Steam generator heat pipe leak detection method and detection system, apparatus and medium

Abstract

This invention relates to the field of nuclear reactor safety monitoring technology, specifically to a method and system for detecting leaks in heat transfer tubes of steam generators, as well as related equipment and media. The invention involves repeatedly injecting high-pressure cooling water into a container containing heavy liquid metal with jet diameters of varying sizes to simulate leakage of high-pressure cooling water into the heavy liquid metal due to a crack in the heat transfer tube. After each injection of cooling water, sample response data of bubble-induced bubbles are collected. These bubbles are formed by the vaporization of the leaked cooling water under the action of the high-temperature heavy liquid metal. Finally, a quantitative relationship between the response parameters and the crack size in the heat transfer tube is constructed based on multiple sets of jet diameters and sample response data. In actual monitoring of the heat transfer tube, by monitoring the response parameter values ​​in real time and substituting these values ​​into this quantitative relationship, the crack size can be monitored in real time, and it can be determined in real time whether the crack size has reached the point of rupture.

Description

Technical Field

[0001] This invention relates to the field of nuclear reactor safety monitoring technology, specifically to a method and system for detecting leaks in heat transfer tubes of steam generators, as well as equipment and media. Background Technology

[0002] The nuclear reactor releases heat to heat the heavy liquid metal in the main coolant pool. The heavy liquid metal is the main coolant in the sealed container. The purpose of sealing is to maintain a stable pressure in the container. The heavy liquid metal acts as a primary loop heat exchanger and exchanges heat with the steam generator (composed of heat transfer tube bundles) arranged in the pool. The heavy liquid metal transfers the heat it absorbs to the high-pressure cooling water in the secondary loop in the heat transfer tubes. After absorbing the heat, the cooling water forms steam for power generation.

[0003] The primary loop heat exchanger and the secondary loop high-pressure cooling water are both arranged in a pool to form a pool-type integrated design. This design can improve the core power density, simplify the overall system layout, and eliminate the intermediate loop. However, it also brings new safety challenges: the secondary loop high-pressure subcooled water flows in the heat transfer tube bundle. Once a microcrack appears in the heat transfer tube, the cooling water on the high-pressure side will be injected into the low-pressure, high-temperature heavy liquid metal coolant pool under the pressure difference, which may lead to a steam generator heat transfer tube rupture accident.

[0004] Existing technology uses accelerometers mounted on the outer wall of the container to collect vibration signals. If a heat transfer tube ruptures, the cooling water inside will form bubbles under high temperature. The dynamics of these bubbles will excite container vibration, thus monitoring the vibration signal can detect whether the heat transfer tube has ruptured. However, this existing technology is a reactive measure, not a preventative measure. Therefore, it cannot prevent heat transfer tube rupture accidents from occurring.

[0005] Therefore, existing technologies still need to be improved and enhanced. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method, system, equipment, and medium for detecting leaks in heat transfer tubes of steam generators, thus resolving the issues in existing technologies regarding preventing heat transfer tube rupture accidents.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for detecting leaks in a heat transfer tube of a steam generator, wherein the leak detection method includes constructing a quantitative relationship between a response parameter caused by a leak and the crack size of the heat transfer tube; the step of constructing the quantitative relationship includes: Multiple jet diameters are set, and cooling water is sequentially injected into the heavy liquid metal in the container with the multiple jet diameters. The injected cooling water is used to simulate cooling water leaking from the heat transfer tube. The heat transfer tube is a pipe that constitutes a steam generator. The steam generator exchanges heat with the heavy liquid metal. The jet diameter is used to simulate the crack size of the heat transfer tube. After each injection of the cooling water, response sample data triggered by bubbles are collected, wherein the bubbles are formed by heating the cooling water with the heavy liquid metal; Based on multiple jet diameters and their corresponding response sample data, a quantitative relationship between the response parameters and the crack size of the heat transfer tube is constructed.

[0008] In one implementation, multiple jet diameters are set, and cooling water is sequentially injected into the heavy liquid metal in the container at the multiple jet diameters, including: An injection device with multiple orifices is provided on the outer wall of the container, and the orifices are sealed and connected to the container. The injection device is controlled to sequentially inject cooling water into the heavy liquid metal in the container through orifices of different diameters, wherein the orifice diameter is used to control the jet diameter of the cooling water.

[0009] In one implementation, the aperture size ranges from [40µm to 200µm].

[0010] In one implementation, sample data of the response triggered by the bubble are collected, including: The vibration data of the container is obtained using a vibration acceleration sensor. The vibration of the container is caused by bubbles formed by the heating of cooling water by the heavy liquid metal reaching the container. The sound pressure sensor is used to collect sample sound pressure data induced by the bubble, and the sample vibration data and the sample sound pressure data are used as the response sample data.

[0011] In one implementation, the quantitative relationship includes a vibration crack relationship between vibration frequency and crack size, and a sound pressure crack relationship between sound pressure and crack size; the leakage detection method further includes: When cooling water is injected into the heat transfer tube, the measured vibration data of the container and the measured sound pressure data inside the container are collected. The vibration crack relationship is applied to the measured vibration data to solve for the size of the first crack; The second crack size is determined by applying the acoustic pressure crack relationship to the measured acoustic pressure data. Based on the first crack size and the second crack size, the leakage detection results are obtained.

[0012] In one implementation, based on the first crack size and the second crack size, a leakage detection result is obtained, including: A high-frequency elastic wave is collected using an acoustic emitter, and the high-frequency elastic wave is correlated with the bubble. Based on the first crack size, the second crack size, and the high-frequency elastic wave, the leakage detection result is obtained.

[0013] Secondly, embodiments of the present invention also provide a detection system, wherein the system includes: A vibration acceleration sensor is used to collect vibration data of a container, the vibration of which is related to whether bubbles overflow from the heat transfer tube inside the container due to rupture. A sound pressure sensor is used to collect sound pressure data inside a container, and the sound pressure data is related to bubbles; An acoustic emitter is used to collect the high-frequency elastic waves excited by the bubble.

[0014] In one implementation, the system further includes a protection component for protecting the sound pressure sensor; the protection component includes: A metal outer shell is fixed to the container and is in sealed communication with the interior of the container; A ceramic heat-insulating bracket is fixed to the inner wall of the metal casing and is used to fix the sound pressure sensor. A cooling gas pipe runs through the inner wall of the metal casing to provide a working environment within a set temperature range for the sound pressure sensor.

[0015] Thirdly, embodiments of the present invention also provide a terminal device, wherein the terminal device includes a memory, a processor, and a steam generator heat transfer tube leakage detection program stored in the memory and executable on the processor. When the processor executes the steam generator heat transfer tube leakage detection program, it implements the steps of the steam generator heat transfer tube leakage detection method described above.

[0016] Fourthly, embodiments of the present invention also provide a computer-readable storage medium storing a steam generator heat transfer tube leakage detection program, wherein when the steam generator heat transfer tube leakage detection program is executed by a processor, the steps of the steam generator heat transfer tube leakage detection method described above are implemented.

[0017] Beneficial Effects: This invention repeatedly injects high-pressure cooling water into a container of heavy liquid metal with jet diameters of varying sizes to simulate the leakage of high-pressure cooling water into the heavy liquid metal due to a crack in the heat transfer tube. Sample response data of bubble-induced bubbles is collected after each injection; these bubbles are formed by the vaporization of leaked cooling water under the action of the high-temperature heavy liquid metal. Finally, a quantitative relationship between the response parameters and the crack size of the heat transfer tube is constructed based on multiple sets of jet diameters and sample response data. In actual monitoring of the heat transfer tube, by monitoring the response parameter values ​​in real time and substituting them into this quantitative relationship, the crack size can be monitored in real time. Based on the crack size, it can be determined in real time whether the crack has reached the rupture point, allowing for appropriate countermeasures to be implemented before the heat transfer tube ruptures, thus preventing safety accidents. Attached Figure Description

[0018] Figure 1 This is an overall flowchart of the present invention; Figure 2 This is a schematic diagram of the laser microporous plate injection device in an embodiment of the present invention; Figure 3 This is a schematic diagram of sensor installation in an embodiment of the present invention; Figure 4 This is a flowchart of signal processing and analysis in an embodiment of the present invention; Figure 5 This is a schematic diagram comparing the micro-leakage detection spectrum in an embodiment of the present invention; Figure 6 This is a block diagram illustrating the internal structure of a terminal device provided in an embodiment of the present invention. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0020] Research has revealed that nuclear reactors release heat to heat heavy liquid metal in the main coolant pool. The heavy liquid metal is the main coolant in a sealed container. The purpose of sealing is to maintain a stable pressure in the container. The heavy liquid metal acts as a primary loop heat exchanger and exchanges heat with the steam generator (composed of heat transfer tube bundles) arranged in the pool. The heavy liquid metal transfers the heat it absorbs to the high-pressure cooling water in the secondary loop inside the heat transfer tubes. After absorbing the heat, the cooling water forms steam for power generation.

[0021] The primary loop heat exchanger and the secondary loop high-pressure cooling water are both arranged in a pool to form a pool-type integrated design. This design can improve the core power density, simplify the overall system layout, and eliminate the intermediate loop. However, it also brings new safety challenges: the secondary loop high-pressure subcooled water flows in the heat transfer tube bundle. Once a microcrack appears in the heat transfer tube, the cooling water on the high-pressure side will be injected into the low-pressure, high-temperature heavy liquid metal coolant pool under the pressure difference, which may lead to a steam generator heat transfer tube rupture accident.

[0022] Existing technology uses accelerometers mounted on the outer wall of the container to collect vibration signals. If a heat transfer tube ruptures, the cooling water inside will form bubbles under high temperature. The dynamics of these bubbles will excite container vibration, thus monitoring the vibration signal can detect whether the heat transfer tube has ruptured. However, this existing technology is a reactive measure, not a preventative measure. Therefore, it cannot prevent heat transfer tube rupture accidents from occurring.

[0023] To address the aforementioned technical problems, this invention provides a method, system, equipment, and medium for detecting leaks in heat transfer tubes of steam generators, thus resolving the issues in existing technologies regarding preventing heat transfer tube rupture accidents.

[0024] Example 1: This example provides a method for constructing a quantitative relationship, which characterizes the correspondence between response parameters caused by leakage and the crack size of the heat transfer tube. This construction method can be applied to terminal devices, which can be terminal products with data processing capabilities, such as computers. In this example, as... Figure 1 As shown, the construction method specifically includes the following steps: S100, multiple jet diameters are set, and cooling water is sequentially injected into the heavy liquid metal in the container with the multiple jet diameters. The injected cooling water is used to simulate cooling water leaking from the heat transfer tube. The heat transfer tube is a pipe that constitutes a steam generator. The steam generator exchanges heat with the heavy liquid metal. The jet diameter is used to simulate the crack size of the heat transfer tube.

[0025] S200, after each injection of the cooling water, response sample data triggered by bubbles are collected, wherein the bubbles are formed by heating the cooling water with the heavy liquid metal.

[0026] S300, based on the multiple jet diameters and the response sample data corresponding to each of the multiple jet diameters, construct a quantitative relationship between the response parameters and the crack size of the heat transfer tube.

[0027] Step S100 includes the following specific steps: an injection device with multiple orifices is provided on the outer wall of the container, the orifices being sealed and connected to the container; the injection device is controlled to sequentially inject cooling water into the heavy liquid metal inside the container through orifices of different orifices, the orifices being used to control the jet diameter of the cooling water.

[0028] The injection device in this embodiment is a laser micro-orifice plate injection device. The laser micro-orifice plate injection device is provided with laser micro-holes with a diameter of 40um to 200um. The laser micro-holes are circular through holes precisely machined on a 1mm thick AISI 316 stainless steel plate using drilling technology. The equivalent hydraulic diameter of the circular through hole corresponds to the equivalent opening size of the micro-crack in the actual heat transfer tube of the steam generator. Under the same pressure difference conditions, it can generate flow characteristics and bubble generation behavior similar to the actual micro-crack, thereby simulating the leakage process of micro-cracks of different sizes in the heat transfer tube.

[0029] When the aperture of the laser micro-orifice is 40µm and the pressure of the high-pressure cooling water injected through the laser micro-orifice is 1-2MPa, it simulates the lower limit of microcracks in the heat transfer tube. This laser micro-orifice is in a normal and usable state. That is, when the aperture of the laser micro-orifice is 40µm, it is possible to inject cooling water into heavy liquid metal with a pressure of 1-2MPa.

[0030] When the aperture of the laser micro-orifice is 60µm and the pressure of the high-pressure cooling water injected through the laser micro-orifice is 1-3MPa, it simulates a typical micro-crack in a heat transfer tube. At this time, the laser micro-orifice is prone to blockage.

[0031] When the aperture of the laser micro-orifice is 100µm and the pressure of the high-pressure cooling water injected through the laser micro-orifice is 2-4MPa, it simulates the lower limit of microcracks in the heat transfer tube, and this laser micro-orifice is in a normal and usable state.

[0032] When the aperture of the laser micro-orifice is 150 μm and the pressure of the high-pressure cooling water injected through the laser micro-orifice is 2-5 MPa, it simulates the lower limit of microcracks in the heat transfer tube, and this laser micro-orifice is in a normal and usable state.

[0033] When the aperture of the laser micro-orifice is 200 μm and the pressure of the high-pressure cooling water injected through the laser micro-orifice is 2-5 MPa, it simulates the lower limit of microcracks in the heat transfer tube, and this laser micro-orifice is in a normal and usable state.

[0034] like Figure 2 As shown, the injection device is located at the bottom of the outer wall of the container. The laser micro-orifice is connected to the heavy liquid metal inside the container, and the laser micro-orifice is sealed to the container. A one-way valve is installed inside the laser micro-orifice, allowing only high-pressure cooling water to be injected into the heavy liquid metal through the laser micro-orifice, while preventing the heavy liquid metal from leaking to the outside of the container through the laser micro-orifice.

[0035] In this embodiment, the pressure range of the injected high-pressure cooling water is 1MPa to 5MPa, which is used to simulate the high-pressure cooling water in the heat transfer tube.

[0036] In this embodiment, the heavy liquid metal is a lead-bismuth eutectic alloy (LBE). In simulating the leakage of high-pressure cooling water from a heat transfer tube due to a crack, this embodiment does not place the actual heat transfer tube in the heavy liquid metal; instead, a laser microporous plate injection device is used to inject high-pressure cooling water into the heavy liquid metal.

[0037] like Figure 2 As shown, the injection device injects high-pressure cooling water into heavy liquid metal (including LBE) through laser micro-holes of different diameters. High-pressure cooling water is injected into heavy liquid metal through laser micro-holes of different diameters to simulate high-pressure cooling water leaking into heavy liquid metal through cracks of different sizes in heat transfer tubes.

[0038] The injection device in this embodiment is equipped with a Coriolis mass flow meter, and the leakage flow control range is 0.01 g / s to 0.55 g / s.

[0039] In this embodiment, the laser microplate injection device can also be placed directly in heavy liquid metal, as long as the injection device is a high-temperature resistant device.

[0040] The S100 uses the same laser micro-hole to inject high-pressure cooling water into the heavy liquid metal at least three times. After each injection of high-pressure cooling water, response sample data is repeatedly collected to increase the number of samples and thus improve the accuracy of the final fitted quantitative relationship.

[0041] The acquisition of response sample data induced by bubbles in step S200 includes: using a vibration acceleration sensor to collect sample vibration data of the container, wherein the vibration of the container is caused by bubbles formed by the heating of cooling water by the heavy liquid metal reaching the container; using a sound pressure sensor to collect sample sound pressure data induced by the bubbles, and using the sample vibration data and the sample sound pressure data as the response sample data.

[0042] In other words, leaked high-pressure cooling water will form bubbles under high temperature. These bubbles, due to dynamics, reach the solid phase of the container and are received, causing the container to vibrate. The vibration frequency of the container is the sample vibration data. In this embodiment, a vibration acceleration sensor located at the top inside the container is used to collect the sample vibration data.

[0043] The sample sound pressure data represents the sound pressure fluctuation signal excited by the bubble. In this embodiment, the sound pressure fluctuation signal is collected using a sound pressure sensor located at the top inside the container.

[0044] In this embodiment, the quantitative relationship in step S300 includes the relationship between crack size and vibration frequency and the relationship between crack size and sound pressure parameter.

[0045] Among them, crack size With vibration frequency The relationship between them, i.e., the vibration crack relationship: , Represents the overall calibration coefficient. The unit is um. The unit is Hz. The unit is Hz·m.

[0046] Crack size With sound pressure parameters The relationship between them, namely the acoustic pressure crack relationship:

[0047] In the formula, This represents the orifice flow coefficient, which has one dimension. The pressure difference between the inside and outside of a heat transfer tube placed in heavy liquid metal, expressed in MPa. Density of heavy liquid metal, expressed in kg / m³; The intercept coefficient represents the system's background sound pressure level, which is the sound pressure level of the background noise in the system itself when there is no leakage in the heat transfer tube. The slope coefficient represents the sensitivity of the sound pressure level to changes in flow rate.

[0048] The purpose of simulating a heat transfer tube crack in this embodiment is to collect data on the occurrence of cracks in the heat transfer tube. value, The value will The value and The value and the corresponding crack size Substitute the value into the two relations above to solve. , , , Find the value of . , , , After obtaining the value, we get two applicable relations.

[0049] Example 2: This example provides a detection system, including a vibration acceleration sensor, a sound pressure sensor, a sound emitter, and a protective component for protecting the sound pressure sensor.

[0050] like Figure 3As shown, the top of the container has a flange, and a vibration acceleration sensor (a high-sensitivity HSA accelerometer) and protective components are fixed to the outside of the flange. The sound pressure sensor is located inside the protection assembly. Figure 3 The PCB130E20 is a room temperature microphone, and there are four PCB130E20 microphones in total.

[0051] The vibration acceleration sensor covers low- to mid-frequency structural vibration signals from 0.5 kHz to 7 kHz.

[0052] In this embodiment, a ceramic fiber heat insulation pad with a thickness of not less than 5 mm is installed between the vibration acceleration sensor and the high-temperature area, and a thermocouple is set near the sensor mounting base for real-time temperature monitoring. When the temperature at the vibration acceleration sensor exceeds 230°C or the temperature at the sound pressure sensor exceeds 70°C, the system automatically triggers an alarm and stops the experiment.

[0053] The protection component prevents external sound pressure fluctuations from interfering with the sound pressure sensor's acquisition of sound pressure fluctuations inside the container, ensuring the acquisition of the true sound pressure fluctuations excited by bubbles generated by leaking high-pressure cooling water. Since the sound pressure sensor is in contact with the high-temperature environment inside the container, the cooling environment provided by the protection component also prevents the sound pressure sensor from being damaged by the high temperature.

[0054] The sound pressure sensor in this embodiment covers gas phase sound pressure signals from 10 Hz to 8 kHz.

[0055] like Figure 3 As shown, the protective assembly consists of a nested metal shell, a ceramic heat insulation bracket, and a cooling gas pipe. The metal shell is the outermost sealed shell and is fixed to the flange on the top of the container. The metal shell is connected to the inside of the container through a through hole on the flange. The connection between the metal shell and the inside of the container allows the sound pressure sensor located inside the metal shell to collect the sound pressure fluctuation signal excited by the bubbles inside the container.

[0056] The ceramic heat insulation bracket is fixed to the inner wall of the metal shell, and the sound pressure sensor is fixed on the ceramic heat insulation bracket. The ceramic heat insulation bracket serves as an intermediate heat insulation layer, thermally isolating the sound pressure sensor from the high-temperature metal shell.

[0057] A cooling gas conduit runs from the outside of the metal casing through its internal cavity, meaning it penetrates the inner wall of the metal casing. This conduit provides a set temperature range for the sound pressure sensor. The cooling gas conduit extends through the side wall of the metal support to the cavity between the ceramic heat-insulating support and the microphone body. Cold argon gas flows through this conduit into the cavity and then across the microphone surface, carrying away heat. The heated argon gas exits through the conduit on the opposite side, forming a continuous cooling loop to maintain the microphone, whose operating temperature limit is no more than 50°C, within a safe temperature range.

[0058] The acoustic emitter collects spontaneously radiated high-frequency elastic stress waves, which are generated by dynamic events such as bubble collapse and collision. The acoustic emission sensor is a passive receiving sensor, installed outside the reaction vessel, and acoustically coupled to the monitored liquid metal through a self-made stainless steel waveguide. It is used to receive high-frequency elastic stress waves with frequencies higher than 10 kHz excited by bubble dynamic events in the liquid metal and container structure.

[0059] In this embodiment, the acoustic emission sensor, vibration acceleration sensor, and sound pressure sensor complement and cooperate in the frequency band. After the three types of signals are collected independently, they are processed together by data analysis software. The micro-leakage status of the heat transfer tube is judged by comprehensive analysis of multi-frequency band characteristics, and mutual verification is used to improve the reliability of detection.

[0060] The frequency domain analysis functions of the data analysis software include: Fast Fourier Transform (FTFT) power spectral density analysis, used to identify characteristic frequency peaks in the leakage signal with an amplitude increase of not less than 10 dB compared to the background signal; 1 / 3 octave band analysis, used to calculate the sound pressure level of each frequency band and establish a quantitative relationship between the total sound pressure level and the leakage flow rate; and Short Time Fourier Transform (SFT) time-frequency analysis, used to observe the dynamic evolution of characteristic frequencies over time during bubble formation, rise, and collapse.

[0061] The data analysis software also performs cross-correlation analysis on the vibration signal and the sound pressure signal. It determines that the two types of signals originate from the same bubble dynamics event by the presence of obvious cross-correlation peaks near zero delay. It also quantifies the linear correlation between the signal characteristics and the operating parameters by calculating the Pearson correlation coefficient between the characteristic parameters and the leakage flow rate and injection pressure. A correlation coefficient of not less than 0.8 is considered a strong correlation.

[0062] If the signals collected by the three sensors do not match, they are collected again until the signals collected by the vibration acceleration sensor and the sound pressure sensor match the signals collected by the acoustic emission sensor. Then, the crack size of the heat transfer tube is calculated based on the signal collected by the vibration acceleration sensor and the crack size of the heat transfer tube is calculated based on the signal collected by the sound pressure sensor. The average of these two crack sizes is taken as the final crack size.

[0063] This embodiment can also add a high-temperature accelerometer (HTA) to the high-sensitivity accelerometer (HSA). The HTA is installed inside the container, and its operating temperature is no lower than 482°C. This high-sensitivity accelerometer is used to acquire structural vibration signals with a high signal-to-noise ratio under low vibration levels. The HTA is used as the primary signal (because it is closer to the bubble and has less characteristic frequency distortion), while the HSA is used for redundancy verification. If the characteristic frequencies identified by both are consistent, the reliability is high; if they are inconsistent, the HTA is given priority.

[0064] Alternatively, HSA is responsible for the low-frequency range of 0.5–2kHz (low-frequency vibrations of bubble formation and detachment), and HTA is responsible for the mid-to-high-frequency range of 2–7kHz (high-frequency components of collapse impact). The two segments are spliced ​​together to form a complete characteristic spectrum, and the crack size is calculated using the whole-end characteristic spectrum.

[0065] This embodiment can also add a high-temperature probe microphone (PCB 377B26 type) that extends deep into the container to the PCB130E20 microphone (i.e., sound pressure sensor). The stainless steel probe tube of the high-temperature probe microphone can withstand a temperature of not less than 800°C and has a frequency response range of 2Hz to 20kHz.

[0066] An external PCB130E20 microphone is used to acquire a complex background noise baseline. During data processing, the system executes an adaptive thresholding algorithm to subtract the environmental noise baseline from the measured signal, thereby improving the detection sensitivity of weak signals with minute leaks. By calculating the cross-correlation function between the signal acquired by the external sensor and the signal acquired by the internal high-temperature probe microphone PCB 377B26, it is determined whether the signals simultaneously exhibit peaks near zero delay. If the two types of signals are highly correlated, it can be confirmed that the signal originates from internal bubble dynamics events, not external environmental interference, thus reducing the false alarm rate.

[0067] This embodiment also includes a multi-channel data acquisition unit, a charge amplifier, and data analysis software. The charge amplifier is connected to the vibration acceleration sensor and is used to convert the charge output signal of the vibration sensor into a voltage signal. The multi-channel data acquisition unit is connected to the output of the charge amplifier and the sound pressure sensor, respectively. The multi-channel data acquisition unit is used to simultaneously acquire the vibration electrical signal output by the vibration acceleration sensor and the sound pressure electrical signal output by the sound pressure sensor. The data analysis software is used to perform joint time-domain and frequency-domain analysis on the acquired signals.

[0068] Among them, the analog-to-digital converter of the multi-channel data acquisition instrument has a bit depth of no less than 16 bits, a sampling rate of no less than 20kHz per channel, and achieves time synchronization between the vibration channel and the sound pressure channel through the IEEE1588 synchronization protocol, with a synchronization accuracy better than 100 nanoseconds.

[0069] Example 3, based on Example 1, provides a leakage detection method, which includes the following specific steps S400, S500, S600, and S700: S400: When cooling water is injected into the heat transfer tube, the measured vibration data of the container and the measured sound pressure data inside the container are collected.

[0070] In step S400, during the process of injecting cooling water into the heat transfer tube, the vibration data of the container and the sound pressure data inside the container are collected in real time to monitor whether cracks appear in the heat transfer tube and the size of the cracks, thereby monitoring the safety of the nuclear reactor inside the container in real time. The sound pressure data is the sound pressure fluctuation signal excited by the bubbles formed by the leaking cooling water in the heat transfer tube.

[0071] S500, apply the vibration crack relationship to the measured vibration data to solve for the first crack size.

[0072] The measured vibration data in this embodiment are the actual collected vibration frequencies, and these vibration frequencies are used as... Substitute the value into (The vibration crack relationship) can then be solved. The value of is the size of the first crack.

[0073] S600, apply the sound pressure crack relationship to the measured sound pressure data to solve for the second crack size.

[0074] Measured sound pressure data The value will Substitute the value into (Acoustic pressure crack relationship), which can then be solved. The value of is the second crack size.

[0075] S700, based on the first crack size and the second crack size, obtain the leakage detection result.

[0076] If the size of the first crack and the size of the second crack differ significantly, the nuclear reactor operation must be stopped and an alarm issued. If the size of the first crack and the size of the second crack are not significantly different, the two sizes are weighted and calculated, and the weighted result is used as the final crack size. The degree of leakage in the heat transfer tube is determined based on the final crack size, and this degree of leakage is used as the leakage detection result.

[0077] In this embodiment, the final crack size is used as... Substitute the value into Solve for the leakage mass flow rate. The value of (g / s) is used to determine the appropriate value based on the given information. The value determines whether an alarm should be triggered.

[0078] The following is based on Figure 4 Taking an example, the implementation process of the detection method of the present invention will be described in detail: The first step is background signal acquisition: Under the condition of no water injection, vibration acceleration signal and sound pressure signal are collected for no less than 5 minutes as baseline data for subsequent analysis.

[0079] The second step is to collect leakage signals: start the high-pressure water injection system and inject high-pressure cooling water into the high-temperature liquid lead-bismuth alloy through the laser micro-hole plate. Simultaneously collect vibration acceleration signals, sound pressure signals, and real-time pressure and flow data of the injection system. Repeat the experiment under the same working condition no less than 3 times, and the signal characteristic deviation between repeated experiments should not exceed ±5%.

[0080] The third step is signal preprocessing: abnormal segments are removed and background noise is subtracted from the acquired data, and the signals are synchronized and aligned in time according to the IEEE 1588 timestamp.

[0081] The fourth step is time-domain analysis: extract the peak acceleration, root mean square acceleration, and peak factor of the vibration signal, and extract the peak sound pressure level and root mean square sound pressure level of the sound pressure signal; use the background signal amplitude plus 3 times the standard deviation as an adaptive threshold to automatically identify bubble pulse events and count the pulse event rate per unit time.

[0082] Step 5, Frequency Domain Analysis: Perform FFT self-power spectral density analysis on the preprocessed signal in the frequency band from 0.5Hz to 8kHz, with Hanning window as the window function and frequency resolution not less than 1Hz; perform 1 / 3 octave band (CPB) analysis; and perform STFT time-frequency analysis with a window length of 512 points and an overlap rate of 50%.

[0083] Step 6, Correlation Verification: Calculate the cross-correlation function between the vibration signal and the sound pressure signal. If a significant peak appears near zero delay, the two signals are determined to be from the same source. Calculate the Pearson correlation coefficient between the characteristic parameters and the leakage flow rate and injection pressure. If the correlation coefficient is not less than 0.8, it is determined to be a strong correlation.

[0084] Step 7, Feature Matching and Leakage Judgment: Match the identified feature frequency peaks with a pre-established database, based on... Determine the crack size range based on Quantitatively assess leakage flow rate.

[0085] Figure 5The diagram shows a comparison between the power spectral density curve of the background signal and the power spectral density curve of the 60µm crack leakage signal. At a frequency of 1400 Hz, the power spectral density of the leakage signal shows a significant local maximum (peak). This peak only appears under leakage conditions and is not present in the background signal, hence it is called the "characteristic frequency peak". This indicates that when the frequency of 1400 Hz appears, the amplitude of the leakage signal minus the amplitude of the background signal is greater than 10 dB. In other words, if a peak at least 10 dB higher than the background signal appears near 1400 Hz, it indicates that there is a minor leak in the heat transfer tube.

[0086] The following specific experiments illustrate the detailed process of Example 1: I. System Hardware Selection and Parameter Configuration 1.1 Vibration Accelerometer Sensor Assembly High-Temperature Charge-Type Piezoelectric Accelerometer (HTA, Built-in): Sensitivity 30 pC / g; Measurement range ±1500g; Frequency response range 0.5kHz to 7kHz (±5%), Extended response 0.3kHz to 9kHz (±10%); Maximum operating temperature 250℃; Installation resonant frequency greater than 27kHz; Sensor housing material stainless steel; Weight approximately 25 grams; M5 thread mounting; Signal output via a dedicated 10-meter high-temperature resistant cable (rated temperature 200℃). The gap between the sensor mounting surface and the flange should not exceed 0.01mm; Installation torque controlled between 25Nm and 30Nm; Surrounded by a ceramic fiber heat insulation pad of not less than 5mm; A K-type thermocouple is attached next to the mounting base for real-time temperature monitoring; Automatic alarm triggered when the temperature exceeds 230℃.

[0087] High-sensitivity accelerometer (HSA, external type): mounted on the outside of the top flange of the reaction vessel, with extended low-frequency response, hermetic sealing design, ESD protection, and a signal-to-noise ratio superior to conventional accelerometers at low vibration levels, mechanically coupled through the flange through-hole.

[0088] 1.2 Pocket Charge Amplifier Gain is 1mV / pC (160Hz reference); frequency response is 0.5Hz to 50kHz (-3dB); linearity is better than ±1%; output impedance is less than 100Ω; standard power supply is 24V / 4mA. Before use, the gain must be verified with known charge signals of 100pC, 500pC, and 1000pC, and the linearity error must be ≤±1%; the noise floor must be ≤50µVrms when there is no input.

[0089] 1.3 Acoustic pressure sensor array and argon gas cooling protection system Room temperature prepolarized microphone (PCB 130E20 type, i.e. sound pressure sensor body, 4 pieces): prepolarized condenser type, integrated with IEPE preamplifier; diameter 7mm; dynamic range 122dB; maximum operating temperature 50℃; gain selectable ×1, ×10, ×100.

[0090] High-temperature probe microphone (PCB 377B26, i.e. sound pressure sensor body, 1 piece): 160mm stainless steel probe tube withstands temperatures up to 800℃; frequency response 2Hz to 20kHz (flat); mounted in the central through hole of the flange, with the probe extending into the air space.

[0091] Combination Figure 2 The three-layer structure (from outside to inside) of the argon gas cooling protection system for the PCB 130E20 room temperature microphone is as follows: Metal bracket: Sealed flange through hole to prevent internal gas leakage, providing support for the microphone, and cooling gas inlet and outlet on the side wall.

[0092] Ceramic heat-insulating bracket: Fixed to the inner wall of the metal bracket, the material is high-temperature ceramic, forming a heat-barrier layer between the metal shell and the microphone body, ensuring that the microphone temperature does not exceed 50℃.

[0093] Cooling gas conduit: This conduit runs through the side wall of the metal support and extends into the cavity between the ceramic support and the microphone body. Cool argon gas is introduced and flows across the microphone surface, dissipating heat through convection. Hot argon gas is discharged from the opposite conduit, creating a continuous circulation. Argon gas is chemically inert and does not react chemically with the LBE or the container materials.

[0094] 1.4 Acoustic Emission Sensor and Waveguide Acoustic emission (AE) sensors are passive receivers. Their working principle involves passively receiving the high-frequency elastic stress waves spontaneously emitted by the measured object (in this system, dynamic events such as bubble collapse and rising collisions in liquid metal), rather than actively emitting sound waves. The AE sensor is installed outside the reaction vessel and acoustically coupled to the liquid lead-bismuth alloy inside the vessel via a self-made AISI316L austenitic stainless steel waveguide. The waveguide transmits the high-frequency acoustic emission signals generated in the liquid metal along a solid-state waveguide path to the sensor installed outside the vessel, avoiding direct exposure of the sensor to the high-temperature liquid metal environment. This allows for the reception of high-frequency elastic stress wave signals with frequencies higher than 10kHz.

[0095] 1.5 Multi-channel data acquisition instrument 16-channel, 24-bit ADC, maximum sampling rate 256kHz / channel, supports single-ended DC, differential DC, AC, IEPE, and strain inputs; IEPE excitation voltage programmable selection: 3.3V / 5V / 10V / 12V; built-in 16GB storage; IEEE1588 synchronization accuracy better than 100ns; supports offline mode. Vibration signal chain: HTA (M5 interface) → 10m high-temperature shielded cable → charge amplifier (M5 input / BNC output) → shielded cable → vibration channel of the data acquisition unit. Sound pressure signal chain: IEPE microphone (BNC interface) → shielded cable → sound pressure channel of the data acquisition unit (IEPE powered, output voltage ≥22V must be confirmed). All signal cables and power cables should be at least 30cm apart and laid parallel to each other.

[0096] II. Sensor Calibration Accelerometer: Standard vibration table calibrated at room temperature, covering frequencies of 0.5Hz, 10Hz, 100Hz, 1kHz, and 7kHz; correction values ​​are entered and compensated by software. Sound Pressure Sensor: Sound calibrator calibrated at 1kHz and 114dB, with accuracy meeting IEC 61672 Class 1 standards and IEC 1094-4 requirements. All calibration reports are archived for traceability.

[0097] III. Example: Leakage Detection Experiment of φ60µm Microplate Inject a predetermined amount of LBE into the reaction vessel, raise the temperature to 180℃ at a rate of 5℃ / min, and maintain the temperature for 30 minutes (temperature difference within the vessel ≤ ±3℃). Install a φ60µm laser microporous plate (equivalent to a cracked 60µm heat transfer tube), inject at a pressure of 3MPa, and maintain a mass flow rate of approximately 0.05g / s.

[0098] After the high-pressure water comes into contact with the LBE at the micropore outlet, it vaporizes violently and the bubble goes through four stages: (1) Generation stage: the surface tension, buoyancy and viscosity work together to form the bubble nucleus. The bubble nucleus expands and generates radial impact force, which is transmitted to the container wall through the liquid metal to generate initial pulse vibration; (2) Detachment stage: when the buoyancy is greater than the surface tension, the bubble detaches from the micropore and generates instantaneous impact pulse; (3) Rising stage: the bubble rises under the action of buoyancy and triggers continuous vibration; (4) Collapse stage: the bubble breaks at the gas-liquid interface and releases energy instantaneously to generate broadband pulse vibration and sound pressure wave.

[0099] IV. Specific Implementation Steps for Signal Processing Step 1, Background signal acquisition: Acquisition time ≥ 5 minutes, background noise of vibration channel must be ≤ 0.001g RMS, sound pressure channel must be ≤ 10µV RMS.

[0100] Step 2, Leakage signal acquisition: Start recording 1 minute before water injection, continue for ≥10 minutes, and align all channels using IEEE1588 timestamps.

[0101] Step 3, signal preprocessing: remove abnormal data segments; subtract background mean; synchronize and align multiple signals in time.

[0102] Step 4, FFT self-power spectral density analysis: Hanning window, frequency resolution ≤1Hz, frequency band 0.5Hz to 8kHz. Taking this example (φ60µm, 180℃, 3MPa): at 3300Hz, there is an environmental noise peak (approximately -68dBSPL) present in both background and leakage conditions, which is determined to be an interference peak and not used as a criterion; at 1400Hz, the characteristic frequency peak amplitude appears only during water injection, approximately -38dBSPL, while the background amplitude is approximately -78dBSPL, with an amplitude difference of approximately 40dB, far exceeding the 10dB criterion threshold. Therefore, 1400Hz is determined to be the characteristic frequency peak (Bubble Tag) of the φ60µm crack, and substituted into... The equivalent crack diameter can be calculated by reverse calculation.

[0103] Step 5, 1 / 3 octave band (CPB) analysis: Calculate the sound pressure level for each frequency band from 6.3 Hz to 8 kHz. In this embodiment, the most significant improvement is observed in the 1250 Hz to 1600 Hz band. Establish a logarithmic fitting relationship between the total sound pressure level and the leakage flow rate. Used for real-time traffic estimation.

[0104] Step 6, STFT time-frequency analysis: Window length 512 points, overlap rate 50%, generate time-frequency-amplitude three-dimensional acoustic spectrum, observe the dynamic evolution of characteristic frequencies over time.

[0105] Step 7, Cross-correlation function analysis (event origin verification): Calculate the cross-correlation function between the vibration and sound pressure signals; if a peak occurs at τ≈0ms, it confirms that the two types of signals originate from the same source. In this embodiment, the peak correlation coefficient is approximately 0.82, which is greater than the strong correlation threshold of 0.8, confirming that the leakage event actually occurred.

[0106] V. Establishment of Multi-condition Experimental Matrix and Characteristic Frequency Database.

[0107] Temperature conditions: 180℃, 200℃, 240℃; Crack size conditions: 40µm, 60µm, 100µm, 150µm, 200µm laser microporous plates; Leakage flow rate conditions: Injection pressure 1MPa / 3MPa / 5MPa, mass flow rate 0.01g / s to 0.55g / s (5 gradients); The same condition was repeated 3 times, with a deviation ≤±5%. The characteristic frequency, amplitude, half-power bandwidth, and total sound pressure level data under all conditions were archived in a three-level structure of "temperature-aperture-flow rate" to form a micro-leakage characteristic frequency database. The calibration coefficients k, a, and b were obtained by fitting from this database, providing standardized parameter references for online monitoring and quantitative early warning of micro-leakage in heat transfer tubes during actual operation.

[0108] In summary, this invention simultaneously acquires structural vibration signals propagating through a solid-phase medium and sound pressure fluctuation signals propagating through a gas-phase medium. The cross-correlation function verifies the event homology of the two types of signals, and the two-dimensional cross-confirmation mechanism significantly reduces the false alarm rate of a single sensor in complex reactor vibration and noise environments. The adaptive threshold algorithm automatically subtracts the environmental noise baseline during signal preprocessing, further improving the detection reliability under weak signal conditions.

[0109] By combining a metal-ceramic composite bracket with a reverse circulation cooling structure using cold argon, a high-sensitivity microphone with an upper operating temperature limit of 50°C can be stably used in a location near a high-temperature flange; a high-temperature probe microphone can directly probe into the gas space of a container by means of a stainless steel probe tube that can withstand temperatures of no less than 800°C; and a high-temperature accelerometer with an operating temperature of no less than 482°C can be directly immersed in a liquid metal area, fundamentally solving the problem of sensor adaptation in high-temperature environments.

[0110] Based on the above embodiments, the present invention also provides a terminal device, the principle block diagram of which can be as follows: Figure 6 As shown, the terminal device includes a processor, memory, network interface, and display screen connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides the environment for the operation of the operating system and computer programs in the non-volatile storage media. The network interface is used to communicate with external terminals via a network connection. When the computer program is executed by the processor, it implements a method for detecting leaks in the heat transfer tubes of a steam generator. The display screen of the terminal device can be an LCD screen or an e-ink screen.

[0111] Those skilled in the art will understand that Figure 6 The schematic diagram shown is only a partial structural diagram related to the present invention and does not constitute a limitation on the terminal device to which the present invention is applied. The specific terminal device may include more or fewer components than shown in the figure, or combine certain components, or have different component arrangements.

[0112] In one embodiment, a terminal device is provided, comprising a memory, a processor, and a steam generator heat transfer tube leakage detection method program stored in the memory and executable on the processor. When the processor executes the steam generator heat transfer tube leakage detection method program, it implements the following operation instructions: Multiple jet diameters are set, and cooling water is sequentially injected into the heavy liquid metal in the container with the multiple jet diameters. The injected cooling water is used to simulate cooling water leaking from the heat transfer tube. The heat transfer tube is a pipe that constitutes a steam generator. The steam generator exchanges heat with the heavy liquid metal. The jet diameter is used to simulate the crack size of the heat transfer tube. After each injection of the cooling water, response sample data triggered by bubbles are collected, wherein the bubbles are formed by heating the cooling water with the heavy liquid metal; Based on multiple jet diameters and their corresponding response sample data, a quantitative relationship between the response parameters and the crack size of the heat transfer tube is constructed. When cooling water is injected into the heat transfer tube, the measured vibration data of the container and the measured sound pressure data inside the container are collected. The vibration crack relationship is applied to the measured vibration data to solve for the size of the first crack; The second crack size is determined by applying the acoustic pressure crack relationship to the measured acoustic pressure data. Based on the first crack size and the second crack size, the leakage detection results are obtained.

[0113] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided by this invention can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for detecting leaks in heat transfer tubes of a steam generator, characterized in that, The leak detection method includes constructing a quantitative relationship between the response parameters caused by the leak and the crack size of the heat transfer tube; the step of constructing the quantitative relationship includes: Multiple jet diameters are set, and cooling water is sequentially injected into the heavy liquid metal in the container with the multiple jet diameters. The injected cooling water is used to simulate cooling water leaking from the heat transfer tube. The heat transfer tube is a pipe that constitutes a steam generator. The steam generator exchanges heat with the heavy liquid metal. The jet diameter is used to simulate the crack size of the heat transfer tube. After each injection of the cooling water, response sample data triggered by bubbles are collected, wherein the bubbles are formed by heating the cooling water with the heavy liquid metal; Based on multiple jet diameters and their corresponding response sample data, a quantitative relationship between the response parameters and the crack size of the heat transfer tube is constructed.

2. The method for detecting leaks in the heat transfer tubes of a steam generator as described in claim 1, characterized in that, Multiple jet diameters are set, and cooling water is sequentially injected into the heavy liquid metal in the container at the multiple jet diameters, including: An injection device with multiple orifices is provided on the outer wall of the container, and the orifices are sealed and connected to the container. The injection device is controlled to sequentially inject cooling water into the heavy liquid metal in the container through orifices of different diameters, wherein the orifice diameter is used to control the jet diameter of the cooling water.

3. The method for detecting leaks in the heat transfer tubes of a steam generator as described in claim 2, characterized in that, The aperture size ranges from [40um, 200um].

4. The method for detecting leaks in the heat transfer tubes of a steam generator as described in any one of claims 1-3, characterized in that, Collect sample data of the response triggered by bubbles, including: The vibration data of the container is obtained using a vibration acceleration sensor. The vibration of the container is caused by bubbles formed by the heating of cooling water by the heavy liquid metal reaching the container. The sound pressure sensor is used to collect sample sound pressure data induced by the bubble, and the sample vibration data and the sample sound pressure data are used as the response sample data.

5. The method for detecting leaks in the heat transfer tubes of a steam generator as described in claim 1, characterized in that, The quantitative relationships include the vibration crack relationship between vibration frequency and crack size, and the sound pressure crack relationship between sound pressure and crack size; the leakage detection method further includes: When cooling water is injected into the heat transfer tube, the measured vibration data of the container and the measured sound pressure data inside the container are collected. The vibration crack relationship is applied to the measured vibration data to solve for the size of the first crack; The second crack size is determined by applying the acoustic pressure crack relationship to the measured acoustic pressure data. Based on the first crack size and the second crack size, the leakage detection results are obtained.

6. The method for detecting leaks in the heat transfer tubes of a steam generator as described in claim 5, characterized in that, Based on the first crack size and the second crack size, the leakage detection results are obtained, including: A high-frequency elastic wave is collected using an acoustic emitter, and the high-frequency elastic wave is correlated with the bubble. Based on the first crack size, the second crack size, and the high-frequency elastic wave, the leakage detection result is obtained.

7. A detection system, characterized in that, The system includes: A vibration acceleration sensor is used to collect vibration data of a container, the vibration of which is related to whether bubbles overflow from the heat transfer tube inside the container due to rupture. A sound pressure sensor is used to collect sound pressure data inside a container, and the sound pressure data is related to bubbles; An acoustic emitter is used to collect the high-frequency elastic waves excited by the bubble.

8. The detection system as described in claim 7, characterized in that, The system also includes a protection component for protecting the sound pressure sensor; the protection component includes: A metal outer shell is fixed to the container and is in sealed communication with the interior of the container; A ceramic heat-insulating bracket is fixed to the inner wall of the metal shell and is used to fix the sound pressure sensor. A cooling gas pipe runs through the inner wall of the metal casing to provide a working environment within a set temperature range for the sound pressure sensor.

9. A terminal device, characterized in that, The terminal device includes a memory, a processor, and a steam generator heat transfer tube leakage detection program stored in the memory and executable on the processor. When the processor executes the steam generator heat transfer tube leakage detection program, it implements the steps of the steam generator heat transfer tube leakage detection method as described in any one of claims 1-6.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a steam generator heat transfer tube leakage detection program, which, when executed by a processor, implements the steps of the steam generator heat transfer tube leakage detection method as described in any one of claims 1-6.

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