JPH0520719B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an in-core instrumentation tube loaded in a nuclear reactor core, and particularly relates to an in-core instrumentation tube with an improved support structure for the reactor core. Regarding piping.

(Prior Art) As is well known in the past, nuclear reactors are equipped with a neutron source region monitor (SRM), intermediate Detectors of the neutron instrumentation system (hereinafter referred to as neutron detectors) such as the area monitor (IRM) and the polar area output monitor (LPRM) are housed in the in-core instrumentation tube and are distributed, and the output parts of each part of the reactor core are be monitored. This type of in-core instrumentation tube is designed with consideration to the lifespan of the neutron detector, the irradiation life of the in-core instrumentation tube itself, etc.
They are replaced in a planned manner during periodic inspections.

Conventional examples of such in-furnace instrumentation tubes are shown in Figures 7 to 1.
It is shown in Figure 0.

As shown in FIG. 7, the in-core instrumentation tube 1 has a hollow and elongated instrumentation tube body 2, and a neutron detector (not shown) is housed within the instrumentation tube body 2. As shown in FIG. In the case of a boiling water reactor, the in-core instrumentation tube 1 is loaded vertically into the core 4 of the reactor pressure vessel 3, and one end (upper end) thereof is supported by an upper grid plate 5a serving as a core support plate. , the other end (lower end) passes through a core support plate 5b, which is a lower core support plate part, and is supported by an in-core housing 6 and an in-core flange 7 provided at the bottom of the reactor pressure vessel 3.

FIG. 8 shows the support structure for the upper end of the in-core instrumentation tube 1, and FIG. 9 shows the support structure for the lower end.

As shown in FIG. 8, a pressure contact portion 8 is provided at the upper end portion of the instrumentation tube main body 2. As shown in FIG. The pressure contact portion 8 is comprised of a support tube 9 slidably fitted into the instrumentation tube main body 2 and a compression coil spring 10 that urges the support tube 9 upward. A large diameter portion 11 is formed at the upper end of the support tube 9, and the large diameter portion 11 is press-fitted into a recess 12 provided on the lower surface of the upper lattice plate 5a by the elastic force of a compression coil spring 10.

Further, as shown in FIG. 9, a tapered portion 13 is formed at the lower end of the instrumentation tube main body 2, and the diameter gradually decreases toward the bottom. It is in pressure contact with the seat 14. This pressure contact force is obtained by the weight of the in-core instrumentation tube 1, the elastic force of the compression coil spring 10, the reactor water pressure, etc., and provides the tapered portion 13 and the seat 14 with a sealing action that sufficiently prevents leakage of reactor water. . The in-core housing 6 is integrally fixed to the bottom of the reactor pressure vessel 3 by welding or the like, and the in-core flange 7 is fixed to the in-core housing 6 with fasteners 15 such as bolts.

7 and 10 show the operation of attaching and detaching the in-core instrumentation tube 1 to and from the reactor core 4. As shown in FIG.

When installing, first, as shown in FIG. 10A, the in-core instrumentation pipe 1 is suspended by the overhead crane 16.
Then, as shown in Figure B, the lower end of the in-core instrumentation tube 1 is inserted into the in-core housing 6 through the gap in the upper grid plate 5a and the through hole 17 in the core support plate 5b. Thereafter, as shown in FIG. Insert the pressure contact part 8 of the tube 1. Note that when inserting the pressure contact portion 8 into the recess 12, the support tube 9 is pushed down at one end by the jig 19 against the elastic force of the compression coil spring 10, and the large diameter portion 11
This is done by positioning the jig 19 in the recess 12 and then opening the jig 19.

(Problems to be Solved by the Invention) In the conventional in-core instrumentation tube described above, one end (upper end) of the instrumentation tube body is connected to the upper grid plate 5 which is the core support plate.
A pressure contact portion 8 for pressure contact with a is constituted by a support tube 9, a compression coil spring 10, and the like. For this reason, the configuration of the pressure contact portion 8 is complicated and includes a large number of parts. In addition, due to long-term use, the large diameter portion 11 at the upper end of the support tube 9 may become stuck to the recess 12 of the upper lattice plate 5a, the compression coil spring 10 may deteriorate, etc.
The support tube 9 is crimped and fixed to the upper grid plate 5a, resulting in a so-called stuck state, which makes it impossible to perform the removal operation opposite to the above-mentioned mounting operation, and there are also problems such as the need to cut the instrumentation tube body 2 with a cutting device. be.

The present invention has been developed in view of these circumstances, and it is possible to simplify the structure of the pressure welding part, reduce the number of parts, and furthermore, it can be easily and reliably attached to and detached from the reactor core, eliminating problems such as static. The purpose is to provide an in-furnace instrumentation tube that does not require an in-core instrumentation tube.

[Structure of the invention]

(Means for Solving the Problems) The present invention houses a neutron detector in a hollow, long instrumentation tube body, and brings a press-contact portion provided at one end of the instrumentation tube body into contact with a core support plate portion. In the in-core instrumentation tube that is placed in contact with the reactor and loaded into the reactor, the pressure-welded part is made of a shape memory alloy, which has a shape memory that expands under high temperatures during reactor operation and contracts under low temperatures when the reactor is shut down. It is characterized by being given.

(Function) According to the in-furnace instrumentation tube according to the present invention, the pressure welded portion is made of a shape memory alloy, and the pressure welded portion is given shape memory that contracts at low temperatures and expands at high temperatures. In low-temperature conditions when the reactor is shut down, such as when installing or replacing the in-core instrumentation tube, it becomes loose relative to the supporting depressions formed in the core support plate, etc., and the in-core instrumentation tube attachment and detachment are difficult. can be done freely and reliably. In addition, under high temperatures during reactor operation,
Since the press-contact portion expands due to the shape memory effect, the expansion action causes the press-contact portion to come into pressure contact with a support depression, etc., and is securely fixed to the reactor core.

Therefore, there is no need to use support tubes, compression coil springs, etc. as in the prior art, and the structure is simple and the number of parts is reduced. In addition, since the shape memory effect is reliable, a situation such as sticking of the pressure contact portion to the support plate portion does not occur.

(Example) An example of the present invention will be described below with reference to FIGS. 1 to 6.

Figure 1 shows the reactor pressure vessel 21 of a boiling water reactor.
The reactor core 22 is loaded with in-core instrumentation tubes 23, and the reactor core 22 is shown to be at a high temperature due to reactor operation. As shown in FIG. 1, in this embodiment as well, the in-core instrumentation tube 23 is a hollow long instrumentation tube main body 2.
A neutron detector is housed in the instrumentation tube body 2.
4 is brought into contact with the upper lattice plate 26 which is the core support plate part, and the other end (lower end) of the instrumentation tube body 24 is passed through the core support plate 27 to in-core housing 28. The tapered portion 31 is brought into close contact with the seat 30 of the in-core flange 29.

In this thing, the pressure contact part 25 is the instrumentation pipe main body 2
It is a crown-shaped part made of a shape memory alloy that is fitted and fixed to the outer circumferential surface of 4. That is, the crown-shaped component serving as the pressure contact portion 25 has a cylindrical base portion 25a and a plurality of arm portions 25b protruding from one end thereof, and each of the arm portions 25b is radially moved by the shape memory effect. It is supposed to expand and contract. Note that a roller 25c is rotatably provided at each end of the arm portion 25b. The shape memory effect of the arm portion 25b is such that it expands under high temperatures during nuclear reactor operation and contracts under low temperatures when the nuclear reactor is shut down. As a result, under the operating state of the reactor shown in FIG. 1, the arm portion 25b expands in the radial direction and is in pressure contact with the recess 32 provided on the lower surface of the upper lattice plate 26 via the roller 25c.

FIG. 2 shows an enlarged view of the structure of the upper end of the in-core instrumentation tube 23 having such a pressure contact part 25, FIG. 3 also shows its planar shape, and FIG. 4 shows the entire upper grid plate 26. It shows the planar shape of .

As shown in FIGS. 2 to 4, an insertion hole 33 is provided at the intersection of the upper grid plate 26 corresponding to the installation position of the in-furnace instrumentation tube, which communicates with the center of the recess 32 for abutting the pressure welding part 25. It is drilled. Then, the instrumentation tube body 2
No. 4 is provided with an annular guide portion 34 at the distal end (upper end side) of the pressure contact portion 25, and the guide portion 34 is brought into sliding contact with the inner circumferential surface of the insertion hole 33.
As shown in FIG. 3, this guide portion 34 has pins 35 for preventing rotation protruding from each other at 90° intervals at different angles of 45° in the circumferential direction from the arm portion 25b of the pressure contact portion 25. Each of the pins 35 abuts against the corners on both sides facing the insertion hole 33 of the upper grid plate 26, thereby preventing rotation of the instrumentation tube body 24, and preventing the pressure contact portion 25 from rotating.
This prevents the arm portion 25b from coming off the recess 32 of the upper lattice plate 26.

Further, an instrumentation tube main body 24 is provided at the upper end of the guide portion 34.
A hanging ring 36 for lifting and lowering is provided.

Next, the action will be explained.

At low temperatures when the reactor is shut down, the arm portion 25b of the press-contact portion 25 contracts to a smaller diameter than the insertion hole 33 of the upper grid plate 26 due to the shape memory effect, as shown in FIG.

Therefore, when loading the in-core instrumentation tube 23 into the reactor core, as shown in FIG. 6A, an overhead crane 37
The suspension ring 36 is suspended by the above, and the in-core instrumentation pipe 23 is suspended from above the reactor pressure vessel 21 through the insertion hole 33 of the upper grid plate 26. Then, as shown in FIG. 6B, the lower end of the instrumentation tube body 24 is further lowered into the in-core housing 2.
8 and into the in-core flange 29. When suspended to the maximum extent, the arm portion 25b of the pressure contact portion 25 is placed in the recess 32 of the upper lattice plate 26, and
The guide portion 34 slides into the insertion hole 33, resulting in the state shown in FIG. Therefore, the hook 37a of the overhead crane 37 can be removed.

The above-mentioned operation of lifting and lowering the in-furnace instrumentation tube 23 only requires lowering it straight at the same location, and there is no need to move it in the lateral direction. Therefore, Figures 10 A to D
There is no need for complicated operations such as horizontal movement and mounting and fixing of the upper end of the in-furnace instrumentation tube to the upper grid plate using jigs as in the conventional example shown in Figure 2, making the installation process simpler than the conventional example. It becomes.

In addition, when removing it, it is sufficient to perform the operation in reverse to the above-mentioned mounting procedure, and in this case also, the removal work is significantly reduced compared to the conventional operation.

After the installation of the in-core instrumentation tube 23, when the inside of the reactor becomes high temperature by starting the reactor operation, the arm part 25b of the pressure welding part 25 expands due to the shape memory effect, and as shown in FIG. Then, as shown in FIG. 2, it is pressed against the recess 32 of the upper grid plate 26 via the roller 25c. As a result, the in-core instrumentation tube 23 is connected to the core 2.
2 and is securely fixed.

Moreover, even though the in-furnace instrumentation tube is easy to handle, the configuration of the pressure contact portion 25 as a fixing means is simpler than that of the conventional one, and the number of components can be reduced.

Furthermore, unlike the conventional structure, the arm part 25b of the pressure welding part 25 is reliably contracted as shown in FIG. A situation such as sticking to the grid plate 26 does not occur. Therefore, there is no need to cut the in-furnace instrumentation tube 23, and in this sense as well, work efficiency can be improved, and this also contributes to reducing radiation exposure and improving safety.

In the embodiment described above, a guide part 34 is provided at the upper end of the instrumentation tube main body 24, and this guide part 34 is inserted into the insertion hole of the upper grid plate 26, and the in-furnace instrumentation tube 23 is lifted up through the suspension ring 36. Although the attachment and detachment can be performed only by hanging, this is the most desirable embodiment, and the present invention is not limited to this. In addition, it may be attached and detached from the side with respect to an upper lattice plate provided with only depressions, as in the conventional case.

Further, the configuration of the pressure contact portion 25 is not necessarily limited to the shape shown in the above embodiment, but may be implemented in other shapes. In short, the pressure contact portion may have any structure as long as it can be supported in contact with the core support plate portion such as the upper grid plate 26.

〔Effect of the invention〕

As described above, according to the in-core instrumentation tube according to the present invention, the press-contact portion for abutting and supporting the core support plate portion is made of a shape memory alloy, so that the in-core instrumentation tube has a relatively simple configuration. In addition, it is possible to reliably attach it to the reactor core with a configuration that has a small number of parts, and it also has the advantage of being able to prevent sticking and the like.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of the in-core instrumentation tube according to the present invention, FIG. 3 is a plan view of FIG. 2, FIG. 4 is an overall plan view of the upper grid plate for inserting the in-furnace instrumentation tube of the present invention, and FIG. 5 is an enlarged view showing the compressed state of the pressure welding part. , Figure 6A,
B is an explanatory diagram showing the action, FIG. 7 is an overall configuration diagram showing a conventional example, FIG. 8 is an enlarged view showing the upper end configuration of a conventional in-furnace instrumentation tube, and FIG. 9 is also showing the lower end. The enlarged views and FIGS. 10A to 10D are explanatory diagrams showing the operation of attaching and detaching the conventional in-furnace instrumentation tube. 22... Core, 23... In-core instrumentation tube, 24... Instrumentation tube main body, 25... Pressure contact part, 26... Upper grid plate (core support plate part), 32... Hollow, 33... Insertion hole, 34... Guide part.

Claims (1)

[Scope of Claims] 1. A neutron detector is housed in a hollow long instrumentation tube body, and a pressure welding part provided at one end of the instrumentation tube body is brought into contact with a core support plate part to be inserted into a nuclear reactor. In the in-core instrumentation tube to be loaded, the pressure-welded portion is made of a shape memory alloy, and is provided with shape memory that expands under high temperatures during reactor operation and contracts under low temperatures during reactor shutdown. In-furnace instrumentation tube. 2. The instrumentation tube main body is provided with an annular guide portion on the distal end side of the pressure welding portion, and the guide portion is brought into sliding contact with the inner circumferential surface of the insertion hole drilled in the core support plate portion, so that the instrumentation tube main body is The in-core instrumentation tube according to claim 1, which is supported in a core support plate portion through the insertion hole so as to be insertable and removable.