JPH0750075B2 - Pellet inspection method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pellet inspection method for inspecting a chip loaded in a fuel rod for chipping, dimensional abnormality, density abnormality, contamination of impurities, or the like.

"Prior Art" Generally, a pellet to be loaded into a fuel rod of this type is manufactured by forming a compact of a nuclear fuel powder such as uranium dioxide into a cylindrical shape and sintering it. Further, this type of pellet may have a chip on its outer periphery in the manufacturing process, and it is necessary to inspect it.

By the way, conventionally, the visual inspection of the pellets has been conducted visually by an inspector, and the inspection target is after sintering in order to surely eliminate defective pellets and enhance the requestability of the inspection. Spans all pellets.

[Problems to be Solved by the Invention] However, as described above, it is troublesome and extremely inefficient to visually inspect all the pellets after sintering, and the burden on the inspector is large. There is.

The present invention has been made in view of the above circumstances, and an object thereof is to reliably and smoothly inspect pellets for defects, dimensional abnormalities, density abnormalities, inclusion of impurities, etc. using an eddy current sensor. It is to provide a pellet inspection method capable of improving the work efficiency in addition to the above.

[Means for Solving the Problems] In order to achieve the above object, the present invention inserts a first guide tube inside an absolute value type eddy current sensor, and at the same time, inserts a first guide tube inside an absolute value type eddy current sensor. The second guide tube is inserted, the pellet is inserted into the first guide tube, the pellet is inspected by the absolute value type eddy current sensor, and then the pellet is inserted into the second guide tube. The pellet is inserted and inspected by the self-comparative eddy current sensor.

"Operation" In the pellet inspection method of the present invention, the pellet is first inspected by an absolute value type eddy current sensor,
Abnormality in pellet density, change in ferromagnetic impurity content, abnormal metal mixing, gadolinia (Gd) pellet mixing, outer diameter abnormality,
Then, the presence or absence of a defect is detected, and then an inspection by a self-comparative eddy current sensor is performed to detect the presence or absence of adhesion of pellet chips, abnormalities at right angles to end faces, abnormal shapes, chamfer abnormalities.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In the figure, reference numeral 1 is an absolute value type eddy current sensor for detecting an eddy current using one coil 2, and reference numeral 3 is a self-comparison type for performing an eddy current detection by differentially coupling a pair of coils 4. It is an eddy current sensor. Then, first and second guide tubes 5 and 6 are inserted into the eddy current sensors 1 and 3, respectively. Further, in the self-comparative eddy current sensor 3, in order to improve the sensitivity thereof, the clearance between the second guide tube 6 and the pellet P is set to be the same as the clearance between the first guide tube 5 and the pellet P. It is set smaller than that. The diameter of the inlet side of the second guide tube 6 is formed so that the pellet P can be easily inserted.
Further, the eddy current sensors 1 and 3 are arranged on the same straight line (on the conveying path of the pellet P) with a predetermined space therebetween.

Furthermore, on the upstream side of both eddy current sensors 1 and 3,
As shown in FIG. 2 and FIG.
A loading belt 7 and a pair of forced feed rollers 8 for conveying to the 6 side are installed, and both eddy current sensors 1,
An unloading belt 9 is installed on the downstream side of 3. And, in this unloading belt 9,
An abnormal product ejecting section 10 for laterally ejecting the pellet P determined to be abnormal is arranged.

When inspecting the presence or absence of abnormalities in the pellets using the pellet inspection apparatus configured as described above, first, the pellets P are placed on the loading belt 7 and conveyed, and
It is sandwiched between the forced feed rollers 8 and transferred to the absolute value type eddy current sensor 1 side. As a result, the pellets P moving in a state of being continuously arranged are inserted into the first guide tube 5, and the absolute value type eddy current sensor 1 causes an abnormal density, a change in the content of ferromagnetic impurities, a metal Detection of abnormal mixture, gadolinia (Gd) pellet mixture, outer diameter abnormality, and defect.

Next, the pellet P exiting the inside of the first guide tube 5 is placed on the unloading belt 9 and transferred, and in the abnormal product discharging section 10, it is judged as abnormal by the absolute value type eddy current sensor 1. The pellet P is discharged laterally, and the pellet P determined to be normal is sent to the self-comparison eddy current sensor 3 side.

Then, the pellets P sandwiched by the pair of forced feed rollers 8 and sent to the self-comparison type eddy current sensor 3 side are
Of the self-comparative eddy current sensor 3 inserted into the guide tube 6 of No. 3, and the pellet chip adherence, end face perpendicularity abnormality,
The presence or absence of abnormal shapes, abnormal chamfers, and defects is detected.

Subsequently, the pellet P exiting the inside of the second guide tube 6 is placed on the unloading belt 9 and transferred, and is determined to be abnormal by the self-comparative eddy current sensor 3 in the abnormal product discharge section 10. The pellets P that have been judged to be normal are conveyed as they are, while the pellets P that have been discharged are discharged laterally.

[Advantages of the Invention] As described above, according to the present invention, the first guide tube is inserted inside the absolute value type eddy current sensor, and the second guide tube is inserted inside the self-comparison type eddy current sensor. And inserting the pellet into the first guide tube and inspecting the pellet with the absolute value type eddy current sensor, and then inserting the pellet into the second guide tube. Since the pellet is inspected by the self-comparison type eddy current sensor, the pellet is first inspected by the absolute value type eddy current sensor, so that the density abnormality of the pellet, the change in the content of the ferromagnetic impurities, the abnormal metal mixture, Adhesion of pellet chips by detecting the presence of gadolinia (Gd) pellets, abnormal outer diameter, and defects, and then inspecting with a self-comparative eddy current sensor.
By detecting the presence or absence of an abnormal right angle at the end surface, abnormal shape, chamfer abnormality, and defect, it is possible to detect abnormal pellets reliably and smoothly, and it is possible to improve work efficiency. Have.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention,
FIG. 1 is a schematic explanatory view of a detection unit, FIG. 2 is a schematic plan view of a conveyance unit, and FIG. 3 is a schematic front view of the same. 1 ... Absolute value type eddy current sensor, 3 ... Self-comparison type eddy current sensor, 5 ... First guide tube, 6 ... Second guide tube, P ... Pellet.

Claims (1)

[Claims] 1. A pellet inspection method for inspecting pellets using an eddy current sensor, comprising: inserting a first guide tube inside an absolute value type eddy current sensor and at the same time inside a self-comparison type eddy current sensor. After inserting the second guide tube and inserting the pellet into the first guide tube and inspecting the pellet with the absolute value type eddy current sensor, the pellet is inserted into the second guide tube. And inspecting the pellet with the self-comparative eddy current sensor.