JPH0261682B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gap measuring probe for continuously measuring gaps between, for example, rods standing in rows.

For example, in a nuclear reactor fuel assembly, a number of control rod guide tubes are inserted and fixed through a plurality of support grids spaced apart from each other, lower nozzles are attached to the lower part of the control rod guide tubes, and a number of control rod guide tubes are fixed to the support grids. After the fuel rods are inserted at predetermined intervals, an upper nozzle is attached to the upper end of the control rod guide tube.

Therefore, in the fuel assembly, the fuel rods are arranged in rows above the lower nozzle.

A large number of such fuel assemblies are loaded into the reactor core,
During use, cooling water flows between a large number of fuel rods, and heat is transferred to the cooling water from the fuel rods that generate heat. At this time, in order to effectively transfer heat from the fuel rods to the cooling water, it is necessary to maintain the gaps between the fuel rods, the control rod guide tubes, and the distance between the fuel rods to predetermined dimensions. Therefore, before using the fuel assembly, it is necessary to accurately measure whether the gaps between the fuel rods, the control rod guide tubes, and the fuel rod gaps are within allowable dimensional ranges.

However, each fuel rod gap is narrow, around 3 mm, and the control rod guide tube and fuel rod gaps are even narrower than each fuel rod gap, so it is difficult to measure the fuel rod gap at the back of the fuel assembly. must be measured deep inside the narrow control rod guide tubes and fuel rod gaps.

Therefore, a gap gauge attached to the tip of a wire, various other gap measuring devices have been used, and other new measurement methods have been devised, but each has its advantages and disadvantages, and is still not used. The reality is that nothing satisfying has emerged.

This invention was made in view of the above circumstances,
A pair of spacers facing each other on both sides of the tip of a thin elastic plate, and a probe tip that has elasticity and when free, the tip side opens in the thickness direction of the elastic plate and has a strain gauge on its inner surface and protrudes from the elastic plate. By attaching a probe tip between the rods, it is possible to accurately measure the narrow gap between the rods at the back of the rows of rods by inserting a probe tip between the rods and observing the change in resistance of the strain gauge caused by the deformation of the probe tip. The purpose of the present invention is to provide a gap measurement probe that can be used.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 9. Reference numeral 1 in FIG. 1 is a thin, approximately rectangular elastic plate, which is made of high-strength beryllium copper that has been heat-treated as a long plate with a thickness of 0.15 mm and a width of about 18 mm, and is highly elastic.

There are two rectangular window holes 2 at the tip of the elastic plate 1.
3 are formed slightly apart in the length direction of the elastic plate 1. A bent portion 1a is formed at the base of the elastic plate 1 by bending a portion of the base at a right angle. A pair of spacers 4 and 5 are fixed to the edges of the window hole 2, as shown in FIG. These spacers 4, 5
is a rectangular plate with a thickness of 0.4 mm. Spacers 4, 5
The dimension between each outer surface of is approximately 1 mm.

Also, on both sides of the portion between the window holes 2 and 3 of the elastic plate 1, chip spacers 6 and 7 are provided as shown in FIG.
and a pair of probe chips 8 and 9 are attached in an overlapping manner. Chip spacer 6,
7 is a rectangular plate made of beryllium copper with a thickness of 0.3 mm. The probe chips 8 and 9 are highly elastic plates made of beryllium copper with a thickness of 0.12 mm, and have a base that is the same shape and size as the chip spacers 6 and 7, and an elastic plate that protrudes from this base toward the spacers 4 and 5. It consists of a triangular part extending from 1. This triangular part has a uniform strength beam structure in which the bending stress is equal at any position of the triangular part, and the top thereof has slopes 10 and 11 as shown in FIG. It is formed. slope 10,1
1 is formed symmetrically with respect to the bisector of the apex angle of the triangular portion. Further, as shown in FIG. 2, the probe tips 8 and 9 are provided symmetrically with respect to the elastic plate 1, with their tips open so as to form a substantially V-shape as a whole. The tips of the triangular parts of the probe tips 8 and 9 are curved so that the elastic plate 1 side is concave as shown in FIG.
3 is formed. The rising height h of the arcuate portions 12, 13 when they are free is about 2.1 mm, and therefore the maximum distance between the outer surfaces of each of the arcuate portions 12, 13 is about 5.2 mm.

Further, strain gauges 14 and 15 are attached to approximately the center of the inner surfaces of the triangular portions of the probe tips 8 and 9 (side surfaces of the elastic plates 1). Lead wires 16 are connected to each of these strain gauges 14 and 15, and these lead wires 16 are passed through the window hole 3 and gathered on one side of the elastic plate 1, and are passed along the elastic plate 1. 1 and is connected to a connector 17 attached to the base end. Each lead wire 16 is made of an insulated wire, and is superimposed on the adhesive insulating tape 18 attached to the elastic plate 1, and is further covered with another adhesive insulating tape 18. By pasting it on the elastic plate 1
It is attached so that it does not move. In addition, on the surface of the elastic plate 1 opposite to the surface to which the lead wire 16 is attached with the adhesive insulating tape 18, as shown in FIG. An adhesive insulating tape 18 is attached. Note that the lead wire 16 connected to the connector 17 is connected so that a bridge circuit is assembled within the connector 17.
A bridgebox 19 is electrically connected to the bridgebox 19, and an amplifier 20, an analog-to-digital converter 21, and a gap measurement dimension display 22 are electrically connected to the bridgebox 19, as shown in FIG.

Therefore, when measuring the fuel rod gaps, control rod guide tubes, and fuel rod gaps in a fuel assembly, a gap measurement probe configured as described above is inserted into these gaps at its tip (probe tip 8, Insert from the side where 9 is attached. At this time, since the tips of the probe tips 8 and 9 are curved, they are smoothly bent inward and enter the gap between the fuel rods. When the probe tips 8 and 9 bend, the strain gauge 1
The electrical resistances 4 and 15 change, and the output of the bridge circuit passes through an amplifier 20 and an analog-to-digital converter 21 and is displayed on a gap measurement size display 22 as a fuel rod gap size measurement value.

To measure the gaps between the fuel rods deep inside the fuel assembly, measure the control rod guide tube and fuel rod gap, which are narrower than the gaps between the fuel rods, in the same manner as above, and then advance the gap measurement probe deeper into the gap. Then measure the gap between each fuel rod in the inner part in the same manner as above. In this case, the probe tips 8 and 9 at the tip of the gap measurement probe are curved, and the elastic plate 1 can be freely bent, so that the gap measurement probe can easily penetrate deep into the fuel assembly.

Furthermore, even when the gap measurement probe is inserted into a particularly narrow fuel rod gap, control rod guide tube, or fuel rod gap, the slopes 10 and 11 are formed at the tips of the probe tips 8 and 9 as described above. It is possible to avoid the tips of the probe tips 8 and 9 from coming into contact with each other.
can be protected.

Also, when the gap measurement probe enters each fuel rod gap, control rod guide tube, or fuel rod gap, if these gaps are very narrow (when narrower than the distance between the upper surface of spacer 4 and the lower surface of spacer 5 in Fig. 2).
In this case, the spacers 4 and 5 hit the fuel rod and control rod guide tubes, and the gap measurement probe cannot be advanced beyond that position. Therefore, even in this case, damage to the probe tips 8 and 9 can be prevented.

In addition, since the probe tips 8 and 9 have a triangular structure with equal strength as described above,
When the probe tips 8, 9 are bent, the bending stress is the same at any position of the triangular part, and therefore, there is a slight bending stress due to a deviation in the mounting position of the strain gauge to the probe tips 8, 9. It is also possible to prevent gap measurement errors from occurring.

In addition, a gap measurement probe is inserted into the gap between the fuel rods and the gap between the control rod guide tube and the fuel rod and meandering, and the contact state of the probe tip 8 with the fuel rod or control rod guide tube and the contact condition of the probe tip 9 with the fuel rod or the control rod guide tube are measured. Even if the resistances of the strain gauges 8 and 9 are different, since the resistances of the strain gauges 8 and 9 are combined by the bridge circuit, highly accurate measurement results can always be obtained.

The measurement range of the fuel rod gap and the gap between the control rod guide tube and the fuel rod can be changed by changing the sizes of the probe tips 8 and 9.

As explained above, according to the present invention, a thin elastic plate has a pair of opposing spacers on both side surfaces of the tip thereof, and has elasticity, so that when free, the tip side opens in the thickness direction of the elastic plate and creates a strain on the inner surface. Since the probe is equipped with a gauge and a probe tip protruding from an elastic plate, it is possible to easily and accurately measure the outer gap when inserted into a gap between rod-like bodies arranged in a row. It is possible to meander due to the elasticity of the elastic plate,
As a result, even if the passage consisting of the rod-shaped body gap is slightly curved or the width of this passage varies partially, even the narrow rod-shaped body gap at the back can be directly, continuously, and accurately measured. Furthermore, even if the state of contact of the probe tip with the rod-shaped body located on one side of the elastic plate is different from the state of contact of the probe tip with the rod-shaped body of the probe tip located on the other side of the elastic plate, both Since the resistances of the strain gauges installed on the probe tip are combined, highly accurate measurement results can always be obtained.Also, if the gap between the rods is very narrow, the spacer will hit the rod and it will not be possible to measure the gap further. Since the probe cannot be advanced, damage to the gap measurement probe can be prevented. Furthermore, since the probe tip has a triangular plate shape with an equal-strength beam structure, the bending stress is the same at any position on the probe tip when the probe tip is bent, so the stress on the probe tip is reduced. It is possible to prevent measurement errors caused by misalignment of the mounting position of the gauge.
In addition, since the tip of the probe tip is curved so that the elastic plate side is concave, when inserting the measuring probe between the rod-shaped bodies, the pair of probe tips will be caught on the rod-shaped body. Since they are bent in the direction of approaching each other without damaging the body or the probe tip, the measuring probe can be smoothly inserted between the rod-shaped bodies, making measurement easier.

[Brief explanation of drawings]

1 is a side view showing an embodiment of the present invention, FIG. 2 is a bottom view thereof, FIG. 3 is a side view of the probe tip, FIG. 4 is a sectional view of the probe tip, and FIG. 5 is a sectional view of the probe tip. FIG. 6 is a perspective view showing the relationship between the gap measuring probe and the rod-shaped body, and FIG. 7 is a schematic explanatory view showing the state in which the probe tip is inserted into the gap between the rod-shaped bodies. , 8th
The figure is a block diagram showing the connection of a display, etc. to the gap measuring probe. 1... Elastic plate, 4, 5... Spacer, 6, 7...
...Spacer for tip, 8, 9... Probe tip, 14, 15... Strain gauge.

Claims (1)

[Claims] 1 Opposed to both sides of the distal end of a thin elastic plate, spacers are arranged in pairs sequentially from the distal end to the proximal end of the elastic plate, and have elasticity so that when free, the distal end side opens in the thickness direction of the elastic plate. A pair of probe tips protruding from an elastic plate provided with a strain gauge on the inner surface is attached, and an electric circuit is connected to the probe tip, and the probe tip has a triangular plate shape with a structure of equal strength beams. , and a tip of the probe tip is curved so that the elastic plate side is concave, and the gap is measured by inserting the probe tip into the gap.