance was compared with the field data obtained from Uljin NPP unit 2 reactor. All tests were carried out at temperatures of 50oC ? 250oC and pH of 8.5 ? 10. The pH at a given temperature was controlled by adding different agents. Laboratory data indicate that the corrosion rate of carbon steel decreased as the pH increased under the test conditions and the highest corrosion rate was measured at 150oC. This high corrosion rate may be related to high dissolution and instability of Fe oxide (Fe3O4) at 150oC. It was also found that an addition of ethanolamine (ETA) to ammonia was more effectivefor anticorrosion than ammonia alone, and that mixed treatment reduced 50% of iron or more at pHs of 9.5 or higher, especially in the steam generator (SG) and the moisture separator & re-heater (MSR).

1028 ワイヤメッシュ積層構造による微小液滴除去手法の開発

The moisture separator reheater (MSR) is a facility which is used to improve the thermal efficiency for the nuclear power plant. We have been developing the technique to improve moisture separation efficiency of MSR using wire-mesh combined with wave-shaped vanes. The objective of this study is to clarify the wire-mesh configurations which can minimize the exit moisture by droplet diameter measurement. We confirmed that droplet diameters were increased and the exit moisture was reduced as the number of layer was increased. Within our experiment range, six layered wire-mesh with 0.65 mm diameter can minimize the moisture, which is reduced from 0.45% without wire-mesh to 0.08%.

Development of wall thinning screening system and its application to a commercial nuclear power plant

A new non-destructive evaluation (NDE) method has been developed for metal pipes for the detection wall thinning. The method has been showed to be suitable for applications to electric power generation plants where flow accelerated corrosion (FAC) of carbon steel piping is a significant cause of increased maintenance and plant personnel casualty. The wall thinning screening system (WalSS) was developed in two major phases. In the first phase, the equipotential switching direct current potential drop (ES-DCPD) method was developed for piping wall (Ryu et al., 2008a, 2010). In the second phase, in this paper, a quantitative detection criteria was developed. The relative ES-DCPD change of 3.8% has been defined as the screening criteria for wall thinning schematization. This criteria means that the component with measured ES-DCPD change greater than 3.8% is called for a more comprehensive examination. In the criteria development, all variables were taken into consideration based on commercial plant piping inspection data such as initial thickness distributions, wall thinning shape and nominal thickness. The developed WalSS based on ES-DCPD was applied to a moisture separator reheater (MSR) drain line of a commercial nuclear power plant (NPP) during a scheduled overhaul. The measured ES-DCPD change was 2.16%, which is lower than the ES-DCPD criteria, identifying the pipe having adequate wall thickness. This is confirmed by site thickness inspection using ultrasonic technique (UT).

Dynamic Simulation on Secondary System of Nuclear Power Plant

The secondary system of Qinshan phase I nuclear power plant is simulated in this study. According to the characteristics of the JTopmeret model, the system is divided into six parts for modeling, which are the deaerator, the high pressure (HP) turbine, the low pressure (LP) turbine, the moisture separator reheater (MSR), the condensate system, and the feedwater system. All parts are built as the graphic automatic models in JTopmeret and debugged on the large-scale simulation platform GSE to complete the steady-state and dynamic simulation of the models. The results show that the steady-state and dynamic processes of the models are consistent with the characteristics of the actual system. It verifies the correctness of the simulation models. Thus, this research is able to provide guidance for the operation analysis and the equipment debugging of the secondary system of the nuclear power plant.

Eddy current testing of type-439 stainless steel tubing using magnetic saturation technique

The type-439 ferritic stainless steel tubing is typically used for a moisture separator reheater (MSR) in a nuclear power plant turbine system. MSR employ heavier wall tubing than that of other reheaters. Generally, service-induced damage can occur on the outside diameter surface of the type-439 ferritic stainless steel tubing, and the most typical damage mechanism is the vibration-induced tube-to-tube support plate (TSP) wear and the fatigue cracking. In this study, the optimized magnetic flux density of an eddy current probe for the inspection of type-439 stainless steel tubing has been analyzed, and a specific magnetic saturation probe was designed. We have successfully evaluated the capability of the magnetic saturation eddy current technique to detect and measure flaws in the type-439 stainless steel tubing of moisture separator reheater.

Recent Moisture Separator Reheater Design Technologies

The moisture separator reheater (MSR) is a key piece of equipment in reheat systems in nuclear steam turbines that use saturated main steam, where it helps improve turbine efficiency and suppress flow-accelerated corrosion. Fundamental to achieving a compact, reliable MSR design are methods for predicting mist separator vane performance and suppressing tube drainage instability. First, we devised a method for predicting separator performance based on the observation of mist separation behavior under an air-water test. We then developed a method for predicting performance under steam conditions from air-water test data and verified it by means of a comparison with the actual results of a steam condition test. The instability of tube drainage associated with both subcooling and temperature oscillation at turbine partial load, which might adversely affect the seal welding of the tubes to the tube sheet due to thermal fatigue, was measured on an existing unit to clarify the behavior. We then developed a technique for increasing venting steam, which had been operating at a constant flow rate, to suppress instability and verified its effectiveness. Both methods were applied to current MSR models, which were adopted for nuclear power plant turbines commercially placed in service from 1984 to 2009, and the effectiveness of the methods was demonstrated. The separator vane mist carryover rate was less than 0.1%, and tube drainage instability was suppressed, demonstrating the effectiveness of the simple design concept of a two-flow U-tube instead of the prevailing four-flow U-tube design. We put forth a new concept in the design of MSRs for 1700 MW class advanced pressurized water reactor (APWR) units based on associated technologies, along with advanced technology for the compact design of pressure vessels and multidisciplinary optimum design for evaluating heat exchanger tube bundles.

Modeling and optimization of a nuclear power plant secondary loop

Increasing the thermodynamic efficiency of fossil fuel or nuclear power plants can lead to significant economic gains. Consequently, the continuous quest of searching higher efficiency in power plants has resulted in the development of innovative tools to comply with these needs. Although a large inventory of simulation tools is available for industrial applications, sometimes it is more appropriate to develop in-house models that are best suitable for treating specific energy systems. In the present work, a combined simulation-optimization tool was developed and used to optimize the secondary loop of a CANDU-6 nuclear power plant (i.e., Gentilly-2 nuclear station). Based on previous studies an optimizer module has been coupled with a thermodynamic model, written in Matlab, used as a plant simulation tool. It includes models that take into account the responses of major thermal units, i.e., condenser, moisture separator reheater and feedwater heaters. The simulation package is used to estimate the behavior of the power station according to the variation of a given number of plant operation parameters. The methodology permits a set of best trade-off operating conditions of the secondary loop to be determined, and thus providing a better and more realistic support to plant operators. The results also clearly show that there is plenty of potential to improve the overall performance of the power station.

Moisture Separator Reheater for NPP Turbines

This paper introduces the development of the current model Moisture Separator Reheater (MSR) for nuclear power plant (NPP) turbines, commercially placed in service in the period 1984-1997, focusing on the mist separation performance of the MSR along with drainage from heat exchanger tubes. A method of predicting the mist separation performance was devised first based on the observation of mist separation behaviors under an air-water test. Then the method was developed for the application to predict under the steam conditions, followed by the verification in comparison with the actual results of a steam condition test. The instability of tube drainage associated with both sub-cooling and temperature oscillation might adversely affect the seal welding of tubes to tube sheet due to thermal fatigue. The instability was measured on an existing unit to clarify behaviors and the development of a method to suppress them. Both methods were applied to newly constructed units and the effectiveness of the methods was demonstrated.