JP2017032402A - Water level detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water level detection device capable of detecting a water level with a simple structure.SOLUTION: A water level detection device is equipped with an optical transmission path 30 which has a curved part; and moving portions 40 and 50 which are hooked to the optical transmission path 30, move according to water level changes, and have a hooking portion 26b changing a curvature of the curved part. From a state in which a lower side float 50 floated by buoyancy supports an upper side float 40 with repulsive force between a first magnet 51 and a second magnet 41, if a water level is changed to move the lower side float 50, the upper side float 40 moves with the lower side float 50, and the curvature of the curved part is changed by the hooking portion 26b.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a water level detection device.

  Against the backdrop of an accident at the Fukushima Daiichi Nuclear Power Station resulting from the Great East Japan Earthquake, there is a need to strengthen safety measures against serious accidents such as nuclear power plant facilities and severe disasters. In particular, when a serious accident occurs, a measuring instrument for accurately grasping the state in the reactor containment vessel is important. One of them is a water level measurement system that functions even when hot water or high-temperature steam flows out of a severe accident in the reactor containment vessel. At present, an electric water level meter that detects an electrical resistance or a temperature change by the water level is used for measuring the water level in the containment vessel.

  As an electric water level gauge, for example, in Patent Document 1, the temperature distribution of the pipe surface measured by a plurality of thermometers using thermocouples is used to correct the temperature of the density of water in the pipe. A reactor water level gauge for determining the water level is described.

  However, such electric water level gauges have difficulties in radiation resistance, high temperature resistance, and maintainability, and the installation of power cables and instrumentation cables is large in order to perform multipoint measurement at the water level. There is a problem.

  In addition, in the emergency containment vessel, high levels of radiation dose, pressure, temperature rise, and flammable gas are generated. Therefore, there are many problems in applying the conventional sensor as it is, such as a risk of malfunction or malfunction in a general-purpose sensor, or ignition of a combustible gas.

  Above all, for the water level sensor that detects the water level, the pressure type that detects the water pressure has been used in many cases. However, the reactor containment vessel is filled with gas or the water pressure is higher than the expected water level. This may cause malfunction such as causing abnormal pressure. In addition, there were FBG (Fiber Bragg Grating) optical fiber type water level sensors and optical fiber type water level sensors using Faraday elements, but the FBG optical fiber forms a diffraction grating in the optical fiber. In addition, heat resistance and radiation resistance are not sufficient.

  Therefore, Patent Document 2 discloses an optical fiber type water level sensor using a Faraday element, in which light is incident on a Faraday proximity sensor having a built-in Faraday element, and the water level sensor detects the water level based on the intensity of the reflected light. . In this water level sensor, a magnet is accommodated inside a float that moves up and down in accordance with the water level, and when the water level rises, the float rises, so that a magnetic field is applied to the Faraday element by the magnet. Then, the light incident on the Faraday proximity sensor is rotated by the Faraday element, and the intensity of the reflected light becomes weak. Thereby, it is detected that the water level is equal to or higher than the reference water level.

  However, the Faraday proximity sensor of Patent Document 2 has a problem that the configuration of the sensor becomes complicated, such as a polarizer that passes light to the Faraday element and a reflection mirror that passes through the Faraday element. Further, the Faraday element also has a problem that the heat resistance is not sufficient.

JP-A-5-288590 JP2012-73120A

  The present invention has been made in view of the above-described conventional problems, and provides a water level detection device capable of detecting a water level with a simple configuration. Moreover, the water level detection apparatus excellent in heat resistance and radiation resistance is provided.

The water level detection device of the present invention,
An optical transmission line having a curved portion;
A movable part that is hooked to the optical transmission line, moves in accordance with a change in water level, and has a hook part that changes the curvature of the curved part,
Equipped with.

  A movable part moves according to a water level change, and the curvature of a curve part is changed by a hook part. When the curvature increases, the number of times the light carried in the optical transmission path is reflected inside the optical transmission path increases, and the optical path becomes longer. Therefore, the light emitted from the optical transmission path is attenuated and the light intensity is reduced. By detecting this decrease in light intensity, it is possible to detect the water level by detecting the movement of the movable part due to the water level change. Since the water level detection device is composed of the optical transmission path and the movable part, the water level can be detected with a simple configuration without using a special element.

The movable part is
A lower float having a first magnet and floating in water by buoyancy;
A second magnet that repels the first magnet, and an upper float that slides in conjunction with the optical transmission path;
The optical transmission path and the upper float have a sealed structure,
When the lower float moves due to a change in water level from the state in which the lower float floating by buoyancy supports the upper float by the repulsive force of the first magnet and the second magnet, the upper float moves. Preferably, the float moves with the lower float, and the curvature of the curved portion is changed by the hooking portion.

  By configuring the movable part with at least the lower float and the upper float, the structure becomes simple, the water level detection device can be manufactured easily and inexpensively, and the stability can be enhanced. Since the upper float moves by repulsion by the first magnet of the lower float, the upper float and the lower float can be separated. Therefore, even if the optical transmission path and the upper float are sealed, the curvature of the curved portion of the optical transmission path can be changed with the movement of the lower float due to the water level change. Therefore, since the optical transmission path and the upper float have a sealed structure, it is possible to realize a water level detection device having excellent heat resistance, radiation resistance, water resistance, corrosion resistance, and pressure resistance.

  The optical transmission line is preferably a radiation-resistant optical fiber wound in an annular shape.

  By using a radiation-resistant optical fiber as an optical transmission line, light transmission loss can be reduced and the optical transmission line can be used even in an environment with a large radiation dose. By winding the optical fiber in an annular shape, it is possible to increase the amount of attenuation of light when pressed by the movable part, so that a slight change in the water level can be detected and the detection accuracy can be improved.

One end of the optical fiber has a reflecting portion,
It is preferable that the light incident from the other end of the optical fiber is reflected by the reflecting portion at the one end of the optical fiber and returned from the other end.

  The light incident from the other end of the optical fiber and transported in the optical fiber is reflected by the reflection portion at one end and returns to the optical transmission path toward the other end. Therefore, light can be received from one end of the optical fiber and the emitted light can be received. Thereby, light can be incident and light can be received only at one end of the optical fiber, and the structure can be simplified.

A light oscillating portion for making light incident on the optical transmission path;
A light receiving unit that receives light emitted from the optical transmission path;
A measuring unit for measuring the intensity of light received by the light receiving unit;
A determination unit that compares the light intensity value measured by the measurement unit with a predetermined threshold and determines that the water level has reached a predetermined position;
It is preferable to further include a control unit having

  By configuring the measurement unit and the determination unit separately from the optical transmission line, the measurement unit and the determination unit can be installed remotely from the optical transmission line, providing excellent radiation resistance and heat resistance, and high safety. A water level detection device can be realized.

  According to the water level detection device of the present invention, the water level detection device is constituted by the optical transmission path and the movable part, so that the water level can be detected with a simple configuration.

1 is a schematic view of a water level detection device according to an embodiment of the present invention. The perspective view of a detection part. Front sectional drawing of the detection part of FIG. 2 at the time of a water level rise. The disassembled perspective view of an optical fiber accommodating part. Front sectional drawing of the detection part of FIG. 2 at the time of a water level fall. The figure which shows the optical path of the light conveyed in the optical fiber when the curvature of an optical fiber is small. The figure which shows the optical path of the light conveyed in an optical fiber when the curvature of an optical fiber is large. Schematic which shows the modification which connects a some detection part and control part via an optical switch. Schematic which shows the relationship between the detection part and control part which concern on the modification of the both ends of an optical fiber. Schematic which shows the state which connected the some detection part with the cable and connected only the uppermost detection part to the control part. The graph which shows the relationship between the actual water level and the intensity | strength of the light received with a control part in the water level detection apparatus of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the water level detection device 1 according to the present embodiment includes a plurality of detection units 10 and a plurality of control units 80 connected to one detection unit 10 via a cable 4. The plurality of detectors 10 are installed on the inner wall surface of the reactor containment vessel 2 at appropriate intervals in the vertical direction. The controller 80 is installed outside the reactor containment vessel 2. The control unit 80 receives light incident on the detection unit 10 via the cable 4 and reflected and returned from the detection unit 10.

  As shown in FIG. 2, the detection unit 10 includes a lid body 11, an upper outer cylinder 12, a lower outer cylinder 13, and a stopper 14. The detection unit 10 is made of a metal such as SUS304.

  The upper outer cylinder 12 has a cylindrical shape with the lower part closed, and a plurality of screw holes 12b are provided at equal intervals in the circumferential direction to fix the lower outer cylinder 13 to a lower extension 12a extending downward from the lower part. Yes.

  The lower outer cylinder 13 has a cylindrical shape with substantially the same diameter as the upper outer cylinder 12 and is disposed below the upper outer cylinder 12. The lower outer cylinder 13 has a plurality of long holes 13a extending in the vertical direction provided at equal intervals in the circumferential direction and a plurality of round holes 13b provided on the lower surface in order to allow water to enter and exit. The lower outer cylinder 13 is fitted to the lower extension 12a of the upper outer cylinder 12 at the top, and is fixed to the upper outer cylinder 12 by screwing through the screw hole 12b.

  The lid body 11 has a circular plate shape in plan view, and is disposed so as to close the upper opening of the upper outer cylinder 12, and is fixed to the upper outer cylinder 12 by screwing as shown in the sectional view of FIG. Yes. By closing the upper part of the upper outer cylinder 12 with the lid 11, the inside of the upper outer cylinder 12 is in a sealed state.

  The stopper 14 is substantially L-shaped, and one end is fixed to the upper part of the lid 11 with screws. The other end is a free end, and the detection unit 10 is fixed to the wall surface by affixing the side surface portion 14 a forming the other end to the inner wall surface of the reactor containment vessel 2. Fixing may be performed by screwing.

  As shown in FIG. 3, the optical fiber housing portion 20 and the upper float 40 are disposed inside the upper outer cylinder 12. The optical fiber housing portion 20 is fixed to the lid 11 via two square columnar support columns 31 and a ring-shaped support plate 32.

  As shown in FIG. 4, the optical fiber housing part 20 has a housing case body 21, a front cover 22, and a back cover 23, which are fixed by screwing. A storage space 24 is provided between the storage case main body 21 and the front cover 22. A wound optical fiber 30, a support member 25, and a sliding member 26 are disposed in the accommodation space 24.

  The storage case body 21 has a rectangular box shape with an open lower end. An insertion hole 21 b through which the optical fiber 30 is inserted is formed in the top wall 21 a of the housing case body 21. Inside the storage case main body 21, a pair of guide walls 21c extending from the top wall 21a and curved so as to widen downward, and a curved curve projecting upward to connect the lower ends of the pair of guide walls 21c. A wall 21d is formed. The housing case body 21 includes a curved wall 21d and a side wall 21e to form a housing space 24 for housing the wound optical fiber 30. Two bosses 21 f for arranging the support member 25 are provided in the center of the housing case main body 21. In addition, two long holes 21g extending in the vertical direction for sliding the sliding member 26 are provided below. A protrusion 21 h is provided between the pair of guide walls 21 c above the accommodation space 24.

  The front cover 22 has a rectangular box shape with upper and lower ends opened. Two long holes 22a extending in the vertical direction for sliding the sliding member 26 are provided below.

  The support member 25 has a semi-elliptical plate shape with a hole, and an outer peripheral groove 25a for fitting and supporting the wound optical fiber 30 is formed on the outer peripheral surface. The support member 25 has two holes 25b corresponding to the two bosses 21f of the storage case main body 21, and the boss 21f is inserted into the holes 25b between the storage case main body 21 and the front cover 22. It is pinched and fixed. The support member 25 fixed in the accommodation space 24 is arranged at a predetermined interval inside the curved wall 21d so that the upper portion of the outer peripheral groove 25a and the protrusion 21h face each other and sandwich the optical fiber 30 therebetween. Yes.

  The sliding member 26 is hooked by a rectangular frame 26a with a hole and a wound optical fiber 30, and the optical fiber 30 is pulled from the inside to the outside in a radius of curvature direction. A hook-shaped hook portion 26b provided at the upper portion and four stoppers 26c provided on both surfaces of the frame body 26a are provided. The sliding member 26 is sandwiched between the housing case main body 21 and the front cover 22 in a state where four stoppers 26 c are inserted into the long holes 21 g of the housing case main body 21 and the long holes 22 a of the front cover 22, respectively. Therefore, the sliding member 26 is arranged to be slidable in the vertical direction with respect to the housing case main body 21 and the front cover 22 within a range in which the stopper 26c can move within the long holes 21g and 22a. A screw hole 26d for screwing and fixing the upper float 40 is provided on the lower surface of the sliding member 26.

  Thus, since the optical fiber 30, the sliding member 26, and the upper float 40 are sealed and accommodated in the upper outer cylinder 12, they can withstand high-temperature hot water and steam. Further, since water does not adhere to the end face of the optical fiber 30 in the sealed upper outer cylinder 12, attenuation of reflected light at the end face can be eliminated.

  The end of the wound optical fiber 30 is held by a socket 33 provided on the support plate 32. The socket 33 holds an end portion of the cable 4 connected to an optical oscillation unit 81 (see FIG. 1) to be described later, and connects the optical fiber inside the cable 4 and the optical fiber 30 inside the optical fiber housing unit 20. . The cable 4 includes a stainless steel tube and an optical fiber passed through the tube. By protecting the optical fiber with a stainless steel tube, heat resistance, water resistance and airtightness are enhanced.

  As shown in FIG. 3, the upper float 40 has a cylindrical shape, and the second magnet 41 is disposed inside. The diameter of the upper float 40 is smaller than the inner diameter of the upper outer cylinder 12. The upper float 40 is screwed to the sliding member 26 via a screw hole 26d. Accordingly, the upper float 40 slides inside the upper outer cylinder 12 together with the sliding member 26.

  By using the radiation-resistant optical fiber 30 as the optical transmission line 30, the light transmission loss can be reduced, and the optical transmission line 30 can be used even in an environment with a large radiation dose. Specifically, the optical fiber 30 has excellent radiation resistance because fluorine is added to a quartz core to suppress and repair the generation of defects due to radiation. The optical fiber 30 is not limited to the one to which fluorine is added, and the material thereof is not particularly limited as long as it is an optical fiber excellent in radiation resistance. The reflecting portion at one end of the optical fiber 30 is mirror-finished and wound and supported by a support member 25 described later, and the other end is held by a socket 33. The mirror-finished tip of the optical fiber 30 is plated with metal by using, for example, titanium having excellent corrosion resistance. However, the tip is not limited to metal vapor deposition plating, and the tip may be capped with a radiation resistant resin made of polyetheretherketone (PEEK) having excellent heat resistance and radiation resistance. These prevent noise from entering from the tip of the optical fiber 30. Further, the reflecting portion at one end of the optical fiber 30 does not necessarily have to be mirror-finished and does not have to be subjected to special processing. This is because the optical fiber reflects light at the interface where the optical transmission medium ends without mirror finishing. However, from the viewpoint of improving the reflectivity and suppressing the decrease in reflectivity when the dirt adheres to the reflecting surface, the reflecting portion at one end of the optical fiber 30 is preferably mirror-finished.

  When the sliding member 26 is positioned above the optical fiber 30, the hooking portion 26b does not pull the optical fiber 30 (see FIG. 3). When the sliding member 26 is positioned below the optical fiber 30, the optical fiber 30 is pulled downward by the hooking portion 26b, and the wound ring-shaped optical fiber 30 is stretched to have an elliptical shape (see FIG. 5). ).

  In the present embodiment, the optical fiber 30 is wound in an annular shape five times. The number of turns is not limited to five and is arbitrary. When the number of turns is increased, the number of portions where the curvature of the optical fiber 30 is changed by being pulled by the hooking portion 26b increases, and the amount of change in light intensity increases, so that the detection accuracy is improved. However, if the number of turns is increased too much, the hooking portion 26b is pushed back by the elasticity of the optical fiber 30, and the optical fiber 30 becomes difficult to bend. Accordingly, there is a possibility that the water level cannot be detected. Therefore, the water level may be wound so as to be deformed by being pulled by the hooking portion 26b. The wound optical fiber 30 may be bundled by being surrounded by a metal fastener, or may be bundled by attaching a metal weight. By winding the optical fiber 30 in an annular shape, it is possible to increase the amount of attenuation of light when pulled by the hooking portion 26b, so that a slight change in the water level can be detected and the detection accuracy can be improved.

  As shown in FIG. 3, a lower float 50 and a floating body 52 are disposed inside the lower outer cylinder 13.

  The lower float 50 has the same configuration as the upper float 40, and houses a first magnet 51 instead of the second magnet 41 therein. The diameter of the lower float 50 is smaller than the inner diameter of the lower outer cylinder 13. Accordingly, the lower float 50 can slide inside the lower outer cylinder 13. The first magnet 51 and the second magnet 41 are magnetized so that their opposing surfaces are repelled so as to repel each other.

  The floating body 52 has a substantially cylindrical shape with a hollow inside, and is fixed to the lower float 50 with screws at the top. The floating body 52 floats on the water that has entered the lower outer cylinder 13 due to its buoyancy. Therefore, the floating body 52 moves up and down in the lower outer cylinder 13 together with the lower float 50 as the water surface that has entered the lower outer cylinder 13 rises or falls.

  The control unit 80 (see FIG. 1) includes a light oscillation unit 81 and a light receiving unit 82 connected to the detection unit 10 via the cable 4 and the optical circulator 85, a measurement unit 83 connected to the light reception unit 82, and a measurement unit. And a determination unit 84 connected to 83. The light oscillation unit 81 is a light source and makes light incident on the optical fiber 30 via the cable 4. The light receiving unit 82 receives light returning from the optical fiber 30 via the cable 4. The measuring unit 83 measures the intensity of light received by the light receiving unit 82. The determination unit 84 compares the light intensity value measured by the measurement unit 83 with a predetermined threshold value, and determines that the water level has reached a predetermined position.

  Since the control unit 80 is configured separately from the detection unit 10, the control unit 80 is remote from the detection unit 10, for example, outside the reactor containment vessel 2 or in a radiation management area away from the reactor containment vessel 2. Can be installed in facilities. Therefore, there is no need to install a sensor or the like using an electrical signal in the reactor containment vessel. By installing the control unit 80 outside the reactor containment vessel 2, it is not necessary to provide a new power source in the reactor containment vessel 2, and piping work is not required, and the detection unit 10 can be easily installed in a narrow space. In addition, since an optical fiber is used as the cable 4, the water level can be detected even when the cable 4 has a long distance of several kilometers or more.

  Next, operation | movement of the detection part 10 installed in the inner wall face of the reactor containment vessel 2 is demonstrated.

  As shown in FIG. 3, when the water level is above the lower outer cylinder 13 of the detection unit 10, the lower float 50 and the floating body 52 float due to the buoyancy received from the water that has entered the lower outer cylinder 13, Located on the upper side of the side outer cylinder 13, the upper end of the lower float 50 is in contact with the bottom of the upper outer cylinder 12. Further, since the second magnet 41 in the upper float 40 repels the first magnet 51 in the lower float 50, the upper float 40 is positioned at the upper part of the movable range together with the sliding member 26. That is, the stopper 26 c of the sliding member 26 is positioned at the upper ends of the long holes 21 g and 22 a of the housing case main body 21 and the front cover 22. At this time, since the catching portion 26b of the sliding member 26 is separated from the optical fiber 30, the optical fiber 30 is kept in a ring shape.

  When light enters the optical fiber 30 from the light oscillating unit 81, the light transported in the optical fiber 30 is reflected by one end (reflecting unit) of the optical fiber 30 and the other end (the end where the light is incident). Return to. And the light radiate | emitted from the other end part is received by the light-receiving part 82, and the measurement part 83 measures the intensity | strength of the received light. The determination unit 84 compares the light intensity value measured by the measurement unit 83 with a predetermined threshold value, and determines that the water level has not reached the lower float 50. The predetermined threshold is a value determined by the length of the cable 4 or the like. As described above, since the light incident from one end of the optical fiber 30 is emitted from the incident end, the detection unit 10 and the control unit 80 can be connected via only one cable 4 to detect the water level. The structure of the device 1 can be simplified.

  As shown in FIG. 5, when the water level is lowered, water is drained from the lower outer cylinder 13 through the long hole 13 a and the round hole 13 b, and the lower float 50 and the floating body 52 are in sliding contact with the inner surface of the lower outer cylinder 13. Move downward according to the water level. Then, the repulsive force received by the second magnet 41 in the upper float 40 from the first magnet 51 in the lower float 50 is weakened, and the upper float 40 slides on the inner surface of the lower outer cylinder 13 by its own weight together with the sliding member 26. While moving down. Thereby, the hooking portion 26b of the sliding member 26 comes into contact with the lower end portion of the optical fiber 30, and pulls the optical fiber 30 downward. In this state, the optical fiber 30 is elastically deformed into an elliptical shape.

  FIG. 6 shows an optical path 89 of light carried in the optical fiber 30 when the curvature of the optical fiber 30 is small. FIG. 7 shows an optical path 89 of light carried in the optical fiber 30 when the curvature of the optical fiber 30 is large. When the optical fiber 30 is bent and the curvature is increased, the number of times the light transported in the optical fiber 30 is reflected inside the optical fiber 30 increases, and the optical path becomes longer. Therefore, the light emitted from the optical fiber 30 is attenuated and the light intensity is reduced. The decrease in light intensity is measured by the measuring unit 83, and the determination unit 84 compares the predetermined intensity with a predetermined threshold value, thereby detecting the movement of the lower float 50 due to a change in the water level and detecting the water level. Since the water level detection device 1 is configured by the optical fiber 30, the movable unit, and the control unit 80, the water level can be detected with a simple configuration without using a special element.

  As described above, since the second magnet 41 of the upper float 40 moves against the first magnet 51 of the lower float 50, the upper float 40 and the lower float 50 can be arranged separately. Therefore, even if the optical fiber accommodating portion 20, the sliding member 26, and the upper float 40 are sealed in the upper outer cylinder 12, the optical fiber 30 is moved along with the movement of the lower float 50 and the floating body 52 due to the water level change. Can be deformed. Therefore, since the optical fiber housing portion 20 is sealed and only the lower float 50 and the floating body 52 are brought into contact with water, the water level detection device 1 having excellent water resistance, corrosion resistance, and pressure resistance can be obtained. Further, since the optical fiber 30 can be deformed only by the movable part composed of the sliding member 26, the upper float 40, the lower float 50, and the floating body 52, the structure becomes simple and the water level detection device 1 can be simply and inexpensively. It can be manufactured and stability can be improved.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible.

  As long as the optical fiber 30 has a curved portion, the optical fiber 30 is not limited to a configuration wound in a ring shape, and may be configured by a combination of a straight line and a curved line, for example. Further, in addition to the configuration wound in a ring shape in front view shown in FIGS. 3 and 5, it may be wound in a ring shape in plan view.

  In the embodiment, the detection unit 10 and the control unit 80 are connected via the cable 4 in a one-to-one relationship. However, as shown in FIG. 8, an optical switch 60 is provided between the plurality of detection units 10 and one control unit 80, and a configuration is adopted in which the detection unit 10 connected to the control unit 80 is switched by the optical switch 60. Also good. With this configuration, it is possible to reduce the cost by making the control unit 80 one, simplifying the configuration of the water level detection device 1.

  In the embodiment, one end of the optical fiber 30 is mirror-finished to reflect light. However, as shown in FIG. 9, one end of the optical fiber 30 may be connected to the light oscillation part 81 via the cable 4 and the other end may be connected to the light receiving part 82 via the cable 4. This eliminates the step of mirror-finishing one end of the optical fiber 30 to reduce the manufacturing cost, and saves the trouble of providing the optical circulator 85, thereby simplifying the configuration.

  Further, as shown in FIG. 10, a plurality of detectors 10a to 10d arranged along the wall surface of the reactor containment vessel 2 are connected by the cable 4, and only the optical fiber 30 of the uppermost detector 10a is connected to the controller 80. You may employ | adopt the structure connected to. In this water level detection device 1, both ends of the optical fiber 30 of the detection units 10b and 10c are connected to the cable 4, and the tip of the optical fiber 30 of the detection unit 10d is mirror-finished, for example. When the water level drops and the water is drained sequentially from the uppermost detection unit 10a, water is drained from any of the detection units 10a to 10d by measuring the decrease in the intensity of light received by the control unit 80. Can be detected. On the contrary, when the water level rises, it is possible to detect from which of the detection units 10a to 10d the water has risen by measuring the increase in the intensity of light received by the control unit 80.

  FIG. 11 shows the relationship between the water level in the reactor containment vessel 2 and the intensity of light received by the control unit 80 in the embodiment shown in FIG. In the state where the water level is higher than the uppermost detection unit 10a, the light intensity is the strongest. And if a water level falls from this state and the lower float 50 and the floating body 52 of the detection part 10a begin to fall at A point, the intensity | strength of the light received with the fall of a water level (the lower float 50 and the floating body 52) will become. Decrease and stop at point B where the detection unit 10a comes out of the water completely. When the water level further falls and the lower float 50 and the floating body 52 of the detection unit 10b start to drop at the point C, the intensity of the light received with the drop in the water level decreases, and the detection unit 10b completely comes out of the water D It stops at the point. When the water level falls from this state and the lower float 50 and the floating body 52 of the detection unit 10c start to drop at the point E, the intensity of the light received with the lowering of the water level decreases, and the detection unit 10c is completely removed from the water. Stops dropping at the F point. When the water level further falls and the lower float 50 and the floating body 52 of the detection unit 10d begin to descend at the point G, the intensity of the light received with the lowering of the water level decreases, and the detection unit 10d completely exits the water. It stops at the point. When all the detection units 10a to 10d are completely out of the water, the light intensity becomes the weakest.

  In the above embodiment, the water level detection device 1 is used to detect the water level in the reactor containment vessel 2, but it may be used to detect the water level in a place other than the reactor containment vessel 2.

DESCRIPTION OF SYMBOLS 1 Water level detection apparatus 2 Reactor containment vessel 4 Cable 10,10a, 10b, 10c, 10d Detection part 11 Cover body 12 Upper outer cylinder 12a Screw hole 13 Lower outer cylinder 13a Long hole 13b Round hole 14 Stopper 14a Side part 20 Optical fiber housing portion 21 Housing case body 21a Top wall 21b Insertion hole 21c Guide wall 21d Curved wall 21e Side wall 21f Boss 21g Long hole 21h Projection 22 Front cover 22a Long hole 23 Back cover 24 Storage space 25 Support member 25a Outer peripheral groove 25b Hole Part 26 Sliding member (movable part)
26a Frame 26b Hooking part 26c Stopper 26d Screw hole 30 Optical fiber (optical transmission line)
31 Support pillar 32 Support plate 33 Socket 40 Upper float (movable part)
41 Second magnet 50 Lower float (movable part)
51 First magnet 52 Floating body (movable part)
60 Optical switch 80 Control unit 81 Optical oscillation unit 82 Light receiving unit 83 Measuring unit 84 Judgment unit 85 Optical circulator 89 Light path

Claims (5)

An optical transmission line having a curved portion;
A movable part that is hooked to the optical transmission line, moves in accordance with a change in water level, and has a hook part that changes the curvature of the curved part,
A water level detection device comprising: The movable part is
A lower float having a first magnet and floating in water by buoyancy;
Having a second magnet repelling the first magnet, and comprising an upper float interlocking with the lower float;
The optical transmission path and the upper float have a sealed structure,
When the lower float moves due to a change in water level from the state in which the lower float floating by buoyancy supports the upper float by the repulsive force of the first magnet and the second magnet, the upper float moves. The water level detection device according to claim 1, wherein the float moves with the lower float, and the curvature of the curved portion is changed by the hooking portion.   The water level detection device according to claim 1, wherein the optical transmission line is a radiation-resistant optical fiber wound in a ring shape. One end of the optical fiber has a reflecting portion,
The water level detection device according to claim 3, wherein light incident from the other end of the optical fiber is reflected and returned by a reflecting portion at the one end of the optical fiber and emitted from the other end. A light oscillating portion for making light incident on the optical transmission path;
A light receiving unit that receives light emitted from the optical transmission path;
A measuring unit for measuring the intensity of light received by the light receiving unit;
A determination unit that compares the light intensity value measured by the measurement unit with a predetermined threshold and determines that the water level has reached a predetermined position;
The water level detection device according to claim 1, further comprising a control unit having

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