Large-scale nuclear power system reliability analysis method based on parallel computing

Abstract

The invention discloses a parallel computing-based large-scale nuclear power system reliability analysis method, which belongs to the field of nuclear power system reliability analysis and comprises the following steps of: constructing a nuclear power system fault tree model T according to a functional principle, a fault mode and a reliability logic relationship of a nuclear power system; identifying fault tree sub-trees capable of being independently analyzed in the nuclear power system fault tree model T by using a fault tree partitioning method, and constructing a vertex directed graph of fault tree sub-tree vertexes capable of being independently analyzed based on the connection relationship of the fault tree sub-trees; and identifying an analysis sequence of the fault tree sub-trees by using the vertex directed graph and based on a topological sorting method, and then analyzing the nuclear power system fault tree model T in parallel according to the sequence to obtain a top event occurrence probability of the nuclear power system fault tree model T. The method can be applied to analysis of a large-scale fault tree model in a nuclear power system.

Description

Technical Field

[0001] The present application relates to a method for analyzing the reliability of a large-scale nuclear power system based on parallel computing, and belongs to the field of reliability analysis of nuclear power systems. Background Art

[0002] With the development of nuclear power technology and the increase in the power supply ratio of nuclear power plants, it has a significant impact on the country's industry and people's lives. Due to the high harmfulness of nuclear leakage, the requirements for the reliability and safety of nuclear power are extremely high. However, the nuclear power system is complex in structure and has many operating conditions, resulting in a large-scale and logically complex fault tree for the constructed nuclear power system. Therefore, accurately analyzing the reliability of nuclear power has become a major problem in the reliability design and analysis of nuclear power systems.

[0003] Existing analysis techniques usually adopt the method of accurate modeling and approximate analysis, only analyzing the causes of some key and important events, while ignoring some events with relatively low occurrence probabilities. Although the analysis efficiency is improved, it cannot meet the requirements of comprehensively analyzing the system reliability. With the development of parallel computing technology and some parallel frameworks or tools, it has become possible to analyze the reliability of large-scale nuclear power systems using parallel computing technology. Summary of the Invention

[0004] According to one aspect of the present application, there is provided a method for analyzing the reliability of a large-scale nuclear power system based on parallel computing, which can be applied to the analysis of large-scale fault tree models in nuclear power systems.

[0005] The method for analyzing the reliability of a large-scale nuclear power system based on parallel computing is characterized by including the following steps: S1: Construct a fault tree model T of the nuclear power system according to the functional principle, fault mode, and reliability logical relationship of the nuclear power system; S2: Use the fault tree block method to identify the fault tree subtrees that can be independently analyzed in the nuclear power system fault tree model T, and construct a vertex directed graph of the vertices of the fault tree subtrees that can be independently analyzed based on the connection relationship of the fault tree subtrees ; S3: Use the vertex directed graph , and based on the topological sorting method, identify the analysis order of the fault tree subtrees, and then analyze the nuclear power system fault tree model T in parallel according to this order to obtain the occurrence probability of the top event of the nuclear power system fault tree model T.

[0006] Further, the S2 includes: S21: Use the linear block method to identify the vertices of the fault tree subtrees that can be independently analyzed in the fault tree model. The set of the vertices of the fault tree subtrees is denoted as , where n represents the number of vertices of the fault tree subtrees; S22: Based on the connection relationship of the fault tree subtree and the fault tree subtree vertex, construct a vertex directed graph that is mapped to the fault tree subtree vertex ,in, is the set of fault tree subtree vertices, and E is the edge formed by these vertices.

[0007] Furthermore, the S3 includes: S31: Using the vertex directed graph ,identify parallelizable fault tree subtrees based on the topological sorting method; S32: According to the independent parallel and analysis dependency relationships of the fault tree subtrees, the fault tree subtrees are converted into corresponding binary decision diagrams in sequence to obtain analysis results of the fault tree subtrees, and the fault tree subtrees are replaced with newly created nodes until the probability of occurrence of the top event of the nuclear power system fault tree model T is obtained.

[0008] Furthermore, in S31, identifying parallelizable fault tree subtrees based on a topological sorting method includes: 1) Create an empty queue Q, which is used to store a set of nodes with an in-degree of 0 , initialize the topological sorting result queue R, so that the topological sorting result queue R contains a node set ; 2) Traverse each node in the vertex directed graph G and calculate its in-degree; 3) Add all nodes with in-degree 0 to the empty queue Q; 4) Take values from queue Q in sequence until queue Q is empty, and then take out the node set from queue Q , create a new empty node set ,from Take out the nodes one by one , traverse the nodes All adjacent nodes of , the node The in-degree of the node is reduced by 1; if If the in-degree of is reduced to 0, the node Joining a node collection ; Traverse the nodes After connecting all adjacent nodes, the node Delete from the vertex directed graph G; node set After the node traversal is completed, the node set Join queue Q and topological sort result queue R; The obtained topological sorting result queue R is a queue containing multiple node sets that can be processed in parallel.

[0009] Furthermore, the S32 includes: a) Traverse the topological sorting result queue R, extract the vertices of the fault tree subtrees that can be analyzed in parallel, and convert the fault tree subtrees into binary decision diagrams in parallel for parallel analysis; b) After the parallel analysis is completed, create a new node and assign the analysis result to the new node, and then replace the original fault tree subtree with the new node; c) Repeat the above steps until the topological sorting result queue R is empty, and obtain the analysis result of the fault tree model T of the large-scale nuclear power system.

[0010] Furthermore, the implementation of converting the fault tree subtree into a binary decision diagram in parallel includes: ; ; ; ; ; ; Among them, represents the left branch of the binary decision diagram with event x as the vertex; represents the right branch of the binary decision diagram with event x as the vertex; represents the left branch of the binary decision diagram with event y as the vertex; represents the right branch of the binary decision diagram with event y as the vertex; and respectively represent the binary decision diagrams corresponding to the fault tree subtree containing event x and the fault tree containing event y; " " represents the logical AND operation, and " " represents the logical OR operation; represents the result of the logical AND operation of two binary decision diagrams with the same vertex; represents the result of the logical OR operation of two binary decision diagrams with the same vertex; represents the result of the logical AND operation of two binary decision diagrams with different vertices and x < y; represents the result of the logical OR operation of two binary decision diagrams with different vertices and x < y.

[0011] The beneficial effects that this application can produce include: The large-scale nuclear power system reliability analysis method based on parallel computing provided by this application can decompose the large-scale fault tree model of the nuclear power system that could not be processed originally through parallel computing, analyze the decomposed model in parallel, and finally merge the analysis nodes of each module to obtain the analysis result of the large-scale fault tree model in the nuclear power system. Description of the Drawings

[0012] Figure 1 It is the flowchart of the steps of the large-scale nuclear power system reliability analysis method based on parallel computing in an implementation manner of this application; Figure 2 It is the flowchart of the large-scale nuclear power system reliability analysis method based on parallel computing in an implementation manner of this application; Figure 3 It is the fault tree model of the opening failure of the shutdown circuit breaker of the IP channel in the nuclear reactor emergency shutdown system in an implementation manner of this application; Figure 4 It is the directed graph formed by mapping the vertices of the subtree module of the fault tree in an implementation manner of this application; Figure 5 It is the fault tree subtree in an implementation manner of this application The converted binary decision diagram; Figure 6 It is the updated fault tree model after replacing the subtree in an implementation manner of this application; Figure 7 It is the fault tree subtree in an implementation manner of this application The converted binary decision diagram; Figure 8 It is the replacement subtree in an implementation manner of this application The updated fault tree model after replacement. Detailed Implementation Manner

[0013] The following describes this application in detail with reference to the embodiments, but this application is not limited to these embodiments.

[0014] As Figure 1-8 shown, the large-scale nuclear power system reliability analysis method based on parallel computing is characterized by including the following steps: S1: Construct a fault tree model T of the nuclear power system according to the functional principle, fault mode, and reliability logic relationship of the nuclear power system; S2: Use the fault tree block method to identify the fault tree subtrees that can be independently analyzed in the fault tree model T of the nuclear power system, and construct a vertex directed graph of the vertices of the fault tree subtrees that can be independently analyzed based on the connection relationship of the fault tree subtrees; S3: Utilize the vertex directed graph and, based on the topological sorting method, identify the analysis order of the subtree of the fault tree, and then analyze the nuclear power system fault tree model T in parallel according to this order to obtain the occurrence probability of the top event of the nuclear power system fault tree model T.

[0015] Specifically, based on the design principle and operation mechanism of the nuclear power system, clarify the functions and mutual relationships of each component. Identify various possible fault modes in the nuclear power system, including hardware failures, software errors, human operation mistakes, etc. Determine the logical relationships between faults, such as "AND", "OR", etc., to construct the fault tree model. Integrate the above information to construct a fault tree model that can reflect the reliability characteristics of the nuclear power system. Identify the subtrees in the fault tree model that can be analyzed independently. These subtrees are relatively independent logically and can be processed in parallel. Divide the fault tree model into multiple subtrees, and each subtree represents an independent fault analysis unit. Based on the connection relationships of the fault tree subtrees, construct a vertex directed graph. The vertices in the graph represent the fault tree subtrees, and the edges represent the logical dependency relationships between the subtrees. Utilize the vertex directed graph to determine the analysis order of the fault tree subtrees through topological sorting. Topological sorting can ensure that when analyzing a subtree, all its dependent subtrees have been analyzed. Analyze each fault tree subtree in parallel according to the order of topological sorting. Since the subtrees are logically independent, they can be analyzed simultaneously, thus greatly improving the analysis efficiency. After the parallel analysis is completed, integrate the analysis results of each subtree to calculate the occurrence probability of the top event of the nuclear power system fault tree model T.

[0016] Therefore, through parallel computing technology, the time for reliability analysis of large-scale nuclear power systems can be significantly shortened. During the parallel analysis process, ensure the sequentiality of subtree analysis through topological sorting, thus guaranteeing the accuracy of the analysis results. And this method is applicable to the reliability analysis of nuclear power systems of various scales and complexities.

[0017] In the specific implementation process, taking the emergency shutdown system of a nuclear reactor as an example, if the shutdown breaker of the IP channel fails to open or the shutdown signal fails, either event will result in the output event, that is, the failure of the shutdown breaker of the IP channel to open. Therefore, an OR gate is used to represent this static failure behavior. When the operator performs manual shutdown, human error or the failure of the manual switch will cause the manual shutdown signal to fail. Therefore, an OR gate is used to represent this static failure behavior. In the same protection channel, the failure of the "local trip" signal logic voting or the failure of the APU (Accelerated Processing Units) module will both cause the automatic shutdown signal to fail. Therefore, the logical relationship between them can be described by an OR gate. The reasons for the failure of the APU module include backplane bus locking, processor failure, power supply failure, and rack failure. Any possible reason will cause the APU module to fail. Therefore, an OR gate is used to describe this static failure behavior. The "local trip" signal undergoes a two-out-of-four logic voting to generate an emergency shutdown signal. For the two-out-of-four logic voting, if 3 input failures are satisfied, the output fails. Therefore, a three-out-of-four voting gate is used to represent this static characteristic. The failure of the input modules of the IP protection channel, IIP protection channel, IIIP protection channel, and IVP protection channel is affected by the sensors, signal preprocessing units, and signal acquisition and processing units of each protection channel. The failure of these components will cause the input of the corresponding protection channel to fail. Therefore, an OR gate is used to represent this static characteristic.

[0018] When the automatic shutdown signal fails, the operator can achieve the emergency shutdown of the reactor through the manual shutdown switch. When both the automatic shutdown signal and the manual shutdown signal fail, the output event, that is, the shutdown signal fails. Therefore, an AND gate is introduced to describe this characteristic; the fault logics of other module characteristics can also be obtained through the above analysis.

[0019] The fault tree model of the failure of the shutdown breaker of the IP channel obtained through analysis is as Figure 3 shown.

[0020] The S2 includes: S21: Using the linear partitioning method, identify the vertices of the fault tree subtrees that can be analyzed independently in the fault tree model. The set of the vertices of the fault tree subtrees is denoted as , where n represents the number of vertices of the fault tree subtrees; S22: Based on the connection relationship of the fault tree subtrees and the vertices of the fault tree subtrees, construct a vertex directed graph that forms a mapping with the vertices of the fault tree subtrees , where, is the set of vertices of the fault tree subtrees, and E is the edges formed by these vertices.

[0021] Specifically, linear block partitioning is a method that decomposes a complex system into multiple relatively independent parts, which is suitable for block processing of fault tree models. In the fault tree model, the linear block partitioning method is used to identify the fault tree subtree vertices that can be analyzed independently. These subtree vertices are relatively independent in logic and can be analyzed separately without being affected by other subtrees. After linear block partitioning, a set of fault tree subtree vertices is obtained. Each vertex in this set represents a fault tree subtree that can be analyzed independently. The set of fault tree subtree vertices can be expressed as ,in, Indicates the nth fault tree subtree vertex.

[0022] Furthermore, the connection relationship between fault tree subtrees refers to the logical dependency between different subtrees. For example, the output of one subtree may be the input of another subtree. By analyzing these connection relationships, the logical order and dependency between subtrees can be determined. The vertices in the vertex directed graph correspond to the elements in the fault tree subtree vertex set V, that is, each fault tree subtree vertex is mapped to a vertex in the directed graph. The edge E in the directed graph represents the connection relationship between the fault tree subtrees. If subtree v i Depends on subtree v j , then add a line from v to the directed graph j Point to v i The vertex directed graph can be represented as , where V is the vertex set and E is the edge set.

[0023] It's worth noting that the vertex-directed graph clearly represents the logical order and dependencies between fault tree subtrees, providing a foundation for subsequent topological sorting and parallel analysis. This vertex-directed graph allows us to identify which subtrees can be analyzed in parallel and which need to wait until the analysis of their dependent subtrees is complete.

[0024] Among them, using the linear block method, the vertices of the fault tree subtrees that can be analyzed independently in the fault tree model can be obtained as shown in Table 1.

[0025] Table 1

[0026] Based on these vertices and their connection relationships in the original fault tree model, we can get the following: Figure 4 The vertex directed graph G is shown.

[0027] The S3 includes: S31: Using the vertex directed graph ,identify parallelizable fault tree subtrees based on the topological sorting method; S32: According to the independent parallel sum and analysis dependency relationship of the fault tree subtrees, convert the fault tree subtrees into corresponding binary decision diagrams in sequence to obtain the analysis results of the fault tree subtrees, and replace the fault tree subtrees with newly created nodes until the occurrence probability of the top event of the nuclear power system fault tree model T is obtained.

[0028] Further, in S31, identifying parallelizable fault tree subtrees based on the topological sorting method includes: 1) Create an empty queue Q, where the empty queue Q is used to store the set of nodes with in-degree 0 , initialize the topological sorting result queue R, and make the topological sorting result queue R contain the node set ; 2) Traverse each node in the vertex directed graph G and calculate its in-degree; 3) Add all nodes with in-degree 0 to the empty queue Q; 4) Take values from the queue Q in sequence until the queue Q is empty. Take out the node set from the queue Q, create a new empty node set , take out nodes from in sequence, traverse all adjacent nodes of node , subtract 1 from the in-degree of node ; if the in-degree of node is reduced to 0, then add node to the node set ; after traversing all adjacent nodes of node , delete node from the vertex directed graph G; after the nodes in the node set are traversed, add the node set to the queue Q and the topological sorting result queue R; Among them, the obtained topological sorting result queue R is a queue containing multiple sets of nodes that can be processed in parallel. At the same time, the topological sorting result queue R has the characteristic of first in first out, ensuring the analysis dependency relationship of nodes at different levels.

[0029] Specifically, topological sorting is a method of linearly sorting the vertices of a directed acyclic graph (DAG) such that for each directed edge (u, v) in the graph, vertex u always comes before vertex v in the sorting. In fault tree analysis, topological sorting can determine the dependency relationship between subtrees, thereby identifying subtrees that can be processed in parallel.

[0030] Among them, the empty queue Q is used to store the set of nodes with in-degree 0. At initialization, the queue Q is empty. The topological sorting result queue R is used to store the final topological sorting result and is initialized to be empty. Traverse the vertex directed graph G, and for each node in the graph, calculate its in-degree (i.e., the number of edges pointing to this node). Add all nodes with in-degree 0 to the queue Q: these nodes have no dependencies and can be analyzed or processed immediately. Take values from the queue Q in sequence: until the queue Q is empty. Create a new empty set of nodes to temporarily store the set of nodes being currently processed. Take out the set of nodes from the queue Q and process the nodes in it one by one. Traverse all adjacent nodes of the node, and decrement the in-degree of the node by 1 to indicate that one of its dependencies has been processed. If the in-degree of the node is decremented to 0, add the node to the empty set of nodes, indicating that the node can now be analyzed or processed. After processing all adjacent nodes of the node, delete the node from the graph. Add the set of nodes to the queue Q and the topological sorting result queue R to indicate that the processing of this set of nodes is completed and the next set of nodes can be processed in parallel. The topological sorting result queue R contains multiple sets of nodes that can be processed in parallel. The nodes in each set of nodes have no direct dependencies, so they can be processed in parallel. Through the topological sorting result queue R, the analysis order of the fault tree subtrees can be determined, thus enabling efficient parallel analysis.

[0031] It is worth noting that through topological sorting, the dependency relationships between the fault tree subtrees can be clarified, thereby determining the analysis order. Identify the sets of nodes that can be processed in parallel to improve the analysis efficiency. By ensuring that all dependent nodes have been analyzed before analyzing a node, the deadlock problem in the analysis process is avoided.

[0032] Furthermore, the S32 includes: a) Traverse the topological sorting result queue R, take out the vertices of the fault tree subtrees that can be analyzed in parallel, and convert the fault tree subtrees into binary decision diagrams in parallel for parallel analysis; b) After the parallel analysis is completed, create a new node and assign the analysis result to the new node, and then replace the original fault tree subtree with the new node; c) Repeat the above steps until the topological sorting result queue R is empty to obtain the analysis result of the large-scale nuclear power system fault tree model T.

[0033] Specifically, a set of vertices of the fault tree subtrees that can be analyzed in parallel is taken out from the queue R and converted into a binary decision diagram. Here, the binary decision diagram is a data structure for representing Boolean functions and can efficiently handle logical operations and probability calculations. Each fault tree subtree is converted into the form of a binary decision diagram in parallel for efficient logical operations and probability analysis. Using parallel computing resources, each binary decision diagram is analyzed to calculate its corresponding fault probability or other reliability metrics. After the parallel analysis is completed, new nodes are created for each analysis result. The fault probabilities or other reliability metrics obtained from the parallel analysis are assigned to the new nodes. The original fault tree subtrees are replaced with the new nodes to update the entire fault tree model. Repeat the above steps (a) and (b) until the topological sorting result queue R is empty. When the queue R is empty, all the fault tree subtrees have been analyzed, and the final analysis result of the large-scale nuclear power system fault tree model T is obtained.

[0034] Therefore, through parallel conversion to binary decision diagrams and parallel analysis, computing resources are fully utilized, and the analysis efficiency is significantly improved. Through strict parallel analysis and result integration, the accuracy and reliability of the final analysis result are ensured. It is applicable to the reliability analysis of large-scale and complex nuclear power systems and can efficiently handle complex fault tree models.

[0035] Meanwhile, the implementation of parallel conversion of fault tree subtrees into binary decision diagrams includes: ; ; ; ; ; ; where represents the left branch of the binary decision diagram with event x as the vertex; represents the right branch of the binary decision diagram with event x as the vertex; represents the left branch of the binary decision diagram with event y as the vertex; represents the right branch of the binary decision diagram with event y as the vertex; and represent the binary decision diagrams corresponding to the fault tree subtree containing event x and the fault tree containing event y respectively; “ ” represents the logical AND operation, and “ ” represents the logical OR operation; represents the result of the logical AND operation of two binary decision diagrams with the same vertex; Represents the result of the logical OR operation of two binary decision diagrams with the same vertices; Represents the result of the logical AND operation of two binary decision diagrams with different vertices and x < y; Represents the result of the logical OR operation of two binary decision diagrams with different vertices and x < y.

[0036] Specifically, the set of nodes with in-degree 0 , add it to the queue Q, and also add it to the topological sorting result queue R, obtaining , ; Take out from the queue Q , create a new empty set of nodes , from take out the node M6, visit the adjacent node M4 of M6, reduce the in-degree of M4 by 1, and update its in-degree to 3; then take out the node M7, visit the adjacent node M4 of M7, reduce the in-degree of M4 by 1, and update its in-degree to 2; then take out the node M8, visit the adjacent node M4 of M8, reduce the in-degree of M4 by 1, and update its in-degree to 1; then take out the node M9, visit the adjacent node M4 of M9, reduce the in-degree of M4 by 1, and update its in-degree to 0. At this time, add the node M4 to the set . Then take out the node M10, visit the adjacent node M5 of M10, reduce the in-degree of M5 by 1, and update its in-degree to 1; then take out the node M11, visit the adjacent node M5 of M11, reduce the in-degree of M5 by 1, and update its in-degree to 0. At this time, add the node M5 to the set , at this time ; Add the set to the queue Q and the queue R. At this time , ; Take out the set of nodes in the queue Q again and repeat the above process to obtain the final topological sorting result array: ; Among them, , , , .

[0037] According to the results obtained above, the fault tree subtrees with as vertices can be parallelly converted into binary decision diagrams. The binary decision diagrams after the conversion of these nodes are as shown in Appendix Figure 5 .

[0038] After obtaining the results of the subtree of the fault tree, replace the original subtree of the fault tree with a single node. The updated fault tree model is as shown in the appendix Figure 6 as follows

[0039] Then, perform parallel conversion and analysis on the subtrees M4 and M5 of the fault tree. The obtained binary decision diagram is as shown in the appendix Figure 7 as follows. Replace the original subtree with a single node. The updated fault tree model is as shown in the appendix Figure 8 as follows. Perform conversion on the subtree M7 of the fault tree in sequence, and finally process the fault tree T1 to obtain the final analysis result

[0040] It should be noted that the present invention provides a method path for analyzing the fault tree model of a large-scale nuclear power system, which can solve the large-scale fault tree model and provide strong support for analyzing the reliability of the large-scale nuclear power system

[0041] The above are only several embodiments of the present application and do not impose any form of limitation on the present application. Although the present application is disclosed with preferred embodiments as above, it is not intended to limit the present application. Any person skilled in the art, without departing from the scope of the technical solution of the present application, making some changes or modifications using the disclosed technical content is equivalent to equivalent implementation cases and all fall within the scope of the technical solution

Claims

1. A reliability analysis method for large-scale nuclear power systems based on parallel computing, characterized in that It includes the following steps: S1: Construct a fault tree model T of the nuclear power system according to the functional principle, fault mode and reliability logic relationship of the nuclear power system; S2: Use the fault tree block method to identify the fault tree subtrees that can be independently analyzed in the nuclear power system fault tree model T, and construct a vertex directed graph of the vertices of the fault tree subtrees that can be independently analyzed based on the connection relationships of the fault tree subtrees ; S3: Utilize the vertex directed graph , and based on the topological sorting method, identify the analysis order of the sub-trees of the fault tree, and then analyze the nuclear power system fault tree model T in parallel according to this order to obtain the occurrence probability of the top event of the nuclear power system fault tree model T.

2. The reliability analysis method of a large-scale nuclear power system based on parallel computing according to claim 1, wherein The S2 includes: S21: Using the linear block method, identify the vertices of the fault tree sub-trees that can be analyzed independently in the fault tree model. The set of these vertices of the fault tree sub-trees is denoted as , where n represents the number of vertices of the fault tree sub-trees; S22: Construct a vertex directed graph that forms a mapping with the vertices of the fault tree subtree based on the connection relationships of the fault tree subtrees and the vertices of the fault tree subtrees , where is the set of vertices of the fault tree subtree, and E is the edge formed by these vertices.

3. The reliability analysis method for large-scale nuclear power systems based on parallel computing according to claim 1, characterized in that The S3 includes: S31: Use the vertex directed graph , and identify parallelizable fault tree subtrees based on the topological sorting method; S32: According to the independent parallel and analysis dependence relationships of the fault tree subtrees, sequentially convert the fault tree subtrees into corresponding binary decision diagrams, obtain the analysis results of the fault tree subtrees, and replace the fault tree subtrees with newly created nodes until the occurrence probability of the top event of the nuclear power system fault tree model T is obtained.

4. The reliability analysis method of a large-scale nuclear power system based on parallel computing according to claim 3, wherein In the S31, identifying the fault tree subtrees that can be parallelized based on the topological sorting method includes: 1) Create an empty queue Q, which is used to store the set of nodes with in-degree 0 , initialize the topological sorting result queue R, and make the topological sorting result queue R contain the node set ; 2) Traverse each node in the vertex directed graph G and calculate its in-degree; 3) Add all the nodes with in-degree 0 to the empty queue Q; 4) Take values from queue Q in sequence until queue Q is empty, and then take out the node set from queue Q , create a new empty node set ,from Take out the nodes one by one , traverse the nodes All adjacent nodes of , the node The in-degree of the node is reduced by 1; if If the in-degree of is reduced to 0, the node Joining a node collection ; Traverse the nodes After connecting all adjacent nodes, the node Delete from the vertex directed graph G; node set After the node traversal is completed, the node set Join queue Q and topological sort result queue R; Among them, the obtained topological sorting result queue R is a queue containing multiple sets of nodes that can be processed in parallel.

5. The reliability analysis method for large-scale nuclear power systems based on parallel computing according to claim 4, characterized in that The S32 includes: a) Traverse the topological sorting result queue R, take out the vertices of the fault tree subtrees that can be analyzed in parallel, and convert the fault tree subtrees into binary decision diagrams in parallel for parallel analysis; b) After the parallel analysis is completed, create a new node and assign the analysis result to the new node, and then replace the original fault tree subtree with the new node; c) Repeat the above steps until the topological sorting result queue R is empty, and obtain the analysis result of the large-scale nuclear power system fault tree model T.

6. The reliability analysis method of a large-scale nuclear power system based on parallel computing according to claim 5, wherein The implementation of converting the fault tree subtrees into binary decision diagrams in parallel includes: ； ； ； ； ； ； Among them, represents the left branch of the binary decision diagram with event x as the vertex; represents the right branch of the binary decision diagram with event x as the vertex; represents the left branch of the binary decision diagram with event y as the vertex; represents the right branch of the binary decision diagram with event y as the vertex; and respectively represent the subtree of the fault tree containing event x and the binary decision diagram corresponding to the fault tree containing event y; " " represents a logical AND operation, " represents a logical OR operation; Indicates the result of the logical AND operation on two binary decision diagrams with the same vertices; Indicates the result of the logical OR operation on two binary decision diagrams with the same vertices; Represents the result of the logical AND operation of two binary decision diagrams with different vertices and x < y; Represents the result of the logical OR operation of two binary decision diagrams with different vertices where x < y.

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