JPH06102103A - X-ray stress measurement apparatus - Google Patents

Abstract

PURPOSE:To precisely measure residual stress on the surface of a material receiving neutron irradiation. CONSTITUTION:An X-ray tube 1 emitting an incident X-ray 2 for an object 3 to be measured, a shielding body 10 for shielding a gamma-ray 6 emitted from the object 3, a monochromator 11 for separating a primary diffraction X-ray 3 emitted from the object 3 and making it monochromatic and a detector of a proportional counter tube 12 having energy dependance on a detection X-ray for detecting a secondary diffraction X-ray separated with the monochromator 11 are comprised. The object 3 is a neutron-irradiated material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray measuring apparatus for measuring residual stress on the surface of a material such as a reactor pressure vessel or a reactor internal structure which has been irradiated with neutrons, that is, the surface of an object to be measured.
The present invention relates to a linear stress measuring device.

[0002]

2. Description of the Related Art The presence of high tensile residual stress in a material of a structure is problematic from the viewpoint of structural integrity. For example, if the fatigue strength decreases due to the effect of the average stress of the residual tensile stress, or if the material is sensitized due to the effect of welding, etc. in austenitic stainless steel, etc., the residual stress and the water environment cause stress Corrosion cracking occurs. Also, in the part that receives high neutron irradiation, such as the internal structure of the reactor,
Irradiation-induced stress corrosion cracking is likely to occur due to residual tensile stress.

Residual stress of a structure is generated in the base metal portion due to cold bending during manufacturing or in the vicinity of the welded portion due to heat history during welding. Therefore, it is important to measure and evaluate the residual stress at the end of manufacturing or construction in order to ensure soundness.

By the way, recently, a surface modification technique for compressing the residual stress on the material surface of the structure, such as shot blasting or ice blasting, has been developed and its application is under consideration. As part of the applicability study,
It is essential to make sure that the irradiated material reliably undergoes compressive residual stress due to these surface modification techniques.

X-ray stress measurement is the only method capable of non-destructively and accurately measuring residual stress.
An example of the configuration of the conventional X-ray stress measuring device will be described with reference to FIG.

That is, in the X-ray stress measuring apparatus shown in FIG. 2, the incident X-ray 2 generated by the X-ray tube 1 is applied to the DUT 3 and the diffracted X-ray 4 is detected by a proportional counter, a scintillation counter or the like. The intensity distribution of the diffracted X-ray 4 is measured by the instrument 5. Residual stress can be measured by obtaining changes in diffraction peak angles at a plurality of X-ray incident angles ψ.

[0007]

When the DUT 3 is irradiated with neutrons, a large number of γ-rays 6 having the same properties as the diffracted X-rays 4 are emitted from the DUT 3 as the background. The γ-ray 6 is measured as noise by the detector 5 together with the diffracted X-ray 4.

As a result, as shown in FIG. 3, a diffraction intensity distribution 8 including noise having a background intensity higher than that of the original diffraction intensity distribution 7 is obtained.
The SN ratio (I _P / I _B ) between the intensity I _P of the diffraction peak 9 of the diffracted X-ray 4 and the background intensity I _B becomes small.

For this reason, the stress measurement accuracy becomes very poor, and in the measurement of a material with a high irradiation dose, the diffraction peak intensity becomes equal to or lower than the noise level of the γ-ray from the irradiation material, and the measurement cannot be performed. There will be issues such as becoming possible.

The present invention has been made to solve the above-mentioned problems, and for example, a reactor pressure vessel of a nuclear power plant,
An object of the present invention is to provide an X-ray stress measuring device capable of accurately measuring the residual stress on the surface of the object to be measured, which has been irradiated with neutrons such as internal structures of a reactor.

[0011]

SUMMARY OF THE INVENTION The present invention is an X-ray tube and a shield for making incident X-rays from the X-ray tube incident on a neutron-irradiated DUT and shielding background noise from the DUT. A monochromator that separates the body, the continuous X-rays of the first-order diffracted X-rays from the object to be measured and the characteristic X-rays into a single color, and detects the second-order diffracted X-rays reflected by the monochromator. And a proportional counter detector having energy dependence on the X-rays.

[0012]

Function: X-rays are incident on the object to be measured from the X-ray tube. A shield such as a lead plate shields background γ rays from the DUT. A continuous X-ray of the first-order diffracted X-ray and a characteristic X-ray are separated (monochromatic) by a monochromator. The separated second-order diffracted X-rays are detected by a proportional counter.

In the X-ray stress measuring apparatus according to the present invention, the degree to which the detector measures the γ-rays of the background noise from the DUT that has been irradiated with neutrons is greatly improved, and the diffraction X The peak of the line (characteristic X-ray) can be accurately detected. As a result, the stress can be measured and the accuracy can be secured in the same level as the non-irradiated material.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the X-ray stress measuring apparatus according to the present invention will be described with reference to FIGS. The X-ray stress measurement apparatus in FIG. 1 is an X-ray tube 1 for injecting X-rays 2 onto a neutron-irradiated DUT 3, and a shield 10 sequentially arranged as a diffracted X-ray measurement system from the DUT 3. Monochromator 11
And a proportional counter 12.

In the above embodiment, the incident X-ray 2 generated from the X-ray tube 1 is applied to the measurement surface of the DUT 3 as in the conventional X-ray stress measuring apparatus. X-ray diffraction direction is incident X
Since the wavelength of the line 2 and the measurement lattice plane of the DUT 3 are determined by the Bragg's equation, the object to be measured 3 is shielded by a shield 10 such as a lead plate except in the vicinity of the diffraction angle direction of the first-order diffracted X-ray 13. The amount of .gamma.

However, the γ ray from the unshielded portion is 1
Further, the monochromator 11 is used since it passes together with the next-order diffracted X-ray 13. The monochromator 11 is a curved crystal having a high reflection efficiency, such as graphite, and
Lines and γ-rays can be separated from the white component to be monochromatic. The γ-ray 6 from the DUT 3 is close to white, and what is necessary for the stress measurement is the characteristic X-ray of the diffracted X-ray.

Therefore, with the monochromator 11, 1
By reflecting the second diffraction X-ray 13 and obtaining the second diffraction X-ray 14,
The noise level due to the γ-rays 6 from the DUT 3 can be greatly reduced, and the diffracted X-rays whose diffraction peaks are clearly obtained can be guided to the proportional counter 12.

As the proportional counter 12, there are a Geiger-Muller (GM) counter, a scintillation counter (SC), a proportional counter (PC) and the like. In the present embodiment, the energy dependence of the X-rays to be counted is used. By adopting a certain proportional counter 12, the high energy γ-rays from the DUT 3 are identified and not counted.

As a result, as shown in FIG. 3, in the conventional X-ray stress measuring device (see FIG. 2), the diffraction intensity distribution 8 having the high background intensity was used. Only γ-ray noise from the material can be significantly reduced,
The diffraction intensity distribution 7 is obtained so that the original diffraction peak 9 from the DUT 3 can be obtained clearly. In addition, θ is a diffraction angle and represents an angle between the lattice plane of the material and the diffracted X-ray.

That is, the SN ratio of the intensity I _P of the diffraction peak 9 of the diffracted X-ray and the background intensity I _B (I _P /
Since good data of I _B ) can be obtained, the stress can be measured by X-ray diffraction, and the accuracy comparable to that of the unirradiated material can be expected.

[0021]

According to the present invention, it is possible to accurately measure the residual stress in the surface layer of the irradiated object to be measured, which was difficult with the conventional apparatus. As a result, the irradiation-induced stress corrosion cracking susceptibility can be grasped by measuring the residual stress of the structural material inside the reactor, which is useful for soundness evaluation and the application of surface modification technology that compresses the residual stress on the material surface of the structure. There are advantages such as the ability to measure confirmations that are essential for sex studies.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an X-ray stress measuring apparatus for irradiated material according to the present invention.

FIG. 2 is a configuration diagram showing a conventional X-ray stress measurement device.

FIG. 3 is a diffraction intensity distribution diagram for explaining the effect of the conventional example and the present invention example.

[Explanation of symbols]

1 ... X-ray tube, 2 ... Incident X-ray, 3 ... DUT, 4 ... Diffraction X
Lines, 5 ... Detector, 6 ... γ-ray, 7 ... Diffraction intensity distribution, 8 ... Diffraction intensity distribution including noise, 9 ... Diffraction peak, 10 ... Shield, 11 ... Monochromator, 12 ... Proportional counter, 13 … First-order diffracted X-rays, 14… Second-order diffracted X-rays.

Claims (1)

[Claims] 1. An X-ray tube, a shield for making incident X-rays from the X-ray tube incident on a neutron-irradiated object to be measured, and shielding background noise from the object to be measured, and the object to be measured. Dependence of energy on the monochromator that separates the continuous X-rays of the first-order diffracted X-rays and the characteristic X-rays into a single color and the X-rays that detect the second-order diffracted X-rays obtained by reflecting from the monochromator An X-ray stress measuring device, comprising: a proportional counter detector having