JPH05232286A - Measuring apparatus of dimensions of channel box - Google Patents

Abstract

(57) [Summary] [Purpose] In a channel box dimension measuring device in which a sensor or probe for measuring the amount of deformation or oxide film thickness is attached to a frame inserted in a CR rack, The shaking is prevented and the measurement can be performed accurately. [Structure] A channel box (4) to be inserted into the frames (1) and (2) is laterally supported by an upper frame (2) above a lower frame (1) of a measuring device, and the channel box (4) is supported. It has a structure in which a roller (5) rotatable in the insertion direction of (4) is provided so as to face each other with the channel box (4) interposed therebetween.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a channel box dimension measuring device for measuring deformation and oxide film thickness of a channel box which has already been used in a nuclear power plant, installed in a spent fuel storage pool. Is.

[0002]

2. Description of the Related Art The core of a boiling water reactor (BWR) in which a channel box is used is composed of a plurality of fuel assemblies, control rods, etc., and the fuel assemblies are a large number of fuels arranged in a square matrix. It has a structure in which the rod is housed in the channel box.

The above-mentioned channel box is deformed, such as bulging, bending, or twisting, with time due to the influence of fast neutron flux in the core and nonuniformity of material properties of the channel box due to long-term operation of the reactor. It causes, but when the amount of deformation of this channel box increases,
The passage of the control rod may be narrowed and its insertion and withdrawal may be hindered. Therefore, the deformation of the channel box is extremely important when considering the safety of the reactor. Need to be kept.

When the channel box made of a zirconium alloy is significantly corroded, the thickness of the channel box is reduced and the strength of the channel box is lowered.
This may impair the safety of the nuclear reactor. Furthermore, if the thickness of the oxide film accompanying this corrosion grows beyond a certain value,
The oxide film peels off from the surface of the channel box and falls into the inside of the reactor, which causes an increase in the radiation dose inside the reactor. Therefore, the corrosion of the channel box is one of the factors that influence the life of the channel box, and it is necessary to understand the progress of corrosion.

Therefore, in order to judge whether or not a channel box used for a certain period can be reused, it is necessary to accurately know both the deformation of the channel box and the amount of corrosion. Similarly, the amount of corrosion is determined by, for example, the measurement of the oxide film thickness by an eddy current sensor.

[0006]

By the way, the measuring device used for the above-mentioned measurement is often installed in a control rod storage rack (hereinafter referred to as a CR rack) in the spent fuel storage pool, and in this case, a channel box. The modification is performed by suspending the fuel assembly with the channel box attached by a fuel exchanger and lowering the fuel assembly inside the measuring device or while it is landed on the lower part of the measuring device. In the measurement while lowering the channel box, the channel box is held by contacting the channel fastener of the leaf spring structure provided on the top of the lattice box simulating the lattice plate and completely landing on the channel box. The box will always sway, and when landing, the channel box will Some fuels are held by the measuring device via a snner, but the fasteners are not attached by dropping or replacement, and those have to be measured without landing on the upper part even when landing. It has a problem that good measurements cannot be made.

In order to be able to measure the oxide film thickness at any position along the entire length of the channel box, if the oxide film measuring sensor is only on the upper part of the measuring device, the measurement should be carried out with the fuel suspended. However, even in such a case, the measurement is performed in a swaying state where the channel box is not held as described above.

The present invention has been made in order to cope with the above-mentioned actual situation, and by providing the measuring device with a support structure for the channel box, the swing of the channel box in the pool is suppressed, and the above-mentioned dimensions are provided. The purpose is to carry out the measurement more accurately.

[0009]

That is, the features of the channel box size measuring device of the present invention which meet the above-mentioned object are as follows.
In a dimension measuring device for a channel box, which is provided with dimension measuring means such as an ultrasonic sensor or a probe for directing to a channel box inserted in the frame at an appropriate position of a measuring device frame inserted in a CR rack, On the upper part of the device frame, a channel box to be inserted into the frame is supported from the side, preferably by urging, and rollers capable of rotating in the insertion direction of the channel box are arranged to face each other with the channel box interposed therebetween.
It's in a pair or more.

[0010]

In the measuring device of the present invention having the above-mentioned structure, the channel box inserted into the frame of the device is sandwiched and held by the rollers arranged so as to face each other, and in this state, the channel box is moved up and down, Alternatively, since it is possible to measure the dimensions such as deformation by landing on the floor, it is possible to prevent the channel box from swinging and to perform the above-mentioned measurement accurately.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view showing an upper frame of a channel box size measuring apparatus according to an embodiment of the present invention, and FIG. 2 is an overall view of a measuring instrument main body according to the embodiment. The apparatus is installed in water. It consists of a measuring device main body and a control unit (not shown) installed in the air. As shown in FIG. 2, the measuring device body is a cylindrical measuring device lower frame (1) which is inserted in a fitted state by externally fitting a guide pin (10) to a CR rack (R) in a spent fuel storage pool. And an upper frame (2) attached to the upper part of the lower frame (1). The lower part of the lower frame (1) can be fitted with the lower part of the channel box inserted as shown in FIG. Is formed.

An ultrasonic sensor (3) for measuring the amount of deformation (swelling, bending, twisting) is provided at a plurality of locations on the upper frame (2) and the lower frame (1), and at these frames (1) and (2). Channel box to be inserted (4)
It is installed in the direction of. The ultrasonic measurement is performed by inserting the channel box (4) into the main body of the measuring instrument by a fuel exchange machine, while continuously measuring the descending measurement by the ultrasonic sensor (3a) at the uppermost stage and landing the channel box (4). There is a static measurement in which the channel box (4) is measured while the measurement is performed, and the bulge of the channel box (4) is calculated by the downward measurement, and the bending and twist of the channel box (4) are calculated from the downward measurement data and the static measurement data. In each of the downward measurement and the static measurement, the fluctuation of the channel box affects the measurement accuracy, but if it is a small periodic fluctuation, there is no problem, but if the fluctuation is large and irregular, sufficient measurement accuracy cannot be secured. It will be. Therefore, in the present invention, by attaching a roller for holding the channel box (4) to the upper frame (2), it is possible to prevent shaking and perform accurate measurement.

That is, in the apparatus according to the embodiment of the present invention, as shown in FIG. 1, the upper frame (2) supports the channel box to be inserted from the side, and the channel box is inserted in the inserting direction, that is, in the vertical direction. Rollers (5) made of a rotatable elastic material are provided so as to face each other so as to sandwich a square tubular channel box from four sides. The rotating shaft (6) of the roller (5) is provided slidably in the horizontal direction,
The roller (5) is biased in a direction opposite to each other with a constant force so that the outer dimension of the channel box can be followed by the spring (7) and the channel box (4) can be automatically centered. .. By providing such a roller (5) on the upper frame (2),
Even if the channel box shakes before it is inserted into the measuring instrument body, the lower end of the channel box has rollers (5).
When the position reaches, the roller (5) presses the channel box, so that there is no shaking during measurement. The possibility of damaging the channel box is eliminated by making the roller (5) rotatable following the insertion / extraction of the channel box.

The device of the present invention can also measure the oxide film thickness on the surface of the channel box. The oxide film thickness is measured by bringing an eddy current probe or the like into contact with the surface of the channel box. In this embodiment, one oxide film measurement probe (8) is provided on each of the four faces of the upper frame (2). It has a moving mechanism (9) such as a hydraulic cylinder because it is provided and needs to be moved back and forth to come into contact with the channel box.

In order to measure the oxide film thickness at an arbitrary position in the axial direction of the channel box, the position to be measured is moved to the position of the oxide film probe (8) while the channel box is suspended by the fuel exchanger. Move
The probe (8) must be moved forward, but in this case as well, it is conceivable that accurate measurement cannot be performed because the measurement location or the contact angle changes when the channel box is swaying. However, even with respect to such a problem, by providing the roller (5) as described above, it becomes possible to measure the oxide film thickness at any place without shaking of the channel box.

The roller (5) is provided on the upper frame (2) as shown in FIG. 1 in order to improve the holding property.
It is preferable to arrange two rollers on one surface side by side, but the position of these rollers (5) interferes with the channel fastener (4a) provided at one corner of the upper end of the channel box (4). It should be set not to. Further, the roller (5) is installed at the same height as the channel fastener (4a) when the channel box (4) is landed as shown in FIG. 1, so that the channel box (4) has an actual core. It is also possible to have the same state as when supported at the height of the channel fastener inside.

[0018]

As described above, according to the channel box size measuring apparatus of the present invention, the channel box which is equipped with the probe and the sensor and which is inserted into the CR rack is disposed on the upper side of the frame. A roller that is supported by the channel box and that can rotate in the insertion direction of the channel box is provided so as to face each other with the channel box sandwiched therebetween. The swinging channel box is sandwiched by the rollers arranged facing each other, and the amount of deformation and the oxide film thickness can be accurately measured over the entire length of the channel box without shaking. When urged to dispose on four sides, guide the centering when inserting the channel box and insert in that state. In which a marked effect of the occupied reliably performed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an upper frame of a dimension measuring device for a channel box according to an embodiment of the present invention.

FIG. 2 is an overall view of a measuring device body of the same embodiment.

[Explanation of symbols]

 (1) Lower frame of measuring device (2) Upper frame of measuring device (3) Ultrasonic sensor (3a) Ultrasonic sensor (4) Channel box (4a) Channel fastener (5) Roller (6) Rotating shaft (7) Spring ( 8) Probe (9) Moving mechanism (10) Guide pin (R) CR rack

Claims (2)

[Claims] 1. A channel box provided with a dimension measuring means such as an ultrasonic sensor or a probe at an appropriate position of a measuring device frame which is inserted into a control rod storage rack so as to be oriented toward the channel box inserted into the frame. In the dimension measuring device, a roller that supports a channel box to be inserted into the frame from the side and is rotatable in the insertion direction of the channel box is provided on the upper part of the measuring device frame so as to face each other with the channel box sandwiched therebetween. A channel box dimension measuring device characterized in that 2. The channel according to claim 1, wherein the rollers are urged in directions opposite to each other by springs or the like, and the rollers are attached to four sides of the frame so as to support four sides of the channel box. Box size measuring device.