Nuclear power plant aging management strategy optimization method based on risk insight

Abstract

The invention belongs to the technical field of nuclear power plant safety evaluation, and particularly relates to a nuclear power plant aging management strategy optimization method based on risk insight. According to a nuclear power plant aging management object list, a plurality of SSC groups are divided according to an aging mechanism similarity and function similarity principle; developing a multi-stress accelerated aging model based on deterministic theory analysis, evaluating to obtain the aging degree of the SSC group, and evaluating to obtain the aging consequence of the SSC group by adopting various disaster risk models based on probability theory analysis; an aging risk matrix of the two-dimensional SSC group is established, a plurality of grade intervals are divided in a user-defined mode, and aging risk grades of the SSC group are obtained; and optimizing a management strategy in the aging management outline according to the aging risk of the SSC group. The method has the beneficial effects that the performance degradation condition of the aging management object and the influence on the overall safety of the nuclear power plant are comprehensively considered, the aging risk level of the aging management object is obtained, the aging management content and preventive action frequency are optimized, and the distribution of aging management resources of the nuclear power plant is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nuclear power plant safety evaluation, and particularly relates to a nuclear power plant aging management strategy optimization method based on risk insight. BACKGROUND

[0002] With the current situation that domestic nuclear power plants face the expiration of design life, the National Nuclear Safety Administration issued the Technical Policy for Extension of Validity of Nuclear Power Plant Operation License (Trial) in 2015, and actively promotes the technical research of operation license extension (OLE) demonstration. The aging management of structures, systems and components is not only the key content of the safety overall evaluation (IPA) review in the OLE application, but also an important guarantee for the safety level of the unit during the design life and the extended life of the nuclear power plant.

[0003] Currently, the physical aging management of SSCs in nuclear power plants adopts a proactive aging management strategy with predictability and pertinence. Through various specific aging management outlines, the activities such as various preventive maintenance outlines, aging effect detection and corrective actions of the power plant are coordinated to achieve the prevention and correction of the aging effect of the aging management objects. The potential management logic of the aging management outlines of domestic and foreign nuclear power plants is guided by the aging mechanism, and corresponding preventive measures, monitoring / detection, failure criteria and corrective actions are developed for various aging mechanisms. The allocation of aging management resources does not consider the differences in service environment, work load and safety importance of the same type of different aging management objects, which may easily cause the problem of over-management of some aging management objects. SUMMARY

[0004] The purpose of the present application is to provide a nuclear power plant aging management strategy optimization method based on risk insight, which obtains the aging degree through deterministic analysis and calculation, obtains the aging consequences through probabilistic analysis and calculation, establishes an aging risk matrix, and realizes the quantitative evaluation of the aging risk of the aging management objects, thereby solving the problem of non-targeted and lack of quantitative analysis of the nuclear power plant aging management strategy.

[0005] The technical solution of the present application is as follows: a nuclear power plant aging management strategy optimization method based on risk insight, according to the list of nuclear power plant aging management objects, a plurality of SSC groups are divided according to the principles of similar aging mechanism and similar function; a multi-stress accelerated aging model based on deterministic analysis is developed to evaluate the aging degree of the SSC group, and various disaster risk models based on probabilistic analysis are used to evaluate the aging consequences of the SSC group; an aging risk matrix of the two-dimensional SSC group is established, a plurality of grade intervals are self-defined, and the aging risk grade of the SSC group is obtained; and the management strategy in the aging management outline is optimized according to the aging risk size of the SSC group.

[0006] The method comprises the following steps:

[0007] Step 1: Information collection and grouping of aging management objects;

[0008] Step 2: SSC group aging risk assessment;

[0009] Step 3: Optimizing the management strategy of the aging management program, and continuously updating the aging management program.

[0010] The step 1 collects information tables related to the aging risk insights of the structures, systems and components in the list of aging management objects in the aging management program, and divides the list of aging management objects into a plurality of SSC groups according to the attribute characteristics of the SSCs in the information tables.

[0011] The information collection table of the step 1 includes the name of the aging management object, the material type, the service environment, the function and the aging mechanism type for aging degree assessment; the probabilistic safety analysis (PSA) model: internal event model and external event model for aging consequence assessment; and other related design data and operation limits.

[0012] The step 2 calculates the individual aging degree of the aging management objects in the SSC group according to the deterministic analysis method, calculates the safety importance of the aging management objects in the SSC group to the whole nuclear power plant according to the probabilistic analysis method, establishes the aging risk matrix of the SSC group, and obtains the aging risk grade of each SSC group.

[0013] The step 2 includes the evaluation of the individual aging degree, which is based on the general aging mechanism expression as the basic framework, uses the measured aging performance index data in the daily monitoring / detection activities of the nuclear power plant for correction, and analyzes the growth multiple RAW=P(Φ| Xi＝1 ) / P(Φ) of the core damage frequency or the large radioactive release frequency of the nuclear power plant caused by the basic event (SSC group failure) when the SSC group fails under various disaster risks, wherein P(Φ) represents the failure probability of the whole nuclear power plant, P(Φ| Xi＝1 ) represents the failure probability of the whole nuclear power plant when the basic event (SSC group failure) occurs, and 1≤RAW; the aging risk matrix of the SSC group is established, and the aging risk grade division is completed, a two-dimensional aging risk matrix is established according to the obtained analysis results of the aging degree and the aging consequence of the SSC group, the horizontal coordinate of the matrix is the aging consequence importance RAW, and the vertical coordinate is the aging degree δ=α·ζ, wherein ζ is an expert judgment correction coefficient.

[0014] The step 3 adjusts the management strategy in the aging management outline according to the aging risk level obtained in the step 2, and specifically comprises: adjusting the management strategy in the aging management outline, including the frequency optimization of the aging preventive measures and the aging management activities, maintaining the original management strategy for the SSC group with high aging risk, and reducing the management frequency for the SSC group with medium or low aging risk, and concentrating the aging management resources in the area with high aging risk.

[0015] The application has the beneficial effects that, compared with the existing fixed-period aging management strategy of the nuclear power plant, the aging management strategy optimization method based on the risk insight comprehensively considers the performance degradation of the aging management object and the influence on the overall safety of the nuclear power plant through two evaluation dimensions of aging degree and aging consequence, obtains the aging risk level of the aging management object, guides the optimization of the aging management content and the frequency of preventive action, and improves the allocation of the aging management resources of the nuclear power plant. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a schematic diagram of the aging management strategy optimization framework for the nuclear power plant.

[0017] Figure 2 It is a schematic diagram of the aging risk assessment method based on the risk insight.

[0018] Figure 3 It is a schematic diagram of the aging risk matrix of the aging management object. DETAILED DESCRIPTION

[0019] The application will be further described in detail below in combination with the drawings and specific embodiments.

[0020] A nuclear power plant aging management strategy optimization method based on risk insight comprises the following steps: according to the list of the aging management objects of the nuclear power plant, merging to form a plurality of SSC groups according to the principle of similar aging mechanism and similar function; developing a multi-stress accelerated aging model based on determinism analysis to evaluate and obtain the aging degree of the SSC group; using various disaster risk models based on probability analysis to evaluate and obtain the aging consequence of the SSC group; establishing a two-dimensional aging risk matrix of the SSC group, which can be self-defined to divide a plurality of interval ranges according to the management requirement, and obtain the aging risk level of the SSC group; and optimizing the management strategy in the aging management outline according to the aging risk of the SSC group.

[0021] The aging degree of the SSC group is evaluated as δ = a · ζ, where a is an aging life loss rate calculated by an aging model, and ζ is an expert judgment correction coefficient. The aging model is a multi-stress accelerated aging model that takes a general aging mechanism expression as a basic framework, uses the aging performance index data of daily monitoring / detection activities of the nuclear power plant for correction, and comprehensively considers the effects of multiple aging mechanisms. The expert judgment correction coefficient is obtained by expert scoring on key parameters affecting the aging process according to the experience of the same profession and the latest research progress in aging mechanism.

[0022] The risk insight-based nuclear power plant aging management strategy optimization method is characterized in that the aging consequence of the SSC group is evaluated as RAW = P (Φ | X i =1) / P (Φ), where P (Φ) represents the failure probability of the whole nuclear power plant, and P (Φ | X i =1) represents the failure probability of the whole nuclear power plant when the basic event (SSC group failure) occurs. The aging consequence analysis comprehensively covers various disaster risks that the nuclear power plant may face, including internal event PSA models, fire PSA models, flooding PSA models and other external disaster PSA models, and takes the maximum value of RAW of all model calculation results as the conservative value of the aging consequence.

[0023] The risk insight-based nuclear power plant aging management strategy optimization method is characterized in that the two-dimensional SSC group aging risk matrix determines the aging risk level of the SSC group from two dimensions of aging degree and aging consequence, and the number of aging risk levels can be customized according to management requirements. According to the aging risk level result of the SSC group, the aging management strategy optimization is guided, including the supplement of the key attention object of the aging risk and the adjustment of the management activity frequency.

[0024] Embodiment:

[0025] As shown in Figure 1 , it is a framework of a risk insight-based aging management strategy optimization method involved in the embodiment, which includes the following steps:

[0026] Step 1: Information collection and aging management object grouping

[0027] According to the list of aging management objects in the aging management outline, a summary information table related to the aging risk insight of the structures, systems and components (SSCs) in the list is obtained. At the same time, according to the attribute characteristics of the SSCs in the information table, the aging management object list is divided into multiple SSC groups. Specifically, it includes:

[0028] The information summary table should include the aging management object name, material type, service environment, function and aging mechanism type for aging degree evaluation; the probabilistic safety analysis (PSA) model for aging consequence evaluation: internal event model and external event model; and other related design data and operation restrictions.

[0029] The aging management object grouping should fully consider the same function and similar aging conditions of SSCs. Due to the redundancy design principle of nuclear power units, there are a large number of SSCs with the same function. Under the premise of ensuring the same function, SSCs with similar service environment and aging mechanism are combined into one SSC group to reduce the workload of subsequent aging risk evaluation.

[0030] Step 2: Aging risk evaluation of SSC group

[0031] According to the deterministic analysis method, the individual aging degree of the aging management object in the SSC group is calculated; according to the probabilistic analysis method, the safety importance of the aging management object in the SSC group to the whole nuclear power plant is calculated; the aging risk matrix of the SSC group is established, and the aging risk level of each SSC group is obtained, which is described in detail in Figure 2 . Specifically, it includes:

[0032] The evaluation of individual aging degree is based on the general aging mechanism expression as the basic framework, and the measured aging performance index data in the daily monitoring / detection activities of the nuclear power plant are corrected to develop a multi-stress accelerated aging model that considers multiple aging mechanisms. Then the equivalent life loss of SSC is calculated. Compared with the design life, the aging life loss rate of SSC is α = equivalent life loss / design life, and 0 ≤ α ≤ 1.

[0033] The consequence of the overall safety impact of the nuclear power plant is determined by analyzing the growth multiple RAW = P(Φ| Xi＝1 ) / P(Φ) of the core damage frequency or the large radioactive release frequency of the nuclear power plant caused by the basic event of SSC group failure under various disaster risks, where P(Φ) represents the failure probability of the overall nuclear power plant, and P(Φ| Xi＝1 ) represents the failure probability of the overall nuclear power plant when the basic event (SSC group failure) occurs, and 1 ≤ RAW.

[0034] At the same time, whether the risk guidance type SSC grading and in-service inspection technology is applied is considered in the analysis. If the related technology has been applied to the nuclear power unit, the safety importance of the overlapping SSC can be directly used as the aging consequence importance; if the related technology has not been applied to the nuclear power unit, the safety importance of the aging management object under various disaster risk conditions needs to be identified in combination with the plant risk model (including: internal event PSA model, fire PSA model, flooding PSA model and other external disaster PSA model).

[0035] The aging risk matrix of the SSC group is established, and the aging risk level is divided. According to the obtained analysis results of the aging degree and the aging consequence of the SSC group, a two-dimensional aging risk matrix is established, the horizontal coordinate of the matrix is the aging consequence importance RAW, and the vertical coordinate is the aging degree δ = α·ζ, wherein ζ is an expert judgment correction coefficient. According to the management requirements and the experience of the same profession, the nuclear power plant can self-define the interval number of the importance RAW and the coefficient δ to obtain the aging risk level with different details. As shown in FIG. 8, a 3*3 specification aging risk matrix is given, the aging risk level of the upper right corner area is the highest, and the aging risk level of the lower left corner area is the lowest. Figure 3

[0036] Step 3: Optimize the management strategy of the aging management outline, and continuously update the aging management outline.

[0037] According to the aging risk level obtained in step 2, the management strategy in the aging management outline is adjusted, and the content of the aging management outline is continuously updated according to the review feedback or the latest aging mechanism research results. Specifically, the following is included:

[0038] Adjusting the management strategy in the aging management outline mainly includes optimizing the frequency of the aging preventive measures and the aging management activities. For the SSC group with high aging risk, the original management strategy is maintained, and for the SSC group with medium and low aging risk, the management frequency is reduced, and the aging management resources are concentrated in the high aging risk area.

[0039] Continuously updating the content of the aging management outline is to feed back the information of the aging management review, the experience of the same profession and the latest aging mechanism research progress into the risk insight aging management framework, update the aging input information and correct the aging risk assessment results.

[0040] In summary, the aging management strategy optimization method based on risk insight is established, the aging risk level of the aging management object of the nuclear power plant is evaluated from two dimensions of aging possibility and aging risk consequence, and the management strategy in the optimized aging management outline is obtained according to the aging risk level, and finally the aging management resources of the nuclear power plant are concentrated on the objects with high value report.

[0041] The above specific implementation can be adjusted in different ways by those skilled in the art without departing from the principles and purposes of the present application, the protection scope of the present application is subject to the claims and is not limited by the above specific implementation, and each implementation scheme within the scope is subject to the constraint of the present application.​

Claims

1. A risk insight based nuclear power plant aging management strategy optimization method, characterized by: According to the aging management object list of nuclear power plant, multiple SSC groups are divided according to the principle of similar aging mechanism and similar function; A multi-stress accelerated aging model based on deterministic analysis is developed to evaluate the aging degree of SSC groups, and various disaster risk models based on probability analysis are used to evaluate the consequences of SSC group aging; A two-dimensional aging risk matrix of SSC groups is established, multiple grade intervals are defined, and the aging risk level of SSC groups is obtained; According to the aging risk of SSC groups, the management strategy in the aging management outline is optimized.

2. A risk insight based nuclear power plant aging management strategy optimization method as claimed in claim 1, wherein, The method comprises the following steps: Step 1: information collection and aging management object grouping; Step 2: SSC group aging risk evaluation; Step 3: optimization of the management strategy of the aging management outline, and continuous updating of the aging management outline.

3. A risk insight based nuclear power plant aging management strategy optimization method as claimed in claim 2, characterized by: In step 1, according to the aging management object list in the aging management outline, information tables related to the aging risk of the structures, systems and components in the list are obtained, and the aging management object list is divided into multiple SSC groups according to the attribute characteristics of the SSCs in the information table.

4. A risk insight based nuclear power plant aging management strategy optimization method as claimed in claim 3, characterized by: The information summary table in step 1 includes the name of the aging management object, the material type, the service environment, the function and the aging mechanism type for aging degree evaluation; the probability safety analysis (PSA) model for aging consequence evaluation: internal event model and external event model; and other related design data and operation restrictions.

5. A risk insight based nuclear power plant aging management strategy optimization method as claimed in claim 2, wherein: In step 2, the individual aging degree of the aging management objects in the SSC group is calculated according to the deterministic analysis method, and the safety importance of the aging management objects in the SSC group to the whole nuclear power plant is calculated according to the probability analysis method. An aging risk matrix of SSC groups is established to obtain the aging risk level of each SSC group.

6. A risk insight based nuclear power plant aging management strategy optimization method as claimed in claim 5, characterized by: The step 2 includes the assessment of the aging degree of the individual, which is based on a general aging mechanism expression, and the measured aging performance index data in the daily monitoring / detection activities of the nuclear power plant are corrected, and the consequences of the overall safety impact of the nuclear power plant are determined by analyzing the basic event of SSC group failure under various disaster risks, to determine the growth multiple RAW=P(Φ Xi＝1 ) / P(Φ) of the core damage frequency or the large radioactive release frequency of the nuclear power plant when the basic event occurs, wherein P(Φ) represents the failure probability of the overall nuclear power plant, P(Φ Xi＝1 ) represents the failure probability of the overall nuclear power plant when the basic event occurs, and 1≤RAW; an aging risk matrix of the SSC group is established, the aging risk level is divided, and a two-dimensional aging risk matrix is established according to the obtained aging degree of the SSC group and the analysis result of the aging consequences, the horizontal coordinate of the matrix is the aging consequence importance RAW, and the vertical coordinate is the aging degree δ=α·ζ, wherein ζ is an expert judgment correction coefficient.

7. A risk insight based nuclear power plant aging management strategy optimization method as claimed in claim 2, wherein: In step 3, the aging risk level obtained in step 2 is used to adjust the management strategy in the aging management outline, which specifically includes: adjusting the frequency of the aging preventive measures and the aging management activities in the management strategy of the aging management outline, maintaining the original management strategy for SSC groups with high aging risk, reducing the management frequency for SSC groups with medium and low aging risk, and concentrating the aging management resources in the high aging risk area.

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