JP2016061628A - Fuel inspection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel inspection apparatus capable of shortening time required to measure the thickness of an oxide film on a surface of each fuel rod in a fuel assembly for a boiling-water reactor.SOLUTION: A fuel inspection apparatus for inspecting a fuel assembly, for a boiling-water reactor, in which a spacer that bundles cylindrical fuel rods extending vertically into a square lattice state and bundles cylindrical cells surrounding the respective fuel rods holds a horizontal distance between the fuel rods, is provided with a rod 10, a probe 20, and a pressing section 30. The rod 10, the probe 20, and the pressing section 30 can pass through a passing region surrounded by outer surfaces of the plurality of cells. The probe 20 is provided near a tip end of the rod 10. The pressing section 30 presses the probe 20 against the fuel rods.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel inspection apparatus for inspecting a fuel assembly for a boiling water reactor.

  In general, a core of a light water reactor is loaded with a fuel assembly obtained by bundling a plurality of fuel rods each having a nuclear cladding loaded into a cylindrical cladding tube. The fuel assembly loaded in the light water reactor is exposed to high temperature water. For this reason, the oxide film formed on the surface of the fuel rods causes corrosion of the cladding tube and affects the nuclear thermal hydraulic characteristics. Therefore, in order to evaluate the safety and soundness of the fuel rods It is necessary to measure the thickness of the oxide film formed on the fuel rod cladding tube.

  A fuel assembly for a boiling water reactor (BWR) is loaded into a nuclear reactor in a state where a rectangular channel box is mounted. In general, when measuring the oxide film thickness of the fuel rod of the BWR fuel assembly, the channel box is once removed and the inspection probe is pressed against the fuel rod from the side surface.

JP 2010-145233 A JP 2010-91403 A

  If the channel box is removed when measuring the oxide film thickness of the fuel rod of the BWR fuel assembly and then attached again after the measurement, the time required for the measurement becomes longer. Further, when an inspection such as measurement of the oxide film thickness of the fuel rod of the BWR fuel assembly is performed by a method in which an inspection probe or the like is brought into contact with the fuel rod from the side, it is difficult to access other than the fuel rods on the outer periphery.

  Therefore, an object of the present invention is to shorten the time required for measuring the oxide film thickness on the surface of the fuel rod of the boiling water nuclear reactor fuel assembly.

  In order to achieve the above-mentioned object, the present invention provides a horizontal spacing between the fuel rods by a spacer in which cylindrical fuel rods extending in a vertical direction are bundled in a square lattice and cylindrical cells surrounding the fuel rods are bundled. In a fuel inspection apparatus for inspecting a boiling water nuclear reactor fuel assembly holding a plurality of cells, a support that can pass through a passage region surrounded by outer surfaces of the plurality of cells, a probe that can pass through the passage region, and And pressing means for pressing the probe against the fuel rod attached to the support so as to pass through the passage region.

  According to the present invention, the time required for measuring the oxide film thickness on the surface of the fuel rod of the boiling water reactor fuel assembly is shortened.

It is a side view of 1st Embodiment of the fuel inspection apparatus which concerns on this invention. It is an elevation sectional view at the time of inserting 1st Embodiment of the fuel inspection apparatus which concerns on this invention in the fuel assembly of a measuring object. It is a cross-sectional view at the time of inserting 1st Embodiment of the fuel inspection apparatus which concerns on this invention in the fuel assembly of a measuring object. It is a probe vicinity enlarged cross-sectional view at the time of the test | inspection using 1st Embodiment of the fuel inspection apparatus which concerns on this invention. It is a probe vicinity enlarged sectional view at the time of the test | inspection using 1st Embodiment of the fuel inspection apparatus which concerns on this invention. It is the probe vicinity enlarged cross-sectional view which showed the attitude | position at the time of moving the probe of 1st Embodiment of the fuel inspection apparatus which concerns on this invention to an inspection position. It is a probe vicinity cross-sectional view in the modification of 1st Embodiment of the fuel inspection apparatus which concerns on this invention. It is a side view of 2nd Embodiment of the fuel inspection apparatus which concerns on this invention. It is a probe vicinity enlarged cross-sectional view at the time of the test | inspection using 2nd Embodiment of the fuel inspection apparatus which concerns on this invention. It is a probe vicinity enlarged sectional view at the time of the test | inspection using 2nd Embodiment of the fuel inspection apparatus which concerns on this invention. It is a probe vicinity enlarged sectional view at the time of the test | inspection of 3rd Embodiment of the fuel inspection apparatus which concerns on this invention. It is a probe vicinity enlarged front view at the time of the test | inspection of 3rd Embodiment of the fuel inspection apparatus which concerns on this invention.

Several embodiments of a fuel inspection apparatus according to the present invention will be described with reference to the drawings. These embodiments are merely examples, and the present invention is not limited thereto. The same or similar components are denoted by the same reference numerals, and redundant description is omitted.
[First Embodiment]
FIG. 1 is a side view of a first embodiment of a fuel inspection apparatus according to the present invention.

  The fuel inspection apparatus includes a rod 10, a probe 20, and a pressing unit 30. The pressing unit 30 is two plates 32 connected by a hinge 31. One plate 32 of the pressing unit 30 is rotatably attached to one end of the bar 10. Two pressing portions 30 are provided so as to face the side surface of the rod 10. The rod 10 is made of a highly rigid material.

  The rod 10 is hollow. A tension bar 12 extends inside the bar 10. One end of the tension bar 12 is connected to the end opposite to the hinge 31 of the plate 32 that is not attached to the bar 10 of the pressing part 30. The other end of the tension bar 12 protrudes from the end opposite to the pressing portion 30.

  The probe 20 is fixed to, for example, a hinge 31 of the pressing unit 30. The probe 20 is for eddy current measurement, for example. The measurement surface of the probe 20 is provided so as to be located on the side opposite to the rod 10.

  FIG. 2 is an elevational sectional view when the fuel inspection device of the present embodiment is inserted into the fuel assembly to be measured. FIG. 3 is a cross-sectional view when the fuel inspection apparatus of the present embodiment is inserted into the fuel assembly to be measured.

  The fuel assembly 90 to be measured includes a lower tie plate 91, an upper tie plate 92, a fuel rod 93, and a spacer 94. The fuel rod 93 is obtained by loading a cylindrical cladding tube made of a zirconium alloy with a cylindrical uranium pellet. A plurality of fuel rods 93 extend between the lower tie plate 91 and the upper tie plate 92 in parallel with each other. The lower end of the fuel rod 93 is supported by the lower tie plate 91. The fuel rods 93 are arranged in a square grid of 9 rows and 9 columns, for example. A predetermined distance is maintained between the adjacent fuel rods 93 by spacers 94. The fuel assembly 90 is loaded into the reactor core in a state in which a rectangular tube-shaped channel box 99 is mounted.

  The spacer 94 has a band 95 and a cell 96. Cells 96 are arranged at positions corresponding to the respective fuel rods 93. A band 95 is provided so as to surround all the cells 96. Each cell 96 is substantially cylindrical. A gap 97 is formed at the center of the four cells 96 arranged in 2 rows and 2 columns. In addition, voids are also formed in the upper tie plate 92 at positions corresponding to these voids 97. In the fuel inspection apparatus, the rod 10, the probe 20, and the pressing portion 30 are formed so as to be able to pass through the gap 97 of the spacer 94 and the gap of the upper tie plate 92. By extending the rod 10, the probe 20 is moved to a predetermined inspection position.

  FIG. 4 is an enlarged cross-sectional view of the vicinity of the probe at the time of inspection using the fuel inspection apparatus of the present embodiment. FIG. 5 is an enlarged sectional view of the vicinity of the probe at the time of inspection using the fuel inspection apparatus of the present embodiment.

  When the probe 20 reaches a predetermined inspection position, the tension bar 12 is pulled. As a result, the pressing portion 30 swells in the normal direction of the rod 10 and the hinge 31 moves to the fuel rod 93 side. In this way, the probe 20 is pressed against the surface of the fuel rod 93, and the oxide film thickness on the surface of the fuel rod 93 is measured by, for example, an eddy current measurement method.

  The probe 20 is rotatably provided with the rod 10 as an axis. The probe 20 may be rotated together with the rod 10. By appropriately rotating, the probe 20 is pressed perpendicularly to the fuel rod 93 for inspection. In the case of inspection using ultrasonic waves, it can be easily determined from the detection signal whether or not it is pressed vertically.

  As described above, when the fuel inspection apparatus according to the present embodiment is used, the fuel rod can be inspected without removing the channel box 99, so that the time required for the inspection can be shortened. As a result, the exposure of workers is reduced.

  In the present embodiment, the pressing portion 30 is provided symmetrically with respect to the rod 10. For this reason, since the pair of pressing portions 30 are supported when the other is pressed against the fuel rod 93, the probe 20 can be pressed more strongly against the fuel rod 93. As a result, inspection accuracy is improved. Moreover, since measurement at two locations can be performed simultaneously, it contributes to shortening of the inspection time.

  As the pressing portion 30, a single flexible plate may be used. In this case, the probe 20 is attached to the center of this plate. Even in such a pressing portion 30, when the tension rod 12 is pulled, the plate bends, the central portion moves toward the fuel rod 12, and the probe 20 can be pressed against the fuel rod 93. In the case where a flexible plate is used, if the tensile force from the tension bar 12 is not applied to the plate due to some problem, the plate will be extended, and the possibility that it cannot pass through the gap 97 of the spacer 94 is small.

  A total of two pressing portions 30 are provided at positions symmetrical with respect to the rod 10, but a total of four pressing portions 30 may be provided every 90 degrees. In this case, four fuel rods can be inspected simultaneously.

  Instead of the tension bar 12, a wire may be used. In this case, the pressing unit 30 is set so as to return to the original state by gravity or the like instead of inserting / removing the tension bar 12. The wire or tension bar 12 is provided inside the bar 10. If provided inside, the possibility of being caught by each part of the fuel assembly or other structural members of the spent fuel pool is reduced.

  The wire or tension bar 12 may be provided outside the bar 10. The tension bar 12 or an alternative wire may be provided outside the bar 12. If it is provided outside, manufacturing and maintenance are facilitated.

  When the oxide film thickness of the fuel rod 96 is measured, it is necessary to remove the soft clad adhering to the surface of the fuel rod 96. Therefore, for example, a means for removing soft clad such as a brush may be provided at the tip of the rod 10. Alternatively, apart from the fuel rod inspection device, a soft clad may be removed by attaching a brush or the like to the tip of the rod. While removing the soft clad with a brush, the clad may be separated from the vicinity of the fuel rod 96 by water injection, or may be sucked into a pipe or the like.

  When measuring the thickness of the oxide film of the fuel rod 93, zero point calibration of the probe 20 may be required. Therefore, it is recommended to separately measure fuel rods that are standard in water. For example, the calibration fuel rod may be provided above the partial-length fuel rod, or may be disposed above the upper tie plate 92.

  FIG. 6 is an enlarged cross-sectional view of the vicinity of the probe showing the posture when the probe of the fuel inspection device of the present embodiment is moved to the inspection position. In FIG. 6, the posture of the probe when it reaches the inspection position is indicated by a broken line.

  As in this embodiment, when handling a thin tube at a depth of several meters, it is difficult to accurately determine the position in the rotational direction. Therefore, in the present embodiment, when the probe 20 is moved to the inspection position, the pressing portion 30 is opened, and the spacer 94 is passed in the direction rotated 45 degrees with respect to the fuel rod 93 to be inspected. The horizontal width of the pressing portion 30 in the open state is set as wide as possible so that it can pass through the longest gap in the region surrounded by the four cells 96 of the spacer 7. As a result, the pressing portion 30 assumes a posture rotated substantially 45 degrees around the rod 10 with respect to the fuel rod 93 to be inspected. In this state, after the probe 20 is moved to the inspection target position, the probe 20 is directly opposed to the fuel rod 93 to be inspected by rotating the rod 10 to the opposite side by 45 degrees. A mechanism for rotating the rod 10 at an angle of 45 degrees may be provided at the end of the rod 10 opposite to the probe 20.

  In the inspection, it is important to grasp the position information in the axial direction as well as the position in the rotational direction. In order to grasp the position in the axial direction, for example, an encoder or a measure for measuring the feed amount of the rod 10 may be provided.

  One of the purposes of grasping the position in the rotation direction is to check whether the probe 20 is in contact with the center of the fuel rod 93. In order to grasp the position in the rotation direction, a mark may be provided in a specific direction of the rod 10 and confirmed from the outside of the fuel assembly 90 with a camera or the like. Or you may grasp | ascertain the position of the rotation direction of the stick | rod 10 by providing a reflecting plate in the specific direction of the stick | rod 10, irradiating a laser beam from the outside, and confirming the reflected light. Further, the position of the rod 10 in the rotational direction may be grasped by measuring the interval between the probes 20 in a state where the two probes 20 are in contact with the fuel rod 93. Since the two fuel rods 93 to be measured are positioned diagonally to each other in a square lattice, the interval between the probes 20 is the smallest when the probe 20 is in contact with the center of the fuel rod 93. That is, it can be confirmed that the probe 20 is in contact with the center of the fuel rod 93 by performing measurement at a position where the probe 20 is in contact with the fuel rod 93 and the interval between the probes 20 is minimized. The interval between the probes 20 can be measured by measuring the opening amount of the hinge 31 or the like.

  FIG. 7 is a cross-sectional view of the vicinity of the probe in a modification of the present embodiment.

  In this modification, a square tube 50 is used instead of the cylindrical rod 10. The rectangular tube 50 is as large as possible so that it can pass through the region surrounded by the four cells 96 of the spacer 94 in a state rotated by 45 degrees with respect to the square lattice on which the fuel rods 93 are arranged. That is, the rectangular tube 50 can pass through the region surrounded by the four cells 96 of the spacer 94 only in a state where it is rotated substantially 45 degrees with respect to the square lattice on which the fuel rod 93 is disposed. For this reason, the pressing unit 30 is substantially rotated 45 degrees around the rod 10 with respect to the fuel rod 93 to be inspected.

Further, in this modification, the tension rod 12 and the pressing portion 30 need only be accommodated in the square tube 50, so that the space is wider than the cylindrical rod 10, and the degree of freedom in design is improved. The tension rod 12 and the pressing portion 30 may be accommodated in the square tube 50, and the tip of the square tube 50 may be extended before the tension rod 12. In this case, the tension bar 12 and the pressing portion 30 are protected, and the possibility of breakage due to contact with the spacer 94 or the like can be reduced. Further, by providing a tapered portion at the tip of the square tube 50, the insertion property into the gap such as the spacer 94 is improved.
[Second Embodiment]
FIG. 8 is a side view of the second embodiment of the fuel inspection apparatus according to the present invention.

  In the present embodiment, instead of the pressing portion 30 (see FIG. 2 and the like) of the first embodiment, a bag that is inflated by injecting a fluid such as gas or liquid, that is, a balloon 40 is provided. The rod 10 is formed in a hollow shape so as to inject a gas or liquid into the balloon 40 and to discharge the gas or liquid from the balloon. The probe 20 is attached to the surface of the balloon.

  FIG. 9 is an enlarged cross-sectional view of the vicinity of the probe at the time of inspection using the fuel inspection apparatus of the present embodiment. FIG. 10 is an enlarged sectional view of the vicinity of the probe at the time of inspection using the fuel inspection apparatus of the present embodiment.

  When the probe 20 reaches a predetermined inspection position, air or water is injected from the rod 10 into the balloon 40. Thereby, the balloon 40 is inflated, and the surface of the balloon 40 is moved to the fuel rod 93 side. In this way, the probe 20 is pressed against the surface of the fuel rod 93, and the oxide film thickness on the surface of the fuel rod 93 is measured by, for example, an eddy current measurement method.

  As described above, even when the fuel inspection apparatus according to the present embodiment is used, the fuel rod can be inspected without removing the channel box 99, so that the time required for the inspection can be shortened.

If the hollow rod 10 is used as means for injecting gas or liquid into the balloon 40, it is not necessary to use a separate tube for injecting gas or liquid, which contributes to a reduction in the number of parts. If a rubber balloon 40 that can be easily broken with a needle or the like is used, and the gas or liquid cannot be discharged from the balloon 40 for some reason, the fuel assembly can be easily broken by breaking the balloon 40 with the needle. Can be taken out from.
[Third Embodiment]
FIG. 11 is an enlarged vertical sectional view of the vicinity of the probe during the inspection of the third embodiment of the fuel inspection apparatus according to the present invention. FIG. 12 is an enlarged front view of the vicinity of the probe at the time of inspection by the fuel inspection apparatus of the present embodiment.

  In the present embodiment, the probe 20 is fixed to the support plate 60. The support plate 60 is a rectangular plate that is long in the axial direction, that is, in the same direction as the fuel rod 96. The support plate 60 extends on both sides in the axial direction with respect to the probe 20.

  When such a fuel inspection apparatus is used, when the probe 20 is pressed against the fuel rod 93, the support plate 60 serves as a support, and the probe 20 can be pressed vertically against the fuel rod 93. That is, when one end of the probe 20 contacts the fuel rod 93 first, the contacted tip does not move further toward the fuel rod 93, and the other tip approaches the fuel rod 93. As a result, the support plate 60 is positioned in parallel to the fuel rod 96. Accordingly, by fixing the front surface of the probe 20 so as to be parallel to the support plate 60, the contact angle between the probe 20 and the fuel rod 93 can be made vertical.

  Here, although the structure which added the support plate 60 to 1st embodiment was demonstrated, even if it adds the support plate 60 also to the modification of 1st embodiment, or 2nd embodiment. Good.

DESCRIPTION OF SYMBOLS 10 ... Rod, 12 ... Tensile rod, 20 ... Probe, 30 ... Pushing part, 31 ... Hinge, 32 ... Plate, 40 ... Balloon, 50 ... Square tube, 60 ... Support plate, 90 ... Fuel assembly, 91 ... Lower type Rate, 92 ... Upper tie plate, 93 ... Fuel rod, 94 ... Spacer, 95 ... Band, 96 ... Cell, 97 ... Air gap, 99 ... Channel box

Claims (5)

A fuel assembly for a boiling water reactor in which cylindrical fuel rods extending in the vertical direction are bundled in a square lattice shape and a cylindrical cell surrounding the fuel rods is bundled to maintain a horizontal interval between the fuel rods. In a fuel inspection device for inspecting
A support capable of passing through a passage region surrounded by the outer surfaces of the plurality of cells;
A probe capable of passing through the passage region; and
A pressing means that is capable of passing through the passage region and is attached to the support and presses the probe against the fuel rod;
A fuel inspection apparatus comprising:   2. The fuel inspection apparatus according to claim 1, wherein the pressing unit includes a plate having one end fixed to the support and a tension unit that pulls the opposite end in the vertical direction.   3. The fuel inspection apparatus according to claim 2, wherein at least two of the plates are pulled at the ends by the same pulling means.   The fuel inspection apparatus according to claim 2, wherein the support is a cylinder, and the pulling means is a wire that passes through the inside of the cylinder. 2. The fuel inspection apparatus according to claim 1, wherein the pressing means is a bag that expands when fluid is injected.

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