CN112784447B

CN112784447B - Nuclear power plant accident modeling method for DET and RELAP5 program dynamic coupling framework

Info

Publication number: CN112784447B
Application number: CN202110270617.5A
Authority: CN
Inventors: 王贺; 孙大彬; 陈浩尹; 李磊; 夏庚磊; 王新越
Original assignee: Harbin Engineering University
Current assignee: Harbin Engineering University
Priority date: 2021-03-12
Filing date: 2021-03-12
Publication date: 2022-09-09
Anticipated expiration: 2041-03-12
Also published as: CN112784447A

Abstract

The invention discloses a nuclear power plant accident modeling method for a DET and RELAP5 program dynamic coupling framework, which comprises the following steps: determining a minimum functional unit according to a safety related system influencing an accident process; identifying correlation among the minimum functional units, and determining a DET simulation object; according to the DET simulation object, constructing a DET simulation model of the discrete dynamic event tree; identifying the DET branch moment when the state transition of the DET simulation object occurs by analyzing an output result file of each simulation step length of the RELAP5 program; according to the DET simulation object state transition type, the restart input files for the calculation of the DET successful branch and failed branch RELAP5 program are updated and generated, and the RELAP5 program is backtracked until all branches reach the end node. The invention has the advantage that the autonomous coupling of the dynamic event tree method with the determinism security analysis program RELAP5 can be realized.

Description

Nuclear power plant accident modeling method for DET and RELAP5 program dynamic coupling framework

Technical Field

The invention relates to the field of safety analysis of a nuclear power plant, in particular to a nuclear power plant accident modeling method for a DET and RELAP5 program dynamic coupling framework.

Background

The traditional nuclear power plant safety analysis method comprises a determinacy safety analysis method and a probability safety evaluation method; wherein, the security analysis method of the determinism generally adopts RELAP5 and other software; the probabilistic security evaluation method is based on a traditional event tree/fault tree method. The single deterministic theory and the probability theory have limitations in analyzing the dynamic characteristics of the nuclear power plant accidents; therefore, in order to realize explicit modeling of a possible complex interaction model between hardware/software/processes/human behaviors in the evolution process of a complex system of a nuclear power plant, a dynamic event tree method is developed.

At present, a Discrete Dynamic Event Tree (DDET) is a method (hereinafter, except for special description, the DDET is abbreviated as DET) in which a dynamic event tree method is widely applied in practical engineering applications, the DET method generates a series of event sequences containing time dynamic changes according to effective branching rules thereof, and specifically determines a system evolution path by determining branching conditions, that is, when the conditions are satisfied, the complex system evolves on different branching paths, and further obtains a series of event sequence sets for generating a DET model; after the DET model is generated, all event sequences represented by branches can be subjected to simulation by using a deterministic theory security analysis method, namely deterministic theory analysis can be developed; through the dynamic coupling of the DET and the deterministic theory analysis software, the possibility of calculating the analysis result, namely the occurrence probability can be obtained besides the traditional deterministic theory analysis calculation result, and further risk-guidance-type decision support information is provided for the design, operation and management of the nuclear power plant.

In the method for dynamically coupling the DET and the determinacy analysis software, in order to avoid the problems of difficult acquisition of event state transition probability and event correlation in the evolution process, the modeling level of the DET is generally basic equipment, and in order to realize dynamic coupling, the RELAP5 program modeling level also needs to be equipment level; the existing RELAP5 program using the device level has the following problems:

(1) the device-level based RELAP5 model is very complex and requires detailed device simulation data; however, detailed relevant data of the equipment is not necessarily obtained in the process of designing and analyzing accidents of the nuclear power plant, so that the data collection integrity and accuracy are uncertain;

(2) the complexity of the RELAP5 program model is high, and the computational stability of the RELAP5 program accident simulation process caused by modeling errors is reduced;

(3) the increased number of state transitions for the device-level DET modeling will result in a geometric progression of DET branch states, an increased amount of computation coupled with the dynamic of the RELAP5 program, and a reduced computational efficiency.

Disclosure of Invention

In order to solve the problems and overcome the defects of single deterministic theory safety analysis and probability safety evaluation of the traditional nuclear power plant, the invention provides a nuclear power plant accident modeling method for a DET and RELAP5 program Dynamic coupling framework, the analysis method can realize that a Dynamic Event Tree (DET) method is autonomously coupled with a deterministic theory safety analysis program RELAP5/MOD4.0 program, more scientifically obtain the Dynamic characteristics under the nuclear power plant accident condition, further analyze the influence of random failure of a system, equipment or personnel on the safety characteristics under the nuclear power plant accident condition, reduce the conservatism in the traditional analysis method, provide decision support for the design, operation and management of the nuclear power plant, and further improve the safety and economy of the nuclear power plant; and the analysis method is also applicable to security analysis of other complex systems using the RELAP5 program.

The invention is realized by the following technical scheme:

compared with the prior art, the invention has the advantages that: a nuclear power plant related safety system modeling method for a DET and RELAP5 dynamic coupling framework, comprising the steps of:

s1, determining a minimum functional unit according to the safety related system influencing the accident process;

s2, identifying the correlation among the minimum functional units, and determining a DET simulation object;

s3, constructing a DET simulation model of the discrete dynamic event tree according to the DET simulation object;

s4, applying the simulation time and the simulation time step length of the RELAP5 program according to the DET simulation object, and operating the RELAP5 program;

s5, outputting a result file of the simulation time step according to the RELAP5 program, and analyzing the result file to acquire time information of the state transition control TRIP variable change of the DET simulation object;

s6, identifying the DET branch moment when the state transition of the DET simulation object occurs, and acquiring a RELAP5 restart number for backtracking restart of a RELAP5 program according to the branch rule of the DET simulation model;

s7, determining the state transition type of the DET simulation object, updating the restart input file calculated by the RELAP5 program, and generating the restart input file calculated by the RELAP5 program for the successful branch and the failed branch of the DET;

s8, determining the backtracking restart time of the RELAP5 program according to the DET branching time, backtracking and executing the RELAP5 program by taking a generated restart input file calculated by the RELAP5 program of the DET successful branching and the DET failed branching and a simulation time step size RELAP5 calculation result file as input so as to finish the simulation of the next simulation time step size of the DET successful branching and the DET failed branching;

s9, looping the process from step S4 to step S8 until the simulation time reaches the user-specified simulation task time, and the dynamic coupling of the DET and RELAP5 programs is finished.

Through the technical scheme, compared with the existing coupling scheme of the DET and RELAP5 programs of the equipment level, the modeling complexity of the RELAP5 program is reduced, the calculation stability of the RELAP5 program is improved, and the analysis efficiency of the coupling of the DET and the RELAP5 program is improved.

Compared with system-level RELAP5 modeling, the technical scheme has simple modeling, can conveniently process the correlation between system functions, can accurately simulate the system state transition in the DET and RELAP5 program dynamic coupling process, conveniently obtains the state transition probability, and finally obtains the actual system dynamic behavior including probability information.

Further, the specific implementation method of step S3 is as follows:

firstly, identifying the correlation of minimum functional units and determining independent minimum functional units;

giving a trigger condition, and determining a state transition process and a failure mode of the minimum functional unit meeting the trigger condition;

thirdly, determining the transition probability of the minimum functional unit according to the failure mode of the minimum functional unit;

if the minimum functional units are independent, independent functional modeling is carried out on each minimum functional unit by utilizing RELAP 5;

and fifthly, setting a demand type TRIP variable and a running type TRIP variable by taking the minimum functional unit as a simulation object according to a method in the coupling simulation of DET and RELAP5, and simulating a state transition process of the minimum functional unit by using a coupling framework of DET and RELAP 5.

Through the technical scheme, the technical scheme of the minimum functional unit avoids the problems of system success criteria, system component unit correlation and the like when determining the system-level state transition failure mode and the transition probability in the DET and RELAP5 program dynamic coupling process, thereby simplifying the analysis process.

Further, in step (iv), if the minimum functional unit is not independent, the control logic of the independent minimum functional unit is modified in the RELAP5 model according to the following formula:

CC3 CC2 and CC1

wherein:

CC1 is the judgement logic for controlling the state transition of the minimum function unit FM1 simulation object;

CC2 is the judgment logic of the state transition of the simulation object of the initial control minimum function unit FM2 in RELAP 5;

the CC3 expresses the FM2 simulation object state transition actual control logic of the correlation between FM1 and FM 2;

the meaning of CC3 is that when CC1 is true, the logic of CC3 and CC2 are consistent, otherwise they are always in the initial state.

By the technical scheme, based on the technical scheme of the minimum functional unit with correlation and the TRIP setting scheme, the state transition process of the DET simulation object with functional correlation can be conveniently simulated; compared with the existing calculation scheme, the method can conveniently process the correlation and quantitatively obtain the transition probability of the system in different state transition processes.

Further, in step S4, programming an initial RELAP5 program input file for simulating a nuclear power plant accident according to a deterministic analysis method, wherein the safety-related system is modeled according to the steps of S1-S3, and the input card file includes an initial RELAP5 input file root.i and an initial restart calculation file r 0.i; where "Root" represents any file name that meets the requirements of the RELAP5 program, "R0" represents a file name, and ". i" represents a file type.

Through the technical scheme, the DET model and the RELAP5 program can be used for automatically realizing dynamic coupling, so that the system state transfer in the accident evolution process of the simulated nuclear power plant can be realized, and the influence of the success criterion and the system correlation of the dynamic process determination system on the simulation process is avoided.

Further, in step S4, the RELAP5 initial reboot calculation file r0.i file includes (r) the RELAP5 program reboot 103 card; secondly, controlling the time step of the RELAP5 program by a 201 card; thirdly, TRIP card of the RELAP5 program; the TRIP cards comprise all TRIP cards related to the DET simulation object state transition, and each TRIP card number is added with an identifier.

Through the technical scheme, the technical scheme is the necessary minimum link for dynamically coupling the DET and RELAP5 programs; by the technical scheme, the automatic dynamic coupling of the DET and the RELAP5 program can be realized; compared with the mode that an analyst manually modifies the restart file, the analysis efficiency is improved, and the possibility of errors generated during manual setting is reduced.

Further, in steps S5 and S6, the specific method of identifying the DET branch time at which the DET simulation object state transition occurs is as follows:

the first step: obtaining time information of the change of the state transition control TRIP variable of the DET simulation object according to the step S5;

the second step: judging whether a branch exists in the simulation time step length; if no branch exists, the initial restart file R of RELAP5 is updated ₀ The simulation time in the i, the simulation time of the time control card in the RELAP5 program input card is the sum of the simulation time at the end and the simulation step length of the RELAP5 program, and then the RELAP5 program is operated again with the initial restart calculation file R0.i and the result file root.r as input;

thirdly, the step of: if the branch exists, the minimum time for triggering the state transition TRIP of the DET simulation object is obtained through analyzing the result file, and then a RELAP5 restart number corresponding to the RELAP5 backtracking restart information block number is obtained according to the branch rule of the DET simulation model.

Through the technical scheme, compared with a mode that an analyst manually modifies and restarts the file, automatic identification and updating are achieved, analysis efficiency is improved, manual analysis burden is reduced, and the possibility of manual analysis errors is reduced.

Further, in step S8, the DET backtracking restart number identification method is as follows:

the step (1): identifying the minimum trigger time TRIPTimemin and a TRIP number corresponding to the TRIPTimemin according to a TRIP trigger time set acquired at the DET branching time, and comparing and selecting the DET simulation object state transition of the minimum TRIPNummin in the TRIP numbers corresponding to the TRIPTimemin for branching;

step (2): judging whether the DET simulation object corresponding to the TRIPTimemin is of a single state transition type or not, and if so, executing the step (4); otherwise, executing the step (3);

step (3): the simulation object of the simulation step length DET can have multiple state transitions, all Restart information block information in the root.o file is analyzed, the state transition time with the minimum branch simulation object of the step length DET is obtained through comparison, the state transition time is assigned to TRIPTimemin, and then the step (4) is executed;

step (4): replacing the corresponding element in { TRIPT1, TRIPT 2., TRIPT N }, by TRIPTimemin, and then performing step (5).

Step (5): the DET trace back restart information block number BloNum is calculated.

Through the technical scheme, the technical scheme is a necessary link for realizing the dynamic coupling of the DET and RELAP5 programs; by the scheme, the restarting time point can be accurately determined and serves as a starting point of the program backtracking of RELAP 5.

Further, the BloNum is calculated by using the following formula:

Δt＝CpuTime _max ×ResFre

wherein:

BloNum: the number of the RELAP5 backtracking restart information blocks is calculated according to the minimum TRIP trigger time TRIPTimemin of the DET simulation object state transition;

CpuTimamax: the RELAP5 program inputs the CPU maximum simulation step time in the time control card in the card;

INT [ ]: taking an integer function;

ResFre: the RELAP5 program inputs the restart frequency of the time control card in the card;

TRIPTimemin: the minimum TRIP trigger time of the state transition of the DET simulation object in the current RELAP5 simulation step calculation result;

Δ t: the RELAP5 program enters the time interval of two restart blocks in the time control card in the card.

Through the technical scheme, the restart number is calculated by using a theoretical formula through the internal regulation of the RELAP5 program, and the calculation speed is high compared with the mode of analyzing and comparing the text of the output file based on the RELAP5 program.

Further, in step S5, the method for updating the RELAP5 restart file is that after each simulation step of the RELAP5, the restart file needs to be updated according to the following two cases: firstly, the DET branch does not have the state transition of the DET simulation object; and the state transition of the DET simulation object exists in the DET branch.

Through the technical scheme, the scheme is a necessary link in the dynamic coupling process of the DET and RELAP5 programs; there are only two cases when restarting a file update: the DET branch is present and the DET branch is not present.

Further, for DET branch no DET emulation object state transitions, RELAP5 restarts the file update method as follows:

step 1: updating the 1 st restart number of the 103 card in the restart file of the current node RELAP5 to the simulation result of the current simulation step length;

step 2: updating the simulation ending time SimTime of the 1 st bit of the time control card of the 201 in the restart file of the current node RELAP5 according to the following formula;

SimTime＝SimTime+ΔT

wherein: SimTime: the RELAP5 program inputs the simulation time of the time control card in the card, namely the simulation time when the current node is finished; Δ T: each simulation step size of the RELAP5 program.

Through the technical scheme, when the state of the DET simulation object is not transferred, the RELAP5 program automatically enters the next simulation step length, so that the evolution process of the accident is automatically simulated.

Compared with the prior art, the invention has the following advantages:

(1) the invention provides a nuclear power plant accident analysis implementation method with a deterministic theory and a probabilistic theory dynamically coupled based on a discrete dynamic event tree method and a RELAP5 program, overcomes the defect of the coupling influence of the random failure of systems, equipment and operators and the dynamic process of a nuclear power plant in the process of handling the nuclear power plant accident by using the traditional safety analysis method, improves the coupling analysis efficiency, reduces the dependence on the experience and judgment of analysts, and achieves realistic analysis results;

(2) according to the invention, a large number of nuclear power plant accident simulation results can be automatically obtained, so that the safety characteristics of the nuclear power plant under the accident working condition are obtained, support is provided for the decision support of nuclear power plant design, operation and management based on risk guidance, the design, operation and management of the nuclear power plant are optimized, and finally the safety and economy of the nuclear power plant are improved;

(3) the discrete dynamic event tree method is generally used in dynamic probability safety analysis, and the RELAP5 program is commercial software widely used in the field of nuclear safety analysis of the nuclear power plant, is convenient to be accepted by nuclear power engineering and personnel, and is beneficial to practical popularization and application;

(4) the method has wide applicability, and can simulate most nuclear power plant system, equipment and personnel operation state transfer and system process parameter change processes in the nuclear power plant accident analysis process;

(5) the method is high in universality, can be used for dynamic performance analysis of nuclear power plant accidents and transients, and is also suitable for performance analysis of other complex systems which can be simulated by using a RELAP5 program.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a diagram of a DET model structure of the state evolution of a nuclear power plant;

FIG. 3 is a diagram illustrating the dynamic coupling of the DET and RELAP5 programs;

FIG. 4 is a diagram of a single state transition of a DET simulation object;

FIG. 5 is a diagram of multiple state transitions of a DET simulation object;

FIG. 6 is FM _j A demand invalidation logic block diagram;

FIG. 7 is FM _j A run invalidation logic block diagram.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

A nuclear power plant safety-related system modeling method for a DET and RELAP5 procedure dynamic coupling framework, as shown in fig. 1, comprising the steps of:

s5, outputting a result file of the simulation time step according to the RELAP5 program, and analyzing the result file to acquire the time information of the change of the state transition control TRIP variable of the DET simulation object;

s8, determining the backtracking restart time of the RELAP5 program according to the DET branch time, and backtracking and executing the RELAP5 program by taking the generated restart input files calculated by the RELAP5 program of the DET successful branch and the DET failed branch and the simulation time step RELAP5 calculation result files as input so as to finish the simulation of the next simulation time step of the DET successful branch and the DET failed branch;

Based on the above technical solution, the specific implementation principle of step S1 is as follows:

step 1, determining the originating event IE to be analyzed _i (initial Event)(i＝1，n)

Step 2: determining minimum functional units FM _j (Function Module)

In particular, analyze IE _i Safety function SF to be performed by a nuclear power plant after an event _k (Safety Function); determining an execution safety-related function SF according to a nuclear power plant design _k All corresponding security correlation systems ssm (safety system). According to system SS _m Preliminarily determines the minimum functional unit FM to be simulated in the process of dynamic coupling simulation of DET and RELAP5 _j 。

Minimum functional unit FM _j The device is a single minimum function combination consisting of basic equipment such as pumps, valves and the like or actions of operators; FM _j Satisfy physical independence between them, i.e. FMj allow functional correlation between them, but FM _j There is no functional common device in between.

On the basis of the above technical solution, the specific implementation process of step S2 is as follows:

if the minimum functional units are independent, independent functional modeling is carried out on each minimum functional unit by using RELAP 5;

On the basis of the technical scheme, the specific implementation method of the step I is as follows:

using the correlation matrix shown in the following Table, the FM is identified _j Functional dependencies between; in the present invention FM is not taken into account _j With functional logic loops in between, i.e. FM _j Only one-way failure transfer relation exists between the two; FM is shown in the following table ₁ And FM ₂ The meaning that there is functional dependency is if FM ₁ Failure, then FM ₂ And also fails. If FM _j Does not affect any other functional unit, then FM _j Are functionally independent, as FM in the following table ₃ 。

Watch FM _j Correlation identification matrix of

	FM ₁	FM ₂	FM ₃	FM _j
					FM ₁	-	Is that	Whether or not	Whether or not
FM ₂	Whether or not	-		Whether or not
					FM ₃	Whether or not	Whether or not	-	Whether or not
FM _j	Is that	Whether or not		-

On the basis of the scheme, the concrete implementation method of the step II is as follows:

in the present invention FM is not taken into account _j And (4) repairing after failure. FM _j Possible state transitions and corresponding failure modes are shown in fig. 5. In the invention, FM is _j The failure modes of the system are divided into two types of demand failure (N type) and operation failure (R type);

suppose FM _j Initially at S ₀ Is in standby mode. When the trigger condition C is satisfied ₁ A state transition will occur. There are two possibilities for state transitions, transition success and transition failure. FM if transfer is successful _j Is in the state of S ₁ State, i.e. operational stateState. If the transfer fails, FM _j The state is maintained unchanged. When the condition C is satisfied ₁ The failure mode of temporal transfer failure becomes demand failure (N-type). When FM _j At S ₁ After a period of time, satisfies the time trigger condition C ₂ Then FMj a state transition will occur. If the transfer is successful, the FM is indicated _j Loss of function, corresponding to a failure mode of operation (type R); FM _j If the state is not changed, then FM _j Still performing a function, system FM _j And (4) success.

On the basis of the technical scheme, the concrete implementation method of the step III is as follows:

according to FM _j Functional definition of (1), analysis of FM according to the method in the following Table _j Is composed of _i (functional parts or operations constituting minimum functional units) with FM _j The relationship between failure modes.

Watch FM _j Compositional unit failure mode analysis

Form FM _j Unit UN of _i The failure mode is divided into a demand failure (N type) and an operation failure (R type).

Analysis by the above Table, in FM _j A block diagram for establishing a logical relationship for system functions in case of demand failure, as shown in fig. 6;

if non-series units are present in FIG. 6, such as the parallel relationship of pump 1 and pump 2 in FIG. 6, this can be handled in two ways:

(1) if the part has important influence on the simulation result, splitting the part into an independent minimum functional unit; and re-analyzing according to the analysis steps of the minimum functional unit, and establishing a RELAP5 functional model.

(2) And evaluating the influence of the non-serial link on the IEi dynamic evolution process by using methods such as experience, theoretical analysis, case trial calculation and the like. If the effect is acceptable, the non-tandem failure link can be treated as a tandem unit using the reliability relationship, and can be programmed at RELAP5In pair FM _j The non-series link is conservatively considered in the modeling simulation process.

After determining FMj the logic diagram, a probability of failure on demand is calculated FMj based on the reliability rationale. The calculation formula of the reliability block diagram shown in fig. 6 is as follows:

establishing FMj logic block diagram of operation failure according to the same principle, wherein the logic block diagram of operation failure in the table is shown in FIG. 6; if there is a non-serial link in the FMi operation failure logic diagram, such as the parallel relationship between pump 1 and pump 2 in fig. 6, two ways can be used to process:

(1) if the part has important influence on the simulation result, the part is divided into an independent minimum functional unit. Analyzing again according to the analysis step of the minimum functional unit, and establishing a RELAP5 functional model;

(2) and evaluating the influence of the non-serial link on the IEi dynamic evolution process by using methods such as experience, theoretical analysis, case trial calculation and the like. If the effect is acceptable, the non-tandem failure link can be treated as a tandem unit using the reliability relationship, and can be treated as a pair FM in the RELAP5 procedure _j The non-series link is conservatively considered in the modeling simulation process.

After the logic block diagram is determined FMj, according to the reliability parameters of the logic block diagram units and the reliability theory, the accumulated failure probability distribution CDF of FMj operation failure changing with time is obtained by using Monte Carlo simulation and other random sampling methods _j (t)。

On the basis of the scheme, in the step (IV), if FM is carried out _j Independent and FM _j If there is only a single failure mode of demand failure or operational failure, RELAP5 is used for each FM _j Independent functional modeling is performed. And use FM _j Setting demand-type TRIP variable and operation TRIP variable according to the method in the coupled simulation of DET and RELAP5 as simulation objects, and simulating FM by using the coupled frame of DET and RELAP5 _j The state transition process of (1);

if FM _j Independent, but FM _j There are two failure modes in the accident simulation process, namely FM _j The state transition from standby to running and then to running failure, the analog FM _j The RELAP5 of the two failure mode state transitions has functional relevance and needs to be reflected in the RELAP5 model, and the common operation failure is premised on demand failure. I.e. only when FM _j After successful start, FM _j There is a possibility of operational failure.

On the basis of the above scheme, in step (iv), if the minimum functional unit is not independent, the control logic of the independent minimum functional unit is modified in the RELAP5 model according to the following formula:

CC3 CC2 and CC1

wherein:

CC1 is the judgment logic for controlling the state transition of the minimum function unit FM1 simulation object;

the CC3 expresses FM2 simulation object state transition actual control logic of the correlation between FM1 and FM 2;

On the basis of the above technical solution, the specific implementation process of step S3 is as follows:

taking the minimum functional unit as a DET simulation object, and performing the following analysis according to a DET analysis method:

as shown in fig. 2, each node in the diagram represents a specific state of the nuclear power plant formed by combining DET simulation object states, wherein a root node represents an initial state of the nuclear power plant during the dynamic coupling simulation of DET and RELAP5, an intermediate node represents a combination of different states of a system and equipment of the nuclear power plant, and an end node represents a certain termination state of the nuclear power plant, such as a core damage of the nuclear power plant or a stable state of the nuclear power plant;

the DET and RELAP5 dynamically coupled will start from the root node, and the state of the DET simulation object will be transferred with time, namely, one state transfer from the parent node to the child node representing the simulation object;

when the DET simulation object state transition triggering condition is met, the state transition of the DET simulation object only has two states of state transition success and state transition failure, a parent node is evolved into a success node and a failure node corresponding to a new branch generated by the DET model, wherein the upper node represents the success node, and the node coding mode is 'parent node name-1'; the lower node represents a transfer failure node, and the node coding mode is 'father node name-2'; the end node represents the termination of the DET coupling with the RELAP5, and the node name is encoded in "parent node name-f".

Based on the above scheme, as shown in fig. 2, when DET is coupled with the RELAP5 program, calculations are performed between each node; unlike the traditional event tree approach, the time at which a node branch occurs in DET is determined by the physical process simulated by RELAP5, reducing the empirical dependence or conservative engineering decisions of analysts in the traditional approach.

Examples

Based on the above technical solution, the specific implementation process of the steps S4-S8 is as follows:

as shown in fig. 3, the following is defined for the symbols shown in the figure:

CpuTimemax: the RELAP5 program inputs the CPU maximum simulation step time in the time control card in the card;

ErrNum: RELAP5 abort count;

MT: running state transition DET simulates the state transition task time of the object;

NorNum: normal time to terminate the count of RELAP 5;

ResNum: a RELAP5 restart number corresponding to the RELAP5 backtracking restart information block number BloNum;

SimTime: the RELAP5 program inputs the simulation time of the time control card in the card, namely the simulation time when the current node is finished;

TaskTime: the task time of the simulation of coupling the DET and the RELAP5 is also the simulation termination time of the final termination of the simulation of RELAP 5;

ResNumLast: the last restart number in the current RELAP5 simulation step calculation result file;

Δ t: the RELAP5 program inputs the restart frequency in the time control card in the card;

Δ T: each simulation step size of the RELAP5 program.

The general process of dynamically coupling the DET and RELAP5 programs is described below in conjunction with fig. 3:

step 1: writing a DET and RELAP5 coupled simulation accident analysis input file root.i and an initial restart file R0.i file;

step 2: in the DET root node, taking a RELAP5 accident analysis input file root.i as an initial input file, taking SimTime ═ delta T as simulation time, and running a RELAP5 program;

and 3, step 3: after the RELAP5 simulation step length is finished, generating result files of root.o and root.r respectively; analyzing the time information of the change of the state control TRIP variable of the DET simulation object in the root.o file;

and 4, step 4: judging whether a branch exists in the simulation step length; if no branch exists, updating the simulation time in the initial restart file R0.i of RELAP5, and then running RELAP5 analysis again with R0.i and root.r as input, wherein SimTime is SimTime + delta T;

and 5, step 5: if the branch exists, obtaining the TRIPTimemin of the DET simulation object state transition TRIP trigger by analyzing the root.o file, and then obtaining a RELAP5 program backtracking restart number ResNum according to a rule;

and 6, step 6: updating R0.i according to the state transition type of the DET simulation object, and respectively generating a DET successful branch RELAP5 and restarting an input file Root-1.i and a DET failed branch RELAP5 and restarting an input file Root-2. i;

and 7, step 7: respectively operating the node output file names of RELAP5 and RELAP5 by taking a successful branch restart file and a failed branch restart file, such as Root-1.i and Root-2.i, and a root.r file calculated and output by a current node RELAP5 as input, and updating the node output file names according to rules, such as Root-1.i and Root-1. o;

and 8, step 8: and (4) circulating the process from the step 2 to the step 7 until the RELAP5 simulation time SimTime of the node reaches the simulation task time TaskTime.

On the basis of the scheme, in the step 1, a minimum function unit is used as a DET simulation object, and initial RELAP5 program input card files for simulating the nuclear power plant accident are programmed according to a deterministic theory analysis method, wherein the input card files comprise an initial RELAP5 input file root.i and an initial restart calculation file R0.i; where "Root" represents any file name that meets the requirements of the RELAP5 program, "R0" represents a file name, "i" represents a file type.

In the step 1, the RELAP5 initial restart calculation file R0.i file comprises (i) and (103) restart programs of RELAP 5; secondly, controlling the time step of the RELAP5 program by a 201 card; thirdly, TRIP card of the RELAP5 program; the TRIP cards comprise all TRIP cards related to the state transition of the DET simulation object, and a star identifier is added in front of each TRIP card number; identifying whether a branch exists by analyzing TRIP trigger time corresponding to the state transition of the DET simulation object in the RELAP5 output file; where "-" is the filename, and the "-" file will change step by step with the coupling of DET to RELAP5 program and the branching of DET, as exemplified by fig. 2 in conjunction with the 1 st DET branch of the root node in fig. 3:

the first step: obtaining time information of the change of the state transition control TRIP variable of the DET simulation object according to the step 3;

the second step: judging whether a branch exists in the simulation time step length; if no branch exists, the initial restart file R of RELAP5 is updated ₀ The simulation time in the i, the simulation time of the time control card in the RELAP5 program input card is the sum of the simulation time at the end and the simulation step length of the RELAP5 program, and then the initial restart calculation file R0.i and the result file root.r are used as inputIn, the RELAP5 program is operated again;

thirdly, the steps of: if the branch exists, the minimum time for triggering the state transition TRIP of the DET simulation object is obtained through analyzing the result file, and then a RELAP5 restart number corresponding to the RELAP5 backtracking restart information block number is obtained according to the branch rule of the DET simulation model.

The method for judging and identifying whether the DET branch exists in the simulation time step is as follows:

the step (1): initializing a set variable { TRIPT1, TRIPT2, …, TRIPT N } of the state transition TRIP trigger time of the DET simulation object and a set variable { NowTRIPT1, NowTRIPT 2, …, NowTRIPT N } of the TRIP trigger event of the current node, each trigger time being "-1". Wherein N represents the number of TRIP logics associated with the state transition of the DET simulation object;

step (2): opening a file output by RELAP5, extracting all trigger times of TRIP numbers related to DET simulation object state transition in the last Restart information module in the output file root.o, and obtaining a current simulation step DET simulation object state transition TRIP trigger time set { NowTRIPT1, NowTRIPT 2, …, NowTRIPT N };

step (3): correspondingly comparing the elements { TRIPT1, TRIPT2, …, TRIPT N } and { NowTRIPT1, NowTRIPT 2, … and NowTRIPTN } one by one to obtain an information set { NowTRIPTi } of TRIP trigger time change, wherein i belongs to (1, N); if { NowTRIPTi } is empty, the state transition of the step size DET simulation object does not occur, the DET branch does not exist, and the identification of the step size DET branch is finished. And if the { NowTRIPTi } is not empty, the state transition process of the DET simulation object exists in the step size simulation, a DET branch exists, and the identification of the DET branch of the step size is finished.

On the basis of the above scheme, in step 6, the object state transition categories are simulated according to DET, wherein the DET simulation object state transition categories are divided into two categories:

one type of demand state transfer

The demand type state transition is abbreviated as "N" type state transition, and means that when a state transition trigger condition is met, the state of the DET simulation object is transited. Whether the state transition succeeds or not has randomness, and the randomness is independent of time and is represented by discrete random variables. Examples of the demand state transition include start or stop of a high-voltage safety injection system in a nuclear power plant, and the like;

another type of operating state transition

The running state transition is abbreviated as 'R' type state transition, and means that the triggering condition of the state transition of the DET simulation object is time, and the transition time is random and is expressed by a continuous random variable of time. Examples of the operation state transition include continuous operation of the high-pressure safety injection system or failure after a period of operation, and the like.

Based on the above solution, with reference to fig. 2 in combination with the branch at the end of the 2 nd simulation step length of the RELAP5 output file in fig. 3, that is, the 2 Δ T, it is explained that the DET backtracking restart number identification method is as follows:

step (4): replacing the TRIPTimemin with the corresponding element in { TRIPT1, TRIPT 2.., TRIPT N }, and then performing the step (5).

On the basis of the above scheme, BloNum is calculated by using the following formula:

Δt＝CpuTime _max ×ResFre

wherein:

INT [ ]: taking an integer function;

Δ t: the RELAP5 program inputs the time interval between two restart blocks in the time control card in the card.

Through the formula, the state transition time of the simulation object is smaller than that of the DET in the process of one simulation step length, and the number of the nearest RELAP5 information block is BloNum; through the analysis of the root.o output file of the simulation step RELAP5, a restart number ResNum required by RELAP5 backtracking calculation corresponding to BloNum can be found; the restart number in the restart card of the RELAP5 is updated by using ResNum, and the RELAP5 simulation can be continuously run at the time point corresponding to ResNum by combining with the r file of the current node RELAP5, such as root.r in FIG. 3.

On the basis of the technical scheme, in the step (2) and the step (3), according to the possible state transition times in the accident analysis process, the state transition of the DET simulation object is divided into single transition and multiple transitions;

single state transition for DET simulation object (see FIG. 4), where S ₀ For the DET simulation object initial State, S ₁ Simulating the object target state for the DET; the single transfer process is when the state transfer triggering condition C is met ₁ And the DET simulation object generates state transition and changes from an initial state to a target state. Probability of failure of state transition is P ₁ The probability of successful state transition is 1-P ₁ 。

In addition, the single state transition of the simulation object is divided into a demand type single state transition and an operation type single state transition; and according to the RELAP5 program TRIP type of the trigger condition, the demand type single state transition is divided into two types: variable TRIP trigger state transition and logic TRIP trigger state transition:

specifically, the TRIP card information of the demand-type single state transition DET simulation object of the variable-type TRIP triggered state transition is as follows:

CC1 variable code 1 parameter RelationAccord variable code 2 parameter attachment constant 1

Wherein:

CC 1: TRIP card numbers for controlling DET simulation object demand state transfer;

variable code: variable type code specified in the RELAP5 program;

relation symbol: logical relationships in the RELAP5 program, such as greater than, less than, greater than or equal to, etc.;

l: indicating that CC1 belongs to a lock attribute, i.e., when the logical value of CC1 can only change 1 time.

The control logic shown above is: when the relationship of the parameter value of the variable code 1 and the sum of the parameter value of the variable code 2 and the attachment constant conforms to the logical relationship expressed by the relation symbol, the TRIP logical value identified by the CC1 is true, and the simulation object is in the initial state S0; otherwise, the TRIP value identified by CC1 is false, and the simulation object will transition from the initial state S0 to the target state S1. The last mark "1" of the CC1 represents that the TRIP logic identified by the CC1 is changed only once, i.e., locked, i.e., remains unchanged after being changed, and represents that the DET simulation object is transferred only once in the RELAP5 accident simulation process.

In addition, during the coupling process between DET and RELAP5, the opposite logic can be used, that is, the initial state S0 is assumed when the TRIP logic of CC1 is "false", and the target state is assumed when the TRIP logic of CC1 is "true".

The TRIP card information of the demand-type single state transition simulation object of the logic-type TRIP triggered state transition is as follows:

CC2 variable code 3 parameter RelationPart variable code 4 parameter attachment constant 1

CC3 CC1 logical relation character CC 21

The control logic of the variable TRIP is similar to the TRIP card information of the demand single state transition DET simulation object of the variable TRIP trigger state transition; wherein the logical relation symbol in the CC3 includes: three categories of "and", "or", and "XOR"; the logic TRIP identified by CC3 is used as a variable for controlling the state transition of the DET simulation object; the trigger logic shown above is: the TRIP logic value of CC3 is obtained by the TRIP logic values of CC1 and CC2 according to the operation of the logical relation symbol; when the TRIP value of CC3 obtained after the logic operation of CC1 and CC2 is 'false', the simulation object is in an initial state SO; otherwise, if the TRIP value of CC3 is "true", the simulation object will transition from the initial state S0 to the target state S1; the final mark '1' of the CC1, the CC2 and the CC3 represents that the TRIP logic is locked only once, namely remains unchanged after being changed, and represents that the DET simulation object is transferred only once in the RELAP5 accident simulation process; the opposite logic may also be used in the DET coupling process with RELAP 5.

In the actual analysis process, the logic type TRIP requirement type single state transition TRIP card information may be more complex than the logic relationship in the TRIP card information of the requirement type single state transition simulation object of the logic type TRIP trigger state transition, and may include a plurality of variable type TRIP cards and a plurality of logic type TRIP cards to form a mixed logic; but the logic of the TRIP which finally controls the state transition of the DET simulation object will be composed of a plurality of parameter type TRIPs into a full "or" and "or" mixed type;

the TRIP card information of a typical run-type single state transition emulation object is as follows:

CC1 time 0 "le" time of null MT time l-1

Wherein:

CC 1: TRIP card numbers for controlling the single running state transition of the DET simulation object;

MT: the task time is a random variable;

l: a locking expression;

the logical meaning of TRIP represented above is: true when RELAP5 program system time is equal to or less than MT; at this time, the DET simulation object is in an initial state S ₀ (ii) a When RELAP5 program system time is greater than MT, it is "false", at which time the TRIP logic value identified by CC1 changes, and the DET simulation object state changes from the initial running state S ₀ Conversion to target S ₁ And state locking after 1 transfer.

In summary, the TRIP logic of the control DET simulation object state transition of the demand type single state transition and the operation type single state transition is different.

The DET simulation object multiple state transitions are shown in FIG. 5, where S ₀ For the DET simulation object initial State, S ₁ Simulating an object target state for the DET;

the specific multiple state transition process is as follows: when the state transition triggering condition C is satisfied ₁ In time, the DET simulation object generates the 1 st state transition from the initial state S ₀ Transition to target state S ₁ . Probability of failure of state transition is P ₁ The probability of successful state transition is 1-P ₁ . At this time, S ₁ Will be the new initial state, and S ₀ It becomes the target state. When triggering condition C ₂ When the conditions are met, the 2 nd state transition of the DET simulation object is carried out from the current initial state S ₁ Transition to target state S ₀ The probability of failure of state transition is P ₂ The probability of success is 1-P ₂ 。

The running state can be continuously transferred, the continuous transfer belongs to a variable TRIP type, and the TRIP logic of the continuous transfer is as follows:

CC1 time 0 "le" time of null MT1 time l

CC2 time 0 "le" time of CC1 MT2 time l

CC3 CC1 XOR CC2 l

The TRIP control logic expressed by the running state continuous transition (RR type) TRIP card information is as follows: when the RELAP5 system simulation time is less than MT1, CC1 is true, CC2 is true, CC3 is false, the DET simulation object is in the initial state S0; when the RELAP5 system simulation time is not less than MT1, the CC1 is false, the CC2 is true, the CC3 is true, the DET simulation object state is transferred from the initial state S0 to the target state S1, the possibility of transfer failure is a probability value P1 corresponding to the MT1 time, and the probability of transfer success is 1-P1; when the RELAP5 system simulation time is greater than the CC1 trigger time plus MT2 time, CC1 is locked as "false", CC2 is "true", CC3 is "false", DET simulation objects will transition from the current initial state S1 to the target state S0. Because the TRIP logic expressed by both CC1 and CC2 has locked, the CC3 logic will no longer change. That is, the DET simulation object only makes two state transitions.

Typical demand/run state hybrid serial transfer TRIP number information is as follows:

CC1 is analogous to TRIP logic of single demand state transition DET simulation object

CC2 time 0 "le" time of CC1 MT time l

CC3 CC1 XOR CC2 n

Wherein:

CC 1: TRIP logic for controlling the demand state transition, wherein the TRIP logic information is similar to that of single demand state transition, and the tail l represents only 1 time of change;

CC 2: the principle of the TRIP logic for controlling the operation state transfer is similar to that of single operation state transfer, and the tail 'l' represents only 1 time of change;

CC 3: TRIP number to control demand/run hybrid state continuous transitions. The expressed logic is similar to logic type TRIP trigger state transition. Specifically, the logic of the truth table is satisfied.

The judgment logic for the demand/state continuous transfer TRIP card information expression is as follows: assuming that the initial state is the CC1 is false, the CC2 is false, the CC3 is false through the XOR logical operation of the CC1 and the CC2, and the DET simulation object is in the initial state; when the CC1 is "true", the CC2 is "false", the CC3 is "true" through the xor logical operation of the CC1 and the CC2, the DET simulation object has the state transition of the 1 st time, the state of the DET simulation object is transitioned from the initial state S0 to the target state S1, the probability of the transition failure is a probability value F1 corresponding to the MT1 moment, and the probability of the transition success is 1-F1; when the CC1 is "true", the CC2 is "true", the CC3 is "false" through the xor logical operation of the CC1 and the CC2, the DET simulation object has the state transition of the 2 nd time, the DET simulation object state transitions from the initial state S1 to the target state S0, the probability of the transition failure is the probability value P2 corresponding to the MT time, and the probability of the transition success is 1-P2. Since the TRIP logic values of CC1 and CC2 are locked, CC3 will not change any more, and the DET simulation object will always be maintained in the initial state.

On the basis of the above scheme, in the step 4, the method for updating the restart file by the RELAP5 is that after each simulation step length of the RELAP5, the restart file needs to be updated according to the following two cases: firstly, the state transition of the DET simulation object does not exist in the DET branch; and the state transition of the DET simulation object exists in the DET branch.

Specifically, for the DET branch where there is no DET simulation object state transition, the RELAP5 restart file update method is as follows:

SimTime＝SimTime+ΔT

Specifically, there is a DET simulation object state transition for the DET branch, and the RELAP5 restart file update method is as follows:

step 1: updating the 1 st bit restart number of the 103 card in the current node RELAP5 restart file to ResNum;

step 2: updating the simulation end time SimTime of the 1 st bit of the time control card of 201 in the file I for restarting the current node RELAP5 according to the following formula:

wherein: INT [ ]: taking an integer function; TRIPTimemin: the minimum TRIP trigger time of the state transition of the DET simulation object in the current RELAP5 simulation step calculation result; Δ t: the time interval of two restarting information blocks in the time control card in the input card of the RELAP5 program; Δ T: simulation step size for each RELAP5 program;

and 3, step 3: and (4) updating the DET simulation object state transition control TRIP information in a classified mode.

The single-demand state transfer restarting file updating method is divided into two categories, namely variable TRIP transfer criterion and logic TRIP transfer criterion; wherein the variable TRIP transfer criterion is as follows:

the TRIP card information in the file is restarted after the DET state transition is successful;

the TRIP card information in the DET state transition failed branch restart file needs to be updated, and the overall scheme of TRIP logic updating in the failed branch variable TRIP type single-demand state transition RELAP5 restart file is as follows: modifying parameter values of comparison parameters in the variable TRIP card according to the logic relationship of the variable TRIP, and enabling the logic relationship of the variable TRIP not to occur by modifying the comparison parameter values; after the parameters are compared after updating, deleting the 'star' identifier corresponding to the TRIP card number in the restart file, so that the state of the DET simulation object of the failed branch during the backtracking calculation of RELAP5 can not generate state transition within the time of a simulation task; the specific DET simulation object state transition variable type TRIP trigger condition update rule is shown in the following table.

Serial number	Logical relationships in TRIP	Additional constant after 6 th bit updating of TRIP card
			1	GE、GT、EQ	1E23
2	LE、LT	-1E-23

The logical TRIP transfer criteria are as follows:

the logic TRIP single-time demand state transition is divided into two types; the 1 st: all logical TRIPs use the "OR" OR "AND" relationship:

if the determination condition of the state transition of the DET simulation object is finally equivalent to the "OR" AND "relationship of all the variable TRIP, the total update scheme of the restart file of the failure branch RELAP5 is as follows: when the state transition of the DET simulation object is identified, all the variable TRIP cards related to the current state transition of the DET simulation object are updated according to the updating rules in the table. That is, when the DET simulation object satisfies the state transition condition, the transition conditions of the DET simulation object are all set as the determination logic that cannot be realized in the restart file of the DET failed branch. After the parameters are compared after updating, the 'star' identifier corresponding to the TRIP card number in the restart file is deleted, and when the RELAP5 backtracks for simulation, the state of the DET simulation object will not change within the time range of the simulation task.

The 2 nd: using an "XOR" relationship in logical TRIP

If the judgment condition of the state transition of the DET simulation object is finally converted into an XOR relationship, no universal modification rule exists, and the judgment logic of the actual DET simulation object needs to be combined to modify according to the type 1 idea.

Method for updating restart file in single-running state transition

The single-run state transition only involves 1 time random variable for controlling the state transition of the DET simulation object; according to the state transition task time obtained by discretization of the analysts, the DET simulation object has a plurality of DET branches.

The general scheme of the method for restarting the file updating after the single operation state transition is as follows: when the discretization task time triggering condition is met, the file TRIP card is successfully branched and restarted without change; the time offset of the TRIP logic of the task time variable for controlling the state transition of the DET simulation object in the failed branch restart file is updated one by one in sequence according to the discretized task time specified by the analyst, as shown below.

Serial number	Run-on state transfer TRIP logic	Additional constant of variable logic 6 th bit
			1	CC1 time 0ge time of MT time l	MT1、MT2、…、MTn

The specific process is as follows: initially, the DET simulation object state transition time is MT1, and when the trigger condition is triggered, the successful branch restart file TRIP information is unchanged. The state transition time of the failed branch is replaced with MT 2. When the RELAP5 performs backtracking calculation, the DET simulation object in the RELAP5 simulation of successful branching will be state-transferred at MT 1; the status of the failed branch at MT1 does not change. When the MT2 task branch trigger condition is satisfied, the 2 nd branch is taken. The successful branch restart file TRIP information is not changed, and the state transition time of the failed branch is replaced with MT 3. And so forth until the user-specified last task time.

The file updating scheme of the demand/operation mixed state transition restart is as follows:

step 1: when the 1 st demand/run state transition trigger condition is met, the DET branches. The successful branch restarting file is updated according to the updating method of the successful branch of the single operation state transition DET of the demand/operation; and the failed branch restarting file is updated according to the updating method of the failed branch of the single operation state transition DET of the demand/operation.

Step 2: when the 1 st requirement/operation state transition success branch meets the 2 nd state transition condition, the success branch restarting file is updated according to the updating method of the operation/requirement single operation state transition DET success branch, and the final logic locking identification bit of the DET simulation object state transition control TRIP card is updated to be 1; and updating the failed branch restarting file according to an updating method of the failed branch of the single operation state transition DET of the operation/requirement.

Effects of the embodiment

Initializing DET and RELAP5 dynamic coupling related parameters according to accident characteristics and simulation computing resource conditions, including:

BloNum: recalling a restart information block number according to RELAP5 calculated by the minimum TRIP trigger time TRIPTimemin of DET simulation object state transition, wherein the initial value is 0;

CpuTimamax: the CPU maximum simulation step length time in a time control card in a RELAP5 program input card is customized by an initial value;

ErrNum: RELAP5 abnormal termination count, initial value 0;

MT: the state transition task time of the operation type state transition DET simulation object is determined, the number of the task time random variables needed is determined according to the number of the operation type state transition objects, and each task time random variable is dispersed according to a user-defined discrete mode to obtain a discrete task time sequence;

NorNum: normal time of RELAP5 ends counting, and the initial value is 0;

ResFre: the restart frequency of a time control card in the RELAP5 program input card is customized by a user;

ResNum: a RELAP5 restart number corresponding to a RELAP5 backtracking restart information block number BloNum, and having an initial value of 0;

SimTime: the simulation time of a time control card in the RELAP5 program input card, namely the simulation time when the current node is finished, and the initial value is delta T;

TaskTime: the task time of the DET and RELAP5 coupled simulation is also the simulation termination time of the final termination of RELAP5 simulation, and the initial value is user-defined;

TRIPTimemin: the minimum TRIP trigger time of the DET simulation object state transition in the current RELAP5 simulation step calculation result is set to be 0;

ResNumLast: the last restart number in the current RELAP5 simulation step calculation result file is set to be 0 as an initial value;

Δ t: the RELAP5 program inputs the restart frequency in the time control card in the card, and the initial value is user-defined;

Δ T: the initial value is user-defined each time the simulation step size of the RELAP5 program.

As shown in fig. 3, the DET and RELAP5 programs dynamically embody the coupling process:

step 1: putting an initial RELAP5 input file root.i and an initial restart file R0.i of a DET root node into a calculation queue as a pair of files;

step 2: and judging whether a RELAP input file exists in the calculation queue. If the RELAP5 input file exists, selecting a RELAP5 input file as the input of a RELAP5 program according to the principle of last-in first-out, assuming the file name to be a. i, operating the RELAP5 simulation, and obtaining the output results of RELAP5, i and r; if the RELAP5 input file does not exist in the calculation queue, executing the step 5;

and 3, step 3: and taking the o as an input, and judging whether the DET branch exists or not by utilizing a DET branch judging method. If no DET branch exists, the restart file of the previous RELAP5 simulation step size corresponding to the type without DET branch is updated. The restart file corresponding to the root node root.i is an initial R0.i; the other restart file names are consistent with the input file name of the current simulation step RELAP 5; putting the updated restart file i and the r file r of the corresponding RELAP5 into a calculation queue as a calculation case; then executing the step 2;

if yes, executing step 4;

and 4, step 4: according to the DET simulation object category, generating restart files of DET successful branches and failed branches according to a restart file updating method, wherein the restart files are named as-1. i and-2. i respectively, and form two calculation cases with r files of RELAP5 and r files respectively to be placed in a calculation queue, and then executing the step 2;

and 5, step 5: each DET branch reaches the simulation task time or RELAP5 simulation termination condition specified by the user, and the dynamic coupling of the DET and the RELAP5 program is finished;

in conclusion, after the DET is dynamically coupled with the RELAP5 program, the physical characteristics of the nuclear power plant with different branch sequences can be extracted by analyzing the input files of each branch node and each terminal node; the safety characteristics of the nuclear power plant and the like can be obtained through statistical analysis, cluster analysis and the like.

The above-described embodiments are merely illustrative of one or more embodiments of the present invention, which are described in more detail and detail, but are not to be construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.

Claims

1. A nuclear plant accident modeling method for the DET and RELAP5 procedure dynamic coupling framework, comprising the steps of:

s2, identifying the correlation among the minimum functional units, and determining the DET simulation object;

s3, constructing a DET simulation model of the discrete dynamic event tree according to the DET simulation object; the specific process comprises the following steps: identifying the correlation of minimum functional units and determining independent minimum functional units; giving a trigger condition, and determining a state transition process and a failure mode of the minimum functional unit meeting the trigger condition; determining the transfer probability of the minimum functional unit according to the failure mode of the minimum functional unit; if the minimum functional units are independent, independent function modeling is carried out on each minimum functional unit by utilizing a RELAP5 program, and if the minimum functional units are not independent, the control logics of the independent minimum functional units are modified in a RELAP5 program model according to the following formula: CC3 CC2 and CC1, wherein:

CC3 expresses the state transition actual control logic of FM2 simulation object of the correlation between FM1 and FM2 in the DET and RELAP5 program coupling framework; the meaning of CC3 is that when CC1 is true, the logic of CC3 and CC2 are consistent, otherwise it is always in the initial state; setting demand type TRIP variable and operation type TRIP variable according to a method in the DET and RELAP5 program coupling simulation by taking the minimum functional unit as a simulation object, and simulating the state transition process of the minimum functional unit by utilizing the DET and RELAP5 coupling framework;

s4, according to the DET simulation object, determining the simulation time and the simulation time step length of the RELAP5 program, and operating the RELAP5 program; the DET simulation object determined here is an analysis object of the nuclear power plant initial accident, and an initial RELAP5 program input card file for programming and simulating the nuclear power plant accident according to the deterministic theory analysis method, wherein the input card file comprises an initial RELAP5 input file root.i and an initial restart calculation file R ₀ I; wherein "Root" represents any file name meeting the requirements of RELAP5 program, "R ₀ "represents a file name,". i "represents a file type;

s6, identifying the DET branch moment when the state transition of the DET simulation object occurs, and acquiring a RELAP5 restart number for the program backtracking restart of RELAP5 according to the branch rule of the DET simulation model; here identify DET simulation object State transition issueThe specific method of the branch time of the raw DET is as follows: the first step is as follows: obtaining time information of the change of the state transition control TRIP variable of the DET simulation object according to the step S5; the second step: judging whether a branch exists in the simulation time step length; if no branch exists, the initial restart file R of RELAP5 is updated ₀ The simulation time in i, the simulation time of the time control card in the input card of the RELAP5 program is the sum of the simulation time at the end and the simulation step size of the RELAP5 program, and then the calculation file R is calculated by the initial restart ₀ I and the result file root.r are input, and the RELAP5 program is operated again; thirdly, the steps of: if the branch exists, acquiring the minimum time for triggering the state transition TRIP of the DET simulation object by analyzing the result file, and then acquiring a RELAP5 restart number corresponding to the RELAP5 backtracking restart information block number according to the branch rule of the DET simulation model; the DET backtracking restart number identification method here is as follows: the step (1): identifying the minimum trigger time TRIPTime according to the TRIP trigger time set acquired at the DET branch moment _min And TRIPTime _min Comparing and selecting TRIPTime corresponding to TRIP number _min Minimum TRIPNum in corresponding TRIP number _min The state transition of the DET simulation object is branched; step (2): determining TRIPTime _min If the corresponding DET simulation object is of a single state transition type, executing the step (4); otherwise, executing the step (3); step (3): the simulation object of the simulation step DET can have multiple state transitions, all Restart information block information in the root.o file is analyzed, the state transition time with the minimum branch simulation object of the step DET is obtained through comparison, and the state transition time is assigned to TRIPTime _min Then executing the step (4); step (4): will TRIPTime _min Replacing corresponding elements in { TRIPT1, TRIPT2, …, TRIPTN }, and then executing the step (5); step (5): calculating the number BloNum of the DET backtracking restart information block, wherein the BloNum is calculated by using the following formula:

Δt＝CpuTime _max ×ResFre

wherein:

BloNum: minimal TRIP trigger time TRIPTime for emulating object state transitions according to DET _min The calculated RELAP5 backtracks the restart information block number;

CpuTime _max : the RELAP5 program inputs the CPU maximum simulation step time in the time control card in the card;

INT [ ]: taking an integer function;

TRIPTime _min : the minimum TRIP trigger time of the state transition of the DET simulation object in the current RELAP5 simulation step calculation result;

Δ t: the time interval of two restarting information blocks in the time control card in the RELAP5 program input card;

s7, determining the state transition type of the DET simulation object, updating the restart input file calculated by the RELAP5 program, and generating the restart input file calculated by the RELAP5 program for the successful branch and the failed branch of the DET; the method for updating the RELAP5 restart file is that after each RELAP5 simulation step length is finished, the restart file needs to be updated according to the following two types of conditions: the DET branch does not have DET simulation object state transition, and at this time, the RELAP5 restarts the file update method as follows: step 1: updating the 1 st restart number of the 103 card in the restart file of the current node RELAP5 to the simulation result of the current simulation step length; step 2: updating the simulation ending time SimTime of the 1 st bit of the time control card of the 201 in the restart file of the current node RELAP5 according to the following formula;

SimTime＝SimTime+ΔT

wherein: SimTime: the RELAP5 program inputs the simulation time of the time control card in the card, namely the simulation time when the current node is finished; delta T: simulation step size for each RELAP5 program; and (2) when the DET branch has the state transition of the DET simulation object, the RELAP5 restarts the file updating method as follows: step 1: updating the 1 st bit restart number of the 103 card in the current node RELAP5 restart file to ResNum; step 2: updating the simulation end time SimTime of the 1 st bit of the time control card of 201 in the file I for restarting the current node RELAP5 according to the following formula:

wherein: INT [ 2 ]]: taking an integer function; TRIPTime _min : the minimum TRIP trigger time of the state transition of the DET simulation object in the current RELAP5 simulation step calculation result; Δ t: the time interval of two restarting information blocks in the time control card in the RELAP5 program input card; delta T: simulation step size for each RELAP5 program; and 3, step 3: updating the state transition control TRIP information of the DET simulation object in a classified manner;

s8, determining the backtracking restart time of the RELAP5 program according to the DET branching time, and backtracking and executing the RELAP5 program by taking a generated restart input file calculated by the RELAP5 program of the DET successful branching and the DET failed branching and a simulation time step size RELAP5 calculation result file as input so as to finish the simulation of the next simulation time step size of the DET successful branching and the DET failed branching;

s9, looping the process of steps S4-S8 until the simulation time reaches the user-specified simulation task time, and the dynamic coupling of the DET and RELAP5 programs is finished.

2. The nuclear plant accident modeling method for the DET and RELAP5 procedural dynamic coupling framework of claim 1, wherein in step S4, the RELAP5 initially restarts the computation file R ₀ The i file comprises a (r) RELAP5 program restart 103 card; RELAP5 program time step length control 201 card; TRIP card of RELAP5 program; the TRIP cards comprise all TRIP cards related to the DET simulation object state transition, and each TRIP card number is added with an identifier.