JPS61198097A - Nuclear reactor stop device - 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 the Invention] The present invention relates to a nuclear reactor shutdown device, a %C dual fast breeder reactor shutdown device.

[Technical background of the invention and its problems] In general, in a nuclear reactor, when an abnormality occurs in equipment other than the core of the reactor, or in the case of a planned reactor shutdown, the reactor shutdown signal activates the drive unit. The reactor is separated from the control rod elements, and the reactor is configured to come to a nuclear shutdown when the control rod elements in the area C2 of the core fuel section fall. However, in the event that the reactor Reactor shutdown signal was generated due to abnormality C: Despite this, the control rod elements did not fall and the reactor was shut down. Since no control rod is inserted into the output, the rated output value is maintained.

As a result, an inconsistency occurs in the outgoing core flow, the coolant temperature rises, and there is a possibility of a core collapse accident in which the fuel cladding tube melts and the fuel pellets are damaged.

This will be explained with reference to the drawings.

FIG. 10 is a schematic longitudinal sectional view of a conventional fast breeder reactor. As shown in the figure, a reactor core 41 and a coolant 42 for cooling the reactor core 41 are housed in the reactor vessel 40. The core fuel section 43 is surrounded by a blanket.

That is, an upper shaft blanket section 45 and a lower shaft blanket section 46 are disposed at the upper and lower C2 of the core fuel section 43, respectively, and an outer diameter blanket section C is disposed around the upper and lower shaft blanket sections. Nine, the reactor core fuel section 43 is composed of fuel assemblies, and between the fuel assemblies (Y), control rod assemblies are arranged. A control rod element 48 in which absorber pellets are enclosed is loaded, and during steady operation of the nuclear reactor, it is raised to a predetermined position C2 drive 4149 (Y) depending on the combustion state of the core fuel during operation.

When the reactor is shut down, the drive rod 49 and the control rod element 48 are separated in response to the reactor shutdown signal C, and the control rod element 48 falls into the area of the core fuel section 43, causing the reactor to undergo a nuclear shutdown. However, reactor abnormality I: Therefore, if the control rod element 48 does not fall even though the reactor shutdown signal is generated, the main circulation pump will stop due to the reactor shutdown signal and the core flow rate will attenuate, but the reactor output will remain at the rated output. This causes a mismatch between the reactor power and the core flow rate, which increases the coolant temperature, melts the fuel cladding, and ultimately damages the fuel pellets, leading to a core collapse accident. There is a possibility of migration.

In addition, during reactor operation (when an earthquake occurs, the control rods are fixed to the reactor upper plug 501, so a phase difference occurs between the vertical vibration of the reactor core and the vertical vibration of the control rods during an earthquake.
If the magnitude of the earthquake is large because the positive reactivity is inserted and the reactor output increases abnormally, a 1:ilt core damage accident may occur.

Furthermore, if an abnormality occurs in the reactor and a reactor shutdown signal is not generated due to a failure of the reactor core or other abnormality detection system, the The core may melt and collapse due to reactivity insertion.

Therefore, the probability of a failure to shut down the reactor is extremely small, and even if a failure to shut down the reactor does occur, it is certain (the Yumiko reactor can be shut down, and the There has been a demand for a nuclear reactor shutdown system that can prevent core damage from occurring due to C: not being inserted.

[Purpose of the Invention] The present invention has been made in view of the above circumstances, and its purpose is to reduce the frequency of occurrence of failures, reduce the amount of relative displacement between the Ctri neutron absorber and the reactor core during an earthquake, and furthermore (: Even in the event of a reactor shutdown failure accident, we can prevent a core damage accident from occurring (
To provide a reactor shutdown device that can prevent nuclear reactor shutdown.

[Summary of the Invention] In order to achieve the above object, the present invention provides a fuel assembly for a nuclear reactor core, a wrapper tube parallel to the fuel assembly and its interior (a wrapper tube through which coolant rises, and an interior of the wrapper tube). A capsule installed in the capsule, a electromagnetic fluid stored inside this capsule, a hollow tube enclosing a neutron absorber that can move up and down (up and down) inside this electromagnetic fluid, and a This relates to a nuclear reactor shutdown device C2 equipped with an electromagnet current control system.

[Embodiments of the invention] Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic vertical sectional view of an embodiment of the present invention. As shown in the same figure, a coolant flow path 2 is formed inside the wrapper tube 1, and a capsule 3 is supported and fixed within this flow path 2 by a capsule fixing rod 4. Coolant flows from the wrapper tube orifice 16 and passes through the flow path 2 to cool the core fuel section.

The inside of the capsule 3 is filled with a dimagnetic fluid 5 and an electromagnet 6 is provided. Polar face l'i of electromagnet 6
As shown in the cross-sectional view of Fig. 3 (circumferential direction of Yukabu Cell 3)
It is divided into 3 areas and 1 unit, and this polar surface is oriented in the capsule axis direction, that is, in the core side direction (:
The magnets are installed so as to cover at least a region a corresponding to the core fuel section C, and are configured so that the magnetic field distribution of the electromagnets 6 in the core height direction has a maximum value in the core fuel section C. .

The power cable of the electromagnet 6 is connected to a reactor stop signal control circuit (not shown) outside the reactor via a cable 7 inside the capsule and a cable 8 outside the capsule. The cable 7 inside the capsule and the cable 8 outside the capsule are configured so that the power to the electromagnet 6 is cut off (:).
The C1 is connected via a removable connector 9 so that it can be separated from the capsule 3 at any time.

Incidentally, a magnetic fluid 5 is provided inside the capsule 3, and a hollow tube body 11 is disposed in this magnetic fluid.

This hollow tubular body 11 is made of a non-magnetic material ζ2 that is insensitive to the magnetic field I, and this hollow tubular body 1J is in an airtight state (
1. A neutron absorber 12, such as a boron compound, is enclosed in the space C''' along with a gas space 13 and a weight 14 made of a non-magnetic material that does not respond to the magnetic field I:g, such as stainless steel. This gas space 131- is used to hold the gas emitted from the neutron absorber and to adjust the density when the hollow tube body 11 is made.
:is set up. Just in case, this hollow tube body 11 is the guide rod 1.
Although radial movement within the capsule 3 is constrained by C'-0, axial movement within the capsule 3 is not mechanically constrained. □By the way, this hollow tube body 1]
The average density ρAB is set to be within the range of Equation 11 (Y) below by appropriate distribution between the loading amount of the neutron absorber 12, the volume of the gas space 13, and the weight 14.

ρM (ON ≦= ρAB ρM<1)------
--------(1) Here, ρM(0) is the average density of the magnetic fluid near the electromagnet pole face when the U electromagnet 6 stops excitation, that is, when the current is 05-, and ρM(I) is the electromagnet's average density. The maximum is the magnetic fluid density when current is flowing.

Then, a wrapper tube I in which the capsule 3 having the above configuration is arranged.
An appropriate number determined from the nuclear property requirements of the Fi reactor core is loaded in the core region of FIG. 8, which will be described later.

Next, the functions of the nuclear reactor shutdown device of this embodiment will be explained.

First, when the reactor is in operating state M4 (; the reactor shutdown system is in state C2 as shown in FIG. 1).
The electromagnet 6 is in an excited state because it is connected to the power supply (Y) from the internal cable 7 via the connector 9 and the external cable 8. Therefore, the fine magnetic particles in the electromagnetic fluid 5 are in the vicinity of the pole face of the electromagnet 6. In other words, the core fuel is concentrated in the core fuel part a. Since the magnetic fluid density in this region becomes pH (I), it becomes higher than the average density ρAn of the hollow tube body 11 in which the neutron absorber is enclosed. The empty tube body 11 has a density difference with the magnetic fluid (it is located above the electromagnet pole face, that is, above the core fuel part).The state at this time will be further explained with reference to FIG. 4. This figure shows the relationship between the magnetic fluid density distribution 17 in the core height direction and the density of the hollow tube enclosing the neutron absorber and its position. Since it is smaller than the density, the neutron absorber is located 8C- above the core fuel part.

Next, when a reactor shutdown signal is generated or the power is lost, the reactor shutdown system is in a state C as shown in FIG. 2 ζ2. That is, since the excitation of the electromagnet 6 is stopped at this time, the average density of the magnetic fluid decreases, and its value becomes ρM(0). Since the average density ρAB of the hollow tube 11 in which the neutron absorber 12 is enclosed is set to be larger than ρM(0) from the above equation (1), the excitation of the electromagnet 6 stops C2 and falls. do. This fallen hollow tube body 11ha guide rod 1
0C: The movement is restrained by the stopper 15j, so that the neutron absorber 12 mounted on the hollow tube body 11 descends to the point where the mounted neutron absorber 12 covers the core fuel section. As a result, the reactor nuclear (:) is stopped.The state at this time will be further explained with reference to Figure 5.The figure shows the magnetic fluid density distribution in the core height direction at C: when excitation is stopped. This figure shows the relationship between the density of I8 and the hollow tube body and its position. It is located in the core fuel section C2.

Therefore, the relationship between the magnitude of the electromagnet's current and the density of the magnetic fluid is as shown by line 19 in Figure 6. The density of the C2 magnetic fluid is proportional to the magnitude of the current, and the increase in current (as 1: The stopping position of the neutron absorber can be raised or lowered. Therefore, the nuclear reactor can be stopped. It is possible to obtain any reactor output state over the entire power range C2 from rated output C2 to rated output C2.In other words, by matching the density of the magnetic pole surface of the magnetic fluid with the average density of the hollow tube body, neutron It is possible to create a state in which the absorber is partially inserted into the core fuel section 12 and stopped.The magnetic fluid density distribution at this time is represented by a curve 20 as shown in FIG. control of the amount of current (to be able to obtain all the stopping and holding positions of the neutron absorber required during reactor operation, such as full insertion of the neutron absorber into the reactor core fuel section, full withdrawal and 9 partial insertion, etc.) It means.

Furthermore, an application example of the nuclear reactor shutdown device of the present invention will be explained.

Figure 8 shows a system diagram when the reactor shutdown device of the present invention and the conventional reactor shutdown device are used together, and a flow meter, a thermometer, etc. are used as an abnormality detection system. It constitutes a backup reactor shutdown system. As shown in the figure, a reactor vessel 30 houses a core fuel section 25 equipped with a conventional reactor shutdown equipment #26 and a reactor shutdown equipment ft27 of the present invention.

When the control rod drive signal 21 is now issued, the control rod drive system and the electromagnet current control system 23 + the signal 21 are powered by the control rod drive system 23, and the control rods are driven in the conventional reactor shutdown device 26 by the output signal of this system 23. In the reactor shutdown device 27 of the invention, the magnetic fluid density is controlled. Man, normal furnace stop signal 22
When this signal 22C is outputted, this signal 22C is manually inputted to the control rod drive system and the electromagnet current control system 23, and from the output signal C2 of this system 23, the control rod falls in the conventional reactor shutdown device 26, and the reactor shutdown of the present invention occurs. In the device, the supply of the electromagnet is stopped by the electromagnet current breaker 24C2 via the electromagnet current control system.

In addition, in the event that an abnormality occurs in the reactor, C: Nevertheless, if the reactor shutdown signal does not occur, or if the reactor shutdown signal occurs but conventional control rods cannot be inserted, the reactor core An abnormality in the flow rate is detected by a flow meter, or an abnormality in the outlet temperature of the assembly is detected by a thermometer 29. These abnormality detection signals are manually input to the electromagnetic current breaker 24, and as a result of the current being cut off, the nuclear reactor is brought to a nuclear shutdown due to the operation of the reactor shutdown device 27 of the present invention. , Even in the event of a reactor shutdown failure accident as described above, the reactor is safely shut down.

Figure 9 shows a system diagram when the reactor shutdown device of the present invention is used in all reactor shutdown systems, and flowmeters, thermometers, etc. are used as abnormality detection systems, and one of them is a backup system. It constitutes the reactor shutdown system. Note that the same components as those in FIG. 8 will be described with the same reference numerals. In the figure, when the control rod drive signal 21 is now issued, the electromagnet current control system 311
: is input, and the output signal of this system 31 controls the magnetic fluid density of the reactor shutdown device 27 of the present invention. Furthermore, when the normal furnace shutdown signal 22 is issued, this signal 22 is input to the electromagnet current control system 31, and the output signal of this system 31 causes the electromagnet current to flow through the electromagnet current control system 31 in the furnace shutdown device of the present invention. The breaker 24 stops the excitation of the electromagnet. In addition, in the event that a reactor shutdown signal is not generated even though an abnormality has occurred in the reactor, the abnormality in the core flow rate can be detected with a flowmeter, or the abnormality in the assembly exit temperature can be detected with a thermometer. Detected at 29.

Then, these abnormal signals σm magnet current breaker 24
As a result of cutting off the current input to the reactor, the reactor can be nuclearly shut down.

As described above, one or both of the reactor shutdown system fjt of the present invention, the main reactor shutdown system, and the backup reactor shutdown system can be used. By combining the signal from the thermometer or flowmeter installed in the reactor C unit, the reactor shutdown system signal is used to cut off the excitation of the barb independent C1 paper magnet, and even in the event of a reactor shutdown failure accident, core damage C It is possible to safely shut down a nuclear reactor before transitioning to a nuclear reactor.

[Effects of the Invention] As explained above, the nuclear reactor shutdown device of the present invention (according to Yu) is composed of only static elements except for the hollow tube in which the neutron absorber is enclosed, so that failures do not occur. The frequency is significantly reduced compared to conventional reactor shutdown equipment, and in the event of an earthquake, the reactor shutdown equipment is integrated with the reactor core and separated from structures outside the core, so the neutron absorber and core fuel Therefore, the reliability of the reactor shutdown equipment during normal operation is improved, and the amount of positive reactivity inserted into the reactor core during earthquakes is reduced, significantly improving the safety of the reactor. .

Furthermore, when the reactor shutdown device of the present invention and the conventional reactor shutdown device are used together, even if an accident occurs in which a reactor shutdown signal is generated and the control rods are not inserted due to a failure of the control rod drive device. Since the reactor shutdown device of the present invention operates with a different driving principle for the neutron absorber, it can prevent accidents that cause core damage! - can be prevented, improving the safety of nuclear reactors.

Furthermore, a normal reactor shutdown signal is generated by combining an abnormality detection signal from at least a flowmeter or a thermometer installed at the fuel assembly exit of the reactor core with the electromagnetic current cutoff circuit of the reactor shutdown device of the present invention. Even in the event of an accident, the nuclear reactor can be shut down safely, so it is possible to prevent a core damage accident from occurring.

[Brief explanation of the drawing]

1 and 2 are schematic vertical cross-sectional views of one embodiment of the present invention during nuclear reactor operation and nuclear reactor shutdown, respectively, and FIG. 3 is a schematic cross-sectional view along the line [1l-Ill of FIG. 1. , Fig. 4 and Fig. 5 are magnetic fluid density distribution diagrams during reactor operation and reactor shutdown as shown in Fig. 1 and Fig. 2, respectively, and Fig. 6 shows the magnetic fluid density and electromagnet according to the present invention. A diagram for explaining the relationship between currents. FIG. 7 is a magnetic fluid density distribution diagram when the neutron absorber of the present invention is inserted into the core fuel section (1 and a half), and FIG. 8 is a flow meter, Figure 9 is a system diagram when a thermometer etc. is used as an abnormality detection system, and Figure 1O is a system diagram when only the reactor shutdown device of the present invention is used and a flow meter and a thermometer are used as an abnormality detection system. is a schematic vertical cross-sectional view of a conventional fast breeder reactor. 1... Wrapper tube 2... Coolant channel 3...
Capsule 4...Capsule fixing rod 5...Magnetic fluid 6...Electromagnet 7.8...Cable
9... Connector 10... Guide rod 11...
・Hollow tube body 12...Neutron absorber 13...Gas space 14...z+) -15...Stopper representative Patent attorney Yoshiaki Inomata (and 1 other person) 1st
Figure 2 @ Figure 3 Figure 5 pJL movement 4: IL No. 6I51! zu beast-11shiG [75,5→-ノ11. G ro↓λ1mu1
Figure 7 Figure 8 Figure 9

Claims (6)

[Claims] (1) A fuel assembly in the reactor core, a Lapper tube parallel to the fuel assembly into which coolant rises, a capsule installed inside the Lapper tube, and an electromagnetic device housed in the capsule. A nuclear reactor comprising a fluid, a hollow tube enclosing a neutron absorber that can move up and down in the electromagnetic fluid, and an electromagnetic current control system that controls the elevation and descent of the hollow tube. Stop device. (2) The reactor shutdown device according to claim 1, wherein the hollow tube body includes a gas space, a neutron absorber, and a weight. (3) A thermometer and/or a flow meter are arranged near the fuel assembly outlet, and an independent reactor shutdown device is provided using an abnormality detection signal from the thermometer and/or flow meter. Nuclear reactor shutdown device as described in section. (4) A nuclear reactor shutdown device according to claim 1, which uses both an electromagnet current control system and a control rod drive system. (5) The nuclear reactor shutdown device according to claim 1, wherein the electromagnet current control system includes an electromagnet and a power cable connected to the inside of the capsule and the outside of the capsule via a detachable connector. (6) The magnetic field distribution of the electromagnet in the core height direction has a maximum value at least in the vicinity of the core fuel part.
Nuclear reactor shutdown device as described in section.