JPH0261593A - Self-actuation type electromagnet for control rod holding mechanism - Google Patents

Abstract

PURPOSE:To surely cut off control rods at the time of temperature abnormal increase by incorporating heat sensitive magnetic materials among a coil and all the attraction faces. CONSTITUTION:A first iron core is rotation symmetry, structure in which a center leg part 20a and a peripheral cylindrical part 20b are connected in the upper part thereof is made and a coil is wound on the center leg part 20a. The lower end faces of the leg part 20a and the cylindrical part 20b are attraction faces respectively and a second circular plate-like iron core 22 which becomes are an armature is attracted. Further, respective heat sensitive magnetic materials 26a, 26b are provided between a coil attaching part and an attraction face of the iron core 20. In the case where temperature does not reach Curie temperature, magnetic flux which generates in the coil 24 almost passes in a magnetic circuit because the magnetic materials 26a, 26b are ferromagnetic substances and sufficient attraction works on an attraction face X, Y to hold control rods. Further, when circumstance temperature exceeds a Curie point, the magnetic materials 26a, 26b lose magnetization and the magnetic flux density of the attraction faces X, Y is remarkably lowered. As the result, the attraction decreases to cur off the iron core, which drops to stop a reactor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a self-actuating electromagnet that automatically inserts a control rod into a reactor core in order to emergency stop a nuclear reactor when an abnormality occurs.

To be more specific, the present invention provides temperature-sensitive magnetic materials between all the attraction surfaces of one iron core and the coil mounting portion, so that the residual magnetic flux above the Curie point is concentrated on a specific attraction portion. This invention relates to a self-actuating electromagnet for a control rod holding mechanism, which prevents this from occurring and increases the change in attraction force above the Curie point, thereby improving operational reliability.

[Prior Art] In general, fast reactors and the like are equipped with a mechanism for inserting control rods into the reactor core in the event of an abnormality in order to increase the reliability of reactor shutdown. In order to increase the reliability of this mechanism, a configuration has been proposed that uses self-actuating electromagnets to hold the control rods so that the reactor can be safely stopped without relying on external operations or signals. ing.

As shown in FIG. 7, a conventional self-actuating electromagnet combines a first iron core 10 and a second iron core 12, incorporates a coil 14 therein, and incorporates a temperature-sensitive magnetic material into a part of the iron core. 1
The two iron cores 10 and 12 are rotationally symmetric bodies, and the coil 14 is wound around the central leg of the first iron core IO. The temperature-sensitive magnetic material 16 is incorporated into the outer cylindrical portion of the cup-shaped second iron core 12 .

Such self-actuated electromagnets are installed in the high temperature coolant near the reactor core. When some abnormality occurs in the core and the ambient temperature rises to exceed the Curie point of the temperature-sensitive magnetic material 16, the temperature-sensitive magnetic material 16 loses its magnetism and the magnetic circuit is interrupted at that portion. Therefore, since the magnetic resistance of the entire magnetic circuit increases, the magnetic flux density passing through the attraction surfaces X and Y decreases. Therefore, the suction force decreases, and the second iron core 12 is separated from the first iron core 10 and falls due to the control rod's own weight. This is the operating principle of this self-actuated electromagnet.

[Problem to be solved by the invention] However, unlike an electric circuit, a magnetic circuit has a certain degree of magnetic permeability in space, so even if a part of the iron core is magnetically blocked, magnetic flux passing through the space remains. . This residual adsorption force is a major problem with this electromagnet. This is because in order to reliably disconnect the control rod, the suction force after disconnection must be sufficiently small compared to the control rod's own weight.

Figures 8A and B show examples of simulation results of magnetic flux distribution when the ambient temperature does not exceed the Curie point and when it exceeds the Curie point.
To simplify the drawing, only the right half of the magnetic flux distribution is shown. If the temperature-sensitive magnetic material 16 loses its magnetism and a part of the magnetic circuit is magnetically cut off by exceeding the Curie temperature, a large amount of magnetic flux will leak into space near the temperature-sensitive magnetic material 16 with high magnetic resistance. .

In terms of -a, the magnetic flux density is large in a portion close to the coil 14, and becomes smaller as it is closer to the cutoff portion. Since the attraction force depends on the magnetic flux density passing through the attraction surface, the attraction force after interruption will vary depending on the relative positional relationship between the attraction surface, the interruption section, and the coil.

In the case of the conventional shape, the magnetic flux density is small because the attracting surface Y is far from the coil 16 and close to the cutoff part, but the dividing surface X is far from the coil 16.
Since it is close to 4 and far from the cutoff part, the magnetic flux density remains quite large. As a result, a considerably large adsorption force remains even beyond the Curie point, which poses a problem in reliability as a reactor shutdown mechanism.

In order to reduce this residual adsorption force, methods such as reducing the cross-sectional area of the iron core in the central leg or creating a gap between the adsorption surfaces can be considered, but this would increase the magnetic resistance of the entire magnetic circuit, making the Curie The adsorption force under the steady state of operation below the point also decreases. A method of reducing the number of ampere turns will similarly reduce the suction force under steady operating conditions.

Therefore, as long as the basic structure as in the prior art is used, it has not been possible to reduce the adsorption force above the Curie temperature without sacrificing the adsorption force at the Curie temperature.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a system in which the suction force below the Curie point is sufficiently large, and the suction force above the Curie point is sufficiently small, so that there is no fear of malfunction during steady operation. The object of the present invention is to provide a self-actuating electromagnet for a control rod holding mechanism that can reliably disconnect the control rods when the temperature rises abnormally.

[Means for Solving the Problems] The present invention, which can achieve the above objects, includes an iron core and a coil with a structure that can be divided into two, and a temperature-sensitive magnetic material is incorporated into a part of the iron core to adjust the ambient temperature. In an electromagnet that holds and disconnects the control rod by adsorbing and separating the two iron cores, a temperature-sensitive magnetic material is placed between all the adsorption surfaces of the iron core on which the coil is attached and the coil mounting part. This is a self-actuated electromagnet for the control rod holding mechanism.

For example, one iron core is cut out at the center of a cylindrical body to create a roughly U-shaped structure, and a coil is wound around each leg of the core, and the winding of both coils is done at a certain point and on both suction surfaces. It is preferable to have a structure in which a temperature-sensitive magnetic material is provided in between, and the other iron core serving as the armchair is shaped like a disk.

[Function] With the above structure, when the ambient temperature rises above the Curie point of the temperature-sensitive magnetic material, the coil and all attraction surfaces are not directly magnetically short-circuited by the iron core, and all attraction surfaces are cut off from the coil. Ru. Therefore, the magnetic flux density of all the attraction surfaces is only a part of the magnetic flux that leaked into the space from the coil side of the temperature-sensitive magnetic material of the interrupting part.
The suction force is extremely small and almost no suction force is generated.Therefore, the change in suction force before and after the Curie point is extremely large, so there is almost no possibility of malfunction during normal operation, and the reliability of the disconnection operation when an abnormality occurs is increased.

[Embodiment] FIG. 1 is a sectional view showing an embodiment of a self-actuating electromagnet according to the present invention. Further, FIGS. 2A and 2B are explanatory diagrams showing the magnetic flux distribution below the Curie point and the magnetic flux distribution above the Curie point, and in order to simplify the drawings, only the right half of the magnetic flux distribution is drawn.

The first iron core 20 is a rotationally symmetric body, and has a structure in which a central leg portion 20a and an outer peripheral cylindrical portion 20b are continuous at the upper portion, and a coil 24 is wound around the central leg portion 20a. The lower end surfaces of the central leg portion 20a and the outer cylindrical portion 20b serve as suction surfaces, respectively, and a disk-shaped second iron core 22 serves as an armature.
adsorbs. Although not shown in the drawings, a control rod is actually suspended from the second iron core 22 as in the conventional case.

In this electromagnet, temperature-sensitive magnetic materials 26a and 26b are installed between the coil attachment portion of the first iron core 20 and the attraction surface, respectively.

As can be seen from FIG. 2A, when the Curie temperature is not reached, since the temperature-sensitive magnetic materials 26a and 26b are ferromagnetic, almost all the magnetic flux generated in the coil 24 passes through the magnetic circuit and is attracted. Face X.

At Y, the magnetic flux density is large and sufficient adsorption force is exerted.

This holds the control rod in place.

When the ambient temperature exceeds the Curie point, the temperature-sensitive magnetic materials 26a, 2
6b loses its magnetism, then as shown in Figure 2B,
Since the magnetic flux is bypassed before the attracting surface, the magnetic flux density at the attracting surfaces X and Y is significantly reduced. As a result, the adsorption force decreases, and the second iron core 22 is separated and falls due to the control rod's own weight, stopping the reactor.

However, in the case of such a structure, there is a problem that the temperature-sensitive magnetic material 26a installed in the central leg portion has inferior temperature responsiveness compared to the temperature-sensitive magnetic material 26b installed in the outer peripheral cylindrical portion. When quick operation is required, a more preferable structure is shown in FIGS. 3 to 5. FIG. 4 shows the IV-IV cross section in FIG. 3, and FIG. 5 shows the V-IV cross section in FIG. 3. A V cross section is shown.

In this embodiment, the first iron core 30 basically has the shape of a cylindrical body with a groove-like cutout in the center, and has a structure in which the legs 30a and 30b on both sides are continuous at the upper part. It is. A coil 34a is attached to each leg 30a, 30b.
, 34b are wound on the end suction surfaces of the two legs 30a, 30b, which attract the disc-shaped 20th iron core 32, which becomes the armature. Temperature-sensitive magnetic materials 36a and 36b are incorporated between them.

In addition, the magnetic flux distribution before and after the Curie point is shown in Figure 6A and B. When the ambient temperature is below the Curie point, almost all of the magnetic flux flows through the magnetic circuit, and the magnetic flux density on the attraction surface is high enough to generate a sufficiently large attraction force. On the other hand, when the ambient temperature exceeds the Curie point, the generated magnetic flux leaks through the space and bypasses it, so only a portion of the magnetic flux leaking into the space flows through the attraction surface. However, in this embodiment, the temperature-sensitive magnetic materials 36a and 36b are made longer, or both temperature-sensitive magnetic materials are made longer. If the dimension between 36a and 36b is narrower, the magnetic flux density on the attraction surface when the Curie point is exceeded can be further reduced.

[Effects of the Invention] In the present invention, as described above, temperature-sensitive magnetic materials are incorporated between the coil and all the attraction surfaces, so when the ambient temperature exceeds the Curie point, all the attraction surfaces are connected to the coil. Since the magnetic flux density is extremely small on all attraction surfaces, almost no attraction force is generated, and the reliability of disconnection in the event of an abnormality is significantly improved. In addition, by increasing the number of ampere turns and the cross-sectional area of the iron core, the adsorption force below the Curie point can be sufficiently increased, reducing the possibility of malfunction during steady operation and ensuring reliability as a self-operating electromagnet. Significantly improved.

In particular, it is preferable to make one of the iron cores have a U-shaped structure, since all the temperature-sensitive magnetic materials are located on the outside, resulting in good temperature response. Correspondingly, if the second iron core that serves as the armchair is made into a disk shape, the relative rotation between the first iron core and the second iron core can be taken into consideration when resetting the control rod after it falls. There is no need to do this, and there is no problem with workability.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of a self-actuating electromagnet according to the present invention, FIGS. 2A and B are explanatory diagrams showing the magnetic flux distribution before and after the Curie point, and FIG. An explanatory diagram showing an example, FIG. 4 is its rV-IV sectional view, and FIG.
The figure is a v--■ cross-sectional view, and FIGS. 6A and 6B are explanatory diagrams showing the magnetic flux density distribution before and after the Curie point. In addition, FIG. 7 is a sectional view showing an example of the prior art, FIG. 8A,
B is an explanatory diagram showing the magnetic flux density distribution before and after the Curie point. 10.20.30...first iron core, 12,22°32
...Second iron core, 14, 24.34a, 34b...
- Coils, 16, 26a, 26b, 36a. 36b...Temperature-sensitive magnetic material. Patent applicant: Power Reactor and Nuclear Fuel Development Corporation Representative, Shigeru Miyoshi 1st IIA 2゜31st! ! Figure 4 Figure 5 Figure Figure

Claims (1)

[Claims] 1. Equipped with an iron core and a coil with a structure that can be divided into two, a temperature-sensitive magnetic material is incorporated into a part of the iron core, and control is achieved by attracting and separating the two iron cores according to the ambient temperature. A control rod holding mechanism for an electromagnet for holding and separating rods, characterized in that a temperature-sensitive magnetic material is provided between all adsorption surfaces of the iron core on which the coil is attached and the coil attachment part. Self-actuated electromagnet. 2. One of the iron cores has a roughly U-shaped structure, with the center of the cylindrical body cut out, and coils are wound around each of its legs, and a temperature-sensitive sensor is installed between both coil attachment parts and both adsorption surfaces. 2. A self-actuating electromagnet according to claim 1, wherein a magnetic material is provided and the other iron core serving as the armature has a disk shape.