JP5840400B2 - Method and apparatus for measuring concentration of metal surface adhering component - Google Patents

Description

  The present invention relates to a method and an apparatus for measuring the concentration of a metal surface adhesion component. More specifically, the present invention is suitable for the measurement of a small amount of components adhering to a metal surface, for example, a salinity adhering to the surface of a metal canister in a concrete cask used for long-term storage of spent fuel of a nuclear power plant. The present invention relates to a measurement method and apparatus.

  As an intermediate storage method until the reprocessing of spent nuclear fuel in the nuclear reactor, the spent fuel is stored in a metal storage container (canister), sealed, and then stored in a concrete storage container (concrete cask) before the intermediate storage facility. It is considered to be stored in the building. The slow heat function in this concrete cask storage facility is secured by both the concrete cask and the building. Slow heat in the concrete cask is equipped with a ventilation port at the bottom and top of the concrete cask, and a natural air cooling system that ventilates the concrete cask by natural ventilation caused by rising air warmed by cooling the canister is adopted. Has been. In addition, for the gradual heat in the building, a natural air cooling method is adopted in which an exhaust tower having a chimney effect and a ventilation opening are provided, and the building is ventilated by natural ventilation. This intermediate storage facility is often constructed near the coast in consideration of safety.

  Therefore, salt particles carried from the coast due to strong winds from the sea may be contained in the air, and the salt content does not stop in the building but further penetrates into the concrete cask to seal the spent nuclear fuel. May adhere to the surface of the canister and cause stress corrosion cracking called SCC. In order to prevent the occurrence of SCC, it is necessary that the salinity concentration adhering to the canister surface does not exceed the limit surface adhering substance concentration with respect to the occurrence of SCC. For this purpose, it is necessary to accurately measure the salinity concentration adhering to the canister surface.

  Conventional methods for measuring the amount of salt attached to the surface of the canister include the smear method in which the amount of salt attached to the surface is wiped off with a cloth and the amount of salt attached to the cloth is measured by chemical measurement or the like. There has been proposed a method (patent document 1) in which the amount of adhesion is measured by irradiating sea salt particles with laser light on an exhaust path taken out of the concrete cask together with the atmosphere, receiving the reflected light, and spectrally analyzing it.

  In the latter measurement method described in Patent Document 1, laser light is irradiated to the outer peripheral surface of the canister from a laser device installed outside the concrete cask through a transmission fiber, and sea salt particles adhering to the outer peripheral surface of the canister are irradiated with laser light. While removing the blast, the ablation plume is taken out of the concrete cask by vacuuming with a suction hose with the removed sea salt particles drawn into the concrete cask, and the sea salt particles are taken into the measuring unit and measuring head. The sea salt particles are irradiated with a laser, and the reflected light is received and dispersed into a spectrum, and the concentration of the sea salt particles, that is, the adhesion amount is measured from the spectrum by a detector.

  Here, the sea salt particles removed from the outer peripheral surface of the canister are sucked out of the concrete cask through the suction hose. At this time, a laser is irradiated in the measuring head and the reflected light is sent to the measuring device. In the measuring apparatus, the spectrum is dispersed and the concentration of the sea salt particles, that is, the amount of adhesion is measured from the spectrum by the detector. For this reason, it is necessary to retain the sea salt particles removed in the measurement head during the measurement. Therefore, the flow of the sea salt particles moving in the suction hose is temporarily stopped in the measurement head by taking measures such as stopping the blower or blocking the measurement head from the blower. .

JP 2007-271634 A

  However, in the smear method in which the adhered components are wiped off with a cloth, there is a problem in that radioactive waste increases because the cloth wiped off with salt is activated. Moreover, since remote measurement is difficult, there is a risk that an operator who performs the measurement will be exposed to an explosion. Furthermore, there was a problem that measurement in real time was impossible. Furthermore, when measuring a small amount of salt, there is a problem that the measurement accuracy is poor.

  In the salinity concentration measuring method described in Patent Document 1, the concentration measurement is performed after the salinity particles peeled off from the canister by the laser are drawn into the measuring head outside the concrete cask, so before reaching the measuring head. Since salinity adheres to the tube wall in the middle of the suction hose, the entire amount of the separated salinity particles cannot be taken into the measuring head and measured. In addition, sea salt particles are temporarily stopped at the measuring head by means such as blocking the measuring head against the blower, so even when the flow is stopped, the salt that has already passed through the measuring head or has not reached the measuring head is also measured. The head cannot be captured. For this reason, the measurement accuracy is poor. Therefore, according to the salinity concentration measuring method described in Patent Document 1, not only quantification / quantitative evaluation is possible, but also the sensitivity is poor as an index for evaluating the occurrence of SCC.

  Further, the salinity concentration measuring method described in Patent Document 1 uses a measuring head outside a concrete canister for a plume containing sea salt particles blown off from the surface of a metal canisque by laser blast removal and other adhering components such as magnesium and sodium. Since the reflected light is measured by applying a laser beam after being taken in, only the presence of some luminescent components can be found, and the luminescence intensity of chlorine cannot be specified, so the salinity concentration is accurately measured. Can not.

  Further, the salinity concentration measuring device described in Patent Document 1 is a concrete cask after sucking a blast portion for removing salt adhering to the surface of a metal canister in a concrete cask and a plume containing sea salt particles and other adhering components. Since it has a large and complicated structure that is divided into a measurement unit and a measurement head that irradiates the laser after taking it out of the laser and sends the reflected light to the measurement device, in a narrow space immediately after the ablation Trace adhering components such as salt particles cannot be detected.

  Then, an object of this invention is to provide the method and apparatus which can measure the trace component adhering to the metal surface with sufficient sensitivity. Another object of the present invention is to provide a method for measuring the concentration of a component adhering to a metal surface that can be measured in real time and does not generate waste during the measurement process. Furthermore, an object of the present invention is to provide a method for measuring the concentration of a metal surface adhering component that enables measurement of the adhering trace component on the target metal surface.

In order to achieve such an object, a method for measuring the concentration of a trace component adhering to a metal surface facing a narrow space according to the first aspect of the present invention includes at least a laser and a spectroscope in addition to the narrow space. The concentration measuring device main body having a means and a light receiving element and a controller for controlling the laser and the light receiving element is arranged, and the metal surface is irradiated with laser light through an optical transmission unit inserted along the metal surface in a narrow space. Metal surface by ablating adhering substances and turning them into plasma, and emitting light from the plasmaized substances to the spectroscopic means outside the narrow space through the light transmission part and separating the light, and obtaining a light emission spectrum with the light receiving element The trace component adhering to the surface is specified and the concentration of the trace component is obtained.

The invention according to claim 2 is the method for measuring the concentration of a component adhering to the metal surface according to claim 1, wherein the metal surface is an outer surface of a metal canister that contains spent fuel, and the narrow space is a metal canister. It is formed between the inner peripheral surface of the concrete cask which accommodates.

  Here, in the method for measuring the concentration of the metal surface adhesion component of the present invention, the traveling means for supporting the laser beam irradiation part that irradiates the outer surface of the metal canister, the outer surface of the metal canister and the inner peripheral surface of the concrete cask Preferably, the distance between the irradiation unit and the outer surface of the metal canister is kept constant.

  In the method for measuring the concentration of a metal surface adhesion component according to the present invention, the target trace component is not particularly limited, but is preferably a salt that causes stress corrosion cracking. In order to detect the salinity, it is preferable to use any one of 837.59 nm chlorine emission line, 517.26 nm magnesium emission line, 518.36 nm magnesium emission line, and 833.31 nm chlorine emission line.

Further, in the method for measuring the concentration of the component adhering to the metal surface according to the present invention, the irradiation with the pulsed laser beam is sufficient even once, but it is preferably performed a plurality of times. The multiple irradiations of the pulsed laser beam may be performed from the same direction, but in some cases, as directed to the invention according to claim 7 , the irradiation is directed toward the metal surface and adheres to the metal surface. Performed in a first step of ablating a minor component and a second step of exciting particles that were irradiated in parallel with the metal surface toward the plasma formed by the ablation and were not excited in the first step You may make it do. Furthermore, when performing multiple times of irradiation, the laser beam irradiated in the first step is weaker than the laser beam irradiated in the second step, and at least the adhesion to be measured, as in the invention according to claim 8. It is sufficient to eject the trace component from the metal surface, and the laser light irradiated in the second step is sufficient to excite the attached trace component ejected in the first step to emit light. preferable.

The invention according to claim 9 is the method for measuring a concentration of a component adhering to a metal surface according to any one of claims 1 to 8 , wherein the oxygen emission intensity of the emission line indicating the trace component adhering to be measured is measured. The correlation between the ratio of the emission line to the emission intensity and the concentration of the adhering trace component is obtained, and the concentration of the attached trace element is obtained from the ratio of the emission intensity of the attached trace element to the emission intensity of the oxygen emission line at the time of measurement. .

The invention described in claim 10 is the method for measuring the concentration of a component adhering to a metal surface according to any one of claims 1 to 9 , wherein the measurement of light emission from a plasma substance and the laser beam immediately before that are measured. A time difference of 1 μs to 10 μs is given between irradiation and irradiation.

The invention according to claim 11 is the method for measuring the concentration of a metal surface adhering component according to any one of claims 7 to 10 , wherein the laser beam is irradiated in the first step and the laser beam is irradiated in the second step. A time difference of 0.5 μs to 5 μs is given to the laser beam.

An apparatus for measuring the concentration of a trace component adhering to a metal surface facing a narrow space according to the present invention includes at least a laser, a spectroscopic means, a light receiving element, and a controller for controlling the laser and the light receiving element. A concentration measuring device main body arranged outside a narrow space, and an optical transmission unit inserted along a metal surface into a narrow space including an optical system for laser light transmission and an optical system for light emission measurement The laser beam is irradiated to the metal surface through the optical transmission unit to ablate the adhering substance and turn it into plasma, and the light emitted from the plasmaized substance is guided to the spectroscopic means outside the narrow space through the optical transmission unit. by obtaining an emission spectrum at the light receiving element as well as spectral Te, so that both the identifying trace components to be attached to the metal surface to determine the concentration of the minor component.

The invention according to claim 13 is the concentration measuring device for metal surface adhering component according to claim 12, wherein the metal surface is an outer surface of a metal canister for storing spent fuel, and the narrow space is a metal canister. It is assumed to be formed between the inner peripheral surface of the concrete cask that houses

The invention according to claim 14 is the apparatus for measuring the concentration of a metal surface adhering component according to claim 13, which is provided between the outer surface of the metal canister and the inner peripheral surface of the concrete cask and is used for laser light transmission. The optical system includes a traveling unit that supports the irradiation unit and maintains a constant distance between the irradiation unit and the outer surface of the metal canister.

The invention according to claim 15 is the metal surface adhering component concentration measuring device according to any one of claims 12 to 14 , wherein the laser ablate the adhering substance by irradiating the inspected metal surface with laser light. And a second laser that irradiates the material ablated with the first laser light to form plasma by irradiating the laser light, and the controller opens the gates of the first laser, the second laser, and the light receiving element. It controls the time difference from the start time.

The invention according to claim 16 is the concentration measuring apparatus for a metal surface adhesion component according to any one of claims 12 to 14 , wherein the light transmission part is a hollow tube, and an optical system for laser light transmission. And a light emitting measurement optical system and a seal member that is in close contact with the metal surface is provided at the tip opening facing the metal surface, and when the laser irradiation, the seal member and the metal surface are in close contact, It is preferable that the inside of the hollow tube can be depressurized while fixing the irradiation point.

Further, the invention according to claim 17 is the metal surface adhesion component concentration measuring apparatus according to claim 16 , wherein the optical system for laser light transmission and the optical system for light emission measurement are optical fibers, and each light The fiber is arranged so that the tip surface of the fiber faces the metal surface.

Further, the invention according to claim 18 is the concentration measuring apparatus for a metal surface adhering component according to claim 16, wherein the hollow tube has a condensing lens and reflects only the wavelength of the laser beam, and the laser beam is reflected on the metal surface. The optical system for laser beam transmission, which has a wavelength-selective mirror that irradiates the light source, and the plasma emission generated by ablation of a trace component adhering to the metal surface is placed behind the wavelength-selective mirror and transmitted through the wavelength-selective mirror And an optical system for light emission measurement having a reflection mirror that does not depend on the wavelength for reflecting the plasma emission, so that laser light and plasma emission are propagated in the hollow tube.

The invention according to claim 19 is the concentration measurement apparatus for a metal surface adhering component according to any one of claims 12 to 14 , wherein the light transmission section includes an optical fiber for laser light transmission and a light emission measurement device. These optical fibers are arranged so that the tip surface of each optical fiber faces the metal surface.

According to a twentieth aspect of the present invention, there is provided the metal surface adhering component concentration measuring apparatus according to any one of the twelfth to nineteenth aspects, between the start of opening the gate of the light receiving element and the laser beam irradiation just before the gate opening. Is given a time difference of 1 μs to 10 μs.

Furthermore, the invention according to claim 21 is the metal surface adhesion component concentration measuring device according to any one of claims 12 to 20 , wherein the laser light is irradiated in the first step and the second step is irradiated. A time difference of 0.5 μs to 5 μs is given to the laser beam.

According to the method and apparatus for measuring the concentration of a metal surface adhering component of the present invention, the material adhering to the metal surface is ablated by irradiating a pulsed laser beam to measure the light emitted from the material that has been converted into plasma, and then performing spectroscopic analysis. Since the emission intensity for each wavelength is obtained, the concentration of the adhered substance can be measured with a sensitivity that can be sufficiently utilized for each evaluation. That is, it can be determined whether or not there is an attached substance. Specifically, in the experiments by the present inventors, it was confirmed that there was a measurement sensitivity for chlorine having a surface salinity of about 0.1 g / m ² . This measurement sensitivity is sufficient to evaluate the influence of stress corrosion cracking. In addition, since the plasma emission near the metal surface irradiated with laser light is directly measured, the structure of the measurement unit can be reduced, so that a metal canister housed in a confined space such as a concrete cask can be used. It can be applied to the measurement of salinity adhering to the surface. Of course, it is also possible to measure the trace components attached to the open metal surface, such as a metal cask.

  In addition, because remote and real-time measurement is possible, there is a danger of workers being exposed to exposure when measuring the amount of salt attached to the surface of a metal canister in a concrete cask used to store spent fuel. And the newly generated radioactive waste (cloth wiped with salt), which is a problem in the Snia method, will disappear. Even with a small amount of adhering salt, the plasma emission generated with ablation is measured and dispersed to obtain emission intensity proportional to the concentration, so that the concentration of salt can be measured accurately. Therefore, the index for evaluating the occurrence of SCC is not only sensitive, but also enables quantification and quantitative evaluation.

  Further, according to the concentration measuring method and apparatus for the metal surface adhering component of the present invention for measuring the concentration of the trace component adhering to the metal surface facing the narrow space, the concentration measuring device is provided outside the narrow space. The main body is placed, and the metal surface is irradiated with laser light through an optical transmission part inserted along the metal surface in a narrow space to ablate the adhering substance and turn it into plasma, and emit light from the plasmaized substance. Since it is guided to the spectral means outside the narrow space through the optical transmission unit and splits the spectrum, the emission spectrum is obtained with the light receiving element, so that the salt particles immediately after ablation, etc. The concentration of the trace amount adhering component can be obtained. Therefore, the salinity concentration adhering to the outer surface of the metal canister accommodated in the concrete cask can be measured.

  In addition, in the detection of salinity, when using one of the 837.59 nm chlorine emission line, 517.26 nm magnesium emission line, 518.36 nm magnesium emission line, and 833.31 nm chlorine emission line, the sensitivity to chlorine and magnesium Concentration is obtained.

  In addition, when the pulsed laser light irradiation is performed a plurality of times, the emission of the ablated element can be measured without omission, so that the measurement sensitivity is improved. In other words, the particles excited by ablation are effectively reheated or reexcited by the second laser beam to extend the emission lifetime of the excited atoms and are ejected from the metal surface without being converted to plasma by the first ablation. Since the particles of the attached components are also excited, it is possible to increase the ablation efficiency and improve the measurement sensitivity while suppressing damage to the material with lower power. In addition, since the energy of the first laser pulse can be reduced, damage due to laser light on the canister surface can be reduced.

  In particular, the first step of irradiating a pulsed laser beam toward the metal surface to ablate the trace components adhering to the metal surface, and parallel to the metal surface toward the plasma formed by ablation In the second step of exciting particles that have been irradiated and not excited in the first step, the ablated material is further irradiated with laser light into the atmosphere (plasma plume) atomized by ablation. By reheating or reexcitation, the emission lifetime of the excited atom can be extended and the emission peak can be made remarkable. Moreover, since the plasma plume is reheated or reexcited, the particles ejected by the air plasma are also excited, increasing the ablation efficiency and improving the emission intensity. For this reason, it can measure with the sensitivity which can be fully utilized for evaluation of a density | concentration between adhesion substance density | concentration and emitted light intensity. In addition, since the energy of the laser pulse in the first step can be lowered, damage due to the laser beam on the canister surface can be reduced.

  Furthermore, the laser beam irradiated in the first step is weaker than the laser beam irradiated in the second step, and is sufficient to eject at least the attached trace component to be measured from the metal surface. If the laser light emitted in step 1 is sufficient to excite the attached trace components ejected in the first step and emit light, the measurement sensitivity can be improved while minimizing damage from the laser light on the canister surface. Can be raised.

  Furthermore, the correlation between the ratio of the emission intensity of the emission line indicating the attached trace component to be measured to the emission intensity of the emission line of oxygen to the emission intensity of the emission trace element was determined, and the emission intensity of the attached trace component at the time of measurement was determined. When determining the concentration of adhering trace components from the ratio to the emission intensity of the emission line, the linearity of the graph is improved, so there is more correlation between the element selected as an indicator for the measurement of adhering trace components and the concentration of adhering trace components. Since it is required with high accuracy, quantification of the concentration becomes high accuracy.

  Further, in the method for measuring the concentration of the component adhering to the metal surface of the present invention, by giving a time difference of 1 μs to 10 μs between the measurement of light emission from the plasma substance and the irradiation of the laser beam immediately before the measurement, Since the emission spectrum can be obtained by receiving the light at the light receiving element at the timing when the emission peak becomes remarkable with the influence removed, the measurement sensitivity can be increased. When ablating a trace amount of components on the metal surface, the white noise is weak because the peak power of the laser is small, but even in this case, if the light receiving element gate start time is early, the white light noise is stronger than the emission line intensity. Therefore, measurement is impossible, and if it is slow, the intensity of the bright line is attenuated and sensitivity is not obtained. Therefore, in this case, the time difference between the start of opening the gate of the light receiving element and the irradiation of the laser beam immediately before it is preferably adjusted to a range of 1 μs to 10 μs as in the case of the double pulse.

  In the method for measuring a concentration of a metal surface adhesion component according to the present invention, by giving a time difference of 0.5 μs to 5 μs between the laser beam irradiated in the first step and the laser beam irradiated in the second step. The effect of additional heating can be obtained, and sufficient additional heating can be applied before the excited particles are scattered.

  Further, in the concentration measuring apparatus for a metal surface adhesion component according to the present invention, the optical transmission is performed by a sealable hollow tube having a built-in optical system for laser light transmission and an optical system for light emission measurement, and a tip opening fixed to the metal surface. When the laser beam is irradiated, the sealing member and the metal surface are in close contact with each other, so that the irradiated portion can be fixed and stabilized, and at the same time, the inside of the hollow tube can be decompressed. Since it can suppress, only the plasma from an adhesion trace component is generated, and measurement accuracy improves.

Furthermore, in the case where the optical system for laser light transmission and the optical system for light emission measurement of the optical transmission unit composed of a sealable hollow tube are composed of optical fibers, the propagation of laser light and plasma light emission However, there are few restrictions on the movement of the optical transmission unit in a narrow space. The same applies to the invention of claim 18 in which an optical system such as a condensing lens or a mirror is incorporated. In addition, by using optical components only in the optical fiber or the irradiating unit, the optical transmission unit and the irradiating unit can be reduced in size, and measurement in a narrow part becomes possible.

  Further, in the concentration measuring apparatus for the metal surface adhesion component of the present invention, when the light transmission part is composed of a bare laser light transmission optical fiber and a light emission measurement optical fiber, the metal surface in a narrower space can be measured. Detection of adhering trace components and concentration measurement can be performed.

  Further, in the method and apparatus for measuring the concentration of a metal surface adhering component of the present invention, traveling means for supporting an irradiation part of an optical system for laser light transmission between the outer surface of the metal canister and the inner peripheral surface of the concrete cask. In the case where it is provided, since the distance from the outer surface of the metal canister can be kept constant even if the irradiation unit is moved, the irradiation unit can be prevented from shaking. For this reason, the distance between the irradiation part and the outer surface of the metal canister changes, and the positional relationship between the focal point of the laser beam and the outer surface of the metal canister shifts in the vertical direction of the outer surface, or the irradiation direction of the laser beam changes. The shift can be prevented, and ablation can be satisfactorily performed even when measuring at another position.

The conceptual diagram at the time of applying the measuring system which implements the density | concentration measuring method of the metal surface adhesion component of this invention to the aspect which measures the density | concentration of the salt which adheres to the surface of the metal canister in a concrete cask is shown. It is a conceptual diagram which shows 1st Embodiment of an optical transmission part. It is a conceptual diagram which shows 2nd Embodiment of an optical transmission part. It is a principle figure which shows an example of the experimental apparatus for confirming the effect of the density | concentration measuring method of the metal surface adhesion component of this invention. It is explanatory drawing which shows the mode of SUS304L (concentration 0.1 g / m < ² >) and an irradiation location. It is an optical microscope photograph which shows the surface state of SUS316L after irradiation. 3 is an electron micrograph showing the surface state (concentration: 0.1 g / m ² ) of SUS316L after irradiation. It is a graph which shows the example of evaluation of the emitted light intensity resulting from each element. FIG. 2 is a principle diagram (left diagram) showing a laser irradiation method with a single pulse and an explanatory diagram (right diagram) showing a temporal relationship between laser light and ICCD. It is a graph which shows the emission spectrum (495-525 nm) at the time of a single pulse measurement. It is a graph which shows the emission spectrum (830-850 nm) at the time of a single pulse measurement. It is a graph which shows the surface salt concentration dependence (495-525 nm) of the emission spectrum in a single pulse. It is a graph which shows the surface salt concentration dependence (830-850 nm) of the emission spectrum in a single pulse. It is a graph which shows the surface salt concentration dependence of the emitted light intensity of Cl at the time of single pulse measurement. It is a graph which shows the surface salt concentration dependence of the emitted light intensity of Mg at the time of a single pulse measurement. It is a graph which shows the surface salt concentration dependence of the emitted light intensity of Cr at the time of single pulse measurement. FIG. 2 is a principle diagram (left diagram) showing a laser irradiation method with a double pulse, and an explanatory diagram (right diagram) showing a temporal relationship between laser light and ICCD. It is a graph which shows the emission spectrum (495-525 nm) at the time of double pulse measurement. It is a graph which shows the emission spectrum (830-850 nm) at the time of double pulse measurement. It is a graph which shows the surface salt concentration dependence (495-525 nm) of the emission spectrum in a double pulse. It is a graph which shows the surface salt concentration dependence (830-850nm) of the emission spectrum in a double pulse. It is a graph which shows the surface salinity concentration dependence of the emitted light intensity of Cl at the time of double pulse measurement. It is a graph which shows the surface salt concentration dependence of the emitted light intensity of Mg at the time of double pulse measurement. It is a graph which shows the surface salt concentration dependence of the emitted light intensity of Cr at the time of double pulse measurement. It is a graph which shows the correlation with the ratio of the light emission intensity of Cl with respect to the light emission intensity of oxygen at the time of double pulse measurement, and surface salinity concentration. A diagram showing the ablation mode. The left figure shows the case of a single pulse, and the right figure shows the case of a double pulse. The graph shows the concentration dependence of the number of particles ejected by the laser and the emission intensity, the upper figure shows the relationship between the total amount of particles ejected by the laser and the surface salinity, and the lower figure shows the emission intensity and the surface salinity concentration. The relationship is shown. The conceptual diagram which shows other embodiment at the time of applying the measuring system which implements the density | concentration measuring method of the metal surface adhesion component of this invention to the aspect which measures the density | concentration of the salt which adheres to the surface of the metal canister in a concrete cask. It is. It is a conceptual diagram which shows a traveling means. It is a conceptual diagram for demonstrating transmission of the laser beam and light emission by a collinear irradiation system. It is a conceptual diagram which shows the front-end | tip of a bundle fiber. It is a conceptual diagram for demonstrating transmission of the laser beam and light emission by a vertical-horizontal irradiation system. It is a conceptual diagram which shows the front-end | tip of the optical fiber which transmits a 2nd laser beam.

  Hereinafter, the configuration of the present invention will be described in detail based on embodiments shown in the drawings.

  The method for measuring the concentration of a component adhering to a metal surface according to the present invention measures the concentration of a trace component adhering to the metal surface, such as salt, and irradiates the metal surface to be inspected with a pulsed laser beam. Then, the adhering substance is ablated, and then light emission from the substance converted into plasma by ablation is measured and analyzed to identify a trace component adhering to the metal surface and obtain its concentration.

  The concept of the concentration measuring method and apparatus for the metal surface adhesion component of the present invention will be described with reference to the experimental apparatus shown in FIG. FIG. 4 is a conceptual diagram of a double-pulse measurement system that implements a method for measuring the concentration of a metal surface adhesion component. This adhering substance measuring system includes a first laser (ablation laser) 1 for ablating an adhering substance by irradiating the surface of a metal 6 to be inspected with a laser beam 11, and a substance ablated with the first laser light 11. A second laser 2 that irradiates the atmosphere (ablation plume) 19 with the second laser light 12 to promote plasma formation; a spectroscope 4 that decomposes light emission 13 from the plasma-converted substance for each wavelength; A light receiving element 5 having a gate function for obtaining light emission spectrum by receiving light emission 13 from a plasma substance dispersed through a spectroscope 4 with a controlled time difference, a first laser 1, a second laser 2, and a light receiving element. The electric signals from the controller 3 and the light receiving element 5 that control the time difference between the gate opening start time of 5 and the light receiving element 5 are captured, stored, and necessary. Integrating in response to, and a analysis computer 18 identifies the excited atoms from the frequency of the peak of the emission spectrum, it is obtained so as to measure the adhering substance concentration from the peak height. The spectroscope 4 decomposes the captured light into a spectrum, and further measures a spectral intensity distribution (a distribution of emission intensity having wavelength dependency) using the light receiving element 5.

As the first and second lasers, laser beams 11 and 12 are irradiated on the metal surface to ablate the adhering substance and have a peak power sufficient to make it plasma, for example, Nd: YAG laser, fiber laser, titanium sapphire A kind of pulsed laser such as laser, glass laser, CO ₂ laser, excimer laser or the like is used. That is, if it is a pulse laser, a nanosecond laser or an ultrashort pulse laser can be used. Then, the controller 3 sets the delay time of the Q switch of the second laser 2 with respect to the trigger signal of the first laser 1, so that the second laser beam 12 differs from the first laser beam 11 by a predetermined time difference. It is generated with (delay time). Further, the first laser 1 and the second laser 2 may be the same type of laser or different lasers.

Here, it is desirable that the conditions as a laser (ablation laser) for ablating the adhered substance on the metal surface satisfy at least one of the following two irradiation conditions.
1. Pulse width 1-20 nanoseconds and fluence 4-12 J / cm ²
2. The pulse width is 1 picosecond or less and the energy fluence is 1 J / cm ² or less. Since the pulse width differs between the ultrashort pulse and the nanosecond pulse, the energy fluence condition changes. Accordingly, in terms of the unit of peak power (W / cm ² ), in the case of an ultrashort pulse (pulse width of 1 psec or less), 10 ¹² W / cm ² or less, in the case of a nanosecond pulse (pulse width of 10 nsec), 6 × 10 ^{8 to} 2 × 10 ⁹ W / cm ² or less.
The first condition is a condition when the laser intensity is low, and the laser output and the irradiation time for laser ablation are preferably irradiated in a pulsed manner with a relatively low energy fluence (W / cm ² ). Specifically, according to the experiments of the present inventors, as a result of measurement in the range of 4~12J / cm ^2, it can be measured in the same range, that capable in 12 J / cm ² sufficient measurement It was confirmed that it was not possible to measure at 0.4 J / cm ² . Although the upper limit of the fluence has not been confirmed by experiments, it is presumed that at 100 J / cm ² , the metal surface to be inspected is not affected and the measurement is not hindered. Therefore, it is possible in the range of fluence 4 to 100 J / cm ² . The first pulse width condition is within the specification range of a general nanosecond laser (Nd: YAG, excimer laser, etc.). In other words, it was found that measurement can be performed by irradiating within the above fluence range using a nanosecond laser.
The second condition is a condition when an ultrashort pulse laser is used, and is 1 J / cm ² or less, more preferably sufficiently smaller than 1 J / cm ² . The energy fluence in the case of using this ultrashort pulse satisfies the condition (peening condition) in which the tensile residual stress decreases, and the tensile residual stress does not increase by laser irradiation. That is, the present inventors have found that the irradiation of laser light under peening conditions can ablate the attached trace components without inducing stress corrosion cracking in the metal material.
The above laser conditions are almost the same with respect to the analysis of attached trace components. In addition, the canister temperature (up to about 100 ° C) has almost no effect on accuracy.

  The first laser 1 and the second laser 2 ablate the surface (ablation plume) 19 of the material ablated with the second laser light 12 after the surface of the sample 6 is ablated with the first laser light 11. Arranged for reheating or re-excitation. For example, in the case of the present embodiment, the first laser beam 11 is irradiated so as to be orthogonal to the surface of the sample 6, and the second laser beam 12 is irradiated parallel to the surface of the sample 6 so as to pass through the ablation plume. Is provided. Since the second laser light turns air instead of the material into plasma, even if the peak power of the laser light is increased, the damage to the material is not increased, and the first laser is used to suppress the damage to the material. Even if light is ablated at a lower power, plasma is generated.

  Here, the laser light irradiation time difference between the first laser light 11 and the second laser light 12 is that after the ablation by the first laser 1, white light noise is reduced and the excited atoms are in the ablation plume 19. Is a time during which the remaining state is secured, and is preferably given in the range of 0.5 μs to 5 μs, for example. In addition, when ablating a trace amount component adhering to a metal surface, white noise is weak because the peak power of the laser is small, but even in this case, if the light receiving element 5 has a fast gate start time, the white light noise is increased to the emission line intensity. Since it is stronger than that, it cannot be measured, and if it is slow, the intensity of the bright line is attenuated and sensitivity is not obtained. Therefore, in this case, the time difference between the start of opening the gate of the light receiving element and the irradiation of the laser beam immediately before it is preferably adjusted to a range of 1 μs to 10 μs as in the case of the double pulse.

  In the experimental apparatus, ablation by laser light irradiation and light emission from the ablation plume 19 are measured by an optical system using an optical lens or a mirror, but in some cases, the light is directly guided by an optical fiber. By doing so, it may be irradiated or taken into the spectroscope 4. An optical fiber usually does not pass light in the ultraviolet region (with a wavelength of 200 nm or less), so it is effective when measuring light emission in the vacuum ultraviolet region or the like. Of course, it is also preferable to improve the measurement sensitivity by increasing the intensity of the separated light by condensing on the optical fiber using a lens. Alternatively, a bundle fiber may be used as the optical fiber, and the coupling efficiency between the optical fiber and the spectroscope may be improved by matching the output shape of the optical fiber to a line shape and the slit shape of the spectroscope. It is also possible to set the condensing of the laser light and the condensing of the emitted light coaxially. Thereby, the system can be simplified.

  As the spectroscope 4, in this embodiment, a spectroscope that converts wavelength information into spatial information using a diffraction grating is used. However, the present invention is not limited to this, and a bandpass filter, for example, can also be used. When the number of substances to be measured is limited to one or a few, prepare a bandpass filter that matches the emission line and the nearby background wavelength, and measure the light intensity after passing through each bandpass filter. Thus, it is possible to measure the intensity of light emission with respect to the background, that is, the intensity of the emission line of the measurement target substance. In this case, measurement reliability can be improved by using a bandpass filter having two or more wavelengths as the background-measurement bandpass filter. As described above, it is possible to remarkably simplify the apparatus configuration and to significantly reduce the manufacturing cost by performing spectroscopy using the bandpass filter.

  As the light receiving system, it is preferable to use the spectroscope 4 and the ICCD camera 5, or the spectroscope 4 and a photomultiplier tube (not shown). In this embodiment, an ICCD camera is used as the light receiving element 5 having a gate function. The ICCD camera can acquire the intensity distribution (spectrum) for each wavelength converted into spatial information by a spectroscope having a diffraction grating at a time, and can simultaneously acquire the emission spectra of many substances. Many substances can be measured at once. In addition, since the gate can be applied with high time resolution, it is possible to reduce background noise due to plasma bremsstrahlung by adjusting the delay time until the gate opening starts and the gate opening time as described above. is there. Further, since the signal intensity can be enhanced by the image intensifier, the S / N ratio of the measurement can be improved. However, the light receiving element 5 need not be limited to an ICCD camera, and for example, a normal light receiving element such as a normal CCD camera or a linear photodiode may be used. In this case as well, a large number of substances can be measured at once by using the spectroscope having a diffraction grating at the same time. As the light receiving element, a single light receiving element such as a photomultiplier tube or a photodiode can be used. In this case, since it is not possible to obtain an intensity distribution (spectrum) for each wavelength at the same time, a large number of substances cannot be measured at the same time, but only a single or a small number of substances need to be measured, or many The measurement of these substances is also applicable when it is not necessary to measure each substance simultaneously. For example, when only a single substance or a small number of substances need to be measured, it can be used together with a bandpass filter as described above, and the emission wavelength of the substance to be measured and the background wavelength in the vicinity thereof can be measured at one or several points simultaneously. Good. As a result, the apparatus can be remarkably simplified and the manufacturing cost can be reduced. In addition, when it is not necessary to measure each substance simultaneously even when measuring a large number of substances, the intensity distribution (spectrum) for each wavelength can be measured while rotating the diffraction grating using, for example, a spectroscope having a diffraction grating. That's fine. This is effective when measuring phenomena with little variation with respect to time.

  In the case of the present embodiment, the ICCD camera 5 is connected to a computer 18 equipped with various analysis programs for analyzing the spectral intensity distribution, and the information of the emission intensity for each frequency captured by the ICCD camera 5 is input. This data is stored, integrated, analyzed, and displayed on the display as an emission spectrum, or the presence or absence of salt on the metal surface, and further, the concentration of salt, etc. are measured from information on the emission intensity for each frequency. The computer 18 includes a storage device (not shown), and stores in advance a spectral intensity distribution of plasma emission generated when a laser component is irradiated with a trace component having a known concentration on a metal surface. It is preferable to provide a calibration curve so as to detect a change in the concentration of the target substance or atoms by comparing the emission intensity with reference data or referring to the calibration curve. If it is not necessary to store the emission spectrum and integrate or analyze it as necessary, the personal computer 18 is not required and the emission spectrum is simply displayed on the monitor display attached to the ICCD camera 5 for monitoring. You may do it.

  According to the method and apparatus for measuring the concentration of adhering substances on the metal surface of the present invention configured as described above, the concentration of trace components adhering to the metal surface can be measured as follows.

  First, the metal surface is irradiated with a laser beam to ablate the adhering component, and the emitted light is observed. Here, the first laser beam 11 is condensed on the metal surface 6a by the lens 7 to generate ablation plasma, and the second laser beam 12 is a plasma plume 19 generated by the first laser beam irradiation. It is condensed by the lens 8 inside. The emitted light passes through the optical fiber 17, is dispersed by the spectroscope 4 having a diffraction grating, and is received by the ICCD camera 5. The ICCD camera 5 can acquire the intensity distribution (spectrum) for each wavelength converted into spatial information by the spectroscope 4 having a diffraction grating at a time, and can simultaneously acquire emission spectra of a large number of substances. Yes, it is possible to measure many substances at once.

  Here, the 837.59 nm chlorine emission line, the 517.26 nm magnesium emission line, the 518.36 nm magnesium emission line, and the 833.31 nm chlorine emission line indicate the presence of salinity. Since there is a proportional relationship between the emission intensity of these emission lines and the salinity concentration, the presence of the salinity and its concentration are required.

  FIG. 1 shows a case where the method and apparatus for measuring the concentration of adhering substances on a metal surface according to the present invention is applied to an embodiment for measuring the concentration of salt adhering to the surface (outer surface) of a metal canister in a concrete cask. The conceptual diagram of the measurement system which implements the canister adhesion salt concentration measuring method is shown. This adhering substance measuring system has a peak sufficient to ablate the adhering substance and turn it into plasma by irradiating the surface of the metal 6 to be inspected (in this embodiment, a metal canister, hereinafter simply referred to as a canister) with laser light. Power laser 1, a spectroscope that measures light emission from a plasma substance and decomposes it for each wavelength, and a gate function that receives light from a plasma substance that has been dispersed through the spectroscope and obtains an emission spectrum Including an analysis device 21 including a light receiving element having a laser and a controller for controlling a time difference between the laser and the gate opening start time of the light receiving element, an optical system for laser light transmission, and an optical system for light emission measurement. Between the cask 26 and the metal canister 6 accommodated therein, that is, the inner peripheral surface of the concrete cask 26 and the metal key. Thin space between the outer surface of Nisuta 6 is configured optical transmission unit that is inserted in the (narrow portion) 27 along the surface of the canister 6 and (scope) 33.

  Therefore, when the salinity concentration adhering to the surface of the metal canister 6 accommodated in the concrete cask 26 is measured, the laser 1 and the analyzer 21 including the spectroscope are arranged outside the concrete cask 26. Then, the surface of the metal canister 6 is irradiated with a laser beam through the optical transmission unit 33 inserted into the concrete cask 26 to ablate the salt content and turn into plasma, and the light emission is narrowed through the optical transmission unit 33. 27 is guided to the analyzing device 21 outside 27 through the optical fiber 22 and dispersed, and an emission spectrum is obtained by the light receiving element, whereby a trace component adhering to the surface of the metal canister 6 is specified and its concentration is obtained.

  Here, the analysis device 21 including the spectroscope is installed at a position away from the concrete cask 26 and performs analysis. As described above, if the measurement is performed with a stand-off system capable of measuring away from the concrete cask 26 except for the optical transmission unit 33, it is possible to reduce the time for the inspector to approach the concrete cask 26 at the time of inspection. . Further, the optical transmission unit 33 composed of the hollow tube 23 is provided so as to be movable up and down along the surface of the metal canister 6 by a scope drive system 25 placed on the lid of the concrete cask 26. The optical transmission unit 33 is provided to rotate around the metal canister 6 together with the scope drive system 25 by rotating the lid of the concrete cask 26 that is configured to be rotatable. Therefore, the salt attached to the entire outer peripheral surface of the metal canister 6 can be removed and measured as needed by rotating the lid of the concrete cask 26 and raising and lowering the optical transmission unit 33 by the scope drive system 25. . However, in practice, since the entire circumference inspection is troublesome, it is preferable to inspect only the welded portion where SCC is most likely to occur.

  As shown in FIG. 2 or FIG. 3, the optical transmission unit 33 has a hollow tube 23 with a built-in optical system for laser light transmission and an optical system for light emission measurement. A seal member 28 that is in close contact with the metal surface is provided at the tip opening of the irradiation unit 24 that faces the surface of the canister 6. The seal member 28 and the surface of the metal canister 6 (metal surface) are in close contact during laser irradiation. By doing so, the inside of the hollow tube can be depressurized while fixing the irradiation point. As the seal member 28, for example, O-ring rubber or the like is used.

  Here, the optical system for laser light transmission and the optical system for light emission measurement, for example, as shown in FIG. 2, reflect only the wavelength of the condensing lens 7 and the laser light 11 and reflect the laser light 11 to the metal surface. 6 is disposed behind the wavelength selective mirror 29 to select the wavelength of the plasma emission generated by the ablation of the trace component adhering to the metal surface 6. An optical system for light emission measurement including a reflection mirror 30 that does not depend on the wavelength for reflecting the plasma emission that has passed through the mold mirror 29 is provided inside the hollow tube 23, and the inside of the hollow tube 23 emits laser light and plasma. May be propagated.

  Further, the optical system for laser light transmission and the optical system for light emission measurement may be constituted by optical fibers as shown in FIG. 3, for example. In this case, the tip surfaces of the laser light transmitting optical fiber 31 and the light emission measuring optical fiber 32 face the metal surface along the L-shaped bent shape of the tip of the hollow tube 23 of the light transmitting portion 33. So that it is bent.

  Although not shown, the optical transmission unit 33 is configured by only the exposed optical fiber 31 for laser light transmission and the optical fiber 32 for light emission measurement without using the hollow tube 23. May be. In this case, the optical fibers 31 and 32 are wound around a take-up drum or the like disposed outside the concrete cask 26 and suspended in a narrow space 27 between the metal canister and the concrete cask 26. The cable is lowered and moved up and down with the end of the cable bent so as to face the metal surface.

  In the case of the optical transmission unit 33 illustrated in FIGS. 1 to 3, there is a case where it is difficult to adopt a configuration in which the second laser light is irradiated in parallel with the metal surface. Depending on the case, a double pulse system using the same optical system or optical fiber may be used. For example, by shifting the focal position between the two laser beams 11 and 12 arranged coaxially, or by changing the size of the irradiation surface by causing the second laser beam 12 to cross obliquely with respect to the metal surface. The same effect can also be obtained by adjusting the energy of the laser beam and the area of the irradiated surface so that the peak power is lower than the upper limit value. Further, the same effect can be obtained by lowering the laser energy of the second laser beam. Specifically, when the material is ablated for additional heat for the second time, damage to the metal surface is also caused by the same strength in the first and second times, or by the distribution of peak power that the second time is weaker than the first time. The plasma can be generated without incurring and the measurement sensitivity can be increased. Further, the sealing member 28 at the distal end opening of the hollow tube 23 is brought into close contact with the surface of the canister 6 and the inside of the hollow tube 23 is evacuated by connecting the base end side to a vacuum pump or the like, thereby converting the air into plasma. Therefore, only the plasma from the attached trace component is generated, and the measurement accuracy can be improved.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, in the present embodiment, the description has mainly been given of the double pulse that irradiates the first laser 1 and the second laser 2 with a time difference. However, the present invention is not particularly limited to this, and is applied to the metal surface to be inspected. A pulse of laser light is irradiated to ablate the adhering substance, light emission from the substance made plasma by ablation is imaged with a light receiving element to obtain an emission spectrum, and the adhering substance concentration is measured from the emission spectrum. Also good.

  Further, in the case of the double pulse, the two laser beams 11 and 12 need not be limited to those arranged to irradiate so as to be orthogonal to each other, and although not shown, for example, two laser beams arranged coaxially By changing the size of the irradiated surface by shifting the focal position between 11 and 12, or by obliquely crossing the second laser beam 12 with respect to the metal surface, the laser can be reduced to the peak power upper limit value or less. The same effect can be obtained by adjusting the energy of light and the area of the irradiated surface. In addition, there is an advantage that the configuration of the apparatus is simple when arranged coaxially. Further, the same effect can be obtained by lowering the laser energy (J) of the second laser beam. Specifically, when the material is ablated for additional heat for the second time, damage to the metal surface is also caused by the same strength in the first and second times, or by the distribution of peak power that the second time is weaker than the first time. The plasma can be generated without incurring and the measurement sensitivity can be increased.

  Further, it is provided between the outer surface of the metal canister 6 and the inner peripheral surface of the concrete cask 26, and supports the irradiation unit 24 of the optical system for laser light transmission, and is provided outside the irradiation unit 24 and the metal canister 6. A traveling means 36 that maintains a constant distance from the surface may be provided. Examples of this case are shown in FIGS. In addition, the same code | symbol is attached | subjected to the same structural member as the structural member described in FIGS. 1-4, and those description is abbreviate | omitted.

  In the present embodiment, the irradiation unit 24 of the optical transmission unit 33 is configured by inserting the tip of the optical fiber 31 of the optical system for laser light transmission into the heat-resistant case 37 and accommodating optical components such as lenses and mirrors. doing.

  The heat-resistant case 37 has a sealed structure in order to reduce damage of the optical device due to high radiation and high temperature as much as possible, and includes a structure in which a high atomic number material such as iron and a low atomic number material such as acrylic are combined. If further cooling is required, a fan may be installed inside the heat-resistant case 37 for air cooling, or cooling water may be filled to perform circulating water cooling. When the cooling water is used, the cooling water decelerates the fast neutron beam to the thermal neutron, so that damage to the optical device due to the neutron beam is reduced. Further, the heat-resistant case 37 is provided with a quartz window 37a for laser irradiation and light emission measurement.

  An apparatus insertion fixing base 38 having a through hole for inserting the irradiation unit 24 is installed on the upper part of the cask lid 26a. A device 39 for raising and lowering the irradiation unit 24 to be inserted is installed on the device insertion fixing base 38. Examples of the lifting device 39 include a take-up crane using a wire rope and a driving device using a guide rail. However, it is not restricted to these. In the present embodiment, a take-up crane using a wire rope 41 is employed as the lifting device 39. The wire rope 41 is connected to the upper part of the heat-resistant case 37. When such a method of suspending the irradiation unit 24 is used, it is possible to reduce the size and weight of the suspended device, and even if the narrow portion 27 is moved for a long stroke, the fluctuation of the irradiation unit 24 can be suppressed. .

  Further, a distance meter 40 such as a laser range finder is installed on the fixed base 38 in order to grasp the position (height) of the irradiation unit 24. As a result, the irradiation unit 24 can be accurately driven in the vertical direction. However, instead of providing the distance meter 40, for example, the position of the irradiation unit 24 may be grasped on the basis of the feed amount of the wire rope 41.

  Under the heat-resistant case 37, traveling means 36 that suppresses the fluctuation of the heat-resistant case 37 and maintains the distance from the metal canister 6 at a predetermined distance is attached. The traveling means 36 of this embodiment includes wheels 42 and a carriage 43. The carriage 43 is attached to the bottom surface of the heat-resistant case 37, and has wheels 42 that roll on the surface 6 a (mating side) of the metal canister 6 and wheels 42 that roll on the inner peripheral surface 26 b (mating side) of the concrete cask 26. It is attached. Each wheel 42 is pressed against the other side surface by the suspension. The wheel 42 is, for example, a caster, and changes its direction following the movement of the irradiation unit 24. The distance between the wheel 42 on the metal canister 6 side and the wheel 42 on the concrete cask 26 side is matched to the distance between the narrow portions 27 (the distance between the surface 6 a of the metal canister 6 and the inner peripheral surface 26 b of the concrete cask 26). It is adjustable.

  In the present embodiment, the number of the wheels 42 is the metal canister 6 side: two wheels (horizontally arranged), and the concrete cask 26 side: one wheel, and the surface 6a of the metal canister 6 or the concrete cask 26 having a gentle curvature. This configuration is suitable for rolling the inner peripheral surface 26b. However, the number of wheels 42 is not limited to this. For example, the metal canister 6 side: the concrete cask 26 side may be two wheels: two wheels, one wheel: one wheel, one wheel: two wheels. good.

  The vertical movement of the irradiation unit 24 is performed by the lifting device 25, and the horizontal movement (the circumferential direction of the metal canister 6) is performed by rotating the cask lid 26a of the concrete cask 26. That is, by moving the wire rope 41 that suspends the irradiation unit 24 in the vertical direction and the horizontal direction, the irradiation unit 24 is moved to a desired position while the traveling means 36 is traveling. At this time, each wheel 42 of the traveling means 36 is pressed against the metal canister 6 or the concrete cask 26 by the suspension, and so-called a structure that stretches between the metal canister 6 and the concrete cask 26. Shake is suppressed.

  However, means for moving the irradiation unit 24 is not limited to pulling in the vertical and horizontal directions by the wire rope 41. For example, a motor for rotating the wheel 42 and a motor for changing the direction of the wheel 42 are provided in the carriage 43, and the direction and the rotation drive of each wheel 42 are controlled by remote operation by wireless communication or wired communication so that the irradiation unit 24 can be set in a desired manner. You may make it move to a position.

  FIG. 30 shows an example of a laser light and light emission transmission method. A bundle of an optical fiber 31 for laser light transmission and an optical fiber 32 for light emission measurement in order to transmit light between the lasers 1 and 2 installed outside the concrete cask 26 and between the analyzer 21 and the irradiation unit 24. (Bundle fiber 44) is used. In the present embodiment, a plurality of light emission measuring optical fibers 32 are arranged around one laser light transmitting optical fiber 31. The tips of the optical fibers 31 and 32 are inserted into the ferrule 45 and fixed (FIG. 31). The ferrule 45 is fixed to the heat resistant case 37. In the present embodiment, the laser beams 11 and 12 transmitted through the optical fiber 31 for laser beam transmission are collected by the convex lens 46, changed in direction by 90 degrees by the total reflection mirror 47, and then changed from the quartz window 37a to the metal canister. 6 is irradiated perpendicularly to the surface of 6.

  In the present embodiment, a double pulse method is adopted, and as a laser, a first laser (ablation laser) 1 for ablating the adhered substance by irradiating the surface 6a of the metal 6 to be inspected with a laser beam 11, There is provided a second laser 2 that irradiates the atmosphere (ablation plume) 19 of the substance ablated with the first laser light 11 with the second laser light 12 to promote plasma formation. In the present embodiment, the first laser beam 11 and the second laser beam 12 are transmitted through the same optical fiber 31. Therefore, the laser beams 11 and 12 are superimposed using an optical element 48 such as an optical coupler or a polarization beam splitter and incident on the optical fiber 31.

  Plasma emission generated on the surface of the metal canister 6 is collected on the bundle fiber 44 along an optical path opposite to the laser beams 11 and 12 (quartz window 37a → total reflection mirror 47 → convex lens 46 → bundle fiber 44). . The emitted light is transmitted through the optical fiber 32 for light emission measurement and is incident on the spectroscope 4 of the analysis device 21. In this way, by making the optical path of irradiation and light reception the same, the positional deviation between the surface on which the laser is focused and the light receiving surface is eliminated in principle, and the irradiation unit 24 can be downsized by reducing the number of optical components. Become. In addition, although the example which employ | adopted the double pulse system was demonstrated here, of course, you may employ | adopt a single pulse system.

  FIG. 32 shows another example of a laser light and light emission transmission method. The same members as those shown in FIG. 30 are denoted by the same reference numerals. Compared with the example of FIG. 30, there is a difference in the irradiation direction of laser irradiation. The first laser beam 11 irradiated perpendicularly to the surface of the metal canister 6 is turned into plasma by the first laser beam 11 irradiated to the surface of the metal canister 6, and the second laser beam irradiated in parallel to the surface of the metal canister 6. 12 re-excites the plasma. The second laser beam 12 irradiated in parallel is condensed by an off-axis elliptical mirror 49. In FIG. 30, the laser beam for plasma generation (first laser beam) 11 and the laser beam for re-excitation (second laser beam) 12 are transmitted through the same optical fiber 31, but the method of FIG. Then, separate optical fibers 31, 31 are used. Thereby, since the laser beam 12 for re-excitation is not irradiated on the surface of the metal canister 6, it becomes possible to set the laser light intensity high without worrying about damage to the metal canister 6. In addition, it is possible to reduce thermal damage caused by the laser light received per optical fiber.

  In this example, the quartz window 37a of the heat-resistant case 37 is provided obliquely, and the laser light 12 for re-excitation is irradiated from the quartz window 37a to the outside of the heat-resistant case 37 and hits the ablation plume 19 (not shown). ing.

  Also in this example, a bundle fiber 44 is used in which a plurality of optical fibers 32 for light emission measurement are arranged around one laser light transmission optical fiber 31 that transmits the first laser light 11. The second laser beam 12 is transmitted by one laser beam transmission optical fiber 31. The tip of the optical fiber 31 that transmits the second laser light 12 is inserted into the ferrule 50 and fixed toward the off-axis elliptical mirror 49 (FIG. 33).

  By providing the traveling means 36 in the irradiation unit 24, the distance from the surface 6 a of the metal canister 6 can be kept constant even if the irradiation unit 24 is moved, and the shaking of the irradiation unit 24 can be prevented. . Therefore, the distance between the irradiation unit 24 and the surface 6a of the metal canister 6 changes, and the positional relationship between the focal points of the laser beams 11 and 12 and the surface 6a of the metal canister 6 shifts in the vertical direction of the surface 6a. It is possible to prevent the irradiation directions of the laser beams 11 and 12 from being deviated, and it is possible to perform ablation satisfactorily even when measuring at other positions.

  Furthermore, in the present embodiment, the method of obtaining light emission by converting a trace amount component adhering to the metal surface, for example, salt, into plasma has mainly been described by taking laser irradiation, but is not particularly limited to this, for example, electrical It is also possible to use different methods. For example, it is possible to generate plasma by performing gap discharge using a spark plug or needle electrode, and the basic configuration of other devices such as a laser system and a light receiving system can be changed by simply replacing the laser irradiation part with an electrode. Do not need.

Furthermore, in the present embodiment, the case where the concentration of salt adhered to the surface of a metal canister housed in a concrete cask is mainly described, but the present invention is not particularly limited to this and can be widely applied to all metals. Thus, the presence and concentration of all trace components adhering to the metal surface can be determined. In addition, the metal surface is not limited to the one facing a narrow space, and can be applied to one facing an open space. In this embodiment, it is confirmed that there is a sensitivity of about 0.1 g / m ² with respect to the salinity adhering to the metal surface, and quantification of the adhering substance (salt content) concentration by the luminescence intensity of any element. In some cases, for example, an index value (threshold value) for determining the possibility of occurrence of stress corrosion cracking due to the salinity of a metal canister is determined, and whether or not it is exceeded You may make it judge whether.

  An experiment was conducted to confirm the detection sensitivity and concentration measurement of trace adhesion components on the metal surface. An experimental layout of the double pulse system is shown in FIG. The first and second lasers 1 and 2 are two Q-switched Nd: YAG lasers (manufactured by Continuum, Powerlite 8010), the pulse repetition frequency is 10 Hz, the first laser 1 has an energy of 30 mJ, and the second laser 2 Generates laser light with an energy of 100 mJ. The timing of laser irradiation is controlled by one timing controller 3. The emitted light 11 of the first laser 1 is incident on the object (sample) 6 perpendicularly and is focused on the sample 6 by the lens 7 having a focal length of 250 mm, thereby generating an ablation plasma plume 19. The emitted light 12 of the second laser 2 is incident on the sample 6 in parallel and is focused on the plasma plume 19 generated by the first laser 1 using the lens 8 having a focal length of 250 mm. Light emitted from the plasma plume 19 is collimated by a lens 14a having a diameter of 50 mm and a focal length of 150 mm installed at a position 150 mm from the focal point of the first laser 1, and a lens 14b having a focal length of 200 mm and a sharp cut filter 15. Then, the light is condensed on the optical fiber head 16 and transmitted through the optical fiber 17. Thereafter, the light is spectrally separated by a spectroscope (manufactured by Jobin Yvon, HR460) 4 and received by an ICCD camera 5. The ICCD camera 5 can operate the gate delay time and the gate width by a signal synchronized with the laser oscillation. In the figure, reference numerals 9 and 10 are reflection mirrors, and 20 is a moving stage.

(experimental method)
In this experiment, the second harmonic (532 nm) is oscillated from the two Nd: YAG laser devices 1 and 2, and the first laser beam 11 of 30 mJ is applied to the surface of the SUS304L plate (metal plate 6) as shown in FIG. The second laser 12 of 100 mJ was incident in parallel. The first and second laser beams 11 and 12 are both condensed by the convex lenses 7 and 8 for ablation, and the first laser beam 11 is used to evaporate (ablate) the salt on the surface of the SUS304L plate. The second laser beam 12 was used to additionally heat the ablated salt. In order to measure the light emission 13 of the plasma 19 generated by ablation, a light receiving system composed of plano-convex lenses 14a and 14b and a sharp cut filter 15 blocking the low wavelength side is constructed, and an ICCD is connected via the optical fiber 17 and the spectroscope 4. Light was received by the camera 5. The diameter of the condensed first laser beam 11 is about 0.5 mm, and since there is a variation in the salinity concentration depending on the irradiation position, a plurality of places are irradiated, and the integrated average of the emission intensity for each irradiation is obtained to obtain the concentration. Compared with. For this purpose, the metal plate 6 was moved during irradiation using the moving stage 20, and light emission was measured while changing the position for each irradiation. This time, the average of 20 shots of light emission intensity was averaged by the personal computer 18 in one measurement.

  In this experiment, SUS304L in which artificial seawater (see Table 1 for ingredients) was sprayed uniformly in a mist was used. FIG. 5 shows the entire photograph of SUS304L sprayed and the state of the laser irradiation spot. Since SUS304L is irradiated with a laser while moving, a horizontal row of irradiation marks as shown corresponds to one measurement.

As described below, a method using only the laser 1 (single pulse) and a method using the lasers 1 and 2 simultaneously (double pulse) were performed as described later.

(Experimental result)
6 and 7 show the state after laser irradiation. Salinity is removed around the periphery of the laser beam.

  In general, it is known that plasma generated by ablation emits white light over the entire visible light range. Therefore, the measured emission spectrum is the sum of light emitted by exciting each element and white light. Further, since the white light intensity varies from measurement to measurement, it is necessary to consider the background for each shot. Therefore, a baseline that was linearly approximated based on the back line near the spectrum peak was determined, and the emission intensity attributable to each element was evaluated as shown in FIG. Further, when obtaining the intensity from the emission spectrum, the spectrum was subjected to a simple moving average (11 points, corresponding to about 0.3 nm) for smoothing.

(Single pulse measurement result)
In the single pulse measurement, as shown in FIG. 9, the light emission was measured by opening the shutter of the ICCD camera for 500 nsec after 1.7 msec from the laser 1 irradiation.

  An emission spectrum in a wavelength range of 495 nm to 525 nm is shown in FIG. The emission line of chromium (Cr) (495.48 nm, 520.60 nm) was measured from the emission spectrum obtained when SUS304L with no salt content was irradiated with laser. This is considered to be because Cr was excited by ablation of SUS304L. In the case where salt was attached, the emission line of magnesium (Mg) (517.19 nm, 518.36 nm) was further measured. The reason why the emission lines of other elements were not confirmed is considered to be that only the light emission of the background level was obtained because the concentration was low. In the wavelength range of 830 nm to 850 nm, an oxygen (O) emission line (844.60 nm) was measured. It is considered that the O emission line is observed because O in the air was excited by the plasma generated by ablation. In the case where salt adhered, chlorine (Cl) emission lines (833.31 nm, 837.59 nm) were measured. From the results of the single pulse, it was found that emission spectra from SUS304L, adhering salt and air were obtained as shown in Table 2.

  Next, emission spectra obtained by irradiating laser to SUS304L having different concentrations are shown in FIGS. In general, the higher the concentration, the higher the emission intensity. However, in the wavelength range of 830 nm to 850 nm, the higher the concentration, the lower the emission intensity.

14, 15, and 16 show the concentration dependency of the emission intensity of Cl, Mg, and Cr. Error bars in the figure represent the standard deviation of five measurements. Although light emission due to the absence of a concentration 0.0 g / m ² in Cl and Mg is the background level, the higher is significantly emission intensity from ^{0.1 g / m 2, 0.1 g} / m 2 approximately It can be evaluated that there is sensitivity. And the higher the concentration, the lower the emission intensity and the tendency to saturate at 0.8 g / m ² or more. The reason why the emission intensity of Mg is about 100 times higher than that of Cl is because the energy level of excited Cl is high. The reason why the concentration dependence of the emission intensity of Cl and Mg is slightly different is considered to be because the number of excited atoms of each element changes depending on the plasma density and temperature. With respect to Cl and Mg, the emission intensity of Cr tends to decrease with respect to the concentration except for 0.1 g / m ² .

(Double pulse measurement result)
Based on the results of the single pulse, double pulse measurement was performed that would allow measurement without reducing the ablation efficiency and reducing damage to SUS304L. In this method, a laser beam different from the laser beam for ablation is used to ionize air before SUS304L to generate plasma (hereinafter, air plasma). Since the ablated element is excited by air plasma, it can be expected that the emission intensity is increased.
In the double pulse, the laser 2 was irradiated 2.0 msec after the laser 1 was irradiated as shown in FIG. 17, and the light emission was measured by opening the shutter of the ICCD camera for 500 nsec after another 1.7 msec.

The emission spectrum at the time of double pulse measurement is shown in FIG. 19 and FIG. A spectrum similar to that of single pulse measurement is obtained, but the emission intensity is higher than that of single pulse measurement. Further, since air plasma is generated, the emission intensity of O is relatively higher than other emission lines.
20 and 21 show the concentration dependence of the emission spectrum. As shown in FIG. 21, as the concentration increases, the emission intensity of O decreases while the emission intensity of Cl, Mg, and Cr increases.

FIG. 22 shows the concentration dependence of the emission intensity of Cl. Unlike single pulse measurement, the emission intensity is proportional to the concentration. This is the same for the emission intensity of Mg as shown in FIG. Since the emission intensity at a concentration of 0.1 g / m ² is about three times higher than that at a concentration of 0.0 g / m ^2, it can be said that this measurement method has a sensitivity of a concentration of about 0.1 g / m ^2. . The concentration dependency of the emission intensity of Cl and Mg tends to be slightly saturated at a concentration of 0.8 g / m ² or more. On the other hand, the light emission intensity of Cr is constant except for 0.0 and 1.0 g / m ² as shown in FIG. In addition, as shown in FIG. 25, the ratio of the emission intensity of the emission line indicating the trace component to be measured, for example, the emission line (833.31 nm) indicating chlorine in the case of salinity, to the emission intensity of the emission line of oxygen. When the correlation with the trace component concentration was obtained, the linearity of the graph was improved. Therefore, the inventors have obtained the knowledge that the concentration of adhering trace components can be quantified from the ratio of the emission intensity of the adhering trace component to the emission intensity of the oxygen emission line at the time of measurement. From this, since the correlation between the element selected as the measurement index of the attached trace component and the attached concentration of the attached trace component can be obtained with higher accuracy, the concentration can be quantified with higher accuracy.

Next, the ablation aspect suggested from the results of the single pulse and double pulse measurement results and the concentration dependence of the emission intensity related to the quantitative measurement are examined.
In the present invention in which the adhered substance on the metal surface is ablated by irradiation with a pulse laser, it is possible to measure the concentration by completely plasmaizing or exciting the measurement target. However, in the case of this experiment, in order to reduce damage to SUS304L, it is necessary to reduce the laser beam intensity. As a result, when the concentration is high, the ablation efficiency is lowered due to the low intensity of the laser beam, and the results suggest that there is no proportional relationship between the emission intensity and the concentration. On the other hand, the double pulse results show a proportional relationship between the emission intensity and the concentration. From this, it is considered that the reason why the emission intensity and the concentration were not proportional in the single pulse measurement was that all particles were not excited by the laser. Since the laser light intensity is low under the conditions of this experiment, it is considered that some of the particles ejected by the laser do not become plasma as shown in FIG. Since such particles increase as the concentration increases, the emission intensity decreases relatively as shown in FIG. On the other hand, if it is assumed that all particles ablated with air plasma are excited, in the case of a double pulse, all these particles are also excited, and it is considered that the emission intensity is proportional to the concentration. From this, it can be said that the double pulse is appropriate for measuring the concentration without reducing the damage to SUS304L.

On the other hand, single pulse measurement has the simplest measurement system and can be evaluated as having a sensitivity of a concentration of about 0.1 g / m ² . However, since a proportional relationship between the emission intensity and the salinity concentration is not observed, it is difficult to perform quantitative measurement. Similarly, in the double pulse measurement, the emission intensity tends to be slightly saturated rather than linear with respect to the concentration. In order to perform quantitative measurement with high accuracy, as shown in the graph of FIG. 25, the correlation between the ratio of the emission intensity of the emission line indicating the attached trace component to be measured to the emission intensity of the emission line of oxygen and the concentration of the attached trace component It is preferable to obtain a linear relationship between the emission intensity and the concentration by obtaining the relationship. In addition, the inside of the light transmission part including the laser irradiation surface of the metal surface, the optical system for laser light transmission, and the optical system for light emission measurement is evacuated at least during the laser irradiation, thereby suppressing the formation of air plasma and the trace components attached The measurement accuracy can be improved by generating only the plasma.

  On the other hand, even if the salinity concentration is the same, the emission intensity corresponding to the concentration may vary depending on the air atmosphere (temperature and composition). In addition, since the amount of ablation varies depending on the temperature of SUS, it is expected that a difference in sensitivity will be seen compared to measurement at room temperature. In that case, it is necessary to correct the sensitivity by installing a sample with a known concentration in the cask, or to clarify the dependence of various characteristics of the emission intensity in advance.

As a result of the non-contact measurement of the surface salinity concentration according to the present invention in which the adhered substance on the metal surface is ablated by pulse laser irradiation, the surface salinity concentration is 0.1 g / m ^{2 in} both the single pulse and double pulse measurement methods. It was confirmed that there was a measurement sensitivity to a certain degree of chlorine. In addition, as a result of performing an experiment with the laser beam intensity lowered to reduce damage to SUS304L, the single pulse measurement did not show a proportional relationship between the emission intensity and the concentration, but the concentration was 0.1 g / m ^2. It was found that there was a degree of sensitivity. On the other hand, in the double pulse measurement, both are in a proportional relationship, and it has been found that the concentration can be quantitatively measured by taking sensitivity correction into consideration.

DESCRIPTION OF SYMBOLS 1 1st laser 2 2nd laser 3 Controller which gives time difference 4 Spectrometer 5 Light-receiving element (ICCD camera) which has a gate function
6 Metal surface to which a trace component to be inspected is attached 11 First laser beam 12 Second laser beam 13 Light emission 17 Optical fiber 18 Personal computer 19 Ablation plume 21 Analyzing device 22 Optical fiber 23 Hollow tube 24 Irradiation unit 25 Scoring unit drive System 26 Concrete cask 27 Narrow part 28 Rubber 29 Reflecting mirror (depends only on the wavelength of the laser beam)
30 Total reflection mirror (independent of wavelength)
31 Optical fiber for laser light transmission 32 Optical fiber for light emission measurement 36 Traveling means

Claims (21)

  In a method for measuring the concentration of a trace component adhering to a metal surface facing a narrow space, at least the laser, the spectroscopic means, the light receiving element, and the laser and the light receiving element are controlled outside the narrow space. A concentration measuring device main body having a controller is arranged, and the metal surface is irradiated with laser light via an optical transmission unit inserted along the metal surface in the narrow space, and the adhered substance is ablated and converted into plasma, Light emitted from the plasma substance is guided to the spectral means outside the narrow space through the light transmission unit and dispersed, and an emission spectrum is obtained by a light receiving element, so that a minute amount attached to the metal surface. A method for measuring the concentration of a component adhering to a metal surface that determines the concentration of the trace component while specifying the component. The metal surface is an outer surface of a metal canister that houses spent fuel, and the narrow space is formed between an inner peripheral surface of a concrete cask that houses the metal canister. The method for measuring the concentration of a metal surface adhesion component according to claim 1 . A traveling means for supporting a laser beam irradiating portion for irradiating the outer surface of the metal canister is provided between the outer surface of the metal canister and the inner peripheral surface of the concrete cask, and the irradiating portion and the metal canister. The method for measuring the concentration of a component adhering to a metal surface according to claim 2 , wherein the distance from the outer surface of the metal is kept constant. The method for measuring the concentration of a metal surface adhering component according to any one of claims 1 to 3 , wherein the trace component is a salt content. The salt detection uses any one of 837.59 nm chlorine emission line, 517.26 nm magnesium emission line, 518.36 nm magnesium emission line, and 833.31 nm chlorine emission line. 4. A method for measuring the concentration of a component adhering to a metal surface according to 4 . The concentration measuring method of the metal surface adhesion component according to claim 1, any one of the 5, characterized in that irradiation of the pulsed laser beam is performed multiple times. Irradiation of the pulsed laser beam includes a first step of ablating a trace component adhering to the metal surface and adhering to the metal surface, and the metal surface toward the plasma formed by the ablation. 7. A method for measuring a concentration of a metal surface adhering component according to claim 6 , comprising: a second step of exciting particles that are irradiated in parallel with each other and that are not excited in the first step. The laser beam irradiated in the first step is weaker than the laser beam irradiated in the second step, and is sufficient to eject at least the attached trace component to be measured from the metal surface. The concentration of the metal surface adhesion component according to claim 7 , wherein the laser light irradiated in the step is sufficient to excite and emit light of the attached trace component ejected in the first step. Measurement method. Obtain the correlation between the ratio of the emission intensity of the emission line indicating the attached trace component to be measured to the emission intensity of the emission line of oxygen and the concentration of the attached trace component, and determine the oxygen intensity of the attached trace component at the time of measurement. 9. The method for measuring a concentration of a component adhering to a metal surface according to any one of claims 1 to 8 , wherein the concentration of the adhering trace component is obtained from a ratio of the emission line to the emission intensity. Of light emitted from the plasma substance measured to a metal surface adhesion component according to any one of claims 1-9 it is intended to provide a time difference 1μs~10μs between irradiation of the immediately preceding laser beam Concentration measurement method. According to any one of claims 7 10 is intended to provide a time difference 0.5μs~5μs between the laser light provided by the first laser light and the second step of irradiating at step Concentration measurement method for metal surface adhesion components.   An apparatus for measuring the concentration of a trace component adhering to a metal surface facing a narrow space, comprising at least a laser, a spectroscopic means, a light receiving element, and a controller for controlling the laser and the light receiving element. A concentration measuring device main body arranged outside, an optical transmission system that includes a laser light transmission optical system and a light emission measurement optical system, and is inserted along the metal surface into the narrow space, The metal surface is irradiated with laser light through the light transmission unit to ablate the adhering substance and turn into plasma, and light emitted from the plasmaized substance is emitted outside the narrow space through the light transmission unit. By guiding the spectroscopic means to perform spectroscopic analysis and obtaining an emission spectrum by the light receiving element, the trace component adhering to the metal surface is identified and the concentration of the trace component Device for measuring the concentration of a metal surface adhering component to be obtained. The metal surface is an outer surface of a metal canister that houses spent fuel, and the narrow space is formed between an inner peripheral surface of a concrete cask that houses the metal canister. The concentration measuring device for a metal surface adhering component according to claim 12 . Provided between the outer surface of the metal canister and the inner peripheral surface of the concrete cask, and supports the irradiation part of the optical system for laser light transmission, and the irradiation part and the outer surface of the metal canister The metal surface adhesion component concentration measuring apparatus according to claim 13, further comprising traveling means for maintaining a constant distance between the metal surface adhesion component and the metal surface adhesion component. The laser irradiates the surface of the metal to be inspected with laser light to ablate the adhered substance, and the second laser irradiates the material ablated with the first laser light to form plasma. It consists of a laser, the controller first laser, a metal according to any one of claims 12 to 14 is to control the time difference between the gate opening start time of the second laser and the light receiving element Concentration measuring device for surface adhesion components. The light transmission portion is a hollow tube, and includes a sealing member that has a built-in optical system for laser light transmission and an optical system for light emission measurement, and is in close contact with the metal surface at a tip opening facing the metal surface. are, at the time of laser irradiation, wherein said sealing member and said by the metal surface are in close contact, any one of claims 12 to 14 is a hollow tube at the same time fixing the irradiation point that allows vacuum Concentration measuring device for metal surface adhesion components. Wherein and the optical system for the light emission measuring optical system of the laser light for transmission, an optical fiber, according to claim 16 in which the distal end surface of each optical fiber is disposed so as to face the metal surface Concentration measuring device for metal surface adhesion components. The hollow tube is attached to the metal surface with a condensing lens, an optical system for laser light transmission having a wavelength selective mirror that reflects only the wavelength of the laser light and irradiates the metal surface with the laser light. An optical system for light emission measurement comprising a reflection mirror that is arranged behind the wavelength selective mirror and reflects the plasma emission that has been transmitted through the wavelength selective mirror and that is independent of the wavelength. The metal surface adhesion component concentration measuring device according to claim 16 , further comprising: a laser beam and plasma emission propagating through the hollow tube. The optical transmission unit is composed of an optical fiber for laser beam transmission, the optical fiber for emission measurement, claim 12 distal end face of each optical fiber is one that is arranged so as to face the metal surface To 14. The concentration measuring device for a metal surface adhesion component according to any one of 1 to 14 . Device for measuring the concentration of the metal surface adhesion component according to any one of claims 12 to 19 is intended to provide a time difference 1μs~10μs between the gate opening initiation and irradiation of the immediately preceding laser beam of the light receiving element . According to any one of claims 12 to 20 is intended to provide a time difference 0.5μs~5μs between the laser light provided by the first and the second step the irradiated laser beam in step Concentration measuring device for metal surface adhesion components.