Method for analyzing crevasse accident of pressurized water reactor based on ATF fuel

Abstract

The invention provides an ATF fuel-based pressurized water reactor break accident analysis method, which comprises the following steps: S1, checking an ATF scheme parameter demand table, and identifying important fuel parameters required in accident analysis; s2, according to important parameters of the fuel, mechanism phenomena and key model research of the ATF fuel is carried out, and distinguishing points of the ATF fuel and existing nuclear fuel are identified; s3, carrying out applicability evaluation on the first accident analysis program according to the distinguishing points; s4, if not, a fuel model in the first accident analysis program is improved, and a second accident analysis program suitable for AFT fuel is obtained; and S5, analyzing the typical crevasse accident by adopting a second accident analysis program, verifying whether the important phenomena in the step S1 and the step S2 are embodied or not, and if so, carrying out crevasse accident analysis on the pressurized water reactor based on the ATF fuel by adopting the second accident analysis program. According to the invention, qualitative and quantitative evaluation can be carried out on the nuclear power plant break accident adopting the ATF scheme.

Description

Technical Field

[0001] The invention mainly relates to the technical field of nuclear power reactors, and in particular to a pressurized water reactor rupture accident analysis method based on ATF fuel. Background Art

[0002] Accident Tolerant Fuel (ATF) is a new generation of fuel system developed to improve the ability of fuel elements to withstand severe accidents. Compared with existing nuclear fuels, this new fuel system can withstand severe accident conditions for a longer period of time while maintaining or improving its performance under normal operating conditions. The material properties of accident-tolerant fuel can slow down the deterioration of the situation, buy more precious time for people to take emergency measures, and greatly reduce the risk of radioactive materials breaking through safety barriers and leaking into the environment.

[0003] The new fuel is different from the existing nuclear fuel in terms of mechanism phenomena and physical property models. The existing accident analysis methods will no longer be applicable, and the acceptance of breach accidents may also change accordingly. However, there is currently no breach accident analysis method for ATF fuel. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a pressurized water reactor rupture accident analysis method based on ATF fuel, so as to solve the problem that the existing accident analysis method is not applicable.

[0005] To solve the above technical problems, the present invention provides a method for analyzing a rupture accident of a pressurized water reactor based on ATF fuel, comprising: step S1: checking the ATF scheme parameter requirement table to identify important fuel parameters required in the accident analysis; step S2: based on the important fuel parameters, conducting research on the mechanism phenomena and key models of the ATF fuel, and identifying the differences between the ATF fuel and the existing nuclear fuel; step S3: conducting an applicability evaluation on a first accident analysis program based on the differences; step S4: if it is not applicable, improving the fuel model in the first accident analysis program to obtain a second accident analysis program suitable for AFT fuel; step S5: using the second accident analysis program to analyze a typical rupture accident to verify whether the important phenomena of steps S1 and S2 are reflected, and if so, using the second accident analysis program to perform a rupture accident analysis on a pressurized water reactor based on ATF fuel.

[0006] Optionally, the important fuel parameters include: ATF fuel mechanism model, ATF fuel physical property model, ATF fuel geometric dimensions, ATF fuel flow and heat transfer characteristics, acceptance criteria used in accident analysis, and engineering factors.

[0007] Optionally, the mechanism phenomena include: oxidation and corrosion phenomena of the cladding, including the reaction of the cladding with high-temperature water and water vapor; cladding deformation phenomena, including thermal expansion, creep, and explosion; cladding quenching phenomena; core block deformation phenomena, including cracking, sintering, and repositioning; cladding failure model and judgment method, which corresponds to the acceptance criteria for ATF under a breach accident.

[0008] Optionally, the key models include: a fuel mechanism model, a fuel thermal conductivity model and a fuel deformation model.

[0009] Optionally, the applicability evaluation of the first accident analysis program based on the distinguishing points includes: whether the program can simulate key fuel phenomena; whether the program contains models corresponding to key fuel phenomena; whether the fuel model used by the program is accurate, and whether the applicable range of temperature and pressure parameters meets the range of ATF fuel in accident analysis.

[0010] Optionally, improving the fuel model in the first accident analysis program includes: evaluating the conservatism of the model in the first accident analysis program, model conservatism means that applying the model will lead to worse consequences in accident analysis, dividing the existing program models into conservative and non-conservative categories, and improving the non-conservative models; supplementing the missing mechanism models.

[0011] Optionally, identifying important fuel parameters required in accident analysis includes: forwardly identifying important fuel parameters required in accident analysis through phenomenon identification and sorting tables combined with engineering experience; and reversely identifying important fuel parameters required in accident analysis through acceptance criteria identification.

[0012] Optionally, the method further includes: if the important phenomena of step S1 and step S2 are not reflected, returning to step S1 to re-identify the important fuel parameters.

[0013] Optionally, using the second accident analysis procedure to conduct a breach accident analysis on a pressurized water reactor based on ATF fuel includes: determining the fuel type of the ATF fuel, the fuel types including ATF single component in-pile, ATF mixed core and ATF full core; when the fuel type of the ATF fuel is ATF full core, the second accident analysis procedure uses the full core flow channel correction condition to carry out the maximum cladding temperature and maximum local oxidation amount assessment.

[0014] Optionally, it also includes: when the fuel type of the ATF fuel is an ATF hybrid core, determining whether the ATF hybrid core is a starved component; if so, the second accident analysis program only modifies the node resistance of the thermal component and conducts an assessment of the maximum cladding temperature and the maximum local oxidation amount.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] The present application provides a method for analyzing a rupture accident in a pressurized water reactor based on ATF fuel. The method is based on the ATF scheme, identifies ATF mechanism phenomena and key models, evaluates the accident analysis procedure and improves it as needed, and also proposes analysis methods for three situations: single rod / single component entry, mixed core, and full core. The method can carry out qualitative and quantitative evaluation of rupture accidents in nuclear power plants that adopt the ATF scheme. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are included to provide a further understanding of the present application. They are included and constitute a part of the present application. The accompanying drawings illustrate embodiments of the present application and together with the present specification serve to explain the principles of the present invention. In the accompanying drawings:

[0018] Figure 1 The present invention is a flowchart of a method for analyzing a pressurized water reactor breach accident based on ATF fuel according to an embodiment of the present invention.

[0019] Figure 2 yes Figure 1 Flow chart of an embodiment of step S1 in FIG.

[0020] Figure 3 yes Figure 1 Flow chart of an embodiment of step S3 in FIG.

[0021] Figure 4 yes Figure 1 Flow chart of an embodiment of step S4 in FIG.

[0022] Figure 5 yes Figure 1 Flow chart of an embodiment of step S6 in FIG. DETAILED DESCRIPTION

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0024] The most widely used fuel in pressurized water reactors at present is zirconium alloy cladding and ceramic uranium dioxide pellets. The acceptance criteria used in breach accident analysis are based on this scheme. There are three quantitative indicators directly related to the fuel properties, including maximum cladding temperature (PCT), maximum local oxidation amount (LMO) and global oxidation amount (CMO).

[0025] In order to improve the accident resistance of nuclear fuel, one solution is to prepare a high-temperature oxidation-resistant coating on the surface of the existing zirconium alloy cladding by using surface modification technology to improve the performance of the zirconium alloy cladding. Another solution is to completely change the fuel material, such as using a new silicon carbide composite cladding material that is resistant to high temperatures, corrosion, and deformation. Regardless of which solution is adopted, the new fuel must be different from the existing fuel in terms of mechanism phenomena and physical property models. After changing the fuel, the existing accident analysis method will no longer be applicable, and the acceptance of breach accidents may also change accordingly. However, there is currently no breach accident analysis method that can cope with fuel changes.

[0026] In response to the above problems, the present application provides a pressurized water reactor rupture accident analysis method based on ATF fuel. The method is based on the ATF scheme, identifies ATF mechanism phenomena and key models, evaluates the accident analysis procedures and improves them as needed, and also proposes analysis methods for three situations: single rod / single component entry, mixed core, and full core. It can carry out qualitative and quantitative evaluation of rupture accidents in nuclear power plants that adopt the ATF scheme.

[0027] Figure 1 FIG. 1 is a flow chart of a method for analyzing a pressurized water reactor breach accident based on ATF fuel according to an embodiment of the present invention. Figure 1 As shown, the ATF fuel-based pressurized water reactor breach accident analysis method 100 includes:

[0028] Step S1: Check the ATF scheme parameter requirement table to identify the important fuel parameters required in accident analysis.

[0029] Figure 2 yes Figure 1 Flow chart of step S1 in an embodiment. Figure 2 As shown, the important fuel parameters needed for accident analysis include:

[0030] Step S11: Through the Phenomena Identification and Ranking Table (PIRT), combined with engineering experience, positively identify the important fuel parameters required in accident analysis.

[0031] Compared with the original method of conservatively analyzing most phenomena and components, the PIRT method lists the phenomena of a certain accident condition of a power plant according to different accident stages and components, and divides the phenomena into low, medium, high or other numerical quantitative levels according to their importance, focusing on analyzing more important events and phenomena, thereby improving the efficiency of accident analysis and procedure verification.

[0032] Step S12: Reversely identify the important fuel parameters required for accident analysis through acceptance criteria identification.

[0033] Optionally, important fuel parameters include, but are not limited to: ATF fuel mechanism model, ATF fuel physical property model, ATF fuel geometric dimensions, ATF fuel flow and heat transfer characteristics, acceptance criteria used in accident analysis, and engineering factors.

[0034] Step S2: Based on the important parameters of the fuel, conduct research on the mechanism phenomena and key models of the ATF fuel to identify the differences between the ATF fuel and existing nuclear fuels.

[0035] Optionally, the existing nuclear fuel is zirconium alloy clad ceramic uranium fuel.

[0036] Optionally, the mechanism phenomena include but are not limited to:

[0037] Oxidation and corrosion of the cladding, including the reaction of the cladding with high-temperature water and steam;

[0038] Cladding deformation phenomena, including thermal expansion, creep, and bursting;

[0039] Cladding quenching phenomenon;

[0040] Pellet deformation phenomena, including cracking, sintering, and repositioning;

[0041] The cladding failure model and judgment method, which corresponds to the acceptance criteria of ATF under breach accidents.

[0042] Optionally, key models include but are not limited to: a fuel mechanism model, a fuel thermal conductivity model, and a fuel deformation model.

[0043] Step S3: Evaluate the applicability of the first accident analysis procedure based on the distinguishing points.

[0044] Optionally, the key models are divided into three types according to the difference points: models that are applicable to existing fuel models, models that are significantly different from existing fuel models but can be evaluated in conservative aspects and are conservatively encapsulated by the original model, and models that are significantly different from existing fuel models and cannot evaluate conservative directions or cannot be conservatively encapsulated. The first two models are qualitatively demonstrated to have no effect on the loss of coolant accident (LOCA) or can be conservatively encapsulated, and only the third model is quantitatively analyzed. The loss of coolant accident is a typical accident in the safety analysis of nuclear power plants, and different breach locations and breach sizes will directly affect the handling and consequences of the accident.

[0045] According to the identified model, the applicability of the existing accident analysis program is evaluated. This step requires identifying the fuel-related model of the breach analysis program, and also considering the scope of application and uncertainty of the model. It should be noted that due to the differences in the programming methods of different programs, program calculation errors often occur. Therefore, the model may be modified during the program debugging process. At this time, it cannot be directly judged that the program model is not applicable, but the source of the program model data should be clarified, and then the difference between the program prototype fuel and the new fuel model parameters should be compared to determine whether the program model is conservative and whether it can be applied.

[0046] Figure 3 yes Figure 1 Flow chart of step S3 in an embodiment. Figure 3 As shown, the applicability evaluation of the first accident analysis procedure (existing accident analysis procedure) based on the distinguishing points includes:

[0047] Step S31: whether the program can simulate the key fuel phenomenon;

[0048] Step S32: whether the program contains a model corresponding to the key fuel phenomenon;

[0049] Step S33: Whether the fuel model used by the program is accurate, and whether the applicable range of temperature and pressure parameters meets the range of ATF fuel in accident analysis.

[0050] Step S4: If it is not applicable, the fuel model in the first accident analysis program is improved to obtain a second accident analysis program applicable to AFT fuel.

[0051] Improve the inapplicable fuel model in the accident analysis program identified in step S3, conduct secondary development of the program, and verify the program capability through single test and overall test.

[0052] Figure 4 yes Figure 1 Flow chart of step S4 in an embodiment. Figure 4 As shown, the method for improving the fuel model in the first accident analysis program includes:

[0053] Step S41: Evaluate the conservatism of the model in the first accident analysis program. Model conservatism means that applying the model will lead to worse consequences in accident analysis. The existing program models are divided into conservative and non-conservative categories, and the non-conservative models are improved.

[0054] Step S42: Supplement the missing mechanism model.

[0055] Step S5: Use the second accident analysis program to analyze the typical breach accident to verify whether the important phenomena of step S1 and step S2 are reflected. If so, go to step S6, otherwise go to step S1.

[0056] Typical breach accidents should include the most challenging accidents for fuel and fully reflect fuel phenomena. An example is a large breach cold end double-end fracture accident.

[0057] In other words, analyze typical breach accidents to verify whether the important phenomena in steps S1 and S2 are reflected. If not, re-carry out important parameter identification and phenomenon analysis.

[0058] Step S6: using the second accident analysis program to perform a breach accident analysis on the ATF fuel-based pressurized water reactor.

[0059] Figure 5 yes Figure 1 Flow chart of step S6 in an embodiment. Figure 5 As shown, step S6 includes:

[0060] Step S61: Determine the fuel type of the ATF fuel, the fuel types include ATF single component in-core, ATF mixed core and ATF full core.

[0061] Step S62: When the fuel type of the ATF fuel is ATF single component loading, qualitatively evaluate the maximum cladding temperature and the maximum local oxidation amount.

[0062] Since the ATF single component is small in size, it will not have much impact on the overall state of the core. In addition, the ATF single component is generally placed in a low-power area with a low temperature, so a qualitative evaluation is recommended.

[0063] Step S63: When the fuel type of the ATF fuel is ATF full core, the second accident analysis program adopts the full core flow channel correction condition to carry out the maximum cladding temperature and the maximum local oxidation amount assessment.

[0064] Assuming that all components in the core are replaced with new components (ATF fuel), only the fuel model of the analysis program needs to be changed, and no additional modeling requirements are generated. This is a simpler analysis method compared to the hybrid core.

[0065] Step S64: When the fuel type of the ATF fuel is an ATF hybrid core, determine whether the ATF hybrid core is a starved component. If yes, proceed to step S65: If not, go to step S63.

[0066] Step S65: The second accident analysis program only modifies the thermal component node resistance and conducts the maximum cladding temperature and maximum local oxidation assessment.

[0067] ATF hybrid core refers to a core in which part of the components are replaced with new components (ATF fuel). In a hybrid core, differences in geometric parameters, grid positions, local resistance coefficients, and other differences in fuel assemblies can lead to core flow redistribution. The breach analysis focuses on the impact of the reduction in mass flow rate in the hot channel on the peak temperature (PCT) of the fuel cladding. This method first determines in which fuel assembly the minimum coolant flow occurs through analysis of the outer diameter of the fuel rod and the grid, and defines this assembly as a "starved assembly". Due to the low flow rate and lack of sufficient cooling, the PCT will be higher than expected in an accident. If the core is exposed, the oxidation amount will also be higher. Therefore, the hot assembly can be set as the fuel assembly during the accident analysis process, and the mutual influence between different assemblies can be simulated by modifying the hot channel resistance, and conservative results can be calculated.

[0068] Optionally, the breach accident analysis of the ATF fuel-based pressurized water reactor also includes: modifying the full core resistance condition through a second accident analysis procedure and conducting a global oxidation assessment.

[0069] Compared with the existing breach accident analysis methods, the present invention is based on the ATF scheme, identifies the ATF mechanism phenomenon and key models, improves the accident analysis procedure, and conducts qualitative and quantitative evaluation on breach accidents in nuclear power plants using the ATF scheme.

[0070] Flowcharts are used in the present application to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed accurately in order. On the contrary, various steps may be processed in reverse order or simultaneously. At the same time, other operations may be added to these processes, or one or more operations may be removed from these processes.

[0071] The basic concepts have been described above. Obviously, for those skilled in the art, the above invention disclosure is only used as an example and does not constitute a limitation of the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and amendments to the present application. Such modifications, improvements and amendments are suggested in the present application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of the present application.

[0072] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0073] Some aspects of the present application may be performed entirely by hardware, entirely by software (including firmware, resident software, microcode, etc.), or by a combination of hardware and software. The above hardware or software may be referred to as "data blocks", "modules", "engines", "units", "components" or "systems". The processor may be one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DAPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, or combinations thereof. In addition, various aspects of the present application may be expressed as computer products located in one or more computer-readable media, which include computer-readable program codes. For example, computer-readable media may include, but are not limited to, magnetic storage devices (e.g., hard disks, floppy disks, tapes ...), optical disks (e.g., compact disks CDs, digital versatile disks DVDs ...), smart cards, and flash memory devices (e.g., cards, sticks, key drives ...).

[0074] A computer-readable medium may include a propagated data signal containing computer program code, such as in baseband or as part of a carrier wave. The propagated signal may have a variety of manifestations, including electromagnetic, optical, etc., or a suitable combination. A computer-readable medium may be any computer-readable medium other than a computer-readable storage medium, which may be connected to an instruction execution system, device or apparatus to communicate, propagate or transmit a program for use. The program code on the computer-readable medium may be propagated via any suitable medium, including radio, cable, fiber optic cable, radio frequency signal, or similar medium, or any combination of the above mediums.

[0075] Similarly, it should be noted that in order to simplify the description of the disclosure of this application and thus help understand one or more embodiments of the invention, in the above description of the embodiments of this application, multiple features are sometimes combined into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the object of this application are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0076] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0077] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0078] In addition, it should be noted that the use of words such as "first" and "second" to define components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and cannot be understood as limiting the scope of protection of this application. In addition, although the terms used in this application are selected from well-known and commonly used terms, some terms mentioned in the specification of this application may be selected by the applicant at his or her discretion, and their detailed meanings are explained in the relevant parts of the description of this article. In addition, it is required to understand this application not only by the actual terms used, but also by the meaning implied by each term.

[0079] In some embodiments, numbers describing the number of components and attributes are used. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise specified, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the setting of such numerical values ​​is as accurate as possible within the feasible range.

[0080] Although the present application has been described with reference to the current specific embodiments, ordinary technicians in this technical field should recognize that the above embodiments are only used to illustrate the present application, and various equivalent changes or substitutions may be made without departing from the spirit of the present application. Therefore, as long as the changes and modifications to the above embodiments are within the essential spirit of the present application, they will fall within the scope of the claims of the present application.

Claims

1. A method for analyzing a pressurized water reactor breach accident based on ATF fuel, characterized in that: include: Step S1: Check the ATF scheme parameter requirement table to identify the important fuel parameters required in the accident analysis; Step S2: Based on the important parameters of the fuel, conduct research on the mechanism phenomenon and key models of the ATF fuel to identify the differences between the ATF fuel and existing nuclear fuels; Step S3: evaluating the applicability of the first accident analysis procedure according to the distinguishing points; Step S4: If not applicable, improving the fuel model in the first accident analysis program to obtain a second accident analysis program applicable to AFT fuel; Step S5: Use the second accident analysis program to analyze a typical breach accident to verify whether the important phenomena of step S1 and step S2 are reflected. If so, use the second accident analysis program to analyze the breach accident of the ATF fuel-based pressurized water reactor.

2. The method for analyzing a pressurized water reactor breach accident according to claim 1, characterized in that: The applicability evaluation of the first accident analysis procedure based on the above-mentioned distinctions includes: Whether the program can simulate fuel-critical phenomena; Whether the program contains models corresponding to key fuel phenomena; Whether the fuel model used in the program is accurate, and whether the applicable range of temperature and pressure parameters meets the range of ATF fuel in accident analysis.

3. The method for analyzing a pressurized water reactor breach accident according to claim 1, characterized in that: The improvement of the fuel model in the first accident analysis procedure includes: Evaluate the conservatism of the model in the first accident analysis procedure. Model conservatism means that the application of the model will lead to worse consequences in accident analysis. Divide the existing program models into conservative and non-conservative categories, and improve the non-conservative models. Supplement the missing mechanistic model.

4. The method for analyzing a pressurized water reactor breach accident according to claim 1, characterized in that: The breach accident analysis of a pressurized water reactor based on ATF fuel using the second accident analysis procedure includes: Determine the fuel type of ATF fuel, wherein the fuel type includes ATF single component in-core, ATF mixed core and ATF full core; When the fuel type of the ATF fuel is ATF full core, the second accident analysis procedure adopts the full core flow channel correction condition to carry out the maximum cladding temperature and the maximum local oxidation amount assessment.

5. The method for analyzing a pressurized water reactor breach accident according to claim 4, characterized in that: Also includes: When the fuel type of the ATF fuel is an ATF hybrid core, it is determined whether the ATF hybrid core is a starved component. If so, the second accident analysis program only modifies the hot component node resistance and conducts a maximum cladding temperature and maximum local oxidation amount assessment.

6. The method for analyzing a pressurized water reactor breach accident according to claim 1, characterized in that: Identification of important fuel parameters required in accident analysis include: Through phenomenon identification and ranking tables, combined with engineering experience, the important fuel parameters required in accident analysis are positively identified; Acceptance criteria are used to identify the critical fuel parameters required in the accident analysis.

7. The method for analyzing a pressurized water reactor breach accident according to claim 1, characterized in that: Also includes: If the important phenomena in step S1 and step S2 are not reflected, return to step S1 to re-identify the important fuel parameters.

8. The method for analyzing a pressurized water reactor breach accident according to claim 1, characterized in that: The important fuel parameters include: ATF fuel mechanism model, ATF fuel physical property model, ATF fuel geometric dimensions, ATF fuel flow and heat transfer characteristics, acceptance criteria used in accident analysis, and engineering factors.

9. The method for analyzing a pressurized water reactor breach accident according to claim 1, characterized in that: The mechanism phenomena include: Oxidation and corrosion of the cladding, including the reaction of the cladding with high-temperature water and steam; Cladding deformation phenomena, including thermal expansion, creep, and bursting; Cladding quenching phenomenon; Pellet deformation phenomena, including cracking, sintering, and repositioning; The cladding failure model and judgment method, which corresponds to the acceptance criteria of ATF under breach accidents.

10. The method for analyzing a pressurized water reactor breach accident according to claim 1, characterized in that: The key models include: fuel mechanism model, fuel thermal conductivity model and fuel deformation model.

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