Destructive evaluation device, method, and program

Abstract

To provide a destruction evaluation technology for structures that does not become excessively conservative or non-conservative, even when the destruction forms (brittle fracture, elastic-plastic fracture) of an evaluation region change over time.SOLUTION: A destruction evaluation device 10 comprises: a database that stores, for each region of a structure, an action history 11 of factors that promote degradation over time; a selection unit 18 that selects an evaluation region 20 of the structure on the basis of design information 17; a discrimination unit 21 that discriminates a destruction form 23 from the standpoints of at least an elastic-plastic fracture and a brittle fracture, on the basis of the structural dynamic information 12 and action history 11 of the evaluation region 20; an acquisition unit 22 that acquires registered information 25 of cracks present in the evaluation region 20; and an evaluation unit 26 that evaluates the destruction of the evaluation region 20, correlating the destruction form 23 to the existent cracks.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a technique for evaluating the destruction of an aged structure. [Background technology]

[0002] As nuclear power plants age, the importance of integrity assessment of structures is increasing. Stable operation and improved availability of nuclear equipment are extremely important in terms of the safety and economy of the entire plant. Typical aging phenomena in nuclear equipment include stress corrosion cracking (SCC) and the occurrence and progression of cracks due to fatigue. In integrity assessment, a fracture assessment due to crack progression is carried out based on fracture mechanics for equipment in which cracks have been detected during inspection or in which the presence of cracks is suspected.

[0003] The fracture assessment method for structures requires the use of an appropriate assessment method depending on the fracture mode, and there are prescribed regulations for this. For example, fracture assessment methods for structures with cracks include the linear fracture mechanics assessment method and the elastic-plastic fracture mechanics assessment method. The linear fracture mechanics assessment method is applied to brittle materials, and stress intensity factors are generally used for fracture assessment. The elastic-plastic fracture mechanics assessment method is applied when large plastic deformation (large-scale yielding) occurs at the crack tip and ductile crack propagation is taken into account, and fracture resistance curves (hereafter referred to as JR curves) are generally used for fracture assessment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-65921 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-294880 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-167925 Summary of the Invention [Problem to be solved by the invention]

[0005] Mechanical tests under conditions corresponding to the structure's operating environment and material tests using test specimens placed at specific locations on the structure during operation are used to understand changes in the structure's material properties and to perform destructive assessments of the structure. However, the material property data obtained through such tests is representative data for the environment and specific location. The influence of the environment varies from part to part on the structure. For this reason, the above-mentioned tests pose a challenge in understanding changes in material properties in the target location and performing destructive assessments that reflect the influence of these property changes.

[0006] The linear fracture mechanics evaluation method, which is one of the methods for evaluating the integrity of structures, is an evaluation method that targets brittle fracture. According to this evaluation method, the stress intensity factor K at the tip of a crack that has occurred in a structure is calculated based on the fracture toughness value (K Ic ), the structure is assessed to be at risk of unstable fracture. However, while the linear fracture mechanics assessment method is appropriate for low-toughness materials or materials whose toughness has decreased due to aging, it is inappropriate for high-toughness materials whose toughness does not decrease.

[0007] For this reason, applying linear fracture mechanics evaluation methods to high-toughness materials whose toughness does not decrease over their service life poses the problem of overly conservative or unconservative fracture assessment of structures. For such high-toughness materials, elastic-plastic fracture assessment methods should be applied, but if the toughness decreases over time, there is also the problem of overly conservative or unconservative fracture assessment of structures.

[0008] The embodiments of the present invention have been made taking these circumstances into consideration, and aim to provide a fracture evaluation technique for structures that will not result in an overly conservative or unconservative evaluation of the integrity of a structure, even if the fracture mode (brittle fracture, elasto-plastic fracture) of the evaluated portion changes over time. [Means for solving the problem]

[0009] The destruction assessment device according to the embodiment includes a database that stores the action history of factors that promote aging deterioration for each part of a structure, a selection unit that selects an evaluation part of the structure based on design information, a discrimination unit that discriminates the destruction form from the standpoint of at least elastic-plastic destruction and brittle destruction based on the structural mechanics information and the action history of the evaluation part, an acquisition unit that acquires registration information of cracks present in the evaluation part, and an assessment unit that evaluates destruction of the evaluation part by matching the destruction form to the existing cracks. [Effects of the Invention]

[0010] An embodiment of the present invention provides a fracture evaluation technique for structures that does not result in an overly conservative or unconservative evaluation of structural integrity, even if the fracture mode (brittle fracture, elastic-plastic fracture) of the evaluated area changes over time. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram showing a destruction evaluation device according to a first embodiment of the present invention. [Figure 2] A graph showing the relationship between the J integral value (Japp) of a crack at stress σ (σ1<σ2<σ3) and the ductile crack growth resistance Jmat (JR curve) when the fracture mode is elastic-plastic fracture. [Figure 3] FIG. 10 is a block diagram showing a destruction evaluation device according to a second embodiment. [Figure 4] 3 is a flowchart illustrating the steps of a destruction assessment method according to an embodiment and an algorithm of a destruction assessment program. DETAILED DESCRIPTION OF THE INVENTION

[0012] (First embodiment) Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a block diagram showing a destruction assessment device 10A (10) according to a first embodiment of the present invention. As described above, the destruction assessment device 10A includes a database that stores action histories 11 of factors promoting aging deterioration for each portion of a structure, a selection unit 18 that selects an evaluation portion 20 of the structure based on design information 17, a discrimination unit 21 that discriminates a fracture mode 23 from the viewpoint of at least elastic-plastic fracture and brittle fracture based on structural mechanics information 12 and the action history 11 of the evaluation portion 20, an acquisition unit 22 that acquires registered information 25 of cracks present in the evaluation portion 20, and an evaluation unit 26 that evaluates the fracture of the evaluation portion 20 by matching the fracture mode 23 to the present cracks.

[0013] The database (not shown) stores structural mechanics information 12 and structure design information 17 in addition to the above-mentioned action history 11. In this embodiment, the evaluation portion 20 of the structure is assumed to be piping, vessels, equipment, welds, etc. made of metal members that become embrittled over time in the high temperature, high pressure, and high radiation environment of a nuclear power plant.

[0014] The evaluation portion 20 is selected by the selection portion 18 based on the design information 17 of the structure through user operation of the operation portion 16. Specifically, a list of the structure and its constituent portions is displayed on the screen based on the design information 17, and the user is prompted to select the portion where he or she wishes to perform destructive evaluation, as the evaluation portion 20. There are no particular restrictions on the evaluation portion 20 to be selected, and it may be any portion in a reactor internal structure of a nuclear power plant where age-related deterioration is a concern.

[0015] Furthermore, the design information 17 is linked to the action history 11 of factors that accelerate aging deterioration for each part of the structure, and both are stored in a database (not shown). The acceleration factors stored as the action history 11 are not limited to the temperature, pressure, and radiation dose described above, but are applicable as long as they have the effect of accelerating the aging deterioration of the structure. These acceleration factors are not only data detected by sensors 19 placed on the structure, but also virtual data derived from operating conditions, which are stored as the action history 11.

[0016] It is also possible that there is no action history 11 or structural mechanics information 12 corresponding to the evaluation portion 20 selected by the selection unit 18. In this case, the failure mode 23 of the evaluation portion 20 can be determined directly from the observation results of a test piece placed near the evaluation portion 20. Alternatively, the action history 11 and structural mechanics information 12 of another portion with similar conditions may be applied to the evaluation portion 20.

[0017] The failure modes23 of structures are broadly classified into three types: linear elastic failure (brittle failure), elastic-plastic failure, and plastic collapse. Of these, linear elastic failure (brittle failure) occurs when plastic deformation is limited near the crack tip (small-scale yielding), causing the crack to propagate rapidly and resulting in failure. Linear elastic failure (brittle fracture) is a failure mode23 observed in high-strength, low-toughness (low-ductility) metals.

[0018] In elastic-plastic fracture, the crack propagates and fractures after relatively large plastic deformation (large-scale yielding) at the crack tip. Elastic-plastic fracture is a fracture mode23 observed in low-strength, high-toughness (high-ductility) metals. In plastic collapse, the crack does not propagate, the tip becomes blunt, and the entire cross section yields and fractures. Plastic collapse is a fracture mode23 observed in extremely high-toughness (high-ductility) metals.

[0019] The structural mechanics information 12 is classified into stress data, structural data, and material property data, each of which is stored in a database (not shown). The stress data is information relating to the stress and allowable stress applied to the evaluation portion 20.

[0020] The structural data is information relating to the dimensions of the structure including the evaluation portion 20. Specifically, it includes the shape and dimensions of the structure, the shape and dimensions of each part constituting the structure, the shape and dimensions of the base material, the shape and dimensions of the welds connecting the base materials, etc. The structural data may also include design information when the structure was manufactured.

[0021] The material property data is information about the material properties of the constituent material of the evaluation portion 20. Specifically, the material property data includes the stress-strain curve, plane strain fracture toughness (K Ic ), elastic-plastic fracture toughness value (JIc ), fracture resistance curve (JR curve), and other material property data.

[0022] Based on the action history 11 and the structural mechanics information 12, the discrimination unit 21 discriminates the fracture mode 23 of the evaluation portion 20 from two options, elastic-plastic fracture and brittle fracture, or three options including plastic collapse in some cases, and transfers the results to the evaluation unit 26. Note that the discrimination unit 21 is not limited to the above two or three options, and may have four or more options.

[0023] The discrimination of the fracture mode 23 in the discrimination unit 21 is performed, for example, by a two-parameter evaluation method. Here, the two-parameter evaluation method is a method for discriminating the fracture mode using a fracture assessment diagram (FAC) consisting of linear fracture mechanics parameters and plastic collapse parameters. Information required for this two-parameter evaluation method is provided from the action history 11 and structural mechanics information 12.

[0024] In the case of a nuclear power plant, the registered crack information 25 is information on the shape and dimensions of cracks detected by flaw detection tests conducted during pre-service inspections (SPI) and in-service inspections (ISI). Examples of flaw detection tests include surface inspections such as penetrant inspections and magnetic particle inspections, and volumetric inspections such as radiography and ultrasonic inspections. Registered information 25 includes information based on actual measurements regarding the classification of cracks (planar cracks, linear cracks, lamination cracks, etc.), the location and direction of cracks in the structure, and the dimensions of cracks (length, depth, etc.).

[0025] The acquisition unit 22 acquires registration information 25 of cracks present in the evaluation portion 20 selected by the selection unit 18, and transfers it to the evaluation unit 26. The evaluation unit 26 evaluates the damage of this evaluation portion 20 based on the damage form 23 corresponding to the crack present in the evaluation portion 20, and causes the output unit 27 to output the evaluation result.

[0026] The evaluation unit 26 applies a crack propagation simulation corresponding to brittle fracture to the evaluation portion 20 determined to have undergone brittle fracture, and performs a fracture evaluation. Similarly, for cracks in the evaluation portion 20 determined to have undergone elastic-plastic fracture or plastic collapse, the evaluation unit 26 applies a crack propagation simulation corresponding to either elastic-plastic fracture or plastic collapse, and performs a fracture evaluation. Note that the parameters required for each simulation are provided from the structural mechanics information 12, and it is also possible to apply an evaluation formula 15 corresponding to each simulation.

[0027] When the fracture mode 23 is determined to be brittle fracture, the evaluation unit 26 determines the stress intensity factor K of the crack included in the evaluation region 20 based on the structural mechanics information 12. Then, this stress intensity factor K is used as the fracture toughness K Ic If it exceeds this value, the crack growth rate (da / dt) is further determined. Then, the crack size in the future (at the next inspection time) is estimated, and the result can be output from the output unit 27.

[0028] Furthermore, when the fracture mode 23 is determined to be an elastic-plastic fracture, the evaluation unit 26 further determines the J integral value of the crack included in the evaluation region 20 based on the stress intensity factor K and the structural mechanics information 12. Then, this J integral value is used as the fracture toughness J Ic Based on whether the crack propagation exceeds the threshold value, it is also determined whether the crack propagation will continue in the future, and the result is output from the output unit 27.

[0029] Furthermore, the evaluation unit 26 can correct the discrimination parameters of the fracture mode 23 in the discrimination unit 21 and the determination parameters of the stress intensity factor K and the propagation rate (da / dt) so as to eliminate the difference between the crack size estimated in the past (at the time of the previous inspection) and the crack size actually measured at the present time. Ic Instead, failure evaluation can be performed using Weibull stress.

[0030] Figure 2 shows the J integral value (J) of the crack at stress σ (σ1<σ2<σ3) when the fracture mode 23 is elastic-plastic fracture. app ) and ductile crack growth resistance Jmat 10 is a graph showing the relationship between the load (stress σ) on the evaluation portion 20 and the J integral value (J app ) increases, and the elastic-plastic fracture toughness value (J Ic Elastic-plastic fracture begins at a stress σ1 that exceeds

[0031] As the stress further increases to σ2, stable fracture occurs, but as the crack progresses (Δa), J mat Since the JR curve also increases, the crack propagation stops at a2. If the load on the evaluation area 20 increases further and exceeds the stress σ3 that satisfies the following equations (1) and (2), unstable fracture occurs, and the crack continues to propagate even if the stress σ is constant. J app ≧J mat (1) ∂J app / ∂a=dJ mat / da (2)

[0032] (Second embodiment) Next, a second embodiment of the present invention will be described with reference to Fig. 3. Fig. 3 is a block diagram showing a destruction assessment device 10B (10) according to the second embodiment. In addition to the configuration of the destruction assessment device 10A of the first embodiment, the destruction assessment device 10B of the second embodiment further includes a virtual crack estimation unit 32, a convergence calculation unit 28, and a soundness determination unit 29. In Fig. 3, parts having the same configuration or function as those in Fig. 1 are designated by the same reference numerals, and duplicated explanations will be omitted.

[0033] When the registered information 25 of the crack in the evaluation portion 20 is unknown, the estimation unit 32 estimates the presence of a virtual crack based on the existing information 31. Here, the registered information 25 of the crack is unknown when a flaw detection test has not been conducted in the evaluation portion 20 of interest or when the crack has not been detected due to suspected omission. Furthermore, the existing information 31 may be the registered information 25 of a crack detected in another portion that has the same action history 11 and structural mechanics information 12, or information on a crack detected in a corresponding portion of another nuclear power plant.

[0034] The convergence calculation unit 28 calculates parameters for performing fracture assessment based on at least one of a statistical method and a numerical analysis. For example, the parameters constituting the Weibull stress calculation formula need to be determined by a statistical method, but the convergence calculation unit 28 can automatically determine the optimal parameters.

[0035] The determination unit 29 determines the soundness of the structure based on the evaluation result of the damage at the evaluation portion 20 executed by the evaluation unit 26, and outputs the determination result to the output unit 27. Based on this soundness determination result, a maintenance plan for the structure during future inspection periods can be formulated. Alternatively, the soundness of the structure against the expected strength of a disaster such as a major earthquake can be determined.

[0036] The steps of the destruction assessment method according to the embodiment and the algorithm of the destruction assessment program will be described with reference to the flowchart in Figure 4. First, the action history 11 of factors promoting aging deterioration is stored in a database for each part of the structure (S11). Then, an evaluation part 20 of the structure is selected based on design information 17 (S12).

[0037] If there is structural mechanics information 12 and action history 11 corresponding to the selected evaluation area 20 (S13, No), the fracture mode 23 of the evaluation area 20 is determined from the perspective of elastic-plastic fracture and brittle fracture based on this structural mechanics information 12 and action history 11 (S15).

[0038] On the other hand, if there is no structural mechanics information 12 and action history 11 corresponding to the selected evaluation portion 20 (S13, Yes), analogous information such as the action history 11 and structural mechanics information 12 of other portions with similar conditions or the results of test specimens is obtained (S14), and the failure mode 23 of the evaluation portion 20 is determined (S15).

[0039] Next, if there is registered information 25 for a crack present in the selected evaluation area 20 (S16, No), the registered information 25 for this crack is obtained, and the fracture form 23 is matched to this crack to evaluate the fracture of the evaluation area 20 (S18), and information on future crack progression, etc. is output as a result.

[0040] On the other hand, if there is no registered information 25 for cracks present in the selected evaluation area 20 (S16, Yes), analogous information such as crack information for other areas with similar conditions is obtained (S17), and the fracture form 23 is matched to this crack to evaluate the fracture of the evaluation area 20 (S18), and information on future crack progression, etc. is output as the evaluation result.

[0041] Then, based on the evaluation results of the damage in the evaluation portions 20, the soundness of the structure is judged (S19), and the judgment results are output to the output unit 27. Then, the flow from (S12) to (S19) is repeated until all evaluation portions 20 have been selected (S20 No, Yes, END).

[0042] According to at least one of the embodiments of the destruction assessment device described above, the destruction mode of the evaluation portion that changes over time can be evaluated from the perspective of brittle fracture and elastic-plastic fracture, thereby making it possible to prevent the evaluation of the soundness of the structure from being overly conservative or unconservative.

[0043] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as the inventions described in the claims and their equivalents.

[0044] The destruction assessment device described above includes a control device with a highly integrated processor such as a dedicated chip, FPGA (Field Programmable Gate Array), GPU (Graphics Processing Unit), or CPU (Central Processing Unit), a storage device such as ROM (Read Only Memory) or RAM (Random Access Memory), an external storage device such as HDD (Hard Disk Drive) or SSD (Solid State Drive), a display device such as a monitor, input devices such as a mouse and keyboard, and a communication I / F, and can be realized with a hardware configuration using a normal computer. Therefore, the components of the destruction assessment device can also be realized by a computer processor and can be operated by a destruction assessment program.

[0045] The destruction assessment program may be provided by being pre-installed in a ROM, etc. Alternatively, the program may be provided by being stored in an installable or executable file format on a computer-readable storage medium such as a CD-ROM, CD-R, memory card, DVD, or flexible disk (FD).

[0046] The destruction assessment program according to this embodiment may be stored on a computer connected to a network such as the Internet and provided by downloading it via the network. The destruction assessment device may also be configured by combining separate modules that independently perform the functions of the components and are interconnected via a network or dedicated lines. [Explanation of symbols]

[0047] 10 (10A, 10B)...destruction evaluation device, 11...action history, 12...structural mechanics information, 15...evaluation formula, 16...operation unit, 17...design information, 18...selection unit, 19...sensor, 20...evaluation area, 21...discrimination unit, 22...acquisition unit, 23...fracture form, 25...crack registration information, 26...evaluation unit, 27...output unit, 28...convergence calculation unit, 29...judgment unit, 31...existing information, 32...estimation unit.

Claims

1. A database that stores the history of factors that accelerate deterioration over time for each part of a structure, and a selection unit that selects an evaluation portion of the structure based on design information; a discrimination unit that discriminates the fracture mode from the viewpoint of at least elastic-plastic fracture and brittle fracture based on the structural mechanics information of the evaluation portion and the action history; an acquisition unit that acquires registration information of cracks present in the evaluation portion; and an evaluation unit that evaluates the destruction of the evaluation portion by matching the destruction form to the existing crack.

2. 2. The destructive evaluation device according to claim 1, A destruction evaluation device including an estimation unit that estimates an existing virtual crack based on existing information when registered information of the crack in the evaluation portion is unknown.

3. 3. The destructive evaluation device according to claim 1 or 2, A destruction evaluation device including a convergence calculation unit that calculates a parameter for evaluating destruction of the evaluation portion based on at least one of a statistical method and a numerical analysis.

4. 3. The destructive evaluation device according to claim 1 or 2, A destruction evaluation device in which the destruction of the evaluation portion is evaluated based on an evaluation formula corresponding to the destruction mode.

5. 3. The destructive evaluation device according to claim 1 or 2, The destructive evaluation device, wherein the action history is a detected amount of at least one of temperature and neutrons based on a sensor output.

6. 3. The destructive evaluation device according to claim 1 or 2, The action history is obtained from the observation results of a test piece placed near the evaluation location.

7. 3. The destructive evaluation device according to claim 1 or 2, The structural mechanics information includes at least one of stress data, structural data, and material property data of the structure.

8. 3. The destructive evaluation device according to claim 1 or 2, The fracture evaluation device distinguishes the fracture mode from the viewpoint of plastic collapse in addition to the elastic-plastic fracture and the brittle fracture.

9. 3. The destructive evaluation device according to claim 1 or 2, A destruction assessment device comprising a judging unit that judges the soundness of the structure based on the assessment result of the destruction at the assessment portion.

10. A step of accumulating the action history of factors that accelerate aging deterioration in a database for each part of the structure; selecting an evaluation portion of the structure based on design information; A step of determining a fracture mode from the viewpoint of at least elastic-plastic fracture and brittle fracture based on the structural mechanics information of the evaluation portion and the action history; acquiring registration information of cracks present in the evaluation portion; and evaluating the failure of the evaluation portion by matching the failure form to the existing crack.

11. On the computer, A step of storing the action history of factors that accelerate aging deterioration in a database for each part of the structure; selecting an evaluation portion of the structure based on design information; a step of determining a fracture mode from the viewpoint of at least elastic-plastic fracture and brittle fracture based on the structural mechanics information of the evaluation portion and the action history; acquiring registration information of cracks present in the evaluation portion; a destruction evaluation program that executes a step of evaluating destruction of the evaluation portion by matching the destruction form to the existing cracks.

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