JPH0713670B2 - Control rod position detector - Google Patents

Description

Description: [Object of the Invention] (Field of Industrial Application) The present invention relates to a control rod position detection device for use in a nuclear reactor, and more particularly to a control rod position detection device for a boiling water reactor.

(Prior Art) Generally, in a boiling water reactor, a control rod connected to a control rod driving device provided at a lower portion of a reactor pressure vessel is configured to be inserted into and removed from a core to control a reactor output. There is. This will be described with reference to the drawings.

FIG. 7 is a partial cross-sectional view of a conventional boiling water reactor. As shown in FIG. 7, a large number of control rod drive mechanisms 2 are provided below the reactor pressure vessel 1 and the tops of the control rod drive mechanisms 2 are provided. It is configured to control the reactor power by inserting or withdrawing the control rod 3 connected to the core into or from the core 4.

By the way, the control rod drive mechanism 2 is driven by an electric motor 6 as shown in FIG. A drive shaft 7 whose rotation is controlled by the electric motor 6 is supported by a bearing 8. A shaft sealing member 13 is attached to the cylinder body 18 and is watertightly sealed. A screw 11 is provided on the upper peripheral surface of the drive shaft 7, and the screw 11 has a nut.
12 are screwed together. The nut 12 is connected via a piston 10 to a control rod (not shown) that is inserted into the core, and its rotation is prevented. Therefore, the nut 12 moves up and down in the figure by the rotation of the electric motor 6, so that the control rod (not shown) is inserted into and extracted from the core 4. At this time, the rotation of the electric motor 6 is detected by a rotation detector (not shown).
Indicated as the position of. On the other hand, the control rod drive mechanism 2 is equipped with an accumulator (not shown) on the outside.
It is connected to the control rod drive mechanism 2 by 14.

Thus, in case of a reactor emergency, the accumulator energy is released. By pushing the piston 10 upward by the energy, a control rod (not shown) is rapidly inserted into the core (hereinafter referred to as scrum), and the reactor is shut down. At the end of the scrum, the piston 10 collides with the damper sleeve 15 and further has a mechanism for smoothly stopping by compressing the shock absorber 16.

At this time, a permanent magnet 9 is provided below the piston 10, and a tube 19 having a large number of reed switches 17 arranged in the axial direction at prescribed intervals is provided in the control rod drive mechanism housing flange.
Since the piston 10 equipped with the permanent magnet 9 is moved upward by the energy of the accumulator (not shown) in the scrum by penetrating 5a and provided outside the control rod drive mechanism, the lead is read every time the permanent magnet 9 passes. Switch 17
Will contact one after another.

On the other hand, an electric circuit is configured in advance via each reed switch 17, and each time the reed switch 17 makes contact, the electric circuit operates, so by processing that signal, the control rod in the scrum The position is being detected.

When detecting the control rod position during the above scram, the piston 10
The lower permanent magnet 9 cannot be attached to a large size due to the limitation of the installation location, and therefore, the tube 19 needs to be placed at a distance closest to the magnet 9 in order to accurately detect it with a weak magnetic force. However, although the length of the tube 19 is about 2 to 3 m, the diameter of the tube 19 must be reduced because it penetrates the control rod drive mechanism housing flange 5a. Therefore, the tip position of the tube 19 must be close to the control rod drive mechanism housing 5. There was a difficulty in getting it installed.

(Problems to be Solved by the Invention) The present invention has been made in view of the above circumstances, and an object thereof is to make it possible to easily install a tube in which reed switches are arranged at an accurate position with a simple configuration. It is to provide a control rod position detection device.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention arranges a tube in which a plurality of reed switches are arranged in an axial direction outside a control rod drive mechanism housing, and controls the tube. In a control rod position detecting device for detecting the control rod position by activating the reed switch by a permanent magnet provided under a piston connected to the rod, a guide is provided at a predetermined position of the control rod drive mechanism housing to control the position of the tube. It is characterized in that the tube is arranged at a predetermined position during installation.

(Operation) According to the present invention, since the tube is easily attached to the predetermined installation location by the guide, the position of the control rod can be accurately detected.

(Example) The Example of this invention is described with reference to drawings.

FIG. 1 is a side view of an embodiment of the present invention, and as shown in FIG. 1, it has already been explained that a guide 20 is provided in the control rod drive mechanism housing 5 at a position where the upper end of the position detection tube 19 comes. Since it is different from FIG. 8 described above, the same parts as those in FIG. 8 are designated by the same parts and the description thereof will be omitted.

2 is a sectional view as seen from the direction of the one-dot chain line arrow in FIG. 1, and FIG. 3 is a perspective view of only the guide 20. As you can see from these figures, the lower part of the guide 20 is wide and tapered, so even if the position detection tube 19 moves slightly, the position will be automatically determined when the tube 19 is inserted to the normal position. ing.

FIG. 4 shows the positional relationship with the reactor pressure vessel heat insulating material 21 when the guide 20 of the above embodiment is used. In the figure, even if the position detection tube 19 is designed at a position penetrating the heat insulating material 21, the tube 19 for the hole of the penetration part
It becomes easy to position. Further, it goes without saying that the same effect can be obtained even if the guide 20 is installed on the material support structure portion side of the present invention. Further, when the tube 19 penetrates the heat insulating material 21, the upper end of the tube 19 is exposed to the heat of the atomic pressure container 1, and therefore, it is possible to prevent the heat effect by configuring the guide 20 with a heat insulating material.

Further, it is preferable to use non-magnetized austenitic stainless steel (the same material as the control rod drive mechanism housing) or a similar material as the material of the guide.

FIG. 5 is a side view of another embodiment of the present invention. As shown in FIG. 5, when positioning is a concern with the upper guide 20 alone, an intermediate guide is provided in the middle portion of the control rod drive mechanism housing 5.
Only the point where 22 is provided is different from the above-mentioned embodiment, and other configurations are the same as the above-mentioned embodiment, and therefore, the same parts are denoted by the same reference numerals and the description thereof is omitted.

FIG. 6 is a side view of still another embodiment of the present invention. As shown in FIG. 6, only the guide 23 is provided over the entire length of the tube 19 instead of the guide 20 of the first embodiment. Different from the first embodiment, other configurations are the same as those of the first embodiment.
Since it is the same as the embodiment described above, the same parts are designated by the same reference numerals and the description thereof will be omitted. In this example, the tube 19
It is also possible to use a material whose rigidity is not so high.

[Effects of the Invention] As described above, according to the control rod position detection device of the present invention, its installation is easy and accurate, so that the control rod position can be accurately detected, and the reliability of plant operation is improved. The excellent effect of contributing to the improvement of

[Brief description of drawings]

FIG. 1 is a side view of an embodiment of the present invention, FIG. 2 is a sectional view in the direction of the arrow in FIG. 1, and FIG. 3 is a perspective view of the guide of FIG.
FIG. 4 is a view showing the positional relationship with the pressure vessel heat insulating material when the guide of FIG. 1 is used, FIG. 5 is a side view of another embodiment of the present invention, and FIG. 6 is still another embodiment of the present invention. Side view of the embodiment of
FIG. 7 is a partial sectional view of a conventional boiling water reactor, and FIG. 8 is a schematic sectional view of a conventional control rod drive mechanism. 2 …… Control rod drive mechanism 5 …… Control rod drive mechanism housing 6 …… Motor 17 …… Reed switch 19 …… Tube 20,23 …… Guide 22 …… Intermediate guide 21 …… Heat insulation

Claims (2)

[Claims] 1. A tube having a plurality of reed switches arranged in an axial direction is arranged outside a control rod drive mechanism housing,
In a control rod position detecting device for detecting the control rod position by operating the reed switch by a permanent magnet provided under a piston connected to the control rod, a tube is provided by providing a guide at a predetermined position of the control rod drive mechanism housing. The control rod position detecting device is characterized in that the tube is arranged at a predetermined position during installation. 2. The control rod position detecting device according to claim 1, wherein the guide is made of a material that is not magnetized.