JPS5950919B2 - Heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to heat exchangers, and more particularly to an intermediate heat exchanger for rapid growth, for example, in which sodium leakage in heat transfer tubes and tube sheets can be easily detected.

[Technical background of the invention]

As is well known, the reactor cooling system equipment of a fast breeder reactor plant consists of a reactor system that includes the reactor core, a primary cooling system, and a secondary cooling system that transfers the heat generated in this reactor system to the turbine generator system. and water/steam systems.

Furthermore, for the purpose of heat exchange between the primary cooling system and the secondary cooling system, an intermediate heat exchanger (hereinafter referred to as a heat exchanger) is provided between the primary cooling system and the secondary cooling system.

) is installed. This heat exchanger is one of the main pieces of equipment in the reactor cooling system of a fast breeder reactor, and in order to perform stable heat exchange, it is necessary to ensure the integrity of the many heat transfer tubes arranged inside. be done.

However, considering the long-term operation of the plant, it cannot be assumed that the heat exchanger tubes will remain sound throughout the life of the plant, and it is necessary to periodically inspect the heat exchanger tubes. There is.

Conventionally, inspection of heat exchanger tubes in fast breeder reactor heat exchangers involves draining all the primary and secondary coolant in the heat exchanger and inserting a small inspection device into the heat exchanger tubes to check their integrity. The soundness of the heat transfer tubes is confirmed by checking or leakage tests using helium gas, etc.

[Problems with background technology]

However, the inspection is extremely difficult because the inspection time is enormous and the primary coolant remaining in the heat exchanger is activated, making inspection performance poor.

Under these circumstances, the following needs have arisen for heat exchangers for fast breeder reactors.

(1) We would like to reduce the inspection time of heat exchanger tubes as much as possible and contribute to improving the operating efficiency of the plant.

(2) We want to simplify the inspection method for heat exchanger tubes and reduce the risks for inspectors as much as possible.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention has been made to satisfy the above-mentioned needs, and is to provide a heat exchanger that can easily and accurately detect coolant leakage in heat exchanger tubes and tube sheets.

[Summary of the invention]

The present invention is a heat exchanger characterized in that a liquid level gauge is provided in the inlet pipe connected to the upper and lower headers of the heat exchanger.

According to the present invention, the liquid level of the secondary coolant in the inlet pipe and the outlet pipe is held constant, and the liquid level of the secondary coolant in the inlet pipe is pressurized with an inert gas and left for a certain period of time. Detection of sodium leakage in heat exchanger tubes and tube sheets can be easily and accurately confirmed based on the presence or absence of sodium leakage.

[Embodiments of the invention]

Hereinafter, one embodiment of the heat exchanger according to the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a longitudinal section of a heat exchanger according to the present invention.

As is clear from this figure, the main body of the heat exchanger 1 according to the present invention is constructed by integrally attaching a hemispherical upper header 17' and a lower header 18 to the upper and lower ends of a cylindrical outer shell 7. has been done.

A primary coolant-containing nozzle 2 for introducing the primary coolant is connected to the side surface slightly above the middle of the outer shell 7, and a lower header 18 of the outer shell 7 for introducing the primary coolant. A primary coolant outlet nozzle 3 is attached.

A secondary coolant artificial pipe 4 and a secondary coolant outlet pipe 5 are attached to the upper header 17.

The drain pipe 6 extends to the lower part of the inner shell 10, and the artificial pipe 4 penetrates the upper part 17, extends slightly below the lower tube plate 11 in the inner shell 10, and is fixed.

Further, a liquid level gauge 14 is inserted into this secondary coolant inlet pipe 4.

On the other hand, a bottomed inner shell 10 is provided inside the outer shell 7 via a support member 10a, and the inner shell 10 has a primary coolant inlet window 12 and a primary coolant inlet window 12 for introducing and extracting the primary coolant. Primary coolant outlet windows 13 are provided vertically apart from each other.

Inside the inner shell 10, a large number of heat transfer tubes 9 are bundled together and supported by an upper tube sheet 8 and a lower tube sheet 11. Below 11 is 2
A second coolant lower chamber 16 is formed respectively.

Further, a partition wall 19 is provided in the gap 37 between the outer shell 7 and the inner shell 10 to partition the introduction and discharge of the primary coolant.

The heat exchanger 1 configured in this way is as shown in FIG.
It is installed between the primary cooling pipe 22 and the secondary cooling pipe 26 and transmits the heat generated in the nuclear reactor 20 to the steam generator 24.

A primary main circulation pump 21 and a secondary main circulation pump 23 are provided in the primary cooling pipe 22 and the secondary cooling pipe 26 to circulate the coolant.

Connected to the secondary cooling pipe 26 are filling drain pipes 30 and 31 for filling the secondary cooling pipe 26, the heat exchanger 1, and the steam generator 24 with coolant or draining the coolant from them. Stop valves 34 and 35 are provided in the middle.

The filling and draining pipes 30 and 31 are connected to a dump tank 25 for storing coolant.

The secondary cooling pipe 26 also includes inert gas pipes 28 and 29 for filling the inside of the secondary cooling pipe 26, the heat exchanger 1, and the steam generator 24 with inert gas when draining the coolant. are connected, and there are stop valves 32 and 3 in the middle.
3 is provided.

Inert gas pipes 28 and 29 are connected to an inert gas supply device 27 for supplying inert gas.

Next, the operation of the device according to the above configuration will be explained.

As described above, the heat exchanger 1 configured in this manner transfers heat generated in the reactor 20 to the steam generator 24 via the primary cooling pipe 22 and the secondary cooling pipe 26 during normal operation of the nuclear reactor plant. It is intended to be transmitted to.

The primary coolant flows from the primary coolant nozzle 2, rises through the gap 37 between the outer shell 7 and the inner shell 10, and passes through the primary coolant artificial window 12 provided in the inner shell 10 to enter the inner shell. It descends inside the shell 10, reaches the primary coolant outlet window 13, descends through the gap 37 between the outer shell 7 and the inner shell 10 below the partition wall 19, and flows out from the primary coolant outlet nozzle 3.

On the other hand, the secondary coolant flows into the secondary coolant inlet pipe 4 provided in the upper header 7 of the outer shell 7 and enters the secondary coolant lower chamber 1.
6, the coolant rises inside the heat transfer tube 9 and exchanges heat with the primary coolant, then reaches the secondary coolant upper chamber 15 and flows out from the secondary coolant outlet pipe 5.

Inspection of the heat exchanger tubes 9 of the heat exchanger 1, which operates in this way during normal operation of the plant, stops heat generation in the reactor 20 and maintains a constant temperature of the coolant in the reactor 20 and the primary cooling piping 22. After holding the secondary cooling pipe 26 and the steam generator 2
Perform this with the secondary coolant in 4 drained.

That is, the stop valve 35 provided in the filling drain pipe 31 connected to the secondary cooling pipe 26 is opened, and the secondary coolant in the secondary cooling pipe 26 and the steam generator 24 is drained and stored in the dump tank 25. .

At the same time, inert gas is supplied by the inert gas supply device 27 to the secondary cooling pipe 26 and the space containing the secondary coolant in the steam generator 24 via the inert gas pipe 29 and the stop valve 33. It is supplied as follows.

Further, the secondary coolant in the heat exchanger 1 is drained using a secondary coolant drain pipe 6 included in the secondary coolant inlet pipe 4.

The secondary coolant filled in the secondary coolant upper chamber 15, secondary coolant lower chamber 16 and heat transfer tubes 9 in the heat exchanger 1 is filled with inert gas supplied by the inert gas supply device 27. It flows into the secondary coolant inlet pipe 4 and the secondary coolant outlet pipe 5 and pressurizes the secondary coolant liquid level.

As a result, the secondary coolant in the heat exchanger 1 flows from the lowest end of the secondary coolant drain pipe 6 that opens into the secondary coolant lower chamber 16, rises inside this pipe 6, and is filled. The water is drained to the dump tank 25 via the drain pipe 30 and the stop valve 34.

At this time, in order to accurately inspect the heat exchanger tubes 9, the drain level in the heat exchanger 1, that is, the liquid level of the secondary coolant, is adjusted to the secondary coolant artificial pipe 4 and the outlet as shown in FIG. It is maintained at the position 36, which is the vertical part of the pipe 5.

At this time, since sodium, a liquid metal, is used as a coolant in a fast breeder reactor, considering the relatively high melting point of sodium (approximately 100°C), the temperature of the secondary coolant isolated in the heat exchanger 1 is However, the primary coolant in the heat exchanger 1 is filled, and the primary coolant in the reactor 20 and the primary cooling piping 22 is also filled and the temperature reaches 200°C. It is maintained at a constant temperature in the vicinity.

Therefore, the secondary coolant isolated in the heat exchanger 1 is maintained at a temperature close to that of the primary coolant via the heat transfer tubes 9.

Under such conditions, the heat exchanger tubes 9 of the heat exchanger 1 are inspected.

That is, after closing the stop valves 34 and 35 provided in the filling drain pipes 30 and 31, which were open for the secondary coolant drain operation, the secondary coolant inlet of the heat exchanger 1 is closed. The piping 4 and the outlet piping 5 are pressurized with inert gas.

As described above, the inert gas flows into both the secondary coolant inlet pipe 4 and the secondary coolant outlet pipe 5.

At this time, the secondary cooling pipe 26 and the steam generator 24 are also pressurized and maintained at a constant pressure because the secondary coolant is drained.

Therefore, since both the secondary coolant artificial pipe 4 and the secondary coolant outlet pipe 5 of the heat exchanger 1 are pressurized with uniform pressure from both the inert gas pipes 28 and 29, the secondary coolant inlet pipe 4
The coolant liquid level 36 inside is always kept constant.

Under such conditions, the transmission is carried out by leaving it for a certain period of time and measuring the fluctuation of the coolant liquid level 36 in the secondary coolant inlet pipe 4 using the liquid level gauge 14 installed in the secondary coolant inlet pipe 4. Check the soundness of the heat tube 9.

That is, the secondary coolant present in the heat exchanger 1 is contained in the secondary coolant upper chamber 15, a portion of the secondary coolant inlet pipe 4 and the secondary to secondary coolant outlet pipes 5, the heat exchanger tubes 9, and the secondary coolant upper chamber 15. Material lower chamber 1
It is 6.

Therefore, by pressurizing the secondary coolant upper chamber 15 and making the pressure higher from the primary coolant side, if there is any damage such as cracks or pinholes in the heat transfer tube 9, the secondary coolant will pass through the relevant part. As the coolant flows into the primary coolant, the coolant liquid level 36 in the secondary coolant inlet pipe 4 falls.

By detecting this with the liquid level gauge 14, damage to the heat exchanger tubes 9 can be confirmed.

Furthermore, if the drop in the coolant liquid level 36 is not confirmed by the liquid level gauge 14, it can be confirmed that the heat exchanger tubes 9 are healthy.

The accuracy of this detection method assumes the pipe diameter of the intermediate heat exchanger and the coolant capacity in the intermediate heat exchanger of a practical class fast breeder reactor, and the accuracy of the liquid level gauge is ±2 cm, and the accuracy of temperature correction is ±2 cm. 2℃
Assuming that, if a pressurized test is conducted for 2 days (48 hours), it will be possible to detect secondary coolant leakage of approximately 16 cc/miH.

This corresponds to leakage due to a pinhole with a diameter of about 0.1 mm.

If the liquid level 36 of the coolant is not kept in the secondary coolant inlet pipe as in the present invention but is kept in the secondary coolant upper chamber 15, the detection accuracy of secondary coolant leakage will be the same as described above. It becomes about 72cc/min under the condition of.

Conversely, in order to obtain the same detection accuracy, a test period of 9 days, which is 4.5 times as long as in the case of the present invention, is required.

Note that the liquid level gauge 14 can be attached not only to the inlet pipe 4 but also to the outlet pipe 5.

〔Effect of the invention〕

As explained above, the present invention has a liquid level gauge attached to the secondary coolant inlet or outlet piping of a heat exchanger, and during a leakage detection test, a free liquid level is provided in the piping and the intermediate heat exchanger Leakage of coolant in the primary and secondary pounds can be detected with high accuracy from a drop in the free liquid level.

Therefore, according to the present invention, the method for inspecting heat exchanger tubes is facilitated, and the heat exchanger tubes can be inspected with high precision, thereby reducing the risk to the inspector as much as possible.

This shortens the inspection time for the heat exchanger tubes, which ultimately increases the reliability of the plant and improves the operating rate.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a vertical sectional view showing an embodiment of the heat exchanger according to the present invention, and Fig. 2 is a system diagram for explaining the application location of the heat exchanger shown in Fig. 1. It is. 2... Primary coolant inlet nozzle, 3... Primary coolant outlet nozzle, 4... Secondary coolant inlet piping, 5... Secondary coolant outlet piping, 6... Secondary Coolant drain pipe, 12
...Primary coolant inlet window, 13...Primary coolant outlet window, 14...Liquid level gauge.

Claims (1)

[Claims] 1. An inner shell that has a large number of heat transfer tubes inside and has a primary coolant inlet window and a primary coolant outlet window on the upper and lower side surfaces, and a primary coolant inlet nozzle and a primary coolant outlet nozzle that cover this inner shell. an outer shell having an upper header and a lower header connected to both ends of the outer shell, a secondary coolant outlet pipe connected to the upper header, and extending through the upper header to the lower part of the inner shell. The existing secondary coolant inlet pipe and the
A heat exchanger comprising a liquid level gauge attached to a secondary coolant inlet pipe or a secondary coolant outlet pipe.