JP5215949B2 - Artificial barrier environment monitoring device - Google Patents

Description

  The present invention relates to an artificial barrier environment monitoring device that determines the presence or absence of corrosion of an overpack enclosing radioactive waste, and more particularly to an artificial barrier environment monitoring device using an optical fiber type metal corrosion detection sensor.

  In general, an overpack is used as a high-level radioactive material container that contains high-level radioactive waste. High-level radioactive waste extracted from spent nuclear fuel such as nuclear power plants is sealed in vitrified material, placed in a carbon steel overpack, surrounded by clay such as bentonite as a buffer, and several hundred underground Buried at the meter. Such overpacks and cushioning materials are called artificial barriers.

  In artificial barriers that have been disposed of, there is a concern that overpack corrosion or outflow of radioactive materials from vitrified bodies due to overpack corrosion due to inflow of groundwater from natural barriers (such as bedrock).

  Therefore, there is a need for corrosion status monitoring devices for geological disposal facilities for high-level radioactive material containers, but these are still in the research stage. The corrosion status monitoring device under study generally measures each environmental factor (temperature, pH, moisture, oxygen content, hydrogen content, etc.) that causes corrosion using a dedicated measuring instrument, and the results and corrosion status of each. Correlation between environmental factors and corrosion is obtained from the correlation with the results of visual observation, electron microscope observation or X-ray analysis, and the corrosion factors are analyzed.

  Conventionally, for environmental factor measurement, temperature is thermistor, thermocouple, pH is glass electrode method, colorimetric method, antimony electrode method, quinhydrone electrode method, etc. pH meter, other moisture meter, oxygen concentration meter, hydrogen concentration meter, etc. Is used. Corrosion environment monitoring using these measuring instruments targets metal corrosion in an aerobic environment.

  However, in these methods, the sensor itself is large, and the signal line between the sensor unit and the measuring device is metal and has a long distance (several hundred meters), so signal noise (effect of electromagnetic noise) May occur.

  Therefore, the present inventors have proposed an artificial barrier environment monitoring device that measures pH, moisture, oxygen, and hydrogen using features such as Brillouin scattering and surface plasmon resonance of an optical fiber sensor (for example, Patent Document 1). reference). By using an optical fiber sensor as the sensor, the soundness of the artificial barrier can be maintained and no electromagnetic noise can be received when the sensor is installed. Note that Brillouin scattering and surface plasmon resonance of an optical fiber sensor are described in Patent Document 2, for example.

JP 2007-93413 A JP 2005-10025 A Japanese Patent No. 3642984

Introduction to near-field nanophotonics Genichi Otsu, Jun Kawada / edition Optronics

  However, as for metal corrosion in soil, there is corrosion due to redox reaction in an anaerobic environment due to sulfate-reducing bacteria and the like in addition to aerobic corrosion due to oxygen and moisture. On the other hand, in the method described in Patent Document 1, it is impossible to monitor metal corrosion in an anaerobic environment by directly detecting sulfate-reducing bacteria.

  The present invention uses near-field light for metal corrosion monitoring in an anaerobic environment. In general, the resolution of material surface observation is limited by the wavelength level of light, but near-field light is emitted when light is applied to a material structure that is smaller than the wavelength of light or from a hole that is smaller than the wavelength of light. It is light, which is present as light that does not propagate near the substance. Since this near-field light has unique information on the surface of the substance, it is used for high-density reading to a near-field light microscope or an optical recording medium (see, for example, Patent Document 3 and Non-Patent Document 1).

  An object of the present invention is to provide an artificial barrier environment monitoring device capable of monitoring metal corrosion even in an anaerobic environment of an artificial barrier buried deep underground.

(1) In order to achieve the above object, the present invention is an artificial barrier environment monitoring device for judging the presence or absence of corrosion of an overpack enclosing radioactive waste, and is installed around the overpack, Optical fiber metal corrosion detection sensor to be measured, and surface plasmon resonance of the near-field light that is a detection value from the optical fiber metal corrosion detection sensor, to determine the shift amount to the long wavelength side of the propagation light wavelength proportional to the amount of bio-bacteria By comparing the amount of bio-bacteria calculated from the amount of shift of the propagation light wavelength obtained by the fiber sensor measurement controller to the long wavelength side with the fiber sensor measurement controller with a predetermined value, the corrosion of the overpack e Bei corrosion determination unit that determines whether an optical fiber in which a plurality of said optical fiber metal corrosion detection sensor is provided, the overpack Is wound on the outer periphery, the plurality of optical fibers metal corrosion detection sensor is installed at equal intervals, said plurality of optical fiber metal corrosion detection sensor is installed so that the position in the circumferential direction with respect to the overpack is shifted so that It is a thing.
With such a configuration, metal corrosion can be monitored even in an anaerobic environment of an artificial barrier buried deep underground.

(2) In the above (1), preferably, the optical fiber metal corrosion detection sensor is provided on the outer periphery of the core of the optical fiber, and has a metal vapor deposition film having a hole smaller than the wavelength of the light output to the optical fiber. It is intended to provide.
(3) In the above (2), preferably, the optical fiber metal corrosion detection sensor is provided with a sensor portion reinforcing member installed on an outer periphery of the metal vapor deposition film.
(4) In the above (2), preferably, the holes provided in the metal deposition film of the optical fiber metal corrosion detection sensor are provided at equal intervals in the circumferential direction and the axial direction of the optical fiber metal corrosion detection sensor. It is.

  According to the present invention, metal corrosion can be monitored even in an anaerobic environment of an artificial barrier buried deep underground.

It is a conceptual diagram of the training behavior in the environment made into the object with the artificial barrier environment monitoring apparatus by one Embodiment of this invention. It is a block diagram of the artificial barrier environment monitoring apparatus by one Embodiment of this invention. It is a whole block diagram of the optical fiber sensor used for the artificial barrier environment monitoring apparatus by one Embodiment of this invention, FIG. 3 (A) is front sectional drawing, FIG.3 (B) is B- of FIG. FIG. 3B is a cross-sectional view taken along line B, FIG. 3C is a cross-sectional view taken along line CC in FIG. 3A, and FIG. 3D is a cross-sectional view taken along line DD in FIG. FIG. 4 is a configuration diagram of a main part of an optical fiber sensor of an artificial barrier environment monitoring device according to an embodiment of the present invention, FIG. 4 (A) is a plan view, and FIG. 4 (B) is a front sectional view; (C) is a side sectional view. It is a block diagram which shows the structure of the artificial barrier environment monitoring apparatus by one Embodiment of this invention. It is a block diagram which shows the principal part detailed structure of the artificial barrier environment monitoring apparatus by one Embodiment of this invention.

Hereinafter, the configuration and operation of an artificial barrier environment monitoring apparatus according to an embodiment of the present invention will be described with reference to FIGS.
First, the concept of the training behavior in the environment targeted by the artificial barrier environment monitoring apparatus according to the present embodiment will be described with reference to FIG.
FIG. 1 is a conceptual diagram of training behavior in an environment targeted by an artificial barrier environment monitoring apparatus according to an embodiment of the present invention.

  In the formation area near the artificial barrier in high-level radioactive waste disposal, heat release from waste, groundwater intrusion from surrounding rock, generation of swelling pressure of buffer due to groundwater, stress change in surrounding rock, and Thermal, hydraulic, mechanical, and chemical processes such as chemical reactions with oxygen and carbon dioxide and groundwater interact with each other, and it is necessary to capture these phenomena as the formation behavior. Yes.

  For this reason, in this embodiment, a heat-water-stress-chemical training model for analyzing the environment in the artificial barrier and the surrounding formation region is constructed, and the health of the artificial barrier is evaluated.

  Figure 1 shows the correlation between heat transfer, moisture transfer, stress / deformation, and chemical reaction shown in the artificial barrier environment monitoring device, with the addition of chemical reaction and corrosion by bio-fungi such as sulfate-reducing bacteria. Yes. Biobacteria are inhabited by an environment where water, heat, and redox reaction are possible, and are generally known as examples of metal corrosion occurring in an oxygen-free environment.

Next, the configuration of the artificial barrier environment monitoring apparatus according to the present embodiment will be described with reference to FIG.
FIG. 2 is a configuration diagram of an artificial barrier environment monitoring apparatus according to an embodiment of the present invention.

  The artificial barrier environment monitoring device includes an artificial barrier environment monitoring device 100, a data collector 200, a fiber sensor measurement controller 300, an optical fiber 400, and a plurality of surface plasmon resonance optical fiber sensors 500.

  On the other hand, the overpack OP, which is a high-level radioactive substance storage body, is placed in a natural barrier NB such as a rock, and a buffer material BM is provided around the overpack OP.

  The optical fiber 400 reciprocates from the fiber sensor measurement controller 300 to the overpack OP. The first end of the optical fiber 400 is connected to the fiber sensor measurement controller 300, wound around the outer periphery of the overpack OP a plurality of times, and then returns to the fiber sensor measurement controller 300 again. The second end is connected to the fiber sensor measurement controller 300. The optical fiber 400 is a loop type. The length of the optical fiber 400 between the fiber sensor measurement controller 300 and the overpack OP is several hundred meters.

  A plurality of surface plasmon resonance optical fiber sensors 500 are installed at predetermined intervals in a portion of the optical fiber 400 that is wound around the outer periphery of the overpack OP. The detailed configuration of the surface plasmon resonance optical fiber sensor 500 will be described later with reference to FIG. If the diameter of the overpack OP is 1 m, the optical fiber 400 is wound 11 turns in the illustrated example. Therefore, the total length of the optical fiber 400 wound around the overpack OP is about 40 m, and, for example, ten fiber sensors 500 are installed at equal intervals in the portion. In addition, the fiber sensor 500 is installed so that the position of the circumferential direction with respect to the overpack OP may shift | deviate.

  The fiber sensor measurement controller 300 includes a laser beam transmitter 310, a channel switch 320, and a spectrometer 330. Here, since a plurality of overpacks OP are installed inside the natural barrier NB, and the optical fiber 400 and the surface plasmon resonance optical fiber sensor 500 are installed in each of them, the channel switch 320 is targeted. Used to switch overpack OP.

  Based on the data collection start signal S1 output from the artificial barrier environment monitoring apparatus 100, the data collector 200 transmits a data collection command S2 to the laser light transmitter 310 and the channel switch 320. Based on this, the laser beam transmitter 310 transmits a laser beam, and uses the channel switch 320 to send a pulsed laser beam to the optical fiber 400 for a predetermined overpack OP. The laser beam transmitter 310 outputs visible light or near-infrared laser light.

  A wavelength shift occurs due to surface plasmon resonance with respect to the corrosion generated by the biobacteria in the anaerobic environment of the surface environment of the overpack OP. The wavelength-shifted light is captured by the optical fiber sensor 500, sent again to the spectroscope 330 through the channel switch 320, the light intensity of the wavelength shifted wavelength is obtained, and the value is sent to the data collector 200. The corrosion information collected in the data collector 200 is sent to the artificial barrier environment monitoring apparatus 100 together with the measurement time. The artificial barrier environment monitoring apparatus 100 displays the collected information in real time and also displays history information to monitor the corrosion status of the overpack OP.

Next, the configuration of the optical fiber sensor 500 used in the artificial barrier environment monitoring apparatus according to the present embodiment will be described with reference to FIGS. 3 and 4.
FIG. 3 is a front sectional view and a side sectional view showing the overall configuration of the optical fiber sensor used in the artificial barrier environment monitoring apparatus according to the embodiment of the present invention. 3B is a cross-sectional view taken along the line BB in FIG. 3A, FIG. 3C is a cross-sectional view taken along the line CC in FIG. 3A, and FIG. It is DD sectional drawing of (A). FIG. 4 is a configuration diagram of a main part of the optical fiber sensor of the artificial barrier environment monitoring apparatus according to the embodiment of the present invention. 4A is a plan view, FIG. 4B is a front sectional view, and FIG. 4C is a side sectional view.

  As shown in FIG. 3, the optical fiber 400 includes a core 410, a clad 420, and a coating (jacket) 430.

  The optical fiber sensor 500 includes a metal vapor deposition film 510 formed in close contact with the outer periphery of the core 410 and a sensor portion reinforcing member 520 installed on the outer periphery. The metal vapor deposition film 510 generates near-field light on the surface of the core 410 of the optical fiber, and is made of gold or silver. The generated near-field light is amplified by plasmon resonance generated on the surface of the metal vapor-deposited film 510 and takes in information according to the environmental condition in the vicinity of the sensor. Information corresponding to the environmental conditions in the vicinity of the sensor is determined by the wavelength shift amount of the propagating light.

  Since the optical fiber metal corrosion detection sensor 500 directly uses the portion of the core 410 of the optical fiber, the sensor reinforcing member 520 includes the optical fiber cladding 420 or the optical fiber coating 430, as shown in FIG. , (C), it is inserted in three places at intervals of 120 degrees. This shape may be any shape that is optimal as a reinforcing structure, and may be a method other than the 120 ° 3 location shown in FIG.

  Next, the configuration of the metal vapor deposition film 510 that generates the near-field light shown in FIG. 3 will be described with reference to FIG.

  The metal vapor-deposited film 510 is a gold or silver vapor-deposited film, but is vapor-deposited so that the film has a hole 512 when the vapor-deposited film is formed. The shape of the hole 512 is square or circular as illustrated. The size of the hole 512 is smaller than the wavelength of light (visible light or near infrared light) output from the laser light transmitter 310. More preferably, the size is several tens of nm. When light having a wavelength of several hundreds of nm is used, the size is about 1/10 of the size. Further, the thickness of the metal vapor deposition film 510 is also set to about several tens of nm.

  The near-field light generating metal deposition film 510 covers the surface of the core 410 of the optical fiber. A part of the light totally reflected on the surface of the core 410 of the optical fiber is light of several tens nm smaller than the propagation wavelength (visible light or near infrared light: several hundreds nm) from the hole 512 having a size of several tens nm (proximity (Field light) oozes out to the surface of the optical fiber sensor core 410 and generates near-field light according to the environment in the vicinity of the optical fiber metal corrosion detection sensor 500. This near-field light is amplified by surface plasmon resonance. Since the amplification energy absorbs energy from the light propagating through the core 410 of the optical fiber, the wavelength of the propagating light is shifted to the long wavelength side. This shift amount is proportional to the amount of bio-bacteria generated.

Next, the configuration of the artificial barrier environment monitoring device 100 used in the artificial barrier environment monitoring device according to the present embodiment will be described with reference to FIGS. 5 and 6.
FIG. 5 is a block diagram illustrating a configuration of an artificial barrier environment monitoring apparatus according to an embodiment of the present invention. FIG. 6 is a block diagram illustrating a detailed configuration of a main part of the artificial barrier environment monitoring apparatus according to the embodiment of the present invention.

  As shown in FIG. 5, the artificial barrier environment monitoring apparatus 100 includes a collected data processor 110 and a data collection start / end controller 120. The collected data processor 110 includes a corrosion determination device 111, a data display device 113, a latest data receiver 115, a measured value storage device 117, and a past data reference device 119.

  The corrosion determination unit 111 includes a corrosion determination rule for determining whether or not the overpack is corroded by biobacteria. The corrosion determiner 111 receives the surface from the data collector 200 shown in FIG. 2 via the latest data receiver 115 against the corrosion generated by the biobacteria in the anaerobic environment of the overpack OP surface environment. Information on the shift amount shifted in wavelength by plasmon resonance is input.

  Further, in order to monitor the amount of bio, the latest data receiver 115 and the measured value storage 117 of the collected data processor 110 store the bio-bacteria amount measurement value 115A, and the past data reference unit 119 stores the bio-bacterial amount reference value 119A. doing.

  The corrosion determiner 111 includes a determiner 111A, a determiner 111B, a determiner 111C, and a determiner 111D.

  The discriminator 111A discriminates whether or not the difference between the initial value and the current value of the biobacteria exceeds a reference value that can be determined to have a corrosive effect due to the biobacteria.

  Here, the configuration of the discriminator 111A will be described with reference to FIG. The size determination device 111A2 determines whether or not the difference between the initial value 119B of the bio-bacteria amount and the current value 115A shown in FIG. 5 is larger than the reference value 119A shown in FIG. When the difference between the initial value 119B of the bio-bacteria amount and the current value 115A is larger than the reference value 119A that may cause corrosion ((current bio-bacteria measurement value-initial bio-bacteria-quantity measurement value)> reference value ), The size determination unit 111A2 determines that there is a significant change in the amount of bio-bacteria with respect to the occurrence of corrosion, and sends condition establishment information to the determination unit 111B and the condition determination unit 111C in FIG.

  In FIG. 5, the discriminator 111B discriminates whether or not the deviation from the reference value 119A continues for a prescribed period. The discriminator 111C discriminates whether or not both of the discriminators 111A and 111B are established at the same time, and when both are established at the same time, the discriminator 111D determines that there is corrosion due to the biobacteria.

  The determination result is displayed on the graph display portion 113A, the numerical value display portion 113B, and the corrosion evaluation display portion 113C of the data display 113.

As explained above, the use of a fiber optic metal corrosion detection sensor makes it possible to monitor the artificial barrier environment of high-level radioactive waste buried in several hundred meters underground so that high-level radioactive waste does not leak outside. It can be used as an overpack metal corrosion device.

DESCRIPTION OF SYMBOLS 100 ... Artificial barrier environment monitoring apparatus 110 ... Collected data processor 111 ... Corrosion judgment device 113 ... Data display device 115 ... Latest data receiver 117 ... Measurement value storage device 119 ... Past data reference device 111A, 111B, 111C, 111D ... Discrimination 119A ... reference value for the amount of bio-bacteria that can cause corrosion,
120 ... Data collection start / end controller 200 ... Data collector 300 ... Fiber sensor measurement controller 400 ... Optical fiber 410 ... Core 420 ... Cladding 430 ... Cover (jacket)
500 ... Optical fiber metal corrosion detection sensor 510 ... Metal deposition film 512 ... Hole 520 ... Sensor part reinforcement

Claims (4)

An artificial barrier environment monitoring device that determines the presence or absence of corrosion of an overpack enclosing radioactive waste,
An optical fiber metal corrosion detection sensor that is installed around the overpack and measures biobacteria,
A fiber sensor measurement controller that obtains a shift amount to the long wavelength side of the propagation light wavelength proportional to the amount of biobacteria by surface plasmon resonance of the near-field light that is a detection value from the optical fiber metal corrosion detection sensor;
Corrosion determination means for determining the presence or absence of corrosion of the overpack by comparing the amount of bio-bacteria calculated from the shift amount of the propagation light wavelength obtained by the fiber sensor measurement controller toward the longer wavelength side with a predetermined value. Bei to give a,
An optical fiber provided with a plurality of optical fiber metal corrosion detection sensors is wound around the outer periphery of the overpack,
The plurality of optical fiber metal corrosion detection sensors are installed at equal intervals,
It said plurality of optical fiber metal corrosion detection sensor, EBS environmental monitoring device according to claim installed Rukoto so positioned in circumferential direction with respect to the overpack is shifted. The artificial barrier environment monitoring device according to claim 1,
The optical fiber metal corrosion detection sensor is provided on the outer periphery of the core of the optical fiber, and includes a metal vapor deposition film having a hole smaller than the wavelength of the light output to the optical fiber. In the artificial barrier environment monitoring device according to claim 2,
The optical fiber metal corrosion detection sensor includes a sensor part reinforcing member installed on an outer periphery of the metal vapor deposition film. In the artificial barrier environment monitoring device according to claim 2,
The artificial barrier environment monitoring device, wherein the holes provided in the metal vapor deposition film of the optical fiber metal corrosion detection sensor are provided at equal intervals in the circumferential direction and the axial direction of the optical fiber metal corrosion detection sensor. .

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