JP2023141990A - Maintenance importance determination system, maintenance importance determination method, and maintenance importance determination program - Google Patents

Abstract

To provide a maintenance importance determination system capable of identifying a device that has a large impact on safety or economic efficiency when function decreases or is lost.SOLUTION: A maintenance importance determination system 1 includes: a storage unit 57 that stores an influence table 22 indicating the degree of influence of each system function achieved by a series of a device on a nuclear power plant, and an element function table 25 indicating the degree of necessity of the element function in which system function is decomposed; an element function identification part 13 that identifies an important element function using the degree of necessity of the element function and the degree of influence of the system function to which the element function belongs; and a device identification unit 14 that identifies a device necessary to achieve the important element function identified by the element function identification unit 13.SELECTED DRAWING: Figure 1

Description

The present invention relates to a maintenance importance determination system, a maintenance importance determination method, and a maintenance importance determination program.

In the field of nuclear safety, probabilistic risk assessment (PRA) is a well-known method that quantitatively evaluates the frequency and impact of core damage, which is a serious accident event, and evaluates the product of these as "risk." It is being

In order for power supply companies to provide low-cost, stable, and continuous power supply to power users, they must improve the safety and/or economic efficiency of power plants, not only by preventing core damage, but also by reducing the probability of occurrence of high-risk events. It is necessary to reduce the impact (risk). Therefore, there is a need for a method that can be expected to be more effective in improving safety and/or economic efficiency using limited resources.

Patent Document 1 discloses an equipment importance evaluation support system 11 that inputs plant design/operation information and risk information, evaluates the importance of plant equipment/equipment, and outputs importance rank information of the plant equipment/equipment. An invention is described that includes a risk information evaluation system 12 that inputs the plant design/operation information and risk information, determines whether or not online maintenance can be performed, and outputs information on whether or not online maintenance can be performed.

JP2006-252311A

It is more effective to maintain and improve safety or economic efficiency by sorting out the risks of functional deterioration or loss of equipment used in power plants and performing maintenance focused on items with the greatest risk. However, analyzing the frequency of event occurrences requires a huge amount of man-hours, so in the short term it is difficult to identify the equipment by analyzing the frequency of event occurrences for all equipment installed at a power plant. And it's not realistic.

Therefore, an object of the present invention is to identify devices that have a large impact on safety or economic efficiency when their functions are degraded or lost.

In order to solve the above-mentioned problems, the maintenance importance determination system of the present invention includes an influence table showing the degree of influence on a nuclear power plant caused by each system function achieved by a series of equipment, and a system function in which the system functions are decomposed. a storage unit that stores an element function table indicating the degree of necessity of the element function, the degree of necessity of the element function, and the degree of influence of the system function to which the element function belongs, and an element that identifies the important element function; The device includes a function specifying unit and a device specifying unit that specifies equipment necessary to achieve the important element function specified by the element function specifying unit.

In the maintenance importance determination method of the present invention, the element function identification unit uses the degree of influence on the nuclear power plant by the system functions achieved by a series of equipment and the degree of necessity of the element functions in which the system functions are decomposed. The method is characterized by comprising the steps of specifying an important elemental function, and a step in which a device specifying section specifies a device necessary for achieving the important elemental function specified by the elemental function specifying section.

The maintenance importance determination program of the present invention uses the degree of influence on a nuclear power plant due to system functions achieved by a series of equipment and the degree of necessity of the element functions into which the system functions are broken down to determine whether the system is important or not. A procedure for identifying important elemental functions and a procedure for identifying equipment necessary to achieve the identified important elemental functions are carried out.
Other means will be explained in the detailed description.

According to the present invention, it is possible to identify devices that have a large impact on safety or economic efficiency when their functions are degraded or lost.

FIG. 1 is a configuration diagram of a maintenance importance determination system according to the present embodiment. FIG. 2 is a hardware configuration diagram of a server that constitutes a maintenance importance determination system. FIG. 2 is a diagram illustrating the functions of a nuclear power plant system broken down and the equipment that implements them. It is a flowchart of maintenance importance determination processing. It is a figure explaining an influence degree table. FIG. 3 is a diagram illustrating an influence rank table. 12 is a flowchart of a process for determining a method for evaluating the degree of influence of a system function. It is a figure explaining a necessity rank table. It is a flowchart of the process which generates a necessity rank table. It is a figure explaining a degree of necessity definition table. It is a figure explaining an element function table. FIG. 2 is a diagram illustrating a device table that shows the correspondence between devices that affect system functions and element functions. FIG. 3 is a diagram illustrating a device table that shows the correspondence between devices that affect system functions, system monitoring parameters, and element functions. FIG. 3 is a diagram illustrating a table that identifies devices that affect system functions.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the respective figures. The present invention is based on the following PDCA (Plan Do Check Action) cycle. Note that in this embodiment, equipment, equipment, and parts are collectively referred to as "equipment."
The first step in the PDCA cycle is creating a resource investment plan. In this step, the planner creates a resource investment plan for maintaining and improving safety and/or economic efficiency based on the evaluation results based on the maintenance importance. Here, the planner formulates a plan for implementing and upgrading maintenance, starting with the equipment with the highest maintenance importance. The planner can then apply conventional methods of reducing maintenance man-hours, such as disassembling and inspecting equipment, to devices with low maintenance importance.

The second step in the PDCA cycle is the implementation of a resource investment plan. This is to maintain and improve safety and economic efficiency, and plant managers implement measures to maintain and improve the safety and economic efficiency of nuclear power plants. Specifically, measures to maintain and improve the safety and economic efficiency of nuclear power plants include inspections, tests, inspections of systems and equipment, and management such as patrols during operation, as well as equipment failure probability analysis, This is the advancement of maintenance through predictive diagnosis of deterioration or loss of equipment functionality, deterioration diagnosis, and performance monitoring.

The third step in the PDCA cycle is to confirm the effectiveness of implementing the resource investment plan. In this third step, plant managers quantify the effectiveness of measures to maintain and improve safety and economic efficiency, and as a result of the analysis, confirm whether there was a significant risk of deterioration or loss of equipment performance. do. The plant manager then feeds back the evaluation results.

An example of the third step is, for example, a step of analyzing the failure probability of equipment. Based on risk information, plant managers can optimize maintenance tasks and reduce failure probability. Plant managers also monitor system and equipment performance and functional trends to diagnose system and equipment conditions. This makes it possible to extend the maintenance period for equipment that is in good condition. Therefore, maintenance costs for the entire plant can be reduced while maintaining predetermined performance and functions of the equipment. Furthermore, by shortening the maintenance cycle for equipment whose condition is deteriorating, the entire plant can be suitably maintained.
The fourth step of the PDCA cycle is a step of accumulating implementation information and plant operation information, and a step of evaluating the importance of equipment according to the present invention. When this fourth step is completed, the next first step is executed again.

This analysis method identifies devices that have a large impact on safety and/or economic efficiency when their functionality deteriorates or is lost, as devices that may pose a high risk.
In this analysis method, equipment evaluation information is used as input information for implementation plans such as target equipment management, risk analysis, sensing of existing equipment or performance monitoring, and deterioration diagnosis. In addition, this analysis method makes it possible to extract low-risk devices by expanding the scope of evaluation, which can be used as input information for maintenance optimization, etc.

FIG. 1 is a configuration diagram of a maintenance importance determination system 1 according to the present embodiment.
The maintenance importance determination system 1 includes the server 5 shown in FIG. The maintenance importance level determination system 1 also stores an impact rank table 21, an impact table 22, a necessity rank table 23, a necessity definition table 24, and an element function table 25 in its storage unit 57, respectively. The maintenance importance determination system 1 extracts devices that have a large impact on safety or economy when their functionality is degraded or lost.

The element function identification unit 13 identifies important element functions using the degree of necessity of the element function and the degree of influence of the system function to which this element function belongs.
The device specifying unit 14 specifies devices necessary to achieve the important element functions specified by the element function specifying unit 13. The device identifying unit 14 further identifies devices that affect each system function.

The influence rank table 21 is a table that defines the degree of influence of the system functions achieved by a series of devices on the functions of the nuclear power plant, and will be explained in detail with reference to FIG. 5 below.
The influence table 22 shows the degree of influence on the nuclear power plant of each system function achieved by a series of devices, and will be explained in detail with reference to FIG. 7, which will be described later. This impact table 22 shows the impact of system functions on the nuclear power plant as the effects of the reduction or loss of system functions, such as "safety impact", "power generation impact", "property protection", It is defined by including one of the following aspects: ``degree of impact on the environment and human disasters.''

The necessity rank table 23 is a table that defines ranks of necessity, and will be explained in detail with reference to FIG. 8, which will be described later.
The necessity definition table 24 is a table that defines the necessity of element functions, and will be explained in detail with reference to FIG. 10, which will be described later.

The element function table 25 is a table that includes element functions obtained by decomposing system functions and their degree of necessity, and will be explained in detail with reference to FIG. 11, which will be described later. This element function table 25 is created using the necessity rank table 23.

The device table 26 is a table showing the correspondence between element functions and devices necessary to achieve the functions, and will be explained in detail with reference to FIG. 12, which will be described later.

FIG. 2 is a hardware configuration diagram of the server 5 that constitutes the maintenance importance determination system 1. As shown in FIG.
The server 5 is, for example, a computer installed in a data center. The server 5 includes a CPU (Central Processing Unit) 51, a storage section 57, a ROM (Read Only Memory) 52, a RAM (Random Access Memory) 53, an operation section 54, a display section 55, and a communication section 56.

The CPU 51 is a central processing unit and executes a program 571 stored in the storage unit 57. The program 571 is a program that is executed by the CPU 51 and executes each process shown in FIG.
The CPU 61 implements each functional unit shown in FIG. 1 by executing the program 571.

The storage unit 57 is a large-capacity storage device, and includes, for example, a hard disk drive, a flash memory, or the like.

The RAM 53 is a volatile memory, and functions as a work area that temporarily stores various programs executable by the CPU 51, input data, output data, parameters, and the like. The ROM 52 is a nonvolatile memory, and stores, for example, a BIOS (Basic I/O System).

The operation unit 54 includes a keyboard including cursor keys, numeric input keys, various function keys, etc., and a pointing device such as a mouse. The operation unit 54 detects a press signal of a key pressed on a keyboard or an operation signal from a mouse. The CPU 51 executes various processes based on operation signals from the operation unit 54.

The display unit 55 includes, for example, a monitor display such as an LCD (Liquid Crystal Display). The display unit 55 displays various screens based on display signals input from the CPU 51. Further, the display section 55 and the operation section 54 can also employ touch panel displays.

FIG. 3 is a diagram illustrating the functions of the nuclear power plant system broken down and the equipment that implements them.
A nuclear power plant includes a system 3 consisting of a series of equipment related to a certain function, and system functions 31 to 33 achieved by the equipment of system 3. Nuclear power plant functions include integrity, safety, and power generation capacity. System functions 31 to 33 refer to functions possessed by each system necessary for achieving the functions of the nuclear power plant.

The system 3 is, for example, a nuclear reactor cooling system, a measurement control system, or the like. When the system 3 is a reactor cooling system, the system functions 31 to 33 include, for example, a main steam isolation function, a high pressure core spray function, a low pressure core spray function, a reactor auxiliary equipment cooling function, and the like.

When the system 3 is a measurement control system, the system functions 31 to 33 include, for example, a system function, a control rod drive function, a boric acid water injection function, a reactor protection system interlock function, and the like. Here, the system function 31 is highlighted with hatching because its degree of influence exceeds a predetermined level.

Elemental functions 311 to 313 belonging to the system function 31 are functions obtained by decomposing the system function 31 into individual elements, such as pressure resistance, water supply/ventilation, flow path configuration, heat exchange, purification, measurement, and control. The element functions 311 to 313 are functions necessary to achieve the system function 31. Here, the element functions 311 and 312 are highlighted with hatching because their degree of necessity exceeds a predetermined level.

Devices 3111 to 3131 are devices that support each element function 311 to 313. Since the devices 3111 to 3131 are devices related to the performance of the element functions 311 and 312, they are highlighted with hatching.
The element functions 321 and 322 belonging to the system function 32 are functions obtained by decomposing the system function 32 into each element. The device 3211 is related to the performance of the element functions 321 and 322. Element functions 331 and 332 belonging to the system function 33 are functions obtained by decomposing the system function 33 into each element.

FIG. 4 is a flowchart of maintenance importance determination processing.
In order to evaluate equipment that has a large impact on safety or economic efficiency when its functions deteriorate or are lost, each system is broken down into system functions, elemental functions of system functions, and equipment related to the performance of elemental functions.

First, the nuclear power plant manager defines evaluation methods for each degree of influence and degree of necessity (step S11). Then, the administrator determines the degree of influence of each system function (step S12), and extracts element functions related to the system function (step S13). The administrator evaluates the degree of necessity of the element function (step S14).

The element function identification unit 13 of the maintenance importance level determination system 1 identifies important element functions based on the degree of influence of the system function on the functions of the nuclear power plant and the degree of necessity of the element function (step S15). Then, the equipment identification unit 14 of the maintenance importance level determination system 1 identifies equipment that has a large impact on important element functions (step S16), and when it has identified equipment that has a large impact on the system functions (step S17), as shown in FIG. 4 ends the maintenance importance determination process. Thereby, the maintenance importance determination system 1 evaluates the magnitude of the influence of the element function on the functions of the nuclear power plant as the importance. In other words, the maintenance importance determination system 1 supports the extraction of equipment whose safety should be improved on a priority basis by evaluating elements and impacts.

FIG. 5 is a diagram illustrating the influence rank table 21.
The influence rank table 21 is a table that defines the influence of system functions on the functions of the nuclear power plant. The influence rank column is a column that stores influence ranks A to D. Each row of this influence rank table 21 is arranged in descending order of influence.
The influence degree (1) column to the influence degree (3) column are columns that store definitions of the degree of influence of each system function 31 to 33, respectively.

FIG. 6 is a flowchart of a process for determining a system function influence evaluation method.
The manager of this nuclear power plant organizes the effects on the plant functions when the system functions are impaired as items (step S21). Then, the administrator defines the degree of influence for each item (step S22). Here, the administrator defines the maximum impact, the minimum impact, and other intermediate impacts on the system function within a range that can be distinguished as the degree of impact. The administrator ranks the definition of the degree of influence of each item (step S23) and determines the method of evaluating the degree of influence of the system function from the influence items organized in the degree of influence rank table 21 (step S24). 6 ends.

FIG. 7 is a diagram illustrating the influence level table 22.
In FIG. 7, the impact evaluation of the system function is quantified as an impact rank, and the highest applicable value is evaluated as the impact. The scope of evaluation changes from the entire system to each system function. In this embodiment, the degree of influence of each system function is determined using an influence degree determination table based on definition and ranking, such as the influence degree table 22.

In the safety impact level column, impact level 4 includes equipment of class 1 in the safety importance classification or SA equipment (safety measures equipment). Impact level 3 is comprised of the following equipment of class 2 in the safety importance classification. Impact level 2 is comprised of the following equipment of class 3 in the safety importance classification. Impact level 1 is composed of non-class equipment in the safety importance classification.

In the impact level column on power generation, impact level 4 indicates that there is a possibility that power generation will be stopped. Impact level 3 means that there is a possibility of causing fluctuations in the power generation output. Impact level 2 does not affect the generator output, but may require some functional operational restrictions. Impact level 1 means that there is no impact on power generation.

Impact level 3 in the property protection impact column refers to equipment that may require large-scale construction work, such as the replacement or repair of multiple devices, during restoration. Impact level 2 refers to devices that may require replacement or repair on a device-by-device basis during recovery. Impact level 1 refers to equipment that may require replacement or repair on a part-by-part basis during restoration.

In the impact level column on environmental/human disasters, impact level 4 refers to equipment that may cause environmental pollution or affect the safety of employees' lives. Impact level 3 is equipment that may cause environmental pollution or affect employee safety. Impact level 2 refers to equipment that may cause minor environmental pollution other than the above.

The above-mentioned method of assigning influence points and determining boundaries of definitions is based on the maximum value of the rank hierarchy. However, the influence is not limited to this, and the sum of the ranks of each cell may be used as the degree of influence.

FIG. 8 is a diagram illustrating the necessity rank table 23. This necessity rank table 23 is a table in which ranks of necessity of element functions for performing system functions are defined. The necessity rank column stores necessity ranks, and here the necessity ranks from A to D are stored. When the degree of necessity rank is A, it is the highest degree of necessity. When the degree of necessity rank is D, it is the minimum degree of necessity. The definition column stores definitions corresponding to these necessity ranks.

FIG. 9 is a flowchart of the process of generating the necessity rank table 23.
The manager of this nuclear power plant defines the degree of necessity for each item (step S31). After the administrator ranks the necessity definitions (step S32), the process of FIG. 9 ends.

FIG. 10 is a diagram illustrating the degree of necessity definition table 24. This degree of necessity definition table 24 is an example of defining the degree of necessity of element functions for performing the system function.
Elemental functions that are essential for achieving the requested function have a degree of necessity of 5.

An elemental function that is necessary to achieve the required function, but whose reduction or loss does not significantly affect the required function, has a degree of necessity of 2. Elemental functions that are not indispensable to achieve the required function, but should be secured in Betterment, have a necessity level of 2.

An elemental function that is necessary to achieve the required function but is unlikely to be degraded or lost has a necessity level of 1. Elemental functions that are not necessary to achieve the requested function have a degree of necessity of 0.

FIG. 11 is a diagram illustrating the element function table 25.
ANSI/ANS-58.14 Appendix D "Typical Component Functions" lists 25 typical functions that must be evaluated when determining the safety-related classification of a component or part. These 25 types of functions are taken as elemental functions for decomposing the system functions. However, the present invention is not limited to this, and the system functions may be broken down into elemental functions with reference to these 25 types of functions. At this time, the device importance determination system 1 appropriately sets the granularity of the element function depending on the degree of influence of the system function.

When creating the aforementioned influence rank table 21 (see FIG. 5), element functions are appropriately selected from the viewpoint of what purpose they are intended for. When evaluating the importance of equipment, the granularity of elemental functions is determined from the perspective of how it will be applied to system functions.
In the component function table 25 of this embodiment, component functions commonly possessed by each system are classified with reference to ANSI/ANS-58.14 Appendix D "Typical Component Functions."

Here, elemental functions are classified into seven types: pressure resistance, water supply/ventilation, flow path configuration, heat exchange, purification, measurement, and control. Pressure resistance is a function that holds the contained fluid and prevents it from flowing out. Water supply and ventilation are functions that apply pressure to fluid and send it out. The flow path configuration is the function of passing fluid at a required flow rate or blocking it. Heat exchange is the function of cooling or heating a fluid. Purification is the function of removing impurities in a fluid. Measurement is a function of measuring a process amount and transmitting a signal or directly giving an instruction. Control is a function that controls process amounts.

FIG. 12 is a diagram illustrating a device table 26 that shows the correspondence between devices that affect system functions and element functions.
In this equipment table 26, each row shows the equipment that affects the system function, and each column shows the element function. Each matrix shows the equipment necessary to accomplish the element function. When "○" is shown in the matrix, it indicates that the equipment is necessary to achieve the element function. When an "x" is shown in the matrix, it indicates that the device is not necessary to accomplish the element function.

FIG. 13 is a diagram illustrating a device table 27 in which correspondences between devices that affect system functions, system monitoring parameters, and element functions are registered.
As a means of confirming and ensuring the stability of a nuclear power plant, it is effective to grasp and monitor not only event changes in individual equipment, but also what kind of parameter changes may occur. As an example, we extracted system monitoring parameters that can fluctuate due to changes in each element function.

In this equipment table 27, each row shows equipment and system monitoring parameters that affect system functions, and each column shows element functions. In each matrix, equipment necessary to achieve the element function and system monitoring parameters necessary to monitor the element function are shown. When "○" is shown in the matrix, it indicates that the equipment or system monitoring parameter is necessary for achieving or monitoring the element function. When an "x" is shown in the matrix, it indicates that the equipment or system monitoring parameter is not necessary for achieving or monitoring the element function.

FIG. 14 is a diagram illustrating a table 28 for identifying devices that affect system functions and calculating their importance.
Each row of table 28 indicates an element function. In each column of the table 28, a system function 31 that is a certain system function, system monitoring parameters, and devices that influence the system function are lined up. The degree of influence of this system function 31 is 4 points. The degree of necessity for pressure resistance, which is an elemental function, is 5 points. The evaluation of the breakdown voltage, which is an elemental function obtained by decomposing the system function 31, is 20 points, which is obtained by multiplying the degree of influence of the system function 31 by the degree of necessity of the voltage resistance.

Equipment that influences the system function 31 and achieves the pressure-resistant element function is a pump, a compressor/air blower/exhaust fan, a heat exchanger, a filtration/demineralizer filter, and piping. Therefore, these devices are given an evaluation score of at least 20 points. This evaluation score indicates the importance of these devices.

The degree of necessity for the elemental functions of water supply and ventilation is rated 5 points. The evaluation of water supply/ventilation, which is an elemental function obtained by decomposing the system function 31, is 20 points, which is the degree of influence of the system function 31 multiplied by the degree of necessity of water supply/ventilation. Equipment that affects the system function 31 and achieves the elemental functions of water supply and ventilation are a pump, a compressor, and an air blower/exhaust fan. Therefore, these devices are given an evaluation score of at least 20 points.

There are two points regarding the necessity of control, which is an elemental function. The evaluation of control, which is an elemental function obtained by decomposing the system function 31, is 8 points, which is obtained by multiplying the degree of influence of the system function 31 by the degree of necessity of control. There are no devices in the example that influence the system functions 31 and perform elemental functions of control.

In this way, the evaluation score of the importance of the element function is calculated from the degree of influence of the system function and the degree of necessity of the element function. Here, for each elemental function, the equipment necessary to achieve that elemental function is organized. Therefore, if there is overlap in the elemental functions achieved by devices, the importance of the device is calculated by the maximum value or the total value of the importance of the corresponding elemental functions. In this way, the monitoring parameters of equipment and element functions required to achieve important element functions are organized, and the influence on system functions is identified.

The manager of a nuclear power plant can use the evaluation results of the importance of each elemental function and the importance of each device as input information for resource investment planning, etc.

(Modified example)
The present invention is not limited to the embodiments described above, and includes various modifications. For example, the embodiments described above are described in detail to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. It is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is also possible to add, delete, or replace some of the configurations of each embodiment with other configurations.

Part or all of the above configurations, functions, processing units, processing means, etc. may be realized by hardware such as an integrated circuit. Each of the above configurations, functions, etc. may be realized by software by a processor interpreting and executing a program for realizing each function. Information such as programs, tables, and files that realize each function can be stored in a storage device such as a memory, hard disk, or SSD (Solid State Drive), or in a storage medium such as a flash memory card or a DVD (Digital Versatile Disk). can.

In each embodiment, the control lines and information lines are those considered necessary for explanation, and not all control lines and information lines are necessarily shown in the product. In reality, almost all components may be considered interconnected.

1 Equipment importance determination system 13 Element function identification unit 14 Equipment identification unit 21 Impact rank table 22 Impact table 23 Necessity rank table 24 Necessity definition table 25 Element function tables 26, 27 Equipment table 28 Table 3 Systems 31 to 33 System functions 311 to 313 Element functions 321, 322 Element functions 331, 332 Element functions 3111 Equipment 3121 Equipment 3131 Equipment 3211 Equipment 5 Server 51 CPU
52 ROM
53 RAM
54 Operation unit 55 Display unit 56 Communication unit 57 Storage unit 571 Program

Claims (6)

a storage unit storing an influence table indicating the degree of influence on the nuclear power plant by each system function achieved by a series of equipment, and an element function table indicating the degree of necessity of element functions obtained by decomposing the system functions;
an element function identification unit that identifies the important element function using the degree of necessity of the element function and the degree of influence of the system function to which the element function belongs;
a device identifying unit that identifies equipment necessary to achieve the important elemental function identified by the elemental function identifying unit;
A maintenance importance determination system characterized by comprising: The equipment identification unit further identifies equipment that affects each of the system functions;
The maintenance importance determination system according to claim 1. The element function table is created using necessity ranks for the element functions.
The maintenance importance determination system according to claim 1. The impact level table shows the impact level of the system function on the nuclear power plant, as the impact of the reduction or loss of the system function, in terms of "safety impact", "power generation impact", and "property protection". ” or “degree of impact on the environment and human disasters.”
The maintenance importance determination system according to claim 1. a step in which the element function identification unit identifies important element functions using the degree of influence on the nuclear power plant by the system functions achieved by a series of equipment and the degree of necessity of the element functions in which the system functions are broken down; and,
a step in which the equipment identifying unit identifies equipment necessary to achieve the important elemental function identified by the elemental function identifying unit;
A method for determining the importance of maintenance, comprising: to the computer,
A procedure for identifying important elemental functions using the degree of influence on the nuclear power plant by the system functions achieved by a series of equipment and the degree of necessity of the elemental functions in which the system functions are broken down;
steps for identifying equipment necessary to achieve the identified important elemental functions;
A program to determine the importance of maintenance.

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