JPS5816714B2 - control rod drive device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control rod drive device that moves control rods inserted into a nuclear reactor up and down and performs scram.

Conventionally, the control rod drive mechanism (hereinafter abbreviated as CRD)
The configuration was as shown in the figure.

In this configuration, an annular holding electromagnet 4 with an open center is fixed in a cylindrical outer extension tube 6, and an inner extension tube 3 to which a control rod is connected is inserted through the center opening of the holding electromagnet 4.

An armature 5 that comes into contact with the lower surface of the holding electromagnet 4 is fixed to the inner extension tube 3, and the lower surface of the holding electromagnet 4 and the upper surface of the armature 5 are each formed flat.

In this configuration, the holding electromagnet 4 is excited and the armature 5 is
can be suctioned and the inner extension tube 3 can be suspended from the outer extension tube 6.

However, in order to improve adhesion between the holding electromagnet 4 and the armature 5, the contact surfaces between the two are made flat, and with this shape, when the armature 5 falls to a certain distance from the holding electromagnet 5 after scram, the CRD drive unit Small foreign matter such as shavings and dust in the atmosphere may adhere to the upper surface of the armature 5.

When the holding electromagnet 4 is lowered with the foreign matter attached to the upper surface of the armature 5 and the holding electromagnet 4 and the armature 5 are brought into close contact with each other, the armature 5 is hung on one side due to the foreign matter d, and a gap is formed by the foreign matter d.

Since the magnetic force decreases in proportion to the square of the distance, the interference of the foreign matter d causes the overall holding force of the holding electromagnet 4 to decrease.

The present invention has been made in view of the above-mentioned drawbacks, and it is an object of the present invention to provide a control rod drive device that can stably obtain the holding force of the holding electromagnet by preventing foreign matter from remaining on the upper surface of the armature.

An embodiment of the present invention will be described below with reference to FIG.

The CHD, which performs vertical movement of control rods that control the reactivity of the reactor core and scram, is composed of a drive mechanism section, an extension section, and a holding mechanism section, and is installed on a rotating plug in the upper core mechanism.

The drive mechanism section is composed of a drive section 1 and a pole screw 2. The drive section 1 is fixed to the upper part of the reactor core, and the pole screw 2 is vertically supported by the drive section 1.

The pole screw 2 has a thread formed on its outer periphery.

The extension tube part includes a cylindrical inner extension tube 3 and this inner extension tube 3.
The upper end of the outer extension tube 3 is screwed into the pole screw 2.

The inner extension tube 3 connects a control rod to its lower portion, and is moved up and down within the reactor core as the outer extension tube 6 moves.

The holding mechanism section is composed of a holding electromagnet 8 and an armature 9. The holding electromagnet 8, which is fixed above the inside of the outer extension tube 6, has an annular shape, and its central opening is slightly larger in diameter than the inner extension tube 3. The inner extension tube 3 is inserted into this central opening.
or can be inserted.

A flange-shaped large-diameter portion 3a is formed on a part of the outer circumference of the inner extension tube 3, and an annular armature 9 is fixed to the upper surface of the large-diameter portion 3a by a port 7.

The upper surface of this armature 9 is formed to be inclined downwardly toward the outside, and the lower surface of the holding electromagnet 8 is inclined at the same angle as the inclination angle of the armature 9, so that the lower surface of the holding electromagnet 8 and the armature The upper surface of 9 can be brought into close contact.

Next, the operation of this embodiment will be explained.

When the drive unit 1 is operated, the pole screw 2 becomes stuck,
The outer extension tube 6 is moved up and down by the action of a screw formed on the outer periphery.

When a current is passed through the holding electromagnet 8, it is excited and attracts the armature 9.

When stopping the nuclear reactor, the current flowing through the holding electromagnet 8 is cut off to demagnetize it, and the armature 9 is removed from a certain height.
, the inner extension tube 3 is disconnected, and the control rod connected to the inner extension tube 3 is dropped.

Thereafter, the control rods must be pulled up through the inner extension tube 3 in order to restart the reactor.

For this purpose, the drive mechanism is operated to lower the outer extension tube 6 and the holding electromagnet 8, and after bringing the lower surface of the holding electromagnet 8 into close contact with the upper surface of the armature 9, current is applied to the holding electromagnet 8 to excite it, and the armature 9 is Suction.

Then, when the drive mechanism section is reversed, the inner extension tube 3 and the control rod are attracted and pulled out.

When holding and separating the inner extension tube 3, the upper surface of the armature 9 separates from the lower surface of the holding electromagnet 8, so foreign objects may fall onto the upper surface of the armature 9.
Since the upper surface of the armature 9 is inclined, foreign matter can slide out of the upper surface of the armature 9 without adhering to it.

Incidentally, as shown in FIG. 3, the joint surface between the holding electromagnet 10 and the armature 11 may be a chevron-shaped inclined joint surface.

The inclined joint surface in Fig. 2 is linearly inclined from the inner extension tube side end to the outer extension pipe side end, and the inclined joint surface in Fig. 3 has both the inner and outer extension side ends from the center. and is sloped linearly such that it is also in a low position, and the claims encompass both of these concepts.

Since the present invention is configured as described above, it is possible to prevent foreign matter from adhering to the upper surface of the armature, and the contact surface between the holding electromagnet and the armature can always be in close contact with each other, so that the holding force by the holding electromagnet can be maintained at the same level as the initial one. can be obtained with high reliability.

[Brief explanation of drawings]

Fig. 1 is a vertical sectional view showing a conventional control rod drive mechanism in which foreign matter has been mixed in, Fig. 2 is a longitudinal sectional view showing one embodiment of the present invention, and Fig. 3 is a main part showing another embodiment. FIG. 3...Inner extension tube, 4,8...Holding electromagnet, 5゜9...Armature, 6...
・Outside extension tube.

Claims (1)

[Claims] 1. A holding electromagnet for holding the inner extension tube to which the control rod is connected is attached to the upper part of the outer extension tube that moves up and down by the drive mechanism, and the inner extension tube has a large-diameter collar-like part on a part of its outer periphery. The armature is installed on this large diameter portion,
An inclined joint surface is formed between the upper surface of the armature and the lower surface of the holding electromagnet, and at least one of the inner extension pipe side end and the outer extension pipe side end of this inclined joint surface is at a position lower than the pond part. A control rod drive device characterized in that the inclined joint surface is linearly inclined.