JPS62140094A - Method of detecting abnormal content of gadolinium (gd) of nuclear fuel pellet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention automatically detects nuclear fuel pellets that abnormally contain gadolinium, which are sent sequentially along a transport path. It relates to a detection method that can detect, in particular, a non-destructive method that utilizes the property that the electrical resistance of nuclear fuel pellets (hereinafter simply referred to as pellets) depends on the gadolinium content. This paper relates to a detection method that can perform continuous and continuous detection.

"Conventional technology" In order to balance the neutron density of nuclear reactor fuel,
Usually, pellets to which several percent of gadolinium (Gd) is added may be used.

In this case, it is extremely important to keep the gadolinium content constant in order to keep the quality of the pellets constant.

Therefore, gadolinium content is inspected during the pellet manufacturing process. In this case, the conventional detection method has been sampling inspection using chemical analysis techniques.

``Problem that the invention seeks to solve'' However, this inspection has the drawback of requiring manpower and time, and since it is a sampling inspection, it is not carried out on all pellets, and it is not possible to achieve complete control. The drawback was that it was difficult.

For this reason, there has been a strong desire to improve the reliability, speed up, and save labor of non-destructive testing.

Non-destructive testing methods such as magnetic analysis and eddy current testing can be considered as methods to meet these demands, but the former requires extremely extensive measurement methods and is difficult to detect if the pellets contain even a small amount of magnetic material. This method is difficult to put into practical use because the latter method has the disadvantage of causing errors in the measured values due to the influence of the latter method, and the latter method has the disadvantage of large errors due to differences in the shape of the pellets. Under these circumstances, the inventors of the present invention conducted extensive research and discovered that the electrical resistance of the pellets is highly dependent on the gadolinium content.

The present invention has been made based on this discovery, and provides a method for non-destructively and continuously detecting pellets that abnormally contain gadolinium using a relatively simple device. It is something to do.

``Means for Solving the Problems'' The present invention provides a roller in the pellet conveyance path that is pressed against the conveyed pellets with a required pressure and is rolled as the pellets are conveyed. , a pair of electrodes are provided on the outer periphery of the roller, and a pellet detector is provided in the conveyance path, the pellets sent on the conveyance path are detected by the detector, and based on this detection signal, the pellets are detected. A constant current is passed between the pair of electrodes that are in contact with each other, the voltage drop therebetween is measured to determine the resistance value of the pellet, and it is determined whether the resistance value is within a tolerance range determined in advance by experiment. The present invention is configured to detect whether or not the amount of gadolinium (Gd) contained in the pellet is abnormal.

“Examples” Examples of the present invention will be described below. 1 and 2 are diagrams showing an example of an apparatus for carrying out the present invention.

In Fig. 1, reference numeral l indicates a pellet conveyance path, and a cylindrical pellet P made on the upstream side of this conveyance path I is in a state in which the conveyance path 1 is tilted so that its axis is parallel to the pellet conveyance direction. The fuel rods are fed into a Zircaloy cladding tube (not shown) disposed downstream of the transport path 1, and used as reactor fuel rods.

A pair of rollers 2A12B are provided on both sides of the pellet conveyance path 1.
are arranged. These rollers 2A12B are made of a material having appropriate elasticity, such as urethane rubber, and the rollers 2A and 2B are rotatably supported via bearings 4 on shafts 3A and 3B that are orthogonal to the pellet conveying direction. (See Figure 2). The shafts 3A and 3B are supported by a bifurcated distal end portion 5a of a shaft support arm 5, and the base end side of this support arm 5 is supported by a shaft 6 arranged parallel to the shafts 3A and 3B.
It is rotatably supported by A and 6B. Further, a spring 7 is provided between the support arms 5.5, and is thereby biased in a direction in which both arms 5.5 approach each other. In other words, the rollers 2A12B are pressed against the pellet P with a required pressure by receiving a force that causes them to approach each other around the shafts 6A and 6B, and the pellet P is transferred at a constant speed and with a constant transfer force. When it is done, it is supposed to be rolled along with it.

The rollers 2A and 2B have outer circumferences as shown in FIG.
It is recessed in an arc shape corresponding to the outer circumferential shape of the pellet P, and electrodes 8A and 8B that electrically contact the pellet I) are provided at the center thereof along the entire circumference. Further, a ring-shaped conductor 9A is placed on the upper part of the rollers 2A and 2B.
9B is mounted coaxially to each roller, and these conductors 9A.

9B is a lead wire 10A connected to the electrodes 8A and 8B.

It is connected via 10B. In addition, the conductors 9A, 9
B is attached to the support arm 5 and is in contact with one electrode blank IIA, IIB;
IB is connected to a constant current power supply I3 and a voltmeter 14 via cords 12A and 12B, respectively.

Further, a detector I5 is provided on the pellet transport path 1, and the presence or absence of each pellet P being transported on the transport path 1 is detected by this detector I5.

Next, a case will be described in which the method of the present invention is implemented using the above-mentioned apparatus.

The pellets P that are sequentially transferred along the conveyance path l are transported by the roller 2.
When the roller 2A passes between A and 2B, it is pressed against the pellet P with the required pressure.

2B is rolled integrally. Moreover, when the pellet P passes both rollers 2A and 2B, it comes into contact with a pair of electrodes 8A and 8B.

A constant current power source 13 is connected to the electrodes 8A, 8B, and a constant current flows through the pellet P in contact with the electrodes 8A, 8B.

Here, the pellet P passing between the rollers 2A and 2B
is located exactly in the middle of the roller and its longitudinal center portion contacts both electrodes 8A, 8B, the pellet detector 15
detects this. At this time, based on the signal emitted from the detector I5, a constant current flows through the pellet I), and the voltage drop between the electrodes 8A and 8B is measured by the voltmeter 14. Find the resistance value of P.

The resistance value of the pellet P obtained in this way is
It is determined whether the amount of gadolinium contained in the pellet P is within the permissible range or not by determining whether it is within the permissible range determined in advance through experiments.

Next, based on this, the detector 15 is
If a pellet discharging mechanism (not shown) provided downstream of the rollers 2A and 2B is activated at the time when the pellet P abnormally containing gadolinium detected as described above is conveyed, the same effect can be achieved. Abnormal pellets P can be automatically discharged.

As described above, according to the present invention, it is possible to test all pellets P for abnormally containing gadolinium, and in addition, 1. This can be done continuously.

FIG. 3 shows another example of an apparatus for carrying out the method of the present invention.

In this example, above the conveyor belt 20, this belt 20
A roller 21 having appropriate elasticity and being able to roll freely is provided so as to be pressed against the pellet P conveyed by a predetermined pressure by a force such as a spring. Further, on the outer periphery of this roller 21, electrodes 22A and 22B, which form a pair with each other, are connected to the pellets F that are sent.
A plurality of sets are provided at predetermined intervals in the circumferential direction so as to correspond to t:I:1. These multiple electrodes 22A12
Among the electrodes 2B, the electrodes located directly below the roller 21 and both of which contact the pellet P are brushes 24A and 24B1 attached to the arm 23 for supporting the roller and cords 25A and 25B connected to the brushes 24A and 24B. Connected to constant current power supply and voltmeter via. Further, 26 indicates a pellet detector.

With this device, the present invention can be carried out in the same way as described above. Further, this device has only one roller 2I and only one arm 23, which simplifies the configuration compared to the device shown in FIGS. 1 and 2, which has two of them. It has the advantage that it can be made smaller.

In the above example, the roller is caused to roll by the frictional force with the transported pellets P, but it is also possible to provide a drive mechanism to the roller and forcibly rotate the roller 2. good.

"Effects of the Invention" As detailed above, the present invention provides the following advantages:
A roller is provided that is pressed with a required pressure against the conveyed pellets and rotates as the pellets are transported, a pair of electrodes are provided on the outer periphery of the roller, and a pellet detector is installed in the conveyance path. The pellets sent along the transport path are detected by the detector, and based on this detection signal, a constant current is passed between the pair of electrodes with which the pellets come in contact, and the voltage drop therebetween is measured. This is because the configuration is such that the resistance value of the pellet is determined, and it is determined whether the resistance value is within an allowable range determined by experiment in advance to detect whether or not the amount of gadolinium contained in the pellet is abnormal. , pellets containing abnormal gadolinium can be detected non-destructively and continuously, and can be used as an effective means for product inspection of pellets in the reactor fuel rod manufacturing process.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an example of an apparatus for carrying out the method according to the embodiment of the present invention, Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 is a method according to the present invention. FIG. 3 is a perspective view showing another example of an apparatus for implementing l...Pellet conveyance path, 2A, 2B...Roller, 5...Arm, 8A, 8B...Electrode, 13...Constant current power supply , 14... Voltmeter, I5... Detector, 20... Conveyor belt, 2I... Roller, 22A, 22B... Electrode, 26... ··Detector.

Claims (1)

[Claims] In the pellet conveyance path, a roller is provided which is pressed with a required pressure against the conveyed pellets and is rolled as the pellets are conveyed, and a pair of electrodes is provided on the outer periphery of the roller, and a roller is provided on the outer circumference of the roller. A pellet detector is provided inside, and the pellet sent on the conveyance path is detected by the detector, and based on this detection signal, a constant current is passed between the pair of electrodes that the pellet comes into contact with, and a voltage drop therebetween is caused. The resistance value of the pellet is determined by measuring the resistance value of the pellet, and it is determined whether the resistance value is within an allowable range determined in advance by experiment, and the gadolinium (G
d) A method for detecting abnormal gadolinium (Gd) content in nuclear fuel pellets, which comprises detecting whether the amount is abnormal.