JPH01260396A - Nuclear reactor stop device - Google Patents

Abstract

PURPOSE:To improve scram response by striking the flow of coolant on an electromagnet after a Curie point electromagnet is fixed on the lower end of an extension tube to arrange between a control rod made of magnetic substance and the extension tube and high temperature and low temperature coolants are mixed by stirring. CONSTITUTION:A Curie point electromagnet 10 is arranged on the lower end of an extension tube 7 and the upper end of a control rod 13 axially and movably inserted is magnetically connected to the Curie point electromagnet 10 in a guide tube 20 of the lower end of the control rod planted in a reactor core 11. Low temperature coolant 22 flowing out from the guide tube 20 of the lower part of the control rod and a large quantity of high temperature coolant 23 flowing out from another guide tube 21 of the lower part of the control rod are mixed by turning flow and stirring flow due to a flow-out hole 19 set in a support 18 and the coolant at a uniform temperature after mix is struck on the Curie point electromagnet 10. Thus response to abnormally increasing temperature of the coolant is made good and the scram of a nuclear reactor can securely be performed.

Description

[Detailed Description of the Invention] "Object of the Invention" (Industrial Field of Application) The present invention relates to a reactor shutdown device for a fast breeder reactor, and in particular, to automatically shut down a nuclear reactor when normal control rods do not operate. This invention relates to an externally installed nuclear reactor shutdown device suitable for shutting down a nuclear reactor.

(Prior technology) In fast breeder reactors that use liquid sodium as a coolant, the output of nuclear fuel in the reactor core is controlled, and when reactor operation reaches a transient state, neutrons in the reactor are absorbed and reacted with nuclear reaction. Emergency stop operations are being carried out, and control rods are used for these operations.

This control rod is made up of a plurality of absorption pins installed in a trumpet tube whose upper and lower ends are supported by a lattice plate, and a gripping portion is formed at the top of the trumpet tube. These control rods are inserted into the reactor core region or ignited to change the amount of neutron absorption and control the nuclear reactions in the reactor. When reactor operating conditions become transient, control rods are quickly inserted into the reactor core to stop the nuclear reaction. Rapid insertion is performed by a control rod drive @ and gravity drop.

Conventionally, various types of control rod drive grooves and reactor shutdown devices have been proposed. Among these, we believe that the method of connecting control rods by directly magnetically attracting them with a magnet is more advantageous than other methods due to its simple structure and the fact that no mechanical movement is required for the approach and separation operations. It is being

This magnet-based nuclear reactor shutdown device was installed in the fourth
As shown in the figure.

In the drawings, reference numeral 41 is a long cylindrical upper guide tube;
An extension tube 42 is provided within the upper guide tube 41 so as to be movable in the axial direction. At the lower end of this extension tube 42, a Curie point electromagnet 43 is installed, which is a rod-shaped Curie point magnetic material with a coil wound around it.

This Curie point electromagnet 43 is constantly attracted to a magnetic body at the upper end of a control rod 44 provided with a neutron absorbing material.

On the other hand, at the lower end of the upper guide tube 41, an outflow hole 45 is provided at the upper part.
A cylindrical introduction pipe 46 is connected and fixed. A fuel assembly lower guide pipe 48 and a control rod lower guide pipe 47 are provided in the core 49 below the introduction pipe 46 . A coolant 51 flows upward in the control rod lower guide pipe 47, and a coolant 52 flows upward in the fuel assembly lower guide pipe 48.

The introduction pipe 46 has a structure in which the coolant flowing out from the area of the control rod 44 and the six fuel assemblies surrounded by the fuel assembly lower guide pipe 48 with the control rod 44 at the center is guided to the Curie point electromagnetic EJ 43. There is. Inside the introduction pipe 46 are thermocouples 53 for measuring the outlet temperature of the high-temperature coolant 52 flowing out from each fuel assembly, and within the introduction pipe 46 are thermocouples 53 that measure the outlet temperature of the high-temperature coolant 52 flowing out. As a protection against the
A measurement line porous support 54 is installed. A large number of outflow holes 55 are provided in a plurality of rows so that the high-temperature coolant 52 from the core fuel assembly that has flowed out from the lower part of the support 54 on both sides of the measurement line porous support 54 can efficiently flow out.

The upper part of the measurement line porous support 54 is a blind plate 56 for mixing with the low temperature coolant 51 from the control rod assembly. Note that this support 54 has a structure that also serves to protect the control rod 44 from collision force caused by its vertical movement.

According to the conventional nuclear reactor shutdown system having such a configuration, the sodium coolant 51 and the coolant 52 that have ascended through the control rod lower guide pipe 47 and the fuel assembly lower guide pipe 48 are mixed in the introduction pipe 46 . Then, while mixing, it rises further,
It flows out of the introduction pipe 46 via the outflow hole 45.

On the other hand, when the temperature of the coolant 51, 52 rises abnormally and reaches the Curie temperature, which is the set value of the Curie point electromagnet 43, the Curie point electromagnet 43 loses its magnetism. Due to this action, the adsorption force of the control rod 44 disappears, and the control rod 44 is automatically inserted and dropped into the reactor core to perform a scram.

(Problems to be Solved by the Invention) According to such a conventional nuclear reactor shutdown device, the coolant 52 (constantly outlet temperature 500 to 550°C) flowing out from the fuel assembly lower guide pipe 48 flows through the control rod lower guide pipe. The temperature is higher than that of the coolant 51 flowing out from the coolant 47 (normal outlet temperature: 400° C.), and the flow rate is faster. Therefore, the static pressure of the coolant 52 decreases, and the coolant flow state is such that the low-temperature coolant 51 flows toward the high-temperature coolant 52 side, and a laminar flow of low-temperature and high-temperature coolants exists in the upper part of the inlet pipe 46. However, the two are not mixed sufficiently. A part of this mixed coolant flows into the introduction pipe 4.
After the flow is reversed at the upper part of 6, the current flows back to the Curie point electromagnet 43. When the temperature of the coolant 51, 52 rises abnormally due to the flow of the coolant near the Curie point electromagnet 43,
There was a problem in that it took a considerable amount of time for the Curie point electromagnet 43 to reach the Curie point and interrupt the magnetic flux, resulting in insufficient scram response. In addition, a method has been proposed in which multiple guide vanes are installed in Zapo I~54 in order to mix low-temperature coolant and high-temperature coolant by swirling flow, but since the guide vanes are placed in the fluid, flow resistance Not only does this increase, but fluid vibration of the guide vanes may also become a problem.

The present invention has been made in view of these points, and an object of the present invention is to provide a nuclear reactor shutdown device that has good responsiveness to an abnormal temperature rise of a coolant and can reliably scram a nuclear reactor.

[Structure of the Invention] (Means for Solving the Problems) The nuclear reactor shutdown device of the present invention includes a cylindrical upper guide pipe, and a flow hole fixedly installed at the lower end of the upper guide pipe. An introduction pipe, an extension pipe provided movably in the axial direction within the introduction pipe and the upper guide pipe, a Curie point electromagnet fixedly installed at the lower end of the extension pipe, and a Curie torpedo that is attracted to and attached to the stone. A control rod made of a removable magnetic material, a control rod lower guide tube provided around the control rod below the introduction tube, and a fuel assembly lower guide tube provided around the control rod lower guide tube. a plurality of substantially single-shaped measurement line supports are attached to the inner surface of the introduction pipe at substantially equal intervals along the axial direction, facing the upper part of the fuel assembly;
A measurement line is inserted into the inner corner of the support, and a plurality of coolant outflow holes are provided in a vertical row on only one side of the support.

(Function) According to the present invention, first, low-temperature coolant flows out from the control rod lower guide tube, and high-temperature coolant flows out from the fuel rod lower guide tube as a Ueno flow, and is guided into the introduction pipe. The flow direction of the high temperature coolant from inside the measurement line support in this introduction pipe is controlled to promote mixing of the low temperature and high temperature coolant, and the coolant flows out from the flow hole. Therefore, the coolant whose temperature has become uniform flows directly to the Curie point electromagnet. If the temperature of the coolant rises for some reason and reaches the Curie point, the Curie point electromagnet loses its magnetic flux and the control rod separates from the lower end of the extension tube, causing a scram.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view schematically showing an entire embodiment of the present invention. In the drawings, reference numeral 1 is a shielding plug;
The upper opening of the reactor vessel (not shown) is closed. A long cylindrical upper guide tube 3 is inserted into the through hole 2 provided in the shielding plug 1. It is fixed to the plug 1 by a provided flange portion 4. The upper portion of the upper guide tube 3 is connected to a housing 5, and a motor (not shown) is mounted on the top of the housing 5.

On the other hand, the lower part of the upper guide tube 3 is immersed in liquid sodium 6, which is the coolant of the nuclear reactor. An extension tube 7 is inserted into the upper guide tube 3 so as to be movable in the axial direction, and a nut 8 is fixedly installed at the top of the extension tube 7, and this nut 8 is screwed onto a screw shaft 9 rotated by a motor. It is. A Curie point electromagnet 10 is installed at the lower end of the extension tube 7. An axially movable control rod 13 is inserted into the control rod lower guide tube 20 implanted in the reactor core 11, and the upper end of the control rod 13 is connected to the Curie pyroelectric! It is magnetically coupled to the i-stone 10. Therefore, when the drive motor is rotated, the screw shaft 9 rotates and the nut 8. The extension tube 7 and the control rod 13 move up and down together.

Note that the neutron shield 1 installed at the top of the upper guide tube 3
4 and the extension tube 7 through a bellows 15, the reactor sodium atmosphere and the upper mechanism of the control rod drive mechanism are isolated. The lower end of the upper guide tube 3 is provided with an introduction tube 16 having an outflow hole 17 at its upper portion. Inside this introduction pipe 16, an L-shaped measurement line support 18 and a measurement line 24 that were provided around the extension pipe 7 and control rod 13 are provided, and an opening is provided on only one side of the measurement line support 18. A large number of outflow holes 19 are provided in total. Note that a blind plate 25 is provided on the upper part of the support 18.

FIG. 2 is a partially enlarged cross-sectional view showing the vicinity of the Curie point electromagnet 10 in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line -■ in FIG. As is clear from FIGS. 2 and 3, a cylindrical introduction pipe 16 is attached to the lower end of the upper guide pipe 3, and an outlet hole 17 is provided at the upper part as a coolant outlet flow path. . On the inner surface of this inlet pipe 16, substantially single-shaped measuring line supports 18 for supporting the measuring line 24 are provided on the upper parts of the fuel assemblies 26, 27, 28, 29, 306, and 31, facing each other. This support 1
A plurality of outflow holes 19 are arranged in tandem in the axial direction on one side of the support 8 so that the coolant flowing between the introduction pipe 16 and the support 18 can flow out. Note that the measurement wire 24 is provided to be inserted into the inner corner portion of the measurement wire support 18.

On the other hand, in the core 11 below the introduction pipe 16, there is a cylindrical control rod lower guide pipe 20 and a fuel assembly lower guide pipe 2 around it.
1 is provided. A sodium coolant 22.2 is passed through the control rod lower guide pipe 20 and the fuel assembly lower guide pipe 21.
3 is flowing upward.

According to such a first embodiment, the control rod lower guide tube 20
A low temperature coolant 22 flows out from the fuel assembly lower guide pipe 21, and a large amount of high temperature coolant 23 flows out from the fuel assembly lower guide pipe 21.

The low-temperature coolant 22 and the high-temperature coolant 23 are connected to the introduction pipe 1.
6 and rises, a plurality of outflow holes 19 provided on only one side of the measurement line support 18 cause a swirling flow and the outflow hole 1 of the measurement line support 18 as shown by the arrow in FIG.
9 collides with the other side where it does not exist, forming an inward stirring flow and merging. Due to this merging, the high-temperature coolant 23 and the low-temperature coolant 22 are mixed in the upward flow process. Thereafter, the temperature becomes uniform, and the flow hits the Curie point electromagnet 10, and the outflow hole 1
7 to the outside.

At this time, under normal operating conditions, the temperature of the coolant after mixing has not reached the Curie point of the Curie point electromagnet 10. However, if the temperature of the coolant rises for some reason and reaches the Curie point, the Curie point electromagnet 10 loses its magnetism and loses its magnetic force. As a result, the control rod 13 is moved to the Curie point electromagnet 10.
It is separated from the reactor and inserted into the reactor core 11 by gravity fall, and a scram is performed.

According to the above embodiment, the control rod lower guide tube 20
Low-temperature coolant 22 flowing out from the control rod lower guide tube 21
A large amount of high-temperature coolant 23 flowing out from the support 18 can be sufficiently mixed by swirling flow and stirring flow through the outflow hole 19 installed in the support 18, and the coolant 23 after mixing can be roughly transferred to the Curie point electromagnet 10 of the temperature sensing part. A coolant with a uniform temperature can be applied. For this reason, when the temperature of the coolant rises for some reason and an event that requires scramming occurs, the scram response can be improved.

[Effects of the Invention] According to the present invention, the low-temperature coolant flowing out of the control rod lower guide tube does not flow directly into the Curie point electromagnet, but instead the high-temperature and low-temperature coolants swirl around the Curie point electromagnet and mix. You can hit the trail. Therefore, the time from when the temperature of the coolant abnormally rises to when the magnetic body reaches the Curie point and blocks the magnetic flux can be made shorter than in the past.

In addition, by promoting the mixing of the convex and low-temperature coolant, it is possible to eliminate temperature non-uniformity in the circumferential direction and axial direction of the Curie point electromagnet, and at the same time improve responsiveness. Because of this, the reliability of the nuclear reactor shutdown device can be increased.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the entire embodiment of a nuclear reactor shutdown device according to the present invention, FIG. 2 is a partially enlarged cross-sectional view of FIG. 1, and FIG.
The figure is a view taken along the line ■--■ in FIG. 2, and FIG. 4 is a sectional view of a conventional nuclear reactor shutdown system. DESCRIPTION OF SYMBOLS 1... Shielding plug, 2... Through hole 3... Upper guide pipe, 4... Flange part 5... Housing,
6...Liquid sodium 7...Extension tube,
8... Nut 9... Screw shaft 10... Curie point electromagnet 11... Core, 13... Control rod 14... Neutron shield, 15... Bellows 16...
・Introduction pipe, 17...Outflow hole 18...Measurement line support 19...Outflow hole 20...Control rod lower guide tube 21...Fuel assembly lower guide tube 22...Low temperature coolant 23 ...High temperature coolant 24...Measuring line 25...Blind plates 26-31...Fuel assembly (8733) agent Patent attorney Yoshiaki Inomata (idiot)
1 person) Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A cylindrical upper guide tube partially filled with sodium coolant, an introduction tube fixedly installed at the lower end of the upper guide tube and provided with an outflow hole at the upper part, and an axial direction inside the introduction tube and the upper guide tube. an extension tube movably installed at the bottom of the introduction tube; a Curie point electromagnet fixed to the lower end of the extension tube; a control rod made of a magnetic material that can be attracted to and detached from the Curie point electromagnet; The control rod lower guide tube is provided around the control rod, and the fuel assembly lower guide tube is provided around the control rod lower guide tube. A plurality of approximately L-shaped measurement wire supports are installed at approximately equal intervals along the axial direction facing the support, the measurement wires are inserted into the inner corner portions of the supports, and a plurality of cooling materials are installed on only one side of the supports. A nuclear reactor shutdown device characterized by having outflow holes arranged in a vertical line.