JPS6049275B2 - Control rod position detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for detecting the position of a control rod using a magnetically actuated position switch in a control rod and control rod drive mechanism of an atomic cublant.

Conventional nuclear power plant control rod position detection devices
As shown in Fig. 2, a pair of permanent magnets 6 are provided in the control rod drive mechanism, and position switches 7 are fixed at a constant pitch in the indicator tube 8.
As the permanent magnet 6 moves up and down, the permanent magnet 6
The position switch 7 located at the corresponding position is excited by this permanent magnet 6 and becomes conductive, and the position of the control rod 2 is detected by this conduction signal.

In FIG. 1, 3 is a control rod housing, 5 is a drive piston, and 4 is an index tube. Pressurized water applied to the drive piston 5 drives the control rod 2 connected to the index tube 4 in the vertical direction. The permanent magnet 6 has a built-in piston 5. (The position switch has a structure in which two opposing metal pieces are placed in a glass container, and the two metal pieces come into contact by applying a magnetic field from outside the container.) The installation position of the position switch is as follows. The control rods 2 are installed at the positions where they should normally stop and between the normal stop position and the normal stop position (i.e., the drift position), and for convenience, the former are given even numbers and the latter odd numbers to distinguish each position. There is.

Even numbered normal position position switches have all their cables pulled out to the outside, and odd numbered drift position position switches have their cables connected in series and
Each signal was configured logically and guided to a signal processing device, processed, and detected the position of the control rod. The conventional method is functionally satisfactory, but in order to accurately detect the position, several dozen position switches (30 to 30) are required for each control rod. Yes, boiling water reactor II
Since there are over 185 control rods in the OOMW class,
The number of position switches was in the thousands, and the handling of the cables required a great deal of effort.

As a countermeasure for this, simply remove the odd numbered position switches corresponding to the drift positions, and when all the even numbered position switches corresponding to the normal positions are non-conducting,
One possible method is to assume that the control rods are in a drift position.

However, this method has a major problem when applied to control rod position detection devices in nuclear power plants, as it is difficult to distinguish between a control rod in its normal position but a position switch that is open and in a drift position. It was hot. The present invention has been made in view of the above circumstances, and its purpose is to detect control rod positions by omitting position switches corresponding to odd-numbered drift positions while having functions equivalent to or superior to conventional methods. It's about getting the equipment. An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows the configuration of a control rod position detection device for a boiling water reactor.

A cylindrical control rod housing 3 that penetrates the reactor pressure vessel 1 and includes the entire control rod drive mechanism is provided at the lower part of the reactor pressure vessel 1, and an index tube 4 is provided in this cylindrical control rod housing 3.

A driving piston 5 is attached to the lower end of the index tube 4, which acts as a piston rod, and a control rod 2 is connected to the upper part of the index tube 4 through a coupling.As the driving piston 5 moves, the index tube and the control rod 2 goes up and down. The index tube 4 and the drive piston 5 are hollow cylinders, and the inside thereof is an indicator tube 8.
is fixed with the control rod housing 3 and includes a position indicating probe.

The position indicator probe is made of non-magnetic metal, with a series of hermetically sealed magnetically actuated position switches 7 mounted on the probe, and the entire probe protected by a non-magnetic metal tube. . In addition, a magnetic operation position switch is provided at the bottom of the drive piston 5. Three pairs of permanent magnets 6-1, 6-2, and 6-3 are mounted at a pitch of 112, which is the mounting pitch of 7.

The magnetic field of this permanent magnet extends outward through the piston 5, the non-magnetic wall of the position-indicating probe, and operates a position switch 7 close to the magnet. That is, indicator tube 8 in index tube 1-4.
A series of magnetically actuated position switches 7 attached to an indicator probe included in a A permanent magnet 6 attached to the permanent magnet 6 operates the individual position switches 7 in its vicinity.

A number of grooves are cut into the indicator tube 8, and the grooves engage collet fingers (not shown), so that the control rod drive mechanism is normally stopped at this groove position.

A position switch 7 is attached corresponding to this groove, and a series of even numbers are assigned from the bottom corresponding to the position. In FIG. 3, when the control rod is normally latched (when the control rod drive mechanism is stopped at the groove position of the indicator tube 8), in the example of FIG. 4, the upper and lower permanent magnets 6-
1, 6-3, the position switch 7-1 indicates the normal position.
2 and 7-14 are electrically connected, and the permanent magnet 6-2 in the intermediate position
There is no position switch that operates accordingly.

Signals from each position switch 7-12, 7-14 are input to the signal processing device 32 via the signal line 33, and in the above case, the control rod position is determined to be 12. Furthermore, control rod 2
is in the drift position (when the control rod drive mechanism is stopped out of the groove position of the index tube 4),
For example, when the positional relationship is as shown in FIG. 5, there is no position switch 7 that operates corresponding to the upper and lower permanent magnets 6-1, 6-3, and the position switch 7-14 is operated by the permanent magnet 6-2 in the intermediate position. conducts, and the signal processing device 32 determines that the control rod is at the drift position 13.

Therefore, when the position switches 7-N and n+2 are conductive, the control rod 2 is in the normal position n, and the position switch 7-N is in the normal position n.
When only n is conductive, the control rod 2 is drifting and the position can be determined to be n-1. Although the above embodiment describes a control rod position detection device for a boiling water reactor, it is of course possible to implement the present invention also for control rods of nuclear reactors such as a pressurized water reactor, a new converter reactor, and a fast breeder reactor. Since the present invention is configured as described above, it has the following effects.

(1) Position switches corresponding to odd-numbered positions can be omitted without loss of functionality.

(2) The drift state position (odd position) of the control rod, which could not be detected using the conventional method, can be determined.

(3) With (1) and (2) above, costs including cables can be reduced, and reliability and maintainability can be greatly improved.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a control rod drive mechanism showing a conventional position detection device, Fig. 2 is an explanatory diagram showing a conventional control rod position detection device, and Fig. 3 shows a control rod position detection device according to the present invention. Explanatory drawings including partial cross-sections, FIGS. 4 and 5, are diagrams for explaining the present invention in detail. 1... Reactor pressure vessel, 2... Control rod, 3... Control rod housing, 4... Index tube, 5... Drive Piston, 6-
1, 6-2, 6-3...Permanent magnet, 7...
-Position switch, 8...Indicator tube, 32...Signal processing device, 33...Signal line from position switch, 34...Position detection signal.

Claims (1)

[Claims] 1. In a control rod position detection device consisting of a permanent magnet provided so as to be movable together with the control rod, and a large number of position detection switches moved by the magnetic flux of the permanent magnet and provided at regular intervals in a stationary state, the permanent At least 3 magnets
A control rod position detecting device characterized in that an odd number of the position detecting switches are provided at a distance of 1/2 of the mounting interval of the position detecting switches.