JPH0428901A - Steam generator and its operating method - 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] [Object of the Invention] (Industrial Application Field) The present invention relates to a steam generator applied to, for example, a liquid metal cooled fast breeder reactor plant and a method of operating the same, and in particular, to This invention relates to a steam generator using a steam generator and its operating method.

(Prior Art) Liquid sodium is generally used as a coolant in liquid metal cooled fast breeder reactor plants.

Since this liquid sodium reacts violently with water, particularly high reliability is required of the steam generator, which is a heat exchanger between sodium and water. Therefore, as one of the measures to improve the reliability of such a steam generator, the use of a double heat exchanger tube that doubles the boundary between sodium and water has been considered.

FIG. 7 shows the configuration of a conventional steam generator using double heat exchanger tubes.

The steam generator has a main body shell 1 in the form of a vertically closed closed cylinder, and inside this main body shell 1, a heat exchanger tube bundle consisting of a large number of double heat exchanger tubes 2 is installed in the longitudinal direction. The double heat exchanger tube 2 has a small diameter inner tube inserted into a large diameter outer tube, and the upper and lower ends of the inner tube protrude longer than the upper and lower ends of the outer tube.

Inside the upper end of the main body 1, an upper sodium tube plate 3 that divides the inside of the side in the vertical direction and a steam side tube plate 4 arranged above it are integrated, and an upper gas plenum 5 is arranged between the two tube plates 3 and 4. A formed main steam pipe plate 6 is installed.

Further, a water supply tube plate 10 having a lower sodium tube plate 7, a water side tube plate 8, and a lower gas plenum 9 is similarly installed inside the lower end side of the main body body 1.

The upper and lower ends of the outer tube of the double heat exchanger tube 2 are joined to the upper sodium tube sheet 3 and the lower sodium tube sheet 7, and the upper and lower ends of the inner tube are joined to the upper sodium tube sheet 3 and the lower sodium tube sheet 7. Through. It opens above the steam side tube sheet 4 and below the water side tube sheet 8. Thereby, the gap between the inner and outer tubes communicates with the upper gas plenum 5 and the lower gas plenum 9.

Further, a sodium inlet nozzle 11 is provided on the upper side of the main body shell 1 for introducing liquid sodium into the space between the upper sodium tube plate 3 and the lower sodium tube plate 7 on that side. A sodium outlet nozzle 12 is provided on the lower side for leading sodium out of the shell.

Furthermore, a steam water chamber 14 equipped with a main steam nozzle 13 is formed at the upper end of the main body shell 1, and a water supply ice chamber 16 equipped with a water supply nozzle 15 is formed at the lower end of the main body shell 1. The inner tube of the double heat exchanger tube 2 communicates with the steam water chamber 14 and the water supply ice chamber 16.

The upper gas plenum 5 and the lower gas plenum 9 are filled with inert gas, and each of these plenums 5.9 is provided with a leak detector 17.18.

Thus, high-temperature sodium flows into the side from the sodium inlet nozzle 11 in the upper part of the main body shell 1, then descends within the shell and flows out of the shell from the sodium outlet nozzle 12. On the other hand, water is supplied from the water supply nozzle 15 at the bottom of the main body 1 to the water supply pipe plate 1.
0, flows into the double heat exchanger tube 2, and rises. and,
On the way up, the steam is heated by heat exchange with sodium outside the tube, enters the main steam water chamber 14 through the main steam tube plate 6, and is guided to a required location through the main steam nozzle 13.

In the steam generator using double heat transfer tubes with the above configuration, if a leak should occur in the inner tube or outer tube of the double heat transfer tubes, this should be detected as soon as possible and both the inner tube and the outer tube should be removed. Before penetrating leakage occurs, it is necessary to identify the leaky heat exchanger tube and stop the leakage tube. By doing the above, it is possible to prevent accidents caused by violent reactions with water, which is the primary coolant, in the event of a leak, improving the reliability of the steam generator and, ultimately, the reliability of the fast breeder reactor plant. can be improved.

FIG. 8 is a flowchart showing a method of operating the steam generator in the event that a leak occurs in the double heat exchanger tube 2. For example, if a leak occurs in the inner tube of the double heat exchanger tube 2, the leaked steam passes through the gap between the outer tube and the inner tube and is detected by the leak detector 17, 18 (step a). Once a leak has been detected, the plant is shut down (step b) and the liquid sodium is drained out of the shell (step C). Then, the leaking heat exchanger tube is identified (step d), and the leaking heat exchanger tube is stopped (step e). After the stopper is turned off, liquid sodium is again filled into the body (step f), operation is resumed (step g), and rated operation is started (step h).

(Problems to be Solved by the Invention) Conventionally, for example, when a leak occurs in an inner tube, a leaky heat exchanger tube is identified by the following method. First, the insides of the water supply water chamber 16 and the heat transfer tubes 2 are filled with water to create a water surface on the upper surface of the steam tubes in the main steam water chamber 14. Next, the heat exchanger tube 2 is passed through the upper gas plenum 5 and the lower gas plenum 8.
The helium gas in the gap between the outer tube and the inner tube is pressurized. Then, the steam side tube plate 4 is heated by helium gas that is ejected from the gap between the double tubes to the inside of the inner tubes through the leak holes in the inner tubes.
The leaking heat exchanger tube can be identified by detecting air bubbles that form on the water surface installed on the top surface of the tube or by measuring the sound generated when it erupts.

By the way, in the conventional steam generator described above, the double pipe 2 is a straight pipe type, and in the case of a 1 million KWe class fast breeder reactor plant with a four-loop configuration, each reactor accommodates approximately 4000 heat transfer tubes. ing. It is necessary to stop the plant for a long period of time to stop the leaking heat exchanger tube from among such a large number of heat exchanger tubes. The identification of the leaky heat exchanger tube was explained above using the leak in the inner tube as an example, but if the leak occurs in the outer tube, identifying the leaky heat exchanger tube is even more difficult and requires a long time. Conceivable.

The present invention has been made in view of the above circumstances, and it is possible to detect a leak without delay when a leak occurs from an inner tube or an outer tube constituting a double heat exchanger tube, and to easily identify the heat exchanger tube where the leak occurs. Another object of the present invention is to provide a steam generator and an operating method thereof that can quickly restore plant operation after a leak occurs.

[Structure of the invention]

(Means for Solving the Problems) A steam generator according to the present invention has a large number of heat transfer tubes arranged in a main body barrel through which liquid metal flows, and heat exchanges water supplied to the heat transfer tubes with the liquid metal. A steam generator that generates steam by heating the heat exchanger tube, wherein the heat exchanger tube is a double heat exchanger tube consisting of an outer tube and an inner tube, and an inert gas is filled in the gap between the inner and outer tubes of the double heat exchanger tube. A riff detector is connected via a gas plenum, and the leak detector can detect leakage of liquid metal or water from either the inner or outer tubes. It is characterized in that an independent gas plenum and leak detector are installed for each composition, and an isolation or stopper means is provided for each set or each individual double heat exchanger tube.

In addition, the method of operating a steam generator according to the present invention includes circulating liquid metal within a main body body in which a large number of double heat transfer tubes each consisting of an outer tube and an inner tube are arranged, and supplying the liquid metal to the inner tube of the double heat transfer tubes. The target is a steam generator that generates steam by heating water through heat exchange with the liquid metal, and an inert gas is sealed in the gap between the inner and outer tubes of the double heat transfer tube, and the tube is connected to this gap. In a method for operating a steam generator that stops water supply or steam outflow from the double heat transfer tube when a leak in the inner tube or the outer tube is detected by a leak detector, the type or composition of the inert gas is In addition to being different for each heat exchanger tube, as a leak detection function by the leak detector,
The present invention is characterized in that a function for determining the type or composition of the inert gas is provided, thereby identifying a double heat exchanger tube in which a leak is occurring, and causing the leaking heat exchanger tube to be isolated or stopped.

(Function) According to the steam generator according to the present invention, when a leak occurs in the inner tube of the double heat exchanger tube, the leaked water is leaked from the gap between the inner tube and the outer tube of the double heat exchanger tube. It is detected by a leak detector through the gas plenum to which the heat exchanger tubes are connected. On the other hand, when a leak occurs in the outer tube of a double heat transfer tube, inert gas is generated in the sodium from the leak hole in the outer tube, and by detecting the inert gas in the sodium, the leak can be detected. Detected.

In these cases, the double heat exchanger tubes are divided into multiple sets, and each set is equipped with an independent gas plenum and leak detector, so leaks can be detected without delay and the leaking heat exchanger tube can be identified. It's easy to do.

Furthermore, according to the method of operating a steam generator according to the present invention, by analyzing the detected inert gas, it is possible to immediately determine which set of main steam tube sheets a leak has occurred in the double heat exchanger tubes connected to it. Prove. Regardless of whether there is an inner pipe leak or an outer pipe leak, the main steam stop valve and water supply stop valve of the set in which the leak is detected are closed, and the remaining set of double heat exchanger tubes is used to uniformly spread the heat to each layer in the radial direction. With this feature, the double heat transfer tube steam generator can continue to operate.

Therefore, plant operation can be quickly restored after a leak occurs, and there is no need to stop the plant for a long period of time.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 5.

FIG. 1 shows the overall structure of the steam generator.

In this steam generator, an inner cylinder 32 is arranged at the center of a vertically long main body 31, and a large number of helical coil-shaped double heat transfer tubes 33 are arranged in layers around the inner cylinder 32 to form a tube bundle. ing. Eight main steam pipe plates 34 are provided on the upper side of the main body body 31, and the same number of water supply pipe plates 3 are provided in pairs.
5 is provided at the lower part of the main body trunk 31.

As shown in FIG. 4, the main steam tube plate 34 includes an upper sodium tube plate 36, a steam side tube plate 37, and an upper gas plenum 38.
The upper gas plenum 38 is equipped with an independent leak detector 40 via a plenum nozzle 39. A main steam water chamber 41 is connected to the main steam pipe plate 34, and the main steam water chamber 41 is provided with a main steam nozzle 42 and a lid 43.

Although detailed illustration of the water supply pipe plate 35 is omitted, substantially the same as the main steam pipe plate 34, a lower sodium tube plate,
It is composed of a water supply pipe plate and a lower gas plenum equipped with an independent leak detector 44, and is connected to a water supply water chamber 45.

Further, as shown in FIG. 1, a sodium inlet nozzle 46 is installed at the top of the main body shell 31, and
At the bottom of 1, a sodium outlet nozzle 47 is installed.

The interior of the double heat exchanger tubes 33 communicates with the pair of main steam tube plates 34 and water supply tube plates 35 as described above, and is uniformly arranged in each layer of the helical coiled tube bundle.

FIGS. 2 and 3 show different configuration examples of the double heat exchanger tubes 33 used in the above-mentioned steam generator.

In the one shown in FIG. 2, the double heat transfer tube 33 has a double pressure-resistant boundary formed by an outer tube 33a and an inner tube 33b, and a gap 48 between the two tubes 33a and 33b is filled with an inert gas that conducts heat. Filled with high-grade helium gas.

This gap 48 is connected to the upper gas plenum 38 and the lower gas plenum, and four grooves 48a are formed on the inner surface of the outer pipe 33a.
It is designed for single detection.

Also, in the case shown in FIG. 3, the double heat transfer tube 33 is connected to the outer tube 3.
-3a and the inner tube 33b have a double pressure-resistant boundary, and the gap 48 between both tubes is filled with helium gas having high thermal conductivity as an inert gas. This gap 48 is connected to the upper gas plenum 38 and the lower gas plenum. In this double heat exchanger tube 33, the outer tube 3
A porous metal layer 48b is provided between the inner tube 33a and the inner tube 33b to further improve leak detection characteristics.

By the way, for helium gas, there is a pair of main steam tube plates 34.
A different tag gas is mixed in each set of water supply pipe plates 35. As this tag gas, for example, a mixed gas of krypton and xenon is used. By changing the component ratio of this mixed gas, it is possible to detect it as a different tag gas.

Further, as shown in FIG. 1, a main steam pipe 50 and a water supply pipe 51 are connected to the main steam nozzle 42 and the water supply nozzle 49 provided in the main steam water chamber 41 and the water supply ice chamber 36, respectively. These main steam pipes 50 and water supply pipes 51
is provided with a main steam stop valve 52 and a water supply stop valve 53, and is further connected to a main steam header 54 and a water supply header 55.

Note that the leak detector 40.44 is the inner pipe 3.
Moisture detector used for leak detection in 3b and outer tube 33
There are pressure gauges and the like used to detect leaks in the inner tube 33a and the inner tube 33b. Although not shown, a helium gas detector is installed on the sodium side outlet piping of the steam generator, and the outer tube 3
3a is detected, and the components of the tag gas mixed in the helium gas are analyzed to determine which set of heat exchanger tubes 33 has caused the leak.

Next, the operating method of the steam generator of this embodiment will be explained using FIG. 5. High-temperature sodium flows into the main body shell 31 from the sodium inlet nozzle 46, descends inside the main body shell 31, and flows through a double transmission constituting a helical coil tube bundle before flowing out from the sodium outlet nozzle 47 to the outside of the shell. Heat is exchanged with the water rising inside the heat tube 33. On the other hand, water flows from the water supply header 55 through the water supply pipe 51 into the water supply water chamber 36, and from there passes through the water supply pipe plate 35 and rises inside the helical coil-shaped double heat transfer tube 33. This rising water becomes steam on the way, enters the main steam water chamber 41 via the main steam pipe plate 34, and flows into the main steam header 54 via the main steam pipe 50.

In the event that a leak occurs in the inner tube 33b of the double heat exchanger tube 33, the water that has flowed out will pass through the gap 48 between the outer tube 33a and the inner tube 33b of the double heat exchanger tube 33. The gas flows into the gas plenum of the main steam tube plate 34 or the water supply tube plate 35 to which the heat transfer tubes are connected, and is detected as a leak by the leak detectors 40, 44 (step A).

If a leak is detected, the plant is shut down (Step B)
Alternatively, the output decreases (step C), the main steam stop valve 52 and water supply stop valve 53 of the heat exchanger tube set in which the leak has been detected are closed (step D), and inert gas is filled in the heat exchanger tubes. . Then, in case of shutdown, the plant is restarted (step E) and the plant is 7/8, i.e. approximately 8
It is operated at 5% output (Step F). Double heat exchanger tube 3
3 is uniformly distributed in each layer of the helical coiled tube bundle, so even if water is not passed through 1/8 of the heat transfer tubes, the radial performance of the tube bundle, that is, the temperature distribution, is maintained approximately uniformly. Driving becomes possible. After that, during planned shutdowns such as regular plant inspections (Step G), the tube bundle of the double heat exchanger tubes is investigated, the leaking heat exchanger tube is identified and plugged, and operation is then returned to the rated output. (Step H).

According to the operating method of this embodiment, it only takes a few days to return to operation, making it possible to return to operation more quickly than with the conventional operating method, which required several months for the same work. It is something.

In addition, when a leak occurs in the outer tube 33a of the double heat transfer tube 33, helium gas flows out into the sodium inside the main body shell 31 through the gap 48. This helium gas is detected by a helium gas detector installed in 80 pipes of the steam generator, and by analyzing the tag gas mixed in the helium gas, it can be determined in which set of heat transfer tube bundles the leak has occurred. It becomes clear. The operation method after that is inner pipe 3
The same is true for the leak in 3b.

The specific effects of this embodiment will be explained. In this embodiment, a long helical coil-shaped double heat exchanger tube 33 is used and eight sets of water supply tube plates 35 and main steam tube plates 34 are used, so a high-speed 4-loop configuration of 1 million KWe class is used. When comparing steam generators for breeder reactors, the conventional steam generator shown in Fig. 7 has approximately 4,000 heat transfer tubes connected to one tube plate, but in this example, approximately 4,000 heat transfer tubes are connected to one tube plate. It only takes about 60 pieces. Therefore, the volume of the gas plenum portion is small, leakage can be detected quickly, and the heat exchanger tube in which the leakage occurs can be easily identified.

In addition, since the leak detectors 40 and 44 are installed independently on each tube sheet, and a different type of tag gas is sealed in the helium gas sealed in the gas plenum for each set of double heat transfer tubes 33, Whether it is a leak in the inner tube 33b, the outer tube 33
Even if there is a leak in a, it can be easily determined which set of double heat exchanger tubes 33 is causing the leak.

Furthermore, since a stop valve 52.53 is installed in each set of water supply pipe 51 and main steam pipe 50, this stop valve 52.53
By closing the double heat exchanger tubes 33, operation can be continued with the remaining set of double heat exchanger tubes 33. This operation can also be performed without stopping plant operation. Further, since each set of double heat exchanger tubes 33 is arranged uniformly in the radial direction, even if the above operation is performed, uniform performance can be exhibited.

FIG. 6 shows another embodiment of the invention.

In this embodiment, the leak detectors 40, 44 are shared by a plurality of main steam tube plates 34 and water supply tube plates, respectively, and each set of heat exchanger tubes can be detected independently using the switching devices 61, 62. has been done. The other configurations are the same as those in the previous embodiment. According to this embodiment, by using the switches 61, 62, the number of leak detectors 40, 44 can be reduced, resulting in cost reduction and placement advantages.

In each of the above embodiments, each tube sheet is divided into eight groups, but the number of groups or pieces can be freely set according to design choices.

〔Effect of the invention〕

As described above, according to the steam generator according to the present invention, long double heat exchanger tubes are used, an independent main steam tube plate and a water supply tube plate are provided for each set, and independent leak detection is performed in the gas plenum of these tubes. By using a configuration in which a ratio device is provided, leakage can be detected without delay, and the heat exchanger tube in which the leakage occurs can be easily identified.

Furthermore, according to the method of operating a steam generator according to the present invention, by analyzing the detected inert gas, it can be immediately determined in which set of main steam tube sheets rift has occurred in the double heat exchanger tubes connected to it. Therefore, whether it is an inner pipe leak or an outer pipe leak, the main steam stop valve and water supply stop valve of the set in which the leak is detected are closed, and the remaining set of double heat exchanger tubes are used. The double heat exchanger tube steam generator can continue to operate with uniform characteristics in each layer in the radial direction. Therefore, plant operation can be quickly restored after a leak occurs, and there is no need to stop the plant for a long period of time.

Therefore, according to the present invention, it is possible to improve the reliability of a fast breeder reactor plant, and moreover, it is possible to achieve effects such as greatly contributing to improving the operating efficiency of the fast breeder reactor plant.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram showing one embodiment of a steam generator according to the present invention, Fig. 2 is a sectional view of a double heat exchanger tube, Fig. 3 is a sectional view of another double heat exchanger tube, and Fig. 4 is a sectional view of the main steam pipe plate, FIG. 5 is a flowchart showing the method of operating the steam generator, FIG. 6 is a block diagram showing another embodiment of the steam generator according to the present invention, and FIG. 7 is a conventional steam generator. FIG. 8, which is a block diagram showing an example, is a flowchart showing a conventional operating method. 31...Main body shell, 32...Inner tube, 33...Double heat transfer tube, 33a...Outer tube, 33b...Inner tube, 34...
・Main steam pipe plate, 35... Water supply pipe plate, 36... Upper sodium tube plate, 37... Steam side tube plate, 38... Upper gas plenum, 39... Plenum nozzle, 40...
Leak detector, 41... Main steam ice chamber, 42... Main steam nozzle, 43... Lid body, 44... Leak detector,
45... Water supply ice chamber, 46... Sodium inlet nozzle, 47... Sodium outlet nozzle, 48... Gap,
49... Water supply nozzle, 50... Main steam pipe, 51...
- Water supply pipe, 52... Main steam stop valve, 53... Water supply stop valve, 54... Main steam header, 55... Water supply header, 61.62... Switch.

Claims (1)

[Scope of Claims] 1. A steam system in which a large number of heat transfer tubes are disposed within a body shell through which liquid metal flows, and water supplied to the heat transfer tubes is heated by heat exchange with the liquid metal to generate steam. A generator, wherein the heat transfer tube is a double heat transfer tube consisting of an outer tube and an inner tube,
In addition, an inert gas is filled in the gap between the inner and outer tubes of the double heat transfer tube, and a leak detector is connected via the gas plenum, and this leak detector can detect leaks of liquid metal or water from either the inner or outer tube. In that case,
The large number of double heat exchanger tubes is divided into a plurality of sets, each set is provided with an independent gas plenum and a leak detector, and each set or each double heat exchanger tube is provided with isolation or stopper means. A steam generator characterized by: 2. A liquid metal is passed through a main body body in which a large number of double heat transfer tubes consisting of an outer tube and an inner tube are arranged, and water supplied to the inner tube of the double heat transfer tube is heated by heat exchange with the liquid metal. The target is a steam generator that generates steam using a double heat transfer tube, and an inert gas is sealed in the gap between the inner and outer tubes of the double heat transfer tube, and a leak detector connected to this gap is used to detect leaks in the inner tube or outer tube. In the method of operating a steam generator, stopping water supply or steam outflow of the double heat exchanger tube when detected,
The type or composition of the inert gas is made different for each double heat exchanger tube, and the leak detector is provided with a function of determining the type or composition of the inert gas as a leak detection function, thereby preventing leaks from occurring. 1. A method for operating a steam generator, comprising: identifying a double heat exchanger tube that is leaking, and isolating or stopping the leaking heat exchanger tube.