Method for analyzing migration and deposition of activated corrosion products in main pipe of pressurized water reactor unit

Abstract

The application discloses a method for analyzing migration and deposition of activated corrosion products of a pressurized water reactor unit main pipeline, and comprises the following steps: selecting a particle phase deposition-erosion model on a CFD platform; self-defining a dissolution-precipitation mechanism model; determining calculation working conditions and boundary conditions of the CFD platform; wherein the calculation working conditions comprise: transient operation working conditions of the unit under different three-dimensional flow fields, temperature fields and pressure fields in a unit overhaul stage; performing fluid grid division on a pre-built main pipeline model; after the grid is imported into the CFD platform and the particle phase deposition-erosion model and the dissolution-precipitation mechanism model are set and coupled, the deposition rate of the activated corrosion products of the main pipeline under the transient operation working conditions of the unit under different three-dimensional flow fields, temperature fields and pressure fields in the unit overhaul stage is solved to be more accurate and effective, which is of great significance to safe and economic operation of a nuclear power unit.

Description

Technical Field

[0001] This invention relates to the field of nuclear power plant operation and overhaul technology, and in particular to a method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit. Background Technology

[0002] During unit operation and overhaul, activated corrosion products from the reactor core and steam generator will enter the main pipeline and migrate and deposit in other systems in large quantities. The corrosion of the primary loop structural materials of the pressurized water reactor (PWR) under high temperature and pressure conditions not only affects reactor safety, but the migration of corrosion products with the coolant in the primary loop can also cause activation reactions under neutron field irradiation in the reactor core, leading to the production of radionuclides. The radiation fields generated by these radionuclides deposited throughout the primary loop are the main source of personal dose received by maintenance personnel during PWR overhauls, and the presence of a shutdown dose field significantly increases the cost of power plant maintenance.

[0003] The migration models of activation corrosion products of primary loop structural materials at home and abroad (such as PACTOLE, CORA-II, CRUDSIM, etc.) divide the primary loop into several nodes according to the in-pile and out-of-pile conditions and the corresponding physical states. The transport mechanism between nodes is modeled and calculated using semi-empirical formulas, and the corresponding algebraic equations or first-order differential equations are applied to describe the processes involving the conversion rate. The conversion coefficients are either obtained through theoretical calculations or derived by comparing with the actual operation data of the reactor.

[0004] Existing models primarily rely on concentration-difference driven mass balance and concentration equations for solving problems, representing one-dimensional system-level modeling and analysis methods. Furthermore, current models are largely based on stable unit operating conditions, lacking the ability to analyze the migration and deposition of activated corrosion products under transient operating conditions.

[0005] Existing technical solutions do not take into account the influence of the complex three-dimensional flow field, temperature field and pressure field of pipelines in actual units on the deposition and migration of activated corrosion products, and cannot analyze and obtain a relatively accurate deposition rate of activated corrosion products in pipelines under transient operating conditions of the unit. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to address at least one deficiency of the related technologies mentioned in the background: the existing technical solutions do not consider the influence of the complex three-dimensional flow field, temperature field and pressure field of the pipeline in the actual unit on the deposition and migration of activated corrosion products, and cannot analyze and obtain a relatively accurate deposition rate of activated corrosion products in the pipeline under the transient operating conditions of the unit. The present invention provides a method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit.

[0007] The technical solution adopted by this invention to solve its technical problem is: to construct a method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit, comprising the following steps:

[0008] Model selection steps: Select the granular phase deposition-erosion model on the CFD platform;

[0009] Model customization steps: Based on the mechanism of ion-state activated corrosion products precipitating into particulate activated corrosion products and particulate activated corrosion products dissolving into ion-state activated corrosion products, a custom dissolution-precipitation mechanism model is established;

[0010] Initialization steps: Determine the calculation conditions and boundary conditions of the CFD platform; wherein, the calculation conditions include: transient operating conditions under different three-dimensional flow fields, temperature fields and pressure fields during the unit overhaul stage;

[0011] Mesh generation steps: Perform fluid mesh generation on the pre-built main pipeline model;

[0012] Calculation steps: After importing the mesh into the CFD platform and setting and coupling the particle phase deposition-erosion model and the dissolution-precipitation mechanism model, the deposition rate of the activated corrosion products of the main pipeline under transient operating conditions of different three-dimensional flow fields, temperature fields and pressure fields during the unit overhaul stage is obtained.

[0013] Preferably, in the method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to the present invention, the method further includes:

[0014] Geometric modeling steps: Perform three-dimensional geometric modeling based on the structural dimensions of the main pipeline to obtain the main pipeline model.

[0015] Preferably, in the method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to the present invention, the structural dimensions of the main pipeline include: pipe section length, pipe diameter, bend radius of curvature, and weld length.

[0016] Preferably, in the method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to the present invention, the model selection step further includes:

[0017] Based on the flow of coolant carrying particulate-phase activated corrosion products in the main pipeline, a multiphase flow model and a turbulent flow model are selected on the CFD platform.

[0018] Preferably, in the method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to the present invention, the method further includes:

[0019] Correction steps: Compare and verify the deposition rate obtained from the calculation steps with the measured deposition rate under transient operating conditions of different three-dimensional flow fields, temperature fields and pressure fields during the overhaul of the unit. If the deviation is greater than the threshold, then correct the selection and settings of the model.

[0020] Preferably, in the method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to the present invention, the boundary conditions include: a velocity inlet and a no-slip boundary.

[0021] Preferably, in the method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to the present invention, the velocity inlet is the inlet of the main pipeline model, and the non-slip boundary is the inner wall surface of the main pipeline model.

[0022] Preferably, in the method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to the present invention, the method further includes:

[0023] Based on multiple sets of structured grids, the grid division step and the calculation step are executed respectively. Grid independence is verified based on the maximum deposition rate. Considering the convergence time and calculation accuracy, a set of benchmark grids is determined.

[0024] Preferably, in the method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to the present invention, the calculation conditions further include: the unit power operation conditions.

[0025] The present invention also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit as described in any of the preceding claims.

[0026] By implementing this invention, the following beneficial effects are achieved:

[0027] This invention is based on three-dimensional CFD analysis technology. It sets up and couples a particle phase deposition-erosion model and a dissolution-precipitation mechanism model on the CFD platform. It also comprehensively considers the influence of transient operating conditions under different three-dimensional flow fields, temperature fields and pressure fields during the unit overhaul stage on the migration and deposition of activated corrosion products in the main pipeline. It can more accurately and effectively predict the deposition rate distribution of activated corrosion products in the main pipeline, which is of great significance to the safe and economical operation of nuclear power units. Attached Figure Description

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0029] Figure 1 This invention describes the interconversion relationship of the morphology of activated corrosion products within the hot section, transition section, and cold section.

[0030] Figure 2This is a flowchart of the method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to the present invention;

[0031] Figure 3 This is a cloud map showing the deposition rate of the hot-section activated corrosion products of this invention. Detailed Implementation

[0032] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0033] It should be noted that the flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0034] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software or in different network and / or processor devices and / or microcontroller devices.

[0035] The main piping of a pressurized water reactor unit connects the reactor, steam generator, and main pumps, forming a closed loop for transferring reactor heat, known as the primary loop. A typical pressurized water reactor has three identical loops, each with a main piping section consisting of a hot section (from reactor outlet to steam generator inlet), a transition section (from steam generator outlet to main pump inlet), and a cold section (from main pump outlet to reactor inlet).

[0036] During unit operation and overhaul, activated corrosion products in the reactor core and those deposited in the SG will enter the main pipeline and migrate and deposit to other systems. Therefore, based on CFD (Computational Fluid Dynamics) analysis technology, coupled with a mechanism model of the migration and deposition process of activated corrosion products, in-depth analysis of the migration and deposition process of activated corrosion products in the main pipeline and the three-dimensional deposition distribution of activated corrosion products in the main pipeline is of great significance for the safe and economical operation of nuclear power units.

[0037] The activated corrosion products in the primary main pipeline are mainly classified into two types based on their morphology: dissolved ionic activated corrosion products and particulate activated corrosion products. The morphology transformation process is as follows: During flow, as the local solubility decreases, the ionic activated corrosion products in the coolant precipitate out as particulate activated corrosion products in the coolant. These particulate activated corrosion products aggregate and grow, eventually depositing on the pipe wall of the main pipeline. Conversely, under the erosive action of the coolant, the activated corrosion products on the deposit layer become particulate and enter the coolant. These particulate activated corrosion products then transform into ionic activated corrosion products as the local solubility changes. The interconversion relationships of activated corrosion product morphologies in the hot section, transition section, and cold section are as follows: Figure 1 As shown.

[0038] Specifically, such as Figure 2 As shown, one embodiment of the present invention discloses a method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit, comprising the following steps:

[0039] Model selection steps: Select the granular phase deposition-erosion model on the CFD platform;

[0040] Model customization steps: Based on the mechanism of ion-activated corrosion products precipitating into particulate-activated corrosion products and particulate-activated corrosion products dissolving into ion-activated corrosion products, a custom dissolution-precipitation mechanism model is established.

[0041] Initialization steps: Determine the calculation conditions and boundary conditions of the CFD platform; among which, the calculation conditions include: transient operating conditions under different three-dimensional flow fields, temperature fields and pressure fields during the unit overhaul stage;

[0042] Mesh generation steps: Perform fluid mesh generation on the pre-built main pipeline model;

[0043] Calculation steps: After importing the mesh into the CFD platform and setting up and coupling the particle phase deposition-erosion model and the dissolution-precipitation mechanism model, the deposition rate (kg / m) of the activated corrosion products of the main pipeline under transient operating conditions of different three-dimensional flow fields, temperature fields, and pressure fields during the unit overhaul stage is obtained. 2 / s), Figure 3 The deposition rate contour plot of the hot-section activated corrosion products is shown.

[0044] All of the above steps can be performed based on user input commands, including model selection, model customization, mesh generation, and calculation. Furthermore, all of these steps can be completed on the CFD platform, or the model customization and mesh generation steps can be completed in other software programs, while the model selection, initialization, and calculation steps can be completed on the CFD platform.

[0045] Specifically, in this embodiment, the method further includes:

[0046] Geometric modeling steps: Perform 3D geometric modeling based on the structural dimensions of the main pipeline to obtain the main pipeline model. The structural dimensions of the main pipeline include: pipe segment length, pipe diameter, bend radius of curvature, and weld length.

[0047] In this embodiment, the model selection step further includes:

[0048] Based on the flow of coolant carrying particulate activated corrosion products in the main pipeline, a multiphase flow model and a turbulent flow model are selected on the CFD platform.

[0049] Based on the activity of the source nuclides in the unit design, the mass flow rates of different nuclides are calculated. Generally, the proportion of nuclides in the coolant is less than 10%, belonging to the rarefied phase. Therefore, the multiphase flow model should adopt the discrete phase (DPM) model, considering the interaction force between the continuous phase and the discrete phase. During the migration and deposition of corrosion products, the distribution of the turbulent field has a key influence. Therefore, the standard k-epsilon model is selected as the turbulence model, the erosion model is selected for particle deposition in the particle phase deposition-erosion model, and the accretion model is selected for particle erosion in the particle phase deposition-erosion model.

[0050] To ensure the accuracy of the analytical method, the method also includes:

[0051] Correction steps: Compare and verify the deposition rate obtained from the calculation steps with the measured deposition rate under transient operating conditions of different three-dimensional flow fields, temperature fields and pressure fields during the unit overhaul stage. If the deviation is greater than the threshold, then correct the selection and setting of the model, that is, at least one of the following: multiphase flow model, turbulence model, particle phase deposition-erosion model and dissolution-precipitation mechanism model, until the verification is passed.

[0052] In this embodiment, the calculation conditions also include: unit power operation conditions.

[0053] Accordingly, the calculation steps also solve for the deposition rate of activated corrosion products in the main pipeline under the unit's power operating conditions.

[0054] The correction process also compares and verifies the deposition rate obtained from the calculation step with the measured deposition rate under different three-dimensional flow fields, temperature fields, and pressure fields during the unit's power operation and the transient operation under different three-dimensional flow fields, temperature fields, and pressure fields during the unit's overhaul stage.

[0055] In this embodiment, to improve analysis efficiency, the method further includes:

[0056] Based on multiple sets of structured grids, the grid generation and calculation steps are performed separately. Grid independence is verified based on the maximum deposition rate. Considering the convergence time and calculation accuracy, a benchmark grid is determined. That is, if a grid of 2 million can achieve the deposition rate of a grid of 3 million, then a grid of 2 million is selected.

[0057] In this embodiment, the boundary conditions include: a velocity inlet and a no-slip boundary. The velocity inlet is the inlet of the main pipe model, and the no-slip boundary is the inner wall surface of the main pipe model.

[0058] One embodiment of the present invention discloses a computer-readable storage medium storing a computer program thereon. When the computer program is executed by a processor, it implements the method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit as described in the above embodiment, which will not be repeated here.

[0059] By implementing this invention, the following beneficial effects are achieved:

[0060] This invention is based on three-dimensional CFD analysis technology. It sets up and couples a particle phase deposition-erosion model and a dissolution-precipitation mechanism model on the CFD platform. It also comprehensively considers the influence of transient operating conditions under different three-dimensional flow fields, temperature fields and pressure fields during the unit overhaul stage on the migration and deposition of activated corrosion products in the main pipeline. It can more accurately and effectively predict the deposition rate distribution of activated corrosion products in the main pipeline, which is of great significance to the safe and economical operation of nuclear power units.

[0061] It is understood that the above embodiments only illustrate some implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that for those skilled in the art, without departing from the concept of the present invention, the above embodiments or technical features can be freely combined, and several modifications and improvements can be made. These all fall within the protection scope of the present invention. That is, the embodiments described "in some embodiments" can be freely combined with any of the embodiments above and below. Therefore, all equivalent transformations and modifications made within the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit, characterized in that, Includes the following steps: Model selection steps: Select the granular phase deposition-erosion model on the CFD platform; Model customization steps: Based on the mechanism of ion-state activated corrosion products precipitating into particulate activated corrosion products and particulate activated corrosion products dissolving into ion-state activated corrosion products, a custom dissolution-precipitation mechanism model is established; Initialization steps: Determine the calculation conditions and boundary conditions of the CFD platform; wherein, the calculation conditions include: transient operating conditions under different three-dimensional flow fields, temperature fields and pressure fields during the unit overhaul stage; Mesh generation steps: Perform fluid mesh generation on the pre-built main pipeline model; Calculation steps: After importing the mesh into the CFD platform and setting and coupling the particle phase deposition-erosion model and the dissolution-precipitation mechanism model, the deposition rate of the activated corrosion products of the main pipeline under transient operating conditions of different three-dimensional flow fields, temperature fields and pressure fields during the unit overhaul stage is obtained.

2. The method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to claim 1, characterized in that, The method further includes: Geometric modeling steps: Perform three-dimensional geometric modeling based on the structural dimensions of the main pipeline to obtain the main pipeline model.

3. The method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to claim 2, characterized in that, The structural dimensions of the main pipeline include: pipe section length, pipe diameter, bend radius of curvature, and weld length.

4. The method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to claim 1, characterized in that, The model selection step also includes: Based on the flow of coolant carrying particulate-phase activated corrosion products in the main pipeline, a multiphase flow model and a turbulent flow model are selected on the CFD platform.

5. The method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to claim 1 or 4, characterized in that, The method further includes: Correction steps: Compare and verify the deposition rate obtained from the calculation steps with the measured deposition rate under transient operating conditions of different three-dimensional flow fields, temperature fields and pressure fields during the overhaul of the unit. If the deviation is greater than the threshold, then correct the selection and settings of the model.

6. The method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to claim 1, characterized in that, The boundary conditions include: velocity inlet and no-slip boundary.

7. The method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to claim 6, characterized in that, The velocity inlet is the inlet of the main pipe model, and the non-slip boundary is the inner wall surface of the main pipe model.

8. The method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to claim 1, characterized in that, The method further includes: Based on multiple sets of structured grids, the grid division step and the calculation step are executed respectively. Grid independence is verified based on the maximum deposition rate. Considering the convergence time and calculation accuracy, a set of benchmark grids is determined.

9. The method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit according to claim 1, characterized in that, The calculation conditions also include: unit power operation conditions.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the method for analyzing the migration and deposition of activated corrosion products in the main pipeline of a pressurized water reactor unit as described in any one of claims 1-9.

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