A method and system for fault diagnosis of a micro fission ionization chamber

Abstract

This invention relates to a method and system for diagnosing faults in microfission ionization chambers, comprising: monitoring microfission ionization chambers in the same pressurized water reactor nuclear power unit; and when any microfission ionization chamber experiences an anomaly in calibration coefficient or plateau tilt, obtaining the fault type of the microfission ionization chamber to be diagnosed; if the fault type is an excessive calibration coefficient, then a preset calibration coefficient diagnostic method is used to diagnose the microfission ionization chamber to be diagnosed; if the fault type is an abnormally large or excessive plateau tilt, then a preset plateau tilt diagnostic method is used to diagnose the microfission ionization chamber to be diagnosed. This invention uses a preset calibration coefficient diagnostic method based on the physical meaning of the calibration coefficient, providing more comprehensive diagnostic evidence. Simultaneously, the use of a preset plateau tilt diagnostic method solves the problem of insufficient evidence when judging solely based on an abnormally large or excessive plateau tilt. Moreover, the diagnostic method of this invention has clear logic and sufficient evidence, enabling effective diagnosis.

Description

Technical Field

[0001] This invention relates to the technical field of nuclear reactors, and more specifically, to a method and system for diagnosing faults in a micro-fission ionization chamber. Background Technology

[0002] The operating technical specifications for 1000MW-class improved pressurized water reactor nuclear power units stipulate that the neutron measurement system (NMS) of the core measurement system must be available when the nuclear power is greater than 50% FP (FP being rated power). For a nuclear power unit, a device or system is considered available if it can be demonstrated that it can perform the specific functions assigned to it by the design and also possess the required performance level; otherwise, it should be considered unavailable.

[0003] NMS uses five CFUF-43P miniature fission ionization chambers (MFCs) to measure the neutron flux in the reactor core. The MFCs operate in current mode and are sensitive within a specific volume. 235 When U is irradiated with neutrons, it undergoes fission, and the fission fragments deposit energy within the sensitive volume through the ionization of the working gas. In traditional MFC fault diagnosis, the primary criterion for determining MFC usability is that the plateau slope (hereinafter referred to as plateau slope) of the MFC saturation characteristic curve does not exceed 0.2%·V. -1 And the calibration coefficient of MFC should be between [0.92, 1.08].

[0004] Several pressurized water reactor (PWR) nuclear power units have experienced issues during commissioning and startup where the calibration coefficient of new microfiber detectors (MFCs) exceeded acceptance standards. Typically, MFCs with out-of-range calibration coefficients need to be replaced. The MFC calibration coefficient is automatically calculated by the nuclear magnetic resonance (NMS). Traditional fault diagnosis methods do not clearly define the physical meaning of this calibration coefficient, and its use as a basis for MFC fault diagnosis stems from international PWR operation and maintenance experience. For a long time, there has been a lack of necessary justification for using the calibration coefficient as a single technical indicator to determine the usability of an MFC. As a mature nuclear radiation detector, the MFC's manufacturing process and performance levels have reached industrial application standards. After manufacturing, MFCs need to be inspected and calibrated in a test reactor before being shipped. The probability of a new MFC becoming unusable in the early stages of operation is low. Therefore, it is necessary to study methods for using the MFC calibration coefficient for MFC fault diagnosis and to develop new fault diagnosis methods based on the research results.

[0005] Operational experience data from MFC indicates that the ideal slope should be between [0.02, 0.10]%·V. -1 One MFC can typically perform approximately 3000 core neutron measurement tasks. When the plateau tilt exceeds 0.10%·V... -1At this time, it is usually necessary to check the operating status of MFC. In some units, after the initial power increase to 50% FP, individual MFCs experienced a slope exceeding 0.2%·V. -1 The maintenance department replaced the MFC with excessive plateau tilt; however, a few units also had abnormally large MFC plateau tilt (approximately 0.15% V). -1 Although the slope did not exceed 0.2%·V -1 However, despite adopting a conservative maintenance strategy, the maintenance department still replaced the MFCs with abnormally large plateau slopes. Although MFCs with abnormally large or excessive plateau slopes were replaced during the commissioning phase, there is still a lack of systematic research on whether using plateau slope as a single technical indicator to diagnose the usability of MFCs is appropriate.

[0006] MFCs are expensive to import and become highly radioactive after activation. Unnecessary replacements due to fault diagnosis errors not only cause unplanned shutdowns and spare parts consumption, but also expose personnel performing the replacement work to unnecessary radiation exposure. Therefore, it is necessary to study MFC fault diagnosis methods to achieve more accurate fault diagnosis.

[0007] In the existing scheme, before drawing the reactor core power distribution map, the MFC undergoes calibration factor and plateau tilt checks, which are performed by operators using the control system. After the check is completed, the NMS automatically outputs the MFC calibration factor and plateau tilt, which are then compared by operators with the corresponding acceptance criteria. If the calibration factor or plateau tilt exceeds the standard, the MFC's fault diagnosis result is "unusable."

[0008] However, the existing solutions have the following problems:

[0009] 1) The physical meaning of the MFC calibration coefficient is not clear, so it is not sufficient to judge that MFC is unusable based solely on the calibration coefficient exceeding the standard;

[0010] 2) The reason why the MFC that passed the manufacturer's inspection and left the factory had abnormally large or excessive plateau tilt in the early stage of operation is unknown. The reasons for the abnormally large or excessive plateau tilt of the new MFC in the early stage of operation, and whether the plateau tilt can be restored to a more ideal level through certain treatment measures, need further research. Therefore, it is not sufficient to judge that the new MFC is unusable based solely on the abnormally large or excessive plateau tilt.

[0011] 3) The method of diagnosing MFC faults based on plateau inclination and calibration coefficient is too simplistic. Existing fault diagnosis technologies do not fully encompass the electrical and core characteristics of MFC, which may lead to misdiagnosis.

[0012] 4) The working logic of existing MFC fault diagnosis technology is unclear, and there is too little technical basis for fault diagnosis. When performing MFC fault diagnosis, staff lack effective fault diagnosis methods, which is not conducive to systematically and effectively diagnosing MFCs suspected of having faults. Summary of the Invention

[0013] The technical problem to be solved by the present invention is to provide a method and system for diagnosing faults in a micro fission ionization chamber, addressing the shortcomings of the existing technology.

[0014] The technical solution adopted by this invention to solve its technical problem is: to construct a fault diagnosis method for a micro fission ionization chamber, comprising the following steps:

[0015] Each microfission ionization chamber in the same pressurized water reactor nuclear power unit is monitored, and it is determined whether the microfission ionization chamber has an abnormal calibration coefficient or plateau tilt.

[0016] If any micro-fission ionization chamber in the same pressurized water reactor nuclear power unit experiences a calibration coefficient or plateau tilt anomaly, the fault type of the micro-fission ionization chamber to be diagnosed is obtained; the micro-fission ionization chamber to be diagnosed is the micro-fission ionization chamber that has experienced a calibration coefficient or plateau tilt anomaly.

[0017] If the fault type of the micro fission ionization chamber to be diagnosed is that the calibration coefficient exceeds the standard, then the micro fission ionization chamber to be diagnosed is diagnosed using the preset calibration coefficient diagnosis method.

[0018] If the fault type of the micro fission ionization chamber to be diagnosed is an abnormally large or excessive plateau tilt, then the preset plateau tilt diagnosis method is used to diagnose the micro fission ionization chamber to be diagnosed.

[0019] In the fault diagnosis method for a micro fission ionization chamber described in this invention, the step of diagnosing the micro fission ionization chamber by using a preset calibration coefficient diagnosis method if the fault type of the micro fission ionization chamber to be diagnosed is an excessive calibration coefficient includes:

[0020] The physical meaning of determining the calibration coefficient of the micro-fission ionization chamber; the physical meaning of the calibration coefficient of the micro-fission ionization chamber is: the normalized value of the thermal neutron sensitivity of any micro-fission ionization chamber in the same unit relative to the reference thermal neutron sensitivity;

[0021] Based on the physical meaning of the calibration coefficient of the micro fission ionization chamber, the acceptance criteria for the micro fission ionization chamber exceeding the calibration coefficient standard are determined.

[0022] The micro fission ionization chamber to be diagnosed is diagnosed according to the acceptance criteria for exceeding the calibration coefficient.

[0023] In the fault diagnosis method for the micro-fission ionization chamber described in this invention, the physical meaning of determining the calibration coefficient of the micro-fission ionization chamber includes:

[0024] Determine the reference calibration mode for the micro-fission ionization chamber;

[0025] Based on the established reference calibration mode, all micro fission ionization chambers in the same pressurized water reactor nuclear power unit are controlled to enter the same measurement path for calibration.

[0026] After calibration, the average current of each micro-fission ionization chamber is obtained;

[0027] The average current of each micro-fission ionization chamber is compared with the reference current to obtain the calibration coefficient of each micro-fission ionization chamber.

[0028] Acquire the thermal neutron sensitivity of each micro-fission ionization chamber;

[0029] Based on the average current and thermal neutron sensitivity of each micro-fission ionization chamber, the relationship between the average current and thermal neutron sensitivity and the average thermal neutron flux rate along the core measurement path is determined.

[0030] The physical meaning of the calibration coefficient of the micro-fission ionization chamber is determined based on the relationship between the average current and thermal neutron sensitivity and the average thermal neutron flux rate along the core measurement path.

[0031] In the micro-fission ionization chamber fault diagnosis method described in this invention, the relationship between the average current and thermal neutron sensitivity and the average thermal neutron flux rate along the core measurement path satisfies:

[0032] The average current in each micro-fission ionization chamber is equal to the product of the thermal neutron sensitivity and the average thermal neutron flux rate along the core measurement path.

[0033] In the fault diagnosis method for the micro fission ionization chamber described in this invention, the acceptance criterion for the micro fission ionization chamber exceeding the calibration coefficient is as follows:

[0034] If the calibration coefficient of the micro-fission ionization chamber is within the reference coefficient range, then the calibration coefficient of the micro-fission ionization chamber is determined to be within the standard.

[0035] If the calibration coefficient of the micro fission ionization chamber exceeds the reference coefficient range, then the calibration coefficient of the micro fission ionization chamber is determined to be out of standard.

[0036] In the micro-fission ionization chamber fault diagnosis method of the present invention, the step of diagnosing the micro-fission ionization chamber to be diagnosed according to the acceptance criteria for the calibration coefficient exceeding the standard includes:

[0037] Obtain the factory-set thermal neutron sensitivity of the faulty micro-fission ionization chamber;

[0038] Obtain a baseline thermal neutron sensitivity;

[0039] The calibration coefficient of the micro-fission ionization chamber to be diagnosed is calculated based on the factory thermal neutron sensitivity of the micro-fission ionization chamber to be diagnosed and the reference thermal neutron sensitivity.

[0040] The calibration coefficient of the micro fission ionization chamber to be diagnosed is compared with the reference coefficient;

[0041] The micro-fission ionization chamber to be diagnosed is diagnosed based on the comparison results.

[0042] In the micro-fission ionization chamber fault diagnosis method of the present invention, the step of diagnosing the micro-fission ionization chamber to be diagnosed based on the comparison results includes:

[0043] If the comparison result is that the calibration coefficient of the micro-fission ionization chamber to be diagnosed exceeds the range of the reference coefficient, then:

[0044] The automatic calibration coefficients of the micro fission ionization chamber to be diagnosed are obtained; the automatic calibration coefficients are the calibration coefficients calculated by the neutron measurement system.

[0045] If the calibration coefficient of the micro fission ionization chamber to be diagnosed is the same as the automatic calibration coefficient, then the diagnosis result of the micro fission ionization chamber to be diagnosed is: the reason for the calibration coefficient exceeding the standard is that the relative deviation of the factory thermal neutron sensitivity is too large, and the micro fission ionization chamber to be diagnosed is usable.

[0046] In the micro-fission ionization chamber fault diagnosis method of the present invention, the step of diagnosing the micro-fission ionization chamber to be diagnosed based on the comparison results includes:

[0047] If the comparison result is that the calibration coefficient of the micro-fission ionization chamber to be diagnosed is within the range of the reference coefficient, then:

[0048] The calibration coefficients of the micro fission ionization chamber to be diagnosed are compared with the upper and lower limits of the reference coefficient range, respectively.

[0049] If the difference between the calibration coefficient of the micro fission ionization chamber to be diagnosed and the upper limit value is within a preset range, or the difference between the calibration coefficient of the micro fission ionization chamber to be diagnosed and the lower limit value is within a preset range, then the diagnostic result of the micro fission ionization chamber to be diagnosed is: the reason for the calibration coefficient exceeding the standard is that the micro fission ionization chamber to be diagnosed and the reference micro fission ionization chamber cause a difference in the change of thermal neutron sensitivity during the operation of the unit.

[0050] In the micro-fission ionization chamber fault diagnosis method of the present invention, the step of diagnosing the micro-fission ionization chamber to be diagnosed based on the comparison results includes:

[0051] If the comparison result is that the calibration coefficient of the micro-fission ionization chamber to be diagnosed is within the range of the reference coefficient, then:

[0052] The calibration coefficient of the micro fission ionization chamber to be diagnosed is compared with a preset value;

[0053] If the difference between the calibration coefficient of the micro fission ionization chamber to be diagnosed and the preset value is within the deviation range, then the diagnosis result of the micro fission ionization chamber to be diagnosed is: the reason for the calibration coefficient exceeding the standard is that the difference between the micro fission ionization chamber to be diagnosed and the reference micro fission ionization chamber in the operation of the unit is greater than the threshold.

[0054] In the micro-fission ionization chamber fault diagnosis method of the present invention, the step of diagnosing the micro-fission ionization chamber to be diagnosed based on the comparison results further includes:

[0055] If the difference in thermal neutron sensitivity of the micro-fission ionization chamber to be diagnosed during operation in the unit is greater than a threshold, then:

[0056] The automatic calibration coefficient of the micro fission ionization chamber to be diagnosed is compared with the upper limit of the reference coefficient range;

[0057] If the automatic calibration coefficient is greater than the upper limit value, the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the calibration coefficient exceeding the standard is that the thermal neutron sensitivity of the reference micro-fission ionization chamber has abnormally decreased, and the reference micro-fission ionization chamber is unusable.

[0058] In the micro-fission ionization chamber fault diagnosis method of the present invention, the step of diagnosing the micro-fission ionization chamber to be diagnosed based on the comparison results further includes:

[0059] If the difference in thermal neutron sensitivity of the micro-fission ionization chamber to be diagnosed during operation in the unit is greater than a threshold, then:

[0060] The automatic calibration coefficient of the micro fission ionization chamber to be diagnosed is compared with the lower limit of the reference coefficient range;

[0061] If the automatic calibration coefficient is less than the lower limit, the diagnostic result of the micro fission ionization chamber to be diagnosed is: the reason for the calibration coefficient exceeding the standard is that the thermal neutron sensitivity of the micro fission ionization chamber to be diagnosed has decreased abnormally, and the micro fission ionization chamber to be diagnosed is unusable.

[0062] In the micro-fission ionization chamber fault diagnosis method of the present invention, if the fault type of the micro-fission ionization chamber to be diagnosed is abnormally large or exceeds the standard, then the micro-fission ionization chamber to be diagnosed is diagnosed using a preset plateau tilt diagnosis method, which includes:

[0063] Obtain the electrical parameters of the micro fission ionization chamber to be diagnosed;

[0064] Determine whether the electrical characteristics of the micro fission ionization chamber to be diagnosed are qualified based on the electrical parameters.

[0065] If not, the micro-fission ionization chamber to be diagnosed is then diagnosed based on the electrical characteristics described.

[0066] If so, then obtain the nuclear characteristic parameters of the micro fission ionization chamber to be diagnosed;

[0067] The micro-fission ionization chamber to be diagnosed is diagnosed based on the nuclear characteristic parameters.

[0068] In the micro-fission ionization chamber fault diagnosis method of the present invention, the electrical parameters include: the insulation resistance of the faulty micro-fission ionization chamber and its measurement circuit;

[0069] The step of determining whether the electrical characteristics of the micro-fission ionization chamber to be diagnosed are qualified based on the electrical parameters includes:

[0070] The insulation resistance of the micro fission ionization chamber to be diagnosed and its measurement circuit is compared with a reference resistance value.

[0071] If the insulation resistance of the micro fission ionization chamber to be diagnosed and its measuring circuit is less than the reference resistance value, then the electrical characteristics of the micro fission ionization chamber to be diagnosed are deemed unqualified.

[0072] The diagnostic process for the micro-fission ionization chamber based on the electrical characteristics includes:

[0073] If the insulation resistance of the micro-fission ionization chamber to be diagnosed and its measuring circuit is less than the reference resistance value, then the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the excessive or out-of-range plateau is that the insulation resistance of the micro-fission ionization chamber to be diagnosed and its measuring circuit is abnormal, and the micro-fission ionization chamber to be diagnosed is unusable.

[0074] In the micro-fission ionization chamber fault diagnosis method of the present invention, the electrical parameters include: the leakage current of the faulty micro-fission ionization chamber and its measurement circuit;

[0075] The step of determining whether the electrical characteristics of the micro-fission ionization chamber to be diagnosed are qualified based on the electrical parameters includes:

[0076] The leakage current of the micro fission ionization chamber to be diagnosed and its measurement circuit is compared with the reference current.

[0077] If the leakage current of the micro fission ionization chamber to be diagnosed and its measuring circuit is greater than the reference current, then the electrical characteristics of the micro fission ionization chamber to be diagnosed are deemed unqualified.

[0078] The diagnostic process for the micro-fission ionization chamber based on the electrical characteristics includes:

[0079] If the leakage current of the micro-fission ionization chamber to be diagnosed and its measuring circuit is greater than the reference current, then the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the excessive or excessive plateau slope is that the leakage current of the micro-fission ionization chamber to be diagnosed and its measuring circuit is abnormal, and the micro-fission ionization chamber to be diagnosed is unusable.

[0080] In the micro-fission ionization chamber fault diagnosis method of the present invention, the electrical parameters include: the capacitance of the faulty micro-fission ionization chamber and its measurement circuit;

[0081] The step of determining whether the electrical characteristics of the micro-fission ionization chamber to be diagnosed are qualified based on the electrical parameters includes:

[0082] Determine whether the capacitance of the micro fission ionization chamber to be diagnosed and its measurement circuit is within the reference capacitance range;

[0083] If the capacitance of the micro fission ionization chamber to be diagnosed and its measuring circuit is not within the reference capacitance range, then the electrical characteristics of the micro fission ionization chamber to be diagnosed are deemed unqualified.

[0084] The diagnostic process for the micro-fission ionization chamber based on the electrical characteristics includes:

[0085] If the capacitance of the micro-fission ionization chamber to be diagnosed and its measuring circuit is not within the reference capacitance range, then the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the excessive or out-of-range plateau is that the gap between the high-voltage electrode and the collecting electrode of the micro-fission ionization chamber to be diagnosed is abnormal, and the micro-fission ionization chamber to be diagnosed is unusable.

[0086] In the micro-fission ionization chamber fault diagnosis method of the present invention, the nuclear characteristic parameters of the micro-fission ionization chamber to be diagnosed include: measurement current and plateau slope;

[0087] The diagnostic process for the micro-fission ionization chamber based on the nuclear characteristic parameters includes:

[0088] Obtain the measurement current of the micro fission ionization chamber to be diagnosed;

[0089] Determine whether the measured current of the micro fission ionization chamber to be diagnosed has a step value or a spike value;

[0090] If so, the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the excessive or excessive plateau tilt is the abnormal measurement current, and the micro-fission ionization chamber to be diagnosed is unusable;

[0091] If not, then the micro-fission ionization chamber to be diagnosed is diagnosed based on the slope.

[0092] In the micro-fission ionization chamber fault diagnosis method of the present invention, the step of diagnosing the micro-fission ionization chamber to be diagnosed based on the plateau inclination includes:

[0093] Control the micro fission ionization chamber to be diagnosed to perform pretreatment tasks;

[0094] After completing the preprocessing task, the preprocessed plateau of the micro fission ionization chamber to be diagnosed is obtained;

[0095] The micro-fission ionization chamber to be diagnosed is diagnosed based on the pre-processed plateau inclination.

[0096] In the micro-fission ionization chamber fault diagnosis method of the present invention, the step of diagnosing the micro-fission ionization chamber to be diagnosed based on the pre-processed plateau inclination includes:

[0097] Determine whether the pre-treated slope is within the range of the first slope;

[0098] If so, the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the excessive or excessive plateau tilt is that a trace amount of impurity gas enters the sensor body, causing abnormal nuclear characteristics of the faulty micro-fission ionization chamber. When the plateau tilt of the micro-fission ionization chamber to be diagnosed returns to the normal range, the micro-fission ionization chamber to be diagnosed returns to a usable state.

[0099] In the micro-fission ionization chamber fault diagnosis method of the present invention, the step of diagnosing the micro-fission ionization chamber to be diagnosed based on the pre-processed plateau inclination includes:

[0100] Determine whether the pre-treated slope is within the range of the second slope;

[0101] If so, the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the micro-fission ionization chamber is faulty but usable, and the micro-fission ionization chamber to be diagnosed will be replaced within the preset maintenance period.

[0102] In the micro-fission ionization chamber fault diagnosis method of the present invention, the step of diagnosing the micro-fission ionization chamber to be diagnosed based on the pre-processed plateau inclination includes:

[0103] Determine whether the pre-processed slope is greater than the upper limit value of the slope;

[0104] If so, the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the excessive or excessive plateau tilt is that the micro-fission ionization chamber to be diagnosed is unusable.

[0105] The present invention also provides a fault diagnosis system for a micro fission ionization chamber, comprising:

[0106] The monitoring unit is used to monitor each microfission ionization chamber in the same pressurized water reactor nuclear power unit and determine whether the microfission ionization chamber has an abnormal calibration coefficient or plateau tilt.

[0107] The acquisition unit is used to acquire the fault type of any micro-fission ionization chamber to be diagnosed if an abnormal calibration coefficient or plateau tilt occurs in any micro-fission ionization chamber in the same pressurized water reactor nuclear power unit; the micro-fission ionization chamber to be diagnosed is the micro-fission ionization chamber that has experienced an abnormal calibration coefficient or plateau tilt.

[0108] The first diagnostic unit is used to diagnose the micro fission ionization chamber to be diagnosed if the fault type is that the calibration coefficient exceeds the standard, by using a preset calibration coefficient diagnostic method.

[0109] The second diagnostic unit is used to diagnose the micro fission ionization chamber to be diagnosed if the fault type is abnormally large or exceeds the standard by using a preset plateau inclination diagnostic method.

[0110] The micro-fission ionization chamber fault diagnosis method and system of the present invention have the following beneficial effects: It includes monitoring micro-fission ionization chambers in the same pressurized water reactor nuclear power unit, and obtaining the fault type of the micro-fission ionization chamber to be diagnosed when any micro-fission ionization chamber experiences a calibration coefficient or plateau tilt anomaly; if the fault type is a calibration coefficient exceeding the standard, then a preset calibration coefficient diagnosis method is used to diagnose the micro-fission ionization chamber to be diagnosed; if the fault type is a plateau tilt anomaly that is too large or exceeds the standard, then a preset plateau tilt diagnosis method is used to diagnose the micro-fission ionization chamber to be diagnosed. The present invention uses a preset calibration coefficient diagnosis method based on the physical meaning of the calibration coefficient, providing more sufficient diagnostic evidence. Simultaneously, the use of a preset plateau tilt diagnosis method solves the problem of insufficient evidence when judging solely based on a plateau tilt anomaly that is too large or exceeds the standard. Moreover, the diagnostic method of the present invention has clear logic and sufficient evidence, enabling effective diagnosis. Attached Figure Description

[0111] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0112] Figure 1 This is a flowchart illustrating the fault diagnosis method for a micro-fission ionization chamber provided in an embodiment of the present invention;

[0113] Figure 2 This is a schematic diagram of the process for diagnosing the micro fission ionization chamber to be diagnosed using a pre-set calibration coefficient diagnostic method provided in an embodiment of the present invention;

[0114] Figure 3 This is a schematic diagram of the process for diagnosing the micro-fission ionization chamber to be diagnosed using a preset plateau tilt diagnostic method provided in an embodiment of the present invention.

[0115] Figure 4 This is a schematic diagram of the measured current curve of the MFC provided in the embodiment of the present invention;

[0116] Figure 5 This is a schematic diagram of the micro-fission ionization chamber fault diagnosis system provided in an embodiment of the present invention. Detailed Implementation

[0117] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0118] This invention provides a fault diagnosis method for micro-fission ionization chambers. This method addresses the problems of insufficient evidence to determine the unusability of a micro-fission ionization chamber based solely on an excessive calibration coefficient; insufficient evidence to determine the unusability of a new micro-fission ionization chamber based solely on an abnormally large or excessive plateau tilt; overly simplistic methods for fault diagnosis of micro-fission ionization chambers based on plateau tilt and calibration coefficients, which fail to fully encompass the electrical and nuclear characteristics of the chamber and pose a risk of misdiagnosis; and the lack of an effective fault diagnosis process for personnel performing fault diagnosis of micro-fission ionization chambers.

[0119] like Figure 1 The diagram shown is a schematic flowchart of an optional embodiment of the micro-fission ionization chamber fault diagnosis method provided by the present invention.

[0120] Specifically, the fault diagnosis method for this micro fission ionization chamber includes the following steps:

[0121] Step S101: Monitor each micro fission ionization chamber in the same pressurized water reactor nuclear power unit and determine whether the micro fission ionization chamber has an abnormal calibration coefficient or plateau tilt.

[0122] Among them, abnormal calibration coefficients or slopes indicate that the parameters exceed or are close to exceeding the standard (abnormally large).

[0123] In this embodiment of the invention, the monitoring and judgment of whether the calibration coefficient or plateau tilt anomaly occurs in all micro fission ionization chambers of the same pressurized water reactor nuclear power unit can be carried out using the usual monitoring and judgment methods, and the invention does not make specific limitations.

[0124] Step S102: If any microfission ionization chamber in the same pressurized water reactor nuclear power unit malfunctions, the fault type of the microfission ionization chamber to be diagnosed is obtained. The microfission ionization chamber to be diagnosed is one that has experienced calibration coefficient or plateau tilt anomalies.

[0125] In this embodiment of the invention, the fault types of the micro fission ionization chamber include: exceeding the calibration coefficient, or abnormally large or excessive plateau tilt.

[0126] Step S103: If the fault type of the micro fission ionization chamber to be diagnosed is that the calibration coefficient exceeds the standard, then the preset calibration coefficient diagnosis method is used to diagnose the micro fission ionization chamber to be diagnosed.

[0127] In some embodiments, if the calibration coefficient of any micro fission ionization chamber in the same pressurized water reactor nuclear power unit is found to be out of standard, a preset calibration coefficient diagnosis method is used to diagnose the micro fission ionization chamber with the out-of-standard calibration coefficient (i.e., to diagnose the micro fission ionization chamber to be diagnosed).

[0128] In a preferred embodiment, such as Figure 2 As shown, if the fault type of the micro fission ionization chamber to be diagnosed is an excessive calibration coefficient, then the diagnostic method using the preset calibration coefficient will be used to diagnose the micro fission ionization chamber, including:

[0129] Step S201: Determine the physical meaning of the calibration coefficient of the micro fission ionization chamber.

[0130] Step S202: Based on the physical meaning of the calibration coefficient of the micro fission ionization chamber, determine the acceptance criteria for the calibration coefficient of the micro fission ionization chamber exceeding the standard.

[0131] Step S203: Diagnose the micro fission ionization chamber to be diagnosed according to the acceptance criteria for exceeding the calibration coefficient.

[0132] Specifically, in some embodiments, determining the physical meaning of the calibration coefficients for micro-fission ionization chambers includes: determining a reference calibration mode for the micro-fission ionization chambers; controlling all micro-fission ionization chambers in the same pressurized water reactor nuclear power unit to enter the same measurement path for calibration according to the determined reference calibration mode; obtaining the average current of each micro-fission ionization chamber after calibration; comparing the average current of each micro-fission ionization chamber with a reference current to obtain the calibration coefficients for each micro-fission ionization chamber; obtaining the thermal neutron sensitivity of each micro-fission ionization chamber; determining the relationship between the average current and thermal neutron sensitivity and the average thermal neutron flux rate on the core measurement path based on the average current and thermal neutron sensitivity of each micro-fission ionization chamber; and determining the physical meaning of the calibration coefficients for the micro-fission ionization chambers based on the relationship between the calibration coefficients of each micro-fission ionization chamber and the average current and thermal neutron sensitivity and the average thermal neutron flux rate on the core measurement path.

[0133] In this embodiment of the invention, based on the working principle of the micro-fission ionization chamber, it is known that the relationship between the average current and thermal neutron sensitivity and the average thermal neutron flux rate on the core measurement path satisfies the following: the average current of each micro-fission ionization chamber is equal to the product of the thermal neutron sensitivity and the average thermal neutron flux rate on the core measurement path.

[0134] In this embodiment of the invention, the physical meaning of the calibration coefficient of the micro-fission ionization chamber is: the normalized value of the thermal neutron sensitivity of any micro-fission ionization chamber in the same unit relative to the reference thermal neutron sensitivity. Therefore, by checking the calibration coefficient, the relative change in the thermal neutron sensitivity of the micro-fission ionization chamber (MFC) can be found.

[0135] In this embodiment of the invention, the acceptance criterion for the calibration coefficient of the micro-fission ionization chamber exceeding the standard is as follows: if the calibration coefficient of the micro-fission ionization chamber is within the reference coefficient range, then the calibration coefficient of the micro-fission ionization chamber is determined to be within the standard; if the calibration coefficient of the micro-fission ionization chamber exceeds the reference coefficient range, then the calibration coefficient of the micro-fission ionization chamber is determined to be exceeding the standard. The reference coefficient range is [0.92, 1.08]. Therefore, when the calibration coefficient of the MFC is within [0.92, 1.08], the calibration coefficient of the MFC does not exceed the standard; when the calibration coefficient of the MFC is not within [0.92, 1.08], the calibration coefficient of the MFC exceeds the standard.

[0136] In some embodiments, diagnosing a micro-fission ionization chamber to be diagnosed based on the acceptance criteria of exceeding the calibration coefficient includes: obtaining the factory thermal neutron sensitivity of the micro-fission ionization chamber to be diagnosed; obtaining the reference thermal neutron sensitivity; calculating the calibration coefficient of the micro-fission ionization chamber to be diagnosed based on the factory thermal neutron sensitivity and the reference thermal neutron sensitivity; comparing the calibration coefficient of the micro-fission ionization chamber to be diagnosed with the reference coefficient; and diagnosing the micro-fission ionization chamber to be diagnosed based on the comparison result.

[0137] If the comparison result is that the calibration coefficient of the micro-fission ionization chamber to be diagnosed exceeds the reference coefficient range, then: obtain the automatic calibration coefficient of the micro-fission ionization chamber to be diagnosed; the automatic calibration coefficient is the calibration coefficient calculated by the neutron measurement system; if the calibration coefficient of the micro-fission ionization chamber to be diagnosed is the same as the automatic calibration coefficient, then the diagnosis result of the micro-fission ionization chamber to be diagnosed is: the reason for the calibration coefficient exceeding the standard is that the relative deviation of the factory thermal neutron sensitivity is too large, and the micro-fission ionization chamber to be diagnosed is usable.

[0138] If the comparison result shows that the calibration coefficient of the micro-fission ionization chamber to be diagnosed is within the reference coefficient range, then: compare the calibration coefficient of the micro-fission ionization chamber to be diagnosed with the upper and lower limits of the reference coefficient range, respectively; if the difference between the calibration coefficient of the micro-fission ionization chamber to be diagnosed and the upper limit is within a preset range, or the difference between the calibration coefficient of the micro-fission ionization chamber to be diagnosed and the lower limit is within a preset range, then the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the calibration coefficient exceeding the standard is that the micro-fission ionization chamber to be diagnosed and the reference micro-fission chamber cause a difference in the change of thermal neutron sensitivity during operation in the unit, and the micro-fission ionization chamber to be diagnosed should not be judged as unusable solely based on the calibration coefficient. The upper limit is 1.08, and the lower limit is 0.92.

[0139] Alternatively, if the comparison result is that the calibration coefficient of the micro-fission ionization chamber to be diagnosed is within the reference coefficient range, then: compare the calibration coefficient of the micro-fission ionization chamber to be diagnosed with the preset value; if the difference between the calibration coefficient of the micro-fission ionization chamber to be diagnosed and the preset value is within the deviation range, then the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the calibration coefficient exceeding the standard is that the difference in the change of thermal neutron sensitivity between the micro-fission ionization chamber to be diagnosed and the benchmark micro-fission chamber during the operation of the unit is greater than the threshold. The threshold can be determined according to actual needs, as long as it can be determined that the difference in the change of thermal neutron sensitivity during the operation of the unit is too large. The preset value is 1.0.

[0140] If the difference in thermal neutron sensitivity change of the micro fission ionization chamber to be diagnosed during operation in the unit exceeds the threshold, then: the automatic calibration coefficient of the micro fission ionization chamber to be diagnosed is compared with the upper limit of the reference coefficient range; if the automatic calibration coefficient is greater than the upper limit, the diagnosis result of the micro fission ionization chamber to be diagnosed is: the reason for the calibration coefficient exceeding the standard is that the thermal neutron sensitivity of the reference micro fission ionization chamber has abnormally decreased, and the reference micro fission ionization chamber is unusable.

[0141] Alternatively, if the difference in thermal neutron sensitivity change of the micro fission ionization chamber to be diagnosed during operation in the unit is greater than the threshold, then: the automatic calibration coefficient of the micro fission ionization chamber to be diagnosed is compared with the lower limit of the reference coefficient range; if the automatic calibration coefficient is less than the lower limit, the diagnosis result of the micro fission ionization chamber to be diagnosed is: the reason for the calibration coefficient exceeding the standard is that the thermal neutron sensitivity of the micro fission ionization chamber to be diagnosed has abnormally decreased, and the micro fission ionization chamber to be diagnosed is unusable.

[0142] In one specific embodiment, five new micro fission ionization chambers (assumed to be MFCs 1 to 5) are simultaneously installed in the same pressurized water reactor nuclear power unit. When the calibration coefficient of a certain micro fission ionization chamber exceeds the standard, the specific steps for fault diagnosis are as follows:

[0143] Step 1: Determine the physical meaning of the calibration coefficients for the microfission ionization chamber. That is, the normalized value of the thermal neutron sensitivity of a specific MFC within the same unit relative to the thermal neutron sensitivity of the selected benchmark MFC. This can be expressed by the formula:

[0144] C n =S n / S1 (1)

[0145] Where C represents the calibration coefficient, S represents the thermal neutron sensitivity, and n = 1, 2, 3, 4, 5.

[0146] The physical meaning of the calibration coefficient of the micro-fission ionization chamber can be determined according to the following steps:

[0147] Step A1: Select the reference calibration mode for the neutron measurement system (NMS), so that all micro fission ionization chambers of the same unit enter the same measurement path for calibration.

[0148] Step A2: After the reference calibration is completed, the average current collected by each MFC during the calibration process is obtained by searching through NMS. That is, the average current of the first MFC is I1, the average current of the second MFC is I2, the average current of the third MFC is I3, the average current of the fourth MFC is I4, and the average current of the fifth MFC is I5.

[0149] Step A3: Obtain the thermal neutron sensitivity of each MFC at the time of manufacture. The thermal neutron sensitivities of MFCs 1 to 5 at the time of manufacture are represented as: S1, S2, S3, S4, and S5, respectively.

[0150] Step A4: Using the average current I1 of MFC No. 1 as the benchmark for calculating the calibration coefficients, compare I1, I2, I3, I4, and I5 with I1 respectively to obtain the corresponding calibration coefficients C1, C2, C3, C4, and C5, i.e., C n =I n / I1(n=1,2,3,4,5).

[0151] Step A5: Based on the working principle of MFC, the average current is equal to the product of the thermal neutron sensitivity and the average thermal neutron flux rate (Φ) along the core measurement path, i.e., I... n =S n *Φ(n=1, 2, 3, 4, 5).

[0152] Step A6: Formula (1) can be obtained from steps A4 and A5.

[0153] Step 2: According to formula (1), the absolute value of the deviation of S2, S3, S4 and S5 relative to S1 in the same unit must be less than 8% in order to meet the requirements of the calibration coefficient acceptance standard.

[0154] Therefore, based on the acceptance criteria obtained in the second step, we can see that the scope of application of the acceptance criteria based solely on the calibration coefficient is limited. It is not possible to judge that MFC is unusable simply because the calibration coefficient of MFC exceeds the range of [0.92, 1.08].

[0155] Step 3: When it is determined that the calibration coefficient of any one of the 5 MFCs exceeds the range of [0.92, 1.08] (i.e. the calibration coefficient exceeds the standard), the calibration coefficient of the MFC to be diagnosed should be calculated using formula (1) based on the factory thermal neutron sensitivity of the MFC (the micro fission ionization chamber to be diagnosed) with the calibration coefficient exceeding the standard and the factory thermal neutron sensitivity of the MFC selected as the reference.

[0156] Step 4: If the calibration coefficient of the MFC to be diagnosed calculated in Step 3 is basically the same as the automatic calibration coefficient, then the reason why the calibration coefficient of the MFC to be diagnosed exceeds the standard is that the relative deviation of the factory thermal neutron sensitivity is too large. The diagnosis result at this time is: the MFC to be diagnosed is usable.

[0157] Step 5: If the calibration coefficient of the MFC to be diagnosed calculated in Step 3 is not excessive, but is close to the upper or lower limit, the reason for the excessive calibration coefficient is that the thermal neutron sensitivity changes due to the MFC running in the unit for a period of time. It should not be judged that the MFC is unusable just because the calibration coefficient is excessive.

[0158] Step 6: If the calibration coefficient of the MFC to be diagnosed calculated in Step 3 is within the limit and is approximately 1.0, then the reason for the calibration coefficient exceeding the limit is that the difference in thermal neutron sensitivity caused by the MFC running in the unit for a period of time is too large. It is known that the thermal neutron sensitivity will gradually decrease after the MFC is put into operation in the unit. Therefore, in this case, fault diagnosis should be carried out according to the direction of change of the calibration coefficient measured by NMS.

[0159] Step 7: If the situation in Step 6 occurs, when the calibration factor measured by NMS is greater than 1.08, the fault diagnosis result is that the thermal neutron sensitivity of the reference MFC has abnormally decreased, and the reference MFC is unusable.

[0160] Step 8: If the situation described in step

[11] occurs, when the calibration coefficient measured by NMS is less than 0.92, the fault diagnosis result is that the thermal neutron sensitivity of the MFC with the calibration coefficient exceeding the standard has decreased abnormally, and the MFC with the calibration coefficient exceeding the standard is unusable.

[0161] Step S104: If the fault type of the micro fission ionization chamber to be diagnosed is abnormally large or exceeds the standard, then the preset plateau inclination diagnosis method is used to diagnose the micro fission ionization chamber to be diagnosed.

[0162] In some embodiments, if an abnormally large plateau tilt (exceeding 0.10% V) is detected in any microfission ionization chamber of the same pressurized water reactor nuclear power unit, -1 ) or exceeding the standard (more than 0.20%·V) -1 When the condition is met, the preset residual diagnostic method is used to diagnose the micro fission ionization chamber to be diagnosed.

[0163] In a preferred embodiment, such as Figure 3 As shown, if the fault type of the micro-fission ionization chamber to be diagnosed is abnormally large or exceeds the standard, then the preset plateau tilt diagnosis method is used to diagnose the micro-fission ionization chamber to be diagnosed, including:

[0164] Step S301: Obtain the electrical parameters of the micro fission ionization chamber to be diagnosed.

[0165] Step S302: Determine whether the electrical characteristics of the micro fission ionization chamber to be diagnosed are qualified based on the electrical parameters.

[0166] Step S303: If not, then diagnose the micro fission ionization chamber to be diagnosed based on its electrical characteristics.

[0167] Step S304: If yes, then obtain the nuclear characteristic parameters of the micro fission ionization chamber to be diagnosed.

[0168] Step S305: Diagnose the micro-fission ionization chamber to be diagnosed based on the nuclear characteristic parameters.

[0169] Optionally, in this embodiment of the invention, the electrical parameters include: the insulation resistance of the micro fission ionization chamber to be diagnosed and its measurement circuit.

[0170] The process of determining whether the electrical characteristics of the micro-fission ionization chamber to be diagnosed are qualified based on electrical parameters includes: comparing the insulation resistance of the micro-fission ionization chamber to be diagnosed and its measuring circuit with a reference resistance value; if the insulation resistance of the micro-fission ionization chamber to be diagnosed and its measuring circuit is less than the reference resistance value, then the electrical characteristics of the micro-fission ionization chamber to be diagnosed are determined to be unqualified. The diagnosis of the micro-fission ionization chamber to be diagnosed based on electrical characteristics includes: if the insulation resistance of the micro-fission ionization chamber to be diagnosed and its measuring circuit is less than the reference resistance value, then the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the large or excessive plateau slope is that the insulation resistance of the micro-fission ionization chamber to be diagnosed and its measuring circuit is abnormal, and the micro-fission ionization chamber to be diagnosed is unusable. Optionally, in this embodiment of the invention, the reference resistance value can be 10. 7 Ω.

[0171] Specifically, assuming all cables of the MFC and its measurement circuit are correctly connected, use an insulation resistance tester to check the insulation resistance of the MFC and its measurement circuit from the NMS cabinet side. The voltage used for the check should not be less than the operating voltage of the MFC. Under normal circumstances, the insulation resistance of the MFC and its measurement circuit should not be less than 10 ohms. 9 Ω, when the insulation resistance of the MFC and its measurement circuit drops to less than 10 7 When Ω, the fault diagnosis result is unavailable.

[0172] Furthermore, in this embodiment of the invention, the electrical parameters also include: the leakage current of the micro fission ionization chamber to be diagnosed and its measurement circuit.

[0173] The process of determining whether the electrical characteristics of the micro-fission ionization chamber to be diagnosed are qualified based on electrical parameters includes: comparing the leakage current of the micro-fission ionization chamber to be diagnosed and its measuring circuit with a reference current; if the leakage current of the micro-fission ionization chamber to be diagnosed and its measuring circuit is greater than the reference current, then the electrical characteristics of the micro-fission ionization chamber to be diagnosed are determined to be unqualified. The diagnosis of the micro-fission ionization chamber to be diagnosed based on electrical characteristics includes: if the leakage current of the micro-fission ionization chamber to be diagnosed and its measuring circuit is greater than the reference current, then the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the large or excessive plateau slope is that the leakage current of the micro-fission ionization chamber to be diagnosed and its measuring circuit is abnormal, and the micro-fission ionization chamber to be diagnosed is unusable. Optionally, in this embodiment of the invention, the reference current can be: 10 -7 A.

[0174] Specifically, with all cables for the MFC and its measurement circuit correctly connected, control the NMS to move the MFC to the group selector output position (travel code 2000). Use a picoampere meter to check the leakage current of the MFC and its measurement circuit from the NMS cabinet side. Under normal circumstances, the leakage current of the MFC and its measurement circuit is 10. -9 The leakage current of the MFC and its measurement circuit reaches the A-level, which is on the order of A. -7 At the A-level, the leakage current is relative to the measured current under 10% FP operating conditions (10 -5 The magnitude (A) is no longer negligible, and the fault diagnosis result is unavailable.

[0175] Furthermore, in this embodiment of the invention, the electrical parameters also include: the capacitance of the micro fission ionization chamber to be diagnosed and its measurement circuit.

[0176] The determination of whether the electrical characteristics of the micro-fission ionization chamber to be diagnosed are qualified based on electrical parameters includes: determining whether the capacitance of the micro-fission ionization chamber to be diagnosed and its measuring circuit is within the reference capacitance range; if the capacitance of the micro-fission ionization chamber to be diagnosed and its measuring circuit is not within the reference capacitance range, then the electrical characteristics of the micro-fission ionization chamber to be diagnosed are deemed unqualified. The diagnosis of the micro-fission ionization chamber to be diagnosed based on electrical characteristics includes: if the capacitance of the micro-fission ionization chamber to be diagnosed and its measuring circuit is not within the reference capacitance range, then the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for a large or excessive plateau slope is an abnormal gap between the high-voltage electrode and the collecting electrode of the micro-fission ionization chamber to be diagnosed, and the micro-fission ionization chamber to be diagnosed is unusable. Optionally, in this embodiment of the invention, the reference capacitance range can be: [15.5, 18.5] nF.

[0177] Specifically, assuming all cables of the MFC and its measurement circuit are correctly connected, use a capacitance tester to check the capacitance of the MFC and its measurement circuit. Under normal circumstances, the capacitance of the MFC and its measurement circuit is [15.5, 18.5] nF. When the capacitance exceeds the range of [15.5, 18.5] nF, it indicates that the gap between the high-voltage electrode and the collector electrode of the MFC has changed abnormally, and the fault diagnosis result is unusable.

[0178] Furthermore, if all the above electrical parameter checks pass, it indicates that the electrical characteristics of the microfiber ionization chamber to be diagnosed are qualified. In this case, it is also necessary to check the nuclear characteristics of the MFC. Among them, the nuclear characteristic parameters used for fault diagnosis include: the measured current and plateau slope of the MFC.

[0179] Specifically, the diagnosis of the micro-fission ionization chamber to be diagnosed based on nuclear characteristic parameters includes: obtaining the measurement current of the micro-fission ionization chamber to be diagnosed; determining whether there is a step value or a peak value in the measurement current of the micro-fission ionization chamber to be diagnosed; if so, the diagnosis result of the micro-fission ionization chamber to be diagnosed is: the reason for the large or excessive plateau slope is the abnormal measurement current, and the micro-fission ionization chamber to be diagnosed is unusable; if not, the micro-fission ionization chamber to be diagnosed is diagnosed based on the plateau slope.

[0180] Furthermore, in this embodiment of the invention, diagnosing the micro-fission ionization chamber to be diagnosed based on the plateau inclination includes: controlling the micro-fission ionization chamber to be diagnosed to perform a preprocessing task; after completing the preprocessing task, obtaining the preprocessed plateau inclination of the micro-fission ionization chamber to be diagnosed; and diagnosing the micro-fission ionization chamber to be diagnosed based on the preprocessed plateau inclination.

[0181] The diagnosis of the micro-fission ionization chamber to be diagnosed based on the pre-treated plateau tilt includes: determining whether the pre-treated plateau tilt is within the first plateau tilt range; if so, the diagnosis result of the micro-fission ionization chamber to be diagnosed is: the reason for the excessive or excessive plateau tilt is that trace impurity gas enters the sensor body, causing abnormal nuclear characteristics of the micro-fission ionization chamber to be diagnosed; when the plateau tilt of the micro-fission ionization chamber to be diagnosed returns to the normal range, the micro-fission ionization chamber to be diagnosed returns to the usable state.

[0182] In some embodiments, diagnosing the micro-fission ionization chamber to be diagnosed based on the pre-processed plateau inclination includes: determining whether the pre-processed plateau inclination is within the range of the second plateau inclination; if so, the diagnosis result of the micro-fission ionization chamber to be diagnosed is: the micro-fission ionization chamber to be diagnosed is faulty but usable, and the micro-fission ionization chamber to be diagnosed is replaced within a preset maintenance period.

[0183] In some embodiments, diagnosing the micro-fission ionization chamber to be diagnosed based on the pre-processed plateau tilt includes: determining whether the pre-processed plateau tilt is greater than the upper limit of the plateau tilt; if so, the diagnosis result of the micro-fission ionization chamber to be diagnosed is: the reason for the plateau tilt being too large or exceeding the limit is that the micro-fission ionization chamber to be diagnosed is unusable.

[0184] In some embodiments, the diagnosis of the micro fission ionization chamber to be diagnosed based on the pre-processed plateau inclination further includes: after replacing the micro fission ionization chamber to be diagnosed during a preset maintenance period, obtaining the replaced plateau inclination; determining whether the replaced plateau inclination is within the first plateau inclination range; if the replaced plateau inclination is within the first plateau inclination range, then the diagnosis result of the micro fission ionization chamber to be diagnosed is: the micro fission ionization chamber to be diagnosed is usable.

[0185] In some embodiments, the diagnosis of the micro-fission ionization chamber to be diagnosed based on the pre-processed plateau inclination further includes: after replacing the micro-fission ionization chamber to be diagnosed within a preset maintenance period, obtaining the replaced plateau inclination; determining whether the replaced plateau inclination is within the range of the second plateau inclination; if the replaced plateau inclination is within the range of the second plateau inclination, then the diagnosis result of the micro-fission ionization chamber to be diagnosed is: the micro-fission ionization chamber to be diagnosed is usable, and aging management of the micro-fission ionization chamber to be diagnosed is initiated, and the micro-fission ionization chamber to be diagnosed is replaced within the preset maintenance period.

[0186] In some embodiments, the diagnosis of the micro fission ionization chamber to be diagnosed based on the pre-processed plateau inclination further includes: after replacing the micro fission ionization chamber to be diagnosed during a preset maintenance period, obtaining the replaced plateau inclination; determining whether the replaced plateau inclination is greater than the upper limit value of the plateau inclination; if the replaced plateau inclination is greater than the upper limit value of the plateau inclination, the diagnosis result of the micro fission ionization chamber to be diagnosed is: the micro fission ionization chamber to be diagnosed is unusable.

[0187] In one specific embodiment, the process of performing nuclear characteristic checks includes the following steps:

[0188] Step 1: Check the measurement current collected by the micro fission ionization chamber to be diagnosed after completing the neutron fluence measurement of a certain measurement path. The normal measurement current is a relatively smooth curve (curve s1 in the figure). When there is a step change or spike in the measurement current (curves s2 and s3 in the figure), the diagnosis result is unusable.

[0189] Step 2: The new MFC experienced an abnormally large slope (exceeding 0.10% V) during the initial operation phase. -1In the event of a problem with the MFC being diagnosed (e.g., exceeding limits), after ruling out faults in electrical characteristics and measurement current, the MFC should be sent into the reactor core under high nuclear power conditions to perform several measurement tasks. The neutrons in the reactor core will decompose and consume the impurity gases within the MFC's sensitive compartment. This process serves as pretreatment for the microfission ionization chamber to be diagnosed.

[0190] Step 3: After processing according to the method in step

[06] , if the slope of the diagnosed MFC can be restored to [0.02, 0.10]%·V -1 If the temperature is within the range and can remain stable, the diagnosis is that a trace amount of impurity gas has entered the sensitive body, causing abnormal changes in the nuclear characteristics of the MFC. When the diagnosed plateau slope returns to a relatively ideal level, the MFC returns to a usable state.

[0191] Step 4: After processing according to the method in Step 3, if the slope of the diagnosed MFC is still between (0.10, 0.20)%·V -1 If the range is within the acceptable range, the diagnosis result is usable, but the diagnosed MFC should be replaced at the appropriate service window.

[0192] Step 5: If the slope of the diagnosed MFC still exceeds the standard after processing according to the method in Step 3, the diagnosis result is unusable.

[0193] Step 6: After an MFC that has been operating normally under 100% FP conditions for a period of time develops a problem of excessive slack, the operating voltage of the MFC should be adjusted to a value not less than the actual saturation voltage, provided that electrical characteristics and current measurement faults have been ruled out.

[0194] Step 7: After step 4 is completed, if the slope of the diagnosed MFC can be restored to [0.02, 0.10]%·V -1 If the result falls within the specified range, the diagnosis is considered valid.

[0195] Step 8: After step 4 is completed, if the slope of the diagnosed MFC can be restored to (0.10, 0.20)%·V -1 If the range is within the acceptable range, the diagnosis result is usable, but MFC aging management should be initiated, and the diagnosed MFC should be replaced during the appropriate maintenance window.

[0196] Step 9: If the slope of the diagnosed MFC still exceeds the standard after step 4 is completed, the diagnosis result is unusable.

[0197] like Figure 5 The diagram shown is a schematic representation of an optional embodiment of the micro-fission ionization chamber fault diagnosis system provided by the present invention. This micro-fission ionization chamber fault diagnosis system can be applied to the micro-fission ionization chamber fault diagnosis method disclosed in the embodiments of the present invention.

[0198] Specifically, the micro-fission ionization chamber fault diagnosis system includes:

[0199] Monitoring unit 501 is used to monitor each microfission ionization chamber in the same pressurized water reactor nuclear power unit and to determine whether the microfission ionization chamber has an abnormal calibration coefficient or plateau tilt.

[0200] The acquisition unit 502 is used to acquire the fault type of any microfiber ionization chamber in the same pressurized water reactor nuclear power unit when a calibration coefficient or plateau tilt anomaly occurs. The microfiber ionization chamber to be diagnosed is the one experiencing the calibration coefficient or plateau tilt anomaly.

[0201] The first diagnostic unit 503 is used to diagnose the micro fission ionization chamber to be diagnosed if the fault type of the micro fission ionization chamber to be diagnosed is that the calibration coefficient exceeds the standard. In this case, the preset calibration coefficient diagnostic method is used to diagnose the micro fission ionization chamber to be diagnosed.

[0202] The second diagnostic unit 504 is used to diagnose the micro-fission ionization chamber to be diagnosed if the fault type of the chamber is abnormally large or exceeds the standard by using a preset plateau inclination diagnostic method.

[0203] This invention discloses a fault diagnosis method for microfission ionization chambers (MFCs), clarifying the physical meaning of the calibration factor and its calculation method. It points out the limitations of using the calibration factor acceptance criteria provided by equipment suppliers for MFC fault diagnosis, and redesigns the method for MFC fault diagnosis using the calibration factor. This improves the feasibility of the MFC fault diagnosis method and reduces the false diagnosis rate when directly using the calibration factor acceptance criteria. This method has been verified during the first startup of a 1000MW-class improved pressurized water reactor nuclear power unit, avoiding the false diagnosis problem caused by the calibration factor exceeding the standard due to differences in the factory thermal neutron sensitivity of the MFC. Currently, in nuclear power units under China General Nuclear Power Group (CGN), the MFC calibration factor is no longer used as the sole technical indicator for diagnosing the usability of an MFC.

[0204] Meanwhile, the electrical and core characteristics of MFC were systematically studied. The insulation resistance, leakage current, and capacitance of the MFC measurement circuit were selected as electrical characteristic parameters for fault diagnosis, and the plateau slope and measurement current of MFC were selected as core characteristic parameters for fault diagnosis. The corresponding acceptance criteria were also clarified.

[0205] In addition, for new MFCs that experience abnormally large or excessive plateau tilt during the initial operation period, after ruling out electrical characteristic faults in the diagnosed MFC, a treatment method is proposed: "The diagnosed MFC should be sent into the reactor core under high nuclear power conditions to perform several measurement tasks, and the impurity gases in the MFC's sensitive body should be decomposed and consumed by the neutrons in the reactor core."

[0206] Furthermore, a method for fault diagnosis based on the electrical and core characteristics of the MFC and acceptance criteria is presented. The method stipulates that the electrical characteristics of the MFC should be checked first when conducting fault diagnosis. After eliminating electrical characteristic faults, the core characteristics of the MFC should be checked, thus clarifying the working logic of MFC fault diagnosis. At the same time, the possible situations encountered during fault diagnosis are analyzed, and diagnostic methods are given for each.

[0207] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0208] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0209] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0210] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They do not limit the scope of protection of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for fault diagnosis of a micro fission ionization chamber, characterized in that, Includes the following steps: Each microfission ionization chamber in the same pressurized water reactor nuclear power unit is monitored, and it is determined whether the microfission ionization chamber has an abnormal calibration coefficient or plateau tilt. If any micro-fission ionization chamber in the same pressurized water reactor nuclear power unit experiences a calibration coefficient or plateau tilt anomaly, the fault type of the micro-fission ionization chamber to be diagnosed is obtained; the micro-fission ionization chamber to be diagnosed is the micro-fission ionization chamber that has experienced a calibration coefficient or plateau tilt anomaly. If the fault type of the micro fission ionization chamber to be diagnosed is that the calibration coefficient exceeds the standard, then the micro fission ionization chamber to be diagnosed is diagnosed using a preset calibration coefficient diagnosis method, which includes: determining the physical meaning of the calibration coefficient of the micro fission ionization chamber. The physical meaning of the calibration coefficient of the micro-fission ionization chamber is: the normalized value of the thermal neutron sensitivity of any micro-fission ionization chamber in the same unit relative to the reference thermal neutron sensitivity; based on the physical meaning of the calibration coefficient of the micro-fission ionization chamber, the acceptance criteria for the calibration coefficient of the micro-fission ionization chamber exceeding the standard are determined; the micro-fission ionization chamber to be diagnosed is diagnosed according to the acceptance criteria for the calibration coefficient exceeding the standard. If the fault type of the micro fission ionization chamber to be diagnosed is an abnormally large or excessive plateau tilt, then the preset plateau tilt diagnosis method is used to diagnose the micro fission ionization chamber to be diagnosed.

2. The fault diagnosis method for a micro fission ionization chamber according to claim 1, characterized in that, The physical meaning of determining the calibration coefficient of the micro-fission ionization chamber includes: Determine the reference calibration mode for the micro-fission ionization chamber; Based on the established reference calibration mode, all micro fission ionization chambers in the same pressurized water reactor nuclear power unit are controlled to enter the same measurement path for calibration. After calibration, the average current of each micro-fission ionization chamber is obtained; The average current of each micro-fission ionization chamber is compared with the reference current to obtain the calibration coefficient of each micro-fission ionization chamber. Acquire the thermal neutron sensitivity of each micro-fission ionization chamber; Based on the average current and thermal neutron sensitivity of each micro-fission ionization chamber, the relationship between the average current and thermal neutron sensitivity and the average thermal neutron flux rate along the core measurement path is determined. The physical meaning of the calibration coefficient of the micro-fission ionization chamber is determined based on the relationship between the average current and thermal neutron sensitivity and the average thermal neutron flux rate along the core measurement path.

3. The fault diagnosis method for a micro fission ionization chamber according to claim 2, characterized in that, The relationship between the average current and thermal neutron sensitivity and the average thermal neutron flux rate along the core measurement path satisfies: The average current in each micro-fission ionization chamber is equal to the product of the thermal neutron sensitivity and the average thermal neutron flux rate along the core measurement path.

4. The fault diagnosis method for a micro fission ionization chamber according to claim 1, characterized in that, The acceptance criteria for the micro fission ionization chamber exceeding the calibration coefficient standard are as follows: If the calibration coefficient of the micro-fission ionization chamber is within the reference coefficient range, then the calibration coefficient of the micro-fission ionization chamber is determined to be within the standard. If the calibration coefficient of the micro fission ionization chamber exceeds the reference coefficient range, then the calibration coefficient of the micro fission ionization chamber is determined to be out of standard.

5. The fault diagnosis method for a micro fission ionization chamber according to claim 4, characterized in that, The diagnostic process for the micro-fission ionization chamber to be diagnosed, based on the acceptance criteria for exceeding the calibration coefficient, includes: Obtain the factory-set thermal neutron sensitivity of the micro-fission ionization chamber to be diagnosed; Obtain a baseline thermal neutron sensitivity; The calibration coefficient of the micro-fission ionization chamber to be diagnosed is calculated based on the factory thermal neutron sensitivity of the micro-fission ionization chamber to be diagnosed and the reference thermal neutron sensitivity. The calibration coefficient of the micro fission ionization chamber to be diagnosed is compared with the reference coefficient; The micro-fission ionization chamber to be diagnosed is diagnosed based on the comparison results.

6. The fault diagnosis method for a micro fission ionization chamber according to claim 5, characterized in that, The diagnosis of the micro-fission ionization chamber to be diagnosed based on the comparison results includes: If the comparison result is that the calibration coefficient of the micro-fission ionization chamber to be diagnosed exceeds the range of the reference coefficient, then: The automatic calibration coefficients of the micro fission ionization chamber to be diagnosed are obtained; the automatic calibration coefficients are the calibration coefficients calculated by the neutron measurement system. If the calibration coefficient of the micro fission ionization chamber to be diagnosed is the same as the automatic calibration coefficient, then the diagnosis result of the micro fission ionization chamber to be diagnosed is: the reason for the calibration coefficient exceeding the standard is that the relative deviation of the factory thermal neutron sensitivity is too large, and the micro fission ionization chamber to be diagnosed is usable.

7. The fault diagnosis method for a micro fission ionization chamber according to claim 5, characterized in that, The diagnosis of the micro-fission ionization chamber to be diagnosed based on the comparison results includes: If the comparison result is that the calibration coefficient of the micro-fission ionization chamber to be diagnosed is within the range of the reference coefficient, then: The calibration coefficients of the micro fission ionization chamber to be diagnosed are compared with the upper and lower limits of the reference coefficient range, respectively. If the difference between the calibration coefficient of the micro fission ionization chamber to be diagnosed and the upper limit value is within a preset range, or the difference between the calibration coefficient of the micro fission ionization chamber to be diagnosed and the lower limit value is within a preset range, then the diagnostic result of the micro fission ionization chamber to be diagnosed is: the reason for the calibration coefficient exceeding the standard is that there is a difference in the change of thermal neutron sensitivity between the micro fission ionization chamber to be diagnosed and the reference micro fission chamber during the operation of the unit.

8. The method for fault diagnosis of a micro fission ionization chamber according to claim 5, characterized in that, The diagnosis of the micro-fission ionization chamber to be diagnosed based on the comparison results includes: If the comparison result is that the calibration coefficient of the micro-fission ionization chamber to be diagnosed is within the range of the reference coefficient, then: The calibration coefficient of the micro fission ionization chamber to be diagnosed is compared with a preset value; If the difference between the calibration coefficient of the micro fission ionization chamber to be diagnosed and the preset value is within the deviation range, then the diagnosis result of the micro fission ionization chamber to be diagnosed is: the reason for the calibration coefficient exceeding the standard is that the difference between the micro fission ionization chamber to be diagnosed and the reference micro fission ionization chamber in the operation of the unit is greater than the threshold.

9. The fault diagnosis method for a micro fission ionization chamber according to claim 8, characterized in that, The diagnostic process for the micro-fission ionization chamber to be diagnosed based on the comparison results also includes: If the difference in thermal neutron sensitivity of the micro-fission ionization chamber to be diagnosed during operation in the unit is greater than a threshold, then: The automatic calibration coefficient of the micro fission ionization chamber to be diagnosed is compared with the upper limit of the reference coefficient range; If the automatic calibration coefficient is greater than the upper limit value, the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the calibration coefficient exceeding the standard is that the thermal neutron sensitivity of the reference micro-fission ionization chamber has abnormally decreased, and the reference micro-fission ionization chamber is unusable.

10. The fault diagnosis method for a micro fission ionization chamber according to claim 8, characterized in that, The diagnostic process for the micro-fission ionization chamber to be diagnosed based on the comparison results also includes: If the difference in thermal neutron sensitivity of the micro-fission ionization chamber to be diagnosed during operation in the unit is greater than a threshold, then: The automatic calibration coefficient of the micro fission ionization chamber to be diagnosed is compared with the lower limit of the reference coefficient range; If the automatic calibration coefficient is less than the lower limit, the diagnostic result of the micro fission ionization chamber to be diagnosed is: the reason for the calibration coefficient exceeding the standard is that the thermal neutron sensitivity of the micro fission ionization chamber to be diagnosed has decreased abnormally, and the micro fission ionization chamber to be diagnosed is unusable.

11. The fault diagnosis method for a micro fission ionization chamber according to claim 1, characterized in that, If the fault type of the micro fission ionization chamber to be diagnosed is an abnormally large or excessive plateau tilt, then the pre-set plateau tilt diagnosis method is used to diagnose the micro fission ionization chamber to be diagnosed, including: Obtain the electrical parameters of the micro fission ionization chamber to be diagnosed; Determine whether the electrical characteristics of the micro fission ionization chamber to be diagnosed are qualified based on the electrical parameters. If not, the micro-fission ionization chamber to be diagnosed is then diagnosed based on the electrical characteristics described. If so, then obtain the nuclear characteristic parameters of the micro fission ionization chamber to be diagnosed; The micro-fission ionization chamber to be diagnosed is diagnosed based on the nuclear characteristic parameters.

12. The fault diagnosis method for a micro fission ionization chamber according to claim 11, characterized in that, The electrical parameters include: the insulation resistance of the faulty micro-fission ionization chamber and its measurement circuit; The step of determining whether the electrical characteristics of the micro-fission ionization chamber to be diagnosed are qualified based on the electrical parameters includes: The insulation resistance of the micro fission ionization chamber to be diagnosed and its measurement circuit is compared with a reference resistance value. If the insulation resistance of the micro fission ionization chamber to be diagnosed and its measuring circuit is less than the reference resistance value, then the electrical characteristics of the micro fission ionization chamber to be diagnosed are deemed unqualified. The diagnostic process for the micro-fission ionization chamber based on the electrical characteristics includes: If the insulation resistance of the micro-fission ionization chamber to be diagnosed and its measuring circuit is less than the reference resistance value, then the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the excessive or out-of-range plateau is that the insulation resistance of the micro-fission ionization chamber to be diagnosed and its measuring circuit is abnormal, and the micro-fission ionization chamber to be diagnosed is unusable.

13. The method for fault diagnosis of a micro fission ionization chamber according to claim 11, characterized in that, The electrical parameters include: the leakage current of the faulty micro-fission ionization chamber and its measurement circuit; The step of determining whether the electrical characteristics of the micro-fission ionization chamber to be diagnosed are qualified based on the electrical parameters includes: The leakage current of the micro-fission ionization chamber and its measurement circuit of the device to be diagnosed is compared with the reference current. If the leakage current of the micro fission ionization chamber to be diagnosed and its measuring circuit is greater than the reference current, then the electrical characteristics of the micro fission ionization chamber to be diagnosed are deemed unqualified. The diagnostic process for the micro-fission ionization chamber based on the electrical characteristics includes: If the leakage current of the micro-fission ionization chamber to be diagnosed and its measuring circuit is greater than the reference current, then the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the excessive or excessive plateau slope is that the leakage current of the micro-fission ionization chamber to be diagnosed and its measuring circuit is abnormal, and the micro-fission ionization chamber to be diagnosed is unusable.

14. The method for fault diagnosis of a micro fission ionization chamber according to claim 11, characterized in that, The electrical parameters include: the capacitance of the faulty micro-fission ionization chamber and its measurement circuit; The step of determining whether the electrical characteristics of the micro-fission ionization chamber to be diagnosed are qualified based on the electrical parameters includes: Determine whether the capacitance of the micro fission ionization chamber to be diagnosed and its measurement circuit is within the reference capacitance range; If the capacitance of the micro fission ionization chamber to be diagnosed and its measuring circuit is not within the reference capacitance range, then the electrical characteristics of the micro fission ionization chamber to be diagnosed are deemed unqualified. The diagnostic process for the micro-fission ionization chamber based on the electrical characteristics includes: If the capacitance of the micro-fission ionization chamber to be diagnosed and its measuring circuit is not within the reference capacitance range, then the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the excessive or out-of-range plateau is that the gap between the high-voltage electrode and the collecting electrode of the micro-fission ionization chamber to be diagnosed is abnormal, and the micro-fission ionization chamber to be diagnosed is unusable.

15. The method for fault diagnosis of a micro fission ionization chamber according to claim 11, characterized in that, The nuclear characteristic parameters of the micro-fission ionization chamber to be diagnosed include: measurement current and plateau slope; The diagnostic process for the micro-fission ionization chamber based on the nuclear characteristic parameters includes: Obtain the measurement current of the micro fission ionization chamber to be diagnosed; Determine whether the measured current of the micro fission ionization chamber to be diagnosed has a step value or a spike value; If so, the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the excessive or excessive plateau tilt is the abnormal measurement current, and the micro-fission ionization chamber to be diagnosed is unusable; If not, then the micro-fission ionization chamber to be diagnosed is diagnosed based on the slope.

16. The fault diagnosis method for a micro fission ionization chamber according to claim 15, characterized in that, The diagnosis of the micro-fission ionization chamber to be diagnosed based on the plateau inclination includes: Control the micro fission ionization chamber to be diagnosed to perform pretreatment tasks; After completing the preprocessing task, the preprocessed plateau of the micro fission ionization chamber to be diagnosed is obtained; The micro-fission ionization chamber to be diagnosed is diagnosed based on the pre-processed plateau inclination.

17. The method for fault diagnosis of a micro fission ionization chamber according to claim 16, characterized in that, The diagnosis of the micro-fission ionization chamber to be diagnosed based on the pre-processed plateau slope includes: Determine whether the pre-treated slope is within the range of the first slope; If so, the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the excessive or excessive plateau tilt is that a trace amount of impurity gas enters the sensor body, causing abnormal nuclear characteristics of the faulty micro-fission ionization chamber. When the plateau tilt of the micro-fission ionization chamber to be diagnosed returns to the normal range, the micro-fission ionization chamber to be diagnosed returns to a usable state.

18. The method for fault diagnosis of a micro fission ionization chamber according to claim 16, characterized in that, The diagnosis of the micro-fission ionization chamber to be diagnosed based on the pre-processed plateau slope includes: Determine whether the pre-treated slope is within the range of the second slope; If so, the diagnostic result of the micro fission ionization chamber to be diagnosed is: the micro fission ionization chamber to be diagnosed is faulty but usable, and the micro fission ionization chamber to be diagnosed will be replaced within the preset maintenance period.

19. The fault diagnosis method for a micro fission ionization chamber according to claim 17, characterized in that, The diagnosis of the micro-fission ionization chamber to be diagnosed based on the pre-processed plateau slope includes: Determine whether the pre-processed slope is greater than the upper limit value of the slope; If so, the diagnostic result of the micro-fission ionization chamber to be diagnosed is: the reason for the excessive or excessive plateau tilt is that the micro-fission ionization chamber to be diagnosed is unusable.

20. A fault diagnosis system for a micro fission ionization chamber, characterized in that, include: The monitoring unit is used to monitor each microfission ionization chamber in the same pressurized water reactor nuclear power unit and determine whether the microfission ionization chamber has an abnormal calibration coefficient or plateau tilt. The acquisition unit is used to acquire the fault type of any micro-fission ionization chamber in the same pressurized water reactor nuclear power unit when a calibration coefficient or plateau tilt anomaly occurs; the micro-fission ionization chamber to be diagnosed is the micro-fission ionization chamber that has experienced a calibration coefficient or plateau tilt anomaly. The first diagnostic unit is used to diagnose the micro-fission ionization chamber to be diagnosed if the fault type is calibration coefficient exceeding the standard. This diagnosis employs a preset calibration coefficient diagnostic method, which includes: determining the physical meaning of the calibration coefficient of the micro-fission ionization chamber; the physical meaning of the calibration coefficient of the micro-fission ionization chamber is: the normalized value of the thermal neutron sensitivity of any micro-fission ionization chamber in the same unit relative to the reference thermal neutron sensitivity; based on the physical meaning of the calibration coefficient of the micro-fission ionization chamber, determining the acceptance criteria for calibration coefficient exceeding the standard; and diagnosing the micro-fission ionization chamber to be diagnosed according to the acceptance criteria for calibration coefficient exceeding the standard. The second diagnostic unit is used to diagnose the micro fission ionization chamber to be diagnosed if the fault type is abnormally large or exceeds the standard by using a preset plateau inclination diagnostic method.

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