JPH0559398B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a mechanism in which control rods are suspended and held by electromagnets during normal operation, and are separated and inserted into the reactor core in order to stop the reactor in an emergency. In more detail, a nuclear reactor is provided with joints that can freely change the connection angle above and below the electromagnets to prevent malfunctions in holding and separating the control rods due to fluid vibrations of the coolant. This relates to the control rod holding mechanism.

[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, etc., in order to increase the reliability of reactor shutdown. In order to increase the reliability of this mechanism, a configuration has been proposed that incorporates self-actuating electromagnets so that the reactor can be safely shut down without relying on external operations or signals.

An example of this type of control rod holding mechanism is the structure shown in FIG. A control rod 10 having a neutron absorber is located in a guide tube 12 in the reactor core and is held in a reactor coolant 14 (usually liquid sodium in a fast breeder reactor). The control rod holding mechanism is the drive shaft 1
6 and a self-actuating electromagnet 18 located at its lower end.
etc., and the control rod 10 is held by the magnetic attraction force of the electromagnet 18.

The self-actuating electromagnet 18 has a two-part iron core, which is a combination of first and second iron cores 20 and 22, and a coil 24, and has a temperature-sensitive magnetic material 26 incorporated in a part of the magnetic circuit. It is. Note that the reference numeral 28 indicates a non-magnetic connecting member.

A self-actuating electromagnet 18 is placed within the reactor coolant 14 as previously described. Therefore, if some abnormality occurs in the furnace and the ambient temperature rises, the temperature-sensitive magnetic material 26 will respond to the abnormal temperature and lose its magnetism, resulting in a decrease in the magnetic attraction force at the adhesion part between the iron cores 20 and 22. However, the separated control rod 10 falls due to its own weight, stopping the reactor.

[Problems to be Solved by the Invention] As described above, the control rod 10 is normally suspended in the in-core coolant 14, and shakes due to vibrations caused by the flow of the coolant. Therefore, electromagnet 1
Bending stress is generated in the suction portions of the iron cores 20 and 22 of the divided structure forming the structure 8. Since the drive shaft 16 to which the control rod 10 and the electromagnet 18 are fixed is long, its bending moment becomes quite large, and one end of the suction surface opens due to the bending stress. This causes a sudden decrease in the magnetic attraction force, resulting in a malfunction in which the control rod 10 falls during steady operation.

In particular, with a self-actuating electromagnet that incorporates a temperature-sensitive magnetic material 26, the magnetic attraction force during steady operation cannot be set too large in order to ensure the operation of separating the rolling rod in the event of an abnormal temperature, so there is a risk of malfunction due to fluid vibration. The quality is high.

The purpose of the present invention is to eliminate the drawbacks of the prior art as described above, and to reduce the bending moment generated on the attraction surface of the electromagnet due to fluid vibration, thereby preventing malfunctions in which control rods are separated during steady operation. In addition, the magnetic attraction force generated by the electromagnet during steady operation can be set to a low level, thereby significantly improving the reliability of the self-actuated reactor shutdown mechanism. It's about doing.

[Means for Solving the Problems] The present invention, which can achieve the above objects, provides an electromagnet in combination with a two-part iron core coil at the lower end of the drive shaft, and uses the electromagnet to suspend and hold the control rod. This disconnection mechanism is a control rod holding mechanism for a nuclear reactor that has joints above and below the electromagnet that can change the connection angle.

For example, a ball-and-socket joint is suitable as the joint part that can freely change the angle of the connecting part.

[Operation] When joints such as ball-and-socket joints are provided above and below the electromagnet, the mutual connection angles of the members connected by these joints can be freely varied. In other words, the electromagnet is suspended from the drive shaft via the upper joint, and the control rod is suspended from the electromagnet via the lower joint, so if the control rod and electromagnet are shaken by fluid vibration, , because it bends at those joints, the bending stress generated on the adsorption surface of the electromagnet's divided iron core becomes extremely small.

Therefore, there is no risk of the electromagnet being disconnected during steady operation, and the magnetic attraction force generated in the electromagnet can be smaller than in the prior art.

[Embodiment] FIG. 1 is an explanatory diagram showing an embodiment of a control rod holding mechanism according to the present invention. An electromagnet 18 is located below the drive shaft 16, and a control rod 10 is suspended from it. The control rod 10 is inserted into the guide tube 12 and located within the reactor coolant 14 . This basic configuration is similar to the prior art shown in FIG. 2 above.

The electromagnet 18 used may also be basically the same as in the prior art. That is, the first and second iron cores 2
It has a two-part iron core and a coil 24, and a temperature-sensitive magnetic material 26 is incorporated in a part of the magnetic circuit. Reference numeral 28 indicates a non-magnetic connecting member.

Here, the present invention is significantly different from the prior art in the coupling structure between the drive shaft 16 and the electromagnet 18 and between the electromagnet 18 and the control rod 10.

As can be seen from Fig. 1, in the present invention, the ball
Joints 30 and 32 such as socket joints are used to provide a mechanism that allows the mutual connection angle to be freely varied. In other words, electromagnet 18
The drive shaft 16 is suspended by the upper joint 30, and the control rod 10 is suspended by the lower joint 30.
2 to the electromagnet 18.

When the control rod 10 and electromagnet 18 shake due to fluid vibration, the upper and lower joints 30, 3
2, the iron cores 20, 22 of the electromagnet 18
The bending stress generated on the suction surface between the two is extremely small. Therefore, there is no risk of separation at the suction surface due to bending stress during steady operation. Furthermore, since the bending stress generated on the attraction surface is small, it is possible to set the magnetic attraction force to be smaller than before.

Comparing the magnitude of the shaking when the control rod is actually attracted and held using the same electromagnet and then shaken, it is found that when the control rod has joints as in the present invention, the shaking width is much larger. It was confirmed that it did not fall.

Note that since the bending moment generated in the above configuration is approximately proportional to the length of the upper joint 30 and the lower joint 32, the distance between these two joints 30 and 32 should be set as small as possible. is desirable.

The structure of the joint is not particularly limited.
Although a ball and socket joint as shown in FIG. 1 is preferable, other mechanisms may be used as long as the connection angle can be freely varied.

[Effects of the Invention] As described above, the present invention is a control rod holding mechanism for a nuclear reactor in which joints are provided above and below the electromagnet with variable connection angles. When a bending moment is applied to the control rod and electromagnet, the joints cause them to swing around the vertical axis, which reduces the bending stress generated on the attraction surface. Therefore, during steady operation, the electromagnet is disconnected and the control rod This has the effect of preventing malfunctions that may occur if the device falls.

Additionally, for the above reasons, the magnetic attraction force generated by the electromagnet during steady operation can be set low, making it easier to disconnect the control rods when the temperature inside the reactor rises abnormally, greatly improving the reliability of the self-actuated reactor shutdown mechanism. improve.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of a control rod holding mechanism according to the present invention, and FIG. 2 is an explanatory diagram showing an example of a conventional technique. 10... Control rod, 12... Guide tube, 14... In-reactor coolant, 16... Drive shaft, 18... Electromagnet, 2
0, 22... Iron core, 24... Coil, 26... Temperature-sensitive magnetic material, 30, 32... Joint part.

Claims (1)

[Claims] 1. In a mechanism in which an electromagnet consisting of a two-split iron core and a coil is provided at the lower end of the drive shaft, and the electromagnet suspends and holds and disconnects the control rod, the upper and lower parts of the electromagnet are connected to each other. A control rod holding mechanism for a nuclear reactor, characterized in that a control rod holding mechanism for a nuclear reactor is provided with joints whose connection angles can be freely changed. 2. The control rod holding mechanism according to claim 1, wherein the joint is a ball and socket joint.