Moisture Separator Research Articles

A Reduced-Order Model of a Nuclear Power Plant with Thermal Power Dispatch

This paper presents reduced-order modeling of thermal power dispatch (TPD) from a pressurized water reactor (PWR) for providing heat to nearby heat consuming industrial processes that seek to take advantage of nuclear heat to reduce carbon emissions. The reactor model includes the neutronics of the reactor core, thermal–hydraulics of the primary coolant cycle, and a three-lump model of the steam generator (SG). The secondary coolant cycle is represented with quasi-steady state mass and energy balance equations. The secondary cycle consists of a steam extraction system, high-pressure and low-pressure turbines, moisture separator and reheater, high-pressure and low-pressure feedwater heaters, deaerator, feedwater and condensate pumps, and a condenser. The steam produced by the SG is distributed between the turbines and the extraction steam line (XSL) that delivers steam to nearby industrial processes, such as production of clean hydrogen. The reduced-order simulator is verified by comparing predictions with results from separate validated steady-state and transient full-scope PWR simulators for TPD levels between 0% and 70% of the rated reactor power. All simulators indicate that the flow rate of steam in the main steam line and turbine systems decrease with increasing TPD, which causes a reduction in PWR electric power generation. The results are analyzed to assess the impact of TPD on system efficiency and feedwater flow control. Due to the simplicity of the proposed reduced-order model, it can be scaled to represent a PWR of any size with a few parametric changes. In the future, the proposed reduced-order model will be integrated into a power system model in a digital real-time simulator (DRTS) and physical hardware-in-the-loop simulations.

Structural Integrity Assessment and Fatigue Evaluation of Feed Water Nozzle of 700MWe PHWR Steam Generator

Steam Generator (SG) is a prime component in Indian Pressurized Heavy Water Reactors (PHWRs). The Steam Generator consists of an inverted vertical U-tube bundle in shell for primary flow (Heavy water). The shell side is designed for recirculation. Steam Generator is a Safety Class-1 component and designed & fabricated as per the requirements of ASME Section III, Subsection-NB.Secondary side of the steam generator consists of a shell, Feed Water Nozzle (FWN), Steam Outlet Nozzle, moisture separator, drier, tubes and shroud. The principal material of construction for secondary side pressure boundary is of low alloy carbon steel. Secondary side of steam generator is subjected various loadings (Dead weight, pressure, pipe reactions & thermal) during normal plant condition as well as transient conditions including severe transient like crash cool down where in the thermal gradients are much higher. To take care of these thermal transient loadings a special thermal sleeve type of design has been incorporated in the FWN.As mentioned above, FWN is subjected to thermal transients throughout its life and susceptible to high thermal gradient which makes it important to evaluate for structural integrity and fatigue failure. This paper covers the approach & results for structural integrity assessment (stress evaluation) and fatigue evaluation (cumulative fatigue damage factor) of Feed Water Nozzle of 700MWe PHWR SG for various Service levels A, B, D & Design. These service conditions comprise of thermal & pressure transients during operating and accidental conditions. Detailed integrity check performed for all conditions by stress categorization at critical locations and qualify primary & secondary stresses against ASME Section III allowable.

Simulation of decay heat removal by active means following emergency shutdown in SFRs

Decay heat removal (DHR) is an important safety function in sodium-cooled fast reactors (SFRs). Dedicated systems are provided in the plant for performing DHR functionalities. Transients following reactor shutdown need to be studied to understand the dynamics of DHR systems, design the systems, and establish reactor safety. DHR systems can operate by active as well as passive means, thanks to the phenomenon of natural circulation. In the present work, a DHR system riding on the Balance of Plant (BoP) of a typical medium-sized SFR has been modeled and incorporated into the in-house developed plant dynamics code DYANA-P. DYANA-P already has models of primary and secondary circuits of SFR. With this code enhancement, the simulation of DHR in an integrated manner became possible. In particular, thermal models of the Moisture Separator Tank (MST), Decay Heat Removal Condenser (DHRC), and hydraulic model of the DHRC flow circuit were developed. Two-phase one-dimensional mass, momentum, and energy conservation equations with homogeneous flow assumptions were used to create the models. Simulation of SCRAM in a typical SFR has been carried out to demonstrate the applications of the modified code. Two different DHR deployment schemes were studied and compared – 1. Using DHR systems designed for high pressure of ∼170 bar, 2. Using DHR systems designed for low pressure of ∼15 bar. In the first scheme, reactor cooling was achieved at the desired rate of ∼20 K/h. In the second scheme, the reactor cooling rate will be higher at ∼60 K/h.

Dynamic Simulation of MFT and BT Processes on a 660 MW Ultra-Supercritical Circulating Fluidized Bed Boiler

In order to study the dynamic characteristics of the 660 MW ultra-supercritical circulating fluidized bed (CFB) boiler when the main fuel trip (MFT) and boiler trip (BT) are triggered, a dynamic simulation model of the 660 MW ultra-supercritical circulating fluidized bed boiler was established on the Apros simulation platform. The model dynamically simulated the MFT and BT processes at 100% BMCR, 75% THA, and 50% THA conditions, respectively. The steady-state simulation results showed a high accuracy compared with the designed parameters. The dynamic simulation results showed that after triggering the MFT and BT, owing to the huge thermal inertia, the bed temperature and steam temperature decreased lowly. For 100% BMCR and 75% THA conditions, the moisture separator always worked in dry state during the MFT and BT processes. For the 50% THA condition, the moisture separator quickly switched from dry to wet operation after the boiler triggers MFT and BT and gradually switched from wet to dry operation after MFT and BT were reset.

A Numerical Study on the Characteristics of the Pressurized Water Reactor’s (PWR) Primary Moisture Separator Using the Particle Tracking Method

The primary moisture separator—a key component in the PWR nuclear power plant—determines the quality of supplied steam to a turbine. Investigating its characteristics is important because supplying steam with excessive droplet entrainment results in damages to pipes, valves, and turbines in power plant circuits. In this numerical study, the particle tracking method in the Eulerian–Lagrangian methodology is used to investigate the characteristics of a primary moisture separator. Various swirl vanes with different bending angles, vane quantities, and vane locations are chosen to investigate the effect of design parameters on characteristics of the primary moisture separator. Additionally, the water droplet size is considered to vary from 0.01 to 50 μm in this study. The pressure drop between the inlet and outlet, the steam quality at the orifice outlet, and the particle collection ratio are discussed in this paper. The results show that steam quality increases as the bending angle decreases, and increasing the number of swirl vanes increases both the pressure drop and the steam quality.

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.

An Experimental Performance Evaluation for a Swirl-Vane Separator Using an Air-Water Test Facility

The most important design parameters of a moisture separator to optimize the efficiency of a nuclear power plant are the moisture carry over and pressure drop. An air-water test facility was constructed to evaluate the design parameters for various types of conventional moisture separators in Korea. In this study, a half scale of swirl-vane separator was designed, and test conditions were defined based on the scaling law to cover a wide range of operating conditions. The moisture carry over was measured using an isokinetic sampling system for 34 different flow conditions. The MCO was in range of 0.30–7.05% according to the test conditions. Single and two-phase flow experiments were also carried out to identify the two-phase pressure drop characteristics. Based on the obtained results, the proposed empirical correlation model was extended to a submerged separator and applying these results to a full scale system is discussed in this paper.

Development and Experimental Validation for Quantifying the Moisture Carryover in a Moisture Separator Using an Air/Water Test Facility

The moisture carryover (MCO) of the primary separator in a steam generator is the most important design parameter to ensure high efficiency in a steam generator. There is an inherent limitation to experimentally evaluate the MCO under the prototype conditions. In this study, the air/water test facility was constructed based on the similarity law, and a new isokinetic system was developed to quantify the MCO. Several experiments were performed for the mass quality ranging from 0.315 to 0.382. The accuracy and versatility of the experimental method was verified experimentally using a full and half scale of separators. The test results were compared with the prototype results. It was proved to be a reliable experimental method for evaluating the MCO of the moisture separator.

Development of Empirical Correlation of Two-Phase Pressure Drop in Moisture Separator Based on Separated Flow Model

Pressure drop across the moisture separator installed in the steam generator of a nuclear power plant affects the power generation efficiency, and so accurate pressure drop prediction is important in generator design. In this study, an empirical correlation is proposed for predicting the two-phase pressure drop through a moisture separator. To ensure the applicability of the correlation, a series of two-phase air-water experiments were performed, and the results of the present test and of the benchmark test of high-pressure steam-water were used in developing the correlation. Based on the experimental results, quality, dimensionless superficial velocity, density ratio of the working fluid, and the geometrical factor were considered to be important parameters. The two-phase pressure drop multiplier was expressed in terms of these parameters. The empirical correlation was found to predict the experimental results within a reasonable range.

증기발생기의 표준형 습분분리기 내부 유동 특성에 관한 수치해석

In the present study, a series of numerical analysis was performed to identify the flow characteristics inside the CE-type moisture separator applied to domestic steam generators. To investigate the similarity between normal operation condition of the prototype separator and experimental condition using air-water test facility with real scale and 1/2 scale test sections, single phase and two-phase calculations were carried out. The results of the single phase calculations showed that the outward flows through the flow holes on the wall turned out to be similar trend regardless of the working fluid and inlet conditions on real scale geometry. However, the pressure loss coefficient for the 1/2 scale geometry was relatively larger than that for the real scale geometry. In the two-phase calculation, Eulerian-Lagrangian method was adapted to investigate the behavior of the droplets. Two extreme conditions for the post impingement behavior of the droplet, which were escape and rebound conditions; were applied and the results between them were compared.

Development of a prediction model relating the two-phase pressure drop in a moisture separator using an air/water test facility

The pressure drop of a moisture separator in a steam generator is the important design parameter to ensure the successful performance of a nuclear power plant. The moisture separators have a wide range of operating conditions based on the arrangement of them. The prediction of the pressure drop in a moisture separator is challenging due to the complexity of the multi-dimensional two-phase vortex flow. In this study, the moisture separator test facility using the air/water two-phase flow was used to predict the pressure drop of a moisture separator in a Korean OPR-1000 reactor. The prototypical steam/water two-phase flow conditions in a steam generator were simulated as air/water two-phase flow conditions by preserving the centrifugal force and vapor quality. A series of experiments were carried out to investigate the effect of hydraulic characteristics such as the quality and liquid mass flux on the two-phase pressure drop. A new prediction model based on the scaling law was suggested and validated experimentally using the full and half scale of separators. The suggested prediction model showed good agreement with the steam/water experimental results, and it can be extended to predict the steam/water two-phase pressure drop for moisture separators.

습분분리기 압력강하 상사법칙 개발에 대한 실험적 연구

습분분리기 압력강하 상사법칙 개발에 대한 실험적 연구

증기발생기 습분분리기 습분동반율에 대한 물/공기 실험적 연구

The separation efficiency of the moisture separator in a steam generator is the most important key parameter to ensure the safety of turbine and to obtain high efficiency in a nuclear power plant. The objective of this research is to investigate which experimental method can be used for evaluating the performance of the separator, namely moisture carry over (MCO), of the prototype separator. The air/water test facility based on the similarity law was constructed and developed an experimental method to quantify the MCO. For a various mass quality ranged from 0.277 to 0.382, several experiments were carried out to evaluate the MCO and to verify the experimental method. The obtained results were compared to data on the prototype condition and showed a good agreement with that of the prototype conditions.

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.

Special Section: Selected Papers From the Ninth International Symposium on Supercritical Water-Cooled Reactors

Special Section: Selected Papers From the Ninth International Symposium on Supercritical Water-Cooled Reactors

The new ways to increase the efficiency of thermal hydraulic processes in systems of separation and reheating of NPP wet steam turbines

Systems of moisture separators - reheaters (SMSR) were created simultaneously with the powerful turbines development of nuclear power plants operating on a wet steam from the early 60s of the 20th century. This lengthy experience made the opportunity to identify the moisture separators - reheaters (MSRs) drawbacks, to determine the objectives for their design and computation improvement in order to increase thermodynamic efficiency, MSR devices and MSR systems reliability in general. Based on maintenance experience and results of our and other researchers’ model and field studies this article discusses potential ways of further development and improvement, taking into consideration both SMSR components (separation and reheating) under conditions of their flow in one apparatus.

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.

Factors and Mechanisms Causing Wear of Turbine Heating Steam Condensate Pipeline Components at a Nuclear Power Plant

The article considers the specific features related to operation of the power valve and orifice lines within turbine plant piping systems whose inlets receive water medium with saturation parameters (separated moisture or condensate). It is shown that transportation of working medium in these piping systems is accompanied by pressure drop, boiling, and formation of various two-phase flow patterns from bubble in the initial segment to dispersed-annual in the end segment. Under certain conditions, a slug flow pattern can occur, which behaves as a source of piping vibration. Practical experience has shown that the use of homogenizing inserts for suppressing vibration load in the heating steam condensate (HSC) discharge lines downstream of the moisture separator reheaters (MSRs) of nuclear power plant (NPP) turbines often leads to intensified local flow-accelerated corrosion and pipeline failures. The article considers examples illustrating failures of piping segments downstream of homogenizing inserts and presents statistical data on damageability of heating steam and separated moisture piping of NPP turbines. The steam–water flow patterns in the MSR HSC transportation line of an NPP turbine are determined. The results from hydrodynamic modeling of working medium flow under the conditions of an abrupt expansion at the outlet from the homogenizing insert channel are presented. It is shown that the location of zones characterized by the maximum wear of piping downstream of homogenizing inserts in the MSR HSC discharge lines is determined by the flow pattern and specific features of the working medium flow hydrodynamics. It has been established that droplet impingement erosion is the dominating mechanism causing destruction of stainless-steel piping segments downstream of the homogenizing inserts in the MSR HSC lines of NPP turbines. It is important to note that, if the pipeline is made of carbon or low alloy steel, its metal experiences a combined effect of droplet impingement erosion and flow-accelerated corrosion. The obtained study results can be used in elaborating measures aimed to prevent wear of piping components in the heating steam condensate and separated moisture discharge lines of NPP turbines.

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