A device for simulating a U-shaped heat exchange tube fracture accident and a method of using the device

Abstract

The present invention discloses a device for simulating a U-shaped heat exchange tube rupture accident and a method of use, belonging to the technical field of nuclear reactor steam generators. The device of the present invention comprises a steam generator and a bypass pipe. A pressure and flow control module is provided on the bypass pipe, which is used to adjust the bypass pipe to form a working pressure drop and then form different flow rates to simulate different degrees of rupture of the U-shaped heat exchange tube, and monitor and record the changes in parameters such as radioactivity and temperature at different positions on the secondary side. The present invention helps to discover the changing rules of key parameters of the steam generator after the U-shaped heat exchange tube leaks, so as to monitor the real-time working conditions of the steam generator heat exchange tube during the operation of the nuclear power plant, give preventive warnings in advance, and take measures to prevent the occurrence of related accidents.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear reactor steam generators, and particularly relates to a device for simulating a U-shaped heat exchange tube rupture accident and a use method thereof. Background Art

[0002] The steam generator is the hub connecting the reactor and the steam turbine. As the pressure-bearing boundary between the primary and secondary sides of a nuclear power plant, its dynamic characteristics affect the safe operation of the entire reactor unit, especially the steam generator heat exchanger tube rupture (SGTR), which requires more research, including research on the rupture of single or multiple heat exchanger tubes.

[0003] At present, there are many studies on heat exchange tube rupture accidents, mainly focusing on analyzing the causes of heat exchange tube rupture accidents, accident handling and the hazards caused. During the operation of nuclear power plants, due to poor water quality control, the silt accumulation of steam generators corrodes the tube walls, or the fatigue rupture, erosion or wear caused by mechanical damage to the tube walls during long-term operation, the steam generator (SG) tube wall will be thinned. When the tube wall is thinned to a certain extent, the steam generator (SG) tube wall may suddenly leak or rupture, resulting in a steam generator heat exchange tube rupture (SGTR). After the accident occurs, it is first necessary to determine the location of the damaged steam generator and then isolate it.

[0004] When a steam generator heat exchanger tube rupture (SGTR) accident occurs, the coolant on the primary side flows into the secondary side through the steam generator (SG), causing the loss of primary coolant, which may lead to insufficient core cooling, core melting, and radioactive release. Therefore, it is necessary to study the change law of key parameters of the steam generator after the heat exchange tube leaks, so as to monitor the real-time working conditions of the steam generator heat exchange tubes in real time during the operation of the nuclear power plant, and take effective measures in time to prevent the occurrence of related accidents when necessary. This research is of great significance.

[0005] Among them, simulation of heat exchange tube rupture accidents is a very effective technical means.

[0006] At present, the research in this field focuses on developing new steam generator heat exchange tubes and their components. There is no very simple and practical special technical means for studying heat exchange tube rupture accidents. Summary of the invention

[0007] In view of the above analysis, the present invention aims to provide a device and a method for simulating a U-shaped heat exchange tube rupture accident, so as to solve the problem that it is impossible to simply, quickly and accurately study the changing laws of key parameters of the steam generator after the heat exchange tube leaks.

[0008] The purpose of the present invention is mainly achieved through the following technical solutions:

[0009] A device for simulating a U-shaped heat exchange tube rupture accident comprises a steam generator and a bypass pipe connected to the outside of the steam generator; the steam generator is provided with a U-shaped heat exchange tube; the inner cavity of the U-shaped heat exchange tube is the primary side of the heat exchange tube and the outer cavity is the secondary side of the heat exchange tube; the outer wall of the U-shaped heat exchange tube is provided with a monitoring module; the bypass pipe is provided with a flow control module and a pressure control module, and the bypass pipe connects the primary side of the heat exchange tube and the secondary side of the heat exchange tube of the steam generator.

[0010] The steam generator is provided with an upper shell and a lower head, with a tube sheet in the middle; the U-shaped heat exchange tube is connected to the upper side of the tube sheet; the inner cavity of the steam generator is divided into a primary side of the heat exchange tube and a secondary side of the heat exchange tube;

[0011] A longitudinal partition is arranged inside the lower head to separate the first cavity and the second cavity of the lower head; the two ends of the U-shaped heat exchange tube are respectively connected to the first cavity and the second cavity of the lower head; a primary side inlet of the heat exchange tube is arranged on the outer wall of the first cavity; and a primary side outlet of the heat exchange tube is arranged on the outer wall of the second cavity.

[0012] The side wall of the upper shell is provided with a secondary side inlet of the heat exchange tube, and the top end is provided with a secondary side outlet of the heat exchange tube.

[0013] A heat exchange tube bundle sleeve is sleeved around the inner wall of the upper shell; the lower end of the heat exchange tube bundle sleeve is suspended on the upper part of the tube plate; the upper end of the heat exchange tube bundle sleeve is close to the secondary side outlet of the heat exchange tube.

[0014] The monitoring module includes a temperature detection module and a radioactivity detection module which are arranged on the outer wall of the U-shaped heat exchange tube.

[0015] The radioactive detection module includes a plurality of radioactive sampling devices and / or N10I (Tl) scintillation detectors arranged at scattered points, and the temperature detection module is a plurality of thermocouples arranged at scattered points.

[0016] The bypass pipeline includes a bypass main path and a plurality of bypass branches connected in parallel to a part of the bypass main path, and the flow rates of the bypass main path and the plurality of bypass branches are different.

[0017] The pressure control module is arranged on the bypass main road; the flow control module is arranged on the bypass main road part and several bypass branches connected in parallel; the pressure control module includes several pressure drop regulating valves; the flow regulating module is several ball valves.

[0018] A method for using the device for simulating a U-shaped heat exchange tube rupture accident comprises the following steps:

[0019] S1. Build a physical model of the device for simulating the U-shaped heat exchange tube rupture accident according to the scale;

[0020] S2: Calculate the pressure drop of the bypass pipeline for the scaled-down model, and adjust the initial pressure drop of the bypass pipeline to the theoretical value;

[0021] S3: Selecting the flow rate of the bypass pipe to simulate different degrees of rupture of the U-shaped heat exchange tube;

[0022] S4: Monitor and record the value changes of the monitoring module set on the secondary side

[0023] Compared with the prior art, the present invention can achieve at least one of the following technical effects:

[0024] 1) The device and method of this invention can be used to simulate and calculate the changes in steam generators and reactors caused by heat exchange tube rupture. When the heat exchange tube ruptures, that is, the flow regulating ball valve is in the open state, at this time, due to the pressure difference between the primary side of the heat exchange tube and the secondary side of the heat exchange tube, the fluid on the primary side of the heat exchange tube enters the secondary side of the heat exchange tube. At this time, the temperature detection module arranged on the secondary side of the heat exchange tube can be used to obtain the temperature change of the fluid on the secondary side of the heat exchange tube, and the radioactivity detection module can be used to monitor the change of the radioactivity level, thereby providing a reference for early warning of accidents and taking accident intervention measures in advance, further improving nuclear safety culture, and ensuring the safe operation of nuclear power plants.

[0025] 2) The present invention achieves simulation of the U-shaped heat exchange tube rupture accident by arranging a bypass pipeline outside the steam generator to connect the primary side of the heat exchange tube with the secondary side of the heat exchange tube, and making the pressure difference (i.e., pressure drop) between the inlet and outlet of the bypass pipeline in the initial state equal to the pressure difference (i.e., pressure drop) between the primary side and the secondary side of the heat exchange tube in normal operation, so that the simulation device structure is simple and the simulation result is accurate. The simulation method of the present invention is simple, easy to promote, and has broad application prospects.

[0026] Other features and advantages of the present invention will be described in the following description, and part of them may become obvious from the description, or may be understood by practicing the present invention. The purpose and other advantages of the present invention may be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference numerals refer to like components throughout the drawings.

[0028] Figure 1 is a schematic diagram of a device for simulating a U-shaped heat exchange tube rupture accident;

[0029] Figure 2 is a schematic diagram of the bypass pipeline;

[0030] Figure 3This is a cross-sectional view of the steam generator.

[0031] Reference numerals

[0032] 1-5: Segment positions of each section near the primary side on the bypass main line; 101-upper shell; 102-U-shaped heat exchange tube; 102-1: primary side of heat exchange tube; 102-2: secondary side of heat exchange tube; 103-lower head; 104-tube sheet; 105-partition; 106: primary side inlet of heat exchange tube; 107: primary side outlet of heat exchange tube; 108-secondary side inlet of heat exchange tube; 109-secondary side outlet of heat exchange tube; 1010: first chamber; 1011: second chamber; 110: heat exchange tube bundle sleeve Cylinder; 111: water-gas separator; 12: first regulating valve; 13: second regulating valve; 14: first ball valve; 15: second ball valve; 20: bypass pipeline; 201: radioactivity detection module; 202: temperature detection module; 6: bypass branch; 6-1 to 6-3: segmentation markers on the bypass branch; 7 bypass main road; 7-1 to 7-7: segmentation positions of each section on the bypass main road; 8 to 10: segmentation positions of each section on the secondary side of the bypass main road; 30: steam generator DETAILED DESCRIPTION

[0033] The following combination Figures 1 to 3 , and the device and method of the present invention are described in detail in more detail. These embodiments are only for comparison and explanation purposes, and the present invention is not limited to these embodiments.

[0034] In this embodiment, it is specifically preferred that the steam generator heat exchange tube is a U-shaped heat exchange tube.

[0035] like Figure 1-3 As shown, the steam generator includes an upper shell 101, a U-shaped heat exchange tube 102, a tube sheet 104 and a lower head 103; the U-shaped heat exchange tube 102 is arranged in the upper shell 101, and the tube sheet 104 is arranged between the upper shell 101 and the lower head 103 to separate the upper shell 101 from the lower head 103; the U-shaped heat exchange tube 102 penetrates the tube sheet 104, and the fluid inlet of the first fluid and the fluid outlet of the first fluid are both arranged on the tube sheet 104, so that the inner cavity of the lower head 103 is connected with the inside of the U-shaped heat exchange tube 102 to form a primary side 102-1 of the heat exchange tube; in the upper shell 101 above the tube sheet 104, the cavity formed by the outer side of the U-shaped heat exchange tube 102 is the secondary side 102-2 of the heat exchange tube.

[0036] The lower head 103 is provided with an inlet 106 and an outlet 107 of the primary side 102-1 of the heat exchange tube; the side wall of the upper shell 101 is provided with an inlet 108 of the secondary side 102-2 of the heat exchange tube; and the top of the upper shell 101 is provided with an outlet 109 of the secondary side 102-2 of the heat exchange tube.

[0037] A longitudinal partition 105 is arranged in the lower head 103, dividing the lower head 103 into a first cavity 1010 and a second cavity 1011. The primary side inlet 106 of the heat exchange tube is arranged on the first cavity 1010, and the primary side outlet 107 of the heat exchange tube is arranged on the second cavity 1011; the fluid inlet of the U-shaped heat exchange tube 102 is arranged on the tube sheet 104 above the first cavity 1010, and the fluid outlet of the U-shaped heat exchange tube 102 is arranged on the tube sheet 104 above the second cavity 1011. The first fluid, i.e., the coolant in the primary side, preferably a high-temperature fluid medium, enters the first cavity 1010 from the primary side inlet 106 of the heat exchange tube, then enters the U-shaped heat exchange tube 102, and then enters the second cavity 1011 from the fluid outlet of the U-shaped heat exchange tube 102, and then flows out from the primary side (102-1) outlet 107 of the heat exchange tube, completing the primary side flow of the first fluid (high-temperature fluid medium, coolant).

[0038] In the upper shell 101, a water-gas separator 111 is also arranged on the upper part of the U-shaped heat exchange tube 102; a heat exchange tube bundle sleeve 110 is installed under the water-gas separator. The heat exchange tube bundle sleeve 110 is a sleeve arranged along the inner wall of the upper shell 101, and the lower end is suspended above the tube sheet 104, so that the secondary side fluid enters the central part from the bottom of the U-shaped heat exchange tube 102 and then runs upward. Optionally, the outer wall of the heat exchange tube bundle sleeve 110 and the inner wall of the upper shell 101 are arranged in parallel and spaced apart in the vertical section of the U-shaped heat exchange tube 102, and the diameter gradually increases at a position close to the U-shaped section of the vertical section of the U-shaped heat exchange tube 102, and gradually decreases at a position of the U-shaped section of the U-shaped heat exchange tube 102, and finally bends in the direction of the secondary side outlet 109 of the heat exchange tube at a position close to the top of the U-shaped section of the U-shaped heat exchange tube 102, and extends with a gradually decreasing diameter until it approaches the secondary side outlet 109 of the heat exchange tube. A top opening is left between the topmost position of the heat exchange tube bundle sleeve 110 and the top inner wall of the upper shell 101, so as to facilitate the second fluid to circulate back to the interior of the secondary side 102-2 of the heat exchange tube.

[0039] The second fluid, i.e., the coolant in the secondary side, preferably a low-temperature medium, enters from the secondary side inlet 108 of the heat exchange tube, flows downward along the annular slit formed by the inner wall of the upper shell 101 and the outer wall of the heat exchange tube bundle sleeve 110, passes through the bottom opening of the tube sheet 104, enters the space formed by the inner wall of the heat exchange tube bundle sleeve 110 and the outer wall of the U-shaped heat exchange tube 102, and runs upward. After the second fluid absorbs the heat of the first fluid at the U-shaped heat exchange tube 102, it reaches the water-gas separator 111, and the gas formed is dissipated from the secondary side outlet 109 of the heat exchange tube, and the separated liquid flows back to the slit formed by the inner wall of the upper shell 101 and the outer wall of the heat exchange tube bundle sleeve 110, and flows downward; the secondary side flow of the second fluid (low-temperature medium) is completed.

[0040] In the specific embodiment of the present invention, the temperature, radioactivity and other parameters in the flow adjustment process of simulating the U-shaped heat exchange tube rupture accident are detected. A monitoring module is also set on the outer wall of the U-shaped heat exchange tube 102. The monitoring module includes a temperature detection module 202 and a radioactivity detection module 201. The radioactivity detection module 201 can be a radioactivity sampling device, a N10I (Tl) scintillation detector, or both, and is used to collect radioactivity in the secondary side fluid. 16 N (radioactive element nitrogen 16 carried by the primary side fluid, the primary side fluid may also carry other radioactive elements, such as γ, etc.) content; the temperature detection module 202 is a plurality of thermocouples, preferably armored thermocouples, which mainly collect the temperature changes of the secondary side fluid.

[0041] More specifically, the radioactivity detection module 201 and the temperature detection module 202 can be set up in series, with scattered points evenly distributed on the outer wall of the U-shaped heat exchange tube 102. For a single heat exchange tube 102, it is equally divided into 4 sections along the height direction, and a detection module is set in the middle of each section of the heat exchange tube. For different heat exchange tubes 102, detection modules are set for the internal heat exchange tube and the external heat exchange tube respectively, and the parameter values ​​of different positions due to different ruptures of the U-shaped heat exchange tube 102 are recorded respectively. These values ​​reflect the degree of influence of different ruptures of the U-shaped heat exchange tube 102 on the point, which is conducive to summarizing and establishing the relationship between the rupture position and the radioactivity concentration, and the relationship between the secondary side temperature change and the primary side flow loss and the rupture position in the numerical model.

[0042] The device for simulating the rupture accident of the U-shaped heat exchange tube 102 provided in the specific embodiment of the present invention further includes a bypass pipe 20 .

[0043] The main purpose of setting the bypass pipe 20 is: through the regulation of the pressure and flow of the bypass pipe 20 under the guidance of theoretical data, the pressure and flow changes at the scene of the heat exchange tube rupture accident inside the nuclear reactor steam generator are reflected through the bypass pipe 20 in a simple and intuitive way, and by changing the flow in the bypass pipe 20, it is achieved The rupture flow value when the heat exchange tube rupture accidents of varying degrees occur. In this process, the temperature and radioactivity and other parameters of the secondary side fluid at the U-shaped heat exchange tube 102 have different changes at different positions. These changes in parameters such as temperature and radioactivity are observed and recorded, so as to obtain the theoretical relationship between parameters such as temperature and radioactivity and accidents of varying degrees of heat exchange tube rupture in the numerical model.

[0044] The bypass pipe 20 is arranged outside the steam generator, and its inlet is arranged at the primary side 102 - 1 of the heat exchange tube, and its outlet is arranged at the secondary side 102 - 2 of the heat exchange tube.

[0045] The bypass pipeline 20 of the specific embodiment of the invention includes a bypass main path 7 and a bypass branch 6 connected in parallel to a part of the bypass main path 7. Specifically, the bypass main path 7 is connected to the inlet and the outlet and forms a closed loop with the steam generator; the bypass branch 6 is arranged in parallel with the part of the bypass main path 7, and the bypass branch 6 is arranged between the bypass main path 7 and the steam generator to form an inner circle of the closed loop.

[0046] A pressure control module is provided on the bypass main path 7, which is used to adjust the pressure drop of the bypass line 20 in the initial state (i.e., adjust the pressure difference between the inlet and outlet of the bypass line 20) to achieve the pressure drop during normal operation (i.e., the pressure difference between the primary side of the heat exchange tube and the secondary side of the heat exchange tube). The pressure drop of the bypass line 20 in the initial state is a theoretical value obtained by calculation (the calculation process of the theoretical value is shown in formulas 1 to 5, and the calculation results are shown in tables 1 to 3). The function of the pressure control module is to adjust the pressure drop between the inlet and outlet of the bypass main path 7 in the initial state to match the pressure drop of the primary side 102-1 and the secondary side 102-2 of the heat exchange tube during normal operation.

[0047] Optionally, the pressure control module is a first regulating valve 12 and a second regulating valve 13 arranged in series on the bypass main path 7, and the first regulating valve 12 and the second regulating valve 13 are close to the entrance of the bypass pipe 20 where the primary side 102-1 of the heat exchange tube flows out. The two regulating valves have different pressure drop adjustment ranges, and matching them can make the pressure drop adjustment more accurate, and can accurately simulate the theoretically calculated pressure drop values ​​of the primary and secondary sides when the U-shaped heat exchange tube 102 works normally. Preferably, the adjustment range of the first pressure regulating valve 12 is greater than that of the second pressure regulating valve 13, and the second pressure regulating valve 13 is used for fine-tuning.

[0048] Flow regulating modules are respectively arranged on the bypass main road 7 and the bypass branch road 6 at the local parallel connection, and the two parallel pipelines are used respectively to enable the bypass pipeline 20 to generate different flow rates corresponding to the fault levels of rupture of the U-shaped heat exchange tube 102 to generate ruptures of different sizes. Specifically, the flow regulating modules respectively arranged on the bypass branch road 6 and the local parallel bypass main road 7 are the first ball valve 14 and the second ball valve 15. Thus, the bypass branch road 6 and the first ball valve 14 and the second ball valve 15 are used respectively in the two parallel pipelines to enable the bypass pipeline 20 to respectively achieve different degrees of rupture faults of the U-shaped heat exchange tube 102 at different flow rates, and generate ruptures of different sizes. Specifically, by opening the first ball valve 14 or the second ball valve 15, the pressure drop of the fluid inlet and the fluid outlet in the bypass pipeline 20 is equal to the pressure drop of the primary side 102-1 of the U-shaped heat exchange tube and the secondary side 102-2 of the heat exchange tube. At this time, it is equivalent to introducing the primary side fluid into the secondary side fluid through the bypass pipe 20, which essentially simulates that after the U-shaped heat exchange tube 102 is broken, the primary side fluid in the U-shaped heat exchange tube 102 directly enters the outside of the heat exchange tube 102 and mixes with the secondary side fluid. In this process, the temperature detection module 202 and the radioactivity detection module 201 in the monitoring module perform operations and collect various parameters.

[0049] Optionally, the second ball valve 15 and the first ball valve 14 are respectively provided so that the first ball valve 14 is larger than the second ball valve 15 to accurately simulate the flow of the secondary side fluid when the U-shaped heat exchange tube 102 has different degrees of rupture.

[0050] Optionally, the fluid inlet of the bypass pipe 20 is arranged near the primary side inlet 106 of the heat exchange tube, and is introduced into the first fluid cavity from the first cavity 1010; the fluid outlet of the bypass pipe 20 is arranged at the secondary side 102-2 of the heat exchange tube, and flows into the space formed by the inner wall of the heat exchange tube bundle sleeve 110 and the outer wall of the U-shaped heat exchange tube 102.

[0051] The outlet of the bypass pipe 20 can be set at any place close to the outer wall of the U-shaped heat exchange tube 102 on the secondary side to simulate the situation where the U-shaped heat exchange tube 102 breaks. In this specific embodiment, the outlet of the bypass pipe 20 is preferably set at a lower position at the secondary side 102-2 of the heat exchange tube, so that the outlet of the bypass pipe 20 can be set near the outer wall of the U-shaped heat exchange tube 102 without touching the heat exchange tube bundle sleeve 110, more effectively simulating the state of the U-shaped heat exchange tube 102 when it breaks, while reducing the processing steps and avoiding the damage to the heat exchange tube bundle sleeve 110 that may be caused by processing.

[0052] At this point, the preferred structure of the bypass line 20 is completed.

[0053] Preferably, the armored thermocouple in the temperature detection module 202 is installed outside the heat exchange tube, mainly collecting the temperature change of the secondary side fluid, and the radioactive sampling device and the N10I (Tl) scintillation detector in the radioactive detection module 201 are installed outside the heat exchange tube, mainly collecting the secondary side fluid 16 N (nitrogen 16, a monitorable example added to the coolant to monitor radioactivity, can also be gamma particles) content. Complete the construction of the preferred detection module.

[0054] In summary, the present invention achieves simulation of the rupture accident of the U-shaped heat exchange tube 102 by setting a bypass line 20 outside the steam generator 30 to connect the primary side 102-1 of the heat exchange tube and the secondary side 102-2 of the heat exchange tube. Different flow rates of the bypass line 20 can simulate rupture accidents of the U-shaped heat exchange tube 102 of different degrees, and record the change values ​​of different parameters of different fault degrees at different locations.

[0055] The outlet of the bypass pipeline 20 can be set near different positions of the U-shaped heat exchange tube 102, and the radioactivity detection module 201 and the temperature detection module 202 can be set at different positions on the outer wall of the U-shaped heat exchange tube 102. It is also possible to set multiple bypass pipeline 20 branches and select different ball valves to simulate different degrees of U-shaped heat exchange tube 102 rupture conditions, and record the temperature, radioactivity and other parameters under various conditions. This will be of great benefit to the establishment of a numerical model of the relationship between the rupture position and the radioactivity concentration, temperature, etc., thereby helping to predict the occurrence of nuclear reactor accidents.

[0056] In the present invention, the following assumptions are made when theoretically calculating the pressure drop of the bypass pipe 20:

[0057] 1) The bypass pipe 20 is actually an external insulation layer, so the temperature change of the fluid is not considered, and it is assumed that the bypass pipe 20 flows isothermally;

[0058] 2) When the first ball valve 14 and the second ball valve 15 are in a fully open state, there is no sudden expansion or contraction of the flow passage, so the pressure drop loss here is not considered;

[0059] 3) When calculating, the friction pressure drop and local shape resistance (elbows and reducers) of the bypass pipe 20 along the way are taken into account.

[0060] The calculation process of the initial pressure drop of the bypass line 20 (the pressure drop between the primary side and the secondary side of the steam generator when the U-shaped heat exchange tube 102 works normally) is as follows:

[0061] Table 1 shows the parameters of the primary side and the secondary side of the heat exchange tube when the U-shaped heat exchange tube 102 is working normally. Steps a to c are the calculation process of the pressure drop (friction pressure drop, local pressure drop, and lift pressure drop) at each position in the bypass pipeline 20 in the initial state. First, the pressure drop of each part in the bypass pipeline in the initial state is calculated using formulas (1) to (5) to obtain the total pressure drop value of the bypass pipeline. The calculation results are shown in Tables 2 and 3. Finally, according to the total pressure drop value of the bypass pipeline, the pressure drop of the entire bypass pipeline is matched with the pressure drop of the primary side and the secondary side of the heat exchange tube when the U-shaped heat exchange tube 102 is working normally using a pressure drop regulating valve.

[0062] a) Friction pressure drop:

[0063] Calculate the friction pressure drop for single-phase flow:

[0064]

[0065] Where: Δp f is the friction pressure drop (Pa), f is the friction coefficient (dimension is 1), L is the channel length (m), D is the equivalent diameter of the channel (m), ρ is the density of the fluid (kg / m 2 ), V is the velocity of the fluid (m / s). Here, f is called the Darcy-Weisbach friction coefficient, which is related to factors such as the flow properties (laminar and turbulent), flow state (unstructured flow and fully developed flow), heating conditions (isothermal and non-isothermal), channel geometry, and surface roughness of the fluid.

[0066] For a rough circular channel, the commonly used empirical formula in the entire turbulent region is:

[0067]

[0068] In the above formula, ε is the absolute roughness of the pipeline material surface. For stainless steel pipelines, it is 0.015mm; Re is the Reynolds number.

[0069] In one embodiment of the present invention, the channel is circular, so the above formula can be evolved into:

[0070]

[0071] Where Q is the flow rate at the channel inlet (kg / s).

[0072] b) Local pressure drop:

[0073] The local pressure loss at elbows, tapers, expanders and tees can be expressed using the same calculation formula:

[0074]

[0075] K in the above formula is the form resistance coefficient.

[0076] c) Increase the pressure drop:

[0077] The pressure drop of the coolant when flowing through a non-horizontal channel can be calculated using the following formula:

[0078] Δp el =ρg×(z2-z1)=ρgΔz (5)

[0079] Wherein, Δz is the height of the coolant lifting of the primary side fluid (wherein, Δz represents the height of the coolant lifting of the primary side fluid; see Appendix Figure 2 This calculation considers the height of the coolant of the primary side fluid at the positions 2, 3, and 4 in the bypass pipe 20 from the position 2 to the position 4. The height taken in this formula is the height in the vertical direction from the center point of the pipe at position 2 of the bypass main line 7 to the center point of the pipe at position 4).

[0080] The following is a description of the embodiment with specific calculations:

[0081] Table 1

[0082]

[0083]

[0084] The design flow rate of the primary side 102-1 of the heat exchange tube is 1.936 kg / s (the flow rate adopted by the scaled model), and there are 49 U-shaped tubes in total. The data in Table 1 gives the parameters of the adopted steam generator model.

[0085] In this embodiment, the first regulating valve 14 and the second regulating valve 15 of DN25, the second ball valve 15 of DN25 and the first ball valve 14 of DN30 are selected respectively. When the U-shaped heat exchange tube 102 in the simulated steam generator is broken from the primary fluid inlet, the fluid at 160°C (simulated calculated temperature) flows out from the primary side 102-1 of the heat exchange tube, enters the designed bypass pipe 20, and then flows into the vicinity of the secondary side U-shaped heat exchange tube.

[0086] At this time, the pressure drop of the bypass pipe 20 is theoretically calculated.

[0087] The second ball valve 15 provided on the bypass main line 7 is fully opened, and the first ball valve 14 provided on the bypass branch line 6 is fully closed, and the pressure drop of each marked point (serial number 1-13 in the table) of the bypass pipeline 20 is calculated, as shown in Table 2:

[0088]

[0089]

[0090] The second ball valve 15 provided on the bypass main line 7 is fully closed, and the first ball valve 14 provided on the bypass branch line 6 is fully opened, and the pressure drop of the bypass pipeline 20 is calculated, as shown in Table 3 (indicated by serial numbers 1-13 in the table):

[0091]

[0092]

[0093] This embodiment refers to the table of form resistance coefficients of elbows, connecting pipes and valves in Appendix V of "Nuclear Reactor Thermal Analysis".

[0094] In this embodiment, a steam generator 30 with 49 U-shaped heat exchange tubes 102 is used in a reduced scale, in combination with an optimal bypass pipeline 20 and an optimal detection module, to form a complete device for simulating a U-shaped heat exchange tube rupture accident.

[0095] Specifically, the method for using the device for simulating a U-shaped heat exchange tube rupture accident of the present invention comprises the following steps:

[0096] S1. Numerical modeling of the device simulating the U-shaped heat exchange tube rupture accident and construction of a scaled physical simulation model:

[0097] The scaled model of the steam generator and bypass pipe is built using 3D design software, which can retain all the geometric features of the scaled model and save it in a file format that supports CFD meshing, parts drawings and other user-required formats;

[0098] Based on the digital model, raw materials were purchased and a physical model of the device simulating the U-type heat exchange tube rupture accident was built.

[0099] Preferably, the three-dimensional design software is solidwords. The establishment of the digital model can well guide the construction of the physical model device. The method for using the device for simulating the U-shaped heat exchange tube fracture accident of the present invention can also omit the step of numerical modeling.

[0100] S2. For the reduced scale model, calculate the pressure drop of the bypass pipe 20 and adjust the initial pressure drop of the bypass pipe 20 to the theoretical value;

[0101] First, the pressures on the primary side and the secondary side of the heat exchange tube during normal operation are determined according to the reduction ratio, and the pressure drop between the primary side and the secondary side of the heat exchange tube during normal operation is obtained (see Table 1). Then, the pressure drop of each part in the bypass pipeline 20 is calculated respectively using the theoretical formula for pressure drop calculation (see Formulas 1 to 5). Finally, according to the calculated pressure drop, the pressure of the bypass pipeline 20 is adjusted through the pressure regulating valves (the first regulating valve 12 and the second regulating valve 13) until the pressure drop of the bypass pipeline 20 is equal to the pressure drop of the primary side and the secondary side of the heat exchange tube.

[0102] S3. Select the flow rate of the bypass pipe 20 to simulate the different degrees of rupture of the U-shaped heat exchange tube 102;

[0103] In this specific embodiment, the flow rate of the bypass main path 7 is consistent with the flow rate of the entire U-shaped heat exchange tube, and the diameter of the bypass branch 6 is half of the flow rate of the bypass main path 7.

[0104] If the diameter of the U-shaped heat exchange tube rupture is half of the tube diameter, the first ball valve 14 at the bypass branch 6 on the bypass pipe 20 can be opened to simulate the flow from the primary side of the heat exchange tube to the secondary side of the heat exchange tube caused by the rupture of the heat exchange tube;

[0105] If the U-shaped heat exchange tube 102 is completely broken, the second ball valve 15 at the bypass main path 7 partially connected in parallel on the bypass pipe 20 can be opened to simulate the flow from the primary side of the heat exchange tube to the secondary side of the heat exchange tube caused by the rupture of the heat exchange tube.

[0106] Pipe diameters with other flow values ​​can also be connected in parallel to simulate accidents with different breaches.

[0107] S4. Monitor and record the value changes of the monitoring module set on the secondary side:

[0108] In this specific embodiment, when the U-shaped heat exchange tube 102 is simulated to rupture, the high-temperature first fluid carrying radioactive elements flows into the secondary side, causing the second fluid on the secondary side to heat up and carry radioactive elements; the radioactivity and temperature changes on the secondary side are monitored at different flow rates; and the parameter values ​​at different times and positions are recorded.

[0109] Monitoring the changes in radioactivity concentration helps to understand the distribution of radioactivity on the secondary side and establish the relationship between the breach location and radioactivity concentration; monitoring the temperature changes on the secondary side can establish the relationship between the temperature changes on the secondary side and the flow loss on the primary side.

[0110] The method can also be adjusted to change the outlet position of the bypass pipeline 20 to any possible ruptured U-shaped heat exchange tube position, monitor the secondary side radioactivity and temperature changes at different flow rates, and record the parameter values ​​at different times and positions.

[0111] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A device for simulating a U-shaped heat exchange tube rupture accident, characterized in that: It comprises a steam generator (30) and a bypass pipe (20) communicating with the outside of the steam generator (30); A U-shaped heat exchange tube (102) is arranged in the steam generator (30); the inner cavity of the U-shaped heat exchange tube (102) is the primary side (102-1) of the heat exchange tube, and the outer cavity is the secondary side (102-2) of the heat exchange tube; a monitoring module is arranged on the outer wall of the U-shaped heat exchange tube (102); The bypass pipe (20) is provided with a flow control module and a pressure control module. The bypass pipe (20) is connected to the primary side (102-1) and the secondary side (102-2) of the heat exchange tube of the steam generator (30). The steam generator (30) is provided with an upper shell (101) and a lower head (103), and a tube sheet (104) is provided in the middle. The U-shaped heat exchange tube (102) is connected to the upper side of the tube sheet (104); the inner cavity of the steam generator (30) is divided into the primary side (102-1) and the secondary side (102-2) of the heat exchange tube. ) and the secondary side (102-2) of the heat exchange tube, a longitudinal partition (105) is arranged inside the lower head (103) to separate the first chamber (1010) and the second chamber (1011) of the lower head (103); the two ends of the U-shaped heat exchange tube (102) are respectively connected to the first chamber (1010) and the second chamber (1011) of the lower head (103), the outer wall of the first chamber (1010) is provided with a heat exchange tube primary side inlet (106); the outer wall of the second chamber (1011) is provided with a heat exchange tube primary side outlet (107); The side wall of the upper shell (101) is provided with a heat exchange tube secondary side inlet (108), and the top end is provided with a heat exchange tube secondary side outlet (109); A heat exchange tube bundle sleeve (110) is sleeved around the inner wall of the upper shell (101); the lower end of the heat exchange tube bundle sleeve (110) is suspended on the upper part of the tube sheet (104); the upper end of the heat exchange tube bundle sleeve (110) is close to the secondary side outlet (109) of the heat exchange tube, and the monitoring module comprises a temperature detection module (202) and a radioactivity detection module (201) arranged on the outer wall of the U-shaped heat exchange tube (102); The bypass pipeline (20) comprises a bypass main path (7) and a plurality of bypass branches (6) connected in parallel to a part of the bypass main path (7); the flow rates of the bypass main path (7) and the plurality of bypass branches (6) are different; a pressure control module is arranged on the bypass main path (7); a flow control module is arranged on a part of the bypass main path (7) and the plurality of bypass branches (6) connected in parallel; the pressure control module comprises a plurality of pressure drop regulating valves; and the flow control modules are a plurality of ball valves.

2. The device for simulating a U-shaped heat exchange tube rupture accident according to claim 1, characterized in that: The radioactivity detection module (201) comprises a plurality of radioactivity sampling devices and / or N10I (Tl) scintillation detectors arranged at scattered points, and the temperature detection module (202) is a plurality of thermocouples arranged at scattered points.

3. A method for using the device for simulating a U-shaped heat exchange tube rupture accident according to any one of claims 1 to 2, comprising the following steps: S1. Build a physical model of the device for simulating the U-shaped heat exchange tube rupture accident according to the scale; S2: Calculate the pressure drop of the bypass pipeline (20) for the scaled-down model, and adjust the initial pressure drop of the bypass pipeline (20) to a theoretical value; S3: selecting the flow rate of the bypass pipe (20) to simulate different degrees of rupture of the U-shaped heat exchange tube (102); S4: Monitor and record the value changes of the monitoring module set on the secondary side.

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