JPS6282394A - Stop device for nuclear 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 a nuclear reactor shutdown device for a fast breeder reactor.

[Technical Precedence of the Invention II] Generally, in a fast breeder reactor, a
I [Output is controlled by inserting or withdrawing the I rod. The control rods are inserted and withdrawn by a control rod drive mechanism installed in the shielding plug of the reactor vessel.

Furthermore, when a nuclear reactor is to be shut down, all of the control rods are inserted into the reactor core.

By the way, when an abnormality occurs, such as an earthquake, an emergency shutdown of the nuclear reactor (hereinafter referred to as a scram) is performed, and the scram is performed by inserting all control rods into the reactor core at high speed. At this time, if the control rod is inserted at high speed by the control rod drive mechanism, the insertion speed will be slow, and in the event that the control rod drive I side malfunctions, the scram operation will become impossible. Temau. Conventionally, the holding mechanism that connects the control rods to the control rod drive mechanism is forcibly opened using a scram signal, and the control rods are inserted into the reactor core using gravity.

[Problems with Background Art] However, the above configuration has the following problems. That is, if a failure should occur in the circuit that outputs the scram signal, there is a possibility that the scram operation will become impossible. Therefore, a so-called backup reactor shutdown device has been developed that operates independently and shuts down the reactor when an abnormality occurs in the reactor, without relying on the scram signal. The backup reactor shutdown device has a holding mechanism that holds the control rods in the withdrawn state and maintains the reactor temperature (coolant temperature).
When the temperature of the control rod exceeds a predetermined temperature, the Curie point electromagnet built into the holding mechanism exceeds the Curie point and becomes a non-magnetic material, and as a result, the holding mechanism releases the control rod and the control rod is pulled into the reactor core by its own weight. It means falling inside.

However, when such a backup reactor shutdown system is used, in addition to the control rods for reactor control and the control rods for the reactor shutdown system activated by scram signals, the control rods necessary to shut down the reactor are required. It is necessary to install them separately, and as a result, the number of control rods increases, resulting in a problem that the reactor core and eventually the reactor become larger.

[Purpose of the Invention] The present invention has been made based on the above points, and its purpose is to
It is an object of the present invention to provide a nuclear reactor shutdown device that can reduce the number of control rods and effectively downsize the reactor core and ultimately the reactor.

[Summary of the Invention] That is, the nuclear reactor shutdown device according to the present invention includes an outer extension tube having a latch finger at the lower end, and a finger rod disposed on the inner peripheral side of the outer extension tube and provided at the lower end to expand the latch finger. and an inner extension tube that engages the latch finger with the handling head connected to the upper end of the control rod; and the control rod is inserted into the reactor core through the extension tube connected to the upper end of the extension tube.・A drive unit that releases the connection with the extension tube by outputting a scram signal and urgently inserts the extension tube and control rod into the reactor core while holding them together, and the outer extension tube and inner extension tube. A Curie point electromagnet mechanism is provided on one side and has a Curie point electromagnet that becomes non-magnetic when heated above the Curie point, and an attracted part is provided on the other side and is attracted by the Curie point electromagnet mechanism. When the temperature of the coolant rises and the Curie point electromagnet mechanism is heated to above the Curie point, its magnetic force is demagnetized and the attraction between the Curie point electromagnet mechanism and the non-attracting part is released, thereby causing the inner extension tube to fall. The latch finger is disengaged from the handling head and the control rod is inserted into the reactor core.

In other words, in addition to the scram operation being performed by the scram operation signal, even in the unlikely event that the scram signal is not output, if the coolant temperature rises due to an abnormality in the reactor and rises to a preset temperature or higher, the Curie point N The Curie point electromagnet of the magnet mechanism becomes non-magnetic and the attraction of the attracted part is released, thereby breaking the connection between the extension tube and the control rod and inserting the control rod into the reactor core, thereby performing a scram operation. . In this way, it is an object of the present invention to provide a nuclear reactor shutdown device that has the functions of both a scram operation using a scram signal and a scram operation when the scram signal is not output for some reason.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is a vertical sectional view showing a schematic configuration of a loop fast breeder reactor according to this embodiment.

Reference numeral 1 in the figure is a reactor vessel, and a coolant 2 and a reactor core 3 are housed within this reactor vessel 1.

The reactor core 3 is composed of a plurality of fuel assemblies, control rods 3A, etc. (not shown). Further, the upper opening 1A of the reactor vessel 1 is closed by a shielding plug 4. A core upper mechanism 5 is disposed above the reactor core 3, passing through the shielding plug 4. A control rod drive mechanism 6 is disposed in this upper core mechanism 5 . This control rod drive mechanism 6
Insertion and withdrawal of the control rods 3A into and from the reactor core 3 is controlled by the control rods 3A.

According to the above configuration, the coolant 2 is supplied below the core 3 via the coolant inflow pipe 11 and flows upward through the core 3. At that time, the temperature rises due to the heat of nuclear reaction in the core 3, and the core 3
flows upward. The coolant 2 that has flowed out is introduced into an intermediate heat exchanger (not shown) via the coolant outflow pipe 12, where it is cooled by exchanging heat with the secondary coolant, and is pressurized by the circulation pump, and the coolant inflow is It is introduced into the reactor vessel 1 again via the pipe 11. The same cycle is repeated thereafter.

Next, the configuration of the control rod drive mechanism 6 will be explained with reference to FIGS. 2 and 3. The control rod drive mechanism 6 includes a drive section 21 located above the reactor vessel 1, and a drive section 21 located above the reactor vessel 1.
An extension tube 2 connected to the lower end of the tube and raised and lowered by a drive unit 21
2, and an upper guide tube 2 arranged around the outer periphery of this extension tube 22.
It is composed of 3. On the other hand, on the core 3 side, a plurality of wrapper tubes 31 and guide tubes 32 are arranged at predetermined intervals. These trumpet tube 31 and guide tube 32
The lower end of the upper core support plate 4 constitutes the high pressure plenum 41.
2a and a lower core support plate 42b. The coolant 2 flowing within the high-pressure blemish 41 flows into the trumpet tube 31 and the guide tube 32, and flows upward in the respective tubes. The trumpet tube 3 contains core fuel 45, and the guide tube 32 contains the control rods 3A.
is inserted. The control rod 3A is filled with a neutron absorbing material, and a handling head 46 connected to a control rod latch mechanism, which will be described later, is attached to the upper part of the control rod 3A.

The drive unit 21 has the following configuration. Second
The illustration number 51 is a drive motor, and this drive motor 51
is installed above the casing 52. A pole screw 54 is connected to the drive shaft 53 of the drive motor 51, and a magnet 55 is disposed at the upper outer periphery of the pole screw 54. On the other hand, a piston rod 56 is connected to the upper part of the extension tube 22, and the piston rod 56 is attracted to the magnet 55. Further, the magnet 55 is connected to the pole screw 54.
It is fixed to a pole nut 57 which is screwed into the pole nut 57. Therefore, when the drive motor 51 rotates, it is converted into vertical movement by the pawl screw 54 and pawl nut 57, thereby causing the extension tube 22 to move up and down. However, this is the case when the piston rod 56 is kept attracted by the magnet 55. When the scram signal is output, the attraction by the magnet 55 is released, and the extension tube 22, that is, the control rod 3A, is thereby inserted into the reactor core 3 at high speed. At that time, gas pressure acts within the acceleration cylinder 52 (the casing 52 also serves as an acceleration cylinder).

That is, the gas system piping 61 is located at the upper end of the acceleration cylinders 5 and 2.
is connected, and during scram, this gas system piping 61
High pressure gas is supplied into the acceleration cylinder 52 via.

The high pressure gas is supplied to the piston rod 56
and the extension pipe 22 are connected to each other via the connection If14t162.

As shown in FIG. 3, the extension tube 22 is composed of an inner extension tube 22a and an outer extension tube 22b.

A shield 65 is installed at the upper part of the inner extension tube 22a, and a finger rod 66 is provided at the lower end of the shield 65. Further, the reference numeral 67 in the figure is also a shielding body. A latch finger 71 is attached to the lower end of the outer extension tube 22b, and the latch finger 71 is expanded outwardly by a finger rod 66 at the lower end of the inner extension tube 22a and is attached to the handling head 46 from the inside. They are engaged, thereby connecting the extension tube 22 side and the control rod 3A.

A Curie point electromagnet t[81 is installed above the latch finger 71 of the outer extension tube 22b. Reference numeral 82 in the figure is a frame body of the Curie point electromagnet m structure 81, and this frame body 82 is composed of an upper support plate 82a, a lower support plate 82b, and a cylindrical body 82C. There is a Curie point N inside the frame 82! i-stone 85 is installed. This Curie point electromagnet 85 has a hollow cylindrical shape and is provided with an electromagnetic coil 86 inside. The inner extension tube 22a is inserted through the hollow portion. Further, there is a space 87 below the Curie point electromagnet 85, and within this space 87 there is a attracted plate 91 of the inner extension tube 22a. is located.

Therefore, when the Curie point electromagnet 85 is operating, the attracted plate 91 is attracted and is in the state shown in FIGS. 2 and 3. Note that below the adsorption target plate 91! 1! It has a built-in li spring 92. Note that the reference numeral 101 in the figure is a coil spring, and this coil spring 101 always urges the inner extension tube 22a downward. This makes it possible to quickly disconnect the inner extension tube 22a. The original number 102 in Figure 2 is bellows. In addition, the original number 111 in Figure 3 is a coolant introduction pipe, and the number 11
2 is an electromagnet covered window. The coolant 2 is supplied to the Curie point 1 through the coolant introduction pipe 111 and the electromagnet covered window 112.
It is intended to efficiently introduce it near the t1 stone mechanism 81 to improve the abnormal temperature response.

The operation will be explained based on the above configuration. First, the case of normal operation when the temperature of the coolant 2 is normal will be described.

In this case, the engagement between the handling head 46 of the control rod 3A and the latch finger 71 must be maintained, and the control rod 3Δ must be connected to the extension tube 22. That is, the coil 86 is energized, the Curie point N magnet 85 is in an excited state, and the armature 91 of the inner extension tube 22a is attracted to the Curie point electromagnet 85. At the same time, the drive unit 21
The magnet 55 of
inserted into or pulled out. This controls the output of the core 3.

Next, a case will be described in which an abnormality occurs in the reactor and a scram operation is performed. In this case, a scram signal is output from a safety protection system (not shown).

The output of this scram signal demagnetizes the magnet 55 of the drive section 21. At the same time, the gas system piping 61
High pressure gas is supplied into the acceleration cylinder 52 via.

As a result, the piston rod 56 separates from the magnet 5 and falls while being accelerated by the high pressure gas. As the piston rod 56 falls, the control rod 3A is urgently inserted into the reactor core 3 via the connection mechanism 62 and the extension tube 22.

At that time, the handling head 46 of the control rod 3A and the extension tube 2
The latch finger 71 on the second side remains connected.

This causes a scram operation and an emergency shutdown of the reactor.

Next, a case will be described in which the scram signal is not output for some reason and normal scram operation becomes impossible. In this case, the temperature of the coolant 2 increases due to an abnormality occurring in the nuclear reactor.

Due to the temperature rise of the coolant 2, the Curie point electromagnet 85
is also heated and its temperature rises. When the temperature of the Curie point electromagnet 85 exceeds the Curie point, the Curie point electromagnet 85 becomes a non-magnetic material and loses its attractive force. As a result, the attraction between the Curie point electromagnet 85 and the armature 91 of the inner extension tube 22a is released, and the inner extension tube 22a falls. At this time, since the coil 101 acts on the inner extension tube 22a, the fall of the inner extension tube 22a is promoted. This inner extension tube 22
Due to the fall of the latch finger a, the expansion of the latch finger 71 by the finger rod 66 is released, and as a result, the latch finger 7
1 and the handling head 46 is released, and the control (
) The rod 3A separates from the extension tube 22 and falls into the reactor core 3. This causes a scram operation and an emergency shutdown of the reactor.

According to this embodiment, the following effects can be achieved.

(1) First, it is possible to provide a backup reactor shutdown function without installing separate control rods. In other words, even if normal scram operation becomes impossible due to a failure in the scram signal output system, the Curie point electromagnet 85 installed in the same control rod drive mechanism becomes non-magnetic due to temperature rise above the Curie point. As a result, the connection between the extension tube and the control rod 3A is released, the control rod 3A is urgently inserted into the reactor core 3, and a scram operation is reliably performed. Therefore, it is possible to effectively simplify the configuration of the reactor core and, in turn, the reactor, while maintaining the backup reactor shutdown function.

(2) Also, the inner extension tube 22a has a coil spring 101
As a result, when the Curie point N magnet 85 is demagnetized during scram, the inner extension tube 2
2a can be accelerated, and a quick scram operation can be provided.

(3) Furthermore, the Curie point electromagnet mechanism 81 according to this embodiment can be easily applied to existing equipment. That is, the Curie point 'R magnet mechanism 81 according to this embodiment may be interposed between the inner extension tube 22a and the outer extension tube 22b, and the other structures can be used as they are.

[Effects of the Invention] As detailed above, the reactor shutdown device according to the present invention provides a nuclear reactor shutdown device that can perform both a scram operation based on a scram signal and a scram operation when the scram signal is not output. As a result, the control rod for the back-up reactor shutdown device and the mechanism that opposes it, which were required in the past, are no longer required, greatly simplifying the configuration. 1, which in turn makes it possible to downsize the nuclear reactor.

[Brief explanation of drawings]

Figures 1 to 3 are diagrams showing one embodiment of the present invention.
The figure is a vertical cross-sectional view showing the schematic configuration of a loop fast breeder reactor, Figure 2 is a vertical cross-sectional view showing the configuration of a reactor shutdown device, and Figure 3 is an enlarged view of the ■ part in Figure 2. . 3...Reactor core, 3A...Control rod, 22...Extension tube,
22a...Inner extension tube, 22b...Outer extension tube, 4
6... Handling head, 66... Finger rod, 71... Latch finger, 81... Curie point electromagnet mechanism, 85... Curie point electromagnet, 91...
Adsorption plate. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (2)

[Claims] (1) An outer extension tube having a latch finger at the lower end, and a finger rod disposed on the inner peripheral side of the outer extension tube and having the lower end, the latch finger is expanded and the latch finger is connected to the upper end of the control rod. an extension tube that is connected to the upper end of the extension tube and is connected to the upper end of the extension tube, and a control rod is inserted into and withdrawn from the reactor core through the extension tube, and the extension tube is connected to the extension tube by outputting a scram signal. a drive unit that releases the connection with the control rod and urgently inserts the extension tube and control rod into the reactor core while holding them together;
a Curie point electromagnet mechanism having a Curie point electromagnet that is provided in either one of the outer extension tube and the inner extension tube and becomes non-magnetic when heated above the Curie point;
and an adsorbed part provided on the other side and attracted by the Curie point electromagnet mechanism, and when the temperature of the coolant rises and the Curie point electromagnet mechanism is heated to the Curie point or higher, its magnetic force is demagnetized and the Curie point electromagnet is activated. The mechanism is configured such that the attraction between the mechanism and the non-adsorption part is released, the inner extension tube falls, the engagement between the latch finger and the handling head is released, and the control rod is inserted into the reactor core. A nuclear reactor shutdown device featuring: (2) The nuclear reactor shutdown device according to claim 1, wherein the inner extension tube is always urged downward by a coil spring.