A nuclear power plant engineering renovation evaluation method combined with probabilistic safety analysis

Abstract

The present invention relates to a nuclear power plant engineering transformation evaluation method combined with probabilistic safety analysis, belonging to the field of nuclear power plant safety technology, the method comprises the following steps: S1, collecting information on the engineering transformation to be implemented; S2, conducting qualitative safety analysis on the engineering transformation; S3, judging whether the engineering transformation meets the safety judgment criterion 1 according to the analysis results, if not, it is recommended not to implement; S4, establishing a full-range PSA model; S5, using the full-range PSA model for analysis, determining the degree of influence of the engineering transformation on the full-range PSA results; S6, judging whether the engineering transformation meets the safety judgment criterion 2, if it meets, it indicates that the engineering transformation has an acceptable impact on the safety of the nuclear power plant; if not, it indicates that the engineering transformation has a large impact, and it is recommended not to implement; S7, formulating a nuclear power plant performance supervision strategy after the engineering transformation is implemented. The method provided by the present invention can ensure that the impact of the engineering transformation on the safety of the power plant is comprehensively and reasonably evaluated, and effectively manage the power plant engineering transformation.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear power plant safety, and in particular relates to a nuclear power plant engineering reconstruction evaluation method combined with probabilistic safety analysis. Background Art

[0002] During the operation of nuclear power plants, engineering modifications will be carried out according to the actual situation of the power plants to ensure the safe operation of the nuclear power plants. In the past, the safety evaluation of engineering modifications was mainly based on the perspective of deterministic analysis to determine the impact of engineering modifications on the safety of nuclear power plants, such as: impact on safety-related systems / equipment, impact on non-safety-level systems / equipment, etc.

[0003] Probabilistic safety analysis (PSA) uses probability theory to comprehensively and systematically evaluate the safety level of power plants. It is a necessary nuclear power plant design method required by regulations and an important part of the nuclear power plant safety analysis report. PSA adopts a realistic analysis method, which is different from the traditional deterministic analysis. For example, the auxiliary feedwater pump was modified in the design, and the deterministic analysis will not be affected; but this modification may affect the results of PSA. Therefore, when evaluating the engineering modification from the perspective of the impact on power plant safety, only considering the original deterministic theory will result in incomplete consideration of the impact of the engineering modification on power plant safety, which will lead to unreasonable evaluation results. It is necessary to evaluate the engineering modification in combination with the degree of impact of the engineering modification on the PSA results, establish an appropriate analysis process, and ensure that the impact of the engineering modification on power plant safety is comprehensively and reasonably evaluated. Summary of the invention

[0004] In order to solve the defects of the prior art, the purpose of the present invention is to provide a nuclear power plant engineering renovation evaluation method combined with probabilistic safety analysis, through which the impact of engineering renovation on power plant safety can be comprehensively and reasonably evaluated, and power plant engineering renovation can be effectively managed.

[0005] In order to achieve the above purpose, a technical solution adopted by the present invention is:

[0006] A nuclear power plant engineering renovation evaluation method combined with probabilistic safety analysis includes the following steps:

[0007] S1. Collect information on the proposed engineering renovation;

[0008] S2. Conducting qualitative safety analysis based on the collected engineering transformation information;

[0009] S3. According to the qualitative safety analysis results, determine whether the engineering modification meets the safety determination criterion 1. If it does, proceed to step S4; if it does not, recommend that the nuclear power plant not implement the engineering modification, and the evaluation ends.

[0010] S4, establish a full-scale PSA model;

[0011] S5. Analyze using the full-scale PSA model to determine the degree of impact of the engineering modification on the full-scale PSA results;

[0012] S6. Based on the PSA analysis results, determine whether the engineering modification meets the second safety determination criterion. If so, it indicates that the safety impact of the engineering modification on the nuclear power plant is acceptable; if not, it indicates that the safety impact of the engineering modification on the nuclear power plant is relatively large, and it is recommended not to implement the engineering modification;

[0013] S7. Develop a strategy for monitoring the performance of the nuclear power plant after the implementation of the engineering modification and the evaluation is completed.

[0014] Furthermore, in the nuclear power plant engineering modification evaluation method combined with probabilistic safety analysis as described above, the qualitative safety analysis in step S2 is specifically to determine whether the analyzed engineering modification meets the requirements of regulatory standards, the principle of defense in depth and the principle of safety margin.

[0015] Furthermore, in the nuclear power plant engineering modification evaluation method combined with probabilistic safety analysis as described above, the regulatory standards requirements refer to regulatory standards related to the design and operation of nuclear power plants;

[0016] The defense-in-depth principle mainly includes maintaining a reasonable balance between barriers, maintaining design features, avoiding over-reliance on procedural behavior as a supplementary measure, maintaining system redundancy, independence and diversity, maintaining measures to deal with potential common cause failures, maintaining fission product barriers, and maintaining adequate measures to prevent human errors;

[0017] The safety margin principle refers to meeting the relevant specifications and standards for nuclear power plant design.

[0018] Further, in the nuclear power plant engineering renovation evaluation method combined with probabilistic safety analysis as described above, the safety judgment criterion 1 in step S3 is specifically:

[0019] It meets the power plant design regulatory standards, the power plant defense in depth principle, and the principle of maintaining sufficient safety margin for the power plant.

[0020] Further, in the nuclear power plant engineering modification evaluation method combined with probabilistic safety analysis as described above, the full-range PSA model in step S4 includes a level 1 PSA for internal events, a level 2 PSA for internal events, an internal fire PSA, an internal flooding PSA and an earthquake PSA, the level 1 PSA is for analyzing the frequency of core damage, and the level 2 PSA is for analyzing the frequency of radioactive release to the environment.

[0021] Further, in the nuclear power plant engineering renovation evaluation method combined with probabilistic safety analysis as described above, the second safety determination criterion in step S6 is specifically:

[0022] It does not affect PSA results;

[0023] Or the CDF increment is ≤10% of the power plant's benchmark CDF, and the LRF increment is ≤10% of the power plant's benchmark LRF, and the CDF increment is ≤1.0E-06 / reactor-year, and the LRF increment is ≤1.0E-07 / reactor-year.

[0024] Furthermore, in the nuclear power plant engineering renovation evaluation method combined with probabilistic safety analysis as described above, the performance supervision strategy of the power plant after the implementation of the engineering renovation is formulated in step S7, which specifically includes compiling or modifying relevant maintenance technical procedures and management procedures, carrying out equipment performance monitoring, and reliability statistics and tracking.

[0025] The nuclear power plant engineering reconstruction evaluation method combined with probabilistic safety analysis described in the present invention has the following significant technical effects:

[0026] The present invention evaluates engineering transformation based on qualitative safety analysis and PSA, formulates risk determination criteria and power plant engineering transformation supervision strategy, and establishes appropriate analysis processes, systematically considering the impact of engineering transformation on the safety level of the power plant, which can ensure that the impact of engineering transformation on the safety of the power plant is comprehensively and reasonably evaluated, and effectively manage the power plant engineering transformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flow chart of a nuclear power plant engineering renovation evaluation method combined with probabilistic safety analysis provided in an embodiment of the present invention;

[0028] Figure 2 It is a flow chart of another nuclear power plant engineering renovation evaluation method combined with probabilistic safety analysis provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with specific embodiments and the accompanying drawings.

[0030] Figure 1 and Figure 2 A flow chart of a nuclear power plant engineering modification evaluation method combined with probabilistic safety analysis provided in an embodiment of the present invention is shown. The method evaluates the engineering modification based on qualitative safety analysis and probabilistic safety analysis (PSA), formulates risk determination criteria and power plant engineering modification supervision strategies, and systematically considers the impact of engineering modification on the safety level of the power plant. The method includes the following steps:

[0031] S1. Collect information on the proposed engineering renovation.

[0032] According to the actual situation of the power plant, collect the information of the planned engineering transformation, including engineering transformation projects, transformation contents, analysis of the impact on nuclear safety, etc.

[0033] S2. Conduct qualitative safety analysis based on the collected information on the proposed engineering renovation to determine the impact of the analyzed engineering renovation on regulatory standards, the principle of defense in depth and the principle of safety margin.

[0034] Regulations and standards include the Nuclear Safety Law, Nuclear Power Plant Design Safety Regulations, Nuclear Power Plant Operation Safety Regulations and other regulations and standards related to the design and operation of nuclear power plants.

[0035] The principle of defense in depth mainly includes maintaining a reasonable balance between barriers, maintaining design features, avoiding over-reliance on procedural behavior as a supplementary measure, maintaining system redundancy, independence and diversity, maintaining measures to deal with potential common cause failures, maintaining fission product barriers, maintaining adequate measures to prevent human errors, and maintaining the purpose of power plant design guidelines.

[0036] The safety margin principle refers to meeting the relevant specifications and standards for nuclear power plant design without changing the safety analysis margin relative to the acceptable criteria contained in the final safety analysis report (FSAR report).

[0037] S3. Determine the proposed engineering modification according to safety judgment criterion one. If it meets safety judgment criterion one, use full-range PSA to conduct further analysis. If it does not meet safety judgment criterion one, it indicates that it has a great impact on the safety of the power plant, and it is recommended that the power plant not implement it.

[0038] The details of the safety judgment criteria formulated by the present invention are shown in Table 1.

[0039] Table 1 Safety criteria for determining the impact of engineering transformation on power plant safety

[0040]

[0041] Note: CDF is the core damage frequency; LRF is the large radioactive release frequency.

[0042] S4. Establish a full-scale PSA model.

[0043] The full-scope PSA model should include at least internal event level 1 PSA, internal event level 2 PSA, internal fire PSA, internal flooding PSA and earthquake PSA to ensure that all major risk influencing factors are taken into account.

[0044] Level 1 PSA refers to the analysis of the frequency of core damage; level 2 PSA refers to the analysis of the frequency of radioactive release to the environment. Level 2 PSA is a further analysis based on level 1 PSA.

[0045] S5. Use the full-scale PSA model to perform analysis and determine the extent to which the analyzed engineering modifications affect the PSA results.

[0046] S6. Determine the engineering transformation under analysis according to the second safety judgment criterion. If it meets the second safety judgment criterion, it indicates that it has little impact on the safety of the power plant and the power plant can implement it. If it does not meet the second safety judgment criterion, it indicates that it has a greater impact on the PSA results and has a greater impact on the safety of the power plant, and it is recommended that the power plant not implement it.

[0047] S7. Develop a strategy for monitoring power plant performance after the engineering transformation is implemented.

[0048] The power plant shall compile or modify relevant maintenance technical procedures and management procedures according to the characteristics of the engineering transformation, and carry out supervision activities such as equipment performance monitoring, reliability statistics and tracking.

[0049] At this point, the evaluation process for nuclear power plant engineering renovation has been completed.

[0050] The implementation process of the present invention is described below by taking the engineering transformation of a high-pressure injection system of a pressurized water reactor nuclear power plant as an example.

[0051] 1) Collect engineering renovation information

[0052] The content of the high-pressure safety injection system engineering transformation is: it is planned to adjust the regular test cycle of the high-pressure safety injection system from one month to two months.

[0053] 2) Conduct qualitative safety analysis and assessment

[0054] After qualitative safety analysis, the engineering transformation of the periodic test cycle of the high-voltage injection system meets the power plant design regulations and standards, the power plant defense in depth principle and the principle of maintaining sufficient safety margin for the power plant. Therefore, the engineering transformation meets the first safety judgment criterion.

[0055] 3) Conduct full-range PSA quantitative analysis and determination

[0056] The process of modifying the full-scale PSA model based on the engineering modification information of the periodic test cycle of the high-pressure injection system, evaluating the impact on sequence development, and determining the initiating events, safety function and system failures and successful combinations that may lead to undesirable consequence states (such as core damage).

[0057] The calculated analysis results are shown in Table 2 below.

[0058] Table 2 Analysis results of the impact of high-pressure injection system engineering transformation on full-range PSA

[0059] Safety indicators Increment Rate of change CDF 5.90E-8 / pile-year 4.24％ LRF 1.72E-9 / pile-year 3.26％

[0060] According to the analysis results in Table 2, the CDF change is ≤10% of the safety target, and the LRF change is ≤10% of the safety target, and the CDF change is ≤1.0E-06 / reactor-year, and the LRF change is ≤1.0E-07 / reactor-year, which meets the safety judgment criterion 2. Therefore, the evaluation result of the engineering transformation is that the impact on the safety of the power plant is very small and can be ignored, and the power plant can be implemented. In the specific implementation of adjusting the regular test cycle of the high-voltage injection system, it is necessary to formulate corresponding regular test work procedures, work arrangements, work coordination mechanisms, etc. according to the situation of the power plant, and supervise the relevant performance conditions.

[0061] The present invention provides a nuclear power plant engineering renovation evaluation method combined with probabilistic safety analysis, which evaluates the engineering renovation based on qualitative safety analysis and probabilistic safety analysis (PSA), formulates risk determination criteria and power plant engineering renovation supervision strategies, and establishes appropriate analysis processes, systematically considers the impact of engineering renovation on the safety level of the power plant, can ensure that the impact of engineering renovation on the safety of the power plant is comprehensively and reasonably evaluated, and effectively manages the power plant engineering renovation.

[0062] The above embodiments are merely illustrative of the present invention, and the present invention may also be implemented in other specific ways or other specific forms without departing from the gist or essential features of the present invention. Therefore, the described embodiments should be considered illustrative rather than restrictive in any respect. The scope of the present invention should be described by the appended claims, and any changes equivalent to the intent and scope of the claims should also be included within the scope of the present invention.

Claims

1. A nuclear power plant engineering renovation evaluation method combined with probabilistic safety analysis, comprising the following steps: S1. Collect information on the proposed engineering renovation; S2. Conducting a qualitative safety analysis of the engineering transformation based on the collected engineering transformation information, specifically determining whether the analyzed engineering transformation meets the requirements of regulatory standards, the principle of defense in depth, and the principle of safety margin; S3. According to the qualitative safety analysis results, determine whether the engineering modification meets the safety determination criterion 1. If it does, proceed to step S4; if it does not, recommend that the nuclear power plant not implement the engineering modification, and the evaluation ends. S4, establish a full-scale PSA model; S5. Analyze using the full-scale PSA model to determine the degree of impact of the engineering modification on the full-scale PSA results; S6. According to the PSA analysis result, determine whether the engineering modification meets the second safety determination criterion, wherein the second safety determination criterion is: not affecting the PSA result; Or the CDF increment is ≤10% of the plant's benchmark CDF, and the LRF increment is ≤10% of the plant's benchmark LRF, and the CDF increment is ≤1.0E-06 / reactor-year, and the LRF increment is ≤1.0E-07 / reactor-year; If the requirements are met, it indicates that the safety impact of the engineering modification on the nuclear power plant is acceptable; if the requirements are not met, it indicates that the safety impact of the engineering modification on the nuclear power plant is relatively large, and it is recommended not to implement the engineering modification; S7. Develop a strategy for monitoring the performance of the nuclear power plant after the implementation of the engineering modification and the evaluation is completed.

2. The nuclear power plant engineering renovation evaluation method combined with probabilistic safety analysis according to claim 1 is characterized in that: The regulatory standards requirements are those related to the design and operation of nuclear power plants; The defense-in-depth principle mainly includes maintaining a reasonable balance between barriers, maintaining design features, avoiding over-reliance on procedural behavior as a supplementary measure, maintaining system redundancy, independence and diversity, maintaining measures to deal with potential common cause failures, maintaining fission product barriers, and maintaining adequate measures to prevent human errors; The safety margin principle refers to meeting the relevant specifications and standards for nuclear power plant design.

3. The nuclear power plant engineering reconstruction evaluation method combined with probabilistic safety analysis according to claim 2 is characterized in that: The safety determination criteria 1 in step S3 are specifically: It meets the power plant design regulatory standards, the power plant defense in depth principle, and the principle of maintaining sufficient safety margin for the power plant.

4. The nuclear power plant engineering renovation evaluation method combined with probabilistic safety analysis according to claim 1 is characterized in that: The full-range PSA model in step S4 includes the first-level PSA for internal events, the second-level PSA for internal events, the internal fire PSA, the internal flooding PSA and the earthquake PSA. The first-level PSA is used to analyze the frequency of core damage, and the second-level PSA is used to analyze the frequency of radioactive release to the environment.

5. The nuclear power plant engineering renovation evaluation method combined with probabilistic safety analysis according to any one of claims 1 to 4, characterized in that: The performance supervision strategy of the power plant after the implementation of the engineering transformation in step S7 specifically includes the preparation or modification of relevant maintenance technical procedures and management procedures, the implementation of equipment performance monitoring, reliability statistics and tracking.

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