JPS6359443B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for measuring the spacing between a large number of longitudinally mounted fuel elements constituting a nuclear fuel assembly.

Generally, nuclear fuel assemblies loaded into a nuclear reactor are
As the fuel elements continue to burn, individual fuel elements may become bent, resulting in changes in fuel element spacing.

If the above-mentioned interval becomes narrower due to such a change, it becomes difficult to perform appropriate water cooling in the vicinity of the fuel element, and an abnormal temperature rise occurs.

In addition, if such a change in spacing occurs, it may become impossible to reload a nuclear fuel assembly with a narrow fuel element spacing. must be inspected.

However, the conventional testing methods are
The irradiated nuclear fuel assembly in the tank was visually observed using an underwater television camera, and fuel element spacing was thereby inspected.

For this reason, according to the inspection, it is not only possible to obtain quantitative results and the inspection accuracy is extremely low because it is based on visual measurement, but also that it is not possible to visually inspect the fuel element spacing at the outermost periphery of the nuclear fuel assembly. Unfortunately, the internal fuel elements could not be inspected, and there were defects such as bends that could not be detected.

The present invention has been developed in various ways in view of these conventional difficulties.The present invention is designed to perform a swinging operation corresponding to the spacing between the fuel elements by swinging a swinging measuring rod inserted between the fuel elements. By converting the oscillation angle during the oscillation into the output of the eddy current meter displacement meter, it is possible to measure the spacing quantitatively and with high reliability. By making the oscillating measurement rod freely insertable up to 100 degrees, and by operating the rod in an oscillating manner, other fuel elements do not interfere with the measurement of the relevant spacing, making it possible to measure all fuel element spacings. It attempts to make it possible.

To describe the present invention in detail with reference to the drawings, as shown in FIG. 1, an inspection stand 3 is installed in an underwater tank 1, and a nuclear fuel assembly as shown in FIG. 2 is mounted on the stand 3. 4 is provided with an assembly holder 5 that is mounted vertically, and the holder 5 illustrated in the drawing has a lower chuck 5' fixed to the base 6,
The upper chuck 5'' is composed of pillars 7, which are erected on both the left and right sides of the front.
7', and a movable part 10 that is movable up and down relative to the base 8 by a drive motor 9 and can be moved left and right (back and forth in FIG. 1).

Furthermore, the inspection stand 3 is equipped with a scanning base 11 which can be driven up and down in parallel with the longitudinal axis of the nuclear fuel assembly 4 vertically held by the assembly holder 5, and the scanning base 11 is equipped with a scanning base 11 which can be driven up and down in parallel with the longitudinal axis of the nuclear fuel assembly 4, which is vertically held by the assembly holder 5. For this purpose, a screw rod 13 rotated by a drive motor 12 is installed vertically between and parallel to the pillars 7 and 7', and by driving the screw rod 13, the scanning base 11 is moved between the pillars 7 and 7'. It is designed to move up and down using the guide.

The scanning base 11 has fuel elements 14, 14 of the nuclear fuel assembly 4 vertically mounted and held therebetween.
Swing measuring rod 1 that can be attached and detached from the side as shown in the figure
In this case, if necessary, the measuring rods 15 can be installed in parallel for the number of intervals of the fuel elements 14, 14, etc., thereby making it possible to measure a plurality of intervals at once.

The basic embodiment of the oscillating measuring rod 15 shown in FIG. At the same time, a metal plate 18 is provided on the base end side of the rod 16, which also protrudes downward along the axis.
By rotating the probe reciprocally as shown by arrows A and A', the probe 17 is tilted between the fuel elements 14, 14, . If the fuel element 14 is rotated until it comes into contact with the fuel element 14, the fuel element interval G
The probe 17 can be displaced by the swing angle Θ corresponding to the oscillation angle Θ.

In the present invention, an eddy current displacement meter 19 is provided opposite the surface of the metal plate 18, so that when the measuring element 17 is rotated by the swing angle Θ as described above, the metal plate 18 is Since the distance between the sensor surface 19' of the displacement meter 19 and the metal plate 18 changes, the strength of the eddy current generated on the surface of the metal plate 18 changes accordingly. This is taken out as an output of the eddy current displacement meter 19, and the output is introduced as an input to the measurement section 20.

Now, the configuration in which the swing measuring rod 15 is incorporated into the scanning base 11 will be explained using the embodiment shown in FIG. 5.
A transfer plate part 22 is engaged with the base part 21 of No. 1 through dovetail grooves 23, etc., and is movable reciprocally in the directions of arrows B and B' by a power source (not shown) and its transmission machine. The swing measuring rod 15 is rotatably supported by the fixed shaft bearing part 24 as described above, and the rotary shaft rod 16 provided with the gauge head 17 protrudes from the shaft bearing part 24 toward the screw rod 13 side. At the same time, on the base end side of the coaxial rod 16 extending rearward from the coaxial bearing part 24, an eddy current displacement meter 19 is provided on the metal plate 18 so as to project downwardly from the metal plate 18.

Further, in the illustrated example, a balance plate 25 is horizontally fixed to the above-mentioned extending portion of the rotary rod 16, and springs 26, 26' are interposed between the left and right ends of the balance plate 25 and the transfer plate part 22. When no rotational force is applied to the oscillating measuring rod 15, the measuring stylus 17 always returns to the origin (starting point) in an upright state.

In addition, in order to rotate the measuring rod 15 and cause the measuring element 17 to swing from side to side, the illustrated power transmission means includes a pair of upper and lower wind plates 27, 27 at the end of the rotating shaft rod 16. ' are provided protrudingly, these are housed in the air chamber 28, and this air chamber 28 is accessed from the outside.
This purpose is achieved by selectively applying wind pressure as shown by arrows C and C'.

Here, FIG. 6 shows another embodiment of the oscillating measuring rod 15, in which case the first measuring rod 15'
and a second measuring rod 15'', and the first side fixed rod 15' has a plate-shaped first measuring rod 17' protruding from the tip of a rotary shaft rod 16, similar to the one in FIG. Although not shown in FIG. 6, a first metal plate is provided on the proximal end side, whereas the second measuring rod 15'' is fitted onto the rotary shaft rod 16 so as to be rotatable. It consists of a rotary pipe 29, a second probe 17'' provided at its tip, and a second metal plate (not shown).

The first measuring stylus 17' and the second measuring stylus 17'' are moved from the double return origin where they are in contact with each other.
They simultaneously rotate in the left and right directions due to the wind pressure, etc., and by providing the eddy current displacement gauges 19 facing each other on the first and second metal plates, one operation corresponds to the swing angle Θ. This means that the configuration can be configured to obtain the desired output.

Therefore, in order to use this, as described above with reference to FIG. By moving in the directions B and B', the probe 17 of the oscillating measuring rod 15 is interposed between the fuel elements 14 and 14 to be measured as shown in FIG. The swinging operation of the probe 17 may be performed by a desired power source such as wind pressure as described above, and thus the entire fuel element spacing of the assembly 4 can be scanned over its entire length.

In this way, the eddy current displacement meter 19 can obtain an eddy current or eddy current voltage corresponding to the swing angle Θ, but the measuring section 20 in the next stage can display the eddy current voltage on a cathode ray tube or chart, for example. The difference between the images corresponding to the start and end points of the reciprocating oscillation of the probe 17 is read, and the readings obtained are based on the measurements of the metal plate 18 and the eddy current displacement meter 19. Since the sensor surface 19' and the sensor surface 19' are not in a parallel state but in an inclined state and are displaced opposite each other, the calibration distance with respect to the inclination of this metal plate is measured in advance, and by comparing and converting with this value, the true All you have to do is read it as an interval value.

Also, without using a cathode ray tube as mentioned above,
The measuring section 20 may be configured to A/D convert the output signal from the eddy current displacement meter 19, perform the A/D conversion on a computer, and output the signal as a digital value.

The present invention, as embodied by the above embodiments,
The inspection stand installed underwater in the pool is equipped with an assembly holder that vertically holds the nuclear fuel assembly and a scanning base that can be driven up and down parallel to the longitudinal axis of the nuclear fuel assembly. A removable oscillating measuring rod is provided between the fuel elements of the nuclear fuel assembly on the base body, and this oscillating measuring rod is rotated around the axis of the measuring rod by a desired power source. , the measuring head provided thereon can be brought into contact with each of the adjacent fuel elements, and the swing measuring rod is provided with a metal plate that rotates in conjunction with the swinging of the measuring head, A measuring section is provided which extracts an output corresponding to the oscillation angle Θ of the measuring head using an eddy current displacement meter installed opposite the metal plate, and determines the distance between the two fuel elements based on the output. Therefore, it is possible to quantitatively measure the fuel element spacing in the pool without any danger and perform highly accurate inspections.In addition, it is possible to carry out inspections over the entire length of the fuel elements, and it is also possible to perform oscillation measurements. The rod can be inserted not only between the fuel elements on the outer periphery of the nuclear fuel assembly, but also into the inside of the nuclear fuel assembly, and the rod can be inserted into the fuel element by swinging motion, so that when swinging, the rod can be inserted into the fuel element. The fuel element does not interfere with the movement, and therefore measurements can be carried out smoothly even when the fuel element is charged internally.

Furthermore, since there is no contact between the metal plate and the eddy current displacement meter, it is possible to combine durability and high accuracy, which results in reloading with new nuclear fuel assemblies and other nuclear fuel assemblies with different fuel histories. In this case, the appropriateness of the loading position can be accurately evaluated based on the quantitative value of the fuel element spacing, and it is possible to provide something that can be fully expected from the standpoint of preventing fuel damage.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side explanatory view showing the entire fuel element spacing measuring device according to the present invention, FIG. 2 is a partially cutaway perspective view showing an example of a nuclear fuel assembly to be measured, and FIG. The figure is an explanatory plan view showing the oscillating measuring rod of the device in use, FIG. 4 is a perspective view of the main part showing one embodiment of the measuring rod, and FIG. 5 is an illustration of the scanning base provided in the device. An enlarged perspective view of main parts showing an embodiment,
FIG. 6 is a perspective view showing the tip side of the swing measuring rod, which is different from FIG. 5. 1...Pool, 2...Underwater, 3...Inspection stand,
4... Nuclear fuel assembly, 5... Assembly holder, 11
... Scanning base, 14 ... Fuel element, 15 ... Oscillating measurement rod, 15' ... First measurement rod, 15'' ... Second
Measuring rod, 16... Rotating shaft rod, 17... Measuring head, 1
7'...First probe, 17''...Second probe, 18
... Metal plate, 19 ... Eddy current displacement meter, 20 ... Measuring section, 29 ... Rotating pipe.

Claims (1)

[Scope of Claims] 1. An inspection frame installed in the water of a pool includes an assembly holder that vertically holds a nuclear fuel assembly, and a scanning base that can be driven up and down parallel to the longitudinal axis of the nuclear fuel assembly. The scanning base is equipped with a removable oscillating measuring rod between the fuel elements of the nuclear fuel assembly, and the oscillating measuring rod is driven by a desired power source to move the axis of the measuring rod. By rotating the oscillating measuring rod around the center, the measuring stylus provided on the oscillating measuring rod can freely come into contact with both of the above-mentioned adjacent fuel elements. A metal plate that moves and rotates is provided, and an eddy current displacement meter installed opposite the metal plate extracts an output corresponding to the swing angle Θ of the probe, and the distance between the two fuel elements is determined by the output. 1. A fuel element spacing measuring device for a nuclear fuel assembly, characterized in that the fuel element spacing measuring device for a nuclear fuel assembly is provided with a measuring section that determines the length. 2. The oscillation measurement rod includes a rotating shaft rod, a plate-shaped measuring element protruding laterally along the axis from the tip thereof, and a measuring rod located on the base end side of the rotating shaft rod and extending laterally along the axis. A fuel element spacing measuring device for a fuel assembly according to claim 1, comprising a metal plate protruding from a metal plate. 3. The oscillation measuring rod is located on the base end side of the rotary shaft rod, and has a plate-shaped first measuring element that protrudes laterally along the axis from the tip of the rod. a first measuring rod consisting of a first metal plate projecting laterally; a rotary pipe rotatably fitted to the rotary shaft rod; and a rotary pipe protruding laterally along the axis from the tip thereof; and a plate-shaped second measuring element that can freely come into contact with the first measuring element, and a second metal plate that is located on the base end side of the rotary pipe and protrudes laterally along its axis. 2. The fuel element spacing measuring device for a nuclear fuel assembly according to claim 1, further comprising a second measuring rod.