JP3129387B2 - Reactor shutdown device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor such as a fast breeder reactor, a light water reactor or the like, when the reactor cooling temperature rises abnormally, disconnects the electromagnet and inserts the control rod into the control rod guide tube of the reactor core. Accordingly, the present invention relates to a reactor shutdown device for emergency shutdown of a reactor.

[0002]

2. Description of the Related Art A conventional reactor shutdown device will be described with reference to FIGS. 5 and 6. In FIG. 5, 1 is a control rod, 2 is a control rod drive, 3 is a control rod drive shaft, and 4 is a control rod drive shaft. An electromagnet attached to the lower end of 3, 5 is a control rod guide tube, 6 is a fuel assembly standing around the control rod guide tube 5, 7 is a core fuel in each fuel assembly 6, 8 is a coolant , 9 are coolant inlet pipes, 1
Reference numeral 0 denotes a flow hole provided above the coolant introduction pipe 9.

In FIG. 6, reference numeral 11 denotes an electromagnet iron core attached to the lower end of the control rod drive shaft 3, reference numeral 12 denotes a coil incorporated inside the electromagnet iron core 11, and the electromagnet 4 denotes the electromagnet iron core 11. And the coil 12. 1
4 is an inner iron core attached to the center of the upper end of the control rod 1;
5 is a cylindrical temperature sensing alloy attached to the outer periphery of the upper end of the control rod 1, 13 is an outer iron core attached to the outer periphery of the upper end of the temperature sensing alloy 15, 16 is a magnetic path, and 17 is the electromagnet 11 And the outer iron core 13 and the inner iron core 14.

In the reactor shutdown device shown in FIGS. 5 and 6, a control rod drive shaft 2 is supported by a control rod drive device 2.
The control rod 1 is attracted and held by an electromagnet 4 attached to the lower end of the control rod drive shaft 3, and the control rod 1 is inserted into a control rod guide tube 5 of the core. The fuel assembly 6 standing around the control rod guide tube 5 contains a core fuel 7, and the coolant 8 flowing into the fuel assembly 6 from the lower part of the fuel assembly 6 is
The coolant 8 itself absorbs the heat generated by the core fuel 7, and the temperature of the coolant 8 itself rises, flows into the coolant introduction pipe 9 installed above the fuel assembly 6 from above the fuel assembly 6, and the coolant is introduced. It is discharged from a flow hole 10 provided on the upper part of the pipe 9.

The electromagnet 4 attached to the lower end of the control rod drive shaft 3 is located inside the coolant introduction pipe 9 and
Is less than the normal temperature of the reactor 8 by two times.
It is made of a magnetic material (pure iron or chromium molybdenum steel) having a high Curie point of about 00 ° C. and a high saturation magnetic flux density. The outer iron core 13 and the inner iron core 14 attached to the upper end of the control rod 1 are made of the same material as that of the electromagnet iron core 11. It is made of a magnetic material having a high Curie point of about 150 ° C. and a high saturation magnetic flux density.

When an electric current is supplied to the coil 12, the electromagnetic iron core 11, the outer iron core 13, the inner iron core 14, and the temperature sensing alloy 1
5, a closed magnetic path 16 is formed, and the electromagnetic core 11
Sufficient holding force is generated on the suction surface 17 between the control rod 1 and the outer iron core 13 and the inner iron core 14, and the control rod 1 is sucked. In this state, if any abnormality occurs and the temperature of the coolant 8 flowing out of the fuel assembly 6 rises abnormally, the temperature of the temperature sensing alloy 15 approaches the Curie point due to heat transfer from the coolant 8. Since the saturation magnetic flux density of the temperature sensing alloy 15 decreases and the magnetic flux passing through the magnetic path 16 decreases, the electromagnet 4
, The control rod 1 is cut off, falls into the control rod guide tube 5, and the nuclear reaction is suppressed to prevent an accident.

[0007]

The conventional reactor shutdown device shown in FIGS. 5 and 6 has the following problems. That is,
When the reactor shutdown device is applied to a high-speed breeding passage of 500 to 1,000,000 KW class, the temperature of the coolant 8 flowing out of the fuel assembly 6 at normal time is about 550 to 600 ° C,
The temperature sensing alloy 15 requires a magnetic material having a Curie point of 650 to 750 ° C. (specifically, a ternary alloy of nickel, cobalt, and iron). Cobalt is activated by irradiation with neutrons. Therefore, it is desired to use as little cobalt as possible.

The present invention has been made in view of the above problems, and has as its object to provide a reactor shutdown device capable of greatly reducing the amount of cobalt activated by neutron irradiation. The point is to try.

[0009]

In order to achieve the above object, the present invention provides a control rod drive shaft located in a reactor coolant above a reactor core and vertically driving the control rod drive shaft. A control rod driving device, a control rod inserted into a control rod guide tube of the reactor core, and an electromagnet attached to a lower end of the control rod drive shaft to attract the upper end of the control rod to the lower end of the control rod drive shaft By disconnecting the electromagnet and inserting the control rod into the control rod guide tube of the reactor core, in a reactor shutdown device for emergency shutdown of the reactor, the control rod is attracted by the electromagnet. An inner core is attached to the end face, and an annular flat temperature sensing alloy whose Curie point is higher than the normal reactor cooling temperature is attached to the outer periphery of the upper surface of the inner core,
An annular outer iron core is attached to the upper surface of the temperature sensing alloy (claim 1).

[0010] In the reactor shutdown device according to the first aspect, a plurality of temperature sensing alloys may be stacked and installed between the inner core and the outer core.

[0011]

When the reactor cooling temperature rises abnormally, the electromagnet is cut off, and the control rod is inserted into the control rod guide tube of the reactor core. An inner iron core is attached to the upper end surface, and an annular flat temperature sensing alloy whose Curie point is higher than the normal reactor cooling temperature is attached to the outer periphery of the upper surface of the inner iron core. Iron core is attached,
The amount of cobalt activated by neutron irradiation is significantly reduced. That is, when the weight of the control rod is about 80 kg, in the conventional reactor shutdown device, a cylindrical member is used as the temperature sensing alloy, for example, an outer diameter of 90 mm, an inner diameter of 45 mm and a height of
0 mm and a volume of 1.43 × 10 ⁵ mm are used. On the other hand, in the reactor shutdown device of the present invention, an annular flat temperature sensing alloy, for example, having an outer diameter of 90 mm,
Inside diameter 45mm, height 5mm, volume 0.24 × 10 ⁵
mm, the volume of the temperature sensing alloy is reduced to 1/6 of the conventional volume, and the amount of cobalt activated by neutron irradiation is significantly reduced.

[0012]

【Example】

(First Embodiment) Next, a reactor shutdown device according to the present invention will be described with reference to a first embodiment shown in FIGS. 1 and 2. Reference numeral 21 denotes a control rod drive shaft, and 22 denotes a lower end of the control rod drive shaft 21. The attached electromagnet core, 23 is a coil incorporated inside the same electromagnet core 22, and the electromagnet is composed of these electromagnet core 22 and coil 2
3.

The electromagnet core 22 is made of a magnetic material (for example, pure iron or chromium molybdenum steel) having a Curie point higher than a normal reactor cooling temperature by about 200 ° C. or more and having a high saturation magnetic flux density. . 24 is a control rod,
26 is an inner iron core attached to the upper end of the control rod 24;
Is an annular flat temperature sensing alloy attached to the outer periphery of the upper surface of the inner iron core 26, 25 is an annular outer iron core attached to the upper surface of the temperature sensing alloy, and the outer iron core 25 is
2 is made of the same material. The temperature sensing alloy 27 is made of a magnetic material having a Curie point higher by about 50 to 150 ° C. than a normal reactor cooling temperature and having a high saturation magnetic flux density.

Next, the operation of the reactor shutdown device shown in FIGS. 1 and 2 will be specifically described. During normal operation, when a current is supplied to the coil 23, the closed magnetic path 2 is formed by the electromagnet core 23, the outer core 25, the inner core 26, and the temperature sensing alloy 27.
8 is formed, and a sufficient holding force is generated on the suction surface 29 between the electromagnet iron core 23 and the outer iron core 25 and the inner iron core 26, so that the control rod 1 is sucked.

In this state, if any abnormality occurs and the temperature of the coolant flowing out of the fuel assembly rises abnormally, the temperature of the temperature sensing alloy 27 reaches the Curie point due to heat transfer from the coolant 8. As the temperature approaches, the saturation magnetic flux density of the temperature sensing alloy 27 decreases, and the magnetic flux passing through the magnetic path 28 decreases. Using the magnetic potential method,
FIG. 4 shows the results obtained by performing a magnetic field analysis. As is clear from FIG. 4, the attraction force is less than half of the weight of the control rod 24 of about 80 kg, and the holding force of the electromagnet is reduced.
Is cut off, falls into the control rod guide tube, and the nuclear reaction is suppressed, thereby preventing an accident.

(Second Embodiment) Next, a reactor shutdown apparatus according to the present invention will be described with reference to a second embodiment shown in FIG. 3. In this embodiment, a reactor is provided between an inner iron core 26 and an outer iron core 25. A temperature sensing alloy 27 and a temperature sensing alloy 30 having different components from the same temperature sensing alloy 27 are provided in an overlapping manner. In this example,
For example, if there are multiple candidate materials for temperature sensing alloys to be used in actual equipment and the durability of each temperature sensing alloy is to be checked, the test can be performed by incorporating multiple temperature sensing stiffnesses into one electromagnet and testing at the same time. Rationality can be achieved.

[0017]

When the reactor cooling temperature rises abnormally
Then, the electromagnet is cut off and the control rod is inserted into the control rod guide tube of the core.
A nuclear reactor that shuts down the reactor by inserting
At the furnace shutdown device, the inner iron core is attached to the upper end surface of the control rod
The normal reactor cooling temperature is
An annular flat temperature sensing alloy with a higher Curie point than
And attach an annular outer iron core to the upper surface of the temperature sensing alloy
Use of cobalt activated by neutron irradiation
The amount can be significantly reduced. That is, the weight of the control rod is about 80.
kg, the conventional reactor shutdown device can
A cylindrical alloy is used, for example, an outer diameter of 90 mm and an inner diameter of 45 m
m, height 30mm, volume 1.43 × 10 ^Fivemm
You are using In contrast, the reactor shutdown device of the present invention
In the case of a temperature-sensing alloy, use an annular flat
90mm, 45mm inside diameter, 5mm height, 0.2 volume
4 × 10^Fivemm of temperature-sensitive alloy
The volume is reduced to 1/6 of the conventional volume and released by neutron irradiation.
The amount of cobalt to be used can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing a first embodiment of a reactor shutdown device of the present invention.

FIG. 2 is an enlarged longitudinal side view showing a temperature sensing alloy portion of the reactor shutdown device.

FIG. 3 is a vertical sectional side view showing a second embodiment of the reactor shutdown device of the present invention.

FIG. 4 is an explanatory diagram showing a test result of an attraction force of an electromagnet of the reactor shutdown device.

FIG. 5 is a vertical side view showing a conventional reactor shutdown device.

FIG. 6 is an enlarged longitudinal side view showing an electromagnet part of the reactor shutdown device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Control rod drive shaft 22 Electromagnetic iron core 23 Coil 24 Control rod 25 Outer iron core 26 Inner iron core 27 Annular flat temperature sensing alloy 28 Magnetic path 29 Joining surface

Claims (2)

(57) [Claims] 1. A control rod drive shaft located in a reactor coolant above a reactor core, a control rod drive device for vertically driving the control rod drive shaft, and a control inserted into a control rod guide tube of the core. A rod, and an electromagnet attached to a lower end of the control rod drive shaft, the upper end of the control rod being attracted to the lower end of the control rod drive shaft. The electromagnet is separated, and the control rod is connected to the core. In the reactor stop device for emergency stop of the reactor by inserting it into the control rod guide tube, an inner core is attached to the upper end surface of the control rod attracted by the electromagnet, and the inner core is attached to the outer periphery of the upper surface of the inner core. A reactor shutdown device comprising: an annular flat temperature sensing alloy having a Curie point higher than a normal reactor cooling temperature; and an annular outer iron core attached to an upper surface of the temperature sensing alloy. 2. The reactor shutdown device according to claim 1, wherein a plurality of said temperature sensing alloys are placed between said inner core and said outer core.