JPS6045395B2 - Electromagnet non-contact ONMAG detection circuit for reactor control rods - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-contact ONMAG detection circuit for electromagnets for nuclear reactor control rods, and more specifically, a non-contact type detection circuit for detecting whether a control rod absorber has arrived at or left an electromagnet for a nuclear reactor control rod. This invention relates to a circuit for detecting

Generally, control rod electromagnets used in nuclear reactors are constantly exposed to high radiation and in completely sealed locations.

During nuclear reactor operation, it is necessary to extract some kind of signal from a detection unit provided in contact with the electromagnet in order to confirm whether the control rod absorber, which is activated by adsorption to the electromagnet, is attracted or separated. Conventionally, the detection part uses a mechanical contact system such as a limit switch or read relay, for example, as shown in FIG. is the guide rod 4
The detection switch 1 is activated by pushing up and a detection signal is output. Although this method is inexpensive, the structure of the electromagnet is complicated, and the detection switch part cannot be made completely airtight, so the contact points are exposed to high radiation and heavy steam inside the reactor, causing corrosion and The drawback was that oxidation caused conductivity deterioration and further insulation deterioration, making it unusable. If the above-mentioned failure occurs while a detection switch is being used in a nuclear reactor, it is not easy to replace just the detection switch part due to the high radiation environment, and in fact, the entire expensive control rod must be replaced. I had no choice but to replace it. Therefore, an object of the present invention is to provide a non-contact detection circuit that eliminates mechanical contacts in the detection section, uses a non-contact system, eliminates contact failure, and can improve reliability as an electromagnet for reactor control rods. It is. In the following, the invention will be explained in detail with reference to illustrated embodiments. FIG. 2 shows an embodiment according to the present invention.

A DC electromagnet excitation power source 1 is connected to the excitation coil 12 of the electromagnet 10.
4 is connected, and a detection coil 13 is provided within the electromagnet 10. When the detection power supply 15 is connected to the detection coil 13 via the resistor 21 and a voltage of AC4OOHzlOV is applied, the output voltage (detection voltage) of the amplifier 16 will be the same as the electromagnet excitation current value when the adsorbent is attached to the electromagnet. When there is (0NMAG
) of curve 32 in Fig. 3, and when the adsorbent is far apart (
0FFMAG) shows each characteristic of curve 31 in the figure. Straight line 30 shows the reference voltage of the output of amplifier 16 relative to the electromagnet excitation current. This characteristic change in 0NMAG and 0FFMAG is caused by the magnetic flux inside the electromagnet changing depending on the adsorption state of the adsorbent, and the inductance of the detection coil changing. Therefore, a voltage change corresponding to the change in the inductance of the detection coil is detected in the resistor 21. It is. Actually the third
As shown in the figure, a lower voltage value is detected at 0NMAG than at OFFMAG. child. The voltage detected as described above and amplified by the amplifier 16 and the reference voltage from the amplifier 17 are compared by the amplifier 18. When the detected voltage is higher than the reference voltage, the display 19 displays 0FFMAG, and conversely, when it is lower, the display 19 displays 0NMAG!
cormorant. In this way, it is possible to know the adsorption state of the adsorbent without using mechanical contacts. The electromagnet used in the present invention has a maximum excitation current of 1 [A] DC, 470 [AT],
The electromagnet is made of yoke material N-50 (nickel 50%), and the detection coil is a wound core with a core diameter of approximately 1 cm.The N-50 core has 1100 [turns] and the TN4L core has 1300 [turns]. They are connected in series and fixed to the bottom of the electromagnet. This electromagnet is currently excited with an exciting current of 400 [Rn. A], and the detection voltage is approximately 1.5 DC at 0FFMAG.
[■], DC approx. 1.0 [■] at 0NMAG, and a voltage difference of about 0.5 [V] DC is obtained. Therefore, the reference voltage is set to 1.25 [V] DC and compared with the detected voltage.

The key points in the above detection method are the number of turns of the detection coil and the detection power supply (AC4OOHzlOV), but various detection coils can be used based on the characteristics of the main electromagnet (coil material, number of turns, shape, etc.) through experiments. I know it's possible. Therefore, power supplies with various frequencies are used in the detection power supply, and the voltage value may also vary. As mentioned above, the effect of the present invention is that failures are eliminated by making the detection section contactless.

It should be noted that the electromagnet and device according to the present invention have been used in nuclear reactor operation for more than one year and have been proven to have no failures.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional detection method.

Claims (1)

[Claims] 1. In a reactor control rod electromagnet non-contact ONMAG detection circuit including an electromagnet having an excitation coil and an excitation power source,
A detection coil fixed in the electromagnet, a power supply for excitation of the detection coil connected in series to both ends of the detection coil via a resistor, and one end of the resistor connected in parallel to each other via a forward diode. a voltage detection circuit, the other end of which is connected to one end of the resistor and capacitor connected in parallel, a first amplifier that amplifies the output voltage of the voltage detection circuit; a second amplifier that generates a voltage; a third amplifier that compares the output voltage of the first amplifier and the output voltage of the second amplifier;
and a display that displays the output of the third amplifier, and detects a change in the inductance of the detection coil due to a change in the magnetic flux in the electromagnet as a voltage drop across the resistor, and this detected voltage An electromagnet contact ONMAG trench detection circuit for a nuclear reactor control rod, characterized in that it detects whether an adsorbent has left or arrived at the electromagnet depending on whether the voltage is higher or lower than a reference voltage.