JP2912973B2 - Stopper for fast breeder reactor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor control apparatus for starting / stopping and controlling a reactor by inserting a control rod into a reactor core, and particularly to an operation of an emergency reactor shutdown apparatus. The present invention relates to a fast breeder reactor stopping device provided with a self-operation confirmation mechanism suitable for confirming the above.

[Conventional technology]

The reactor shutdown device of the fast breeder reactor, for example, detects an abnormal event of the reactor with a thermocouple or the like as a change in the core exit temperature of the fuel assembly, converts this to an electric signal and transmits it to the control rod drive mechanism,
The drive mechanism operates to release the control rod containing the neutron-absorbing substance that was gripped by the gripper, thereby starting the insertion of the control rod into the core. From this, failure of electrical equipment including the thermocouple of the reactor shutdown device and mechanical equipment that drives the coupling mechanism with the control rods such as the gripper causes a serious accident for the reactor. Despite such electrical and mechanical equipment failures, the control rod is automatically disengaged from the coupling mechanism, and a reactor shutdown device that has a self-acting function that automatically drops the core by its own weight and shuts down the reactor spontaneously is required. Is done.

Conventionally, many self-acting reactor shutdown devices that take into account the above requirements have been proposed in order to respond to abnormal reactor events that may lead to particularly serious accidents such as coolant flow reduction events and reactivity insertion events. ing. For example, Japanese Patent Laid-Open No. 1-15
As shown in Japanese Patent No. 5295, a coupling mechanism comprising a magnetic body having a Curie point at a coupling portion between a control rod and an extension shaft extending from the control rod drive mechanism and an electromagnet for attracting the magnetic substance is constituted, When an abnormal event occurs, when the temperature of the outlet of the fuel assembly rises and the temperature of the magnetic body reaches the Curie point, the magnetic attraction force with the electromagnet weakens and the electromagnet cannot hold the weight of the control rod, and the control rod Due to its own weight, it automatically falls into the core and stops the furnace. The configuration will be described below. In FIG. 7, a reactor vessel 1 has a plurality of fuel assemblies 6 supported by a core support plate 5 in a coolant sodium 4 having an upper end opening closed by a shielding plug 2 and a rotary plug 3 and contained therein. It has a core 7. An upper core mechanism 8 supported by the shield plug 2 and the rotary plug 3 is provided on the core 7, and an upper guide tube 10 connected to an upper control rod driving mechanism 9 is provided in the upper core mechanism 8. ing. During the operation of the reactor, the position of the control rod is determined by an electromagnet 14 disposed below the extension shaft 13 in which a magnetic body 12 having a Curie point disposed thereon is driven by the control rod driving mechanism 9 in the upper guide tube 10. It is adsorbed and is thereby held in the upper guide tube 10. The sodium coolant 4 flows into the reactor vessel 1 from the coolant inlet 15 and enters the reactor core 7, and the fuel assembly 6 and the lower guide tube 16 serving as a receiver when the control rods 11 are inserted into the reactor core 7. The coolant flows out from the reactor vessel 1 to the coolant outlet 17, but a part of the coolant sodium 4
And enters the coolant outlet 17 via the upper guide tube coolant outlet 18. As shown in FIGS. 8 and 9, the structure of the connecting portion of the control rod 11 and the extension shaft 13 is to improve the transmission of the core outlet temperature of the fuel assembly 6 to the magnetic body 12 and the electromagnet 14. A plurality of inlets and grooves through which a coolant flows, such as a control rod coolant inlet 19, a coolant passage groove 20, and an electromagnet coolant outlet 21, are provided, and the magnetic body 12, the coil 22 of the electromagnet 14, and the upper guide tube 10 are provided. The contact area between the coolant 4 and the coolant 4 is increased so that a temperature difference between the rated operation and the abnormal operation, that is, a difference in the control rod holding force depending on the temperature can be increased. In FIG. 9, reference numeral 23 denotes a centering projection provided so as to match the positions of the control rod 11 and the extension shaft 13 on the axis.
Is a power cable to the coil 22.

[Problems to be solved by the invention]

The self-acting type atomic stop device is originally positioned as an auxiliary device for backing up the reactor stop device using a conventional coupling method such as a gripper as a main device in a coupling mechanism between the control rod and the extension shaft, It has the role of performing an emergency shutdown of the reactor in place of a main unit that cannot respond to an abnormal event of the reactor due to electrical or mechanical equipment failure. In the self-acting reactor shutdown device according to the prior art, once the self-actuation function of the device starts to operate, the control rod is inserted into the core and cannot be stopped halfway. By the way, the magnetic material and the electromagnet used for the coupling mechanism between the control rod and the extension shaft are immersed in high-temperature sodium under a high radiation dose for a long time. As a result, the initial characteristics of the magnetic material and the electromagnet change, and the control rod cannot be dropped into the core as initially set when an assumed abnormal event occurs in the furnace, or the control rod falls into the core when no abnormal event occurs. It is feared that the furnace will be shut down unnecessarily. The point that the reliability has not been established is a problem of the self-acting reactor shutdown device. For this reason, the self-acting function of the self-acting reactor shutdown device (ie, accurately detecting abnormal events of the reactor,
It is necessary to periodically check the function of reliably dropping the control rod into the core). In particular, as a commercial furnace, it is required to increase the operation time from furnace start to shutdown in order to increase the operation rate, and it is necessary to periodically check the self-operation function even during the operation of the furnace. However, in the prior art, the self-operating function of the device cannot be confirmed without disturbing the operation state of the reactor during the rated output operation of the reactor, particularly without the risk of shutting down the reactor. There was a problem to adopt as.

An object of the present invention is to solve the above-mentioned problems and to provide a fast breeder reactor shutdown device that raises the control rod of the reactor and checks the self-operation function without affecting the output of the reactor during rated output operation. It is in.

[Means for solving the problem]

An object of the present invention is to provide a stopping device for a fast breeder reactor having a control rod inserted into a reactor core to stop a nuclear reactor, a magnetic body fixed to an upper end of the control rod, and an electromagnet for attracting and holding the upper end of the magnetic body. A heating means disposed in the electromagnet for heating the electromagnet and the magnetic body to simulate an abnormal event of the nuclear reactor, a columnar portion provided on the core of the electromagnet so as to be movable in the axial direction, and a tip thereof A connecting rod having a stopper provided on the connecting rod, load detecting means for detecting a load applied to the connecting rod on the control rod side, and a connecting rod drive for driving the connecting rod to insert and withdraw the stopper to the control rod side A predetermined means provided between a lower end of a projection provided on the control rod side and an upper end of a stopper of the connection rod when the magnetic body is attracted to the electromagnet and the stopper is inserted into the control rod side. Having dimensional gap Is achieved by providing a stopping device of the fast breeder reactor, characterized.

The object is that the connecting rod driving means is a motor whose output shaft moves in the axial direction when energized, and a connecting shaft having an upper end connected to the output shaft of the connecting rod driving means and an upper end fixed to a lower end of the connecting shaft. A lower end is connected to an upper end of the connecting rod, a rotatable joint, a ball screw provided between the connecting rod and the inside of the electromagnet, and a stopper is formed inside the control rod to be rotated by contact. This is achieved by providing a fast breeder reactor shutdown device having a spiral groove.

The object is to provide a stop device for a fast breeder reactor having a vertical groove instead of the spiral groove and a half-periphery or less groove orthogonal to the vertical groove immediately below the vertical groove. Achieved.

The above object is achieved by providing a fast breeder reactor stop device in which the gap is set to a range that does not lower the output of the reactor when the gap is equal to or greater than the detection limit of the load detecting means.

[Action]

According to the above configuration, when the self-operating function of the device is checked at the time when the electromagnet attracts the magnetic material having a temperature equal to or lower than the Curie point and holds the control rod, the connecting rod driving means controls the extension shaft and the electromagnet. The connecting rod movably provided on the core is driven, and a stopper provided at the tip thereof is inserted into a predetermined position on the control rod side.

At this time, the lower end of the projection provided inside the control rod and the upper end of the stopper of the connection rod face each other with a gap of a predetermined size.

Next, the heating means arranged in the electromagnet heats the electromagnet and the magnetic body in order to simulate an abnormal event of the reactor, and when the temperature of the magnetic body reaches the Curie point, the magnetic body loses magnetism and moves between the magnet and the electromagnet. The attraction force is reduced, and the electromagnet cannot hold the weight on the control rod side, so that the control rod side falls away. However, the control rod does not fall to between the cores of the reactor, but the upper end of the stopper of the connecting rod abuts the lower end of the projection provided inside the control rod to support the control rod. The gap of the predetermined size remains, and the power of the reactor is not reduced. When the control rod falls, its weight is applied to the connection rod via the protrusion provided inside the control rod and the stopper of the connection rod, so the load is detected by the load detection means provided on the connection rod to confirm the self-operation function. Do.

Further, since the load detecting means is provided on the extension shaft of the control rod, the fall of the control rod can be similarly detected.

After confirming the self-actuation function, stop heating the electromagnet and magnetic material by the heating means, rotate the connecting rod in the reverse direction, pull up the control rod to bring the electromagnet and magnetic material into close contact, and when the temperature of the magnetic material falls below the Curie point To excite the electromagnet to attract the magnetic material to the electromagnet and hold the control rod. The connecting rod is further rotated, and the stopper is stored inside the electromagnet, and the device returns to the normal state.

〔Example〕

Hereinafter, an embodiment of the self-acting reactor shutdown apparatus according to the present invention will be described. The reference numerals used in the embodiments are the same as those described in the conventional example when they are the same.

FIG. 1 is a sectional view showing the structure of this embodiment, and FIG.
The figure shows an enlarged view of the joint between the control rod and the electromagnet shown in FIG. In FIG. 1, a control rod 11 is provided with an extension shaft 13 driven by a control rod driving mechanism (not shown) positioned above a magnetic body 12 having a Curie point disposed above the control rod 11. It is magnetically attracted and held by the electromagnet 14 disposed at the lower portion. In this embodiment, the connection rod 25 is inserted into an insertion hole 26 provided on the surface of the control rod 11 to be joined to the electromagnet 14 for checking the operation function. And the stopper 27 provided at the tip of the connection rod 25 is positioned at a predetermined position in the insertion hole 26, in this case, at the lowermost end in the insertion hole 26. This predetermined position can be arbitrarily determined and is not limited to the present embodiment. In this state, the upper surface of the stopper 27 and the groove of the groove of the insertion hole 26
The space 29 is formed between the lower surface of the space 28 and the space 29. The insertion of the connection rod 25 into the insertion hole 26 of the control rod 11 is performed by driving a drive motor 30 provided above the extension shaft 13, and here, a connection shaft 31 driven by the drive motor 30 as up and down movement. When the movement is transmitted to the universal joint 32, the bellows 33 is provided below the extension shaft 13 (in this embodiment, it is provided inside the electromagnet 14 but may be provided above the universal joint 32). The connecting rod 25 is further vertically and rotationally moved by the ball screw 34 mechanism, and a stopper provided on the connecting rod 25 is provided.
The lower surface of 27 is in contact with the upper surface of the flange 28 of the groove of the insertion hole 26, and is inserted while rotating. After the connecting rod 25 reaches the predetermined position of the insertion hole 26, the slapper is
The change in the force applied to 27 can be detected by load cell 35 provided above drive motor 30. Of the coolant sodium 4 rising in the upper guide tube 10, the control rod coolant inlet 19
The flow that has entered and passed through the ball screw 34 passes through the coolant outlet 36 of the extension shaft 13 and exits from the upper guide pipe coolant outlet 18. In this state, the method of confirming the self-operation function of the self-operation type reactor shutdown device according to the present embodiment is as follows.
The power of the heating heater 37 provided in the power supply 14 is turned on, whereby the electromagnet 14 and the magnetic material at the upper end of the control rod 11 joined thereto are turned on.
The magnetic material 12 is heated to reach the temperature Curie point of the magnetic material 12.
This weakens the magnetic attraction with the electromagnet 14, the electromagnet 14 cannot hold the weight of the control rod 11, and the control rod 11 falls.

FIG. 3 shows a state after the control rod has fallen. Control rod dropped
11 is supported and stopped by the connecting rod 25 in a state where the lower surface of the flange 28 of the groove of the insertion hole 26 is in contact with the upper surface of the connecting rod 25.
Therefore, the control rod is opposite to the state shown in FIG. 1 and FIG.
A space 38 is formed between the lower surface of the stopper 27 and the upper surface of the flange 28 of the groove of the insertion hole 26. When the control rod 11 falls, two load cells, that is, load cells (not shown) provided on a control rod drive mechanism disposed above the extension shaft 13 and monitoring a change in total weight including the control rod 11 and the connection rod 25 are provided. And the load cell 35 above the connecting rod 25 and normally not weighing the control rod 11
Can be detected by the signal from.

Next, the return method after confirming the self-actuation function of the present embodiment is as follows.
First, the power of the heater 37 in the electromagnet 14 is turned off, the driving direction of the drive motor 30 is reversed, and the connecting rod 25 is pulled up. At this time, the control rod 11 is supported on the upper surface of the stopper 27 of the connection rod 25, and the movement of the stopper 27 of the connection rod 25 causes the electromagnet 14 to move.
Ascending surface. In this state, wait until the temperature of the electromagnet 14 and the magnetic body 12 decreases and the magnetic attraction force recovers.
In order to confirm the recovery of the magnetic attraction force by the magnetic material 12, the connection rod 25 is inserted again into the insertion hole 26 of the control rod 11, and the signal of the load cell 35 at this time is monitored, and the signal is used before the confirmation test of the self-operation function. It is determined by whether or not it is the same. That is, if the suction force is not completely recovered, the weight of the control rod 11 is added to the stopper 27. After the control rod 11 is completely attracted and held by the electromagnet 14, the connection rod 25 is further pulled up, and the stopper 27 is
14 Store in the lower part.

FIG. 4 shows a restored state of the present embodiment. Stopper 27
Is stopped above the insertion hole 26 of the control rod 11, and performs the function of the centering projection 23 as in the conventional device.

FIG. 5 shows an embodiment of the shape of the groove 28 of the groove of the insertion hole 26 of the control rod 11 which is nearly twisted or band-shaped. In this case, connecting rod 25
The stopper 27 is inserted into the insertion hole 26 while rotating.

The extension shaft 13 in the figure is a power cable to the coil 22.
24 and the heater power cable 41 for heating penetrate.

FIG. 6 shows another embodiment of the collar 28 described above. In contrast to FIG. 5, the collar 28 temporarily stops at a half of the circumference of the insertion hole 26, from which a vertical hole 39 is formed immediately below, and at the lower end of the vertical hole 39 again about 1/2 of the circumference in the circumferential direction. An elongated lateral hole 40 is formed. The insertion of the connecting rod 25 is substantially the same as the method described with reference to FIGS.
39 When the rotation is blocked by the wall of the opening, the driving force of the driving motor 30, that is, the downward pushing force is transmitted to the ball screw 34 through the universal joint 32 as it is, and the bellow 33 that supports the ball screw 34.
Extend downward, and the stopper 27 is inserted into the vertical hole 39. When the stopper 27 reaches the opening of the side hole 40, the stopper in the rotation direction is released, and the stopper 27 rotates in the side hole 40 and hits a wall at a predetermined position and stops. At this time, the stopping force is measured by a rotational force detector of the connection shaft 31 (not shown), and when the stopping force exceeds a predetermined value, the rotation of the drive motor 30 is stopped or idling. The return method is performed by reversing the above operation.

The above describes the case where the present invention is applied to a fast breeder reactor using liquid metal as a coolant.However, application to other types of reactor shutdown devices using water or gas as a coolant is naturally possible, Although the present invention has been described with reference to the above embodiment, the present invention is not limited to the embodiment.

〔The invention's effect〕

According to the present invention, a heating means for heating a magnetic body to simulate an abnormal event of a nuclear reactor and separating a control rod, a means for holding the separated control rod at a drop distance equal to or longer than a detection limit of a detector, By providing the detector for confirming the drop of the control rod, it is possible to confirm the self-operation function of the reactor shutdown device without causing disturbance to the operation of the reactor.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing the entire configuration of a reactor shutdown device having a self-acting function according to an embodiment of the present invention, and FIG.
FIG. 3 is an enlarged vertical cross-sectional view of the main part shown in the figure after the start of the test, FIG. 3 is an enlarged vertical cross-sectional view of FIG. 2 when the test is completed, FIG. 4 is an enlarged vertical cross-sectional view of FIG. 4 is a sectional perspective view of a main part shown in FIG. 4, FIG. 6 is a cross-sectional perspective view showing another embodiment of the main part shown in FIG. 5, and FIG. 7 is an overall configuration of a conventional nuclear reactor. FIG. 8 is an enlarged longitudinal sectional view of the reactor shutdown device shown in FIG. 7, and FIG. 9 is a sectional perspective view of the reactor shutdown device shown in FIG. 11 ... control rod, 12 ... magnetic material, 13 ... extension shaft, 14 ... electromagnet, 22 ... coil, 25 ... connection rod, 26 ... insertion hole, 27 ... stopper, 28 ... collar 29 ... space, 30 ... drive motor, 31 ... connecting shaft, 32 ... universal joint, 33 ... bellows, 34 ... ball screw, 35 ... load cell, 37 ... heater for heating, 39 ... vertical hole, 40 …… The side hole.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Shigehiro Shimoyashiki 1168 Moriyama-cho, Hitachi City, Ibaraki Prefecture Energy Laboratory, Hitachi, Ltd. (56) References JP-A-57-56785 (JP, A) JP-A-56 -160687 (JP, A) JP-A-55-74491 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G21C 9/02

Claims (4)

(57) [Claims] 1. A fast breeder reactor having a control rod inserted into a reactor core to stop a nuclear reactor, a magnetic body fixed to an upper end of the control rod, and an electromagnet for attracting and holding the upper end of the magnetic body. In the apparatus, a heating means disposed in the electromagnet to heat the electromagnet and the magnetic body to simulate an abnormal event of the nuclear reactor, a columnar portion provided on the core of the electromagnet so as to be movable in the axial direction, and A connecting rod having a stopper provided at the tip, a load detecting means for detecting a load on the control rod side applied to the connecting rod, and a connecting rod for driving the connecting rod to insert and withdraw the stopper to and from the control rod side A drive unit, provided between the lower end of the protrusion provided on the control rod side and the upper end of the stopper of the connection rod when the magnetic body is attracted to the electromagnet and the stopper is inserted into the control rod side; Having a gap of a predetermined size FBR stop device according to claim. 2. The connecting rod driving means is a motor whose output shaft moves in the axial direction when energized. An upper end is connected to an output shaft of the connecting rod driving means, and an upper end is connected to a lower end of the connecting shaft. A rotatable joint that is fixed and has a lower end connected to the upper end of the connecting rod, a ball screw provided between the connecting rod and the inside of the electromagnet, and formed inside the control rod that rotates when the stopper abuts The stopping device for a fast breeder reactor according to claim 1, wherein the stopping device has a spiral groove. 3. The method according to claim 2, wherein a vertical groove and a groove not more than a half circumference orthogonal to the vertical groove are provided immediately below the vertical groove in place of the spiral groove. For fast breeder reactor. 4. The fast breeder reactor shut-down device according to claim 1, wherein the gap is set to a range which is not less than a detection limit of the load detecting means and does not lower the output of the reactor.