JPH0480694A - Control rod driving 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] [Object of the Invention] (Industrial Application Field) The present invention relates to a control rod drive mechanism for a fast breeder reactor, and particularly to a control rod drive mechanism that can improve heat removal performance and maintainability. Regarding.

(Prior Art) FIG. 3 is a sectional view of the fast breeder reactor 1. The upper part of the reactor vessel 2 is sealed with a shielding plug 3, and a reactor core 4 is inside the reactor vessel 2.
will be installed. A plurality of control rods 5 are inserted into and removed from the reactor core 4 in order to control its output, and the control rods 5 are driven by a control rod drive mechanism 6 that penetrates the shielding plug 3 and move up and down inside the reactor vessel 2. . Note that the control rod drive mechanism 6 is supported by an earthquake-resistant support 7 above the shielding plug 3.

FIG. 4 is an axial cross-sectional view of the control rod drive mechanism 6. The control rod drive mechanism 6 has a housing 8 that opens downward and an upper guide tube 9 that is connected to the lower end of the housing 8. A drive motor 10 is housed above the inside of the housing 8. The drive motor 10 communicates with a plurality of (two in the figure) ball screws 12 via a plurality of transmission gears 11 that also have a speed reduction function. A ball nut 13 is screwed into each of these ball screws 12, and an electromagnet 15 is suspended from the ball nut 13 via a support pipe 14.

The electromagnet 15 attracts a latch plate 16 in the energized state, which is connected above with a piston 17, which is connected to the housing 8.
It slides inside the acceleration cylinder 18 provided inside. In addition,
Pressurized gas is supplied to the acceleration cylinder 18 from a gas storage tank 19 provided outside the housing 8 .

By the way, from the latch plate 16, the latch mechanism 20
An extension tube 21 that moves up and down inside the upper guide tube 9 is suspended, and a control rod 24 is further suspended at the lower end of the extension tube 21 via a latch finger 22 and a handling head 23. In addition, the extension pipe 21 and the upper guide pipe 9
A bellows 25 is installed between them to maintain airtightness above the housing 8 and the upper guide tube 9.

When the drive motor 10 is operated, its rotational force is transmitted to the ball screw 12 while being appropriately decelerated by the transmission gear 11. Then, as the ball screw 12 rotates, the ball nut 13 screwed therewith moves up and down along the ball screw 12.

Here, when the electromagnet 15 is in an excited state, the ball nut 1
3 is transmitted to the extension tube 21 and the control rod 24 via the electromagnet 15 and the latch plate 16, and the control rod 24 is moved up and down to be inserted into and removed from the reactor core 4.

In addition, the piston 17 connected to the latch plate 16 also
The piston 17 moves up and down in the acceleration cylinder 18, and at this time, the piston 17 is constantly pressed downward by the pressurized gas sent from the gas storage tank 19.

Therefore, under normal conditions, the electromagnet 15 of the control rod drive mechanism 6 is energized, the control rod 24 is moved up and down at an appropriate speed by the mechanism described above, and is inserted into and removed from the reactor core to adjust its output (the output decreases when inserted). , the output increases during extraction).

By the way, when some kind of abnormality occurs in the reactor core and the reactor is to be stopped urgently, it is necessary to quickly insert the control rods 24 into the reactor core. Therefore, at this time, the electromagnet 15 is switched off. Then, the latch plate 16 separates from the electromagnet 15, and the control rod 24 falls due to the weight of the latch plate 16, piston 17, extension tube 21, and control rod 24, but at this time, the pressing force of the pressurized gas is further applied to the piston 17. , the control rods 24 fall at a speed greater than free fall simply due to their own weight and serve the purpose of an emergency shutdown of the reactor core.

(Problem to be Solved by the Invention) However, since the control rod drive mechanism 6 described above suspends the extension tube 21 and the control rod 24 by the electromagnet 15, a strong electromagnetic force is required, and the electromagnet 15 becomes large. do. Therefore, the amount of heat generated from the electromagnet 15 increases;
Since the electromagnet 5 is large in size, the housing 8 that houses the electromagnet 15 also has a large diameter. Therefore, the heat removal performance of the control rod drive mechanism 6 deteriorates due to the dual effects of increasing the amount of heat generated and increasing the diameter of the housing 8.

Furthermore, if the diameter of the housing is increased for the above-mentioned reasons, the space between the control rod drive mechanisms 6 will be pinched, increasing spatial constraints during maintenance, which will cause problems.

Furthermore, since a mechanism for sealing pressurized gas in the housing 8 is provided separately as the acceleration cylinder 18, the housing becomes long, and as shown in FIG. 3, it becomes difficult for the control rod drive mechanism 6 to stand on its own. Earthquake support 7 is required to provide earthquake resistance. For this reason, there was a drawback that the above-mentioned heat removal performance and maintainability were further deteriorated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control rod drive mechanism for a fast breeder reactor that can particularly improve heat removal performance and maintainability.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a housing that opens downward, an upper guide pipe connected to the lower end of the housing, and a gas storage tank that supplies pressurized gas into the housing. A drive motor housed in the housing, a ball screw connected to the drive motor via an electromagnetic clutch, and a ball nut screwed to the ball screw move the control rod up and down through the housing and the upper guide tube, and suspend the control rod. A control rod drive mechanism is provided that has a hanging extension tube and a sealing mechanism that keeps a housing airtight while surrounding the extension tube.

The present invention also includes a housing opening downward, an upper guide pipe connected to the lower end of the housing, a gas storage tank for supplying pressurized gas into the housing, a drive motor housed in the housing, and a drive motor. It moves up and down inside the nozzing and upper guide pipe through a pinion connected via an electromagnetic clutch and a rack that meshes with this pinion.
The present invention also provides a control rod drive mechanism having an extension tube for suspending a control rod, and a sealing mechanism that surrounds the extension tube and keeps the housing airtight.

(Operation) The control rod drive mechanism of the present invention uses an electromagnet that suspends a latch plate to suspend a combination of a ball nut and a ball screw or a rack and pinion that suspends a control rod from a drive motor via an electromagnetic clutch. This makes it possible to reduce the diameter of the nozzle. Further, since the control rod drive mechanism of the present invention is provided with a sealing mechanism that keeps the housing airtight, an acceleration cylinder is not required by sealing pressurized gas in the housing, and the length of the housing can be shortened. Therefore, by making these diameters smaller and shorter, there is no need for seismic support, and heat removal performance and maintainability can be improved.

(Example) The present invention will be described in detail below with reference to FIGS. 1 and 2.

FIG. 1 shows a control rod drive mechanism 30 according to a first embodiment of the present invention.
FIG. Portions corresponding to those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

A ball screw 32 is connected to the bottom of the drive motor 10 provided above inside the housing 8 via an electromagnetic clutch 31. A ball nut 34 attached to a guide case 33 is screwed into the ball screw 32.
engages with a guide key 35 installed on the inner wall of the housing 8, and moves up and down within the housing 8 in conjunction with the up and down movement of the ball nut 34.

The extension tube 21 is suspended from the lower end of the guide case 33 via the latch mechanism 36, and the control rod 2 is suspended from the lower end of the extension tube 21.
4 is suspended.

In this embodiment, a sealing mechanism 37 is interposed between the upper guide tube 9 and the extension tube 21 to keep the housing 8 airtight. Pressurized gas is supplied into the housing 8 from a gas storage tank 19.

Now, in this control rod drive mechanism 30, under normal conditions, the electromagnetic clutch 31 is placed in an excited state and connected, and 100 rotations of the drive motor are transmitted to the ball screw 32 via the electromagnetic clutch 31. When the pol screw 32 rotates, the ball nut 34 screwed into it also receives rotational force, but since the guide case 33 to which the ball nut 34 is attached is engaged with the guide key 35, the guide case 33 and the ball nut 34 does not rotate, but moves up and down along the ball screw 32.

When the guide case 33 moves up and down, the extension tube 21 suspended from its lower end slides against the seal mechanism 37 in an airtight manner.
A control rod 24 suspended from the extension tube 21 is inserted into and removed from the reactor core to adjust the output of the reactor core.

On the other hand, during an emergency shutdown of the nuclear reactor, the excitation of the electromagnetic clutch 31 is cut off and the electromagnetic clutch 31 is disengaged. Then, the ball screw 32 is rotated and released from the electromagnetic clutch 31, but the weight of the guide case 33, latch mechanism 36, extension tube 21, and control rod 34 is applied to the ball nut 34 screwed onto the ball screw 32, and the guide The case 33 is pressed downward by pressurized gas sent from the gas storage tank 19.

For this reason, the guide case 33 uses the guide key 3 due to the weight of itself and the objects suspended below it and the pressing force of the pressurized gas.
Begins an accelerated fall along 5. At this time, the ball screw 31 rotates as the ball nut 34 attached to the guide case 33 descends. Also, the latch mechanism 36
When the control rod 24 lands on the bottom of the reactor core, the seal mechanism 3
Stop descending above 7.

Therefore, in this embodiment, neither an electromagnet for suspending the extension tube via a conventional latch mechanism nor a dedicated acceleration cylinder for filling pressurized gas is used, so the housing can be made smaller in diameter and shorter in length. Both the power adjustment by inserting and removing control rods during normal operation of the reactor and the rapid insertion of control rods during scram can be performed without any problems. Therefore, since the control rod drive mechanism of this example is not equipped with a large electromagnet, the amount of heat generated is low to begin with, but by making the diameter smaller and shorter, heat removal performance can be improved, and space constraints during maintenance can also be eased. be done. In particular, by making the structure shorter, it is possible to increase its self-reliance, eliminate the need for seismic support, and further improve heat removal and maintainability.

FIG. 2 shows a control rod drive mechanism 4 according to a second embodiment of the present invention.
0 is an axial cross-sectional view of FIG. Portions corresponding to those in FIG. 1 are denoted by the same reference numerals, and explanation thereof will be omitted.

In the control rod drive mechanism 40 of this embodiment, the electromagnetic clutch 31 includes a cap gear 41 having a deceleration function and a sprocket 4.
2 and a pinion 44 are connected via a chain 43,
Further, the pinion 44 meshes with a rack 45 provided in the axial direction of the housing 8. The rack 45 suspends the extension tube 21 via the latch mechanism 36 at its lower end.

In this embodiment as well, a sealing mechanism 37 is provided between the extension pipe 21 and the upper guide pipe 9 to keep the inside of the housing 8 airtight, and pressurized gas is supplied from the gas storage tank 19 into the housing 8. .

In normal times, the control rod drive mechanism 40 operates as in the first embodiment.
The electromagnetic clutch 31 is brought into an excited state and connected. As a result, the rotation of the drive motor 10 is transmitted to the cap gear 41 via the electromagnetic clutch 31, and further transmitted to the pinion 44 via the sprocket 42 and chain 43 while being decelerated.

When the pinion 44 receives the rotational force of the drive motor 10,
Since the rack 45 rotates while meshing with the rack 45, the rack 45 moves up and down within the housing 8 as the pinion 44 rotates. When the rack 45 moves up and down, the extension tube 21 suspended at its lower end slides against the seal mechanism 37 in an airtight manner, and the control rods (not shown) suspended from the extension tube 21 are inserted into and removed from the reactor core. Adjust the output of

On the other hand, during an emergency shutdown of the nuclear reactor, the excitation of the electromagnetic clutch 31 is cut off and the electromagnetic clutch 31 is disengaged. The pinion 44 is then released from the rotation of the drive motor 10, but the rack 45 that meshes with the pinion 44 is loaded with the weight of itself, the latch mechanism 36, the extension tube 21, and the control rod. The latch mechanism 36 is pressed downward by pressurized gas sent from the gas storage tank 19.

For this reason, the rack 45 engages with the rotationally released pinion 44 due to its own weight and the suspended object below it, and the pressing force of the pressurized gas, and begins to fall at an accelerated rate while rotating the pinion 44. .

Therefore, in this embodiment as well, as in the first embodiment,
Since neither an electromagnet for suspending the extension tube nor a dedicated acceleration cylinder for sealing pressurized gas is used, the housing can be made smaller in diameter and shorter in length, and as in the first embodiment, heat removal performance and maintainability can be improved.

〔Effect of the invention〕

As explained above, the control rod drive mechanism of the present invention can achieve a reduction in diameter and length, thereby improving heat removal performance and maintainability.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views of control rod drive mechanisms according to the first and second embodiments of the present invention, Figure 3 is a schematic cross-sectional view of a fast breeder reactor, and Figure 4 is a conventional control rod drive mechanism. FIG. 3 is a cross-sectional view of the mechanism. 8...Housing, 9...Upper guide tube, 10...
Drive motor, 21... Extension tube, 24... Control rod, 3
1... Electromagnetic clutch, 32... Ball screw, 34...
...Ball nut, 36...Latch mechanism, 37...
Seal mechanism, 44... pinion, 45... rack.

Claims (1)

[Claims] 1. A housing opening downward, an upper guide pipe connected to the lower end of the housing, a gas storage tank for supplying pressurized gas into the housing, a drive motor housed in the housing, and The motor moves up and down within the housing and upper guide tube through a ball screw connected to the drive motor via an electromagnetic clutch and a ball nut screwed into the ball screw.
and a control rod drive mechanism having an extension tube for suspending the control rod, and a sealing mechanism that keeps the housing airtight while surrounding the extension tube. 2. A housing that opens downward, an upper guide pipe connected to the lower end of the housing, a gas storage tank that supplies pressurized gas into the housing, a drive motor housed in the housing, and a drive motor and an electromagnetic clutch. A pinion connected through the pinion, an extension tube that moves up and down within the housing and upper guide tube through a rack that engages with the pinion, and suspends the control rod, and a seal mechanism that keeps the housing airtight while surrounding the extension tube. A control rod drive mechanism having a control rod drive mechanism.