JPS61230084A - Control rod 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 the Invention] The present invention relates to a control rod device ζ2 for a nuclear reactor, and particularly to a control rod device C in which a safety rod among the control rods is passed through.

[Technical background of the invention and its problems]

Generally, power control of a nuclear reactor is performed by inserting and withdrawing control rods into the reactor core. Control rods for fast breeder reactors include
Depending on the purpose, there are safety bullets for emergency stop, shim rods for coarse control, and fine control rods.

Among these, control rods used as safety rods need to be reliably inserted into the reactor core in the event of an abnormality in the reactor, for example, when a nuclear fuel assembly causes abnormal combustion or local blockage. For this reason, there is a demand for a control rod device with a self-insertion function that can automatically insert it into the reactor core without going through a special nuclear reactor installation system in the event of the above-mentioned abnormalities. Publication No. 59-42837 (
The two described have been devised. In the control rod device disclosed in this publication, an abnormal temperature rise in the nuclear fuel assembly is transmitted to the coolant in the guide tube by heat conduction, thereby automatically inserting the control rod. However, in this case.

The coolant itself in the nuclear fuel assembly does not directly flow into the guide tube, and only heat is transferred by conduction, so heat is transferred slowly and a quick response may not be obtained.

[Purpose of the invention]

The present invention has been made based on the above circumstances, and its purpose is to provide a control rod device for a nuclear reactor that can quickly and reliably insert control rods into the reactor core in the event of an abnormal temperature rise in a nuclear fuel assembly. It is about providing.

[Summary of the invention]

The present invention achieves the above object, and includes a guide tube and a control rod body housed in the guide tube so as to be movable up and down. In a control rod device for a nuclear reactor, a side wall of a guide tube has a communication hole that connects the outer cylinder and the guide tube, and a valve mechanism that opens only when the temperature exceeds a predetermined temperature is fixed to the control rod body.

Only when this valve mechanism is closed, the control rod body receives buoyancy and floats up.

[Embodiments of the invention]

Invention 1: An embodiment of such a control rod device will be described below with reference to FIGS. 1 and 2. FIG. 1 shows a part of the inside of a nuclear reactor when a control rod device 1 is installed in a fast breeder reactor C. In the figure, 1 is a furnace vessel (
A partition plate (not shown) is shown which partitions the interior into upper and lower parts, and thus a low-pressure blemish 2 is formed above the partition plate IC. Further, there is a lower plate 3 below the partition plate 1, a low-pressure plenum 4 is formed below the lower plate 3, and a high-pressure plenum 3 is formed between the partition plate 1 and the lower plate 3.

The lower plate 3 and the partition plate l have a plurality of pairs of openings 6 and 7 facing each other, and a cylinder 8 that connects the partition plate 1 and the lower plate 3 is fixed to these pairs of openings 6 and 7. . The cylinder 8 has a flow passage hole 8, and a nuclear fuel assembly 9 and a control rod device 10 are installed on the cylinder 8.

The nuclear fuel assembly 9 includes a cylindrical channel box 9m having a regular hexagonal cross section,
A plurality of nuclear fuel rods 1 are housed vertically in a channel box 9a.
1, and an entrance nozzle lla coaxially connected to the lower end of the flow path box 9a. Only a part of the height of the nuclear fuel rods 11 serves as a heat generating part 12, forming a reactor core. The entrance nozzle lla is inserted into the circumference 8, and an inflow hole 13 is bored at a position opposite to the flow passage hole 13al of the entrance nozzle core 1 cylinder.

The control rod device 10 is configured as follows.

The side surface of the control rod device IO is covered with a guide tube 14 having a regular hexagonal cross section, and the lower end of the guide tube 14 is coaxially connected to a guide tube entrance nozzle 15.

The guide tube entrance nozzle 15 is inserted into the circumference 8, and a guide tube inlet 16 is bored in the guide tube entrance nozzle 15 at a position facing the cylindrical flow passage hole 8a. A control rod body 18 is disposed within the guide tube 14 so as to be movable up and down. (Figure 1 shows the state in which the control a rod main body 18 has moved downward.) The control @m main body 18 includes a plurality of neutron absorption rods 19 and a lower body 20 that supports and fixes them at the lower part.
It consists of a cylinder body 21 that covers the entire side surface of the neutron absorption rod 19, a plate body 4 that covers the upper part of the cylinder body 21, and a valve mechanism and a coolant outlet pipe 24 attached to this plate body 22. There is.

The valve mechanism mechanism includes a valve hole 25 bored in the plate body 22 and a valve 26 that passes through the valve hole 25 and is movable up and down relative to the plate body 22.
and a coil spring 27 fixed to a holding plate 52 which has one end fixed to the valve 26 and the other end fixed to the coolant outlet pipe 24.

The coil spring 27 is made of a shape memory alloy and is heated to a predetermined temperature (
For example, in the case of 5oo c ) or more, it stretches and pushes down the valve 26, forming a flow path between the valve 26 and the valve hole 5 (the state shown in FIG. 1). Further, when the coil spring 27 is at a temperature below the predetermined temperature, it contracts and pulls up the valve 26, thereby closing the flow path between the valve 26 and the valve hole 25.

The coolant outlet pipe 24 is erected upward from the plate body 22 .

It passes through the plate body 22 and has an outlet side above.

Furthermore, there is a grip part 29 at the upper part of the coolant outlet pipe 24, which is structured to be gripped by an operating rod (not shown) hanging down from above, if necessary.

Inside the guide tube 14, when the control rod main body 18 moves downward C2, the neutron absorption rod 19 is at the same height as the heat generating part 12.

Near the height of the upper end of the heat generating part 12 of the flow path box 9a and the guide tube 14 and above it
．． 33, through which the adjacent nuclear fuel assemblies 9 and the nuclear fuel assemblies 9 and the control rod assembly ([10] are in contact. Communication holes A and 35 are bored through the channel box 9a or the guide tube 14, and the channel boxes V are arranged so as not to communicate with each other.

a The opening of the communication hole 35 inside the guide tube 14 (; indicates a guide root zone, so that the coolant flowing from the communication hole 35 does not directly collide with the control rod body 18.

In the reactor having the above configuration, during normal operation of the reactor, the coolant flows from the high-pressure plenum 5 through the channel hole 8a, through the inlet 13 and the guide tube inlet 16, and into the channel box 9a and the guide tube 14. Inflow. The coolant in the channel box 9a receives heat from the heat generating portion 12 and its temperature rises.

Most of the heated coolant rises as it is and passes above the channel box 9a, but a portion of the heated coolant passes through the communication hole 35 and enters the guide tube 14 of the control rod device 10. flows into.

An upward flow is generated in the guide tube 14 by the coolant flowing from the guide tube inlet 16, and the control rod body 18 is pushed up by this upward flow. At this time, coil spring 2
7 is below the predetermined temperature, the coil spring 27 is in a contracted state, and therefore the valve 26 is pulled up and the flow path between the valve 26 and the valve hole 25 is closed. The coolant that has risen inside the cylindrical body 21 passes through the coolant outlet pipe and flows out from the outlet side. At this time, the outlet hole and the grip part 2
9 projects upward from the upper end of the guide tube 14. The flying height of the control rod body 18 is regulated by a control rod (not shown) placed above the grip part 29. Therefore, changing the regulating position of the control rod ζ: Therefore, the control rod body 18
position can be controlled.

Next, if there is an abnormal temperature rise in the heat generating part 12 of the nuclear fuel assembly 9 for some reason, the abnormally high temperature coolant will flow into the communication hole 34.
．． 35 into the guide tube 14. Therefore, when the temperature of the coil spring n exceeds the predetermined temperature, it expands, and the valve 26 is pushed downward, creating a flow path between the valve 26 and the valve hole 5. Therefore, most of the coolant that has risen inside the cylinder body 21 flows through the valve hole 25, and the pressure on the lower surface of the plate body 22 is reduced. In this way, the floating blade applied to the control rod body 18 is lowered, and the control rod body 18 is lowered and stops with the lower body 20 in contact with the lower support body 50 (the state shown in FIG. 1).

At this time, the neutron absorption rod 19 is located at the same height as the heat generating part 12 of the nuclear fuel assembly 9, thereby suppressing the reactivity of the reactor and stopping the reactor.

In addition, if the flow rate of coolant flowing into the guide tube 14 from the guide tube inlet 16 decreases due to a coolant loss accident, etc., the guide tube 14
Decrease in rising flow rate C: Therefore, the floating blade of the control rod body 18 decreases. At this time, since the above-mentioned abnormal temperature rise of the heat generating part 12 also occurs at the same time, the opening operation of the valve mechanism n and the effect of reducing the upward flow rate in the guide tube 14 overlap, and C: the control rod body 18 descends reliably.

In this embodiment, the coolant that has passed inside the cylindrical body 21 and the coolant that has passed outside the cylinder are mixed near the outlet 4;
During normal operation, this portion is outside the guide tube 14. Therefore, even if coolants having different temperatures are mixed here, structures such as the guide pipe will not be adversely affected.

Next, a modification of the present invention will be described. First, the information board 53
Although this is to prevent thermal shock to the control rod body 18, it is not always necessary. Further, as the valve mechanism, a thermostatic valve mechanism may be used near the opening of the communication hole 31. In addition, in the above embodiment, the coolant flows into the guide tube 14 from six communication holes 31 around the circumference, but if there is variation in the temperature of these coolants, a circumferential temperature distribution will occur in the coil spring n, and It is also conceivable that the valve mechanism valve may not operate properly due to thermal deformation due to In order to prevent this, the flow flowing into the guide tube 14 from the communication hole 35 can be swirled, but for this purpose, there are methods such as attaching guide vanes or directing the communication hole 35 in the diagonal circumferential direction of the guide tube 14. Alternatively, there is a method of attaching a bent nozzle to the outlet of the communication hole 35.

Further, in the above embodiment, the valve opens when the coil spring is expanded, but the same function can be provided even if the valve is opened when the coil spring is compressed.

The nuclear reactor is not limited to the high-speed express reactor.

〔Effect of the invention〕

According to the present invention, in the event of an abnormal temperature rise in a nuclear fuel assembly, control rods can be quickly and reliably inserted into the reactor core, thereby making it possible to obtain a safe and reliable nuclear reactor.

[Brief explanation of drawings]

1 and 2 show a part of the inside of a nuclear reactor in which an embodiment of the control rod device according to the present invention is installed in the reactor. Entrance line vertical sectional view, 2nd
The figure is a sectional view of the machine along line B-B in FIG. 1. 9...Nuclear fuel assembly 9a...Flow path box 10...
・Control inspection device 12... Heat generating part 14... Guide tube 16... Guide tube inlet 18... Control rod body 19... Neutron absorption rod 21... Cylindrical body 22... Plate body n...valve mechanism
Sae... Coolant outlet pipe 25... Valve hole
26...Valve 2780. Coil spring four...
Outlet 30.31... Spacer pad ah, 35... Communication hole Representative Patent attorney Noriyuki Chika (and 1 other person) ~ 4 Figure 1 Figure 2

Claims (3)

[Claims] (1) A guide tube that is installed parallel to the nuclear fuel assembly installed in the core and covered by an outer cylinder, through which coolant flows upward, and a guide tube that can be freely raised and lowered within this guide tube. In a control rod device for a nuclear reactor, which includes a control rod body housed in the control rod body, a communication hole connecting the outer cylinder and the guide tube is bored in the side wall of the guide tube, and the control rod body is fixed with a valve mechanism that opens only when the ambient temperature reaches a predetermined temperature or higher, and the control rod body floats up due to the buoyancy of the upward flow only when the valve mechanism is closed. A control rod device for a nuclear reactor. (2) The control rod device for a nuclear reactor according to claim 1, wherein a shape memory alloy spring whose shape changes at the predetermined temperature is used in the valve mechanism. (3) The control rod for a nuclear reactor according to claim 1, wherein the communicating hole passes through a spacer pad provided on a side surface of the outer cylinder and the guide tube, and the outer cylinder and the guide tube. Device.