JPH03289593A - Shutting down device of fast breeder reactor - Google Patents

Abstract

PURPOSE:To confirm a self starting function of nuclear reactor shut down device by providing a heating means to cut off a control rod by heating up a magnetic body, and a holding means of the cut off control rod at a falling distance longer than detection level of a detector. CONSTITUTION:A control rod 11 at which upper part a magnetic body 12 having a Curie point is arranged, is magnetically attracted and held by an electro magnet 14 which is arranged at a lower part of an extention axis 13 driven by a control rod drive mechanism which is located at an upper position and in an upper guide tube 10. By switching on an electric source of heater 37 provided in the electro magnet 14, the electro magnet 14 and the magnetic body 12 being located at an upper end of the control rod 11 and fitting with the magnet 14, are heated up to make temperature of the magnetic body 12 reach the Curie point. Therewith, magnetic attraction force of the electro magnet 14 is weakened to an extent unble to hold weight of the control rod 11 and consequently the control rod 11 falls down.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a nuclear reactor control device that starts, stops, and controls a nuclear reactor by inserting control rods into a reactor core, and particularly relates to the operation of an emergency reactor shutdown device. The present invention relates to a fast breeder reactor shutdown device equipped with a self-operation confirmation mechanism suitable for confirming.

[Conventional technology]

The reactor shutdown system of a fast breeder reactor, for example, detects an abnormal event in the reactor as a change in the core outlet temperature of the fuel assembly using a thermocouple, etc., converts this into an electrical signal and transmits it to the control rod drive mechanism, which activates the drive mechanism. By releasing the control rod containing the neutron-absorbing material held by the Grits, the control rods begin to be inserted into the reactor core.This allows control of electrical equipment including thermocouples of the reactor shutdown equipment, grippers, etc. Failure of the mechanical equipment that drives the coupling mechanism with the rods will cause a serious accident for the reactor, so in the event of an abnormality in the furnace, the control rods will automatically connect to the coupling mechanism despite the failure of the electrical system or mechanical equipment. There is a need for a nuclear reactor shutdown device that has a self-actuating function that falls into the reactor core under its own weight and automatically shuts down the reactor.

In the past, many self-actuating reactor shutdown devices have been proposed that take into account the above requirements in order to respond to abnormal reactor events that may lead to particularly serious accidents, such as coolant flow rate reduction events and reactivity insertion events. ing. For example, JP-A-1-15
As shown in Japanese Patent No. 5295, a coupling mechanism consisting of a magnetic material having a Curie point and an electromagnet that attracts this magnetic material is constructed at the coupling part between the control rod and the extension shaft extending from the control rod drive mechanism, and If an abnormal event occurs, the exit temperature of the fuel assembly increases and the temperature of the magnetic material reaches the Curie point, the magnetic adsorption force with the electromagnet weakens and the electromagnet is no longer able to hold the weight of the control rod, causing the control rod to Due to its own weight, it automatically falls into the reactor core and shuts down the reactor. Its configuration will be explained below. In FIG. 7, a reactor vessel 1 has an upper end opening closed with a shielding plug 2 and a rotary plug 3, and a reactor core containing a plurality of fuel assemblies 6 supported by a core support plate 5 in a built-in coolant sodium 4. 7.

An upper core mechanism 8 supported by a shielding plug 2 and a rotating plug 3 is disposed on the reactor core 7, and within the upper core mechanism 8 is an upper guide tube 10 connected to an upper control rod drive mechanism 9.
is provided. The position of the control rod during reactor operation is determined by the extension shaft 1 in which the magnetic body 12 having a Curie point disposed above is driven by the control rod drive mechanism 9 in the upper guide tube 10.
3 is attracted by an electromagnet 14 placed at the bottom thereof, and is thereby held within the upper guide tube 10. The coolant sodium 4 flows into the reactor vessel 1 from the coolant population 15 and enters the reactor core 7, and when the fuel assembly 6 and control rods 11 are inserted into the reactor core 7, the coolant sodium 4 flows through the lower guide pipe 16, etc., which becomes a receiver. A portion of the sodium coolant 4 enters the upper guide pipe 10 and reaches the coolant outlet 17 via the upper guide pipe coolant outlet 18. In addition, as shown in FIGS. 8 and 9, the control rod 11 and the extension shaft 1
3 has a structure including a control rod coolant inlet 19, a coolant flow groove 20, and an electromagnet coolant outlet in order 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 entrances and exits and grooves are provided through which the coolant such as No. 21 flows, and the contact area between the coil 22 of the magnetic body 12 and the electromagnet 14 and the coolant sodium 4 flowing into the upper guide tube 10 is increased, so that the coolant is cooled during rated operation. Efforts have been made to ensure a large temperature difference during abnormal conditions, that is, a large difference in control rod holding force due to temperature. In addition, 23 in Fig. 9 indicates the control rod 11 and the extension shaft 1.
2 is a centering convex portion provided to align the coupling position on the axis of the coil 22, and 24 is a power cable to the coil 22.

[Problem to be solved by the invention]

The self-actuating nuclear shutdown system was originally positioned as an auxiliary device to back up the reactor shutdown system, which uses conventional coupling methods such as grippers for the coupling mechanism between control rods and extension shafts. It has the role of emergency shutdown of the reactor in place of the main equipment, which is unable to respond to abnormal reactor events in the event of electrical or mechanical equipment failure. In the conventional self-actuating nuclear reactor shutdown system, once the self-actuating function of the system begins to operate, the control rods are inserted into the reactor core and cannot be stopped midway. By the way, the magnetic material and electromagnet used in the coupling mechanism between the control rod and the extension shaft are immersed in high-temperature sodium for a long time under a high radiation dose. As a result, the initial characteristics of the magnetic material and electromagnets change, and the control rods may not fall into the reactor core as initially set when an assumed abnormal event occurs in the reactor, or conversely, the control rods may fall into the reactor core even though no abnormal event occurs. There is a concern that this may cause the furnace to stop unnecessarily. The problem with self-actuated reactor shutdown equipment is that reliability has not been established. For this reason, it is necessary to periodically check the self-actuating function of the self-actuating reactor shutdown system (i.e., the ability to accurately detect abnormal events in the reactor and ensure that the control rods fall into the reactor core). Particularly for commercial furnaces, in order to increase the operating rate, it is desired to lengthen the operating time from furnace startup to shutdown, and it is necessary to periodically check the self-operation function even during the operation period of the furnace. However, with the conventional technology, the structure makes it impossible to check the self-operation function of the device without disturbing the operating state of the reactor during the rated power operation of the reactor, especially without the risk of shutting down the reactor. There were problems in adopting it as such.

The purpose of the present invention is to solve the above-mentioned problems and provide a fast breeder reactor shutdown device that lifts the reactor control rod and checks the self-operation function without affecting the reactor's output during rated power operation. There is a particular thing.

[Means to solve the problem]

The above object is a fast breeder reactor shutdown device that includes a control rod that is inserted into the reactor core to shut down the reactor, a magnetic body fixed to the upper end of the control rod, and an electromagnet that attracts and holds the upper end of the magnetic body. , a heating means disposed within the electromagnet to heat the electromagnet and the magnetic body to simulate an abnormal event in the nuclear reactor, and a columnar portion movable in the axial direction provided at the core of the electromagnet and its tip. a connecting rod having a stopper provided on the connecting rod, a load detection means for detecting a load on the control rod side applied to the connecting rod, and a connecting rod drive for driving the connecting rod to insert and withdraw the stopper from the control rod side. and a predetermined predetermined portion provided between a lower end of a protrusion provided on the control rod side and an upper end of the stopper of the connecting rod when the magnetic body is attracted to the electromagnet and the stopper is inserted into the control rod side. This is achieved by providing a fast breeder reactor shutdown device characterized in that it has a gap of the same size.

The above object is that the connecting rod driving means is a motor whose output shaft moves in the axial direction when energized; a rotatable joint whose lower end is connected to an upper end of the connecting rod; and a ball screw provided between the connecting rod and the inside of the electromagnet.

This is achieved by providing a fast breeder reactor shutdown device having a spiral groove formed inside the control rod, with which the stopper abuts and rotates.

The above object is achieved by providing a fast breeder reactor shutdown device having a vertical groove in place of the spiral groove and a groove of half a circumference or less perpendicular to the vertical groove directly below the vertical groove. achieved.

The above object is achieved by providing a fast breeder reactor shutdown device in which the gap is set within a range that is greater than the detection limit of the load detection means and does not reduce the output of the reactor.

[Effect]

According to the above configuration, when checking the self-operation function of the device when the electromagnet attracts a magnetic material whose temperature is below the Curie point and holds the control rod, the connecting rod driving means moves the extension shaft and the electromagnet. A connecting rod movably provided on the core is driven, and a stopper provided at its tip is inserted into a predetermined position on the control rod side.

At this time, the lower end of the protrusion provided inside the control rod and the upper end of the stopper of the connecting rod are opposed to each other with a gap of a predetermined size interposed therebetween.

Next, the electromagnet and the magnetic material are heated by a heating means installed inside the electromagnet in order to simulate an abnormal event in a nuclear reactor. When the temperature of the magnetic material reaches the Curie point, the magnetic material loses its magnetism and the distance between the electromagnet and The attraction force of the electromagnet decreases, and the electromagnet is no longer able to hold the weight of the control rod, so the control rod separates and falls. However, the control rods did not fall according to the core amount of the reactor, and the upper end of the stopper of the connecting rod came into contact with the lower end of the protrusion provided inside the control rod to support the control rods, and the distance of the control rods fell was the same as originally specified above. If the control rod falls, the weight of the control rod will be applied to the connecting rod via the protrusion provided inside the control rod and the stopper of the connecting rod, so the connection The self-operating function is confirmed by detecting the load using the load detection means installed on the rod.

Furthermore, since a load detection means is conventionally provided on the extension shaft of the control rod, falling of the control rod can be similarly detected.

After confirming the self-operation function, stop heating the electromagnet and magnetic body by the heating means, rotate the connecting rod in the opposite direction, pull up the control rod, bring the electromagnet and magnetic body into close contact, and when the temperature of the magnetic body falls below the Curie point. The electromagnet is excited and the magnetic material is attracted to the electromagnet to hold the control rod. The connecting rod is further rotated, the stopper is housed inside the electromagnet, and the device returns to its normal state.

〔Example〕

Embodiments of the self-actuating nuclear reactor shutdown device according to the present invention will be described below. Note that the same reference numerals are used in the embodiments when the same as those explained in the conventional example.

FIG. 1 is a sectional view showing the configuration of this embodiment, and FIG. 2 is an enlarged view of the joint between the control rod and the electromagnet in FIG. In FIG. 1, a control rod 11 has a magnetic material 12 having a Curie point disposed in its upper part and an upper guide tube 10.
In this embodiment, the connecting rod 2 is magnetically attracted and held by an electromagnet 14 disposed at the bottom of an extension shaft 13 that is driven by a control rod drive mechanism (not shown) located above the rod.
5 is inserted into the insertion hole 26 provided on the surface of the control rod 11 that connects with the electromagnet 14 to confirm the operating function, and the stopper 27 provided at the tip of the connection rod 25 is placed at a predetermined position within the insertion hole 26.
In this case, the state shown is that it is located at the lowest end within the insertion hole 26. This predetermined position can be arbitrarily determined and is not limited to this embodiment. In this state, the stopper 27
A space 29 is formed between the upper surface and the lower surface of the groove end 28 of the insertion hole 26. Control rod 1 of connecting rod 25
1 into the insertion hole 26 is performed by driving a drive motor 30 provided above within the extension shaft 13. Here, the movement of the connection shaft 31 driven by the drive motor 30 as a vertical movement is caused by the movement of the connection shaft 31 into the universal joint 32. When the transmission is transmitted, the pole screw 34 mechanism supported by the bellows 33 provided below in the extension shaft 13 (in this embodiment, it is provided inside the electromagnet 14, but it may also be provided on the upper universal joint 32 side) Connection rod 25
A rotational motion is further added to the vertical motion, and the lower surface of the stopper 27 provided on the connecting rod 25 comes into contact with the upper surface of the groove end 28 of the insertion hole 26 and is inserted while rotating. Connecting rod 2
After the stopper 5 reaches a predetermined position in the insertion hole 26, a change in the force applied to the stopper 27 can be detected by a load cell 35 provided above the drive motor 30 during a self-actuation function test of the device or the like.

Of the coolant sodium 4 rising through the upper guide pipe 10,
The flow enters through the control rod coolant inlet 19, passes through the ball screw 34, passes through the coolant outlet 36 of the extension shaft 13, and exits from the upper guide tube coolant outlet 18. In this state, the method of confirming the self-operation function of the self-operating nuclear reactor shutdown device according to this embodiment is to turn on the power to the heater 37 provided in the electromagnet 14, and thereby connect the electromagnet 14 and the The magnetic body 12 at the upper end of the control rod 11 is heated, and the temperature of the magnetic body 12 reaches the Curie point. This weakens the magnetic attraction force between the electromagnet 14 and the electromagnet 14.
4 can no longer hold the weight of the control rod 11 and the control rod 11
falls.

Figure 3 shows the state after the control rod fell. Fallen control rod 1
1 is supported and stopped by the connecting rod 25 with the lower surface of the collar 28 of the groove of the insertion hole 26 in contact with the upper surface of the connecting rod 25. Therefore, contrary to the state shown in FIGS. 1 and 2, a space 38 is created between the lower surface of the stopper 27 of the control rod 25 and the upper surface of the groove end 28 of the insertion hole 26. Furthermore, the control rod 11 is prevented from falling by two load cells (not shown) installed in the control rod drive mechanism, which is disposed above the extension shaft 13 and monitors changes in the total weight of the control rod 11 and the connecting rod 25. This can be detected by a signal from the load cell 35, which is located above the connecting rod 25 and is not normally loaded with the weight of the control rod 11.

Next, the return method after confirming the self-operation function of this embodiment is to first turn off the power to the heater 37 in the electromagnet 14, reverse the driving direction of the drive motor 30, and pull up the connecting rod 25. At this time, the control rod 11 is supported on the upper surface of the stopper 27 of the connecting rod 25, and the movement of the stopper 27 of the connecting rod 25 causes the electromagnet 14 to be connected and raised. In this state, wait until the temperature of the electromagnet 14 and the magnetic body 12 decreases and the magnetic attraction force recovers. To confirm that the magnetic attraction force due to the electromagnet 14 and the magnetic body 12 has recovered, insert the connecting rod 25 and the control rod 11 again. It is inserted into the hole 26, the signal of the load cell 35 at this time is monitored, and a judgment is made based on whether the signal is the same as before the self-actuation function confirmation test. That is, if the suction force is not completely recovered, the weight of the control rod 11 will be applied to the stopper 27. After the control rod 11 is completely attracted and held by the electromagnet 14, the connecting rod 25 is further pulled up and the stopper 27 is attached to the electromagnet 14.
Store inside the bottom.

FIG. 4 shows the returned state of the stopper 27 in this embodiment.
The lower end of the control rod 11 stops above the insertion hole 26 of the control rod 11, and functions as a centering protrusion 23 in the same way as in the conventional device.

Insertion hole 26 for control rod 11 which is twisted or nearly band-shaped as shown in FIG.
An example of the shape of the groove top 28 is shown.

In this case, the stopper 27 of the connecting rod 25 is inserted into the insertion hole 26 while rotating.

Note that a power cable 24 to the coil 22 and a heater power cable 41 pass through the extension shaft 13 in the figure.

FIG. 6 shows another embodiment of the collar 28.

In contrast to FIG. 5, the tail 28 is once compared to the 172nd circumference of the insertion hole 26, and from there, a vertical hole 39 is formed directly below, and at the lower end of the vertical hole 39, it again extends about 1/2 circumference in the circumferential direction. A horizontal hole 40 is formed.

The method for inserting the connecting rod 25 is almost the same as that described in FIGS. 1 to 5, but when the stopper 27, which has initially rotated, is prevented from rotating by the wall of the opening of the vertical hole 39, the driving force of the drive motor 30 is reduced. That is, the downward pushing force is directly transmitted to the ball screw 34 via the universal joint 32, the bellows 33 supporting the ball screw 34 extends downward, and the stopper 27 is inserted into the vertical hole 39. When the stopper 27 reaches the opening of the horizontal hole 40, the rotational direction is no longer restrained, and the stopper 27 rotates inside the horizontal hole 40 and stops against the wall at a predetermined position. At this time, the blocking force is measured by a rotational force detector (not shown) of the connecting shaft 31, and when it exceeds a certain value, the rotation of the drive motor 30 is stopped or idled. The restoration method is performed by reversing the above-mentioned operation.

Although the present invention has been described above for a fast breeder reactor that uses liquid metal as a coolant, it is of course possible to apply the present invention to other types of reactor shutdown devices that use water or gas as a coolant. Further, although the present invention has been explained using the above embodiments, the present invention is not limited to the embodiments.

〔Effect of the invention〕

According to the present invention, in order to simulate an abnormal event in the yX sub-reactor, heating means heats the magnetic material to separate the control rod, and means holds the separated control rod at a fall distance exceeding the detection limit of the detector. By providing a detector for confirming the fall of a control rod, it is possible to confirm the self-operation function of the reactor shutdown device without causing any disturbance to the operation of the reactor.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing the overall configuration of a nuclear reactor shutdown device having a self-operating function according to an embodiment of the present invention, and FIG.
Figure 3 is an enlarged longitudinal sectional view of the main parts shown in the figure after the start of the test, Figure 3 is an enlarged longitudinal sectional view of Figure 2 when the test is completed, Figure 4 is an enlarged longitudinal sectional view of the main parts shown in Figure 3 after the test has been returned to normal, and Figure 5 is is a cross-sectional perspective view of the 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 nuclear reactor according to the prior art. 8 is an enlarged vertical sectional view of the reactor shutdown device shown in FIG. 7, and FIG. 9 is a cross-sectional perspective view of the nuclear reactor shutdown device shown in FIG. 8. DESCRIPTION OF SYMBOLS 11... Control rod, 12... Magnetic body, 13... Extension shaft, 14... Electromagnet, 22... Coil, 25...
Connection rod, 26... Insertion hole, 27... Stopper, 28
...Brim, 29...Space, 30...Drive motor,
31... Connection shaft, 32... Universal joint, 33... Bellows, 34... Ball screw, 35... Load cell, 37... Heater, 39... Vertical hole, 40... Side hole.

Claims (1)

[Claims] 1. A control rod that is inserted into the reactor core to stop the reactor, a magnetic body fixed to the upper end of the control rod, and a magnetic body that attracts the upper end of the magnetic body.
A fast breeder reactor shutdown device having a holding electromagnet, a heating means disposed within the electromagnet and heating the electromagnet and the magnetic body to simulate an abnormal event in the nuclear reactor;
a connecting rod having a columnar part movably provided in the axial direction on the core of the electromagnet and a stopper provided at the tip thereof; a load detection means for detecting a load on the control rod side applied to the connecting rod;
a connecting rod driving means for driving the connecting rod to insert and withdraw the stopper from the control rod side; and a connecting rod driving means for driving the connecting rod to insert and withdraw the stopper from the control rod side; and a connecting rod driving means for driving the connecting rod to insert and withdraw the stopper from the control rod side; A stop device for a fast breeder reactor, comprising a gap of a predetermined size provided between a lower end of a protrusion provided on the connecting rod and an upper end of the stopper of the connecting rod. 2. The connecting rod driving means is a motor whose output shaft moves in the axial direction when energized; a rotatable joint connected to the upper end of the connecting rod, a ball screw provided between the connecting rod and the inside of the electromagnet, and a spiral shape formed inside the control rod that rotates when the stopper comes into contact with the rotary joint. 2. The fast breeder reactor shutdown device according to claim 1, further comprising a groove. 3. The high-speed growth according to claim 2, characterized in that, instead of the spiral groove, there is a vertical groove and, directly below the vertical groove, a groove of half the circumference or less that is orthogonal to the vertical groove. Furnace shutdown device. 4. The fast breeder reactor shutdown device according to claim 1, wherein the gap is within a range that is greater than the detection limit of the load detection means and does not reduce the output of the reactor.