CABLE SELECTION METHOD AND CABLE SELECTION APPARATUS FOR FIRE PROTECTION IN A NUCLEAR POWER PLANT BASED ON A PROBABILISTIC SAFETY ANALYSIS

Abstract

The present application presents a cable selection method and a cable selection apparatus for fire protection in a nuclear power plant based on probabilistic safety analysis, and the cable selection method consists of: performing a quantitative analysis on an improved probabilistic fire safety analysis model to calculate and obtain a fire risk result for a nuclear power plant; obtaining an initial list of flame-resistant sheathed cables according to the fire risk result for the nuclear power plant; and identifying and designing cables in the initial list of flame-resistant sheathed cables with the improved probabilistic fire safety analysis model to obtain a quantitative fire risk result;and to judge whether the quantitative fire risk result satisfies a probabilistic safety objective, and if it does not, to add additional cables that may be affected by a fire within the initial list of flame-resistant coated cables until the quantitative fire risk result satisfies the probabilistic safety objective, and obtain a target list of flame-resistant cable protection. The cable selection method can quantitatively identify high-risk cables as requiring flame-resistant protection and optimize fire prevention investment in a nuclear power plant to achieve a balance between safety and economy with maximum reach.

Description

CABLE SELECTION METHOD AND CABLE SELECTION APPARATUS FOR FLAME PROTECTION IN A NUCLEAR POWER PLANT BASED ON A PROBABILISTIC SAFETY ANALYSIS Technical field The present application pertains to the technical field of nuclear power plant design, and specifically relates to a cable selection method and a cable selection apparatus for fire protection in a nuclear power plant based on probabilistic safety analysis (PSA). Preliminary art A large number of cables present in a nuclear power plant constitute a significant source of internal fire hazards, and once burned or damaged by fire, the cables will also have significant effects on the normal operation and safety functions of the nuclear power plant. Especially given the characteristics of fire spread, in the event of a major fire, it is very likely that a large number of cables... 1777455 of 60 some local regions may be damaged. If cables in different redundant safety trains are damaged by the same fire, serious damage to nuclear safety will occur. Therefore, for cables that may have a common failure mode in the nuclear power plant, flame-resistant coating or physical insulation is necessary. The traditional qualitative analysis method based on determinism is currently used in cable fire protection analysis. In the later stages of the construction design phase, a qualitative fire break analysis is performed for each fire area or fire zone in nuclear safety buildings, based on a cable database. A cable fire protection list is then determined through the identification, functional analysis, fire risk analysis of potential common fire mode points, and treatment of confirmed common fire mode points. The current deterministic method of cable fire protection analysis cannot provide quantitative risk results, and consequently, a balance between safety and economy cannot be achieved in the nuclear power plant with the resulting cable fire protection list. 1777455 of 60 Summary With reference to the aforementioned deficiencies in the prior art, the technical problem to be solved by means of this application is to present a cable selection method and a cable selection apparatus for flame protection in a nuclear power plant based on probabilistic safety analysis that can quantitatively identify high-risk cables as cables requiring flame protection and optimize investment in flame prevention in a nuclear power plant to achieve a balance between safety and economy with the maximum scope. An embodiment of the present application presents a method for selecting cables for fire protection in a nuclear power plant based on probabilistic safety analysis, which consists of: constructing an initial probabilistic fire safety analysis model; performing a circuit failure analysis and a post-fire human reliability analysis; replacing an analysis result in an initial probabilistic fire safety analysis model; and performing a fire scene analysis to acquire an improved analysis model. 1777455 of 60 fire-resistant probabilistic safety; the performance of a quantitative analysis on the improved probabilistic safety model in the event of a fire to calculate and obtain a fire risk result for a nuclear power plant; obtaining an initial list of fire-resistant coated cables according to the fire risk result of the nuclear power plant, and the identification and design of cables in the initial list of fire-resistant coated cables with the improved probabilistic fire-resistant safety model to obtain a quantitative fire risk result once the cables have been designed;and the fact of judging whether the quantitative fire risk result satisfies a probabilistic safety objective, and if it is not satisfactory, further obtaining of additional cables that may be affected by a fire according to the fire risk result of the nuclear power plant, adding the additional cables to the initial list of flame-resistant coated cables with the improved probabilistic safety analysis model until the quantitative fire risk result meets the probabilistic safety objective, and then stop adding cables to the initial list of flame-resistant coated cables and obtain a target (witness) list of flame-resistant protection of the cables. Preferably, after obtaining the target list of 1777455 of 60 fireproof protection of cables, the cable selection method further consists of: calculating a risk result for a group of cables in the target list of fireproof protection of cables depending on whether the group of cables is coated or not, comparing a first risk result when the group of cables is not coated with a second risk result when the group of cables is coated, and obtaining an optimized target list of fireproof protection of cables according to a comparison result. Preferably, obtaining the optimized target list of cable flame protection according to the comparison result includes: if the comparison result shows that a difference between the first risk result when the cable group is not sheathed and the second risk result when the cable group is sheathed is less than a predetermined threshold value, removing the cables corresponding to the cable group from the target list of cable flame protection to obtain the optimized target list of cable flame protection; and if not, retaining the cables corresponding to the cable group in the target list of cable flame protection. Preferably, the default threshold value is 0.1% of a 1777455 of 60 probabilistic safety index requirement. Preferably, the construction of an initial probabilistic safety analysis model includes: the construction of a logical risk model from event trees, fault trees and basic information based on a level 1 internal event probabilistic safety analysis model for a nuclear power plant by taking into consideration the fire risk characteristics; obtaining a division of fire compartments, devices and cables on which the probabilistic fire safety analysis is performed, and an ignition frequency of the fire compartments, and taking the division of fire compartments, devices and cables, and the ignition frequency of the fire compartments as input conditions of the logical risk model to obtain the initial probabilistic fire safety analysis model. Preferably, obtaining the division of fire compartments, devices and cables on which the probabilistic fire safety analysis is performed, and the ignition frequency of the fire compartments includes: defining an analysis boundary of the nuclear power plant, and dividing a region within the analysis boundary of the nuclear power plant 1777455 of 60 in a plurality of fire compartments based on a fireproof division in a fire control design; identify the devices of the probabilistic fire safety analysis in the fire compartments, and determine a range of the probabilistic fire safety analysis to obtain the devices on which the probabilistic fire safety analysis is performed; identify the cables of the probabilistic fire safety analysis in the fire compartments based on the devices on which the probabilistic fire safety analysis is performed, and construct a correlation between the cables of the probabilistic fire safety analysis and the devices of the probabilistic fire safety analysis; identifying an ignition source in the fire compartments to calculate and obtain the ignition frequency of the fire compartments. Preferably, obtaining the devices on which the probabilistic fire safety analysis is performed includes: constructing an initial list of devices for probabilistic fire safety analysis, and adding all devices that may be damaged by fire to an initial list of devices for probabilistic fire safety analysis according to the system design information, the information of the 1777455 of 60 arrangement of technological and electrical devices of the nuclear power plant; the performance of a failure mode and effects analysis on the devices in the initial list of devices for probabilistic fire safety analysis, and the removal of devices whose failures will affect the normal operation and safe shutdown of the nuclear power plant from the initial list of devices for probabilistic fire safety analysis. Preferably, the ignition source includes both fixed and temporary ignition sources, and the calculation and obtaining of the ignition frequency of the fire compartments includes: calculating a sum of frequencies ^is.r of all ignition sources in the fire compartments to obtain the ignition frequency of the fire compartments, where the ignition frequency ^isj of a single ignition source is calculated using the following formula: ^ISJ=AAAspL where A is a universal ignition frequency of the IS ignition source; wl is a positional weighting factor of the ignition sources; 1777455 of 60wis.|.l is an ignition source weight factor that indicates a quantity weight factor of ignition sources IS corresponding to a region L of the nuclear plant in a fire compartment J. Preferably, performing a circuit failure analysis includes: analyzing the failure modes of cables or circuits that may cause a target device to fail and determining a probability value for each failure mode; and performing a post-fire human reliability analysis includes: assessing the effects of fire on human actions using a human factors analysis, and determining and quantifying human failure events that occurred during the development and quantification of the probabilistic fire safety analysis model and a probability value for each human failure event. Preferably, obtaining an initial list of flame-resistant sheathed cables in accordance with the fire risk assessment of the nuclear power plant includes: identifying the high-risk cables according to the fire risk assessment of the nuclear power plant, and merging the high-risk cables with a list of flame-resistant sheathed cables obtained based on the determination to obtain an initial cable list with 1777455 of 60 fireproof coating. Furthermore, another embodiment of the present application presents a cable selection apparatus for fire protection in a nuclear power plant based on probabilistic safety analysis, comprising a design module, a calculation module, a obtaining module and a determination module, wherein the design module is configured to build an initial model of probabilistic fire safety analysis;where the calculation module is connected to the design module and is configured to perform a circuit failure analysis and a post-fire human feasibility analysis, substitute an analysis result into an initial probabilistic fire safety analysis model, and perform a first fire scene analysis to obtain an improved probabilistic fire safety analysis model, where the calculation module is further configured to perform a quantitative analysis of the improved probabilistic fire safety analysis module to calculate and obtain a fire risk result for a nuclear power plant; where the acquisition module is connected to the calculation module and is configured to obtain an initial list of fire-resistant sheathed cables according to the fire risk result for the nuclear power plant, and identify and design cables; 1777455 of 60 in the initial list of flame-resistant coated cables with the improved probabilistic flame safety analysis model to obtain a quantitative fire risk result once the cables have been designed;and where the determination module is connected to the acquisition module and is configured to judge whether the quantitative fire risk result satisfies a probabilistic safety objective, and if it does not, further obtain additional cables that may be affected by a fire according to the fire risk result of the nuclear power plant, add the additional cables to the initial list of flame-resistant coated cables, and perform identification and design on the initial list of flame-resistant coated cables with the improved probabilistic flame-resistant safety analysis model until the quantitative fire risk result satisfies the probabilistic safety objective, and then stop adding cables to the initial list of flame-resistant coated cables and obtain a target list of flame-resistant protection of the cables. Preferably, the cable selection device for fire protection in a nuclear power plant based on probabilistic safety analysis also comprises an optimization module, where the calculation module is further configured 1777455 of 60 to calculate a risk result for a group of cables in the target list of fire protection for cables depending on whether the group of cables is coated or not, and where the optimization module is connected to the calculation module and the determination module and is configured to compare a first risk result when the group of cables is not coated with a second risk result when the group of cables is coated according to the quantitative fire risk result obtained by means of the calculation module, and obtain an optimized target list of fire protection for cables according to a comparison result. This application has the following advantageous effects: it presents a method for selecting cables requiring flameproofing based on a probabilistic safety analysis (PSA) technology. In this method, cables of significant risk are quantitatively identified to obtain a target list of cables requiring flameproofing. The selection method can not only identify common-mode failures and overlapping failures with complex logic, but can also accurately and quantitatively assess the risk variation of a nuclear power plant caused by its cladding. 1777455 of 60 of each cable, so that maximum safety improvement can be achieved with minimal economic investment. At the same time, the use of this method can also effectively reduce conservatism. Brief description of the figures Figure 1 is a flowchart of a cable selection method for fire protection in a nuclear power plant based on probabilistic safety analysis in accordance with Realization 1 of the present application; Figure 2 is a flowchart of the cable selection method for fire protection in a nuclear power plant based on probabilistic safety analysis in accordance with Implementation 2 of this application; Figure 3 is a first schematic diagram of an event tree model in a probabilistic fire safety analysis according to the specific realizations of the present application; Figure 4 is a second schematic diagram of an event tree model in a probabilistic fire safety analysis according to the specific realizations of the present application; and 1777455 of 60 Figure 5 is a third schematic diagram of an event tree model in a probabilistic fire safety analysis according to the specific realizations of the present application. Detailed description of the achievements In order to make the subject matter, technical solution, and advantages of this application clear and evident, it shall be described in detail below with regard to figures and embodiments. It is understood that the description of specific embodiments is intended solely to explain, not to restrict, this application. Implementation 1: As shown in Figure 1, the present embodiment presents a method for selecting cables for fire protection in a nuclear power plant based on probabilistic safety analysis, which consists of the following steps: Step 101: Construction of an initial probabilistic fire safety analysis model (fire PSA model); Step 102: Performing a circuit failure analysis and a 1777455 of 60 post-fire human reliability analysis, replacing an analysis result in the initial probabilistic fire safety analysis model, and performing a fire scene analysis to obtain an improved probabilistic fire safety analysis model; Step 103: Performing a quantitative analysis on the improved probabilistic fire safety analysis model to calculate and obtain a fire risk result for a nuclear power plant; Step 104: Obtaining an initial list of flame-resistant sheathed cables according to the fire risk result of the nuclear power plant, and identifying and designing cables in the initial list of flame-resistant sheathed cables with the improved model of the probabilistic fire safety analysis to obtain a quantitative fire risk result once the cables have been designed; and Step 105: Judge whether the quantitative fire risk result satisfies a probabilistic safety objective, and if it does not, further obtain additional cables that may be affected by a fire according to the fire risk result of the nuclear power plant, adding the additional cables to the initial list of flame-resistant sheathed cables, and performing the identification and 1777455 of 60 design of the initial list of flame-resistant coated cables with the improved probabilistic flame safety analysis model until the quantitative flame risk result meets the probabilistic safety objective, and then stop adding cables to the initial list of flame-resistant coated cables and obtain a target list of flame protection of the cables. In the present embodiment, cables requiring flame-resistant sheathing are identified and designed using an improved probabilistic flame-resistant safety analysis model to obtain a quantitative fire risk result. Then, it is determined whether additional cables that could be affected by a fire are added to the initial list of flame-resistant sheathed cables, depending on whether the quantitative fire risk result satisfies the probabilistic safety objective. This yields the target list of flame-resistant cables. Compared to the flame-resistant cable protection list obtained using determinism, the target list of flame-resistant cables obtained in the present embodiment is based on quantitative analysis and is more precise, allowing the balance between safety and economy to be achieved to the greatest extent. Optionally, after obtaining the target list of 1777455 of 60 fireproof cable protection, the method of selecting cables for fireproof protection in the nuclear power plant based on probabilistic safety analysis further consists of: calculating a first risk result and a second risk result of a group of cables in the target list of fireproof cable protection depending on whether the group of cables is coated or not, comparing the first risk result when the group of cables is not coated with the second risk result when the group of cables is coated, and obtaining an optimized target list of fireproof cables according to a comparison result. In the present embodiment, the cables on the target list for fireproofing are divided into multiple cable groups, and the corresponding risk results are calculated for each cable group, both when sheathed and when unsheathed. The number of cables on the target list for fireproofing is further optimized based on a comparison of these two risk results, and the economic investment in fire prevention protection can be further optimized according to a prerequisite that ensures the safety of the nuclear power plant. Optionally, obtaining the optimized target list 1777455 of 60 of the flameproof protection of cables according to the comparison result includes: if the comparison result shows that a difference between the first risk result when the cable group is not coated and the second risk result when the cable group is coated is less than a predetermined threshold value, the cables corresponding to the cable group are removed from the target list of flameproof protection of cables to obtain the optimized target list of flameproof protection of cables; and if this is not the case, the cables corresponding to the cable group are retained in the target list of flameproof protection of cables. Optionally, the default threshold value is 0.1% of a probabilistic safety index requirement. In the present embodiment, if the difference between the first risk result (when the cable group is uncoated) and the second risk result (when the cable group is coated) for a cable group A is less than 0.1% of the probabilistic safety index requirement, this means that the first risk result when cable group A is uncoated is roughly equal to the second risk result when cable group A is coated, while the coating will entail a considerable economic investment. To achieve a balance between the 1777455 of 60 safety and economy in the nuclear power plant, the corresponding cables included in cable group A are removed from the target list of flameproof cable protection. Optionally, the construction of the initial probabilistic fire safety analysis model in Step 101 of the present embodiment includes: the construction of a logical risk model from event trees, fault trees, and basic information based on a level 1 internal event probabilistic safety analysis model for a nuclear power plant by taking into consideration the fire risk characteristics; obtaining a division of compartments, fire devices, and cables on which the probabilistic fire safety analysis is performed, and a fire compartment ignition frequency; and taking the compartment division, fire devices and cables, and fire compartment ignition frequency as input conditions of the logical risk model to obtain the initial probabilistic fire safety analysis model. In the present embodiment, a specific processing procedure is carried out for obtaining the division of the compartments, devices and fire-fighting cables on which it is performed 1777455 of 60 the probabilistic fire safety analysis, and the ignition frequency of the fire compartments shall be described, in detail, in Implementation 2. Optionally, performing the circuit failure analysis includes analyzing the failure modes of cables or circuits that can cause a key device to fail and determining a probability value for each failure mode; performing the post-fire human reliability analysis includes evaluating the effects of the fire on human actions using a human factors analysis, and determining and quantifying the human failure events that occurred during the development and quantification of the probabilistic fire safety analysis model and a probability value for each human failure event. Optionally, obtaining an initial list of flame-resistant sheathed cables according to the fire risk result of the nuclear power plant includes: identifying the high-risk cables according to the fire risk result of the nuclear power plant, and merging the high-risk cables with a list of flame-resistant sheathed cables obtained based on the determination to obtain an initial list of flame-resistant sheathed cables. 1777455 of 60 In the present embodiment, the initial list of flame-resistant cables is generated by merging the high-risk cables obtained in Step 103 of this embodiment, based on the fire risk assessment of the nuclear power plant, with the deterministically derived list of flame-resistant cables. This results in a more comprehensive initial list of flame-resistant cables to meet the safety requirements of the nuclear power plant. Furthermore, by optimizing the subsequently obtained target list of flame-resistant cables, specific cables can be conservatively selected from the deterministically derived list of flame-resistant cables. This makes the present embodiment advantageous for achieving an optimal list of flame-resistant cables that balances safety and cost-effectiveness. Implementation 2: Figure 2 shows a flowchart of the cable selection method for fire protection in a nuclear power plant based on probabilistic safety analysis according to the present embodiment, and consists of the following steps: 1777455 of 60 Step (1): divide regions that may be affected by a fire, i.e.: achieve a result of division of fire compartments. A nuclear power plant analysis boundary is defined, and a region within that boundary is divided into multiple fire compartments based on a fire-resistant partition in a fire control design. The purpose of defining the nuclear power plant analysis boundary is to ensure that the defined boundary covers all regions that make a potentially significant contribution to fire hazards. The nuclear power plant analysis boundary extends from a protected area of ​​the nuclear power plant and includes all regions of the power plant related to the normal and emergency operation of a reactor, support systems, and power generation (e.g., a steam turbine building).The region within the analysis boundary of the nuclear power plant must be divided into a plurality of fire compartments to conduct a probabilistic safety analysis (PSA) of an internal fire. The purpose of dividing the fire compartments is to divide the nuclear power plant into a series of practical analysis units. 1777455 of 60 corresponding to devices and cables in the nuclear power plant to investigate the effects of fire. In the present embodiment, for a nuclear power plant with a pressurized water reactor as an example, the regions that may be affected by a fire include a reactor building, a safety building, an electrical building, an auxiliary nuclear building, a diesel generator building and the like, and the fire compartments include a fireproof zone of the reactor building, a medium-pressure safety injection pump room of the safety building, a storage battery train A room, an AC or DC uninterruptible power distribution train A room, an electronic instrument control room and the like up to several hundred compartments. Step (2): Identifying probabilistic safety analysis devices in fire compartments. The devices used in the probabilistic fire safety analysis of fire compartments are identified, and a range for the probabilistic fire safety analysis is determined to obtain the devices on which the probabilistic fire safety analysis is performed. The devices used in the probabilistic analysis of 1777455 of 60 fire safety refers to the power plant devices involved in a probabilistic fire safety analysis response model for the nuclear power plant. Metals with high melting points, such as steel, are unlikely to be damaged by a fire, and passive mechanical devices such as a manual valve, check valve, filter, heat transfer system, and the like need not be included in a probabilistic fire safety analysis device list.To ensure the integrity of the probabilistic fire safety analysis device list, an initial list is prepared. All devices that could be damaged by fire are then added to this initial list based on system design data and information regarding the layout of the nuclear power plant's electrical and technological equipment. This initial list includes all structures, systems, and devices whose fire failure could directly damage the reactor core or trigger an initiating event, as well as all those necessary to mitigate the initiating event and prevent the nuclear power plant from reaching a critical condition. 1777455 of 60 stable safe (SSC), and a range of analysis of the probabilistic fire safety analysis is determined by a range of the list of probabilistic fire safety analysis devices. All devices that could be affected by fire are included in the initial list of devices for the probabilistic fire safety analysis. However, some of these devices do not affect the normal operation and safe shutdown of the nuclear power plant and therefore do not need to be designed using a probabilistic fire safety analysis model. Consequently, it is necessary to further refine or filter the initial list of devices for the probabilistic fire safety analysis to obtain a list that adequately supports the analysis and design work for the probabilistic fire safety analysis of internal fires. Before filtering the initial probabilistic fire safety analysis list, a Failure Mode and Effects Analysis (FMEA) is performed on the devices in the initial probabilistic fire safety analysis list to analyze the consequences that may be caused by the different failure modes in a fire, and then it is determined whether the corresponding 1777455 of 60 devices are retained in the probabilistic fire safety analysis device list according to some filtering criteria (e.g., devices whose failures will not affect normal operation and safe shutdown of the nuclear power plant are removed from the initial probabilistic fire safety analysis device list). In the present embodiment, the train room A of an uninterrupted alternating current or direct current power distribution system of a nuclear power plant with a pressurized water reactor is taken as an example of the fire compartments, and the main devices in the fire compartments are listed below in Table 1. Table 1. Probabilistic fire safety analysis devices Device Code Device Type Device Description EDA001TB Distribution Board 110V DC Distribution Cabinet 1777455 of 60 EDG001TB Distribution Board 110V DC Distribution Cabinet ECC001TB Distribution Board 48V DC Distribution Cabinet EAG001TB Distribution Board 220V AC Distribution Cabinet EDA001RD Storage Battery Charger and Inverter 110V Storage Battery Charger EDA002RD Storage Battery Charger and Inverter 110V Storage Battery Charger ECC001RD Storage Battery Charger and Inverter 48V Storage Battery Charger ECC002RD Battery Charger and Inverter 1777455 of 60 48V storage battery EAG001DL Storage battery charger and inverter 220V inverter EAG001TR Shunt transformer Step (3): Identification of fireproof safety probabilistic analysis cables in fire compartments. Fire safety probabilistic analysis cables refer to the cables relevant to fire safety probabilistic analysis devices. In selecting fire safety probabilistic analysis cables based on the fire safety probabilistic analysis list, cables are selected that include power supply cables, control cables, disposal cables, and instrument cables, etc., relevant to the fire safety probabilistic analysis devices. In this step, all cables that could affect the operation of the devices are listed in a fire safety probabilistic analysis list, and a correlation between the analysis cables is established. 1777455 of 60 fire safety probabilistic and fire safety probabilistic analysis devices. In the present embodiment, the correlation between “cables”, “associated devices” and “straightening positions” is built into the probabilistic fire safety analysis cable list for each cable in the fire compartments, and the main cables in the fire compartments are listed below in Table 2. The associated devices in Table 2 refer to the devices associated with the cables in the fire compartments whose operation may be affected.For example, one end of the fire safety probabilistic analysis cables in one fire compartment is connected to the fire safety probabilistic analysis devices in the fire compartment, and the other end of the fire safety probabilistic analysis cables is connected to devices whose operation may be affected by cable failures in the other fire compartment, or all the fire safety probabilistic analysis devices respectively connected to both ends of the fire safety probabilistic analysis cable in the fire compartment are in the other fire compartment. 1777455 of 60 Table 2. Probabilistic analysis of fire-resistant safety cables Serial Cable Code Associated Device Adverse Failure Mode TFAC0595 A TFA081VV Closure Failure EAWB0234 A TFA081VV Closure Failure PRSC0164 A PRS208VV Spurious Closure PRSC0169 A PRS308VV Spurious Closure ETEB0242 A PRS208VV Spurious Closure ETEB0244 A PRS308VV Spurious Closure ETEB0241 A PRS208VV Spurious Closure ETEB0243 A PRS308VV Spurious Closure ETEB0240 A PRS108VV Spurious Closure PRSC0159 A PRS108VV Spurious Closure ETEB0239 A PRS108VV Spurious Closure ETEB0241 A PRS208VV Spurious Closure ETEB0243 A PRS308VV Spurious Closure PCSC0102 A PCS101VD Operation 1777455 of 60 Serial cable code Associated device Adverse failure mode Spurious PCSC0112 A PCS103VD Spurious operation PCSC0122 A PCS112VD Spurious operation PCSC0202 A PCS201VD Spurious operation PCSC0212 A PCS203VD Spurious operation PCSC0222 A PCS212VD Spurious operation PCSC0302 A PCS301VD Spurious operation PCSC0312 A PCS303VD Spurious operation PCSC0322 A PCS312VD Operation 1777455 of 60 Serial cable code Associated device Spurious adverse failure mode Step (4): Identify an ignition source and calculate an ignition frequency for the fire compartments. An ignition source is a source of fire that can cause a fire, and ignition sources in a nuclear power plant include both fixed and temporary ignition sources. Fixed ignition sources refer to ignition sources with fixed positions and known combustion parameters that were already present in a nuclear power plant design, such as an electrical cabinet, an electric motor, etc. Temporary ignition sources refer to temporary fires with indeterminable positions and combustion parameters that are introduced through temporary storage or human activity. Calculating ignition frequency is fundamental to fire scene analysis and fire quantification. The ignition frequency of a fire compartment is the sum of the ignition frequencies (εisj) of all ignition sources within the compartments. 1777455 of 60 against fire. The ignition frequency ^isj of the ignition source is calculated using the following formula: ^is.f=where ^is is a universal ignition frequency of the IS ignition source; wl is a positional weighting factor of the ignition sources; wis,|.l is an ignition source weight factor that indicates a quantity weight factor of the ignition sources IS corresponding to a region L of the nuclear plant in a fire compartment J. In the present embodiment, fixed ignition sources include storage batteries, electric pumps, diesel generators, air compressors, chargers, electrical cabinets, busbars, junction boxes, hydrogen tanks, etc. Temporary ignition sources include cable fires caused by welding or cutting, temporary fires caused by welding or cutting, temporary high-temperature work, etc. The ignition frequency is calculated by counting the number of ignition sources in the 1777455 of 60 fire compartments, and the ignition frequency of the fire compartments is shown below in Table 3. Table 3. Ignition frequency of fire compartments Power Plant Operating Status Initiating Event Initiating Event Frequency ( / reactor / year) Fixed Ignition Sources Temporary Ignition Sources Total A: Full Power EDA Loss 6.29E-04 3.33E-05 6.62E-04 B: Low Power EDA Loss 2.54E-06 1.35E-08 2.67E-06 C: SG Cooling Shutdown Mode EDA Loss 4.76E-06 9.48E-07 5.71E-06 1777455 of 60 D: RHR cooling shutdown mode EDA loss 1.35E-05 2.68E-06 1.62E-05 E: Micro loop aperture EDA loss 4.21E-06 8.35E-07 5.05E-06 F: Loop aperture EDA loss 6.35E-06 1.26E-06 7.61E-06 Step (5): Development of a probabilistic fire safety analysis model The probabilistic fire safety analysis model is a logical risk model constructed from event trees, fault trees, and basic information, taking into account the characteristics of the fire risk. A fire compartment division, the selection of devices and cables, and the calculation of the ignition frequency are used as input conditions for the logical risk model. Using the probabilistic fire safety analysis model, a realistic response for the nuclear power plant in the event of a fire can be designed, and the ignition frequency can be calculated. 1777455 of 60 core damage (CDF) of the reactor caused by fire, and the risks caused by fire in the nuclear power plant can be quantified. The construction of the probabilistic fire safety analysis model in the nuclear power plant is completed based on an existing probabilistic internal event safety analysis model of level 1 that has high-energy and low-energy and shutdown conditions to reflect the actual circumstances of the design, completion, and operation (i.e., existing operational experiences) of the nuclear power plant. Since the fire safety probabilistic analysis model is built on the basis of the level 1 internal event safety probabilistic analysis model, the following technical elements in the level 1 internal event safety probabilistic analysis model are also included in the fire safety probabilistic analysis model: Analysis of the operational status of the power plant; Analysis of the initiating event; Analysis of the event sequence; System analysis; 1777455 of 60 Human reliability analysis; Data analysis. In the present embodiment, the initiating event in the fire compartments is the loss of a DC power source in train A. The event sequence analysis is primarily performed in accordance with existing regulations for accident handling and can be transferred to event trees of the internal event (loss of DC power source in train A) for processing. Devices in a fire will have specific failure modes and failure probabilities, and it is necessary to modify or complete the fault trees in an internal event model. The presence of a fire will have several adverse effects on the execution of human actions, and the human reliability analysis recalculates a failure probability for events due to human error in accordance with the effects of the fire.The fire risk model in fire compartments is shown, as an example, in Figures 3-5. Step (6): Performing a circuit failure analysis The primary purpose of circuit failure analysis is to 1777455 of 60 analyze the failure modes of cables or circuits that cause a failure of a target device and determine a probability value for the occurrence of each failure mode. A circuit failure mode analysis (FMA) is performed by conducting a detailed analysis of the cables or circuits relevant to the target device. This analysis determines the device's response to different cable or circuit failure modes and identifies cables that will not affect the device's necessary functions. Circuit failures are primarily caused by cable exposure to fire, which damages the cable insulation and leads to circuit malfunction. Therefore, a circuit FMA mainly involves analyzing cable failure modes and the corresponding circuit response to those failure modes. In this embodiment, a probability value for the occurrence of each circuit failure mode is determined according to the circuit characteristics. The results of the circuit failure analysis of the fire compartments are shown below in Table 4. Table 4. Cables that will fail due to fire 1777455 of 60 Serial cable code Associated device Adverse failure mode Failure reason (ground short / hot brittle) Failure probability value TFAC0595 A TFA081VV Closure failure Grounding 1 EAWB0234 A TFA081VV Closure failure Grounding 1 PRSC0164 A PRS208VV Spurious closure Hot brittle 0.4 PRSC0169 A PRS308VV Spurious closure Hot brittle 0.4 ETEB0242 A PRS208VV Spurious closure Hot brittle 0.4 ETEB0244 A PRS308VV Spurious closure Hot brittle 0.4 ETEB0241 A PRS208VV Spurious closure Hot brittle 0.4 1777455 of 60 Serial cable code Associated device Adverse failure mode Failure reason (short to ground / brittle when hot) Failure probability value ETEB0243 A PRS308VV Spurious closure Brittle when hot 0.4 ETEB0240 A PRS108VV Spurious closure Brittle when hot 0.4 PRSC0159 A PRS108VV Spurious closure Brittle when hot 0.4 ETEB0239 A PRS108VV Spurious closure Brittle when hot 0.4 ETEB0241 A PRS208VV Spurious closure Brittle when hot 0.4 ETEB0243 A PRS308VV Spurious closure Brittle when hot 0.4 PCSC0102 A PCS101VD Spurious operation Not analyzed 1 1777455 of 60 Serial cable code Associated device Adverse failure mode Failure reason (short to ground / hot brittle) Failure probability value PCSC0112 A PCS103VD Spurious operation Not analyzed 1 PCSC0122 A PCS112VD Spurious operation Not analyzed 1 PCSC0202 A PCS201VD Spurious operation Not analyzed 1 PCSC0212 A PCS203VD Spurious operation Not analyzed 1 PCSC0222 A PCS212VD Spurious operation Not analyzed 1 PCSC0302 A PCS301VD Spurious operation Not analyzed 1 PCSC0312 A PCS303VD Spurious operation Not analyzed 1 1777455 of 60 Serial cable code Associated device Adverse failure mode Reason for failure (short to ground / hot brittle) Failure probability value PCSC0322 A PCS312VD Spurious operation Not analyzed 1 Step (7): Conducting a post-fire human reliability analysis The effects of fire on human actions are evaluated using appropriate human factors analysis, and the determination and quantification of human error events occurring during the development and quantification of the probabilistic fire safety analysis model and a probability value for each human error event. In the Human Reliability Analysis (HRA) of a fire, the human reliability analysis before the initiating event is the same as the probabilistic safety analysis of an internal event, and a human reliability analysis after the initiating event (category C) is primarily performed in relation to a method recommended by the NUREG-1921 guidelines. 1777455 of 60 is carried out in three stages of testing, scope and detailed analysis. In this embodiment, a human response procedure following a fire is derived from a field human factors interview at a nuclear power plant. The human response to the fire has the following characteristics: 1) a more complex accident scene; 2) higher personnel pressure and a greater workload; 3) worse environmental conditions for carrying out an action; 4) relatively low skill due to a lack of training and experience in fire scene investigation; and 5) a specific analysis required for the fire in a master control room. In human reliability analysis, a quantitative analysis is performed based primarily on the NUREG-1921 guidelines, in which fire scenes are divided mainly into master control room fires and non-master control room fires. Human error events recently added to the probabilistic fire safety analysis, such as an operator leaving their workstation and leaving the master control room in master control room fire scenes, are quantified primarily through expert testimony due to the complexity of their analysis. 1777455 of 60 quantification. Step (8): Conducting a fire scene analysis A fire scene is a set of elements that describes a fire event. The fire scene is defined based on the characteristics and results of a fire originating from one or more ignition sources. A detailed fire scene analysis is necessary for the highest-risk compartments. The compartment-scale fire analysis is refined from the fire scene analysis and incorporated into the probabilistic fire safety analysis model to assess the fire risk of each fire scene. A preliminary quantitative analysis was conducted on fire compartment units, and a preliminary fire risk assessment was performed based on the conservative assumption that a fire originating from any ignition source could damage all devices and cables within the compartments. However, in reality, the development and spread of a fire is closely linked to the types of ignition sources, environmental conditions, and other factors, and therefore some 1777455 of 60 ignition sources may only affect a limited area and will not damage all devices and cables in the fire compartments. As a result, in order to assess the fire risk more effectively, it is necessary to perform the analysis at the scale of the fire scene for the fire compartments preserved in the quantitative test. In the present embodiment, a preliminary quantitative result for the fire compartments is 7.84E-05 / reactor / year, and it is necessary to perform a detailed analysis and replace the results of the circuit failure analysis and the post-fire human reliability analysis in the probabilistic fire safety analysis model. Step (9): Quantifying a fire risk outcome Through a quantitative analysis of the probabilistic fire safety analysis model, a fire risk for the nuclear power plant is calculated and obtained, and the main contribution of fire to the reactor core damage frequency is determined. The specific calculation method is a technology known in the prior art, in which a logical model is built in software, a minimum failure set (MCS) is calculated and generated using the logic of the logical model, and then a calculation is performed using the data inputs in the logical model. 1777455 of 60 Uncertainty analysis The purpose of uncertainty analysis is to qualitatively address and quantitatively evaluate the uncertainty in the analysis results. The probabilistic safety analysis model attempts to simulate the actual circumstances of the nuclear power plant, but sometimes, in order to simplify the model and facilitate the work, it is unavoidable to introduce some simplified or idealized assumptions to the complex procedures and phenomena, which will introduce uncertainty into the analysis results. Sensitivity analysis The purpose of sensitivity analysis includes evaluating the sensitivity of reactor core damage frequency to data such as initiating events, human errors, etc., analyzing and addressing design assumptions that have a potentially significant impact on the results, and determining a series of sensitivity analysis cases, changing the parameter values ​​of the cases by a factor of 10 (the sensitivity factor is usually set at 10) to calculate the degree of influence of those. In the present implementation, the quantitative analysis is carried out on the probabilistic fire safety analysis model, and 1777455 of 60 calculates and a quantitative result is obtained from the fire scene analysis of the compartments shown below in Table 5, which is a reference risk result without considering the fireproof protection of the cables. Table 5. Reference risk result without considering the flame-resistant protection of the cables Power Plant Operating Status Initiating Event Frequency ( / reactor / year) CDF ( / reactor / year) A: Full Power EDA Loss 6.62E-04 6.63E-08 B: Low Power EDA Loss 2.67E-06 2.58E-10 C: SG Cooling Shutdown Mode EDA Loss 5.71E-06 6.96E-09 D: Loss Mode 1.62E-05 2.49E-09 1777455 of 60 RHR cooling closure EDA E: micro loop opening EDA loss 5.05E-06 3.43E-10 F: loop opening EDA loss 7.61E-06 1.59E-08 Σ 9.66E-04 9.23E-08 Step (10): Identify and design an initial list of flame-resistant coated cables Cables posing a significant risk are identified based on a quantitative result from an internal probabilistic fire safety analysis model. These high-risk cables are then compared and combined with a deterministic list of fire-resistant sheathed cables to generate the initial list of such cables. These cables are then identified and designed within the probabilistic fire safety analysis model. In the present embodiment, the cables in the fire compartments include an auxiliary water supply system 1777455 of 60 (TFA), a secondary passive lateral waste heat removal (PRS) system, and a passive containment heat removal (PCS) system. Since the devices relevant to TFA and PRS in Table 4 are essential to perform the same safety function, these cables must be protected simultaneously; otherwise, removing a flame-resistant coating from either cable will result in a core damage frequency greater than 1E-8 / reactor / year. The PCS is employed to perform another safety function and is designed in a three-train configuration. Probabilistic safety analysis indicates that at least two successfully functioning PCS trains are required for the PCS system to perform its function; therefore, it is ensured that at least two trains of the PCS cables in Table 4 are coated to prevent fire.The target cables corresponding to TFA, PRS and PCS are identified in the probabilistic fire safety analysis model, and the probabilistic fire safety analysis model is modified according to the following three schemes:. 1. To protect the cables relevant to TFA and PRS; 2. To protect a train from PCS cable; 3. To protect two trains from PCS cables. 1777455 of 60 Step (11): Judge whether a quantitative fire risk outcome satisfies a probabilistic safety objective The probabilistic fire safety analysis model with the initial list of flame-resistant coated cables contemplated in Step (9) is quantified, and if the result of the quantitative risk analysis does not satisfy the probabilistic safety target (e.g., in China: CDFall is 1E-5 / reactor / year, and LRFall is 1E-6 / reactor / year), other key cables that may be affected by fire are identified by means of the probabilistic fire safety analysis model, and it is continually requested that the flame-resistant coating be increased until the probabilistic safety target is satisfied. In the present embodiment, the probabilistic fire safety analysis model that has the three schemes in Step (10) is quantified so that the quantitative result of the fire risk satisfies the probabilistic safety objective. Step (12): Calculate a risk variation depending on whether the cables are sheathed or not Through repeated iterations of a cable fire protection list and a quantitative calculation of the probabilistic safety model, the risk variation is calculated depending on whether the cable group 1777455 of 60 is sheathed or not. On the precondition that the probabilistic safety objective is met, the risks of various schemes (i.e., different cable groups) are compared and analyzed, and reasonable testing criteria are adopted. For a scenario in which the risk increase is small, the cables may not be fire-sheathed. An acceptable risk increase can be calculated as follows: A general requirement for the CDFall or LRFall safety probabilistic index is determined according to the nuclear safety regulatory requirements of the country where the nuclear power plant is located. If removing the flameproof coating from a given cable results in an increase in the CDF of less than 0.1% of the safety probabilistic index requirement, the removal is acceptable. For example, in China, CDFall is 1E-5 / reactor / year, and LRFall is 1E-6 / reactor / year. Therefore, if removing the flameproof coating from a given cable results in an increase in the CDF of less than 1E-8 / reactor / year and an increase in the LRF of less than 1E-9 / reactor / year, the removal is acceptable. In the present embodiment, a calculation is performed on a first scene in which the target cables are sheathed and a second scene in which the target cables are not sheathed. 1777455 of 60 respectively and the core damage frequencies of the two scenes are evaluated. The scene in which the cables are not sheathed is taken as the reference scene, and the risk results of the three flameproofing schemes are calculated respectively, as shown below in Table 6. Table 6. Risk results obtained when considering different fireproofing schemes for cables POS (Plant Operating Status) Reference Scheme ( / reactor / year) To protect the cables relevant to TFA and PRS; ( / reactor / year) To protect one PCS cable train; ( / reactor / year) To protect two PCS cable trains. ( / reactor / year) A: Full power 6.63E-08 1.13E-09 6.63E-08 5.24E-08 B: Low power 2.58E-10 1.99E-12 2.58E-10 2.03E-10 1777455 of 60 POS (Plant Operating Status) Reference Scheme ( / reactor / year) To protect the cables relevant to TFA and PRS; ( / reactor / year) To protect one PCS cable train; ( / reactor / year) To protect two PCS cable trains. ( / reactor / year) C: Cooling shutdown mode SG 6.96E-09 5.59E-11 6.96E-09 6.84E-09 D: Cooling shutdown mode RHR 2.49E-09 2.49E-09 2.49E-09 2.08E-09 E: Loop micro-opening 3.43E-10 3.43E-10 3.43E-10 2.92E-10 1777455 of 60 POS (Plant Operating Status) Reference Scheme ( / reactor / year) To protect the cables relevant to TFA and PRS; ( / reactor / year) To protect one train of the PCS cable; ( / reactor / year) To protect two trains of the PCS cables. ( / reactor / year) F: loop opening 1.59E-08 1.59E-08 1.59E-08 1.59E-08 Σ 9.23E-08 1.99E-08 9.23E-08 7.77E-08 Step (13): Obtaining an optimized list of flameproof cable protection Through repeated iterations of Steps (10) to (12), the flameproofing schemes for the cables are compared and analyzed. Given the prior condition that the probabilistic safety objective is met, an optimal solution is selected that concurrently provides both safety and economy, resulting in a final optimized list of flameproofing solutions for the cables. In the present implementation, through comparison and analysis of Based on the 60 risk results from Table 6 (1777455), it is concluded that the cable protection scheme relevant to TFA and PRS offers the greatest risk-balancing benefit. Specifically, it is determined that cables EAWB0234, TFAC0595, ETEB0242, ETEB0241, and PRSC0164... ETEB0244, ETEB0243, PRSC0169, ETEB0240, ETEB0239, PRSC0159 of the compartments are selected for fireproof protection to reduce fire risks. For high-risk fire compartments throughout the nuclear power plant, fireproof cables can be selected according to the preceding steps. Implementation 3: The present embodiment presents a cable selection device for fire protection in a nuclear power plant based on probabilistic safety analysis, comprising a design module, a calculation module, a data acquisition module, and a determination module, wherein the design module is configured to construct an initial model of probabilistic fire safety analysis; wherein the calculation module is connected to the design module and is configured to perform a circuit failure analysis and 1777455 of 60 a post-fire human feasibility analysis, the substitution of an analysis result in an initial probabilistic fire safety analysis model, and the performance of a first fire scene analysis to obtain an improved probabilistic fire safety analysis model, wherein the calculation module is further configured to perform a quantitative analysis of the improved probabilistic fire safety analysis module to calculate and obtain a fire risk result for a nuclear power plant;where the acquisition module is connected to the calculation module and is configured to obtain an initial list of flame-resistant sheathed cables according to the fire risk result of the nuclear power plant, and to identify and design cables in the initial list of flame-resistant sheathed cables with the improved probabilistic fire safety analysis model to obtain a quantitative fire risk result once the cables have been designed; and where the determination module is connected to the acquisition module and is configured to judge whether the quantitative fire risk result satisfies a probabilistic safety objective, and if it does not, to further obtain additional cables that may be affected by a fire according to the fire risk result of the nuclear power plant, and to add the additional cables to the list; 1777455 of 60 initial list of flame-resistant coated cables, and perform the identification and design on the initial list of flame-resistant coated cables with the improved probabilistic flame safety analysis model until the quantitative result of the fire risk satisfies the probabilistic safety objective, and then stop adding cables to the initial list of flame-resistant coated cables and obtain a target list of flame protection of the cables. Optionally, the cable selection device for fire protection in a nuclear power plant based on probabilistic safety analysis further comprises an optimization module, wherein the calculation module is further configured to calculate a first risk result and a second risk result for a group of cables in the target list of fire protection cables depending on whether the group of cables is sheathed or not, and wherein the optimization module is connected to the calculation module and the determination module and is configured to compare the first risk result when the group of cables is not sheathed with the second risk result when the group of cables is sheathed according to the quantitative fire risk result obtained by means of the calculation module, and obtain an optimized target list of fire protection cables according to a 1777455 out of 60 comparison result. It is evident to those familiar with the prior art that the structure of the present application is not limited to the details of the exemplary embodiments described above, but that the present application may be incorporated into other specific forms without departing from the spirit and substance of the present application. Therefore, in all respects, the embodiments are to be regarded as illustrative rather than restrictive, and the scope of the invention is to be defined by the appended claims rather than by the preceding description. Accordingly, the present application is intended to cover all changes or modifications that fall within the meaning and scope of the equivalent elements of the claims. Any reference numbers appearing in the claims shall not be construed as limiting the claim in question. Furthermore, it should be understood that although the document is described in terms of implementations, this should not mean that each implementation includes only a separate technical solution. The document is described in this way only for the sake of clarity and should be considered as a whole, and the technical solutions in different embodiments may also be combined. 1777455 of 60 appropriate with each other to create other implementations that can be understood by those people knowledgeable in the previous art.

Claims

CLAIM 1. A method of selection for fire protection in a nuclear power plant based on a probabilistic fire safety analysis, characterized in that it consists of: (1) dividing a region that may be affected by a fire, by dividing a region within the analysis limits of the nuclear power plant into a plurality of fire compartments corresponding to the devices and cables of the nuclear power plant; (2) identifying the probabilistic fire safety assessment devices in the fire compartments and determining a range of the probabilistic fire safety assessment, forming a list of probabilistic fire safety assessment devices;(3) Identify fire safety probabilistic assessment cables in fire compartments based on the fire safety probabilistic assessment device list, and establish a correlation between fire safety probabilistic assessment cables and fire safety probabilistic assessment devices; (4) Identify an ignition source and calculate and acquire an ignition frequency; (5) Construct an initial fire safety probabilistic analysis model; (6) Perform a circuit failure analysis and a post-fire human reliability analysis, substitute an analysis result into the initial fire safety probabilistic analysis model, and perform a fire scene analysis to obtain an improved fire safety probabilistic analysis model;(7) perform a quantitative analysis on the improved probabilistic fire safety analysis model to calculate and obtain a fire risk result for a nuclear power plant; (8) form an initial list of flame-resistant sheathed cables in accordance with the quantitative analysis result of the improved probabilistic fire safety assessment model, and identify and design the cables in the initial list of flame-resistant sheathed cables with the improved probabilistic fire safety analysis model to obtain a quantitative fire risk result once the cables have been designed;and (9) judging whether the quantitative fire risk assessment satisfies a probabilistic safety objective, and if it does not, furthermore, identifying key cables that may be affected by fire using the probabilistic fire safety assessment model, and continually requesting increased flame-resistant coatings until the probabilistic safety objective is met; (10) calculating a risk variation based on whether a group of cables is coated or not, and in a situation where the risk increase is small, the cables may not be coated for fire prevention; and (11) obtaining an optimized list of flame-resistant cable protection. Ten claims follow;