JPS6358003A - Metallic ionization detector - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for detecting liquid metal leakage due to heat exchanger tube breakage in a double-tube heat exchanger, particularly for sodium, water, and steam in fast breeder reactors. The present invention relates to a heat exchanger tube liquid metal leak detector suitable for double-tube steam generators.

[Conventional technology]

For conventional double tube heat exchangers, see Nuclear Technology, Volume 55, Nuclear 2 (November 1981).
Month) pages 270 to 279 (NU-CLEARTE
CNOLO(EY, VOLUMH55, NLICLE
AR2NOVE MBIER1981PP270-279
) is discussed. An example of this is shown in FIG.

A large number of double pipes are installed vertically inside the outer wall.

Liquid metal flows in from 1 and water flows in from 3. Water flows from the bottom to the top inside the many double-walled pipes.

The liquid metal flows from top to bottom outside the double outer tube.

Water becomes water vapor through heat exchange with liquid metal. The water vapor flows out from 4, and the cooled liquid metal flows out from 2.

An inert gas 9 is sealed between the inner tube 7 and the outer tube 6, so that in the unlikely event that the inner tube 7. Alternatively, when the outer tube 6 is damaged, the liquid metal 8 and water are directly released.

The steam 10 contacts and prevents reaction.

If the double outer tube 6 were to break, the liquid metal 8 would be mixed into the inert gas 9. If this mixed liquid metal is detected early, it is possible to prevent a large-scale liquid metal-water reaction accident due to the progression of damage to the heat transfer tubes in the heat exchanger.

The principle of a metal ionization detector is shown in FIG. A liquid metal aerosol 14 is ionized and ionized by a filament 16 kept at a high temperature, and an ionic current is passed between the filament and a collector 17. By detecting this ionic current, minute liquid metal leakage is detected.

FIG. 8 shows an example in which a conventional liquid metal ionization detector is installed in a double-tube heat exchanger. Further, FIG. 9 shows a schematic diagram of the structure of the liquid metal ionization detector.

In FIG. 8, the inert gas between the inner tube and the outer tube of the heat exchanger (hereinafter referred to as the intermediate layer) passes through the pipe 25,
The ionization detector 24 is guided by the blower 23 . The interior of the piping and detector is kept at high pressure. Therefore, the 9th
The detector housing 29 shown in the figure needs to have a sealed pressure-resistant structure.

[The problem that the invention attempts to solve]

(1) In the prior art, as shown in FIG. 8, in order to detect leakage of liquid metal due to heat exchanger tube breakage, inert gas inside the heat exchanger is supplied to the ionization detector 24 via piping 25 and blower 23.
I needed to lead to. This method has the problem of increasing the scale of the leakage liquid metal detection equipment.

(2) Also, regarding the time from the start of liquid metal leakage due to damage to the outer tube of the heat transfer tube to detection, in the conventional technology, as shown in Figure 8, it takes time to detect because the piping is routed from the heat exchanger to the ionization detector. There was a problem that it took a while.

(3) Furthermore, the prior art had the disadvantage that, as shown in FIG. 9, the pressure inside the ionization detector was high, so the jacket 29 needed to have a hermetically sealed pressure-resistant structure.

(4) With the conventional technology, it is difficult to identify the location of a damaged heat exchanger tube, and in the unlikely event that a problem occurs, it is difficult to locate the damaged heat transfer tube. ! 8 When an outer tube breaks, there is a problem in that the damaged heat transfer tube must be found among all of the many heat transfer tubes in the heat exchanger.

The purpose of the present invention is to reduce the scale of liquid metal leakage detection equipment by eliminating piping and blowers, and to shorten the time from the start of liquid metal leakage to its detection. The purpose is to remove the hermetic pressure envelope.

Furthermore, it is possible to identify the position of a damaged heat exchanger tube in order to remove it at an early stage.

[Means for solving problems]

Reducing the scale of liquid metal leakage detection equipment in double tube wall heat exchangers for the above purposes, shortening the time from the start of liquid metal leakage to detecting it, and eliminating the sealed pressure-resistant jacket of the metal ionization detector. This can be accomplished by incorporating a metal ionization detector into the intermediate layer of the heat exchanger shown in FIG.

Further, regarding the identification of the position of the damaged heat exchanger tube, by dividing the intermediate layer region in the heat exchanger shown in FIG. 6 into several blocks with partition plates, it becomes possible to identify the position of each block. In addition,
At this time, the partition plate does not require a completely sealed structure.

[Effect]

The metal ionization detector is built into the heat exchanger intermediate layer.
Eliminates the need to transport sample gas from the heat exchanger to the detection unit, and eliminates the need for attached equipment such as piping and blowers. Therefore, the scale of detection equipment can be much smaller than before. Furthermore, installing the metal ionization detector directly within the heat exchanger also shortens the time it takes for the leaked liquid metal aerosol to reach the metal ionization detector.

In addition, the metal ionization detector can be built into the heat exchanger intermediate layer.

Since the outside is placed in the same pressure field, there is no need for a pressure-tight sealed structure for the detection section, and the pressure-tight envelope for the detector can be eliminated.

Furthermore, the built-in metal ionization detector enables non-forced circulation of the inert gas in the intermediate layer, eliminating stagnation of inert gas that does not enter the forced circulation flow path and enabling uniform sampling. do.

By providing a partition in the intermediate chamber and dividing a large number of heat exchanger tube groups into blocks, it becomes possible to identify the position of the damaged heat exchanger tube in the unlikely event that the heat exchanger tube breaks.

〔Example〕

An example of an embodiment of the present invention is a double tube steam generator (hereinafter referred to as double tube SG) of a fast breeder reactor (hereinafter referred to as FBR). This will be explained using FIGS. 4 and 5.

Figure 1 is a system diagram of an FBR heat exchange system using double pipe SG according to the present invention, and Figures 2 and 3 are diagrams of double pipe SG.
A schematic diagram of an ionization detector installed in an inert gas chamber, FIGS. 4 and 5 are schematic diagrams of blocks of the inert gas chamber.

In FIG. 1, sodium (hereinafter abbreviated as Na) in the heating source 30 is guided into the double pipe 5G32 by the main circulation pump 31. Na surrounds the outside of the outer tube inside the double tube 5G32. Double 'l? The Na cooled by heat exchange with the water flowing inside the inner tube inside the 5G32 exits the 5G32 and is led to the heating source 30 again to be heated. On the other hand, the steam heated and vaporized by heat exchange with Na in the double pipe 5G32 is guided from the upper part of the 5G32 to the turbine 33 and the condenser 34, and after condensation, it is returned to the lower part of the double pipe 5G32 by the pump 35. Inflow.

By the way, as shown in Figure 6, there is an inert gas space between the inner and outer heat exchanger tubes, which is connected to the inert gas chamber (another name for the intermediate layer region) at the top of the heat exchanger. . Second
In the figure, the mounting position of a leak sodium ionization detector according to the invention is shown.

This figure is a sectional view of the intermediate layer region shown in FIG. 6.

The attachment of the ionization detector 39 also indicates the condition. By housing the detector main body in an inert gas chamber, the pressure difference between the inside and outside of the detector becomes zero, eliminating the need for a hermetically sealed pressure-resistant jacket. FIG. 3 shows how the metal ionization detector is installed in the intermediate layer of the heat exchanger without the sealed pressure-resistant jacket.

In the unlikely event that the outer tube of the heat transfer tube is damaged and Na leaks as shown in Figure 2, Na will diffuse into the inert gas chamber and the ionization detector 39
However, since it can be detected directly in an inert gas chamber, its response is quick.

FIG. 4 shows an example in which the inside of the inert gas chamber is divided into blocks by partitions Fj, 41, and heat transfer 1140 groups are divided into groups. A detector 39 is installed in each block.

Due to the double structure, sodium leakage can be detected early in the unlikely event that the outer tube of the heat transfer tube is damaged. In this case, the partition plate 41 does not require a complete sealing structure. This is because, as shown in Figure 5, even if several ion detectors detect leakage,
Based on the detected amount, it is possible to know which heat transfer tube wall is damaged.

In addition, the built-in detector enables non-forced circulation of the inert gas in the intermediate layer, eliminating stagnation of inert gas that does not enter the forced circulation flow path, enabling uniform sampling. Make it. Furthermore, a hermetically sealed pressure-resistant structure of the metal ionization detector detection section is not required, and the hermetically sealed pressure-resistant jacket of the detector can be omitted.

Providing a partition plate in the intermediate layer and dividing a large number of heat exchanger tube groups into blocks makes it possible to identify the position of the damaged heat exchanger tube in the event of breakage of the heat exchanger tube, and to quickly detect the broken heat exchanger tube.

〔Effect of the invention〕

According to the present invention, accessory equipment such as a piping blower can be removed,
This can shorten the time it takes for leaked liquid metal aerosol to reach the ionization detector, allowing early detection of damage to the heat exchanger tube.

[Brief explanation of the drawing]

Figure 6 is a schematic diagram of the structure of a double tube wall heat exchanger, Figure 7 is a diagram explaining the detection principle of an ionization detector, Figure 8 is a system diagram of a conventional liquid metal leakage detection equipment, and Figure 9 is a diagram of a conventional ionization detector. FIG. 2 is a schematic diagram of a detector structure. FIG. 1 shows F of an embodiment of the present invention.
BR's heat exchange system system diagram, Figure 2 is a schematic diagram of the built-in heat exchanger of the present invention, Figure 3 is an example diagram of the inert gas chamber division of the present invention, Figures 4 and 5. is a schematic diagram of the inert gas chamber block.

Claims (1)

[Claims] 1. Metal is installed in the intermediate layer region communicating with the gap between the inner tube and the outer tube of a double tube heat exchanger in which the heat exchanger tube wall portion is composed of an inner tube and an outer tube. A metal ionization detector featuring: 2. A metal ionization detector according to claim 1, characterized in that the outer covering between the electrodes has a non-sealed structure. 3. The metal ionization detector according to claim 1, characterized in that a partition is provided to divide the intermediate layer region, thereby making it possible to identify the position of each block of the leaky heat exchanger tube.