JP3002384B2 - Contact-type displacement measurement mechanism for fuel assemblies in reactors - Google Patents

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 system capable of measuring the displacement of a fuel assembly for a nuclear reactor without removing the fuel assembly from the nuclear reactor, without removing the fuel assembly from the reactor. It concerns 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 Fuel assemblies are displaced and deformed during operation of a nuclear reactor by various factors. It is extremely important to accurately grasp the behavior of such a fuel assembly for safely operating a nuclear reactor. However, in a fast reactor using liquid sodium as a coolant, the fuel assemblies are 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 an ordinary method such as that performed in a nuclear reactor using cooling water.

[0003] Refueling is performed as shown in FIG.
As shown in FIG. 1A, the gripper 10 of the fuel handling machine is moved to a predetermined position, and is slowly lowered with the claws 12 closed to be inserted into the handling head 14 at the top of the fuel assembly. Then, as shown in B of the same figure, the claws 12 are opened, the fuel assembly is grasped, and the fuel assembly is lifted. 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, if the gripper 10 and the handling head 14 are misaligned due to deformation and displacement of the fuel assembly even if the fuel assembly is positioned at a regular position (reference address position) of the fuel assembly (see FIG. This is because even if the gripper 10 of the fuel handling machine is lowered, it cannot be inserted into the handling head 14 when the gripper 10 of the fuel handling machine is lowered.

Conventionally, in a fast reactor using liquid sodium as a coolant, as a method of measuring the displacement of the fuel assembly, a gripper position of a fuel handling machine is intentionally depressed as shown by an imaginary line b in FIG. Is deviated from the reference address position of the fuel assembly to be inspected to cause eccentricity, causing a poor gripping (abnormal gripping position) condition. After finding the range that can be gripped, the central position of the handling head of the fuel assembly is calculated There is a way to ask.

[0005]

However, in this method, since a taper is provided at the upper part of the handling head, any of the gripper coming down and the taper portion of the handling head causes the taper near the misalignment limit. Even so, the gripper can be lowered, and the graspable range and the center position of the fuel assembly cannot be accurately evaluated.

Therefore, conventionally, a fuel assembly to be measured has been taken out of the reactor and measured. However, the method of taking out the fuel assembly from the reactor vessel and measuring its displacement / deformation requires a lot of time, and the work is extremely complicated and difficult. In addition, the displacement and deformation of the fuel assembly to be measured occur during the operation of the reactor, and in order to accurately grasp the behavior, measurement is most preferably performed in the reactor. However, there is also a problem that the original purpose of the measurement cannot be sufficiently achieved.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned disadvantages of the prior art, and to provide a simple, accurate, and reliable nuclear reactor of the type using 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 relates to a contact type displacement measuring mechanism for a fuel assembly in a nuclear reactor.
As shown in FIG. 2, a displacement measuring jig 20 hung by a gripper 10 of a fuel handling machine and insertable into a handling head 14 of a fuel assembly, and a displacement measuring ring provided below the inside of the handling head 14 It is composed of a combination of the parts 30. The displacement measuring jig 20 includes a gripper 22 that can be gripped and separated by the plurality of claws 12 of the gripper 10,
Below that, a column or cylindrical portion 24 for measurement that can be inserted into the hanging head 14 of the fuel assembly has a continuous structure. Further, the displacement amount measuring ring unit 30
Has a concentric staircase structure on its inner peripheral surface, the diameter gradually increasing as it goes upward. Then, the amount of misalignment is read from the amount of insertion of the gripper when the lower end of the displacement measuring jig 20 contacts the step of the displacement measuring ring 30.

[0009]

When the gripper of the fuel handling machine is positioned at a regular position (reference address position) of the fuel assembly for measuring the displacement, if the fuel assembly is deformed and the misalignment occurs between them, When the gripper of the fuel handling machine is lowered, interference (contact) occurs between the displacement measuring jig and the step-like displacement measuring ring. The fuel handling machine itself has a position detector and a load cell, and when interference occurs between the displacement measurement jig and the step-like displacement measurement ring during measurement, the load fluctuation 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 insertion amount (stroke) of the gripper.

[0010]

FIG. 2 is a detailed structural view 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. The contact-type displacement measuring mechanism is provided below the inside of the handling head 14 and a displacement amount measuring jig 20 that is suspended by the gripper 10 at the tip of the fuel handling machine and can be inserted into the handling head 14 of the fuel assembly. It is composed of a combination of the displacement measuring ring section 30.

The displacement measuring jig 20 includes a gripper 10.
The gripping portion 22 has a structure that can be gripped and released by opening and closing the claw portion 12 of the fuel assembly.
A circular cylindrical portion 24 for measurement which can be inserted into the inside has a continuous structure. In the upper part of FIG.
2 shows an open gripping state, and the right half shows a released state in which the claw portion 12 is closed. Here, the gripping portion 22 has a structure similar to the handling head 14 at the top of the fuel assembly, and has a groove 26 on the inner periphery where the end of the claw portion 12 of the gripper 10 fits. A misalignment prevention mechanism 28 is provided. The jig center misalignment prevention mechanism 28 maintains the center axis of the gripper 10 and the center of the cylindrical portion 24 so that the claw 12 of the gripper 10 is completely opened (gripped). The end portion of the claw portion 12 and the displacement measuring jig 20 are brought into line contact with each other so as to prevent a gap from occurring, and a function of preventing misalignment is achieved. Here, the shape of the ring is a ring having an arc-shaped cross section, but it is naturally necessary to correspond to the shape of the end face of the claw portion 12. Tubular part 24
As described above, the outer shape is circular, the diameter is φ ₀ , and the central axis thereof is coincident with the central axis of the grip portion 22.

The displacement measuring ring portion 30 has a concentric step structure on its inner peripheral surface, the diameter of which gradually increases as it goes upward. The number of stages is n here, and changes from φ ₁ to φ _n at a pitch of height h. The displacement measurement ring 30 is located between the main body portion of the fuel assembly and the top handling head 14. The displacement measuring ring section 30 is preferably processed integrally with the handling head 14. By integrally processing, it is possible to reliably prevent a flow failure due to a drop or the like.

In the contact displacement measuring mechanism of the present invention,
The amount of misalignment is read from the insertion amount (stroke) of the gripper when the lower end of the circular cylindrical portion 24 of the displacement measuring jig 20 contacts the step of the displacement measuring ring 30. Gripper 10
Is lowered at a regular position (without eccentricity at the reference address position). When the gripper 10 of the fuel handling machine is positioned at the regular position of the fuel assembly for measuring the displacement amount, if the fuel assembly deforms and the misalignment occurs between the two, the gripper 10 of the fuel handling machine is lowered. At this time, interference (contact) occurs between the lower end of the cylindrical portion 24 of the displacement measuring jig 20 and the step-like displacement measuring ring portion 30. Since the fuel handling machine itself has a position detector and a load cell, if interference occurs between the displacement measuring jig 20 and the displacement measuring ring 30 during measurement, the load of the load is measured. Fluctuation and the phenomenon that the fuel handling machine cannot be lowered can be confirmed.
The position of the gripper of the fuel handling machine at this time is detected, and the amount of misalignment is read from the insertion amount (stroke) of the gripper. Then, the range of the misalignment amount can be obtained from the following equation.

As shown in FIG. 2, the displacement measuring ring 3
When the step height pitch of the staircase of 0 is h, when the lower end of the cylindrical portion 24 of the displacement measuring jig 20 interferes with the first stage ring (inner diameter: φ ₁ ) of the displacement measuring ring portion 30. The position of S
₁ (confirmation by calculation and actual measurement), and assuming that the above read position is S ₂ , (a) when S ₁ = S ₂ （(φ ₁ −φ ₀ ) <center misalignment <1/2 ( φ ₂ −
φ ₀ ) (b) When S ₁ ≠ S ₂ | S ₁ −S ₂ | / h = n, that is, the difference in position is n (integer) times the pitch h of the stairs. , 1/2 (φ _{n + 1} −φ ₀ ) <center misalignment <1/2 (φ _{n + 2} −
φ ₀ ) ... After all, when S ₁ = S ₂ , n = 0, and the range of misalignment can be obtained 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 about 5 mm. However, if the position detection accuracy of the fuel handling machine is within ± 4mm,
5 mm to increase the number of steps from the viewpoint of further improving 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 assumed that the handling of the fuel assembly is not hindered, the total height of the displacement measurement ring portion 30 is determined, and the number of steps is determined by determining the stair height as described above.

As described above, the gripper 10 is basically lowered at a regular position (without eccentricity). However, in order to confirm the direction of eccentricity to some extent, the gripper 10 is repeatedly deliberately shifted from the regular position. By descending 10, it is possible to determine the center position of the true fuel assembly and determine the misalignment direction. The accuracy of the measured value depends on the number of steps and the inner diameter (φ _n ) of the displacement measuring ring. In this embodiment, the case where a step height having a constant pitch is employed in the displacement measuring ring unit 30 has been described. However, the step height of the stairs according to the accuracy of the position detector of the fuel handling machine may be arbitrarily applied. Is also possible.

In this displacement measuring mechanism, a handling head having a displacement measuring ring with a stepped displacement measuring ring is combined with a displacement measuring jig which can be fitted with a gripper of a fuel assembly. Therefore, 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 as in the conventional method, and to reduce the misalignment amount closer to the true value in the furnace. It becomes possible to measure.

[0018]

As described above, the present invention has the following advantages. Even in a nuclear reactor using an opaque coolant such as liquid sodium, measurement of displacement and deformation of the fuel assembly in the reactor vessel can be remotely performed. Measurement is easy and can be performed in the same manner and time as during normal refueling work. The structure is simple, and both manufacturing and maintenance costs can be reduced. The step-like displacement measuring ring portion added to the fuel assembly handling head can be mounted at a position where it does not hinder normal fuel handling, and because of the ring shape, the flow of the coolant passing through the fuel assembly. 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 step-like displacement measurement ring and a displacement measurement jig that can be fitted with the gripper of the fuel handling machine, the disadvantage of the conventional method is that the The operation of correcting the misalignment can be avoided, and the misalignment amount closer to the true value can be measured in the furnace.

[Brief description of the drawings]

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

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

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

FIG. 4 is an explanatory diagram of a handling state of a fuel assembly by a fuel handling machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Gripper 12 Claw part 14 Handling head 20 Displacement amount measuring jig 22 Gripping part 24 Cylindrical part 30 Displacement measuring ring part

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G21C 19/19

Claims (1)

(57) [Claims] 1. A combination of a displacement 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 measuring ring provided below the inside of the handling head. The displacement measuring jig has a structure in which a gripping portion that can be gripped and separated by the gripper and a measurement columnar portion or a cylindrical portion that can be inserted into the hanging head of the fuel assembly below the gripping portion are continuous. The displacement measuring ring has a concentric staircase structure on the inner peripheral surface, the diameter of which gradually increases toward the top, and the lower end of the displacement measuring jig contacts the step of the displacement measuring ring. A contact type displacement measuring mechanism for a fuel assembly in a nuclear reactor, wherein a misalignment amount is read from a gripper insertion amount at the time of contact.