JP2000193782A - Helium leak inspection method and its device for nuclear fuel rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect helium leak from nuclear fuel rods and efficiently specify the position of the penetrated defects of the leakage. SOLUTION: Inspection ranges of a nuclear fuel rod 12 are separated in the length direction and initial helium leak inspection is conducted by using a vacuum chamber 18A having a length corresponding to the unit inspection range. In the case, as the results of the initial inspection, helium gas leak from the nuclear fuel rod 12 is detected, inspection is conducted in the range limited in the unit inspection range where helium gas leak is detected in the initial inspection by using a vacuum chamber 18B having a length corresponding to unit inspection range further separating the initial unit inspection range. In this manner, inspection is repeated by limiting in turn the leak part of helium gas in the previous inspection to specify the position of a penetrated defect of the nuclear fuel rod eventually with a specific width.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting helium leakage of a nuclear fuel rod, and more particularly to a method of detecting the presence and location of a penetration defect through which helium gas leaks. The present invention relates to a leak inspection method and a device therefor.

[0002]

2. Description of the Related Art Since nuclear fuel rods occupy an important factor in the safety of a nuclear reactor, their standards have been advanced and strict inspections have been carried out on many items under strict quality control. Among the inspection items, a leak test is specified for helium gas sealed inside the nuclear fuel rod. In this helium leak test, defects existing in the welded part of the end plug of the nuclear fuel rod and the cladding tube, etc. are specified. Helium gas leaks have been tested. In this type of helium leakage inspection, after a nuclear fuel rod is loaded in a vacuum vessel, the inside of the vacuum vessel is maintained at a high vacuum, and a leak detection device detects a leaked helium gas.

When leakage of helium gas is detected in a nuclear fuel rod, it is necessary to specify a helium gas leakage site in order to take measures. This is because the detection of helium gas by the leak detection device cannot identify the leak position in the nuclear fuel rod. Conventionally, the leakage site after the leakage of the helium gas is detected is visually inspected by an inspector, and is also performed by using an ultrasonic inspection method, an eddy current inspection method, or the like.

[0004]

The visual inspection method is a method in which an inspector visually searches for a defect present in the end plug welding portion of the nuclear fuel rod and the surface of the cladding tube, so that the inspection takes a very long time. . Even if a defect is found, it is difficult for an inspector with considerable experience to make an accurate judgment as to whether or not the defect is actually a penetration defect in which helium has leaked.

[0005] On the other hand, in non-destructive inspection methods such as ultrasonic inspection and eddy current inspection, a defect site can be identified in a short time by an automated inspection device. It may be difficult to determine whether or not. In such a case, it was not possible to determine whether there was a penetration defect or not unless a photograph of a cross section of the fuel rod was taken at the defect site. In addition, it was necessary to use different inspection devices for the cladding tube and the end plug welding part.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to solve the above-mentioned problems of the prior art and to make it possible to detect the leakage of helium and to specify the position of the leaking penetration defect efficiently. It is an object of the present invention to provide a method and an apparatus for inspecting a helium leak from a rod.

[0007]

To achieve the above object, the present invention relates to a helium leak inspection method for detecting helium gas leaking from a nuclear fuel rod and inspecting for penetration defects on a nuclear fuel rod basis. The inspection range is divided in the longitudinal direction of the nuclear fuel rod, the first helium leak inspection is performed using a vacuum chamber of a length corresponding to the unit inspection range, and as a result of the first inspection, helium gas is released from the nuclear fuel rod. If a leak is detected, use a vacuum chamber with a length equivalent to the unit inspection range obtained by further dividing the initial unit inspection range into equal units. An inspection limited to the inspection range is performed, and thereafter, an inspection for sequentially limiting the leaked portion where helium gas is detected in the previous inspection is repeatedly performed, and finally, a predetermined width is determined. Identifying the position of the through defects in nuclear fuel rods, it is characterized in.

In the above-mentioned inspection method, the first inspection uses a vacuum chamber having a length of half the length of the nuclear fuel rod,
Thereafter, a vacuum chamber having a length half of that of the vacuum chamber used in the previous inspection is used in the next inspection, and each time the inspection is performed, the helium gas leakage site is set to one unit of the previous unit inspection range.
It is preferable to sequentially limit the range to / 2.

The inspection apparatus according to the present invention for carrying out the above inspection method is a helium leak inspection apparatus for detecting helium gas leaking from a nuclear fuel rod and inspecting a penetration defect for each nuclear fuel rod. Chamber row in which a plurality of helium leak inspection vacuum chambers whose lengths are sequentially shortened are arranged in the length direction, and the nuclear fuel rods to be inspected are arranged by an arbitrary length in the arrangement direction of the vacuum chamber row. And a means for detecting helium gas leaking from the nuclear fuel rods.

In the above configuration, each of the vacuum chambers is composed of a divided type chamber divided into an upper chamber which can be moved up and down and a lower chamber mounted on a gantry.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a method and apparatus for inspecting helium leakage of a nuclear fuel rod according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic side view of a helium leak inspection apparatus according to one embodiment of the present invention. Reference numeral 10 indicates the entire helium leak inspection device. Reference numeral 12 denotes a nuclear fuel rod to be inspected.
The mounts 13 and 14 are longer than the nuclear fuel rods 12, and are installed in series in the length direction. Stand 1
A plurality of transport rollers 15 are provided on the sections 3 and 14 as means for transporting the nuclear fuel rods 12 at intervals. In this case, in the gantry 13, the transport rollers 15 are arranged so that the interval becomes narrower toward the downstream according to the length of a divided vacuum chamber described later, and in the gantry 14, they are arranged at a constant interval. . The nuclear fuel rod 12
The gantry 1 is supported laterally by the transport rollers 15.
3 move on. Each transport roller 15 is connected to a roller lifting device 16 so as to be able to move up and down.

FIG. 2 shows a divided vacuum chamber.
The vacuum chamber 18 is configured as a vacuum chamber having a cylindrical chamber having an inner diameter substantially equal to the outer diameter of the nuclear fuel rod 12 and having a longitudinal direction divided into two. In FIG.
Lower chamber 1 of a pair of upper and lower vacuum chambers 18
8a is shown. Reference numeral 19 denotes a sealing member for hermetically sealing the vacuum chamber 18.

As shown in FIG. 1, the lower chamber 18a
Constitutes one vacuum chamber in combination with the upper chamber 18b. On the gantry 13, a vacuum chamber row is formed by vacuum chambers having different lengths. In FIG. 1, in order to distinguish each vacuum chamber, 18A, 18B, 18C, 18
D, 18E and 18F. Each of these vacuum chambers is configured so that the length on the downstream side is half that of the adjacent length.

Each of the vacuum chambers 18A, 18B, 18C, 18D, 18
E and 18F are each supported by the support part 20 in a horizontal posture. In this case, the lower chamber 18a is fixed to the tip of the support 20 and the upper chamber 18b
Is mounted so as to be able to ascend and descend through a chamber elevating unit 21.

Each of the vacuum chambers 18A, 18B, 18
C, 18D, 18E, 18F are connected to an exhaust pipe 22, which is connected to a vacuum pump 23. The gas sucked by the vacuum pump 23 is supplied to the helium detector 24. This helium detector 24
Detects helium gas contained in exhaust gas.

Next, a method for inspecting helium leakage of a nuclear fuel rod by using the helium leakage inspection apparatus configured as described above will be described. FIG. 3 shows the operation of the vacuum chamber 18A for performing the first helium leak inspection with the half of the length of the nuclear fuel rod 12 as a unit inspection range.

In FIG. 3A, the conveying roller 15
The upper chamber 18b is in the raised position and moves the nuclear fuel rod 12 to the inspection position. When the front half of the nuclear fuel rod 12 reaches the lower chamber 18a, as shown in FIG.
6 lowers the transport roller 15 and places the nuclear fuel rod 12 on the lower chamber 18a.

Next, as shown in FIG. 3 (c), the upper chamber 18b is lowered to seal the inspection portion of the nuclear fuel rod 12 with the lower chamber. In this manner, in the vacuum chamber 18A in which the lower chamber 18a and the upper chamber 18b are closed, the gas inside is exhausted by the vacuum pump 23. The evacuation process is monitored by a control device (not shown). When the degree of vacuum in the vacuum chamber 18A reaches a predetermined value, the vacuum pump 23 stops and the evacuation ends. The helium detection device 24 performs a detection process calibrated by a standard sample, and detects a helium gas contained in the exhaust gas, if the helium gas is contained. The detection data is transmitted to an arithmetic unit (not shown) to make a pass / fail judgment.

If no helium gas is detected, it is determined that the gas passes, and the inside of the vacuum chamber 18A is opened to the atmospheric pressure. Then, in the order of FIGS. 3B and 3A, the upper chamber 18b and the transport roller 15 are raised, and are ready to move the other half of the nuclear fuel rod 12. When the other half of the nuclear fuel rod 12 moves above the lower chamber 18a, the inspection is performed in the same order as described above.

As a result of the inspection performed twice in the vacuum chamber 18A, if helium gas is not detected, the fuel rods 12 are transported to the adjacent pedestal 14 by the transport rollers 15 assuming that the fuel rods 12 have no defect. Inspection ends.

On the other hand, if the inspection in the vacuum chamber 18A is judged to be rejected, the nuclear fuel rods 12 are sequentially moved to the vacuum chambers 18B, 18C, 18D, 18E,
It is transported to 18F and inspected, and the position of the penetration defect of the nuclear fuel rod 12 is sequentially narrowed down to a narrow range.

As shown in FIG. 4A, the nuclear fuel rod 12
If there is a penetrating defect at the position indicated by the symbol x, the position of the penetrating defect is specified in the range of L / 2 by the vacuum chamber 18A having a half length L of the nuclear fuel rod 12.

Next, as shown in FIG. 4B, the inspection using the vacuum chamber 18B having a length of L / 4 is performed by dividing the range in which a defect is found in the previous inspection into two. Thereby, the range including the penetrating defect is narrowed to the range of L / 4.

Thereafter, by using a half length of the vacuum chamber of the previous inspection and inspecting a range where a defect is found in the previous inspection, in this embodiment,
Finally, it can be narrowed down to the range of L / 2. For example, if the length of the nuclear fuel rod 12 is 64 cm, the position of the penetration defect can be specified up to a width of 1 cm.

As described above, the position of the penetrating defect is 1c.
When the aperture is narrowed down to the m width, the vacuum chamber 18F shown in FIG. When the amount of movement is small in this way, a feed device 30 that can precisely feed the nuclear fuel rods 12 in the axial direction is provided separately from the transport rollers 15 instead of the transport rollers 15 for moving the nuclear fuel rods 12. Is preferred.

Although the embodiment of the present invention in which the length of each chamber of the vacuum chamber row is shortened by 1/2 has been described above, the present invention is not limited to this. It may be shortened by three. In the embodiment, six vacuum chambers are arranged. However, it is needless to say that the number of arrangements is appropriately determined according to the length of the nuclear fuel rods and the range of penetration defects to be finally narrowed down.

[0027]

As is apparent from the above description, according to the present invention, it is possible to efficiently detect the leakage of helium and specify the position of the leaked penetration defect efficiently at the site such as the cladding tube and the end plug welding portion. It can be done automatically without depending on it.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a helium leak inspection device for a nuclear fuel rod according to the present invention.

FIG. 2 is a perspective view showing a lower chamber of a vacuum chamber provided in the helium leak inspection device for a nuclear fuel rod according to the embodiment.

FIG. 3 is an operation explanatory view of the inspection device according to the embodiment.

FIG. 4 is a view for explaining a situation in which positions of penetration defects of a nuclear fuel rod are sequentially narrowed down in a vacuum chamber row.

[Explanation of symbols]

 Reference Signs List 10 helium leak inspection device 12 nuclear fuel rod 15 transport roller 16 transport roller elevating device 18 vacuum chamber 18a lower chamber 18b upper chamber 22 exhaust pipe 23 vacuum pump 24 helium detector

Claims (5)

[Claims] 1. A helium leak inspection method for detecting a helium gas leaking from a nuclear fuel rod and inspecting a penetration defect for each nuclear fuel rod, wherein an inspection range is divided in a longitudinal direction of the nuclear fuel rod, and the unit inspection is performed. Perform the first helium leak test using a vacuum chamber of a length corresponding to the range, and if the result of the first test indicates that helium gas leaks from the nuclear fuel rods, the first unit test range is further divided equally Using a vacuum chamber with a length equivalent to the unit inspection range, an inspection was performed to limit the leak site to the unit inspection range in the inspection range where helium gas was detected in the first inspection. It repeatedly performs inspections to sequentially limit the helium gas leakage sites detected in the inspection, and finally identifies the positions of penetration defects in the nuclear fuel rods with a predetermined width. For helium leakage from nuclear fuel rods. 2. In the first inspection, one half of the length of the nuclear fuel rod is used.
A vacuum chamber with a length of is used. Thereafter, a vacuum chamber of half the length of the vacuum chamber used in the previous test is used in the next test. 2. The method for inspecting helium leakage of a nuclear fuel rod according to claim 1, wherein the inspection range is sequentially limited to a half of the inspection range. 3. A helium leak inspection apparatus for detecting a helium gas leaking from a nuclear fuel rod and inspecting a penetration defect for each nuclear fuel rod, comprising: a plurality of helium leak inspection vacuums whose lengths are geometrically reduced in order. A vacuum chamber array in which chambers are arranged in the length direction, a transfer means for transferring the nuclear fuel rods to be inspected by an arbitrary length in the array direction of the vacuum chamber rows, and a helium gas leaking from the nuclear fuel rods Means for detecting helium leakage of a nuclear fuel rod. 4. The helium of a nuclear fuel rod according to claim 3, wherein the vacuum chamber rows are arranged such that the lengths of the respective vacuum chambers are sequentially reduced to １ ／. Leak inspection device. 5. The vacuum chamber according to claim 4, wherein each of the vacuum chambers comprises a divided chamber divided into an upper chamber which can be moved up and down and a lower chamber mounted on a gantry. Helium leak inspection system for nuclear fuel rods.