JPH0474679B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) This invention relates to the outer diameter and The present invention relates to a defect detection device.

(Prior Art) In general, in a fuel assembly for a pressurized water reactor, a dozen or so simple guide tubes s are arranged between fuel rods n arranged in a 14×14 square arrangement as shown in FIG. In each section where the collection of rectangular planes is divided into four equal parts by the vertical and horizontal center lines as shown in the dotted line, one wire is placed at each corner of the rectangle smaller than the outline of the collection, and on the vertical and horizontal sides at regular intervals from this point. A total of 4 pipes are arranged, one on the inside, and one on the inside diagonally, and their upper and lower ends are connected to the upper and lower nozzles, and when the reactor is operating, these simple guide pipes As shown in Figure A, rods A made of stainless steel or Zircaloy, approximately 4 m long and approximately 10 mm in diameter, are arranged in the same number and in the same manner as the simple pipes S, and are bundled with an end plate B and connected via a coil spring C. By inserting an interpolant T such as a burnable poison assembly (BPA), control rod (RCC), or neutron source that can be suspended by a hold-down bar d, the state of nuclear fission in the fuel assembly can be controlled. It works to suppress combustion at the beginning of operation.

For safety control purposes, fuel assemblies that have been operated for a certain period of time are removed from the reactor, stored in a spent fuel pit (storage pool), and inspected for bending of the fuel rods, changes in color, and the presence or absence of flaws and deformation. Inspections are being conducted using underwater TVs, and only visual inspections using underwater TVs have been conducted for burnable poison aggregates and fuel inserts such as control rods. Some of these rods are transported on a trial basis to a post-irradiation testing facility (hot laboratory) far from the power plant, where they are disassembled and changes in the rod's outer diameter are measured using a stylus-type testing machine. However, the reality is that many things are stored as they are.

(Problems to be Solved by the Invention) By the way, during the operation of a nuclear reactor for a certain period of time, vibrations of the rods occur due to the high-speed flow flowing inside the reactor.
In addition, since the control rod (RCC) is repeatedly inserted and withdrawn, there is a possibility that the rod may be deformed or damaged. Furthermore, when loading a new type of insert into the furnace, it is necessary to confirm the validity and safety of this design.
Moreover, there is a strong desire to perform on-site inspections in a short period of time without transporting to a hot laboratory.

Therefore, this invention enables the user to easily check the state of changes in the rod and the presence or absence of damage on-site, without having to transport the fuel insert to a distant facility or dismantle it. The purpose is to confirm the gender.

(Means for Solving the Problems) Based on the above object, the present invention provides a substrate having a planar rectangular shape at the center of a substrate positioned and placed on a storage rack for fuel assemblies in a storage pool. Provide a through hole larger than the rods in the same arrangement as the rods of the fuel insert arranged as shown in FIG.
A plurality of through holes of the same size are provided in the same arrangement on one side to serve as a calibration section, and the measurement section is divided into a plurality of sections. Attach one or more measuring devices, each consisting of a block having an eddy current flaw detection coil and a differential transformer of the required length attached to two orthogonal outer surfaces of the block, via the small diameter pipe portion of each block, One of the divisional measuring parts mentioned above is made up of a block of the required height and a box, and a tree direction position detection device having a built-in rotor with a disk at the tip is attached to the box through the above block, and one of the blocks at different positions Alternatively, it is characterized in that the states of multiple rods are detected simultaneously and sequentially.

(Operation) Prior to detecting the fuel insert, the rod of the pseudo insert is inserted into the block of the measuring device, the block of the axial position detection device, and the through hole of the board, and the differential transformer of each measuring device is inserted. The fuel insert is then suspended on the lifting rod of the handling tool, and the lower end of the rod in place can be passed through the eddy current testing coil of the instrument and into the small diameter pipe section. The lower end of the rod should be able to fit into the lower end mounting part of the block diagram of the position detection device, and the lower end of the other rod should be able to fit into the through hole of the board, and in that state, the coils of each differential transformer should be energized. An alternating magnetic field is created inside the coil through alternating current through the eddy current flaw detection coil, and the rotation angle of the rotor of the position detection device can be detected, thus lowering the insert and changing the outer diameter of the rod at the fixed position. The displacement of the core axis of the differential transformer due to this is sequentially measured as a voltage value, and at the same time the presence or absence of cracks and holes is detected.The position detection device sequentially detects the measurement positions, and once the first rod has been detected, The operation of pulling up the insert, rotating it by a required angle, measuring the outer diameter of the next rod in a fixed position, and detecting the presence or absence of flaws is repeated several times to detect all the rods.

(Embodiment) An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a horizontally long board having a required width, and a pair of front and rear guide pins 1a are provided at regular intervals on the lower surface of one end. At the same time, four guide pins 1a (this may be only the inner two) are attached to the other end in pairs at the same intervals on the front, back, left and right, and these guide pins 1a are The substrate 1 is fitted into the storage racks R on both sides of three of the storage racks R arranged in parallel at predetermined intervals in the storage pool to accommodate the current fuel assemblies. It is designed to be retained.

The part of the substrate 1 located above the upper end opening of the central storage rack R has an insert T such as an aggregate of burnable substances.
The through holes 1b having the same diameter as the guide simple tubes s for inserting the rods a are arranged in the same manner, that is, within each section where the rectangular plane of the fuel assembly is divided into quarters by the vertical and horizontal center lines, One piece is placed at each corner of an imaginary quadrilateral smaller than the outer outline of the assembly, which matches the arrangement position of the thimble tube s, one piece is placed on the vertical side and the horizontal side, and one piece is placed inside on the diagonal at regular intervals. The four guide pins 1a are provided so that they are positioned respectively, and the diameter and arrangement state of the fuel is provided in the portion corresponding to the upper end opening of the storage rack R on the right where the four guide pins 1a fit. A through hole 1c for inserting and supporting a reference rod of a simulated insert T' (Fig. 5) for calibrating a measuring device, which will be described later, which has the same length as the rod a of the insert T. is provided in the same state as the through hole 1b.

On the substrate 1 in the part corresponding to the upper end opening of the central storage rack R (hereinafter referred to as the measurement part), there is a columnar rectangular block 2 and a differential gear mounted perpendicularly in two directions outward from the block 2. Four measuring instruments A consisting of transformers 3 and one axial position detecting device B (hereinafter simply referred to as a position detecting device) for detecting a measurement position are provided as follows.

That is, in the first section of the four sections of the rectangular plane of the fuel assembly, the measuring device A is provided so as to surround the corner through hole 1b, and in the second section, the measuring device A is provided. It is arranged so as to surround the through hole 1b on the inside on the diagonal line, and in the part corresponding to the third section, the two measuring instruments A are installed so as to surround the through hole 1b on the vertical and horizontal sides of the quadrilateral, respectively. In the fourth section, a position detection device B is provided so as to surround the through hole 1b on the vertical side of the quadrilateral.

By the way, the parts corresponding to the first to fourth divisions shown in FIGS. 2 and 3 are for convenience, and are not limited to this, It is also possible to make the part of , and then sequentially move clockwise or counterclockwise from that point to the part of . In short, measure the outer diameter of the fuel insert rod in three parts,
It is sufficient if the position can be detected in one part.

As shown in FIGS. 3 and 4, the columnar block 2 of the measuring instrument A installed in the above and 2 parts is low in height and approximately pentagonal in plan.
At the lower end, a small diameter pipe part 2a (Fig. 4) whose inner diameter is large enough to allow the rod a of the fuel insert T to be inserted therethrough is provided eccentrically so as to be located inside the base plate 1. Portion 2a is through hole 1b of substrate 1
The block 2 is inserted into the block 2 and fixed from below with a nut 2g, and a supporting outer cylinder 3a of a required length is fixed to the lower position of two mutually orthogonal outer surfaces of the block 2. A cylindrical differential transformer 3 is attached to the cylinder 3a via a cylinder screw 3b and a protective inner cylinder 3c, and a primary coil and two differentially connected secondary coils are sealed in the head of the transformer 3. The coils are individually connected to a power source and a meter, and a core shaft 3d disposed at the center of the coil is connected to an inner cylinder 3c and an outer cylinder 3.
It extends inwardly along line a, and its tip passes through a horizontal hole 2d provided in the block 2, but is urged inward at its rear end by a coil spring 3f disposed between it and the cap. Its tip is designed so that when the rod a of the fuel insert is inserted into the small diameter pipe portion 2a of the block 2, that is, the through hole 1b of the base plate 1, the rod a comes into contact with the circumferential surface at an interval of 90 degrees. A collar 3e is provided in the middle of the core shaft 3d, and an inner cylinder 3c
It is designed to prevent movement beyond a certain level between the stop step portion formed therein.

On the other hand, the inner part of the block 2 above the small diameter tube part 2a at the lower end is cut off as shown in FIG. Two upright surfaces 2b are formed, and guide rollers 2c are rotatably attached to the upper and lower positions of each upright surface 2b, and a slightly larger diameter roller is installed between two differential transformers 3 facing the cutout. A horizontal hole 2e is provided, and a support 2f of a third guide roller 2c is provided in the horizontal hole 2e with a spring biased toward the resection side. It is designed to hold the peripheral surface from three sides. As shown in FIG. 4, an eddy current flaw detection coil 4 is provided concentrically with the small diameter tube portion 2a at an intermediate position between the upper and lower guide rollers 2c in the cut portion of the block 2.

Then, in the part, there are two measuring instruments A as described above, and the differential transformers 3 extending outward through the through holes 1b along the vertical and horizontal sides of the virtual quadrilateral on the measurement 1 are placed so that they do not collide with each other. mounted on.

On the other hand, since the measuring device A is installed in the diagonally inner through hole 1b of the imaginary quadrilateral in the section, the small-diameter tube section 2a for attachment is attached to the other side so as not to interfere with the measuring device A installed in the section. The columnar block 2 is longer and higher than that of the part, and the rod a at the relevant position of the fuel insert is
In order to prevent the measuring device A from coming into contact with the adjacent rod a during measurement, the block 2 has a constricted shape on both sides of one diagonal line, and the tips of the supporting outer cylinders 3a of the two-way differential transformer 3 are each shaped like a beak. The only difference from other parts of measuring device A is that it is thin and attached to two orthogonal sides of block 2.
Other configurations, such as the rod a being surrounded by guide rollers 2c from three sides during measurement and the differential transformer 3 being sealed and supported by triple cylindrical bodies, are exactly the same.

In a further part, a block 5 for mounting an axial position detection device B, whose height is approximately equal to block 2 of the measuring device A in the part, is installed in the through hole 1b along the vertical side of the virtual quadrilateral on the substrate 1. The lower end of is inserted,
The device is fixed in a slightly counterclockwise rotated state, and a bracket 6b is installed at a required height position of this block 5, and a cylindrical box 6a is attached to the bracket 6b so as to be able to move slightly in the axial direction. , Also, in the box 6a, there is a disc 6d at the tip.
A plurality of coil springs 6s are stretched between the bracket 6b and the rear end arm of the box 6a, and one adjustment rod 6e is provided. The disc 6d is brought into contact with one side of the circumferential surface of the rod a of the insert inserted into the through hole 1b during measurement, and the rotation angle of the disc 6d and rotor 6c due to the vertical movement of the rod a is recorded. It is adapted to detect a measuring device.

As shown in FIGS. 1 and 2, a handling tool 10 (a fifth
A supporting frame 7 is provided for receiving the dummy insert T', and a part (hereinafter referred to as the calibration part) located above the upper end opening of the right rack is also provided with a support frame 7 for receiving the dummy insert T'. A support frame 8 is provided to support the.

Reference numeral 9 denotes a wire hook for hanging measurement 1 with a crane.

When using the above configuration, the first
Guide pins 1a at both ends as shown in the figure and Fig. 5.
into three storage racks R that do not house fuel assemblies arranged side by side in the pool, place the substrate 1 on the racks R, and polish the outer surface into the through hole 1c of the simulated insert provided in the calibration section. A simulated insert T' is prepared by inserting a reference rod a' with a 20 mm diameter, and, prior to measuring the rod of the fuel insert T, the rod is suspended by a crane from the bridge 20 above the pool. Skill tool 1
Attach the mock insert T' to the chuck 13a at the lower end of the lifting rod 13 of 0, bring it above the measurement part of the board 1, and attach it to the holding frame 12 integrated with the column pipe 11.
The leg 12a of the tool 10 is brought into contact with the supporting frame 7 to support the tool 10, and the small winch 14 at the upper end operation section is operated to lower the lifting rod 13, and the reference rod a' is measured 1.
It is inserted through the central through hole 1b, the block 2 of each measuring device A, and the block 5 of the position detection device B. At that time, each differential transformer 3 of the four measuring instruments A is energized, and the voltage characteristics exhibited by each transformer 3 in two directions (X direction, Y direction) perpendicular to the reference diameter of each rod a' are investigated. The so-called zero point setting of each transformer is performed.

Once the reference measurement is completed in this way, the simulated interpolation
Pull up T' from the substrate measurement section and return it to the adjacent calibration section.

Next, the handling tool 10 is moved and operated to remove the fuel insert T attached to the used fuel assembly.
The chuck 13a of the lifting rod 13 is connected to the upper end, the fuel insert T is extracted from the assembly and stored in the holding frame 12, and the cylinders 15 on both sides of the holding frame are opened by operating the button at the upper end operation part. operate,
The holding plate 15a is brought close to the rod side surface of the insert T to prevent the insert T from shaking, and in this state, the tool 10 is again moved above the measurement part of the substrate 1, and the fifth
As shown in the figure, the legs 12a of the holding frame 12 are placed on the support frame 7 to support the tool 10. (Figure 5 shows the measurement in progress, with rod a protruding downward, but initially not protruding).

Thus, by operating the winch 14 of the operating section, the lifting rod 13 is lowered, and the lower end of each rod a of the insert T is connected to each eddy current flaw detection coil 4 in the area of the first to fourth four measuring instruments A. , so that it can enter the small-diameter pipe section 2a, and in the part of the position detection device B, it can enter the through hole at the lower end of the mounting block 5, and in other parts, it can enter the through hole 1b of the board 1. . At this time, in the first measuring device A in the part shown in FIG. The tip of the core shaft 3a of the dynamic transformer 3 comes into contact with the second measuring device A at the point where the lower end of the diagonally inner rod a is held by three guide rollers 2c.
The tip of the core shaft 3a of the differential transformer 3 is in contact with surfaces that are oriented 90 degrees apart, and the third measuring device A in the section is placed against the lower end of the rod a on the vertical side. In the fourth measuring device A, each guide roller 2c and the core shaft 3a of each differential transformer are in the same state with respect to the lower end of rod a on the horizontal side,
In the further part, the disk 6d of the position detection device B comes into contact with the lower end surface of the rod a on the vertical side.

Taking this state as the measurement starting point, the coils of the differential transformers 3 of each measuring instrument are energized, and an alternating current is passed through the eddy current flaw detection coil 4 to create an alternating magnetic field within the coil. The rotation angle can be detected, and the insert T is gradually lowered. In this way, changes in the outer diameters of the four rods a at fixed positions in the mutually perpendicular X and Y directions are sequentially measured as voltage values associated with the displacement of the core shafts 3d of each differential transformer 3.
At the same time, the presence or absence of flaws or defects in the rod a can be detected by checking for disturbances in the current flowing through the rod a due to the alternating magnetic field of the eddy current flaw detection coil 4. On the other hand, as the rod a descends, the position detection device B Due to the rotation of the disk 6d and the rotor 6c, the descending distance of the rod a, that is, the insert T, is detected as the rotation angle of the rotor 6c.

Then, the core axis 3 of measuring instrument A for rod a
The difference between the contact height of a and the contact height of the disc 6d of the position detection device B or the difference between the contact height of the disc 6d and the set height of the eddy current flaw detection coil 4 is corrected as a constant, and each rod Changes in the outer diameter and the presence or absence of defects at each height position of a can be reliably detected.

In this way, when the measurement of the first four rods a is completed, each differential transformer 3 is connected to the eddy current flaw detection coil 4.
At the same time, the function of the position detection device B is stopped, and the insert T is lifted above the substrate 1 via the lifting rod 3, and the holding plate 15a on the holding frame is moved back to release the restraint on the insert T. Solved, then rotate the interpolated object T by 90 degrees, and hold the holding plate 15 in that state.
Lower the insert T while restraining it with a, insert new rods a corresponding to each measuring device A and position detection device B into each block 2 and 5, and set the respective height positions of these rods a. Detect changes in the outer diameter and the presence or absence of flaws in the rod, and when the detection is complete, raise the insert T again, rotate it further 90 degrees, lower it, and repeat the operation three times to detect the undetected rod a. By doing this, all 16 rods a can be detected.

(Effects of the Invention) As described above, since the present invention is configured as described above, a large number of fuel interpolators such as burnable poison rod assemblies and control rods used in fuel assemblies of pressurized water reactors can be used. It is possible to accurately detect changes in the outer diameter of an insert after use, as well as the presence or absence of cracks and holes, without dismantling it on-site (storage area), and whether it is possible to reload the insert. Judging whether or not the product is acceptable and confirming the quality of the design can be done easily and efficiently, improving the safety of storage management, and
Since it does not have a driving part such as a motor, it has the advantage of fewer failures.

[Brief explanation of drawings]

FIG. 1 is a front view of an embodiment of the invention. Figure 2 is its plan view. FIG. 3 is a partially cutaway plan view of the substrate measuring section. FIG. 4 is a partially cutaway front view taken along the line X--X in FIG. 3. FIG. 5 is a front view of the state in which the fuel insert is detected. FIG. 6A is a front view of the fuel insert. Figure B is a schematic plan view of the fuel assembly with the fuel insert inserted. In the figure, 1... board, 1a... guide pin, 1
b, 1c...Through hole, 2...Block, 2a...Small diameter pipe section, 2b...Upright surface, 2c...Guide roller, 2f...Support, 3...Differential transformer, 3a
...Supporting outer cylinder, 3b...Cylinder screw, 3c...Inner cylinder,
3d... Core axis, 4... Eddy current testing coil, 5...
Block, 6a...Cylindrical box, 6b...Bracket, 6c...Rotor, 6d...Disc, A...
... Measuring device, a... Rod, b... Axial position detection device, T... Fuel insert.

Claims (1)

[Claims] 1 At the center of the board, which is positioned and placed on the storage rack for fuel assemblies in the storage pool,
A measurement section is formed by providing insertion holes larger than the rods in the same arrangement as the rods of the fuel inserts, which are arranged to form a rectangular plane, and a plurality of through holes of the same size are also arranged in the same arrangement on one side. The measuring section is divided into a plurality of sections, and the measuring section except for one section has a block having an eddy current flaw detection coil at a mid-height position, and the measuring section is divided into a plurality of sections. One or more measuring devices consisting of differential transformers of the required length are attached to the two outer surfaces of the blocks in a perpendicular state through the small diameter pipe section of each block. It consists of a rod block and a box, and an axial position detection device containing a built-in rotor with a disk at the tip is attached to the box via the block, and it is possible to simultaneously check the status of one or more rods at different positions. A device for detecting the outer diameter and defects of a fuel insert, characterized in that the detection is performed sequentially.