JPS58219490A - Control rod drive mechanism - 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 a control rod drive mechanism for a fast breeder reactor.

[Technical background of the invention°]

A conventional example will be described and explained with reference to FIGS. 1 and 2.

Generally, a reactor core 2 composed of a plurality of fuel assemblies, control rods 1, etc. is installed in a reactor vessel (not shown) of a fast breeder reactor. The output of the reactor core 2 is controlled by inserting the control rod 1 into or withdrawing it from the reactor core 2 along a lower guide tube 4 supported by a core support plate 3 by a control rod drive mechanism.

Therefore, the configuration of the control rod drive mechanism will be explained.

In the figure, 5 indicates a housing. A drive unit 6 is housed in the upper part of the housing 5. An outer extension tube 7 is connected to the lower end of the drive section 6, and can be moved up and down by the drive section 6.

A finger 8 that can be opened and closed is provided at the tip of the outer extension tube 7. An inner extension tube 9 is housed inside the outer extension tube 7.

An armature 1o is provided at the upper end of this inner extension tube 9, and an operating rod 1v is provided at the lower end. This operating rod 11 has a large diameter portion 1
It has 11'f. Then, by turning on and off the power of the electromagnet 12 provided above the armature 10, the armature 1
0 is configured to be attracted to or detached from the electromagnet 12, thereby causing the inner extension tube 9 to move up and down. As the inner extension tube 9 moves up and down, the operating rod 11 also moves up and down, and as it rises, the large diameter portion JJA of the operating rod 11 causes the fins to spread out the fins 8 from the inside, thereby holding the control rod 1. Also, when the operating rod 11 is lowered, the fins 8 close and release the control rod 1 from being held. In the figure, 13 and 14 show the stroke bellows and latch bellows, respectively. Both the stroke bellows 13 and the latch bellows 14 form a boundary with the inside of the nuclear reactor, and absorb all the displacement caused by the vertical movement of the outer extension tube 2 and the circle 1 11 extension tube 9, and reliably maintain the i-field. The configuration is as follows. In addition, 17.1 in the figure
8.19 shows Ar, acceleration spring, and damping spring, respectively.

According to the control rod drive mechanism with the configuration described below, under normal conditions, as shown in FIG. Either it is inserted in a certain position or it is completely pulled out from inside the core 2.

At this time, the inner extension tube 9 is pulled upward by the attraction of the electromagnet 12 and the armature 10, and the large diameter portion I of the operating rod 11
JA's fin is pushing the 8 from the inside. When adjusting the core 2 output, the outer extension pipe 7 is
This is done by moving the control rods up and down and considering the position of the control rods 1 in the core 2.

Next, when some kind of accident occurs and the reactor core 2 is to be scrammed, the power to the electromagnet 12 is turned off by a signal from an external signal system, and the attraction between the electromagnet 12 and the armature 10 is released. As a result, the inner extension tube 9 descends, and the biasing of the fingers 8 in the opening direction by the operating rod 11 is released.
falls into the reactor core 2 due to its own weight. The above is the scrum operation.

[Problems with background technology]

According to the above configuration, since the scram operation is performed by signals from the external signal system, if an abnormality occurs in the external signal system and the scram signal cannot be output, or if the electromagnet 12. If an abnormality occurs in the armature 10, there is a possibility that scram cannot be performed.

[Purpose of the invention]

An object of the present invention is to provide a control rod drive mechanism that can perform scram 1r: even if an abnormality occurs in the means for forcibly performing scram, and can improve safety.

[Summary of the invention]

The control rod drive mechanism according to the present invention includes a housing, a drive section housed in a housing, an outer extension tube that protrudes from the lower end of the drive and is movable up and down, and a control rod drive mechanism that is provided at the lower end of the outer extension tube and operates to open and close. fins for holding or releasing control rods; an inner extension tube that is housed inside the outer extension tube and can move up and down; The device is completely equipped with an operating rod that opens and closes the fins when the fins move, and a melting member that connects the inner extension tube and the operating rod and melts when the temperature rises to a predetermined temperature.

That is, the inner extension tube and the operating rod are connected via a melting member, and the melting member melts when the temperature rises to a predetermined temperature.

Therefore, even if an abnormality occurs in the means for forcibly performing scram, when the ambient temperature rises to a predetermined value, the molten member will melt and the connection between the inner extension pipe and the operating rod will loosen, causing the operating rod to fall downward. The control rods are no longer held by the fins, and scrams can be performed, greatly improving safety.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIGS. 3 to 5.

A reactor vessel (not shown) of a fast breeder reactor accommodates a reactor core 102 made up of a plurality of fuel assemblies (not shown), control rods 6-101, and the like.

Then, the control rod 101 is inserted into or pulled out of the reactor core 102 by the control rod drive mechanism along the lower guide tube 104 supported by the core support plate 103.
2 output control is performed.

Next, the configuration of the control rod drive mechanism will be explained.

In the figure, 105 indicates a housing. Kono no Tsuji 10
A drive unit 106 is accommodated in the upper part of the inside of the drive unit 5 . An outer extension tube 107 is connected to the lower end of this drive section 106, and is configured to be movable up and down by the drive section 106.

A finger 108 that can be opened and closed is provided at the tip of the outer 11+11 extension tube 107. In addition to the above rules, extension tube 1
An inner extension tube 109 is housed inside the tube 07. An armature 110 is provided at the upper end of this inner extension tube 109, and an operating rod 111 is connected to the lower end. This operating rod 111 has a large diameter portion 111. By turning on and off the power to the electromagnet 112 provided above the armature 110, the armature 110 is attracted to or detached from the electromagnet 112, thereby causing the inner extension tube 109 to move up and down. As the inner extension tube 109 moves up and down, the operating rod 111 also moves up and down. When the operating rod 11 is raised, the large diameter portion 111 of the operating rod 11 pushes out the fingers 108 from inside, thereby causing the control rod 10
1f is held and when the operating rod 11 is lowered again, finger 1
θ8 is closed to release the control rod 101 from being held. In the figure, 113 and 114 indicate a stroke bellows and a latch bellows, respectively.

Cono stroke bellows 113 and latch bellows 1
14 together form a boundary with the inside of the reactor vessel, and the boundary is reliably maintained even if the outer extension tube 107 and the inner (111) extension tube 109 move up and down. Reference numerals 116 and 117 indicate Ar spool, acceleration ssol ring, and damping spring, respectively.

Next, the configuration of the connecting portion between the inner extension tube 109 and the operating rod 111 will be explained. In FIG. 4, an annular four part 109A is formed at the lower end of the inner (+111 extension tube) 09. On the other hand, the operating rod 111 has a thyroid convex part 111kf that fits into the above-mentioned thyroid four part 109k. The convex portion 111A is installed with a portion thereof fitted into the four thyroid portions 109A through an aluminum alloy 118 as a new member.The aluminum alloy 118 has an ambient temperature of about 6
When the temperature rises to around 00°C, it melts. and aluminum alloy 11
8 melts, the operating rod 111 as shown in FIG.
The structure is such that the four thyroid parts 111A completely fit into the four thyroid parts 109 by gradually falling down. That is, when some kind of accident occurs and the entire scram operation is performed, the external signal system (not shown) or the electromagnet 112. Even if an abnormality occurs in the armature 110 and the scram operation cannot be performed forcibly, when the ambient temperature rises to about 6,000 degrees, the aluminum alloy 118 will melt and the operating rod 11 will fall, causing the fins to fall. 9- is configured to release the control rod 101 from being held by the control rod 108 and enable scram operation.

According to the control rod drive mechanism configured as described above, during normal operation, the control rods 101 are inserted into a certain position within the reactor core 102 by the vertical movement of the outer extension tube 107 while being held by the fingers 108. Everything has been pulled out from within. At this time, the inner extension tube 109 is connected to the electromagnet 112.
The large diameter portion 111 of the push rod 11 is pulled upward by the attraction of the armature 110, and the fingers 108 are pushed inwards. When adjusting the output of the core 102, the outer extension tube 107 is moved up and down in the above state, and the control s10 is inserted into or withdrawn from the core 102, or the insertion position is changed.

Next, when some kind of accident occurs and the reactor core 102f is to be scrammed, the power to the front electromagnet 112 is turned off by a signal from an external signal system (not shown), and the attraction between the electromagnet 112 and the armature 110 is released. Thereby the inner extension tube 1
09 is lowered, the urging of the finger 108 in the open direction 10- by the operating rod 111 is released 45, and the control rod 101 is moved into the core 1 by its own weight.
02 and a scrum takes place.

Next, if an abnormality occurs in the external signal system and the scram signal cannot be output, or if the electromagnet 112. armature 1
A case will be described in which an abnormality occurs in 10 and the entire scram operation cannot be performed forcibly. In this case, the temperature inside the reactor vessel increases, and the ambient temperature near the connecting portion between the inner extension pipe 109 and the operating rod 111 also increases. When the ambient temperature rises to about 600° C., the aluminum alloy 118 melts, and the operating rod 111 falls until the annular convex portion 111B completely fits into the annular concave portion 109A of the inner extension tube 1θ9. Then, the fins on the large diameter part 111 of the operating rod 111 release the bias in the opening direction of the control rod 108, causing the control rod 101 to fall into the reactor core 102 and perform a scram.

In other words, the inner 1μ11 extension tube 109 has an annular recess 1.09A.
The operation rod 111 is provided with an annular convex portion 111B that fits into the annular concave portion 109A, and the convex portion 111Bff! It has a configuration in which it is fitted into a J-shaped recess 109A. Therefore, even if the external signal system fails and the scram signal cannot be output, or the electromagnet 112 or armature 110 fails and the scram operation cannot be performed forcibly, the ambient temperature will rise to approximately 600°C. Then, the front Vi1 sia aluminum alloy 118 melts, making it possible to perform scram operations thereafter.

〔Effect of the invention〕

The control rod drive mechanism according to the present invention includes a housing, a drive section housed in the housing, an outer extension tube that protrudes from the lower end of the drive and is movable up and down, and a control rod drive mechanism provided at the lower end of the outer extension tube that opens and closes. The fins for holding or releasing the control rod are provided with an inner extension tube housed inside the outer extension tube and movable up and down, and a fin provided at the lower end of the inner extension tube that moves up and down. This structure includes an operating rod that opens and closes the fingers, and a melting member that connects the inner extension tube and the operating rod and melts when the temperature rises at a predetermined temperature.

That is, the inner extension tube and the operating rod are connected via a melting member, and the melting member melts when the temperature rises to a predetermined temperature.

Therefore, even if an abnormality occurs in the means for forcibly performing scram, when the ambient temperature rises to a predetermined value, the molten member will melt and the connection between the inner extension pipe and the operating rod will loosen, causing the operating rod to fall downward. The control rods are released from being held by the fingers, making it possible to perform a scram, which has great effects, such as greatly improving safety.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing conventional examples, and Figure 1 is a control 4
A diagram showing the configuration of the control rod drive mechanism in a state where iJ is held,
Figure 2 is a diagram showing the configuration of the control rod drive mechanism during scram,
Figures 3 to 5 are diagrams showing one embodiment of the present invention.
The figure shows the configuration 13- of the control rod drive machine during normal times when the control rods are held, FIG. It is a sectional view showing composition same as the above at the time of scram. 101...Control rod, 105...Housing, 1o6
, - Drive unit, 107... Outer extension tube, 10B... Finger, 109... Inner extension tube, 111... Operating rod, 118... Aluminum alloy (melting member). Applicant's agent Patent attorney Takehiko Suzue 14- Japanese Patent Publication No. 58-219490 (5) Figure 3 914 Figure 5 Flash 490

Claims (2)

[Claims] (1) A housing, a drive unit housed in the housing, an outer extension tube that protrudes from the lower end of the drive and can be moved up and down, and a control rod held at the lower end of the outer extension tube that opens and closes. Alternatively, a fin for releasing control rod holding is provided at the lower end of the inner extension tube which is housed inside the outer 11111 extension tube and can move up and down, and the fin opens and closes by moving up and down. A control rod drive mechanism comprising: an operating rod; and a melting member that connects the inner extension tube and the operating rod and melts when the temperature rises to a predetermined temperature. (2) The control rod drive mechanism according to claim 1, wherein the melting member is made of an aluminum alloy.