JP2014002074A - Crack development prediction system and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow development of a crack generated on a plant structure to be highly accurately predicted.SOLUTION: A crack development prediction system includes: a potentiometry method measurement system 31 for measuring a potential difference in the vicinity of a crack of reactor primary system piping 21 during plant operation; a strain measurement system 32 for measuring a strain value in the vicinity of the crack of the piping during the plant operation; and an operation device 33 comprising a residual stress value calculation section 34, an evaluation residual stress distribution generation section 35, a stress intensity factor calculation section 36 and a crack development amount prediction operation section 37. The residual stress value calculation section 34 calculates a residual stress value of a leading end of the crack on the basis of a crack shape calculated by potential difference data measured, strain value data measured or the like. The evaluation residual stress distribution generation section 35 obtains an evaluation residual stress distribution by using the residual stress value. The stress intensity factor calculation section 36 calculates a stress intensity factor of any position of the crack on the basis of the evaluation residual stress distribution or the like. The crack development amount prediction operation section 37 obtains a crack development speed determined by a correlation with the stress intensity factor, performs an operation of a crack development amount during a plant in-service period and predicts the crack development amount.

Description

  The present invention relates to a crack propagation prediction system and method for predicting the growth of a crack generated in a plant structure.

  In nuclear power plants such as boiling water reactors and pressurized water reactors, plant structures such as the reactor primary system piping that come into contact with the reactor primary system water, which is high temperature water, are exposed to the usage environment of high temperature water. Stress corrosion cracking (SCC) may occur. In the unlikely event that a crack due to stress corrosion cracking occurs in such a plant structure, the progress of the crack is monitored during the operation period of the nuclear power plant in order to evaluate its soundness. It is important to estimate the quantity from the viewpoint of maintaining the soundness of the nuclear power plant.

  Patent Documents 1 to 4 propose methods and apparatuses for calculating the amount of crack propagation in plant structures such as piping. In Patent Documents 1 and 2, pressure, temperature, and axial force are detected in real time in pipes that receive internal pressure, heat, and mechanical load, and stress generated in the pipes is calculated to determine the relationship with the crack propagation curve. An apparatus for calculating the amount of crack propagation is disclosed.

  Patent Document 3 discloses a method and system for performing simple crack growth prediction when receiving an unsteady load. Furthermore, Patent Document 4 discloses a method of constructing a residual stress database based on the measurement results of the residual stress on the surface and inside measured by various methods, and performing crack growth evaluation based on the database.

JP-A-9-145578 JP 10-38829 A JP 2003-172673 A JP-A-2005-351644

W. Cheng, I.D. Finnie, “The Crack Compliance Method for Residual Stress Management,” Welding in The World, Vol. 28, no. 5/6, p. 103 (1990)

  If a crack has occurred in the plant structure of a nuclear power plant, in order to improve the accuracy of predicting the amount of crack growth during the operation period of the plant, the residual stress distribution of the evaluation target part during plant operation is grasped. It is effective to do. However, the techniques described in Patent Documents 1 to 4 described above are for detecting the residual stress of the plant structure during the regular inspection of the plant, and the residual stress distribution during the plant operation in a pipe welded portion having a crack or the like. Is not fully considered.

  The object of the present invention has been made in consideration of the above-mentioned circumstances, and can predict the progress of a crack generated in a plant structure with high accuracy and improve the reliability and safety of the plant. It is to provide a crack propagation prediction system and method.

  A crack growth prediction system according to the present invention is a crack growth prediction system for predicting the growth of a crack generated in a plant structure, and a potential difference method for measuring a potential difference in the vicinity of the crack of the plant structure during plant operation. Based on data from a measurement system, a strain measurement system that measures a strain value near the crack of the plant structure during plant operation, and the potentiometric measurement system and the data from the strain measurement system, the amount of progress of the crack is determined. A computing device for predicting, the computing device comprising a residual stress value calculating unit, an evaluation residual stress distribution creating unit, a stress intensity factor calculating unit, and a crack propagation amount predicting calculating unit, and the residual stress value Based on the crack shape calculated from the potential difference data from the potentiometric measurement system, the strain value data from the strain measurement system, etc., the calculation unit is a residual at an arbitrary position of the crack. A residual stress distribution profile that is assumed in advance in the target part of the plant structure using the residual stress value calculated by the residual stress value calculator. The residual stress distribution for evaluation is obtained by correcting the stress, and the stress intensity factor calculation unit calculates the stress intensity factor at an arbitrary position of the crack based on the residual stress distribution for evaluation and the crack shape, etc. The crack growth amount prediction calculation unit is configured to calculate a crack growth amount during a service period of the plant by obtaining a crack growth rate determined by correlation with the stress intensity factor and to predict the crack growth rate. It is characterized by that.

  The crack growth prediction method according to the present invention is a crack growth prediction method for predicting the growth of a crack generated in a plant structure. In the crack growth prediction method, the potential difference and strain value in the vicinity of the crack of the plant structure are determined during plant operation. Based on the first step to be measured, the crack shape calculated from the potential difference data measured in the first step, the strain value data measured in the first step, etc. By correcting the residual stress distribution profile assumed in advance in the target part of the plant structure using the second step of calculating the residual stress value at the position and the residual stress value calculated in the second step. Based on the third step of obtaining the residual stress distribution for evaluation, the crack shape, the residual stress distribution for evaluation obtained in the third step, etc. The crack growth rate determined by the correlation between the fourth step of calculating the stress intensity factor at any position of the above and the stress intensity factor calculated in the fourth step is determined during the service period of the plant. And a fifth step of calculating and predicting the crack growth amount.

  According to the crack propagation prediction system and method according to the present invention, a strain value or the like in the vicinity of a crack in a plant structure is measured during plant operation, and a residual stress distribution for evaluation is accurately obtained based on this measurement data. Therefore, it is possible to predict the progress of a crack generated in the plant structure with high accuracy from the evaluation residual stress distribution and the like, thereby improving the reliability and safety of the plant.

The system block diagram of the nuclear power plant used as the evaluation object of one Embodiment of the crack growth prediction system which concerns on this invention. FIG. 1 shows the measurement status of the reactor primary system piping in FIG. 1, (A) is a side sectional view, (B) is an enlarged view of IIB in FIG. 2 (A), and (C) is IIC-IIC in FIG. 2 (B). Sectional drawing which follows a line. The block diagram which shows one Embodiment of the reactor primary system piping from the III arrow of FIG. 2 (B), and the crack growth prediction system applied to this nuclear reactor primary system piping. The flowchart which shows the prediction procedure of the crack growth amount which one Embodiment of the crack growth prediction system of FIG. 3 performs. Explanatory drawing explaining how to obtain | require the residual stress distribution for evaluation from the residual stress value calculated from measurement data.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a system configuration diagram of a nuclear power plant to be evaluated in one embodiment of a crack growth prediction system according to the present invention. The nuclear power plant shown in FIG. 1 is a boiling water reactor, and this boiling water reactor is generally configured as follows.

  That is, a reactor containment vessel (both not shown) is installed in the reactor building, and a reactor pressure vessel 10 is installed in the reactor containment vessel. A reactor core 11 and cooling water are accommodated in the reactor pressure vessel 10, and when this cooling water flows from the lower side of the core 11 to the upper side, the temperature of the core 11 is increased by taking away the heat of nuclear reaction. The heated cooling water is in a two-phase flow state of steam and water and flows into a steam separator 12 provided above the core 11.

  The cooling water is separated into water and steam by the steam separator 12, and the separated steam is dried by removing moisture from the steam dryer 13 provided above the steam separator 12. This dry steam is supplied to the turbine system through the main steam pipe 14 connected to the reactor pressure vessel 10, and is supplied to work in this turbine system. On the other hand, the water separated by the steam separator 12 flows downward from the core 11 by the action of the jet pump 15 and again flows upward from the bottom of the core 11. Thereafter, the same cycle is repeated.

  The reactor pressure vessel 10 includes a vessel main body 16 and a lid body 17 provided so as to close an upper opening of the vessel main body 16. The container body 16 includes a cylindrical body 16A and a lower mirror 16B connected to the lower end of the body 16A. Inside the fuselage 16A of the reactor pressure vessel 10 is housed in-reactor structures such as the core shroud 18 and the jet pump 15, and the lower mirror 16B is passed through the control rod drive mechanism 19 and the in-core instrumentation tube 20. A through hole (not shown) is provided.

  Reactor primary piping 21 such as a reactor recirculation piping 21A, a coolant purification piping 21B, and a bottom drain line 21C is connected to the outside of the reactor pressure vessel 10 as a plant structure. The reactor primary system pipe 21 has a flow of reactor primary system water, and therefore the inner surface 22 of the reactor primary system pipe 21 shown in FIG. 2 is in contact with the reactor primary system water.

  The crack propagation prediction system 30 (FIG. 3) of the present embodiment predicts the growth of the crack 24 generated on the inner surface 22 near the welded portion 23 of the reactor primary system pipe 21. The crack growth prediction system 30 includes a potentiometric measurement system 31, a strain measurement system 32, and an arithmetic device 33 that calculates the amount of crack growth.

  As shown in FIGS. 2 and 3, the potentiometric measurement system 31 measures a potential difference near the crack 24 in the reactor primary piping 21 during operation of the nuclear power plant. And a plurality of current application lines 39, a plurality of voltage measurement lines 40, and a potentiometric measurement device 41.

  The potentiometric measurement point 38 is on the outer surface 25 of the reactor primary pipe 21 and in the vicinity of the crack 24, that is, on the outer surface 25 of the reactor primary pipe 21, the thickness of the reactor primary pipe 21 with respect to the crack 24. Installed on the opposite side. This potential difference measurement point 38 is a contact point for applying a current near the crack 24 of the reactor primary system pipe 21 or measuring a potential difference near the crack 24 of the reactor primary system pipe 21.

  The current application line 39 and the voltage measurement line 40 are attached to the potential difference measurement point 38 by, for example, spot welding. Among the potential difference measurement points 38, voltage measurement lines 40 are connected to and attached to a plurality of pairs of potential difference measurement points 38 substantially facing the crack 24, and the potential difference measurement points 38 to which the voltage measurement lines 40 are attached are attached. A current application line 39 is connected to and attached to a pair of outer potentiometric measurement points 38. These current application line 39 and voltage measurement line 40 are connected to a potentiometric measurement device 41.

  The potentiometric measuring device 41 applies a current to the vicinity of the crack 24 of the reactor primary system pipe 21 via the current application line 39, and calculates a potential difference near the crack 24 of the reactor primary system pipe 21 via the voltage measurement line 40. The potential difference data is captured, processed (for example, digitally processed), and output to a residual stress value calculation unit 34 (described later) of the arithmetic device 33. The measurement of potential difference data by the potential difference measurement system 31 is performed continuously or intermittently during operation of the nuclear power plant.

  The strain measurement system 32 measures a strain value in the vicinity of the crack 24 of the reactor primary system pipe 21 during operation of the nuclear power plant (BWR), and includes a strain measurement sensor 43 and a strain measurement device 44. Is done. The strain measurement sensor 43 is near the crack 24 on the outer surface 25 of the reactor primary pipe 21, that is, on the outer surface 25 of the reactor primary pipe 21, and is connected to the crack 24. On the opposite side in the thickness direction, the electrodes are attached by spot welding or the like inside the plural pairs of potential difference measurement points 38 to which the voltage measurement lines 40 are attached, facing the crack 24. The strain measurement sensor 43 is a strain gauge or an optical fiber having heat resistance against the temperature (about 270 to 280 ° C.) of the outer surface 25 of the reactor primary system pipe 21 during the operation period of the nuclear power plant.

  The strain measuring device 44 is connected to the strain measuring sensor 43 using a signal line 45. The strain measuring device 44 takes in a strain value near the crack 24 of the reactor primary system pipe 21 measured by the strain measuring sensor 43, processes the strain value data (for example, digital processing), and calculates the computing device 33. To the residual stress value calculation unit 34 (described later). Measurement of strain value data by the strain measurement system 32 is performed continuously or intermittently during operation of the nuclear power plant.

  The arithmetic unit 33 uses the potential difference data from the potentiometric measurement system 31 and the strain value data from the strain measurement system 32 to generate a crack 24 generated on the inner surface 22 near the welded portion 23 of the reactor primary system pipe 21. The amount of progress is predicted. The calculation device 33 includes a residual stress value calculation unit 34, an evaluation residual stress distribution generation unit 35, a stress intensity factor calculation unit 36, and a crack growth amount prediction calculation unit 37. FIG. 4 shows a procedure for predicting the crack growth amount by the arithmetic unit 33.

  In FIG. 4, a potential difference measurement procedure by the potential difference measurement system 31 and a strain value measurement procedure by the strain measurement system 32 are shown as a first step S <b> 1, and a residual stress value calculation by the residual stress value calculation unit 34 of the arithmetic device 33 is second. This is shown as steps S2-1 and S2-2. In addition, the creation of the evaluation residual stress distribution by the evaluation residual stress distribution creation unit 35 of the calculation device 33 is shown as a third step S3, and the calculation of the stress intensity factor by the stress intensity factor calculation unit 36 of the calculation device 33 is the fourth step. This is shown as S4, and the crack growth amount prediction by the crack growth amount prediction calculation unit 37 of the calculation device 33 is shown as a fifth step S5.

  The residual stress value calculation unit 34 of the calculation device 33 first calculates the crack shape (crack length and crack depth) of the crack 24 by calculating the potential difference data from the potential difference measurement system 31. Determine (S2-1). Next, the residual stress value calculation unit 34 has the above-described crack shape, strain value data from the strain measurement system 32, and structural data of the reactor primary system piping 21 (for example, the wall thickness, inner diameter, outer diameter, etc. of the piping). Based on the above, the residual stress value at an arbitrary position of the crack 24 (in this embodiment, the crack tip) is calculated for each measurement time by the potentiometric measurement system 31 and the strain measurement system 32 by the crack compliance method (S2). -2).

  Here, the crack compliance method is a method for evaluating the residual stress inside the object from the strain released when the crack is introduced into the residual stress field in the welded part of the object. It can be applied to plant structures and online monitoring. The details of this crack compliance method are described in Non-Patent Document 1, for example.

  As shown in FIGS. 4 and 5, the evaluation residual stress distribution creating unit 35 of the arithmetic unit 33 uses the residual stress value change data 46 continuously or intermittently calculated by the residual stress value calculating unit 34. Thus, by correcting the corresponding region of the residual stress distribution profile 47 assumed in advance in the welded portion 23 that is the target portion of the reactor primary system pipe 21 so as to coincide with the change data 46 of the residual stress value, A residual stress distribution 48 for evaluation along the thickness direction of the reactor primary pipe 21 is obtained from the crack tip 24 (S3).

  That is, the residual stress distribution profile 47 assumed in the welded portion 23 of the reactor primary system pipe 21 is expressed by an approximate expression such as a sixth-order expression, for example, and the residual stress distribution profile 47 is calculated by the residual stress value calculation section 34. The coefficients of the approximate expression are determined by calculation so as to overlap numerically within the range of the change data 46 of the residual stress value. Thereby, a new relational expression corresponding to the change data 46 of the residual stress value calculated by the residual stress value calculation unit 34 is obtained, and this relational expression is set as an evaluation residual stress distribution 48. This evaluation residual stress distribution 48 indicates a residual stress distribution along the thickness direction of the reactor primary system pipe 21 from the crack tip of the crack 24 in the reactor primary system pipe 21.

  Here, the residual stress distribution profile 47 assumed in the welded portion 23 of the reactor primary system pipe 21 is the structural data (pipe thickness, inner diameter, outer diameter, etc.) of the reactor primary system pipe 21 and welding conditions. Obtained from the analysis result based on the finite element method based on the above, or obtained from the result actually measured by the mock-up test body manufactured by using the same material and the same manufacturing method as the reactor primary system pipe 21 having the weld 23. It is a thing.

  As shown in FIGS. 3 and 4, the stress intensity factor calculation unit 36 of the computing device 33 includes an evaluation residual stress distribution 48 obtained by the evaluation residual stress distribution creation unit 35 and a residual stress value calculation unit 34. Using the crack shape of the crack 24 calculated in this way and external stress such as stress or thermal stress due to internal pressure acting on the reactor primary system pipe 21, an arbitrary position of the crack 24 (in this embodiment, the crack 24 The stress intensity factor at the crack tip is calculated (S4).

  The crack growth amount prediction calculation unit 37 of the calculation device 33 first calculates the crack growth rate of the crack 24. This crack growth rate is determined by the correlation between the material used for the reactor primary pipe 21, the environment in which the reactor primary pipe 21 is used, and the stress intensity factor at the crack tip. Therefore, the crack growth amount prediction calculation unit 37 uses the stress intensity factor at the crack tip calculated by the stress intensity factor calculation unit 36, the material used in the nuclear reactor primary piping 21, the environment in which the crack is propagated, and the like. By referring to the speed database, the crack growth speed of the crack 24 is obtained. Next, the crack growth prediction unit 37 predicts the crack growth rate during the service period from the obtained crack growth rate and an arbitrarily set service period (for example, 1 year or 10 years) in the nuclear power plant. The crack growth amount of the rucksack 24 is calculated (S5).

  The above crack growth rate database takes into account stress corrosion cracking (SCC) and corrosion fatigue depending on the mechanical factors acting on the target piping, and crack growth rate due to stress corrosion cracking and cracking due to corrosion fatigue. Propagation rate, stress corrosion cracking and crack growth rate due to corrosion fatigue are prepared.

With the configuration as described above, the present embodiment has the following effects.
Since the potential difference measurement system 31 measures the potential difference in the vicinity of the crack 24 generated on the inner surface 22 of the reactor primary system piping 21 and the strain measurement system 32 measures the strain value during the plant operation, the arithmetic unit 33 Based on the potential difference data and the strain value data, the evaluation residual stress distribution 48 (FIG. 5) along the pipe thickness direction from the crack tip of the crack 24 can be obtained with high accuracy. As a result, the calculation device 33 predicts the progress amount of the crack 24 generated in the primary reactor piping 21 with high accuracy using the residual stress distribution 48 for evaluation, and the reliability of the nuclear power plant (BWR) Safety can be improved.

  As mentioned above, although embodiment of this invention was described, this embodiment is shown as an example and is not intending limiting the range of invention. This embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention.

  For example, in the present embodiment, the case where the plant structure is the reactor primary system piping 21 of a nuclear power plant (particularly a boiling water reactor) has been described, but a nuclear power plant, a thermal power plant or a chemical plant equipped with a pressurized water reactor. It may be a structure such as piping in a plant or the like.

21 Primary reactor piping (plant structure)
22 inner surface 23 welded portion 24 crack 25 outer surface 30 crack growth prediction system 31 potentiometric measurement system 32 strain measurement system 33 arithmetic unit 34 residual stress value calculation unit 35 evaluation residual stress distribution generation unit 36 stress intensity factor calculation unit 37 Crack growth prediction unit 38 Potential difference measurement point 43 Strain measurement sensor 47 Residual stress distribution profile 48 Residual stress distribution for evaluation

Claims (10)

In the crack growth prediction system that predicts the growth of cracks generated in plant structures,
A potentiometric measurement system for measuring a potential difference near the crack of the plant structure during plant operation;
A strain measurement system for measuring a strain value near the crack of the plant structure during plant operation;
An arithmetic unit that predicts the amount of crack propagation based on data from the potentiometric measurement system and the strain measurement system;
This computing device comprises a residual stress value calculation unit, an evaluation residual stress distribution creation unit, a stress intensity factor calculation unit, and a crack growth amount prediction calculation unit,
The residual stress value calculation unit is based on the crack shape calculated from the potential difference data from the potentiometric measurement system, the strain value data from the strain measurement system, etc., and the residual stress value at an arbitrary position of the crack. To calculate
The evaluation residual stress distribution creation unit is evaluated by correcting a presumed residual stress distribution profile in a target part of the plant structure using the residual stress value calculated by the residual stress value calculation unit. Find the residual stress distribution for
The stress intensity factor calculation unit calculates a stress intensity factor at an arbitrary position of the crack based on the residual stress distribution for evaluation and the crack shape, etc.
The crack growth amount prediction calculation unit is configured to calculate a crack growth rate during a service period of a plant by calculating a crack growth rate determined by correlation with the stress intensity factor, and to predict the crack growth rate. Crack growth prediction system characterized by The plant structure is a reactor primary system pipe that is in contact with nuclear reactor primary water of a nuclear power plant, and the crack is a crack generated on an inner surface near a welded portion of the reactor primary system pipe. The crack growth prediction system according to claim 1, characterized in that it is characterized in that: The strain measurement system includes a strain gauge or an optical fiber as a strain measurement sensor for measuring a strain value near the crack, and the strain measurement sensor is provided on the outer surface of the reactor primary system pipe and near the crack. The crack growth prediction system according to claim 2, wherein: The potentiometric measurement system includes a potentiometric measurement point for applying a current or measuring a potential difference, and the potentiometric measurement point is provided near the crack on the outer surface of the reactor primary system piping. The crack growth prediction system according to claim 2 or 3, wherein The residual stress value calculation unit of the arithmetic unit is based on the crack shape calculated from the potential difference data from the potentiometric measurement system, the strain value data from the strain measurement system, and the structure data of the plant structure. The crack propagation prediction system according to any one of claims 1 to 4, wherein a residual stress value at an arbitrary position of the crack is calculated by a method. The assumed residual stress distribution profile used in the evaluation residual stress distribution creating unit of the arithmetic unit is an analysis result by a finite element method based on the structural data of the plant structure, welding conditions, or the like, or the plant structure The crack growth according to any one of claims 1 to 5, wherein the crack growth is obtained by a result measured with a mop-up specimen manufactured with the same material and the same manufacturing method. Prediction system. In the crack growth prediction method that predicts the growth of cracks generated in plant structures,
A first step of measuring a potential difference and a strain value in the vicinity of the crack of the plant structure during plant operation;
Based on the crack shape calculated from the potential difference data measured in the first step and the strain value data measured in the first step, the residual stress value at an arbitrary position of the crack is calculated. The second step;
A third step of obtaining a residual stress distribution for evaluation by correcting a residual stress distribution profile assumed in advance in the target part of the plant structure using the residual stress value calculated in the second step;
A fourth step of calculating a stress intensity factor at an arbitrary position of the crack based on the crack shape and the residual stress distribution for evaluation obtained in the third step;
Obtaining a crack growth rate determined by correlation with the stress intensity factor calculated in the fourth step, and calculating and predicting a crack growth amount during the service period of the plant; A crack growth prediction method characterized by comprising: The plant structure is a reactor primary system pipe that is in contact with nuclear reactor primary water of a nuclear power plant, and the crack is a crack generated on an inner surface near a welded portion of the reactor primary system pipe. The crack growth prediction method according to claim 7, characterized in that it is characterized in that: The second step is based on the crack shape calculated from the potential difference data measured in the first step, the strain value data measured in the first step, and the structure data of the plant structure. The crack growth prediction method according to claim 7 or 8, wherein a residual stress value at an arbitrary position of the crack is calculated by a compliance method. The assumed residual stress distribution profile used in the third step is the analysis result by the finite element method based on the structural data and welding conditions of the plant structure, or the same material and the same as the plant structure. The crack growth prediction method according to any one of claims 7 to 9, wherein the crack growth prediction method is obtained by a result obtained by actual measurement with a mop-up specimen manufactured by a manufacturing method.

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