A coarse-fine grid combined method for fast core DNBR calculation

Abstract

The present application belongs to the technical field of core online monitoring thermal safety margin calculation, and particularly relates to a coarse and fine grid combined core fast DNBR calculation method. The method comprises the following steps: step 1, dynamically dividing subchannels; step 2, arranging subchannel calculation models; and step 3, automatically driving subchannel programs. The present application has the beneficial effect that the present application uses real-time three-dimensional power distribution obtained from an online monitoring system to locate hot spot areas of a core, automatically establishes subchannel grids combined by gradually coarsening fine grids in hot areas to coarse grids of the whole core based on the hot spot positions, and establishes subchannel models with both precision and speed by combining configuration parameters, so that accurate minimum DNBR and positions of the core can be obtained in real time. The whole method is deeply embedded in the online monitoring system, from reading power distribution, model establishment to obtaining results and feeding back to the system platform for presentation, and is fully automated to avoid human intervention.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of in-core online monitoring thermal safety margin calculation, and particularly relates to a coarse-fine grid combined in-core fast DNBR calculation method. BACKGROUND

[0002] The existing DNBR calculation process for the in-core is mostly simplified or conservative, such as

[0003] 1) Based on the power distribution of the assembly or quarter assembly, the sub-channel simulation is directly performed in combination with the same channel flow, and the calculation process is relatively rough, and the result is greatly different from the true value;

[0004] 2) Based on the assembly power and the preset assembly conservative distribution, the conservative power distribution of the assembly rod bundle is converted, and the DNBR calculation is realized based on the conservative power distribution.

[0005] The above two methods cannot reasonably reflect the actual DNBR of the current in-core state, and if the detailed sub-channel calculation is performed based on the current in-core actual power rod power distribution, the calculation amount is too large, and the real-time presentation in the online monitoring system cannot be realized. SUMMARY

[0006] The application aims to provide a coarse-fine grid combined in-core fast DNBR calculation method, which is used for solving the automatic and efficient DNBR calculation ability in the in-core online monitoring process, and the method is embedded in the online monitoring system, can automatically establish the sub-channel division combined with the coarse-fine grid from the fine grid in the hot area to the coarse grid in the whole core according to the real-time hot spot position of the in-core, and automatically match and arrange all the sub-channel information and control parameter information in the online monitoring system in combination with the arrangement and geometric parameters of the assembly and the in-core, the real-time state parameters and the in-core power distribution of the in-core, and the prefabricated sub-channel calculation control parameters, finally, the sub-channel calculation module is driven to complete the calculation based on the arranged calculation information, and the minimum DNBR value and the position information are fed back to the online monitoring system, so that the complete closed loop of the fast and automatic sub-channel calculation is formed.

[0007] The technical scheme of the application is as follows: a coarse-fine grid combined in-core fast DNBR calculation method, comprising the following steps:

[0008] Step 1: dynamically dividing sub-channels;

[0009] Step 2: arranging the sub-channel calculation model;

[0010] Step 3: automatically driving the sub-channel program.

[0011] The dynamic sub-channel division in step 1 is divided into three levels of hotspot fine grid, transition lumped grid and component lumped grid, forming a combination of fine and coarse grids from the hotspot fine grid area to the whole core.

[0012] The step 1 comprises:

[0013] Step 11: first, based on the three-dimensional power distribution of the core transmitted by the online monitoring system, the location of the hottest point of the core under the current power distribution and the location of the rod bundle are found out, a 3x3 component area is defined as the core solving area of the fine grid, and if the hot component is in the edge area of the core, the 3x3 component area is removed;

[0014] Step 12: fine grid division is performed on the 3x3 hot component area, according to the determined hot rod bundle position, a 8x8 sub-channel fine grid area is defined as the minimum DNBR solving key area, and the fine grid area is taken as the center, the 3x3 and 3x8 transition channel areas are divided in clockwise order from the top left corner, and then the remaining channels in the hot component area are lumped, first, the two groups of lumped channels are completed in the upper right lower left order in the transition channel area, the first layer is the lumped channel with the maximum size of 14x7 to the edge of the hot component area, and the second layer is the remaining channel lumped part to the edge of the hot component; then the remaining four corner isolated areas are divided into lumped coolant channels;

[0015] Step 13: after completing the fine grid core area and the surrounding transition lumped area in the hot component area, the component coolant channel is lumped in the whole core, first, the hot component area is taken as the center, and four component lumped channel areas are formed in clockwise order based on the component channel, then the component lumped size is gradually coarsened outward according to the sequential channel rule, and finally the whole core modeling is completed.

[0016] Step 14: after reasonable division of the sub-channel, the sub-channels are numbered and the correlation information between the channels is sorted in order from the hot area fine grid, the lumped transition area to the component lumped area.

[0017] The step 2 obtains the division information of the whole core coolant sub-channel after dynamic sub-channel division according to the core power distribution, including the position size, number and correlation information of the sub-channel, the geometric parameters, resistance parameters and power distribution of the channel, and the basic parameters required by the sub-channel analysis program are preset through the configuration file, including the component and core arrangement parameters and model calculation parameters.

[0018] The step 2 comprises arranging the information required by the sub-channel program based on the above-mentioned parameter information and sub-channel division information, providing the core assembly distribution in the core layout parameter, the rod bundle distribution in the assembly, the grid distribution in the assembly, and the geometric size information of the rod bundle and the assembly, and defining the coolant sub-channel types surrounded by different types of rod bundles in the file as the basis for judging the statistical sub-channel geometric information; the model calculation parameter provides the fluid property table generation range control parameter, the grid resistance coefficient, the axial grid, the heat transfer relationship formula and the friction relationship formula coefficient, and the program solving control parameter;

[0019] The step 2 comprises the operating state parameter, which specifies the boundary conditions required by the sub-channel program model, including the inlet temperature, the inlet flow, the outlet pressure and the power distribution; thus, the sub-channel program input card will first arrange the geometric size of all sub-channels and the correlation according to the sub-channel division result and in combination with the core layout parameter, then set the calculation control parameter in the input card by the model calculation parameter, and finally complete the preparation of the input card by updating the boundary conditions and the power distribution by using the state parameter of the online monitoring system.

[0020] The step 3 comprises automatically performing the sub-channel thermal hydraulic and DNBR calculation after completing the sub-channel modeling, and statistically obtaining the minimum DNBR value of the whole core and the core position thereof.

[0021] The present application has the beneficial effects that the present application uses the real-time three-dimensional power distribution obtained from the online monitoring system to locate the hot spot area of the core, automatically establishes the sub-channel grid combined with the fine grid in the hot area gradually coarsening to the coarse grid of the whole core based on the hot spot position, establishes the sub-channel model with consideration of the precision and speed in combination with the configuration parameter, and can obtain the accurate minimum DNBR and position of the core in real time. The whole method is deeply embedded in the online monitoring system, from reading the power distribution, model establishment to obtaining the result and feeding back to the system platform for presentation, and is fully automated to avoid the intervention of personnel. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a schematic diagram of the distribution of hot assemblies in different positions of the core;

[0023] Figure 2 It is a schematic diagram of the division mode of the fine grid in the hot assembly;

[0024] Figure 3 It is a calculation flowchart of one embodiment of the coarse and fine grid combined core fast DNBR calculation method provided by the present application. DETAILED DESCRIPTION

[0025] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0026] The application provides a coarse and fine grid combined core fast DNBR calculation method, which can dynamically establish a full-core coarse and fine grid combined sub-channel model based on a hot spot position by embedding the method in a square assembly core online monitoring system, and can quickly complete the calculation of the full-core DNBR based on the model, and specifically comprises the following steps:

[0027] Step 1: Dynamic division of sub-channels

[0028] The online monitoring system obtains the power distribution of the core in real time during operation, and factors such as control rod action can cause the hot spot position of the core to change at any time. In order to ensure the rod bundle level fine grid channel of the hot spot area, the sub-channel division will be reconstructed in real time according to the hot spot area so as to accurately calculate the minimum DNBR value of the core. The dynamic sub-channel division in the method of the application is divided into three levels of hot spot fine grid, transition lumped grid and assembly lumped grid as a whole, forming a sub-channel division combined with coarse and fine grids from the hot spot fine grid area to the full core, and the method path is

[0029] Step 11: First, based on the three-dimensional power distribution of the core transmitted by the online monitoring system, the position of the hottest point of the core (hot assembly) and the position of the hottest rod bundle (hot rod bundle) under the current power distribution are found. A 3x3 assembly area is defined as the core solving area requiring fine grid with the hot assembly as the center. In order to fully ensure the modeling degree of freedom, the hot assembly can be at any position in the core, and if it is in the edge area of the core, the 3x3 assembly area is removed when forming the 3x3 assembly area.

[0030] Step 12: Fine grid division is performed on the 3x3 hot assembly area. According to the determined hot rod bundle position, a 8x8 sub-channel fine grid area is defined as the minimum DNBR solving key area with the coolant channel formed by the four clockwise rods of the hot rod bundle as the center. Starting from the upper left corner, the 3x3 and 3x8 lumped coolant transition channel areas are sequentially divided clockwise with the fine grid area as the center. Then the remaining channels in the hot assembly area need to be lumped, first completing two sets of lumped channel division in the upper right and lower left of the transition channel area, the first layer is a lumped channel with a maximum size of 14x7 to the edge of the hot assembly area, and the second layer is the remaining channel lumped part to the edge of the hot assembly; then the isolated areas on the remaining four corners are divided into lumped coolant channels.

[0031] Step 13: After completing the fine grid core area and the surrounding transition lumped area in the hot assembly area, assembly coolant channel lumping division needs to be performed in the full core. First, the hot assembly area is taken as the center to form a channel area based on the assembly channel with a maximum of four assembly lumping channels clockwise, then the assembly lumping scale is gradually thickened outward according to the sequential channel rule, and finally the full core modeling is completed.

[0032] Step 14: After the reasonable division of sub-channels, the sub-channels are numbered in turn from the hot zone fine grid, the transition zone to the assembly lumped zone, and the inter-channel correlation information is arranged.

[0033] The sub-channel position scale, numbering, and correlation information obtained in the path process of the above-mentioned dynamic sub-channel division method will be passed to the downstream module, and the geometric parameters of all channels and adjacent channels are arranged in combination with the configuration file, which serves as the basis for further preparing the sub-channel calculation program model downstream.

[0034] Step 2: Arrange the sub-channel calculation model

[0035] After the dynamic sub-channel division according to the core power distribution, the division information of the full-core coolant sub-channels is obtained, mainly the position scale, numbering, and correlation information of the sub-channels. The geometric parameters, resistance parameters, and power distribution information of the channels need to be arranged. To ensure high-degree sub-channel division modeling, the required basic parameters for the sub-channel analysis program input are preset through the configuration file, mainly including assembly and core layout parameters and model calculation parameters. In addition, the operating state parameters of the core are updated in real time by the online monitoring system. Based on the above-mentioned parameter information combined with the sub-channel division information, the information required for the sub-channel program calculation is arranged:

[0036] The core layout parameters provide the core assembly distribution, the rod bundle distribution within the assembly, the grid distribution within the assembly, and the geometric size information of the rod bundle and assembly. The file also defines the coolant sub-channel types surrounded by different types of rod bundles, which serve as the basis for judging the geometric information of the sub-channels.

[0037] The model calculation parameters provide the fluid property table generation range control parameters, grid resistance coefficients, axial grids, heat transfer relationship coefficients, and friction relationship coefficients, as well as program solving control parameters. These parameter information is necessary for sub-channel calculation and does not need to be changed during the dynamic sub-channel division process.

[0038] The operating state parameters specify the boundary conditions required by the sub-channel program model, mainly including inlet temperature, inlet flow rate, outlet pressure, and power distribution. During the implementation of the method, these parameters are updated in real time by the online monitoring system to pass the boundary conditions and power distribution in each sub-channel to the sub-channel program model.

[0039] The sub-channel program input card will first arrange the geometric size and correlation of all sub-channels according to the sub-channel division results combined with the core layout parameters, then set the calculation control parameters in the input card by the model calculation parameters, and finally update the boundary conditions and power distribution by the state parameters of the online monitoring system to complete the preparation of the input card.

[0040] Step 3: Automatically drive the sub-channel program

[0041] Since the online monitoring system is continuously running, the method of the present application will also be continuously implemented, so it is necessary to automatically perform the calculation of the sub-channel thermal hydraulic and DNBR after the completion of the sub-channel modeling, and to statistically obtain the minimum DNBR value of the whole core and the position thereof in the core. After the completion of the arrangement of the sub-channel model, the method continuously performs the import of the calculation model into the sub-channel analysis program to realize the calculation and feedback of the DNBR information to the online monitoring system, so as to display it to the operator for judgment.

[0042] The features of the present application are as follows:

[0043] The arrangement information of the preset square assembly rod bundle and the core assembly, the axial distribution information of the assembly grid, and the sub-channel types of all possible rod bundle type combinations are provided as the basis for the parameter arrangement after the arrangement of the dynamic sub-channel; the fixed parameters of the sub-channel thermal hydraulic calculation under the dynamic sub-channel grid are separated, mainly including the fluid property generation table, the axial grid, the heat transfer relationship formula and the friction relationship formula coefficient, and the calculation control parameters, etc., which are directly set when generating the input information of the sub-channel analysis program; the program dynamically divides the sub-channels according to the position of the hottest point in the assembly and the rod bundle of the real-time three-dimensional power distribution of the core, divides all the coolant channels of the core into three levels of hot spot fine grid, transition lumped grid and assembly lumped grid, realizes the combination of the coarse and fine grid sub-channel division model from the hot area to the whole core, automatically completes the geometric and calculation parameter arrangement of all the sub-channels according to the sub-channel model obtained by the dynamic sub-channel division method, and automatically completes the power distribution and boundary condition setting of all the sub-channels; after the modeling of the program, the sub-channel analysis program library is automatically driven, the model information is imported, the sub-channel thermal hydraulic and DNBR calculation of the whole core is quickly realized, and the minimum value of the DNBR and the information of the assembly, the rod bundle and the axial position are transmitted to the online monitoring system. The model is established for the conventional square assembly pressurized water reactor, and is configured in the corresponding online monitoring system to realize the transmission of data and the real-time calculation of the DNBR.

[0044] The present application is aimed at the square assembly core and is a driving module of the online monitoring system, so the calculation sequence will be unfolded after the calling instruction is issued by the online monitoring driver. First, the above-mentioned assembly and core geometric parameters and calculation model parameters, etc. are configured, and then the following steps are implemented:

[0045] The three-dimensional power distribution of the core obtained by the online monitoring system and the state parameter information of the core flow, inlet temperature and outlet pressure, etc. are read;

[0046] The position of the hottest assembly and rod bundle of the whole core power is obtained according to the three-dimensional power distribution of the core, and the position information is transmitted to the automatic sub-channel establishment module;

[0047] The sub-channel division is divided in the automatic sub-channel establishment module. Firstly, the fine grid method is called to divide and number the position of the hot rod of the hot component. Then, the transition lumped grid method is called to divide and number the lumped coolant channel around the fine grid. Finally, the component lumped grid method is called to establish and number the lumped component coolant channel of the whole core from the position of the hot component.

[0048] The correlation information of the numbering of all the coolant channels is obtained and delivered to the sub-channel model preparation module. The module reads the configuration parameters to set the geometric parameters, power distribution, calculation parameters and boundary conditions of all the sub-channels, and prepares the input information required for the sub-channel calculation.

[0049] The sub-channel analysis program library is driven, the prepared sub-channel model information is imported, the thermal fluid and DNBR calculation of the whole core sub-channel is quickly realized, and the minimum value of the DNBR and the information of the component, rod bundle and axial position are delivered to the online monitoring system.

[0050] If the online monitoring system is not terminated, the system will drive the module to execute the steps a to f cyclically to complete the DNBR monitoring calculation at each time point.

[0051] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: the technical solutions recorded in the foregoing examples are modified, or some or all of the technical features are replaced, without making the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A fast DNBR calculation method for cores combining coarse and fine grids, characterized by: The steps include: Step 1: Dynamically divide sub-channels; The dynamic sub-channel division in step 1 is generally divided into three levels: hotspot fine grid, transition lumped grid, and component lumped grid, forming a sub-channel division that gradually coarsens from the hotspot fine grid area to the entire core. The step 1 comprises: Step 11: First, based on the three-dimensional core power distribution transmitted by the online monitoring system, find the location of the component and rod bundle where the hottest point in the core is located under the current power distribution. Define a 3x3 component area centered on the hot component as the core solution area requiring a fine mesh. If the hot component is at the edge of the core, remove the component-free location when forming the 3x3 component area. Step 12: Fine mesh the 3x3 thermal component area. Based on the determined thermal rod bundle position, define an 8x8 sub-channel fine mesh area as the minimum DNBR solution key area with the coolant channel formed by the four rod bundles clockwise from the thermal rod bundle as the center. Starting from the upper left corner, the fine mesh area is divided into 3x3 and 3x8 lumped coolant transition channel areas in clockwise order. Then, the remaining channels in the thermal component area are lumped. First, two groups of lumped channel divisions are completed in the upper right, lower left, and upper right directions of the transition channel area. The first layer is based on the lumped channels with a maximum size of 14x7 from the edge of the thermal component area, and the second layer is the lumped part of the remaining channels to the edge of the thermal component. Then, the isolated areas in the remaining four corners are divided into lumped coolant channels. Step 13: After completing the fine-grid core area and the surrounding transition lumped area within the thermal component region, lumped component coolant channels are divided throughout the entire core. Starting with the thermal component region as the center, four component lumped channel areas are formed clockwise based on the component valence channel. Then, the component lumped scale is gradually coarsened toward the periphery according to the sequential channel rule, and finally, the entire core modeling coverage is completed. Step 14: After the sub-channels are reasonably divided, number the divided sub-channels in sequence from the hot zone fine grid, the lumped transition zone to the component lumped zone and organize the correlation information between the channels; Step 2: Arrange the sub-channel calculation model; Step 3: Automatically drive the sub-channel program.

2. The method for fast core DNBR calculation using a combination of coarse and fine grids according to claim 1, characterized in that: The step 2 obtains the division information of the coolant sub-channels of the entire reactor after the dynamic sub-channel division according to the core power distribution, including the location scale, numbering and association information of the sub-channels, organizes the geometric parameters, resistance parameters and power distribution of the channels, and presets the basic parameters required for the sub-channel analysis program input through the configuration file, including component and core layout parameters and model calculation parameters.

3. The method for fast core DNBR calculation using a combination of coarse and fine grids according to claim 2, characterized in that: The step 2 includes organizing the information required for sub-channel program calculation based on the above parameter information combined with the sub-channel division information. The core layout parameters provide the core component distribution, the rod bundle distribution within the component, the grid distribution within the component, and the geometric size information of the rod bundle and the component. The file defines the coolant sub-channel types surrounded by different types of rod bundles as the basic judgment basis for statistical sub-channel geometric information; the model calculation parameters provide the fluid property table generation range control parameters, grid resistance coefficient, axial grid, heat transfer relationship and friction relationship coefficient, and program solution control parameters.

4. The method for fast core DNBR calculation using a combination of coarse and fine grids according to claim 3, characterized in that: The step 2 includes operating state parameters that specify the boundary conditions required by the sub-channel program model, including inlet temperature, inlet flow, outlet pressure and power distribution; thus, the sub-channel program input card will first be based on the sub-channel division results, combined with the core layout parameters to organize the geometric dimensions and correlations of all sub-channels, and then the calculation control parameters in the input card are set by the model calculation parameters, and finally the boundary conditions and power distribution are updated using the state parameters of the online monitoring system to complete the preparation of the input card.

5. The method for fast core DNBR calculation using a combination of coarse and fine grids according to claim 1, characterized in that: The step 3 includes automatically calculating the sub-channel thermal hydraulics and DNBR after completing the sub-channel modeling, and calculating the minimum DNBR value of the entire stack and its core position.

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