JPH08220029A - Nondestructive inspection device and inspection method for radioactive pollutants - Google Patents

Abstract

(57) [Abstract] [Purpose] Providing a nondestructive inspection device and inspection method for radioactive contaminants that perform nondestructive, high-accuracy determination of deterioration of equipment structural materials from γ rays generated by irradiation or radiation contamination. To do. A nondestructive inspection apparatus for radioactive contaminants according to the first aspect of the present invention is 0.511M generated by a reaction with an electron in a subject by irradiating the subject with a positron generated from a positron beam source.
In a nondestructive inspection device that measures the shape change of the photoelectron peak of eV annihilation γ-rays with a detector, a collimator 16 with a shield is provided on the front surface of the Ge detector 13 to limit the number of radiation flux from the subject 7. The positron beam source 1 is installed outside the visual field of the opening of the collimator 16 with a shield so that the irradiation region of the positron beam source 1 is contained within the visual field of the Ge detector 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is used during periodic inspections to confirm the soundness of radioactive or contaminated metal such as piping and structural materials used in nuclear reactor facilities. The present invention relates to a nondestructive inspection device and inspection method for radioactive pollutants.

[0002]

2. Description of the Related Art Conventionally, there has been known a technique of irradiating a subject with a positron and measuring the lifetime of the positron and the energy spread of annihilation γ-rays to determine the deterioration of the material of the subject. The positron in the substance is decelerated and heated, reacts with the electron in a nearly stationary state, disappears, and emits two 0.511 MeV γ rays. At this time, since the Doppler effect depends on the kinetic energy of the annihilation partner, it is possible to obtain information on the kinetic energy of the partner electron by precisely measuring the energy of the annihilation γ-ray.

Normally, when the other party is an electron in the shell, the energy spreads up to about 2 keV. On the other hand, in the case of free electrons, the spread of energy is negligibly small compared to the former case. Therefore, it is possible to discriminate the two by measuring the energy spectrum of the annihilation γ-rays with a γ-ray detector having a sufficiently high energy resolution such as a Ge detector.

When the sample is a perfect crystal, the positrons that have been heated have a positive charge, and therefore have the highest probability of existence at a position away from the ionic shell, that is, at an interstitial position. However, if there are defects such as vacancies or aggregates in the crystal, free electrons will ooze out from the surroundings in that part, and when viewed from the surroundings, they will become negatively charged and positrons will be captured. .

Since the defect portion has few inner shell electrons and few free electrons, the life until annihilation becomes long. The lifetime of positrons without defects is unique to each metal,
It is about 100 to 200 picoseconds, and the life of a subject with defects may be extended up to twice that on average.

Further, the probability of reaction with electrons in the shell is low,
As described above, the influence of energy spread due to the Doppler effect is reduced. Therefore, the concentration of defects can be measured by measuring the lifetime after the positron is generated or the energy spread of annihilation γ-rays.

The block diagram of FIG. 22 shows an inspection apparatus for measuring the lifetime of a positron in a subject.
As the nuclide, a nuclide that simultaneously emits positrons such as Na-22 and γ rays is used. The γ-ray 2b generated from the positron beam source 1 is detected by the γ-ray detector 3b, and is taken into the start signal of the time-wave height converter 6 via the timing discretization 4b and the delay 5.

The 0.511 MeV γ-ray 2a generated by the reaction between the electron and the positron in the subject 7 is detected by another γ-ray detector 3a, passes through the timing discriminator 4a, and passes through the time-to-peak converter 6. It is taken in by the start signal, converted into a pulse having an output wave height corresponding to the time difference between the two, and becomes the input to the linear gate 8.

On the other hand, the respective signals from the γ-ray detectors 3a and 3b are sent to the preamplifiers 9a and 9b and the linear amplifier 10 respectively.
a, 10b, and single channel wave height discriminators 11a, 11b
And becomes a simultaneous counting input of the linear gate 8. Finally, the output of the linear gate 8 is digitized by the multi-channel analyzer 12 and stored as a time spectrum to obtain the average lifetime.

The block diagram of FIG. 23 shows an inspection apparatus using the γ-ray energy spectrum measuring method. The positron beam source 1 is provided between the objects 7 to be inspected, and the Ge detector is arranged in close proximity thereto. The annihilation γ rays detected by 13 are the preamplifier 9 and the linear amplifier 10, and the multi-channel analyzer 12
, 0.511 MeV annihilation gamma ray is measured in the form of gamma ray energy spectrum.

The photopeak corresponding to 0.511 MeV γ-ray is
As shown in (a) of the distribution characteristic diagram of 24, it is represented by the sum of the annihilation component of the dotted line 14 with the electrons in the shell with a wide energy spread width and the solid line 15 with the annihilation component of the free electrons with a narrow energy spread width, The rate of change of the S parameter, which is the ratio of the central area A as shown in FIG. 24 (b) and the peripheral area (B ₁ + B ₂ ) is a measure of the defect concentration. ).

S = A / (B ₁ + B ₂ ) ... (1)

As an example, the annealing characteristic diagram of FIG.
Mn-irradiated with neutrons with a flux of 1.5 × 10 ¹⁸ n / cm ^2.
The change rate of the S parameter after annealing of a Ni-Mo alloy (A533-B) is shown. Annealing is performed for 1 hour under different conditions of temperature, and most defects cannot be removed by annealing at 473 K or less, and defects are advanced at more than 473 K, and electrons in the shell with wide energy spread in the annihilation γ-ray spectrum The S parameter decreases as the disappearance component (B ₁ + B ₂ ) of and increases.

A similar change occurs in the lifetime of positrons. This change corresponds to the phenomenon that the decrease in material hardening due to neutron irradiation disappears from the result of annealing as shown in the annealing and hardening degree characteristic diagram in Fig. 26. By measuring the S parameter or positron lifetime. , Shows that the change of material due to neutron irradiation can be measured. As the positron source 1, Ge-68, Co other than the above Na-22
-55 can be used.

[0015]

The above-mentioned prior art is based on the measurement in a laboratory for a small sample, and, for example, in the case where an attempt is made to measure a contaminated equipment in a nuclear reactor facility. In this case, there is a possibility that the subject 7 itself is contaminated with radioactivity, or that it has radioactivity due to activation by neutron irradiation. In addition, there is a possibility that the measurement may be performed under the influence of γ-rays emitted from peripheral pollution equipment, and there are the following problems.

(1) A collimator with a shield having a small-diameter opening is installed in front of the detector in order to avoid the influence of γ-rays from surrounding contaminant devices and to avoid the detector from being saturated by γ-rays from the subject. Method is used.

In such a method, as shown in FIG.
As shown in Fig. 5, in the arrangement where the positron beam source 1 is placed in the field of view of the detectors 3a, 3b, 13 positrons disappear on the surface of the collimator with a shield near the detector, resulting in 0.511MeV extinction γ. The line 2b overlaps with the 0.511MeV annihilation γ-ray 2a generated as a result of the extinction in the original subject 7, and the original signal / noise discrimination ratio (hereinafter referred to as S / N ratio) of the information from the detector deteriorates. To do.

(2) In the method of measuring energy,
The photopeak characteristic diagram in Fig. 27 due to the scattering of γ-rays generated from radionuclides that emit relatively high energy such as Co-60, which is the main constituent of radioactive contamination, and the scattering inside the detector. As shown in, the counting rate under the photoelectric peak of 0.511 MeV annihilation γ-ray increases.

As a result, compared with the case where there is no influence of external γ rays, the error in calculating the central area A and the peripheral area B ₁ + B ₂ of the photoelectric peak shown in FIG. It will increase and accurate evaluation will not be possible. As a countermeasure against this, it is necessary to increase the number of positron beam sources 1 or to increase the measurement time, which inevitably causes problems such as handling restrictions and increased exposure to the measuring personnel.

(3) As for the method of measuring the lifetime of positrons, it is required to measure an extremely short time of the order of 100 nanoseconds, so a detector with a slow pulse response time such as NaI scintillation detector (scintillation decay time 2
30 nanoseconds) cannot be used.

For this reason, conventionally, a plastic scintillation detector which has a very fast pulse response time (scintillation decay time of about 2 nanoseconds) has been used. However, in the case of this plastic scintillation detector, it is not possible to obtain high detection efficiency when a small detector having a low density is used, and it is necessary to lengthen the measurement time.

Further, since the energy discrimination property is poor,
It is impossible to discriminate the γ-rays generated from the subject 7 or the peripheral pollutant device from the γ-rays generated almost simultaneously with the emission of the positrons and the annihilated γ-rays in terms of energy. For this reason, the subject 7 etc. is radioactive or the surrounding γ
When the influence of the rays is strong, if the counting rate accompanying such background increases, the coincidence coincidence count of γ-rays becomes large, which may cause difficulty in deteriorating the measurement accuracy of the time difference.

(4) When measuring the subject 7 contaminated with radioactive substances, avoid exposure of the measurer, or if the subject 7 is installed at a position where the measurer cannot access Since it is also assumed, remote operation is required. In such a case, the circuit conditions are affected by humidity and temperature, and depending on the radioactivity of the subject 7,
It is necessary to correct the effect of signal pileup due to the high count rate.

Particularly for the latter, γ incident on the detector
The line count rate varies depending on the amount of radioactivity of the subject 7, and the higher the count rate, the greater the width of the photoelectric peak (energy resolution), the shape of the count rate, or the influence of the time shift of the lifetime measurement. In the energy measurement method, an increase variation in energy resolution at the photoelectric peak is measured in the determination of the measurement result, and the variation in energy resolution depends on an environmental factor, a count rate factor, or a material factor of the subject 7. There was a problem in that it requires a technique that can be confirmed at the site without requiring human intervention.

(5) When the amount of radioactivity of the object to be measured is extremely large, from the viewpoint of the radiation resistance of the object to be measured and the exposure of the measurement personnel, the measurement is performed in a state where water is filled around the object. Is also envisioned. However, in such a case, since the range of positrons in water is short, it is necessary to perform measurement while the positron beam source 1 and the subject 7 are in close contact with each other.

In this case, radioactive contamination of the positron beam source 1,
Alternatively, iron rust adhering to the surface of the subject may cause energy loss and absorption of positrons emitted from the positron beam source 1, which may reduce the apparent efficiency of annihilation γ-rays. In some cases, the positron beam source 1 may be damaged.

(6) In the method using the positron beam source 1, the radioactivity of the positron beam source 1 is increased in order to secure a sufficient S / N ratio when the radioactivity of the subject 7 is high. However, there was a problem that legal restrictions and exposure prevention restrictions were unavoidable to that extent.

The object of the present invention is to evaluate the deterioration of equipment structural materials by irradiation or radiation contamination.
It is an object of the present invention to provide a nondestructive inspection device and an inspection method for radioactive pollutants, which are nondestructive from a line, less exposed to radiation, and highly accurate.

[0029]

In order to achieve the above object, a nondestructive inspection apparatus for radioactive contaminants according to the invention of claim 1 irradiates a subject with a positron emitted from a positron beam source, 0.511MeV annihilation γ generated by the reaction with other electrons
In a nondestructive inspection device for measuring the change in the shape of the photoelectron peak of a line with a Ge detector, a collimator with a shield for limiting the number of radiation flux from the subject is provided in front of the Ge detector and the positron beam source is shielded. The collimator with a body is installed outside the field of view, and the irradiation area of the positron beam source is set to Ge.
It is characterized in that it is placed within the field of view of the detector.

The nondestructive inspection apparatus for radioactive pollutants according to the invention of claim 2 irradiates a subject with positrons generated from a positron beam source, and is generated by a reaction with electrons in the subject.
In a non-destructive inspection device for measuring the shape change of a photoelectron peak of 511 MeV annihilation γ-rays by a Ge detector, a collimator with a shield for limiting the number of radiation flux from the object is provided in front of the Ge detector. The radiation source is installed in the field of view of the opening of the collimator with a shield, in close proximity to the object and the object, and a transmission type detector is installed between the positron source and the object to reach the object. A part of the energy of positrons is lost in the transmission type detector, extracted as an electrical or optical signal, and the signal from the Ge detector is simultaneously counted, so that the annihilation reaction between the electron in the analyte and the positron It is characterized in that the energy spectrum of the 0.511 MeV annihilation γ-ray generated by is obtained and the deterioration of the material of the object is judged from the photoelectric peak shape.

In the nondestructive inspection apparatus for radioactive pollutants according to the third aspect of the present invention, the positron emitted from the positron beam source is applied to the subject to generate an annihilation reaction between the electrons in the subject and the positron. In a nondestructive inspection device that measures a signal equivalent to 0.511 MeV annihilation γ-rays with a γ-ray detector, a collimator with a shield that limits the number of radiation flux from the subject is provided in front of the γ-ray detector. The positron beam source is installed close to the subject and the subject within the visual field of the opening of the collimator with a shield, and the transmission type detector is installed between the positron beam source and the subject. Due to the annihilation reaction between the electron and the positron in the object measured by the γ-ray detector, in which a part of the energy of the positron reaching the Phase of generated 0.511 MeV annihilation γ-ray And judging the subject material degradation from the time difference between the signal to be.

The nondestructive inspection device for radioactive pollutants according to a fourth aspect of the present invention is characterized in that the positron beam source is arranged outside the measurement field of view of the annihilation γ-ray detector.

According to a fifth aspect of the present invention, there is provided a non-destructive inspection apparatus for radioactive contaminants, wherein a collimator with a shield for limiting the number of radiation flux from the subject is provided in front of the Ge detector or the γ-ray detector. The positron beam source is provided and installed near the subject within the field of view of the collimator with a shield and the subject, and the transmission type detector is installed between the positron source and the subject to detect the subject. A thin scintillator plate in which a positron source is deposited or embedded on the surface opposite to the subject surface in a detection device that extracts a part of the energy of the positrons reaching the Is provided so that a part of the energy of the positron from the positron beam source reaches the object to be examined in the thin scintillator plate and the optical signal corresponding to the lost energy is directly detected. Wherein the input to the electron multiplier light through the Hikari Inami guide.

According to a sixth aspect of the present invention, there is provided a nondestructive inspection apparatus for radioactive contaminants, wherein a collimator with a shield for limiting the number of radiant flux from the subject is provided in front of the Ge detector or the γ-ray detector. The positron beam source is provided and installed near the subject within the field of view of the collimator with a shield and the subject, and the transmission type detector is installed between the positron source and the subject to detect the subject. A detector for extracting a part of the energy of the positrons that arrive at the transmission type detector as an electric or optical signal by losing it in the transmission type detector has a transmission type scintillator plate, a thicker than the transmission type scintillator plate, and a scintillator. It is sandwiched between layers of a material transparent to light to cause a part of the energy of positrons to be lost in the transmission type scintillator plate, and an optical signal corresponding to this loss energy is transmitted. Wherein the input to the photomultiplier tube from Nchireta plate through direct or light guide.

According to a seventh aspect of the present invention, there is provided a non-destructive inspection apparatus for radioactive contaminants, wherein a collimator with a shield for limiting the number of radiation flux from the subject is provided in front of the Ge detector or the γ-ray detector. The positron beam source is provided and installed near the subject within the field of view of the collimator with a shield and the subject, and the transmission type detector is installed between the positron source and the subject to detect the subject. In the inspection device for simultaneously counting the signal from the Ge detector or the γ-ray detector by extracting a part of the energy of the positrons reaching to the inside of the transmission type detector as an electric or optical signal, A positron beam source that emits positrons having a maximum energy of 0.3 MeV or more is used as the positron beam source, and a β-ray absorber of 80 mg / cm ² or less is arranged between the subject and the transmission type detector. To do.

In the nondestructive inspection device for radioactive contaminants according to the present invention, a collimator with a shield for limiting the number of radiation flux from the subject is provided in front of the Ge detector or the γ-ray detector. A Ge detector or a γ-ray detector is provided in a watertight manner, and an air curtain or the like is provided between the Ge detector or the γ-ray detector and a positron beam source facing the subject in water, and a space is provided between the positron beam source and the subject. Is formed.

According to a ninth aspect of the present invention, there is provided a nondestructive inspection device for radioactive pollutants, which comprises a collimator with a shield for restricting the number of radiation fluxes from the subject in front of the Ge detector or the γ-ray detector. A positron source calibration filter provided with a positron source and having a thickness equal to or larger than the maximum range of positrons between the subject and the positron source and made of the same material as the subject or a different β-ray absorber Is provided so as to be freely inserted and removed by a calibration filter drive mechanism.

In the nondestructive inspection method for radioactive pollutants according to the invention of claim 10, the positron emitted from the positron beam source is irradiated to the subject to generate a reaction with electrons in the subject.
In a non-destructive inspection device for measuring 511 MeV annihilation γ-rays, a positron source calibration filter that is freely inserted and removed between the subject and the positron source is automatically inserted and removed by a calibration filter drive mechanism, and a positron Γ at the time of measuring the object in the inserted state and the pulled out state of the source calibration filter
By measuring the line spectrum, this signal time difference or 0.51
It is characterized in that the degree of deterioration of the subject is determined from the difference in the photopeak shape of 1 MeV extinction γ-rays.

A non-destructive inspection apparatus for radioactive pollutants according to an eleventh aspect of the present invention is a collimator with a shield for limiting the number of radiant fluxes from the inside of a subject on the front surface of the Ge detector or the γ-ray detector, A positron beam source is provided and the Ge
A calibration source that emits γ-ray energy close to 0.511 MeV annihilation γ-rays is provided in the vicinity of the detector or the detector for γ-rays by a calibration radiation source drive mechanism so that the calibration source can be inserted and removed, and It is characterized in that the β-ray absorber is provided between and by a β-ray absorber drive mechanism so as to be freely inserted and removed.

In the nondestructive inspection method for radioactive contaminants according to the invention of claim 12, the positron emitted from a positron beam source is irradiated to the subject to generate a reaction with electrons in the subject.
In non-destructive inspection equipment that measures 511 MeV annihilation gamma rays, β
The β-ray absorber is inserted by the drive mechanism for the radiation absorber to make the positron beam source non-irradiated to the subject, and the energy spectrum of the γ-ray emitted from the calibration radiation source is obtained to obtain the photoelectric conversion of the γ-ray. In addition to obtaining the peak shape, the calibration source drive mechanism was used to obtain the energy spectrum of 0.511 MeV annihilation γ-rays when the calibration source was not installed and the positron source was irradiated to the subject. It is characterized in that the shape of the photopeak of the annihilation γ-ray is obtained and the deterioration degree of the material is judged from the rate of change of both.

According to a thirteenth aspect of the present invention, there is provided a first non-destructive inspection apparatus for radioactive pollutants which is arranged so that a positron-irradiated region on the surface of a subject is placed in a visual field at a position where the positron beam source cannot be directly placed in the visual field. The γ-ray detector and the second γ arranged at a position where the collimator with a shield is provided in front of the positron-beam source that emits positron and γ-rays almost at the same time so that the subject does not directly enter the field of view through the positron-beam source. A second detector for γ-rays, the emitted γ-rays are measured by the second detector for γ-rays, and this is used as a start time, and the annihilation γ-rays are measured by the first detector for γ-rays; The feature is that the lifetime of the positron is obtained from the difference between the two.

In the nondestructive inspection apparatus for radioactive pollutants according to the fourteenth aspect of the present invention, the positron irradiation source is placed in a position where it cannot be directly seen, and the positron irradiation area on the surface of the subject is placed in the visual field.
e A detector for γ-ray that cannot pass the positron source directly into the field of view by providing a collimator with a shield in front of the positron source that uses nuclides that emit positron and γ-rays almost simultaneously It is provided that the emitted γ-ray is measured by the γ-ray detector and used as a coincidence counting signal, and the γ-ray spectrum is measured by the Ge detector in synchronism with the coincidence counting signal to measure the extinction γ-ray photoelectric peak. The feature is that deterioration of the material of the subject is determined from the shape.

According to a fifteenth aspect of the present invention, in the nondestructive inspection apparatus for radioactive pollutants, a collimator with a shield for limiting the number of radiation flux from the subject is provided on the front surface of the Ge detector. In an inspection device in which the irradiation area of 0.511 MeV annihilation γ-rays is contained within the field of view of the Ge detector, the surface layer of the specimen is contaminated or radioactive by the radioactive substance containing positron-emitting nuclides such as Zn-65 and Co-58. When positron itself contains positron-emitting nuclides such as Zn-65 and Co-58 by neutron activation, it occurs as a result of annihilation reaction between positron emitted from radioactive pollutant, electron in analyte and positron.
It is characterized in that an energy spectrum of 0.511 MeV annihilation γ-ray is obtained and the deterioration of the material of the object is judged from the photoelectric peak shape.

A non-destructive inspection apparatus for radioactive pollutants according to a sixteenth aspect of the present invention comprises a collimator with a shield arranged so that the same positions of the test objects can be included in the fields of view of each other without containing the fields of view of the detectors with each other. In the inspection apparatus provided with the first γ-ray detector and the second γ-ray detector including the collimator with a shield, the surface layer of the subject is Zn-65, Co-5
Zn-65, which is contaminated by radioactive substances containing positron-emitting nuclides such as 8 or the subject itself is activated by neutrons
When a positron-emitting nuclide such as Co-58 is included, it is generated at the same time as the positron generation from Co-58 by each γ-ray detector.
It is characterized by detecting 0.810 MeV γ-rays and 0.511 MeV annihilation γ-rays generated as a result of the annihilation reaction between electrons and positrons in the subject, and determining the material deterioration of the subject from the time difference between the signals.

The nondestructive inspection apparatus for radioactive pollutants according to the invention of claim 17 comprises a collimator with a shield arranged so that the same positions of the objects to be examined can be included in each other's fields of view without containing the fields of view of the detectors with each other. In a tester equipped with a γ-ray energy measuring detector capable of discriminating γ-ray energy and a Ge detector equipped with a collimator with a shield, the surface layer of the object itself is a positron-emitting nuclide such as Zn-65 or Co-58. When the sample itself contains positron-emitting nuclides such as Zn-65 and Co-58 due to neutron activation or contamination with radioactive materials containing Co-58, An energy spectrum of annihilation γ-rays is obtained by simultaneously counting the count output signals in a narrow window region including the energy region of 0.810 MeV as a gate signal of the energy signal of the Ge detector. And judging the material deterioration of the object from the photoelectric peak shape of dark γ rays.

The nondestructive inspection apparatus for radioactive pollutants according to the eighteenth aspect of the present invention comprises a collimator with a shield which is arranged so that the same position of the subject can be included in the visual field without the mutual view of the detectors. Equipped with γ-ray detectors for measuring two lifetimes, positron-annihilation γ-rays are detected by the first γ-ray detector,
Further, in the inspection device for measuring the γ-rays simultaneously generated at the time of positron emission by the second γ-ray detector and measuring the lifetime of the positrons from the time difference between the two, the two γ-ray detectors are CaF
Characterized in that it is a ₂ scintillation detector.

A nondestructive inspection method for radioactive pollutants according to a nineteenth aspect of the present invention is the first detection for γ-rays within a subject of positrons emitted from positron-emitting nuclides that emit positrons and γ-rays almost simultaneously. The detector measures the positron annihilation γ-rays, detects the γ-rays simultaneously generated at the time of positron emission by the second γ-ray detector, and obtains the time difference signal of the fast component pulses of the output signals from both detectors. From the output signal of the delay component generated from the detector, two gate signals having a wave height in a narrow energy region corresponding to γ-ray energy and positron annihilation γ-ray energy which are simultaneously generated at the time of positron emission are acquired, and the time difference signal is gated. This is characterized by measuring the lifetime of positrons.

In the nondestructive inspection method for radioactive pollutants according to the invention of claim 20, the annihilation γ-ray spectrum is determined as the sum of γ-ray peaks having two kinds of standard deviations in determining the shape of the annihilation γ-ray spectrum of positrons. It is characterized in that the degree of deterioration of the material of the subject is determined by the approximation and the counting ratio of each γ-ray peak.

In the nondestructive inspection method for radioactive pollutants according to the twenty-first aspect of the present invention, the photoelectric peak count rate of Co-60 is obtained from the γ-ray spectrum of a Ge detector for an object that may receive neutrons. By taking into account the geometrical efficiency, the radioactivity concentration of Co-60 contained in the subject is converted, and the neutron irradiation integrated dose of the subject is evaluated from this radioactivity concentration. It is characterized in that the photopeak shape of 0.511 MeV γ-ray due to the above positron annihilation is measured, and the degree of deterioration of the test material is judged from both the radioactivity concentration of Co-60 and the photopeak shape of 0.511 MeV γ-ray.

In the nondestructive inspection method for radioactive pollutants according to the invention of claim 22, when determining the degree of deterioration of the material of the object to be tested, which is a radioactive contaminant, iron rust etc. that has adhered to the surface of the object in advance is physically detected. It is characterized in that it is removed by selective decontamination.

[0051]

According to the first aspect of the invention, the 0.511MeV annihilation γ-rays generated from the subject by the positron beam source are input to the Ge detector, but the 0.511MeV annihilation γ-rays generated in the shielded collimator are shielded. It is absorbed by the body and does not reach the Ge detector 13. Therefore, 0.51 generated in a shielded collimator
1MeV annihilation γ-ray does not overlap with the input of Ge detector and has high S / N
The ratio is obtained.

The signal from the Ge detector is digitized by a multi-channel analyzer through a preamplifier and a linear amplifier, and disappears γ represented by S parameter.
The shape parameter of the photopeak of the line is calculated.

According to a second aspect of the present invention, the positron emitted from the positron beam source has a part of its energy lost by the transmission type detector and is taken out as a signal. 0.511 MeV annihilation in combination with electron of subject γ
The line is emitted and converted into an electric signal by the Ge detector.

Only the signal from the Ge detector which is incident at the same time as the transmission type detector becomes the input of the multi-channel analyzer and is accumulated in the form of γ-ray spectrum. This spectrum is coincident with the signal accompanying the transmission of positrons. Except for accidental events, only the contribution of the signal associated with the disappearance of the positron in the subject 7 is included. Further, the γ-ray spectrum is used as a material deterioration index by calculating the S parameter, which is the count rate ratio between the central portion of the photoelectric peak and the peripheral portion.

According to the third aspect of the present invention, a part of the energy of the positron reaching the object from the electron beam source is lost in the transmission type detector, and this signal and the γ ray detector are measured. Deterioration of the material of the object is judged from the time difference between the signal corresponding to the 0.511 MeV annihilation γ-ray resulting from the annihilation reaction between the electron in the object and the positron.

According to a fourth aspect of the present invention, the Ge detector, the positron beam source and the transmission type detector are installed in another collimator with a shield so that they do not come into view of each other. Annihilation γ-rays generated by the reaction with the material itself of the positron source and γ-rays generated by the positron-ray source, so that the annihilation γ-rays generated from the subject by the Ge detector
The S / N ratio is improved when measuring the line.

According to the fifth aspect of the present invention, while the positrons reach the object, a part of the energy of the positrons is lost in the scintillator thin plate, and an optical signal corresponding to the lost energy passes through the light guide from the scintillator thin plate. , Or directly input to the photomultiplier tube for measurement.

According to the sixth aspect of the present invention, while the positrons reach the object, a part of the energy of the positrons is lost in the scintillator thin plate, and the optical signal corresponding to the lost energy is collected by the rear ride guide. It is efficiently measured through the ride guide or directly by the photomultiplier tube.

According to a seventh aspect of the present invention, a positron beam source that emits positrons having a maximum energy of 0.3 MeV or more is used as the positron beam source, and a β-ray beam of 80 mg / cm ² or less is provided between the subject and the transmission type detector. Since the absorber is placed, β-rays from Co-60, etc. due to surface contamination of the subject are absorbed by the β-ray absorber and do not affect the transmission type detector. Reach the subject without any problem.

According to the eighth aspect of the present invention, the collimator with a shield in which the positron beam source is arranged is made to face an object in water through a cavity forming cover, and a space for measurement is secured by an air curtain or the like. To do. The invention according to claim 9 is
The positron beam source calibration filter provided between the detector equipped with the positron beam source and the subject is calibrated by the calibration filter driving device.
Switch to the installed state or the non-installed state, and measure the γ ray in each.

According to a tenth aspect of the present invention, the positron beam source calibration filter is automatically inserted / removed, and the γ-ray spectrum at the time of measuring the object in each of the insertion state and the withdrawal state of the filter is measured, and the signal time difference is measured. Alternatively, the degree of deterioration of the subject is determined from the difference in the photopeak shape of 0.511 MeV extinction γ-rays. According to the invention of claim 11, the β-ray absorber is inserted and removed by a β-ray absorber drive mechanism between the positron beam source and the subject, and the calibration line source provided near the detector is a calibration line. The source drive mechanism irradiates or does not irradiate the detector.

According to a twelfth aspect of the present invention, the β-ray absorber is inserted between the positron beam source and the subject so that the subject is not irradiated with the positron beam source, and the positron beam is emitted from the calibration source. The γ
Obtain the energy spectrum of the gamma ray to obtain the shape of the photoelectric peak of the gamma ray, and obtain the energy spectrum of the 0.511 MeV annihilation gamma ray when the calibration radiation source is not installed and the positron radiation source is irradiated to the subject. From this spectrum, the shape of the photopeak of the annihilation γ-ray or the positron lifetime is obtained, and the degree of deterioration of the material is judged from the rate of change of both.

According to a thirteenth aspect of the present invention, the annihilation γ-rays are measured by the first γ-ray detector that does not put the positron beam source in the visual field and the positron beam is not put in the visual field. The emitted γ-rays are measured by the second γ-ray detector that puts the radiation source in the field of view, and this is used as the start time, and the annihilation γ-rays measured by the first γ-ray detector are used as the end time. The lifetime of the positron is calculated from the difference between the two.

According to a fourteenth aspect of the present invention, the emitted γ-rays are measured by a γ-ray detector that does not directly put the subject in the field of view, and the γ-rays are used as coincidence counting signals. A γ-ray spectrum is measured in synchronization with the coincidence counting signal by a Ge detector that accommodates a positron-irradiated region on the surface of the subject in the field of view, and deterioration of the material of the subject is determined from the photopeak shape of the annihilated γ-ray.

According to a fifteenth aspect of the present invention, a detector installed in a collimator with a shield causes 0.511 MeV annihilation γ-rays resulting from an annihilation reaction between positrons emitted from the subject itself and electrons in the subject and positrons. And get the energy spectrum of
The deterioration of the material of the subject is determined from the photopeak shape.

According to the sixteenth aspect of the present invention, a collimator with a shield is arranged so that γ rays emitted from the subject itself can be placed in the same position of the subject in each other's field of view without keeping the detectors' respective fields of view. 0.511 MeV with the first gamma ray detector
Detects annihilated γ-rays, and the second γ-ray detector detects 0.81
Each 0 MeV γ ray is measured, and the deterioration of the material of the subject is determined from the time difference between the two signals.

According to a seventeenth aspect of the present invention, a collimator with a shield is provided so that the γ-rays emitted from the subject itself can be placed in the same position of the subject in each other's visual field without keeping the detectors' respective visual fields. Measure with a gamma ray detector. Of the signals from the γ-ray energy measurement detector, Co-5
8 The output signal of the narrow window region including the 0.810 MeV energy region is used as the gate signal of the energy signal of the Ge detector, and the annihilation γ-ray energy spectrum is obtained by simultaneous counting to obtain the annihilation γ-ray photoelectric peak. The deterioration of the material of the subject is judged from the shape.

According to the eighteenth aspect of the present invention, the γ-rays simultaneously generated at the time of positron emission are measured, and the lifetime of the positrons is measured from the time difference between the two. A first γ-ray detector that measures annihilation γ-rays and a second γ-ray detector that measures γ-rays, including a collimator with a shield arranged so as to fit in the field of view,
Since it is a CaF ₂ scintillation detector, it is possible to discriminate the gate signal in terms of energy, and the positron lifetime measurement accuracy can be obtained with high accuracy.

In the nineteenth aspect of the present invention, the γ-rays emitted from the subject itself are detected by the first γ-ray detector and the γ-rays are detected by the second γ-ray detector. Then, while obtaining the time difference signal of the high-speed component pulse of the output signal from both detectors,
From the output signals of the delay components generated from both detectors, two gate signals having wave heights in a narrow energy region corresponding to γ-ray energy and positron annihilation γ-ray energy which are simultaneously generated at the time of positron emission are acquired, and the gate is applied to the time difference signal. The lifetime of the positron is measured by applying.

According to the twentieth aspect of the invention, in determining the shape of the annihilation γ-ray spectrum of positrons, the annihilation γ-ray spectrum is approximated as the sum of γ-ray peaks having two kinds of standard deviations,
The degree of deterioration of the material of the subject is determined by the counting ratio of each γ-ray peak.

The invention according to claim 21 obtains the photoelectric peak count rate of Co-60 from the γ-ray spectrum of the Ge detector for the object that may receive neutrons, and considers the geometrical efficiency. Converted to the radioactivity concentration of Co-60 in the subject, evaluate the neutron irradiation integrated dose of the subject from this radioactivity concentration, and at the same time, measure the 0.511 MeV γ-ray photoelectric energy due to positron annihilation on the same γ-ray spectrum. The peak shape is measured, and the degree of deterioration of the test material is judged from both the radioactivity concentration of Co-60 and the photoelectric peak shape of 0.511 MeV γ rays.

According to a twenty-second aspect of the present invention, when inspecting a material of an object that is a radioactive pollutant, the material is attached to the surface of the object in advance so that accurate material characteristics can be obtained without annihilation of positrons irradiated by the cladding. Remove iron rust etc. by physical decontamination.

[0073]

EXAMPLE In the present invention, in order to solve the above-mentioned problem (1), the positron beam source 1 is arranged facing the subject 7 by a collimator with a shield placed in front of the detector, and Set the source 1 in a position that is not directly visible from the detector. As a result, 0.511 MeV annihilation γ-ray 2 incident on the detector 2
a is limited to that generated in the subject 7, and the annihilation γ-ray 2b due to the shield or the like is absorbed by the shield itself and does not reach the detector.

To solve the above problem (2), a signal when a positron is generated is taken out separately, and the γ is detected by the Ge detector 13.
This can be achieved by inputting the same signal as a coincidence counting signal during line spectrum analysis. This applicable method is a method of reducing background contribution by coincidence counting,
And the improvement of the method for identifying the shape of annihilation γ-ray photopeaks.

First, as a method of reducing the background contribution by coincidence counting, (a) as a positron source 1, a nuclide that emits γ-rays at the time of positron emission such as Na-22 and Co-58 is used and separately A method is adopted in which the γ-rays generated at substantially the same time when positrons are generated are selectively energy-selected and counted by the γ-ray detector, and the Ge detector 13 is used as a simultaneous counting input to simultaneously measure and count.

In this case, the γ-rays emitted from the peripheral equipment such as Co-60 or the subject 7 are sorted out in terms of time and energy except for coincidence counting, and only the positron annihilation γ-rays 2a are extracted. Are selectively counted. Note that this method requires simultaneous measurement with two γ-ray detectors, and since the overall efficiency is low, it is effective when there are few restrictions on the measurement time.

(B) A transmissive detector is sandwiched between the positron beam source 1 and the subject 7 to obtain a signal corresponding to the energy loss of the positron in the transmissive detector, which is placed at the rear. The γ-ray energy signal of the detector is simultaneously counted.
This method does not have a nuclide restriction as the positron beam source 1, and there are few restrictions on handling such as exposure to γ rays from the positron beam source 1 itself.

Further, the interference due to γ-rays emitted from the peripheral equipment or the subject 7 can be ignored by making the transmission type detector as thin as possible in order to avoid coincidence coincidence. Furthermore, since the signal associated with the transmission of β rays is used, the counting efficiency as a simultaneous counting output can be secured up to almost 100%, and the efficiency of the entire measurement system can be made higher than that of the method (a).

(C) As a method of reducing the background contribution by inverse coincidence counting, as shown in the photoelectric peak characteristic diagram of FIG. 27, the so-called Compton scattering part on the γ-ray spectrum in the Ge detector is a Ge detector. This is caused by the loss of some energy due to Compton scattering inside and the scattered γ-rays escaping to the outside of the detector.

In order to reduce such a component, the Ge detector is covered with a large shield except for the incident direction of the 0.511 MeV annihilation γ-ray 2a from the subject 7, and the Ge detector is reversed. It can be reduced by performing coincidence counting.
That is, the components that have lost part of the energy due to Compton scattering in the Ge detector and escaped to the outside of the detector are likely to lose energy due to Compton scattering or photoelectron absorption reaction in the shield.

Therefore, in such an event,
It is possible to reduce the Compton scattering component in the energy region of the annihilation γ-ray by performing the inverse coincidence counting of the signal from the shield and the signal of the Ge detector. However, this method is not very effective when the contribution of scattered radiation inside the subject is large because the subject 7 becomes large.

(D) In the method of measuring the energy of annihilation γ-rays by improving the method for identifying the shape of annihilation γ-ray photopeaks,
Also, γ obtained by the Ge detector for energy measurement method
It is possible to significantly improve the S / N ratio by analyzing the line spectrum data by the following method. That is, the photopeak of the annihilation γ-ray is approximated as the sum of two Gaussian functions shown in the following equation (2) and the flat Compton scattering part.

[0083]

[Equation 1]

Here, n _j is the count in the j-th channel, A ₁ and A ₂ are constants, σ ₁ and σ ₂ are the standard deviations (unit: unit deviation) of the energy widths of the annihilation γ rays from the defective portion and the non-defective portion. : Channel), and J _ave is the average channel of _photopeaks . The unknowns in this equation (2) are A ₁ , A ₂ , σ ₁ , σ ₂ and n _const , which are obtained by the method of least squares. As the index parameter for determination, A ₁ / A ₂ is used instead of the S parameter defined by the equation (1) described in the above description of the related art.

In the conventional extinction γ-ray photoelectric peak analysis method, the influence of the skirt of the peak was a large error factor in the S parameter evaluation, but in this method, the shape data of the central part and the data of the central part are equivalent. Since the weight is taken into account in the calculation,
This is an evaluation method that is less susceptible to statistical fluctuations due to background compared to the conventional S parameter.

(E) The first solution to the above problem (3) is to use Na-22 as the positron beam source 1 and to detect the γ-rays in which the positron beam source 1 is in the field of view, and the subject. For both γ-ray detectors that have the positron irradiation part of 7 in the field of view, B
An F ₂ scintillation detector is employed to eliminate the effects of γ-ray background by incorporating energetic discrimination in time measurement by the following means.

The BF ₂ scintillation detector is
It contains both the high-speed component (0.6 nanoseconds) and the delay component (630 nanoseconds) in the scintillation component, and the latter has energy discriminability proportional to the incident energy.

Therefore, the lifetime of the positron is measured from the signal time difference signal of the fast component in the detector, and both the γ-ray energy signal accompanying the positron emission and the annihilated γ-ray energy signal are discriminated from the delayed component, and the three If only those items that have been simultaneously counted are selected as life information, good life measurement performance can be obtained even when the γ-ray background has a large contribution during measurement.

(F) A second solution is to provide a transmission detector between the positron beam source 1 and the subject 7 and use it as a start signal in the time measurement method. According to this, the influence of the γ-ray background can be reduced by making the transmission type detector thin, and since a plastic scintillation detector can be used, a high-speed time signal can be obtained. Further, as compared with the conventional method of measuring the life time associated with counting γ rays, it is possible to improve the detection efficiency of the measurement signal processing system for the same reason as described in (b) for the above problem (2).

(G) For the above problem (4), there are an energy measuring method and a life measuring method. First, regarding the energy measurement method, the variation of the energy resolution with respect to the annihilation γ-ray photopeak due to the variation of the count rate, etc.
511 MeV) is used to measure the spectral shape using a nuclide that is close in energy, and the determination is made based on the difference from the spectral shape of the annihilation γ-ray during measurement of the object.

(H) Regarding the next life measurement method, the same or different standard sample as the object to be inspected is placed at the intersection of the field of view of the detector and the irradiation part of the positron beam source when measuring the object to be inspected. The deterioration of the material is determined from the difference in life from time. For the above problem (5), a positron source 1 in water
A method of forming a cavity between the subject and the subject 7 is effective. As the cavity forming method, the subject 7 and the positron beam source 1 are covered with an air curtain or a physical cavity, and a gas is sent to the inside.

To solve the above problem (6), a method of using radioactive contamination in the subject 7 or a method using a positron emitting nuclide contained in the activated radioactivity depending on the contamination state of the subject 7 can be applied. is there. Among the radioactive materials produced by activation in a nuclear reactor, those with a relatively long half-life are Cr-5.
1, Mn-54, Co-60, Fe-55, Co-58, Zn-65, Ni-59
and so on. However, after a certain amount of operation time, Co-60 becomes the main nuclide.

Among these nuclides that emit positrons are Co-58 and Zn-65. Co-58 has a half-life of 71.3 days and emits positrons with a maximum energy of 0.474 MeV at a rate of 15% per decay. Then, the rest decays to the excited state of Fe-58 by electron capture, and emits γ-rays of 8.11MeV in 9.4 picoseconds to become stable Fe-58. Zn-65 also undergoes positron decay with a branching ratio of 1.14% and decays to the ground state of Cu65, which does not involve simultaneous gamma ray emission.

On the inner surface of the subject 7 and on the contaminated structural material, these nuclides bond with the electrons inside the subject 7 in the same manner as they emit positrons from the surface and irradiate them with positrons from the outside. Then, the annihilation γ-rays are emitted, and the amount of internal defects can be diagnosed by changing the lifetime of the positron or the energy resolution of the annihilation γ-rays. As described above, when the amount of radioactivity of the subject is high, the positron beam source 1 is externally applied to the subject 7
Instead of applying to the above, it is intended to diagnose the deterioration of the material by using such spontaneous annihilation γ-rays.

At this time, Co-60 is expected to have the highest radioactivity among the nuclides that emit γ-rays, and the energy measurement method and the lifetime measurement are performed in the same manner as the method of irradiating positrons from the outside. In both cases, the obstructive effects shown in the above-mentioned issues (2) and (3) cannot be avoided.

Therefore, the 8.11MeV γ-rays emitted at the same time as the positrons in Co-58 were measured by a detector other than the one for measuring the annihilation γ-rays, and the simultaneous counting shown in (a) in the above energy measurement method, or It is effective to remove the influence of background by coincidence counting shown in (e) by the time measurement method.

An embodiment of the present invention will be described with reference to the drawings. It should be noted that the same components as those of the above-described conventional technique are designated by the same reference numerals, and detailed description thereof will be omitted. The first embodiment is
As shown in the configuration diagram of FIG. 1, the inspection apparatus is an energy measuring method. The Ge detector 13 in the detection device is a Ge detector using γ rays from a radioactive substance contained in the subject 7.
In order to prevent the deterioration of the energy resolution of the photoelectric peak part due to the saturation of 13 or pile-up due to the high count rate,
A collimator 16 with a shield or a shield (not shown) is provided.

Further, the positron beam source 1 is installed close to the opening of the collimator 16 with a shield, and the Ge detector is used.
A preamplifier 9 for amplifying an output signal, a linear amplifier 10 and a multi-channel analyzer 12 are connected to the circuit 13.

The function of the above configuration is that 0.511 MeV annihilation γ generated in the substance forming the collimator 16 with the shield.
The line is absorbed in the shielded collimator 16 and does not reach the Ge detector 13. The positron emitted from the positron beam source 1 loses kinetic energy in the subject 7, and is combined with the electron of the subject 7 to emit 0.511 MeV annihilation γ-rays 2a emitted in opposite directions to disappear.

The signal from the Ge detector 13 is the preamplifier 9
And a linear amplifier 10 and digitized by a multi-channel analyzer 12,
It is stored in the memory in 12 in the form of a gamma ray energy spectrum. Further, the data is loaded into a calculator (not shown), and the shape parameter of the annihilation γ-ray photoelectric peak represented by the S parameter is calculated. Therefore, the subject 7
The 0.511MeV γ-rays input from the Ge detector 13 to the Ge detector 13 do not overlap with the 0.511MeV annihilation γ-rays generated in the shielded collimator 16 and a high S / N ratio is obtained.

In the second embodiment, as shown in the configuration diagram of FIG.
The inspection device is a front surface of the Ge detector 13 installed in the collimator 16 with a shield, and a thin transmission type detector 17 is installed between the positron source 1 and the object 7 placed close to the object 7. A detection device is configured. Further, the Ge detector 13 includes a preamplifier 9a and a linear amplifier 10a, and a delay amplifier 18, and the transmissive detector 17 includes a preamplifier 9b and a linear amplifier 10b.
A single channel wave height discriminator 11 and a gate and delay generator 19 are connected.

Further, the delay amplifier 18 and the gate-and-delay generator 19 are connected to the linear amplifier 10 and the multi-channel analyzer 12. In addition, Ge-68 or the like is used as the positron beam source 1 in addition to Na-22, and the transmission type detector 17 is a thin plastic scintillation detector surrounded by a light guide, or a transmission type Si.
A semiconductor detector or the like can be used. Also, the subject 7
In order to avoid as much as possible the effect of γ-rays emitted from the radioactive pollutants, it is desirable that the transmission detector 17 be as thin as possible.

The operation of the above configuration is that the positron emitted from the positron beam source 1 partially absorbs some energy.
It is lost inside and taken out as an electrical or optical signal. The positrons that have lost a part of their energy lose kinetic energy in the subject 7, are combined with the electrons of the subject 7, and are emitted in the opposite directions to each other.
Emit and disappear.

As a result, the signal from the transmission type detector 17 is amplified and shaped by the preamplifier 9b, the linear amplifier 10b, and the single-channel wave height discriminator 11 and then appropriately delayed by the gate and delay generator 19 to obtain a rectangular pulse. After being shaped into, the gate signal of the linear gate 8 is input.

On the other hand, the 0.511 MeV annihilation γ-ray 2a generated in the subject 7 is converted into an electric signal by the Ge detector 13 installed behind the positron beam source 1 and the transmission type detector 17, and the preamplifier is used. 9a, the linear amplifier 10a and the delay amplifier 18 serve as the linear input of the linear gate 8 after a certain time delay. Also,
Only those incident simultaneously with the transmission type detector 17 are input to the multi-channel analyzer 12, converted into a digital signal proportional to the pulse wave height, and stored in the memory in the multi-channel analyzer 12 in the form of a γ-ray spectrum.

This spectrum is coincident with the signal associated with the transmission of positrons, and except for an accidental event, only the contribution of the signal associated with the disappearance of the positron in the subject 7 is included. In addition, the γ-ray spectrum shows the central portion A and the peripheral portion B of the 0.511 MeV γ-ray photoelectric peak shown in FIG.
_The S parameter, which is the count rate ratio of ₁ + B ₂ , is calculated and used as the material deterioration index.

In the third embodiment, as shown in the configuration diagram of FIG.
In the inspection device, the detection device has the same configuration as that of the second embodiment shown in FIG. 2, but the γ-ray detector 3 is installed in the collimator 16 with a shield, and the front face of the γ-ray detector 3 is provided. Between the subject 7 and the electron beam source 1 and a thin transmission type detector.
17 are installed. A preamplifier 9a and a timing discretizer 4a are connected to the γ-ray detector 3, and the preamplifier 9a is connected to a multi-channel analyzer 12 via a linear amplifier 10a and a single-channel wave height discriminator 11a. Connected to 8.

On the other hand, the transmission type detector 17 has a preamplifier 9b.
Is connected to the timing gate 4b, and the preamplifier 9b is connected to the linear gate 8 via a linear amplifier 10b and a single-channel wave height discriminator 11b. Further, the timing discriminator 4b is connected to the time wave height converter 6 through the delay 5 together with the timing discretion 4a, and the time wave height converter 6 is connected to the linear gate 8.

The operation of the above configuration is as follows.
A part of the energy of the positron that reaches the subject 7 is lost in the transmission type detector 17 and is extracted as an electrical or optical signal. A signal corresponding to 0.511 MeV annihilation γ-ray 2a resulting from the annihilation reaction between the electron and the positron in the subject 7 measured by this signal and the γ-ray detector 3 installed behind the positron source 1. The deterioration of the material of the subject 7 is determined from the time difference between

Here, the time difference between generation and disappearance of positrons is about several hundred nanoseconds, and a plastic scintillation detector or the like is optimal as the transmission type detector 17, and in the case of this plastic scintillation detector, The time signal is required to be high speed.

For this reason, the dynode output of the photomultiplier tube connected to the plastic scintillator is directly input to the timing discretory 4b, converted into a rectangular signal of a short width, and then delayed by the delay 5 for a certain time, and the time-to-height is converted. It is used as a start signal input to the device 6.

On the other hand, since the γ-ray detector 3 installed behind the positron beam source 1 and the transmission type detector 17 is required to have high signal speed, it is desirable to use a plastic scintillation detector or the like. When a scintillation detector is used as the γ-ray detector 3, the dynode output of the photomultiplier tube is directly input to the timing discriminator 4a as in the case of the transmission type detector 17, and is converted into a rectangular signal having a short width. Then, it is input as a stop signal of the time-to-wave height converter 6.

Finally, the output wave height is converted in proportion to the time difference between the start signal and the stop signal, and the linear gate 8
The linear input signal of On the other hand, the anode signals of the γ-ray detector 3 and the transmission type detector 17 are shaped and amplified by the preamplifiers 9a and 9b and the linear amplifiers 10a and 10b, respectively, and are then subjected to constant wave heights by the single channel wave height analyzers 11a and 11b. Only signals in the window area are sorted.

When Na-22 is used as the positron source 1, 1.275 MeVγ produced by the K-22 excited state after β ⁺ decay
The S / N ratio of the signal is improved by limiting only the window region corresponding to the peak energy of the line. The signals from the single channel wave height analyzers 11a and 11b are input to the gate of the linear gate 8 after the delay time is adjusted by the delay 5, and the signals of the three parties including the signal from the time wave height converter 6 are simultaneously input. An output signal is generated only when

The signal from the linear gate 8 thus obtained is the input of the multi-channel analyzer 12, and the lifetime distribution of positrons as shown in the distribution characteristic diagram of FIG. 4 is obtained. As the change of the average lifetime, the material of the subject 7 is changed. Deterioration degree can be determined.

In the fourth embodiment, as shown in the configuration diagram of FIG.
The inspection apparatus does not have the Ge detector 13 installed in the collimator 16 with a shield and the positron beam source 1 and the transmission type detector 17 installed in another collimator 16a with a shield, which are not in the field of view, and A detection device is configured by being arranged so as to face the subject 7.

The Ge detector 13 is connected to the preamplifier 9a, the linear amplifier 10a and the delay amplifier 18, and the transmission type detector 17 is connected to the preamplifier 9b and the linear amplifier 10b and the single channel wave height discriminator 11. A gate and delay generator 19 is also connected. Further, the delay amplifier 18 and the gate-and-delay generator 19 are configured to be connected to the linear amplifier 10 and the multi-channel analyzer 12.

The fourth embodiment is different from the second and third embodiments in that the annihilation γ caused by the reaction of the positron with the shielded collimator 16 and the material itself of which the positron beam source 1 is made.
Since there is no interference of the γ-rays generated from the γ-rays and the positron beam source 1 itself, the S / N ratio can be greatly improved when measuring the annihilated γ-rays generated from the subject 7.

In the fifth embodiment, as shown in the block diagram of FIG.
As in the case of FIG. 5 of the fourth embodiment, the detection device is a γ-ray detector 3, a positron beam source 1 and a transmission type detector 17, which are installed in the collimators with shields 16 and 16a, respectively, and their mutual fields of view. It is arranged so as not to enter. The measurement signal processing system has the same structure as that of the third embodiment shown in FIG.

The action of the above construction is that, as compared with the third embodiment, the annihilation γ caused by the reaction of the positron with the collimator 16 with the shield and the material itself which constitutes the positron beam source 1.
Since there is no interference between the X-ray and the γ-ray generated from the positron beam source 1 itself, in the measurement of the annihilation γ-ray generated from the subject 7,
The S / N ratio can be significantly improved.

The sixth embodiment relates to a detector as shown in the configuration diagram of FIG. 7. In the second to fifth embodiments, the positron beam source 1 and the transmission type detector 17 are installed separately. The case is shown. In the sixth embodiment, the positron beam source 1 is placed on the scintillator thin plate 20 which is in contact with or close to the subject 7.
Is deposited on the surface opposite to the subject 7 surface as shown in FIG. 7A, or as shown in FIG. 7B, the scintillator thin plate.
It is embedded in the scintillator thin plate 20, and light guides 21 are provided on both sides of the scintillator thin plate 20 and further combined with a photomultiplier tube 22.

The scintillator thin plate 20 is preferably as thin as possible from the viewpoint of preventing the pile-up of signals due to γ-rays generated from the subject 7 and the influence of random coincidence as much as possible. As the type of this scintillator, a plastic scintillation detector, a glass scintillation detector, or the like is used from the viewpoint of the time characteristics, processability, and strength of the output signal. Further, the scintillator thin plate 20 is covered on its side by a ride guide 21 made of acrylic or the like, and a photomultiplier tube 22 is provided.
Is optically coupled to.

According to the above construction, while the positrons reach the subject 7, a part of the energy of the positrons is lost in the scintillator thin plate 20, and the optical signal from the scintillator thin plate 20 corresponding to the lost energy is lost. , Through the light guide 21,
Alternatively, it is directly detected by the photomultiplier tube 22 as an optical signal.

In the seventh embodiment, as shown in the side view of FIG. 8A and the plan view of FIG. 8B in the configuration diagram of FIG. 8, the detector is used and the positron beam source 1 is brought into contact with or close to the subject 7. The scintillator thin plate 20 and a light guide 21 thicker than the scintillator thin plate 20 and transparent to scintillator light are sandwiched by the rear ride guides 21a in layers.
In addition, a photomultiplier tube 22 via a transparent light guide 21.
It is configured to be optically coupled to.

With the above-described structure, the positron is used as the subject 7
Part of the energy of the positrons is lost in the scintillator thin plate 20 while reaching the temperature, and the optical signals from the scintillator thin plate 20 corresponding to the loss energy are transmitted to the ride guides 21, 21a.
Photomultiplier tube 22 through or directly as an optical signal
Get by.

In the seventh embodiment, since a relatively thick plate-shaped rear ride guide 21a is installed behind the positron beam source 1, the light collecting efficiency is greatly improved as compared with the sixth embodiment. It is possible to improve the S / N ratio of the signal, and it is possible to make the scintillator thin plate 20 thin without considering the physical strength and the light collection efficiency.

Therefore, the influence of pile-up or coincidence coincidence due to γ-rays can be reduced, the dynamic range of the measurement system can be improved, and the object 7 having higher radioactivity can also be measured. Further, the annihilation γ-rays generated in the subject 7 are hardly attenuated by the scintillator thin plate 20 or the rear ride guide 21a placed at the rear part of the scintillator thin plate 20 and therefore affect the rear photomultiplier tube 22. Little impact.

In addition, as a side effect, positrons emitted to the opposite surface of the subject 7 are back-scattered in the rear ride guide 21a, pass through the scintillator thin plate 20 and are directed forward in the subject 7. There is also an effect of increasing the amount of annihilated positrons, and as a result, the amount of radioactivity of the positron beam source 1 is increased and the measurement time can be shortened.

In the eighth embodiment, as shown in the block diagram of FIG.
The inspection apparatus is provided with a measure for use in the subject 7 whose surface is contaminated with radioactive material, and the configuration of the detection apparatus in this inspection apparatus is almost the same as that shown in FIG. 2 of the second embodiment. However, the opening of the collimator 16 with a shield is sealed by the β-ray absorber 23 as a filter.
The measurement signal processing system is also configured in the same manner as that of the second embodiment shown in FIG.

The operation of the above structure is a method of solving the problem when the transmission type detector 17 is used for the subject 7 whose surface is contaminated with radioactive material. The surface and inner surface are contaminated by radioactivity due to contact.

The β-rays from Co-60 contained in the contaminants are incident on the transmission type detector 17 placed in the vicinity of the subject 7, and the transmission type detector 17 accompanying the positron signal and pile-up.
, Which deteriorates the accuracy of the lifetime measurement method by the coincidence coincidence counting, or increases the background by the coincidence coincidence counting in the energy measurement method.

However, in the case of a nuclear reactor facility, the main β-ray emitting nuclide is Co-60, and the maximum energy of β-rays emitted with the decay of this Co-60 is 0.3 MeV. Therefore, if the β-ray absorber 23 capable of completely blocking 0.3 MeV is installed on the front surface of the positron beam source 1, the number of positrons reaching the surface of the subject 7 from the positron beam source 1 is not significantly reduced, and It is possible to reduce the counting contribution by β rays from the surface contamination incident on the transmission type detector 17 for coincidence counting placed on the substrate.

In order to completely remove β rays emitted from Co-60, the minimum amount of aluminum is 80 mg / cm 2.
A thickness of ² is required. In the eighth embodiment, a positron beam source 1 that emits a positron with a maximum energy of 0.3 MeV or more is used in the first to seventh embodiments, and 80 mg between the subject 7 and the transmission type detector 17 is used. It can be applied by placing a β-ray absorber 23 of / cm ² or less.

Here, as the positron beam source 1, Ge-68 (Ga
-68), maximum energy 1.9 MeV, Na-22, maximum energy
It is possible to use 0.54MeV. In addition, positron source 1
Since the absorption rate of the positron itself from the above is associated with the installation of the β-ray absorber 23 is only several tens of percent at most, there is almost no influence on the measurement.

In the ninth embodiment, as shown in the block diagram of FIG.
This relates to countermeasures when conducting a nondestructive inspection using a positron beam source 1 in water. This means that when the radioactivity of the subject 7 is extremely high, the inspection work needs to be performed in water. In addition,
Since the range of positrons in water is less than 1 mm,
In water, it is necessary to bring the positron beam source 1 into almost contact with the subject 7, and attention must be paid to the contamination or damage of the positron beam source 1.

As shown in FIG. 10, the detector is a collimator 16 with a shield in which a Ge detector 13 is installed inside and a positron beam source 1 is arranged at the tip of the opening side.
While being sealed with 24, a cavity forming cover 25 for covering the positron beam source 1 and the subject 7 to secure a space is provided in a portion of the collimator 16 with a shield facing the subject 7. The measurement signal processing system has the same configuration as that of the second embodiment shown in FIG.

As an operation of the above-mentioned structure, the cavity forming cover 25 is provided with the pressurized gas injection hole 26, and the cavity forming cover 25 is further brought into close contact with the collimator 16 with the shield and the subject 7 to be applied. By supplying compressed air 27 from the pressurized gas injection hole 26, a cavity and an air curtain are formed between the positron beam source 1 and the subject 7, and the range of positrons in the space between the positron beam source 1 and the subject 7 Keep the distance.

The tenth embodiment relates to an energy measuring method. As shown in the block diagram of FIG. 11, the inspection apparatus has a Ge detector 13 installed inside as a detection apparatus, and the positron beam source 1 at the tip on the opening side. The collimator with a shield 16 in which the
A positron source calibration filter 28 and a calibration filter driving mechanism 29 are provided between the positron source 1 and the positron source 1. The measurement signal processing system has the same configuration as that shown in FIG. 2 of the second embodiment.

The positron beam source calibration filter 28 provided between the subject 7 and the positron beam source 1 is a plate having a thickness equal to or larger than the maximum range of positrons, and is automatically remoted by the calibration filter driving mechanism 29. Move in the direction of arrow 29a and move to positron beam source 1
To shield and open.

All the positrons emitted from the positron beam source 1 react with the electrons in the positron beam source calibration filter 28,
Although 0.511 MeV annihilation γ-rays are generated, the material for the positron beam source calibration filter 28 is aluminum or a sample of the same material as the object 7 to be annealed and sufficiently removed of defects. It should be noted that aluminum is most suitable for the reference of the subject 7 which is less affected by internal defects and has no defects.

The operation of the above configuration is as follows. The positron source calibration filter 28 is switched between the installed state and the non-installed state to measure the object 7, and the γ-ray spectrum in each is obtained by the Ge detector 3, A S-parameter is calculated for each photopeak of annihilation γ rays by a computer (not shown). S-parameters are calculated from the above equation (1) in the installed state and the installed state of the same absorbing substance, and if these are S ₁ and S ₂ , (S ₁ -S ₂ ) will be used as a new index. It is possible to judge the material state of No. 7.

The eleventh embodiment relates to a life measuring method. As shown in the block diagram of FIG. 12, the inspection apparatus has a γ-ray detector 3 installed inside as a detection apparatus and a positron beam source at the opening. 1 and a collimator 16 with a shield in which a transmission type detector 17 is arranged,
A positron beam source calibration filter 28 and a calibration filter drive mechanism 29 are provided between the shielded collimator 16 and the subject 7. The measurement signal processing system has the same structure as that shown in FIG. 3 of the third embodiment.

The operation of the above construction is such that instead of the S parameter calculation in the tenth embodiment, the positron life is measured and the positron source calibration filter 28 is automatically moved in the direction of the arrow 29a by the calibration filter driving mechanism 29. Then, it is carried out in each state, and the material state of the subject 7 is judged using the life time difference as a new index.

In the twelfth embodiment, as shown in the block diagram of FIG.
In the energy measuring method in the above 10th embodiment in the inspection device, it is necessary to perform the energy resolution measurement peculiar to the detector due to environmental requirements and fluctuations in the counting rate each time actual measurement is performed, and the emission γ near 0.511 MeV γ It has a function to enable on-site calibration of a γ-ray emitting nuclide having a line energy using a standard radiation source.

The collimator 16 with a shield in which the Ge detector 13 is installed has the positron beam source 1 arranged facing the subject 7 on the opening side, and further between the positron beam source 1 and the subject 7. The β-ray absorber 23 that can be automatically moved in the direction indicated by the arrow 32a by the absorber drive mechanism 32 is installed.

Further, a calibration radiation source 30 is provided between the Ge detector 13 and the β-ray absorber 23 in the vicinity of the Ge detector 13, and the calibration radiation source 30 is a calibration radiation source driving device 31. Arrow 31a
The collimator 16 with a shield is provided with either a movable position in the direction and a position where calibration measurement can be performed in front of the calibration radiation source 30 or an accommodating part 31b provided in a recess in the collimator 16 with a shield. The measurement signal processing system has the same configuration as that of the first embodiment shown in FIG.

The function of the above structure is as follows:
By moving 23 by the absorber drive mechanism 32, the positron beam source 1 can bring the subject 7 into an open state for a positron irradiation state, and a closed state for a non-irradiation state. During the calibration measurement, the front surface of the positron beam source 1 is closed by the β-ray absorber 23, and the γ-ray spectrum of the annihilated γ-ray is measured by the Ge detector 3 under the influence of the radiation from the subject 7.

Note that Ru-106 (0.
51186MeV), Ru-103 (0.49708MeV), Be-7 (0.477605Me)
V) etc. Further, at the time of measurement, the β-ray absorber 23 on the front surface of the positron beam source 1 is opened, and the subject 7 measures the γ-ray spectrum of annihilation γ-rays in the material under the positron irradiation from the positron beam source 1.

From the γ-ray spectrum obtained in this state,
A S-parameter is calculated for each photopeak of annihilation γ rays by a computer (not shown). If the S-parameter calculated value is the arrangement state and the non-arrangement state of the β-ray absorber 23 are S ₁ and S ₂ , (S ₂ −S ₁ ) can be used as a new index to determine the material state of the subject 7. .

In the thirteenth embodiment, as shown in the block diagram of FIG.
In the detection device of the inspection device, the first γ-ray detector 33 for annihilation γ-rays is used as the object 7 in the collimator 16 with a shield.
However, the positron beam source 1 arranged at the tip on the opening side of the collimator 16 with a shield is installed at a position where direct irradiation is not performed.

Further, the second γ-ray detector 34 for simultaneous emission γ-rays is provided with another shield which obliquely intersects the axis of the shielded collimator 16 of the first γ-ray detector 33. It is installed in the body-equipped collimator 16a and contains the positron beam source 1 in the field of view. However, the subject 7 is composed of a collimator 16a with a shield that is shaped so as not to fit directly into the visual field.

Therefore, the positron beam source 1 can be placed in the field of view of the second γ-ray detector 34, but is arranged so as not to directly irradiate the first γ-ray detector 33. The irradiation site of the collimator 16 with the shield by the positron of
The first γ-ray detector 33 is arranged so as not to fit in the visual field.

As the first γ-ray detector 33 and the second γ-ray detector 34, a plastic scintillation detector is effective because of its fast time response, and this 13th embodiment also detects the same. It shows the case of using a vessel. The measurement signal processing system has the same structure as that shown in FIG. 3 of the third embodiment.

The operation of the above structure is such that Na-22 can be used as the positron source 1, and the second γ-ray detector 34 for simultaneous emission γ-rays causes positron decay from the positron source 1. The signal corresponding to the accompanying 1.275 MeV emission γ-ray becomes the start signal input of the time wave height converter 6 via the timing discretory 4b.

Since the second detector 34 for γ-rays does not directly put the subject 7 in the visual field, the incident γ-rays are 1.275 MeV emission γ-rays accompanying positron decay from the positron source 1.
And 0.511 MeV γ rays generated from the positron peripheral shield. On the other hand, a first γ-ray detector for annihilation γ-rays, which is arranged so as to view the irradiation region of the positron on the subject 7
33 includes 0.511 MeV annihilation γ-rays and γ-rays emitted from the radionuclide contained in the subject 7.

Since the signals corresponding to both are input to the stop and start signals of the time wave height converter 6 via the respective timing discreties 4a and 4b, basically, it is the coincidence between them that coincident coincidence counting is performed. Excludes only 1.275MeV γ-rays emitted by positron decay and 0.511MeV γ-rays generated in the positron subject 7.

From this, the difference between the two becomes the lifetime of the positron in the object 7. Note that, in the 13th embodiment, unlike the arrangement of the conventional lifetime measuring method, Co-60 which emits two γ rays, which are nuclides likely to be contained in the subject 7, is shown in FIG. In the arrangement of the conventional example shown, since one γ-ray detector 3b does not include the subject 7 in the visual field, Co-6
The possibility of simultaneous counting with 0 γ-rays can be reduced compared to the conventional case.

In the fourteenth embodiment, as shown in the block diagram of FIG.
In the invention for the energy measuring method, the detection device in the inspection device has the same structure as that of the thirteenth embodiment, but the γ-ray detector 13 for annihilation γ-rays is provided in the shielded collimator 16.
However, for the simultaneous emission γ-rays, for example, a γ-ray detector 3 such as a NaI scintillation detector is installed in the shielded collimator 16. The measurement signal processing system has the same configuration as that of the second embodiment shown in FIG.

The operation of the above configuration is that the positron emitted from the positron beam source 1 loses kinetic energy in the subject 7,
Combined with the electrons of the subject 7 and emitted in opposite directions.
0.511 MeV annihilation Emits γ-rays and disappears. The 0.511 MeV annihilation γ-ray is converted into an electric signal by the Ge detector 13. The signal from the Ge detector 13 is input to the linear gate 8 after a predetermined time delay by the preamplifier 9a, the linear amplifier 10a, and the delay amplifier 18.

On the other hand, the γ-rays generated simultaneously are converted into electric signals by the γ-ray detector 3, and the preamplifier 9b and the linear amplifier are used.
After amplification and shaping by 10b, only the one corresponding to the narrow energy region corresponding to the energy of the emitted γ-rays is selected by the single-channel wave height discriminator 11, and the gate-and-generator 19 is used as an appropriate delay and simultaneous counting input for analog-digital conversion. It is input to the gate signal of the linear gate 8 after being shaped into an adapted rectangular pulse.

In the linear gate 8, only the one which is incident on the signal gamma ray detector 3 from the Ge detector 13 at the same time and emits a signal is input to the multi-channel analyzer 12 and converted into a digital signal proportional to the pulse height. And is stored in the memory in the multi-channel analyzer 12 in the form of γ-ray spectrum.

The same spectrum is obtained by simultaneously counting the γ-rays that are generated almost at the same time when the positron is generated, and includes only the contribution of the signal associated with the annihilation of the positron in the subject 7 excluding accidental events. It is not. From the γ-ray spectrum, the S parameter, which is the count rate ratio of the central portion A and the peripheral portions B ₁ and B ₂ of the 0.511MeV γ-ray photoelectric peak shown in FIG. 24 (b), is calculated by the above equation (1). And use it as a material deterioration index.

In the fifteenth embodiment, the positron beam source 1 is used when the subject 7 itself is contaminated or activated by neutrons.
The measurement is performed without the need for, for example, the subject 7
Zn-65, Co-5 contained in the surface of the body or inside the specimen 7
The energy spectrum of 0.511 MeV annihilation γ-rays resulting from the annihilation reaction between positrons emitted from positron-emitting nuclides such as 8 and the electrons and positrons in the specimen 7 is obtained.

As shown in the configuration diagram of FIG. 16, the inspection device is constructed by installing a Ge detector 13 in a collimator 16 with a shield which is opened in front to prevent choking of the detector, and the detection device. It comprises a preamplifier 9 for amplifying the signal from the Ge detector 13, a linear amplifier 10 for shaping the waveform, and a measurement signal processing system by a multi-channel analyzer 12 for converting the output into a digital signal proportional to the pulse height. ing.

The operation of the above-described structure is that the positron emitted from the positron-emitting nuclide in the subject 7 itself and the subject 7
0 resulting from the annihilation reaction between inner electrons and positrons.
The energy spectrum of 511 MeV annihilation gamma rays is detected by the Ge detector 13, and the deterioration of the material of the subject 7 is judged from the photoelectric peak shape.

The spectrum stored in the memory of the multi-channel analyzer 12 in the form of a γ-ray spectrum includes the contribution of only the signal associated with the disappearance of the positron in the object 7, and is 0.511 shown in FIG. By calculating the S parameter, which is the ratio of the count rates of the central portion A of the photoelectric peak of MeV γ rays and the peripheral portions B ₁ and B ₂ , it is used as an index of material deterioration.

In the sixteenth embodiment, as shown in the block diagram of FIG.
The inspection device includes a first γ-ray detector 33 for annihilation γ-rays installed in the shielded collimator 16 and a second γ-ray detector for simultaneous emission γ-rays installed in another shielded collimator 16a. The γ-ray detector 34 and the γ-ray detector 34 are arranged so as not to enter each other's field of view and face the subject 7 to form a detection device.

Further, as the first γ-ray detector 33 and the second γ-ray detector 34, a plastic scintillation detector is optimal because high-speed signals are required. The measurement signal processing system has the same structure as that shown in FIG. 3 of the third embodiment.

The operation of the above-described structure is such that Co
-60 and other nuclides that emit γ-rays are included. Of these, Co-58 contains 0.811 MeVγ at the same time as positron generation.
Generate a line. Therefore, 0.511 MeV annihilation γ caused by the annihilation reaction between the same γ-ray and the electron and positron in the subject 7
The positron lifetime is measured from the time difference between the signal and the line.

In the seventeenth embodiment, as shown in the block diagram of FIG.
The inspection device is a Ge detector 13 which is a main detector installed in the collimator 16 with a shield, and a Ge detector as a detector for measuring γ-ray energy which is a sub-detector installed in another collimator 16a with a shield. 13a is installed, the Ge detectors 13 and 13a are not in the field of view of each other, and are arranged so as to face the subject 7 to configure the detection device.

As a detector for measuring γ-ray energy, G
Although the e detectors 13 and 13a are used and are optimal in terms of energy resolution, they can also be used for organic scintillation detectors such as NaI scintillation detector. The measurement signal processing system has the same configuration as that shown in FIG. 2 of the second embodiment.

As the operation of the above-mentioned constitution, in the Ge detectors 13 and 13a for measuring γ-ray energy, the energy window region including the photoelectric peak of 0.811 MeV γ-ray emitted from Co-58 contained in the subject 7 is obtained. Then, the single-channel wave height discriminator 11 is set. By using this signal as the coincidence counting gate signal of the Ge detector 13a, it is possible to obtain the γ-ray energy spectrum only by the annihilation γ-rays of the positrons associated with the γ-rays of Co-58.

In addition, nuclides such as Co-60, which emits a plurality of γ-rays at the same time, are not subject to coincidence counting because they are discriminated in terms of energy by both detectors. It becomes possible to measure without removing the effect of γ-rays emitted from other γ-ray nuclides such as Co-60.

In the eighteenth embodiment, as shown in the block diagram of FIG.
The inspection device includes a first detector 33a for annihilation γ rays installed in the shielded collimator 16 and another shielded collimator 16a.
A second detector 34a for simultaneous emission γ-rays installed inside is installed, and the first detector 33a and the second detector 34a are not in the field of view of each other and are arranged facing the subject 7. Then, the detection device is configured. The first detector 33a and the second detector 34a are both CaF ₂ scintillation detectors.

Regarding the measurement signal processing system, the first detector 33
A preamplifier 9a and a high-pass filter 35a are connected to a, and the preamplifier 9a is connected to a linear gate 8 via a linear amplifier 10a and a single-channel wave height discriminator 11a. Further, the high-pass filter 35a is connected to the time-to-wave height converter 6 via the timing discretory 4a.

A preamplifier 9b and a high-pass filter 35b are connected to the second detector 34a. The preamplifier 9b includes a linear amplifier 10b and a single-channel wave height discriminator 11b.
To the linear gate 8 via. In addition, the high pass filter 35b includes a timing discriminator 4b and a delay 5
It is connected to the time wave height converter 6 via. Furthermore, the output of the time-to-wave height converter 6 is connected to the multi-channel analyzer 12 via the linear gate 8.

The operation of the above configuration is as follows. The output signals from the CaF ₂ scintillation detector of the first detector 33a for annihilation γ-rays and the second detector 34a for simultaneous emission γ-rays are High pass filter 35
The signals are input to the timing discriminators 4a and 4b through a and 35b, and are converted by the time wave height converter 6 into signals proportional to the time difference.

On the other hand, regarding the delay component, the preamplifier 9
a, 9b, and linear amplifiers 10a, 10b, a signal proportional to the energy loss of the incident γ-ray inside the detector,
A window corresponding to the photoelectric peak energy of γ-rays emitted at the same time as the emission of positrons is set by the single-channel wave height discriminators 11a and 11b. The signal corresponding to the time difference is gated by the linear gate 8 and obtained as a time spectrum by the multi-channel analyzer 12.

The eighteenth embodiment is different from the thirteenth embodiment or the sixteenth embodiment in that the CaF ₂ scintillation detector is used instead of the plastic scintillation detector usually used for time measurement, which has poor energy resolution. By using a detector, it is possible to discriminate the gate signals in terms of energy, and it is possible to prevent the time spectrum from being distorted due to the coincidence coincidence.

The nineteenth embodiment relates to a specific procedure of the method for evaluating the photopeak shape of annihilation γ-rays, and as shown in (d) above, the γ-ray spectrum data is obtained by using the procedure shown in FIG.
For example, the spectrum data in the vicinity of annihilation γ-rays accumulated in the multi-channel analyzer 12 is transmitted to a computer (not shown) via the interface. In the computer, analysis is performed according to the description in (d) above,
The extinction γ-ray spectrum is approximated as the sum of γ-ray peaks having two kinds of standard deviations, and the deterioration degree of the material is determined by the counting ratio of each γ-ray peak.

The twentieth embodiment relates to the evaluation of the soundness of the structure material, and the concentration of Co-60 differs depending on the component of the subject and the history of neutron irradiation, but the subject component and the history of neutron irradiation are known. In some cases, as shown in the radioactivity concentration characteristic diagram of Fig. 20, it is obtained as a constant relationship with the Co-60 radioactivity concentration.

In each of the above Examples, the radioactivity concentration of Co-60 and the total count rate of γ-ray detectors such as Ge detectors, or the photoelectric peak count rate corresponding to γ-rays emitted from Co-60 were determined. When the distance from the shield and the geometrical shape of the subject 7 are known, the Co-60 radioactivity concentration is converted by the conversion constant determined in advance.

On the other hand, considering the positron lifetime or the change of shape parameter of annihilation γ-ray obtained in each example,
As shown in the correlation diagram of positron lifetime etc. in Fig. 21, the correlation with the neutron irradiation dose considering the neutron irradiation history was calculated beforehand by obtaining the photoelectric peak count rate of Co-60 from the γ-ray spectrum of the Ge detector. By considering the biological efficiency, it can be converted into the radioactivity concentration of Co-60 contained in the subject 7.

When a γ-ray detector having a good energy resolution such as a Ge detector or a NaI scintillation detector is adopted for this conversion, 0.511 MeV of the annihilation γ-ray is used.
The photoelectric peaks of Co-60 (1.173 MeV and 1.332 MeV) are not affected by γ-ray, and the count rate of photoelectric peaks is obtained. Alternatively, if the mixture of other nuclides can be ignored, the Co-60 concentration measurement can be performed in parallel with the implementation of the non-destructive inspection by performing energy discrimination so that annihilation γ-rays are not included during counting. .

However, when a detector for γ-rays having a poor energy resolution such as a plastic scintillation detector is used, the above eleventh embodiment is used unless it is judged that the contribution of annihilated γ-rays can be ignored. As shown in FIG. 12, it is necessary to have a mechanism for housing or shielding the positron beam source 1.

Further, the neutron irradiation integrated amount of the subject 7 was evaluated from the same radioactivity concentration with known data, and the energy measurement method was 0.51 due to positron annihilation on the γ-ray spectrum.
It is more appropriate to measure the photoelectric peak shape of 1MeV γ-rays, and to measure the lifetime of positrons by the lifetime measurement method to obtain information on both at each point of the subject 7 and from the correlation diagram as shown in FIG. It is possible to make various determinations.

In the twenty-first embodiment, when the surface of the subject 7 is contaminated by the non-radioactive or radioactive clad, some of the positrons emitted from the outside disappear in the clad on the surface, and the material of the inner surface is There is a possibility that it does not represent the physical characteristics. Further, as described above, the radioactivity attached to the surface has a great influence on the measurement. For this purpose, decontamination is performed prior to the inspection to remove the surface clad. As this decontamination method, physical decontamination suitable for surface contamination with relatively low adhesion such as high pressure jet cleaning and brush cleaning is desirable.

[0188]

As described above, according to the present invention, even if the soundness of the metal with respect to various equipment and structural materials in the nuclear reactor facility is radioactive contamination or activation of the subject,
There is an effect that the radiation exposure of the measurer can be reduced and highly accurate and safe inspection can be performed at the time of periodic inspection.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a nondestructive inspection device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an inspection device according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of an inspection device according to a third embodiment of the present invention.

FIG. 4 is a positron lifetime distribution characteristic diagram of the third embodiment according to the present invention.

FIG. 5 is a configuration diagram of an inspection device according to a fourth embodiment of the present invention.

FIG. 6 is a configuration diagram of an inspection device according to a fifth embodiment of the present invention.

7A and 7B are configuration diagrams of a detection device according to a sixth embodiment of the present invention, in which FIG. 7A is a cutaway side view of a positron beam source deposition, and FIG. 7B is a cutaway side view of a positron beam source embedded and a plan view. .

8A and 8B are configuration diagrams of a detection device according to a seventh embodiment of the present invention, in which FIG. 8A is a cutaway side view and FIG. 8B is a plan view.

FIG. 9 is a configuration diagram of an inspection device according to an eighth embodiment of the present invention.

FIG. 10 is a configuration diagram of an inspection device of a ninth embodiment according to the present invention.

FIG. 11 is a configuration diagram of an inspection device of a tenth embodiment according to the present invention.

FIG. 12 is a configuration diagram of an inspection apparatus of an eleventh embodiment according to the present invention.

FIG. 13 is a configuration diagram of an inspection device of a twelfth embodiment according to the present invention.

FIG. 14 is a configuration diagram of an inspection device of a thirteenth embodiment according to the present invention.

FIG. 15 is a configuration diagram of an inspection device of a fourteenth embodiment according to the present invention.

FIG. 16 is a configuration diagram of an inspection device of a fifteenth embodiment according to the present invention.

FIG. 17 is a configuration diagram of an inspection device of a sixteenth embodiment according to the present invention.

FIG. 18 is a configuration diagram of an inspection device of a seventeenth embodiment according to the present invention.

FIG. 19 is a configuration diagram of an inspection device of an eighteenth embodiment according to the present invention.

FIG. 20 is a radioactive concentration characteristic diagram of the twentieth embodiment according to the present invention.

FIG. 21 is a correlation diagram of positron lifetime etc. of the twentieth embodiment according to the present invention.

FIG. 22 is a block diagram of a conventional inspection device using a positron lifetime measuring method.

FIG. 23 is a block diagram of a conventional inspection apparatus using a γ-ray energy measuring method.

FIG. 24 is a distribution characteristic diagram of the energy spectrum of γ-rays due to positron annihilation in the related art, where (a) shows the distribution of electrons in the shell and free electrons in the defect, and (b) shows the distribution of the central part and the peripheral part.

FIG. 25 is a characteristic diagram of an annealing temperature and an S parameter in a conventional subject.

FIG. 26 is a characteristic diagram of an annealing temperature and a hardening degree in a conventional test object.

FIG. 27 is a photoelectric peak characteristic diagram in the detector.

[Explanation of symbols] 1 ... Positron source, 2a ... 0.511 MeV γ-ray, 2b ... γ-ray,
3, 3a, 3b ... γ-ray detector, 4a, 4b ... Timing discriminating, 5 ... Delay, 6 ... Time wave height converter, 7
... object, 8 ... linear gate, 9, 9a, 9b ... preamplifier, 10, 10a, 10b ... linear amplifier, 11, 11a, 11b ... single-channel wave height discriminator, 12 ... multi-channel analyzer, 13, 13a ... Ge detector, 14 ... An annihilation component curve (dotted line) with an electron in the shell, 15 ... An annihilation component curve with a free electron (solid line), 16, 16a ... Collimator with a shield, 17 ... Transmission type detector, 18 ... Delay Amplifier, 19 ... Gate and delay generator, 20 ... Scintillator thin plate, 21 ... Ride guide, 21
a ... Rear light guide, 22 ... Photomultiplier tube, 23 ... β-ray absorber, 24 ... Watertight lid, 25 ... Cavity forming cover, 26 ... Pressurized gas injection hole, 27 ... Compressed air, 28 ... Positron source Calibration filter, 29 ... Calibration filter driving mechanism, 29a ... Calibration filter moving direction (arrow), 30 ... Calibration source, 31 ... Calibration source driving mechanism, 31a ... Calibration source moving direction (arrow) , 31b ...
Calibration source source, 32 ... β-ray absorber drive mechanism, 32a ...
.beta.-ray absorber moving direction (arrow), 33, 33a ... First gamma ray detector, 34, 34a ... Second gamma ray detector, 35a, 35b ...
High-pass filter, A ... central area, B _1, B ₂ ... periphery area.

Claims (22)

[Claims] 1. A 0.511 MeV generated by reacting with an electron in a subject by irradiating the subject with a positron generated from a positron beam source.
In a nondestructive inspection device for measuring a change in the shape of a photoelectron peak of annihilation γ-rays with a Ge detector, a collimator with a shield for limiting the number of radiation flux from the object is provided in front of the Ge detector, and a positron beam source is also provided. Is placed outside the visual field of the opening of the collimator with a shield so that the irradiation region of the positron beam source is within the visual field of the Ge detector. 2. 0.511 MeV generated by reacting with an electron in a subject by irradiating the subject with a positron generated from a positron source
In a nondestructive inspection device for measuring a change in the shape of a photoelectron peak of annihilation γ-rays with a Ge detector, a collimator with a shield for limiting the number of radiation flux from the subject is provided in front of the Ge detector, and the positron beam is used. The source is installed in the visual field of the opening of the collimator with a shield and is placed close to the subject, and a transmission type detector is installed between the positron source and the subject to reach the subject. Energy is lost in the transmissive detector, extracted as an electrical or optical signal, and the signal from the Ge detector is simultaneously counted, so that the annihilation reaction between the electron and the positron in the analyte A nondestructive inspection device for radioactive pollutants, characterized by obtaining the energy spectrum of the generated 0.511 MeV annihilation γ-rays and judging the material deterioration of the object from the photoelectric peak shape. 3. A γ-ray detector outputs a signal corresponding to 0.511 MeV annihilation γ-ray generated by an annihilation reaction between an electron and a positron in the subject by irradiating the subject with a positron generated from a positron source. In a non-destructive inspection device for measuring, a collimator with a shield for limiting the number of radiation flux from the subject is provided on the front surface of the γ-ray detector, and the positron beam source is within the field of view of the collimator with the shield. The transmission type detector is installed between the subject and the subject and between the positron beam source and the subject, and a part of the energy of the positrons reaching the subject is stored in the transmission type detector. It is caused by the annihilation reaction between the electron in the object and the positron measured by the γ-ray detector after being lost at 1, extracted as an electrical or optical signal.
A nondestructive inspection device for radioactive contaminants, characterized in that deterioration of a material of an object is judged from a time difference from a signal corresponding to 511 MeV annihilation γ-rays. 4. The nondestructive inspection device for radioactive pollutants according to claim 1, wherein the positron beam source is arranged outside the measurement field of view of the annihilation γ-ray detector. 5. A collimator with a shield for limiting the number of radiation flux from the subject is provided on the front surface of the Ge detector or the detector for γ-rays, and the positron beam source is in the field of view of the collimator with the shield. In the transmission type detector, the transmission type detector is installed between the subject and the subject, and a transmission type detector is installed between the positron source and the inside of the transmission type detector. A detection device that extracts the light as an electrical or optical signal after loss by means of a thin scintillator plate with the positron beam source deposited or embedded on the surface opposite to the subject surface, and the positrons from the positron beam source reach the subject. In the meantime, a part of the energy of the electron is lost in the thin scintillator plate, and an optical signal corresponding to the lost energy is input to the photomultiplier tube directly or through an optical guide. Motomeko 2 or radioactive contaminants non-destructive inspection apparatus according to claim 4, wherein. 6. A collimator with a shield for limiting the number of radiation flux from the subject is provided on the front surface of the Ge detector or the detector for γ-rays, and the positron beam source is in the field of view of the opening of the collimator with the shield. In the transmission type detector, the transmission type detector is installed between the subject and the subject, and a transmission type detector is installed between the positron source and the inside of the transmission type detector. The positron beam source is a layer of a positron scintillator plate and a substance that is thicker than the transmissive scintillator plate and transparent to the scintillator light, and is detected as an electrical or optical signal by loss of positron energy. A part of the light is lost in the transmissive scintillator plate, and an optical signal corresponding to this energy loss is photomultiplied directly from the transmissive scintillator plate or through an optical guide. Radioactive contaminants for non-destructive inspection apparatus of claims 2 to 4, wherein the input to. 7. A collimator with a shield for limiting the number of radiation flux from the subject is provided on the front surface of the Ge detector or the detector for γ-rays, and the positron beam source is placed in the opening visual field of the collimator with the shield. In the transmission type detector, the transmission type detector is installed between the subject and the subject, and a transmission type detector is installed between the positron source and the inside of the transmission type detector. In the inspection device for simultaneously counting the signal from the Ge detector or the detector for γ-ray by extracting the positron with a maximum energy of 0.3 MeV or more, the positron emitting the positron having a maximum energy of 0.3 MeV or more. 7. A radiation source is used, and a β-ray absorber having a dose of 80 mg / cm ² or less is arranged between the subject and the transmission type detector. Inspection device. 8. A Ge-detector or a γ-ray detector is arranged in a watertight manner by providing a collimator with a shield for limiting the number of radiation flux from the subject on the front surface of the Ge detector or the γ-ray detector. 7. A space between the positron beam source and the subject is formed by providing an air curtain or the like between the positron beam source and the positron beam source facing the subject in the water. Nondestructive inspection equipment for radioactive pollutants. 9. A collimator with a shield for limiting the number of radiation flux from the subject and a positron beam source are provided on the front surface of the Ge detector or the γ-ray detector, and the subject and the positron beam source are connected to each other. A positron radiation source calibration filter having a thickness equal to or greater than the maximum range of positrons and made of the same material as or different from the β-ray absorber of the subject is provided by a calibration filter drive mechanism so as to be freely inserted and removed. Nondestructive inspection equipment for radioactive pollutants. 10. 0.511M generated by irradiating a subject with positrons generated from a positron beam source and reacting with electrons in the subject
In a nondestructive inspection device for measuring eV annihilation γ rays, a positron source calibration filter that is freely inserted and removed between the subject and the positron source is automatically inserted and removed by a calibration filter drive mechanism, Measure the γ-ray spectrum at the time of measuring the object in the inserted state and the pulled out state of the source calibration filter, and obtain the signal time difference or 0.511 MeV.
The nondestructive inspection method for radioactive contaminants according to claim 9, wherein the degree of deterioration of the subject is determined from the difference in the photopeak shape of the annihilation γ-rays. 11. A Ge detector or γ-ray detector is provided on the front surface of the Ge detector or γ-ray detector with a collimator with a shield and a positron beam source for limiting the number of radiation flux from the subject. A calibration radiation source that emits γ-ray energy close to 0.511 MeV annihilation γ-rays is provided by a calibration radiation source drive mechanism so that the calibration radiation source can be freely inserted and removed, and a β-ray absorber is provided between the subject and the positron radiation source. A non-destructive inspection device for radioactive pollutants, which is provided so as to be freely inserted and removed by a drive mechanism for a β-ray absorber. 12. 0.511 M generated by reacting with an electron in a subject by irradiating the subject with a positron generated from a positron beam source.
In a non-destructive inspection device that measures eV annihilation γ rays, the β-ray absorber is inserted by the drive mechanism for β-ray absorber to make the positron source non-irradiated to the subject and emitted from the calibration source. While obtaining the energy spectrum of the γ-ray to obtain the shape of the photoelectric peak of the γ-ray, the calibration source driving mechanism does not install the calibration source and the positron source is 0.511 in the irradiation state on the subject. Non-destructive inspection method for radioactive pollutants characterized by obtaining the energy spectrum of MeV annihilation γ-rays, determining the shape of the photoelectric peak of annihilation γ-rays from this spectrum, and judging the deterioration degree of the material from the rate of change of both . 13. A first γ-ray detector arranged so that the positron-irradiated region on the surface of the subject is placed in the field of view at a position where the positron beam source cannot be directly placed in the field of view, and positron and γ-rays are emitted almost simultaneously. The second γ-ray detector is provided in front of the positron beam source and is provided with a shielded collimator, and the second γ-ray detector is arranged at a position where the subject does not directly enter the field of view through the positron beam source.
Γ-ray detector is used to measure the emitted γ-ray and set it as the start time, and the first γ-ray detector measures the annihilated γ-ray and set it as the end time. A non-destructive inspection device for radioactive pollutants characterized by demands. 14. A Ge detector that places a positron beam source in a position where it cannot be directly seen and puts the positron irradiation region on the surface of the subject in the field of view, and a positron beam source that uses a nuclide that emits positron and γ-rays almost simultaneously. It is equipped with a collimator with a shield in the front and a γ-ray detector that does not pass through the positron beam source and directly put the subject in the field of view, and measures the emitted γ-rays by the γ-ray detector to obtain a simultaneous counting signal. A nondestructive inspection for radioactive pollutants, characterized in that the γ-ray spectrum is measured by the Ge detector in synchronism with the coincidence counting signal to determine the deterioration of the material of the object from the photopeak shape of the annihilated γ-rays. apparatus. 15. A collimator with a shield for limiting the number of radiation fluxes from the subject is provided on the front surface of the Ge detector so that the irradiation region of 0.511 MeV annihilation γ rays from the subject is within the field of view of the Ge detector. In the inspection device that was stored, the surface layer of the subject itself was contaminated with radioactive substances containing positron-emitting nuclides such as Zn-65 and Co-58, or the subject itself was activated by neutrons to generate Zn-65, Co-58, etc. 0.51 resulting from the annihilation reaction between the positron emitted from the radioactive pollutant, the electron in the analyte, and the positron when it contains a positron-emitting nuclide
A nondestructive inspection device for radioactive contaminants, which obtains the energy spectrum of 1 MeV annihilation γ-rays and judges the deterioration of the material of the object from the photoelectric peak shape. 16. A first γ-ray detector provided with a collimator with a shield and a collimator with a shield arranged so that the same position of a subject can be placed in the field of view of each other without storing the fields of view of the detectors. In the inspection device equipped with the second γ-ray detector, the surface layer of the subject itself is contaminated with radioactive substances containing positron emitting nuclides such as Zn-65 and Co-58 or the subject itself is activated by neutrons. Zn-65, Co-5
When positron-emitting nuclides such as 8 are included, 0.81 is generated at the same time as positron generation from Co-58 in each γ-ray detector.
For radioactive contaminants characterized by detecting 0MeV γ-rays and 0.511MeV annihilation γ-rays resulting from the annihilation reaction between electrons and positrons in the specimen and judging the deterioration of the material of the specimen from the time difference between the two signals Non-destructive inspection device. 17. A gamma ray energy discriminating detector and a gamma ray energy discriminating detector provided with a collimator with a shield arranged so that the same position of a subject can be placed in the visual field of each other without keeping the visual fields of the detectors. In an inspection device equipped with a Ge detector equipped with a collimator with a body, the surface layer of the subject is contaminated with radioactive substances containing positron-emitting nuclides such as Zn-65 and Co-58, or the subject itself is activated by neutrons. When positron-emitting nuclides such as Zn-65 and Co-58 are included, Co
Extinction γ by simultaneously counting the count output signal of the narrow window region including the 0.810 MeV energy region of -58 as the gate signal of the energy signal of the Ge detector.
A nondestructive inspection apparatus for radioactive contaminants, which obtains an energy spectrum of a ray and determines deterioration of a material of an object from a photoelectric peak shape of annihilation γ ray. 18. A γ-ray detector for measuring life, which comprises two collimators with a shield arranged so that the same position of an object can be included in the visual field without accommodating the visual fields of the detectors, In the inspection device for measuring positron annihilation γ-rays with the γ-ray detector and γ-rays simultaneously generated at the time of positron emission with the second γ-ray detector and measuring the positron lifetime from the time difference between the two, Nondestructive inspection device for radioactive pollutants, characterized in that the two γ-ray detectors are CaF ₂ scintillation detectors. 19. A first positron in a test object emitted from a positron-emitting nuclide that emits a positron and a γ-ray at substantially the same time.
The detector for γ-rays measures the positron annihilation γ-rays, and the second detector for γ-rays detects the γ-rays that occur simultaneously when the positrons are emitted, and detects the time difference signal of the high-speed component pulse of the output signals from both detectors. And obtain two gate signals having a wave height in a narrow energy region corresponding to γ-ray energy and positron annihilation γ-ray energy which are simultaneously generated at the time of positron emission from the output signals of the delay components generated from both detectors and obtain the time difference. The nondestructive inspection method for radioactive pollutants according to claim 18, wherein the lifetime of the positron is measured by applying a gate to the signal. 20. In determining the shape of the annihilation γ-ray spectrum of positrons, the annihilation γ-ray spectrum is approximated as the sum of γ-ray peaks having two kinds of standard deviations, and the γ-ray peak count ratio of each γ-ray peak A nondestructive inspection method for radioactive pollutants, characterized by determining the degree of deterioration. 21. For a subject that may receive neutrons, a photoelectric peak count rate of Co-60 is obtained from a γ-ray spectrum of a Ge detector, and the geometric efficiency is taken into consideration. It is converted into the radioactivity concentration of Co-60, and the integrated amount of neutron irradiation of the object is evaluated from this radioactivity concentration.
A non-destructive inspection method for radioactive contaminants characterized by measuring the photopeak shape of 1MeV γ-rays and determining the degree of deterioration of the test material from both the radioactivity concentration of Co-60 and the photopeak shape of 0.511MeV γ-rays. . 22. The method according to claim 1, wherein iron rust or the like previously attached to the surface of the sample is removed by physical decontamination when determining the degree of deterioration of the sample material which is a radioactive contaminant. Item 20: Nondestructive inspection method for radioactive pollutants.