阅读说明：本技术 一种核电站严重事故仪表可用性仿真分析方法及系统 (Nuclear power station serious accident instrument availability simulation analysis method and system ) 是由 刘莉 郭林 陈浠毓 尚雪莲 周世梁 马天宇 陈日罡 王彦君 于 2021-07-20 设计创作，主要内容包括：本发明公开了一种核电站严重事故仪表可用性仿真分析方法及系统,方法包括：S100、基于核电站各仪表的实际电路,构建各仪表的仿真电路；S200、对各仪表的仿真电路中各元器件的不同环境影响因素进行环境试验,得到不同环境下的各元器件参数的变化情况,以及不同环境影响因素的具体参数对电路性能的影响；S300、基于各仪表的实际电路和等效电路,建立仪表电路模型；S400、基于各仪表在不同严重事故下环境影响因素的具体参数以及等效电路的特点,确定所述仪表电路模型中各仪表可能的电路变化模式及仿真方案。本发明能够运用仿真模型对运行及在建电站仪表在严重事故下的可用性进行分析。(The invention discloses a nuclear power station serious accident instrument availability simulation analysis method and a system, wherein the method comprises the following steps: s100, constructing a simulation circuit of each instrument based on an actual circuit of each instrument of the nuclear power station; s200, carrying out environment tests on different environment influence factors of each component in the simulation circuit of each instrument to obtain the change condition of parameters of each component under different environments and the influence of specific parameters of different environment influence factors on the circuit performance; s300, establishing an instrument circuit model based on the actual circuit and the equivalent circuit of each instrument; s400, determining possible circuit change modes and simulation schemes of the instruments in the instrument circuit model based on specific parameters of environmental influence factors of the instruments under different serious accidents and characteristics of equivalent circuits. The invention can analyze the usability of the running and power station building instrument under serious accidents by using a simulation model.)

1. A nuclear power station serious accident instrument availability simulation analysis method is characterized by comprising the following steps:

s100, constructing a simulation circuit of each instrument based on an actual circuit of each instrument of the nuclear power station;

s200, carrying out environment tests on different environment influence factors of each component in the simulation circuit of each instrument to obtain the change condition of parameters of each component under different environments and the influence of specific parameters of different environment influence factors on the circuit performance;

s300, establishing an instrument circuit model based on the actual circuit and the equivalent circuit of each instrument;

s400, determining possible circuit change modes and simulation schemes of the instruments in the instrument circuit model based on specific parameters of environmental influence factors of the instruments under different serious accidents and characteristics of equivalent circuits;

s500, modifying related parameters in an equivalent circuit based on the change condition of parameters of each component of each instrument in different environments, simulating the influence of specific parameters of different environmental influence factors on the circuit performance, and establishing a circuit characteristic with degraded performance in an instrument circuit model;

s600, introducing a noise circuit into the instrument circuit model, merging the noise circuit into a power supply and signal acquisition part of each instrument, accessing an equivalent circuit cable, and establishing a complete circuit model;

s700, setting specific parameters of environmental influence factors according to the calculated severe accident environmental conditions based on the complete circuit model, operating simulation to obtain instrument output signals, namely simulation results, comparing the simulation results of the complete circuit model with typical environmental test results of components of each instrument and/or instrument identification tests, continuously iteratively correcting the specific parameters of the environmental influence factors, and finally achieving the purpose that the actual instrument output is consistent with the instrument output in the test to obtain a final simulation model.

2. The method of claim 1, wherein S200 comprises:

analyzing each component in the simulation circuit of each instrument and carrying out corresponding environmental tests on the components, observing and recording the parameter change of each component in the circuit and the output current waveform of the circuit under different environments, drawing a curve graph of the circuit output changing along with the change of environmental influence factors, and obtaining the influence of different environmental influence factors on the circuit performance.

3. The method of claim 1, wherein S300 comprises:

carrying out simulation modeling according to an actual circuit under the condition that parameters of all components of related components in signal transmission channels of all instruments are known;

and establishing a corresponding equivalent circuit under the condition that parameters of parts of components in a certain component in each instrument signal transmission channel are unknown.

4. The method of claim 1, wherein S600 comprises:

a series voltage source is used for simulating thermal noise on a resistor under the condition of high temperature;

a50 Hz sine wave generator is connected between the shielding part of the output end of the instrument cable and the ground in the instrument circuit model to simulate power frequency interference noise.

5. The method according to any one of claims 1-4, wherein S700 comprises:

according to the available conditions of each instrument of the nuclear power station under serious accidents and the identification requirements of the instruments, the possible abnormal conditions of the output signals of the instruments are divided into the following types: the signal size exceeds the normal signal range, the signal size is lower than the normal signal range, the signal value is unchanged, and unstable oscillation exists.

6. A nuclear power station severe accident instrument availability simulation analysis system is characterized by comprising:

the building module is used for building a simulation circuit of each instrument based on an actual circuit of each instrument of the nuclear power station;

the test module is used for carrying out environmental tests on different environmental influence factors of each component in the simulation circuit of each instrument to obtain the change condition of parameters of each component under different environments and the influence of specific parameters of different environmental influence factors on the circuit performance;

the establishing module is used for establishing an instrument circuit model based on the actual circuit and the equivalent circuit of each instrument;

the determining module is used for determining possible circuit change modes and simulation schemes of the instruments in the instrument circuit model based on specific parameters of environmental influence factors of the instruments under different serious accidents and characteristics of equivalent circuits;

the simulation module is used for modifying related parameters in the equivalent circuit based on the change conditions of parameters of components of each instrument in different environments, simulating the influence of specific parameters of different environmental influence factors on the circuit performance, and establishing circuit characteristics with performance degradation in the instrument circuit model;

the leading-in module is used for leading in a noise circuit in the instrument circuit model, merging the noise circuit into a power supply and signal acquisition part of each instrument, accessing an equivalent circuit cable and establishing a complete circuit model;

and the simulation module is used for setting specific parameters of the environmental influence factors according to the calculated serious accident environmental conditions based on the complete circuit model, running simulation to obtain instrument output signals, namely simulation results, comparing the simulation results of the complete circuit model with typical environmental test results of each component of each instrument and/or instrument identification tests, continuously iteratively correcting the specific parameters of the environmental influence factors, and finally realizing the consistency of the actual instrument output during the test to obtain the final simulation model.

7. The system of claim 6, wherein the testing module is specifically configured to:

analyzing each component in the simulation circuit of each instrument and carrying out corresponding environmental tests on the components, observing and recording the parameter change of each component in the circuit and the output current waveform of the circuit under different environments, drawing a curve graph of the circuit output changing along with the change of environmental influence factors, and obtaining the influence of different environmental influence factors on the circuit performance.

8. The system of claim 6, wherein the establishing module is specifically configured to:

carrying out simulation modeling according to an actual circuit under the condition that parameters of all components of related components in signal transmission channels of all instruments are known;

and establishing a corresponding equivalent circuit under the condition that parameters of parts of components in a certain component in each instrument signal transmission channel are unknown.

9. The system of claim 6, wherein the introduction module is specifically configured to:

a series voltage source is used for simulating thermal noise on a resistor under the condition of high temperature;

a50 Hz sine wave generator is connected between the shielding part of the output end of the instrument cable and the ground in the instrument circuit model to simulate power frequency interference noise.

10. The system of any of claims 6-9, wherein the simulation module is further configured to:

according to the available conditions of each instrument of the nuclear power station under serious accidents and the identification requirements of the instruments, the possible abnormal conditions of the output signals of the instruments are divided into the following types: the signal size exceeds the normal signal range, the signal size is lower than the normal signal range, the signal value is unchanged, and unstable oscillation exists.

Technical Field

The invention relates to the field of nuclear power station serious accident instrument availability simulation analysis, in particular to a nuclear power station serious accident instrument availability simulation analysis method and system.

Background

Both the national and international guidelines for the management of severe accidents in nuclear power plants and the relevant regulatory standards place requirements on the availability of instruments under severe accident conditions, and it is necessary that these instruments should be able to function under the expected severe accident conditions with reasonable confidence. However, there is no specific requirement and uniform knowledge of the method for meter usability assessment.

At present, the availability evaluation of instruments in operating and nuclear power plants under construction generally adopts a test method to identify the instruments, and compares and identifies whether the test conditions can envelop accident environmental conditions or time window environmental conditions needing the instrument to execute functions under the accident working condition. The method has high reliability, visually represents whether the instrument is available, belongs to a 'black box' evaluation method, and does not aim at key components of the instrument. The method is too conservative to a certain extent, and the cost of identification test is high. The invention provides a simulation evaluation method which directly takes an instrument output signal as an evaluation criterion of usability based on instrument circuit simulation modeling and combined with the introduction and analysis of the influence quantity of severe accident environmental conditions. The method can replace or partially replace the traditional instrument identification test, reduces the instrument availability evaluation cost, belongs to a 'white box' evaluation method, can determine key components, positions weak links, can perform advanced design on the instrument, and optimizes the performance of the instrument under the accident condition.

With the rapid development of circuit simulation technology, standard components in circuit simulation software are subjected to a large number of tests and verifications, the component model precision and the model simulation calculation capability are greatly improved, and the method is widely used for the reliability simulation and prediction of integrated circuits of instruments and measurement systems due to the usability and stability of the components. The instrument usability analysis based on circuit simulation has the advantages of short time consumption and low cost, and can be used for positioning key components in a circuit and analyzing the characteristics of the transmitter output under the conditions of component performance degradation and failure.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a nuclear power station serious accident instrument availability simulation analysis method and system, which can analyze the availability of operating and power station instruments under serious accidents by using a simulation model.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a nuclear power station severe accident instrument availability simulation analysis method comprises the following steps:

s100, constructing a simulation circuit of each instrument based on an actual circuit of each instrument of the nuclear power station;

s200, carrying out environment tests on different environment influence factors of each component in the simulation circuit of each instrument to obtain the change condition of parameters of each component under different environments and the influence of specific parameters of different environment influence factors on the circuit performance;

s300, establishing an instrument circuit model based on the actual circuit and the equivalent circuit of each instrument;

s400, determining possible circuit change modes and simulation schemes of the instruments in the instrument circuit model based on specific parameters of environmental influence factors of the instruments under different serious accidents and characteristics of equivalent circuits;

s500, modifying related parameters in an equivalent circuit based on the change condition of parameters of each component of each instrument in different environments, simulating the influence of specific parameters of different environmental influence factors on the circuit performance, and establishing a circuit characteristic with degraded performance in an instrument circuit model;

s600, introducing a noise circuit into the instrument circuit model, merging the noise circuit into a power supply and signal acquisition part of each instrument, accessing an equivalent circuit cable, and establishing a complete circuit model;

s700, setting specific parameters of environmental influence factors according to the calculated severe accident environmental conditions based on the complete circuit model, operating simulation to obtain instrument output signals, namely simulation results, comparing the simulation results of the complete circuit model with typical environmental test results of components of each instrument and/or instrument identification tests, continuously iteratively correcting the specific parameters of the environmental influence factors, and finally achieving the purpose that the actual instrument output is consistent with the instrument output in the test to obtain a final simulation model.

Further, the method as described above, S200 includes:

analyzing each component in the simulation circuit of each instrument and carrying out corresponding environmental tests on the components, observing and recording the parameter change of each component in the circuit and the output current waveform of the circuit under different environments, drawing a curve graph of the circuit output changing along with the change of environmental influence factors, and obtaining the influence of different environmental influence factors on the circuit performance.

Further, the method as described above, S300 includes:

carrying out simulation modeling according to an actual circuit under the condition that parameters of all components of related components in signal transmission channels of all instruments are known;

and establishing a corresponding equivalent circuit under the condition that parameters of parts of components in a certain component in each instrument signal transmission channel are unknown.

Further, the method as described above, S600 includes:

a series voltage source is used for simulating thermal noise on a resistor under the condition of high temperature;

a50 Hz sine wave generator is connected between the shielding part of the output end of the instrument cable and the ground in the instrument circuit model to simulate power frequency interference noise.

Further, the method as described above, S700 includes:

according to the available conditions of each instrument of the nuclear power station under serious accidents and the identification requirements of the instruments, the possible abnormal conditions of the output signals of the instruments are divided into the following types: the signal size exceeds the normal signal range, the signal size is lower than the normal signal range, the signal value is unchanged, and unstable oscillation exists.

A nuclear power station severe accident instrument availability simulation analysis system comprises:

the building module is used for building a simulation circuit of each instrument based on an actual circuit of each instrument of the nuclear power station;

the test module is used for carrying out environmental tests on different environmental influence factors of each component in the simulation circuit of each instrument to obtain the change condition of parameters of each component under different environments and the influence of specific parameters of different environmental influence factors on the circuit performance;

the establishing module is used for establishing an instrument circuit model based on the actual circuit and the equivalent circuit of each instrument;

the determining module is used for determining possible circuit change modes and simulation schemes of the instruments in the instrument circuit model based on specific parameters of environmental influence factors of the instruments under different serious accidents and characteristics of equivalent circuits;

the simulation module is used for modifying related parameters in the equivalent circuit based on the change conditions of parameters of components of each instrument in different environments, simulating the influence of specific parameters of different environmental influence factors on the circuit performance, and establishing circuit characteristics with performance degradation in the instrument circuit model;

the leading-in module is used for leading in a noise circuit in the instrument circuit model, merging the noise circuit into a power supply and signal acquisition part of each instrument, accessing an equivalent circuit cable and establishing a complete circuit model;

and the simulation module is used for setting specific parameters of the environmental influence factors according to the calculated serious accident environmental conditions based on the complete circuit model, running simulation to obtain instrument output signals, namely simulation results, comparing the simulation results of the complete circuit model with typical environmental test results of each component of each instrument and/or instrument identification tests, continuously iteratively correcting the specific parameters of the environmental influence factors, and finally realizing the consistency of the actual instrument output during the test to obtain the final simulation model.

Further, in the system as described above, the test module is specifically configured to:

analyzing each component in the simulation circuit of each instrument and carrying out corresponding environmental tests on the components, observing and recording the parameter change of each component in the circuit and the output current waveform of the circuit under different environments, drawing a curve graph of the circuit output changing along with the change of environmental influence factors, and obtaining the influence of different environmental influence factors on the circuit performance.

Further, in the system described above, the establishing module is specifically configured to:

carrying out simulation modeling according to an actual circuit under the condition that parameters of all components of related components in signal transmission channels of all instruments are known;

and establishing a corresponding equivalent circuit under the condition that parameters of parts of components in a certain component in each instrument signal transmission channel are unknown.

Further, in the system as described above, the introduction module is specifically configured to:

a series voltage source is used for simulating thermal noise on a resistor under the condition of high temperature;

a50 Hz sine wave generator is connected between the shielding part of the output end of the instrument cable and the ground in the instrument circuit model to simulate power frequency interference noise.

Further, in the system as described above, the simulation module is further configured to:

according to the available conditions of each instrument of the nuclear power station under serious accidents and the identification requirements of the instruments, the possible abnormal conditions of the output signals of the instruments are divided into the following types: the signal size exceeds the normal signal range, the signal size is lower than the normal signal range, the signal value is unchanged, and unstable oscillation exists.

The invention has the beneficial effects that: the method can analyze the usability of the running and power station building instrument under the serious accident by using the simulation model, takes the output signal of the instrument as the evaluation basis of the usability, and reduces the conservation compared with the traditional evaluation method.

Drawings

Fig. 1 is a schematic flow chart of a nuclear power plant severe accident instrument availability simulation analysis method provided in an embodiment of the present invention;

FIG. 2 is a block diagram of a nuclear power plant severe accident instrument availability simulation analysis method provided in an embodiment of the present invention;

FIG. 3 is a schematic diagram of a nuclear power plant instrumentation signal transmission loop provided in an embodiment of the present invention;

FIG. 4 is a schematic diagram of an equivalent circuit of a thermal resistance transmitter provided in an embodiment of the present invention;

FIG. 5 is a schematic diagram of an equivalent circuit of a resistor under irradiation conditions as provided in an embodiment of the present invention;

FIG. 6 is a schematic diagram of series connected voltage sources provided in an embodiment of the present invention;

fig. 7 is a schematic diagram of power frequency interference noise simulation provided in the embodiment of the present invention;

fig. 8 is a schematic structural diagram of a nuclear power plant severe accident instrument availability simulation analysis system provided in an embodiment of the present invention.

Detailed Description

In order to make the technical problems solved, the technical solutions adopted, and the technical effects achieved by the present invention clearer, the technical solutions of the embodiments of the present invention will be further described in detail with reference to the accompanying drawings.

The embodiment of the invention provides a nuclear power station serious accident instrument availability simulation analysis method, as shown in fig. 1, the method comprises the following steps:

s100, constructing a simulation circuit of each instrument based on an actual circuit of the nuclear power station instrument;

s200, carrying out environment tests on different environment influence factors of each component in the simulation circuit of each instrument to obtain the change condition of parameters of each component under different environments and the influence of specific parameters of different environment influence factors on the circuit performance;

in the embodiment of the present invention, S200 includes: analyzing each component in the simulation circuit of each instrument and carrying out corresponding environmental tests on the components, observing and recording the parameter change of each component in the circuit and the output current waveform of the circuit under different environments, drawing a curve graph of the circuit output changing along with the change of environmental influence factors, and obtaining the influence of different environmental influence factors on the circuit performance.

S300, establishing an instrument circuit model based on the actual circuit and the equivalent circuit of each instrument;

in the embodiment of the present invention, S300 includes: and carrying out simulation modeling according to an actual circuit under the condition that parameters of all components of related components in each instrument signal transmission channel are known, and establishing an equivalent circuit under the condition that parameters of some components in a certain component in each instrument signal transmission channel are unknown.

S400, determining possible circuit change modes and simulation schemes of the instruments in the instrument circuit model based on specific parameters of environmental influence factors of the instruments under different serious accidents and characteristics of equivalent circuits;

s500, modifying related parameters in an equivalent circuit based on the change condition of parameters of each component of each instrument in different environments, simulating the influence of specific parameters of different environmental influence factors on the circuit performance, and establishing circuit characteristics with performance degradation in an instrument circuit model;

s600, introducing a noise circuit into the instrument circuit model, merging the noise circuit into a power supply and signal acquisition part of each instrument, accessing an equivalent circuit cable, and establishing a complete circuit model;

in the embodiment of the present invention, S600 includes: a series voltage source is used for simulating thermal noise on a resistor under the condition of high temperature; a50 Hz sine wave generator is connected between the shielding part of the output end of the instrument cable and the ground in the instrument circuit model to simulate power frequency interference noise.

S700, setting specific parameters of environmental influence factors according to the calculated severe accident environmental conditions based on the complete circuit model, operating simulation to obtain instrument output signals, namely simulation results, comparing the simulation results of the complete circuit model with typical environmental test results of components of each instrument and/or instrument identification tests, continuously iteratively correcting the specific parameters of the environmental influence factors, and finally achieving the purpose that the actual instrument output is consistent with the instrument output in the test to obtain the final simulation model.

In the embodiment of the present invention, S700 includes: according to the available conditions of each instrument of the nuclear power station under serious accidents and the identification requirements of the instruments, the possible abnormal conditions of the output signals of the instruments are divided into the following types: the signal size exceeds the normal signal range, the signal size is lower than the normal signal range, the signal value is unchanged, and unstable oscillation exists.

For example, as shown in fig. 2, firstly, according to the characteristics of the instrument transmission and signal transmission circuit of the nuclear power plant, an instrument circuit model is established, which includes all instrument circuit key components and all instrument signal transmission channel key components (such as cable connectors, penetrations, cables, junction boxes, etc.), and is compared with the original instrument circuit for the output of the same input, so as to confirm the validity of the circuit model; then, calculating the change conditions of the parameters of each element under different working conditions according to the parameters of each element under different environmental conditions; then, the output condition of the instrument signal under the working condition is obtained by utilizing the element parameters obtained by the test through software simulation, and the usability of the instrument under the working condition is analyzed and compared by taking the output condition of the instrument signal under different working conditions as the basis; and introducing rationality by combining typical instrument identification data and relevant literature test data to verify a model and influence quantity. And determining available and unavailable judgment threshold values of the instrument through circuit simulation, verifying the reliability of the obtained availability judgment threshold values, designing instrument output signal test tests under different environmental condition influence quantities (such as temperature, humidity, irradiation and the like), and verifying the rationality of the selection of the judgment threshold values by combining instrument identification test data. The method takes the output signal of the instrument as the evaluation basis of the availability, and compared with the traditional evaluation method, the conservative property is reduced.

The invention adopts a mode of establishing a circuit model, fully utilizes the functions of circuit simulation software, combines the environmental stress and failure mechanism analysis of electronic elements, researches the change of element parameters, failure modes, noise introduction and the like of instruments in the severe accident environment of a nuclear power plant, establishes a reasonable circuit model, sets reasonable element parameters according to environmental conditions, and adds a reasonable noise source. The variation of the parameter value of the circuit element is calculated by utilizing the temperature scanning function of circuit simulation software, the deviation of the output of the circuit and the rated output is compared for given typical input under different temperatures, and the variation of the measurement precision of the instrument is analyzed.

The following description will be made in detail by taking a capacitive pressure transmitter for serious accidents as an example.

The signal transmission circuit of the whole pressure instrument is divided into three parts: a transmitter section, a signal transmission line section, and a control section, as shown in fig. 3.

Part of the sensing transducer

The capacitive transmitter for serious accidents is a typical 4-20 mA standard signal transmitter.

A signal transmission part

The twisted pair shielded cable is used as the object for researching the connection part, and a layer of metal foil is arranged outside the wire pair of the twisted pair shielded cable, so that the twisted pair shielded cable has better anti-interference performance.

Control chamber part

According to the actual conditions of projects, the signal receiving parts can be different due to different product suppliers, and for the convenience of modeling comparison, for the research of the signal receiving part of the control room, a circuit model with the negative side of a common voltage source and the grounding of the shielding layer is adopted for simulation analysis.

(1) Circuit creation and simulation

Sensing transducer part

And establishing a circuit simulation model according to the actual circuit diagram.

Signal transmission section

The twisted pair shielded connection cable is represented by conductor inductance and dielectric capacitance, wherein the cable shielding layer is a semi-conductive layer with relatively thin resistivity, so that the resistance is not considered, only inductance and capacitance are simulated, and the capacitance and inductance values can be calculated according to a long-line interference model of the conductor.

Control chamber part

The receiver is represented by a power supply, a dc voltage source and a shunt capacitor. The voltage source drives current to a voltage sense resistor in series with the transmitter. The negative side of the voltage source and the shielding are grounded, "in practice, the size of the sense resistor and the location at which it is grounded vary from factory to factory, and will directly affect the susceptibility of the environment-induced circuit degradation in the containment. "

(2) Test verification (if necessary)

After a reasonable simulation circuit, namely the circuit simulation model in (1), is constructed, the physical quantity value (such as resistance value of a resistor, capacitance value of a capacitor, inductance value of an inductor and the like) change conditions of different resistors, capacitors and inductors in different environments are obtained through environment parameter tests of elements in the circuit, and then the output condition of instrument signals of the instrument in the environment is obtained through a simulation test according to the original physical quantity value obtained through a specific environment test.

In order to obtain the influence of environmental conditions such as different temperatures, humidity and the like on the circuit performance, key components of the circuit can be analyzed, corresponding environmental tests can be carried out on the key components, and the change of parameters of the key components in the circuit and the output current waveform of the transmitter circuit under different environmental conditions can be observed and recorded. And drawing a curve graph of circuit output changing along with the change of the environmental influence factors to obtain the influence of different environmental influence factors on the circuit performance.

(3) Instrument circuit model

The meter circuit model is a simulation modeling of the sensing transmitter part in (1). Under the condition that various components and parameters of components such as related instrument circuits, cables, connecting pieces and the like in the instrument measuring channel are known, simulation modeling can be carried out according to actual circuits so as to obtain higher simulation precision. For the condition that the parameters of a certain component in a channel or a part of components in an instrument are unknown, two networks with the same terminal voltage, terminal current and volt-ampere relation at a terminal button can be adopted for carrying out equivalence. The equivalent circuit mainly comprises direct current equivalent, alternating current equivalent and component equivalent. For example, dc equivalent and component equivalent can be considered depending on the circuit characteristics of the transmitter. The equivalence of parts in the instrument is strictly defined according to the equivalence, and the simplified circuit characteristics need to be kept equivalent to the outside.

(4) Determining the impact of different severe accident environmental impact factors on an equivalent circuit

Due to different severe accident sequences and different installation positions of the instruments, the specific parameters of the environmental factors which need to be considered by each instrument are different. After the environmental parameters are calculated, the possible circuit change mode and the simulation scheme are determined according to the characteristics of the given equivalent circuit.

For example: the equivalent circuit of the thermal resistance transmitter is shown in FIG. 4, and key electrical parameters of the equivalent circuit comprise an input leakage resistor R10, wire resistors R2, R3, R4 and R5, wire inductors L2, L3, L4 and L5, a shielding layer resistor R1 and an inductor L1, an input capacitor C1, capacitors C3 and C4 between wires of an instrument cable, a capacitor C5 between the wires of the instrument cable and the shielding layer, capacitors C2, C5 and a resistor R11 between the wires of the instrument cable and the shielding layer, and an output resistor R7. The parameters of the passive elements are then changed according to equation (1) based on the temperature coefficient of the passive elements (resistance and capacitance) and the post-accident ambient temperature.

R＝R_ref[1+α(T-T_ref)] (1)

Wherein R is the resistance of the conductor at temperature T, R_refIs a reference temperature T_refThe resistance of the lower conductor, the reference temperature, is typically 20 ℃, α is the temperature coefficient of the resistive conductor material, and T is the temperature of the conductor, in degrees Celsius, T_refIs the conductor reference temperature in degrees celsius.

When the instrument cable sealing performance degrades, water or moisture enters the inside of the cable, which may cause the capacitance between wires, such as C3 and C4, to increase, thereby lengthening the response time of the temperature measurement.

(5) Establishing circuit characteristics of performance degradation

Some serious environmental factors of accidents may cause the protection of instruments (including cables) to be degraded, the protective shell to be damaged, and the insulation and shielding performance to be degraded. Parameters such as resistance and capacitance between the ground or cables in the equivalent circuit can be modified according to the parameter change rule of the instrument components in different environments, the influence of the actual environment on the equivalent circuit can be simulated, and the circuit characteristics with performance degradation can be established.

Fig. 5 is an equivalent circuit of the irradiated resistance (R is the pre-irradiation resistance). The circuit has a Compton displacement current proportional to gamma dose rate and a permanent resistance change Delta R caused by neutrons; the transient parallel leakage resistance Rs is inversely proportional to the gamma dose rate. The first order approximation of the parallel leakage resistance and compton displacement current is:

(6) circuit for introducing noise

Under severe accident environmental conditions, the electromagnetic environment deteriorates, the anti-interference capability of the instrument is weakened, and various noises can be coupled with the instrument circuit through different ways. Interference voltages are usually introduced in series in the form of inductive coupling, capacitive coupling, electromagnetic radiation, etc., or directly as a result of the difference between the local and remote ground potentials. Noise interference is typically introduced by the power supply lines, signal input and output lines, and the housing. Therefore, the noise circuit can be incorporated into the power supply and signal acquisition part of the instrument, and an equivalent circuit cable is connected to establish a complete measuring circuit. The following provides a simulation method for introducing thermal noise and power frequency interference at high temperature.

Resistance thermal noise simulation

1. The thermal noise at high temperature on resistor R can be simulated by a series voltage source, as shown in fig. 6, with a single-sided spectral density of:

S_V(f)＝4kTR,f≥0

wherein k is Boltzmann constant, and T is the operating temperature of the resistor.

2. Power frequency interference noise simulation

When the shielding layer of the transmitter instrument cable is damaged due to high temperature and irradiation after a serious accident, the resistance of the shielding layer to the ground is reduced, the capacitance is increased, the shielding fails to work for the ground wire, and power frequency interference has obvious influence on circuit output. Depending on the location of the transmitter installation, common mode interference signals are most likely introduced on the instrument cabling path due to parasitic capacitance between the cable and ground. Therefore, a 50Hz sine wave generator can be connected between the shielding part of the output end of the instrument cable and the ground in the circuit model to simulate the power frequency interference, as shown in FIG. 7.

(7) Running simulation program, comparing output waveform

And establishing a complete circuit model of the severe accident condition of the nuclear power plant through the steps, setting an environment variable according to the calculated severe accident environment condition, and running simulation. And the output waveform under the corresponding environment can be obtained through the output quantity of the circuit model. According to the available conditions of the instruments and the requirements of instrument identification of the accident nuclear power station, the possible abnormal conditions of the output signals of the instruments are divided into the following conditions: the signal size exceeds the normal signal range, the signal size is lower than the normal signal range, the signal value is unchanged, and unstable oscillation exists.

The influence of the environment on the availability of the instrument is analyzed, the influence of the accident environment condition on the output signal of the instrument is given, and the possible failure mode and the calculation availability of the availability analysis software in the prediction instrument can be combined.

By adopting the method of the embodiment of the invention, the circuit simulation is carried out on the instrument, and the introduction scheme of the influence quantity of the environmental condition, the simulation modeling method and the simulation modeling process are provided. By establishing an equivalent model of a typical instrument circuit and analyzing the environmental conditions and the fault mode of the instrument, the output waveform of the circuit model which is not interfered by noise and is interfered by noise under the accident condition of the instrument can be obtained. And comparing the simulation result of the circuit model with the typical environment test result of the key component and/or the instrument identification test, and further correcting the simulation model if the threshold value is out of tolerance for evaluation conclusion and failure reason analysis. On the basis of availability evaluation, the circuit simulation method can predict the performance change trend of the instrument in an accident environment to a certain extent, and theoretically explains the influence reason of the environment on the instrument. The evaluation result of the method can be well applied to the management of serious accidents and the analysis of weak links of the nuclear power plant, and can also be used for improving the design of instruments for monitoring the serious accidents and improving the survival capability of the instruments under the serious accidents.

It should be noted that, for simplicity of description, the above-mentioned method embodiments are described as a series of acts or combination of acts, but those skilled in the art will recognize that the present invention is not limited by the order of acts, as some steps may occur in other orders or concurrently in accordance with the invention. Further, those skilled in the art should also appreciate that the embodiments described in the specification are preferred embodiments and that the acts and modules referred to are not necessarily required by the invention.

According to another aspect of the embodiment of the present invention, there is also provided a nuclear power plant severe accident instrument availability simulation analysis system, as shown in fig. 7, including:

the building module 100 is used for building a simulation circuit of each instrument based on an actual circuit of each instrument of the nuclear power station;

the test module 200 is used for performing environmental tests on different environmental influence factors of each component in the simulation circuit of each instrument to obtain the change conditions of parameters of each component in different environments and the influence of specific parameters of different environmental influence factors on the circuit performance;

the establishing module 300 is used for establishing an instrument circuit model based on the actual circuit and the equivalent circuit of each instrument;

the determining module 400 is configured to determine a possible circuit change mode and a simulation scheme of each instrument in the instrument circuit model based on specific parameters of environmental impact factors of each instrument under different severe accidents and characteristics of an equivalent circuit;

the simulation module 500 is used for modifying related parameters in the equivalent circuit based on the change conditions of parameters of components of each instrument in different environments, simulating the influence of specific parameters of different environmental influence factors on the circuit performance, and establishing circuit characteristics with performance degradation in an instrument circuit model;

the leading-in module 600 is used for leading in a noise circuit in the instrument circuit model, merging the noise circuit into the power supply and signal acquisition parts of each instrument, accessing an equivalent circuit cable and establishing a complete circuit model;

the simulation module 700 is used for setting specific parameters of the environmental influence factors according to the calculated severe accident environmental conditions based on the complete circuit model, running simulation to obtain instrument output signals, namely simulation results, comparing the simulation results of the complete circuit model with typical environmental test results of each component of each instrument and/or instrument identification tests, continuously iteratively correcting the specific parameters of the environmental influence factors, and finally achieving the purpose that the actual instrument output is consistent with the instrument output in the test to obtain the final simulation model.

It should be noted that the nuclear power station serious accident instrument availability simulation analysis system and the nuclear power station serious accident instrument availability simulation analysis method belong to the same inventive concept, and detailed description is omitted.

By adopting the system of the embodiment of the invention, the circuit simulation is carried out on the instrument, and the introduction scheme of the influence quantity of the environmental condition, the simulation modeling method and the simulation modeling process are provided. By establishing an equivalent model of a typical instrument circuit and analyzing the environmental conditions and the fault mode of the instrument, the output waveform of the circuit model which is not interfered by noise and is interfered by noise under the accident condition of the instrument can be obtained. And comparing the simulation result of the circuit model with the typical environment test result of the key component and/or the instrument identification test, and further correcting the simulation model if the threshold value is out of tolerance for evaluation conclusion and failure reason analysis. On the basis of availability evaluation, the circuit simulation method can predict the performance change trend of the instrument in an accident environment to a certain extent, and theoretically explains the influence reason of the environment on the instrument. The evaluation result of the method can be well applied to the management of serious accidents and the analysis of weak links of the nuclear power plant, and can also be used for improving the design of instruments for monitoring the serious accidents and improving the survival capability of the instruments under the serious accidents.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include such modifications and variations.