JPH0434478Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to a device for measuring the hold-down spring force of BPA (burnable poison aggregate), which is one of the fuel inserts, and a thimble plug. .

(Prior art) There has been no device that can measure on-site the spring force and spring constant of the hold-down springs attached to the tops of BPA and thimble plugs.

The problem that the invention seeks to solve is to devise an on-site measurement device for the hold-down spring force of a fuel insert.

(Means for solving the problem) In general, BPA and thimble plugs are inserted into a fuel assembly in a storage rack of a spent fuel pit (hereinafter abbreviated as SFP), the upper part of which is shown in Figure 2. It is kept as such. 13 is
In the BPA, 11 is a hold-down ring at the top thereof, and 8 is a hold-down spring, which is inserted into the upper fuel nozzle 12. When the spring force of hold-down spring 8 weakens,
During operation, BPA can easily cause trouble such as vibration in the upper nozzle.

This device measures displacement and load by holding down the hold-down ring 11 with a hydraulic cylinder.

(effect) This will be explained in the following example.

(Example) An embodiment of this device will be described with reference to FIG.

The device is suspended by an SFP bridge crane, and the guide pins 1 are inserted into the holes 14 (see Figure 3) at the three upper corners of the upper fuel nozzle containing BPA. After this, the claw 2 is opened by the claw opening/closing cylinder 3, and the upper nozzle 12 is latched from the inside. Note that the claw 2 is closed by a return spring 10 until it is latched.

Next, after calibrating the differential transformer 5 for displacement measurement using the calibration cylinder 4, the measurement cylinder 6 is driven to push down the measurement bar 7 onto the hold-down ring 11 and hold it down. Deform the spring 8.

The displacement at this time is detected by the differential transformer 5, and the load is detected by the load cell 9, thereby measuring the spring constant.

The reason why the differential transformer 5 is calibrated using the calibration cylinder 4 is because the measured values of the differential transformer 5 may vary due to changes in the water temperature in the water or changes in the temperature of the fuel body. be.

The principle of differential transformer calibration will be explained based on FIG. 4.

When the calibration cylinder 4 is driven downward, the differential transformer 5 is similarly displaced. At this time, since the amount of movement by the cylinder 4 is known in advance, the output of the differential transformer is adjusted. At this time, the measurement bar 7 does not move. During measurement, the measuring cylinder 6 is driven to displace the hold-down spring 8 by the measuring bar 7. The displacement of the measuring bar 7 is detected by the calibrated differential transformer 5, and the calibration cylinder 4 does not move at this time.

It is sufficient to perform this calibration once before a series of measurements.

(Effects of the invention) Until now, on-site inspection of the spring force of BPA hold-down springs had not been conducted, but this device has made it possible.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of an embodiment of the measuring head of the device of the present invention, Fig. 2 is an explanatory view of the state in which BPA is inserted into the fuel, Fig. 3 is a top view of the upper nozzle, and Fig. 4
The figure is a diagram explaining the principle of the differential transformer calibration method. 1... Guide pin, 2... Claw, 3... Cylinder for claw opening/closing, 4... Cylinder for calibration, 5... Differential transformer, 6... Cylinder for measurement, 7... Measuring bar, 8... Hold Downspring, 9...
...Load cell, 10...Return spring, 11...Hold down ring, 12...Upper nozzle, 13...
…BPA.

Claims (1)

[Scope of utility model registration request] In a device for measuring the spring force of a fuel insert hold-down spring while the fuel insert having a hold-down spring at its upper part remains inserted into a fuel assembly in a spent fuel pit storage rack. , a measuring bar that comes into contact with the hold-down ring at the top of the hold-down spring and pushes it down; a measuring cylinder that drives the measuring bar; a differential transformer that measures the downward displacement of the measuring bar; the measuring bar pushes the hold-down spring down; A hold-down spring force measuring device for a fuel insert, characterized in that it has a load cell for measuring a pushing down load, and a calibration cylinder for calibrating the differential transformer for measuring the displacement.