JPH07306294A - Contact type displacement measuring mechanism for fuel assembly in reactor - Google Patents

Abstract

PURPOSE:To provide a mechanism for measuring the displacement of a fuel assembly conveniently, accurately, and surely while setting the fuel assembly, as it is, in a reactor even when an opaque coolant (e.g. liquid sodium) is employed. CONSTITUTION:The displacement measuring mechanism comprises the combination of a displacement measuring jig 20 suspended from the gripper 10 of a fuel handling machine and inserted into the handling head 14 of a fuel assembly, and a displacement measuring ring part 30 disposed at a lower part in the handling head 14. The jig 20 has a continuous structure of a gripping part 22 being gripped by the claw part of the gripper 10 and released therefrom, and a columnar or tubular measuring part 24 disposed under the gripping part 22 and inserted into the handling head 14 of fuel assembly. The ring part 30 is provided, on the inner peripheral surface thereof, with a concentric stepped structure having a diameter increasing gradually upward. Displacement is read out from the inserting amount of gripper when the jig 20 abuts, at the lower end thereof, against the step part of the ring part 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact type displacement measurement capable of measuring the displacement of a fuel assembly for a nuclear reactor without removing the fuel assembly from the reactor. It is related to the mechanism. This technique is particularly useful for detecting the position of a fuel assembly in a sodium cooled fast reactor.

[0002]

2. Description of the Related Art A fuel assembly is displaced / deformed due to various factors during a reactor operation. Accurately grasping the behavior of such a fuel assembly is extremely important for safe operation of a nuclear reactor. However, in a fast reactor using liquid sodium as a coolant, the fuel assembly is submerged in opaque sodium and cannot be observed with the naked eye. Therefore, it is difficult to measure the displacement of the fuel assembly by a normal method such as that used in a nuclear reactor that uses cooling water.

By the way, refueling is performed as shown in FIG.
As shown in A of the same figure, the gripper 10 of the fuel handling machine is moved to a predetermined position, and the claw 12 is closed and slowly lowered to be inserted into the handling head 14 at the top of the fuel assembly. Then, as shown in B of the figure, the claws 12 are opened, the fuel assembly is grasped and pulled up. In order to perform this operation smoothly, the position of the fuel assembly must be accurately grasped in advance. For example, the gripper 10 of a fuel handling machine
However, even if the fuel assembly is positioned at the regular position (reference address position) of the handled fuel assembly, the gripper 10 and the handling head 14 are misaligned due to the deformation and displacement of the fuel assembly (the same). This is because even if the gripper 10 of the fuel handling machine is lowered to the position indicated by the phantom line a in A of the figure), the situation in which it cannot be inserted into the handling head 14 occurs.

Therefore, conventionally, in a fast reactor using liquid sodium as a coolant, as a method for measuring the displacement of the fuel assembly, as shown by a virtual line b in FIG. 4A, the gripper position of the fuel handling machine is intentionally changed. By eccentricity by displacing from the reference address position of the fuel assembly to be inspected, a gripping failure (gripping position abnormality) condition is generated, the gripping area is found, and then the center position of the handling head of the fuel assembly is calculated. There is a way to ask.

[0005]

However, in this method, since the upper part of the handling head is provided with a taper, the action of the descending gripper and the taper part of the handling head may cause the misalignment limit to approach. Even if there was, the gripper could be lowered, and the gripping range and the center position of the fuel assembly could not be accurately evaluated.

Therefore, conventionally, the fuel assembly to be measured has been taken out of the nuclear reactor and measured. However, the method of taking out the fuel assembly from the reactor vessel and measuring the displacement / deformation of the fuel assembly requires a lot of time and has a drawback that the work is extremely troublesome and difficult. Further, the displacement / deformation of the fuel assembly to be measured occurs during the operation of the reactor, and in order to accurately grasp its behavior, it is most preferable to measure inside the reactor, and when it is taken out from the reactor. There was also a problem that the original purpose of measurement could not be achieved sufficiently.

The object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a simple, accurate, and reliable nuclear reactor of the type that uses an opaque coolant such as liquid sodium. Another object of the present invention is to provide a mechanism capable of measuring the displacement of a fuel assembly while being installed in a nuclear reactor.

[0008]

SUMMARY OF THE INVENTION The present invention is a contact type displacement measuring mechanism for a fuel assembly in a nuclear reactor.
As shown in FIG. 3, a displacement amount measuring jig 20 that is hung by the gripper 10 of the fuel handling machine and can be inserted into the handling head 14 of the fuel assembly, and a displacement amount measuring ring provided below the inside of the handling head 14. It consists of a combination of parts 30. The displacement amount measuring jig 20 includes a grip portion 22 that can be gripped and separated by the plurality of claw portions 12 of the gripper 10,
A columnar portion or a cylindrical portion 24 for measurement which can be inserted into the hulling head 14 of the fuel assembly is formed below the continuous structure. Further, the displacement amount measuring ring portion 30
Has a concentric staircase structure on the inner peripheral surface of which the diameter gradually increases toward the top. Then, the misalignment amount is read from the gripper insertion amount when the lower end of the displacement amount measuring jig 20 abuts on the step portion of the displacement measuring ring portion 30.

[0009]

When the gripper of the fuel handling machine is positioned at the regular position (reference address position) of the fuel assembly for measuring the displacement amount, when the fuel assembly is deformed, a misalignment occurs between the two. When the gripper of the fuel handling machine is lowered, interference (contact) occurs between the displacement amount measuring jig and the stepwise displacement amount measuring ring. The fuel handling machine itself is equipped with a position detector and a load cell, and when interference occurs between the displacement measuring jig and the step-like displacement amount measuring ring during measurement, fluctuations in load and The phenomenon that the fuel handling machine cannot be lowered can be confirmed, and the misalignment amount at this time is read from the gripper insertion amount (stroke).

[0010]

FIG. 2 is a detailed structural diagram showing an embodiment of a contact type displacement measuring mechanism for a fuel assembly in a nuclear reactor according to the present invention,
FIG. 3 is an explanatory diagram of the measurement state. This contact type displacement measuring mechanism is provided below the inside of the handling head 14 and a displacement amount measuring jig 20 which is suspended by a gripper 10 at the tip of the fuel handling machine and can be inserted into the handling head 14 of the fuel assembly. The displacement amount measuring ring unit 30 is combined.

The displacement amount measuring jig 20 comprises a gripper 10
The grip portion 22 having a structure that can be gripped and separated by opening and closing the claw portion 12 of the fuel assembly, and the lower portion of the gripping portion 14 of the fuel assembly below the grip portion 22.
A circular cylindrical portion 24 for measurement that can be inserted into the inside has a continuous structure. In the upper part of FIG. 2, the left half is the claw portion 1.
2 shows the gripped state in which the claw portion 12 is opened, and the right half shows the released state in which the claw portion 12 is closed. Here, the grip portion 22 has a structure similar to that of the handling head 14 at the top of the fuel assembly, and has a groove 26 in which the end portion of the claw portion 12 of the gripper 10 fits, and the jig is provided in the groove 26. A misalignment prevention mechanism 28 is provided. The jig misalignment prevention mechanism 28 keeps the center axis of the gripper 10 and the core of the tubular portion 24 aligned, and when the claw portion 12 of the gripper 10 is completely opened (grasped). The ends of the claws 12 and the displacement amount measuring jig 20 are brought into line contact with each other so as to prevent a gap from occurring, and the function of preventing misalignment is achieved. The shape here is a ring having an arcuate cross section, but it is, of course, necessary to correspond to the shape of the end surface of the claw portion 12. Tubular part 24
As described above, the outer shape is circular, its diameter is φ ₀ , and its central axis coincides with the central axis of the grip portion 22.

Further, the displacement amount measuring ring portion 30 has a concentric staircase structure on its inner peripheral surface, the diameter of which gradually increases toward the top. The number of stages is n here, and changes from φ ₁ to φ _n at a pitch of height h. The displacement measuring ring 30 is located between the main body of the fuel assembly and the top handling head 14. This displacement amount measuring ring portion 30 is preferably machined integrally with the handling head 14. By integrally processing, it is possible to surely prevent the flow obstacle due to dropping or the like.

In the contact type displacement measuring mechanism of the present invention,
The misalignment amount is read from the gripper insertion amount (stroke) when the lower end of the circular tubular portion 24 of the displacement measuring jig 20 abuts on the step portion of the displacement measuring ring portion 30. Gripper 10
Is basically lowered at a normal position (without eccentricity at the reference address position). When the gripper 10 of the fuel handling machine is positioned at the proper position of the fuel assembly for measuring the displacement amount, if the misalignment occurs between the two due to the deformation of the fuel assembly, the gripper 10 of the fuel handling machine is lowered. When this is done, interference (contact) occurs between the lower end of the tubular portion 24 of the displacement amount measuring jig 20 and the stepwise displacement amount measuring ring portion 30. Since the fuel handling machine itself has a position detector and a load meter, if interference occurs between the displacement amount measuring jig 20 and the displacement amount measuring ring portion 30 during measurement, the load It is possible to confirm the fluctuation and the phenomenon that the fuel handling machine cannot be lowered.
The position of the gripper of the fuel handling machine at this time is detected, and the misalignment amount is read from the gripper insertion amount (stroke). Then, the range of the misalignment amount can be obtained from the following formula.

As shown in FIG. 2, the displacement amount measuring ring portion 3
When the step height pitch of the stairs of 0 is h and the lower end of the tubular portion 24 of the displacement amount measuring jig 20 interferes with the first stage ring (inner diameter: φ ₁ ) of the displacement amount measuring ring portion 30. The position of S
₁ (confirmation by calculation and actual measurement), and the above-mentioned read position is S ₂ , (a) when S ₁ = S ₂ 1/2 (φ ₁ −φ ₀ ) <amount of misalignment <1/2 ( φ ₂ −
φ ₀ ) (b) When S ₁ ≠ S ₂ | S ₁ −S ₂ | / h = n, that is, the position difference is n (integer) times the stair pitch h, so the range of misalignment is , 1/2 (φ _{n + 1} −φ ₀ ) <center misalignment amount <1/2 (φ _{n + 2} −
φ ₀ ) ... After all, when S ₁ = S ₂ , n = 0, and the range of misalignment can be calculated from all the equations.

For example, in an actual design, the height h of the staircase structure of the displacement measuring ring portion 30 is set to about 5 mm. However, if the position detection accuracy of the fuel handling machine is within ± 4 mm,
5mm to increase the number of steps from the viewpoint of improving the measurement accuracy
The following is also possible. The change in the diameter of the staircase structure, and φ ₂ -φ ₁ = 2mm about, so that the misalignment amount per stage can be confirmed by 1mm accuracy. Since it is premised that the handling of the fuel assembly is not hindered, the total height of the displacement measuring ring portion 30 is determined, and the stair height is determined as described above, whereby the number of stages is determined.

As described above, the gripper 10 is basically lowered at the regular position (without eccentricity), but in order to confirm the direction of the eccentricity to some extent, the gripper 10 is intentionally shifted from the regular position and repeatedly grippered. It is also possible to obtain the center position of the true fuel assembly and obtain the misalignment azimuth by descending 10. The accuracy of the measured value depends on the number of steps of the stairs and the inner diameter (φ _n ) of the displacement measuring ring portion. In this embodiment, the displacement measuring ring unit 30 has been described as having a constant pitch step height. However, it is possible to arbitrarily apply the stair step height according to the accuracy of the position detector of the fuel handling machine. Is also possible.

In this displacement measuring mechanism, a handling head with a displacement amount measuring ring portion having a stepwise displacement amount measuring ring portion is combined with a displacement amount measuring jig that can be fitted by a gripper of a fuel assembly. Therefore, as in the conventional method, it is possible to avoid the action of correcting the misalignment of the fuel assembly due to the gripper being inserted into the handling head, and the misalignment amount closer to the true value in the furnace can be avoided. It becomes possible to measure.

[0018]

Since the present invention is configured as described above, it has the following effects. Even in a nuclear reactor that uses an opaque coolant such as liquid sodium, the displacement and deformation of the fuel assembly can be remotely measured in the reactor vessel. It is easy to measure and can be performed in the same procedure and time as during normal refueling work. The structure is simple, and the manufacturing cost and maintenance cost can be reduced. The staircase displacement measuring ring part added to the fuel assembly handling head can be installed at a position that does not interfere with normal fuel handling, and because of the ring shape, the flow of the coolant passing through the fuel assembly is The road can be secured. It can be used without changing the structure (shape) of the fuel handling machine. By combining a handling head with a stepped displacement measurement ring and a displacement measurement jig that can be fitted with a gripper of a fuel handling machine, the fuel assembly during measurement, which is a drawback of the conventional method, can be It is possible to avoid the effect of correcting the misalignment, and it is possible to measure the misalignment amount closer to the true value in the furnace.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a basic configuration of the present invention.

FIG. 2 is a detailed structural diagram showing an embodiment of a displacement measuring mechanism according to the present invention.

FIG. 3 is an explanatory diagram of a measurement state by the displacement measuring mechanism according to the present invention.

FIG. 4 is an explanatory diagram showing how a fuel handling machine handles a fuel assembly.

[Explanation of symbols]

 10 gripper 12 claw portion 14 handling head 20 displacement amount measuring jig 22 gripping portion 24 tubular portion 30 displacement measuring ring portion

Claims (1)

[Claims] 1. A combination of a displacement amount measuring jig, which is suspended by a gripper of a fuel handling machine and can be inserted into a handling head of a fuel assembly, and a displacement amount measuring ring portion provided below the inside of the handling head. The displacement amount measuring jig has a structure in which a gripping part that can be gripped and separated by the gripper and a measuring columnar part or a cylindrical part that can be inserted into the hulling head of the fuel assembly under the gripping part are continuous. The displacement amount measuring ring part has a concentric staircase structure in which the diameter gradually increases toward the top on the inner peripheral surface thereof, and the lower end of the displacement amount measuring jig contacts the step part of the displacement measuring ring part. A contact displacement measuring mechanism for a fuel assembly in a nuclear reactor, which is characterized by reading an amount of misalignment from a gripper insertion amount when contacted.