JPH01156697A - Automatic shut-down device for nuclear reactor - Google Patents

Abstract

PURPOSE:To guide a high-temp. coolant to a heat sensitive mechanism so that the title device is rapidly operated by installing guides into an upper guide pipe. CONSTITUTION:The guides 101 are installed to the inside circumferential side of the upper guide pipe 14 so as to enclose the lower part of measuring fingers 10. A guide hole 102 is formed to the upper part of each guide 101 and plural bypass holes 103 are provided to the lower part. Since the high-temp. coolant can be thereby distributed toward a Curie point electromagnet 31 as the heat sensitive mechanism, the Curie point electromagnet 3 can be rapidly operated. The damage of the Curie point electromagnet 31 and control rod by collision against the inside surface of the upper guide pipe is prevented and the measuring fingers 10 are guided and protected as well; furthermore, the upper guide pipe 14 is reinforced and, therefore, the earthquake proofness is improved.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Field of Application) The present invention is a fast breeder reactor, and is used to reduce the temperature of the coolant when the regular shutdown device does not perform a scram operation when an accident occurs. This invention relates to an automatic nuclear reactor shutdown device that detects, automatically scrams, and shuts down a nuclear reactor.

(Prior technology) In general, nuclear reactors control the output by inserting and removing control rods with built-in neutron absorbers into the reactor core, but in an emergency such as when an accident occurs, these control rods are fully inserted into the reactor core to control the reactor's output. I'm trying to stop it.

Incidentally, an automatic reactor shutdown device needs to reliably stop the operation of the reactor in an emergency, and is required to have a simple structure and be able to operate reliably. therefore,
This type of device consists of a reactor shutdown system that operates based on a scram signal output during a reactor abnormality using an electric circuit such as a logic circuit or a relay, and external equipment such as a control rod drive mechanism, and a reactor shutdown system that operates based on a scram signal output when a reactor abnormality occurs. In combination with an automatic reactor shutdown system that operates independently and automatically without using a
It is hoped that triple safety measures will be taken.

The configuration of a conventional fast breeder reactor and the configuration of an automatic reactor shutdown device will be explained below with reference to FIGS. 3 to 6. FIG. 3 is a cross-sectional view showing the schematic configuration of a loop fast breeder reactor.
is supported by a core support mechanism 3. The reactor vessel 1 has its upper end closed by a shielding plug 4,
Additionally, a coolant 4a such as liquid sodium is accommodated within the reactor vessel 1.

The low-temperature coolant 4a flows into the lower part of the reactor vessel 1 from the coolant inlet pipe 5 and passes through the reactor core 2 upward. At this time, the temperature of the reactor core 2 increases due to the heat of nuclear reaction, becomes high, and flows out of the reactor vessel 1 through the coolant outlet pipe 6. The high-temperature coolant 4a that has flowed out of the reactor vessel 1 is transferred to an intermediate heat exchanger (not shown) and exchanged heat with the secondary coolant. The coolant 4a, which has become low temperature through heat exchange with the secondary coolant, is sent to the lower part of the reactor vessel 1 again through the coolant inlet pipe 5, and thereafter circulates through this route.

A control rod assembly 7 is loaded in the reactor core 2 together with a fuel assembly. Although a plurality of control rod assemblies 7 are actually provided, only one is shown in the figure. The shielding plug 4 is provided with a core upper mechanism 8 passing therethrough. That is, a large number of measurement fingers 10 are accommodated in a joint body 9 that is provided to penetrate the shielding plug 4 . The tips of these measurement fingers 10 face the upper surface of the core 2, and a temperature detector (not shown) or the like is provided at the tip to measure the temperature of the coolant flowing out of the core 2. Note that the measurement finger 10 is led out of the reactor vessel 1 through a protection tube 11 and a penetration 12.

A control rod drive mechanism 13 is provided above the core upper mechanism 8 . Upper guide tubes 14 protrude from the lower ends of these control rod drive mechanisms 13.
passes through the joint shell 9 and faces the upper end of the control rod assembly 7 loaded in the reactor core 2.

As shown in FIG. 4, the control rod assembly 7 has a lower guide tube 15.
and a control rod 16 housed in the lower guide tube 15 so as to be vertically movable. An entrance nozzle 17 protruding from the lower end of the lower guide tube 15 is connected to the core support plate 1.
8.19 and is inserted into the high pressure plenum 20 formed between them, and has a hydraulic hold-down structure in which removal is prevented by the pressure of the cold member in the island pressure plenum 20. ing. High pressure plenum to 20
A part of the coolant is introduced into the lower guide tube 15 from the entrance nozzle 17, cools the neutron absorber 21 housed in the control rod 16, and then flows into the upper guide tube 14.

Furthermore, a dash ram 22 is protruded from the lower end of the control rod 16, and when the control rod 16 is lowered, the dash ram 22
2 is configured to enter the dashbot 23 and provide a buffer.

An outer extension tube 24 is inserted into the upper guide tube 14, and the outer extension tube 24 is driven up and down by the control rod drive mechanism 13 via a connecting rod 25. A plurality of latch fingers 26 are provided at the lower end of the outer extension tube 24 . These latch fingers 26 are configured to be able to expand and contract in diameter by a latch operation section to be described later, and when the diameter is expanded, they engage with the handling head 27 of the control rod 16 and the control rod 1
6, and if the diameter is reduced, the handling head 2
7 is disengaged.

The outer extension tube 24 is provided with an inner extension tube 29 via the heat-sensitive expansion body 28 .
It is configured to move up and down in accordance with the expansion and contraction of. A latch operating portion 30 is provided at the lower end of the inner extension tube 29, and when the latch operating portion 30 enters into the latch fingers 26, the diameter of these latch fingers 26 is expanded to engage the handling head 27, and When the handle is released from within the latch finger 26, the latch finger 26 contracts in diameter due to its own elastic force and is disengaged from the handling head 27.

Note that through holes 24a, 24 are formed in the side wall and upper end of the outer extension tube 24.
b is provided to cause a portion of the coolant flowing in the upper guide tube 14 to flow along the surface of the heat-sensitive expansion body 28.

In the conventional nuclear reactor automatic shutdown system configured as described above, the control rod drive mechanism 13 moves the outer extension tube 24 up and down while the latch finger 26 is engaged with the handling head 27. 16 core 2
It is inserted into and withdrawn from the reactor core, thereby controlling the reactor core power.

On the other hand, if the fuel outlet temperature becomes abnormally high due to an accident or the like, the temperature of the heat-sensitive expansion body 28 rises and expands due to the circulating coolant as shown by the arrow in FIG. Due to the expansion of the heat-sensitive expandable body 28, a relative displacement occurs between the latch finger 26 and the latch operating section 30, and the latch operating section 30
is lowered and pulled out from inside the latch finger 26, and the engagement between the latch finger 26 and the handling head 27 is released. Thereby, the control rods 16 are moved by gravity to the core 2.
Fall inside and scram the reactor.

FIGS. 5 and 6 show different prior art techniques, respectively.

In these examples, the connecting rod 25 is directly suspended by a Curie pyromagnet 31, and when the Curie point electromagnet 31 exceeds the Curie point due to an abnormal rise in ambient temperature, it loses its magnetic force and the control rod 16 falls. This is based on the principle.

In other words, in the example shown in FIG. 5, in order to activate the cue point 'l1it1 stone 31 due to an abnormal rise in the fuel outlet temperature, the pipe 33 for introducing the coolant is cut from the upper part of the outlet of several fuels 32 to the vicinity of the pyromagnet 31. It is being routed. Further, in the example shown in FIG. 6, the cue pyromagnet 31 is arranged so as to be located near the upper end of the control rod 16 even when the control rod is fully handled,
The coolant flowing out from the fuel 32 reaches the cue point fffffi
I made it so that it would hit stone 31 easily.

According to the above configuration, there are the following problems.

First, in the examples shown in FIGS. 4 and 6, the low-temperature coolant flowing out from the control rod 7 rises in the center, so the thermal expansion body 28 and the pyromagnet 31 act as the outlet coolant for the fuel 32. The disadvantage is that it is difficult to detect temperature rises.

Furthermore, in the example shown in FIG. 5, a pipe 33 is routed above a suitable number of fuels 32, but as explained in FIG. It is difficult to route the piping 33 because it is arranged in a portion where various types of fuel are loaded. In addition, this part is not only directly connected to the thermal striping of the control rods, blanket fuel, or core fuel tubes, but is also exposed to severe thermal conditions such as reactor trips, so the structure may be affected by piping routing. As complexity increases, structural reliability decreases accordingly. Furthermore, due to the vibrator structure, the pressure loss in the flow path becomes large, and the flow rate of the coolant decreases, not only making it impossible to obtain a sufficient temperature rise, but also delaying the time it takes for the coolant to reach the Curie point electromagnet 31.

(Problems to be Solved by the Invention) As described above, in the conventional configuration, there is a problem in that it is not possible to guide the high temperature coolant to the pyromagnet and quickly activate it. The purpose of this invention is to provide an automatic nuclear reactor shutdown device that can guide high-temperature coolant to a pyromagnet and quickly activate it.

[Structure of the Invention] (Means for Solving the Problems) That is, the automatic reactor shutdown device according to the present invention is arranged in an upper guide pipe extending from the lower end of the control rod drive mechanism to above the control rod assembly. Under normal conditions, the control rod is gripped and inserted into and withdrawn from the reactor core to control the core output, and if an abnormality in the fuel outlet temperature is detected by the heat-sensing mechanism, the control rod is released. In an automatic reactor shutdown system that automatically stops a nuclear reactor by dropping it into a reactor core, high-temperature coolant flowing out from fuel disposed close to the control rod assembly in the upper guide tube is directed to the heat-sensitive mechanism. It is characterized by the installation of a guide to guide the user.

(Function) In other words, a guide is installed in the upper guide tube, and through this guide, the high temperature coolant flowing out from the fuel brought close to the control rod assembly is guided to the heat-sensitive mechanism, thereby making the operation of the heat-sensitive mechanism more rapid. That is.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2. Incidentally, the same parts as in the prior art are denoted by the same reference numerals, and the explanation thereof will be omitted.

A guide 10 is installed on the inner peripheral side of the upper guide tube 14 at the position of the measuring finger 10 so as to surround the lower part of the measuring finger 10. A guide hole 102 is formed in the upper part of the guide 101, and a plurality of bypass holes 103 are formed below the guide hole 102. By installing the guide 10 having such a configuration, the high-temperature coolant is allowed to flow toward the pyromagnet 31 as a heat-sensitive mechanism, thereby enabling the electromagnet 31 to operate quickly. Furthermore, by installing the guide 101, the cue point N magnet 31 and the control rod 16 are prevented from colliding with the inner surface of the upper guide tube 14 and damaged, and the measuring finger 10 is guided and protected. The upper guide pipe 14 is reinforced to improve earthquake resistance.

The operation will be explained based on the above configuration.

First, regarding the flow of coolant, the large diameter portion 1 of the upper guide pipe 14
A low-temperature coolant of about 420° C. from the control rod 16 flows into 4a, and a high-temperature coolant of about 580° C. from the fuel 32 flows. At this time, a guide 101 is installed at the position where the coolant from the fuel 32 flows in, so that the high temperature coolant from the fuel 32 flows preferentially into this guide 101 and is queued through the guide hole 102. is guided to the pyromagnet 31. At the same time, the above guide 101
A bypass hole 103 is formed in the bypass hole 10.
The low humidity coolant from the control rod 16 flows through the guide 101 through the
flow inside. As a result, the high-temperature coolant and the low-temperature coolant are excessively mixed in the guide 101 and brought to the desired temperature to the Curie point 31. Therefore, the cue point fi 1 stone 31 operates quickly.

Next, by installing the guide 10, it is possible to prevent damage caused by collision of the pyromagnet 31 and the control rod 16 against the inner surface of the upper guide tube 14. Further, by installing the guide 101, the measurement finger 10 can be guided and protected, and the upper guide tube 14 can be reinforced to improve earthquake resistance.

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

■First, the high temperature coolant is guided into the guide 101 and the guide hole 102.
The pyromagnet 31 can be operated quickly by effectively guiding it to the cue point tda stone 31 via the pyromagnet 31. Thereby, the reliability of the nuclear reactor shutdown device can be greatly improved.

■In addition, at this time, a bypass hole 103 is formed in the guide 101, and the high temperature coolant and low temperature coolant are appropriately mixed through this bypass hole 103, and the pyromagnetic magnet is cured at the optimum temperature. 31, the operation of the pyromagnet 31 becomes optimal.

■Next, by installing the guide 101, the pyromagnet 3
1 and the control rod 16 against the inner surface of the upper guide tube 14 and damage caused by the collision can be effectively prevented, and the integrity of the upper guide tube 14 can be maintained.

(2) Next, by installing the guide 101, the measuring finger 10 can be guided and protected.

(2) Further, by installing the guide 101, the upper guide tube 14 can be reinforced, thereby improving the earthquake resistance of the upper guide tube 14.

It should be noted that the present invention is not limited to the above embodiment,
For example, various arrangements, numbers, shapes, etc. of the guides can be considered. Furthermore, although the above embodiment shows the case of an automatic nuclear reactor shutdown device using a pyromagnet, it can be similarly applied to a case where a heat-sensitive expander is used, and the same method as in the above embodiment can be applied. It is possible to achieve the following effects.

[Effects of the Invention] As detailed above, according to the automatic nuclear reactor shutdown device according to the present invention, a coolant at an appropriate temperature can be effectively introduced into the pyromagnet, thereby speeding up its operation. This has great effects, such as greatly improving the reliability of the reactor shutdown system.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are diagrams showing one embodiment of the present invention.
The figure is a cross-sectional view showing the main parts of the automatic reactor shutdown system, Figure 2 is a cross-sectional view taken along the line ■-■ of Figure 1, Figures 3 to 6 are diagrams used to explain the conventional example, and Figure 3 is a cross-sectional view of a loop type fast breeder reactor, Figure 4 is a cross-sectional view of an automatic reactor shutdown device, Figure 5 is a cross-sectional view of an automatic reactor shutdown device, and Figure 6 is a cross-sectional view of an automatic reactor shutdown device. . 13... Control rod drive mechanism, 14... Upper guide tube, 3
1...Kyuri pyromagnet, 101...Guide. Applicant's Representative Patent Attorney Takehiko SuzueFigure 1Figure 2Figure 3Figure 4Figure 5Figure 16

Claims (1)

[Claims] A heat-sensitive mechanism is provided in an upper guide tube extending from the lower end of the control rod drive mechanism to above the control rod assembly.
Under normal conditions, the control rods are held and inserted into and pulled out of the core to control the core output, and when an abnormality in the fuel outlet temperature is detected by the heat-sensitive mechanism, the control rods are released and fall into the core. In the automatic reactor shutdown system that automatically shuts down the reactor when the control rod assembly is activated, a guide is installed in the upper guide tube to guide high-temperature coolant flowing out from the fuel disposed close to the control rod assembly to the heat-sensitive mechanism. An automatic nuclear reactor shutdown device featuring: