JP4528533B2 - Nuclear power plant equipment inspection method and nuclear power plant equipment inspection system - Google Patents

Description

  The present invention relates to a nuclear power plant equipment inspection method and a nuclear power plant equipment inspection system for safely and efficiently operating a nuclear power plant when there are defects such as cracks in the constituent equipment of the nuclear power plant.

The standards for the construction, maintenance, management, etc. of structures and components in Japanese nuclear power plants are organized by technical standards such as ministerial ordinances and notifications related to the Electricity Business Law and complemented by private regulations. ing. For the technical criteria for non-destructive testing of structures and construction equipment in these nuclear power plant, technical standards (No. Notice 501) such structures, technical standards (Ordinance No. 123) Welding, periodical inspection Implementation Guidelines, in-service period There are inspection regulations (JEAC4205), ultrasonic flaw detection guidelines (JEAG4207), and eddy current flaw detection guidelines (JEAG4208).

  More specifically, the technical standards for nondestructive inspection during the service period of component equipment are stipulated in the Guidelines for Periodic Inspection and Inspection Regulations during Service Period (JEAC 4205 “In-service inspection of light water nuclear power plant equipment”). The specific contents of the technical standards are defined in the ultrasonic flaw detection guideline (JEAG4207) and the eddy current flaw detection guideline (JEAG4208).

  According to these technical standards, in nuclear power plants, the components that are subject to nondestructive inspection are classified according to their importance into Type 1 equipment, Type 3 equipment, and Type 4 containers / pipes. They are classified according to the degree, shape, and components. The technical standards include the accessibility to the component equipment during the nondestructive inspection of each component equipment, the inspection interval of the nondestructive inspection, the component equipment and range to be tested, the inspection method, the evaluation of the inspection result, and the repair method. Items such as replacement methods, records, and reports are specified as standards.

  According to the technical standards in such nuclear power plants, especially when a defect such as a crack occurs in a primary system component, the defect does not take into account whether the defect affects the safety or function of the component. It is obliged to repair or replace components.

On the other hand, in order to reduce the number of inspections of component equipment in nuclear power plants and improve economic efficiency, the importance is calculated for all the components subject to preventive maintenance, and the unreliability of highly important component equipment A nuclear power plant maintenance technique is proposed that displays the correlation between the reliability index such as risk and the like and the total number of inspection points in a graph (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 8-115108 (see page 3 to page 5, FIG. 3)

  According to the current technical standards for non-destructive inspection of nuclear power plant components, even if the defects that occur in the primary system components are harmless, the defect can be repaired or replaced by replacing the primary system. Construction to remove is carried out. For this reason, for example, when construction that affects quality, such as welding, is carried out for defect removal, there is a risk of newly generating another defect in the primary system equipment, which is substantially sound. There is a risk of deteriorating sex.

  Therefore, when defects such as cracks are already harmless in the United States, we have established reliable measures and technologies for defects before they become harmful, without immediately repairing the defects or replacing the primary equipment. The idea of keeping is applied to the operation of nuclear power plants.

  On the other hand, there is a movement in Japan to apply the same nuclear power plant operation method as in the United States. For this reason, the “Nuclear Power Plant Standard Maintenance Standard” reflecting the special characteristics of domestic plant materials used as equipment materials has been issued by the Japan Society of Mechanical Engineers and is being applied to the operation of nuclear power plants.

  In other words, when defects such as cracks occur in nuclear power plant equipment, the technical standards such as the periodic inspection implementation guidelines and in-service inspection regulations established for components without defects are in accordance with nuclear power generation. It is not always appropriate to maintain the safety, economic efficiency and soundness of the plant. For this reason, it is important to establish standards for the inspection of rational components that take into account the safety, economics, and soundness of nuclear power plants.

  On the other hand, in the conventional nuclear power plant maintenance technology, the reliability and economic efficiency of the entire nuclear power plant can be easily grasped from the reliability index of the component equipment, but defects are actually found in the inspection of the specific component equipment. It is difficult to fully grasp the reliability of a nuclear power plant in such a case.

  The present invention has been made in order to cope with such a conventional situation, and even if a component such as a crack exists in a component of the nuclear power plant, the nuclear power plant is not immediately repaired or replaced. It is an object of the present invention to provide a nuclear power plant equipment inspection method and a nuclear power plant equipment inspection system that can be operated safely and efficiently.

In order to achieve the above-described object, the nuclear power plant equipment inspection method according to the present invention divides the constituent equipment of the nuclear power plant into segments, and changes the risk over time for each segment. Is calculated according to the inspection frequency from the destruction probability and the influence degree of each segment of the component device , and the risk is controlled so that the risk of each segment approaches a risk target line indicating a time change of a preset target risk by, in the case where the risk exceeds the allowable value of the target risk or predetermined risks increases the number of inspections by shortening the test interval, if the risk is less than the target risk by increasing the test interval The method is characterized in that the inspection frequency is decreased, and the component device is inspected at the reset inspection frequency.

Further, in order to achieve the above-described object, the nuclear power plant equipment inspection system according to the present invention divides the constituent equipment of the nuclear power plant into segments, and the risk of each segment is as described in claim 11 . Risk calculation means for calculating the time change from the destruction probability and the influence degree of each segment of the component device according to the inspection frequency, and the risk target line indicating the time change of the target risk in which the risk of each segment is set in advance By controlling the risk so that it approaches, if the risk exceeds the target risk or a predetermined risk tolerance, increase the number of inspections by shortening the inspection interval, and if the risk is below the target risk to reduce the inspection frequency by increasing the test interval, der those characterized by having a risk control means for resetting .

In the nuclear power plant equipment inspection method and the nuclear power plant equipment inspection system according to the present invention, even if a defect such as a crack exists in the constituent equipment of the nuclear power plant, the risk is not immediately repaired or replaced. By performing the inspection at an inspection frequency that can be maintained below the allowable value or near the target risk, it is possible to operate the nuclear power plant safely and efficiently.

  An embodiment of a nuclear power plant equipment inspection method and a nuclear power plant equipment inspection system according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a functional block diagram showing a first embodiment of a nuclear power plant equipment inspection system according to the present invention.

  The nuclear power plant equipment inspection system 1 includes a risk calculation means 2 and a risk control means 3, and has a function of setting the inspection frequency of each component equipment in the nuclear power plant.

  The risk calculation means 2 gives the risk control means 3 the function of calculating the time change of the risk (risk level) of any single or plural arbitrary components in the nuclear power plant according to the inspection frequency. With functions. Furthermore, if necessary, the risk calculation means 2 is provided with a segmental risk calculation means 4, and the segment risk calculation means 4 is a segment that is a region obtained by dividing a component device into a plurality of divisions of the risk change of the component device. A separate calculation function is provided.

  At this time, the risk calculation means 2 determines the risk of the component equipment when a defect such as stress corrosion cracking (SCC) or a crack occurs due to fatigue or stress concentration in the component equipment. The calculation is executed from the probability (destruction probability) that the component device breaks due to the development of a defect such as the above and the degree of influence that is an index of the magnitude of the effect when the component device is broken.

  The risk control unit 3 has a function of newly resetting the inspection frequency of the component device or segment by executing risk control on the risk of the component device or segment obtained by the risk calculation unit 2. As a risk control method, if the risk of a component device or segment is greater than the risk reference value at a given time compared to a preset risk reference value, the inspection frequency of that component device or segment is increased. Set a new inspection frequency to reduce the risk, and if it is smaller than the risk reference value, set a new inspection frequency to increase the risk by decreasing the inspection frequency of the component or segment And a combination of these methods.

  In this case, as the risk reference value, an arbitrary value such as a preset target risk, an allowable value of risk, an allowable value considering the safety factor, or the like can be set. For this reason, the risk control means 3 can be provided with a function of performing risk control so that, for example, each risk is brought closer to the target risk by increasing or decreasing the inspection frequency of the component device or segment.

  Further, the risk control means 3 is configured to be able to repeatedly execute risk calculations for constituent devices or segments so as to meet a preset risk condition using a new examination frequency set as necessary.

  Next, the operation of the nuclear power plant equipment inspection system 1 will be described.

  FIG. 2 is a flowchart showing an example of a procedure for setting the inspection frequency of the nuclear power plant by the nuclear power plant equipment inspection system 1 shown in FIG. 1, and the S symbol in the figure indicates each step of the flowchart.

  First, in step S1, the risk calculation means 2 calculates the time change of the risk of each component device of the nuclear power plant for each component device or each segment according to the inspection frequency. The risk of each component device is obtained by the risk calculation means 2 based on the breakdown probability and the influence degree in the component device and each segment.

  Here, the destruction probability of the component device indicates the possibility of the component device being destroyed due to the defect, and the influence degree of the component device indicates the amount of damage of the nuclear power plant when the component device is destroyed. For this reason, the risk of the component device is an index of the component device that simultaneously indicates the magnitude of the possibility that the component device is destroyed due to the defect and the magnitude of the influence when the component device is destroyed.

  Therefore, even if the impact on the nuclear power plant when each component device is destroyed differs for each component device or segment, if each component device or the risk of each segment is used as an index, each component device should be evaluated equally. Can do.

  The time change of the destruction probability of the component equipment can be obtained by predicting from the defect size by known probabilistic fracture mechanics. For this reason, the fracture probability depends on the number of segments and constituent devices to be inspected, that is, the inspection range, in addition to the inspection frequency for measuring the defect size. Furthermore, the failure probability includes not only the inspection frequency and inspection range such as the inspection interval, but also the defect detection failure probability that is the probability of failure to detect defects such as cracks in the inspection, or conversely the probability that defects are detected by inspection. The inspection accuracy of defect size such as certain defect detection probability and crack sizing accuracy also has an effect.

  Therefore, in calculating the fracture probability, in addition to the defect size and the inspection frequency, data such as the inspection range, the defect detection failure probability or the defect detection probability, and the inspection accuracy can be used as parameters.

  FIG. 3 is a diagram showing the relationship between the defect detection probability and the ratio of the crack depth to the plate thickness of the plate member when detecting a crack generated in the plate member by inspection.

  In FIG. 3, the vertical axis indicates the defect detection probability when a crack generated in the plate-like member is detected by inspection, and the horizontal axis indicates the ratio of the crack depth to the plate thickness of the plate-like member. Also, the solid line in FIG. 3 is a probability data curve D1a indicating the defect detection probability when a high-performance inspector performs an inspection, and the broken line is a probability indicating a defect detection probability when a medium-capacity inspector performs an inspection. A data curve D1b and an alternate long and short dash line are a probability data curve D1c indicating a defect detection probability when a low-performance inspector performs an inspection.

  According to the probability data curves D1a, D1b, and D1c in FIG. 3, the defect detection probability increases with the ratio of the crack depth to the plate thickness of the plate-like member, and the defect becomes deeper as the crack is deeper than the plate thickness. It can be seen that the probability that a crack is detected increases. However, the defect detection probability varies depending on the inspection ability of the inspector, and the probability of detecting a defect is higher with a high ability inspector, and conversely, the probability of detecting a defect with a low ability inspector is higher. It turns out that it is low.

  Therefore, it can be seen that the destruction probability depends on the defect detection failure probability or the defect detection probability. Therefore, the defect detection failure probability or the defect detection probability can be used as a parameter in the calculation of the destruction probability.

  FIG. 4 is a characteristic diagram showing an example of the defect sizing accuracy when the depth from the surface of the internal defect is measured by nondestructive inspection by the ultrasonic flaw detection method for the primary recirculation system pipe.

  In FIG. 4, the vertical axis represents the measured value of the depth from the surface of the internal defect obtained by the nondestructive inspection by the ultrasonic flaw detection method, and the horizontal axis represents the actual measurement value by the destructive inspection of the internal defect. In addition, each of the ○ mark, △ mark, □ mark, ● mark, and ■ mark in FIG. 4 indicates an internal defect obtained by nondestructive inspection by ultrasonic flaw detection as a different inspection condition, for example, a different inspector or different inspection object. It is the measured value data of the depth from the surface.

  As can be seen from FIG. 4, each measured value data has an error with respect to the actually measured value. That is, when the error between the measured value data and the actually measured value is zero, the measured value data exists on a straight line (reference straight line) passing through the origin with an inclination indicated by a broken line of 1. For this reason, the difference between the reference line and the measured value data represents an error in the measured value data. Therefore, when the reference straight line is shifted by the average of the errors of the respective measured value data, an error straight line indicated by a solid line in FIG. 4 is obtained. That is, it can be seen that the measured value data has an error on average on the difference between the reference straight line and the error straight line.

  Therefore, since the accuracy of the defect size depends on the inspection accuracy, it can be understood that the failure probability also depends on the inspection accuracy. Therefore, the inspection accuracy can be used as a parameter for calculating the fracture probability.

  In this way, when calculating the failure probability, the detection probability such as the defect sizing accuracy of the inspection method and inspection apparatus and the defect detection failure probability or the defect detection probability which is an index of the inspector's ability are used as parameters. Prediction accuracy can be improved. Furthermore, it is possible to avoid the improvement of the prediction accuracy of an excessive failure probability, simplify the calculation of the failure probability, and adjust the prediction accuracy of the failure probability.

  Even when defects such as cracks and cracks are not detected by nondestructive inspection, the risk is evaluated together with the probability of destruction of components and segments by using the detection accuracy of nondestructive inspection and the probability of failure detection or defect detection. be able to.

  On the other hand, the impact of component equipment includes, for example, maintenance costs in the case of destruction of component equipment, lost profits due to shutdown, repair costs for faulty parts, damage countermeasure costs in the event of failure, radioactive contamination, damage to component equipment Public acceptance can be used, which is an indicator of the likelihood that a condition will be accepted by the general public.

The public acceptance values are ranked and digitized as shown in Table 1.

  As shown in Table 1, the public acceptance is ranked and quantified according to the degree of possibility that the destruction of the component equipment is accepted by the general public. Table 1 is an example in which the public acceptance is ranked into 10 levels and digitized.

  For example, the public acceptance of a component or segment that is evaluated as being rejected by the general public regardless of the conditions is set to 10, and the component is evaluated as being accepted by the general public even if it is destroyed. The public acceptance of the component device or segment to be set is set to 1.

  And the risk of a component apparatus or a segment can be calculated | required as a product of the destruction probability and influence degree of a component apparatus or a segment, for example. In this case, the risk is the expected value of maintenance costs, which is a measure of economic impact, the expected value of lost profits due to shutdown, the expected value of repair costs for failure locations, the expected value of damage countermeasure costs in the event of failure, or social The expected value of radioactive contamination and the expected value of public acceptance, etc., which serve as a measure of general impact.

  On the other hand, the risk of component equipment or segments is not limited to the product of the destruction probability and the impact level of the component equipment or segment, but one or both of the breakdown probability and the impact level are classified into multiple ranks (destruction probability). It is also possible to obtain a risk rank by classifying and ranking.

Table 2 is an example of a risk rank table when risk is set by ranking from the destruction probability and the degree of influence.

  As shown in Table 2, a matrix in which the breakdown probability and the influence degree are classified and ranked in, for example, three levels according to the degree is created in advance, and each component device or segment is assigned to the risk rank matrix to determine the risk rank as a risk. be able to.

  If the risk is determined by ranking as described above, it is possible to efficiently grasp and manage the risk. That is, the risk unit can be made non-dimensional, and the relative time change of the risk can be easily obtained regardless of how the degree of influence is obtained.

  In addition, when risk is calculated by ranking, the risk is the expected value of maintenance cost, the expected value of lost profit due to operation stop, the expected value of repair cost of failure location, and the damage caused by failure. This is equivalent to the expected value of countermeasure costs, the expected value of radioactive contamination that is a measure of social impact, and the expected value of public acceptance.

  In addition, you may obtain | require the risk of a component apparatus and a segment with another standard and method.

  In this way, the risk calculation means 2 calculates the risk, and the segment-specific risk calculation means 4 calculates the risk for each segment.

  FIG. 5 is a structural diagram of a shroud that is an example of components in a nuclear power plant to which the nuclear power plant equipment inspection system 1 shown in FIG. 1 is applied.

The shroud 10 has a structure in which a plurality of cylindrical members are connected coaxially by welding. FIG. 5 is an example of the shroud 10 in which eight welds (H1, H2, H3, H4, H6a, H6b, H7a, H7b) exist. In the shroud 10, there is a possibility that a defect such as damage is generated in each welded portion in the vicinity of a weld line where stress corrosion cracking (SCC) or cracks are likely to occur. For this reason, the inspection part with respect to the shroud 10 which is a component apparatus will be determined according to the number of welding parts. Therefore, as shown in Table 3, the inspection location of the shroud 10 can be divided into a plurality of segments for each welded portion.

  FIG. 6 is an explanatory diagram showing a method of calculating risk by dividing each component device in the nuclear power plant to which the nuclear power plant equipment inspection system 1 shown in FIG. 1 is applied into a plurality of segments.

  The nuclear power plant includes a plurality of component devices (component device 1, component device 2,..., Component device m), and each component device has a plurality of segments for each part where defects such as damage are expected to occur. (Segment 11, segment 12, segment 13,...) Can be divided. For this reason, each segment can be used as a unit for counting locations where defects such as damage occur in a nuclear power plant. Therefore, the segment risk calculation means 4 calculates a risk (risk 11, risk 12, risk 13,...) For each segment of each component of the nuclear power plant.

  FIG. 7 is a conceptual diagram showing the change over time of the risk of the component equipment calculated by the nuclear power plant equipment inspection system 1 shown in FIG. 1 and the inspection frequency setting method.

  In FIG. 7, the vertical axis indicates the risk in each segment of the component equipment, and the horizontal axis indicates the operating time of the nuclear power plant. In addition, a two-dot chain line in FIG. 7 indicates the allowable risk value D2 in each segment, and two solid lines indicate the time change of the risk for the segment 1 and the segment 2 of the component device a obtained by the risk calculation means 2. Are risk change curves D3a and D3b.

  Each risk of the component equipment generally increases with the operation time of the nuclear power plant, but the risk is reduced when the inspection is performed periodically. That is, each of the risk change curves D3a and D3b obtained by the risk calculation means 2 increases as the operating time increases, while the risk decreases discontinuously at the time of the inspection, so as shown in FIG. The curve increases in a sawtooth shape.

  Then, the segment risk calculation means 4 gives the obtained risk change curves D3a and D3b for each segment of each component device to the risk control means 3, respectively.

  Next, in step S <b> 2 shown in FIG. 2, the risk control unit 3 sets the inspection frequency of each segment by performing risk control of the risk for each segment received from the segment-specific risk calculation unit 4. That is, the risk control means 3 first compares the risk for each segment with a preset target risk, and determines the segment risk at a predetermined time of interest, for example, when the risk in at least one segment exceeds the allowable value D2. Are each greater than the target risk.

  In FIG. 7, the alternate long and short dash line is an example of a risk target line D <b> 4 that indicates a time change of a preset target risk. The risk target line D4 is set as, for example, a curve that increases in a polygonal line shape. In FIG. 7, according to the risk change curve D3a of segment 1 and the risk target line D4, it can be seen that the risk of segment 1 is greater than the target risk at the time of interest. Similarly, according to the risk change curve D3b and the risk target line D4 of the segment 2, it can be seen that the risk of the segment 2 is smaller than the target risk at the time of interest.

  Then, the risk control means 3 adjusts the inspection frequency of each segment 1 and 2 and newly sets it. That is, the risk control means 3 increases the inspection frequency for the segment 1 and sets it as a new inspection frequency, while decreasing the inspection frequency for the segment 2 and sets it as a new inspection frequency.

  The two dotted lines in FIG. 7 are the risk control curves D5a and D5b for segment 1 and segment 2 after the risk control by the risk control means 3, respectively.

  For example, the risk control means 3 sets the inspection frequency to n times so that the risk at the time of interest of the segment 1 can be set to the allowable value D2 or less. The example of FIG. 7 is an example in which the inspection frequency of segment 1 is set to double. At this time, the value of n is, for example, the minimum n that can reduce the risk at the time of interest to an allowable value D2 or less, or the difference between the risk target line D4 and the risk control curve D5a at the time of interest is less than a certain value. N can be obtained.

  However, the risk control means 3 may not only set the inspection frequency to n times but also add a new inspection at a specific time.

  That is, when the risk exceeds the target risk or the allowable value D2, the risk control means 3 increases the number of inspections by shortening the inspection interval. Then, by performing re-inspection of defects such as re-measurement of the crack dimensions, the risk is reduced by improving the evaluation accuracy of the breakdown probability of the constituent devices and each segment, and the target risk is approached. As a result, the risk control curve D5a obtained by the newly set inspection frequency of the segment 1 is less than the allowable value D2 at the time of interest and the risk is reduced so as to approach the risk target line D4.

  Furthermore, the risk control means 3 reduces the inspection frequency so that, for example, the risk of the segment 2 can be kept below the target risk over the entire operation time. As a result, the risk control curve D5b obtained by the newly set inspection frequency of the segment 2 increases while maintaining the risk target line D4 or less over the entire operation time, and approaches the risk target line D4. Optimization is performed.

  That is, when the risk is less than or equal to the target risk, the risk control means 3 reduces the inspection frequency by omitting a specific inspection or widening the inspection interval, and controls the risk so as to increase the risk. , Bring the risk closer to the target risk.

  It is also possible to control the risk so that a part of the inspection frequency in a single segment is increased while a part thereof is decreased.

  Further, the risk control means 3 may set the inspection frequency by changing the data such as the defect detection failure probability or the defect detection probability, the inspection accuracy used by the risk calculation means 2 when calculating the risk. Thereby, the inclination of the risk control curves D5a and D5b can be controlled. That is, the defect detection failure probability, the defect detection probability, and the inspection accuracy that can be the required risk control curves D5a and D5b can be set together with the inspection frequency.

  Thus, each segment can be inspected at the inspection frequency set by the risk control means 3 without the risk of each segment exceeding the allowable value D2. Furthermore, if data such as defect detection failure probability or defect detection probability, inspection accuracy, etc. are set, it is possible to grasp the capability required for the inspector, the accuracy of the inspection method and the inspection apparatus.

  That is, the nuclear power plant equipment inspection system 1 immediately repairs or replaces the constituent equipment or the segment when defects such as fatigue or cracks due to causes such as SCC are found in the constituent equipment in the periodic inspection of the nuclear power plant. There is no system that adjusts the inspection frequency by using the time change of the risk of the component equipment or each segment as an index for operating the nuclear power plant safely and efficiently.

  For this reason, according to the nuclear power plant equipment inspection system 1, a defect such as a crack due to fatigue, SCC, or the like is found in a periodic inspection that is conventionally performed on components or segments of the nuclear power plant. Even if there is a failure due to the future operation of the nuclear power plant and the components and segments are destroyed, the time change of the risk for radiation leakage and economic loss is obtained, and the calculated risk is the allowable value D2. By conducting inspections with the inspection frequency that can be kept below or near the target risk, it becomes possible to operate the nuclear power plant safely and rationally. Furthermore, it is possible to efficiently inspect and maintain a nuclear power plant from an economic viewpoint.

  That is, if the risk in each segment of the component equipment is higher than the target risk, for example, if it exceeds the allowable value D2, the probability of destruction can be determined by re-measuring the condition such as the size of the defect by increasing the inspection frequency. At the same time, it is possible to improve the accuracy of prediction of the subsequent risk and reduce the risk to the allowable value D2 or less. For this reason, even if the risk exceeds the target risk and the allowable risk value D2 along with the operation time of the nuclear power plant by performing the regular inspection uniformly in accordance with the periodic inspection implementation guidelines and the inspection regulations during the service period, the inspection frequency By increasing the risk, the risk calculation accuracy can be improved and the risk can be maintained in the vicinity of the target risk or below the allowable risk value D2 for a longer period of time to maintain the soundness of the nuclear power plant.

  On the other hand, according to the nuclear power plant equipment inspection system 1, when the risk in each segment of the component equipment is less than or equal to the target risk, by reducing the inspection frequency, the probability of destruction and the prediction accuracy of the subsequent risk are reduced. The number of inspections can be reduced while bringing the risk closer to the target risk. For this reason, the test | inspection of a component apparatus can be implemented more efficiently.

  In the nuclear power plant equipment inspection system 1, the risk calculation means 2 is not provided with the segment risk calculation means 4, and a single risk is calculated for each component device, and the risk control means 3 for each component device calculates the risk. You may comprise so that it may control. In this case, the risk tolerance D2 is the tolerance for the entire nuclear power plant.

  Furthermore, risk control may be performed on both the component device risk and the segment risk based on a single target risk and a risk reference value such as an allowable value D2.

  Further, in the nuclear power plant equipment inspection system 1, when the risk is larger than the risk reference value such as the target risk or the allowable value D2, the risk control means 3 increases the inspection frequency of the component equipment or segment to newly The function of setting the test frequency as a new test frequency by reducing the test frequency when the risk is smaller than the risk reference value may be omitted.

  FIG. 8 is a functional block diagram showing a second embodiment of the nuclear power plant equipment inspection system according to the present invention.

  The nuclear power plant equipment inspection system 1A shown in FIG. 8 is different from the nuclear power plant equipment inspection system 1 shown in FIG. Since other configurations and operations are not substantially different from the nuclear power plant equipment inspection system 1 shown in FIG. 1, the same components are denoted by the same reference numerals and description thereof is omitted.

  The risk calculation means 2 of the nuclear power plant equipment inspection system 1A includes a segment-specific risk calculation means 4 and an equipment-specific risk calculation means 20.

  The segment-specific risk calculation means 4 includes a function for calculating a temporal change in risk in each segment of a single or a plurality of arbitrary components of the nuclear power plant according to the inspection frequency, and a segment which is a risk of each obtained segment A function of giving another risk to the device-specific risk calculation means 20.

  The device-specific risk calculation means 20 has a function of inputting the segment-specific risk obtained by the segment-specific risk calculation means 4 and setting the segment-specific risk that is the maximum within a single component device as the device-specific risk at the time of interest. And a function of giving the set device-specific risk to the risk control means 3.

  For this reason, the risk control means 3 performs risk control by a method for comparing with a risk reference value such as a target risk or an allowable value D2 set in advance for the risk for each device obtained by the device-specific risk calculation means 20. Reset the inspection frequency for each component.

  Next, the operation of the nuclear power plant equipment inspection system 1A will be described.

  FIG. 9 is a flowchart showing an example of a procedure for setting the inspection frequency of the nuclear power plant by the nuclear power plant equipment inspection system 1A shown in FIG. 8, and the S symbol in the figure indicates each step of the flowchart.

  First, in step S10, the segment risk calculation unit 4 of the risk calculation unit 2 determines the segmental risk, which is the time change of the risk of each segment of the component equipment in the nuclear power plant, according to the inspection frequency, Calculate from

  FIG. 10 is an explanatory diagram showing a method of calculating a risk by the nuclear power plant equipment inspection system 1A shown in FIG.

  By the calculation by the segment risk calculation means 4, as shown in FIG. 10, each segment device (component device 1, component device 2,..., Component device m) has a segment risk (risk 11, risk 12, risk 13). , ...) is calculated. The segment risk calculation means 4 gives the segment risk obtained by the calculation to the device risk calculation means 20.

  Next, in step S11 shown in FIG. 9, the device-specific risk calculation means 20 shown in FIG. 8 receives the segment-specific risk from the segment-specific risk calculation means 4, and becomes the maximum in a single component device at the time of interest. Segment risk is set as equipment risk. For this reason, as shown in FIG. 10, each component device (component device 1, component device 2,..., Component device m) has a risk for each device (risk 1, risk 2,..., Risk m). It is done.

  Here, the time change of the risk for each device becomes a risk change curve for each device which is the same risk change curve as the solid line in FIG. 7, and the risk change for each device where the risk for each device becomes the maximum among the risk change curves for each device. The risk by equipment of the curve can be regarded as a plant risk that is a risk of the entire nuclear power plant.

  Then, the device-specific risk calculation means 20 gives the device-specific risk to the risk control means 3.

  Next, in step S <b> 12, the risk control unit 3 sets the inspection frequency by performing risk control on the device-specific risk received from the device-specific risk calculation unit 20. That is, the risk control means 3 first compares the device-specific risk with a preset target risk, and at a predetermined time of interest, for example, at the time when at least one device-specific risk exceeds the plant risk allowable value D2. It is determined whether each risk is greater than the target risk.

  Next, the risk control means 3 adjusts and newly sets the inspection frequency of each component device. In other words, the risk control means 3 increases the inspection frequency for each component device having a device-specific risk larger than the target risk and sets it as a new inspection frequency, while the device-specific risk is smaller for each component device than the target risk. The inspection frequency is reduced and set as a new inspection frequency.

  As a result, a risk control curve similar to the dotted lines D5a and D5b in FIG. 7 is obtained for each component device by the newly set inspection frequency. Then, each component device can be inspected at a more efficient frequency without the risk of each component device exceeding the allowable value at the set inspection frequency.

  In other words, the nuclear power plant equipment inspection system 1A is a system that uses the risk for each component instead of using the risk for each segment as an index when setting the inspection frequency of the component. Further, at this time, the risk for each component device is set to the maximum risk for each segment.

  According to the nuclear power plant equipment inspection system 1A, in addition to the effects of the nuclear power plant equipment inspection system 1, the number of risks subject to risk control can be reduced, so risk control is performed more easily and efficiently. Thus, the inspection frequency can be set.

  FIG. 11 is a functional block diagram showing a third embodiment of the nuclear power plant equipment inspection system according to the present invention.

  In the nuclear power plant equipment inspection system 1B shown in FIG. 11, the nuclear power plant equipment inspection shown in FIG. 1 is that the classifying means 30 is provided and the risk control means 31 is provided with the class-specific risk control means 31. It is different from the system 1. Since other configurations and operations are not substantially different from the nuclear power plant equipment inspection system 1 shown in FIG. 1, the same components are denoted by the same reference numerals and description thereof is omitted.

  The nuclear power plant equipment inspection system 1B includes a risk calculation means 2, a risk control means 3, and a classification means 30.

  The risk calculation means 2 has the same function as the nuclear power plant equipment inspection system 1 and gives the obtained component equipment or segment risk to the classifying means 30.

  The classifying means 30 receives the risk of the component device or segment obtained by the risk calculating means 2 and classifies the risk into risk classes according to the magnitude of the risk at the time of interest, and the risk for each risk class. A function to be given to the control means 3.

  The risk control means 3 is provided with a risk control means 31 for each class, and the risk control means 31 for each class controls the risk received from the classification means 30 for each risk class. At this time, the class-specific risk control means 31 performs risk control so that the inspection frequencies of the segments or constituent devices belonging to the same risk class are the same.

  Next, the operation of the nuclear power plant equipment inspection system 1B will be described.

  FIG. 12 is a flowchart showing an example of a procedure for setting the inspection frequency of the nuclear power plant by the nuclear power plant equipment inspection system 1B shown in FIG. 11, and the S symbol in the figure indicates each step of the flowchart.

  First, in step S20, the risk calculation means 2 shown in FIG. 11 calculates the risk of the component device and the segment from the destruction probability and the influence degree of the component device and the segment. Then, the risk calculation unit 2 inputs the calculated risk to the classifying unit 30.

  Next, in step S21 shown in FIG. 12, the classifying means 30 shown in FIG. 11 converts the risk of the component device or segment input from the risk calculating means 2 into a plurality of risk classes according to the magnitude of the risk at the time of interest. Classify.

  FIG. 13 is a conceptual diagram illustrating a method for classifying risks into risk classes by the nuclear power plant equipment inspection system 1B shown in FIG.

  In FIG. 13, the vertical axis indicates the risk of the component device or segment, and the horizontal axis indicates the operation time of the nuclear power plant. In addition, each solid line in FIG. 13 is a risk change curve D3 indicating a time change of the risk of the component device or the segment obtained by the risk calculation means 2.

  In general, the change rates of the risk change curves D3 are different from each other, and are distributed as shown in FIG. Therefore, for example, risk class upper limit lines for classifying risks into risk classes are set in advance for each risk size, and the area is divided by the risk class upper limit lines.

  However, a range for classifying risks at a specific time of interest into risk classes may be set.

  The broken line in FIG. 13 shows the risk class upper limit line D6. That is, FIG. 13 is an example in which i risk class upper limit lines D6 are set with the time of interest as the total operating time. For this reason, each risk change curve D3 is classified into i risk classes (risk class 1, risk class 2,..., Risk class i) for each region defined by each risk class upper limit line D6.

  Then, the classifying unit 30 gives the risk of the component device or the segment to the risk control unit 31 for each class of the risk control unit 3 for each risk class.

  Next, in step S22, the risk control unit 31 for each class controls the risk received from the classifying unit 30 for each risk class, and sets a common inspection frequency for components and segments belonging to the same risk class. To do.

  Therefore, the risk control means 31 for each class first compares each risk with a risk target line for each risk class.

  FIG. 14 is a conceptual diagram illustrating a method when risk is controlled for each risk class by the nuclear power plant equipment inspection system 1B shown in FIG.

  In FIG. 14, the vertical axis indicates the risk of the component device or segment, and the horizontal axis indicates the operating time of the nuclear power plant. Further, the broken line in FIG. 14 is the risk class upper limit line D6 of a certain risk class k, the alternate long and short dashed line is the risk target line D4 set in the risk class k, and the alternate long and two short dashes line is the risk tolerance D2 in the risk class k.

  As shown in FIG. 14, a risk tolerance value D2 and a risk target line D4 are set for each risk class. Then, the class-specific risk control means 31 compares each risk included in the same risk class with the same risk target line D4 and allowable value D2.

  Furthermore, the risk control means 31 for each class sets the inspection frequency for each risk class based on the comparison result with the risk target line D4 and the allowable value D2. That is, the class-specific risk control means 31 controls each risk so that the risks included in the same risk class have the same inspection frequency. For example, the test frequency when the maximum risk change curve D3 within the risk class is sufficiently close to the risk target line D4 and the risk class when the maximum risk change curve D3 within the risk class is less than or equal to the allowable value D2 It can be the inspection frequency.

  Therefore, a risk control curve D5 having the same inspection frequency is obtained as indicated by the dotted lines in FIG. Furthermore, since similar risk control is implemented in each risk class, the inspection frequency is set for each risk class.

  And the inspection frequency of a some component apparatus and a segment is unified according to a risk class, and the inspection of a component apparatus and a segment is implemented with the inspection frequency for every risk class.

  According to the nuclear power plant equipment inspection system 1B, in addition to the effects of the nuclear power plant equipment inspection system 1, even if there are many constituent equipment and segments, Since the inspection can be performed with the unified inspection frequency, the inspection frequency can be easily managed.

  Moreover, according to the nuclear power plant equipment inspection system 1B, even when there are a large number of components and segments, risk control is performed so that the same inspection frequency is achieved within the risk class, so risk control is easy. It becomes.

  FIG. 15 is a functional block diagram showing a fourth embodiment of the nuclear power plant equipment inspection system according to the present invention.

  In the nuclear power plant equipment inspection system 1 </ b> C shown in FIG. 15, the risk calculation means 2 is provided with item-specific risk calculation means 40 instead of the segment-specific risk calculation means 4, while the risk control means 3 has multiple risk optimization means. The point 41 is different from the nuclear power plant equipment inspection system 1 shown in FIG. Since other configurations and operations are not substantially different from the nuclear power plant equipment inspection system 1 shown in FIG. 1, the same components are denoted by the same reference numerals and description thereof is omitted.

  The risk calculation means 2 of the nuclear power plant equipment inspection system 1C is provided with item-specific risk calculation means 40, and the risk control means 3 is provided with multiple risk optimization means 41.

  The item-specific risk calculation means 40 has a function of calculating a plurality of risks for each item for a single segment or a plurality of segments or constituent devices and inputting the risk to the plurality of risk optimization means 41 of the risk control means 3. That is, the item-specific risk calculation means 40 has a function of calculating a plurality of risks for each item when calculating the risk for one segment or component device.

  Here, the risk items include, for example, the expected value of maintenance costs, which is a measure of economic impact, the expected value of lost profits due to operation stop, the expected value of repair costs for failure locations, and the cost of damage countermeasures in the event of failure. Items such as the expected value of radioactive contamination, the expected value of public acceptance, and the like.

  The destruction of components and segments in a nuclear power plant has a great impact on the general public's psychology and also affects the operation of the nuclear power plant, so the public acceptance or the product of public acceptance and destruction probability is Certain expectations of public acceptance are considered important. Therefore, it is effective to include at least the expected value of public acceptance of the component devices and segments as risk items.

  The multi-risk optimization unit 41 receives a plurality of item-specific risks from the item-specific risk calculation unit 40 for each component device or segment, and determines each risk item by item in each component device or segment. By performing risk control based on risk reference values such as target risk, it has a function of setting a single inspection frequency for each risk of each component device or segment. For example, when risk control is performed on a plurality of risks by item for a certain segment, the plurality of risk optimization means 41 has a common inspection frequency such that all risks are less than or equal to a preset allowable value for each risk. A function of setting a common inspection frequency that minimizes the sum of differences between all risks and a target risk set in advance for each risk is provided.

  Next, the operation of the nuclear power plant equipment inspection system 1C will be described.

  FIG. 16 is a flowchart showing an example of a procedure for setting the inspection frequency of a nuclear power plant by the nuclear power plant equipment inspection system 1C shown in FIG. 15, and the S symbol in the figure indicates each step of the flowchart.

  First, in step S30, the item-specific risk calculation unit 40 shown in FIG. 15 calculates a plurality of risks for each item of the component device and the segment from the destruction probability of the component device and the segment and the influence degree for each item. Then, the item-specific risk calculation means 40 inputs the calculated risks to the multiple risk optimization means 41.

  Next, in step S31 shown in FIG. 16, the multi-risk optimization means 41 shown in FIG. 15 uses the per-item risk tolerance D2 or the like for each item of the plurality of risks input from the item-specific risk calculation means 40. By performing risk control based on risk reference values such as target risk, a single inspection frequency is set for each risk of each component device or segment.

  FIG. 17 is a conceptual diagram for explaining a method for risk-controlling a plurality of risks for each item by the nuclear power plant equipment inspection system 1C shown in FIG.

  In FIG. 17, the vertical axis of each figure indicates the risk of the component device or segment, and the horizontal axis indicates the operation time of the nuclear power plant. And each figure is a figure which shows the time change of the risk from the item 1 to the item i. In addition, a dashed line in each figure in FIG. 17 is a risk target line D4 set for each item, a two-dot chain line is an allowable risk value D2 in each item, a solid line is each risk change curve D3 for each item in a certain segment, A dotted line is a risk control curve D5 obtained by risk control of the risk change curve D3.

  As shown in each diagram of FIG. 17, the risk is calculated for each item, and is compared with the permissible value D2 and the target risk for each item. For example, the common inspection frequency is set so that the risk of each item is equal to or less than the allowable value D2, and the sum of the differences between the risk control curve D5 and the risk target line D4 in each item is minimized.

  That is, the nuclear power plant equipment inspection system 1 shown in FIG. 1 calculates a single risk for a specific item, which is an index that simultaneously indicates the destruction probability of a component device or segment and the degree of influence in the case of destruction. 15C, the nuclear power plant equipment inspection system 1C shown in FIG. 15 calculates for each of a plurality of risk items and integrally controls each risk to optimize each risk. This is a system for setting such inspection frequency.

  Therefore, in the nuclear power plant equipment inspection system 1C, by considering a plurality of risks at the same time, it is possible to control the risk more rationally and set an appropriate inspection frequency. That is, even when there are a plurality of risks for each item, it is possible to set an optimal inspection frequency so that each risk is less than or equal to the permissible value D2, so that it is possible to maintain the soundness of the nuclear power plant. .

  FIG. 18 is a functional block diagram showing a fifth embodiment of the nuclear power plant equipment inspection system according to the present invention.

  The nuclear power plant equipment inspection system 1D shown in FIG. 18 differs from the nuclear power plant equipment inspection system 1 shown in FIG. 1 in that the risk control means 3 is provided with a repair time setting means 50 and a target equipment setting means 51. To do. Since other configurations and operations are not substantially different from the nuclear power plant equipment inspection system 1 shown in FIG. 1, the same components are denoted by the same reference numerals and description thereof is omitted.

  The risk control means 3 of the nuclear power plant equipment inspection system 1D is provided with a repair time setting means 50 and a target equipment setting means 51.

  The repair time setting means 50 sets the inspection frequency and executes the risk control of the component device and the segment. As a result, when the risk reaches the allowable value at a certain time, the repair time setting means 50 depends on the time when the risk reaches the allowable value. It has a function to set the repair or replacement time for the corresponding component or segment.

  The target device setting unit 51 executes the risk control of the component device or the segment by setting the inspection frequency. As a result, when the risk reaches an allowable value at a certain time, it is the same as or within a certain range of the corresponding component device or segment. It has a function to set a component and a segment belonging to the risk rank as a target for repair or replacement.

  Next, the operation of the nuclear power plant equipment inspection system 1D will be described.

  FIG. 19 is a flowchart showing an example of a procedure for setting the inspection frequency of the nuclear power plant by the nuclear power plant equipment inspection system 1D shown in FIG. 18, and the S symbol in the figure indicates each step of the flowchart.

  First, in step S40, the risk calculation unit 2 shown in FIG. 18 calculates the risk of the component device and the segment from the destruction probability and the influence degree of the component device and the segment, and inputs the risk to the risk control unit 3.

  Next, in step S41, the risk control means 3 shown in FIG. 18 performs the risk control based on the risk reference value such as the allowable value of risk and the target risk, thereby determining the inspection frequency for each risk of each component device or segment. Set. This results in a new risk control curve and risk.

  In step S42, when a new risk control curve for a certain component or segment intersects with the risk tolerance, that is, when it is predicted that the risk will reach the tolerance, the repair time setting means 50 sets the component appliance. Or set the repair or replacement time of the segment. The method for setting the repair or replacement time for components or segments is to set the time when the risk reaches the allowable value, set the time before the risk reaches the allowable value, or set a certain difference between the risk and the allowable value. A method such as a method for obtaining a value is given.

  Next, in step S43, the target device setting unit 51 predicts that the risk will reach an allowable value, and the component device and the segment having the same risk rank as the risk rank to which the component device or segment to which the repair or replacement time is set belongs. Is to be repaired or replaced.

  Then, at the repair or replacement time set by the repair time setting means 50, the component equipment or segment predicted to reach the allowable value at the repair or replacement time, and the component equipment and segment of the same risk rank set by the target equipment setting means 51 Repair or replacement is performed. As a result, the risk of component devices and segments that have been fully repaired and component devices and segments that have been replaced is zero.

  Furthermore, for the components and segments that have been sufficiently repaired or replaced, the risk is calculated again and is subject to risk control, and an inspection according to the inspection frequency is performed.

  Note that the target device setting means 51 is not limited to the same risk rank as the risk rank to which the component device or segment to which the risk is expected to reach the allowable value, but also to the component device or segment belonging to the risk rank within a certain range. It can also be included in the object to be repaired or replaced.

  In such a nuclear power plant equipment inspection system 1D, the risk can be reduced by exchanging or repairing the component equipment or the segment before the risk of the component equipment or the segment reaches the allowable value. In addition, it is possible to repair and replace not only the components and segments where the risk is expected to reach the tolerance, but also the components and segments that are likely to reach the tolerance in the near future. It is possible to prevent the segment from being destroyed.

  The nuclear power plant equipment inspection systems 1, 1A, 1B, 1C, and 1D in the embodiments as described above may be combined with each other. For example, combining the nuclear power plant equipment inspection system 1C and the nuclear power plant equipment inspection system 1D, risk of damage countermeasures when component equipment or segments are destroyed, risk of loss of profits due to unscheduled operation of nuclear power plants In addition, it is possible to set the repair or replacement timing of the component equipment or segment based on the risk control curve obtained by optimizing the risk for each item such as the risk of cost increase due to repair or replacement of the component equipment or segment. Good.

1 is a functional block diagram showing a first embodiment of a nuclear power plant equipment inspection system according to the present invention. The flowchart which shows an example of the procedure at the time of setting the inspection frequency of a nuclear power plant by the nuclear power plant equipment inspection system shown in FIG. The figure which shows the relationship between the defect detection probability in the case of detecting the crack which generate | occur | produced in the plate-shaped member by test | inspection, and the ratio of the crack depth with respect to the plate | board thickness of a plate-shaped member. The characteristic view which shows an example of the defect sizing precision at the time of measuring the depth from the surface of an internal defect by the nondestructive inspection by the ultrasonic flaw detection method with respect to primary recirculation system piping. FIG. 2 is a structural diagram of a shroud that is an example of constituent devices in a nuclear power plant to which the nuclear power plant equipment inspection system shown in FIG. 1 is applied. Explanatory drawing which shows the method of dividing each component apparatus in the nuclear power plant used as the application object of the nuclear power plant equipment inspection system shown in FIG. 1 into a some segment, respectively, and calculating a risk. The conceptual diagram which shows the time change of the risk of the component apparatus calculated by the nuclear power plant equipment inspection system shown in FIG. 1, and the setting method of inspection frequency. The functional block diagram which shows 2nd Embodiment of the nuclear power plant equipment inspection system which concerns on this invention. The flowchart which shows an example of the procedure at the time of setting the inspection frequency of a nuclear power plant by the nuclear power plant equipment inspection system shown in FIG. Explanatory drawing which shows the method of calculating a risk by the nuclear power plant equipment inspection system shown in FIG. The functional block diagram which shows 3rd Embodiment of the nuclear power plant equipment inspection system which concerns on this invention. The flowchart which shows an example of the procedure at the time of setting the inspection frequency of a nuclear power plant by the nuclear power plant equipment inspection system shown in FIG. The conceptual diagram explaining the method at the time of classifying a risk into a risk class by the nuclear power plant equipment inspection system shown in FIG. The conceptual diagram explaining the method at the time of risk control for every risk class by the nuclear power plant equipment inspection system shown in FIG. The functional block diagram which shows 4th Embodiment of the nuclear power plant equipment inspection system which concerns on this invention. The flowchart which shows an example of the procedure at the time of setting the inspection frequency of a nuclear power plant by the nuclear power plant equipment inspection system shown in FIG. The conceptual diagram explaining the method at the time of carrying out risk control of the some risk according to an item with the nuclear power plant equipment inspection system shown in FIG. The functional block diagram which shows 5th Embodiment of the nuclear power plant equipment inspection system which concerns on this invention. The flowchart which shows an example of the procedure at the time of setting the inspection frequency of a nuclear power plant by the nuclear power plant equipment inspection system shown in FIG.

Explanation of symbols

1, 1A, 1B, 1C, 1D Nuclear power plant equipment inspection system 2 Risk calculation means 3 Risk control means 4 Segmental risk calculation means 10 Shroud 20 Equipment-specific risk calculation means 30 Classifying means 31 Class-specific risk control means 40 By item Risk calculation means 41 Multiple risk optimization means 50 Repair time setting means 51 Target device setting means

Claims (11)

Dividing the constituent devices of a nuclear power plant segment, the time change of this segment risks calculated in accordance with the inspection frequency and a degree of influence and the fracture probability of each segment of the constituent devices, the risk of each segment in advance By controlling the risk to approach the risk target line that indicates the time change of the set target risk, if the risk exceeds the target risk or a predetermined risk tolerance, the number of inspections is shortened. And when the risk is less than the target risk, the inspection frequency is reduced by widening the inspection interval, and the inspection of the component equipment is performed at the reset inspection frequency. Equipment inspection method. The nuclear power plant equipment inspection method according to claim 1, wherein risk control is performed so that the risk becomes equal to or less than an allowable value at a predetermined time. The risk is classified into a plurality of risk classes according to the magnitude of the risk at the time of interest, and risk control is performed for each risk class so that the inspection frequency of components or segments belonging to the same risk class is the same. The nuclear power plant equipment inspection method according to claim 1. 2. The nuclear power generation according to claim 1, wherein a single inspection frequency is set by calculating the risk for each of a plurality of items and controlling the risk of each item based on a risk reference value. Plant equipment inspection method. The nuclear power plant equipment inspection method according to claim 1, wherein the degree of influence is public acceptance. The nuclear power plant equipment inspection method according to claim 1, wherein at the time of calculating the destruction probability, at least one of a defect detection failure probability and a defect detection probability is used as a parameter. The nuclear power plant equipment inspection method according to claim 1, wherein inspection accuracy is used as a parameter when calculating the destruction probability. The nuclear power plant equipment inspection method according to claim 1, wherein the risk is obtained as a risk rank by classifying and ranking at least one of the destruction probability and the degree of influence into a plurality of ranks. When the risk reaches an allowable value, the repair or replacement time of the corresponding component device is set according to the time when the risk reaches the allowable value, and the component device is repaired or replaced at the set time. The nuclear power plant equipment inspection method according to claim 1. The risk is classified into a plurality of ranks of at least one of the probability of destruction and the degree of influence, and is determined as a risk rank by ranking, while the risk reaches an allowable value when the risk reaches an allowable value. The nuclear power plant equipment inspection method according to claim 1, wherein the corresponding constituent equipment and the constituent equipment belonging to the same or a risk rank within a certain range as the corresponding constituent equipment are repaired or replaced according to time. A risk calculating means for dividing the component equipment of the nuclear power plant into segments, and calculating the time change of the risk for each segment according to the inspection frequency from the destruction probability and the influence degree of each segment of the component equipment;
If the risk exceeds the target risk or a predetermined risk tolerance by performing risk control so that the risk of each segment approaches a risk target line that indicates a predetermined change in the target risk over time, an inspection interval The risk control means to increase the number of inspections by shortening, reduce the frequency of inspection by expanding the inspection interval when the risk is below the target risk, and to reset
A nuclear power plant equipment inspection system characterized by comprising:

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