Reactor core rapid DNBR calculation method combining coarse and fine grids

Abstract

The invention belongs to the technical field of online monitoring thermal safety margin calculation of a reactor core, and particularly relates to a rapid DNBR calculation method of a reactor core with combination of coarse and fine grids. Comprising the following steps: step 1, dynamically dividing sub-channels; 2, sorting a sub-channel calculation model; and step 3, automatically driving a sub-channel program. The method has the beneficial effects that the hot spot area of the reactor core is positioned by utilizing the real-time three-dimensional power distribution obtained in the online monitoring system, and the sub-channel grid which is gradually coarsened from the hot spot fine grid to the combination of the thick and thin grids of the whole reactor is automatically established based on the hot spot position; and a sub-channel model considering precision and speed is established in combination with configuration parameters, so that the accurate minimum DNBR and position of the reactor core can be obtained in real time. The whole method is deeply embedded into an online monitoring system, and the intervention of avoiding personnel is fully automatically realized from reading power distribution, establishing a model, obtaining a result and feeding back the result to a system platform for presentation.

Description

Technical Field

[0001] The invention belongs to the technical field of core online monitoring thermal safety margin calculation, and in particular relates to a core fast DNBR calculation method combining coarse and fine grids. Background Art

[0002] The existing DNBR calculation process for the core mostly adopts a relatively simplified or conservative calculation method, such as

[0003] 1) Based on the power distribution of the component or a quarter of the component, combined with the same channel flow, the sub-channel simulation is directly performed. This calculation process is relatively rough, and the results are quite different from the actual values;

[0004] 2) Based on the component power and the conservative distribution of the preset components, the conservative power distribution of the component rod bundle is converted, and based on this conservative power distribution, sub-channel simulation is performed to realize the calculation of DNBR.

[0005] Both of the above methods cannot reasonably reflect the actual DNBR of the current core state. At the same time, if detailed sub-channel calculations are performed based on the actual power distribution of the power rods in the current core, the amount of calculation is too large to meet the real-time presentation requirements in the online monitoring system. Summary of the invention

[0006] The purpose of the present invention is to provide a core fast DNBR calculation method combining coarse and fine grids, which is used to solve the problem of automatic and efficient DNBR calculation capability during core online monitoring. The method is embedded in the online monitoring system, and can automatically establish a sub-channel division that gradually coarsens from a fine grid in the hot zone to a coarse and fine grid combination of the entire stack according to the real-time hot spot position of the core, and thereby automatically match and organize all sub-channel information and control parameter information in combination with the layout and geometric parameters of components and cores, real-time core state parameters and core power distribution in the online monitoring system, and prefabricated sub-channel calculation control parameters, and finally, based on the organized calculation information, the sub-channel calculation module is automatically driven to complete the calculation and feedback the minimum DNBR value and position information to the online monitoring system, thereby forming a complete closed loop of fast and automated sub-channel calculation.

[0007] The technical solution of the present invention is as follows: A method for calculating the core fast DNBR by combining coarse and fine grids, comprising the following steps:

[0008] Step 1: Dynamically divide sub-channels;

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

[0010] Step 3: Automatically drive the sub-channel program.

[0011] 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 combines coarse and fine grids from the hotspot fine grid area to the entire 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, find the location of the component and rod bundle where the hottest point of the core is located under the current power distribution, and define a 3x3 component area with the hot component as the center as the core solution area that requires a fine grid. If the hot component is at the edge of the core, remove the position without a component when forming the 3x3 component area;

[0014] Step 12: Fine mesh the 3x3 thermal component area. According to the determined position of the thermal rod bundle, take the coolant channel formed by the four rod bundles clockwise of the thermal rod bundle as the center, define an 8x8 sub-channel fine mesh area as the minimum DNBR solution key area, take the fine mesh area as the center, and divide the 3x3 and 3x8 lumped coolant transition channel areas clockwise from the upper left corner. Then, lumped the remaining channels in the thermal component area. First, complete the lumped channel division of two groups in the upper right, lower left order of the transition channel area. The first layer is based on the lumped channel 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, divide the isolated areas on the remaining four corners into lumped coolant channels respectively;

[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 entire core range. First, the hot component area is taken as the center, and the channel area with four components lumped is 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 whole core modeling coverage is completed;

[0016] Step 14: After the sub-channels are reasonably divided, the divided sub-channels are numbered in sequence from the hot zone fine grid, the lumped transition zone to the component lumped zone, and the correlation information between the channels is sorted out.

[0017] The step 2 obtains the division information of the coolant sub-channels of the whole reactor after the dynamic sub-channel division according to the core power distribution, including the location scale, numbering and related 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.

[0018] The step 2 includes arranging the information required for sub-channel program calculation based on the above parameter information combined with the sub-channel division information, providing the core assembly distribution, 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 in the core layout parameters, and 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;

[0019] 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 sort out 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.

[0020] 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 whole stack and its core position.

[0021] The beneficial effects of the present invention are as follows: the present invention uses the real-time three-dimensional power distribution obtained in the online monitoring system to locate the hotspot area of ​​the core, automatically establishes a sub-channel grid based on the hotspot position, which is gradually coarsened from the fine grid of the hot zone to the coarse and fine grid of the whole stack, and establishes a sub-channel model that takes both accuracy and speed into consideration in combination with the configuration parameters, so that the accurate minimum DNBR and position of the core can be obtained in real time. The entire method is deeply embedded in the online monitoring system, from reading the power distribution, model establishment to obtaining the results and feeding them back to the system platform for presentation, and fully automated to avoid human intervention. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0023] Figure 2 Schematic diagram of the division method of the fine grid in the thermal component;

[0024] Figure 3 The figure is a calculation flow chart of an embodiment of a method for rapid DNBR calculation of a core combining coarse and fine grids provided by the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] The present invention provides a method for calculating the core fast DNBR by combining coarse and fine grids. By embedding the method in the online monitoring system of the square component core, a sub-channel model combining coarse and fine grids of the whole reactor can be dynamically established based on the hotspot position, and the calculation of the DNBR of the whole core can be quickly completed based on the model. The method specifically includes the following steps:

[0027] Step 1: Dynamically divide subchannels

[0028] The power distribution of the core is obtained in real time during the online monitoring operation. Factors such as the movement of the control rods will cause the hotspot position of the core to change at any time. In order to ensure the fine grid channel of the rod bundle level in the hotspot area, the sub-channel division will be reconstructed in real time according to this hotspot area so that the minimum DNBR value of the core can be accurately calculated. The dynamic sub-channel division in the method of the present invention 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 coarse and fine grid combination of the entire core. The method path is:

[0029] Step 11: First, based on the three-dimensional power distribution of the core transmitted by the online monitoring system, find the location of the component (thermal component) and the rod bundle (thermal rod bundle) where the hottest point in the core is located under the current power distribution. Define a 3x3 component area with the thermal component as the center as the core solution area that requires a fine grid. In order to fully ensure the modeling freedom, the thermal component can be located at any position in the core. If it is at the edge of the core, the position without the component is removed when forming the 3x3 component area.

[0030] Step 12: Fine mesh the 3x3 thermal component area. According to the determined position of the thermal rod bundle, 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. With the fine mesh area as the center, divide the 3x3 and 3x8 lumped coolant transition channel areas clockwise from the upper left corner. After that, the remaining channels in the thermal component area need to be lumped. First, complete the lumped channel division of two groups in the upper right, lower left order 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 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 component area, it is necessary to lump the component coolant channels in the entire core. First, with the hot component area as the center, a channel area with a maximum of four components lumped based on the component valence channel is formed clockwise, and then the component lumped scale is gradually coarsened toward the periphery according to the sequential channel rule, and finally the full core modeling coverage is completed.

[0032] Step 14: After the sub-channels are reasonably divided, the divided sub-channels are numbered in sequence from the hot zone fine grid, the lumped transition zone to the component lumped zone, and the correlation information between the channels is sorted out.

[0033] The sub-channel position scale, number and related 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 will be sorted out in combination with the configuration file, which will serve as the basis for further preparation of 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 coolant sub-channel of the whole reactor is obtained, mainly the location scale, number and related information of the sub-channel. It is necessary to organize the geometric parameters, resistance parameters and power distribution information of the channel. In order to ensure high-degree-of-freedom sub-channel division modeling, the basic parameters required for the sub-channel analysis program input are preset through the configuration file, mainly including component and core layout parameters and model calculation parameters. In addition, the operating status parameters of the core are updated in real time by the online monitoring system. Based on the above parameter information combined with the sub-channel division information, the sub-channel program calculates the required information:

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

[0037] 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, etc. These parameter information is necessary information 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, including inlet temperature, inlet flow, outlet pressure, power distribution, etc. During the implementation of the method, these parameters are transmitted in real time by the online monitoring system to update the boundary conditions in the sub-channel program model and the power distribution in each sub-channel.

[0039] Therefore, the sub-channel program input card will first organize the geometric dimensions and correlations of all sub-channels based on the sub-channel division results and the core layout parameters, then set the calculation control parameters in the input card by the model calculation parameters, and finally use the state parameters of the online monitoring system to update the boundary conditions and power distribution to complete the preparation of the input card.

[0040] Step 3: Automatically drive the subchannel program

[0041] Since the online monitoring system is in continuous operation, the method of the present invention will also be continuously implemented. Therefore, it is necessary to automatically calculate the sub-channel thermal hydraulics and DNBR after completing the sub-channel modeling, and calculate the minimum DNBR value of the whole stack and its core location. After the sub-channel model is completed, the method continuously executes the import calculation model into the sub-channel analysis program to realize the calculation and feedback the DNBR information to the online monitoring system, which is displayed to the operator for judgment.

[0042] The present invention is characterized as follows:

[0043] The layout information of the square component rod bundle and the core component, the axial distribution information of the component grid are preset, and the sub-channel types of all possible rod bundle type combinations are provided as the basis for the arrangement of parameters after the dynamic sub-channel division; the sub-channel thermal hydraulic calculation is separated to fix the parameters under the dynamic sub-channel grid, mainly including the fluid physical property generation table, axial grid, heat transfer relationship and friction relationship coefficient and calculation control parameters, etc., which are directly set when generating the input information of the sub-channel analysis program; the program dynamic sub-channel division obtains the position of the component and the rod bundle where the hottest point is located according to the real-time three-dimensional power distribution of the core, and divides all the coolant channels in the core into hot spot fine grids. The sub-channel division model is a combination of coarse and fine grids, which realizes a smooth transition from the hot zone to the whole core. The sub-channel model obtained by the dynamic sub-channel division method, combined with the preset distribution parameters and calculation control parameter information, automatically completes the geometry and calculation parameter arrangement of all sub-channels, and automatically completes the power allocation and boundary condition setting of all sub-channels. After the program completes the modeling, it drives the sub-channel analysis program library by itself, imports the model information, and quickly realizes the thermal fluid and DNBR calculation of the whole reactor sub-channel, and transmits the minimum value of DNBR and the component, rod bundle and axial position information to the online monitoring system. A model is established for the conventional square component pressurized water reactor, and it is configured in the corresponding online monitoring system to realize data transmission and complete the rapid calculation of DNBR in real time.

[0044] The present invention is aimed at the square component core and serves as the driving module of the online monitoring system. Therefore, the calculation sequence will be launched only after the online monitoring driver issues a call instruction. First, the above-mentioned component and core geometric parameters and calculation model parameters are configured first, and then the following steps will be implemented:

[0045] Read the core three-dimensional power distribution and core flow, inlet temperature, outlet pressure and other state parameter information obtained from the online monitoring system;

[0046] According to the core three-dimensional power distribution, the positions of the components and rod bundles where the power hot spots of the entire core are located are obtained, and the position information is transmitted to the automatic sub-channel establishment module;

[0047] In the automatic sub-channel establishment module, the sub-channels are divided by partition. First, the fine grid method is called to divide the hot rods of the hot components into fine grids and number them. Then, the transition lumped grid method is called to divide the lumped coolant channels around the fine grids and number them. Finally, the component lumped grid method is called to establish the lumped component coolant channels of the entire core from the hot zone component position and number them.

[0048] Arrange the numbers of all coolant channels to obtain related information, and pass it to the sub-channel model preparation module, call the module to read the configuration parameters for all sub-channel geometric parameters, power distribution settings, set program calculation parameters and boundary conditions to complete the preparation of input information required for sub-channel calculation;

[0049] Drive the sub-channel analysis library, import the prepared sub-channel model information, quickly realize the calculation of thermal fluid and DNBR of the whole pile sub-channel, and transmit the minimum value of DNBR and the component, rod bundle and axial position information to the online monitoring system;

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

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that modifying the technical solutions described in the aforementioned embodiments, or replacing some or all of the technical features therein by equivalents, does not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A core fast DNBR calculation method combining coarse and fine grids, characterized in that: The steps include: Step 1: Dynamically divide sub-channels; Step 2: Arrange the sub-channel calculation model; Step 3: Automatically drive the sub-channel program.

2. A core fast DNBR calculation method combining coarse and fine grids as claimed in claim 1, characterized in that: 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 combines coarse and fine grids from the hotspot fine grid area to the entire core.

3. A core fast DNBR calculation method combining coarse and fine grids as claimed in claim 2, characterized in that: The step 1 comprises: Step 11: First, based on the three-dimensional power distribution of the core transmitted by the online monitoring system, find the location of the component and rod bundle where the hottest point of the core is located under the current power distribution, and define a 3x3 component area with the hot component as the center as the core solution area that requires a fine grid. If the hot component is at the edge of the core, remove the position without a component when forming the 3x3 component area; Step 12: Fine mesh the 3x3 thermal component area. According to the determined position of the thermal rod bundle, take the coolant channel formed by the four rod bundles clockwise of the thermal rod bundle as the center, define an 8x8 sub-channel fine mesh area as the minimum DNBR solution key area, take the fine mesh area as the center, and divide the 3x3 and 3x8 lumped coolant transition channel areas clockwise from the upper left corner. Then, lumped the remaining channels in the thermal component area. First, complete the lumped channel division of two groups in the upper right, lower left order of the transition channel area. The first layer is based on the lumped channel 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, divide the isolated areas on the remaining four corners into lumped coolant channels respectively; 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 entire core range. First, the hot component area is taken as the center, and the channel area with four components lumped is 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 whole core modeling coverage is completed; Step 14: After the sub-channels are reasonably divided, the divided sub-channels are numbered in sequence from the hot zone fine grid, the lumped transition zone to the component lumped zone, and the correlation information between the channels is sorted out.

4. The method for calculating the core fast DNBR by combining 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 whole reactor after the dynamic sub-channel division according to the core power distribution, including the location scale, numbering and related 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.

5. A core fast DNBR calculation method combining coarse and fine grids as claimed in claim 4, 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, providing 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 the assembly in the core layout parameters, and 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.

6. A method for calculating the core fast DNBR by combining coarse and fine grids as claimed in claim 5, 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 sort out 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.

7. The method for fast DNBR calculation of a core 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 whole stack and its core position.

Images