JPS5927290A - Reactor shutdown 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 that operates in a fast breeder reactor or the like to stop the operation of the reactor when the coolant temperature rises abnormally.

[Technical background of the invention and its problems]

In general, fast breeder reactors are designed to control the exit of the reactor by inserting and removing a control rod containing a neutron absorber into the reactor core, and in the event of an emergency such as an accident, the control rod is fully inserted into the core and the reactor exits. It is designed to stop the driver. However, in such an emergency situation, it is necessary to reliably stop the operation of the reactor, so a reactor shutdown device that has a simple structure and can operate reliably is required. Therefore, this type of device has a reactor shutdown thread that operates using external equipment such as a control rod drive mechanism based on a scram signal issued during a reactor abnormality, and a reactor shutdown thread that operates independently without using such external equipment. It is desired to take double-bundle and triple-layer safety measures by using the single-drop type nuclear reactor shutdown system that operates at the same time. Therefore, the conventional reactor shutdown equipment described below was developed. That is, the control rods are suspended from the bottom of the extension tube and inserted into and removed from the reactor core, but the electromagnets installed between the control rods and the extension tube are energized by a temperature switch. The control rods are dropped into the reactor core.

However, since the temperature switch is installed at the bottom of the extension pipe, it takes a relatively long time to detect an abnormal temperature rise in the coolant, which causes a delay in taking measures against the abnormal temperature rise in the coolant. Ta.

[Purpose of the invention]

The purpose of the present invention is to have a simple structure, to operate reliably, to be able to operate independently from other reactor shutdown systems using the hJ mechanism, and to prevent abnormal temperature rises in the coolant at an early stage. It is an object of the present invention to provide a nuclear reactor shutdown device that is capable of detecting and is capable of inverting.

[Overview of the invention]

The nuclear reactor shutdown device according to the present invention includes a partial guide pipe that is installed upright in the reactor core and through which cooling power flows inside, and an extension that is located above the lower guide pipe and is driven up and down by a drive unit that is provided outside the reactor. a tube, an electromagnet attached to the extension tube to attract and hold the control rod by magnetic force, an upper guide tube that surrounds the extension tube and opens directly above the upper opening of the lower guide tube, and a lower part of the upper guide tube. A temperature switch is attached to the outer circumferential surface of the opening and opens when the temperature of the coolant rises abnormally to cut off the power to the electromagnet. It is equipped with a tube. Therefore, abnormal temperature rise of the coolant can be detected early and countermeasures can be taken quickly.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.

In the figure, 1 is a reactor vessel of a liquid metal cooled rapid breeder reactor, 2 is a reactor core, 3 is a shielding plug, and 4 is a core upper mechanism, and this core upper mechanism 4 is provided with a control rod drive mechanism 5. ing. Reference numeral 6 denotes an upper guide tube constituting the control rod drive mechanism 5. An extension tube 7 is inserted into the upper guide tube 6 so as to be able to rise and fall freely. It is designed to be driven up and down.

On the other hand, a large number of trumpet tubes 9 and guide tubes 10 are vertically loaded in the core 2 in a predetermined arrangement.

These pipes, the /4' pipe 9 and the guide pipe 10 are connected to the high pressure solenum 1
1, supported by upper and lower core support plates 12, 22 constituting 1, and inside each Rano 4 tube 9 and guide tube 10,
A coolant, such as liquid sodium, flowing through the high-pressure plenum 11 flows into each tube from the bottom to the top. The core fuel 13 is built into the Rano 4 tube 9, and the control rod 1 is contained in the guide tube 10.
4 is inserted so that it can be moved up and down. This control rod 14 contains a neutron absorbing material 15 and has a magnetic material 16 at its upper end.

A vL magnet 17 that attracts the magnetic body 16 is attached to the lower end of the extension tube 7.

18 is a cable that supplies power to this electromagnet, and a temperature switch 19 is provided in the middle of this cable 18 to turn on/off electricity to the electromagnet 17. This temperature switch 19 is turned on when the coolant is at a normal temperature. The contact is closed, but when the coolant temperature rises abnormally to a higher temperature than during energized reactor output operation, it deforms due to the heat and opens, cutting off the energization to the electromagnet 17. It is becoming.

The temperature switch 19 is attached to the outer peripheral surface of the lower opening of the upper guide tube 6. A rectifier tube 20 is provided along the outer peripheral surface of the upper S guide tube 6 so as to surround the temperature switch 19.

The upper and lower ends of the rectifier tube 20 are open, and are configured to guide the cooling fluid flowing out from the reactor core 2 around the temperature switch 19.

In one embodiment of the apparatus configured as described above, the temperature switch 19 is closed when the cooling side temperature is normal.
The cable 18 is energized to keep the electromagnet 12 in an energized state at all times.The upper end of the control rod 14, that is, the magnetic body 16, is attracted by the magnetic force, and the control rod 14 is suspended by the drive unit 8. The extension tube 7 is pulled up and the control rods 14 are evacuated from the reactor core region. By doing this, the reactor can be operated at its output, and the coolant is heated in the reactor core 2 to a high temperature and is led out of the reactor vessel 1. The fuel is then guided to an intermediate heat exchanger (not shown), undergoes heat exchange, and is then introduced into the furnace vessel 1 again.

A part of the coolant heats the upper guide tube 6 and the temperature switch 19 is also heated, but when the coolant temperature is normal, the temperature switch 19 remains closed, so the electromagnet 17 is excited. The state is maintained. Therefore, the control rod 14
is held at its upper limit position, and the furnace continues to operate at power.

If some kind of accident occurs such as a decrease in the flow rate of the coolant and the temperature of the coolant rises abnormally, the high temperature coolant guided through the rectifier tube 20 flows around the temperature switch 19. Therefore, the temperature switch 19 is heated by the coolant and detects an abnormal temperature rise of the coolant at an early stage. Therefore, the temperature switch 19 is opened,
The electromagnet 17 is demagnetized, and the control rod 14 falls under its own weight inside the guide tube 10 and is fully inserted into the reactor core. Therefore, the output of the furnace decreases and eventually the furnace stops operating. Incidentally, when such a reactor abnormality occurs, a scram signal is outputted by other safety system devices, and the drive section 8 is operated to forcefully drop the control rod 14.

In this way, according to this embodiment, the control rod 14 can be automatically dropped when the coolant temperature rises abnormally, and this dropping operation is independent of the electrical signal such as the scram signal that is issued when the reactor is abnormal. Since this is carried out independently, in the unlikely event that other reactor shutdown systems, such as a reactor shutdown system that operates the drive unit 8 based on the scram signal and forcibly drops the control rod 14, do not operate normally. Even in this case, the control rods 14 can be reliably dropped into the core region and are safe. Furthermore, the reactor shutdown system of this embodiment is composed of a temperature switch 19 and an electromagnet 17, which have the advantage of being able to operate reliably with a simple structure of m1. Therefore, it is extremely effective as a backup for other reactor shutdown systems, and the safety of the reactor can be significantly improved.

Furthermore, according to this embodiment, the temperature switch 19 is additionally provided on the outer peripheral surface of the lower opening of the upper guide tube 6, and the temperature switch 19
Since it is located directly above the upper opening 10a of the lower guide tube 10, the temperature of the coolant flowing out from the outlet of the guide tube 9 and the guide tube 10 can be reduced compared to the conventional method. Abnormal temperature rise can be detected even earlier by detecting the time.

Moreover, since the temperature switch 19 is surrounded by the rectifier tube 20, the coolant is guided by the rectifier tube 20 and flows around the temperature switch 19, so that an abnormal temperature rise can be detected in an even shorter time◇This invention Of course, this can be applied to so-called output adjustment rods that adjust the output by arbitrarily adjusting the vertical position of the control rod using the drive unit, but it can also be used to simply shut down the reactor without such an output adjustment function. It can also be similarly applied as a safety rod that only has a function.

〔Effect of the invention〕

According to the present invention, an electromagnet that attracts and holds the control rod by magnetic force is provided at the lower part of the extension tube, and a temperature switch is installed around the lower opening of the upper guide tube to open and cut off power to the electromagnet when the coolant temperature rises abnormally. A rectifier tube is installed around the temperature switch to guide the coolant, and the control rod is automatically dropped in the event of an abnormally high temperature during a cooling operation. It can operate as a standalone drop-type reactor shutdown system independent of the rest of the reactor system, and is highly reliable as a multi-layered safety device, as well as being able to detect abnormal temperature rises in the coolant at an early stage. It is.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, with FIG. 1 being a longitudinal cross-sectional view of a high-speed field expansion reactor, and FIG. 2 being a longitudinal cross-sectional view showing a part of the reactor core and the lower part of the control rod drive mechanism. 2... Core, 2... Extension tube, 8... Drive section, 10
...Guide tube, 10IL...Top opening, 14...Control rod, 17...Electromagnet, 19...Temperature switch, 2
0... Rectifier tube.

Claims (1)

[Claims] a lower guide pipe installed in the reactor core and through which coolant flows;
an extension tube located above the lower guide tube and driven up and down by a drive unit provided outside the furnace; an electromagnet attached to the extension tube that attracts and holds the control rod by magnetic force;
An upper guide tube that surrounds the extension tube and opens directly above the upper opening of the lower guide tube; and an upper guide tube that is attached to the outer peripheral surface of the lower opening of the upper guide tube and opens when the coolant temperature rises abnormally to energize the electromagnet. 1. A nuclear reactor shutdown device comprising: a temperature switch for disconnecting; and a rectifier tube surrounding the temperature switch, having open upper and lower ends, and provided around the upper guide tube.