JPS6283692A - Drive mechanism of control rod for fast breeder reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to improvements in control rod drive mechanisms for fast breeder reactors.

[Technical Background of the Invention] Emergency reactor shutdown (hereinafter referred to as scram) systems for control rod drive mechanisms generally used in fast breeder reactors include a gas pressurization system and a spring acceleration system.

In the gas pressurization method, gas pressure is constantly applied to the extension rods that transmit acceleration force and vertical motion to the control rods, and during scrubbing, the control rods are inserted into the reactor core using the gas pressure. be. The subring acceleration method uses a compressed spring as a means of applying acceleration force to the control rods, and uses the spring force of the springs to rapidly insert the control rods into the reactor core during scram.

A conventional example will be explained below with reference to FIGS. 2 and 3.

FIG. 2 is a cross-sectional view showing the configuration of a control rod drive mechanism that employs a spring acceleration method, and reference numeral 1 in the figure is placed through a shield 2 that closes the upper opening of the reactor vessel (not shown). It is a guide tube. Inside the guide tube 1, there is provided an outer extension tube 4 having a latch finger 3 whose diameter can be freely expanded at its lower end and whose upper end is held by an extension tube latch finger 5. The extension pipe latch finger 5 has an electromagnet 6 inside.
It is integrally provided at the lower end of the magnet holder 7 incorporating the magnet holder 7, and moves up and down in the guide tube 1 together with the magnet holder 7. A drive motor 8 is installed at the top of the guide tube 1, and a ball screw 9 is connected to the drive motor 8. A nut 11 connected to the upper end of the magnet holder 7 via a connecting member 10 is screwed into the ball screw 9, and is moved up and down by the rotation of the ball screw 9. That is, the extension tube latch finger 5 and the magnet holder 7 move up and down within the guide tube 1 as the nut 11 moves.

An inner extension tube 12 is slidably inserted into the outer extension tube 4. A finger rod 13 is provided at the lower end of the inner extension tube 12 to enlarge the diameter of the latch finger 3 of the outer extension tube 4. It is adapted to be engaged with the inner surface. Also, the above inner extension pipe 1
The upper end of 2 is introduced into the magnet holder 7 and is held by a link mechanism 16 installed within the magnet holder 7. One end of this link mechanism 16 is connected to an attraction member 17 that is attracted and held by the electromagnet 6, and when the attraction member 17 is separated from the electromagnet 6, the inner extension tube 12 is opened.

Further, an acceleration tube 18 is provided on the lower outer periphery of the outer extension tube 4. The lower end of the accelerating tube 18 is in contact with the upper end surface of the handling head 15, and applies an accelerating force to the control rod 14. That is, between the acceleration tube 18 and the spring receiving portion 19 protruding from the inner circumferential surface of the guide tube 1, an acceleration spring portion 20 formed by connecting a plurality of springs 20a via spring joints 21 is compressed. The acceleration tube 18 applies acceleration force to the control rod 14 by using the spring force of the acceleration spring section 20.

The upper end of the acceleration spring section 20 is connected to the spring receiving section 19.
, and only the lower end is free. The upper end of the acceleration tube 18 is a large-diameter stopper portion 18a, and this collar portion 18a abuts against an annular dashpot portion 22 provided on the inner peripheral surface of the guide tube 1 to accelerate the acceleration. The amount of movement of the tube 18 is regulated. Note that the numbers 23 and 24 in the figure
are stopper portions that restrict the amount of movement of the outer extension tube 4 and the inner extension tube 12, respectively.

The operation will be explained based on the above configuration. First, the control rod 14 is moved up and down by the drive motor 8 during reactor operation. That is, when the drive motor 8 is driven to rotate the ball screw 9, the nut 11 moves up and down in accordance with the direction of rotation of the ball screw 9, and the extension tube latch finger 5 and the magnet holder 7 are moved inside the guide tube 1 accordingly. Move up and down.

This extension tube latch finger 5 and magnet holder 7
The outer extension tube 4 and the inner extension tube 11 holding the control rod 14 move up and down by the downward movement of the control rod 14, causing the control rod 14 to move up and down. As a result, the insertion and withdrawal of the control rods 14 into and out of the reactor core is adjusted, and the output is controlled.

Next, we will explain the case where a nuclear reactor is scrammed in the event of an earthquake. In this case, a scram signal is output, and the electromagnet 6 is demagnetized by the output of the scram signal. Due to this demagnetization of the electromagnet 6, the absorbing member 17 is separated from the electromagnet 6, and the link mechanism 16 holding the inner extension tube 11 is opened. When the link mechanism 16 is opened, the inner extension tube 11 falls and pushes the finger rod 13 downward. As a result, the diameter of the latch finger 3 is reduced.

As a result, the control rods 14 fall into the reactor core and are scrammed. At this time, the spring force of the compressed acceleration spring portion 20 acts downwardly on the acceleration tube 18, and the control rod 14 is accelerated in its fall by the acceleration tube 18, and is rapidly inserted into the reactor core.

[Problems with background technology] According to the above configuration, there were the following problems.

That is, during normal operation, the acceleration spring section 20 is assembled in a compressed state, and when it is released during a scram, it causes meandering, and the spring joint 21 is inclined between the spring joint 21 and the inner surface of the guide tube 1, and its As a result, the acceleration spring portion 20 and the outer extension tube 4 slide while being in contact with each other. When such a phenomenon occurs, the spring force of the acceleration spring section 20 decreases due to sliding resistance, and there is a possibility that the acceleration tube 18 and, by extension, the control rod 14, will not be sufficiently accelerated. In general, spring materials used in the high-temperature atmosphere of fast breeder reactors (approximately 530'C) are made of high-tensile M, which is hard even at high temperatures, in consideration of the phenomenon of fatigue at high temperatures.
(For example, Inconel material, etc.) is used. Therefore, when the above-mentioned contact occurs, there is a possibility that the accelerated pulling section 2o scrapes off the outer surface of the outer extension tube 4.

In response to this, it is possible to reduce the pressure on the sliding surface by forming a large roundness on the surface that may slide, but for dimensional reasons, the spring 20 of the acceleration spring portion 2°
There was a problem in that it was not possible to make the diameter of a that large. [Objective of the Invention] The present invention has been made based on the above points, and its purpose is to transmit the spring force of the acceleration spring part to the acceleration tube and eventually to the control rod in six effects during the reactor scram. An object of the present invention is to provide a control rod drive mechanism for a fast breeder reactor that can accelerate the reactor scram in a short period of time, and improve reliability and safety.

[Summary of the invention] That is, the control rod drive mechanism for a fast breeder reactor according to the present invention has the following features:
a guide tube inserted into the reactor vessel through the shielding lid;
an outer extension tube disposed within the guide tube and holding the control rod by selectively engaging a latch finger provided at the lower end with a handling head of the control rod from the inside;
``An acceleration tube installed on the outer periphery of the bipedal outer extension tube and above the handling head, and installed in a compressed state on the outer periphery of the outer extension tube between the acceleration tube and the spit of the guide tube. During an emergency shutdown of the reactor, the latch fingers are disengaged from the handling head, and when the control rod falls into the reactor core, the multiple springs extend at high speed and accelerate the fall of the control rod through the acceleration tube. A device characterized by comprising: an acceleration spring portion connected in series; and a joint mechanism that connects the springs and has a spherical surface that faces the guide tube and the outer extension tube. It is.

In other words, the portions of the joint mechanism that connect the springs of the acceleration spring portion, facing the guide tube and facing the outer extension tube, are made spherical to reduce the sliding resistance between the joint mechanism, the guide tube, and the outer extension tube. Attempts are made to reduce this.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIG. Note that parts that are the same as those in the prior art are designated by the same reference numerals, and their explanations will be omitted. The acceleration spring part 20 of this embodiment is the joint 10
A plurality of springs 20a are connected in series via 1. This joint 101 is an outer spring joint 102
, an inner spring joint 103, and joints 10 and 4 that connect these outer spring joints 102 and inner spring joints 103. The portion of the outer spring joint 102 facing the guide tube 1 is formed into a spherical shape, and similarly the outer extension tube 4 of the inner spring joint 103 is formed into a spherical shape.
The part facing the is also formed into a spherical shape.

The operation will be explained based on the configuration shown below. First, during normal operation, the control rod 14 is moved up and down by the drive motor 8. That is, when the drive motor 8 is driven to rotate the ball screw 9, the nut 11 moves up and down in accordance with the rotational direction of the ball screw 9, and accordingly, the i-long latch finger 5
And the magnet holder 7 moves up and down within the guide tube 1.

As a result, the outer extension tube 4 and the inner extension tube 11 move up and down, causing the control rod 14 to move up and down.

Next, the reactor scram will be explained. First, for example, when an earthquake occurs and a scram signal is output, the electromagnet 6
The magnet 11 is demagnetized and the suction member 17 is separated from the electromagnet 6.

As a result, the link mechanism 16 that held the inner extension tube 11
is opened, and the inner extension tube 11 falls and pushes the finger rod 13 downward. Due to this action, the diameter of the latch finger 3 is reduced and the engagement with the handling head 15 is released. The control rod 14 then falls into the reactor core.゛-
1- When the control rod 14 falls, the acceleration spring portion 20
The spring force acts on the control rod 14 via the acceleration tube 18.

At this time, since the surface 102 a of the outer spring joint 102 on the guide tube 1 side and the surface 103 a of the inner spring joint 103 on the outer extension tube 4 side are both formed in a spherical shape as described above, the outer spring joint 102 The sliding resistance between the guide tube 1 and the inner spring joint 103 and the outer extension tube 4 are extremely small.

(When the accelerating spring portion 20 expands at high speed from a compressed state, the outer spring joint 102 and the inner spring joint 103 are inclined, or are inclined due to meandering, etc., and come into contact with the guide tube 1 and the outer extension tube 4. Even if it does, the resistance caused by it is small and the spring force of the acceleration spring section 20 does not decrease.Furthermore, since the contact area is always constant and large, the contact surface pressure does not increase, and therefore self-fusion occurs. Therefore, during the reactor scram, the spring force of the acceleration spring section 20 is effectively transmitted to the accelerator tube 18 and eventually to the control rods 14, and the reactor scram is reliably performed in a short time. In the case of this example, since the acceleration spring portion 20 does not come into direct contact with the outer extension tube 4, it goes without saying that the outer extension tube 4 will not be scraped by sliding contact due to the sound of rain.

[Effects of the Invention] As detailed above, according to the fast breeder reactor control rod drive mechanism according to the present invention, the acceleration force of the spring during the reactor scram signal is effectively transmitted to the control rods via the acceleration tube, Nuclear reactor scram can be performed reliably in a short time, and reliability and safety can be greatly improved.

[Brief explanation of drawings]

Fig. 1 is a partial sectional view of a control rod drive mechanism showing an embodiment of the present invention, Figs. 2 and 3 are views used to explain a conventional example, and Fig. 2 is a longitudinal section of the control rod drive mechanism. The plan view and FIG. 3 are cross-sectional views showing a part of FIG. 2 in detail. DESCRIPTION OF SYMBOLS 1... Guide tube, 3... Latch finger, 4... Outer extension tube, 14... Control rod, 15... Handling head, 18... Acceleration tube, 20... Acceleration spring part , 20a... Spring, 101... Joint mechanism,
102...Outer spring joint, 103...Inner spring joint, 104...Inner joint. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (2)

[Claims] (1) A guide tube inserted into the reactor vessel through the shielding lid, and a latch finger placed inside the guide tube and provided at the lower end are selectively engaged with the handling head of the control rod from the inside. an outer extension tube for holding the control rod; an acceleration tube installed on the outer periphery of the outer extension tube above the handling head; It is attached in a compressed state to the outer periphery of the outer extension tube, and when the reactor emergency shutdown occurs, when the engagement between the latch finger and the handling head is released and the control rod falls into the reactor core, it expands at high speed and is controlled via the acceleration tube. An acceleration spring part that accelerates the fall of the rod and is made up of a plurality of springs connected in series, and a joint mechanism that connects the plurality of springs and has a surface facing the guide tube and a surface facing the outer extension tube having a spherical surface. A control rod drive mechanism for a fast breeder reactor, characterized by comprising: (2) The above joint mechanism includes an outer spring joint whose surface facing the guide tube is spherical, an inner spring joint whose surface facing the outer extension tube is spherical, and these outer spring joints and inner spring joints. A control rod drive mechanism for a fast breeder reactor according to claim 1, characterized in that the control rod drive mechanism comprises a connecting inner joint.