Design of an Innovative Moisture Separator Technology for Use in Nuclear Power Plants: Numerical Approach \u2014 Part 1

Many nuclear system codes have been developed for the main purpose of analyzing reactor performance of a nuclear power plant system during steady state and transient conditions. These codes generally include power plant component models for pumps, pipes, steam generators, pressurizers and other components. The parallel development of these nuclear system codes has been supported by government laboratories, universities, private entities and other organizations throughout the world. This has resulted not only in multiple codes, but multiple versions of the same code with different capabilities. The development paths of each code version have been driven by specific needs. The challenge for the user is to select a code that performs well for the desired analysis problem. Therefore, this work compares different aspects of various nuclear system codes. Firstly, it compares the governing equations for mass, momentum and energy in the evaluated system codes. Secondly, it compares all the codes’ closure models. Closure models are used in system codes to model thermal and mechanical non-equilibrium as well as the coupling of the phases. Thirdly, it compares the Separate Effect Tests (SET) and Integral Effect Tests (IET) employed for the verification and validation (V&V) during the development of each system code. These comparisons cover several thermal and hydraulic models, such as heat transfer coefficients for various flow regimes, two phase pressure correlations, two phase friction correlations, drag coefficients and interfacial models between the fields. Fourthly, major assumptions about the governing and closure equations in these codes are compared and discussed. Fifthly, numerical approach of every code is benchmarked with each other since numerical approach not only affects the speed of the system codes but also the accuracy of the results. Sixthly, the limitations of the codes are evaluated because these codes are challenged by analyzing not only existing nuclear power plants, but also next generation nuclear power plants. The nuclear industry is developing new, innovative reactor designs, such as Small Modular Reactors (SMRs), High-Temperature Gas-cooled Reactors (HTGRs) and others. Sub-types of these reactor designs utilize pebbles, prismatic graphite moderators, helical steam generators, innovative fuel types, and many other design features that may not be fully analyzed by current system codes. The results of this work serve as a guide for development of these system codes and indicate areas where models must be improved to adequately address issues with new reactor design and development activities.

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Design of an Innovative Moisture Separator Technology for Use in Nuclear Power Plants: Numerical Approach — Part 1

Volume 1: Beyond Design Basis; Codes and Standards; Computational Fluid Dynamics (CFD); Decontamination and Decommissioning; Nuclear Fuel and Engineering; Nuclear Plant Engineering ◽

10.1115/icone2020-16193 ◽

2020 ◽

Author(s):

Loris Padovan

Keyword(s):

Nuclear Power ◽

Power Plants ◽

Nuclear Power Plants ◽

Water Film ◽

Operating Conditions ◽

Innovative Technology ◽

Separation Performance ◽

Major Advance ◽

Subsequent Formation ◽

Moisture Separator

Abstract The Moisture Separator Re-heater (MSR) is a key component of Nuclear Power Plants (NPP) both in terms of performance and avoiding erosion and erosion/corrosion damage. Wet steam is usually dried in a MSR by inertial separation using separator elements. Depending on the design of a MSR, the technology of separator elements contributes significantly to its size and performance, hence is seen as a subject for in-depth investigation, improvement and innovation. Computational Fluid Dynamics (CFD) has been used to understand the working principles of moisture separating devices, in particular the OpenFOAM platform has been utilized for this scope. Eulerian/Lagrangian models, wall-droplet interaction and water film formation models have been adopted to determine the physical phenomena occurring during the moisture separation process. Additional sub-models have been implemented to make a more robust solver and to solve in a comprehensive way all the possible physical processes: in particular a two-layers turbulence model and a film breakup model have been implemented. An out-of-the-box thinking approach was adopted to devise a new proposed chevron vane. Aerodynamic principles were used to design an innovative concept of separator panel, which can entrap the moisture droplets and water rivulets through a subsequent formation of recirculating steam representing artificial slots (hidden pockets) within the separator channel. The control of the steam separation on precise regions of the separator panel wall, helps the drainage of the water film without the utilization of physical obstacles (pockets or drainage channels). To validate the results achieved from the numerical simulation and to characterize separation performance of a new kind of separator technology, a bespoke test rig has been designed, built and put into operation at typical MSR operating conditions [1]. Throttling calorimeter methodology has been adopted to measure, with very good accuracy, the residual moisture content after the separator. The design developed has shown excellent separation performance. Particularly, this solution will allow improved MSR performance and significantly reduced MSR size. This represents an innovative technology which is a major advance on current technology available within the industry. The novel design features have been patented by General Electric. The first operation of a MSR with this technology is eagerly awaited.

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Design of an Innovative Moisture Separator Technology for Use in Nuclear Power Plants: Experimental Validation — Part 2

Volume 3: Student Paper Competition; Thermal-Hydraulics; Verification and Validation ◽

10.1115/icone2020-16550 ◽

2020 ◽

Author(s):

Carsten Hersberger ◽

Elias Waldvogel ◽

Joshua Bopp ◽

Beat Ribi

Keyword(s):

Moisture Content ◽

Nuclear Power ◽

Power Plants ◽

Nuclear Power Plants ◽

Operating Conditions ◽

Separation Performance ◽

Residual Moisture Content ◽

Test Rig ◽

Residual Moisture ◽

Moisture Separator

Abstract The Moisture Separator Reheater (MSR) is a key component of Nuclear Power Plants (NPP), both in terms of performance and prevention of erosion/corrosion. Wet steam is usually dried in a MSR by inertial separation of the liquid water using separator elements. Depending on the design of the MSR, the technology of the separator elements contributes significantly to its size and performance. An innovative concept of separator panels was conceived by means of aerodynamic principles as outlined in part 1 of this paper [1]. Computational Fluid Dynamics (CFD) has been used to understand the working principles of various moisture separating devices. The investigated separator panels are designed to capture the water droplets in a region of flow separation (invisible pockets) within the separator channels. To characterize the separation performance of these separator panels, a test rig has been developed and built at the University of Applied Sciences Northwestern Switzerland (FHNW). This test rig was then operated at typical MSR operating conditions. To meet the required moisture content and flow conditions, preheated water was injected into the saturated steam flow. In order to measure the residual moisture content after the separation the throttling calorimeter methodology has been adopted. The newly designed panels have shown very good separation performance. According to the measurements carried out, a residual moisture content of less than 0.1 % can be guaranteed. The innovative technology, which clearly differentiates the OEM, for who this research was carried out, from its competitors, will allow considerable size and cost reduction as well as opportunities to retrofit existing MSRs.

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