JPS5956131A - Sensor for measuring spring force of supporting grating - Google Patents

Abstract

PURPOSE:To measure the spring force of the spring part of a supporting grating in a short time, by providing a long-sized member to one side of a plate member fitted with a strain gauge at its lower end part, and linking an extension roll mechanism to the long-sized material and moving it up and down freely along the plate member. CONSTITUTION:The long-sized material 23 is provided lengthwise to one side of the elastic plate member 26 which extends up and down and is fitted with the strain gauge 29 at the lower end part. The extension roll mechanism 24 is coupled with this long-sized material 23. This extension roll mechanism 24 has a roll 46 and is moved up and down freely along the plate member 26, and an elastic coupling member 36 is formed at the intermediate part. This sensor is inserted into the supporting grating, whose spring part and the plate member 26 are deformed to measure the spring force of the supporting grating.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a support grid spring force measuring sensor for measuring the spring force of a support grid elastic support portion of a fuel assembly for a nuclear reactor.

Fuel assemblies loaded in pressurized water type light water reactors currently in use are constructed as shown in FIGS. 1 to 4. That is, an upper nozzle 1 and a lower nozzle 2 are arranged vertically apart from each other, and a plurality of supports are arranged at predetermined intervals between them and have lattice spaces (cells) 4 formed by straps 3. The grid 5 is inserted into the grid space 4 of these support grids 5 at a predetermined interval, and is fixed to the fixed part of the support grid 5, and the upper and lower ends of each are connected to the upper nozzle 1 and the lower nozzle 2. A connected control rod guide tube 6 and a large number of fuel pellets 8 sealed in a cladding tube 7
and a pressing spring 9, and is inserted into a predetermined position in the grid space 4 of the support grid 5, and is a rigid support part (dimple) of the support grid 5.
10 and a large number of fuel rods 12 supported by elastic support parts (spring parts) 11.

The holding force at the contact portion within each cell 4 of the support grid 5 that supports the fuel rods 12 is determined by the thermal expansion of the cladding tube 7 and the support grid 5,
It is set in consideration of various factors such as irradiation growth, reduction in the spring force of the spring part due to irradiation (also called relaxation), coolant flow rate, and flow velocity. If this holding force is excessive, the fuel rods 1 inserted into the support grid 5 may
The fuel rods 12 are easily scratched, and the fuel rods 12 may be bent significantly during combustion. On the other hand, if this holding force is too small, the holding force against the fuel rod 12 will be insufficient due to the relaxation of the spring portion 11 due to the irradiation, and vibrations caused by the cooling water flow will cause the contact portion between the fuel rod 12 and the support grid 5 to Relative motion occurs between the fuel rods, causing so-called fretting wear, which rapidly shortens the life of the cladding tube 7.

As described above, the holding force of the support grid 5 is an important factor that affects the performance of the fuel assembly, but since there is no suitable means for measuring this holding force, it has not been possible to actually measure it. The pushing force of the simulated fuel rods etc. onto the support grid 5 was measured, and the holding force (also called restraint force) for the actual fuel rods could be indirectly estimated from this pushing force.

This invention was made in view of the above-mentioned circumstances, and an object of the present invention is to provide a support grid spring force measurement sensor that can directly measure the spring force of the spring portion in each cell of a support grid.

An embodiment of the present invention will be described below with reference to FIGS. 5 to 7. Reference numeral 21 in FIGS. 5 and 6 is a sensor, and this sensor 21 is composed of a deformable bar 22, a drive shaft 23, and an expansion roller mechanism 24.

The deformed bar 22 has a rectangular cylindrical part 25 formed on the upper part thereof, and a plate-shaped part (
A plate member) 26 is formed and is made of stainless steel. A substantially central portion of the plate-like portion 26 is formed particularly thin and serves as a plate spring portion 27 .

The width 26a of most of the plate-shaped portion 26, excluding its upper portion, is smaller than the outer diameter of the fuel rod. In addition, the plate-shaped portion 26
A substantially rectangular four section 28 is formed on the lower inner surface of the recess 28, and two strain gauges 29 are arranged vertically apart on the bottom surface of the recess 28.
．． 29 is attached.

The center between these two strain gauges 29.29 is the four part 28
It is made to coincide with the center between the top and bottom ends of. In addition, guide grooves 30 extending vertically are formed on both sides of the lower end of the temporary shaped part 26.
A bush 31 with seven flange is fitted inside, and the seven flange 32 is engaged with the upper end surface β of the square tubular portion 25.

7. A drive shaft C (long member) 23 is fitted into the bush 31 with a flange. Threaded portions 33 and 34 are formed at the upper and lower ends of the drive shaft 23, respectively. The screw portion 33 is screwed with a nut (35.35).

The expansion roller mechanism 24 is connected to the threaded portion 34 . This expansion roller mechanism 24 is connected to an elastic connecting member 36.
- A mounting body 37.

The elastic connecting member 36 has a connecting part having a female threaded part 38 at its upper part, a connecting part having a male threaded part 39 at its lower part, and a thin leaf spring part 40 formed between these two connecting parts. The O roller mounting body 37 has a female screw portion 38 screwed onto the screw portion 34 of the drive shaft 23, and is attached to the drive shaft 23 by a nut 41 screwed onto the screw portion 34 so as to be vertically adjustable. , a roller box 44 having a female threaded portion 42 and a fitting protrusion 43 shown in FIG. . The roller box 44 has a fitting protrusion 43 fitted into the guide groove 30 of the deformation bar 22, and a female threaded portion 42.
is screwed into the male threaded portion 39, and is attached to the elastic connecting member 36 with a nut 47 screwed into the male threaded portion 39 so as to be vertically adjustable.

Furthermore, a plate-shaped arm 48, for example, is fixed to a predetermined location of the rectangular tubular portion 250 of the deformable bar 22 by appropriate means. In FIGS. 6 and 7, 5 is a fuel assembly support grid into which the sensor 21 is inserted, 10 is its rigid support part (dimple), 11 is its elastic support part (spring part), and 4 is its grid space. (cell). Note that the roller box 4
・The width 49 shown in FIG. 7 of 4 is the dimple 10 in the cell 4.
° is smaller than the spacing between the spring parts 11, and the distance 46a from the outer surface of the plate-like part 26 to the outer circumferential surface of the roller 46 in FIG. 6 is the same diameter as the outer diameter of the fuel rod. or slightly smaller in size. sensor 21
is the rigid support part 1 when inserted into the grid space 4 of the support grid 5.
Insert it slightly away from the rigid support part 10 so as not to damage it. At this time, the surfaces of the square tubular portion 25, the leaf spring portion 27, and the deformable bar 22 on the rigid support portion 10 side are in a straight line, and are processed to ensure accuracy during insertion. When measuring the spring force, the deformable bar 22 is pressed against the upper and lower rigid supports 10, so the lower outer surface of the deformable bar 22 (the left side in FIG. 6) is the left side surface of the rectangular tubular part 25 in FIG. On the other hand, when the lower part of the deformable bar 22 comes into contact with the rigid support part by moving toward the rigid support part, the plate spring 27 becomes parallel with two inflection points. At this time, there is a slight gap between the left side surfaces of the square tubular part 25 and the lower part of the deformable bar 22 in FIG. The reason why the leaf spring part 40 is provided on the elastic connecting member 36 is to move the roller 46 to follow the elastic support part 11 in the same way as the leaf spring part 27 is provided on the deformable bar 22. The pushing force is also transmitted by this leaf spring 40.

Therefore, the plate thickness of these plate spring parts 27 and 40 is the same as that of the support grid 5.
The support grid spring force implanted as described above is designed to improve measurement accuracy as the minimum thickness necessary for inserting the sensor 21 into the grid space 4 and transmitting the pushing force of the roller 46. The function of the measurement sensor will be explained.

First, the Rd of the support grid 5 is set at a predetermined position using appropriate means so that the rigid support portion 10 and the elastic support portion 11 are positioned in the state shown in FIG.

Next, the arm 48 is driven by an appropriate driving means to move the lower end of the sensor 21 to a desired cell 4 as shown in FIG.
Insert inside. At this time, the plate-shaped portion 26 is lightly fused to the surfaces of the upper and lower dimples 10, 100, and the center line M between the 2'lJ strain gauges 29, 29 shown in FIG. The position of the sensor 21 is adjusted to 1 tlN m to match fW, and this is fixed by appropriate means.

Next, when the drive shaft 23 is lowered by a lifter (not shown) connected to the upper part of the drive shaft 23, the roller box 44 is lowered along the plate-like part 26 via the elastic connecting member 36, The outer peripheral surface of the roller 46 contacts the spring portion 11.

When the drive 111 shaft 23 further descends and the shaft 45 reaches the height of the peak of the chevron of the spring portion 11, the upper and lower dimples 1
The force applied between 0.10 and 0.10 is maximum, deforming the plate-like portion 216. As a result, the resistance values of the two strain gauges 29.29 change, so that the change in resistance IS is indicated as a spring force to a strain gauge (not shown) connected to the strain gauges 29.29. Then, the spring force of the spring section 11 when the fuel rod is inserted between the dimple 10 and the spring section 11 can be directly measured using the data from this strain meter.

Next, the drive shaft 23 is raised by an appropriate distance υ [it] using a lifting tool, and then the arm 48 is driven upward to extract the sensor 21 from the cell 4 .

Thereafter, the above operations (2) to (5) are repeated to measure the spring force of the spring portion 11 in the pond cell 4.

In addition, in the embodiment, the spring portion 11 in each cell 4
Although the spring force of the cells 4 is sequentially measured, the present invention is not limited to this, and a plurality of sensors 21 may be arranged on the arm 48 in accordance with the arrangement pitch of the cells 4. By the operations (2) to (5), 'f, MIrt
The spring force of the spring portion 11 can be directed forward at the same time.

As described above, according to the present invention, a long material is provided along one side of the elastic plate member extending in the vertical direction and having a strain gauge attached to the lower end, and the long material is provided along the plate member on one side. It is small and lightweight because it is connected to a roller and can move up and down along the plate member, and moves up and down an expansion roller mechanism that has an elastic part in the middle However, the spring force of the spring part of the support grid can be directly measured in a short time, and since the roller rolls into contact with the spring part of the support grid during the measurement of the spring force, there is no possibility of damage to the spring part. Deterioration can be prevented. Roughly, multiple sensors, for example on the arm,
By arranging the cells in accordance with the arrangement pitch of the cells of the support grid, the spring forces of a plurality of spring parts of the support grid can be measured simultaneously.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway sectional view showing an example of a nuclear reactor fuel block assembly, Fig. 2 is a sectional view taken along line II-I in Fig. Enlarged cross section D1, Figure 4 is F in Figure 3.
5 is a front view showing an embodiment of the present invention, No. 6 is a side sectional view showing the sensor inserted into the support grid, and No. 71'L'l is a cross-sectional view taken along line inJ. 6 figure 1
1 is a visual loss diagram. 4... Grid space (cell), Death... Support grid,
10... Rigid support part (dimple), 11...
... Elastic support part (spring part), 22 ... Deformation bar,
23... Drive shaft (long member), 24... Expansion solar mechanism, 26... Plate-shaped portion C plate member), 27.
40...Plate spring part, 29...Strain gauge,
36...Elastic connection member, 37...Roller mounting body, 44...Roller box, 46...
roller. Applicant Mitsubishi Yoko Fuel Co., Ltd. - Figure 4 B shown in Figure 1

Claims (1)

[Claims] An elastic plate member extending in the vertical direction and having a strain gauge attached to the lower end, a long member provided on one side of the plate member so as to be movable up and down along the plate member, and a long member connected to the long member. , and is rotatably attached to a roller mounting body that fits into the plate member and is movable up and down along the plate member so that the outer peripheral surface protrudes from the roller mounting body on the opposite side to the plate member. and an elastic connecting member having an elastic portion formed in the intermediate portion thereof, and is characterized in that it is inserted into a support grid to deform the spring portion of the support grid and the plate member. Sensor for measuring support grid spring force.