A method for evaluating the transient equivalence of the primary loop of a nuclear power plant

Abstract

The present invention discloses a method for evaluating the transient equivalence of the primary circuit of a nuclear power plant. The stress states of metal components varying with time under transient one and transient two are respectively obtained, and the stress extreme value moments under transient one and transient two are respectively determined based on the stress states; the evaluation parameters of transient one and transient two are respectively determined according to the stress extreme value moments, and the evaluation parameters include alternating stress intensity, fatigue damage amount, stress peak state and stress valley state; if the alternating stress intensity of transient one is greater than that of transient two, and the fatigue damage of transient one is greater than that of transient two, and the stress peak state of transient one is greater than that of transient two, and the stress valley state of transient one is less than that of transient two, then it is determined that transient one is greater than transient two. The present invention can correctly evaluate the magnitude relationship between transients, ensure that the transients meeting relevant criteria have true envelopability, and has small computational amount and convenient application.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power plant performance tests, and particularly relates to a method for evaluating the transient equivalence of a primary loop of a nuclear power plant. Background Art

[0002] During the operation of a nuclear power plant, it is necessary to ensure the integrity of the pressure-bearing boundary of the reactor primary loop. It is required to monitor, record, statistically analyze, and analyze the changes in key parameters such as the pressure, temperature, and flow rate of the primary loop. This is transient statistics. According to the experience feedback at home and abroad, it is inevitable that some unclassifiable transients will occur during the operation of nuclear power units. The so-called "unclassifiable transients" mainly refer to the actual operating parameters of the unit exceeding the parameter range specified in the original design transient list. The occurrence of unclassifiable transients indicates that there is a deviation between the actual operating state of the unit and the original design state. In this case, it is unrealistic to re-conduct systematic fatigue life assessment work on the mechanical equipment and components of the unit. A practical solution is to prove that the original design analysis document of the unit is still valid and has sufficient safety margins, that is, to select transients from the original design transient list of the unit to envelope the unclassified transients.

[0003] Each transient that occurs in a nuclear power unit will cause a certain amount of fatigue damage to the mechanical equipment and components. The so-called "evaluation of transient equivalence" actually refers to comparing the "sizes" between transients by comparing the fatigue damage caused by different transients to metal components. A nuclear power unit will experience many kinds of transients during its service life, and the order in which the transients occur is unpredictable. To ensure the conservativeness of the calculation results, when evaluating the fatigue life of metal components, it is necessary to pair all transients pairwise through an exhaustive method to find the maximum alternating stress intensity and fatigue damage. At the same time, when comparing the "sizes" between two transients, in addition to considering the alternating stress intensity and fatigue damage generated by them respectively, it is also necessary to consider the factors of stress peaks and stress valleys.

[0004] Therefore, there is a need for a method for evaluating the transient equivalence of a primary loop of a nuclear power plant that can meet the above requirements. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for evaluating the transient equivalence of a primary loop of a nuclear power plant that can solve the problem of unclassifiable transients in nuclear power plants.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for evaluating the transient equivalence of the primary circuit of a nuclear power plant, the transient equivalence evaluation method comprising: respectively obtaining the stress states of metal components varying with time under the action of transient one and transient two, and based on the stress states, respectively determining the stress extreme value moments under the action of transient one and transient two; according to the stress extreme value moments, respectively determining the evaluation parameters of transient one and transient two, wherein the evaluation parameters include alternating stress intensity, fatigue damage amount, stress peak state, and stress valley state; judging according to the evaluation parameters under transient one and transient two, if all the following conditions are satisfied, then judge that transient one is greater than transient two:

[0008] a. The alternating stress intensity of transient one is greater than that of transient two;

[0009] b. The fatigue damage amount of transient one is greater than that of transient two;

[0010] c. The stress peak state of transient one is greater than that of transient two;

[0011] d. The stress valley state of transient one is less than that of transient two.

[0012] Further, the transient equivalence evaluation method further comprises: under the same transient, determining the stress states of the metal components corresponding to two stress extreme value moments varying with time, and calculating the stress range between the two stress extreme value moments, calculating the corresponding principal stress according to the stress range between the two stress extreme value moments, and determining the stress peak state and stress valley state under this transient based on the principal stress.

[0013] Preferably, let the two stress extreme value moments be t i moment and t j moment, the stress state at the t i moment is [σ x，i ,σ y，i ,σ z，i ,σ xy，i ,σ xz，i ,σ yz，i , the stress state at the t j moment is [σ x，j ,σ y，j ,σ z，j ,σ xy，j ,σ xz，j ,σ yz，j ; the transient equivalence evaluation method further comprises calculating the stress range [σ′ i ,σ′ j between the t x moment and the ty , σ' z , σ' xy , σ' xz , σ' yz :

[0014] σ' x = σ x，i - σ x，j

[0015] σ' y = σ y，i - σ y，j

[0016] σ' z = σ z，i - σ z，j

[0017] σ' xy = σ xy，i - σ xy，j

[0018] σ' xz = σ xz，i - σ xz，j

[0019] σ' yz = σ yz，i - σ yz，j

[0020] where σ' x is the stress range in the x - direction, σ x，i is the stress in the x - direction at time t i , and σ x，j is the stress in the x - direction at time t j ; σ' y is the stress range in the y - direction, σ y，i is the stress in the y - direction at time t i , and σ y，j is the stress in the y - direction at time t j ; σ' z is the stress range in the z - direction, σ z，i is the stress in the z - direction at time t i , and σ z，j is the stress in the z - direction at time t j ; σ' xy is the shear stress range in the x - y direction, σ xy，i is the shear stress in the x - y direction at time t i , and σ xy，j is the shear stress in the x - y direction at time t j ; σ' xz is the shear stress range in the x - z direction, σxz，i the shear stress in the x-z direction at time t i is σ xz，j the shear stress in the x-z direction at time t j is σ′ yz is the shear stress range in the y-z direction, σ yz，i the shear stress in the y-z direction at time t i is σ yz，j the shear stress in the y-z direction at time t j is

[0021] Further, the transient equivalence evaluation method further includes: determining the corresponding principal stresses according to the stress ranges [σ′ x , σ′ y , σ′ z , σ′ xy , σ′ xz , σ′ yz , if the stress value with the largest absolute value among the principal stresses is positive, then at this transient, the stress state at time t i is the stress peak state, and the stress state at time t j is the stress valley state, otherwise at this transient, the stress state at time t i is the stress valley state, and the stress state at time t j is the stress peak state.

[0022] Further, the transient equivalence evaluation method further includes: determining the stress peak states of the first transient and the second transient respectively, calculating the stress range and the corresponding principal stresses between the stress peak state of the first transient and the stress peak state of the second transient, and comparing the stress peak state of the first transient and the stress peak state of the second transient based on the principal stress.

[0023] Preferably, let the stress peak state of the first transient be [σ x，A , σ y，A , σ z，A , σ xy，A , σ xz，A , σ yz，A , and the stress peak state of the second transient be [σ x，B , σ y，B , σ z，B , σ xy，B , σ xz，B , σ yz，B ; the transient equivalence evaluation method further includes calculating the stress range [σ″ x , σ″ y, σ″ z , σ″ xy , σ″ xz , σ″ yz :

[0024] σ″ x = σ x，A - σ x，B

[0025] σ″ y = σ y，A - σ y，B

[0026] σ″ z = σ z，A - σ z，B

[0027] σ″ xy = σ xy，A - σ xy，B

[0028] σ″ xz = σ xz，A - σ xz，B

[0029] σ″ yz = σ yz，A - σ yz，B

[0030] wherein, σ″ x is the stress range in the x - direction, σ x，A is the stress in the x - direction under the first transient state, σ x，B is the stress in the x - direction under the second transient state; σ″ y is the stress range in the y - direction, σ y，A is the stress in the y - direction under the first transient state, σ y，B is the stress in the y - direction under the second transient state; σ′ z is the stress range in the z - direction, σ z，A is the stress in the z - direction under the first transient state, σ z，B is the stress in the z - direction under the second transient state; σ′ xy , is the shear stress range in the x - y direction, σ xy，A is the shear stress in the x - y direction under the first transient state, σ xy，B is the shear stress in the x - y direction under the second transient state; σ′ xz is the shear stress range in the x - z direction, σ xz，A is the shear stress in the x - z direction under the first transient state, σ xz，B is the shear stress in the x - z direction under the second transient state; σ′ yz is the shear stress range in the y - z direction, σ yz，Ais the shear stress in the y-z direction under the first transient, σ yz，B is the shear stress in the y-z direction under the second transient.

[0031] Further, the transient equivalence evaluation method further includes: determining the corresponding principal stresses according to the stress ranges [σ″ x , σ″ y , σ″ z , σ″ xy , σ″ xz , σ″ yz . If the stress value with the largest absolute value among the principal stresses is a positive number, then the stress peak state of the first transient is greater than the stress peak state of the second transient; otherwise, the stress peak state of the first transient is less than the stress peak state of the second transient.

[0032] Further, the transient equivalence evaluation method further includes: determining the stress valley states of the first transient and the second transient respectively, calculating the stress range and the corresponding principal stresses between the stress valley state of the first transient and the stress valley state of the second transient, and comparing the stress valley state of the first transient and the stress valley state of the second transient based on the principal stresses. If the stress value with the largest absolute value among the principal stresses is a positive number, then the stress valley state of the first transient is greater than the stress peak state of the second transient; otherwise, the stress peak state of the first transient is less than the stress peak state of the second transient.

[0033] Further, the transient equivalence evaluation method further includes: establishing a finite element analysis model of the metal component before obtaining the stress states under the first transient and the second transient.

[0034] Advantages of the present invention: It can solve the problem that transient problems in nuclear power plants cannot be classified, and simultaneously consider four aspects of factors including the stress peak state, stress valley state, alternating stress intensity, and fatigue damage caused by transients, so as to correctly evaluate the "large and small" relationship between transients, ensure that transients meeting relevant criteria have true envelopability, avoid systematic large-scale fatigue life re-evaluation of mechanical components in nuclear power plants due to unclassifiable transients, and at the same time has the characteristics of small calculation amount and convenient application, filling the gap in the prior art. Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for description in the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0036] Figure 1It is a schematic diagram of the dimensions of the metal component provided by the embodiment of the present invention;

[0037] Figure 2 It is a partial process schematic diagram of the transient equivalence evaluation method provided by the embodiment of the present invention. Detailed implementation manners

[0038] In order to enable those skilled in the art of the present technology to better understand the solution of the present invention, and to more clearly understand the purpose, technical solution and its advantages of the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be noted that the implementation manners not depicted or described in the drawings are forms known to those of ordinary skill in the art. Additionally, although this document may provide examples of parameters that include specific values, it should be understood that the parameters need not exactly equal the corresponding values, but may approximate the corresponding values within an acceptable tolerance of error or design constraints. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention. In addition, the terms "including" and "having" in the specification and claims of the present invention and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, apparatus, product or device that includes a series of steps or units need not be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0039] In an embodiment of the present invention, a transient equivalence evaluation method for the primary loop of a nuclear power plant is provided. This evaluation method includes obtaining the stress state of a metal component changing with time under different transients, that is, obtaining the stress state of the metal component changing with time under transient one to obtain stress state one, and obtaining the stress state of the metal component changing with time under transient two to obtain stress state two; determining the stress extreme moment under this transient based on the stress state, and determining the evaluation parameter under this transient according to this stress extreme moment, where the evaluation parameter includes alternating stress intensity, fatigue damage amount, stress peak state, and stress valley state; making a judgment according to the evaluation parameter. If the alternating stress intensity of transient one is greater than that of transient two, and the fatigue damage amount of transient one is greater than that of transient two, and the stress peak state of transient one is greater than that of transient two, and the stress valley state of transient one is less than that of transient two, then transient one is considered greater than transient two.

[0040] Specifically, in this embodiment, the evaluation method includes the following steps:

[0041] In the first step, the finite element method or other methods are used to calculate the stress state of the metal component changing with time when transient A and transient B act alone, respectively.

[0042] The load data of transient A and transient B are shown in Table 1.

[0043] Table 1 Transient Loads

[0044]

[0045]

[0046] Specifically, when the transient load acts on the metal component, the dimensions of the metal component are as Figure 1 shown. The nozzle and weld materials are stainless steel. Table 2 gives the material property parameters, and Table 3 gives the material fatigue life data. In addition, it should be noted that the material properties and material fatigue life data listed in this embodiment are only for illustrative purposes. The actual situation may be different from the data provided in this embodiment, and the protection scope of the present invention is not limited thereby. Similarly, the Figure 1 dimensions of the metal component shown below are also only for illustrative purposes. In actual applications, the corresponding dimension information and fatigue assessment positions are selected according to requirements, and the protection scope of the present invention is not limited thereby.

[0047] Table 2 Material Properties

[0048]

[0049] Table 3 Material Fatigue Life Data (SN Curve)

[0050] Sa(Pa) 6.00E+09 4.30E+09 2.75E+09 1.98E+09 1.44E+09 9.74E+08 7.45E+08 Number of Cycles 10 20 50 100 200 500 1000 Sa(Pa) 5.90E+08 4.50E+08 3.68E+08 3.00E+08 2.35E+08 1.96E+08 1.68E+08 Number of Cycles 2000 5000 1.00E+04 2.00E+04 5.00E+04 1.00E+05 2.00E+05 Sa(Pa) 1.42E+08 1.26E+08 1.13E+08 1.02E+08 9.90E+07 9.71E+07 9.58E+07 Number of Cycles 5.00E+05 1.00E+06 2.00E+06 5.00E+06 1.00E+07 1.00E+08 1.00E+09 Sa(Pa) 9.44E+07 9.37E+07 Number of Cycles (There might be a typo here as it was "Cvcle" in the original, assuming it should be "Cycles") 1.00E+10 1.00E+11

[0051] First, a finite element analysis model of the metal component is established.

[0052] Specifically, as Figure 1 shown, point F on the inner surface of the nozzle of the metal component is selected as the fatigue assessment position. When performing thermal analysis, a convective heat transfer boundary condition is applied to the inner surface of the component, and an adiabatic boundary condition is applied to the outer surface and the ends. When performing structural analysis, the temperature field results obtained from the thermal analysis are used as thermal loads acting on the analysis component. The axial displacement of the end on the nozzle side is constrained, a pressure load is applied to the inner surface of the analysis component, and the end axial force and bending moment loads caused by the pressure are applied to the end on the branch pipe side.

[0053] Secondly, calculate the stress state of the metal component changing with time when transient A acts alone to obtain Table 4, and calculate the stress state of the metal component changing with time when transient B acts alone to obtain Table 5.

[0054] Table 4 Stress Conditions at Point F of the Metal Component under the Action of Transient A

[0055]

[0056]

[0057] Table 5 Stress conditions at point F of the metal component under the action of transient B

[0058]

[0059]

[0060] It should be noted that since the finite element analysis model established in this embodiment is an axisymmetric model, the stress calculation results only include the stresses in the x, y, and z directions and the shear stress in the x-y direction. The shear stresses in the y-z direction and the x-z direction are both 0.0.

[0061] In the second step, according to the design specifications of nuclear power mechanical components, such as the RCCM specification, calculate the stress extreme value moments, alternating stress intensities, and fatigue damage amounts at the fatigue assessment positions of the metal component when transient A and transient B act alone.

[0062] In the third step, compare the magnitudes of the alternating stress intensities caused by transient A and transient B; compare the magnitudes of the fatigue damage amounts caused by transient A and transient B; respectively determine the stress peak states and stress valley states caused by transient A and transient B, and compare the magnitudes of the stress peak states and stress valley states caused by transient A and transient B.

[0063] The specific descriptions of the second step and the third step are as follows:

[0064] According to the requirements of the design specification, calculate the two stress extreme value moments caused by transient A and the alternating stress intensity Salt_A and fatigue usage amount CUF_A determined by the two stress extreme value moments. In this embodiment, as calculated in combination with Table 4, the stress extreme value states during the action of transient A occur at 205 seconds and 1200 seconds. The alternating stress intensity Salt_A determined by the two stress extreme value states is 1132 MPa, and the fatigue damage amount caused by a single transient A is 1 / 351.

[0065] Moreover, according to the requirements of the design specification, calculate the two stress extreme value states caused by transient B and the alternating stress intensity Salt_B and fatigue usage amount CUF_B determined by the two stress extreme value moments. In this embodiment, as calculated in combination with Table 5, the stress extreme value states during the action of transient B occur at 405 seconds and 1900 seconds. The alternating stress intensity Salt_B determined by the two stress extreme value states is 688 MPa, and the fatigue damage amount caused by a single transient B is 1 / 1268.

[0066] Moreover, the peak stress state and valley stress state caused by transient A and transient B are determined. Taking transient A as an example, the main calculation process is as follows:

[0067] Assume that the two stress extreme states caused by transient A appear at time t i and time t j respectively:

[0068] The stress state at time t i is [σ x，i , σ y，i , σ z，i , σ xy，i , σ xz，i , σ yz，i , where σ x，i is the stress in the x-direction at time t i , σ y，i is the stress in the y-direction at time t i , σ z，i is the stress in the z-direction at time t i , σ xy，i is the shear stress in the x-y direction at time t i , σ xz，i is the shear stress in the x-z direction at time t i , σ yz，i is the shear stress in the y-z direction at time t i .

[0069] The stress state at time t j is [σ x，j , σ y，j , σ z，j , σ xy，j , σ xz，j , σ yz，j , where σ x，j is the stress in the x-direction at time t j , σ y，j is the stress in the y-direction at time t j , σ z，j is the stress in the z-direction at time t j , σ xy，j is the shear stress in the x-y direction at time t j , σ xz，j is the shear stress in the x-z direction at time t j , σ yz，j is the shear stress in the y-z direction at time t j .

[0070] Calculate the stress range [σ′ i and σ′ j between the two times t x and t y, σ′ z , σ′ xy , σ′ xz , σ′ yz :

[0071] σ′x = σ x，i - σ x，j

[0072] σ′ y = σ y，i - σ y，j

[0073] σ′ z = σ z，i - σ z，j

[0074] σ′ xy = σ xy，i - σ xy，j

[0075] Q′ xz = σ xz，i - σ xz，j

[0076] σ′ yz = σ yz，i - σ yz，j

[0077] Calculate the principal stresses [σ′1, σ′2, σ′3] corresponding to the stress range. The calculation formula can be flexibly selected according to the actual situation, and the protection scope of the present invention is not limited thereby. Now, an example is given to illustrate the calculation process of the principal stresses [σ′1, σ′2, σ′3]:

[0078] σ 3 - I1σ 2 + I2σ - I3 = 0

[0079] I1 = σ′ x + σ′ y + σ′ z

[0080]

[0081]

[0082] By solving the above four equations, three roots are obtained, which are the principal stresses [σ′1, σ′2, σ′3].

[0083] When the value of the one with the largest absolute value among the principal stresses [σ′1, σ′2, σ′3] is positive, then it is considered that the stress state at time t i is the stress peak state, and the stress state at time t j is the stress valley state; otherwise, it is considered that at time ti The stress state at time t is the stress valley value state. j The stress state at time t is the stress peak value state.

[0084] In this embodiment, as shown in Table 6, the two stress extreme value states caused by transient A appear at 205 seconds and 1200 seconds respectively. The stress states at the two times are [-7.0, 577.2, 486.9, 0.0, 0.0, 0.0] and [-16.0, -575.1, -410.3, 0.0, 0.0, 0.0] respectively. Thus, according to the above calculation process, the principal stresses [σ′1, σ′2, σ′3] are determined to be [9.0, 1152, 897]. Furthermore, the numerically largest value in absolute terms among the principal stresses, which is 1152, is a positive number. Therefore, the stress state at 205 seconds is the stress peak value state of transient A, and the stress state at 1200 seconds is the stress valley value state of transient A.

[0085] Table 6 Stress extreme values, alternating stress intensity, and fatigue damage amount under the action of transient A

[0086]

[0087] In this embodiment, as shown in Table 7, the stress state at the F point of the metal component under the action of transient B at 405 seconds is the stress peak value state, and the stress state at 1900 seconds is the stress valley value state. The solution process of the evaluation parameters under the action of transient B is the same as that of transient A, which will not be elaborated here.

[0088] Table 7 Stress extreme values, alternating stress intensity, and fatigue damage amount under the action of transient B

[0089]

[0090] It can be seen from Table 6 and Table 7 that Salt_A is greater than Salt_B, and CUF_A is greater than CUF_B.

[0091] After determining the stress peak value state and stress valley value state corresponding to transient A and transient B respectively, compare the magnitudes of the stress peak value states and stress valley value states caused by transient A and transient B. Now, taking the comparison of the stress peak value state of transient A and the stress peak value state of transient B as an example, a specific description is given:

[0092] Let the stress peak value state caused by transient A be [σ x，A , σ y，A , σ z，A , σ xy，A , σ xz，A , σ yz，A , and the stress peak value state caused by transient B be [σ x，B , σ y，B , σ z，B , σxy，B , σ xz，B , σ yz，B , calculate the stress range [σ″ x , σ″ y , σ″ z , σ″ xy , σ″ xz , σ″ yz :

[0093] σ″ x = σ x，A - σ x，B

[0094] σ″ y = σ y，A - σ y，B

[0095] σ″ z = σ z，A - σ z，B

[0096] σ″ xy = σ xy，A - σ xy，B

[0097] σ″ xz = σ xz，A - σ xz，B

[0098] σ″ yz = σ yz，A - σ yz， B

[0099] Wherein, σ″ x is the stress range in the x - direction, σ x，A is the stress in the x - direction under the transient state A, σ x，B is the stress in the x - direction under the transient state B; σ″ y is the stress range in the y - direction, σ y，A is the stress in the y - direction under the transient state A, σ y，B is the stress in the y - direction under the transient state B; σ′ z is the stress range in the z - direction, σ z，A is the stress in the z - direction under the transient state A, σ z，B is the stress in the z - direction under the transient state B; σ′ xy is the stress range in the x - y direction, σ xy，A is the shear stress in the x - y direction under the transient state A, σ xy，B is the shear stress in the x - y direction under the transient state B; σ′ xz is the stress range in the x - z direction, σ xz，Ais the shear stress in the x-z direction under the transient A, σ xz，B is the shear stress in the x-z direction under the transient B; σ″ yz is the stress range in the y-z direction, σ yz，A is the shear stress in the y-z direction under the transient A, σ yz，B is the shear stress in the y-z direction under the transient B.

[0100] Then, according to [σ″ x , σ″ y , σ″ z , σ″ xy , σ″ xz , σ″ yz , the corresponding principal stresses are determined. If the stress value with the largest absolute value among the principal stresses is positive, it is determined that the stress peak state of the transient A is greater than the stress peak state of the transient B; otherwise, it is determined that the stress peak state of the transient A is less than the stress peak state of the transient B. It should be noted that the method of determining the principal stresses according to [σ″ x , σ″ y , σ″ z , σ″ xy , σ″ xz , σ″ yz can refer to the process for the principal stresses [σ′1, σ′2, σ′3] in the above text, or can be flexibly selected according to the actual situation, and the protection scope of the present invention is not limited thereby.

[0101] In this embodiment, the stress peak state caused by the transient A is [-7.0, 577.2, 486.9, 0.0, 0.0, 0.0], and the stress peak state caused by the transient B is [-15.9, 350.9, 296.9, 0.0, 0.0, 0.0]. The stress range between these two stress peak states is [8.9, 226.3, 190.0, 0.0, 0.0, 0.0], and the corresponding principal stresses are [226.3, 190.0, 8.9]. It can be seen that the value with the largest absolute value among the principal stresses, that is, 226.3, is positive, so it is determined that the stress peak state of the transient A is greater than the stress peak state of the transient B. Similarly, it can be determined that the stress valley state of the transient A is less than the stress peak state of the transient B, and the specific process will not be elaborated here.

[0102] Fourth step, based on the above comparison results, evaluate the "size" relationship between the transient A and the transient B.

[0103] In this embodiment, Salt_A (1132 MPa) > Salt_B (688 MPa), and CUF_A (1 / 351) > CUF_B (1 / 1268), and the transient A stress peak state > the transient B stress peak state, and the transient A stress valley state < the transient B stress valley state. Therefore, it is considered that for the fatigue life of metal components, transient A can envelope transient B, that is, transient A is greater than transient B.

[0104] The above are only the preferred embodiments of the present invention, and do not limit the scope of its patents accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, directly or indirectly applied in other related technical fields, shall be similarly included in the scope of patent protection of the present invention.

Claims

1. A transient equivalence evaluation method for the primary circuit of a nuclear power plant, characterized in that The transient equivalence evaluation method includes: respectively obtaining the stress states of the metal component changing with time under transient one and transient two, and based on the stress states, respectively determining the stress extreme value moments under transient one and transient two; according to the stress extreme value moments, respectively determining the evaluation parameters of transient one and transient two, wherein the evaluation parameters include alternating stress intensity, fatigue damage amount, stress peak state, and stress valley state; judging according to the evaluation parameters under transient one and transient two, if all of the following conditions are satisfied, it is judged that transient one is greater than transient two: a. The alternating stress intensity of transient one is greater than that of transient two; b. The fatigue damage amount of transient one is greater than that of transient two; c. The stress peak state of transient one is greater than that of transient two; d. The stress valley state of transient one is less than that of transient two.

2. The transient equivalence evaluation method according to claim 1, wherein The transient equivalence evaluation method further includes: under the same transient, determining the stress states of the metal component corresponding to two stress extreme value moments, calculating the stress range between the two stress extreme value moments, calculating the corresponding principal stress according to the stress range, and determining the stress peak state and stress valley state under this transient based on the principal stress.

3. The transient equivalence evaluation method according to claim 2, wherein it is assumed that The two stress extreme value moments are t i Time and t j moment, the t i The stress state at the moment is [σ x，i , σ y，i , σ z，i , σ xy，i , σ xz，i , σ yz，i ], the t j The stress state at the moment is [σ x，j , σ y，j , σ z，j , σ xy，j , σ xz，j , σ yz，j ]; The transient equivalence evaluation method also includes calculating the t by the following formula i Time and t j The stress range between the moments [σ′ x ,σ′ y ,σ′ z ,σ′x y ,σ′ xz ,σ′ yz ]: σ′ x = σ x，i - σ x，j σ′ y = σ y，i - σ y，j σ′ z = σ z，i - σ z，j σ′ xy = σ xy，i - σ xy，j σ′ xz = σ xz,i - σ xz，j σ′ yz = σ yz，i - σ yz，j Wherein, σ' x is the stress range in the x-direction between the time of t i and the time of t j , σ x，i is the stress in the x-direction at the time of t i ; σ x，j is the stress in the x-direction at the time of t j ; σ' y is the stress range in the y-direction between the time of t i and the time of t j , σ y，i is the stress in the y-direction at the time of t i , σ y，j is the stress in the y-direction at the time of t j ; σ' z is the stress range in the z-direction between the time of t i and the time of t j , σ z，i is the stress in the z-direction at the time of t i , σ z，j is the stress in the z-direction at the time of t j ; σ' xy is the shear stress range in the x-y direction between the time of t i and the time of t j , σ xy，i is the shear stress in the x-y direction at the time of t i , σ xy，j is the shear stress in the x-y direction at the time of t j ; σ' xz is the shear stress range in the x-Z direction between the time of t i and the time of t j , σ xz，i is the shear stress in the x-z direction at the time of t i , σ xz，j is the shear stress in the x-z direction at the time of t j ; σ' y，z is the shear stress range in the y-z direction between the time of t i and the time of t j , σ yz，i is the shear stress in the y-z direction at the time of t i , σ yz，j is the shear stress in the y-z direction at the time of t j .

4. The transient equivalence evaluation method according to claim 3, characterized in that The transient equivalence evaluation method further includes: determining corresponding principal stresses according to the stress ranges [σ′ x , σ′ y , σ′ z , σ′ xy , σ′ xz , σ′ yz ; if the stress value with the largest absolute value among the principal stresses is positive, then at this transient, the stress state at the moment of t i is the stress peak state, and the stress state at the moment of t j is the stress valley state; otherwise, at this transient, the stress state at the moment of t i is the stress valley state, and the stress state at the moment of t j is the stress peak state.

5. The transient equivalence evaluation method according to claim 1, characterized in that The transient equivalence evaluation method further includes: determining the stress peak states of transient one and transient two respectively, calculating the stress range and the corresponding principal stress between the stress peak state of transient one and the stress peak state of transient two, and comparing the stress peak state of transient one and the stress peak state of transient two based on the principal stress.

6. The transient equivalence evaluation method according to claim 5, wherein it is assumed that The stress peak state of the first transient is [σ x，A , σ y，A , σ z，A , σ xy′A , σ xz，A , σ yz，A , and the stress peak state of the second transient is [σ x，B , σ y，B , σ z，B , σ xy，B , σ xz，B , σ yz，B ; The transient equivalence evaluation method further includes calculating the stress range [σ″ x , σ″ y , σ″ z , σ″ xy , σ″ xz , σ″ yz between the stress peak state of the first transient and the stress peak state of the second transient through the following formula: σ″ x = σ x，A - σ x，B σ″ y = σ y，A - σ y，B σ″ z = σ z，A - σ z，B σ″ xy = σ xy，A - σ xy，B σ xz = σ xz，A - σ xz，B σ yz = σ yz，A - σ yz，B where, σ″ x is the stress range in the x - direction between the stress peak state of the first transient and the stress peak state of the second transient, σ x，A is the stress in the x - direction under the first transient, σ x，B is the stress in the x - direction under the second transient; σ″ y is the stress range in the y - direction between the stress peak state of the first transient and the stress peak state of the second transient, σ y，A is the stress in the y - direction under the first transient, σ y，B is the stress in the y - direction under the second transient; σ″ z is the stress range in the z - direction between the stress peak state of the first transient and the stress peak state of the second transient, σ z，A is the stress in the z - direction under the first transient, σ z，B is the stress in the z - direction under the second transient; σ″ xy is the shear stress range in the x - y direction between the stress peak state of the first transient and the stress peak state of the second transient, σ xy，A is the shear stress in the x - y direction under the first transient, σ xy，B is the shear stress in the x - y direction under the second transient; σ″ xz is the shear stress range in the x-z direction between the stress peak state of the first transient and the stress peak state of the second transient, σ xz，A is the shear stress in the x-z direction under the first transient, σ xz，B is the shear stress in the x-z direction under the second transient; σ″ yz is the shear stress range in the y-z direction between the stress peak state of the first transient and the stress peak state of the second transient, σ yz，A is the shear stress in the y-z direction under the first transient, σ yz，B is the shear stress in the y-z direction under the second transient.

7. The transient equivalence evaluation method according to claim 6, wherein The transient equivalence evaluation method further includes: determining corresponding principal stresses according to the stress ranges [σ″ x , σ″ y , σ″ z , σ″ xy , σ″ xz , σ″ yz . If the stress value with the largest absolute value among the principal stresses is positive, the stress peak state of Transient 1 is greater than that of Transient 2; otherwise, the stress peak state of Transient 1 is less than that of Transient 2.

8. The transient equivalence evaluation method according to claim 1, characterized in that, The transient equivalence evaluation method further includes: determining the stress valley states of transient one and transient two respectively, calculating the stress range and the corresponding principal stress between the stress valley state of transient one and the stress valley state of transient two, and comparing the stress valley state of transient one and the stress valley state of transient two based on the principal stress. If the stress value with the largest absolute value in the principal stress is a positive number, the stress valley state of transient one is greater than the stress peak state of transient two, otherwise the stress peak state of transient one is less than the stress peak state of transient two.

9. The transient equivalence evaluation method according to claim 1, wherein The transient equivalence evaluation method further includes: before obtaining the stress states under transient one and transient two, establishing a finite element analysis model of the metal component.

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