Method for judging physical state of gas in containment vessel in integrity test process of Hualong No.1 containment vessel

Abstract

The invention belongs to the technical field of nuclear power containment integrity tests, and particularly relates to a method for judging the physical state of gas in a shell in the Hualong No.1 containment integrity test process. The method specifically comprises simulation analysis software, an in-shell gas simulation model, model calculation grid division, simulation model reliability evaluation and in-shell gas state evaluation. The method has the beneficial effects that (1) a special model for simulating and analyzing the physical state of the gas in the integral test shell of the Hualong No.1 containment shell is established, and the limitation that the traditional test depends on physical prototype test verification is broken through; according to the method, the actual pressing process is simulated through numerical simulation, rehearsal and optimization of test parameters are achieved, and the physical test cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power containment integrity testing technology, specifically relating to a method for determining the physical state of gases inside the containment vessel during the integrity testing process of Hualong One. Background Technology

[0002] The Hualong One is a third-generation pressurized water reactor nuclear power unit independently developed and built in my country. Its containment structure adopts a double-shell design. The outer shell is a reinforced concrete structure primarily designed to prevent external impacts; the inner shell is a prestressed concrete structure with a steel lining, primarily designed to prevent the leakage of radioactive materials into the environment in the event of a loss-of-coolant accident. The containment structure integrity test is a crucial means of verifying whether the containment meets its design functional requirements. This test is one of the major nuclear safety-related special tests during the commissioning and commercial operation of nuclear power plants. It needs to be conducted according to a prescribed testing cycle and is characterized by high risk, complex organization, and occupation of the critical path during major overhauls. This test uses dry air to pressurize the containment to the design pressure at a certain rate to simulate the pressure action within the containment under design baseline accident conditions, verifying the integrity and containment of the containment structure under the design pressure.

[0003] For a long time, the pressurization rate for the overall containment structural integrity test of Hualong One has not exceeded 20 kPa / h. After pressurizing to the design pressure plateau, a waiting period is required until the physical state of the gas inside the containment is relatively stable before the overall containment tightness test can be carried out. Since the pressurization process involves doing work on the gas inside the containment, the higher the pressurization rate, the higher the work efficiency, and the more drastic the changes in the physical state of the gas inside the containment. For example, gas temperature, gas velocity, and gas pressure all rise more rapidly, thus affecting the stabilization process of the gas inside the containment at the highest pressure plateau. However, since its commissioning, Hualong One nuclear power units have not conducted research on the dynamic evolution of the physical state of the gas inside the containment during the integrity test. The energy industry standard, "Containment Tightness Test of Pressurized Water Reactor Nuclear Power Plant" (NB / T 20018-2021), states that "after the containment is pressurized to the test pressure, before the start of the overall test, the gas mass data inside the containment should be stabilized for a period of time, with a stabilization time of at least 4 hours." The standard does not explain the reason for the 4-hour period, nor does it specify the pressurization rate corresponding to this stabilization time. In actual testing, waiting for 4 hours is only a necessary condition; there are situations where the physical state of the gas inside the casing still does not meet the requirements for conducting an overall sealing test after 4 hours. Whether the physical state of the gas inside the casing is stable after 4 hours mainly relies on the experience of the testing personnel, lacking a scientifically quantifiable method. When encountering situations lacking engineering experience, such as when the pressurization rate is increased in a test, thereby altering the initial physical state of the gas inside the casing, there is no specific calculation method for quantifying the physical state of the gas inside the casing, making it inconvenient for on-site testing.

[0004] With the increasing number of Hualong One units in commercial operation in my country, the frequency of containment integrity tests is increasing, and the need to improve the pressure test rate is becoming more and more urgent. There is an urgent need to establish a method to accurately quantify the physical state of the gas inside the containment during the Hualong One containment integrity test process. Summary of the Invention

[0005] The purpose of this invention is to provide a method for determining the physical state of gases inside the containment vessel during the integrity test of the Hualong One submersible. This method combines fluid simulation analysis with field test data analysis to quantify the physical state of gases inside the containment vessel during the integrity test. Fluid simulation analysis establishes the prerequisites for determining the physical state of gases inside the containment vessel; that is, in the absence of measured data, it provides a method for determining the physical state of gases inside the containment vessel by simulating the integrity test process of the Hualong One containment vessel, thereby assessing the feasibility of changing test conditions, such as increasing the pressure test rate. Field test data analysis further quantifies the physical state of gases inside the containment vessel during the test process more precisely, directly guiding on-site implementation.

[0006] The technical solution of the present invention is as follows: A method for determining the physical state of gas inside the containment vessel during the integrity test of Hualong One, comprising the following steps:

[0007] Step 1: Based on the structural drawings of the containment vessel of Hualong One and the floor plans and decoration drawings of each floor at each elevation inside the containment vessel, establish a geometric model of the gas inside the containment vessel in the analysis software;

[0008] Step 2: Import the gas model inside the containment into the analysis software and mesh the gas model inside the containment.

[0009] Step 3: After mesh generation is complete, proceed to the Fluent solver module;

[0010] Step 4: At the pressurization orifice, set the mass flow rate inlet boundary. When using different pressurization rates, the mass flow rate at the inlet boundary is calculated using the following formula:

[0011]

[0012] Where, This refers to the charging rate, which is determined based on the actual values ​​used. The temperature of the gas being filled in; For the constant coefficients of the Hualong One reactor type;

[0013] Step 5: Select the SIMPLEC algorithm with strong convergence;

[0014] Step 6: Initialize the internal gas domain settings;

[0015] Step 7: Perform the solution calculation;

[0016] Step 8: Physical state analysis of the gas inside the shell after pressurizing to the highest test pressure platform;

[0017] Step 9: Determine the stable state of the gas inside the shell based on the normalized physical quantities of the gas inside the shell;

[0018] Step 10: Determining the physical state of the gas inside the containment vessel during the on-site implementation of the Hualong One containment vessel integrity test.

[0019] The analysis software mentioned in step 1 is ANSYS Space Claim, and the dimensions of each part in the geometric model are consistent with the as-built specifications. Figure 1 Based on the floor openings and wall openings, the corresponding empty areas are segmented in the model; based on the elevation, angle and diameter of the pressurization hole, the pressurization hole is excavated on the containment cylinder wall, and the wall surface where the pressurization hole is located is defined as the "inlet" group.

[0020] In step 2, a polyhedron dominated by hexahedrons is used for meshing, and the mesh skew is set to no more than 0.8. The maximum mesh size at the pressurization hole is set to one-tenth of the diameter of the pressurization hole. A boundary layer is added to the walls and equipment surfaces through which the gas flows inside the shell. The boundary layer uses a hexahedron mesh, the number of mesh layers is set to 3, and the y+ value of the mesh near the wall is set to 30~200.

[0021] In step 3, the pressure-based solver and transient solution mode are selected, and -9.81 m / s is set in the z-direction of the model. 2 To determine the gravitational acceleration, activate the energy exchange switch, select "ideal-gas" as the fluid material, and choose the two-parameter Standard turbulence model. Model.

[0022] In step 5, the density, momentum equations, and turbulent kinetic energy discretization are all set to second-order upwind schemes, and the pressure discretization is set to the "PRESTO!" format; the residual convergence criterion is set to 1e-3.

[0023] In step 6, the gauge pressure is set to 0 Pa, the initial velocity of the gas inside the casing is 0 m / s, and the initial temperature of the gas inside the casing is 300.15 K.

[0024] In step 7, the initial calculation sets the time step to 0.01 s, the maximum number of iterations per step to 30, and the total solution time to 10 s. After the solution is completed, a second calculation is performed, with the time step set to 0.1 s and the maximum number of iterations per step to 30, resulting in a total solution time of 10 s. After the second calculation is completed, the formal calculation begins, with the time step set to 1 s and the maximum number of iterations to 30, to calculate the total time required to pressurize. The relationship between this time and the pressurization rate is as follows:

[0025]

[0026] Where, This refers to the charging time; This refers to the pressure rate.

[0027] In step 8, the time-varying curves of the gas temperature field, velocity field, and pressure field inside the shell under the highest test pressure platform obtained from the simulation analysis are extracted. These curves are then normalized to obtain the dimensionless time-varying curves of the average gas temperature, velocity, and pressure inside the shell. The normalization calculation formula is as follows:

[0028]

[0029] Where, These are the normalized dimensionless parameters; The physical quantities of gas inside the shell that change over time; The physical quantity of gas inside the shell at the moment when the highest test pressure plateau is reached.

[0030] The judgment steps in step 9 are as follows:

[0031] First, calculate:

[0032] ,

[0033] In the formula, i, j, and k represent the times that are separated by integer hours, and k = j + 1, i < j < k;

[0034] If the following conditions are met:

[0035]

[0036] It is determined that the physical state of the gas inside the shell has reached stability after k hours of pressure stabilization.

[0037] In step 10, the test data is averaged. The averaging method is as follows:

[0038] 1) Formula for calculating the average gas pressure inside the shell at a certain calculation time:

[0039]

[0040] Where, Let n be the average gas pressure inside the casing, and n be the number of pressure sensors. For a single pressure sensor reading;

[0041] 2) Formula for calculating the average temperature of the gas inside the shell at a certain calculation time:

[0042]

[0043] Where, is the average temperature of the gas inside the casing; m is the number of temperature sensors. For a single temperature sensor reading, The volume factor corresponding to each temperature sensor is determined based on the arrangement position of the temperature sensors during the test. After obtaining the average measured pressure and average temperature of the gas inside the shell, the physical state of the gas inside the shell is determined according to steps 8 to 9.

[0044] The beneficial effects of this invention are as follows: (1) A model specifically designed for the simulation analysis of the physical state of the gas inside the containment vessel during the integral test of Hualong One was established, breaking through the limitations of traditional tests that rely on physical prototype tests for verification. This method simulates the actual pressurization process through numerical simulation, realizes the pre-testing and optimization of test parameters, and reduces the cost of physical tests. (2) Gas inlet boundary conditions that are perfectly matched with the actual pressurization rate are adopted. At the same time, by introducing a gas turbulence model and considering the turbulent heat transfer effect of the gas movement inside the containment vessel, the complex thermal characteristics of the gas and solid wall during the integral test of Hualong One containment vessel are simulated. This solves the problem that the ideal gas equation cannot accurately reflect the convective heat transfer mechanism of the gas inside the containment vessel during the pressurization process, and improves the accuracy of the simulation. (3) Structural mechanics and thermo-fluid mechanics are combined and the physical state parameters (temperature, pressure, velocity) of the gas inside the containment vessel during the integral test are analyzed based on the thermo-pressure coupling effect. An index for evaluating the evolution of the physical state of the gas inside the containment vessel is proposed. Through the analysis of parameter change trends, a quantitative evaluation of the physical state of the gas is realized. (4) Based on the temperature and pressure data of the gas inside the containment vessel collected during the integrity test of Hualong One, a method for determining the physical state of the gas inside the containment vessel based on measured data is further proposed to guide field tests and improve the engineering applicability of the method of this invention. The method proposed in this invention provides a judgment basis based on scientific calculation results and engineering measured data, and has higher reliability and accuracy. Attached Figure Description

[0045] Figure 1 The trend curve of the average temperature of the gas inside the casing after normalization during the pressure stabilization process;

[0046] Figure 2 The present invention provides a flowchart of a method for determining the physical state of gas inside the containment vessel during an integrity test of the Hualong One submersible. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] The present invention provides a method for determining the physical state of the gas inside the containment vessel during the integrity test of the Hualong One containment vessel. Specifically, it is based on running computational fluid dynamics simulation software and the test data of the integrity test of the Hualong One containment vessel structure. In the embodiments of the present invention, ANSYS Fluent software is selected, and the computer used has a CPU core of not less than 16 cores, memory of not less than 32G, and hard disk capacity of not less than 1T.

[0049] like Figure 2 As shown, a method for determining the physical state of the gas inside the containment vessel during the integrity test of the Hualong One submersible includes the following steps:

[0050] Step 1: Based on the structural drawings of the Hualong One containment vessel and the floor plans and finishing drawings of each floor within the containment vessel, create a geometric model of the gas inside the containment vessel in ANSYS Space Claim. The dimensions of each part in the geometric model must match those of the as-built vessel. Figure 1 Based on the floor openings and wall openings, the corresponding empty areas are segmented in the model; based on the elevation, angle and diameter of the pressurization hole, the pressurization hole is excavated on the containment cylinder wall, and the wall surface where the pressurization hole is located is defined as the "inlet" group.

[0051] Step 2: Import the containment gas model into ANSYS Fluent Meshing and mesh the gas model. Use hexahedral-dominated polyhedra for meshing, and set the mesh skew to no more than 0.8; set the maximum mesh size at the pressurization port to one-tenth of the pressurization port diameter; add boundary layers to the walls, equipment surfaces, etc., through which the gas flows, using hexahedral meshes with 3 layers, and set the y+ value of the near-wall mesh to (30~200).

[0052] Step 3: After meshing, enter the Fluent solver module, select the pressure-based solver and transient solution mode, and set the z-axis of the model to -9.81 m / s. 2 To determine the gravitational acceleration, activate the energy exchange switch, select "ideal-gas" as the fluid material, and choose the two-parameter Standard turbulence model. Model.

[0053] Step 4: At the pressurization orifice, set the mass flow rate inlet boundary. When using different pressurization rates, the mass flow rate at the inlet boundary is calculated using the following formula:

[0054]

[0055] In the formula, The pressurization rate is determined based on the actual values ​​used, and the unit is kPa / h, which is the increase in pressure of the gas inside the shell per hour. The temperature of the gas being filled in is measured in Kelvin (K). The constant coefficients for the Hualong One reactor type take into account factors such as the free volume within the reactor shell and the molar gas constant, and have dimensions of [missing information]. The value is 299562.

[0056] Step 5: Select the SIMPLEC algorithm with strong convergence. Set the density, momentum equations, and turbulent kinetic energy discretization to second-order upwind schemes, and the pressure discretization to "PRESTO!" format; set the residual convergence criterion to 1e-3.

[0057] Step 6: Initialize the gas field inside the shell: Set the gauge pressure to 0 Pa, the initial velocity of the gas inside the shell to 0 m / s, and the initial temperature of the gas inside the shell to 300.15 K;

[0058] Step 7: For the initial calculation, set the time step to 0.01 s, the maximum number of iterations per step to 30, and the total solution time to 10 s. After the initial calculation, perform a second calculation, changing the time step to 0.1 s, the maximum number of iterations per step to 30, and the total solution time to 10 s. After the second calculation, proceed to the formal calculation, changing the time step to 1 s, the maximum number of iterations to 30, and calculate the total time required to pressurize. The relationship between this time and the pressurization rate is as follows:

[0059]

[0060] Where, The charging time is in hours. The pressure rate is expressed in kPa / h and ranges from 10 to 40.

[0061] Step 8: Analysis of the physical state of the gas inside the shell after pressurizing to the highest test pressure platform: Extract the temperature, velocity, and pressure field curves of the gas inside the shell under the highest test pressure platform obtained from the simulation analysis over time. After normalization, obtain the dimensionless variation curves of the average temperature, velocity, and pressure of the gas inside the shell over time (e.g., ...). Figure 1 (As shown), the normalization calculation formula is as follows:

[0062]

[0063] Where, These are the normalized dimensionless parameters; For the physical quantities of gas inside the shell that change over time (temperature, velocity, or pressure); The physical quantities (temperature, velocity, or pressure) of the gas inside the shell at the moment when the highest test pressure plateau is reached.

[0064] Step 9: Determine the steady state of the gas inside the shell based on the normalized physical quantities of the gas inside the shell. The determination steps are as follows:

[0065] First, calculate:

[0066] ,

[0067] In the formula, i, j, and k represent times separated by integer hours, and k = j + 1, i < j < k. For example, i = 3, j = 4, and k = 5 represent the times when the voltage is stabilized for 3 hours. Value, when the voltage is stabilized for 4 hours Value, when the voltage is stabilized for 5 hours value.

[0068] If the following conditions are met:

[0069]

[0070] If the gas inside the shell has been pressurized for k hours, then its physical state has reached stability. During simulation analysis, the temperature field, velocity field, and pressure field of the gas inside the shell must all meet the above criteria for determining that the physical state of the gas inside the shell has reached stability.

[0071] Step 10: Determining the physical state of the gas inside the containment vessel during the on-site implementation of the Hualong One containment vessel integrity test.

[0072] Because the gas velocity inside the containment vessel was not measured during the overall integrity test of Hualong One, only the gas temperature and pressure were measured. Therefore, when conducting on-site tests, the measured gas pressure and temperature data were used to determine the physical state of the gas inside the containment vessel. Furthermore, since multiple pressure and temperature measuring points were set up, the test data needed to be averaged first. The averaging method is as follows:

[0073] 1) Formula for calculating the average gas pressure inside the shell at a certain calculation time:

[0074]

[0075] In the formula, The pressure is the average gas pressure inside the casing, expressed in Pa, and n is the number of pressure sensors arranged in the casing. For a single pressure sensor reading.

[0076] 2) Formula for calculating the average temperature of the gas inside the shell at a certain calculation time:

[0077]

[0078] In the formula, The average temperature of the gas inside the casing is expressed in Kelvin (K); m represents the number of temperature sensors deployed. For a single temperature sensor reading, The volume factor for each temperature sensor is determined based on the sensor's placement during the test.

[0079] After obtaining the average measured pressure and temperature of the gas inside the shell, the physical state of the gas inside the shell is determined according to steps 8 to 9.

Claims

1. A method for determining the physical state of gases inside the containment vessel during an integrity test of the Hualong One submersible, characterized in that, Includes the following steps: Step 1: Based on the structural drawings of the containment vessel of Hualong One and the floor plans and decoration drawings of each floor at each elevation inside the containment vessel, establish a geometric model of the gas inside the containment vessel in the analysis software; Step 2: Import the gas model inside the containment into the analysis software and mesh the gas model inside the containment. Step 3: After mesh generation is complete, proceed to the Fluent solver module; Step 4: At the pressurization orifice, set the mass flow rate inlet boundary. When using different pressurization rates, the mass flow rate at the inlet boundary is calculated using the following formula: Where, This refers to the charging rate, which is determined based on the actual values ​​used. The temperature of the gas being filled in; For the constant coefficients of the Hualong One reactor type; Step 5: Select the SIMPLEC algorithm with strong convergence; Step 6: Initialize the internal gas domain settings; Step 7: Perform the solution calculation; Step 8: Physical state analysis of the gas inside the shell after pressurizing to the highest test pressure platform; Step 9: Determine the stable state of the gas inside the shell based on the normalized physical quantities of the gas inside the shell; Step 10: Determining the physical state of the gas inside the containment vessel during the on-site implementation of the Hualong One containment vessel integrity test.

2. The method for determining the physical state of the gas inside the containment vessel during the integrity test of Hualong One as described in claim 1, characterized in that: The analysis software mentioned in step 1 is ANSYS Space Claim. The dimensions of each part in the geometric model are consistent with the as-built drawings. Based on the floor openings and wall openings, the corresponding empty space is divided in the model. Based on the elevation, angle and diameter of the pressurization hole, the pressurization hole is dug out on the containment cylinder wall, and the wall surface where the pressurization hole is located is defined as the "inlet" group.

3. The method for determining the physical state of gas inside the containment vessel during the integrity test of Hualong One, as described in claim 1, is characterized in that: In step 2, a polyhedron dominated by hexahedrons is used for meshing, and the mesh skew is set to no more than 0.

8. The maximum mesh size at the pressurization hole is set to one-tenth of the diameter of the pressurization hole. A boundary layer is added to the walls and equipment surfaces through which the gas flows inside the shell. The boundary layer uses a hexahedron mesh, the number of mesh layers is set to 3, and the y+ value of the mesh near the wall is set to 30~200.

4. The method for determining the physical state of gas inside the containment vessel during the integrity test of Hualong One, as described in claim 1, is characterized in that: In step 3, the pressure-based solver and transient solution mode are selected, and -9.81 m / s is set in the z-direction of the model. 2 Gravitational acceleration, turn on the energy exchange switch, select "ideal-gas" as the fluid material, and select the two-parameter Standard turbulence model. Model.

5. The method for determining the physical state of the gas inside the containment vessel during the integrity test of Hualong One, as described in claim 1, is characterized in that: In step 5, the density, momentum equations, and turbulent kinetic energy discretization are all set to second-order upwind schemes, and the pressure discretization is set to "PRESTO!" format; the residual convergence criterion is set to 1e-3.

6. The method for determining the physical state of the gas inside the containment vessel during the integrity test of Hualong One as described in claim 1, characterized in that: In step 6, the gauge pressure is set to 0 Pa, the initial velocity of the gas inside the casing is 0 m / s, and the initial temperature of the gas inside the casing is 300.15 K.

7. The method for determining the physical state of the gas inside the containment vessel during the integrity test of Hualong One as described in claim 1, characterized in that: In step 7, the initial calculation sets the time step to 0.01 s, the maximum number of iterations per step to 30, and the total solution time to 10 s. After the solution is completed, a second calculation is performed, with the time step set to 0.1 s and the maximum number of iterations per step to 30, resulting in a total solution time of 10 s. After the second calculation is completed, the formal calculation begins, with the time step set to 1 s and the maximum number of iterations to 30, to calculate the total time required to pressurize. The relationship between this time and the pressurization rate is as follows: Where, This refers to the charging time; This refers to the pressure rate.

8. The method for determining the physical state of the gas inside the containment vessel during the integrity test of Hualong One as described in claim 1, characterized in that: In step 8, the time-varying curves of the gas temperature field, velocity field, and pressure field inside the shell under the highest test pressure platform obtained from the simulation analysis are extracted. These curves are then normalized to obtain the dimensionless time-varying curves of the average gas temperature, velocity, and pressure inside the shell. The normalization calculation formula is as follows: Where, These are the normalized dimensionless parameters; The physical quantities of gas inside the shell that change over time; The physical quantity of gas inside the shell at the moment when the highest test pressure plateau is reached.

9. A method for determining the physical state of gas inside the containment vessel during an integrity test of the Hualong One submersible, as described in claim 1, characterized in that: The judgment steps in step 9 are as follows: First, calculate: , In the formula, i, j, and k represent the times that are separated by integer hours, and k = j + 1, i < j < k; If the following conditions are met: It is determined that the physical state of the gas inside the shell has reached stability after k hours of pressure stabilization.

10. The method for determining the physical state of gas inside the containment vessel during the integrity test of Hualong One, as described in claim 1, is characterized in that: In step 10, the test data is averaged. The averaging method is as follows: 1) Formula for calculating the average gas pressure inside the shell at a certain calculation time: Where, Let n be the average gas pressure inside the casing, and n be the number of pressure sensors. For a single pressure sensor reading; 2) Formula for calculating the average temperature of the gas inside the shell at a certain calculation time: Where, is the average temperature of the gas inside the casing; m is the number of temperature sensors. For a single temperature sensor reading, The volume factor corresponding to each temperature sensor is determined based on the arrangement position of the temperature sensors during the test. After obtaining the average measured pressure and average temperature of the gas inside the shell, the physical state of the gas inside the shell is determined according to steps 8 to 9.

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