JP7210366B2 - Nondestructive evaluation method and nondestructive evaluation system - Google Patents

Description

TECHNICAL FIELD Embodiments of the present invention relate to nondestructive evaluation methods and nondestructive evaluation systems.

In the operation of a nuclear power plant for more than 40 years, it is required to ensure the soundness by neutron irradiation embrittlement evaluation of the pressure vessel. Currently, embrittlement assessment is performed from both prediction and actual measurements. The prediction is performed using an embrittlement prediction formula that is a function of the number density of solute atom clusters and dislocation loops, which are embrittlement factors formed in the metal structure by irradiation, the chemical composition of the low-alloy steel, the irradiation rate, and the irradiation time. It is On the other hand, the actual measurement is performed by subjecting a monitoring test piece installed in the nuclear reactor to a destructive test. However, since the number of test pieces installed at the start of operation was equivalent to 40 years of operation, there is concern that the number of monitoring test pieces will be insufficient in the future. As a solution to this problem, a method to minimize the damage to the test piece due to measurement by evaluating the degree of embrittlement using an ultra-micro hardness test, and a method to evaluate the degree of embrittlement non-destructively using ultrasonic waves. etc. are known.

Japanese Patent No. 5562726 JP-A-11-248691

Surveillance Test Method for Reactor Structural Materials (JEAC4201-2007) Japan Electric Association Report of the Central Research Institute of Electric Power Industry: Study on Formulation of Irradiation Embrittlement Prediction Method for Light Water Reactor Pressure Vessel Steel -Development of Irradiation Embrittlement Prediction Method- Central Research Institute of Electric Power Industry

In order to evaluate the number density of solute atom clusters and dislocation loops, which are the input values of the embrittlement prediction formula, it is necessary to prepare observation specimens from the monitoring specimens, and the monitoring specimens are damaged. In addition, in the evaluation method using the ultra-microhardness test, indentations remain on the surface of the test piece after measurement, making re-measurement at the same location impossible. On the other hand, in the ultrasonic evaluation method, although no damage occurs in the specimen after evaluation, it is not possible to separate and evaluate the solute atom clusters and dislocation loops, which are embrittlement factors. Values for the number density of solute atom clusters and dislocation loops cannot be obtained. There is a desire to separately evaluate the number density of solute atom clusters and dislocation loops without damaging the specimen.

The embodiments of the present invention have been made in consideration of such circumstances, and an object thereof is to provide a non-destructive evaluation technique capable of non-destructively evaluating embrittlement factors formed in metal materials. do.

A non-destructive evaluation method according to an embodiment of the present invention includes a step of evaluating an embrittlement factor due to neutron irradiation embrittlement in a metal material based on changes in physical property values of the metal material, and an electrical property value and a magnetic property value The embrittlement factor is evaluated based on changes in at least two of the physical properties including The metal material includes a monitoring test piece and an archival material, and the monitoring test piece is manufactured by the same composition and heat treatment as the material used when manufacturing the pressure vessel containing the nuclear reactor. , which is installed inside the pressure vessel when the reactor starts operating, and the archive material is manufactured by the same composition and heat treatment as the material used when the pressure vessel is manufactured, and is used for the pressure vessel. It is not installed inside and is stored in a place where it is not irradiated with neutrons, and when evaluating the embrittlement factor, the monitoring test piece is taken out from the pressure vessel, and the monitoring test piece and Based on the physical property values obtained from the archive material, the embrittlement factor due to the neutron irradiation embrittlement of the pressure vessel is evaluated, and after the embrittlement factor is evaluated, the monitoring test piece is placed inside the pressure vessel. to be re-installed .

An embodiment of the present invention provides a nondestructive evaluation technique that can nondestructively evaluate embrittlement factors formed in metal materials.

1 is a block diagram showing the nondestructive evaluation system of the first embodiment; FIG. 4 is a flowchart showing a non-destructive evaluation method according to the first embodiment; The block diagram which shows the nondestructive evaluation system of 2nd Embodiment. 8 is a flowchart showing a non-destructive evaluation method according to the second embodiment;

(First embodiment)
The present embodiment will be described below with reference to the accompanying drawings. First, the nondestructive evaluation method and nondestructive evaluation system of the first embodiment will be described with reference to FIGS. 1 and 2. FIG.

Reference numeral 1 in FIG. 1 denotes the nondestructive evaluation system of the first embodiment. This non-destructive evaluation system 1 is used to evaluate materials that constitute a pressure vessel that houses a nuclear reactor in a nuclear power plant. An example of a nuclear power plant is a boiling water reactor (BWR).

The pressure vessel is irradiated for many years by neutrons generated in the nuclear reactor. Therefore, embrittlement occurs in the pressure vessel due to neutron irradiation. A non-destructive evaluation system 1 is used to evaluate the degree of neutron irradiation embrittlement of this pressure vessel. The nondestructive evaluation system 1 may be used to evaluate the degree of neutron irradiation embrittlement of not only the pressure vessel but also other members constituting the nuclear power plant.

A pressure vessel is a member that cannot be disassembled and replaced. Therefore, a large number of monitoring specimens (metallic materials) are installed inside the pressure vessel in advance at the start of operation of the nuclear power plant, and are exposed to neutron irradiation. These monitoring specimens are manufactured with the same composition and heat treatment as the material from which the pressure vessel was manufactured. That is, the monitoring test strip corresponds to the metallic material forming the pressure vessel.

Furthermore, there are archive materials (metallic materials) manufactured by the same composition and heat treatment as the materials used to manufacture the pressure vessel. This archival material corresponds to the metal material forming the pressure vessel. Archival materials are not placed inside the pressure vessel and are stored in a place where they are not exposed to neutron irradiation.

In this embodiment, embrittlement factors due to neutron irradiation embrittlement of pressure vessels are evaluated based on physical property values obtained from monitoring test pieces and archival materials. In the following description, the monitoring test piece and archival material are referred to as metal materials.

In addition, archive materials are regarded as metal materials before neutron irradiation. On the other hand, the surveillance specimen is regarded as a metallic material after neutron irradiation. The neutron irradiation embrittlement of the metal material can be evaluated based on the amount of change in the physical properties of the metal material with different neutron irradiation doses.

A plurality of monitoring specimens having different neutron irradiation periods, ie, periods of being installed in the pressure vessel, may be used. For example, based on the physical property value that the neutron irradiation period is the first period (e.g., 10 years) and the physical property value that is the second period (e.g., 20 years) that is longer than the first period, the metal The embrittlement factor of the material may be evaluated. Note that the first period includes no neutron irradiation period at all, that is, the neutron irradiation period is zero (for example, 0 years).

The metal material forming the pressure vessel is low alloy steel. The low-alloy steel is the total amount of predetermined alloying elements such as Al, B, Co, Cr, Cu, La, Mn, Mo, Nb, Ni, P, Pb, S, Se, and Si contained in iron. is 5% or less of alloy steel.

In this embodiment, the number density of embrittlement factors formed in the structure of the metal material is non-destructively evaluated by evaluating changes in the physical properties of the low-alloy steel due to neutron irradiation. In particular, by applying this embodiment to metal materials corresponding to low-alloy steel for pressure vessels that have been irradiated with neutrons, the number of solute atom clusters and dislocation loops, which are embrittlement factors, formed in the structure of the metal material Density can be evaluated non-destructively.

Since evaluation can be performed simply by measuring the monitoring test piece without destroying it, if the monitoring test piece is removed from the inside of the pressure vessel, it can be reinstalled inside the pressure vessel after evaluation. Furthermore, by using the evaluated number densities of solute atom clusters and dislocation loops as input values for the embrittlement prediction formula, it is possible to evaluate the amount of change in the ductile embrittlement transition temperature, which is an index of embrittlement. Note that the embrittlement prediction formula used is defined by research institutes such as the Central Research Institute of Electric Power Industry (for example, see Non-Patent Documents 1 and 2).

In this embodiment, the embrittlement factor is evaluated based on changes in at least two physical property values. In this way, at least two types of embrittlement factors can be evaluated, including solute atom clusters and dislocation loops.

Also, the physical property value includes at least one of an electrical property value, a magnetic property value, and hardness. By doing so, it is possible to acquire the physical property values of the metal material without destroying it.

Also, the electrical property value is the electrical resistivity. In this way, the electrical characteristic values can be obtained from the metal material in a non-destructive manner, so that the obtaining work can be easily performed.

Also, the magnetic characteristic value is a squareness ratio evaluated by AC magnetization measurement. In this way, the magnetic characteristic value can be obtained from the metal material in a non-destructive manner, so that the obtaining work can be easily performed. The magnetic property values also include coercive force, saturation magnetic flux density, residual magnetic flux density, magnetic permeability, and the like.

Embrittlement factors also include solute atom clusters and dislocation loops. In this way, solute atom clusters and dislocation loops, which are the main factors of neutron irradiation embrittlement, can be evaluated.

Also, the metal material is low alloy steel. In this way, it is possible to evaluate low-alloy steels used in pressure vessels that are most frequently irradiated with neutrons.

Next, the system configuration of the nondestructive evaluation system 1 will be described with reference to the block diagram shown in FIG.

A nondestructive evaluation system 1 includes a nondestructive measurement device 2 and an evaluation device 3 . The nondestructive measuring device 2 measures physical properties of metal materials. The evaluation device 3 evaluates the embrittlement factor of the metal material based on the physical property values measured by the nondestructive measurement device 2 .

The evaluation device 3 of the non-destructive evaluation system 1 of this embodiment has hardware resources such as a CPU, ROM, RAM, and HDD. It consists of a computer implemented using Furthermore, the nondestructive evaluation method of this embodiment is implemented by causing a computer to execute a program.

The evaluation device 3 includes a main control unit 4 , an information input unit 5 , a physical property value acquisition unit 6 , a fragility factor evaluation unit 7 and a display output unit 8 . These are implemented by executing programs stored in the memory or HDD by the CPU.

The main control unit 4 controls the nondestructive evaluation system 1 in an integrated manner.

Predetermined information is input to the information input unit 5 according to the operation of the user who uses the evaluation device 3 . The information input unit 5 includes an input device such as a mouse or keyboard. That is, predetermined information is input to the information input unit 5 according to the operation of these input devices.

The physical property value acquiring unit 6 acquires the physical property values of the metal material measured by the nondestructive measuring device 2 . In other words, the physical property value acquisition unit 6 executes a step of acquiring physical property values. Incidentally, physical property values may be stored.

The embrittlement factor evaluation unit 7 evaluates embrittlement factors of metal materials due to neutron irradiation embrittlement based on changes in physical property values of the metal materials. That is, the embrittlement factor evaluation unit 7 executes a process of evaluating embrittlement factors.

The display output unit 8 performs control to output the evaluation result of the embrittlement factor evaluation unit 7, for example, the calculation result of the embrittlement factor number density.

The non-destructive evaluation system 1 of this embodiment includes a display device such as a display for outputting evaluation results. That is, the display output unit 8 controls the image displayed on the display. The display may be separate from the computer main body, or may be integrated with the computer main body. Furthermore, the display output unit 8 may control the image displayed on the display of another computer connected via the network.

In addition, although a display is exemplified as a display device in the present embodiment, other modes may be used. For example, information may be displayed using a projector. Furthermore, a printer that prints information on a paper medium may be used as an alternative to the display. That is, the target controlled by the display output unit 8 may include a projector or a printer.

Next, nondestructive evaluation processing executed by the nondestructive evaluation system 1 of the first embodiment will be described with reference to the flowchart of FIG. Note that the block diagram shown in FIG. 1 will be referred to as appropriate.

As shown in FIG. 2, first, in step S11, the nondestructive measurement device 2 of the nondestructive evaluation system 1 measures physical property values of the metal material.

In the next step S<b>12 , the physical property value acquisition unit 6 of the evaluation device 3 of the nondestructive evaluation system 1 acquires the physical property values of the metal material measured by the nondestructive measurement device 2 . For example, physical property value 1, physical property value 2, . . . , physical property value n are acquired. However, n≧1. That is, one or more physical property values are acquired.

In the next step S13, the embrittlement factor evaluation unit 7 performs number density calculation of embrittlement factors based on the obtained physical property values. Here, the number density of the embrittlement factor is calculated using Equation 1 below.

here,
x _j is the number density of embrittlement factor j (j = 1, 2, ..., m),
P _i (x ₁ , x ₂ ,..., x _m ) is the physical property value i (i=1, 2,..., n) of the metal material after neutron irradiation,
q _ij (x _j ) is the amount of change in the physical property value i due to the formation of the embrittlement factor j (i=1, 2, . . . , n, j=1, 2, . . . , m);
si is the physical property value _i of the metal material before neutron irradiation (i = 1, 2, ..., n),
is.
However, n≧m≧1.

For one or more physical property values _i (i = 1, 2, ..., n) obtained by non-destructive evaluation of the metallic material, substitute the physical property value of the metallic material (for example, archive material) before neutron irradiation into si Then, the physical property values of the metal material (for example, the monitoring test piece) after neutron irradiation are substituted for P _i (x ₁ , x ₂ , . . . , x _m ). Since q _ij (x _j ) is a function of x _j (j=1, 2, .

In the next step S14, the display output unit 8 outputs the calculation result of the number density of embrittlement factors. Then, the process ends.

(Second embodiment)
Next, a nondestructive evaluation system 1A and a nondestructive evaluation method according to a second embodiment will be described with reference to FIGS. 3 and 4. FIG. The same reference numerals are assigned to the same components as those shown in the above-described embodiment, and overlapping descriptions are omitted.

First, the system configuration of the nondestructive evaluation system 1A of the second embodiment will be described with reference to the block diagram shown in FIG.

The evaluation apparatus 3A of the second embodiment includes a main control unit 4, an information input unit 5, a relational expression creation unit 9, a coefficient determination unit 10, a physical property value acquisition unit 6, a brittleness factor evaluation unit 7, and a mechanical property evaluation unit 11. and a display output unit 8 . These are implemented by executing programs stored in the memory or HDD by the CPU.

The relational expression creating unit 9 creates a relational expression between the embrittlement factor number density and the physical property value. In other words, the relational expression creation unit 9 executes the step of creating the relational expression.

The coefficient determination unit 10 determines coefficients in the relational expression created by the relational expression creation unit 9 . That is, the coefficient determination unit 10 executes the process of determining coefficients.

The mechanical property evaluation unit 11 evaluates mechanical properties of the metal material based on the embrittlement factor calculated by the embrittlement factor evaluation unit 7 . That is, the mechanical property evaluation unit 11 executes a step of evaluating the mechanical properties of the metal material. In this way, specific embrittlement of the metal material can be grasped. The mechanical property is, for example, the ductile-brittle transition temperature. The ductile-brittle transition temperature is the temperature at which the fracture mode of a metal material shifts from the ductile fracture region to the brittle fracture region. By doing so, it is possible to grasp the temperature at which the metal material loses ductility due to a decrease in temperature and becomes brittle.

Next, nondestructive evaluation processing executed by the nondestructive evaluation system 1A of the second embodiment will be described using the flowchart of FIG. Note that the block diagram shown in FIG. 3 will be referred to as appropriate.

The second embodiment is an embodiment in which q _ij (x _j ) in Equation 1, which is the relational expression between the embrittlement factor number density and the physical property value in the first embodiment, is not known. Further, as an example of the physical property value 2, the squareness ratio, which is the ratio of the residual magnetic flux density and the saturated magnetic flux density obtained by AC magnetization measurement, is evaluated. In addition, you may evaluate both from whichever. There are also two types of embrittlement factors: solute atom clusters and dislocation loops.

As shown in FIG. 4, first, in step S21, the relational expression creation unit 9 of the evaluation device 3A of the nondestructive evaluation system 1A creates a relational expression between the embrittlement factor number density and the physical property value.

In the next step S22, the coefficient determining unit 10 determines the coefficient (proportionality coefficient) in the relational expression created by the relational expression creating unit 9. FIG.

In the next step S23, the nondestructive measurement device 2 of the nondestructive evaluation system 1A measures physical property values of the metal material.

In the next step S24, the physical property value acquiring unit 6 acquires the physical property values of the metal material measured by the nondestructive measuring device 2. FIG.

In the next step S25, the embrittlement factor evaluation unit 7 performs number density calculation of embrittlement factors based on the obtained physical property values.

In the next step S26, the display output unit 8 outputs the calculation result of the number density of embrittlement factors.

In the next step S27, the mechanical property evaluation unit 11 inputs the calculation result of the number density of the embrittlement factor calculated by the embrittlement factor evaluation unit 7 into the embrittlement prediction formula and performs calculation.

In the next step S28, the mechanical property evaluation unit 11 evaluates the mechanical properties of the metal material based on the calculation result of the embrittlement prediction formula.

In the next step S<b>29 , the display output unit 8 outputs the evaluation result of the mechanical properties of the metal material of the mechanical property evaluation unit 11 . Then, the process ends.

Next, specific calculation modes executed by the relational expression creation unit 9, the coefficient determination unit 10, the physical property value acquisition unit 6, the embrittlement factor evaluation unit 7, and the mechanical property evaluation unit 11 in the above steps will be described.

As shown in the first embodiment described above, different types of embrittlement factors independently affect physical property values. Since the effect is proportional to each number density, Equation 1 above can be expressed as Equation 2 below using proportionality coefficients a, b, c, and d.

here,
x is the number density of solute atom clusters,
y is the number density of dislocation loops,
R (x, y) is the electrical resistivity of the low alloy steel after neutron irradiation;
r ₀ is the electrical resistivity of the low alloy steel before neutron irradiation,
M (x, y) is the squareness ratio of the low alloy steel after neutron irradiation,
m ₀ is the squareness ratio of the low alloy steel before neutron irradiation,
is.

These proportionality factors are for monitoring specimens of low-alloy steel manufactured with the same composition and heat treatment as the material forming the pressure vessel, or for archival material during the manufacture of the pressure vessel, thermal aging and electronic It can be determined by performing radiation irradiation, forming solute atom clusters and dislocation loops independently, and then evaluating the electrical resistivity and squareness ratio.

As an example, how to obtain the proportionality factor of low alloy steel manufactured under the composition shown in Table 1 and the heat treatment conditions shown in Table 2 will be shown. Table 1 shows the composition of the target low-alloy steel. Table 2 shows the heat treatment conditions of the target low alloy steel.

For example, by thermal aging treatment of low alloy steel, ^1.21022 solute atom clusters with a volume of about ^6.4104 to ^{2.7105 nm3} mainly composed of copper ^are formed. , the electrical resistivity changes by −2.6·10 ⁻¹ μΩ·cm and the squareness ratio changes by 5.1·10 ⁻³ .

Further, when interstitial-type dislocation loops with a diameter of several nanometers to ten and several nanometers are formed by electron beam irradiation at a number density of 1.0·10 ²⁰ /m ³ , the electric resistivity is 6.0. The squareness ratio changes by 1.9·10 ⁻³ with a change of 6·10 ⁻¹ μΩ·cm.

Therefore, by dividing the amount of change in each physical property value by the number density of each embrittlement factor, a = -2.2 10 ^-23 , b = 6.6 10 ^-21 , c = 4.3 ·10 ⁻²⁵ , d=1.9·10 ⁻²³ are obtained.

By using the aforementioned proportional coefficient, the number density of embrittlement factors can be estimated from the amount of change in the physical property value.

For example, if the electrical resistivity and squareness ratio change by X ₁ and Y ₁ with the formation of solute atom clusters, the number density is estimated to be X ₁ /a (=Y ₁ /c). If the electrical resistivity and the squareness ratio change by X ₂ and Y ₂ respectively due to the formation of dislocation loops, the number density is estimated to be X ₂ /b (=Y ₂ /d). The electrical resistivity of the low-alloy steel described above before neutron irradiation is r ₀ =2.5·10 (μΩ·cm), and the squareness ratio is m ₀ =7.4·10 ^-1 . . By substituting these values into Equation 2, the following Equation 3 is obtained.

here,
R (x, y) is the electrical resistivity of the low alloy steel after neutron irradiation;
M (x, y) is the squareness ratio of the low alloy steel after neutron irradiation,
is.

Assume that the following values are obtained as a result of non-destructive evaluation of the electrical resistivity and squareness ratio of the low-alloy steel after neutron irradiation.

R (x, y) = 2.9 10 (μΩ cm)
M(x,y)=8.0· ^10-1

By substituting these values into Equation 3 and solving the simultaneous equations, x=9.8·10 ²² and y=9.3·10 ²⁰ are obtained. It can also be seen that the number of solute atom clusters formed by neutron irradiation is 9.8·10 ²² /m ³ and the number density of dislocation loops is 9.3·10 ²⁰ /m ³ .

Moreover, by using these values as input values for the embrittlement prediction formula, it is possible to evaluate the amount of change in the ductile embrittlement transition temperature, which is an index of embrittlement amount.

The proportionality coefficients a, b, c, and d in Equation 2 can also be obtained using light water reactor monitoring test pieces. As an example, a method of determining the proportionality coefficient using monitoring specimens taken out during the nth and (n+1)th (n is a natural number) periodical inspections of a light water reactor will be described. When the solute atom cluster number density, dislocation loop number density, electrical resistivity, and squareness ratio are x _k , y _k , R _k , and M _k in the monitoring specimen taken out k-th time, the following formula 4 holds. By solving this, the proportionality coefficients a, b, c, and d can be obtained.

here,
r ₀ is the electrical resistivity of the monitoring specimen before neutron irradiation;
m ₀ is the squareness ratio of the monitoring specimen before neutron irradiation,
is.

In the second embodiment, the result of non-destructive evaluation of the electrical resistivity and squareness ratio of the monitoring test piece taken out during the (n+2)th and subsequent periodic inspections is substituted into Equation 2 and solved to perform the monitoring test. The solute atom cluster number density and dislocation loop number density of the piece can be evaluated non-destructively. Note that the monitoring specimens taken out during the nth and (n+1)th periodic inspections require destructive evaluation when evaluating the solute atom cluster number density and the dislocation loop number density.

The nondestructive evaluation method and the nondestructive evaluation system according to the present embodiment have been described based on the first embodiment and the second embodiment, but the configuration applied in any one embodiment is applied to the other embodiment. Alternatively, configurations applied in each embodiment may be combined.

In addition, in the flowchart of the present embodiment, each step is exemplified in a form in which each step is executed in series. good. Also, some steps may be executed in parallel with other steps.

The system of this embodiment includes a dedicated chip, an FPGA (Field Programmable Gate Array), a GPU (Graphics Processing Unit), or a CPU (Central Processing Unit) processor such as a control device highly integrated, ROM (Read Only Memory) or RAM (Random Access Memory), external storage devices such as HDD (Hard Disk Drive) or SSD (Solid State Drive), display devices such as displays, and input devices such as mice or keyboards , and a communication interface. This system can be realized with a hardware configuration using a normal computer.

It should be noted that the program executed by the system of the present embodiment is pre-installed in a ROM or the like and provided. Alternatively, this program can be stored as an installable or executable file on a non-transitory computer-readable storage medium such as CD-ROM, CD-R, memory card, DVD, flexible disk (FD), etc. may be stored and provided.

Also, the program executed by this system may be stored on a computer connected to a network such as the Internet, downloaded via the network, and provided. In addition, this system can also be configured by combining separate modules that independently perform each function of the constituent elements and are interconnected by a network or a dedicated line.

In addition, although this embodiment is applied to a boiling water reactor (BWR: Boiling Water Reactor), it may be applied to other aspects. For example, the present embodiment may be applied to an advanced boiling water reactor (ABWR) or a pressurized water reactor (PWR).

In addition, although the pressure vessel of the light water reactor is evaluated in this embodiment, other modes may be used. For example, the present embodiment may be applied to evaluate a reactor vessel of a nuclear reactor using liquid metal such as sodium as a coolant for cooling nuclear fuel.

According to at least one embodiment described above, embrittlement formed in the metal material is evaluated by including the step of evaluating the embrittlement factor due to neutron irradiation embrittlement in the metal material based on changes in the physical properties of the metal material. Transformation factors can be evaluated non-destructively.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

1 (1A)... non-destructive evaluation system, 2... non-destructive measuring device, 3 (3A)... evaluation device, 4... main control unit, 5... information input unit, 6... physical property value acquisition unit, 7... embrittlement factor evaluation 8 Display output unit 9 Relational expression creation unit 10 Coefficient determination unit 11 Mechanical property evaluation unit.

Claims (10)

A step of evaluating an embrittlement factor due to neutron irradiation embrittlement in the metal material based on changes in physical property values of the metal material;
evaluating the embrittlement factor based on changes in at least two physical property values including electrical property values and magnetic property values;
The electrical property value is electrical resistivity,
The magnetic property value is a squareness ratio evaluated by AC magnetization measurement,
The metallic materials include surveillance test strips and archival materials;
The monitoring test piece is manufactured by the same composition and heat treatment as the material used when manufacturing the pressure vessel containing the nuclear reactor, and is installed inside the pressure vessel when the reactor starts operating,
The archival material is manufactured by the same composition and heat treatment as the material used when manufacturing the pressure vessel, is not installed inside the pressure vessel, and is stored in a place not exposed to neutron irradiation. ,
removing the monitoring specimen from the interior of the pressure vessel when evaluating the embrittlement factor;
Based on the physical property values obtained from the monitoring test piece and the archive material, the embrittlement factor due to the neutron irradiation embrittlement of the pressure vessel is evaluated,
Reinstalling the monitoring specimen inside the pressure vessel after evaluating the embrittlement factor;
Non-destructive evaluation method. assessing the number density of said embrittlement factor;
The nondestructive evaluation method according to claim 1. said embrittlement factors comprise solute atom clusters and dislocation loops;
The nondestructive evaluation method according to claim 1 or 2 . The metal material is low alloy steel,
The nondestructive evaluation method according to any one of claims 1 to 3 . evaluating mechanical properties of the metallic material based on the embrittlement factor;
The nondestructive evaluation method according to any one of claims 1 to 4 . wherein the mechanical property is a ductile-brittle transition temperature;
The nondestructive evaluation method according to claim 5 . Evaluating the embrittlement factor based on the physical property value in which the neutron irradiation period is a first period and the physical property value in which the neutron irradiation period is a second period longer than the first period;
The nondestructive evaluation method according to any one of claims 1 to 6 . In the step of evaluating the embrittlement factor, the number density of the embrittlement factor is calculated using the following formula:

here,
x _j is the number density of embrittlement factor j (j = 1, 2, ..., m),
P _i (x ₁ , x ₂ ,..., x _m ) is the physical property value i (i=1, 2,..., n) of the metal material after neutron irradiation,
q _ij (x _j ) is the amount of change in the physical property value i due to the formation of the embrittlement factor j (i=1, 2, . . . , n, j=1, 2, . . . , m);
si is the physical property value _i of the metal material before neutron irradiation (i = 1, 2, ..., n),
is
provided that n≧m≧1,
The nondestructive evaluation method according to any one of claims 1 to 7 . In the step of evaluating the embrittlement factor, the number density of the embrittlement factor is calculated using the following formula:

here,
x is the number density of solute atom clusters,
y is the number density of dislocation loops,
R (x, y) is the electrical resistivity of the low alloy steel after neutron irradiation;
r ₀ is the electrical resistivity of the low alloy steel before neutron irradiation,
M (x, y) is the squareness ratio of the low alloy steel after neutron irradiation,
m ₀ is the squareness ratio of the low alloy steel before neutron irradiation,
is
The nondestructive evaluation method according to any one of claims 1 to 8 . an embrittlement factor evaluation unit that evaluates embrittlement factors due to neutron irradiation embrittlement in the metal material based on changes in physical property values of the metal material ;
The embrittlement factor evaluation unit evaluates the embrittlement factor based on changes in at least two physical property values including an electrical property value and a magnetic property value,
The electrical property value is electrical resistivity,
The magnetic property value is a squareness ratio evaluated by AC magnetization measurement,
The metallic materials include surveillance test strips and archival materials;
The monitoring test piece is manufactured by the same composition and heat treatment as the material used when manufacturing the pressure vessel containing the nuclear reactor, and is installed inside the pressure vessel when the reactor is started to operate. removed from the interior of the pressure vessel when assessing the embrittlement factor and reinstalled within the interior of the pressure vessel after assessment of the embrittlement factor;
The archival material is manufactured by the same composition and heat treatment as the material used when manufacturing the pressure vessel, is not installed inside the pressure vessel, and is stored in a place not exposed to neutron irradiation. ,
The embrittlement factor evaluation unit evaluates the embrittlement factor due to the neutron irradiation embrittlement of the pressure vessel based on the physical property values obtained from the monitoring test piece and the archive material.
configured as
Nondestructive evaluation system.

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