JPH0786548B2 - Self-actuated electromagnet for control rod retention mechanism - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a self-actuating electromagnet for automatically inserting control rods into a core for emergency shutdown of a reactor when an abnormality occurs,
More specifically, the present invention relates to a self-actuating electromagnet for a control rod holding mechanism, which is provided with a mechanism for preventing seizure / fusion on the iron core adsorption portion of the split structure so that the control rod can be reliably separated. is there.

[Prior Art] Generally, a fast reactor or the like is provided with a mechanism for inserting a control rod into the core in the event of an abnormality in order to enhance the reliability of reactor shutdown. In order to increase the reliability of this mechanism, a configuration has been proposed in which a self-actuated electromagnet is incorporated so that the reactor can be safely shut down without depending on an external operation or a signal.

An example of this type of control rod holding mechanism is shown in FIG. 2A. A control rod 10 having a neutron absorber is located and held in a guide tube 12 in the core. The control rod holding mechanism consists of a drive shaft 14 and a self-actuating electromagnet 16 located at its lower end.
The control rod 10 is held by the magnetic attraction force of the electromagnet 16.

The conventional self-actuating electromagnet 16 has the first and second iron cores 18,2.
The configuration is provided with an iron core having a two-divided structure in which 0s are combined and a coil 22, and a temperature-sensitive magnetic material 24 is incorporated in a part of a magnetic circuit. Reference numeral 26 indicates a non-magnetic connecting material.

The self-actuating electromagnet 16 is placed in the high temperature coolant near the core. Therefore, if any abnormality occurs in the furnace, the ambient temperature rises, and the temperature-sensitive magnetic material 24 loses its magnetism in response to the abnormal temperature, and the magnetic attraction force between the iron cores 18 and 20 is reduced. As shown in FIG. 2B, the control rod 10 is cut off by its own weight to shut down the reactor.

[Problems to be Solved by the Invention] As described above, the self-actuating electromagnet has the iron core having a two-divided structure and can be adsorbed and separated. However, since the electromagnet 16 is installed in the vicinity of the core, the adsorption section will be kept in close contact at high temperature for a long time while receiving a high pressure due to the magnetic attraction force, and the burning at the contact surface between the iron cores in the adsorption section will occur. There is concern about attachment and fusion. Especially in fast reactors, the coolant is liquid sodium at a high temperature of 500 to 550 ° C, and it is known that remarkable fusion occurs between metals. This is an electromagnet 16
Means that even if the magnetic attraction force is lost when it should operate (when the temperature is abnormal), there is a risk that the suspended control rod 10 will not fall, and the reliability as a self-actuated reactor shutdown mechanism is remarkably high. Will be reduced.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to immediately improve the reliability of the self-actuated reactor shutdown mechanism by disconnecting the control rod when the electromagnet loses the magnetic attraction force. An object of the present invention is to provide a self-actuated electromagnet for a control rod holding mechanism.

[Means for Solving the Problems] In the present invention which can achieve the above object, a central magnetic path and an outer magnetic path form a magnetic circuit in which an upper part and a lower part are continuous, and the central part is divided into upper and lower parts. A combination iron core having a structure in which a magnetic path and an outer magnetic path each have an attracting portion, and a coil wound around the central magnetic path are provided. Accordingly, in an electromagnet that holds and disconnects the control rod, at least one of the two adsorbing portions where the iron cores adsorb to each other is made of ceramics so that the surface slightly protrudes from the adsorbing surface of both iron cores. The seizure material is embedded, and at least one of the seizure-resistant materials is connected to the iron core holding the seizure material so that the position of the seizure-resistant material can be adjusted in the axial direction of the control rod. A control in which a minute gap is formed between the cores. It is a self-actuating electromagnet for the rod holding mechanism.

As a more preferable structure, the flame-retardant material is formed into a ring shape and embedded in a metal ring, and the metal ring is screwed to one iron core so that the position can be adjusted in the axial direction of the control rod. There is a configuration to do. Alumina is the most suitable flame-retardant material.

It is possible to attach the flame-retardant material to at least one of the adsorbing portions of the iron cores as described above and to make a slight gap in the other, so that the gap can be finely adjusted by the screw type iron core. desirable.

[Operation] If the difficult-to-seize materials are embedded so that the surface protrudes, and the difficult-to-seize materials come into contact with each other in the adsorption part to form a small gap between the iron cores, even in high-temperature liquid sodium Even if it is placed in the place, seizure / fusion does not occur, and when the electromagnet loses its magnetic attraction force in an emergency, the control rod is immediately disconnected and falls. Therefore, the reliability of furnace shutdown is significantly improved.

By embedding a ring-shaped flame-retardant material in a metal ring and attaching it with a screw type so that the position can be adjusted with respect to one iron core,
It is possible to adjust the gap between the iron cores in the attraction portion to be sufficiently small, and it is possible to suppress the loss of the magnetic attraction force to be sufficiently small.

By the way, it is possible to attach a thin spacer made of flame-retardant material to the contact surface to avoid contact between metals.
The gap size allowed between the iron cores is about 0.1 mm, while the flame-retardant material is generally hard like ceramics, so it is not only difficult to process such thin spacers, Even if it does, it will crack easily due to the compressive force during use. It may be possible to form a thin film of a difficult-to-seize material on the iron core contact surface during thermal spraying or vapor deposition, but there is a very high risk of peeling from the iron core due to the difference in the coefficient of thermal expansion, and damage similar to the above will occur. Since it is easy, sufficient reliability cannot be obtained.

On the other hand, with the structure of the present invention, not only the assembly is easy, but also the mechanical strength is sufficiently high and the reliability is extremely high.

[Embodiment] FIGS. 1A and 1B are explanatory views showing an embodiment of a self-actuating electromagnet for a control rod holding mechanism according to the present invention, where A is a suction holding state and B is a separated state. Are shown respectively.

This self-actuating electromagnet includes a first iron core 30 and a second iron core 32.
And a coil 34. The first iron core 30 has a structure in which a central cylindrical portion 30a and an outer cylindrical portion 30b are continuously integrated at the upper portion. The second iron core 32 connects the upper cylindrical portion 40 and the lower cup-shaped portion 42 with a non-magnetic material 44, and
The structure is such that a cylindrical temperature-sensitive magnetic material 46 is provided in close contact with the outer surfaces of the cylindrical portion 40 and the cup-shaped portion 42 so as to surround it.

The present invention is significantly different from the prior art in that both iron cores 30 and 3
This is the structure of the adsorption part between the two. In the present invention, in at least one of the adsorption portions (indicated by reference numeral I), the difficult-to-burn materials 50 and 52 are embedded so that the surfaces thereof are slightly projected, and the difficult-to-burn materials 50 and 52 are in contact with each other, and the first and second The iron cores 30 and 32 are configured so as to have a minute interval, in other words, to be in a non-contact state.

In this embodiment, the difficult-to-seize material 50, 52 has a ring shape. One of the hard-to-seize materials 50 is embedded in the lower surface of the cylindrical portion 30b of the first iron core 30 so that the surface thereof slightly projects. The other flame-retardant material 52 is embedded in a metal ring 54 with its surface slightly protruding, and the metal ring 54 is attached to the second iron core 32.
Is connected to the cylindrical portion 40 of the screw type by screwing. Therefore, by rotating the metal ring 54, the lower surface of the cylindrical portion 30b of the first iron core 30 and the upper surface of the cylindrical portion 40 of the second iron core 32 are kept in contact with the hard-to-seize materials 50, 52. The gap can be finely adjusted.

As the flame-retardant material 50, 52, for example, when used in liquid sodium such as a fast reactor, Al ₂ O ₃ , SiC, Si ₃ N ₄ ,
Ceramics such as MgO, B ₄ C and TiN are used. However, considering strength, formability, workability, etc., Al ₂ O ₃ (alumina) is most preferable, followed by SiC and Si ₃ N ₄ .

In this embodiment, the other suction portion (indicated by reference numeral II) is also devised so that the gap between the suction surfaces can be kept sufficiently small. A screw type iron core 56 is used and screwed so that it penetrates the bottom surface of the cup-shaped portion 42. By rotating the screw type iron core 56, the tip end surface and the cylindrical portion of the first iron core 30 are rotated. The gap between the bottom surface of 30a can be finely adjusted. Since the first and second iron core gaps need to be about 0.1 mm or less in order to develop a sufficient magnetic attraction force, the screw type fine adjustment mechanism as in the above embodiment is set and adjusted. It is extremely effective in terms of aspects.

With this configuration, the first iron core 30 and the second iron core 32
Is in contact with only the seizure-resistant material 50, 52, and there is a slight gap between the iron cores 30, 32, so seizure / fusion does not occur even in high temperature sodium, and when the magnetic force of the electromagnet is lost. The separation on the suction surface is surely performed.

The first iron core 30 is attached to the drive shaft 36,
A control rod is attached below the iron core 32 of the.

EFFECTS OF THE INVENTION The present invention provides a ceramic-based flame-retardant material for at least one of the iron core adsorption parts having the above-described two-part structure so that the surface thereof slightly protrudes from the adsorption surfaces of both iron cores. At least one of the seizure-resistant materials is embedded so that it can be adjusted in position in the axial direction of the control rod with respect to the iron core that holds it. Since it is a self-actuating electromagnet configured to be in non-contact with a minute gap between them, even if it is used in high temperature liquid sodium for a long time, problems such as seizure and fusion in the adsorption force part occur. First, if the electromagnet loses its magnetic attraction, it is guaranteed that the control rod will fall.

In particular, if a mechanism that allows the hard-to-seize material to move in a threaded manner with respect to the iron core is installed, the gap between the iron cores can be adjusted to a sufficiently narrow and constant value, and thus the loss of the magnetic attraction force can be sufficiently reduced. Is possible.

As a result, the reliability of the self-actuated reactor shutdown mechanism is significantly improved by the present invention.

[Brief description of drawings]

1A and 1B are explanatory views showing an example of a self-actuating electromagnet according to the present invention, and FIGS. 2A and 2B are explanatory views showing an example of a control rod holding mechanism and its operation. 16 …… Self-actuated electromagnet, 30 …… First iron core, 32 …… Second iron core, 34 …… Coil, 44 …… Non-magnetic material, 46 …… Temperature-sensitive magnetic material, 50,52… … Flame resistant material, 54 …… Metal ring, 56
...... Screw-type iron core.

Claims (4)

[Claims] 1. A central magnetic path and an outer magnetic path form a magnetic circuit in which an upper part and a lower part are continuous with each other, and a central magnetic path and an outer magnetic path each have an attracting portion so that the magnetic circuit can be divided into upper and lower parts. An electromagnet that includes a combined iron core of a structure and a coil wound around the central magnetic path, and incorporates a temperature-sensitive magnetic material in a part of a magnetic circuit to hold and disconnect the control rod according to an ambient temperature. At least one of the two adsorbing portions where the cores adsorb to each other is embedded with a ceramic flame-retardant material so that the surfaces of the iron cores slightly protrude from the adsorption surfaces of both iron cores. It is connected to the iron core holding the core so that the position can be adjusted in the axial direction of the control rod, and in the adsorption portion, the hard-to-seize materials contact each other and a minute gap is formed between the iron cores. Self-actuated electromagnet for control rod holding mechanism . 2. One of the flame-retardant materials is embedded in a metal ring, and the metal ring is screw-connected to one iron core so that the position of the metal ring can be adjusted in the axial direction of the control rod. 1
The self-actuated electromagnet described. 3. The flame-retardant material is made of alumina.
The self-actuated electromagnet described. 4. The self-sticking member according to claim 1, wherein one of the adsorbing portions of the iron cores is attached with a flame-retardant material, and the other is attached with a screw type iron core so that the gap between the adsorbing portions can be finely adjusted. Actuated electromagnet.