A simulation processing method for CCFL phenomenon in downcomer based on RELAP5

Abstract

The application discloses a simulation processing method for CCFL phenomenon of a downcomer based on RELAP5, and specifically comprises the following steps: S1, obtaining geometric parameters and operation condition parameters of the downcomer, making a node division scheme, and obtaining node information, wherein the node information comprises a number of circumferential nodes, a number of axial nodes, and a number of single pipe nodes between multiple pipes; S2, writing a RELAP5 program on an Input card, performing a thermal hydraulic calculation, and obtaining a first parameter which changes in real time; S3, extracting a second parameter through a strip card to obtain a third parameter, wherein the third parameter comprises gas-liquid phase flow, pressure and velocity; S4, importing the third parameter into a processing software MATLAB, reading a fourth parameter of the gas-liquid phase according to the node information set in S1; and S5, performing two-dimensional cloud chart drawing on the fourth parameter in S4. The application can quickly obtain required results under different node division schemes and different geometric parameters and operation parameters, and improve analysis efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear power, in particular to a simulation processing method for CCFL phenomenon in downcomer based on RELAP5. BACKGROUND

[0002] Based on the importance of nuclear safety, in order to avoid the occurrence of nuclear safety accidents, or to weaken the impact after the accident as much as possible, and to improve the margin of human intervention after the accident, nuclear power researchers have conducted a lot of accident analysis, established different experimental loops, and developed special software (such as RELAP5) to numerically simulate the calculation of nuclear power plant systems.

[0003] When a coolant loss accident occurs, the coolant flow and pressure in the primary loop decrease, and the coolant may not continue to circulate under normal working conditions. If the safety system has not been activated or has failed, the coolant needs to rely on the backflow to the core for cooling at this time. However, due to insufficient coolant flow in the core, the residual coolant in the core will be vaporized into steam and flow upward, colliding and interacting with the coolant flowing backward from the core direction at the upper part of the core. The flow of the backflow coolant will be affected by the steam and will decrease, and then the CCFL (Countercurrent Flow Limitation) phenomenon will occur, which will affect the accident process. Due to the existence of the CCFL phenomenon, the coolant flow cannot continue to increase, which weakens the heat transfer effect, so the RELAP5 best estimation thermal hydraulic program can be used to simulate and analyze the CCFL phenomenon.

[0004] After the nodes in the downcomer section are virtualized, a large amount of data will be generated, which will cause certain difficulties in subsequent data processing and reduce the analysis efficiency. SUMMARY

[0005] In view of the low efficiency of the CCFL phenomenon simulation analysis in the prior art, the present application provides a simulation processing method for CCFL phenomenon in downcomer based on RELAP5, which can use data analysis software MATLAB programming on the basis of different downcomer node designs to realize fast and convenient processing of calculation results and drawing of result graphs, and improve the analysis efficiency.

[0006] In order to achieve the above purpose, the present application provides the following technical scheme:

[0007] A simulation processing method for CCFL phenomenon in downcomer based on RELAP5, specifically comprising the following steps:

[0008] S1: Obtain the geometric parameters and operating condition parameters of the downcomer, make a node division scheme, and obtain node information, the node information including the number of circumferential nodes, the number of axial nodes, and the number of single pipe nodes between multiple pipes;

[0009] S2: Write a RELAP5 program on the Input card, perform thermal hydraulic calculation, obtain real-time changing first parameters including gas phase and liquid phase superficial velocities and gas phase and liquid phase densities, run the first parameters, and then debug to obtain second parameters;

[0010] S3: Extract the second parameters to obtain third parameters including gas-liquid phase flow, pressure, and velocity;

[0011] S4: Import the third parameters into processing software MATLAB, read fourth parameters of the gas-liquid phase according to the node information set in S1;

[0012] S5: Perform two-dimensional cloud chart drawing on the fourth parameters in S4.

[0013] Preferably, in S1, the geometric parameters and operating condition parameters of the downcomer include the inner and outer diameters of the downcomer, the diameter and length of the cold pipe section, the height of the downcomer, the gap, and the depth of the lower chamber.

[0014] Preferably, in S1, the node division scheme is:

[0015] The downcomer includes a first part, a second part, and a third part connected in sequence, that is, the first part is connected in communication with the second part and the third part;

[0016] The first part includes n first pipe fittings connected in parallel, the second part includes n second pipe fittings connected in parallel, and the third part includes n third pipe fittings connected in parallel; the first pipe fitting is in communication with the second pipe fitting and the third pipe fitting through the corresponding second pipe fitting; and adjacent pipe fittings in each part are connected by multiple pipes to form an annular channel.

[0017] Preferably, it further includes a water injection circuit:

[0018] The output end of the time control body TDV is connected with the input end of the time pipe TDJ, the output end of the time pipe TDJ is connected with the input end of the trigger valve Valve, the output end of the trigger valve Valve is connected with the second pipe fitting of the second part; the time control body TDV gives the water injection boundary condition, the time pipe TDJ gives the injected cooling water flow, and the Valve is a trigger valve.

[0019] Preferably, in S2, the debugging includes card format, water property error, data extraction error, and calculation step debugging.

[0020] Preferably, in the S4, the fourth parameter comprises mass flow, lower chamber water storage, descending section pressure, gas-liquid phase temperature, gas-liquid phase volume fraction, gas-liquid phase density, and gas-liquid phase superficial velocity.

[0021] Preferably, in the S5, when drawing a two-dimensional cloud chart, a calculation time t is first given to the fourth parameter, then coordinate calculation is performed, a matrix of pipe type, multi-joint pipe and single-joint pipe circumferential node variables and pipe type axial node variables at the time t is generated, the matrix is subjected to periodic array to create a two-dimensional grid coordinate, and the coordinate vector is subjected to interpolation; finally, a two-dimensional color block chart is drawn according to the two-dimensional grid coordinate.

[0022] Preferably, in the S2, the first parameter is obtained in the following manner:

[0023]

[0024] In formula (1), H g represents a dimensionless gas phase velocity, H f represents a dimensionless liquid phase velocity, c represents a gas intercept, and m is a "slope"; m and c are empirical coefficients.

[0025]

[0026] In formula (2), j g and j f are gas phase and liquid phase superficial velocities, respectively; ρ g and ρ f are gas phase and liquid phase densities, respectively; w and L are intermediate parameters; g is a gravitational acceleration; D J is a channel characteristic size, which is 2 times the gap value for an annular channel; σ is a surface tension; and β is a variable parameter with a value between 0 and 1.

[0027] In summary, compared with the prior art, the present application has at least the following beneficial effects:

[0028] 1) The required results can be obtained conveniently and quickly under different node division schemes and different geometric parameters and operating parameters; and other data can be processed and analyzed by the same method, thereby improving the analysis efficiency.

[0029] 2) The method of the present application is flexible and convenient, and can be implemented by anyone who has some knowledge of the software MATLAB by writing a corresponding post-processing script through the software, according to the needs of calculation and analysis.

[0030] 3) The model is independent, and the method is universal and can be adapted to different types of RELAP5 calculation and analysis results. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A flow chart of a RELAP5-based downcomer CCFL phenomenon simulation processing method according to an exemplary embodiment of the present application.

[0032] Figure 2 A schematic diagram of a node division scheme according to an exemplary embodiment of the present application.

[0033] Figure 3 A schematic diagram of a simulated liquid phase flow at a break according to an exemplary embodiment of the present application.

[0034] Figure 4 A schematic diagram of a downcomer flow map according to an exemplary embodiment of the present application.

[0035] Figure 5 A schematic diagram of a two-dimensional cloud map according to an exemplary embodiment of the present application. DETAILED DESCRIPTION

[0036] The present application will be further described below in conjunction with embodiments and specific working examples. However, it should not be understood that the scope of the above-mentioned subject matter of the present application is limited to the following examples only, and any technology realized based on the content of the present application falls within the scope of the present application.

[0037] In the description of the present application, it should be understood that the terms “longitudinal”, “transverse”, “upper”, “lower”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, “outer” and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0038] As shown in Figure 1 The present application provides a RELAP5-based downcomer CCFL phenomenon simulation processing method, which specifically comprises the following steps:

[0039] S1: Obtain the geometric parameters and operating condition parameters (such as the inner and outer diameters of the downcomer, the diameter and length of the cold pipe section, the height and gap of the downcomer, and the depth of the downcomer) of the downcomer, and make an appropriate node division scheme.

[0040] In this embodiment, the node division scheme is as follows:

[0041] As shown in Figure 2 The downcomer simulation is divided into three parts, including a first part, a second part and a third part connected in sequence, i.e. the first part is connected in communication through the second part and the third part.

[0042] The first part includes n parallel first pipes, which can be marked as P2XX; the second part also includes n parallel second pipes, which can be marked as B1XX; the third part also includes n parallel third pipes, which can be marked as P3XX; the first pipes are communicated with the corresponding second pipes and third pipes; and the adjacent pipes in each part are connected by multi-joint pipes to form a ring channel.

[0043] The water injection circuit also includes:

[0044] The output end of the time control body TDV is connected with the input end of the time joint TDJ, the output end of the time joint TDJ is connected with the input end of the trigger valve Valve, and the output end of the trigger valve Valve is connected with the second pipe of the second part; the time control body TDV gives the water injection boundary condition, the time joint TDJ gives the injection cooling water flow of the complete loop cooling pipe section, and the Valve is a trigger valve.

[0045] In this embodiment, 16 nodes in the circumferential direction are taken as an example:

[0046] The first part includes 16 parallel first pipes, which are marked as P211-P226 respectively; the second part includes 16 parallel second pipes, which are marked as B111-B126 respectively; and the third part includes 16 parallel third pipes, which are marked as P311-P326 respectively. The first pipes are communicated with the corresponding second pipes and third pipes, for example, P211 is communicated with B111 and P311, P212 is communicated with B112 and P312, and P226 is communicated with B126 and P326.

[0047] The water injection circuit includes a first water injection circuit, a second water injection circuit and a third water injection circuit, which are arranged at 45°-135° according to the experimental circuit. The first water injection circuit includes a first TDV, a first TDJ and a first Valve connected in sequence, and the first Valve is connected with B111; the second water injection circuit includes a second TDV, a second TDJ and a second Valve connected in sequence, and the second Valve is connected with B117; the third water injection circuit includes a third TDV, a third TDJ and a third Valve connected in sequence, and the third Valve is connected with B119; and B125 is connected with the water outlet pipe.

[0048] S2: The RELAP5 program is written on the Input card to perform thermal hydraulic calculation and obtain real-time changing first parameters (gas phase and liquid phase apparent velocity, gas phase and liquid phase density), and the first parameters are loaded into the RELAP5 / MOD3.3 program to run and then debug to obtain second parameters.

[0049]

[0050] In formula (1), H g represents dimensionless gas phase velocity, H f represents dimensionless liquid phase velocity, c represents gas intercept, m is "slope", and m and c are empirical coefficients, which are usually determined by experiments.

[0051]

[0052] In formula (2), j g and j f are gas phase and liquid phase superficial velocities respectively; ρ g and ρ f are gas phase and liquid phase densities respectively; w and L are intermediate parameters; g is gravitational acceleration; D J is channel characteristic size, which is 2 times of gap value for annular channel; σ is surface tension; and β is a variable parameter with a value between 0 and 1.

[0053] In the embodiment, because the first parameter is calculated, the first parameter needs to be debugged to improve accuracy, and the debugging method includes card format, water property error, data extraction error, calculation step debugging, etc.

[0054] S3: The second parameter is extracted by a strip card to obtain a third parameter (the strip card is an existing card), and the third parameter includes gas-liquid phase flow, pressure, velocity, etc., and then the result can be viewed in a Result card.

[0055] S4: The third parameter is imported into a processing software MATLAB, and the required node information (including the number of circumferential nodes, the number of axial nodes, the number of single pipe nodes between multiple pipes, etc. in the node division scheme in S1) is set, and the fourth parameter of the gas-liquid phase is read (which can be directly read by the software), including mass flow, water storage in the lower chamber, pressure in the descending section, gas-liquid phase temperature, gas-liquid phase volume fraction, gas-liquid phase density, gas-liquid phase superficial velocity, etc.

[0056] S5: The fourth parameter in S4 is two-dimensional cloud charted, and a data table is output.

[0057] In drawing the two-dimensional cloud chart, the data of mass flow, gas-liquid phase superficial velocity and the like in the pipe in axial and circumferential directions are processed and a data table (including mass flow, gas-liquid phase superficial velocity, pressure and the like) is output, a calculation time t is given, then coordinate calculation is performed to generate a matrix of pipe type, circumferential node variables of multi-pipe and single-pipe and axial node variables of pipe type at time t (according to loop information, the grid size is set, the row and column spaces are converted into axial and circumferential directions to generate the matrix), the matrix is subjected to periodic array to create two-dimensional grid coordinates (first, the central position angle theta0 of the first part calculated by RELAP5 is set, then the converted central position angle theta1 is given, the linspace function is used to generate a linear interval vector, and the meshgrid function returns two-dimensional grid coordinates), the coordinate vector is subjected to interpolation (cubic cubic spline interpolation method) to obtain better node distribution; finally, two-dimensional color block chart drawing is performed, and a color block chart is drawn according to the real value matrix (the output picture size, color scale icon label and horizontal and vertical coordinate labels are set, and the color type of the color block chart is set by the colormap function), and the size of the matrix element value is displayed in rich colors and shapes (the element value can be corresponded to the color according to the color scale chart).

[0058] As shown in Figure 3 , it is an example of liquid phase flow at the break (the connection between the second pipe and the break loop, i.e. B111) drawn by the method provided by the application; as shown in Figure 4 , it is an example of flow chart of the lower chamber (P311-P312-P3XX-P326-P311.) drawn by the method provided by the application; as shown in Figure 5 , it is a two-dimensional cloud chart drawn by the method provided by the application.

[0059] In this embodiment, when analyzing and processing the results of other types of node division, the method provided by the application can also be adopted, and after the data to be processed is imported into MATLAB, the result pictures (such as gas-liquid phase flow, velocity, pressure, volume fraction and the like) and the corresponding Excel data table output by S5 can be automatically generated.

[0060] Those skilled in the art can understand that the above embodiments are specific embodiments for implementing the application, and in actual application, various changes can be made in form and details without departing from the spirit and scope of the application.

Claims

1. A method for simulating the downcomer CCFL phenomenon based on RELAP5, characterized in that, Specifically comprising the following steps: S1: obtaining the geometric parameters and operating condition parameters of the descending section, making a node division scheme, and obtaining node information, the node information including the number of circumferential nodes, the number of axial nodes, and the number of single pipe nodes between multiple pipes; S2: writing a RELAP5 program on an Input card, performing thermal hydraulic calculation, obtaining real-time changing first parameters including gas phase and liquid phase superficial velocities and gas phase and liquid phase densities, and running the first parameters and then debugging to obtain second parameters; S3: extracting the second parameters to obtain third parameters including gas-liquid phase flow rates, pressures, and velocities; S4: importing the third parameters into processing software MATLAB, reading fourth parameters of the gas-liquid phases according to the node information set in S1; S5: performing two-dimensional cloud chart drawing on the fourth parameters in S4; In S1, the node division scheme is as follows: The descending section includes a first part, a second part, and a third part connected in sequence, i.e., the first part is connected in communication with the second part and the third part; The first part includes n first pipe fittings connected in parallel, and the second part includes n second pipe fittings connected in parallel; The third part includes n third pipe fittings connected in parallel; The first pipe fittings are in communication with the third pipe fittings through corresponding second pipe fittings; and adjacent pipe fittings in each part are connected by multiple pipes to form annular channels; In S2, the first parameters are obtained in the following manner: （1） In equation (1), H g Vg represents the dimensionless gas velocity, H f Vl represents the dimensionless liquid velocity, c A represents the gas intercept, m is the "slope", m and c is an empirical coefficient; ， ， （2） where Vgand V1are the gas and liquid superficial velocities, respectively; j g and j f Vgand V1are the gas and liquid superficial velocities, respectively; ρ g and ρ f pgand piare the gas and liquid densities, respectively; w, L are intermediate parameters; g is the gravitational acceleration; is the channel characteristic dimension, which is twice the gap for a circular channel; σ is the surface tension; β is a variable parameter that takes values between 0 and 1.

2. The method of claim 1, wherein the method is based on RELAP5. In S1, the geometric parameters and operating condition parameters of the descending section include the inner and outer diameters of the descending section, the diameters and lengths of the cold pipe sections, the height of the descending section, the gap, and the depth of the lower chamber.

3. The method of claim 1, wherein the method is based on RELAP5. Further comprising a water injection circuit: The output end of a time control body TDV is connected with the input end of a time pipe TDJ, the output end of the time pipe TDJ is connected with the input end of a trigger valve Valve, and the output end of the trigger valve Valve is connected with the second pipe fittings of the second part; the time control body TDV gives a water injection boundary condition, the time pipe TDJ gives a cooling water injection flow rate, and the Valve is a trigger valve.

4. The method of claim 1, wherein the method is based on RELAP5. In S2, the debugging includes card format, water property errors, data extraction errors, and calculation step debugging.

5. The method of claim 1, wherein the method is based on RELAP5. In S4, the fourth parameters include mass flow rates, lower chamber water storage amounts, descending section pressures, gas-liquid phase temperatures, gas-liquid phase volume fractions, gas-liquid phase densities, and gas-liquid phase superficial velocities.

6. The method of claim 1, wherein the method is based on RELAP5. In S5, when drawing the two-dimensional cloud chart, the fourth parameters are first given a calculation time t, then coordinate calculation is performed, a matrix of pipe types, multi-pipe and single-pipe circumferential node variables, and pipe type axial node variables at the time t is generated, the matrix is subjected to periodic array to create two-dimensional grid coordinates, and the coordinate vectors are subjected to interpolation; finally, two-dimensional color block chart drawing is performed according to the two-dimensional grid coordinates.

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